Extraction and liquefaction of fossil fuels using gamma irradiation and solvents

A new technology for the extraction of liquid hydrocarbon products from fossil fuel resources such as oil shales, tar sands, heavy oils and coals which comprises the mixing of a donor solvent with the fossil fuel and the exposure of the mixture to ionizing radiation. The donor solvent supplies hydrogen for combination with molecules whose bonds are broken by the irradiation process. The method may be conducted at or above ambient temperatures and pressures.

BACKGROUND AND SUMMARY OF THE INVENTION 
This invention relates generally to the processing of fossil fuels, and in 
particular it relates to new and improved methods for the processing of 
certain fossil fuels such as oil shales, tar sands, heavy oils and coal. 
Liquid fuels are an important energy source in many countries of the world 
not only for economic, but also for national security reasons. At the 
present time in history, geo-political factors can bear on the 
availability of useful liquid fuels in those nations which do not have 
ample fossil fuel supplies and/or the appropriate processing capabilities 
to convert the particular fossil fuels into liquid forms. 
Severe disruptions in the world petroleum supply in the 1970's gave rise to 
two energy crises in the United States in that decade. Extensive interest 
was generated in alternate fuel supplies and considerable resources were 
devoted to various developmental programs involving geo-thermal, solar, 
and other non-conventional sources, along with an extensive program whose 
objective was the development of large-scale synthetic fuel operations. 
Although the United States contains substantial fossil fuel reserves, its 
petroleum reserves have been unable to supply its total demand for liquid 
fuel, and therefore importation of petroleum has been required to meet the 
domestic demand. When a rising price for petroleum was imposed by those 
external forces referred to above, significant attention was devoted to 
the development of non-petroleum fossil fuels such as coals, oil shales 
and tar sands. It is estimated that the United States contains reserves of 
these non-petrolerm fossil fuels sufficient to handle the United States' 
energy needs for at least several hundred years. The problem, however, 
arises in converting them economically into useful forms for the various 
applications of hydro carbon-based energy, generally gases and light 
liquids. 
Various technologies have been proposed for extracting liquids or gases 
from these non-petroleum hydrocarbon-bearing resources and many were known 
long before the energy crises of the 1970's. In general, the net energy 
recovery using these technologies have been economically unfavorable in 
comparison to the economics of conventional petroleum sources, even at the 
historical price escalations in crude oil which have essentially remained 
in place since the energy crises of the 1970's. 
Certain other countries of the world are in the same type of energy 
situation as is the United States. They are net importers of petroleum, 
but possess local reserves of non-petroleum fossil fuels which could 
supply domestic liquid fuel needs if suitable technology were available. 
Non-economic considerations may also come to bear on the development and 
expansion of fuel resources, including not only conventional fuel sources, 
but also non-conventional ones. A specific example is the case of nuclear 
energy where the consequences of uncontrolled exposure to large doses of 
nuclear radiation are well-documented. 
Nuclear energy has the potential for freeing certain types of energy 
generation from dependence on liquid or hydrocarbon fuels. For example. 
nuclear power can be used in place of oil, gas or coal for firing an 
electric generating plant. 
Environmental concerns about the use of nuclear energy, whether legitimate 
or otherwise, have retarded the domestic expansion of nuclear energy, and 
today it is not unreasonable to express fear that further significant 
development of nuclear-electric power facilities will take place very 
slowly in the United States. 
While at the present time in history there are ample supplies of petroleum 
and other energy sources, there is no guarantee that this favorable 
situation will continue. Indeed, the United States continues to be 
dependent upon imported petroleum to a very significant extent. Any future 
disruption in petroleum imports will create consequences similar to or 
even more serious than those experienced in the decade of the 1970's. 
The technologies which have been proposed for the development of alternate 
liquid fuel sources, meaning nonpetroleum based resources, take many 
forms. There is extensive technology on the processing of oil shale and 
tar sands to extract useful hydrocarbon products. Ther is also substantial 
technology on the creation of synthetic fuels. 
In general it is fair to say that the net energy recoveries from these 
technologies is such that at today's economics, they are prohibitive to 
commercial exploitation in a free market. 
A representative technology for extracting useful liquid hydrocarbons from 
tar sands and oil shales comprises subjecting these naturally occurring 
raw materials to substantial levels of heat and pressure so that as a 
consequence liquid fractions are obtained. In the case of shale, crushing 
may be required. 
Where such naturally occurring materials are present in ample amounts near 
the earth's surface, conventional mining procedures can be used to obtain 
them. Where this is not the case it is necessary to use in situ 
exploitation with its attendant procedures. 
In any event, as noted above, it is fair to say that the net energy 
recovery using known technologies is not competitive with the present day 
economics of petroleum. 
While it is hoped that the future course of history will not occasion any 
new energy crises, it is a known fact that the world's recoverable 
petroleum reserves are finite. Therefore at some point in time it will be 
necessary to consider alternate fossil fuel sources such as coal, oil 
shale, and tar sands. 
The present invention is directed to a new and improved method for 
extracting useful hydrocarbons from such fossil fuel resources with a 
greater net energy recovery than is obtainable using known technologies. 
Accordingly, the present invention offers significant economic advantage 
over known technologies because it uses nuclear energy to promote 
extraction of useful hydrocarbon products from the naturally occurring 
fossil fuels such as oil shales, tar sands and coal. Stated otherwise, 
this invention utilizes ionizing radiation applied to the naturally 
occurring fossil fuel in conjunction with pressure and temperature 
exposures that are low enough to be reasonable, i.e., cheaper and safer 
than heretofore used. 
In one respect, the present invention obtains its improved efficiency 
through the use of certain solvents in conjunction with exposure to a 
certain level of ionizing radiation such as gamma rays, charged particles 
and neutrons. The usage of solvents in conjunction with gamma irradiation 
has been shown to have a synergistic effect on the extraction of useful 
hydrocarbons from oil shales, tar sands, and coal. 
In the application of the invention to the processing of oil shale, a 
preferred procedure for the practice of the invention comprises the use of 
a hydrogen donor solvent which is driven by the ionizing irradiation to 
cause extraction of hydrocarbons from oil shale raising the 
hydrogen-carbon ratio of the extracted material and at the same time 
eliminate substantial quantities of any sulphur and nitrogen which may be 
present in the natural shale. The process can be conducted at or near 
ambient temperatures and pressures so that external energy inputs to the 
process are minimized and the operating conditions are less demanding and 
expensive. 
The use of hydrogen donor solvents to promote the liquefaction of coal is 
known. In treatment with heat and pressure, it is believed that there is a 
transfer of hydrogen from the solvent to the coal and that the hydrogen 
transfer mechanism is essentially the thermal decomposition of the coal 
into free radicals. It has been discovered in this invention, as an 
example, that the donor solvent "n-heptane" possesses synergistic 
qualities in extraction of hydrocarbon from oil shale when driven by gamma 
radiation under ambient temperature and pressure. Other donor solvents are 
also suitable such as the generic groups represented by cyclohexane, tetra 
hydrofuran (THF) and tetralin. 
Others have considered using radiation to promote the extraction of 
hydrocarbons from tar sands and coal but none have conceived of processes 
which utilize the donor solvents in combination with the radiation to thus 
enable the process to be carried out at low temperatures and pressures. 
In the case of coal, it has been found that radiation by a gamma source can 
serve to obtain liquid hydrocarbon products from crushed coal by 
donor-solvent extraction with the irradiation providing synergistic 
enhancement. 
DESCRIPTION OF THE PREFERRED EMBODIMENT 
The use of irradiation in connection with fossil fuel processing has been 
investigated to a limited extent and has been discussed in published 
papers on the subject. It has been generally accepted that irradiation of 
a sample of a liquid hydrocarbon fossil fuel leads to polymerization and 
thus increased viscosity. Indeed a 1968 report on the "Gamma Irradiation 
of Coal", Information Circular 8377, issued by the U.S. Department of the 
Interior, Bureau of Mines, concluded that "coal is not significantly 
altered by gamma irradiation owing to the resistivity of its highly 
condensed ring structure. High-level gamma irradiation, therefore, is 
unlikely to prove advantageous in coal processing and utilization." 
While these representations may have general validity under the conditions 
that prevailed, it has been discovered that they are not absolute truths. 
The present invention involves the discovery that ionizing radiation, when 
used in a particular manner for the processing and upgrading of certain 
fossil fuels, can provide a recovery which is more favorable than that 
obtained with other technologies involving high temperatures and 
pressures, and hence high cost energy inputs. 
In general, the invention involves the utilization of ionizing radiation of 
certain fossil fuel resources in conjunction with the use of certain 
solvents. Moreover, it can be conducted at or near ambient temperatures 
and pressures so that the massive energy inputs and equipment required by 
other technologies become unnecessary. Indeed it has been discovered that 
there is a synergistic effect between irradiation and particular solvents 
when carried out according to principles of the invention such that 
enhanced yields of liquid hydrocarbons can be obtained from solid fossil 
fuel raw materials, such as oil shale, tar sands and coals. 
One aspect of the discovery is that certain solvents are particularly 
useful in producing such synergism. One of the solvents which has a 
synergistic effect with irradiation to accomplish depolymerization of the 
solid material found in oil shale is n-heptane. This solvent is of the 
type which will be referred to as a donor solvent because it has the 
ability to donate hydrogen ions to carbon bonds which are broken by 
irradiation so that liquid hydrocarbon products may thereby be formed. 
The irradiation of the fuel and solvent mixture is carried out in either an 
open air chamber, an evacuated chamber or a chamber filled with the 
mixture. There is no requirement for a special gaseous atmosphere.

The following examples will demonstrate the synergistic effect of the 
present invention, and each example includes a baseline reference for 
comparison. 
EXAMPLE I 
Two 50 gram samples of granulated oil shale from Ef's Israel were each 
mixed with 50 cc's donor solvent, n-heptane. One sample in solvent was 
subjected to 100 Megarad Co.sup.60 irradiation at the center of an 8 
kilocurie cylindrical Cobalt 60 gamma source. The sample was not 
mechanically stirred during irradiation, which was carried out at ambient 
temperature (40.degree. C. within the source) and at atmospheric pressure. 
No protective cover gas was used; the sample was exposed to air. The 
irradiation took about 6 days. It may be assumed that there was some 
thermal stirring of the solvent and that the dosage was not truly uniform 
throughout the shale due to self-shielding. 
The control was held at about 40.degree. C. during this period. The two 
samples were then each put into individual Soxhlet extractors and run for 
48 hours. The solvent was then drained into open beakers of known weight. 
These were stored at 80.degree. C. (Sand Bath) so that all the solvent was 
evaporated. The yields were measured by re-weighing the beakers. 
The solvent-only (no irradiation, i.e., control) run yielded 0.1 grams of a 
dull, thin, hard plastic-like material coated firmly and fairly uniformly 
over the bottom and lower half of the walls of the beaker. 
The shale irradiated in solvent yielded 0.75 grams of a brown clear liquid 
of moderate viscosity. It flowed slowly, like honey, at room temperature. 
The same shale samples were then each mixed with fresh 50 cc supplies of 
solvent and the process including irradiation repeated. The samples were 
again run in Soxhlet extractors for 48 hours, the solvent drained into 
open, weighed beakers and treated as described above. 
The control produced no additional measurable yield. The irradiated sample 
produced an additional 0.3 grams of a somewhat lighter, less viscous 
liquid. The total yield was now 1.05 grams: ten times the solvent-only 
(control) production. 
Initial elemental analyses were run with a Perkin Elmer elemental analyzer 
set up for C--H--N determinations. Sulfur determination was made by 
activation analysis, using a 2 Megawatt reactor at the University of 
Michigan. 
The yield composition after the second irradiation was: 
I. C--76.18%, H--12.6%; N--0.033%, H/C--1.99; S=0.39.+-.0.43%; No 
measurable residue. 
Yield composition for the first irradiation trial was: 
II. C--78.10%, H--12.96%, N--0.075%, H/C--1.99; S=1.78.+-.0.78%; No 
measurable residue. 
Yield composition of the control sample was measured with material scraped 
from the wall of the beaker: 
III. C--57.93%, H--8.30%, N--0.31%, H/C--1.72; S=6.10.+-.1.31%; Residue 
20.26% (ash). 
It is interesting to note that the compositions of a "typical" oil from 
Ef's shale and a typical raw shale as described in A Guide Book to the Oil 
Shale Deposits in Israel", M. Shirov and D. Ginzburg (1978) are: 
IV. Typical Oil C--79.9%, H--10.2%, N--1.1%, S--7.3%, H/C=1.53 
V. Raw Shale C--9.35%, H--1.16%, N--0.24%, S--1.6%, H/C=1.49; (Averaged 
Data) (organic) 
The analysis by the C--H--N analyzer and activation analysis in applicant's 
laboratory showed: 
VI. Raw Shale C--15.35%, H--1.56%, N--0.35%, S--2.0%, H/C=1.21; (total) 
The H/C ratio for III above, is higher than that for IV above, a "typical" 
Israeli shale oil (1.72 vs. 1.53). The N in the solvent extracted sample 
(non-irradiated) is lower (0.31% vs. 1.1%), but the sulfur values are 
close (6.1% vs. 7.3%). 
More important is the rise in H/C and the rapid decline in N and in S in 
the irradiated samples: 
______________________________________ 
III II I 
______________________________________ 
H/C - 1.72 .fwdarw. 
1.99 .fwdarw. 
1.99 
N (%) - 0.31 .fwdarw. 
0.08 .fwdarw. 
0.033 
S (%) - 6.1 .fwdarw. 
1.78 .fwdarw. 
0.39 
______________________________________ 
Also significant is the clarity and low ash content of the oil from 
irradiated samples as well as the increase in yield; in this case more 
than 10 times. This can be attributed to the effect of the radiation in 
breaking the bond between the hydro-carbon molecules and the inorganic 
matrix. 
The hydrocarbon is not only increased in hydrogen content but also becomes 
a more completely separated phase, making extraction simpler and cleaner. 
Based on the evolved odor of the freshly irradiated specimens, it appears 
that much of the sulfur has been incorporated into light molecules and 
volatilized. 
It appears that the yield increase by bond breakage is particularly 
important in homogenous shales--such as the Israeli shale--where the 
kerogen is fairly uniformly distributed through the mass. 
The operation was conducted at fairly modest radiation input levels (less 
than 1 Megarad per hour) and used low Linear Energy Transfer (LET) 
radiation only. The effects observed should respond to dose rate and to 
LET. All these factors can have a significant influence on the ultimate 
economics of the oil production. 
EXAMPLE II 
Conditions 
1 gram of crushed coal as received from Penn State Coal Sample Bank 
Radiation Dose--75 Megarad Cobalt-60 at 0.84 Megarad per hour. 
Ambient Temperature--samples in 20 ml of solvent exposed to air. 
Nominal Description of solvent in absence of radiation: 
A. Donor-solvent 
B. Solvent only. 
A. I. Control 
Crushed coal stored in "donor-solvent" about 1 week. 
Liquid filtered through filter paper and then evaporated to dryness. 
Result: No visible or measurable yield. 
A. II. Irradiated 
As in I. plus exposure to 75 Megarad. 
Result: Small yield of clear "oil" after evaporation of solvent. 
B. I. Control 
Crushed coal stored in "solvent" as in A. I. 
Result: Mixture lightly colored. Filtered liquid when solvent is evaporated 
yielded dry powder and a small amount of residual heavy dark fluid. 
B. II. Irradiated 
As in I. plus exposure to 75 Megarad. 
Result: Mixture opaque. Yield of filtered liquid, after solvent is 
evaporated, is about 10.times. yield for case B. I. 
EXAMPLE III 
Coal Conversion 
Tests were run on crushed PSOC 130 coal as received from Penn State Coal 
Sample Bank. PSOC 130 is a Pocahontas #3 Medium Volatile Bituminous Coal 
with the relevant elemental analysis supplied as follows: 
Carbon 84.71% Hydrogen 3.94% Nitrogen 1.05% 
Atomic Hydrogen/Carbon=0.57 
Four samples consisting of nine grams each of coal were then each mixed 
with 9 milliliters of the donor solvent, tetra hydrofuran (THF). One 
sample was exposed to 1.times.10.sup.8 Rad of Cobalt 60 radiation at 
ambient temperature and pressure, a second was exposed to 2.times.10.sup.8 
Rad, Cobalt 60, and the last two retained as controls. Dose rate was about 
0.6.times.10.sup.6 Rad per hour. 
After irradiation, the donor solvent was removed by evaporation of about 
125.degree. C. The remaining solid was then processed with pyridine in a 
Soxhlet extractor. The controls received the same treatment but without 
radiation. 
The extracted material was freed of pyridine at 130.degree. C. and then 
analyzed for Carbon, Hydrogen and Nitrogen. The results were: 
______________________________________ 
Rad Dose 
Carbon Hydrogen Nitrogen 
H/C Yield 
______________________________________ 
1 .times. 10.sup.8 
78.01% 7.01% 1.55% 1.08 0.22 gm 
control 84.88 6.92 2.88 0.98 0.07 
2 .times. 10.sup.8 
76.6 7.45 1.25 1.17 0.45 
control 81.1 5.98 2.53 0.88 0.08 
______________________________________ 
The primary effect of the radiation is seen to be the increased yield of 
pyridine soluble hydrocarbon. In addition, there is a higher H/C ratio and 
reduced nitrogen content, all of which demonstrate increased hydrogen 
transfer from the donor solvent. 
For further comparison, tests were run using pyridine as the solvent during 
irradiation as well as for extraction. The results are: 
______________________________________ 
Rad. Dose 
Carbon Hydrogen Nitrogen 
H/C Yield 
______________________________________ 
1 .times. 10.sup.8 
74.9% 5.51% 11.06 0.88 0.238 gm 
control 81.0 6.12 2.76 0.91 0.126 
2 .times. 10.sup.8 
76.5 4.95 9.7 0.78 0.29 
control 77.5 5.44 3.7 0.84 0.07 
______________________________________ 
There is, again, an increase in yield in the irradiated case accompanied, 
however, by a large transfer of nitrogen. The controls show the normal 
pyridine extraction behavior at low temperature. 
Two effects are thus observed. Solvent action is enhanced and, for the 
donor solvents, donor action is improved. There is also the reduction of 
nitrogen, much as was observed for oil shale, when a low nitrogen solvent 
is used. 
Heptane, while somewhat less effective, showed marked increase in both 
solvent action and hydrogen transfer under radiation. Cyclohexane was 
similar in action to THF. 
Softer coal with higher volatile content such as PSOC-1098 showed increases 
in yield under radiation with all the donor solvents. In later tests, 
still being evaluated, 10 milliliters of solvent were used with 1 gram of 
coal. Much larger percentage yields of dissolved coal were obtained. 
The term "donor solvent" is used herein to describe solvents that possess 
the ability to decompose partially and to release hydrogen to the fossil 
fuel. It is believed that the hydrogen transfer is a free radical reaction 
in which coal molecules are thermally cleaved into free radicals which 
seek stabilization. If a donor solvent is present the available hydrogen 
atom stabilizes this free radical by hydrogen transfer. If a sufficiently 
active hydrogen donor solvent is used, the hydrogen transfer mechanism is 
essentially the thermal decomposition of the fossil fuel. 
Under ionizing radiation, two effects can be produced: 
(a) the fossil fuel (coal) molecule can be cleaved even at low temperature; 
(b) a hydrogen donor can be made "active". 
While there are good parallels between the thermal case and the radiation 
driven case, they cannot be carried too far. In general the radiation 
driven case will be chemically reactive at lower temperature (and 
pressure), and the most suitable donors may not be the same. All results 
on which this invention is based have been obtained at room temperature. 
There are clearly combinations of mildly elevated temperature and pressure 
with radiation to create the optimum process. 
Further examples with respect to oil shale are as follows: 
__________________________________________________________________________ 
KEROGEN EXTRACTION AND SHALE OIL UPGRADING FROM U.S. SHALES USING 
DONOR-SOLVENTS AND RADIATION AT AMBIENT TEMPERATURE AND PRESSURE 
Radiation 
Yield (Weight S 
SHALE-Origin 
Donor- 
Dose RAD 
Percent C H H/C N Acti- 
Ash From 
& Properties 
Solvent 
Cobalt 60 
of Shale) 
(Perkin-Elmer Elemental Analyzer) 
vation 
C--H--N 
Remark 
__________________________________________________________________________ 
"Rich" -- -- -- 28.26 
3.31 1.40 
0.74 50.7 Raw 
Colorado.sup.(1) Shale 
Kerogen in 
n-Heptane 
0 See .sup.(1) 
83.78 
12.28 
1.75 
0.88 0 Brown 
Segregated Heavy 
Seams Resin 
n-Heptane 
1 .times. 10.sup.8 
80.97 
13.37 
1.98 
0.30 0 Lt. Brown 
Syrupy 
Liquid 
n-Heptane 
0 83.33 
12.65 
1.82 
0.79 0.23 0 Brown 
Heavy 
Resin 
n-Heptane 
2 .times. 10.sup.8 
83.47 
14.00 
2.01 
0.36 0.07 0 Lt. Brown 
Liquid 
Kentucky.sup.(2) 
-- -- 16.41 
1.98 1.44 
0.52 50.9 Raw 
Sunbury Shale 
n-Heptane 
0 negl. 
Kerogen Dis- 
n-Heptane 
10.sup.8 
1.0 84.88 
14.24 
2.01 
0.05 neg Tan 
persed Liquid 
Through THF 0 0.62 78.86 
9.34 1.42 
1.51 trace Black 
Shale Pitch- 
like 
THF 10.sup.8 
2.8 66.47 
9.29 1.68 
0.32 0 Dk. Brown 
Viscous 
Liquid 
__________________________________________________________________________ 
Footnotes for table 
.sup.(1) For "Rich" Colorado shale, kerogen was extracted first, using 
Soxhlet extractor and donorsolvent. An aliquot of extract in donorsolvent 
was then irradiated. In qualitative observation of the effect of radiatio 
on extraction, crushed shale was irradiated in donor solvent and then 
processed. Yield was about 10% greater than nonirradiated control. 
.sup.(2) For Kentucky Sunbury shale, crushed shale was irradiated in 
donorsolvent and then processed in Soxhlet extractor. 
On the basis of the foregoing examples, it can be seen that a new and 
useful method has been disclosed which possesses significant advantages 
over other technologies. It is to be appreciated that although certain 
ranges, compositions, percentages, etc. have been identified, these are 
intended to be illustrative and not necessarily limiting in character.