We have previously cited the USDOE's Bockrath and Noceti, of the Pittsburgh, PA, Energy Technology Center, relative to their research into the practical liquefaction of coal, and herein is more documentation of their work, and their accomplishments.
Though the following excerpts from the enclosed link might seem lengthy, they are just an abbreviated example of what is available;.we were compelled to edited out much overly-technical detail.
With comment appended:
"Evaluation of the Donor Ability of Coal Liquefaction Solvents
Bradley C. Bockrath and Richard P. Noceti
United States Department of Energy
Pittsburgh Energy Technology Center
P. 0. Box 10940
Pittsburgh, Pennsylvania 15236
Pittsburgh Energy Technology Center
P. 0. Box 10940
Pittsburgh, Pennsylvania 15236
Hydrogen donor solvents are used in most processes for the direct liquefaction of coal. The overall performance of these solvents depends on several qualities, including. the abilities to physically solvate coal and its liquefaction products, to hold coal particles in suspension, to assist transfer of hydrogen from the gas phase to coal by dissolving molecular hydrogen or undergoing hydrogenation/dehydrogenation cycles (hydrogen shuttling), and to donate hydrogen directly to coal. Unknown factors may also be involved. In addition, in the case of commercial application, the solvents must be derived from coal and be suitable for recycle operation as well. In order to fully understand the function and importance of liquefaction solvents, the influence of each property must be studied separately. As a step towards this goal,we have developed a method by which the relative hydrogen donor ability of liquefaction solvents may be evaluated.
Our method of evaluation is based on a generally accepted hypothesis -of the mechanism of coal liquefaction that has been used to rationalize the kinetics of coal liquefaction (1,2) and has been discussed several times in recent reports (for example (3,4,5). According to this mechanism, the initial act is rupture of the weaker covalent bonds in coal. This produces two free radicals in close proximity. These radicals may either abstract hydrogen from any available source (donor solvent, coal or molecular hydrogen), undergo
rearrangement, or add to some other site on either coal or solvent. Recbmbination or addition may lead to production of insoluble or char-like residues that are dearly undesirable. One critical function of the donor solvent is to provide a source of hydrogen. Abstraction of hydrogen by coal-derived free radicals prevents retrogressive reactions that lead to higher molecular weight products, and it directs more coal along the desired pathways to lower molecular weight products. Thus, donors with high potential for hydrogen
transfer are regarded as beneficial to increased liquefaction yields.
rearrangement, or add to some other site on either coal or solvent. Recbmbination or addition may lead to production of insoluble or char-like residues that are dearly undesirable. One critical function of the donor solvent is to provide a source of hydrogen. Abstraction of hydrogen by coal-derived free radicals prevents retrogressive reactions that lead to higher molecular weight products, and it directs more coal along the desired pathways to lower molecular weight products. Thus, donors with high potential for hydrogen
transfer are regarded as beneficial to increased liquefaction yields.
Our approach to evaluation of the donor property was to devise a test that embodies the main features of the free radical mechanism of coal liquefaction. The basic idea is shown in Figure 1. Benzyl radicals are generated by the thermolysis of' a convenient precursor at relatively low temperatures. These radicals then behave like the free radicals generated by the thermolysis of coal at liquefaction temperatures. When benzyl radicals are generated in a donor solvent, the relafive amounts of toluene and bibenzyl produced reflect the relative ability of the solvent to donate hydrogen and to prevent reco'mbination. A variable amount of benzyl radical is also lost, which presumably represents that amount which adds to or combines with the solvent.
Other methods have been used in the past to provide a "solvent quality index. ... Notably, measurement of liquefaction yields produced under specified conditions and with a specified coal has been used to provide a direct empirical evaluation of solvent quality.
Various spectroscopic methods have also been used to estimate the relative amount of benzylic or hydroaromatic hydrogen available for transfer (10,11,l2). These methods serve their intended purposes well. In the present work, we airn at developing a better understanding of the chemistry of liquefaction and the overall performance of liquefactionsolvents by isolating the hydrogen donor ability and free radical scavenger ability for study.
RESULTS AND DISCUSSION
Since many of the cornpounds to be tested as rnodel hydrogen donors are solids at room temperature, it was worthwhile to use an inert liquid as a diluent. Tert-butylbenzene served this purpose well. It possesses only relatively inert aromatic and primary aliphatic hydrogen and sufficient solvent power to dissolve most of the donor solvents to be tested. Decomposition of either benzyl radical precursor in lert-butylbenzene solution produced only srnall yields of toluene.
Material balance studies showed that not all of the benzyl radical present in the precursor was recovered as either toluene or bibenzyl. A sizeable fraction is apparently rernoved by side reactions with the solvent. In pure t-butylbenzene, this accounted for 24% of the benzyl radical, while in a 50/50 wt mixture of
t-butylbenzene and tetralin, it accounted for 32%. In the gas chromatograms of the decornposition products, new peaks appeared which were due to high boiling compounds. In the case of runs done in the
presence of tetralin, GC/MS analyses indicated that three of these peaks had the correct molecular weights for benzyltetralins, benzylnaphihalene and bitetralyl. These products must arise from radical combination and addition reactions.
presence of tetralin, GC/MS analyses indicated that three of these peaks had the correct molecular weights for benzyltetralins, benzylnaphihalene and bitetralyl. These products must arise from radical combination and addition reactions.
The appearance of solvent combination and addition products is in accord with some recently reporteq results from other groups. Collins et. al. (13) reported that after they heated coal with 4C labeled tetralin at 400’ C for I hour, the pyridine solubles were 1.6 1 t. percent tetralin and the residue 2.6 wt. percent tetralin. In pother experirnent (13), “C labeled 1,3 -dipheriylpropane was heated with tetraliri at 400 C for 1 hour. Toluene and ethylbenzene were major products. In addition, methylnaphthalenes, mcthyldihy-dronap!ithalenes, phenylethyltetralins, and phenylcthylnaphthalenes were found. A mechanism was proposed that involved cornbination of phenylethyl with tetralyl radical, followed by further thermolysis to produce methyl substituted .tetralins and: naphthalenes.
Thus at higher temperatures, radical addition to solvent may he followed by (unintelligible) of the newly formed bridge. Evidence for the addition and subsequent dissociation of benzyl radical with tetrafin at temperatures of 400-450°C has also been reported by workers at Gulf (14). Another piece of evidence showing the importance of addition reactions is the report (15) that -negative solvent balances were found during preheater studies. These findings were interpreted to mean that during the initial phase of liquefaction (300’ -4OO0C), coal-derived solvent became bound to the coal so tightly that it could not be Jreed by either distillation or solvent extraction. Subsequent reaction after reaching 450 C changed the solvent balance to positive. Processes analogous to the addition/dissociation reactions described by Collins rnay Pe involved.
The three solvent indices were determined for the decomposition of dibenzylmercury for several solvent mixtures made from different amounts of tetralin .in t-butylbenzene. The data contained in Figure 2 show that the donor index increases with increasing tetralin concentration. Also shown in this figure are data taken from reference (16).for conversign of a bituminous coal to pyridine soluble material after reaction for three minutes at 427 F in mixtures of tetralin with methylnaphthalene, cresol, and picoline. Conversion as well as the donor index goes up as the tetralin concentration in the solvent increases. This comparison is made only to point out the qualitative similarity between the two results since we assume that both coal conversion and toluene yield are related to the relative hydrogen donor ability of the solvent. In both cases the greatest increase in conversion or toluene yield comes at relatively low tetralin concentration.
Tetrahydroquinoline's superior quality has been attributed to a unique combination of readily donatable hydrogen with a heightenedability to solvate coal and its liquefaction products ... an additional reason for the superior liquefaction performance of tetrahydroquinoline may be its ability to add to or combine with
free radicals initially produced by the thermolytic reactions of coal.
free radicals initially produced by the thermolytic reactions of coal.
Comparison of the donor indices with other available quality criteria is made with two sets of solvents. The DCD series are recycle solvents derived from Blacksville coal under different processing conditions in the 1000 Ib/day liquefaction unit at PETC. The values of ... distillation residue from a lightly hydrogenated recycle oil made in the Wilsonville SRC pilot plant from Wyodak coal. F-14is a lightly hydrogenated recycle oil made in the Tacoma SRC pilot plant from Kentucky coal. F-16 is a coal gasification tar from an in situ gasification project near Manna, Wyoming.
REFERENCES
1) G. P. Curran, R. T. Struck and E. Gorin, Ind. Eng. Chem., Process Des. Dev. -6, 166 (1967).
2) W. H. Wiser, Fuel, E,475 (1968).
3) D. D. Vhitehurst, T. 0. Mitchell, M. Farcasiu and 3. J. Dickert, Jr., "The Nature and Origin of Asphaltenes in Processed Coals," EPRl Final Report AF-1298 (1979).
4) R. C. Neavel, Fuel, 55, 237 (1976).
5) I. Wender and 5. Friedman, Proc. 13th. IECEC (Sin Diego, CA., Augut, 1978) Vol. 1, p. 457.
6) B. K. Bandlish, A. W. Garner, M. 1.Hodges and J. W. Timberlake, J. Am. Chem. SOC., 97,5855 (1975).
7) K. C. Bass, J. Organometal, Chern., 2,l(1965).
8) Method No. 43080-60, Analytical Department, Catalytic, Inc.,Wilsonville, Alabama.
9) 3. A. Kleinpeter, F. P. Burke, P. J. Dudt and D. C. Jones, "Process Development for Improved SRC Options," EPRl Interim Report, AF-1158, August, 1979, Palo Alto, Calif.
IO) C. H. Wright and D. E. Severson, Preprints Am. Cliem. Soc., Div. Fuel Chem-16(2), 68 (1972).
11) I<. S. Seshadri, R. G. Ruberto, D. M. Jewell and tl. P. Malone, Fuel, 57, 549 (1978).
12) B. T. Fant, "EDS Coal Liquefaction Process Developmcnt: Phasc IIIA," Annual Technical Report, 1 Jan -31 Dec 1976, ERDA No. FE-2353-9 (1977).
13) Am. Chem. SOC., Fuel Div., g(5), 98 (1977). C. 3. Collins, B.M. Benjamin, V.F. Raaen, P. H. hlaupin and V. H.Roark, Preprints,
14) Eng. Chem., Fundam., E, 195 (1979). C. Cronauer, D. M. Jewell, Y. T. Shah, R. J. Alodi and K. Seshadri, Ind.
15) hl. G.Thomas and R. K. Traeger, Preprints, Am. Chem. SOC., Fuel Div., 2(3), 223 (1979).
16) D. D. IVhitehurst, T. 0.Mitchell, bi. Farcasiu and J. J. Dickert, Jr., "The Nature and Origin of Asphaltenes in Processed Coals, Volume I," EPKI Final Report AF-1298, pg. 1-46 (1979).
17) G. Koclling, Rrennstoff-Cherr$ie, g,23 (1965).
18) D. Hausigk, G. Koelling and F. Ztegler, Brennsroff-Chrmie, 50, S, (19b9).
19) Petrakis and D. W. Grandy, Fuel, 2,227 (1980).
20) F. Silver and R. J. Hurtubisc, "Effect of Solvent Characteristics on Wyodak Coal Liquefaction," Final Technical Progress Report," Department of Energy Report FE-2367-9 (1979).
1) G. P. Curran, R. T. Struck and E. Gorin, Ind. Eng. Chem., Process Des. Dev. -6, 166 (1967).
2) W. H. Wiser, Fuel, E,475 (1968).
3) D. D. Vhitehurst, T. 0. Mitchell, M. Farcasiu and 3. J. Dickert, Jr., "The Nature and Origin of Asphaltenes in Processed Coals," EPRl Final Report AF-1298 (1979).
4) R. C. Neavel, Fuel, 55, 237 (1976).
5) I. Wender and 5. Friedman, Proc. 13th. IECEC (Sin Diego, CA., Augut, 1978) Vol. 1, p. 457.
6) B. K. Bandlish, A. W. Garner, M. 1.Hodges and J. W. Timberlake, J. Am. Chem. SOC., 97,5855 (1975).
7) K. C. Bass, J. Organometal, Chern., 2,l(1965).
8) Method No. 43080-60, Analytical Department, Catalytic, Inc.,Wilsonville, Alabama.
9) 3. A. Kleinpeter, F. P. Burke, P. J. Dudt and D. C. Jones, "Process Development for Improved SRC Options," EPRl Interim Report, AF-1158, August, 1979, Palo Alto, Calif.
IO) C. H. Wright and D. E. Severson, Preprints Am. Cliem. Soc., Div. Fuel Chem-16(2), 68 (1972).
11) I<. S. Seshadri, R. G. Ruberto, D. M. Jewell and tl. P. Malone, Fuel, 57, 549 (1978).
12) B. T. Fant, "EDS Coal Liquefaction Process Developmcnt: Phasc IIIA," Annual Technical Report, 1 Jan -31 Dec 1976, ERDA No. FE-2353-9 (1977).
13) Am. Chem. SOC., Fuel Div., g(5), 98 (1977). C. 3. Collins, B.M. Benjamin, V.F. Raaen, P. H. hlaupin and V. H.Roark, Preprints,
14) Eng. Chem., Fundam., E, 195 (1979). C. Cronauer, D. M. Jewell, Y. T. Shah, R. J. Alodi and K. Seshadri, Ind.
15) hl. G.Thomas and R. K. Traeger, Preprints, Am. Chem. SOC., Fuel Div., 2(3), 223 (1979).
16) D. D. IVhitehurst, T. 0.Mitchell, bi. Farcasiu and J. J. Dickert, Jr., "The Nature and Origin of Asphaltenes in Processed Coals, Volume I," EPKI Final Report AF-1298, pg. 1-46 (1979).
17) G. Koclling, Rrennstoff-Cherr$ie, g,23 (1965).
18) D. Hausigk, G. Koelling and F. Ztegler, Brennsroff-Chrmie, 50, S, (19b9).
19) Petrakis and D. W. Grandy, Fuel, 2,227 (1980).
20) F. Silver and R. J. Hurtubisc, "Effect of Solvent Characteristics on Wyodak Coal Liquefaction," Final Technical Progress Report," Department of Energy Report FE-2367-9 (1979).
21) G. Cohen, S. J. Groszos and D. Sparrow, J. Am. Chem. SOC., 72, 3947 (1950).
22) J. R. Shelton and C. K. Liang, Synthesis, 204 (1971)."
First of all, an early quote: "Hydrogen donor solvents are used in most processes for the direct liquefaction of coal".
Did you, did anyone in Coal Country, know that there was such a multiplicity of coal liquefaction technologies that a statement like "most processes for the direct liquefaction of coal" could even be used?
Second, in a similar vein, note how, in an offhand manner, it is revealed that there were a number of coal liquefaction operations underway around the United States, as in:"Comparison of the donor indices with other available quality criteria is made with two sets of solvents. The DCD series are recycle solvents derived from Blacksville coal under different processing conditions in the 1000 Ib/day liquefaction unit at PETC. The values of distillation residue from a lightly hydrogenated recycle oil made in the Wilsonville SRC pilot plant from Wyodak coal. F-14 is a lightly hydrogenated recycle oil made in the Tacoma SRC pilot plant from Kentucky coal. F-16 is a coal gasification tar from an in situ gasification project near Manna, Wyoming."
In the above exert, they note that WV - "Blacksville" - coal was liquefied in Pittsburgh. Another coal was liquefied in Alabama, in the "Wilsonville SRC" we have documented for you previously. And, coal was shipped all the way from Kentucky to be liquefied in the "Tacoma", Washington, "SRC pilot plant", another US Government coal conversion facility about which we have reported.
They also document "Tetrahydroquinoline's superior quality" as a coal liquefaction solvent. Also known as "Tetralin", that material is a key part of WVU's "West Virginia Process" for direct coal liquefaction.
Finally, make note of the sheer volume of coal liquefaction references they include.
The knowledge, the technology, is real. Why aren't we using it?