Note: Descriptions are shown in the official language in which they were submitted.
~s~
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
. .
; 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
''' , ~
, ,__. ___ _, _ _ .. _ ............................ , .. .. __ .. _ .. _ . _. _, , __.. _. _.. v
;
1083991
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.
~ ~-
. .
: .. . -
.
; 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- ~ ~
I' . . .
.. _ . .. ... .. . . . .
339
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.
~ - 4 -
.
~ 8399~L
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.
_ . . _ . _ .. _ _ . _ .. ..... . .... .. .
... . . . ..... ..
1~3g9~L
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
- 8 -
... ~ ...... . . .
I ~ `
-
~83
~ .
¦ 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 _
.. ~ , .
... .. . .
i .
` ~ 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
, .
. ~ -' 10 -
,
_ _ .. .. . . . ... . .. . . . .
~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
!
. ,
.. . 11 .
. .. . ..
~ 8 ~9 ~
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
ZSM-12
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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: . , ,; ~
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.. _ , _ ..... . . . . .. . ...
~ILOi5 39g~
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 _ -~
.
,
.. . . . . ... . ~ ~ ~
~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
- 15 -
' .'
~ ~ .
~L~3991
. ` ' ' ' ' . .
. ~ . , ` ' .
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:
. ..
. . Void Framework
. Zeollte Volume Dens$t~
. . .
. . 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
~'
. . .' '
.
. ..
~: - ;1~ - `' .
~ . . . ...
.
, _ . .. . . . .. . ... _ .. . .. .
g~ l
~al8399~L .
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
.' ~ .,"' ' ' ' ' .
~:
:~' . - lr- , ~
. . , , ''~`- ,,,
~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.
. . .
~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
,.' ~
,,
.~
,
' ~,
.
. ......... __..... , . ...... .. . .... ,._. ...... .. .. . .....
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 ~ ~
~, :
:~ :
~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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, :; ,
