Note: Descriptions are shown in the official language in which they were submitted.
7Z13
1 BACKGROUND OF THE INVENTION
2 1. Field o~ ~he I~vention
-
3 This invention relates to a process for l-L~uefyillg
4 coal in a non-hy~rogen donor solvent to li~uid hy~roc~ on
products ln the presence of a catalyst prepared in situ
6 rom a small amount of metals added to the mixture of coal
7 and solvent as oil soluble metal compounds.
8 20 Descript~on of th~ Prior Art
.. . _
9 Liquefaction of coal to coal liquids in a hydrogen
donor solvent process is well known. In such a process, a
11 slurry of coal ln a h~drogen donor solvent is reacted in the
12 presence of molecular hydrogen at elevated temperature and
13 pressure. The hy~rogen donor solvent which becomes hydrogen
14 depleted during the coal liquefactîon reaction, in th~
prior art processes~ is generally subjected to a hydrogen~
16 ation stage prior to its being recycled to the liquefaction
-17 zone.
18 It is also known to convert coal to liquid produc~s
19 by hydrogenation of coal which has been impregnated with
an oil-soluble metal naphthenate or by hydrogenation of
21 coal in a liquid rnedium such as a hydrogen donor oil having
22 a boiling range of 250 to 325C. containing an oil-soluble
23 metal naphthenate. Concentrations as low as 0.01% metal
24 naphthenate catalysts, calculated as the metal, were folmd
to be effective for the conversion of coal.
26 A process is known for the liquefaction of su~-
27 bituminous coal in a hydrogen donor oil in the presence of
28 hydrogen, carbon monoxide, water, and an alkali metal or
29 ammonium molybdate in an amount ranging from 0.5 to lO
percent by weight of the coal.
-- 2 --
,
:llV7Z13
t It has now been found that when the coal lique-
2 fac~ion reaction is conducted in the presence of a minor
3 amount of a catalyst produced from an added oil soluble
metal compo~md, effective liquefactio~ of coal wlth molecu~
hydrogen will occur when a non~hydrogen donor solvent is
6 used. Furthermore, the non hydrogen donor solvent can be
7 recycled to the liquefaction zone without intervening
8 hydrogellation. Therefore, utiliza~ion of a nonQhydrogen
9 donor solven~ eliminates the need for an external solvent
hydrogenation stage, such as is generally used in conven-
11 tional coal hydrogen donor solvent liquefaction processes.
12 Additional advant~ges in the utilization of oil-
13 soluble metal compounds in a non~hydrogen donor solvent
14 coal liquefaction process will become apparent in the
following description.
16 The term "hydroconversion" with reference to coal
17 is used herein to designate conversion of coal to liquid
hydrocarbons in the presence of hydrogen.
19 SUMMQRY OF THE INVENTION
In accordance with the invention, there is
21 provided, a process for liquefying coal to produce an oil,
22 which comprises the steps of: (a) forming a mixture o~
23 coal, a non-hydrogen donor solvent and an added oil soluble
24 metal compound, said ~etal being selected from the group
consisting of Groups VB, VIB, VIIB and VIII of the Periodic
26 Table of Elements and mixtures thereof, (b) converting said
27 oil-soluble compound to a catalyst within said mixture in
28 the presence of a hydrogen~containing gas;(c)n~ct~gthe re~ng
29 mixture with a gas comprising molecular hydrogen under coal
~ llquefaction conditions, in a liquefaction zone, and (d)
. .. . ... . ,,, . ., ~
'
~ 1~ 7 ~ ~ 3
I recovering a coal liquefaction product mixture comprising
2 an oil product and solids o
3 In accol-dance with another embodimer,t of ~he
4 invention~ there is provicied a process for liquefying coal
to produce an oil, which comprises: (a) forming a mixture
6 of wet coal, a non-hydrogen donor solvent and an ~dded oil-
7 soluble metal ccmpound, said oil~soluble metal compound
8 being added in an amount ranging from about 10 to about 700
~ wppm, calculated as the elemental metal, based on the weight
of coal in said mixture, said metal being selected from the
ll group consisting of Groups VB, VIB, VIIB and VIII of the
12 Periodic Table of Elements and mixtures thexeo~; (b) con
l3 verting said oil~soluble metal compound to a catalyst within
l4 said mixture in the presence of a hydrogen-containing gas;
(c) reacting the resulting mixture containing said catalyst
6 with a gas comprising hydrogen and from about 5 to about 50
17 mole percen~ carbon monoxide, under coal liquefaction
18 conditions, in a liquefaction zone; and (d) recovering a
l9 coal liquefaction product mixture compri~ing an oil product
and solids.
21 BRIEF DESCRIPTION OF T~E DRAWINGS
22 Figure 1 is a schematic flow plan of one em~odiment
23 of the invention~
24 Figure 2 is a schema~ic flow plan of another
embodiment of the inventionO
26 ~ESCRIPTION OF THE PREFER~ED RMBODIMENTS
27 The process of the invention is generally applica-
28 ble to hydroconvert coal to produce coal liquids (i.e.
normally liquid hydrocarbon products) in a non-hydrogen donor
solvent process. The term "coal" is used herein to designate
,,
-- 4
11~7Z13
a nor~ally solid ca~bonaceous material including all. ranks
2 of coal, SUCll as an~hracite coal, bituminous coal, semi-
3 bituminous coal, subbituminous coal~ ~ignite, peat and
4 mixtures thereof.
In the process shown in Figure 1, the coal, in
6 particulate form, of a size ranging up to about 1/8 inch
7 particle size diameter, suitably 8 mesh (Tyler) is intro-
8 duced by line 10 into a mixing zone 12 in which it is
9 mixed with a non hydrogen donor solvent introduced by
line 14. The solvent and coal are admixed in a solvent-to-
ll coal weight ratio ranging from about 0.8:1 to 4:1~ preferably
12 from about 1:1 to 2:1.
l3 The non-hydrogen donor solvents employed in the
1~ proress of ~he presen~ invention are solvents which contain
less than 0.8 weight percent donatable hydrogen, based o~
l6 ~he weight of the total solvent. Preferably~ the solvent
17 will be a non-hydrogen donor compound or mixture of compounds
18 having an atmospheric boiling point ranging from about 350~.
19 to about 850F , more preferably ranging from about 350F.
to less than about 650F. Suitable non-hydrogen donor sol-
21 vents include aromatic compounds such as aLkylbenzenes, alkyl
22 naphthalenesJ alkylated polycyclic aromatics, heteroaromatics
23 and mixtures thereof, etc., and streams such as unhydro-
24 genated creosote oil, intermediate product streams from
catalytic cracking of petroleum feedstocks, coal derived
26 liquids, shale oil and the like. An oil-soluble metal
27 compQund wherein the metal is selected from the group
2~ consisting of Groups VB, VIB, VIIB, VIII and mixtures
29 thereof of the Periodic Table of Elements is added to the
~ non-hydrogen donor solvent by line 16 so as to form a
; ~
7213
~ mlxture of oil soluble metal compound3 ~on-hydrogen dorlor
z solvent and coal in mixing zone 12. The oil-soluble metal
3 compound is added in an amount su~ficient to provide rom
4 about 10 to less than 2000 wppm) preferab~y from about 25
to 950 wpp~ more preferably, from about 50 to 7~0 wppm,
6 most preferably ~rom about 50 to 400 wppm, of the oil-
7 soluble metal compound9 calculated as the elemental metal,
~ ~ based on the weight of coal in the mixture.
9 Suitable oil-soluble met~l compounds convertible
to active catalysts under procPss conditions include (1)
ll inorganic metal compounds such as halides, oxyhalides,
12 hydrated oxides, heteropoly acids (e~g. phosphomolybdic
13 acid, molybdosilisic acid), (2) metal salts of organic
14 ac~ds such as acyelic and alicyclic aliphatic carboxylic
lS acids containing two or more carbon atoms (eOg. naphthenic
16 acids); aromatic carboxylic acids (eOg. toluic acid);
17 sul~onic acids (e.g. toluenesulfonic acid), sulfinic acids;
18 mercaptans9 xanthic acid9 phenols, di and polyhydroxy
19 aromatic compounds, (3) organometallic eompounds such .~s
metal chelates, e.g~ with 1~3~diketone.~, ethylene diamine,
2l ethylene diamine tetraacetic acld, etc.,
22 (4) metal salts of organic amines such as aliphAtic amines,
23 aromatic amines9 and quaternary ammonium compoundsO
24 `The metal constituent of the oil soluble metal
compound is selected frcm the group consisting of Groups
?6 VB, VIB9 VIIB and VIII of the Periodic Table of Elements,
27 and mixtures thereof, in accordance with the table pub-
28 lished by E. H. Sargent and Company, copyright 1962, Dyna
Slide Company, that is, vanadium, niobium~ tantalum,
chromium, molybdenum, tungsten, manganese, rhenium, iron,
- 6 -
'
li~7213
1 cobalt, nickel and the noble metals including platinum,
2 iridium, pall~dium, osmium, ruthenium and rhodium. Tne
3 preferred metal consti~uent of the oil soluble metal
4 c~mpound is sel.ected from the gro~p consisting of molybdenum5
S vanadium an~ chromium. More preferably, the metal constit-
6 uent of the oi~ soluble metal compound is selected from the
7 group consisting of molybdenum and chromium. Most prefer-
8 ably, the metal constituent of the oil soluble metal compound
9 is molybdenum. Preferred compounds of the metals include
lo the salts of acyclic (straight or branched chain) aliphatic
11 carboxylic acids, ~alts of alicyclic aliphatic carboxylic
12 acids, heteropslyacids; hydrated oxldes, carbonyls, phenolates
13 andorganic amine saltsO More preferred types of metal com~
14 pounds are the heteropoly acids, e.g. phosphomolybd~c aeid.
lS Another preferred metal compound is a salt of an alicyclic
16 aliphatic carboxylic acid guch a~ a metal naphthena~e~
17 The most preferred compounds are molybdenum naphthenate,
18 vanadium naphthenate and chromil~n naphthenate.
19 When the oil~soluble metal compound is added to
the non-hydrogen doncr solventy lt dissolves in the solvent.
21 To fo~m the catalystD the metal compound ~catalyst precursor)
22 is converted within the slurry of coal and non~hydrogen
23 donor solvent.
24 Various methods can be used to convert the dis-
solved metal compound in the coal~solvent slurry to an
26 active catalys~. A preferred method (pretreatment method)
27 of fonming the catalyst rom the oil~solubLe compound af
28 the present invention is to heat the mixture of metal
compound, coal and solvent to a temperature ranging from
about 325C. to about 438C. and at a pressure ranging
.
-
- 7 -
l i~ 7 ~ 1 3
l from about 500 to about 5000 psig, in the presence of a
2 hydrogerl-c~n~aining gas. The hyd~ogen-containi.rlg gas .~ay
3 be pure hydrogen but will generally be a hydrogen stream
4 co;ltaining some other gaseous contaminants9 for example,
the hydrogen~containing effluent produced in reforming
6 processes, e~c.
7 Preferably the hydrogen-containing gas also
comprises hydrogen sulfide. The hydrogen sulfide may com-
9 prise from about 1 to about 90 mole percent, preferably
from about 1 to about 50 mole percent D more prefera~ly from
ll about 1 to 30 mole percent of the hydrogen~containing gas
12 mixture. The pretreatment is conducted for a period ranging
l3 from about ~ min~tes to about 2 hours9 preferably for a
14 period ranging from about 10 minut~ to about 1 hour. The
thermal treatment in the presence of hydrogen or in the
16 presence of hydrogen and hydrogen sulfide iæ believed to
7 facilitate conversion of the metal compound to the corre-
18 sponding metal~containing active cataiysts which act also
19 as coking inhibitors.
The coal-solvent slurry containing the resulting
21 catalyst is then introduced into a coal liquefaction zone
22 which will be subsequently described.
23 Another method of con~erting the oil~soluble me~al
24 compound of the present invention is to react the mixture of
metal compound, coal and non~hydrogen donor solvent with a
26 ~ydrogen-containing gas at coal liquefaction conditions to
2~ produce a catalyst in the chargestock, in situ, in the
28 liquefaction zone. The hydrogen~containing gas may comprise
29 from about 1 to about 30 mole percent hydrogen sul~ide.
Whatever the exact nature o~ the resulting con- ~-
- 8 -
~1072~3
I version products of the givell oil~soluble m~tal compound,
2 the resulting metal componen~ ls a catalytic agent and a
3 coking inhibitor.
4 In the process shown in Figure 1, the mixture of
oil~soluble metal compound9 a non hydrogen donor solvPnt,
such as alpha methylnaphthalene, and coal is removed from
7 mixing zone 12 by line 18 and introduced into pretreatment
8 zone 13 into wllich a gaseous mlxture comprising hydrogen and
9 from about 1 to about 90 mole percent, preferably from about
1 to 50 mole percent, more preferably from about 1 to 30
ll mole percellt hydrogen sulfide is introduced by line 15. The
12 pretreatment zone is maintained at a temperature ranging
13 from about 342C. to about 415C. and at a total pressure
14 ranging from about 500 to abou~ 5000 psig. The pretreatment
is conducted for a period of time ran~ing from about lO
16 minutes to about 1 hourO The pretreatment zone effluent
17 i8 removed by line l9o If desired, a-portion of the hydrogen
18 sulfide may be removed from the effluent. The pretreatment
19 zcne effluent is introdu~ed ~y line 19 into li~uefaction
reactor 22. A hydrogen~containing gas is introduced into
21 liquefaction reactor 22 by Line 200 The hydrogen-containing
22 gas may be pure hydrogen but will generally be a hydrogen
23 stream containing some other gaseous contaminants 9 for
24 example, the hydrogen~contailling effluent produced in
reorming. Suitable hydrogen~¢ontaining gas mixtures for
26 introduction into the liquefaction zone include raw synthesis
27 gas 9 that isS a gas containing hydrogen and from about 5 to
2g about 50, preerably rom about 10 to 30 mole pereent carbon
29 monoxide.
When wet coal (iOe. coal particles associated with
_ g _ .
11'~7Z13
i !
1 water) is u~ilized as feed, it is particularly desirable to
2 utilize a raw syr.Ehes~s gas, ~hæt is~ a gas comprising
3 hydrogen and carbon monoxide. In such an embodiment9 the
4 metal compound, pre~erably a ~.etal~containing organic
compound, is added in an amount ranging from 10 to 700 wppm,
~ preferably from 50 to 500 wppm, calculated as t~e element~l
7 metal9 based on the coal alone~ The gas introduced by line
8 20 may additionally contain hydrogen sulfide in an amount
9 ranging from about 1 to 30 mole percent.
o The coal liquefaction zone is maintained at a
11 temperature ranging from about 343 to 538C. (649.4 to
12 lOOO~F.)J preferably from about 416 to 468C. (780.~ to
13 89g.~F.), more preferably from about 440 to 468C. (824 to
14 875F.), and a hydrogen partial pressure ranging from about
500 psig to about 5000 p5ig~ preferably from about 1000 to
16 about 3000 psig. The space velocity, defined as volumes of
17 the mixture of coal and solvent feedstock per hour per ~olume
18 of reac~or (V/Hr./V), may vary widely depending on the
19 desired conversion level. Suitable 8pace velocities may
range broadly from about 0.1 to 10 volumes feed per hour per
21 volume of reactor, preferably from about 0025 to 6 VlHr./~,
22 more preferably from about O.S to 2 VIHr./V. The coal lique-
23 faction zone effluent is removed from t.he zone by line 24.
24 The effluent comprises gases, an oil product and
a solid residue which is cataly~ic in nature. The ef1uent
26 is passed to a separation zone 26 from wh~ch gases are
27 removed overhead by line 28. This gas may be scrubbed by
28 conventional methods to remove any undesired amount of
29 hydrogen sulfide and carbon dioxide and thereafter it may
~ be recycled into the coal liquefaction zone. The solids may
- 10 -
7Z13
1 be separated from ~he oil product by conventional means,
2 for example, by settling or centrifuging or filtration of
3 the oil-solids slurry. The separated solids are removed
4 from separ~tion zone 26 by lin~ 30~ If desired at least a
portion of the separated solids or solids concentrate may
6 be recycled direc~ly to the coal liquefaction æone via line
7 31 or recycled to the coal-solvent chargestock.
8 The remaining portion of solids removed by line
9 30 may be`discarded as such since normally ~hey do not
contain economically recoverable amounts of char. The oil
11 produc~ is removed rom separation zone 26 by line 32 and
12 passed to a fracti.onation zone 34 wherein a light fraction
13 boiling below about 400Fo (204~44Co) is recovered by line
.~ 14 36. A heavy fraction is removed by line 38 and a.n inter- :
mediate range boiling fraction, that is, a raction boiling
16 from about 400 to about 700F~ (204044 to 371~11Co) at
17 atmospheric pressure, including the non~hydrogen donor
18 solvent, is recovered by line 40O In a preferred embodiment
19 of the present invention9 at ieast a portion of the inter-
mediate fraction having less than 008 weight percent
21 donatable hydrogen, which includes the recovered non-hydrogen
22 donor solvent, is recycled via line 42, without any inter-
23 vening rehydrogenation9 into mixing zone 12 or directly into
24 the coal liquefaction zone.
It should also be noted that in non-catalyzed
26 hydrogen donor coal liquefactio~. processes, ~the heavy
27 bottoms product resulting from fractional distillation of
28 the coal liquefaction oil product contains solids. The
29 solids-containing heavy bottom~ f~action is typically sub-
3~ jected to a fluid coking operation since a substantial
-
1~07Z13
1 po~tion of the carbon of the chargestock emerges with the
2 solids in the form of char that must be recovered. In
3 contrast, in the process of the present invention, ~ince
. 4 the solid residue of the liquefaction zone does not eontain
any significa1lt amou.nt of char, the solids can be separated
6 from the coal liquefaction zone effluent by known means and
7 discarded or used as catalyst. The process of the present
8 invention would permit the elimination of the coking step~
9 Figure 2 shows various process options fox treating
the coal liquefaction zone effluent which is removed from
11 the.coal liquefaction reactor 22 by line 24. The effluent
12 is introduced into a gas-liquid separator 26 where hydrogen
13 and light hydrocarbon~s are removed overhead by line 28.
14 Three preferred process options are available for the liquid
stream containing dispersed catalyst solids which emerge
16 from separator vessel 26 via line 30.
17 In process optlon to be designated 'IA", the liqui~-
18 solids stream is fed by line 32 to concentration zone 34
19 where by means, for example, of distilla~ion, solid precip-
.20 itation or centrifugation, the ~tream i8 ~epara~ed into a
21 clean liquid product, which is withdrawn through li.ne 36,
22 and a concentrated slurry (e.g. 20 to 40 percent by weight)
23 in oil. At least a portion of the concentrated slurry can
24 be re ved as a purge stream through line 38 to control the
buildup of solid materials in the coal liquefaction reactor,
26 and the balance of the slurry is returned by line 40 and
. 27 line 30 to liquefaction reac~or 220 The purge stream may
~ be filtered subsequently to recover c~alyst and liquid
product or it can be burned or gasified.to provide, respec-
tively, heat and hydrogen for the pr3cess.
- 12 -
7~ 1 3
1 In the process option to be designated "B", the
2 purge stream from concen~ration zone 34 is omitted and the
3 entire slurry concentrate withdr~wn through line 40 i~ fed
to separation zone 44 via lines 30 an.d 42. In thi.s æone,
a major por~.ion of the remaining ll~uid phase is separated
6 from the solids by means of centrifugation, filtration or
7 a combination of settling and drawoff 9 etc.. Liquid is
8 removed from ~he ~one through line 46 and solids through
line 48~. At least a portion of the solids and associated
o remaining liquid are purged from the process vi.a line 50 to
ll control the buildup of solids in the process and the balance
12 of the solids ~s recycled to liquefaction reactor 22 via
line 52 which connects to recycle line 30. The solids can
be recycled either as recovered or after suitable cleanup
(not shown) to remove heavy adhering oil deposits and coke.
16 In option designated "C", the slurry of solids in
17 oi. exiting fro~ separator 26 via line 30 is fed direc~ly
18 to separation zone 44 by way of line 42 whereupon solids
l9 and liquid product are separated by means of centrifugation
or filtration. All or part of the solids exi~ing from
21 vessel 44 via line 48 may be purged fronn the process through
22 line 50 and the remainder recycled to ~he liquefac~ion
23 reactor. Liquid product is recovered through line 46. If
24 ~esired, at least a portion o the heavy fraction of the
hydroconverted oil product may be recycled to ~he coal
26 liquefaction zone.
27 The process of the invention may be conducted
28 either ~s a batch or as 8 continuous ~ype proceæs~
29 The following ex~mple i~ presen~ed to illustrate
the invention.
. - 13 -
llV7Z13
1 EXAMPLE
2 C.ompar~ti-~e e~perlmen~.s.were made ln which molyb-
3 denum naphthenate was u~llized as ¢atal~3t precursor in a
4 non~hydrogen donor sol~vent9 tha~ is~ in alpha meth~l-
5 naphthalene~ co~pared to c~ntrol ru.ns in which hydrogenated
6 c:reosote oil, having ~ don~table hydrogen content of 1. 54
7 weight percent, a hydrGgen donor solvent~ was utilized.
8 The chærg~s~ock used in these experiments was a
9 50/50 mixture of Wyodak coal and solvent. The molybdenum
concentra.tion was 404 weight par~s per million molybdenum,
11 calculated as the elemental metalD based on coal alone. In
12 the runs9 in which pretrea~ment was performed, the pretreat-
13 ments gas was a mixture of 18% H2S and 82% hydrogen. The
14 pretreatment conditi3ns were an initial pressure at room
temperature of lS00 psig and a pretreatment ~emperature of
: 16 725F. The liquefaction conditions were 820F. and 200
~ 17 psig hydrogen for 1 hourO The results of these experiments
18 are summari7ed in the tableO
- 14 -
u~
o~ ~
o o ~/
I~
~ ~ 0 C`~ ~ ~
o o --l o ~ o ~
0 _ O C`J
~O~D~
;~
~e`l o~ o
J~ 00
Q) 0
~ u~o ~ ~ ~ ~
~--o ~ ~ o
i~~ o ~ o oo o~
I_i O C~
P4~-1 0
J~
~ ~ ; U ' 'o
,V' ~ o ~
~ ~ o
_1 ~0~ ~ ~ o
O td ~ ~1
ooo~
~d ~rl
~ ~i
~ ~ o
~ ~ bO
a~ d O ~ i~
~ o ~
U ~-rl U ~ ~~d ~.
U h ~ ~ . _1
h C~ ¢ a~
o v
~ ~J i3.~ 1tn 4
O ~ tq + t.) aJ ~
O ~ l 0 ~ I O ~ P
V O c~ ~ g, o o ~Z;
P: ,~ ~ cn v~ ~c
-
~ 7 Z ~ 3
1 As can be seen from the table, run 3 compared with
2 n~n 1 shows ~hat non-hydrogen donor solvent with molyb~emlm
3 added perfcrms slightly ~etter than conventional hydrogen
4 donor solvent (run 1~. Rlm 5 compared with run 1 ~hows
that this proces~ performs much better than conventional
6 hydrogen donor solvent liquefaction. Run 5 compared wlth
7 run ~ shows that preferred conditions for this process are
8 superi.or to catalyzed hydrogen donor solvent liquefaction.
9 ~un 5 versus run 4 shows that under preferr~ conditions, a
non-hydrogen donor solvent has an equivalent performance to
ll a hydrogen donor solvent.
- 16
