Note: Descriptions are shown in the official language in which they were submitted.
1 BACKGROUND OF ~XE INVENTION
2 1. Field of the Invention
3 Thi9 invention is directed to i~proving properties of
4 solid, naturally-occurring carbonaceous material such as
coal and, in par~icular, to improving y~elds and physical
6 characteristics of coal liquefaction distillates and
7 bottoms.
8 2. Description of the Prior Art
g Much work has been done in recent years to make useful
llquids and gases from coal. Various types ~f liquefaction
11 processes have been developed, such as solvent refining,
12 direct hydrogenation with or without a catalyst, catalytic
13 or non-catalytic hydrogenation in the presence o~ a non-
14 donor ~olvent, and catalytic or non-catalytic liquefaction
by the donor solvent method. Exemplary of the solvent
16 hydrogen donor liquefaction process is U~S. Patent 3,617,513.
17 In an effort to increase liquefaction yields, a number
18 of ancillary processes have been developed, such as pretreat-
19 ment of coal prior to the liqueaction process or post-treat-
ment of products derived from the liquefaction process, e.g.,
21 liquefaction distillates, coal liquids and bottoms. Exemplary
22 of pretreatment processes is U.S. Patent 4,092,235, which
23 discloses acid-catalyzed Friedel-Crafts C-alkylation or
24 C-acylation of coal ~o increase the yield of products from
coal liquefaction. The introduction of aliphatic hydro-
26 carbon radicals or acyl radicals, including carbon monoxide,
27 i~to the coal structure is believed to permit a greater
28 quantity of the coal to undergo liqu~faction at suitable
29 liquefaction conditions. The alkylation or acylation
reactions, which may be conducted ~n the presence or absence
31 of added or extraneous catalysts, take place at carbon si~es.
32 Many of the C-alkylation and C-acylation processes
33 require a considerabLe amount of alkylating or acylating
3~ agent in order to accompl sh their purpose. Further, during
the subsequent coal liquefaction process, phenols present in
36 the coal are cleaved to produce water. In liquefaction
64
-- 2 --
1 processes employing hydrogen, an excessive use of hydrogen
2 thus occurs.
3 SUMMARY OF T~ INVENTION
4 In accordance with the invention, properties of solid,
naturall~-occurring carbonaceous materials, such as coal,
6 are improved. Also, coal lique~ac~.ion distillates and
7 bottoms having improved p-operties are formed by a process
8 which comprises (a) treating functionalities having weakly
9 acidic protons in coal by a process selected from the group
consisting of alkylation and acyla~ion, and (b) subjecting
ll the treated coal to liquefaction process. Weakly acidic
12 protons include phenolic, carboxylic and mercaptan func-
13 tionalities. The O-alkylation or O~acylation is conven-
14 iently carTied out by use of a phase trans~er reagent and
an alkylating or acylating agen~. The phase transfer
16 reagent, wnich is recyclable, is, by way o~ example, a
17 quanternary ammonium ~ phosphonium base (R4QOR"), where R
18 is the same or different group seLected from the group
l9 consisting of Cl to about C~0 ~ll.cyl and r6 to abvu~ ~2~ aryL
Q is nitrogen or phosphorus; and R" is selected from the
21 group consisting of hydrogen, Cl to about C~ yl, a~yl
22 a~lylaryl, arylalkyl and ac~e~ 1. The alkyLating and
23 acylati~g agents ar~ ~ cnt~ by the formula R'X where
24 R is a Cl 20 or acyl group and X is a leaving
group selected fr~m the group Gonsisting of halide, sulfa~e,
26 bIsulfate acetate and stearate, wherein X is a~tached to
27 a primary or secondary carbon atom.
28 The O-alkylated or O-acylated coal is then sub~ected to
29 a coal liquefac~ion process to produce distillable coal
liquids. These coal liquids are formed in greater yields and
31 have more desirable properties than those formed from ~he
32 same liquefaction process but using untreated coal. The im-
33 proved physical properties of these coal liquids are reduced
3~ viscosity, lower boiling ranges and increased compatlbility
with petroleum liquids. The excessive use of hydrogen to
36 produce water is also avoided in the liquefaction of
~ ~ ~O Q ~ ~ ~
- 3 -
1 O-alkylated and O-acylated coals employing hydrogen-based
2 liquefaction schemes.
3 BRIEF DESCRIPTION OF THE DRAWING
4 The Figure schematically illustrates one process for
effecting and utilizing the preferred embodiment of this
6 inventiOn.
7 DETAILED DESCRIPTION OF THE INVENTI()N
.
8 The procedure that follows is especially useful for the
g selective o-alkylation or O-acylation of bituminous, sub-
bituminous and lignite coals usually employed in liquefaction
11 processes or other solid, naturally-occurring carbonaceous
12 materials employed in various ca~^bonaceous conversion
13 processes. The ~henolic and carboxylic functlonal sub-
14 stituents in the coal are chemically altered. These two
very polar functional groups are converted to relatively
16 non-polar ethers and esters, respectively. The chemical
17 transformation may be represented as follows:
18 Ar-OH ~ R'X~ Ar-OR'
19 AR-COOH ~ R'X Ar-COOR'
where R' is a Cl to about C~0 alkyl or acyl group,and ~;is
21 an aromatic substituent.
22 The O-alkylation or O-acylation of solid coal by reagents
23 which are in liquid s~lution is greatly influenced by use of
24 a phase transfer reagent. Such a reagent has both lipophilic
and a hydrophilic portion and is capable of transferring a
26 basic species, -OR", from an aqueous phase to either
27 a solid or liquid organic phase, where R" iS ei~her
28 hydrogen or a carbon-bearing functionality. The phase
29 transfer reagent may be generated catalytically, in which
case the process is termed a phase transfer catalysis, which
31 is a well-known reaction; see, e.g. Vol. 99, ~ournal of the
32 American Chemical ~ociety, pp. 3903-3909 (1977). Al~er-
33 natively, the reagent may be generated in a separate step,
34 then used in the alkylation or acylation reaction. If this
latter reaction is employed, then the active form of th~
36 reagent may be regenerated in a subsequent step. In either
Qfi~
-- 4 --
1 case, the overall chemical transformation on the solid
2 coal is the same. A generalized mechanistic scheme of
3 this transformation is shown below:
4 _ R4QX + M:OR'' ~ 4 R4QOR'' ~ M X
Coal-H ~ R4QOR" _ ~Coal-QR4 + ~''OH
6 Q 4 ~ Coal-R' + R4QX
7 The phase transfer reagent is preferably a quaternary
8 base represented by the formula R4QOR" where each R is the
9 same or different group selected from the group consisting
of Cl to about C20, preferably Cl to C6 alkyl and C6 to
11 about C20, preerably C6 to C12 aryl group; Q is nitrogen
12 or phosphorus, preferably nitrogen, and R" is selected from
13 the group consisting of hydrogen, Cl to about C10, pref-
14 erably Cl to C6 a~kyl, aryl, a~kylaryl, arylalkyl and
acetyl group more preferably a Cl to C4 alkyl group and
16 most preferably hydrogen. The phase transfer reagent
17 may be generated by reacting the corresponding quaternary
18 salt R4QX with a metal base ~O~" where X is selected from
19 the group consisting of halide, sulfate, bisulfate,
acetate and stearate. Preferred is when X is a halide
21 selected from the group consisting of chlorine, bromine
22 and iodine, more preferably chlorine. M is selected from
23 the group consisting of alkali metals, more preferably
24 sodium and potassium. As shown above, the quaternary
base is then reacted with the acidic groups on the coal
26 which in turn is reacted with at least one alkylating or
27 acylating agent represented by the formula R'X wherein
28 R' is selected from the group consisting of Cl to about
2~ C20 alkyl or acyl group and X is as previously defined, as
long as X is attached to a primary or secondary carbon
31 atom. Preferably R' is an inert hydrocarbon, that is, a
32 hy~rocarbon group containing only hydrogen and carbon
33 although hydrocarbon groups containing other functionality
34 may also be suitable for use herein, even though less
desirable. It will be noted that the acidic proton H
36 (hydrogen atom) is usually loca-ted on phenolic groups for
37 lower rank coals. The acidic proton may also be located
38 to a lesser extent on sulfur, nitrogen, etc.
~14~fi4
1 Phase transfer reagents such as quaternary ammonium
2 base (R4QOR") are very effective with O-alkylation
3 and O-acylation of coal. These O-alkyla~ion and
4 O-acylation reactions are successful because the -o~"
portion of the molecule is soluble in an organic medium.
6 When this base is present in such a medium, it is not
7 solvated by water or other very polar molecules. As an
8 unsolvated entity, it can react as a very efficient proton
9 transfer reagent. For example,
lQ (coal) - OH + OR"~ b ~coal) - O + R"OH
11 This unsolvated base (also known as a "naked hydroxide"
12 when R'l is hydrogen) can have a wide variety of counter
13 ions. Although the counter ion may be quaternary ammonium
14 or phosphonium species as previously discussed, other
examples o counter ions useful in the practice of the
16 inventlon include "crown ether" complexes of a salt
17 containing the OR" anion and clathrate compounds, complexed
18 with a salt containlng the OR" anion. Salts represented by
1~ MOR", wbere M is as given above, when complexed with crown
2~ Qthers,fr examPle,have been previously demonstrated to
21 evidence a reactivity similar to that found for R4QOR"
~2 compounds.
3 In one embodiment of the process of the invention, a two-
~4 phase solid/liquid system comprising the particular coal in
~5 liquid suspension is formed. The coal is generally ground
26 to a finely divided state and contains particles less than
27 about ~ inch in size, preferably less than about 8 mesh
~8 NBS sieve size, more preferably less than about 80 mesh. The
29 smaller particles~ of course, have greater surface area and
3Q thus alkylation or acylatlon will proceed at a faster rate.
31 Cons~quently, it is desirable to expose as much coal surface
32 area as possible without losing coal as dust or fines or as
33 the economics of coal grinding may dictate. Thus, particle
34 sizes of greater than about 325 mesh are pre~erred.
Although not necessary, a solvent may be added i~ desired.
36 The solvent may be used to dissolve alkylated or acylated
37 carbonaceous product or to dissolve alkylating or acylating
- 6
1 agent (especially if the agent is a solid and is compar-
2 atively isoluble in water). ~he solvent may also be used
3 for more efficient mixing. Many of the common organic
4 solvents may be employed in any reasonable amount, depending
on the desired result.
6 Inasmuch as there are solid coal particles which never
7 dissolve during the course of the reaction, there may be
8 some concern as to the extent of the reaction on these
9 particles. To verify the complete extent of the reaction,
thase particles were collected and worked up separately on
11 numerous runs with a wide variety of alkylating agents as
12 well as coals. Infrared spectral analysis of th~s insoluble
13 portion of the coal reaction mixture showed that in every
14 case, substantially complete alkylatlon of the hydroxyl group
had occurred. This is evidence that the phase transfer reagent
16 must have penetrated the solid coal structure and that the
17 resulting organic salt of the coal must have reacted with
18 the alkylating agent to produce the observed product. Thus,
19 the etherificatlon and esterification reactions are not
merely taking place on the surace of the coal but through-
21 ou~ the coal structure as well.
22 The phase transfer reagent that is used must dissolve
23 in or be suspended in both phases so that it is in intimate
24 contact with both the organic and aqueous phases. During
the course of the reaction, the phase transer reagent will
26 partition itself lnto both of these phases. Quaternary
27 bases are one class of compounds useful as phase transer
28 reagents in the practice o the invention and are given by
29 the formula R4QOR", where R is an alkyl group having at
leas' one carbon atom, and preferably 1 to 2~ carbon a~oms,
31 and more preferably 1 to 6 carbon atoms or an aryl group
32 having 6 to 20 carbon atoms, perferably 6 to 12 carbon
33 atoms. The lower number of carbon atoms is preferred, since
34 such compounds are water soluble and can be removed from
the alkylated or acylated coal by simple water washing. The
36 R groups may be the same or diferent. Examples of B groups
11 4~ 4
-- 7 --
,,
- 1 include methyl, butyl, phenyl and hexadecyl.
2 Examples of quaternary bases useful in the practice
3 of the invention include the following:
4 1. Tetrabutylammonium hydroxide (C4H9)4NOH
2. Benæulhexadecyldimethylammonium hydroxide
(C6H5CH2) (Cl6H33) (cH3)2NoH
7 3. Tetrabutylphosphonium hydroxide, (C4Hg)4POH
3 4. ADOGEN 464, (C8-C10)4NOH (ADOGEN 464 is a
g trademark of Aldrich Chemical Company,
Metuchen, NJ).
11 The metal basa used to convert the quaternary salt to
12 the corresponding base is an alkali metal or alkaline earth
13 metal base such as NaOH, KOH, Ca(OH)2 or NaOCH3. The use of
14 an alkoxide, for example, permits use of the corresponding
alcohol in place of water, which may provide an advantage in
16 process flexibility.
17 In chosing the alkylating and acylating reagent, two
18 considerations must be weighed. First, i~ is desired to
19 add longer chains to the coal which render the product more
petroleum-likP, and therefore more soluble in organic
21 solvents and more compatible with petroleum liquids. On the
22 other hand, shorter chains render the alkylated or acylated
23 coal product more volatile. Second, shor~er chain materials
24 are less expensive and still improve solubility.
In the case of O-alkylation, the carbon to which the
26 leaving group is attached may be either a primary or
27 secondary carbon atom. Primary carbon halides have been
28 found to react faster than the corresponding secondary
29 halides in a phase transfer o phase transfer catalyzed
reaction on carbonaceous materials and are accordingly
31 preferred. While the balance of the carbon-bearing
32 functional group may in general contain other moieties,
33 such as heteroatoms, aryl groups and the like, bonding of
34 the carbon-bearing functional group to ~he p~enolic or
carbonoxylic oxygen is ~hrough either an sp3 hybridized
36 carbon atom (alkylation) of an sp hybridized carbon atom
'
~ ,-
.
- 8 --
l (acylation)- Further, a mixture of alkylating or acylating
2 agents or a mixture of both may be advantageously employed.
3 Such mixtures are likely to be generated in coal-treating
4 plants in other processing steps and thus provide a ready
source of alkylating and/or acylating agents. Examples of
6 alkylating and acylating agents useful in ~he practice of
7 the invention include ethyl iodide, isopropyl chloride,
8 dimethyl sulfate, benzyl bromide and acetyl chloride.
g While alkylating andtor acylating agents are employed
in the practice of the invention, alkylating agents are
ll preferred ~or the following reasons. First, alkylating
12 agents are readily prepared from their hydrocarbon pre-
13 cursors. For example, alkyl halides may be easily pre-
14 pared by free radical halogenation of alkanes, which is
a well~known process. When a system con~aining more than
16 one alkylating or acy}a~ing agent is used, the hydrocarbon
17 precursor is preferably a product stream of a certain cut
18 derived from coal and petroleum processing and the like.
19 This stream may contain minor amounts of components having
various degrees of unsaturation which are also suitable for
21 reacting with the phenolic and carboxylic groups herein as
22 long as X (as previously defined) is attached to an alkyl
23 or saturated carbon atom in the resulting alkylating or
24 acylating agentO Second, acylating reagents are susceptible
to hydrolysis- Since water is ever present in coal and other
26 solid carbonaceous material and is employed in the inventive
27 process, some loss of acylating agent may occur by hydro-
28 lysis. In contrast, alkylating reagents do not evidence the
29 same susceptibility to hydrolysis.
If the 0-alkylation e~ O-acylation is carried out by a
31 catalytic process, then the quaternary sal~, metal base and
32 alkylating or acylating agent are mixed directly with an
33 aqueous slurry of coal. The quaternary salt catalyst may be
34 present in small amounts, typically about 0.05 to 10 w~.% of
the amount of coal used; howe~er, greater amounts may also
36 be employed. The metal base and alkylating or acylating
: , ~ , . .
4~
g
1 agent must be present in at least stoichiometric quantities
2 relative to the number of acidic sites (phenolic, carboxylic,
3 etc.~ on the carbonaceous material, but preferably an
4 excess of each is used to drive the reaction to completion.
Advantageously, a two-fold excess of metal base and
6 alkylating or acylating agent is employed; however, a
7 greater excess may be employed. After the reaction, the
8 excess quaternary base and quaternary salt ca~alyst may be
g removed from the coal by ample water washing ~or recycling.
Excess metal base will also be extracted into the water
11 wash and may be reused. Excess alkylating or acylating
12 agent may be conveniently xemoved from the trea~ed coal
13 by fractional distillation or by solvent extraction with
14 pentane or o~her suitable solvent and may be reused.
To cap of~ all acidic pro~ons in a typical coal
16 employed in the cataly~ic process, less ~han 5 days are
17 required for 100% conversion, employing onl~ a sli~ht excess
18 of alkylating or acyla~ing agent on 80/100 mesh coal under
19 atm~spheric pressure and ambient ~emperature. A greater
excess of alkylating or acylating agent will reduce the
21 reaction time considerably.
22 A faster alkylation or acylation reaction may be
23 obtained in a number of ways, one of which is to add the
24 phase transfer reagent (R4QOR") directly to the carbon-
aceous material rather than to form this reagent ln situ
26 with the reaction in which the carbonaceous material is
27 alkylated or acylated. When this is done, substantially
28 complete conversion of all the phenolic and carboxylic
29 groups are achieved in a matter of minutes. The amount
of quaternary base added ranges from about stoichiometric
31 proportions to about 10 times the total number of acidic
32 sites on the carbonaceous material which are capable o~
33 undergoing alkylation or acylation. As be~ore, the
34 quaternary salt that is generated in the alkylation or
acylation step may be recovered and recycled by reacting
36 it with fresh metal base to regenerate the quaternary
37 base. By employing this two-step process, there is no
3~ contact between metal base and the carbonaceous material,
!
-- 10 --
1 and the reaction is essentially complete in about one hour. ~
- 2 As an example, in 10g of Illinois No. 6 coal, there are
3 35 moles of Ax-OH groups. An excess of a quaternary
4 hydroxide along with an excess of an alkylating agent (about
4 to 5 times each) results in essentially complete alkylatio
6 in less than one hour at ambIent conditions. In contrast,
7 in the phase transfer catalyzed reaction, there is metal
8 ~ase present so that the alkylation ~or acylation) must
9 ~e carried out in an inert atmosphere, such as nitrogen, to
avoid oxidation of the coal. In the case of the non-
11 catalyzed process in which the formation of the transfer
12 reagent is kept separate from the alkylating or acylating
13 reaction, the rate of oxidation of the coal i5 slow enough
14 and is not competitive wIth the alkylation or acylation
reaction~ Thereore, another advantage of this noncatalyzed
16 process is that the use of an inert atmosphere such as
17 nitrogen is not required.
18 The temperature at which the reaction is carried out
may range from ambient to the boiling point of the materials
-20 used. Increased temperature will,of course, speed up the
21 reaction rate.
22 The reaction mixture may be stirred or agitated or mixed
23 in some fashion to increase the interface or surface area
24 between the phases, since there can be aqueous, organic
liquid and solid carbonaceous material phases present.
26 The reaction is carried out at ambient press~re, although
27 low to moderate pressures (about 2 to 20 atmospheres~ may be
28 employed along with hea~ing to increase the reaction rate.
29 Once the reagents and solvents, i~ any, are removed from
the alkylated or acylated carbonaceous material, infrared
31 ~nalysis may be conveniently used to demonstrate that all
32 the hydroxyl groups have been allcylated or acylated. If
33 the added alkyl or acyl group is IR-active, then the
34 appearance of the appropriate infrared frequency is observed.
other well-known analytical methods may also be employed
36 if desired. The ultimate analysis of percent C, H, N, S and O
37 is altered in a fashion which is consistent with the expected
.
Q~j~
1 change due to the added alkyl or acyl substituent. For
2 example, the inc~ease in the H/C ratio of 0-methylated
3 Illinois No . 6 coal indicates that 4.5 methyl groups per
4 100 carbon atoms are added to the coal. The H/C ratio of
5 the untreated Illinois ~oO 6 coal is 0.84 and the H/C ratio
~ after 0-methylation by the process of the invention is 0.890
7 The thermogravimetric analysis of the 0-methylated coal
~3 shows a significant increase in volatile organic content
9 over the untreated coal (38% versus 32%)o The solvent ex-
1~ tractability of the carbonaceous material is greatly in-
11 creased af~er it is 0-alkylated or O~acylated. For example,
12 Illinois No. 6 coal becomes more soluble in common organic
13 solvents after it is oxygen-me~hylated, as shown in Table I
14 below:
T~BLE I
~6 MAXIMU~I S~LUBILITY (at l atm)
17 Toluene TetrahYdrouranPYridine
18 Illinois #6
19 Coal 3% 17% 27%
20 0-methylated
21 Illinois #6 Coal 7% 22% 34%
22 Liquids which are derived b~ solvent extraction of
23 carbonaceous material treated in accordance with the in-
2a vention evidence both improved quality and increased quantity
2~ over coal liquids derived from non-treated coalO For
2~ example, 0-methylation of Illinois No. 6 coal results in
27 34% solubility in pyridine (as compared to 27% for non-
2~ 0-methylated coal; see Table I)o The soluble liquids from
2~ the 0-alkylated or 0-acylated carbonaceous materials have
3(; higher H/C ratio than the soluble products from untreated
31 carbonaceous materialsO
3; The thermogravimetric analysis of the 0-methylated coal
3;~ shows a significant increase in volatile organic content over
3" the untreated coal (38% versus 32%)~
3~ Subsequent to the alkylation or acylation reaction, the
3~ product may be subjected to liq~efaction. The products of
3; t~e liquefaction process are usually light gases, liquid
3~ products and a bottoms fraction. It is con~emplated ~hat all
3t or a portion of the remaining solid residue may be recycled
4~ from the liquefac~ion zone to the alkylation or acyla~ion
6~
.
- 12 -
l zone. Separation of the solids material can be carried out
2 by any known me~ns, such as filtration, vacuum distillation,
3 centrifugation, hydroclones, etc., and preferably by vacuum
4 distillation.
Various types of liquefaction may be employed, such as
6 solvent refining, as exemplified by the P~CO process developed
7 by the Pittsburgh and Midway Coal Company, direct hydrogena-
8 tion with or without a catalyst, catalytic or noncatalytic
9 hydrogenation in the presence of a nondonor solvent,
catalytic or noncatalytic liquefaction by the donor solvent
ll method, the latter being preferred particularly with the
12 presence of hydrogen during the liquefaction stepO One
13 solvent hydrogen donor li~uefaction process is described in
l~ U.S. Patent 3,617,513. As used herein, liquefaction means
the molecular weight degradation of coal as distinguished
16 from mere solvent extraction where essentially no molecular
17 weight degradation takes place, e.g3, extraction with
18 solvents such as benzene, pyridine or tetrahydrofuran at
l9 room temperature or temperatures ranging up to the boiling
point of the extractive solvent. Thus, substantial chemical
21 reaction does notoccur until the temperatures are raised
22 above about 150C, preferably above about 200C4 Liquefaction,
23 as opposed to solvent extraction, is a more severe operation,
24 maximizes light liquid yields, and involves substantial
chemical reaction of the coal. Solvent extraction tends to
26 maximize heavier liquid yields, eOg., fuel oil and higher
27 boiling constituents while involving lit~le or no covalent
28 bond cleavages due to the temperatures involved9 e.gO, less
29 than 200C, preferably less than 150C, still more pre-
ferably less than 115C~ Additionally, maxlmizing light
31 liquid yields allows for separa~ion of the bottoms by dis-
32 tillation, e.g~, vacuum distillation, rather than by filtra-
33 tion, which is used for solvent refined coals3
34 Briefly, hydrogen donor solvent liquefaction utilizes a
hydrogen donating solvent which is composed of one or more
36 donor compounds such as indane, C10 - C12 tetralins, C12 ~ C13
;
4~
- 13 -
1 acenaphthenes, di-~ tetra- and octahydroanthracenes and
2 tetrahydroacenaphthene, as well as ~ther derivatives of
3 partiaily saturated hydroaromatic compounds. The donor
4 solvent can be the product of the coal liquefaction process
and can be a wide boiling hydrocarbon fraction, for example,
6 boiling in ~he range of about 150 to 510C~ preferably
7 about 190 to 425Co The boiling range is not critical
8 except insofar as a substantial portion of the hydrogen donor
9 molecules are retained in the liquid phase under liquefaction
conditions. Preferably, the solvent contains at least about
11 30 wt. %, more preferably about 50 wt. %, based on so;vent,
12 of compounds which are known hydrogen donors under lique~action
13 conditions. Thus, the solvent is normally comprised of donor
14 a~d nondonor compoundsO
Since the donor solvent can be obtained by hydrogenating
16 coal liquids derived from liquefaction, for ex~mple, then the
17 composition of the hydrogen donor solvent will vary depending
18 upon the source of the coal feed, the liquefaction system and
19 its operating conditions and solvent hydrogenation conditionsO
Further details of a hydrogenated liquefaction recycle stream
21 are discussed in U.S. Patent 3,617,513.
22 The coal is slurried in the hydr3gen donor solvent and
23 passed t~ a liquefaction zone wherein the c~nvertible porti~n
24 of the coal is allowed to disperse or react. O-alkylation
and O-acylation of the coal by the process of the invention
26 are believed to render more of the coal c~nvertible as co~-
27 pared to untreated coal
28 The solvent/coal ~ , when about SOwt.% of the solvent
29 is hydrogen donor-type compounds, can range from about 0.5:1
to 4:1, preferably about 1:1 to 2:1. Preferably, the donor
31 solvent contains at least about 25% hydrogen donor compounds,
32 more preferably at least about 33% hydrogen donor compounds.
33 Operating conditions can vary widely, that i5, te~peratures
34 of about 310 ~o 540~C, preferably about 400 to 500C
pressures ~f about 300 to 3000 psig, preferably about 1000
36 to 2500 psig; residence times ~f about 5 minutes t~ 200
V~
-- 14 --
l minutes; and molecular hydrogen input of about 0 to 4 wt.%
2 (based on DAF coal charged to the liquefaction z~ne in the
3 slurry). The primary products removed frDm the liquefaction
4 zone are light gases, liquid products and a slurry of uncon-
verted coal and ash in the heavy oil. Since the liquid
6 state products contain the donor solvent in a hydrogen de-
7 pleted form, the liquid can be fractionated to recover an
8 appropriate boiling range fraction which can then by hydro-
9 genated and returned to the liquefaction zone as recycled~
hydrogenated donor solvent.
ll Recycle solvent, preferably boiling inthe range of about
12 175 to 425C, separated from the liquid product of the li-
13 quefaction zone, can be hydrogenated with hydrogen in the
14 presesce of a suitable hydrogenation catalyst. Hydrogenation
temperatures can range from about 340 to 450C pressures can
16 range from abou~ 650 to 2000 psig and space velocities of 1
17 to 6 weights of liquid per hour per weight of catalyst can be
18 employed. A variety of hydrogenation catalysts can be em-
l9 ployed such as those containing components from Group VIB and
Group VIII, e.g. cobalt molybdate on a suitable support, such
21 as alumina, silica, titania, etc. The hydrogenated product
22 is then fractionated to the desired boiling range and recycled
23 to the liquefaction zone or slurried with the coal prior to
24 the liquefaction zone.
The coal liquids derived from liquefaction may be further
26 processed, employing conventional refining techniques. The
27 coal liqulds will have a lower viscosity and boiling range
28 and will be produced in higher yield and will be more compa-
29 tible with petroleum liquids than coal liquids produced
without the 0-alkylation or 0-acylation process of the inven-
31 tion. If the coal liquid is found still to be insurficiently
32 c~mpatible with certain petroleum liquids, however, the coal
33 liquid may be alXylated or acylated in a separate zone, em-
34 ploying the alkylating or acylating procedures described
above. The same ranges of conditions; reagents, concentra-
36 tions and the like are advantageously employed to produce a
- 15 -
1 coal liquid more compatible with petroleum liquids.2 Light gases, such as C0, C02, H2S and light hydrocarbons
3 generated by tbe liquefaction process may be collected and
4 separated. Light hydrocarbon gases may be halogenated, such
as by a free radical process, to form R'X compounds, which may
6 be recycled to the alkylation or acylation zone, thereby pro-
7 viding at least a partial source of alkylating Dr acylating
8 agent.
9 Coal bottoms from the liquefacti~n zone may be recycled
to the alkylation or acylation æone. Alternatively, coal
11 bottoms may be treated in a separate alkylation or acylation
12 zone. Even if not further processed in this manner, the coal
13 bottoms are more compatible with petroleum liquids and are
14 more soluble in common organic solvents than untreated coal
bottoms
16 Referri~g now to he drawing, coal from storage is
17 crushed and ground to less than about 8 mesh. Sufficient
18 water is added to form an aqueous slurry of the coal which
19 is introduced via line lO to alkylation zone 11. It will be
understood that an acylation zone may alternatively be employed,
21 or indeed an alkylation/acylation mixture zone. An alkylating
22 agent is introduced via line 12 and a quaternary base is intro-
23 duced via line 13. The quaternary base is formed in conver-
24 sion zone 14 by mixing metal base fr~m line 15 and quaternary
salts from line 16. Salt MX is withdrawn via line 17.
26 It is understood that alkylation zone 11 can be one or
27 more alkylation reactions, interspersed by washing steps,
28 into each of which fresh alkylating agent and quaternary base
29 is introduced. Additionally, unreacted coal recovered from
the liquefaction process can be recycled via line 32 for
31 further treatment in the alkylation zone. Alkylated coal,
32 substantially free of alkylating agent and quaternary base is
33 dried (by equipment not shown)~ and then mixed with recycle
34 solvent frDm line 38 to for~, a sDlvent/coal slurry in line 20
and ed to liquefaction zone 21 operating at a temperature bf
36 about 450C and 1500 pslg. Hydrogen is fed ~o the liquefac-
Q~;~
- 16 -
l tion zone through line 22. A preheat furnace ~not shown) is2 often desirable to heat the slurry to reaction temperatures
3 by liquefaction.
4 Light gases, such as CO, CO2~ H2S and light hydrocarbons
are removed from the lique~action zone by line 39. The li-
6 quid product, in a slurry with unconverted coal, is recovered
7 in line 23 and flashed in drum 24 to reduce the pressure, with
8 light gases and Light hydrocarbons being flashed off in line
9 25 and an oil/coal slurry being recovered in line 26. The
light hydrocarbons from line 39 can be treated by conventional
ll means to re~ove CO2 and H2S and then sent to a c3nventional
12 steam refor~ing furnace where the hydrocarbon gases are re-
13 formed to produce hydrogen for use in the process, such as in
14 line 22 (and in line 34). The former, 42, can also be used to
handle off gases from the pipestill 27 (line 28) and fraction-
16 at~r 36 (line 37). A portion of the light gases may be halogen-
17 ated (apparatus not shown) and the alkyl halides fDrmed may be
18 used as a partial or total source of alkylating agent in line
lg 12.
The product of line 26 is then tr~ated in a fractiDnator
21 27 which can be an atmospheric or vacuum pipestill or both.
22 Light gases are removed overhead in line 28 while a recycle
23 solvent stream is removed via line 29 for treatment in sol-
24 vent hydr~treater 33. Liquid product for upgrading by, e.g. 9
catalytic cracking, is recovered in line 3~. A product con-
26 taining the residuum and unconverted coal (botto~s) is ta~en
27 off by line 31, a portion of which can be recycled via line
28 32 to the alkylation zone, or treated in a separated alkyl-
29 atiOn zone and then recombined with the feed to the lique-
faceion zone. In a balanced process, so~e or all or the
31 bottoms can be sent to hydrogen manufacture via line 41 to
32 make hydr~gen for use in the liquefaction zone and the sol-
33 vent hydrotreater.
34 Recycle solvent is catalytically hydrogenated in hydro-
treater 33, hydrogen being supplied in line 34, over a
36 catalyst such as cobalt molybdate on an alumina support.
- 17 -
1 Hydrotreated product is recovered in line 35 and fraction-
2 ated in fractiDnator 36 frDm which recycle hydrogen donor
3 solvent of the desired boiling range is recovered in line
4 38 and recycled to line ~0 to slurry alkylated coal. Addi-
tional liquid prodtlct is recovered in line 40 and may bP
6 subjected co further upgrading. Any light gases formed
7 during hydrotreating can be rem~ved via line 37.
8 Exam~le 1 - Phase Transfer Noncatalyzed Alkylation
9 Rawhide sub-bituminous coal was treated as f311OWS:
A slurry of 30.8g Rawhide coal (-80 mesh) and 300 mmoles
11 (free base) of tetrabutylammonium hydroxide (75% in aqueous
12 solution) were mixed together at ambient temperature and 1
13 atm pressure for a few minutes. Tetrahydrofuran (200 ml) and
14 500 mmoles ~f n-heptyliodide were than added and the reaction
mixture was stirred for nearly three hours. The colorless
16 water layer was then separated and fresh water added to was~
17 out any residual quaternary salt from the organic phase 9 which
18 contained the 0-alkylated coal. The washing was continued un-
l9 til the pH of the wash water was neutral and no precipitate
formed when silver nitrate was added to the wash water. (A
21 byproduct of the alkylation was tetrabutylammonium iodide,
22 which reacted with the silver nitrate to give a precipitate
23 of AgI). The excess heptyliodide, water and THF were removed
24 by vacuum distillation at 100-110C. The alkylated coal was
then analyzed. Infrared analysis revealed essentially com-
26 plete eliminati~n of the hydroxyl band (3100-3500 cm 1), as
27 well as incorporation of thb alkyl ether funcit~nality ~lOOn-
28 1200 cm ) and the ester e&~ functionality (1700-1735 cm ).
i 29 Exam~l_s 2 7 - Phase Transfer NonCatalyzed Alkylati?n
The following runs were made, employing the procedure set
31 forth in Example 1. In each reaction, the quaternary base
32 was tetrabutylammonium hydroxide. The base was present in a~
33 least stoichiometric amount of the number of acidic protons
34 on the coal sample in the case of ~awhide and 2:1 in the case
3s Illinois No. 6.
-- 18 -
TABLE II
2 PHASE TRANS~ER NONCATALYZED REACTIONS Reaction
3 Example Coal(l) Rlx(2~ Time, hr.
4 2 Illinois #6 ~80/100) CH3I, 200%
3 Illinois #6 (-80) C4HgI~ 200% 3
6 4 Illinois #6 (80/100) C7~1sI, 200% 3
7 5 Rawhide (80/100) CH3I, 200%
8 6 Rawhide (80/100) C41~9I, 200% 3
9 7 Rawhide (80/100) C7~1sI, 200% 3
Notes: (1) Mesh size is indicated in par~ntheses
ll (2) Weight percent relative to coal
12 Example 8 - Phase Transfer Catalyzed Alkylation
13 Illinois No. 6 coal was treated as foLlows:
14 Twenty grams of Illinois No. 6 coal (80/100 mesh), 50ml
of a 50% aqueous NaOH solution, 150 ml of toluene, 70 mmoles
16 f CH3I and lg of tetrabutylammonium chloride were mixed to-
17 gether under a nitrogen atmosphere (the order of addition was
18 not important). After five days, the aqueous layer was sep-
l9 arated and the organic phase washed with water until the un-
reacted sodium hydroxide and catalyst were extracted out of
21 the toluene. The toluene, water and excess iodomethane were
22 removed under vacuum at 100C~ The O-alkylated coal was then
23 analyzed. Infrared analysis revealed essentially complete
24 elimination of the hydroxyl band (3100-3500 cm 1), as well as
25 - incorporation of the alkyl ether functionality (1000-1200 cm l)
26 and incorporation of the ester carbonyl functionality (1700-
27 1735 cm 1).
28 Examples 9-35 - Phase Transfer Catalyzed Alkylation
29 The ~ollowing runs were made employing the procedure set
forth in Example 8.
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e ,v v ~ ~ y =;ee; e v v ~ ee ;~ ~e ~e~e~ ~e ;~e~ e ~e ~ ~ J~J u ~ I
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- 20 -
1 Exam~le 36 - L~ faction of Alkylated Coa~
2 Three coal samples were liquefied; each of these samples
3 were run in duplicate with excellent reproducibility. The
4 liquefaction was carried out at 425C using a two-fold excess
of te~ralin in a hydrogen atmosphere, The apparatus used
6 was a tubing bomb unit (a batch liquefaction reactor), The
7 residence time of the sample was two hours. One sample pair
8 was Illinois No. 6 coal which was untreated. Another sample
9 pair was Illinois No. 6 coal which was base treated, then
acidified tBWlacidified), This second pair represents the
11 coal used in the phase transfer alkyla~ion or acylation ex-
12 cept that no alkylating or acylating agent was used. It was
13 a blank run sample in order to ensure that no other component
14 of the phase transfer alkylation reaction conditions actually
caused some effect on the liquefaction. The third sample pair
16 was a phase trznsfer reactant O-perdeuteromethylated Illinois
17 No, 6 coal with 4.5 CD3 groups incorporated in the coal me~rix
18 for every 100 carbon atoms p~esent. The percen~ conversion
19 (on a dry mineral matter free basis~ for each liquefaction
was calculated by the following equation:
21 % Conversion (~MMF) - ~100 (weight of charge-
22 weight of residue)~/~weight of charge/ (100 -
23 mineral matter3/100]
24 The values found are summarized in Table IV below~
TABLE IV
26 COAL CONVERSION
27 Sample% Conversion Reproducbility
28 Illinois No. 6 Coal 54.5 ~ 1,5%
29 BW/Acidified Illinois 56.8 ~ 5.~0
No. 6 Coal
31 O-Perdeute~omethylated 74.S + O.770
32 Illinois No. 6 Coal
33 Mass spectrographic analysis of the gases produced in
34 the three different liquefaction runs revealed some impor~ant
information. First, only in the case of O-perdeutheromethy-
36 lated Illinois No. 6 was there no water produced. This, of
06~
- 21 -
l course, means that there was eficient use of hydrogen. In-
2 stead, this O-methylated coal produced a considerable in-
3 crease in quality of gaseous hydrocarbons: that is, substan-
4 tially no C02, H2S, etc. was found. Methane (found with iso-
topic label), for example, was at a level of 3~0~ above the
6 other two sample types. In contrast, the untreated and the
7 BW/acidified coal gave results very similar to each other.
8 ~uch hi&her levels of e~hane, propane and butane were also
9 observed in the liquefaction of the perdeuteromethylated coal.
However, the total quantity of gas produced in all three
ll cases was about the same.
