US3607073A

US3607073A - Method and apparatus for analysis of fluid mixtures

Info

Publication number: US3607073A
Application number: US746487A
Authority: US
Inventors: Ralph E Stamm
Original assignee: Texaco Inc
Current assignee: Texaco Inc
Priority date: 1968-07-22
Filing date: 1968-07-22
Publication date: 1971-09-21
Anticipated expiration: 1988-09-21
Also published as: NL7106353A; FR2137088B1; GB1304796A; FR2137088A1; DE2118539A1

Abstract

A method and apparatus for continually monitoring a component of a fluid mixture, such as the naphthene content of a hydrocarbon mixture. The apparatus includes a microreactor for subjecting the fluid mixture to a chemical reaction converting, at least in part, a fluid component of the mixture so as to render the fluid component of interest separable from the mixture, and detection means for detecting the fluid component of interest. In a further embodiment a unique computer is provided coupled with the detector for computing the concentration of the fluid component of interest in the fluid mixture. The method of the invention includes reacting the fluid mixture in the aforementioned chemical reaction, and detecting the fluid component of interest. In another version of the method in which the reaction affects more than one component of the mixture converting the affected components to still another component of the mixture, the method includes the further steps of detecting said other component in an unreacted sample of the fluid mixture and generating a signal representative of the concentration in the mixture of the fluid component of interest in accordance with a predetermined relationship between the detected components of the unreacted sample, the reacted sample, and the concentration of the fluid component of interest in the fluid mixture.

Description

United States Patent [72] Inventor Ralph E. Stamm Port Arthur, Tex. [21] AppLNo. 746,487 [22] Filed July 22,1968

[45] Patented [73] Assignee Sept. 21, 1971 Texaco Inc. New York, N.Y.

[54] METHOD AND APPARATUS FOR ANALYSIS OF FLUID MIXTURES 15 Claims, 2 Drawing Figs.

[52] US. Cl 23/230 R, 23/230 M, 23/232 R, 23/232 C, 23/253 R, 23/254 R,235/151.12,235/l51.35

[51] Int. Cl ..G01n31/08, GOln 31/10 [50] Field of Search 23/230, 232, 253, 254; 73/25, 190; 235/151.12, 151.35

F/wii Mfr/Dre Yam Vapor/:2

OTHER REFERENCES Cousins et al., Dehydrogenation As An Aid To The Mass spectrometric Analysis of Naphtenes, Analytical Chemistry, Vol. 33,No. 13,Dec. 1961, PP 1875-1878.

Primary Examiner--Morris O. Wolk Assistant Examiner-R. E. Serwin Attorneys-K. E. Kavanagh, Thomas H. Whaley and Robert J.

Sanders, Jr.

ABSTRACT: A method and apparatus for continually monitoring a component of a fluid mixture, such as the naphthene content of a hydrocarbon mixture. The apparatus includes a microreactor for subjecting the fluid mixture to a chemical reaction converting, at least in part, a fluid component of the mixture so as to render the fluid component of interest separable from the mixture, and detection means for detecting the fluid component of interest. In a further embodiment a unique computer is provided coupled with the detector for computing the concentration of the fluid component of interest in the fluid mixture. The method of the invention includes reacting the fluid mixture in the aforementioned chemical reaction, and detecting the fluid component of interest. In another version of the method in which the reaction affects more than one component of the mixture converting the affected components to still another component of the mixture, the method includes the further steps of detecting said other component in an unreacted sample of the fluid mixture and generating a signal representative of the concentration in the mixture of the fluid component of interest in accordance with a predetermined relationship between the detected components of the unreacted sample, the reacted sample, and the concentration of the fluid component of interest in the fluid mixture.

PATENTED SEPZI 1971 SHEET 1 OF 2 PATENTEU SEPZ] I97! SHEET 2 [IF 2 METHOD AND APPARATUS FOR ANALYSIS OF rwm MIXTURES BACKGROUND OF THE INVENTION This invention relates to a method and apparatus for the analysis of fluid mixtures, and more particularly to the analysis of h trocarbon mixtures.

In laboratory and industrial applications it is frequently necessary to analyze a fluid mixture to determine the concentration of its constituents. This is of particular importance in connection with computer control and optimization of fluid processes in the petroleum-refining industry where the economy of various processes is often predicated upon accurate information of the composition of fluid mixtures undergoing process treatment or the concentration therein of selected fluid components.

Certain fluid mixtures, particularly the hydrocarbons, are difficult to analyze or separate due to the similarity of the physical properties of the fluid components. Thus, the components of the fluid mixture may have similar boiling points, similar adsorption characteristics, or they may be composed of similar nonpolar molecules. Such similarities render the analysis or separation of these fluid mixtures by presently known physical methods, such as chromatography or fractionation, extremely difficult.

An example of a fluid mixture difficult to analyze is found in connection with the catalytic reforming process for the octane improvement of fuels. The process charge stream usually comprises a mixture of aromatics, naphthenes, and parafi'ms. Both the naphthenes and the paraffins may be distinguished from the aromatics. by chromatographic analysis. But the naphthenes cannot be easily distinguished from the parafflns due to the similar physical properties of these components. One method by which such a mixture may be analyzed is by use of a mass spectrometer. However, this technique does not lend itself to online continuous process use in its present state of development. Also, the use of prior art chromatographic analysis techniques to analyze the fluid mixture are unsatisfactory due to the inability of this method to distinguish between certain fluid components having similar physical properties.

For the purpose of computer or automatic control of the catalytic reforming process, it is important to continuously analyze the charge stream for its naphthene content since the naphthenes are the main reactants in the process. The naphthene content of the charge stream is therefore a key variable of the process. Hence, if information thereof is continuously made available to a computer control loop controlling other variables of the process, the process may be optimized, improving its economy and the quality of the product.

The invention as herein disclosed provides a solution to the aforementioned problems by a unique and novel method and apparatus for the continuous analysis of fluid mixtures suitable for many process control applications.

SUMMARY Briefly stated a preferred aspect of the invention provides a method for continually monitoring a component of interest of a fluid mixture having physical properties sufficiently similar to those of other components of the fluid mixture rendering it difficult to separate or distinguish the fluid component of interest therefrom. The method includes reacting a sample of the fluid mixture in a chemical reaction which affects at least one component of the fluid mixture so as to alter at least in part the chemical structure and at least one physical property thereof rendering the fluid component of interest distinguishable from the fluid mixture, and detecting the fluid component of interest. One version of the method includes the step of separating at least a portion of the fluid component of interest from the mixture and then the fluid component of interest thus separated is detected. In one aspect of the method for determining the concentration of the fluid component of 60 interest in a fluid mixture which includes one distinguishable component the reaction converts at least one component of the LII mixture to the distinguishable component, the separating step includes separating the distinguishable component from the mixture subsequent to the reacting step, and the method includes the further steps of detecting the distinguishable component in an unreacted sample of the fluid mixture and generating a signal representative of the concentration in the mixture of the fluid component of interest in accordance with a predetermined relationship relating the detected distinguishable component of the unreacted sample and the reacted sample, with the concentration of the fluid component of interest in the fluid mixture. In a further aspect the method is adapted to monitor the naphthene content of a hydrocarbon mixture comprising paraffin, aromatic, and naphthene components.

Another aspect of the invention provides apparatus in novel combination for continually monitoring a component of a fluid mixture including a microreactor for subjecting a sample of the fluid mixture to the aforementioned chemical reaction, and detection means for detecting the fluid component of interest. Also included are valve and conduit means for transmission of the fluid mixture through the apparatus. In one version of the apparatus the detection means include a chromatograph column and a detector. In a preferred embodiment of the apparatus for monitoring the naphthene content of a hydrocarbon mixture heating means are also provided for maintaining suitable operating temperatures in the microreactor, a noble metal reforming catalyst is employed in the microreactor for converting naphthenes of the fluid mixture to aromatics, and b,b'-thiodipropionitrile or other suitable polar substrate is employed in the chromatograph column for separating the aromatic component from the paraffin and naphthene components of the fluid mixture. In a further em bodiment a unique analog computer is provided coupled with the detector for computing the concentration of the fluid component of interest in the fluid mixture.

In view of the foregoing it is an object of the invention to provide an improved method for the analysis of fluid mixtures.

Another object of the invention is to provide a method for detection of a component of a fluid mixture difficult to distinguish from the mixture by employing a chemical reaction producing identifiable components.

Another object of the invention is to provide a method for determining the concentration in a fluid mixture of a component difficult to distinguish from the mixture.

Another object of the invention is to provide a method for monitoring the naphthene content of a fluid mixture of hydrocarbons.

Another object of the invention is to provide embodiments of apparatus to fulfill the aforementioned objectives.

These and other objects, advantages and features of the invention will be more fully understood by referring to the following descriptions and claims, taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic block diagram illustrating an embodiment of apparatus for practicing the invention.

FIG. 2 is a schematic block diagram of a computer which may be used in-conjunction with the apparatus of FIG. 1 to compute the concentration of the fluid component of interest in the fluid mixture tested.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The fluid mixture being tested is introduced into the apparatus through a conduit 10 from a source 8,. Typically, this fluid mixture can be associated with one of many hydrocarbon refining processes. Thus, for example, the source S, can be a sample stream of the fresh feed of a catalytic-reforming process for the octane improvement of fuels which usually includes a mixture having components of naphthenes, aromatics, and paraffins. It is to be understood that as used herein the term fluid component shall signify any group of one or calibrating the device a calibration standard fluid mixture of 5 known composition is provided from a source S which is coupled with the selection valve 11, by a conduit 12, connected therewith. The selection valve 11, when in its first operative position, permits passage therethrough of the fluid mixture being tested, and when in its second operative position, permits passage therethrough of the calibration standard. Coupled with the outlet port of the selection valve 11 is a conduit 14 which is in turn connected to the inlet port of a samplemeasuring valve 15 which incorporates an outlet port through which flow measured samples of the fluid mixture being tested. The sample-measuring valve 15 also incorporates a vent port in fluid communication with its inlet port for unin terrupted flow of the fluid mixture therethrough and out of its vent port. The latter port is connected by a conduit 16 to a second sample measuring valve 17 which also incorporates a measured sample outlet port and a vent port, the latter port being connected to a vent conduit 18 for flow of the fluid mixture out of the apparatus. In this configuration either the fluid mixture being tested or the calibration standard is present at all times in the bodies of the sample measuring valves 15 and 17, the respective fluid flowing out of the apparatus through the vent conduit 18.

The sample measuring valves 15 and 17 are conventional constant volume liquid-sampling valves which when actuated measure and release to their respective sample outlet ports single samples of predetermined amounts of the fluid mixture present therein. Sample valves providing samples ranging from 1 to 50 microliters can be used in the apparatus. However, for the analysis of napthhenes it is preferred to use sampling valves which provide liquid samples of about microliters.

Connected with the outlet port 01 the sample measuring valve is a conduit 19 which is in turn connected with a vaporizer 20 where the samples are vaporized in the presence of a suitable carrier gas such as hydrogen which is introduced into the vaporizer 20 through a conduit 21 connected with a source of the gas S Generally, many carrier gases can be used provided the gas is of a composition which does not adversely affect to a substantial extent the chemical reaction to which the fluid mixture is subjected. However, the use of hydrogen is preferred in the analysis of the catalytic reforming fresh feed to help prevent coking of the reforming catalyst used in the microreactor discussed below. The vaporized mixture passes from the vaporizer 20 through a conduit 22 connected therewith and enters a microreactor 23. The microreactor 23 includes a section of tubing packed with a suitable catalyst to effect a chemical reaction of the fluid samples converting a major portion of the fluid component of interest thereof into a component distinguishable or separable from the fluid mixture. For the analysis of naphthenes in fluid mixtures comprising at least naphthenes and aromatics, or naphthenes and paraffins, the microreactor 23 is preferably comprised of about 5 feet of about 3/ 16-inch diameter steel tubing filled with 35-80 mesh platinum-reforming catalyst. To further stimulate the reaction of microreactor is in turn mounted within a temperature-controlled enclosure, such as a regulated oven 24, which maintains the microreactor at an elevated temperature. The choice of this temperature and the operating pressure of the apparatus depend upon the fluid mixture being analyzed and are generally not critical. However, these operating conditions should be chosen such that the desired chemical reaction will take place and is most favored thermodynamically. For the analysis of naphthenes the preferred value of the microreactor temperature is approximately in the range of about 200 to 400 C. when the pressure therein is maintained in the vicinity of 45 p.s.i.g. In this case, a major portion of the naphthene component of the samples is converted to aromatics which can be separated from the paraffin and other dissimilar components. Thus, the increase in the aromatic component is indicative of the naphthene content of the samples.

Having thus reacted the samples in a manner rendering separable or distinguishable the fluid component of interest, its concentration in the samples can be determined by separating, or detecting, the fluid component of interest in any of a number of ways, such as by absorption spectroscopy or gas chromatography. For the analysis of naphthenes it is preferred that the detecting be performed with a gas chromatograph column employing a suitable polar substrate.

For this purpose a chromatograph column 25 and an electrically operated conventional backflush valve 26 are provided. The outlet flow of the microreactor 23 passes through a conduit 27 connected with a first port 26a of the backflush valve 26 which incorporates five further ports, 26b through 26f, respectively, to enable forward or reverse flow through the chromatograph column 25. The fifth port 26c of the backflush valve is connected with a vaporizer 28 by a conduit 29. The

vaporizer 28 is in turn connected with the inlet end of the chromatograph column 25 by a conduit 30. The third port 26c is connected with the exit end of the chromatograph column by a conduit 31; the fourth port 26d is connected with an outlet conduit 32; and the second and sixth ports 26b and 26f, respectively, are externally connected to each other by a loop conduit 33.

When the backflush valve 26 is in its first operative position its first port is in fluid communication with its second port, its third port is in fluid communication with its fourth port and its fifth port is in fluid communication with its sixth port. With the valve in this operative position the fluid mixture including the carrier gas from the microreactor entering the backflush valve through its first port passes therethrough and out of its second port, reenters the valve through its sixth port, passes out of the valve through its fifth port, passes through the conduit 29, through the vaporizer 28 and and thence passes through the chromatograph column 25 in a forward direction. The fluid from the chromatograph column passing through the conduit 31 reenters the backflush valve through its third port, and exits therefrom through its fourth port, and passes through the outlet conduit 32.

When the backflush valve 26 is in its second operative position its first port is in fluid communication with its sixth port, its second port is in fluid communication with its third port, and its fourth port is in fluid communication with its fifth port. When the backflush valve is in this operative position the chromatograph column is backflushed by a flow of the carrier gas in the conduit 27 entering the backflush valve through its first port and exiting through its sixth port, reentering the valve through its second port, exiting through its third port and thence passing through the conduit 31, the chromatograph column 25 and the vaporizer 28 in a reverse direction, reentering the backflush valve through its fifth port and exiting therefrom through its fourth port to the outlet conduit 32. The outlet conduit 32 is in turn connected with a pressure regulator 34, for regulating the pressure in the apparatus. For the analysis of naphthenes the preferred pressure is in the range of 30 to 60 p.s.i.g. The pressure regulator is in turn connected with a suitable gas chromatography detector, such as a thermal conductivity detector 35, for detecting the effluent of the chromatograph column. The electrical signals developed by the detector 35 are transmitted to a computer 38 which is further discussed in reference to FIG. 2.

For the analysis of naphthenes in hydrocarbon mixtures the preferred configuration of the chromatograph column 25 comprises a length of about 10 feet of about A-inch diameter steel tubing packed with beta, beta'-thiodipropionitrile deposited by conventional techniques on 60-80 mesh support, such as Chromosorb P. In this configuration the column holds up the aromatic component of the samples while permitting the saturates and other components to pass through first. Then, when the column is backflushed the held-up aromatics are detected as a group passing from the chromatograph column in a reverse direction to the detector 35; the area under the curve defining the detected thermal conductivity response pulse occurring during backflushing of the aromatics being proportional to the aromatics content of the respective fluid samples.

The analysis of the foregoing fluid mixture involves convertin,, .he naphthenes to aromatics. Should the fluid mixture initially contain an appreciable amount of aromatics it is necessary to provide a sampling by the chromatograph column of the fluid mixture in the unreacted condition. Therefore, for the analysis of those fluid mixtures wherein one component is converted to another by the microreactor, it is necessary to provide the capability in the apparatus for direct analytical sampling of the unreacted fluid mixture. Hence, a flow of samples of the fluid mixture is provided from the sample measuring valve 17 through the vaporizer 28, connected with the sample-measuring valve 17 by a conduit 36, and from the out let of the vaporizer 28 to the conduit 30 at the inlet end of the chromatograph column 25. The carrier gas is introduced into the vaporizer 28 through the conduit 29 connected with the backflush valve 26, which receives a flow of the carrier gas from the source S passing through the vaporizer 20 and the microreactor 24. The hydrogen source S is connected with the detector 35 through a conduit 39 to provide a reference against which the thermal conductivity response of the chromatograph column effluent is measured by the detector 35.

The calibration characteristic, that is, the predetermined relationship between the thermal conductivity response measured by the detector 35, and the concentration of the fluid component of interest in the fluid mixture tested may be determined analytically, However, such a procedure is extremely difficult since all of the fluid component of interest may not be converted by the microreactor. Hence, a more suitable procedure is the use of a calibration standard fluid mixture of well-known composition having a concentration of the fluid component of interest similar to, or in the expected range of, the concentration of the fluid component of interest in the fluid mixture being tested. The calibration standard is introduced from a source thereof S through the conduit 12, through the selection valve 11, which when in its second operative position permits a flow of the calibration standard into the sample measuring valve 15, and thence into the balance of the apparatus.

The calibration characteristic of the apparatus is initially determined by two runs of the standard therethrough. In the first run the standard passes through the microreactor and through the chromatograph column for analysis. In the second run the calibration mixture is introduced directly into the chromatograph column for analysis. Once the first calibration is determined, subsequent, or periodic calibrations need be performed only by passing the calibration standard through the microreactor since any subsequent changes in the operating characteristics of the apparatus take place primarily in the microreactor due to changes in the catalyst activity with age.

A time-cycle controller 37, which includes conventional program-timing elements, is provided to control the actuation of the various electrically operated valves through an appropriate timing sequence. Generally, the timing sequence is not critical provided that there is sufficient residence time of the samples in the microreactor and the chromatograph column.

For the analysis of naphthenes in the fresh feed of catalytic reforming processes it is preferred that the time cycle controller 37 provide for the following functions: the injection of a first sample of the fluid mixture being tested into the microreactor for reaction therein, permitting the sample to pass to the chromatograph column and reside therein for a sufficient time interval for adsorption of the aromatics and elution of the saturates content of the sample in the forward direction, thereafter, reversing the flow through the chromatograph column to backflush the aromatics content of the sample and detecting the aromatics content thereof. Subsequently, a second sample of the fluid mixture is injected directly into the chromatograph column and the aromatics detection sequence above is repeated. For the aforementioned analysis of naphthenes a preferred timing sequence is as follows: l) for all normal operation, that is, absent calibration, the selection valve 11 is kept in its first operative position; 2) the sample measuring valve 15 is actuated for about 30 to seconds while a single sample of the fluid mixture is injected into the microreactor; 3) while the sample is reacted and passes through the backflush valve into the chromatograph column, the backflush valve is maintained in its first operative position for a period of about 5 to 15 minutes and then is actuated to its second operative position permitting backflushing of the chromatograph column; 4) the backflush valve then remains in its second operative position for a period of about 7 to 20 minutes while the aromatics pass therethrough and are detected as a group; 5) the backflush valve is then returned to its first operative position; 6) the sample-measuring valve 17 is then actuated for about 30 to 120 seconds to release a single sample of the fluid mixture, which bypasses the microreactor entering into the chromatograph column; 7) the backflush valve 25 remainsin its first operative position for a period of about 5 to 15 minutes permitting forward flow through the chromatograph column and elution of the saturates; 8) then the backflush valve 25 is actuated to its second operative position permitting reverse flow through the chromatograph column and detection of the aromatics as a group; 9) then the backflush valve 25 is returned to its first operative position, and the operating cycle connecting with step number 2 above is repeated. For the initial calibration of the apparatus the selection valve 11 is actuated to its second operative position and the aforementioned operating cycle commencing with step number 2 is executed with respect to the calibration standard fluid mixture. The periodic calibration checks, for checking the catalyst aging, may be performed as often as once a day or once a week depending upon the severity of use of the apparatus. For this calibration check the sequence of steps numbers 2 through 5 are executed while the selection valve 11 is maintained in its second operative position. After the calibration check the selection valve 11 is returned to its first operative position and the normal sequence of operation is reinstated.

The output signals from the detector 35 are transmitted to the computer 38, in which is programmed the predetermined calibration relationship between the detected signals and the concentration in the fluid mixture tested of the fluid component of interest. The computer 38 also is responsive to the time-cycle controller 37 so that is can interpret each of the thermal conductivity signals generated by the detector 35 in proper order. I have found that the following equation expresses the aforementioned predetermined relationship, based upon the results of the calibration run, when a first component of interest of the fluid mixture is analyzed for which is converted to a second component of the fluid mixture by the chemical reaction:

x percent of the second component in the fluid mixture being tested after the reaction,

x, percent of the second component in the fluid mixture being tested before the reaction,

z percent of the second component in the calibration standard mixture after the reaction,

z, percent of the second component in the calibration standard mixture before the reaction,

y, percent of the fluid component of interest in the calibration standard mixture as determined independently such as by mass spectrometetry,

y percent of the fluid component of interest in the fluid mixture being tested.

It should be noted that the time cycle indicated above is merely the suggested time cycle for the analysis of naphthenes and appropriate adjustments may be made with corresponding adjustments of the length of the microreactor and the chro matograph column. Furthermore, similar adjustments can be made for the analysis of other fluid mixtures. Thus, for example, increasing the length of the microreactor or of the chromatograph column results in an increased residence time of the fluid mixture in these respective items, whereby, the timing sequence should be modified accordingly. It is also to be noted while the various automatic valves have been described as electrically operated that pneumatically operated valves may be used in their place. In this instance the time cycle controller would be coupled to conventional electrical-to-pneumatic valve operators. Also to be noted is that various of the conduits illustrated in FIG. 1 may be eliminated by joining some of the equipment items. Thus, for example, the samplemeasuring valves and the Vaporizers may be combined into a single injector assembly. It is also to be noted that since the device is calibrated as discussed above the reaction in the microreactor need not be complete, that is, the reaction need not affect the entire amount in the fluid mixture of the component reacted. Also, the reaction may affect more than one component in the fluid mixture. Thus, for example, in a mixture containing naphthenes, paraffins, and aromatics, a portion of the paraffins may be reformed while a portion of the naphthenes are converted to aromatics. The device, after calibration, is nonetheless able to solve for the naphthene content of the mixture. Similarly, the device may be used to solve for a component of the mixture other than the one reacted. For example, in analyzing a mixture of naphthenes and paraffins to determine the paraffin content, the device can be calibrated to account for the reaction of the naphthenes and the paraffin component may be solved for inferentially. It is also to be appreciated by one skilled in the art that the device can be adapted to analyze a variety of fluid mixtures by appropriate modifications of the catalyst used in the microreactor and the packing material of the chromatograph column. Thus, for example, a noble metal may be used as a catalyst in conjunction with a silicone rubber as substrate material for the analysis of mercaptans as hydrogen sulfide in mixtures of hydrocarbons. Another example is the identification of oleflns and/or aromatics in a hydrocarbon mixture by hydrogenation of said olefins and/or aromatics.

Referring now to FIG. 2 which is a schematic block diagram of a computer which can be used as the computer shown in FIG. 1, the signals from the detector 35 are transmitted to an integrator 50 which also receives timing signals from the time cycle controller 37 so that the integrator is able to distinguish, by time displacement, the electrical pulses received from the detector during the timed sequence of operation. The integrator 50 integrates the area under each of the thermal conductivity response pulses and provides four corresponding output signals, namely, x x,, 2 and 2 as defined in reference to equation (1) above. The x and x1 signals are transmitted to a subtraction element 51 which subtracts the latter, x,, from the former, x and provides an output signal corresponding to this difference, namely, x x,. This signal is in turn transmitted to a multiplication operator 52. The Z and Z1 signals from the integrator are transmitted to a subtraction element 53 which subtracts the latter, z,, from the former, Z and provides an output signal corresponding to 2 -2 This signal is in turn transmitted to a division element 54. For developing a signal corresponding to the percent of the fluid component of interest in the calibration mixture a standard voltage supply 55 is provided for applying a constant voltage to a potentiometer 56 which is manually set to a position corresponding to the value Y,. The Y signal, thus developed, is transmitted to the multiplication element 52, which multiplies the Y, signal by the difference signal from the subtraction element 51, and provides an output signal corresponding to the product, namely, Y ,(xrx This signal is transmitted to the division operator 54 which divides this signal by the diflerence signal from the subtraction element 53, and provides an output signal corresponding to the quotient. The output signal from the division element 54 therefore corresponds to the concentration of the fluid component of interest in the fluid mixture being tested in accordance with equation (1). This signal can be transmitted to a display device or a chart recorder and can be utilized to control the process by application thereof to suitable process control equipment.

It is to be appreciated by one skilled in the art that while electrical computation elements have been discussed above, pneumatic computation elements can be used in their place quite advantageously. It is also to be appreciated by one skilled in the art that a digital computer can be utilized to perform the computational functions of the analog computer of FIG. 2. In this instance, in place of the time-cycle controller, the computer can be preprogrammed to control all the valveswitching functions, including the calibration cycles, and the computer can synchronize the integration steps with the operating sequence.

While the invention has been described with a certain degree of particularity, it can, nevertheless be seen by the examples hereinabove set forth that many modifications and variations of the invention may be made without departing from the spirit and scope thereof.

I claim:

1. A method for detecting a naphthenes component of a hydrocarbon fluid mixture consisting of said naphthenes com ponent for detection and at least a second aromatics component, said naphthenes component having physical properties sufficiently similar to said hydrocarbon fluid mixture rendering it difficult to distinguish from said hydrocarbon fluid mixture, said aromatics component having physical properties rendering said aromatics component more readily distinguishable from said fluid mixture, comprising the steps of:

a. detecting the concentration of said aromatics component in a sample of said fluid mixture;

b. reacting a sample of said fluid mixture in a chemical reaction converting at least a portion of said naphthenes component of said mixture into said aromatics component;

c. detecting the concentration of said aromatics component in said sample of said fluid mixture subsequent to said reacting step (b); and

d. generating a first signal representative of the concentration of said naphthenes component in said fluid mixture by generating said first signal in response to said detecting steps (a) and (c) and in accordance with a predetermined relationship relating said detected aromatics components with the concentration of the same components in a reference second fluid mixture.

2. The method of claim 1 wherein said detecting steps (a) and (c) include generating second and third signals representative thereof respectively,

3. The method of claim 2 wherein said predetermined relationship is determined in accordance with the steps comprismg:

e. detecting the concentration of said second component in a sample of said reference second fluid mixture and generating a fourth signal representative thereof;

f. reacting said sample of said reference second fluid mixture in a chemical reaction converting at least a portion of said first component into said second component, said reaction being performed under substantially the same conditions as said reaction of step (b); detecting the concentration of said second component in said sample of said reference second fluid mixture subsequent to said reacting step (f) and generating a fifth signal representative thereof; and combining said second, third, fourth and fifth signals in a proportional relationship relating the concentration of said second component in said sample of said reference second fluid mixture before and after said reacting step (f) with the concentration of said second component in said sample of said first named fluid mixture before and after said reacting step (b) and with said predetermined concentration of said first component in said sample of said reference second fluid mixture.

4. The method of claim 3 wherein said second, third, fourth and fifth signals are combined in said step (h) substantially in accordance with the following equation:

Y= the concentration of said first component for detection in said first named fluid mixture,

Y, the concentration of said first component in said reference second fluid mixture,

25 the concentration of said second component in said reference second fluid mixture prior to said reaction thereof,

z the concentration of said second component in said reference second fluid mixture subsequent to said reaction thereof,

x, the concentration of said second component in said first named fluid mixture prior to said reaction thereof,

x the concentration of said second component in said first named fluid mixture subsequent to said reaction thereof.

5. The method of claim 4 wherein said first and second fluid mixtures consist essentially of fluid components selected from the group consisting of aromatics, naphthenes, and paraffins, wherein said first fluid component of said fluid mixtures consists essentially of naphthenes, wherein said second component of said fluid mixtures consists essentially of aromatics, wherein said reactions of steps (b) and (f) are performed in the presence of a noble metal catalyst and in the presence of hydrogen for conversion of at least a portion of said naphthenes to aromatics, wherein said method includes the further steps of heating said samples of said first and second fluid mixtures to a temperature in the range of about 200 to 400 C. at least in part during said respective reacting steps (b) and (f), and wherein each of said detecting steps (a), (c) and (g) include the steps of; introducing each respective sample of said fluid mixtures into a gas chromatograph column of a sorbent material having a greater affinity for said aromatics second component of said fluid mixtures, urging said sample to pass into said column by passing a carrier gas therethrough permitting the balance of said respective fluid mixture to pass through said column in a forward direction while said aromatics second component is retarded therein, sweeping said column of said aromatics therein by reversing the flow direction of said carrier gas therethrough, and at least in part during said sweeping step detecting a physical property of the eflluent of the forward end of said column to detect the concentration of said aromatics second fluid component in said respective sample of said fluid mixtures.

65. The method of claim 2 comprising the further step of heating at least in part during said reacting step (b) said firstnamed fluid mixture to a temperature in a range at which said reaction of step (b) is thermodynamically favored.

7. The method of claim 2 wherein said second component of said first-named fluid mixture is distinguishable from said first-named fluid mixture by selective sorbtion of at least one component of said mixture, wherein said reacting step (b) is performed in the presence of a catalyst for converting a substantial portion of said first component into said second component, and wherein said detecting steps (a) and (c) are each performed by the method of chromatography.

8. The method of claim 2 wherein said first component for detection of said first-named fluid mixture consists essentially of naphthenes, wherein said reactions of step (b) is performed in the presence of a noble metal catalyst and in the presence of hydrogen for conversion of at least a portion of said naphthenes to aromatics, and wherein said method includes the further step of heating said sample of said first named fluid mixture to a temperature in the range of about 200 to 400 C. at least in part during said reacting step (b).

9. The method of claim 8 wherein said first fluid mixture consists essentially of fluid components selected from the group consisting of aromatics, naphthenes, and paraffins.

10. An apparatus for detecting a first component of a fluid mixture from a source thereof, said fluid mixture consisting of at least a first component for detection and at least another component said first component having certain physical properties sufiiciently similar to those of said other components rendering it difl'rcult to separate or distinguish said first fluid component, comprising:

a. means including a chamber packed with a catalyst for subjecting fluid mixture to a chemical reaction converting at least a portion of said first component to a second component distinguishable from said fluid mixture, said chamber having an inlet end and an outlet end, said inletend being coupled with said source of said fluid mixture for introduction thereof into said chamber said fluid mixture passing through said outlet end of said chamber after reacting therein;

b. a source of a carrier gas coupled with said inlet end of said chamber for carrying said fluid mixture through said chamber;

0. heating means operatively coupled with said chamber (a) for heating said fluid mixture at least in part during said reaction thereof in said chamber to a temperature in a range at which said reaction is thermodynamically favored;

d. means including a gas chromatograph column and a detector operatively coupled with said outlet end of said chamber (a) for detecting the concentration of said first component in said fluid mixture by detecting said first component converted;

. a source of a reference second fluid mixture having a predetermined concentration therein of said first component, and

f. valve means coupled with said source of said reference second fluid mixture and operatively coupled with said inlet of said chamber (a) for periodically introducing into said chamber said reference second fluid mixture for reaction therein and detection of said first component converted of said second fluid mixture enabling periodic calibration of said apparatus in accordance with a proportional relationship relating said detected first component converted of said reference second fluid mixture with said predetermined concentration therein of said first component, said proportional relationship being representative of the relationship between said detected first component converted of said first named fluid mixture and the concentration therein of said first component, said latter concentration being determinable from said calibration-proportional relationship and said detected first component converted of said first-named fluid mixture.

11. An apparatus according to claim 10 wherein said valve means (f) are further coupled with said source of said firstnamed fluid mixture and wherein said valve means (f) includes a valve having first and second operative positions said valve when in its first operative position permitting flow therethrough of said first-named fluid mixture for detection of said first component thereof, said valve when in its second operative position permitting flow therethrough of said second fluid mixture for calibration of said apparatus in accordance with said proportional relationship, wherein said reacting means (a) further comprises;

a. (g) means including a sample measuring valve coupled with said valve means (f) and operatively coupled with said inlet of said chamber (a,a) for injecting into said chamber periodic samples of substantially constant volume of said first and second fluid mixtures, said sample measuring valve injecting said samples of said first fluid mixture when said valve means (d) is in its second operative position; and

. (h) means including a vaporizer interposed between said sample measuring valve means (a,g) and said chamber (a,a) and coupled with said source of a carrier gas (a,b) for vaporization of said first and second fluid mixtures prior to introduction thereof into said chamber whereby said fluid mixtures are reacted therein in a gaseous state.

12. An apparatus according to claim Ill wherein said first and second fluid mixtures each include a second component distinguishable from said respective fluid mixtures by gas chromatography, the concentration of said second component in said second fluid mixture being predetermined, wherein said first component at least in part converted of said first and second fluid mixtures is at least in part converted to said second component by said respective reactions thereof, wherein said proportional-calibration relationship relates the concentration of said first component for detection in said first fluid mixture with said detected converted first component converted to said second component of said first and second fluid mixtures and with said predetermined concentrations of said first and second components in said reference second fluid mixture, and wherein said apparatus further comprises:

g. means coupled with said source of said first fluid mixture and coupled with said gas chromotograph for injecting into said gas chromatograph vaporized samples unreacted of said first fluid mixture for detection of said second component of said first fluid mixture unreacted, the concentration of said first component in said first fluid mixture being determinable from said detected second component of said first fluid mixture unreacted, said detected first component thereof converted, and said proportionalcalibration relationship.

13. An apparatus according to claim 12 wherein said first component of said first and second fluid mixtures comprises naphthenes, wherein said second component of said first and second fluid mixtures comprises aromatics, wherein said catalyst in said chamber (a,a) comprises a noble metal catalyst for conversion at least in part of said naphthenes to aromatics, wherein said source (a,b) of carrier gas includes hydrogen, wherein said chromatograph column includes a sorbent material therein having a sorbent affinity for aromatics, and wherein said chromatograph column means further includes means including a backflush valve coupled with the inlet and outlet ends of said chromatograph column and coupled with said detector for backflushing said chromatograph column subsequent to each respective injection therein of each of said samples of said first and second fluid mixtures, said chromatograph column being backflushed subsequent to sorbtion therein of at least a portion of said aromatics and passage therethrough of at least a substantial portion of the balance of said respective fluid samples, the backflush flow of said column passing through said detector for detection of the aromatics content of said samples, whereby the concentration of said naphthenes first component in said first fluid mixture is determinable in accordance with said calibration relationship.

14. The apparatus of claim 13 wherein said chamber (a,a) comprises a reaction chamber of about feet of length of about 3/l6-inch diameter steel tubing packed with platinum reforming catalyst having 35 to 80 mesh-particle size, wherein said heating means (a,c) includes a temperature controlled enclosure in which is mounted said reaction chamber, said enclosure including heating means for heating said reaction chamber to a temperature in the range of 200 to 400 C. wherein said chromatograph column comprises a column of about feet of length of about A-inch diameter steel tubing packed with beta, beta-thiodipropionitrile deposited on a support of about 60 to 80 mesh-particle size for adsorbtion of said aromatics component and detection thereof, wherein said detector includes means for generating a detector signal the time integral of which is representative of the concentration in said naphthene first component for detection in said first fluid mixture m accordance with said proportional calibration relationship, said relationship being substantially in accordance with the following equation:

where:

Y= percent of said naphthene first component for detection in said first fluid mixture,

Y percent of said naphthene first component in said reference second fluid mixture,

x percent of said aromatics in said first fluid mixture after said reaction thereof in said chamber,

x percent of said aromatics in said first fluid mixture prior to said reaction thereof,

Z2 percent of said aromatics in said reference second fluid mixture after said reaction thereof, and:

z, percent of said aromatics second component in said reference second fluid mixture prior to said reaction thereof.

15. The apparatus of claim 14 wherein said computing means (i) comprises:

ia. manual entry and signal-generating means for entering into said computer the value of said predetermined concentration of said naphthene first component in said reference second fluid mixture and for generating a concentration second signal representative thereof;

ib. integration means coupled with said detector for integrating said detector signal and for generating third, fourth, fifth and sixth signals representative of said respective concentrations of said detected aromatics component in said fluid samples passed therethrough, said signals being representative respectively of said quantities: 1,, 2 x and x ic. first difference measuring means coupled with said integration means (ib) for generating a difference seventh signal representative of the difference (2 -2,) between said fourth and third signals;

id. second difference measuring means coupled with said integration means (ib) for generating a difference eighth signal representative of the difference (x x between said sixth and fifth signals;

ie. first multiplication means coupled with said second difference measuring means (id) and coupled with said manual entry means (ia) for generating a product ninth signal representative of the product of said concentration second signal and said difference eighth signal; and

if, division means including output means coupled with said first multiplication means (ie) and coupled with said first difference measuring means (ie) for generating an output first signal representative of the quotient of said product ninth signal divided by said difference seventh signal, said output first signal corresponding to the concentration of said naphthene first component for detection in said first fluid mixture in accordance with said proportionalcalibration relationship.

Claims

2. The method of claim 1 wherein said detecting steps (a) and (c) include generating second and third signals representative thereof respectively,
3. The method of claim 2 wherein said predetermined relationship is determined in accordance with the steps comprising: e. detecting the concentration of said second component in a sample of said reference second fluid mixture and generating a fourth signal representative thereof; f. reacting said sample of said reference second fluid mixture in a chemical reaction converting at least a portion of said first component into said second component, said reaction being performed under substantially the same conditions as said reaction of step (b); g. detecting the concentration of said second component in said sample of said reference second fluid mixture subsequent to said reacting step (f) and generating a fifth signal representative thereof; and h. combining said second, third, fourth and fifth signals in a proportional relationship relatIng the concentration of said second component in said sample of said reference second fluid mixture before and after said reacting step (f) with the concentration of said second component in said sample of said first named fluid mixture before and after said reacting step (b) and with said predetermined concentration of said first component in said sample of said reference second fluid mixture.
4. The method of claim 3 wherein said second, third, fourth and fifth signals are combined in said step (h) substantially in accordance with the following equation: Y Y1(x2- x1)/(z2- z1) where: Y the concentration of said first component for detection in said first named fluid mixture, Y1 the concentration of said first component in said reference second fluid mixture, z1 the concentration of said second component in said reference second fluid mixture prior to said reaction thereof, z2 the concentration of said second component in said reference second fluid mixture subsequent to said reaction thereof, x1 the concentration of said second component in said first named fluid mixture prior to said reaction thereof, x1 the concentration of said second component in said first named fluid mixture subsequent to said reaction thereof.
5. The method of claim 4 wherein said first and second fluid mixtures consist essentially of fluid components selected from the group consisting of aromatics, naphthenes, and paraffins, wherein said first fluid component of said fluid mixtures consists essentially of naphthenes, wherein said second component of said fluid mixtures consists essentially of aromatics, wherein said reactions of steps (b) and (f) are performed in the presence of a noble metal catalyst and in the presence of hydrogen for conversion of at least a portion of said naphthenes to aromatics, wherein said method includes the further steps of heating said samples of said first and second fluid mixtures to a temperature in the range of about 200* to 400* C. at least in part during said respective reacting steps (b) and (f), and wherein each of said detecting steps (a), (c) and (g) include the steps of; introducing each respective sample of said fluid mixtures into a gas chromatograph column of a sorbent material having a greater affinity for said aromatics second component of said fluid mixtures, urging said sample to pass into said column by passing a carrier gas therethrough permitting the balance of said respective fluid mixture to pass through said column in a forward direction while said aromatics second component is retarded therein, sweeping said column of said aromatics therein by reversing the flow direction of said carrier gas therethrough, and at least in part during said sweeping step detecting a physical property of the effluent of the forward end of said column to detect the concentration of said aromatics second fluid component in said respective sample of said fluid mixtures.
6. The method of claim 2 comprising the further step of heating at least in part during said reacting step (b) said first-named fluid mixture to a temperature in a range at which said reaction of step (b) is thermodynamically favored.
7. The method of claim 2 wherein said second component of said first-named fluid mixture is distinguishable from said first-named fluid mixture by selective sorbtion of at least one component of said mixture, wherein said reacting step (b) is performed in the presence of a catalyst for converting a substantial portion of said first component into said second component, and wherein said detecting steps (a) and (c) are each performed by the method of chromatography.
8. The method of claim 2 wherein said first component for detection of said first-named fluid mixture consists essentially of naphthenEs, wherein said reactions of step (b) is performed in the presence of a noble metal catalyst and in the presence of hydrogen for conversion of at least a portion of said naphthenes to aromatics, and wherein said method includes the further step of heating said sample of said first named fluid mixture to a temperature in the range of about 200* to 400* C. at least in part during said reacting step (b).
9. The method of claim 8 wherein said first fluid mixture consists essentially of fluid components selected from the group consisting of aromatics, naphthenes, and paraffins.
10. An apparatus for detecting a first component of a fluid mixture from a source thereof, said fluid mixture consisting of at least a first component for detection and at least another component said first component having certain physical properties sufficiently similar to those of said other components rendering it difficult to separate or distinguish said first fluid component, comprising: a. means including a chamber packed with a catalyst for subjecting fluid mixture to a chemical reaction converting at least a portion of said first component to a second component distinguishable from said fluid mixture, said chamber having an inlet end and an outlet end, said inlet-end being coupled with said source of said fluid mixture for introduction thereof into said chamber said fluid mixture passing through said outlet end of said chamber after reacting therein; b. a source of a carrier gas coupled with said inlet end of said chamber for carrying said fluid mixture through said chamber; c. heating means operatively coupled with said chamber (a) for heating said fluid mixture at least in part during said reaction thereof in said chamber to a temperature in a range at which said reaction is thermodynamically favored; d. means including a gas chromatograph column and a detector operatively coupled with said outlet end of said chamber (a) for detecting the concentration of said first component in said fluid mixture by detecting said first component converted; e. a source of a reference second fluid mixture having a predetermined concentration therein of said first component, and f. valve means coupled with said source of said reference second fluid mixture and operatively coupled with said inlet of said chamber (a) for periodically introducing into said chamber said reference second fluid mixture for reaction therein and detection of said first component converted of said second fluid mixture enabling periodic calibration of said apparatus in accordance with a proportional relationship relating said detected first component converted of said reference second fluid mixture with said predetermined concentration therein of said first component, said proportional relationship being representative of the relationship between said detected first component converted of said first named fluid mixture and the concentration therein of said first component, said latter concentration being determinable from said calibration-proportional relationship and said detected first component converted of said first-named fluid mixture.
11. An apparatus according to claim 10 wherein said valve means (f) are further coupled with said source of said first-named fluid mixture and wherein said valve means (f) includes a valve having first and second operative positions said valve when in its first operative position permitting flow therethrough of said first-named fluid mixture for detection of said first component thereof, said valve when in its second operative position permitting flow therethrough of said second fluid mixture for calibration of said apparatus in accordance with said proportional relationship, wherein said reacting means (a) further comprises: a. (g) means including a sample measuring valve coupled with said valve means (f) and operatively coupled with said inlet of said chamber (a,a) for injecting into said chamber periodic samples of substantially constant volume of said first and second fluid mixtures, said sample measuring valve injecting said samples of said first fluid mixture when said valve means (d) is in its second operative position; and a. (h) means including a vaporizer interposed between said sample measuring valve means (a,g) and said chamber (a,a) and coupled with said source of a carrier gas (a,b) for vaporization of said first and second fluid mixtures prior to introduction thereof into said chamber whereby said fluid mixtures are reacted therein in a gaseous state.
12. An apparatus according to claim 11 wherein said first and second fluid mixtures each include a second component distinguishable from said respective fluid mixtures by gas chromatography, the concentration of said second component in said second fluid mixture being predetermined, wherein said first component at least in part converted of said first and second fluid mixtures is at least in part converted to said second component by said respective reactions thereof, wherein said proportional-calibration relationship relates the concentration of said first component for detection in said first fluid mixture with said detected converted first component converted to said second component of said first and second fluid mixtures and with said predetermined concentrations of said first and second components in said reference second fluid mixture, and wherein said apparatus further comprises: g. means coupled with said source of said first fluid mixture and coupled with said gas chromotograph for injecting into said gas chromatograph vaporized samples unreacted of said first fluid mixture for detection of said second component of said first fluid mixture unreacted, the concentration of said first component in said first fluid mixture being determinable from said detected second component of said first fluid mixture unreacted, said detected first component thereof converted, and said proportional-calibration relationship.
13. An apparatus according to claim 12 wherein said first component of said first and second fluid mixtures comprises naphthenes, wherein said second component of said first and second fluid mixtures comprises aromatics, wherein said catalyst in said chamber (a,a) comprises a noble metal catalyst for conversion at least in part of said naphthenes to aromatics, wherein said source (a,b) of carrier gas includes hydrogen, wherein said chromatograph column includes a sorbent material therein having a sorbent affinity for aromatics, and wherein said chromatograph column means further includes means including a backflush valve coupled with the inlet and outlet ends of said chromatograph column and coupled with said detector for backflushing said chromatograph column subsequent to each respective injection therein of each of said samples of said first and second fluid mixtures, said chromatograph column being backflushed subsequent to sorbtion therein of at least a portion of said aromatics and passage therethrough of at least a substantial portion of the balance of said respective fluid samples, the backflush flow of said column passing through said detector for detection of the aromatics content of said samples, whereby the concentration of said naphthenes first component in said first fluid mixture is determinable in accordance with said calibration relationship.
14. The apparatus of claim 13 wherein said chamber (a,a) comprises a reaction chamber of about 5 feet of length of about 3/16-inch diameter steel tubing packed with platinum reforming catalyst having 35 to 80 mesh-particle size, wherein said heating means (a,c) includes a temperature controlled enclosure in which is mounted said reaction chamber, said enclosure including heating means for heating said reaction chamber to a temperature in the range of 200* to 400* C. wherein said chromatograph column comprises a column of about 10 feet of length of about 1/4 -inch diameter steel tubing packed with beta, beta''-thiodipropionitrile deposited on a support of about 60 to 80 mesh-particle size for adsorbtion of said aromatics component and detection thereof, wherein said detector includes means for generating a detector signal the time integral of which is representative of the concentration in said respective samples passed therethrough of said aromatics component, said apparatus of claim 24 further comprising: h. means including a pressure regulator coupled with the outlet end of said chromatograph column for regulating the pressure in said reaction chamber and said chromatograph column in the range of 30 to 60 p.s.i.g.; and i. computing means including integration means coupled with said detector for computing the concentration of said naphthene first component for detection in said first fluid mixture in accordance with said proportional calibration relationship, said relationship being substantially in accordance with the following equation:Y Y1(x2- x1)/(z2- z1) where: Y percent of said naphthene first component for detection in said first fluid mixture, Y1 percent of said naphthene first component in said reference second fluid mixture, x2 percent of said aromatics in said first fluid mixture after said reaction thereof in said chamber, x1 percent of said aromatics in said first fluid mixture prior to said reaction thereof, z2 percent of said aromatics in said reference second fluid mixture after said reaction thereof, and: z1 percent of said aromatics second component in said reference second fluid mixture prior to said reaction thereof.
15. The apparatus of claim 14 wherein said computing means (i) comprises: ia. manual entry and signal-generating means for entering into said computer the value of said predetermined concentration of said naphthene first component in said reference second fluid mixture and for generating a concentration second signal representative thereof; ib. integration means coupled with said detector for integrating said detector signal and for generating third, fourth, fifth and sixth signals representative of said respective concentrations of said detected aromatics component in said fluid samples passed therethrough, said signals being representative respectively of said quantities: z1, z2, x1, and x2; ic. first difference measuring means coupled with said integration means (ib) for generating a difference seventh signal representative of the difference (z2- z1) between said fourth and third signals; id. second difference measuring means coupled with said integration means (ib) for generating a difference eighth signal representative of the difference (x2- x1) between said sixth and fifth signals; ie. first multiplication means coupled with said second difference measuring means (id) and coupled with said manual entry means (ia) for generating a product ninth signal representative of the product of said concentration second signal and said difference eighth signal; and if. division means including output means coupled with said first multiplication means (ie) and coupled with said first difference measuring means (ic) for generating an output first signal representative of the quotient of said product ninth signal divided by said difference seventh signal, said output first signal corresponding to the concentration of said naphthene first component for detection in said first fluid mixture in accordance with said proportional-calibration relationship.