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Energy & Fuels 1992,6, 236-237
Communications Solvent Effect on Diphenylmethane Hydrocracking Table I. Effects of Aromatic and Hydroaromatic Additives on DPM Hydrocrackinep Sir: The hydrogen-donating abilities of various hydroconvn. % selectivitv. mol % aromatics for coal liq~efactionl-~ and model reactionk7 solvent additive [A]/[D] DPM additive PhH PhMe BCH have been extensively studied. According to the conventional view, the hydrogen donor solvent plays a promoDHNb DHA 1.0 0 11.0 DHN 0 59.1 98.0 97.2 2.4 tional role in coal liquefaction by stabilizing thermally DHN DHA 1.0 9.1 85.0 100 100 tr generated radicals, and the catalyst serves to promote DHN AnH 1.0 5.8 100 100 99.8 tr hydrogen transfer from gaseous hydrogen to coal via a DHN DHP 1.0 21.4 86.9 100 99.9 tr hydrogen donor solvent which serves as a hydrogen DHN PhenH 1.0 19.2 70.1 98.4 97.8 1.9 shuttler. However, some alternative i n t e r p r e t a t i o n ~ ~ s ~ ~DHN ~ ~ ~ THN 1.0 46.5 2.5 100 100 tr have been proposed, indicating that the main reaction DHN NPH 46.1 93.1 99.5 99.6 0.5 1.0 DHN THN 5.0 35.5 2.4 100 100 tr route in coal liquefaction is direct hydrogenation by moDHN NPH 19.3 61.7 100 100 tr 5.0 lecular hydrogen rather than by a hydrogen donor solvent, DHN MTs 1.0 33.4 10.8 98.6 98.5 1.4 especially in the presence of an active catalyst and presDHN 1-MN 1.0 11.9 56.2 99.4 94.5 2.9 surized hydrogen. DHN 1-MN 10.0 4.1 39.2 100 99.7 tr With respect to the above propositions, we investigated 1-MN 1-MN 0.8 17.1 100 29.0 96.6 tr the effects of aliphatic, aromatic, and hydroaromatic THN THN 29.5 18.6 3.8 100 97.6 tr solvents on diphenylmethane (DPM) hydrocracking. "DPM 7.5 mmol, FeS, 0.5 g, S 0.05 g, DHN + additive 30 mL, Methyltetralins (MTs, a mixture of 1-methyltetralin and initial H2 pressure 10 MPa, 400 OC, 1 h. *In the absence of FeS, 5-methyltetralin) were prepared by hydrogenating 1and sulfur. [A]/[D]: initial molar ratio of additive to DPM. PhH methylnaphthalene (1-MN) in the presence of stabilized = benzene, PhMe = toluene, BCH = benzylcyclohexane. tr = trace. MTs composition: 17.1% 1-methyltetralin, 82.9% 5nickel at 150 OC. The other reagents such as DPM, decalin methyltetralin. (DHN), tetralin (THN), naphthalene (NpH), 1-MN, 9,lO-dihydroanthracene (DHA), anthracene (AnH), 9,lOhydrocracking in DHN proceeded most readily. The addihydrophenanthrene (DHP), and phenanthrene (PhenH) dition of aromatic and hydroaromatic solvents reduced were purchased commercially and further purified by DPM conversion. It is noteworthy that the inhibiting conventional methods. Synthetic pyrite FeS2was offered effects of the hydroaromatic additives on DPM hydroby Japan Asahi chemical Industry Co. Ltd. cracking increased in the order THN < DHP < DHA, A mixture of 7.5 mmol of DPM, 4.2 mmol of FeS2, and which is consistent with the reaction order for hydrogen 30 mL of solvent(s) was put into a 90-mL stainless steel, abstraction of the hydrogen donors;12i.e., a hydrogen donor magnetically stirred autoclave. To keep the activity of with stronger "hydrogen-donating ability" gives more inFeS2,1.6 mmol of sulfur was added to the reaction system. hibiting effect on FeS2-catalyzedhydrocracking of DPM. After being pressurized by hydrogen to 10 MPa at room This finding is discrepant with the conventional view that temperature (20 "C), the autoclave was heated to 400 "C hydrogen donor solvent promotes coal liquefaction by in 18 min and kept at the temperature for 1h. Then the shuttling hydrogen. autoclave was immediately cooled to room temperature in Ouchi et al.5 and Ogata et investigated hydrogen an ice-water bath. The reaction products were identified transfer in the hydrogenation of the model compounds in by GC-MS if necessary and quantified by GC. several solvents. They have pointed out that the negative Table I demonstrates the effects of several solvents on effects of aromatic solvents including tetralin on the catDPM hydrocracking with FeS2 at 400 "C. In the absence alytic hydrogenation of the model compounds should be of FeS2 and sulfur, DPM was not converted at all. DPM due to the adsorption of the solvents on the catalyst surhydrogenolysis has been reported not to proceed even at face. But the suggestion cannot explain the fact that DHA 430 OC.ll The low reactivity of DPM toward thermal inhibited DPM hydrocracking more severely than NpH reaction can be ascribed to the strong C,-Cdk bond and and 1-MN, because 2-fused-ring aromatic hydrocarbons difficulty in hydrogenating the benzene ring. adsorb on catalyst surface more strongly than single-ring DPM hydrocracking was promoted by FeS2 The main aromatic hydrocarbons. products were observed to be benzene and toluene. The H-atom addition to the ipso position of DPM should be selectivity of benzylcyclohexane was less than 3 % . DPM a crucial step in DPM hydrocracking. FeSz has been reported to facilitate the formation of free-radical interme(1) Neavel, R. C. Fuel 1976, 55, 237. diates such as H and HS*.14J5 In the absence of FeSz and (2) Kamiya, Y.; Nagae, S. Fuel 1985, 64, 1242. sulfur, ca. 10% of DHA was converted to AnH, but DHA (3) Mochida, I.; Takayama, A.; Sakata, R.; Sakanishi, K. Fuel 1990, 4, 81. dehydrogenation did not induce DPM decomposition. (4)Ohe, S.;Ito, H.; Makabe, M.; Ouchi, K. Fuel 1985, 64, 902. McMillen et al.lSstudied DPM decomposition at 400 OC (5) Ouchi, K.; Makabe, M. Fuel 1988,67, 1536. "
(6) Obara, T.; Yokono, T.; Sanada, Y. Fuel 1983,62, 813. (7) Meyer, D.; Oviawe, P.; Nicole, D.; Laner, J. C.; Clement, J. Fuel
1990,69,1309-1321. (8) Vernon, L. W. Fuel 1980,59, 102. (9) Marshall, M.; Jackson, W. R.; Larkins, F. P.; Hatawell, M. R.; Rash, D. Fuel 1982, 61, 121. (10) Skowronski,R. P.; Ratto, J. J.; Goldberg, I. B.; Heredy, L. A. Fuel 1984, 63, 440. (11)Futamura, S.; Koyanagi, S.; Kamiya, Y. Fuel 1988, 67, 1436.
0887-0624I92 12506-0236$03.00IO
I
(12) Poutsma, M. L. Energy Fuels 1990,4, 123. (13) Ogata, E.; Tamura, T.; Kamiya, Y. Proc. Int. Conf. Coal Sci., Maastricht 1987, 243. (14) Thomas, M. G.; Padrick, T. D.; Stohl, F. V. Fuel 1982,61, 761. (15) Srinivasan, G.; Seehra, M. S. Fuel 1982, 61, 1249. (16) McMillen, D. F.; Malhotra, R.; Chang, S.-J.; Ogier, W. C.; Nigenda, S. E.; Fleming, R. H. Fuel 1987, 66, 1611. 0 1992 American Chemical
Societv
Book Reviews
Energy & Fuels, Vol. 6, No.2, 1992 237
kinetically. Their results show that DPM conversion in THN is less than 0.1% even in 20 h reaction. According to the first-order rate constants for DPM decomposition in DHA and DHP at 400 “C published by McMillen et al.,16DPM conversions in DHA and DHP in 1h reaction are less than 0.15%. These results indicate that in the case of noncatalytic reaction H donors such as THN, DHP, and DHA play little role in DPM decomposition. In the presence of FeS2, the hydrogen donor will tend to act as a scavenger of H’. For example, DHA may scavenge H’ according to the following reactions:
.
cco
m+,*=-o0
H2 +
QcQ =-QcQ +
The above reactions decrease free H-atom concentration, hence inhibiting DPM hydrocracking. When a small amount of a additive was used ([additive]/[DPM] = l ) , there was virtually no difference in DPM conversion between THN and NpH, and little difference between DHP and PhenH and between DHA and AnH, because NpH, PhenH, and DHA were rapidly hydrogenated to THN, DHP, and DHA, respectively. 1-MN showed markedly more inhibiting effect on DPM hydrocracking than MTs even in the case of [additive]/[DPM] = 1,while 43.2% of 1-MN remained unhydrogenated (1MN conversion = 56.8%). No appreciable THN or NpH was observed, indicating that the hydrodemethylation of 1-MN was difficult under the reaction condition. Similarly, in the products from the reactions when THN was used no n-butylbenzene was detected, suggesting that the -, bond in THN did not proceed. These cleavage of C
facts indicate that H-atom addition to the ipso position in an aromatic ring does not necessarily result in Cw-C& bond scission. The resonance abilities of the resulting alkyl or arylalkyl radicals are also important in C,-Cdk bond scission. In the case of [additive]/ [DPM] = 5, significant difference in DPM conversion between THN and NpH was observed. These results suggest that aromatic hydrocarbons such as NpH and 1-MN inhibited DPM hydrocracking more remarkably than the corresponding hydroaromatic hydrocarbons. The more inhibiting effects of aromatic hydrocarbons could be due to the stronger adsorption abilities of the aromatic hydrocarbons on catalyst surface in addition to their more scavenging effects on free H atoms during their hydrogenation. The above results suggest that aromatic and hydroaromatic hydrocarbons may be undesirable in FeS2-catalyzed reactions. Although decalin has proven to be an effective solvent for DPM hydrocracking, it may not be suitable for coal liquefaction because of its poor ability to dissolve coal. Thus, it should be essential for coal liquefaction to develop such solvents which can dissolve coal easily but are less reactive. Registry No. DPM, 101-81-5; 1-MN, 90-12-0; DHN, 91-17-8; THN, 119-64-2; NpH, 91-20-3; DHA, 613-31-0; AnH, 120-12-7; DHP, 776-35-2;PhenH, 85-01-8; FeSz, 12068-85-8; C6&, 71-43-2; CBHSCH,, 108-88-3. Xian-yong Wei,* Zhi-min Zong Department of Reaction Chemistry Faculty of Engineering The University of Tokyo
7-3-1, Hongo, Bunkyo-ku, Tokyo 113, Japan Received September 11, 1991 Revised Manuscript Received January 2, 1992
Book Reviews Coal Science 11. Edited by Harold H. Schobert, Keith D. Bartle, and Leo J. Lynch. ACS Symposium Series 461. American Chemical Society: Washington, DC, 1991. $77.95. 337 pp.
This volume is a collection of papers in honor of Peter H. Given, who, in the quarter of a century that ended in 1986, was the worlds foremost researcher in the intricacies of coal science. Given was a cosponsor and a dominant figure of the American Conference on Coal Science, held at Penn State in 1964; the collected papers were subsequently published with the title “Coal Science” as part of the Advances in Chemistry Series in 1966. It was entirely fitting that the American Chemical Society Division of Fuel Chemistry chose to hold a symposium entitled “Advances in Coal Science”, A Symposium in Remembrance of Peter Given” in 1989. Appropriately, the volume is called Coal Science 11. The editors of this volume are to be congratulated for organizing this symposium and for ensuring a collection of papers that effectively mirror the broad interests of Peter Given: the geochemical origin of coal, the chemical constitution and physical properties of coal, the scientific basis of the conversion of coal to liquid fuels, and the fundamental basis of the reactions of coal. Many of Given’s papers are classics and will endure, to one day find their results incorporated into future processes, perhaps for coal liquefaction. The symposium starts, appropriately, with papers on the geochemistry of coal and the nature and properties of the mineral
matter in coal. A number of papers then discuss coal constitution, including data on sulfur forms in coal and heavy oils. Given’s work on basic precepts, predictability, and spectroscopicanalysis of coal and coal products contributed heavily to a series of excellent papers relating to coal liquefaction; this volume carries out his leads. Modern instrumental techniques are well covered in this volume. Writing this is a labor of love for this reviewer. It is fulfilling to see such an appropriate series of papers, most of which are obviously invited contributions, collected with care. The book is rightly a remembrance for a truly outstanding scientist. I recommend this volume to those who are interested in coal science and to those who work in related areas. Irving Wender, University of Pittsburgh
Annual Review of Energy and the Environment, Vol. 16. Edited by J. M. Hollander, R. H. Socolow, and D. Sternlight. Annual Reviews Inc., 1991. 586 pp, +ix. $64.00. The latest in the renamed series Annual Reuiew of Energy, this book contains 18 articles on energy technology and environmental issues. Topics include analyses of various national energy policies and uses, global energy policy issues, energy technologies, impacts of energy use, and analyses of strategies for mitigation of COz effects on climate. The articles are written for the well-educated nonspecialist and are generally clear and
