CA2230849A1 - Gas treating process - Google Patents

Abstract

A process for removing hydrogen sulfide and other components, such as water, low molecular weight hydrocarbons, and carbon dioxide, which are contained in a gaseous feed stream and converting hydrogen sulfide to elemental sulfur and hydrogen. In accordance with the process, a gaseous feed stream containing hydrogen sulfide and other components is contacted with a polar organic solvent having a quinone and a complexing agent dissolved therein. The complexing agent must have a pKb value of less than about 13Ø Reaction of the hydrogen sulfide in the gaseous feed stream with quinone results in an increased conversion of quinone to hydroquinone at low reactor temperatures and H2S partial pressures and in increased sulfur recovery. In additon, the presence of a complexing agent increases hydrogen production selectivity in the dehydrogenation of hydroquinone to quinone and hydrogen. The polar organic solvent also functions to dissolve a significant portion of the other components from the gaseous feed stream which are separated and recovered as products.

Description

C;AS TREATING PROCESS

FIELD OF INVENTION:
The ~.ese,.l invention relates to a ~rucess for removing water, low 5 II.DI~ ~ weight h~ oca-Lo,.s and/or ca.~on ~ cide in ~d~ ;Gn to hycJr~6..
sulfide from a ~ceol ~s str~am in one pr~-~3ss i. .~ unit, and more particularly, to such a ~rocess for removing and recovering water, low IIIDI~ wsight hycl-o~-l,G--s and/or cal~GII dioxids from a ~ses~C stream in a single ~Jrocessing unit wherein hydlo~en sulfide which is initially contained in the 10 DPseo~ls feed stream is also converted to elemental sulfur in the same pr~csssi. ,~ unit.
DESCRIPTION OF RELATED ART:
Numerous industrial ~,.vcesses, particularly those pertaining to the petroleum industry, ~e. .e.~le g~-ceo~ ~-s by-products containing hy.lro~en sulfide, 15 either alone or in a mixture with water and/or other gases, such as, methane,carbon dioxide, low mole~ ~ weight hydl uca- L,ons, ~ luyel l, a..,...G"ia etc. In addition, natural gas which is produced from subterranean ficr.,.dlions often cc:,. ~l~i. .s similar gases to those D~ses~ ~-s by-products llsted above.
Many ~.uc~sses have been developed to remove these COIII~JUI .~. .ls from 20 such ç~as ~ dlllS prior to tran:,pG. tdliol . and~or further p~ ssi. ~a ll .ereof. For example, U. S. Patent No. 3,039,251 (Kamlet~ scloses simulld. .eously removing water, hy.lr~gen sulfide, ..,er~apta..s and CalL~GIl ~ e from gas, such as natural gas, by conlac~i--g said gas with tetrahydrothiophene-1, 1-dioxide (s~ ~rul -- .e) or homologues thereof. U. S. Patent No. 4,359,450 (Blytas 25 et al.) ~liscloses the removal of It2S CO2 and COS from ~seo~s slrea...s d .~ by the r~a~tiGI I of H2S to crystalline or solid sulfur, the abSGI ~,lics. I
of CO2 and COS, the desorption of CO2 and COS, the hydrolysis of COS, and the recovery of H2S. In acco~a..ce with the first step of the ~,rucess, the ~ceo~ ~-s stream is conla-,tt:d with an absorL,e"L mixture CGI ,la;"ing an oxidizing 30 reactant. The absorbent employed are those absorbents which have a high degree of selectivity in abso,l,i.,g CO2, COS and H2S, such as propylene carbonate, N-methyl pyrrolidone, and sulfolane. U. S. Patent No. 3,773,896 (Preusser et al.3 ~iscloses a process or washing the ~seo~ ~s acidic SUBSTITUTE SHEET (R~JLE 26~

W O 97/18028 PCTnUS96/15314 components such as carbon dioxide, hydrogen sulfide and hydrogen cyanide from a gas stream by treating the gas stream with a washing agent that absorbs at least a portion of the gaseous acidic components. The washing agent includes a carboxylic acid amide of morpholine preferably containing between 1 and 7 carbon atoms in the carboxyiic acid chain. Propylene carbonate and sulfolane are identified as previously known washing agents. However, all of these prior art processes require further steps or stages to treat hydrogen sulfide by converting it to products which have further utility, such as sulfur,hydrogen, or hydrogen peroxide.
~0 Further, many processes relating to the petroleum industry generate gaseous by-products containing hydrogen sulfide, either alone or in a mixture with other gases, for example, methane, carbon dioxide, nitrogen, ammonia etc.
For many years, these gaseous by-products were oxidized by common oxidation processes, such as the Claus process, to obtain sulfur. In accordance with the Claus process, hydrogen sulfide is oxidized by direct contact with air to produce sulfur and water. However, several disadvantages of air oxidation of hydrogen sulfide, including loss of a valuable hydrogen source, precise air ratecontrol, removal of trace sulfur compounds from spent air, and an upper limit onthe ratio of carbon dioxide to hydrogen sulfide, led to the development of alternative processes for the conversion of hydrogen sulfide in gaseous by-products to sulfur.
As detailed in U. S. Patent No. 4,592,905 to Plummer et al., one such alternative process involves contacting within a reactor a feed gas containing hydrogen sulfide with an anthraquinone which is dissolved in a polar organic solvent. This polar organic solvent preferably has a polarity greater than about3 Debye units. The resulting reaction between hydrogen sulfide and anthraquinone yields sulfur and the corresponding anthrahydroquinone. The sulfur precipitates from the solution in crystalline form and is recovered as a product while the l ~" ,aini"g solution containing dl Ill 11 dh ydroquinone is thermaliy or catalytically regenerated producing the initial anthraquinone form and releasing hydrogen gas. The anthraquinone is recycled back to the reactor and the hydrogen gas is recovered as a product. A significant disadvantage of this process is that the reaction between hydrogen sulfide and anthraquinone W O 97/18028 PCT~US96/15314 proceeds at a relativeiy slow rate, thereby limiting reactor throughput. Anotherdisadvantage of this process is that the feed gas must be cG~I~pressed to provide H2S partial pressures of from about 6 to about 200 atmospheres which significantiy increases the reactor cost. A further disadvantage of this processis that hydrogenolysis by-products, i.e. anthrones and anthranols, produced during anthrahydroquinone regeneration reduce the selectivity of producing hydrogen and anthraquinone.
Thus, a need exists for a process for removing water, low molecular weight hydrocarbons andlor carbon dioxide as products in addition to hydrogen sulfide from a gaseous stream in a single processing unit while converting hydrogen sulfide which is initially contained in the g~seous feed stream to a useful product in the same processing unit. A further need exists for a process for increasing the rate which hydrogen sulfide reacts with quinone in the ~)rocess for converting hydrogen sulfide to sulfur and hydrogen as described above, while decreasing the tl.S partial pressure of such reaction.
Accol d;, Igly, it is an object of the present invention to provide a process for rernoving water, low molecular weight hy.li oca, bons andlor carbon dioxide as products in addition to removing hydrogen sulfide from a gaseous stream while converting hydrogen sulfide which is initially contained in the gaseous feed stream to elemental sulfur in the same processing unit.
It is another object of the present invention to provide a such a process for the concurrent removal of hydrogen sulfide from a gaseous stream and conversion of hydrogen sulfide to sulfur which is economical.
It is still another object of the present invention to provide a process for increasing the rate of reaction between hydrogen sulfide and a quinone which is dissolved in a polar organic solvent.
It is a further object of the present invention to provide a process for increasing the rate of reaction between hydrogen sulfide and a quinone while significantly decreasing the partial pressure of hydrogen sulfide in the gaseousfeed.
It is a still further object of the present invention to provide a process for increasing hydrogen production selectivity during dehydrogenation of hydroquinone.

CA 02230849 l998-02-27 W O 97/18028 PCT~US96/1~314 SUMMARY OF THE INVENTION
To achieve the foregoing and other obiects, and in accor~la, Ice with the purposes of the present invention, as embodied and broadiy described herein, one cha, d~ri~dlio" of the present invention is a ,c rocess of removing hydrogensulfide and other components from a gas. The process coll~p,ises co"La~ g 2 gaseous stream containing hydrogen sulfide with a polar organic solvent having a quinone dissolved therein. S~ ILidliy all of the h~dluyel) sulfide and at least a portion of a second component of said gaseous stream which Is selected from the group consisting of water, low molecular weight hydl~ GI~S, carbon dioxide or mixtures thereof are dissolved in said polar organic solvent.
In another cl ,a,aclel i~dlion of the present invention, a f~rc cess is providedfor decomposing hydrogen sulfide to sulfur and hydrogen. The process comprises contacting a gaseous stream containing hydrogen sulfide with a polar organic solvent having a quinone dissolved therein. Substantially all of the hydrogen sulfide and at least a portion of a second component of said gaseous stream which is selected from the group consisting of water, low molecular weight hydrocarbons, carbon dioxide or mixtures thereof are dissolved in said polar organic solvent. The hydrogen sulfide is reacted with the quinone to produce sulfur and a hydroquinone in the solvent. The hydroquinone is dehydrogenated to the corresponding ~uinone and hydrogen.

BRIEF DES~:RIPTION OF THE DRAWINGS
The ac.;o",,ua"~/ing drawings, which are incorporated in and form a part o~
the specification, illustrate the embodiments of the present invention and, together with the description, serve to explain the principles of the invention. In the drawings:
FIG. 1 is a graph which depicts the rate constants of the two separate mechanisms for conversion of t-butyl anthraquinone ~TBAQ) to t-butyl anthrahydroquinone ~H1TBAQ) as a function of the pKb value of different complexing agents which are dissolved together with TBAQ into a polar organic solvent;

, CA 02230849 l998-02-27 W O 97tl8028 PCT/US96/15314 FIG. 2 is a graph which depicts the activation energy of the two separ~le mechanisms for conversion of t-butyl anthraquinone (TBAQ) to t-butyl anthrahydroquinone (H2TBAQ) as a function of the pKb value of different complexing agents which are dissolved together with TBAQ into a polar or~~anic solvent;
FIG. 3 is a graph which depicts the conversion of t-butyl anthraquinone (TBAQ) to t-butyl anthrahydroquinone (H2TBAQ) as a function of the ratio of diethylmethylamine (DEMA) complexing agent to TBAQ which are dissolved together into a polar organic solvent;
FIG. 4 is a graph which depicts the rate constants of the two separate mechanisms for conversion of t-butyl anthraquinone (TBAQ) to t-butyl anthrahydroquinone (H2TBAQ) as a function of the partial pressure of hydrogen sulfide in the reactor for feed gases having varying ratios of hydrogen sulfide to carbon dioxide;
1~ FIG. 5 is a graph which depicts sulfur recovery achieved in accor~ar,ce with the process of the present invention as a function of the partial pressure of hydrogen sulfide in the reactor;
FIG. 6 is a graph which depicts hydrogen production selectivity as a function of the ratio of complexing a8ent to total quinone, i.e. t-butyl anthrahydroquinone (H2TBAQ) and t-butyl anthraquinone (TBAQ), during the dehydrogenation of t-b~tyl anthrahydroquinone in the presence of platinum catalysts;
FIG. 7 is a graph which depicts hydrogen production selectivity as a function of the pKb value of different complexing agents which are dissolved 2~ .together with t-butyl anll " al ,ydroquinone ~H2TBAQ) into a polar organic solvent in dehydrogenation reactor feeds;
FIG. 8 is a graph which depicts the conversion of t-butyl anthraquinone (TBAQ) to t-butyl anll"ahydroquinone (H2TBAQ) as a function of the number of injection stages for hydrogen sulfide (H2S) into the ~2S-TBAQ reactor;
FIG. 9 is a graph which depicts sulfur (S~) recovery, as the weight percent of the total S atoms formed in the conversion of t-butyl anthraquinone (TBAQ) to t-butyl anthrahydroquinone (H2~BAQ), as a function of the number of injectionstages for hydrogen sulfide (tl2S) into the HzS-TBAQ reactor;

FIG. 10 is a graph which depicts sulfur (S") recovery as a function of the molar ratio of water to t-butyl anthraquinone (TBAQ) in the process of the present invention; and FIG. 11 is a semi-log~ ill ""ic graph which depicts the hydrogen production seiectivity as a function of the dehydrogenation temperature for separate reaction solutions, one of which does not contain water and another of which contains one mole of water per mole of t-butyl anthraquinone (TBAQ) added prior to the sulfur production stage of the process of the present invention.

DETAI~ED DESCRIPTION OF THE PREFE~RED EMBOD~NIENTS
The present invention relates to the removal of water, low molBcl ll~r weight hydrocarbons, for example ethane, propane, butanes, pentanes and hexanes and/or carbon dioxide in addition to hydrogen sulfide from a gaseous stream in 2 single processing unit wherein hy~ e, I sulfide which is initialiy contained in the gaseous feed stream is also converted to elemental sulfur in the same processing unit. Water, iow molecular hydrocarbons, and carbon dioxide which are removed from the gaseous stream can be recovered as separate products.
In accordance with the process of the present invention, the gaseous feed conLai, ling hydrogen sulfide ~H2S) is contacted in an H2S absorber with a polarorganic solvent having a quinone and a H2S complexing agent dissolved therein.
The solvent solubilizes hydrogen sulfide from the feed gas to form a reaction solution which is transported to and maintained in a polymerization reactor at atemperature and a pressure, as hereinafter discussed, and for a time which is sufficient to convert the hydrogen sulfide and quinone to sulfur and hydroquinone. The solvent also solubilizes in the absorber significant portions of the water, low molecular weight hydrocarbons, i.e. C2 - C6, and/or carbon dioxide present in the gaseous feed stream. In addition, the feed gas may conlai,l other sulfur compounds, such as COS, CS2 and mercaptans, which are dissolved in the polar organic solvent and converted in the process to H2S, recycled to the absorber andfor reactor, and converted to sulfur. Although described throughout this description as separate components of a single processing unit, the absorber and polymerization reactor may be a single W O 97/18028 PCT~US96/15314 reaction vessel, for example a s~irred tank, in which both functions are performed.
In accordance with the present invention, the number of injection stages utilized to introduce the hydrogen sulfide containing feed gas into the absorberor reactor where the gas is contacted with a polar organic solvent containing a quinone and a H2S complexing agent is a factor which siyl ,iricanLly increases the conversion of quinone to hydroquinone and elemental sulfur and to ensure the desired S" sulfur precipitate is formed. The number of injection stages employedto introduce the hydrogen sulfide feed gas into the reactor or absorber is preferably 1 to 6, more preferably 2 to 5 and most preferably 4.
Although not completely understood, the conversion of quinone to hydroquinone in the i-i2S absorber andlor polymerization reactor is believed to occur in accordance with five overall chemical mechanisms. First, the polar organic solvent forms a charge-Lt~" ;rer complex with the quinone ("mechanism 1"). Secondly, H2S reacts with a complexing agent ("CA") to form an ion complex ("mechanism 2") in accordance with the following general reaction:

CA + H2S - CAH+HS- (ion complex) In the conversion of quinone to hydroquinone in the H2S absorber and/or polymerization reactor, sulfanes (i.e., H2SX where X generally equals zn integerfrom 2 to 20) may be formed. These sulfanes can also react with the complexing agent to form ion complexes which have utility in accordance with the present invention. Next, the ion complex reacts with the solvent-quinone compiex in two steps to form elemental sulfur and hydroquinone ("mechanism 3a and 3b"). Lastly, a reaction occurs which poiymerizes elemental sulfur (S) to polymerized sulfur (S~) which then precipitates out of solution ("mechanism 4").
In accordance with the present invention, applicants have discovered that utilizing a polar organic solvent in conjunction with a complexing agent, which has been selected in accordance with certain parameters set forth below, unexpectedly results in very high conversions of quinone to hydroquinone in extremely short periods of time. Further, these results have been achieved at W O 97/18028 PCT~US96/15314 reactor temperatures and H2S partial pressures which unexpectedly are significantly lower than previously thought to be required.
The polar o,~anic solvent utiiized in the process of the present invention is chosen to have a high polarity and yet remain stable at dehydrogenation temperatures Suitable polar organic soivents include N-methyl-2-pyrolidinone, N,N-dimethylacetamide, N,N-dimethylformamaide, sulfolane (tetrahydrothiophene-1, 1 -dioxide), acetonitrile, 2-nitropropane, propylene carbonate and mixtures thereof. The most preferred solvent is N-methyl-2-pyrrolidinone (NMP).
A complexing agent is also incorporated into the polar organic solvent in accordance with the present invention. This complexing agent is believed to react with H2S in accordance with mechanism 2 to form an ion complex (CAH ' I IS~). Thus, selection of a suitable complexing agent is based in part upon the ability of the complexing agent to react with H2S to form an ion complex.
The complexing agent must also be chosen upon its ability to increase the rate consla"~s for mechanisms 3a and 3b while decreasing the activation energies for mechanisms 3a and 3b. It has been discovered that the basicity of these complexing agents, as measured in units of pKb, directly correlates to the increase in rate constants of mechanisms 3a and 3b. In general, employing a complexing agents of decreasing pKb value in the process of the present invention will increase the formation of the ion complex and the rate COI ~sLa"l of mechanism 3a (FIG. 13. In addition, as complexing agent basicity is increased, i.e. p~ decreased, the activation energies of mechanisms 3a and 3b are decreased (FIG. 2). "A~tivation ener~y" represents the energy level required to activate 1 mole of reactants to a state sufficiently above the average energy level of all molecules such that reaction may occur. Thus, use of a complexing agent of high basicity results in increased ion complex formation and therefor increased conversion of quinone. In accor~d~ ~ce with the present invention, thePKb Of complexing agents is less than about 13.0, more preferably less than about 9.0, and most preferably less than about 6Ø The pKb values are based on KW (equilibrium constant) of 14.0 for the dissociation of water. Suitable complexing agents are se~ected from amines, amides, ureas, nitrogen conlai, ling heterocyclic aru,))dlics, quanidines, imidazoles, and mixtures thereof.

W O 97/~8028 PCT~US96/15314 These complexing agenl:s can also be substituted with alkyl, aryl and organic alcohol groups. Examples of suitable complexing agents are n-methylacetamide, pyridine, substituted pyridines, diethylmethylamine, tri-butylamine, methyldiethanolamine and tetramethylurea. The preferred complexing agents are diethylmethylamine ~DEMA~, methyldiethanolamine (MDEA), tri-butylamine, pyridine (PY), and substituted pyridines. Additionally, it is believed that those complexing agents which contain a hydrogen bonding proton, for example, methyldielh~nol amine (MDEA), have a greater impact on increasing the rate of mechanisms 3a and 3b. The ratio of complexing agent to quinone in the polar orya,-;c solvent is also crucial in yielding an unexpectedly high conversion of quinone to hydroquinone ~FIG. 3). The molar ratio of complexing agent to quinone in the polar organic solvent is about ~ :50 to about2:1 and preferably about 1:10 to about 1:1.
In general, the quinone utilized in the process of the present invention is selected from a"lhla~ inones, benzoquinones, napthaquinones, and mixtures thereof and are cl~osen to ",axi,l~i~e its reaction with H2S. Choice of the quinone is based on such properties as the solubility of quinone in the polar organic solvent. Solubility is a function of the groups substituted on the quinone. For example, alkyl quinones have much higher sol~ Ihilities than sulr~ aled quinones.
Useful anthraquinones are ethyl, t-butyl, t-amyl and s-amyl anthraquinones and mixtures thereof because of their relatively high solubilities in most polar organic solvents.
It has further been discovered that, by utilizing a suitable complexing agent in coniunction with a polar organic solvent, both of which are selected in accordance with parameters specified above, that the temperature and tl2S
partial pressure required ~or conversion of quinone can be subst~ntially reducedwhile the percentage of quinone converted to hydroquinone is increased.
Pr~e, ably, the reaction solution, i.e. the polar organic solvent having a suitable quinone, complexing agent and hydrogen sulfide dissolved therein, is maintained in the H2S absorber and/or polymerization reactor at a temperature of from about 0~ C. to about 70~ C., and more preferably about 20~ C. to about 60~ C., and at a H2S partial pressure of from about 0.05 to about 4.0 atmospheres, more preferably about 0.1 to about 3.0 atmospheres, and most W O 97/18028 10 PCT~US96/15314 preferably about 0.5 to about 2.0 a~, I)ospl .eres. These lower temperatures andpressures reduce the design requirements for the H2S ai so~er andlor polyme, i~aLio" reactor which results in significant cost savings. In addition, the cost of co" ,uressing the feed gas to obtain the requisite H;!S partiar pressure is significantly reduced. At these conditions, some unreacted ff2S in addition to C02, water and/or low moiecular weight hydrocarbons may be rernoved from the pol~"~eri ~lion reactor, separated and recovered by any suita~ie means as will be evident to a skilled artisan, sudl as by means of a three phase se,va~or.
Aithough disr~ssed throughout this s,ueciri~Lioi, as being two se~Jaral~ and distinct compound~;, it is within the scope of the present invention to utilize one cor,,,uound as both the polar organic solvent and the complexing agent as long as one compound can satisfy the criteria for both polar organic solvent and complexin~ agent specified herein, i.e. have a high polarity, remain stable at dehydrogenation temperatures, and have a pi~ value of less than about 13Ø
Applicants have further discovered that, by including a S--r~ci~, IL amount of carbon dioxide in the gaseous feed col~laining h~dl uyen sulfide to ensure that a predetermined amount of carbon dioxide is dissolved in the polar organic solvent together with hydrogen sulfide, ti~e rate of reaction between hydrogen sulfide and quinone can be significantly increased over the reaction rate obtained when carbon dioxide is not included in the gaseous feed to the absorber andlor reactor. While it is not exactly understood why carbon dioxide increases this l~a- lio-, rate, it is believed that the presence of carbon dioxide in the gaseous hydro~en sulfide containing reaction solution within the absorber and/or polymerization reactor alters the structure of the quinone, thereby resulting in an increased rate of quinone conversion. In accordance with the process of the present invention, the amount of carbon dioxide present in the gaseous feed should be sufficient to ensure that at least 0.05 mole of carbon dioxide are absorbed into the polar organic solvent per mole of quinone contained therein, more preferably 0.10 moie of carbon dioxide per mole of quinone, and most ~,~rt:r~bly 0.25 mole of carbon dioxide per mole of quinone.
Carbon dioxide may be present in the gaseous stream to be treated in accordance with the present invention or carbon dioxide may be added to the gaseous stream from any readily available source so as to ensure that the W O 97/18028 PCT~US96/15314 amount of carbon dioxide specified above is absorbed from the gaseous stream into the polar organic solvent containing quinone.
The presence of water which is dissolved from the feed gas into the reaction solution also results in an unexpected increase in the recovery of sulfur formed during the conversion of hydrogen sulfide and quinone to sulfur and hydroquinone. While it is not exactly understood wi~y the addition of water to the reaction solution increases the amount of sulfur which can be recovered from the reaction solution, it is believed that the addition of a small amount of water to the reaction soiution likely limits the total solution solubility and water is selectively solubilized over sulfur, i.e. S~.
The treated feed gas is removed from the absorber and/or rea~lor and lranspo, led for further treatment or for use. The insoluble sulfur, e.g. S~ or other forms of polymerized sulfur, is withdrawn from the polymerization reactor as a precipitate in the reaction solution, is separated from solution by filtration, centrifugation or other means known in the art, is washed to remove the polar organic solvent, dissolved hydroquinone, any unreacted ~uinone and complexing agent, and is dried and may be subsequently melted to a liquid form. In accorda, Ice with the present invention, the insoluble sulfur is washedwith a wash solvent. The wash solvent is any liquid hydrocarbon which solubilizes the reaction solution, i.e. the polar organic solvent having quinone, hydroquinone, and complexing agent dissolved therein. This wash solvent has a boiling point of at least about 50~ C, preferably at least about 100~ C, and most preferably at least about 150~ C below that of the polar organic solvent.
Preferred wash solvents are oxygenated hydrocarbons, such as, acetone, 3-pentanone, or mixtures thereof. The reaction solution which is remaining after sulfur removal and which contains hydroquinone, any unreacted quinone, complexing agent, solvent, and unreacted compounds from the feed gas, such as H2S, COS, CS2, CO2, me,ca,utalls and unrecovered sulfur, is heated to and maintained at a temperature of from about 70 C. to about 220 C. and at a pressure of from about 0.01 to about 2.0 atmospheres to convert COS, CS2.
mel w~lans and unrecovered sulfur to H2S. The reaction solution is then fed to a flash tank or fractionator where substantially all unreacted feed gas constituents, including water, C02 and/or low molecular weight hydrocarbons, WO 97/18028 12 PCT~US96/1~314 are removed from solution, separated, and recovered as products. The separation of unreacted feed gas conslil.lents which have been removed from the reaction solution via the fiash tank or r, a~io- Iator can be effect~l~te~ by any suitable means as will be evident to a skilled artisan. For exampleS a three phase sepa,~i.or can be utiiized wherein water having C02 dissolved therein is removed from the bottom of the separator while liquid low molecular weight hydrocan~ons having C02 dissolved therein are also removed from the separator. The remaining gas which consists primarily of unreacted H2S is recycled to the absorber and/or poly",eri~aLion reactor with the incoming feed gas. The reaction solution which is withdrawn from the flash tank or fractionator is further heated to from about 220~ C. to about 3~0~ C. at a pressure sufficient to prevent solvent boiling. The heated solution is then fed to a dehydrogenationreactor where the hydroquinone is catalytically or thermally converted to quinone and hydrogen gas (H2) under the temperature pressure conditions stated above. Quinone in its initial forin is withdrawn from the dehydrogenationreactor dissolved with the complexing agent in the polar organic solvent and is recycled to the H2S-quinone absorber, while the H g~s is recovered as a commercial product.
The presence of a complexing agent in the remaining reaction solution, i.e.
that solution which is withdrawn from the polymerization reactor, which has had sulfur removed therefrom, and which co"lai"s hydroquinone, any unreacted quinone, complexing agent, solvent, and unreacted compounds from the feed gas, is also desirable. As previously mentioned, after being heated to from about 70~ C. to about 220~ C., flashed, and further heated to from about 220~
C. to about 350~ C., the heated solution is then fed to a dehydrogenation reactor where the hydroquinone is catalytically or thermally converted to quinone and hydrogen gas (H2~ under the temperature pressure conditions stated above Dehydrogenation of hydroquinones using metal supported catalysts may cause hydrogenoiysis which results in the undesirable production of water and by-products. In the case of a, llh~ unones, these by-products are a"U ~, o"es and/or a"li " anols. Applicants have discovered that the presence ofa complexing agent in the reaction solution fed to the dehydrogenation reactor results in an unexpected and mariced increase in the seiectivity of hydroquinone W O 97/18028 PCT~US96115314 to quinone and hyd, ~en product, and thus, the all~ndal1l decrease in unwanted hydrogenolysis by-products. The molar ratio of complexing agent to total quinones, i.e. hydroquinone and any unreacted quinone, in the remaining reaction solution within the dehydrogenation reactor is about 1:50 to about 2:1,and more preferably about 1:10 to about 1:1.
Further, the addition of water to the polar organic solvent prior to the sulfur production stage of the process of the present invention results in increased hydrogen product selecl:ivity in the dehydrogenation stage of the process.
Although not completely u".le, ~ od, it is believed that water ~d~ition prior to the sulfur production stage substantially eliminates the production of the free radicals at this stage which are necess~ry for al)Lll~anol production in the later dehydrogenation stage. Anthrone production is effectively eliminated by operating at temperatures less than about 265~ C.
The following example ~le,no, l~ les the practice and utility of the present 1~ invention, but are not to be construed as limiting the scope thereof.

Example 1 A solution of N,N-dimethylacetamide ~DMAC) having 1~ wt% t-butyl anthraquinone (TBAQ) dissolved therein has a complexing agent further incorporated therein at a complexing agent/TBAQ molar ratio of 1:8. Several complexing agents having differing piCb values are incorporated into separate solutions of DMAC and TBAQ and are contacted with a hydrogen sulfide containing gas in a suitable reactor at a temperature of 70~ C. and at a H2S
partial pressure of about 3.~ atmospheres. The complexing agents utilized 2~ are methylacetamide (MAC~, pyridine (PY), diethylmethylamine (i~EMA), N-methyl-2-pyrrolidinone (NMP) and methyldiethanolamine (MDEA). Mechanism 3a occurs in about 10 to 20 minutes and mechanism 3b then follows and continues up to about 60 minutes of reaction time. The rate constants for mechanisms 3a and 3b are calculated and the results are illustrated in FIG. 1.
The rate constant for mechanism 3a exponentially increases with decreasing compiexing agent pi~, value.

W O 97/18028 PCTAUS96/t5314 Example 2 T-butyl a"Ll1ra~-linone (TBAQ) is added to dimethylacetamide (OMAC) in an amount of 15 wt%. Diethylmethyiamine (DEMA), pyridine (PY) or dimethylacetamide (DMAC) are also added to the solution as a complexing a~ent in a moiar ratio of complexing agent to TBAQ of 1/8. The separate solutions are maintained in suitable reactors at different temperatures of from 0~ C. to 70~ C. and at a H2S partial pressure of 3.55 atmospheres. Reaction rate constants are c;~ir~ te~ at each reaction temperature for mechanisms 3a and 3b assuming first order kinetics in TBAQ conversion. The calculated rate constants are correlated to reaction temperature accordi.,g to the Arrhenius model from which activation energies are calculated. As graphically represented in FiG. 2, these results illustrate that as complexing agent pK
decreases from the base case where DMAC is both the solvent and complexing agent, the activation energies for mechanisms 3a and 3b linearly ~lecrease.
This decrease is slightly more pronounced for mechanism 3b than for mechanism 3a.

Example 3 Varying amounts of diethylmethylamine (DEMA) complexing agent are added to N,N dimethylace~,tlide (DMAC) solvent which contains 15 wt% t-butyl anthraquinone (TBAQ). The resuitant solutions are maintained in a suitable reactor at a temperature of 20~ C. and at a H2S partial pressure of 3.55 atmospheres. Total ~8AQ conversion after the end of conversion mechanism 3a, i.e., 6-11 minutes or after 11 minutes of total reaction time is measured. As illustrated in FIG. 3, these results indicate that the conversion of t-butyl a, Ill Irc4uinone (TBAQ) to t-butyl anthrahydroquinone (H2TBAQ) increases with increasing complexing agent/TBAQ ratio. Extrapolation of the data depicted in FIG. 3 indicates that a 100% conversion of TBAQ to H2TBAQ will occur in 6-11 minutes for a ~EMA/~BAQ molar ratio of about 0.75.
Example 4 A gaseous mixture of hydrogen sulfide and carbon dioxide is introduced into a laboratory reactor together with 15 wt% t-butyl anthraquinone (TBAQ) in , a N,N-dimethylacetamide (DMAC) solution. This solution also contains diethylmethylamine (DEMA) as a co",plexi"g agent in a ratio of 1 m~l~ of DEi~A
per 8 moles of TBAQ. The reactor is operated at a constant te~perature of about 20~ C. and at a total pressure of from about 0 85 to 3.5~ atm~spheres.
Three gaseous feeds having varying H2S/CO;! molar ratios of 10010, 4~.5\50.5 and 19.8/80.2 are introduced separately into the reactor and the reaction rate constants for mechanisms 3a and 3b are calculated using a rea~tion model which is first order in TBAQ conce~ lion. The results are illustrated 9l a~JI ,;cally in Fig. 4 and indicate that the reaction rate constants using a mixture of hydrogen suifide and carbon dioxide in the reactor are about twice the rate constants achieved with a pure hydrogen sulfide feed. This result is valid for carbon dioxide/anthraquinone molar ratios in excess of 0.05. This result is alsoachieved at relatively low partial pressures of hydrogen sulfide, e.g. 0.68 atmospheres, thereby reducing cost of gas compression.
Example 5 Gamma-butyrolactone (GBL) having 15 wt% t-butyl ~ uinone (TBAQ) dissolved therein is contacted with a hydrogen sulfide conlai,~ 9 gas in a suitable reactor at a tel "perdlure of 20~ C. and at a H2S partial pressure of 3.17 atmospheres. Gamma-butyroiactone has a polarity of 4.17 Debye units. The reaction is allowed to proceed for one hour and the amount of t-butyl anthraquinone (TBAQ) which is converted to t-butyl a~ Ill ,ral1ydroquinone (HzTBAQ) is measured. TBAQ conversion was zero. This result indicates that utilizing a solvent having a polarity above 3.0 Debye units in the absence of a complexing agent does not necessarily result in acceptable TBAQ conversion.

Example 6 T-~utyl anthraquinone (TBAQ) is added to N,N-dimethylacetamide (DMAC) in an amount of 15 wt%. Diethylmethylamine (DEMA) is also added to the solution as a complexing agent in a molar ratio of complexing agent to TBAQ
of 118. The solution is separately maintained in suitable reactors at a temperature of 20~ C. and at varying H2S partial pressures. The results are iliustrated in FIG. 5. S~ recovery is essentially constant for H~S partial pressures W O 97/18028 PCT~US96/1531 above about 1.52 atmospheres while S" recovery increases for ~ S partial pressures below about 1.52 atmospheres to 100% at a H2S partial pressure of 0.68 dllllOSpl ,e,es. Thus, the reduced H2S partial pressure at which the process of the present invention can be operated results in increased S, recovery.
Example 7 Varying amounts of pyridine complexing agent are added to se~rale dehydrogenation feeds containing t-butyl ~I~U ,r~li ,ydroquinone and introduced to a reactor wherein the al~U ,~ ydroquinone is dehydrogenated to anthraquinone and hydrogen in the presence of a platinum catalyst.
Dehydrogenation is carried out in the reactor at a total pressure of about 4.35 to about 5.71 atmospheres and at a temperature of 265~ C. when the SiO2 catalyst support is used and 285~ C. when the quartz catalyst support is used.
Each feed is reacted for approximately 1.05 minutes. The results are illustratedgraphically in Fig. 6 and i,~.ii~le that the presence of a complexing agent in the reaction solution feed to the dehydrogenation reactor in a ratio of complexing agent to total quinones, i.e. anthrahydroquinone and any unreacted al 1~111 a-~uinone, of about 1:50 to about 2: 1 and p, é:r~, ably about 1: 10 to about 1:1 results in an unexpected and marked increase in the selectivity of anthrahydroquinone to anthraquinone and hydrogen. Thus, unwanted hydrogenolysis by-products, such as anthrones andlor anll)r~,)ols, are also decreased.
Example 8 Pyridine, 2,4 lutidine, and diethylmethylamine ~DEMA~ are each added to separate dehydrogenation feeds which contain 18.7~ wt% t-butyl ~n~h, ~hydroquinone (~2TE3AQ) as complexing agents in the amount of 1 mole of complexing agent per 8 moles of total anthraquinones, i.e. t-butyl a"ll ,rd4uinone (TBAQ) and t-~utyl anthrahydroquinone. Pyridine, 2,4 lutidine, and DEMA have p~ values of 8.8, 7.0 and 3.6, respectively. Each dehydrogenation feed is introduced to a reactor wherein the anthrahydroquinone is dehydrogenated to anthraquinone and hydrogen in the presence of a platinum catalyst on a SiO2 support. Dehydrogenation is carried out in the reactor at a total pressure of about 4.21 atmospheres and at a temperature of 265~ C. Each feed is reacted for approximately a 1 minute W O 97/18028 17 PCT~US96/15314 residence time. The selectivity of t-butyl a, ~ rdhydroquinone to hydrogen and t-butyl ar,ll"~4uinone is 74 %, 88%, and 100% when pyridine, 2,4 lutidine, and DEMA, respectively, are used as the complexing agent in the feed to the deh~d, u~enalion reactor. These results which are illustrated graphically in Fig.
7 indicate that the pK~ of the complexing agent in the reaction solution feed tothe dehydroge, laliorl reactor has an siy"iricanL effect in increasing the selectivity of anthrahydroquinone to anthraquinone and hydrogen. Thus, unwanted hydrogenolysis by-products, such as al~li,rones and/or anthranols, are also decreased.
Example 9 A solution is formed from 24.50 wt% t-butyl anthraquinone (TBAQ), 73.51 wt% n-methyl-2-pyrrolidinone (NMP), 1.67 wt% water and 0.32 wt%
diethylmethylamine (DEMA) and is pumped into the bottom of a reactor containing four HzS injection points equally spaced along the height of the reactor. A separate updraft turbine mixer which rotates at 200 rpm is positionedwithin the reactor at each injection point. Three separate tests are conducted in which the total amount of H2S introduced into the reactor is sufficient to convert 90% of the TBAQ into t-butyl a"li "ai ,ydroquinone (HzTBAQ) and sulfur The entire amount of H2S is introduced into the reactor soleiy via the first injection point in the first test. In the second test, one haif of the total amount of H2S is introduced into the reactor via each of the first and third injection points, while in the third test, one fourth of the total amount of H2S is introduced into the reactor via each of the four injection points. In each test, the solution is pumped at a rate sufficient to create a 10 minute residence time within the reactor prior to the solution exiting the top thereof. The temperature and pressure of the reactor is maintained at 6!~ C. and 1.5 atmospheres in all testsIn all three tests, the effluent solution from the reactor is fed to a second reactor where the effluent is completely back mixed, held at 20 C. and 1.0 atmosphere for a residence time of 20 minutes. Sulfur (S") crystaliization and precipitation occurs in this second reactor. The reaction solution is removed from the second reactor and filtered to remove sulfur. The amount of S~, thus removed is compared to the total amount of S atoms formed in the reaction of TBAQ and H.S. These results indicate that the use of 4 injection stages or W O 97/18028 18 PCTnJS96/15314 points for introduction of HzS into the first reactor was critical for significantly increasing the amount of TBAQ converted into H2TBAQ in the first, eaclor ~FIG.
8) and the amount of S atoms converted into S" for precipitation in the second reactor (FIG. 9).
Example 10 A solution of 2.47 wt% benzoquinone, 24.13 wt% t-butyl anthraquinone(TBAQ), 1.01 wt% diethylmethylamine (DEMA) and 72.39 wt%
N-methyi-2-pyrrolidinone (NMP) is introduced into a reactor and maintained therein at a temperature of 21 C. and a pressure of 1.5 al.,)ospheres. ~EMA
is present in the solution as a complexing agent in a ratio of ().1 moles of DEMA
per mole of total quinones. While in the reactor, the solution is contacted witha hydrogen sulfide containing gas for 0.3 minutes and the temperature in.;reases to 46.7' C. in the reactor. The solution is cooled within the reactor to 20' C. in 8.7 minutes. This reaction results in a 83% conversion of TBAQ to t-1~ butyl anlt " dh ydroquinone and a 67% conversion of benzoquinone to benzohydroquinone.
A solution of 8.7~ wt% benzoquinone, 0.73 wt% diethylmethylamine (DEMA) and 90.52 wt% N-methyl-2-pyrrolidinone (NMP) is introduced into a reactor under conditions which are identical to those set forth above in this Example. DEMA is present in the solution as a complexing agent in a ratio of 0.25 moles of D~MA per mole of benzoquinone. The solution is contacted with a hydrogen sulfide containing gas in the reactor for 0.3 minutes and the temperatL~re increases to 46.7 C. in the reactor. The solution is cooled in the reactor to 20~ C. in 8.7 minutes. This reaction results in a 78% conversion of benzoquinone to benzohydroquinone.
A solution of 18.03 wt% 1,4 napthaquinone, 1.24 wt% diethylmethylamine (DEMA) and 80.73 vvt% N-methyl-2-pyrrolidinone (NMP) is introduced into a reactor under conditions which are identical to those set forth above in this Example. DEMA is present in the solution as a complexing agent in a ratio of 0.125 moles of DFMA per mole of 1,4 napthaquinone. The solution is contacted with a hydrogen sulfide containing gas in the reactor for 0.3 minutes and the temperature increases to 46.7- C. in the reactor. The solution is cooled in the .

W O 97/18028 19 PCT~US96/15314 reactor to 20~ C. in 8.7 minutes. This r~acliG, I results in a 70% conversion of 1,4 napthaquinone to 1,4 napthahydroquinone.
The foregoing examples demo, IsL- ate that benzoquinones and napthaquinones are equally as suitable as anthraquinones for use in the process of the present invention.
Example 1 1 A natural gas feed stream containing 90.41 mole % ",eLl)dne, 2.51 mole % H2S, 1.81 mole % C02, 4.92 mole % natural gas liquid (NGL) and 0.3~ mole % water is introduced into the bottom of an absorber operating at 49 ~ C and 43 atmospheres. The composition of the NGL is 61.94 mole % ethane, 1~.67 moie % propane, 15.95 mole % butanes, 5.69 mole % pentanes and 0.75 moie %
hexanes. Also, a recycle gas stream with a composition of 60.49 mole %
methane, 8.38 mole % H2S, 10.03 mole % C ~2~ 20.79 mole % NGL, and 0.31 mole % water is introduced into the bottom of the absorber. The molar ratio of the recycle gas stream to the feed gas stream is 0.0444.
A recycle absorbent having a composition of 77.91 mole % N-methyl-2-pyrrolidinone(NMP), 7.05 pyridine(PY), 7.27 mole % t-amyl anthraquinone (TAAQ), 0.18 mole % t-amyl a"ll"dl"/droquinone (H2TAAQ), 7.45 mole %
water, 0.0~ mole % H2, and 0.09 mole % H2S is introduced into the top of the absorber in an amount such that 1 mole of TAAQ plus H2TAAQ is introduced per mole of total H2S in the feed gas plus the H2S in two recycle gas streams.
The H2S in the ~eed gas reacts with a portion of the TAAQ to produce H2TAAQ
and sutfur atoms.
A product gas is withdrawn from the top of the absorber. This stream contains 93.40 mole % methane, 0.05 mole % NMP plus PY, 0.04 mole %
water, 0.03 mole % H2, 1.77 moie % CO2, and 4.71 mole % NGL. Essentially all of the methane in the feed gas is recovered to the product gas, and essentialiy all of the H2S is removed from the feed gas and is converted into sulfur.
Recycle absorbent is removed from the absorber and introduced into polymerization reactor where addili~,"al reaction between H2S and TAAQ occurs and sulfur atoms are poiymerized into insoluble S8. This reactor operates at 30~C and 1.7 atmospheres. The resulting slurry of S8 and recycle absorbent is W O 97/18028 PCT~US96/15314 removed from the polymerization reactor and introduced into a fi~ter where essentially all of the H2S in the feed gas is recovered as S8.
Also, a gas phase is removed from the poly" ,e~ i~dlion reactor by a ccmpressor.In this step, the gas phase is cor,l~ sse~ to 42 atmospheres and cooied to 49~
C. A liquid NGL product is then removed from this co" ,prsssed gas phase. ~he amount of this NGL product is 7.18 mole% of the total NGL in the feed gas.
Also, CO2 is removed in this step at 5.1 mole% of that in the feed gas. The remaining gas is then recycled back to the absorber. As discussed above, tne molar ratio of this gas to the feed gas is 0.0444.
The recycle absorbent from the above ril~l dliOI ~ step is then introd~ ~c~ intoa rl aCLjG~ ldlion unit ope~liny at 2.0 atmospheres and temperatures fr~m 149 to210~ C. A water and acid gas mixture is removed from the top of this fractionation unit. The water, which equals 90 mole% of the water in the feed gas, is then recovered from this acid gas as a product. The acid gas is then recycled to the polymerization resctor. The molar ratio of this gas to the feed gas is 0.0366. The co"~position of this acid gas is 2.01 mole % methane, 0.13 mole % NMP, 10.6~ mole % water, 58.39 mole % H2S, 3.38 mole % CO2, 25.44 mole % NGL.
Recycle absorbent essentially free of any unreacted H2S is removed from the bottom of the fractionation unit and introduced into a dehy~,ogel,dLio~) reactor where the H2TAAQ is converted back into TAAQ and H2 product. This reaction occurs at 250~ C and 4.7 atmospheres. The ratalyst used contains Pt on a SiO2 support. The H plus re~ycle absorbent is removed from the dehydrogenation reactor and cooled to 49~ C. H2 is then recovered from the recycle absorbent as a product at molar ratio of 0.9214 to the H2S in the feed gas. The absorbent is then cooled to 49~ C and recycled back to the absorber to start its cycle over again.
Example 12 A natural gas feed stream cc" IL~i. ,i, lg 71.92 mole % methane, ~ 9.95 mole % H2S, 1.43 mole % CO2, 3.91 mole % natural gas liquid (NGL) and 2.79 mole % water is introduced into the bottom of an absorber operating at 36 ~ C and 42 atmospheres The composition of the NGL is 61.86 mole % ethane, 15.72 mole % propane, 15.98 mole % butanes, 5.67 mole % pentanes and 0.77 mole %

W O 97/18028 ~ PCTrUS96/15314 hexanes. Also, a recycle gas stream with a composition of 29.54 mols %
methane, 3.59 mole % H2S, 35.63 mole % CO2, 30.90 mole % NGL, and a.34 mole % water is introd~ ~ce~l into the bottom of the absorber. The molar ratio of the recycle gas stream to the feed gas stream is 1.008.
A recycle absorbent having a co-."~osilion of 80.50 mole % N-methyl-2-pyrrolidinone(NMP), 7.30 pyridine(PY), 7.49 mole % t-amyl anthraquinone (TAAQ), 0.14 mole % t-amyl anthrahydroquinone (It2TAAQ), 4.43 mole %
water, 0.05 mole % H2, and 0.09 mole % H2S is introduced into the top of the absorber in an amount such that 1.34 moles of TMQ plus H2TAAC~ is intro~uced per mole of total H2S in the feed gas plus the H2S in two recycle gasstreams. The H2S in the feed gas reacts with a portion of the TAAQ to produce H2TAAQ and sulfur atoms.
A product gas is withdrawn from the top of the absorber. This stream contains 9~.77 mole % methane, 0.04 mole % NMP, plus PY, 0.04 mole %
water, 0.48 mole % H2, 0.53 moie % C02, and 3.14 mole % NGL. Esse,.Lially all of the methane in ~he feed gas is recovered to the product gas, and essentially all of the H2S is removed from the feed gas and is converted into sulfur.
Recycle absorbent is removed from the absorber and introduced into a poly"1eri~dlion reactor where adc~ilio"al reaction between H2S and TAAQ occurs and sulfur atoms are pol~r" ,eri~ed into insoluble S8. This rea~ol operates at 30~
C and 1.7 atmospheres. The resulting slurry of S8 and recycle absorbent is removed from the polyrnerization reactor and introduced into a fiiter where essentially all of the H2S in the feed gas is recovered as S8.
Also, a gas phase is removed from the polymerization reactor by a colt,plessor. In this step, the gas phase is compressed to 42 atmospheres and cooled to 49~ C. A liquid NGL product is then removed from this compressed gas phase. The amount of this NGL product is 91.7 mole% of the propane through hexane components initially present in the feed gas. Also, CO2 is removed in this step ~t 27.4 mole% of that in the feed gas. The remaining gas is then recycled back to the absorber. As discussed above, the molar ratio of this gas to the feed gas is 1.008.

W O 97/18028 22 PCT~US96/15314 The recycle absorbent from the above filtration step is then introd~lGP~i into a fractionation unit operating at 2.0 atmospheres and temperatures from 71~ C
to 210~ C. A water and acid gas mixture is removed from the top of tt~is fractionation unit. ~he water, which equals 99 mole% of the water in the feed gas, is then recovered from this acid gas as a product. The acid gas is then recycied to the polymerization reactor. The molar ratio of this acid gas to the feed gas is 0.4241. The acid gas co. ~sisls of 1.26 mole% methane, 0.08 mt~le%
NMP, 9.37 mole% water, 54.48 mole% H2S, 15.41 mole% C02, 19.40 mole~h NGL.
Recycle absol be, IL essentially free of any unreacted H2S is removed from the bottoms of tne fractionator and introduced into a dehydrogenation reactor where the H2TAAQ is converted back into TAAQ and H2 product. This reaction occurs at 250~ C and 4.7 ~ os,ul ,er~s. The cataiyst used contains Pt on a Si(:)2 support. The H2 plus recycle absorbent is removed from the dehydrogenation reactor and cooled to 49~ C. H2 is then recovered from the recycle absorbent as a product at molar ratio of 0.921~ to the H2S in the feed gas. The absorbent is then cooled to 49~ C and recycled back to the absorber.
Example 13 T-butyl anLI ,ra.~uinone (TBAQ) is added to N-methyl-2-pyrrolidinone ~NMP) in an amount of 25 wt%. Pyridine (PY) is also added to the solution as a complexing agent in a molar ratio of complexing agent to TBAQ of 1/1 . Varying amounts of water are added to separate portions of the solution. Each portion of the solution is contacted with hydrogen sulfide containing gas in a suitable reactor at a temperature of 20~ C and at a H2S partial pressure of 1.5 2~ atmospheres for 2 hours. The amount of S" recovered is determined by weighing the sulfur which is precipitated out of the solution removed from the reactor. The results are graphically illustrated in FiG. 10. As illustrated in FiG.
10, the amount of S~ recovered, which is expressed as the weight % of total sulfur formed in the reactor, increases with increasing amounts of water which are absorbed into the solution prior to or during the sulfur production stage ofthe process, i.e. during the conversion of hydrogen sulfide and anthraquinone to sulfur and anthrahydroquinone.

CA 02230849 l998-02-27 Example 14 A dehydrogel ~lion ~eed of N-methyl-2-pyrrolidinone ~NMP) COI ,lai, lil ~9 2 wt% t-butyl anthrahydroquinone (H2TBAQ) is introduced to a reactor wherein the t-butyl anthrahydroquinone is dehydrogenated to t-butyl arllll.~4~1inone (TBAQ) and hydl ~~yen in the presence of a platinum catalyst. Dehydlu~e, laliol)is carried out in the reactor at varying hydrogen pressures of about 2.31 to about 6.12 atmospheres to prevent solution boiling at the varying dehyd,u~er,ation temperatures of from about 220~ C to about 290~ C. Two separaLe feeds are reacted under these pé;,rdi"elers. Water is not added to one feed and is added to another feed prior to sulfur production in an amount of about 1 mole of waterper mole of TBAQ. Pyridine (PY) is added as a complexing agent to the latter feed in the amount of one mole of pyridine per mole of TBAQ. Each feed is reacted for approximately 1 minute. The results which are illustrated graphically in Fig. 11 indicate that H2TBAQ selectivity to hydrogen and TBAQ can be increased to 100% below 225~ C if water is added to the NMP solvent prior to the sulfur production stage of the process or absorbed from a gaseous feed stream containing H2S. l~hus, unwanted hydrogenolysis by-products, such as anthrones and/or anll ,ranols, can be effectively eliminated.
While the foregoing preferred embodiments of the invention have been described and shown, it is understood that the alternatives and modifications, such as those suggested and others, may be made thereto and fall within the scope of the invention.

Claims (20)

We claim:

1. A process of removing hydrogen sulfide and other components from a gas comprising:
(a) contacting a gaseous stream containing hydrogen sulfide with a polar organic solvent having a quinone dissolved therein, wherein substantially all ofsaid hydrogen sulfide and at least a portion of a second component of said gaseous stream which is selected from the group consisting of water, low molecular weight hydrocarbons, carbon dioxide or mixtures thereof are dissolved in said polar organic solvent.

2. The process of claim 1 further comprising:
(b) reacting said hydrogen sulfide with said quinone to produce sulfur and a hydroquinone in said solvent.

3. The process of claim 2 further comprising;
(c) separating said sulfur produced in step (b) from said polar organic solvent.

4. The process of claim 3 further comprising:
(d) dehydrogenating said hydroquinone to said quinone and hydrogen.

5. The process of claim 1 wherein said low molecular weight hydrocarbon is ethane, propane, butanes, pentanes, hexanes or mixtures thereof.

6. The process of claim 2 wherein steps (a) and (b) are conducted within a reactor.

7. The process of claim 2 wherein step (a) is conducted within an absorber and said polar organic solvent having substantially all of said hydrogen sulfideand said at least a portion of said second component dissolved therein is transported to a reactor wherein step (b) is conducted.

8. The process of claim 1 wherein said polar organic solvent has a complexing agent dissolved therein.

9. The process of claim 3 further comprising:
(e) removing said second component of said gaseous stream from said polar organic solvent and recovering said second component as at least one product.

10. The process of claim 9 wherein said polar organic solvent contains unrecovered sulfur not separated from said polar organic solvent in step (c) andother sulfur compounds which are initially contained in said gaseous stream and which are dissolved in said polar organic solvent in step (a), said unrecovered sulfur and said other sulfur compounds being converted in step (e) to hydrogen sulfide.

11. The process of claim 10 wherein said other sulfur compounds are COS, CS2 mercaptans or mixtures thereof.

12. A process of decomposing hydrogen sulfide to sulfur and hydrogen comprising:
(a) contacting a gaseous stream containing hydrogen sulfide with a polar organic solvent having a quinone dissolved therein, wherein substantially all ofsaid hydrogen sulfide and at least a portion of a second component of said gaseous stream which is selected from the group consisting of water, low molecular weight hydrocarbons, carbon dioxide or mixtures thereof are dissolved in said polar organic solvent;
(b) reacting said hydrogen sulfide with said quinone to produce sulfur and a hydroquinone in said solvent;
(c) separating said sulfur produced in step (b) from said polar organic solvent; and (d) dehydrogenating said hydroquinone to said quinone and hydrogen.

13. The process of claim 12 wherein said low molecular weight hydrocarbon is ethane, propane butanes, pentanes, hexanes or mixtures thereof.

14. The process of claim 12 wherein steps (a) and (b) are conducted within a reactor.

15. The process of claim 12 wherein step (a) is conducted within an absorber and said polar organic solvent having substantially all of said hydrogen sulfide and said at least a portion of said second component dissolved therein is transported to a reactor wherein step (b) is conducted.

16. The process of claim 12 wherein said polar organic solvent has a complexing agent dissolved therein.

17. The process of claim 12 further comprising:
(e) removing said second component of said gaseous stream from said polar organic solvent and recovering said second component as at least one product.

18. The process of claim 17 wherein said polar organic solvent contains unrecovered sulfur not separated from said polar organic solvent in step (c) andother sulfur compounds which are initially contained in said gaseous stream and which are dissolved in said polar organic solvent in step (a), said unrecovered sulfur and said other sulfur compounds being converted in step (e) to hydrogen sulfide

19. The process of claim 18 wherein said other sulfur compounds are COS, CS2 mercaptans or mixtures thereof.

20. All inventions described herein.