Energy & Fuels 1989,3, 59-64 the liquefaction reaction begins. In conclusion, this study shows that the THQ-methanol and THQ-ethanol systems make Tallourn and Taiheiyo coal swell significantly whereupon a considerable amount of THQ is incorporated into the coals. By liquefaction of
59
the coals thus swelled, a higher liquefaction yield is obtained under mild conditions. Registry No. 1,2,3,4-Tetrahydroquinoline, 635-46-1; methanol, 67-56-1;benzene, 71-43-2;tetralin, 119-64-2;ethanol, 64-17-5; methylcyclohexane, 108-87-2.
Promotion of Coal Liquefaction by Iodomethane. 2. Reaction of Coal Model Compounds with Iodomethane at Coal Liquefaction Temperatures Moetaz I. Attalla,* Michael A. Wilson, Robinson A. Quezada, and Anthony M. Vassallo CSIRO Division of Coal Technology, P.O. Box 136, North Ryde, N S W 2113, Australia Received M a y 5, 1988. Revised Manuscript Received September 29, 1988 The reactions of iodomethane with a number of simple organic substances representative of structural groups in coal have been studied in an attempt to explain the success of iodomethane in promoting coal liquefaction. Iodomethane promotes dehydrogenation of hydroaromatic rings under nitrogen, hydrogenation of aromatic rings, hydrogenolysis of phenols and phenol ethers, and the conversion of pyridine heterocycles to naphthalene and its derivatives under hydrogen. In the presence of molecular hydrogen, hydrogen iodide is as effective as iodomethane. This suggests that iodine is the important reactive moiety and probably functions in hydrogenation and hydrogenolysis by catalyzing the formation of hydrogen radicals from hydrogen gas.
Introduction When coal is reacted with molecular hydrogen under mild liquefaction conditions (6.9 MPa cold charge and 400 OC) in the presence of tetralin and conventional coal liquefaction catalysts, a brittle solid called solvent-refined coal is formed.' However, when coal is reacted with molecular hydrogen at the same pressure and temperature but in the presence of iodomethane, high yields of volatile liquid products are obtained? The reasons for the success of iodomethane in coal liquefaction have not yet been established. Consequently we have examined the reactions of suitable model compounds (representing some of the functional and structural groups in coal) with iodomethane and molecular hydrogen. The compounds studied include pyridine, a series of bicyclic aromatics, hydroaromatics, ethers, and benzylic compounds known to be pyrolysis or hydrogenation product^.^*^ In order to elucidate the mechanism of the reaction, some reactions were also carried out in the presence of hydrogen iodide. I3C-labeled iodomethane was used to investigate the mechanism by which nitrogen is removed from pyridine. Reactions were also carried out in the presence of an inert gas, namely nitrogen, since these conditions may occur in parts of the coal not reached by molecular hydrogen. Experimental Section Iodomethane (reagent grade) was used directly as received from Fluka. The other compounds were all of reagent grade and were obtained from various commercial sources. All were found by gas chromatography to be of suitable purity (>97%) and thus were used without further purification. (1) Jones, D. G.; Rottendorf,H.; Wilson, M. A.; Collii, P. J. Fuel 1980. 59, 19-26. (2) Vassallo, A. M.; Wilson, M. A.; Attalla, M. Energy Fuels 1988,2, 539-547. (3) Collin, P. J.; Gilbert, T. D.; Philp, R. P.; Wilson, M. A. Fuel 1983, 62,450-458.
In a typical reaction procedure, iodomethane and model compound were placed in a glass-lined 1-Lrocking Parr autoclave. The autoclave was pressurized with hydrogen or nitrogen to 6.9 MPa and then heated to 400 "C a t a rate of 4 "C/min. After 1 h a t reaction temperature, the autoclave was allowed to cool to room temperature (5 "C/min) and vented. The reaction products were analyzed on a Packard 437A gas chromatograph fitted with a SGE 12 m X 0.2 mm vitreous microcapillary column packed with methylsilicone (BP 1). The oven temperature was programmed from 20 to 250 "C at 10 "C/min. Specific identification of products was made by coinjection of standards or by a Finnigan 4023 gas chromatograph-mass spectrometer (GC/MS) by comparison with library spectra. An SE-30capillary column (50 m X 0.2mm) was used on the GC/MS. The temperature controller was programmed from 15 to 100 "C at 10 "C/min and then from 100 to 290 "C at 4 "C/min. An electron-impact ionizing voltage of 70 eV was used with a filament emission current of 0.25 mA and an ion source temperature of 200 "C. Data were processed with an INCOS 2300 data processing system. 13C NMR spectra were obtained on a JEOL FX9OQ NMR spectrometer using chromium acetylacetonate as relaxation reagent, a 45" pulse, inverse gated decoupling, and 4 s pulse delays. Details of the NMR analytical method can be found e l s e ~ h e r e . ~The ~ GASPE technique5 was also used to aid assignment. In some experiments aqueous hydrogen iodide was substituted for iodomethane. Details of reaction conditions and products are shown in Table I.
Results and Discussion Reactions. Table I shows that iodomethane accelerates the decomposition of tetralin to naphthalene in both hydrogen (experiments 1and 2) and nitrogen (experiments 3 and 4) atmospheres. Thus under coal liquefaction conditions hydroaromatic rings might be expected to be converted to aromatic rings by iodomethane. It is clear that (4) Wilson, M. A.; Pugmire, R. J.;Vassallo,A. M.; Grant, D. M.; Collin, P. J.; Zilm, K. W. Ind. Eng. Chem. Prod. Res. Deu. 1982,21, 477-483. (5) Cookson,D. J.; Smith, B. E. Org. Magn. Reson. 1981,16, 111-116. (6) Wilson, M. A.; Vassallo, A. M.; Collin, P. J.; Bath, B. D. Fuel
Process. Technol. 1984, 8, 213-229.
0887-0624/89/2503-0059$01.50/00 1989 American Chemical Society
60 Energy & Fuels, Vol. 3, No. 1, 1989
Attalla et al.
Table I. Reaction of Coal Model Compounds with Iodomethane under Hydrogen or Nitrogen at 6.9 MPa for 1 h a t 400 OC w t of fa expt Me1 comproduct product no. compd wt, g used, g gas pound (expt) (calc) components of liquid products' 0.62 0.68 tetralin (64%), naphthalene (20%), 10.0 10.5 0.60 1 tetralin methyltetralins i2%), methylnaphthalenes (2%), tetralin decomposition products (ll%)b 0.60 0.67 0.62 tetralin (95%), naphthalene (5%) 10.0 2 tetralin 0.60 0.83 tetralin (38%), naphthalene (60%), tetralin h 10.0 10.5 3 tetralin decomposition products (1%Ib 0.60 0.68 0.68 tetralin (80%), naphthalene (20%) 10.0 4 tetralin 1.0 1.0 1.0 naphthalene (100%) 10.0 5 naphthalene 1.00 0.27 h tetralin (34%), naphthalene (5%), 30.0 10.0 6 naphthalene methylnaphthalene (2%), unknowns (21%), tetralin decomposition products (37%) 1.0 naphthalene (100%) 10.0 1.0 1.0 7 naphthalene polymeric material h h 30.0 1.0 10.0 8 naphthalene h 1.0 h black polymeric material 1-naphthol 10.0 10.0 9 1.0 1.0 1.0 1-naphthol polymeric material 10.0 10 1-naphthol 1.0 0.59 0.65 tetralin (72%), naphthalene (a%), methylated 11 1-naphthol 10.0 10.0 tetralins (lo%), methylnaphthalenes (10%) 1.0 0.77 0.78 tetralin (36%), naphthalene (24%), 12 1-naphthol 10.0 methyltetralins and naphthalenes (trace), tetralin decomposition product (5%): 1-naphthol (15%), polymeric coupling products (15%) * 1.0 0.39 0.37 tetralin (44%), naphthalene (2%), 10.0 10.0 13 2-naphthol methyltetralins (lo%), methylnaphthalenes (9%),tetralin decomposition products (14%)* 1.0 h 0.53 tetralin (40%), 2-naphthol (13%), tetralin 14 2-naphthol 10.0 decomposition products (3%), polymeric coupling products (15%) h h black polymeric material 10.0 10.0 1.0 15 2-naphthol 1.0 1.0 1.0 2-naphthol plus minor decomposition products 10.0 16 2-naphthol 0.51 10.0 0.48 0.91 10.0 monomethylated tetralins (39%), 17 1-methylnaphthalene 2-methylnaphthalene (17%), 1-methylnaphthalene (4%), dimethyltetralin (a%), dimethylnaphthalene (5%) + others 0.88 10.0 0.91 0.89 1-methylnaphthalene (83%1, 18 1-methylnaphthalene 2-methylnaphthalene (12%), 1-methyltetralin (3%), naphthalene (2%) 0.88 h 2-methylnaphthalene (86%), methyltetralins 10.0 0.91 19 2-methylnaphthalene (11% ), 1-methylnaphthalene (2 % ), tetralin (trace), naphthalene (trace) h 10.0 10.0 0.91 0.48 toluene (3%), xylenes (2%), 2-methyltetralin 20 2-methylnaphthalene (15%), tetralin (lo%), 6-methyltetralin (24% ), 2-methylnaphthalene (17% ), 2,6-dimethyltetralin (4%) 0.91 0.87 h black polymeric material 21 1-methylnaphthalene 10.0 10.0 0.91 0.90 1-methylnaphthalene (100%); some black 0.90 22 1-methylnaphthalene 10.0 polymeric material 0.83 0.53 1,5-dimethyltetralin (22%), 0.37 4.6 23 2,6-dimethylnaphthalene 5 2,6-dimethylnaphthalene (lo%), 6-methyltetralin (10%1, 2-methylnaphthalene (a%), tetralin (4%), 1-methylnaphthalene (3%), and others h 20 d 0.83 0.48 complex mixture of methylnaphthalenes, 24 N-methylpyridinium benzene, methylbenzenes, naphthalene, iodide alkanes, alkylpyridines, methyltetralins, and ethylnaphthalene 0.1d h 20 d 0.33 complex mixture of methylnaphthalenes, 25 N-methylpyridinium iodidee benzene, methylbenzene, naphthalene, alkanes, alkylpyridines, methyltetralins, ethylnaphthalenes 1.0 pyridine (97%), other products (3%) 20 1.0 1.0 26 pyridine h 15.2 1.0 0.5 complex mixture of benzene, alkylbenzene, 27 aniline 10 naphthalene, and alkylnaphthalene, with predominant products being m- and p-xylene 1.0 1.0 1.0 aniline (100%) 28 aniline 10 12.7 1.0 h complex mixture of methylnaphthalenes, 0.39 29 pyridine g benzene, methylbenzene, naphthalene, alkanes, alkylpyridines, methyltetralins, and ethylnaphthalene cis-decalin (47%), trans-decalin (51%), trace 30 cis-decalin (50%), 12.6 0.0 0.0 0.0 others trans-decalin (50%) trans-decalin (51%), cis-decalin (43%), tetralin 0.0 0.04 0.03 31 cis-decalin (50%), 12.6 trans-decalin (50%) (6%),naphthalene (
