CA1083991A - Conversion of coal to high octane gasoline - Google Patents

Abstract

CONVERSION OF COAL TO HIGH OCTANE GASOLINE

ABSTRACT OF THE DISCLOSURE
A process is described for the efficient conversion of coal into high octane, liquid, hydrocarbon gasoline. The process comprises reacting coal with oxygen and water at about 1450 to 1800°F to produce a synthesis gas product comprising carbon oxides, hydrogen and methane; catalyzing the conversion of said carbon oxides and hydrogen to a pro-duct comprising water, C? gas and C? aromatic gasoline by a catalyst comprising a crystalline aluminosilicate zeolite having a silica to alumina ratio of at least 12 and a constraint index of 1 to 12; separating said C? gas into a C? tail gas comprising methane, ethane and ethylene, and an alkylation feed comprising saturated and unsaturated C3 and C4 hydrocarbons; alkylating said alkylation feed in contact with a strong acid at up to about 450°F and up to about 500 psig; admixing C7 and C8 alkylate with said aromatic gasoline; steam reforming said C? tail gas to an auxiliary synthesis gas comprising carbon oxides and hydrogen; and admixing said auxiliary synthesis gas with said coal gasification gas prior to conversion thereof into said aromatic gasoline.

Description

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1~8399~ .
.,' ., ~his lnvention relates to the upgrading of coal.
It more particularly re~ers to the e~ficient conversion o~
: coal into high octa~e~ liquid, hydrocarbon gasolineO
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; It ls well known that many o~ the world's largest users o~ llquid petroleum products have less than adequate stocks and reserves o~ crude oil. These countrles are therefore to a greater or lesser extent dependent upon crude oil obtained from foreign sources to help balance their en~rgy needs. It is also true that man~ o~ these crude oii deficient countries and areas have large coal depoalts. To date however~ no really good process has been developed and co~mercialized ~or the conversion o~ coal to high quality automotive fuel including high octane gasoline.
It is known that coal can be gasified to a i .
mixture o~ carbon oxides and hydrogen, as well as other components, which can be converted directly to aliphatic9 lower octane gasoline by conventional Fischer-q'ropsch catalysis.
A~ 1~ apparent, the quality of gasoline produced by such conventional Fischer-Tro~sch catalysis lea~es something to be desired in terms of octane number. It is un~ortunate~
but such Fischer-Tropsch gasollne is not economically readily upgraded by usual petroleum re~iner~ technolog~, such as noble metal reforming.
There has recently been developed a new approach ~5 to the prob~em of convertin~ coal or other solid ~oss~l ~uels to good quality liquid hydrocarbon gasolineO
According to this new approach~ advantage is taken o~ ~he i unusual ability o~ a special group of crystall-ine alumino-silicate zeolites having a high sillca to alumina ratio ''' , ~

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I and of~er constrained access t~ molecules to their pore I structure to catalyze the conversion of methanol to high! quality gasoline. Thus, coal is converted to synthesis gas i comprising carbon monoxlde and hydrogen l~h1ch is converted to methanol which is in turn converted to high octane aromatic ~j gasoline. In developing thls process and other processes ~¦ relat~d to it, it has become apparent that while it is totally I sound and practicable, certain significant improvements can j be made in lt, by some small modi~ications, depending upon ¦ 10 the partlcular choice of specific upstream processes.
-, It is there*ore an ob~ect of this invention to¦ provide an improved process for converting coal to gasol-ine.
¦ Other and additional objects will become apparent ¦ ~rom a considera~ion o* this entlre specification 1ncluding ¦ 15 the claims and drawing hereof.
Understanding o~ this invent-lon will be facilitated ~i by-re~erence to the accompan~ing drawingsi.n which:
¦ F~gs.-~ to 4 are schematic flow dia~rams of a p~rticular 1- processing embodimen~of this invention.
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; In accord wlth and ful~illing these ob~ects~ one aspect of this inventlon re~ides in a process comprising gasi~ying coal to a gas comprising carbon oxides, hydrogen and methane by a process which i8 capable o~ accomplishing this~ such as the Lurgi process (see for example Scientific ~ American, March 1974, Volume 230, No.3, page l9 etc.). Such ¦ coal gasi~ication processes are presently available con~ercial ; technology which are well documen~ed and commercially -3- ~ ~
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practiced. No invention is here claimed in such coal gas-ification processes per se. After cleanup of this gas, or even without such cleanup, depending upon its sulfur content etc., it is converted to high quality aromatic gasoline by a process utilizing a catalyst comprising a special crystalline aluminosilicate to be described in detail below. Two alternatives are available for this conversion: one wherein the methane containing synthesis gas is contacted with a mixed catalyst comprising as a first component the special zeolite referred to above and detailed below and as a second component, a metal value having good carbon monoxide reduction catalytic activity ; and poor ole~in hydrogenation activity, such as thorium, ruthenium, iron, cobalt or rhodium. This catalyst may also have an alkaline metal, such as potassium, associated ; therewith. The product is water and a full range of saturated and unsaturated hydrocarbons from Cl to about C10. The other alternative is to convert the carbon monoxide and hydrogen content of the methane containing synthesis gas to a product comprising methanol, using for example conventional methanol synthesis technology which is readily available from several commercial licensors, by employing a catalyst comprising zinc and copper. The organic portion of this methanol synthesis product, comprising methanol, is then contacted with a special zeolite catalyst and is thus converted to water and a full range of saturated and unsaturated hydrocarbons from C
to about C10.

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Thus, the present invention in its broadest ;~
aspect relates to a process of converting coal to gasoline comprising: reacting coal with oxygen and water at about :
145C to 1800F to produce a synthesis gas product comprising carbon oxides, hydrogen and methane; catalyzing the conversion of said carbon oxides and hyd~ogen to a ~:
product comprising water C4 gas and ~5 aromatic gasoline by a catalyst comprising a crystalline alumino-silicate zeolite having a silica to alumina ratio of at lea5t 12 and a constraint index of l to 12; separating said C4 gas into a C2 tail gas comprising methane, ethane and ethylene, and an alkylation feed comprising saturated and unsaturated C3 and C4 hydrocarbons;
alkylating said alkylation feed in contact with a strong acid at up to about 450F and up to about 500 psig;
admixing C7 and C8 alkylate with said aromatic gasoline; steam reforming said C2 tail gas to an auxiliary synthesis gas comprising carbon oxides and hydrogen; and admixing said auxiliary synthesis gas with said coal gasification gas prior to conversion thereof into said aromatic gasoline.
Regardless of which of thése one step or polystep conversions are utilized, the product comprises ~:
water and a full complement of hydrocarbons up to about ClO. The hydro-- 4a -~L0~3399~

carbons are separated into C5 gasoline~ which is recovered as such, and a C~ fraction which is resolved ~nto an LPG
fraction comprising predominantly satura~ed C3 and C4 com-ponents, an alkylation feed comprising isobutane and C3 and C4 olefins and a C2 fra~tion comprising ethane, methane, hydro-gen, carbon oxides and other low boilers. ~he alkylation feed is suitably alkylated in contact with an acid catalyst, conventionally a homogeneous acid catalyst such as sulfuric I or hydrofluoric acid, in a conventional manner. Alkylation technology is generally available from various commercial sources and is widely practiced industrially. No invention is here claimed in this unit process per se. The alkylate product thereof is suitably admixed with the a~oresaid aromatic gasoline to produce a remarkably high quality full range gasoline which can be used directly in motor vehicles, even high performance vehicles, without requiring octane appreciators, such as lead compounds.
Alternatively, the said full complement of hydro-carbons may be separated into C5+ gasoline, which is recovered as such, and a C4- fraction which is resolved into an alkylation feed comprising C3 and C4 and a C2- fraction comprising ethane, ethene~ methane, hydrogen, carbon oxides and other low boilers.
The alkylation feed i8 sultable alkylated in contact with an acld catalyst, conventionally a homogeneous acid catalyst such as sulfuric or hydro~luoric acid~ in a conventional manner.
Alkylation technology is generally available from various commercial sources and is widely practiced industrially. No invention is here claimed in this unit process per se. The alkylate product thereof is suitable admixed with the aforesaid aromatic gasoline which can be used directly in motor ~ehicles, _"_ __.. .. . . . ... . . . ... . .. .. ..... . ....... __.. _ __ ~0839~

even high performance vehicles, without requiring octane appreciators, such as lead compounds.
According to this invention, the synthesis gas produced from coal contains methane. This material passes through the methanol synthesis process substantially unaltered.
When the organic portlon of the methanol synthesis product is converted to hydrocarbons as aforesaid, some additional methane and ethane are formed. Alternatively, in the one step direct conversion of synthèsis gas to aromatic gasoline, the methane passes through the reaction substantially unchanged and there are made substantial quantities of methane and ethane.
In either case, the methane and ethane, from coal gasification or otherwise, together wlth hydro~en and carbon oxides if available, are converted by partial oxidation, stearn re~orming or the like with or without water gas shift so as to produce a properly proportioned auxiliary synthesis gas suitable for admixture with the synthesis gas produced by coal gasification and the mixture fed to direct or indirect ~via methanol synthesls) aromatization. Part of the water necessary for this process can be supplied by the water produced in the aromatiza-tion unit process. As re~uired, carbon dioxide can be perlodically or contlnually purged ~rom the system. Since coal is deficient ln hydrogen relative to the carbon-hydrogen ratio desired in the product, either hydrogen must be added to thè
system or carbon must be rernoved from the system. It is pre-~erred to do both in balance by adding water and reJecting carbon dioxide.

~L~839~1 In the alternative the methane and ethane, from coal gasification or otherwise, together with hydrogen and carbon oxides, if available, are subJected to methanation.
Methanation is a known process whereby a mixture of hydrogen, one or more light hydrocarbons and possibly carbon oxides are catalytically converted ko a synthetic natural gas compx-ising methane. Feed to the methanation process may be all or part of the purge gas from the recycle of synthesis gas of the methanol synthesis process together with the whole C4- product of methanol aromatization or the C2- tail gas fraction if an alkylation unit process is employed in the reaction process train. In the case of the direct conversion process, either the whole C4- fraction or the C2- tail gas can constitute the methanation feed. Upstream processing conditions can be ad~ust-ed to proportion the methanatlon feed composition. Hydrogencan be added from outs-lde sources. It ls preferred to feed a composition having a hydrogen to carbon ratio of about 3.7 to 4.2 to l into contact with a hydrogenolysis catalyst such as nickel, cobalt, platinum, ruthenium, etc. The hydrogenolysis (methanation) process is suitably carried out at a temperature of about 525 to 1000~, a pressure of about 1 to ll~ atmospheres absolute and a space velocity of about l to 50 WHSV. The nickel or other catalyst ls suitably solid and may be used in a fixed or fluidized bed arrangement. The catalyst may also be in the form of a coating on the reactor walls. Where a fluldized bed is used, the catalyst is suitably about 0.1 to 1.0 mm particles whereas with a fixed bed system the catalyst is suitably pellets of about 0.2 to 0.5 cm average diameter.

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The product of the hydrogenolysis portion of this process is a synthetic natural gas consisting of about 90% methane. This gas produce may also contain either a small amount of free hydrogen or a small amount of higher homologues or~methane depending upon the atom ratio of the gas feed to hydrogenolysis. These non-methane constituents should be limited to belo~ about 20 percent of the total product.

It is known that at least some present methanol synthesis catalysts are sulfur sensitive and that the special zeolite used in this invention is not sulfur sensitive.
It is therefore within the scope of this inventlon to ad~ust the sulfur content of the synthesis gas produced by coal gasiflcation if needed to accommodate catalysts used with this gas. This technology is per se known and may be employed or not as required.

It has been noted above that the coal gasification process to be used is the ~urgi process. This invention is dependent for its ef~ectiveness upon the inclusion of some significant proportion o~ methane in the feefl to the methanol synthesis unit process as aforesaid. At present the Lurgi coal gasification process seems to be best able to meet this re~uirement and thus has been specified. Other coal gasiflcatlon processes which produce a product comprising proportions of about l to 5 molar parts of hydrogen to carbon ... ~ ...... . . .

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¦ monoxide and O.lto 1 molar parts of carbon diox-lde to carbon j monoxide would similarly be suitable. Since methane ls substantially inert in the carbon monoxide reduction processes ` used herein, its ~roportional presence is not critical. It is not unusual for methane to be present in a proportion of about OD2 to 1 mole per mole of carbon monoxide.
~, ' ' or The special zeolite ~talysts referred to herein utilize members of a special claes of zeolites e~xhibiting eome ¦' unusual properties. These zeolites induce profound trans-' 10 formations o~ aliphatic hydrocarbons to aromatic hydrocarbons ¦$~ ~n commercially desirable yields and are generally highly li effective in alkylation, isomerization, disproportionation 5 ` and other reactions involving aromatic hydrocarbons. Although they ha~e unusually low alumina contents, i.e. high silica to alumina ratios, they are very active e~en with silica to alumina ratios exceeding 30. This acti~ity is ~rpr~sing since ¦I catalytic activity o~ zeolites is generally attributed to framework aluminum atoms and cations associated with these aluminum atoms. These zeolites retain their crystallinity . , ¦' 20 for long periods in æpite o~ the presence of steam even at ¦ h~gh temperatures which induce irreverslble collapse of the j crystal framework of other zeolites, e.gO of the X and A type.
Furthermore~ carbonaceous deposlts, when formed~ may be removed by burning at higher than usual temperatures to restore activity. In many environments, the zeolites of this class exhibi~ very low coke forming capability, conducive to very I long times on stream between burning regenerations.
j An important characteristic of ~he crystal structure ¦ of this class of zeolites is that it provides constrained ~ 30 access to, and egress from, the intra-crystalline free ' ' ~ '' ' `' _ 9 _ .. ~ , .
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` ~ 3399 space b~ virtue o~ having a pore dimension greater than about 5 Anstroms and pore windows of about a ~ize such as would be provided by 10-membered rings of Oxygen atoms. It is to be understood, o* course, that -these rings are those formed by the regular disposition of the tetrahedra making up the anionic ~ramework o~ the crystalline aluminosilicate, the oxygen atoms themselves being bonded to the silicon or aluminum atoms at the centers of the tetrahedra. Briefly, the preferred zeolites useful in type B catalysts in this i 10 invention possess, in combination: a silica to alumina ratio o~ at least about 12, and a structure providing constrained access to the crystalline ~ree space.
The silica to alumina ratio referred to may be determined by conventional analysis. This ratio is meant to represent, as closely as possible, the ratio in the rigid i a~.onic ~ramework o~ the zeolite crystal and to exclude ¦i aluminum in the binder or in cationic or other form within the channels. Although zeolites with a silica to alumina ratio o~ at least 12 are use~ul, it ls preferred to use zeolites having higher ratios o~ at least a~out 30. Such zeolites, a~ter activation, acquire an intracrystalline sorption capacity for normal hexane which is greater than that ~or water, i.e. they exhibit "hydrophobic" properties.
It is believed that this hyarophobic character is advantage-ous in the present invention.
m e zeoliteæ use~ul as catalysts in this invention ~reely sorb normal hexane and have a pore dimension greater i than about 5 Angstroms. In addition, t~eir structure must provide constrained access to some larger molecules. It is sometimes possible to judge ~rom a known crystal structure , .
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~3991 .

whether such constrained access exists. For example? if the only pore windows in a crystal are formed by 8-membered rings of oxygen atoms, then access by molecules of larger cross-section t~an normal hexane is substantially excluded and the ¦ 5 zeolite is not o~ the desired type. Zeolites with windo~s of lO-membered rlngs are preferred, although excessive puckering or pore blockage may render these zeolites substan-' tially ine~ective. Zeolites with windows of twelve-membered rings do not generally appear to offer sufficient constraint to produce the advantageous conversions desired in the instant invention~ although structures can be conceived, due to pore blockage or other cause, that may be opera-tive.
Rather'than attempt to judge ~rom crystal structure whether or not a zeolite possesses the necessary constrained access, a simple determination of the "constraint index" may be made by continuously passing a mixture o~ equal weight o~
normal hexane and 3-methylpentane over a small sample, approxi-' mately l gram or less, of zeolite at atmospheric pressure according to the following procedure. A sample o~ the zeolite, in the ~orm o~ pellets or extrudate, is crushed to a partlcle ~ize about that o~ coarse sand and mounted ln a glass tube. Prior to testing, the zeoli-te is treated with a stream of air at lQ00F ~or at least 15 minutes~ The zeolite is then flushed with helium and the temperature adjusted 25 ' between 550F and 950F to give an overall conversion between ' 10% and 60~. The mixture o~ hydrocarbons ~s passed at l liquid hourly space velocity (i.e., 1 volume o~ liquid hydro-I carbon per volume o~ catalyst per hour) over the zeolite with I ' a helium dilution to give a helium to total hydrocarbon mole !
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ratio of 4:1. After 20 minutes on stream, a sample of the effluent is taken and analyzed, most conveniently by gas chromatography, to determine the fraction remaining unchanged for each of tbe two hydrocarbons.
The "constraint index" is calculated as ~ollows:
Conætraint Index = ~10 (~raction of n-hexane remaining) log ~fraction o~ 3-methylpentane 10 remaining) The constraint index approximates the ratio of the cracking rate constants for the two hydrocarbons Catalysts suitable ~or the present invention are those which employ a zeolite having a constraint index from loO to 12Ø Constraint Index (CI) values for some typical zeolites including some not within the scope of this invention are:
CAS C.I.
ZSM-5 8.3 ZSM-ll 8.7 TMA O~retite 3.7 Beta o.6 ZSM-4(Omega) o.5 Acid Mordenite o.5 - REY 0.4 Amorphous Z5 Silica-alumina o.6 Erionite 38 The above-described Constraint Index is an lmport~nt and even critical, definition of those zeolites which are useful to catalyz~ the instant process. The very nature df 3 this parameter and the recited technique by which it is determined, however, admit o~ the possibility that a given zeolite can be tested under somewhat di~ferent conditions and thereby have different constraint indexes. Constraint Index seems to ~ary somewhat with se~erity of operation (conversion).
There~ore, it will be appreciated that it may be ~ossible to ..

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so select test conditions to establish multiple constraint indexes for a particular given zeolite which may be both inside and outside the above defined range of 1 -to 12.
Thus, it should be understood that the parameter and property "Constraint Index" as such value is used herein is an inclusive rather than an exclusive value. That is, a zeolite when tested by any combination of conditions within the testing definition set forth herein above to have a constraint index of 1 to 12 is intended to be included in the instant catalyst definition regardless that the same identical zeolite tested under other defined conditions may give a constraint index value outside of 1 to 12.
The class of zeolites defined herein is exemplified by ZSM-5, ZSM-ll, ZSM-12, ZSM-21, and other similar materials. U.S. Patent 3,702,~86 describes and claims ZSM-5.
ZSM-ll is more particularly described in U.S. ~ `
Patent 3,709,979.
ZSM-12 is more particularly described in U.S.
Patent 3,832,449.
French Patent 74-12078 describes a zeolite composition, and a method oE making such, designated as ZSM-21 which is useful in this invention. ~ecent evidence has been adduced which suggests that this composition may be composed of at least two (2) different zeolites, one or both of which are the effective material insofar as the catalysis of this invention is concerned.

~-~IL08399 Elther or all of these zeolites is consldered to be within the ~cope of this invention.
The specific zeolites described, when prepared in ~he presence of organic cations, are substantially catalytically inactive, possibly because the intracry~talline free space is occupied by organic cations from the formlng solution. They may be activated by heating in an inert atmosphere at 1000F for one hour, ~or example, followed by base exchange with ammonium salts followed by calcination~
at 1000F in air. The presence of organic cations in the ~orming solution may not be absolutely essential to the formation of this special type zeolite; however, the presence of these cations does appear to favor the formation of this special type of zeolite. More generally, it is desirable to activate this type zeolLte by base exchange with ammonium salts followed by calcinatlon in air at about 1000F for from about 15 minutes to about 24 hours.
Natural zeolites may sometimes be converted to this type zeolite by various activation procedures and other treatments such as base exchange, steaming~ alumina extrac-tion a~d calcination~ alone or in comblnations. Natural minerals which ma~ be so treated inc]ude ferrierlte, brewsterite, stilbite, dachiardite, epistilbLte~ heulandLte and cllnoptllo-lite. The preferred crystalline aluminosilicates are ZSM-5, ZSM-ll~ ZSM-12 and ZSM-21, with ZSM-5 particularly preferred.
The zeolites used as catalysts in this invention may be in the hydrogen form or they may be base exchanged or ~i impregnated to contain ammonium or a metal cation complement.
¦ It is desirable to calcine the zeolite after base~exchange.
The metal cations that may be present include any of the ! c~tions of the metals of Groups I through VIII of the perlodic -1 - 14 _ -~
.
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~L~B3991 table. However, in the case of Group IA metals, the cation content should in no case be so large as to substantially eliminate the activity of the zeolite for the catalysis being employed in the instant invention.
For example, a completely sodium exchanged H-ZSM-5 appears to be largely inactive for shape selective conversions required in the present invention.
In a preferred aspect of this invention, the zeolites useful as catalysts herein are selected as those ha~ing a crystal framework density, in the dry hydrogen form, of not substantially below about 1.6 grams per cubic centimeter. It has been found that zeolites which satisfy all three of these criteria are most desired. Therefore, the preferred catalysts of this invention are those comprising zeolites having a constraint index as defined ahove of about 1 to 12, a silica to alumina ratio of at least about 12 and a dried crystal density of not substantially less than about 1.6 grams per cubic centimeter. The dry density for known structures may be calculated from the number of silicon plus aluminum atoms per 1000 cubic Angstroms, as given, e.g., on page 19 of the article on Zeolite Structure by W. M. Meier. This paper is included in "Proceedings of the Conference on Molecular Sieves, London, April, 1967", published by the Society of Chemical Industry, London, 1968. When the crystal structure is unknown, the crystal framework den-sity may be determined by classical pyknometer techniques.
For example, it may be determined by immersing the dry hyd-rogen form of the zeolite in an organic solvent which is not sorbed by the crystal. It is possible that the unusual ' .' ~ ~ .
~L~3991 . ` ' ' ' ' . .
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susta~ned acti~ty and stability o~ this class of zeolltes is . . associated with ~ts high crystal anionlc framework dens~ty of not les~ than about 1.6 grams per cubic centimeter. This : ~ . high dens~ty of course must.~e associated with a relatively ¦ 5 small.amount of ree space ~ithin the crystal, which might ` be expected to result in more ~ta~le structures. This free space, however, seems to be lmportant as the locus of catalytic acti~ity.
¦ Crystal framework densi~ies o~ some typlcal . ~0 zeolltes including some which are not within the preview of ~his invention are:
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. . Ferrierite O.28 cc/cc 1.76 ~/cc Mordenite .28 1.7 . . ZSM-5, -11 .29 1.79 ... . Dachiardite 32 1 ~2 . Clinoptilolite.34 1.71 . Laumontite 034 1.77 ZSM-4 (Omega).38 . 1.65 Heulandite .39 . 1.69 p ~41 1~57 O~fretite .40 1.5$
Levynite .40 1.5 Erionite .~$ 1.~1 Gmelinite .44 . 1.46 . ...... Chabazite . . 47 1 ~5 ~ . 8 1.27 According to this invention, coal, oxygen and steam : are reacted together at a temperature o~ about 1450 to 1800F
. . to produce a synthesis gas product compr-ising methane, :
: carbon oxides and hydrogen~ This gas may also contain . . .
water. The synthesis gas may be subjected to a water . ` gas shift reactlon if desired so that the rat~o of h~drog~n ~' . . .' ' .
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to carbon monoxide is about 1 to 5 to 1. Ratios of carbon dioxide to carbon monoxide of aboutO.l to 1 to 1 are suitable.
me synthesis gas is ~onverted to high octane ~romatic gasoline by eithe~ a one step direct process or a two ~tep process utilizing a methanol intermediate. In the direct process~ the synthesis gas is converted over a com~lna-tion catalyst having as a ~irst c~mponent the special zeolite referred to above and as the second component, a metal value wh~ch ha~ good carbon monoxide reducing cataly~ic activ~ty and poor olefin hydrogenatlon activity. Exemplary metals are ruthenium~ thorium, rhodium, iron and cobalt.
This direct process is carried out at about 300 to ~00F ~nd 50 to 1500 psigc In the two step process, the synthesis gas is converted in a first stage to a product comprising methanol.
m e catalgst suitably comprises zinc-copper. The process operates at about 350 to 650F and 700 to 2500 psig. Thermo-dynamic equilibria dictate operating at incomplete conversion with a synthesls gas recycle ratio o~ about 4 to 10. m e organic p~rtion of ~he-product comprising methanol is converted to aromatic gasoline over a special zeolite catalyst, as defined abo~e, at about 500 to 1200~. and about 0.5 to 50 LHS~
The products o~ either the direct or the two step Eynthesis conversion are resol~ed into C5 aromatic gasoline, 25~ water~ and C4 hyd~ocarbon gas including thè methaneorlginally produced in the coal gasl~lcation. r~he Cl~ fraction is itselP
resolved into an ~PG fraction compris~ng saturated C3 and C4's, a C2 fraction which is subjected to steam re~ormin~; and a C3 ~ C4 olefin plus isobutane fraction which is alkylated .' ~ .,"' ' ' ' ' .
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. . , , ''~`- ,,, ~083~91 ¦ with a homogeneous acid, e.g., hydro~luoric or sulfuric, catalys~ at up to about 450F and up to abou~ 500 psig.
Referring now to the drawing and particularly to Fig. 1 thereof coal 10, oxygen 12 and steam 14 are suitably reacted 16 to produce a synthesis gas 18 which is admixed with auxiliary synthesis gas 20, to be described below, and the mixture converted 22 to a product comprising methanol 24.
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~he unreacted portion o the synthesis gas 26 may be separated I . into a stream 28 comprising metha~e and a stream 30 comprising carbon monoxide and hydrogen, or it may be further processed witho~t resolution. In either case, a stream comprising methane 28 is steam reformed 34 to produce auxiliary synthesis gas 20. The organic portion o~ the product comprising methanol 24 is converted to gasoline using a special zeolite 36. The ~S product ~rom this conversion comprises water 38, which is recycled either to coal gasification 40 or to steam reforming 42 or both, and hydrocaxbons 46 comprisi~g C5~ aromatic gasoline 44, and C4- hydrocarbon. The hydrocarbon ~raction is resolved in a gas plan~ 47 to recover a C~~ tail gas 50, which i5 fed to the steam reformer 34, and an alkylation feed 52. ~lkylation 54 using an acid catalyst 56 produces alkylate 58 which is blended with the previously produced axomatic gasoline 44 to yield the ~l~al ~ull range, high quality yasoline product 60.
;~ Re~exring now to Fig. 2, the same coal gasifier as in Fig. 1 is used but in this case the synthesis gas 18 is ~ed to a direct conversion unit 70 containing carbon monoxide reducing catalyst and special zeolite catalyst. The product ;; of this direct conversion is separated into water 72, which ~ may be recycled to the steam reformer 34, and hydrocarbons 76 ,.' ~
,, .~

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399~

comprising C5+ aromatic gasoline 74 and C4- gas, which is resolved in a gas plant 78, a C2- tail gas stream 82 which is fed to the stream reformer 34 and an alkylation feed 84 comprising C3 and C4 hydrocarbons. Alkylation 86 utilizes an acid catalyst 88 to produce C7 and C8 alkylate 90 which is admixed with the prior produced aromatic gasoline 74 to cons-titute full range, high octane gasoline product 92.
In the alternati~e the products of either the direct or the two step synthesis conversion are resolved into C5+ aromatic gasoline, water and C4- hydrocarbon gas including the methane originally produced in the coal gasification. The C4- fraction may itself be resolved into a C2- fraction, and an alkylation feed fraction comprising saturated and unsaturated C3 and C4 hydrocarbons which is alkylated with a homogenous acid, e.g., hydro1uoEic or sulfuric, catalyst at up to about 450F and up to about 500 psig. Either the C2- tail gas or the entire C4- product may be methanated o~er a noble metal catalyst at about 525 to 1000 F.
Referring now to the drawing and particularly to Fig. 3 thereof coal 10, oxygen 12 and steam 14 are suitably reacted 16 to produce a synthesis gas 18 which is converted 22 to a product comprising methanol 24. The unreacted portion of ` ' the synthesls gas 26 may be separated into a stream 28 comprising ~ methane and a stream 30 comprising carbon monoxide and h~drogen, ;~ 25 or it may be further processed without resolution. In either case, at least the stream comprising methane 28 is admixed with other down stream products to be detailed below, and the `~
whole subjected to methanation 34. The portion of the product , ! ' ~ comprising methanol 24 is converted to gasoline using a special ~ ~

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~83~91 zeolite 36. The produce from this con~ersion comprises water 38 which is recycled to coal gaslfication 40, and hydrocarbon 41. The hydrocarbon 41 may be resolved in a gas plant 47 to recover C5~ aromatic gasoline 44, a C2- tail gas 50, which is fed to the methanator 34, and an alkylation feed 52. Alkylation 54 using an acid catalyst 56 produces alkylate 58 which is blended with the previously produced aromatic gasoline 44 to yield the final full range, high quality gasoline product 60.
LPG 48 comprises excess C3 and C4 saturates from 54.
Referring now to Fig,4, the same coal gasi~ier as in Fig.3 is used but in this case, the syn~hesis gas 18 is fed to a direct conversion unit 70 containing carbon monoxide ; reducing catalyst and special zeolite catalyst. The product of this direct conversion is separated into water 72, hydro-carbon 76 comprising hydrocarbon wh~ch is resolved in a gas plant 78 to C5~ aromatic gasollne 74, a C2- tail gas stream 82 which is fed to the methanator 34 and an alkylatlon fèed 84 comprising C3 and C4 olefins and isobutane. Alkylation 86 utilizes an , acid catalyst 88 to produce C7 and C8 alkylate 90 which is admixed with the prior produced aromatic gasoline 74 to constitute full range, high octane gasol~ne product 92. LP~ 80 comprlses exce6s C3 and C4 saturates from 86.
The various unit processes of this invention can be carried out in flxed, fluidiæed or transport type catalyst beds. Approprlate heat exchange can be provided as required.
The product gasoline is an excellent lead-free motor fuel. In fact, lt has such high quality that lt can be blended with substantial volumes of lower octane materials such as straight run naphtha to increase lts volume while still maintaining excellent quality.

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Claims (8)

WHAT IS CLAIMED IS:

1. A process of converting coal to gasoline comprising:
reacting coal with oxygen and water at about 1450 to 1800°F to produce a synthesis gas produce comprising carbon oxides, hydrogen and methane;
catalyzing the conversion of said carbon oxides and hydrogen to a product comprising water, C? gas and C?
aromatic gasoline by a catalyst comprising a crystalline aluminosilicate zeolite having a silica to alumina ratio of at least 12 and a constraint index of 1 to 12;
separating said C? gas into a C? tail gas com-prising methane, ethane and ethylene, and an alkylation feed comprising saturated and unsaturated C3 and C4 hydrocarbons:
alkylating said alkylation feed in contact with a strong acid at up to about 450°F and up to about 500 psig;
admixing C7 and C8 alkylate with said aromatic gasoline;
steam reforming said C2 tail gas to an auxiliary synthesis gas comprising carbon oxides and hydrogen; and admixing said auxiliary synthesis gas with said coal gasification gas prior to conversion thereof into said aromatic gasoline.

2. The process claimed in claim 1 including converting said synthesis gas to a product comprising methanol by contact with a catalyst comprising zinc and copper at about 350 to 650°F and about 700 to 2500 psig; recycling unreacted synthesis gas to said methanol synthesis; steam reforming a product light gas comprising methane, and converting a portion of the methanol synthesis product comprising methanol to said product comprising aromatic gasoline by contact thereof at about 500 to 1200°F with said zeolite.

3. The process claimed in claim 1 including contacting said synthesis gas with a catalyst comprising said zeolite as a first component and as a second component a metal value having high catalytic activity for reducing carbon monoxide and low catalytic activity for hydrogenating olefins, at about 300 to 800°F and about 50 to 1500 psig; recovering a fraction and steam reforming such.

4. The process claimed in claim 3 wherein said metal value is at least one member selected from the group con-sisting of thorium, ruthenium, iron, rhodium and cobalt.

5. The process claimed in claim 1 wherein said zeolite is a ZSM-5.

6. A process according to Claim 1 wherein the C? portion of said C? gas is contacted with a methanation catalyst at about 525 to 1000°F to convert such to synthetic natural gas, and there is recovered synthetic natural gas, aromatic gasoline and LPG.

7. A process according to Claim 6 wherein methane-containing off gas from said methanol synthesis is mixed with C? gas from said methanol aromatization and the result-ing mixture is methanated.

8. A process according to Claim 6 or Claim 7 wherein said methanation catalyst is nickel, cobalt, platinum or ruthenium.