Note: Descriptions are shown in the official language in which they were submitted.
1 ~ 6~3~9
1 sAcKGRouND OF T~E INVE~NTION
2 The present invention relates to a method for
3 enhancing the conversion of carbonous materials such as
4 coal, oil shale, and peat, to liquids, by use of specific
type hydrogen donor materials under critical processing
6 conditions.
7 Coal, once the leading source of energy in
8 the United States, is beginning to play a more important
9 role in the nation's energy future. The primary reason
for the ~rowing importance of coal is the rapid depletion
11 of known petroleum and natural gas reserves. These known
12 reserves are being depleted at a rate considerably faster
13 than the rate of discovering new reserves. As the era of
14 petroleum growth draws to a close, the world's energy mix
will have to change. Transition energy sources will be
16 needed as a bridge between petroleum and the potentially
17 unlimited energy sources of the future; such sources
18 being, for example, solar power and nuclear fusion.
19 ~wing to their great abundance, coal and oil shale, are
perceived as the keystones of such a bridge. Consequent-
21 ly, much work is presently in progress to provide eco-
22 nomical ways of converting these resources to valuable
23 liquids and gases. Coal liquefaction processes in which
24 coal, with or without a diluent, is subjected to elevated
temperatures and pressures to convert solid coal to nor-
26 mally liquid hydrocarbonaceous products, are well known.
27 Because the ratio of hydrogen to carbon in
28 coal derived liquids and gases is higher than coal it-
29 self, gases, much emphasis has been put on more efficient
uses of hydrogen in liquefaction processes. In order to
31 use hydrogen more efficiently, processes have been devel-
32 oped wherein a source of hydrogen is an organic compound,
33 usually a solvent, which is capable of donating hydrogen
34 to radicals formed during the decomposition of coal.
~lthough such processes teach the conversion of coal to
36 liquids and gases under various conditions, and with
37 various yields, none are able to achieve relatively high
3 7 ~
1 conversion to liquids under low pressure conditions.
2 SU~RY OF THE INVENTION
_ _
3 In accordance with the present invention,
4 there is provided a method for enhancing the conversion
5 to liquids of solid carbonous materials selected from the
6 group consisting of coal, oil shale, peat and solid
7 products thereof, to liquids. The method comprises con-
8 verting the carbonous material in the presence of a
9 vapor phase hydrogen donor material containing one or more
effective hydrogen donor solvents wherein each effective
11 donor solvent is characterized by: (a) a heterocyclic
12 ring in which the heteroatom is nitrogen, ~b) having at
13 least one donatable hydrogen located on the heterocyclic
14 ring, and (c) becoming more unsaturated and/or aromatic
15 upon the loss of the donatable hydrogen(s). The conver-
16 sion is performed at substantially atmospheric pressure,
17 at an effective vapor residence time and at a tempera-
18 ture from about the boiling point of the hydrogen donor
19 material to about 550~C.
In one embodiment of the present invention,
21 the carbonous material is subbituminous coal, the hydro-
22 gen donor matexial is comprised of 1,2,3,4-tetrahydro-
23 quinoline, the pressure is atmospheric pressure, the
24 maximum conversion temperature is about 500C, and the
donor vapor residence time is about 1 second.
26 In a preferred embodiment of the present
27 invention the carbonous material is coal or oil shale
28 and the hydrogen donor material is recycled from a prod-
29 uct stream resulting from the practice of the present
invention.
31 BRIEF DESC~IPTION OF THE DRA~INGS
32 Figure 1 illustrates the effectiveness of
33 short vapor residence times as claimed herein.
34 Figure 2 illustrates total liquid yield on
coal versus the donatable hydrogen concentration on the
36 nitrogen ring of the type donor solvents employed herein.
~ ~ 6~ 37'3
- 3 --
1 DETAILED DESCRIPTION OF THE INVENTION
. _ . . _ .
2 Compounds claimed herein which are capable of
3 donating hydrogen to carbonous material radicals under
4 the conditions claimed herein are particularly suitable
for the conversion of such materials to liquids. It is
6 believed that the chemical mechanism which may partially
7 account for their exceptional conversion ability results
8 from a solvent-coal physical interaction (e.g., acid-
9 base coordination, etc.), followed by the subsequent
donation of available hydrogen to the reactive carbonous
11 fragments, thereby stabilizing the fragments as they are
12 formed. The hydrogen donor in turn is converted, to a
13 degree, to an aromatic form which may subsequently or
14 concurrently be regenerated.
The art generally teaches that all known
16 hydrogen donor compounds, which generally also serve as
17 solvents for the coal, are suitable for converting coal
18 to liquids and gases. We have surprisingly found that
19 only certain specific types of hydrogen donor compounds
20 or mixtures thereof, when used under the critical reac-
21 tion conditions of the present invention, enhance -the
22 conversion of certain carbonous materials to liquids
23 when compared to the conversion of such carbonous materi-
24 als without the use of the hydrogen donor materials
25 claimed herein.
26 Effecti~e hydrogen donor compounds suitable
27 for use herein include those compounds which: (a) con-
28 tain a heterocyclic ring in which the heteroatom is
29 nitrogen, (b) have at least one donatable hydrogen
30 located on the heterocyclic ring, and (c) have a tendency
31 to become more unsaturated and/or aromatic upon the loss
32 of the donatable hydrogen(s). ~onlimiting examples of
33 such compounds include, 1,2,3,4-tetrahydroquinoline;
34 1,2,3,4-tetrahydroisoquinoline; 1,2,3,4-tetrahydrocarba-
zole; 1,2,3,4,5,6-hexahydrocarbazole; acrilan, piperidine,
36 pyrrolidine, indoline and their alkylated derivates and
37 mixtures thereof. Preferred are 1,2,3,4-tetrahydroquino-
38 line; 1,2,3,4-tetrahydroisoquinoline and indoline.
~ ~ 6~3~9
-- 4
1 It wlll be noted that other conventionally
2 used hydrogen donor materials, which do not meet the
3 re~uirements set forth above, are unsuitable for use in
4 the practice of the present invention. Such donor
materials include tetralin, phenanthrene, C12 and Cl3
6 acenaphthenes, their hydrogenated analogs and indole.
7 The pressure at which the carbonous material
8 is converted herein is preferab]y about atmospheric
g pressure (14.7 psia), although pressures slightly higher
or lower may be employed to facilitate mass transfer in
11 the processing scheme.
12 The temperature at which conversion occurs in
13 the presence of the hydrogen donor vapor may range from
14 the initial boiling point of the hydrogen donor material
to about 550~C. For example, for THQ, it is preferred
16 that the conversion temperature be about 200C to about
17 500C, more preferably from about 250C to about 500C;
18 most preferred is about 350C to about 500C.
19 The residence time at which the donor vapor
is in contact with the solid carbonous material, at con-
21 version temperatures must be an effective residence
22 time. By an effective residence time we mean a time
23 long enough so that reaction with the carbonous material
24 takes place, but short enough so that undesirable
secondary reactions are minimized. Such undesirable
26 reactions include donor solvent degradation (other than
27 loss of hydrogen) and irreversible combinations of donor
28 molecules with either the converted or unconverted car-
29 bonous material. These conditions also minimize unde-
sirable secondary reacl:ions of first formed carbonous
31 material derived fragments. That is, the donor material
32 is preferably removed from the reaction zone, and cooled,
33 substantially immediately after donating its hydrogen.
34 This is generally a time from about 0.1 to about 30
seconds, although less than 10 seconds is generally
36 desired. It will be noted that less than 0.1 second
37 may also be feasible when the invention is employed in
~ 3 6~37~
1 specially designed, short residence time reaction
2 vessels.
3 For economic reasons, a donor vapor residence
4 time is chosen, based on the particular hydrogen donor
material and the temperature employed, such that a mini-
~ mal amount, e.g., no more than about 5 wt.~ of the
7 donor material is lost through degradation, other than
8 by aromatization. The longer the vapor residence time,
9 the greater the degree of donor degradation at any given
temperature; therefore, it is preferred that a donor
11 material and process conditions be chosen such that
12 maximum conversion to liquids occursbefore about 5 wt.
13 of donor i5 spent by degradation. For example, Figure
14 1 herein illustrates that at a maximum temperature of
500C, at atmospheric pressure, at a donor to coal
16 weight ratio of 1 to 1, and with 1,2,3,4-tetrahydro-
17 quinoline as the donor material, substantially maximum
18 conversion to liquids is achieved within a donor vapor
19 residence time of about seven-tenths of a second. Also
illustrated in Figure 1 is a relative plot showing THQ
21 degradation other than by aromatization at 500~C. With
22 the teaching of the present invention as well as general
23 knowledge known in the art, one having ordinary skill in
24 the art can determine a sufficient residence time and
optimum reaction conditions by routine experimentation.
26 ~y choosing the proper vapor residence time,
27 substantially maximum conversion of carbonous material
28 to liquids and recovery of the hydrogen donor material
2~ or its aromatic form in relatively high yields for
hydrogenation and recycling is achieved. Recovery and
31 hydrogenation of this material can be achieved by appro-
32 priate conventional methods suitable for such purposes.
33 Although not wishing to be limited thereby, hydrogena-
34 tion can be accomplished with hydrogen in the presence
of a suitable hydrogenation catalyst. For example,
36 hydrogenation temperatures can range from about 100C
37 to about 450~C at pressures up to about 2000 psi~. A
~ 3 ~3'~
-- 6
l variety of hydrogenation catalysts can be employed such
2 as those containing components from Group VIB and Group
3 VIII, of the Periodic Table oE the Elements, e.g., co-
4 balt, molybdate or nickel molybdate, on a suitable sup-
port, such as alumina, silica, titania, etc. The hy-
6 drogenated product can then be fractionated to the
7 desired boiling range and recycled to the reaction zone.
8 It is within the scope of this invention, and
9 even preferred from a commercial point of view, that a
portion, if not all of the hydrogen donor material
11 employed herein, be derived from the liquids resulting
12 from the practice of this invention. That is, especial-
13 ly in the case of oil shale, liquids derived therefrom
14 are generally rich in cyclic nitrogen-containing com-
pounds which can be separated from the product stream
16 and hydrogenated, by conventional techniques, to give a
17 recycle stream rich in the type hydrogen donor material
18 suitable for use herein. The effectiveness of any par-
19 ticular recycle stream may be determined by measuring
the total donatable hydrogen associated with the hetero-
21 cyclic nitrogen ring of those type donor solvents
22 claimed herein. That is, the recycle stream is analyzed
23 by any appropriate analytical technique, such as gas
24 chromatography, to determine its content of specific
suitable donor solvents and their concentrations, on a
26 weight percent dry carbonous material basis. After the
27 specific type and concentration of suitable donor sol-
28 vents are known, the number of donatable hydrogens on
29 the heterocyclic nitrogen ring of the donor solvent can
be easily calculated. The number of donatable hydrogens,
31 as calculated, can then be compared to a model curve for
32 determining the projected liquid yield for that particu-
33 lar concentration of donatable hydrogens. The recycle
34 stream can then be upgraded with respect to the donor
material depending on the desired liquid yield.
36 Figure 2 herein shows a plot of li~uid yield
37 (weight percent on dry coal basis) versus weight percent
~ ~ ~4379
of donatable hydrogen on heterocyclic nitrogen ring on a dry coal
basis, at a maximum temperature of 500C, 1 atmospheric pressure,
and helium as a sweep gasO The plot was obtained by use of model
hydrogen donor solvents such as 1,2,3,4-tetrahydroquinoline;
1,2,3,4-tetrahydroisoquinoline; 1,2,3,4-tetrahydrocarbazole, and
indoline and mixtures thereof at various solvent to coal ratios.
Similar correlation curves can easily be prepared for oil shale and
peat by routine experimentation by those having ordinary skill in
the art.
The donor solvent/carbonous material ratio, on a weight
basis, can preferably range from about 0.1/1 to about 10/1, more
preferably from about 0.1/1 to about 4Jl. The optimum ratio of
donor material to carbonous material will depend on such things as
the particular carbonous material being converted, the processing
conditions employed, and the type and the concentration of the
particular donor materials comprising the recycle solvent. Of
course, the optimum ratio can be determined by routine experimenta-
tion by one having ordinary skill in the art.
; Generally, any type of coal, peat, oil shale or products
thereof which are normally solid at room temperature may be uti-
lized in the practice of the present invention. When coal is
utilized, liquid yields from bituminous/ subbituminous and lignite
will be particularly enhanced. While not wishing to be limited by
theory, the data herein suggest that there is a correlation between
liquid yield and reactive organic functionality in the feed stock.
Therefore, when coal is employed in the practice of the invention,
lower rank coals are preferred because of their higher content of
reactive organic functionality.
It is preferred that the carbonous material have as high
a surface area as possible; although, it is not economically
justifiable to pulverize the material to a very fine powder.
Consequently, it is desirable to expose as much of the carbonous
material surface
~ .
1 ~6~l3~
-- 8
1 area as possible without losing carbonous material as
2 dust or fines or as the economics of material grinding
3 or process equipment ma~ dictate. Generally, the car-
4 bonous material will be ground to a finely divided
state and will contain a majority of particles less than
6 about 4 mesh, U.S. sieve size. The carbonous material
7 may be dried by conventional drying techniques, for
~ example, heating to a temperature of abo~lt 100C to 110C.
9 In practicing the present invention, the car-
bonous material is fed to a reaction vessel and heated
11 to the re~uired temperatures. The hydrogen donor mate-
12 rial is introduced into the reaction vessel when the
13 temperature of the carbonous material is greater than
14 the boiling point of the donor material.
The present invention may be practiced in
16 various types of reaction vessels. ~onlimiting examples
17 of reaction vessels suitable for use herein include,
18 fixed or fluid bed, as well as free fall or entrained
19 solid reactors. The main constraint in any reactor con-
figuration is to minimize solvent vapor residence times
21 for any given operating temperature, and can be deter-
22 mined routinely by those having ordinary skill in the
23 art.
24 The following examples serve to more fully
describe the manner of practicing the above-described
26 invention, as well as to set forth the best modes con-
27 templated for carrying out various aspects of the inven-
28 tion. It is und~rstood that these examples in no way
29 serve to limit the true scope of this invention, but
rather, are presented for illustrative purposes.
31 COMPARATIVE EXAMPLES A-G
. .
32 For each of these comparative examples 15 grams,
33 of subbituminous coal, ground to 10/20 mesh, U.S. sieve
34 size, was charged at room temperature and atmospheric
pressure into a continuous gas flow batch fixed-coal
36 bed tubular reactor. Each coal sample was subjected to
37 the following temperature/time cycle -
~ ~ 6~3~9
1 I - heat from ambient temperature to
2 250C in 30 minutes;
3 II - hold at 250C for 60 minutes; and
4 III - heat from 250C to 550C in 30 minutes.
Hydrogen, and/or various solvents were used during one
6 or more of the sectlons I, II, and/or III of the temper-
7 ature/time cycle. Table I sets forth the reagents, their
8 use and conversion of coal to liquids and gases for each
9 example.
~ ~ 6~37~
-- 10 --
o ~
rl ~ N
I
O
O
~1
E~
O ~ I I I . I I
\ E~ ~ o
~1 ' I I I ~r
U ~ r~
~q I ~ I ~ I
O E~l o ~ o
.IJ H ~ ~ N N
~ NN N ~ ~ \ 1
~ :c ~c m E~
O~ .~ r~
H ~I N ~I m o
~1 H ~C m
o
~ H ~ m C) a
a) o
~r ~ rl
o
` h
~ ~ rl r~
Q~ 11 11 11 11
q ~
N ~ ~ Ir~ ~ r~ CO C;~ O ~I N ~ ~ Il~
3 ~ ~
1 EX~PLES 1-5
2 The procedure described in Comparative
3 Examples A through G was followed except THQ was intro-
4 duced in such a way that conversion of solid coal in
liquids and gases was enhanced. Table II illustrates
6 the jadicious use of THQ.
J 1 fi~379
-- 12 --
o
O ~1
~ E~
o
U~
~ ~`1 1 1 1 ~
o
H ~I
H
1~ ~ H ¦ t`~
U~
\ H I E~
o
~ 01 0:
~ 3 ~37~
- ]3 -
1 This table when compared with Table I above
2 illustrates the following:
3 (a3 Not all solvents, even some of those
4 generally considered to be effective hydroyen donors
under high pressure conditions, will enhance conversion
6 of coal to liquids and gases at the low pressure condi-
7 tions claimed herein: i.e., compare Comparative Example
8 D with Example 2:
9 ~b~ The presence of hydrogen donor compound
of the type claimed herein is necessary only at elevated
11 temperatures; i.e., compare Comparative Examples C and F
12 with Examples 1-5; and
13 (c) ~ydrogen gas by itself is not effective
14 as the hydrogenating agent for enhancing conversion
under the process conditions of the present invention.
16 (Comparative Examples A and B).
17 EXA~lPLE 6
18 The procedure of the Comparative Examples
19 was again followed except THQ and helium were introduced
at stage III of the temperature/time cycle. No reagents
21 were introduced during stages A and B. The THQ to coal
22 weight ratio was 1/1 and a conversion of 41 wt.% of
23 coal to liquids and gases resulted. This example illus-
24 trates that hydrogen is not even necessary as a sweep
gas.
26 EXAMPLES 7-17 AND_CO~P~RATI~E E~A~lPLES H-N
27 In each of the examples set forth in Table
28 III below, except Examples 9, 10 and 12, 15 grams of
29 subbituminous coal of 10/40 mesh, U.S. sieve size, was
charged at room temperature and atmospheric pressure
31 into a continuous gas flow batch fixed-coal bed tubular
32 reactor. The reactor was heated to 500C at a rate of
33 about 400C per hour and 15 grams of solvent compound
34 was introduced over the temperature range from 250C to
500C. For Example 9, 45 grams of coal ancl 90 grams of
36 solvent were employed; for Example 10, 45 grams of coal
37 and 45 grams of solvent were employedi and fo Example
3 ~1 ~
-- 1'1 --
1 12, 45 grams of coal and 81 grams of solvent were
2 employed. The vapor residence time of any given solvent
3 compound in contact with coal was approximately 1 second
4 and solid residence time at which coal is in contact
with solvent vapor was ahout 40 minutes. Table III
6 below sets forth the solvents used as well as the
7 resulting conversion and yield data.
~ ~ ~437g
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~) ~ ~ ~ ~ U~ ~ N U~ a~ O -H ~ ~ t`'l ~ ~ I` u
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~ ~ ~ ~ o ~ o ,~
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~ Z
.
a~
~ ~ ~c~ ~r o ~ ~ c~ o co o L~
H ¦ C~ D CO ~ O O ~ ~ 0~
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1l
. ~ U~ C~
h ~ u:: r-l ~1 ~ o c~ CJ~ ~ ~ o Ln ~1
O C~C ~7 ~ 1~ ~ ~ ~ ~I ~ ~r tn u~ u~ u~ r In ~ ~ ~:r
3 . ~-~
V
a) 3 0 3
'~ R
b ~ ~ v `
Lr) ~1 ~ ~1 ~ P~ H H ~ ~ a) E-l O Z :1,
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X ~ 3 R, 3 ~ ~ ~ 1` CO a~ o ~1 ~ t~) ~ It~
O O O O O O O
~ ~ ~437~
-.
C~
C)
-rl
a
o ~
_, ~ o
O ~1 N
U:~ 3 ~1
~ Q
h O h
~q o tn
H r~) hra :~ ~ h h
H o a) h
H :~ :5 U O S S :3
h ~ ~15 o
~q ~ ~1 ~ ~ O
o ~ o 4~
O C) o ~ ~ ra
_ , ~
h ~ h ` ` I
al ~ ~ ~1 ~ N
H
~ Q
~ :~ 6~379
- 17 -
l The results shown in this Table III illustrate
2 that in order for the solvent to significantly enhance
3 liquid yield, under the claimed reactor conditions, a
4 donor solvent must be employed which is characterized
by (a) having a heterocyclic ring in which the hetero-
6 atom is nitrogen, (b) having at least one donatable
7 hydroyen located on said heterocyclic ring, and (c)
8 having a tendency to become more unsaturated and/or
9 aromatic by donating its hydrogen. ~his table also
illustrates again, that hydrogen is not needed as a
ll sweep gas in the practice of this invention for enhanc-
12 ing liquid yields.
13 Gaseous product streams resulting from selec-
14 ted examples were analyzed and the results are set forth
in Table IV below.
3 7 9
x
_I o o o ~ o o ~ n o
~,
U~
U)
X
~r u~ ~ ~ ~ r~l ~ ~ ~r ~
o o o o o o ~ ~ o
~ U
a
o
X
~ O . 1~ CC! O ~ o
: ~: U ~ ~ ~ O O' O O O ~ C~ O
V
o
C~O
s X
,~
~ ~ o o o o o o ~ r~ o
.
ta o u v v u v u c~ v ~ ~
o
:~ . V
3 ~ 9
-- 19 --
~I N ~ t-- O r- l
O OO O t r--l 1` O
U~
Ulr--l ~ ~1 ~r ~ r -l
r ¦ ~~1 0 0 0 0 r~l 1-') 0
C~
o
H ~ ~ ~ ¦ 1~ ~ ~ r~ I~ O r-l
3 ~C o I r--l r--l O C~ O ~1 ~D O
~ ~ C~
o
c ~o 1~r--l ~ r--l ri O ~ O
.C r--l O~1 + + l +i+ I + I
+ I ~ 111 cr~ C r.~lC~) + I + I ~D
. X C~ O ~ 1 r~l
r--l r--l O O O O ~--1 U) O
S~
OU C~ U ~ ~) U~) ~ U
o
r~ 9 1~ CO ~ Or--I ~ t~ ~ Ltl
~ r-1 r l I--I r--~ r--l
i :~ 643~
- 20 -
1 The analysis results shown in l'able I~ suggest
2 that the specific type donor solvents as claimed herein,
3 when employed under the claimed process conditions,
4 increase liquid yield at the expense of char and carbon
oxide gases. That is, oxygen is most likely being
6 directed to liquid product as opposed to gaseous product
7 and charO
8 EXAMPLES 18 A~D 19 AMD COMPARATIVE EXAMPEES O ~ND P
.._ ~ __ ... _ . .. ...._.. . _
9 In Example 18, 15 grams of Green River Oil
Shale was charged at room temperature and atmospheric
11 pressure into a continuous gas flow batch fixed-bed
12 tubular reactor. In Example 19, 45 grams of Kentucky
13 Devonian Oil Shale was charged, also at room temperature
14 and pressure, into a continuous gas flow batch fixed-bed
tubular reactor. The reactors were heated to a tempera-
16 ture of about 500C at a rate of about 400C per hour
17 and 25 grams and 42.6 grams of THQ, respectively, were
18 introduced. Identical base runs without THQ were run
19 for comparative purposes. That is, Comparative Example
O is the base for Example 18 and Comparative Example P
21 is the base for Example 19. The vapor residence time of
22 solvent in contact with shale was approximately 1 second
23 and solid residence time at which the shale was in con-
24 tact with solvent vapor was about 40 minutes. Helium was
used as a sweep gas for all examples. The results of
26 liquid and gaseous yield are shown in Table V below.
3 7 9
--21 --
a)
~U~ ~ ~ o
o o
O ~
~ O
~ ~1 OD ~1 0 0 0 0
P~
; a.) 0~ ~ Ln ~ a~ O
E t~ u) ~ ~ . . co
o ~q ~ ~l o ~ o o ~
o
~a o ~ ~ ~ r~
a
~ o ~ ~I ~ m ~ ~r ~ ~
~i ~p~
~ ~I co ~ o o o ~ ~ ~
o o
O ~ OD ~ o
D\~
D h
o C~ o 0~ t~ O
~ 7 ~ 3 '~
- 22 -
1 These examples illustrate that the present
2 invention is suitable for enhancing liquid yields from
3 oil shale.
