CA2120046C - Separately removing mercaptans and hydrogen sulfide from gas streams - Google Patents
Separately removing mercaptans and hydrogen sulfide from gas streamsInfo
- Publication number
- CA2120046C CA2120046C CA002120046A CA2120046A CA2120046C CA 2120046 C CA2120046 C CA 2120046C CA 002120046 A CA002120046 A CA 002120046A CA 2120046 A CA2120046 A CA 2120046A CA 2120046 C CA2120046 C CA 2120046C
- Authority
- CA
- Canada
- Prior art keywords
- trisulfides
- disulfides
- gas stream
- bed
- hydrogen sulfide
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
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- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
- C10L3/00—Gaseous fuels; Natural gas; Synthetic natural gas obtained by processes not covered by subclass C10G, C10K; Liquefied petroleum gas
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/02—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by adsorption, e.g. preparative gas chromatography
- B01D53/04—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by adsorption, e.g. preparative gas chromatography with stationary adsorbents
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/34—Chemical or biological purification of waste gases
- B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
- B01D53/86—Catalytic processes
- B01D53/8603—Removing sulfur compounds
- B01D53/8606—Removing sulfur compounds only one sulfur compound other than sulfur oxides or hydrogen sulfide
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
- B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
- B01J23/74—Iron group metals
- B01J23/745—Iron
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C7/00—Purification; Separation; Use of additives
- C07C7/148—Purification; Separation; Use of additives by treatment giving rise to a chemical modification of at least one compound
- C07C7/14833—Purification; Separation; Use of additives by treatment giving rise to a chemical modification of at least one compound with metals or their inorganic compounds
- C07C7/1485—Purification; Separation; Use of additives by treatment giving rise to a chemical modification of at least one compound with metals or their inorganic compounds oxides; hydroxides; salts
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2253/00—Adsorbents used in seperation treatment of gases and vapours
- B01D2253/10—Inorganic adsorbents
- B01D2253/102—Carbon
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2253/00—Adsorbents used in seperation treatment of gases and vapours
- B01D2253/30—Physical properties of adsorbents
- B01D2253/302—Dimensions
- B01D2253/306—Surface area, e.g. BET-specific surface
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2256/00—Main component in the product gas stream after treatment
- B01D2256/24—Hydrocarbons
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2257/00—Components to be removed
- B01D2257/30—Sulfur compounds
- B01D2257/304—Hydrogen sulfide
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2257/00—Components to be removed
- B01D2257/30—Sulfur compounds
- B01D2257/306—Organic sulfur compounds, e.g. mercaptans
Abstract
The present invention provides a method for separately removing mercaptans and hydrogen sulfide from a gas stream by passing the gas through a bed which includes iron oxide which catalyzes the formation of disulfides and trisulfides from mercaptans and also reacts with at least part of the hydrogen sulfide to form acid-stable solids; causing the di- and trisulfides to exit the bed in the gas phase; and removing and recovering the di- and trisulfides by adsorption or condensation.
Any remaining hydrogen sulfide may be scavenged from the gas stream by passage through a bed containing iron oxide similar to that used first above.
Any remaining hydrogen sulfide may be scavenged from the gas stream by passage through a bed containing iron oxide similar to that used first above.
Description
a~2oo~s SEPARATELY REMOVING MERCAPTANS AND
HYDROGEN SULFIDE FROM GAS STREAMS
The present invention teaches how to remove mercaptans from gas streams also containing hydrogen sulfide with subsequent recovery of disulfides and trisulfides.
Reduced sulfur compounds are often found in gas streams associated with petroleum storage and transfer facilities, sewage treatment plants and pulp and paper mills. Among the most common of these compounds are hydrogen sulfide, which has the odor of rotten eggs and is toxic and corrosive; and mercaptans, espe-cially methyl and ethyl mercaptans, which have very pungent and undesirable odors. It is desirable to remove these compounds prior to further processing or transporting to prevent atmos-pheric pollution and to protect workers and equipment.
Most methods for removing reduced sulfur compounds are primarily directed at hydrogen sulfide, and some of the most widely used hydrogen sulfide removal processes, such as amine scrubbing, are not particularly efficient in removing mercaptans.
Mercaptan removal processes shown in the prior art either oxidize mercaptans to disulfides or to sulfur dioxide as the first step in a Clause sulfur recovery process (U. B. Patent No. 4,422,958), or to sulfates or sulfonates (U.S. Patent Nos. 4,552,734 and 4,552,735), or absorb them onto such adsorbents as treated acti-vated carbon (U. S. Patent Nos. 4,256,728 or 4,072,480).
Mercaptan oxidation to disulfides is well known, but is usually carried out by contacting the mercaptan-containing gas stream with an oxidation catalyst and an oxidation agent such as oxygen in an aqueous alkaline solution. Variations of such catalysts are shown in U.S. Patent Nos. 5,244,643 (sulfonated metal phthalocyanine). 4,491,563 (nickel oxide with oxide of a rare earth metal), 4,311,680 (oxides of iron, chromium, cobalt, lead, manganese, molybdenum, nickel, copper, vanadium zinc, tungsten or 21200 ~6 antimony), or 2,966,453 (porphyrin).
Application of these processes to many industrial situ-ations has involved difficult problems in practice. For example, since it is often desirable to remove both hydrogen sulfide and mercaptans from gas streams, it would be advantageous to be able to remove both by using only one type of reactant or catalytic agent. Often, however, the known mercaptan removal processes re-move hydrogen sulfide inefficiently or not at all.
Additionally, since most mercaptan conversion catalysts which are used in dry beds are supported on inert particulate ma-terials, it is important to keep their surfaces unfouled. How-ever, condensation of the higher-boiling disulfides formed from mercaptans can coat such particulates) thus reducing their activ-ity and their capacity for removing both mercaptans and hydrogen sulf ide .
Finally, it has been difficult to recover pure streams of disulfides in prior art methods without extensive processing.
(See, for example, Mercaptan removal rate exceeds 99~ at Canadian gas plant, by B. Judd, Oil & Journal, p. 81-83 (Aug. 16, 1993)), Disulfides formed when mercaptans are oxidized in aqueous alka-line solution have higher affinity for an organic phase and can be extracted from the aqueous phase by a hydrocarbon, but han-dling of the separate liquid phase and recovery of relatively pure disulfides from the aqueous/organic mixture requires much additional equipment.
Thus, a method to separately remove hydrogen sulfide and mercaptans, from a gas stream by using only a single type of reactive or catalytic agent which allowed for the recovery of economically valuable disulfides and minimized the fouling of the reactive or catalytic agent would be very advantageous.
These advantages and others are provided by the process of the present invention which separately removes mercaptans and b t.
at least part of any hydrogen sulfide from a hydrocarbon gas stream by: providing a bed containing moistened particles includ-ing iron oxide of the type which is not only reactive to hydrogen sulfide but which also catalyzes the formation of disulfides and trisulfides from mercaptans; passing the gas stream into and through the bed, and in so doing, converting the mercaptans to disulfides and trisulfides and reacting at least part of any hy-drogen sulfide to solid products which remain in the bed; causing the gas stream to exit from the bed while the disulfides and trisulfides remain therein in substantially gaseous phase; and removing the disulfides and trisulfides from the gas stream.
In another aspect, the present invention provides a process for removing mercaptans and at least a portion of the hydrogen sulfide from a hydrocarbon gas stream, comprising the steps of:
a. providing a bed containing moistened particles support-ing a particulate form of iron oxide composed of a crystalline phase of Fe304 together with an amorphous Fe203 moiety having a surface area of at least 4.O:m2/g;
b~ passing the gas stream into and through the bed, and in so doing, converting the mercaptans to gaseous disulfides and trisulfides, and reacting at least part of any hydrogen sulfide to solid products which remain in the bed;
c. causing the gas stream to exit from the bed while the disulfides and trisulfides remain in substantially gaseous phase; and d. removing the disulfides and trisulfides from the gas stream.
HYDROGEN SULFIDE FROM GAS STREAMS
The present invention teaches how to remove mercaptans from gas streams also containing hydrogen sulfide with subsequent recovery of disulfides and trisulfides.
Reduced sulfur compounds are often found in gas streams associated with petroleum storage and transfer facilities, sewage treatment plants and pulp and paper mills. Among the most common of these compounds are hydrogen sulfide, which has the odor of rotten eggs and is toxic and corrosive; and mercaptans, espe-cially methyl and ethyl mercaptans, which have very pungent and undesirable odors. It is desirable to remove these compounds prior to further processing or transporting to prevent atmos-pheric pollution and to protect workers and equipment.
Most methods for removing reduced sulfur compounds are primarily directed at hydrogen sulfide, and some of the most widely used hydrogen sulfide removal processes, such as amine scrubbing, are not particularly efficient in removing mercaptans.
Mercaptan removal processes shown in the prior art either oxidize mercaptans to disulfides or to sulfur dioxide as the first step in a Clause sulfur recovery process (U. B. Patent No. 4,422,958), or to sulfates or sulfonates (U.S. Patent Nos. 4,552,734 and 4,552,735), or absorb them onto such adsorbents as treated acti-vated carbon (U. S. Patent Nos. 4,256,728 or 4,072,480).
Mercaptan oxidation to disulfides is well known, but is usually carried out by contacting the mercaptan-containing gas stream with an oxidation catalyst and an oxidation agent such as oxygen in an aqueous alkaline solution. Variations of such catalysts are shown in U.S. Patent Nos. 5,244,643 (sulfonated metal phthalocyanine). 4,491,563 (nickel oxide with oxide of a rare earth metal), 4,311,680 (oxides of iron, chromium, cobalt, lead, manganese, molybdenum, nickel, copper, vanadium zinc, tungsten or 21200 ~6 antimony), or 2,966,453 (porphyrin).
Application of these processes to many industrial situ-ations has involved difficult problems in practice. For example, since it is often desirable to remove both hydrogen sulfide and mercaptans from gas streams, it would be advantageous to be able to remove both by using only one type of reactant or catalytic agent. Often, however, the known mercaptan removal processes re-move hydrogen sulfide inefficiently or not at all.
Additionally, since most mercaptan conversion catalysts which are used in dry beds are supported on inert particulate ma-terials, it is important to keep their surfaces unfouled. How-ever, condensation of the higher-boiling disulfides formed from mercaptans can coat such particulates) thus reducing their activ-ity and their capacity for removing both mercaptans and hydrogen sulf ide .
Finally, it has been difficult to recover pure streams of disulfides in prior art methods without extensive processing.
(See, for example, Mercaptan removal rate exceeds 99~ at Canadian gas plant, by B. Judd, Oil & Journal, p. 81-83 (Aug. 16, 1993)), Disulfides formed when mercaptans are oxidized in aqueous alka-line solution have higher affinity for an organic phase and can be extracted from the aqueous phase by a hydrocarbon, but han-dling of the separate liquid phase and recovery of relatively pure disulfides from the aqueous/organic mixture requires much additional equipment.
Thus, a method to separately remove hydrogen sulfide and mercaptans, from a gas stream by using only a single type of reactive or catalytic agent which allowed for the recovery of economically valuable disulfides and minimized the fouling of the reactive or catalytic agent would be very advantageous.
These advantages and others are provided by the process of the present invention which separately removes mercaptans and b t.
at least part of any hydrogen sulfide from a hydrocarbon gas stream by: providing a bed containing moistened particles includ-ing iron oxide of the type which is not only reactive to hydrogen sulfide but which also catalyzes the formation of disulfides and trisulfides from mercaptans; passing the gas stream into and through the bed, and in so doing, converting the mercaptans to disulfides and trisulfides and reacting at least part of any hy-drogen sulfide to solid products which remain in the bed; causing the gas stream to exit from the bed while the disulfides and trisulfides remain therein in substantially gaseous phase; and removing the disulfides and trisulfides from the gas stream.
In another aspect, the present invention provides a process for removing mercaptans and at least a portion of the hydrogen sulfide from a hydrocarbon gas stream, comprising the steps of:
a. providing a bed containing moistened particles support-ing a particulate form of iron oxide composed of a crystalline phase of Fe304 together with an amorphous Fe203 moiety having a surface area of at least 4.O:m2/g;
b~ passing the gas stream into and through the bed, and in so doing, converting the mercaptans to gaseous disulfides and trisulfides, and reacting at least part of any hydrogen sulfide to solid products which remain in the bed;
c. causing the gas stream to exit from the bed while the disulfides and trisulfides remain in substantially gaseous phase; and d. removing the disulfides and trisulfides from the gas stream.
For gases in which the content of hydrogen sulfide is higher than the content of mercaptans, an additional step may be added to scavenge the hydrogen sulfide. The added step includes passing the gas stream from which disulfides and trisulfides have been removed through means to scavenge remaining hydrogen sulfide therefrom. This step may simply be a repetition of the first two steps described above which involve providing a bed containing moistened particles including iron oxide and passing the gas stream therethrough to remove remaining hydrogen sulfide.
Gases containing mercaptans and various levels of hydrogen sulfide may be the low molecular weight hydrocarbons such as methane, ethane and propane. Such gases may also contain oxygen, nitrogen and other compounds. Depending on the source of the gas, hydrogen sulfide may be present at levels higher or lower than the mercaptans. Gases escaping from crude oil loading or transfer facilities (especially when the oil has been previously treated by one of the common sulfur removal processes) often contain five or six times as much mercaptans as hydrogen sulfide, with mercaptan levels of up to 700 ppm. being common.
In the process of the present invention, a gas stream containing mercaptans and hydrogen sulfide is first contacted - 3a -with a reactive iron oxide of the type which (a) reacts with hy-drogen sulfide to form products which are environmentally stable.
and (b) also catalyzes the formation of disulfides and trisulfides from volatile mercaptans. specifically methyl and ethyl mercaptan. Since it is desirable to minimize the pressure drop when gas is pumped through beds of the iron oxide material, the iron oxide should preferably be in particulate form and sup-ported on larger particles of a rigid inert mineral material.
We have found the iron oxide which was disclosed in U.S. Patent No. 4,246,244 to be preferred, especially when sup-ported on sized particles of calcined montmorillonite clay. That oxide, whose particles are composed of a crystalline phase of Fe304, together with an amorphous Fe203 moiety, has a surface area of at least 4.0 m2/g. It is available commercially, in a preparation having about 20 lb. of iron oxide per cubic foot of inert support material, as SULFATREAT* available from Gas Sweet-ener Associates. St. Louis, Missouri.
As the gas passes through the bed under conditions which will be defined below, the iron oxide catalyzes the conver-sion of mercaptans, especially methyl and ethyl mercaptan, to di-sulfides and trisulfides which pass out of the bed substantially quantitatively in the gas phase. Such disulfides and trisulfides formed from methyl and ethyl mercaptans are typically dimethyl disulfide, ethyl-methyl disulfide, diethyl disulfide, and analo-gous alkyl trisulfides (hereinafter referred to collectively as "di- and trisulfides" or "disulfides and trisulfides"). Presum-ably, other volatile alkyl and aryl mercaptans would be similarly converted. While this reaction is taking place, the iron oxide also reacts with hydrogen sulfide to form products which are sta-ble under environmental conditions. As described in U.S. Patent No. 4,246,244 to one of the present inventors, such products are typically FeS2, S°, Fe304, and other acid-stable, non-FeS iron * Trade Mark sulfide species. Thus, while the iron oxide catalyzes the forma-tion of di- and trisulfides from mercaptans, it is also being consumed by reacting with hydrogen sulfide.
The rate of conversion of mercaptans to di- and trisulfides appears to be substantially the same as the reaction of iron oxide with hydrogen sulfide. Thus, when hydrogen sulfide is present at lower concentrations than mercaptans, a bed de-signed to completely transform mercaptans to di- and trisulfides will also substantially remove hydrogen sulfide from the gas stream. Conversely, if hydrogen sulfide is present in higher concentrations than mercaptans, a bed designed to completely con-vert the mercaptans may permit some unreacted hydrogen sulfide to pass through the bed.
We have learned that it is very important to operate the first bed (which converts mercaptans to di- and trisulfides) under conditions which allow substantially all of the di- and trisulfides to exit the bed in the gas phase. This prevents di-and trisulfides from condensing on and coating or otherwise foul-ing, the supported iron oxides and thereby maintains their capac-ity or effectiveness. Maintaining the di- and trisulfides in the gas phase also allows their removal from the gas stream sepa-rately from the removal of hydrogen sulfide. It is also impor-taut to operate the bed in downflow mode to minimize the accumu-lation of liquid in the bed) The following tests have been run to determine condi-tions which give the desired result for operation of the conver-sion bed.
A standard feed gas was prepared for use in all tests with a composition given below:
Component Concentration (vol. $
Carbon dioxide 4.97 Nitrogen 54.9 Oxygen 1.52 Methane 34.18 Ethane 0.89 Propane 1.44 Butane 1.65 Pentane 0.39 Hexane 0.04 Heptanes+ 0.02 Before feeding the gas to a bed, it was saturated with water at 20°C., with sulfur compounds added to this gas. The feed gas at 112 KPa, with sulfur compounds added in levels shown below, was fed at 0.030 SCF/min. and 18°C, to a 0.906" ID column of 2' height packed with SULFATREAT* Superficial gas velocity was 6.7 ft./min. After reaching stable operating conditions, composition of the inlet and outlet gas (given as ppm, by volume) was as shown:
Gas Components Inlet Concentration Outlet Concentration hydrogen sulfide 47 8 methyl mercaptan 865 260 ethyl mercaptan 619 155 dimethyl disulfide 57 169 methyl-ethyl 90 420 disulfide diethyl disulfide 82 515 dimethyl trisulfide 41 49 methyl-ethyl 62 83 trisulfide diethyl trisulfide 37 79 Summarizing, hydrogen sulfide and mercaptan levels were reduced with a concomitant increase in levels of di- and trisulfides; however, a significant amount of sulfur products did *Trade Mark - 6 r J
i not leave the bed with the gas stream, but remained in the bed.
A column of 0.906" ID and 2' in height was packed with SULFATREAT * Standard feed gas having the composition given in Example 1, and containing sulfur compounds in levels shown below, was fed into the top of the column at 15°C. and 15 KPa pressure at a flow rate of 0.00473 SCF/min., resulting in a superficial gas velocity of 1.06 ft./min. After reaching stable operating conditions) composition of the inlet and outlet gas (given as ppm. by volume) was as shown:
Gas Component Inlet Concentration Outlet Concentration hydrogen sulfide 152 <1 methyl mercaptan 438 <1 ethyl mercaptan 276 < 1 dimethyl disulfide 12.6 57 methyl-ethyl 2.2 134 disulfide diethyl disulfide 33.7 189 dimethyl trisulfide 37.7 202 methyl-ethyl 17.9 388 trisulfide diethyl trisulfide 9.4 227 During the run there was negligible accumulation of sulfur in the column and substantially all of the mercaptans were converted to di- and trisulfides which exited the column in the gas phase.
It is obvious that many variables affect the perform-ance characteristics of the first bed; with temperature, pres-sure, gas composition, gas velocity, residence time in the bed, type of bed packing, and reactivity of the iron oxide being so"ie of the more obvious. While we cannot predict a rp iori which com-bination of these variables will provide the desired result of * Trade Mark _ 7 _ is_' !F-~., _v substantially total conversion of mercaptans with substantially all of the di- and trisulfides exiting the bed in the gas phase) Example 2 shows that simple variations in testing will readily provide workable proportions and conditions to accomplish this result.
Following the conversion step. the di- and trisulfide~
are removed from the gas stream by methods well known in the ar~.
For exampler. the di- and trisulfides may either be condensed an3 recovered as a substantially pure liquid stream, or adsorbed on=o a solid adsorbent, preferably activated carbon. If activated carbon is used. the di- and trisulfides may be recovered and the activated carbon regenerated by well known techniques such as steam stripping or by extraction with a solvent with a high af-finity for the di- and trisulfide oils. Recovered di- and trisulfides may be sold or may be added back to a liquid hydro-carbon as desired.
Since the affinity of activated carbon for di- and trisulfides is very high, gas velocities in a carbon bed may be much higher than those in an iron oxide bed. Thus, a carbon col-umn may be of smaller diameter than the mercaptan converting be3 needed for a given gas stream.
If a significant amount of hydrogen sulfide remains iz the gas stream exiting the conversion step, it may still be pos-sible to use activated carbon for di- and trisulfide removal since the affinity of activated carbon for di- ar.3 trisulfides is greater than for hydrogen sulfide. In this case, however, the carbon column must be designed to adsorb all of the di- and trisulfides while passing through substantially all of the hydro-gen sulfide.
Alternatively, preferential condensation of the di- and trisulfides without condensing hydrogen sulfide could accomplish the same separation. Selection of a condenser is easily done by _ g _ one skilled in the art since the boiling points of the di- and trisulfides (109.7°C. for dimethyl disulfide, and 154°C. for di-ethyl disulfide) are significantly higher than that of hydrogen sulfide (-60.7°C.). The condenser design may be any conventional type such as shell-and-tube) plate-type, or flash chiller type.
The di- and trisulfides may even be condensed by direct contact with a stream of liquid such as a hydrocarbon liquid.
When hydrogen sulfide remains in the gas after the con-version and di- and trisulfide removal steps, it may be scavenged by passing the gas stream through a final iron oxide bed. The iron oxide used in the final bed may be the same as is used in the bed for the conversion step, preferably as in the SULFATREAT
material described above. Alternatively, any adsorbent or reac-tant which removes hydrogen sulfide from a gas stream could be used.
The present invention permits users to purchase and stock only one type of agent which cannot only catalyze the con-version of mercaptans but can also react with hydrogen sulfide to form environmentally stable end products. Previously, it was not known how to carry out separate removal of hydrogen sulfide and mercaptans with use of a single reactive/catalytic agent.
Additionally, the process of the present invention per-mits the recovery of di- and trisulfides in a relatively pure and separate stream without extensive further processing. The recov-ered di- and trisulfide oils may then be sold, added back to a liquid hydrocarbon stream or disposed of as most advantageous.
Finally, by causing the di- and trisulfides to pass through the mercaptan converting bed in gaseous form, coating of the bed particles is reduced and the reactive capacity of the iron oxide is extended.
As various modifications may be made in the procedures herein described and illustrated without departing from the scope * Trade Mark _ 9 -~:~
,..
zlzoo~s .
of the invention, it is intended that all matter contained in the foregoing description shall be taken as illustrative rather than limiting.
Gases containing mercaptans and various levels of hydrogen sulfide may be the low molecular weight hydrocarbons such as methane, ethane and propane. Such gases may also contain oxygen, nitrogen and other compounds. Depending on the source of the gas, hydrogen sulfide may be present at levels higher or lower than the mercaptans. Gases escaping from crude oil loading or transfer facilities (especially when the oil has been previously treated by one of the common sulfur removal processes) often contain five or six times as much mercaptans as hydrogen sulfide, with mercaptan levels of up to 700 ppm. being common.
In the process of the present invention, a gas stream containing mercaptans and hydrogen sulfide is first contacted - 3a -with a reactive iron oxide of the type which (a) reacts with hy-drogen sulfide to form products which are environmentally stable.
and (b) also catalyzes the formation of disulfides and trisulfides from volatile mercaptans. specifically methyl and ethyl mercaptan. Since it is desirable to minimize the pressure drop when gas is pumped through beds of the iron oxide material, the iron oxide should preferably be in particulate form and sup-ported on larger particles of a rigid inert mineral material.
We have found the iron oxide which was disclosed in U.S. Patent No. 4,246,244 to be preferred, especially when sup-ported on sized particles of calcined montmorillonite clay. That oxide, whose particles are composed of a crystalline phase of Fe304, together with an amorphous Fe203 moiety, has a surface area of at least 4.0 m2/g. It is available commercially, in a preparation having about 20 lb. of iron oxide per cubic foot of inert support material, as SULFATREAT* available from Gas Sweet-ener Associates. St. Louis, Missouri.
As the gas passes through the bed under conditions which will be defined below, the iron oxide catalyzes the conver-sion of mercaptans, especially methyl and ethyl mercaptan, to di-sulfides and trisulfides which pass out of the bed substantially quantitatively in the gas phase. Such disulfides and trisulfides formed from methyl and ethyl mercaptans are typically dimethyl disulfide, ethyl-methyl disulfide, diethyl disulfide, and analo-gous alkyl trisulfides (hereinafter referred to collectively as "di- and trisulfides" or "disulfides and trisulfides"). Presum-ably, other volatile alkyl and aryl mercaptans would be similarly converted. While this reaction is taking place, the iron oxide also reacts with hydrogen sulfide to form products which are sta-ble under environmental conditions. As described in U.S. Patent No. 4,246,244 to one of the present inventors, such products are typically FeS2, S°, Fe304, and other acid-stable, non-FeS iron * Trade Mark sulfide species. Thus, while the iron oxide catalyzes the forma-tion of di- and trisulfides from mercaptans, it is also being consumed by reacting with hydrogen sulfide.
The rate of conversion of mercaptans to di- and trisulfides appears to be substantially the same as the reaction of iron oxide with hydrogen sulfide. Thus, when hydrogen sulfide is present at lower concentrations than mercaptans, a bed de-signed to completely transform mercaptans to di- and trisulfides will also substantially remove hydrogen sulfide from the gas stream. Conversely, if hydrogen sulfide is present in higher concentrations than mercaptans, a bed designed to completely con-vert the mercaptans may permit some unreacted hydrogen sulfide to pass through the bed.
We have learned that it is very important to operate the first bed (which converts mercaptans to di- and trisulfides) under conditions which allow substantially all of the di- and trisulfides to exit the bed in the gas phase. This prevents di-and trisulfides from condensing on and coating or otherwise foul-ing, the supported iron oxides and thereby maintains their capac-ity or effectiveness. Maintaining the di- and trisulfides in the gas phase also allows their removal from the gas stream sepa-rately from the removal of hydrogen sulfide. It is also impor-taut to operate the bed in downflow mode to minimize the accumu-lation of liquid in the bed) The following tests have been run to determine condi-tions which give the desired result for operation of the conver-sion bed.
A standard feed gas was prepared for use in all tests with a composition given below:
Component Concentration (vol. $
Carbon dioxide 4.97 Nitrogen 54.9 Oxygen 1.52 Methane 34.18 Ethane 0.89 Propane 1.44 Butane 1.65 Pentane 0.39 Hexane 0.04 Heptanes+ 0.02 Before feeding the gas to a bed, it was saturated with water at 20°C., with sulfur compounds added to this gas. The feed gas at 112 KPa, with sulfur compounds added in levels shown below, was fed at 0.030 SCF/min. and 18°C, to a 0.906" ID column of 2' height packed with SULFATREAT* Superficial gas velocity was 6.7 ft./min. After reaching stable operating conditions, composition of the inlet and outlet gas (given as ppm, by volume) was as shown:
Gas Components Inlet Concentration Outlet Concentration hydrogen sulfide 47 8 methyl mercaptan 865 260 ethyl mercaptan 619 155 dimethyl disulfide 57 169 methyl-ethyl 90 420 disulfide diethyl disulfide 82 515 dimethyl trisulfide 41 49 methyl-ethyl 62 83 trisulfide diethyl trisulfide 37 79 Summarizing, hydrogen sulfide and mercaptan levels were reduced with a concomitant increase in levels of di- and trisulfides; however, a significant amount of sulfur products did *Trade Mark - 6 r J
i not leave the bed with the gas stream, but remained in the bed.
A column of 0.906" ID and 2' in height was packed with SULFATREAT * Standard feed gas having the composition given in Example 1, and containing sulfur compounds in levels shown below, was fed into the top of the column at 15°C. and 15 KPa pressure at a flow rate of 0.00473 SCF/min., resulting in a superficial gas velocity of 1.06 ft./min. After reaching stable operating conditions) composition of the inlet and outlet gas (given as ppm. by volume) was as shown:
Gas Component Inlet Concentration Outlet Concentration hydrogen sulfide 152 <1 methyl mercaptan 438 <1 ethyl mercaptan 276 < 1 dimethyl disulfide 12.6 57 methyl-ethyl 2.2 134 disulfide diethyl disulfide 33.7 189 dimethyl trisulfide 37.7 202 methyl-ethyl 17.9 388 trisulfide diethyl trisulfide 9.4 227 During the run there was negligible accumulation of sulfur in the column and substantially all of the mercaptans were converted to di- and trisulfides which exited the column in the gas phase.
It is obvious that many variables affect the perform-ance characteristics of the first bed; with temperature, pres-sure, gas composition, gas velocity, residence time in the bed, type of bed packing, and reactivity of the iron oxide being so"ie of the more obvious. While we cannot predict a rp iori which com-bination of these variables will provide the desired result of * Trade Mark _ 7 _ is_' !F-~., _v substantially total conversion of mercaptans with substantially all of the di- and trisulfides exiting the bed in the gas phase) Example 2 shows that simple variations in testing will readily provide workable proportions and conditions to accomplish this result.
Following the conversion step. the di- and trisulfide~
are removed from the gas stream by methods well known in the ar~.
For exampler. the di- and trisulfides may either be condensed an3 recovered as a substantially pure liquid stream, or adsorbed on=o a solid adsorbent, preferably activated carbon. If activated carbon is used. the di- and trisulfides may be recovered and the activated carbon regenerated by well known techniques such as steam stripping or by extraction with a solvent with a high af-finity for the di- and trisulfide oils. Recovered di- and trisulfides may be sold or may be added back to a liquid hydro-carbon as desired.
Since the affinity of activated carbon for di- and trisulfides is very high, gas velocities in a carbon bed may be much higher than those in an iron oxide bed. Thus, a carbon col-umn may be of smaller diameter than the mercaptan converting be3 needed for a given gas stream.
If a significant amount of hydrogen sulfide remains iz the gas stream exiting the conversion step, it may still be pos-sible to use activated carbon for di- and trisulfide removal since the affinity of activated carbon for di- ar.3 trisulfides is greater than for hydrogen sulfide. In this case, however, the carbon column must be designed to adsorb all of the di- and trisulfides while passing through substantially all of the hydro-gen sulfide.
Alternatively, preferential condensation of the di- and trisulfides without condensing hydrogen sulfide could accomplish the same separation. Selection of a condenser is easily done by _ g _ one skilled in the art since the boiling points of the di- and trisulfides (109.7°C. for dimethyl disulfide, and 154°C. for di-ethyl disulfide) are significantly higher than that of hydrogen sulfide (-60.7°C.). The condenser design may be any conventional type such as shell-and-tube) plate-type, or flash chiller type.
The di- and trisulfides may even be condensed by direct contact with a stream of liquid such as a hydrocarbon liquid.
When hydrogen sulfide remains in the gas after the con-version and di- and trisulfide removal steps, it may be scavenged by passing the gas stream through a final iron oxide bed. The iron oxide used in the final bed may be the same as is used in the bed for the conversion step, preferably as in the SULFATREAT
material described above. Alternatively, any adsorbent or reac-tant which removes hydrogen sulfide from a gas stream could be used.
The present invention permits users to purchase and stock only one type of agent which cannot only catalyze the con-version of mercaptans but can also react with hydrogen sulfide to form environmentally stable end products. Previously, it was not known how to carry out separate removal of hydrogen sulfide and mercaptans with use of a single reactive/catalytic agent.
Additionally, the process of the present invention per-mits the recovery of di- and trisulfides in a relatively pure and separate stream without extensive further processing. The recov-ered di- and trisulfide oils may then be sold, added back to a liquid hydrocarbon stream or disposed of as most advantageous.
Finally, by causing the di- and trisulfides to pass through the mercaptan converting bed in gaseous form, coating of the bed particles is reduced and the reactive capacity of the iron oxide is extended.
As various modifications may be made in the procedures herein described and illustrated without departing from the scope * Trade Mark _ 9 -~:~
,..
zlzoo~s .
of the invention, it is intended that all matter contained in the foregoing description shall be taken as illustrative rather than limiting.
Claims (13)
1. For separately removing mercaptans and at least part of any hydrogen sulfide from a hydrocarbon gas stream, the process comprising the steps of a. providing a bed containing moistened particles including iron oxide of the type which is not only reactive to hydrogen sulfide but which also catalyzes the formation of disulfides and trisulfides from mercaptans, b. passing the gas stream into and through the bed, and in so doing, converting the mercaptans to disulfides and trisulfides and reacting at least part of any hydrogen sulfide to solid products which remain in the bed, c. causing the gas stream to exit from the bed while the disulfides and trisulfides remain therein in substantially gaseous phase, and d. removing the disulfides and trisulfides from the gas stream.
2. The process defined in Claim 1, together with the subsequent step of passing the gas stream from which disulfides and trisulfides have been removed through means to scavenge remaining hydrogen sulfide therefrom.
3. The process defined in Claim 2, wherein said means to scavenge remaining hydrogen sulfide comprises a repetition of steps a and b.
4. The process defined in Claim 1, wherein the iron oxide is in particulate form and is composed of a crystalline phase of Fe3 0 4 together with an amorphous Fe2 0 3 moiety and has a surface area of at least 4.0 m2g.
5. The process defined in Claim 1, wherein step d.
comprises adsorbing the disulfides and trisulfides onto a bed of activated carbon from which the disulfides and trisulfides can be subsequently recovered by desorption.
comprises adsorbing the disulfides and trisulfides onto a bed of activated carbon from which the disulfides and trisulfides can be subsequently recovered by desorption.
6. The process defined in Claim 1, wherein step d.
comprises causing the disulfides and trisulfides in the gas stream to condense to form a liquid.
comprises causing the disulfides and trisulfides in the gas stream to condense to form a liquid.
7. The process defined in Claim 2, wherein the step involving removing the disulfides and trisulfides from the gas stream comprises passing the gas stream into a bed of activated carbon, adsorbing substantially all of the disulfides and trisulfides onto the activated carbon while passing substantially all of the hydrogen sulfide remaining in the gas stream through such bed, and regenerating the activated carbon and recovering the adsorbed disulfides and trisulfides.
8. The process defined in Claim 2, wherein the step involving removing the disulfides and trisulfides from the gas stream comprises causing the disulfides and trisulfides in the gas stream to condense to form a liquid while permitting substantially all hydrogen sulfide remaining in the gas stream to remain in gaseous phase.
9. A process for removing mercaptans and at least a portion of the hydrogen sulfide from a hydrocarbon gas stream, comprising the steps of:
a. providing a bed containing moistened particles supporting a particulate form of iron oxide composed of a crystalline phase of Fe3O4 together with an amorphous Fe2O3 moiety having a surface area of at least 4.0 m2/g;
b. passing the gas stream into and through the bed, and in so doing, converting the mercaptans to gaseous disulfides and trisulfides, and reacting at least part of any hydrogen sulfide to solid products which remain in the bed;
c. causing the gas stream to exit from the bed while the disulfides and trisulfides remain in substantially gaseous phase; and d. removing the disulfides and trisulfides from the gas stream.
a. providing a bed containing moistened particles supporting a particulate form of iron oxide composed of a crystalline phase of Fe3O4 together with an amorphous Fe2O3 moiety having a surface area of at least 4.0 m2/g;
b. passing the gas stream into and through the bed, and in so doing, converting the mercaptans to gaseous disulfides and trisulfides, and reacting at least part of any hydrogen sulfide to solid products which remain in the bed;
c. causing the gas stream to exit from the bed while the disulfides and trisulfides remain in substantially gaseous phase; and d. removing the disulfides and trisulfides from the gas stream.
10. The process defined in Claim 9, further comprising the subsequent step of recycling the gas stream from which disulfides and trisulfides have been removed back through steps a and b of Claim 9.
11. The process defined in Claim 9, wherein step d comprises adsorbing the disulfides and trisulfides onto a bed of activated carbon from which the disulfides and trisulfides can be subsequently recovered by desorption.
12. The process defined in Claim 9, wherein the step involving removing the disulfides and trisulfides from the gas stream comprises passing the gas stream into a bed of activated carbon, adsorbing substantially all of the disulfides and trisulfides onto the activated carbon while passing substantially all of the hydrogen sulfide remaining in the gas stream through such bed, and regenerating the activated carbon and recovering the adsorbed sulfides and trisulfides.
13. The process defined in Claim 9, wherein the step involving removing the disulfides and trisulfides from the gas stream comprises causing the disulfides and trisulfides in the gas stream to condense to form a liquid while permitting substantially all hydrogen sulfide remaining in the gas stream to remain in gaseous phase.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US18714694A | 1994-01-27 | 1994-01-27 | |
| US08/187,146 | 1994-01-27 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2120046A1 CA2120046A1 (en) | 1995-07-28 |
| CA2120046C true CA2120046C (en) | 1999-09-14 |
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ID=22687783
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002120046A Expired - Fee Related CA2120046C (en) | 1994-01-27 | 1994-03-25 | Separately removing mercaptans and hydrogen sulfide from gas streams |
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| Country | Link |
|---|---|
| US (1) | US5478541A (en) |
| CA (1) | CA2120046C (en) |
Families Citing this family (15)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5858912A (en) * | 1997-04-02 | 1999-01-12 | The Sulfatreat Company | Non-aqueous liquids for moistening an oxide-bearing carrier in sulfur sweetening |
| US5792438A (en) * | 1996-08-20 | 1998-08-11 | The Sulfatreat Company | Process and composition for increasing the reactivity of sulfur scavenging iron oxides |
| US6500237B2 (en) | 1997-08-12 | 2002-12-31 | Adi International Inc. | Removing hydrogen sulfide from a gaseous mixture using ferric ions bonded to calcined diatomite |
| US6063346A (en) * | 1998-06-05 | 2000-05-16 | Intevep, S. A. | Process for scavenging hydrogen sulfide and mercaptan contaminants from a fluid |
| US6887445B2 (en) * | 1998-08-04 | 2005-05-03 | M-I L.L.C. | Process for sulfur scavenging |
| US7264786B2 (en) * | 2004-04-21 | 2007-09-04 | Bj Services Company | Method of scavenging hydrogen sulfide and/or mercaptans from fluid and gas streams |
| US8404031B1 (en) | 2009-10-06 | 2013-03-26 | Michael Callaway | Material and method for the sorption of hydrogen sulfide |
| US8354361B2 (en) | 2009-12-21 | 2013-01-15 | Baker Hughes Incorporated | Method of using dithiazines and derivatives thereof in the treatment of wells |
| US9296940B2 (en) | 2009-12-21 | 2016-03-29 | Baker Hughes Incorporated | Dithiazine derivatives |
| US8022017B2 (en) * | 2009-12-21 | 2011-09-20 | Baker Hughes Incorporated | Method of using dithiazine to inhibit corrosion |
| US8022018B2 (en) * | 2009-12-21 | 2011-09-20 | Baker Hughes Incorporated | Quaternized dithiazines and method of using same in treatment of wells |
| US8759252B1 (en) | 2010-10-06 | 2014-06-24 | Michael D. and Anita Kaye | Material and method for the sorption of hydrogen sulfide |
| CN102172512A (en) * | 2011-03-22 | 2011-09-07 | 翟常忠 | Desulphurizer capable of removing smelly impurities such as thiophene, mercaptan, thioether and hydrogen sulphide by catalytic oxidation and preparation method and application of desulphurizer |
| US8920568B2 (en) | 2011-03-28 | 2014-12-30 | Baker Hughes Incorporated | Method for the dissolution of amorphous dithiazine |
| CN103506130B (en) * | 2013-10-22 | 2016-02-10 | 黄河三角洲京博化工研究院有限公司 | A kind of Catalysts and its preparation method of synthesis of methyl mercaptan |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2850352A (en) * | 1955-01-20 | 1958-09-02 | William W Odell | Beneficiation of gases and vapors |
| BE575509A (en) * | 1958-02-13 | |||
| US2966453A (en) * | 1959-03-13 | 1960-12-27 | Universal Oil Prod Co | Oxidation of mercapto compounds |
| US3391988A (en) * | 1964-07-10 | 1968-07-09 | Gelsenberg Benzin Ag | Process for the removal of mercaptans from gases |
| US3574093A (en) * | 1969-01-22 | 1971-04-06 | Universal Oil Prod Co | Combination process for treatment of hydrocarbon streams containing mercapto compounds |
| US4009251A (en) * | 1973-08-27 | 1977-02-22 | Rhodia, Inc. | Process for the removal of hydrogen sulfide from gaseous streams by catalytic oxidation of hydrogen sulfide to sulfur while inhibiting the formation of sulfur oxides |
| US3923645A (en) * | 1973-09-07 | 1975-12-02 | Ashland Oil Inc | Method for oxidizing mercaptans occurring in petroleum refining streams |
| US4090954A (en) * | 1976-12-22 | 1978-05-23 | Ashland Oil, Inc. | Method for oxidizing mercaptans and mercaptide compounds from aqueous alkaline solutions and hydrocarbon distillates |
| US4072480A (en) * | 1977-01-07 | 1978-02-07 | Calgon Corporation | Dual impregnated activated carbon for improved removal of malodorous sulfur compounds |
| JPS5551422A (en) * | 1978-10-11 | 1980-04-15 | Takeda Chem Ind Ltd | Deodorization |
| US4246244A (en) * | 1979-05-31 | 1981-01-20 | Gas Sweetener, Inc. | Process for scavenging hydrogen sulfide from hydrocarbon gases |
| US4311680A (en) * | 1980-11-20 | 1982-01-19 | The Goodyear Tire & Rubber Company | Method for removal of sulfur compounds from a gas stream |
| FR2501532B1 (en) * | 1981-03-13 | 1985-12-13 | Rhone Poulenc Spec Chim | CATALYST AND METHOD FOR THE TREATMENT OF INDUSTRIAL WASTE GASES CONTAINING SULFUR COMPOUNDS |
| US4491563A (en) * | 1982-12-10 | 1985-01-01 | Phillips Petroleum Company | Process for deodorizing a paraffinic hydrocarbon feedstock |
| US4552735A (en) * | 1983-04-20 | 1985-11-12 | Aquafine Corporation | Process for removing total reduced sulfur compounds from industrial gases using manganese dioxide |
| US4552734A (en) * | 1983-09-08 | 1985-11-12 | Aquafine Corporation | Fluidization process for removing total reduced sulfur compounds from industrial gases |
| FR2581560B1 (en) * | 1985-05-10 | 1987-06-05 | Elf Aquitaine | REGENERATIVE PROCESS FOR THE REMOVAL OF MERCAPTANS CONTAINED IN A GAS |
| US4875997A (en) * | 1988-11-17 | 1989-10-24 | Montana Refining Company | Process for treating hydrocarbons containing mercaptans |
| US5264194A (en) * | 1989-08-30 | 1993-11-23 | Irwin Fox | Restoring reactivity of gas sweetening oxide beds |
| US5320992A (en) * | 1989-08-30 | 1994-06-14 | Irwin Fox | Disposable oxide carrier for scavenging hydrogen sulfide |
| US5244643A (en) * | 1992-02-21 | 1993-09-14 | Uop | Treatment of oxygen containing gaseous hydrocarbons for mercaptan removal |
-
1994
- 1994-03-25 CA CA002120046A patent/CA2120046C/en not_active Expired - Fee Related
-
1995
- 1995-05-12 US US08/440,114 patent/US5478541A/en not_active Expired - Lifetime
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| Publication number | Publication date |
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| US5478541A (en) | 1995-12-26 |
| CA2120046A1 (en) | 1995-07-28 |
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