US3850744A

US3850744A - Method for utilizing a fixed catalyst bed in separate hydrogenation processes

Info

Publication number: US3850744A
Application number: US00336384A
Authority: US
Inventors: J Strom; R Plundo; T Readal
Original assignee: Gulf Research and Development Co
Current assignee: Chevron USA Inc
Priority date: 1973-02-27
Filing date: 1973-02-27
Publication date: 1974-11-26
Anticipated expiration: 1991-11-26

Abstract

Middle distillate virgin oils, such as straight run furnace oil, jet fuel or kerosene are required to meet many commercial specifications, among which are maximum allowable total sulfur content, maximum allowable mercaptan sulfur content and maximum allowable total acid number. Middle distillates which do not meet commercial specifications in regard to total sulfur content can be hydrodesulfurized for the removal of the portion of the total sulfur required for meeting the commercial requirement. Such hydrodesulfurization requires more severe conditions than do processes for reduction of total acid number or for reduction of mercaptan sulfur content so that under the severe conditions required for hydrodesulfurization, excessive total acid number and excessive mercaptan content are automatically concomitantly reduced to commercially acceptable levels. The present invention relates to the hydrotreatment of virgin middle distillates which meet commercial specifications in regard to total sulfur content in the absence of prior hydrotreating or any other treatment, but do not meet commercial specifications in regard to total acid number or in regard to mercaptan sulfur content. According to the present invention, the latter middle distillates are not blended with high total sulfur feeds flowing to hydrodesulfurization processes requiring severe conditions to accomplish reduction in total sulfur content, but are hydrotreated separately under relatively more mild catalytic hydrotreating conditions to reduce mercaptan sulfur content or total acid number at hydrotreating severities which are so mild that there is an extremely limited consumption of hydrogen and a very limited removal of total sulfur. The catalyst employed in the mild hydrotreating processes of this invention is a deactivated hydrotreating catalyst from a more severe hydrodesulfurization or other hydrotreating operation which is no longer of viable use in the more severe operation due to numerous cycles of use and regeneration, due to excessive metals deposit thereon, or any other reason.

Description

United States Patent 1191 Plundo et a1.

[ Nov. 26, 1974 METHOD FOR UTILIZING A FIXED CATALYST BED IN SEPARATE HYDROGENATION PROCESSES [75] Inventors: Robert A. PIundo, Greensbur g;

Thomas C. Readal, McCandless Township; James R. Strom, OHara Township, all of Pa.

[73] Assignee: (gulf Research & Development Company, Pittsburgh, Pa.

22 Filed: Feb. 27, 1973 21 Appl. No.: 336,384

[52] US. Cl 208/210, 208/15, 208/216, 208/263, 208/264 [51] Int. Cl. Clog 31/14 [58] Field of Search 208/210, 216, 263, 264, 208/15 [56] References Cited UNITED STATES PATENTS 2.401.334 6/1946 Burk et a1. 208/216 2,717,857 9/1955 Bronson et a1. 208/216 2,793,986 5/1957 Lanning 208/264 2,921,023 l/l960 Holm 208/263 2.963.425 12/1960 Hansen 208/216 2,998,381 8/1961 Bushnell 208/216 3.413.216 11/1968 Doumani 2081216 3,483.1 19 12/1969 Ehrler 208/264 Primary Examiner-Delbert E. Gantz Assistant Examiner-C. E. Spresser [57] ABSTRACT Middle distillate virgin oils, such as straight run furnace oil, jet fuel or kerosene are required to meet many commercial specifications, among which are maximum allowable total sulfur content, maximum allowable mercaptan sulfur content and maximum allowable total acid number. Middle distillates which do not meet commercial specifications in regard to total sulfur content can be hydrodesulfurized for the removal of the portion of the total sulfur required for meeting the commercial requirement. Such hydrodesulfurization requires more severe conditions than do processes for reduction of total acid number or for reduction of mercaptan sulfur content so that under the severe conditions required for hydrodesulfurization, excessive total acid number and excessive mercaptan content are automatically concomitantly reduced to commercially acceptable levels. The present invention relates to the hydrotreatment of virgin middle distillates which meet commercial specifications in regard to total sulfur content in the absence of prior hydrotreating or any other treatment, but do not meet commercial specifications in regard to total acid number or in regard to mercaptan sulfur content. According to the present invention, the latter middle distillates are not blended with high total sulfur feeds flowing to hydrodesulfurization processes requiring severe conditions to accomplish reduction in total sulfur content, but are hydrotreated separately under relatively more mild catalytic hydrotreating conditions to reduce mercaptan sulfur content or total acid number at hydrotreating severities which are so mild that there is an extremely limited consumption of hydrogen and a very limited removal of total sulfur. The catalyst employed in the mild hydrotreating processes of this invention is a deactivated hydrotreating catalyst from a more severe hydrodesulfurization or other hydrotreating operation which is no longer of viable use in the more severe operation due to numerous cycles of use and regeneration, due to excessive metals deposit thereon, or any other reason.

27 Claims, 8 Drawing Figures 2 o: W 3 Q u. n: .014 I 0.. (I) j. I .012 5 1- L" l 3 .010 T 3 a: Z T 11 .1 10 5 .008

E g 5 as .006 z 5 g 9 D 5 (I) .004 L 3 Z 0 1 LLI O: 9; .002 7 P 3: 2 Lu L11 1 2 0.000 v 400 450 500 5 (204C) (232%.) (260C) 0.

REACTDR TEMPERATURE F PAIENTEDmvzswm sum 1 or 4 FIG.

NON- MERCAPTAN DESULFURIZATION WEIGHT PERCENT EROS ENE X SOUTH LOUISIANA K SOUTH LOU SIANA FURNACE JIL 60 8O NON-MERCAPTAN DESULFURIZATIC JN,

WEIGHT PERCENT PATENTED REV 28 {974 SHEET 2 UP 4 FIG. 3

O OOOOO OOOOO 0 6 432 2528 25 $523. wziomm 2. 2253mm E355 NON- MERCAPTAN DESULFURIZATION,

WEiGHT PERCENT FIG. -4

3.0 0 5 0 5 O 7 m 8 8 9 9 n v YZLI:

REACTOR TEMPERATURE F mmmm Q PATENTED HUV 2 8 I974 TOTAL ACID NUMBER, D664 TOTAL DESULFURIZATICON,

WEIGHT PERCENT SHEET U 0F 4 REACTOR TEMPERATURE: F

FIG. 6

FRESH cATALYsTEE/ I I I 60 CATALYST AT FIFT-i CYCTJI 50 I (3lO'C.) (326'C.) (338'CJ (349C) (360'0) (37lC.) (382(2) AVERAGE REACTOR TEMPERATURE: F.

N PERCENT REDUCTTON TN TOTAL ACID NO. 0664 METHOD FOR UTILIZING A FIXED CATALYST BED IN SEPARATE I-IYDROGENATION PROCESSES This invention relates to a very mild hydrotreatment of virgin middle distillates such as furnace oil, kerosene, jet fuels, light gas oils or diesel oils in order to reduce the total acid number or the mercaptan content of the distillate without greatly reducing the total sulfur content of the oils in the presence of a catalyst which has previously been deactivated in a more severe hydrotreating process. This invention is related to two patent applications filed by the same inventors on even date herewith entitled Method for Reducing the Total Acid Number of a Middle Distillate Oil" and Method for Reducing the Mercaptan Content of a Middle Distillate Oil bearing Ser. Nos. 336,382 and 336,383, respectively.

The middle distillates of this invention boil generally above the naphtha range and generally exclude lubricating oils.

Middle distillates which do not meet commercial requirements in regard to total sulfur content, which is about 0.2 weight percent sulfur for fuel oils destined for use as home heating fuel, are commonly hydrodesulfurized under relatively severe conditions in order to reduce the total sulfur content to a level of at least as low as the commercial requirement. Such hydrodesulfurization processes generally occur in the presence of a Group V] and Group VIII metal containing catalyst such as cobalt-molybdenum nickel-cobaltmolybdenum or Nickel-tungsten on a non-cracking support such as alumina or alumina with a small stabilizing but non-cracking amount of silica which can be, for example, less than 0.5 percent, or less than than 1 percent by weight. Common severe hydrodesulfurization conditions include a temperature range between 650 or 675 and 800F. (343 or 357 and 427C), a pressure of at least 600 psig (42 kglcm and more generally in the range between 1,000 and 2,000 or 3,000 psig (70 and 140 or 210 kg/cm a liquid hourly space velocity between about 0.7 and 2 and a hydrogen circulation rate of between about 2,000 and 3,000 standard cubic feet per barrel of hydrogen (36 and 54 SCM/lOOL), which hydrogen can be about 75 to 80 percent pure. Hydrogen consumption is commonly about 400 standard cubic feet per barrel (72 SCM/lL) at 1,000 psi (70 kg/cm") operation or about 500 standard cubic feet per barrel (9 SCM/IOOL) at 2,000 psi (I40 kglcm operation. These are only examples of severe hydrodesulfurization conditions, and are non-limiting.

ln refinery operations utilizing such hydrodesulfurization operations, virgin middle distillates from a multiplicity of crude oil sources are commonly combined for feeding to such high pressure hydrodesulfurizers. The various middle distillates that are combined may individually fail to meet commercial specifications in regard to less than all standards. A middle distillate which falls to meet commercial requirements in regard to total sulfur content must be treated under the severe high pressure desulfurization conditions described above. However, in accordance with the present invention it has been found that a straight run middle distillate which does meetcommercial total sulfur requirements in the absence of any prior hydrotreatment but fails to meet commercial total acid number requirements and/or commercial mercaptan requirements need not be blended with the high total sulfur fuel can be treated separately in a different reactor under more mild conditions without employing a fresh catalyst but rather employing a catalyst that has been deactivated in a separate reactor under relatively more severe hydrogenation or hydrodesulfurizattion conditions to a state that its use is no longer visible in the severe hydrogenation operation.

High total acid numbers in oils are primarily due to the presence of naphthenic acids in the oil. The acid attacks copper and zinc in fuel handling systems. This type of metals pick-up not only induces metal losses in pipelines which affect metal ratios in alloys but also causes instability leading to sludge formation in the oil which can cause the oil to deposit sludge on injectors, float controls and other critical parts. In one known case a hign neutralization number diesel oil was found to pick up sufficient zinc from a diesel engine to cause engine shutdown. Harmful effects in equipment due to high copper pick-up with employing a high total acid number oil have also been experienced. For these reasons, commerical specifications in the United States require total acid numbers in oils to be below oil as determined by either of two ASTM test methods disclosed below while European commercial specifications generally require total acid numbers below 0.2.

Mercaptans are objectionable in fuel oils employed in homes or industrial plants primarily because they are strongly and unpleasantly oderiferous materials. Furthermore, they are very volatile and unstable compounds and can present a safety problem if present in excessive amounts. However, the prevailing commercial specification for mercaptans of 30 ppm (maximum), or 0.003 weight percent, is based upon odor considerations as this level represents the threshold at which the presence of mercaptans is deflectable by odor. Because of the repugnant odor of mercaptans, a level about 30 ppm of mercaptan in the oil would render the mere presence ofa fuel oil obnoxious in a home of industrial establishment. In addition, since mercaptans are mild acids, they can also contribute to a corrosion problem of the oil. Furthermore, a mercaptan content above 30 ppm has been found to contribute to geltype sludgeformation in an oil, causing plugging in pipelines in which the oil is standing or flowing.

In accordance with the present invention, an extremely mild hydrogenation treatment has been developed for the reduction of total acid number and/or mercaptan sulfur content in virgin oils which already meet commercial total sulfur content requirements, i.e. a maximum sulfur content below 0.2 weight percent sulfur for home heating fuels. The present invention accomplishes a reducton in total acid number and/or mercaptan sulfurcontent in oils which already meet commercial total sulfur content requirements without blending such oils with high total sulfur content oils prior to hydrodesulfurization of high total sulfurcontent oils under severe conditions, as has been the practice in the past. High total sulfur content oils not only require treatment in a high pressure and temperature hydrodesulfurization unit to accomplish hydrodesulfurization, but also require a highly active hydrogehave now found that total acid number and mercaptan content can be reduced under much milder hydrogenation conditions with a degenerated and deactivated hydrogenation catalyst so that such feeds can be separately treated in another reactor without unnecessarily consuming valuable space in high pressure reactors. There has not previously been a sufficiently mild hydrogenation process to make independent hydrogenation of these oils economic and therefore in hydrogenative treatment they formerly were reduced in total acid number or mercaptan sulfur content by aqueous caustic treatment. However, this method may soon have to be abandoned because the aqueous effluent from caustic units represents an unacceptable stream pollutant under present-day environmental standards.

We have now discovered that the degree of hydrogenation required for the reduction of total acid number or mercaptan sulfur content in virgin middle distillates to acceptable commercial levels where the nature of the crude oil source of these oils is such that these oils already satisfy commercial total sulfur requirements, is so low that it is commercially wasteful to blend these oils with hydrodesulfurization feeds wherein the nature of the crude oil source of the oil is such that a major portion of the total sulfur content of the feed must be also reduced. We have discovered that hydrogenative treatment for reduction of total sulfur requires treatment under hydrodesulfurization conditions which are unnecessarily severe for the low sulfur feeds of this invention. For example, we have found that straight run middle distillates which do not satisfy commercial total acid number and/or mercaptan content requirements but do satisfy commercial total sulfur requirements without hydrotreatment can be separately treated to produce commercially acceptable levels in regard to total acid number and/or mercaptan content in units wherein chemical consumption requirements are only from one to five, or even lower, standard cubic feet of hydrogen per barrel of feed (from 0.0l8 to 0.09 standard cubic meters per 100 liters of feed) and unit hydrogen consumption including hydrogen losses are less than 10 or standard cubic feet per barrel of feed (less than 0.l8 to 0.27 standard cubic meters per 100 liters of feed The catalytic activity required to accomplish such a slight chemical hydrogen consumption is so correspondingly slight that use of an active or fresh hydrodesulfurization or hydrogenation catalyst is not only wasteful but accomplishes a level of hydrogenation which is not required by the process. To illustrate, a virgin middle distillate stream is ordinarily relatively olefin-free so that it contains only about one percent by volume of olefins, and these olefins are relatively easy to hydrogenate. However, in accordance with the present invention. these olefins are not hydrogenated to a major extent because such olefin hydrogenation is not generally required to accomplish reduction in total acid number or to accomplish reduction in mercaptan content to commercially acceptable levels. However. ifthe hydrogenation conditions ofthe present invention were sufficiently severe, saturation of these olefins of itself would account for a chemical consumption of hydrogen of about nine standard cubic feet per barrel (0162 standard cubic meters per 100 liters), which is higher than that generally required for the reduction for total acid number and mercaptan content in most feeds.

In order to diminish unnecessary chemical or unit hydrogen consumption beyond that which is required to reduce neutralization number and/or mercaptan sulfur content in a feed stream of this invention to commercially acceptable levels, the present invention ordinarily employs hydrogen pressures below psi (7 kg/cm and also employs as a hydrogenation catalyst a permanently deactivated catalyst as a fixed compact bed in downflow operation, which catalyst has been prevously employed in a separate but high pressure (600 psi or more, 4.2 kg/cm or more) hydrogenation process. The catalyst is only transferred from the severe hydrogenation process after it has experienced many regeneration cycles and its activity loss as compared to its original cycle is so severe that it is no longer a viable catalyst in a high pressure, high hydrogen consumption process except by the use of excessive startof-run temperatures, or unacceptably short cycle life before further regeneration is required. We have discovered, in accordance with the present invention, that these apparently hopelessly deactivated high pressure hydrogenation catalysts which would otherwise be discarded or decomposed for recovery of valuable metals have a vestige of hydrogenation activity remaining which is sufficient for the process of the present invention. It is emphasized, that the catalysts of the present invention would otherwise be discarded or destroyed as being of insufficient activity to be of further use in other refinery hydrogenation processes. These deactivated catalysts can be subjected to a final combustion regeneration for removal of carbon and a sulfidation within their original reactor and at the temperature of their original reactor, prior to transfer to the mild temperature and pressure reactor of this invention. We have successfully employed in the process of this invention Group VI and Group VIII metal on alumina hydrogenation catalysts, such as NiCoMo on alumina, which have experienced at least four or five regenerations by combustion of carbon until in about the fifth cycle the required start-of-run temperature to accomplish a given product sulfur level in a fuel oil hydrodesulfurization process was elevated by 40 to 60F. (22.2 to 333C.) as compared to the initial cycle, thereby rendering the duration of its useful life in the fifth cycle, employing rising temperatures to compensate for desulfurization activity loss, unacceptably short. We have also employed in the process of this invention a deactivated nickel-tungsten-fluorine on silica-alumina hydrocracking catalyst which was sufficiently deactivated so that it was sufficiently inactive for further use as a compact fixed or stationary bed hydrocracking catalyst in downflow operation but still retained sufficient hydrogenation activity to be of use under the mild conditions of this invention wherein the temperatures and pressures were too low to effect significant feed cracking but were sufficient for very mild hydrogenation. Residue hydrodesulfurization catalyst permanently deactivated in downflow operation as a compacted bed by feed metals can also be employed in the present invention without prior demetallization. The only pretreatment required for these catalysts after deactivation in their original processes and prior to similar downflow compact bed use in the process of the present invention is a possible combustive regeneration and/or a possible sulfidation step. such as by passage of a high total sulfur-content oil over the catalyst under hydrodesulfurization conditions, after which these catalysts can be removed from their original reactor to another or secondary reactor, preferably of smaller wall thickness and of different diameter. In their secondary reactor, these catalysts can be employed under low temperature and pressure conditions for a long or indefinite duration, often without further sulfidat'ion or regeneration. We have found the small, residual hydrogenation activity remaining in these catalysts is ample for their employment to accomplish the limited hydrogenation required for the present invention. The following data show that the residual hydrogenation activity present in these aged catalysts is sufficient for reduction of total acid number via neutralization of naphthenic acids by a major extent, such as 75, 80 or 90 percent or more, and by reduction of mercaptan sulfur content via hydrogenation of mercaptan sulfur molecules by a major extent such as by 60, 75, 80 or 90 percent or more, but is insufficient to concomitantly reduce total sulfur by more than a minor amount, i.e., by not more than 10, 20, 30, 40 and less than 50 percent, and is also insufficient to reduce olefin content by more than a minor extent, i.e. not more than 20, 40 and less than 50 percent.

The process conditions for the present invention include temperatures between 300 and 600F. (149 and 315C.), generally, and 400 to 550F. (204 and 288C) preferably, hydrogen pressures below 100 or 150 psi (7 and 10.5 kg/cm generally, and below 75 psi (5.15 kglcm preferably, liquid hourly space velocities between 3 and 10, generally, and between 4 and 8, preferably and hydrogen circulation rates between 200 and 1,200 SCF/B (3.6 and 21.6 standard cubic meters per 100 liters), generally, and 300 to 1,000 SCF/B (5.4 to 18 standard cubic meters per 100 liters), preferably. Hydrogen pressure requirements for this invention are very low. Generally, only sufficient pressure to move the reactants throughthe system at the required space velocity will be adequate. A wide variety of Group V1 and Group Vlll catalytic metals are suitable for the present invention. For example, nickelcobalt-molybdenum on alumina, cobalt-molybdenum, nickel-tungsten or nickel-molybdenum. The support can be alumina, alumina-silica or silica-magnesia, as long as non-cracking conditions are employed.

To illustrate the present invention, in one domestic refinery operation for the preparation of both No. 2 home heating fuels and also kerosenes boiling broadly in the 350 to 700F. (176 to 371C.) range or, more narrowly, in the 400 to 650F. (204 to 343C.) range, the refinery was supplied by five different feed stocks boiling within these ranges originating from different crude sources. These five feed stocks are described in Table l. Two of the feed stocks, a straight run West Texas kerosene and a West Texas straight run furnace oil did not meet commercial requirements in regard to total sulfur content and therefore required high pressure hydrodesulfurization. A furnace oil from a distillation column to which an Ordovician crude was fed contained only 0.11 weight percent total sulfur, meeting commercial specifications, but contained 0.041 weight percent ofmercaptans and had a total acid number less than 0.03, thereby failing to meet commercial specifications in regard to mercaptan content (30 ppm maximum) only, while meeting commercial specifications in regard to total acid number (01 maximum). A furnace oil from a distillation column to which a South Louisiana crude was supplied contained only 0.10 weight percent total sulfur thereby meeting commercial specifications, contained a mercaptan sulfur content of 0.0004,

also meeting commercial specifications, but had a total acid number of 046-7, which is above the commercial specification of 0.1. A kerosene derived from a South Louisiana crude met commercial specifications in regard to total sulfur, mercaptan content, but not in regard to total acid number, having a total acid number of 0.12 which exceeds the maximum allowable 0.10 commercial specification. The various feed stocks shown in Table 1 show that it is possible for a straight run middle distillate feed stock to meet commercial specifications in regard to total sulfur content and in regard to total acid number, but not in regard to mercaptan sulfur content. It is also possible for a straight run feed stock to meet commercial specifications in re gard to total sulfur content and mercaptan sulfur content, but not in regard to total acid number. It is also possible for a straight run middle distillate to meet commercial specifications in regard to total sulfur content but not in regard to either total acid number or mercaptan sulfur content.

In accordance with the present invention, any straight run feed stock which fails "to meet commercial specifications in regard to total sulfur content must be treated in a high pressure vessel capable of accommo-' dating a pressure of 600 to 1,000 psig (42 to kg/cm or more and a temperature of 680F. (360C.) or more to accomplish hydrodesulfurization in the presence of a highly active hydrodesulfurization catalyst, such as a Group V1 and Group VIII metal on a non-cracking support, such as alumina, with or without less than about 1 percent of a non-cracking stabilizing amount of silica, usually in downflow-operation of feed oil and hydrogen. Common catalystic metals include nickel, cobalt, molybdenum, tungsten, etc. in various combinations. However, we have now found that straight run middle distillates which meet commercial total sulfur requirements but fail to meet commercial requirements in regard to total acid number and/or mercaptan sulfur content can be charged to a separate reactor, and at a relatively lower temperature which is always below 650F. (343C), operated at a much lower pressure, such as psig (7 kg/cm or less, with the same or a similar catalyst as was used in the high pressure hydrodesulfurization reactor as a downflow, compact bed but in a permanently deactivated state in regard to the requirements of the high pressure reactor. In this manner, a smaller total flow is passed through the high pressure reactor, said flow being diminished by the feed charged directly to the low pressure reactor, permitting the diameter of the high pressure reactor to be greatly reduced. Since the thickness of the steel wall which is required in a high pressure and high temperature reactor increases greatly with reactor diameter (by contrast, it is known that a thin-walled copper tube can withstand thousands of pounds of pressure if its diameter is only about A. of an inch or 0.63 cm), the present invention permits the high pressure and temperature reactor to be constructed with a smaller diameter and also with a greatly diminished metal thickness, resulting in considerable economic savings. Since the feed streams by-passing the high pressure reactor are hydrotreated at only 100 psig (7 kg/cm or less, and at a lower temperature, i.e. below 500 or 450F. (260 or 232C), than the high pressure reactor, the low pressure reactor will have a greatly reduced steel thickness, as compared to the high pressure reactor, resulting in a considerable overall savings in the fabrication costs in the metal reactors.

The detailed characteristics of the five middle distillate feed stocks described above are shown in Table l,

beds, or can comprise a portion of a single bed contained in the high pressure reactor, omitting the uppermost region of the bed, thereby utilizing in the low pressure reactor only the cleanest, most metals-free below. portion of the catalyst from the high pressure reactor.

TABLE 1 LOW SEVERlTY HYDROTREATING CHARGE INSPECTIONS South South West West Ordovician Louisiana Louisiana Texas Texas Furnace Oil Furnace Oil Kerosene Kerosene Furnace Oil Inspections Gravity, D287: APl 43.9 36.5 43.3 40.0 36.9 Distillation, D86: F.

Over Point 321(160C.) 361( 183C.) 331( 166C.) 340( 171C.) 338(170C.) End Point 617(325C.) 654(345C.) 496(258C.) 567(297C.) 708(375C.)

5% 372(189C.) 424(218C.) 359( 182C.) 385( 196C.) 446(230C.) 367(186C.) 393(201C.) 413(212C.) 407(208C.) 480(249C.) 375( 191C.) 423(217C.) 496(258C.) 383( 195C.) 443(228"C.) 508(264C.) 390(199C.) 5071 463(240C.) 520(27 1C.) 399(2()4C.) 452(233C.) 499(259C.) 487(253C.) 532(278C.) 408(209C.) 7071 513(267C.) 548(298C.) 419(215C.) 541(283C.) 566(297C.) 432(222C.) 573(300C.) 596(313C.) 452(233C.) 520(271C.) 630(332C.) 595(313C.) 622(328C.) 466(241C.) Sulfur, weight percent .11 .10 .69 .92 Sulfur, ppm 267 Mercaptan Sulfur, D1323:

weight percent .041 .0004 .0006 .127 .11 Total acid number, D974 .03 .47 .12 .06 Total acid number, D664 .46 Bromine number, D1159 6.7 7.4

No additional catalyst cost is required for operation of the low pressure reactor, which is the reactor of the present invention, since it operates with catalyst that has been deactivated by repeated regencrations in the high pressure reactor until it is no longer of commercial utility in the high pressure reactor. The deactivated high pressure catalyst is sult'idcd if required in the high pressure reactor prior to withdrawal therefrom at a temperature of about 600 to 650F. (315 to 343C.) by passage of high sulfur-content oil therethrough. If required, it can also be regenerated by combustion in the high pressure reactor. Then the catalyst can be removed from the high pressure reactor by any suitable means, such as through a plug in the bottom thereof.

The catalyst for reuse in the low pressure reactor can comprise the catalyst from the high pressure reactor in its entirety, or, since feed oil is passed downwardly through the high pressure reactor, the reused catalyst can comprise only the bottom bed of a multiplicity of It is possible to utilize the entire bed from the high pressure reactor in the low pressure reactor if the total amount of catalyst is required in the low pressure reac- 35 tor and if the average contamination of the total catalyst bed in the high pressure reactor is not excessive. The catalyst removed from the high pressure reactor is then replaced by a similar amount and quality of fresh catalyst.

40 Table 2, below, shows the test conditions employed and the results obtained when the first three feed stocks listed in Table 1 (which already met commercial total sulfur requrements and therefore did not require high pressure hydrodesulfurization) were treated under the 45 low pressure hydrogen test conditions of this invention 50 pact catalyst bed.

TABLE 2 LOW SEVERITY HYDROTREATING WITH AGED CATALYSTS SUMMARIZED CHARGE STOCK AND TYPICAL PRODUCT INSPECTIONS Ordovician South Louisiana South Louisiana Feed from Table l Furnace Oil Furnace Oll Kerolene Operating Conditions:

Catalyst Aged Aged Aged Reactor Temperature: F. 500(260C.) 475(246C.) 450(232'C.) Reactor Pressure: pailgI (7 k lcm') 100(7 k lcm) 100(7 k lcrn) Space Velocity: Vol/ r/Vol 4.8 4.8 4,8 Gas Circulation Rate:

SCF/B FF 1000 1000 1000 (I9 mllOO liters) (l8 In /100 liters) (Ill m"/l00 liters) Gas Hydrogen Content:

Volume percent 85 85 85 Liquid Product Yield:

Volume ercent FF 100 I00 I00 Hydrogen ulfide Yield:

TABLE 2 Continued LOW SEVERITY HYDROTREATING WITH AGED CATALYSTS SUMMARIZED CHARGE STOCK AND TYPICAL PRODUCT INSPECTIONS Ordovician South Louisiana South Louisiana Feed from Table I Furnace Oil Furnace Oil Kerosene Weight percent FF 0.06 0.04 0.0]

Fresh Hydrotreated Fresh Hydrotreated Fresh Hydrotreated Feed Product Feed Product Feed Prodw Inspections Gravity, D287: API 43.9 43.8 36.5 36.3 43.3 43.2 Distillation, D86: F.

Over Point 32l(l6lC.) 338(l70C.) 36l(l82C.) 357(18lC.) 33l(l66C.) 340(I7IC.) End Point 617(325C.) 629(332C.) 654(345C.) 629(332C.) 496(258C.) 503(262C.) 10% 385(196C.) 388(198C.) 446(230C.) 446(230C.) 367( 186C.) 369(187C.) 423(2I7C.) 43l(222C.) 496(258C.) 495(257C.) 383( I95C.) 385(196C.) 50% 463(239C.) 474(245C.) 520(27IC.) 5l9(27lC.) 399(204C.) I(205C.) 70% 513(267C.) 523(273C.) 548(287C.) 545(285C.) 4I9(2l5C.) 420(215C.) 90% 573(301C.) 583(306C.) 596(3l3C.) 595(313C.) 452(2313C.) l(233C.) Mercaptan Sulfur,

D1323: weight percent 0.041 0.0009 0.0004 0.0006 Total Acid Number, D974 0.03 0.47 0.03 0.12 0.03 Sulfur, ppm 267 186 Sulfur, weight percent 0.1 l 0.05 0.10 0.06

Color, Saybolt, D l 56 Table 2 shows that the present process improves not only mercaptan sulfur content and total acid number but also improves color properties of the feed oil. It also shows there is substantially 100 percent yield of furnace oil or kerosene in the present process.

Table 3, presented below, presents additional test data and product specifications when treating the Ordovian furnace oil under still other single pass conditions than those shown in Table 2.

TABLE 3 OPERATING CONDITIONS Catalyst NiCoMo-on-alumina 4 Aged Volume: cc 262.0 Weight: gms 238.9 Age Days 34.5 BBL/LB FF 12.5 (.004353 mVg) Period Length: hours 63.0 Operating Conditions Reactor Tempera\ure:'F. 430.0 I r (221C) Reactor Pressure: psig l0l.()

(7.07 kglcni Space Velocity FF Vol/Hr/Vul 3.98

Wt/Hr/Wt 3.53 Reactor Gas FF SCF/BBL 604.0

(10.9 SCM/IOOL) Hydrogen Content:

percent by volume 85.6 Weight Balance O/l: percent 99.6 Hydrogen Consumption: SCF/BBL FFC [4.0

Therefore, in the present proc'ess,there is essentially no removal of sulfur atoms from the interior of mole cules as occurs in high pressure hydrodesulfurization with high sulfur'content feeds and which splits the feed molecules into lower molecular weight fragments boiling in the naphtha range, or lower.

The catalyst employed in all the tests-was NiCoMoon-alumina which was previously deactivated in high pressure (600 psig or 42 kg/cm hydrodesulfurization 7 runs employing straight-run middle distillate oil feed stocks which failed to meet the 0.2 weight percent total sulfur specifications. An example of the extent'of deactivation of such a catalyst in a high pressure process is illustrated in FIG. 7. The tests illustrated in FIG. 7 were performed at a temperature of 620 -700 F. (326-37 1C.), 600 psig (42 kg/cm 5.85 LHSV with 900 SCF/B (16.2 SCMIOOL) of 85 percent hydrogen reactor gas. The charge oil was a West Texas furnace oil containing 0.98 weight percent sulfur. The first cycle of the high pressure (600 psig or 42 kg/cm hydrodesulfurization catalyst exhibited the upper temperature response curve shown in FIG. 7, while the lower curve of FIG. 7 shows the temperature response characteristics in thefifth cycle of the catalyst with the same feed, with combustionregeneration between cycles, after whcih 268 barrels of oil per pound of total catalyst (0.094 m /g) was passed throughthe reactor. FIG. 7 shows the aged catalyst was -60F. (27.8

" to 700F. (327 to'37l.C.) reactor temperature range in which the catalyst was aged. Each regeneration of the catalyst results in a higher required start-of-run temperature and a shorter time of operation in the subsequent cycle.

The aged catalyst was then presulfided in the high temperature and pressure hydrodesulfurization reactor with Ordovician furnace oil for 12 hours at: 650F. (343C). 4.0 LHSV at 1000 psig kg/cm). Thereupon. it was employed as a catalyst in'the low temperature and pressure reactor of this inventionwith the results shown in the following figures.

FIG. 1 shows the relationship in the processof the present invention between non-mercaptan or total sul fur content reduction and mercaptan desulfurization number reduction in tests conducted at 100 psig (=7- kglcm 400 to 650F. (204 to 343C), 4-8 LHSV,

300 -l,000 SCF H2)/B (5.4-18 SCM/IOOL). The solid circles of FIG. 1 represent theOrdovicianufurnace oil feed of Table I while the crosses indicatethe West Texas kerosene feed of Table I. As shown in FIG. I, the process of this invention removed about weight:

percent of the mercaptan sulfur before removing only about 15 percent of the total sulfur content of the feed, showing the high selectivity of the present process for removal of mercaptan sulfur while not removing total sulfur. FIG. 1 shows a 50 percent reduction in mercaptan sulfur content occurred with only about 1 or 2 percent reduction in total sulfur content.

FIG. 2 shows the relationship between nonmercaptan or total desulfurization and percent reduction in total acid number with tests conducted under the conditions of the present invention which include 100 psig (7 kglcm 400 to 650F. (204 to 343C), 4-8 LHSV and 300 -I,00O SCF (85% H )/B (5.4 -I8 SCM/IOOL). In FIG. 2, the crosses indicate the South Louisiana kerosene feed of Table 1 and the solid circles indicate the South Louisiana furnace oil feed of Table 1. FIG. 2 shows that the process of the present invention is capable of reducing the total acid number of a feed oil by at least 80 percent while reducing the total sulfur content of the oil only 20 percent, again showing the high selectivity of the present process for treatment of low total sulfur-containing oils. FIG. 2 shows a 50 percent reduction in total acid number occurred with less than about a five percent reduction in total sulfur content.

FIGS. 1 and 2 both show that the reduction in mercaptan sulfur content and the reduction in total acid number both occur much more readily than the undesired total desulfurization reaction. FIGS. 1 and 2 show that 90-95 percent mercaptan desulfurization and 80 percent total acid number reduction occur with only 20 percent total desulfurization.

FIG. 3 illustrates the results of a similar test with the same aged catalyst at 100 -I50 psig (7 10.5 kg/cm The solid circles represent a heavy FCC naphtha feed (not illustrated in Table 1), the hollow circles represent the WestTexas kerosene feed of Table 1, and the triangles represent the West Texas furnace oil feed of Table 1. FIG. 3 shows that, the saturation of olefins occurs at even a slower rate than non-mercaptan or total desulfurization, i.e. at 20 percent total desulfurization only about 6 percent olefin saturation occurred. Therefore, the conditions of the present invention are too mild to accomplish significant olefin saturation. This is an important feature of the present invention because, assuming atypical middle distillate feed contained 1 percent olefin by volume, the saturation of these olefins alone would account for a chemical hydrogen consumption of about 9 SCF/B (0.162 SCM/IOOL).

FIGS. 4, 5 and 6 show results obtained with a fresh hydrogenation catalyst having a similar composition as that employed in the tests of the other Figures, except that the catalyst represented by the lowest curve of FIG. 4 was previously aged for two cycles in a prior high pressure hydrogenation process. These figures show that the present invention can be practiced with a fresh as well as an aged catalyst. although the fresh catalyst will require milder conditions to maintain the low hydrogen consumption levels of this invention. In FIGS. 4, 5A and 5B the feed stock is the Ordovician furnace oil of Table l. The tests of FIG. 4 were performed with a circulation of 1,000 SCF/B (l8 SCM/IOOL) of 85 percent hydrogen at the temperatures, pressures and space velocity conditions indicated. FIG. 4 shows that in accordance with the present invention the feed mercaptan sulfur content can be reduced from a value of 410 in the original feed stock to values as low as 8, 10 or ppm at 450F. (232C).

and can be reduced to a value approaching 0 ppm at a temperature of 500F. (260C.). FIG. 4 shows very little advantage in increasing the pressure from 100 to 200 psi (7 to 14 kg/cm for removal of mercaptan sulfur. FIG. 4 also shows that more than percent mercaptan removal occurred in the process for the feed oil to meet the commercial specification of 30 ppm mercaptan content.

FIGS. 5A and 58, represent tests made with the Ordovician furnace oil feed of Table I and show that hydrogen circulation rate does not have a great effect upon the achievement of 30 ppm of mercaptan sulfur in the oil at the conditions tested.

The tests of FIG. 6 were made with the South Louisiana furnace oil of Table I at psig (7 kglcm with 1,000 SCF/B (18 SCM/100L) of 85 percent hydrogen. These tests show that feed total acid number can be reduced in a feed which had a value of 0.47, to a value of 0.1 at temperatures below 450 to 500F. (232 to 260C.) depending upon space velocity. FIG. 6 shows that nearly 80 percent reduction in acid content occurred in the process for the feed oil to meet the commercial specification of 0.1 total acid number.

FIGS. 4, 5A, 5B and 6 illustrate that a wide range of low severity temperature, pressure and space velocity conditions can be employed with a hydrodesulfurization catalyst to accomplish the required commercial low mercaptan sulfur content and low total acid number values in accordance with this invention.

As stated above, commercial specifications for No. 2 furnace oil require a maximum total sulfur content of 0.2 weight percent sulfur for home heating fuel, a maximum mercaptan content of 30 ppm (0.003 weight percent) and a total acid number of less than 0.1. Total acid number is defined as milligrams of potassium hydroxide (KOH) that is required to neutralize all acidic constituents present in I gram of oil sample (mg KOH/gm sample), according to ASTM test D664 or D974, 1968 Book of ASTM Standards, Volume 17, page 235. About the same results are obtained in total acid number when ASTM test method D974, which employs colorimetric titration, is employed, as in the case of method D664, which employs potentiometric titration. Mercaptan sulfur content is defined as grams of mercaptan sulfur per 10 grams of oil.

It is seen that of the middle distillates listed in Table 1, only the West Texas middle distillates contained more than commercial specifications in regard to total sulfur content. Therefore, it is necessary to hydrodesulfurize these oils at a pressure above 600 psig (42 kg/cm and preferably in the 1,000 to 2,000 psig (70 to kglcm range disclosed above to reduce their sulfur content to 0.2 weight percent sulfur. However, the Ordovician middle distillate and the South Louisiana middle distillates both meet commercial total sulfur content requirements and therefore do not require severe hydrodesulfurization to accomplish reduction of total sulfur content. However, under the practice of the prior art, the Ordovician and South Louisiana middle distillates would have been blended with the West Texas middle distillates to obtain a total refinery middle distillate blend for feeding to the high pressure hydrodesulfurization unit because under the severe hydrogenation conditions required for the reduction of total sulfur content of the West Texas middle distillates, the 410 ppm mercaptan content of the Ordovician middle distillate would easily be reduced to the pressure reactor. This practice is based upon out discovery that for straight run middle distillates the severity of the operation required for the reduction of total acid number and the reduction of mercaptan sulfur content by hydrotreatment is much milder than is required for the reduction of total sulfur content.

The following calculations are presented to illustrate that relatively minuscule quantities of chemical hydrogen consumption are required to accomplish the required reductions in total acid number and mercaptan sulfur content in accordance with this invention.

To reduce the total acid number via hydrogenation, the most prevalant reaction involved is the reaction of an organic naphthenic acid with hydrogen to produce a saturated hydrocarbon plus water, according to the following equation:

From this equation it is seen that three moles of hydrogen are required to saturate one mole of organic acid. The hydrogenation method of neutralization is the method employed in accordance with the present invention.

The ASTM neutralization test method reacts the organic acid with KOH to produce a salt plus water according to the equation:

KOH (It-(1 1110 on o it is seen from this equation that one mole of KOH is required to neutralize one mole of organic acid.

lfthe neutralization or total acid number ofa leedoil is known. the amount of hydrogenrequired to be consumed when reducing the total acid number to the value required by commercial specifications can be cal culated as follows:

Total acid number mg/KOH/gram sample pull density ofsample, gm/cc Molecular weight of KOH 56,!08 mg/mole A total acid number reduction in total acid number (total acid number of untreated oil minus the acid number of the treated product) H consumption (SOF/B) 3785cc l'gal.

1 mole acid 1 mole KOH 3 gm moles H mole acid saturated 42.0 gal. 379 set Bbl mole (A total acid no.)(e,,; )(7.10) SCF H /Bbl oil 1 mole 453.6 gm molcs To convert SCF H- /Bbl oil to SCM/lOOL multiply by 0.018. t In an actual example based on the South Louisiana middle distillate of Table l which has a total acid number of 0.46 wherein the specific gravity of the oil was 36.5 APl (0.8423 g/cc), to reduce the total acid number (Atotal acid number) from 0.46 to 0.10 (A 0.36) the hydrogen consumption is therefore the (A total acid number) times the density of the oil times 7.10; or

Hydrogen consumption =0.36 X 0.8423 X 7.10 2.2 standard cubic feet of hydrogen per barrel (0.04 SCM/lOOL).

It is seen from the above sample calculation that the hydrogen requirement to reduce the total acid number of the South Louisiana middle distillate to meet commercial standards is extremely small, as long as the middle distillate already meets commercial standards in regard to total sulfur content. Therefore, in accordance with this invention not more than about 5 or 10 standard cubic feet of hydrogen per barrel (0.09 to 0.18 SCM/l00L) of middle distillate are required in terms of chemical hydrogen consumption to reduce total acid number of an oil sufficiently to meet commercial requirements of the oil. In terms of total unit hydrogen requirement, including solubility losses, the requirement in hydrogen need not exceed 15, 20, 25 or 30 standard cubic feet per barrel (0.27, 0.36, 0.45 or 0.54 SCM/IOOL).

It can be shown that hydrogen requirements for reducing mercaptan sulfur content to commercially acceptable levels by hydrogen treatment in accordance with the present invention can be even smaller than that shown above for the reduction of total acid number. The reaction involved for the reduction of mercaptan sulfur via hydrogenation proceeds as follows:

From the above equation, it is seen that two moles of hydrogen are required for each mole of mercaptan sulfur which is removed.

The analysis of mercaptans is usually presented in units of parts per million, as follows:

mole KOH mg KOH Hydrogen consumption in SCF/B for mercaptan removal =A Mercaptan S content 106 g Oil 3785 cc 42.0 gal 1 l and generally will not exceed or standard cubic feet per barrel (0.090 or 0.18 SCM/lOOL) in terms of chemical hydrogen consumption, or will not exceed 15,

M t S grns ercap an (gcmc s) gal mercautau mercnptan 2 g moles H gms 1 mole (gm mole mercaptan) X MW...

379 SCF 1 mole gas (A Mercaptan S content) e (3785)(42)(2)(379) To convert SCF HyjBbl to SCM/IOOL multiply by 0.018.

The Ordorician middle distillate shown in Table 1 contained 410 ppm of mercaptan. lts API was 43.9 (0.8067 gm/cc). lts mean average boiling point was 451F. (233C). lts molecular weight, from AP1 and mean average boiling point, is 192. Therefore, to reduce the mercaptan sulfur in the charge from 0.041 weight percent, or 410 ppm, to a product containing 30 ppm, the hydrogen consumption [(410 30) (0.8067) (0.266)]/l92 0.4 standard cubic feet per barrel (0.0072 SCM/lOOL).

It is seen from the above sample calculation that the hydrogen requirement to reduce the mercaptan content of the Ordovician middle distillate to meet commercial standards is extremelysmall, as long as the middle distillate already meets commercial standards in regard to total sulfur content. Therefore, in accordance with this invention not more than about 5 or 10 standard cubic feet of hydrogen per barrel of middle distillate (0.09 or 0.18 SCM/lOOL) are required in terms of chemical hydrogen consumption to reduce mercaptan content of an oil sufficiently to meet commercial requirements of the oil. In terms of total unit hydrogen requirement. including solubility losses and losses in the hydrogen off-gas, the requirement in hydrogen need not exceed 15, or standard cubic feet per barrel (0.27, 0.36 or 0.45 SCM/lOOL). According to the Oil and Gas Journal, Feb. 17, 1969, Volume 67, No. 7. page 78, hydrogen solubility losses are about 0.4 SCF/B (0.0072 SCM/IOOL) times the pressure in atmospheres. Therefore. at 100 psi (7 kg/cm unit pressure, hydrogen solubility losses are 0.4 times 100/l5 z 3 SCF/B (0.054 SCM/lOOL). Table 3 shows total unit hydrogen requirements of only 14 standard cubic feet per barrel (0.0252 SCM/lOOL) when treating the Ordovician middle distillate of Table l.

The above two calculations show the actual mercaptan sulfur removal or acid number reduction is accomplished with hydrogen chemical consumptions only slightly above zero to less than 3 standard cubic feet per barrel (0.054 SCM/lOOL).

It is again seen that for a middle distillate which meets commercial requirements in regard to total sulfur content, the hydrogen consumption requirement for the reduction of mercaptan sulfur to commercially acceptable levels is extremely small and can be below gm mole mercaptan 453.6 gm mole 20 or 25 standard cubic feet per barrel (0.027, 0.36 or 0.450 SCM/IOOL) in terms of total unit hydrogen consumption, including losses. In fact, when a feed meets commercial total sulfur requirements but does not meet commercial total acid number requirements or commercial mercaptan content requirements, the total chemical consumption to meet both of these requirements should not exceed 5 or 10 standard cubic feet per barrel (0.09 or 0.18 SCM/lOOL), or 15 to 25 standard cubic feet per barrel (0.27 to 0.45 SCM/lOOL) when solution losses are considered.

We claim:

1. A relatively low pressure hydrotreating process performed in a first and relatively low pressure reactor comprising passing a first feed oil comprising middle distillate straight run feed oil and hydrogen downwardly over a hydrodesulfurization catalyst that has been deactivated in a prior relatively high pressure hydrodesulfurization process, said prior process being operated in a second and high pressure reactor in downflow operation with a second feed oil at a pressure of at least 600 psi and at a temperature between 650 and 800F. until said catalyst permanently possessed insufficient desulfurization activity for said high pressure process, said catalyst thereupon being removed from said second reactor and charged to said first and low pressure reactor for hydrotreatment of said first feed oil at a pressure no higher than about 150 psi and at a temperature between 400 and 550F.

2. The process of claim 1 wherein not more than 30 weight percent of the total sulfur in the feed oil is removed in the low pressure reactor.

3. The process of claim 1 wherein said middle distillate feeds boil in the range 350 to 700F.

4. The process of claim 1 wherein the catalyst comprises supported Group VI and Group VIII metals and the pressure is no higher than psi.

5. The process of claim 1 wherein the temperature in said low pressure reactor is between 400 and 550F.

6. The process of claim 1 wherein the temperature in said low pressure reactor is below 500F.

7. The process of claim 1 wherein the temperature in said low pressure reactor is below 450F.

8. The process of claim 1 wherein the LHSV in said low pressure reactor is between 4 and 8.

9. The process of claim 1 wherein not more than 20 weight percent ofthe total sulfur in the feed is removed in the low pressure reactor.

10. The process of claim I wherein said middle distillates are furnace oil, kerosene or jet fuel.

11. The process of claim 1 wherein chemical hydrogen consumption excluding unit losses in said low pressure reactor is less than standard cubic feet per barrel.

12. The process of claim 1 wherein unit hydrogen consumption including losses in said low pressure reactor is less than standard cubic feet per barrel.

13. The process of claim 1 wherein the pressure in the low pressure reactor is below 75 psi.

14. The process of claim 1 wherein the chemical hydrogen consumption in the low pressure reactor is less than 5 standard cubic feet per barrel of feed oil.

15. A combination first relatively high pressure and second relatively low pressure hydrotreating process comprising passing a first middle distillate straight run oil having a total sulfur content greater than 0.2 weight percent derived from a first crude oil downwardly over a supported Group VI and Group VIII hydrodesulfurization catalyst in a first and high pressure hydrodesulfurization rector at a pressure above 600 psi and at a temperature between 650 and 800F. to reduce the total sulfur content of said first oil below 02 weight percent until said catalyst is permanently deactivated and possesses insufficient desulfurization activity for said high pressure process, removing said catalyst from said high pressure reactor and passing it to a second and relatively low pressure reactor operated at a pressure below about 150 psi, passing a second middle distillate oil having a total sulfur content less than 0.2 weight percent derived from a second crude oil downwardly over said deactivated catalyst at a pressure no higher than about 150 psi and at a temperature between 400 and 550F. so that the chemical hydrogen consumption in said second reactor is above 0 but below 10 standard cubic feet per barrel.

16. The process of claim 15 wherein not more than 30 weight percent of the total sulfur in the feed oil is removed in the low pressure reactor.

17. The process of claim 15 wherein said middle distillate feeds boil in the range 350 to 700F.

18. The process of claim 15 wherein the catalyst comprises supported Group VI and Group VIII metals and the pressure is no more than psi.

19. The process of claim 15 wherein the temperature in said low pressure reactor is between 400 and 550F.

20. The process of claim 15 wherein the temperature in said low pressure reactor is below 500F.

21. The process of claim 15 wherein the temperature in said low pressure reactor is below 450F.

22. The process of claim 15 wherein the LI-lSV in said low pressure reactor is between 4 and 8.

23. The process of claim 15 wherein not more than 20 weight percent of the total sulfur in the feed is removed in the low pressure reactor.

24. The process of claim 15 wherein said middle distillates are furnace oil, kerosene or jet fuel.

25. The process ofclaim 15 wherein chemical hydrogen consumption excluding unit losses in said low pressure reactor is less than 5 standard cubic feet per barrel.

26. The process of claim 15 wherein there is a color improvement in the middle distillate feed to the low pressure reactor 27. The process of claim 15 wherein there is substantially a 100 percent yield in the middle distillate feed to @32 3 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION .Patent No, 318501744 I Dated November 26, 1974 Inventor) R. A. Plundo, T. C. Readal and J. R. Strom It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Col. 2, line 1, after "fuel" insert -but Col. 2, line 17, "hign" should read high-- Col. 2, 'line 23, "oil" should read -0.l,--

Col.- 2, line 36, "deflectable" should read --detectable- Cols. 7 and 8, Table 1, under "South Louisiana Furnace Oil" opposite "70%", "548 (298C. should read Cols. 7 and 8, Table 2, under "Ordovician Furnace Oil" opposite "Gas Circulation Rate: SCF/B FF", "l9 m /lO0 liters" should read --l8 m /l0 O liters-- Col. 13, line 12, "out" should read --our- Col. 15, last line of equation (0266) should read (0.266)-- 3.31190 ans lead this 22m; day of .---.pr1l l 75.

Attest:

C criminal BAKE? PUT C. Lil-1552' Commissioner of Patents j'lttesting Officer and Trademarks

Claims

1. A RELATIVELY LOW PRESSURE HYDROTREATING PROCESS PERFORMED IN A FIRST AND RELATIVELY LOW PRESSURE RECTOR, COMPRISING PASSING A FIRST FEED OIL COMPRISING MIDDLE DISTILLATE STRAIGHT RUN FEED OIL AND HYDROGEN DOWNWARDLY OVER A HYDRODESULFURIZATION CATALYST THAT HAS BEEN DEACTIVATED IN A PRIOR RELATIVELY HIGH PRESSURE HYDRODESULFURIZATION PROCESS, SAID PRIOR PROCESS BEING OPERATED IN A SECOND AND HIGH PRESSURE OF AT LEAST FLOW OPERATION WITH A SECOND FEED OIL AT A PRESSURE OF AT LEAS 600 PSI AND AT A TEMPERATURE BETWEEN 650* AND 800*F. UNTIL SAID CATALYST PERMANENTLY POSSESSED INSUFFICIENT DESULFURIZATION ACTIVITY FOR SAID HIGH PRESSURE PROCESS, SAID CATALYST THEREUPON BEING REMOVED FROM SAID SECOND REACTOR AND CHARGED TO SAID FIRST AND LOW PRESSURE REACTOR FOR HYDROTREATMENT OF SAID FIRST FEED OIL AT A PRESSURE NO HIGHER THAN ABOUT 150 PSI AND AT A TEMPERATURE BETWEEN 400* AND 550*F.

3. The process of claim 1 wherein said middle distillate feeds boil in the range 350* to 700*F.

4. The process of claim 1 wherein the catalyst comprises supported Group VI and Group VIII metals and the pressure is no higher than 100 psi.

5. The process of claim 1 wherein the temperature in said low pressure reactor is between 400* and 550*F.

6. The process of claim 1 wherein the temperature in said low pressure reactor is below 500*F.

7. The process of claim 1 wherein the temperature in said low pressure reactor is below 450*F.

9. The process of claim 1 wherein not more than 20 weight percent of the total sulfur in the feed is removed in the low pressure reactor.

10. The process of claim 1 wherein said middle distillates are furnace oil, kerosene or jet fuel.

11. The process of claim 1 wherein chemical hydrogen consumption excluding unit losses in said low pressure reactor is less than 10 standard cubic feet per barrel.

12. The process of claim 1 wherein unit hydrogen consumption including losses in said low pressure reactor is less than 15 standard cubic feet per barrel.

15. A combination first relatively high pressure and second relatively low pressure hydrotreating process comprising passing a first middle distillate straight run oil having a total sulfur content greater than 0.2 weight percent derived from a first crude oil downwardly over a supported Group VI and Group VIII hydrodesulfurization catalyst in a first and high pressure hydrodesulfurization reactor at a pressure above 600 psi and at a temperature between 650* and 800*F. to reduce the total sulfur content of said first oil below 0.2 weight percent until said catalyst is permanently deactivated and possesses insufficient desulfurization activity for said high pressure process, removing said catalyst from said high pressure reactor and passing it to a second and relatively low pressure reactor operated at a pressure below about 150 psi, passing a second middle distillate oil having a total sulfur content less than 0.2 weight percent derived from a second crude oil downwardly over said deactivated catalyst at a pressure no higher than about 150 psi and at a temperature between 400* and 550*F. so that the chemical hydrogen consumption in said second reactor is above 0 but below 10 standard cubic feet per barrel.

17. The process of claim 15 wherein said middle distillate feeds boil in the range 350* to 700*F.

18. The process of claim 15 wherein the catalyst comprises supported Group VI and Group VIII metals and the pressure is no more than 100 psi.

19. The process of claim 15 wherein the temperature in said low pressure reactor is between 400* and 550*F.

20. The process of claim 15 wherein the temperature in said low pressure reactor is below 500*F.

21. The process of claim 15 wherein the temperature in said low pressure reactor is below 450*F.

22. The process of claim 15 wherein the LHSV in said low pressure reactor is between 4 and 8.

25. The process of claim 15 wherein chemical hydrogen consumption excluding unit losses in said low pressure reactor is less than 5 standard cubic feet per barrel.

26. The process of claim 15 wherein there is a color improvement in the middle distillate feed to the low pressure reactor.

27. The process of claim 15 wherein there is substantially a 100 percent yield in the middle distillate feed to the low pressure reactor.