Energy & Fuels 1989,3, 342-345
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Nickel-Catalyzed Hydroliquefaction of Morwell Brown Coal at Low Temperatures Using Phenolic Compounds as Solvents Yasuhiro Takemura* and Yoshihito Saito College of Education, Akita University, Akita 010, Japan
Kiyofumi Okada Coal Mining Research Center, Minami-Sakae, Kasukabe 344, Japan
Yutaka Koinuma National Research Intsitute for Pollution and Resources, Tsukuba, Ibaragi 305, Japan Received December 12,1988. Revised Manuscript Received February 7, 1989 To attain a more effective coal liquefaction process, low-temperature (230-270 "C) coal hydroliquefaction was performed by using 15 kinds of single- or double-ring phenolic compounds as solvents and nickel acetate as a catalyst precursor. The role of the phenolic compound in the liquefaction reaction is discussed. With selected compounds, such as 1,7-dihydroxynaphthaleneand resorcinol, Morwell brown coal was catalytically liquefied in a batch autoclave under H2 pressure (10 MPa, cold) to give the conversions of the coal (to benzene/ethanol mixture solubles), which are higher than 70 w t %, at 270 "C for 1h. Among three dihydroxybenzenes, resorcinol showed the highest efficiency for the Ni-catalyzed hydroliquefaction of the coal, though the capability of resorcinol to dissolve coal is the lowest in the absence of Hz. Capabilities of o-phenylphenol and its related compounds to dissolve the coal at 250 "C under Ar pressure (10 MPa, cold) and to hydroliquefy the coal at 270 "C under H2 pressure (10 MPa, cold) were quantified. The respective orders of the conversion of the coal with these compounds are as follows: o-phenylphenol N o-cyclohexylphenol > biphenyl N cyclohexylbenzene. At this temperature, the solvent effect of phenolic functionality is larger than that of the hydroaromatic one. The same result is found with 1-naphthol and 5,6,7,8-tetrahydro-l-naphthol.
Introduction I t has long been recognized that phenolic components of coal liquefaction solvents are effective for conversion of coal.' Orchin and Storch2 reported that compounds having phenolic and hydroaromatic functionalities, such as o-cyclohexylphenol, are the most benefitial for liquefaction of coal. Kamiya et finding the same effect with phenol and cresol, observed that the magnitude of the enhancement depends upon the coal used. The reported effect has been considered to be primarily ascribed to hydrogen-bond formation between the phenolic OH of the solvent and ether linkages in the coal molecules, which enhances the cleavage of the ether bonds.3 Though much knowledge on the solvent effect of phenolic compounds has been accumulated,7-13 the detailed mechanism of the effect is still unknown.14 Though usually coal hydroliquefaction has been conducted at temperatures higher than 400 "C, the above studies have suggested that use of phenolic solvent could (1) Bockrath, B. C. Coal Science; Gorbaty, M. L., Larsen, J. W., Wender, I., Eds.; Academic: New York, 1983; Vol. 2, pp 99-104. (2) Orchin, M.; Storch, H. H. Znd. Eng. Chem. 1948, 40, 1385. (3) Kamiya, Y.; Sato, H.; Yao, T. Fuel 1978, 57, 681. (4) Yao, T.; Kamiya, Y. Bull. Chem. Soc. Jpn. 1979,52, 492. (5) Yao, T.; Kamiya, Y. Nippon Kagaku Kaishi 1980, 893. (6) Kamiya, Y.; Yao, T.; Nagae, S. Bull. Chem. SOC.Jpn. 1982, 55, 3873.
(7) Hurtubise, R. J.; Allen, T. W.; Schabron, J. F.; Silver, H. F. Fuel 1981. 60. 385.
(8) L&en, J. W.; Sams, T. L.; Rodgers, B. R. Fuel 1981, 60, 335. (9) King, H.-H.; Stock, L. M. Fuel 1982, 61,1172. (10) Yoshii, T.;Yaginuma, R.; Ymhikawa, H.; Utoh, S.Fuel 1982,61, 865. ... (11) Hessley, R. K. Fuel Process. Technol. 1983,8, 33. (12) McNeil, R. I.; Cronauer, D. C. Fuel Process. Technol. 1984,9,43. (13) Volker, E. J.; Bockrath, B. C. Fuel 1984, 63, 285. (14) Sharma, R. K.; Raman, K. P.; Miller, B. Fuel 1986,65, 738. ~
make effective coal hydroliquefaction possible even at temperatures far lower than 400 "C. We reported in a previous paper15 that Australian young coals, including Morwell brown coal, tend to be easily hydroliquefied at 310-325 "C in a reaction system of tetralin/H,/Ni catalyst. These studies prompted us to perform the Ni-catalyzed hydroliquefaction of coal at temperatures lower than 300 "C using phenolic compounds as solvents. The present paper reports experimental results on the Ni-catalyzed hydroliquefaction of Morwell coal at 230-270 OC by using the various single- or double-ring phenolic compounds as solvents. Under these mild conditions, each phenolic compound manifests its inherent solvent effect. The results obtained provide information on the mechanism of the solvent effect of phenolic compounds upon liquefaction of coal. Though there have been several studies of the hydroliquefaction of coal at 90 mol %. Hydroquinone is comparatively unstable under the reaction condition concerned. Naphthols and Dihydroxynaphthalenes. Table I11 shows that 1-naphthol is superior to 2-naphthol as a solvent. Comparing the K, values of the two naphthols suggests that hydrogen bonding between phenolic OH and ether linkages in the coal molecules is a trigger for the
Energy & Fuels 1989,3,345-350 liquefaction of the coal. Recoveries of both of the naphthols after the runs were lower than 95 mol %. During the run,a part of each naphthol may combine with the coal liquid to form an adduct.I2 Among three dihydroxynaphthalenes, 1,7- and 1,5-dihydroxynaphthalenes show high conversions of the coal. A run with 1,7-dihydroxynaphthaleneplus the Ni catalyst gives 77 wt % conversion of the coal a t 270 "C,for 1 h. 2,3-Dihydroxynaphthalenecauses low conversion of the coal, indicating that the double-ring phenolic compound, which forms an intramolecular hydrogen bond, is not favorable for liquefaction of the coal. Recovery of 1,7-dihydroxynaphthalene was about 85 mol %. Comparison of the Solvent Effects of the Phenolic Functionality with Those of the Hydroaromatic Functionality. In Table IV are listed percent solvation and percent hydrogenation of coal with o-phenylphenol and its related compounds. The respective orders of the percent solvation and the percent hydrogenation with these compounds are as follows: o-phenylphenol = o-cyclohexylphenol > biphenyl N cyclohexylbenzene. This shows that the solvent effect of the phenolic functionality is larger than that of the hydroaromatic functionality, contradicting the results of Orchin and Storch2 on the dissolution of Bruceton coal at 400 "C in the absence or presence of H2. They stated that the dissolution power of o-cyclohexylphenol is, in the absence of H2, 4 times larger than that of o-phenylphenol. The inconsistency stems from the large difference in the solvation temperature between the two research groups; at 400 "C, the rate of thermolysis of Bruceton coal should be large regardless of the kind of solvent used, and the coal fragments derived abstracted hydrogen from the hydroaromatic ring of o-cyclohexylphenol to give a high percent solvation of coal. Hydrogen
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donation of the hydroaromatic ring clearly caused the conversion of Bruceton coal at 400 "C in the absence of H2. Therefore, the contribution of the hydroaromatic structure of o-cyclohexylphenol to the liquefaction of Bruceton coal should be much larger than that of the phenolic functionality of o-phenylphenol. However, the rate of thermolysis of Morwell coal is small with the solvation temperature of 250 "C employed in this study. In Table IV are listed the reaction results with 5,6,7,8tetrahydro-l-naphthol. The comparison between the results with l-naphthol (in Table 111) and those with 5,6,7,8-tetrahydro-l-naphthol shows that the phenolic functionality contributes to hydroliquefaction of coal much more than the hydroaromatic functionality does.
Summary Ni catalyst/phenolic solvent/H2 is considered to be a novel reaction system for the hydroliquefaction of brown coal at low temperatures. By use of selected phenolic compounds as solvents, Morwell brown coal is catalytically hydroliquefied to give conversions of coal higher than 50 and 70 wt % even at 250 and 270 "C, respectively. Under these low temperatures, each phenolic compound manifests its inherent solvent effect; the solvent effect of the phenolic functionality is larger than that of the hydroaromatic functionality. Registry No. 1,7-DHN,575382; 1,5DHN,83-56-7;2,3-DHN, 92-44-4; tetralin, 119-64-2;phenol, 108-95-2; o-cresol, 95-48-7; m-cresol, 10839-4;p-cresol, 106-44-5; catechol, 120-80-9; resorcinol, 10846-3;hydroquinone, 123-31-9;l-naphthol,90-15-3;2-naphth01, 135-19-3; biphenyl, 92-52-4; cyclohexylbenzene, 827-52-1; ophenylphenol, 90-43-7;o-cyclohexylphenol,119-42-6; 5,6,7,&THl-naphthol, 529-35-1; nickel, 7440-02-0.
Coal Liquefaction by Binary Solvent Systems Composed of Tetralin and Reducible Compounds Hideyuki Tagaya,* Koji Takahashi, Komei Hashimoto, and Koji Chiba* Faculty of Engineering, Yamagata University, 4-3-16 Jonan, Yonezawa, Yamagata 992, Japan Received July 25, 1988. Revised Manuscript Received February 21, 1989 To obtain information on solvent-solvent interactions during coal conversion, three types of coals were liquefied with mixtures of tetralin and compounds having reducible structures. When indene was mixed with tetralin, the hydrogen-shuttling ability of indene or indene oligomers directly contributed to a small increase in coal conversion. Benzophenone and dibenzyl ether abstracted hydrogen from tetralin. However, the detrimental effects of mixing were only observed with the tetralinbenzophenone mixture. This indicated the presence of hydrogen abstraction by benzophenone from coal and caused regressive reactions of coal. Hydrogen abstraction from tetralii and addition reactions of l-olefin to coal may reduce coal conversion.
Introduction In coal liquefaction, the solvent plays a vital role as a hydrogen donor and as a reaction medium to dissolve reactants and The selection of the solvent
is an important factor for effective coal liquefaction, especially for solvent extract liquefaction without a catalysLM We have undertaken coal liquefaction using binary solvent systems. In the liquefaction of Yallourn coal using binary solvents composed of tetralin and polynuclear
(1) Whitahurst, D.D.;Mitchell, T. 0.; Farcasiu, M. Coal Liquefaction; Academic: New York, 1980; pp 274-342. (2) Shah, Y.T.; Krishnamurthy, S.; Ruberto, R. G. In Reaction Engineering in Direct Coal Liquefaction;Shah,Y. T., Ed.;Addison-Wesley: London, 1981; pp 162-209. (3) Bockrath, B. C. In Coal Science;Gorbaty, M. L., Larsen, J. W., Wender, I., Eds.; Academic: New York, 1983; Vol 2, pp 66-109.
(4) Chiba, K.; Tagaya, H.; Kobayashi, T.; Shibuya, Y. I d . Eng. Chem. Res. 1987,26, 1329-1335. (5) Chiba, K.; Tagava, - - H.; Sato, S.: Watanabe, T. J. Fuel SOC.J p n . 1984,63, 195-202. (6) Tagaya, H.;Ando, H.; Suzuki, T.; Murakata, T.; Sato, S.; Chiba, K. Bull. Yamagata Uniu.,Eng. 1988,20, 51-61.
0887-0624/89/2503-0345$01.50/0
0 1989 American Chemical Society
