Method of reducing inorganic and organic sulfur in solid carbonaceous material prior to use of the solid carbonaceous material

The inorganic and organic desulfurization of solid carbonaceous material at elevated temperatures is increased significantly in the presence of copper. The copper serves as a scavenger for the hydrogen sulfide formed to insure a low hydrogen sulfide concentration for the inorganic desulfurization. In addition, in the presence of ethanol or hydrogen, the organic desulfurization of solid carbonaceous material is improved dramatically by the catalytic influence of the copper on the ethanol dehydrogenization and of the copper sulfide formed on the hydrodesulfurization reactions.

BACKGROUND OF THE INVENTION 
There are many references in the literature to the chemical cleaning of 
solid carbonaceous material. While most of these references are directed 
to coal, it is to be understood that the term "solid carbonaceous 
material" includes petroleum coke, metallurgical coke, charcoal, other 
products of coal pyrolysis, and solid products of coal hydrogenation, as 
well as coal. The primary objective of these processes is to remove 
sulphur from the solid carbonaceous material. For the purposes of this 
patent application the discussion of the prior art and the invention will 
be described in conjunction with coal but it is to be understood that it 
is applicable to petroleum coke and charcoal and any other solid 
carbonaceous materials. 
One or more problems associated with the desulfurization of coal based on 
treatment with gases at elevated temperatures involve the loss of the 
heating value of the coal, the corrosive reaction conditions required, 
long reaction times, the need for high temperatures and pressures, the 
high consumption of hydrogen, waste disposal problems, the relatively 
small amounts of sulphur removed from the coal, and the inability to 
market the treated coal. 
The use of ethanol to remove sulfur from coal, disclosed in U.S. Pat. No. 
4,888,029, Shiley, et al, overcomes some of the disadvantages of earlier 
chemical processes. However, the yield obtained by this process upon 
scale-up does not make it economically attractive. 
According to U.S. Pat. No. 4,888,029, which is a one-stage process, in the 
conditions of this patent (300.degree.-500.degree. C.; flowing inert gas 
containing 0.5-2% reaction accelerator) ethanol is dehydrogenated at the 
surface of pyrrhotite and/or troilite (FeS) formed from the pyrite in the 
coal to release atomic hydrogen which reacts with both the sulfur in the 
pyrrhotite and the troilite and with the organic sulfur (which is 
chemically bonded in the coal and very difficult to remove) to form 
gaseous hydrogen sulfide (H.sub.2 S) and acetaldehyde in accordance with 
the following reactions: 
##STR1## 
However, reaction (2) is not thermodynamically favorable in the conditions 
of the method of U.S. Pat. No. 4,888,029 (400.degree.-500.degree. C.) and 
requires a very low concentration of H.sub.2 S in the reaction bed (less 
than 300 ppm) to proceed forward. Such a low H.sub.2 S concentration is 
not attainable in the conditions of the method of this patent. In 
addition, reactions (1) and (3) are not sufficiently catalytically 
activated. 
SUMMARY OF THE INVENTION 
Applicant has observed that when the above described process using an 
alcohol, which is preferably ethanol, or some other hydrogen producing 
agent, is performed in the presence of copper or a copper-containing 
material, desulfurization is dramatically increased. 
While the use of a copper catalyst for the dehydrogenation of ethanol in 
reactions involving liquid and gaseous organic compounds is well known, no 
references have been found for the use of copper or a copper compound to 
dehydrogenate ethanol in the presence of solids, such as coal or other 
solid carbonaceous materials, to release nascent hydrogen. 
In addition, applicant has observed that the copper serves as a scavenger 
for H.sub.2 S to ensure a very low concentration of H.sub.2 S in the 
reaction bed and to form copper sulfide (Cu.sub.2 S) which in turn serves 
as a catalyst for organic sulfur hydrodesulphurization reactions. Thus, 
the copper, unexpectedly, performs a triple role. It or a compound of it 
serves as a catalyst for the ethanol dehydrogenation process when ethanol 
or some other alcohol is used and at the same time the copper serves as a 
scavenger for H.sub.2 S to ensure a low H.sub.2 S concentration for the 
inorganic desulfurization (to shift the equilibrium of the FeS reduction 
reaction (2) above), and to form copper sulfide which in turn serves as a 
catalyst for organic sulfur hydrodesulphurization reactions. The result is 
to dramatically increase the removal of both inorganic and organic sulfur 
from the solid carbonaceous material. One way in which the copper has been 
used for this purpose is to have the copper or an alloy thereof be part of 
the materials of construction for a regenerable reactor. Such an approach 
to combine the acceptor and the catalytical techniques and to remove the 
sulfur through a regenerable reactor or a regenerable reactor lining 
material is previously unknown. 
In addition, applicant has also found that by applying a portion of water 
alternately between portions of ethanol in the process leads to an even 
higher inorganic desulfurization. 
Applicant has found also that applying portions of gaseous hydrogen in a 
copper reactor leads to a desulfurization degree which is attainable by 
hydrodesulfurization (treatment in a hydrogen atmosphere) in a stainless 
steel flow-through reactor only at much higher temperatures and at a high 
gas flow. 
The temperature employed in practicing this process can vary. It has been 
found that a temperature below 400.degree. C. is not economically 
attractive and not effective. Temperatures up to 1000.degree. C. can be 
employed, but the method is effective even in a lower temperature range of 
400.degree.-600.degree. C. 
It is therefore an object of this invention to remove a significantly large 
amount of the sulfur contained in a solid carbonaceous material, such as 
coal, petroleum coke and charcoal, either as pyrites or as organically 
bound sulfur. 
It is a further object of this invention to accomplish the sulfur removal 
using relatively low temperatures. 
It is a further object of this invention to accomplish this in the presence 
of copper. 
These, together with other objects and advantages of the invention will 
become more readily apparent to those skilled in the art when the 
following general statements and descriptions are read in light of the 
appended drawing.

DETAILED DESCRIPTION OF THE INVENTION 
The method of the invention is described in the following examples in which 
the solid carbonaceous material treated is coal. The examples vary in the 
manner in which the coal is treated so as to show the advantages of the 
method constituting the instant invention. 
LABORATORY SET-UP FOR EXAMPLES 
Referring to FIG. 1, five to ten grams of coal 9 were placed on fine copper 
screen 10 supported by perforated plate 11 in copper reactor 12. Copper 
reactor 12 is fixed to stainless steel autoclave 13 at the upper portion 
14 of autoclave 13 by means of the brass tube 15. The brass tube 15 also 
permits the inflow of inert gas and reactants into the copper reactor 12. 
The brass tube 15 is provided with a valve 16. An exit pipe 17 is provided 
with a valve 18 and a pressure gauge 19. Brass tube 15 is also provided 
with a two-way valve 20 which permits the introduction of ethanol or water 
as desired. A copper tube 21 is provided for a temperature probe 22. The 
stainless steel autoclave 13 was inserted into an electric furnace. Inert 
gas was introduced through the brass tube 15 at 50 psig. Nitrogen or 
helium containing 0.5% NO was used. During the experiment involving 
heating to a given temperature and holding it at that given temperature a 
constant flow of 60-80 mL/min of the inert gas was driven through the 
reactor system using a gas pump (not shown). An amount of ethanol, or 
water as the case may be, was warmed up to the boiling temperature of 
water and was introduced through valve 20 in the inert gas line 15 
immediately before the autoclave head 14. The ethanol or water was pumped 
at room temperature with a liquid capacity in the range of 0.4-1 Ml/min 
and led through a preheater before being forced into the inert gas line. 
The ethanol or water was introduced in portions of 0.5 mL/g of coal. The 
first portion was fed immediately after reaching the desired temperature. 
During the introduction of reactant the inert gas flow was reduced to 
about 10-30 Ml/min. The treatment time intervals after each portion (when 
the pressure reverts to its controlled level) were selected with a view to 
ensure a total reaction time of 120 min at a given temperature in each 
experiment. For example, in a typical experiment with five grams of coal, 
three portions of 2.5 Ml liquid ethanol were introduced at a rate of 0.5 
Ml/min (five min for the introduction of each portion) and with 35 min 
treatment time after each portion. 
The experiments were carried out at temperatures in the range of 
400.degree.-600.degree. C. During the experiments with a copper reactor no 
H.sub.2 S was present in the vent flow 17 (the reaction of CdS formation 
in an absorber with cadmium acetate was used for detection). 
0.5% NO in the helium inert gas flow was used as a radical process 
accelerator. This initiator has been used for desulfurization in the 
presence of atomic hydrogen. Other radical reaction activators besides NO 
may be used. For example O.sub.2 is effective as a radical reaction 
activator. 
For the regeneration of the copper reactor successive treatments (blowing 
through) with air (80 mL/min) at 500.degree. C. to 700.degree. C. and with 
hydrogen (30 mL/min) at 200.degree. C. were applied. The bulk of the 
sulfur, retained in the sulfide layer, was burned off for 30 minutes but 
the roasting continued until below 20 ppm SO.sub.2 was present in the air 
stream (about two hours). During the following reduction with hydrogen, an 
additional amount of SO.sub.2 was produced. A two hour reduction time was 
usually employed. After regeneration the reactor was dismantled and 
cleaned by means of an air jet. During the first run after a regeneration 
the reactor was sulfided. The reactor retained practically a constant 
effectiveness in the next four runs. 
Results of experiments performed in the narrow temperature range of 
450.degree.-500.degree. C. and illustrating some effects of the reactor 
and the reactants are set forth in succeeding examples. The percentage 
desulfurization was calculated considering the weight loss of the sample. 
The latter varied, depending on the coal and the conditions, between 21% 
and 34%. 
Two Ohio high-volatile bituminous coals were used in these experiments. 
They were a sample of Ohio #6 (Middle Kittaning) coal obtained from the 
Penn State Coal Bank (PSOC-1518) and a sample of washed Ohio #4A coal, 
collected from the Sands Hill Coal Company. The sulfur analysis data on 
the coal samples used were as follows: Coal Total Sulfur Pyritic Sulfur 
______________________________________ 
Percent, Dry Basis 
Coal Total Sulfur 
Pyritic Sulfur 
Sulfate Sulfur 
______________________________________ 
PSOC-1518 
3.7 0.9 1.1* 
Ohio #4A 4.0 2.0 0.0 
______________________________________ 
*This sulfate sulfur content indicates some oxidation of the sample. 
EXAMPLE 1 
In this case, the coal used was PSOC-1518, -100 mesh, the temperature was 
450.degree. C. and the reactor was stainless steel. No copper was present. 
The gas flow was nitrogen and there was no separate reactant. The 
percentage of sulfur in the starting coal was 3.61% and the percentage of 
sulfur in the finished product was 2.73%. The total desulfurization was 
41.3% and this amounted to 47.7% inorganic and 31.2% organic. The reducing 
agents in this case were only the hydrogen and reductive hydrocarbons 
produced from the coal. This same example was carried on using a glass 
reactor rather than a stainless steel reactor and practically the same 
results were obtained. 
EXAMPLE 2 
The same coal and temperature as used in Example 1 was employed and the 
reactor was the same stainless steel reactor. The gas flow was helium plus 
0.5% NO and there were three portions of ethanol added. The percent sulfur 
in the coal at the start was 3.57%, the percent sulfur in the product was 
2.39% and the percent desulfurization was 47.3% total, 44.2% inorganic and 
51.4% organic. From this it may be concluded that the treatment with 
ethanol in a stainless steel reactor affects only the organic 
desulfurization. The coal pyrolysis is accelerated in the presence of 
atomic hydrogen and the radical reaction activator NO and the organic 
sulfur group hydrogenolysis is enhanced (ferrous sulfide formed as well as 
iron oxides and aluminosilicates from the coal mineral matter can serve as 
catalysts). The presence of atomic hydrogen when ethanol is applied does 
not affect the reduction of FeS.sub.2 and FeS. 
EXAMPLE 3 
The same coal as used in the previous two examples was employed, the 
temperature was 460.degree. C. The reactor however was copper sulfided and 
the gas flow and ethanol proportions were used as in Example 2. The 
initial sulfur in the coal was 3.83% and the sulfur in the product was 
1.27%. The percent desulfurization was as follows: 75.1% total, the 
inorganic being 80.6% and the organic 68.1%. From this it can be concluded 
that the use of a copper reactor strongly affects the inorganic 
desulfurization by the effect on the equilibrium of the FeS reduction. It 
also may be concluded that ethanol is more effective for the organic 
desulfurization in a copper reactor than in a stainless steel reactor. 
That is explained by better catalytic conditions for ethanol 
dehydrogenation and/or by the catalytic influence of a copper sulfide 
covering rather than by a copper scavenger effect. 
EXAMPLE 4 
This shows the effect of a copper reactor without ethanol treatment. Ohio 
4A, -20 mesh coal was employed. The temperature was 480.degree., the 
reactor was copper, sulfided, the same gas as used in Examples 2 and 3 was 
employed but there was no reactant, i.e. no ethanol. The percent sulfur in 
the coal was 3.97%, the percent sulfur in the product was 3.08%, the total 
percent desulfurization was 46.3% and this involved 65.3% inorganic and 
27.9% organic. This shows that the quick removal of H.sub.2 S on the 
reactor walls does not affect the organic desulfurization. This indicates 
that the organic sulfur group hydrogenolysis is determined by the kinetics 
of the reactions and their catalysis rather than by their thermodynamic 
equilibrium. 
EXAMPLE 5 
The same temperature and reactor were used as in Example 4. Ohio No. 4A 
coal, -100 mesh was used. There were three portions of ethanol used as a 
reactant. The percent sulfur in the coal was 3.72%, the percent sulfur in 
the product was 1.56%, the percent desulfurization was 69.6% consisting of 
69.9% inorganic and 69.4% organic. It appears that the PSOC-1518 coal 
sample containing a total of 2% pyritic and sulfate sulfur is easier to 
desulfate than Ohio No. 4A coal containing only 2% pyritic sulfur. Compare 
Examples 3 and 5. 
EXAMPLE 6 
In this case Ohio #4A, -100 mesh coal, a temperature of 500.degree. C., the 
same reactor, and the same gas flow were used as in Example 7. However, 
two portions of ethanol and one portion of water were used. The percent 
sulfur starting in the coal was 3.80%, the percent sulfur in the product 
was 0.98%, the percent desulfurization was 82.7% consisting of 93.2% 
inorganic and 72.6% organic. Thus it will be seen that applying a portion 
of water between two portions of ethanol leads to an even higher pyritic 
desulfurization. That is explained by a shift of the equilibrium of the 
reaction of iron sulfide. 
EXAMPLE 7 
In this case the same coal, reaction temperature, type of reactor, gas flow 
and reactants were used as in Example 6, the percentage of sulfur in the 
starting coal was 3.80%, the percentage of sulfur in the product was 
0.55%, and the percentage of desulfurization was 90.4%. The conditions 
were changed from the previous examples, however, in the following: Before 
the introduction of each portion of reactant the gas flow rate was reduced 
to 5-10 mL/min and maintained at this low level during the entire reaction 
(residence) time of the respective reactant. In this way, keeping the same 
total holding time (120 min) at a given temperature, the residence time of 
the reactants used was increased. In practice, in the three portion 
experiments with 5 g coal and reactant portions of 2.5 Ml (0.5 mL/g coal), 
each reactant was introduced for five minutes (0.5 mL/min) and allowed to 
react for 25 minutes at a reduced gas flow rate of 5-10 mL/min. A higher 
gas flow rate of 80-150 mL/min was maintained only during two intervals of 
15 minutes between the portions when the pressure reverted to its initial 
level (50 psig). 
This shows the positive effect of the increased residence time of the 
reactants on the degree of desulfurization. 
EXAMPLE 8 
The coal, temperature, reactor and gas flow were the same as in the 
previous example. Portions were changed to 1 ml per gram of coal. Only two 
portions were used: One portion of water followed by one portion of 
ethanol. In the case of two portion experiments with 5 grams of coal, the 
conditions with respect to the residence time of the reactants were 
changed as follows: Portions of 5 mL (1 mL/g coal) of each reactant were 
introduced for five minutes (1 mL/min) and allowed to react for 45 minutes 
at a reduced gas flow rate of 5-10 mL/min. During an interval of 20 
minutes between the portions a higher gas flow rate of 80-150 mL/min was 
maintained when the pressure reverted to its initial level of 50 psig 
after having increased to &gt;200 psig during the addition of reactants. 
The percentage of sulfur in the coal was 3.86%, the percentage of sulfur in 
the product was 0.71%, and the total desulfurization was 87.95%. The 
conclusion that may be drawn from this example is that one can use a 
single addition of the ethanol rather than two smaller equivalent amounts 
to get a similar percentage desulfurization. 
EXAMPLE 9 
The same conditions were employed as in the previous Example 8. However, in 
this example instead of applying a 5 mL (0086 mol) ethanol portion, one 
portion of hydrogen gas (0.1 mol) was used. The percentage of sulfur in 
the coal was 3.87%, percentage sulfur in the product was 1.36%, the 
percentage of desulfurization employed was 78.3%, the inorganic 
desulfurization was 88.6% and the organic desulfurization was 68.0%. The 
conclusion that may be drawn from this example is that an equivalent 
portion of ethanol is more effective than an equivalent portion of 
hydrogen. Obviously, hydrogen is also of interest as a reactant but is not 
as effective as ethanol in these conditions. 
__________________________________________________________________________ 
SUMMARY OF RESULTS 
Reactant % S in 
% S in 
Run Temp. Gas No. of the the Desulfurization 
No. 
Coal .degree.C. 
Reactor Flow Portions coal 
product 
Total 
Inorganic 
Organic 
__________________________________________________________________________ 
1 PSOC-1518 
450 Stainless steel 
Nitrogen 
No reactant 
3.61 
2.73 41.3 
47.7 31.2 
100 mesh 
2 PSOC-1518 
450 Stainless steel 
He + 0.5% 
Ethanol, 3 portions 
3.57 
2.39 47.3 
44.2 51.4 
100 mesh NO 
3 PSOC-1518 
460 Copper, sulfided 
He + 0.5% 
Ethanol, 3 portions 
3.83 
1.27 75.1 
80.6 68.1 
NO 
4 Ohio #4A 
480 Copper, sulfided 
He + 0,5% 
No reactant 
3.97 
3.08 46.3 
65.3 27.9 
20 mesh NO 
5 Ohio #4A 
480 Copper, sulfided 
He + 0.5% 
Ethanol, 3 portions 
3.72 
1.56 69.6 
69.9 69.4 
100 mesh NO 
6 Ohio #4A 
500 Copper, sulfided 
He + 0.5% 
Ethanol, 2 portions 
3.80 
0.98 82.7 
93.2 72.6 
100 mesh NO Water, 1 portion 
7 Ohio #4A 
500 Copper, sulfided 
He + 0.5% 
Ethanol, 2 portions* 
3.80 
0.55 90.4 
100 mesh NO Water, 1 portion* 
8 Ohio #4A 
500 Copper, sulfided 
He + 0.5% 
Water, 1 portion** 
3.86 
0.71 87.95 
100 mesh NO Ethanol, 1 portion** 
9 Ohio #4A 
500 Copper, sulfided 
He + 0.5% 
Water, 1 portion 
3.87 
1.36 78.3 
88.6 68.0 
100 mesh NO H.sub.2 Gas 
1 portion (0.1 mol) 
__________________________________________________________________________ 
*Enhanced residence time of the reactants. 
**Enhanced amount of the reactants and of their residence time. 
From the above experimental results it will be seen that the inorganic and 
organic desulfurization of solid carbonaceous material is increased 
significantly using ethanol which dehydrogenates at 
450.degree.-500.degree. C. in the presence of copper. The enhanced 
inorganic desulfurization is determined by the copper scavenger effect. In 
addition, in presence of ethanol, which dehydrogenates, or hydrogen, the 
organic desulfurization of carbonaceous material is improved considerably 
by the catalytic influence of the copper sulfide formed. When ethanol is 
used, one has a better catalytic dehydrogenization of the ethanol in the 
presence of copper. 
While this invention has been described in its preferred embodiment, it is 
to be appreciated that variations therefrom may be made without departing 
from the true scope and spirit of the invention.