1755
Ind. Eng. Chem. Res. 1991,30, 1755-1759
Tritium as a Tracer in Coal Liquefaction. 1. Hydrogen Mobility of Tetralin under Coal Liquefaction Conditions Toshiaki Kabe,* Atsushi Ishihara, and Yasushi Daita Department of Chemical Engineering, Tokyo University of Agriculture and Technology, Koganei, Nakamachi, Tokyo 184, J a p a n
The reaction of tetralin with tritiated molecular hydrogen was carried out at 350-440 "C, 20-60 kg/cm2 for 0-8 h to estimate the hydrogen mobility of tetralin itself. Under these conditions, tetralin was converted to 1-methylindan, naphthalene, and n-butylbenzene, and 1-methylindan was a main product. With a rise in temperature and a passage of time, the amount of tritium transferred from the gas phase into tetralin increased and the hydrogen-exchange ratio of tetralin a t 440 "C, 120 min and 400 "C, 480 min reached 14.3% and 13.5%, respectively. The hydrogen-exchange ratio and the amount of methylindan increased with a hydrogen/tetralin molar ratio. The addition of coal enhanced the hydrogen exchange between gas phase and tetralin. In the absence and presence of coal, tritium was observed in the isolated naphthalene. It is suggested that hydrogen in tetralin changing to naphthalene may be able to exchange with molecular hydrogen.
Introduction Tetralin has been known to be an effective hydrogendonor solvent in coal hydrogenation processes. In such processes, it is important to study the thermal behavior of tetralin. Recently, much attention has been focused on the mechanism of thermolysis of tetralin in the absence and presence of coal (Cronauer et al., 1978,1979; Hooper et al., 1979; Benjamin et al., 1979; Franz and Camaioni, 1980a,b; Penninger, 1982; McPherson et al., 1985; Vlieger et al., 1984; Poutsma et al., 1982; Yen et al., 1976 and references cited therein). For example, Hooper et al. reported that tetralin did not disproportionate to naphthalene and decalin between 300 and 450 OC (Hooper et al., 1979). Benjamin et al. showed that the formation of 1methylindan might be due to the cleavage of the 1-8a bond of tetralin (Benjamin et al., 1979). Franz and Camaioni reported that the isomerization of tetralin to l-methylindan proceeds through 2-tetralyl radical derived from the corresponding perester (Franz and Camaioni, 1980a,b). Penninger reported that the formation of methylindan from tetralin involves a bimolecular step in the reaction with gaseous hydrogen (Penninger, 1982). McPherson also inferred that the mechanism of tetralin isomerization must include a multimolecular step (McPherson et al., 1985). On the other hand, the reactivities of hydrogen in coal and tetralin have been investigated by use of deuterated tetralin through the reaction with coal (Franz, 1979; Franz et al., 1981; King and Stock, 1982; Skowronski et al., 1984; Collin and Wilson, 1983; Wilson et al., 1982,1984;Cronauer et al., 1982; Schweighardt et al., 1976; Brower, 1982 and references cited therein). Cronauer et al. showed that significant hydrogen/deuterium exchange occurred between coal and deuterated tetralin (Cronauer et al., 1982). Showronski et al. clarified the role of gaseous hydrogen and donor solvent in coal liquefaction using gaseous deuterium and deuterated tetralin (Skowronski et al., 1984). However, because of the low solubility of coal to solvents and the lack of quantitative data from 2H NMR, it was difficult in these studies to enable the quantitative analysis of hydrogen transfer among the gas phase, solvent, and coal. We have already reported that tritium and 14Ctracer methods were effective in tracing the reaction pathways of hydrogenations among gas phase, solvent, and coal (Kabe et al., l986,1987a,b, 1989). Further, we showed that the hydrogen-exchange reaction between coal and hydrogen molecules remarkably proceeded with the increase from 350 to 400 "C (Kabe et al., 1990). In our course of studies, we were interested in the hydroaromatic structure 0888-588519112630-1755$02.50/0
Table I. Tritium Distributionn react. react. run temu. "C time. min 1 350 120 2 350 300 3 375 0 4 375 120 5 375 300 6 400 0 7 400 120 8 400 300 ~
radioactivity, dpm in eas uhase in orp Dhase 1 191 019 8673 1087 785 15 102 1 255 785 1943 1231911 37 980 996 268 113 517 1 090 286 7 213 1117883 114463 230 699 877650
"Tetralin, 75 g; H2, 60 kg/cm*; amount of hydrogen in gas phase, 1.34 g; amount of hydrogen in organic layer, 6.82g.
of tetralin itself, which can give hydrogen to coal during liquefaction. Although a number of attempts has been made to elucidate the reactivity of tetralin in the presence of coal, little was known about the behavior of tetralin itself, especially the hydrogen mobility in it under coal liquefaction conditions. In the present paper, we will report the reaction of tetralin with tritiated hydrogen molecules to estimate the hydrogen mobility of tetralin quantitatively using a tritium tracer method.
Experimental Section Materials and Procedure. A commercial guaranteed reagent of tetralin was used without further purification. A typical procedure is as follows: Into a 350-mL autoclave having a glass liner 75 g of tetralin was added. It was charged with tritiated hydrogen molecules at an initial pressure of 60 kg/cm2. The autoclave was stirred with a mechanical stirrer and heated at a heating rate of 10 "C/min, and maintained at the reaction temperature (350-440 "C) for 0-8 h. After the reaction, tetralin and products were analyzed by GC using a OV-17 column (3 mm X 1.0 m) at 160 "C. Gaseous hydrogen was burned to measure the radioactivities of the water produced. The radioactivity was measured with a liquid scintillation counter. The sample of coal used was Wandoan coal (analysis: C, 76.8; H, 6.7; N, 1.1;S, 0.3; 0, 15.1 wt 5% daf, ash, 7.7 wt 3' 6 dry basis). A sample of 25 g of coal was added into the above described system and liquefaction was carried out at 300-400 "C for 0-300 min. The separation and the analysis of products and solvent were performed as described in previous papers (Kabe et al., 1987a,b). Estimation of the Hydrogen-Exchange Ratio. Tables I and I1 show typical examples of the experimental 0 1991 American Chemical Society
1756 Ind. Eng. Chem. Res., Vol. 30, No. 8, 1991 Table 11. Tritium Distribution in the Presence of Coal" radioactivity, dpm react. react. run temp, OC time, min in gas phase in solvent in coal 880290 2345 37098 9 300 120 798 188 28227 86032 120 10 350 103 226 639601 126928 11 400 120 230640 124913 300 413402 12 400
2)
a: Reaction Time, 120 min
J
Tetralin, 75 g; coal, 25 g; H2, 60 kg/cm2; amount of hydrogen in gas phase, 1.24 g; amount of hydrogen in tetralin, 6.82g.
data. The experimental points for the hydrogen-exchange ratio were obtained from such data. Because the radioactivity or the amount of introduced tritium itself does not represent the amount of hydrogen in tetralin related to the hydrogen-exchange reaction between tetralin and molecular hydrogen, the hydrogen-exchange ratio (HER), which represents the ratio of exchanged hydrogen in tetralin, was calculated on the basis of eq 1. The amount of hydrogen
Reaction Temperature P C ]
exchanged between gas phase and organic layer was calculated on the basis of eq 2, in which the extent of hy-
drogen exchange between gaseous hydrogen and organic layer is calculated by subtracting the amount of hydrogen, which was added to organic layer directly from the gas phase, from the amount of hydrogen corresponding to the amounts of tritium transferred to organic layer. (See the Nomenclature section for definitions of the quantities in eqs 1 and 2.)
Results and Discussion Reactions of Tetralin with Tritiated Hydrogen Molecules. The reaction of tetralin with tritiated hydrogen molecule was performed at 350-400 "C, and results are shown in Figure la. In this temperature range, the products were 1-methylindan by isomerization, naphthalene by dehydrogenation, and n-butylbenzene by hydrocracking; the main product was 1-methylindan. With an increase in temperature, the concentration of tetralin decreased and the concentrations of products increased. Decalin by disproportionation was not produced at 350-400 "C. This is consistent with Hooper's result, in which the disproportionation of tetralin to decalin and naphthalene does not occur in the absence of coal (Hooper et al., 1979). When the reaction temperature increased to 440 "C,the yields of 1-methylindan, naphthalene, and n-butylbenzene increased to 11.6,4.8, and 5.2%, respectively, and the increase of 1-methylindan was most remarkable. That the yield of 1-methylindan remarkably increased with a rise from 400 to 440 "C is also consistent with Hooper's report. Figure l b shows the effect of reaction time on the yields of 1-methylindan, naphthalene, and n-butylbenzene. These products increased with a passage of time. When the reaction time was prolonged from 300 to 480 min, yields of products, especially 1methylindan, remarkably increased. Tritium in the gas phase was introduced into tetralin, and the amount of it was estimated by the hydrogen-exchange ratio (see Experimental Section). Figure 2 shows the change of both the hydrogen-exchange ratio and the conversion of tetralin with reaction time and temperature. At 350 "C, the hydrogen-exchange ratio was 0.3% even at 300 min. The conversion of tetralin was also rather low. At 375 and 400 "C,both the hydrogen-exchangeratio (open symbol) and the conversion of tetralin (closed symbol)
Reaction Time iminl
Figure 1. Effects of reaction temperature and reaction time on product yields in the reaction of tetralin with gaseous hydrogen. A, naphthalene; 0,methylindan; V, butylbenzene. Tetralin: 75 g.
"
0
120
2LO
360
-
Reaction Time ( m i d
Figure 2. Effects of reaction time and temperature on hydrogenexchange ratio and conversion of tetralin. Hydrogen-exchange ratio: 0,400OC; 0,375 O C ; A, 350 "c. Conversion of tetralin: @, 400 O C ; W, 375 OC; A, 350 "C. Tetralin: 75 g.
increased with a passage of time and a rise in temperature. It seems that there would be some relationship between the hydrogen exchange and the conversion of tetralin. When the reaction time was prolonged to 480 min, the hydrogen-exchangeratio and conversion of tetralin at 400 "C were 13.5 and 10.1%, respectively. When the reaction temperature increased to 440 " C ,the hydrogen-exchange ratio and conversion of tetralin at 120 min were 14.3 and 21.7%, respectively. We reported that, in coal hydrogenation, the hydrogen-exchange ratio of coal remarkably increased with a rise from 350 to 400 "C to reach more than 40% at 400 "C, 120 min (Kabe et al., 1990). The present results indicate that simple tetralin itself is more difficult to exchange with hydrogen molecules in gas phase than coal. To estimate the relationship between the hydrogen-exchange ratio and conversion of tetralin, the values of the amount of exchanged hydrogen per amount of converted tetralin (gatom/mol) a t each temperature were plotted against reaction time in Figure 3. Values at 375 and 400
Ind. Eng. Chem. Res., Vol. 30, No. 8, 1991 1757 Table 111. Yieldr of Products and Hydrogen-Exchange Ratioa run 13 14 15 16 17 18 19 7 20d
amt of tetralin, g 15 30 30 30 50 75 75 75 75
hydrogen press., kg/cmz 20 20 45 60 60 20 40 60 0
hydrogen/tetralin, mol/mol 2.70 1.21 2.70 3.69 2.14 0.42 0.83 1.25 0.00
HER,*
conv of tetralin, % 18.22 7.08 10.33 10.88 4.96 2.15 2.52 2.91 3.01
%
4.45 3.23 5.12 10.90 6.39 0.67 1.22 2.04
a h a c t i o n temperature, 400 O C ; reaction time, 120 min. *HER = hydrogen-exchange ratio. butylbenzene. dNitrogen atmosphere (1 kg/cmz).
4
1
MI
BB
5.78 2.58 2.45 2.36 1.07 0.85 0.80 0.81 1.70
11.51 3.88 6.07 6.16 2.66 1.15 1.33 1.44 1.24
1.07 0.74 1.89 2.34 1.27 0.24 0.45 0.64 0.20
NP, naphthalene; MI, methylindan; BB,
5
-s
yields of products: %
NP
Y
5
e
-
210cc 01
m r: O
d
5-
C
m
2 (minl Figure 3. Effects of reaction time and temperature on amount of ex&anged hydrogen (AEH)/amount of c o n v e d tetralin (ACT). 0, 400 'c; 0,375 A, 350 O C . Reaction Time
0 x
I
0
'c;
"C increased with a passage of time and gave a linear relationship. However, those values at 375 "C were larger than those at 400 "C a t each reaction time. This shows that the hydrogen exchange between tetrah and molecular hydrogen strongly depends on temperature although it may occur at the time when tetralin converts (vide infra). Further, the values at 375 "C, 300 min and 400 "C, 300 min were 25.3 and 16.5 g-atom/mol, respectively, more than 12 g-atom in 1 mol of tetralin. This shows that tritium has been introduced into not only converted tetralin (products), but also remaining tetralin. These results indicate that there would be an intermediate such as tetralyl radical which converts to a product or returns to tetralin and further can exchange with hydrogen molecules in those routes as shown in eq 3. On the other hand, the value of
AEH/ACT at 350 "C was somewhat constant. The mechanism at 350 "C may be different from that at 375 and 400 "C. Effects of Amount of Tetralin and Hydrogen Pressure. Table 111 shows effects of the amount of tetralin and hydrogen pressure on the hydrogen-exchange ratio, the conversion of tetralin, and the product distribution at 400 "C, 120 min. The hydrogen-exchange ratio and the amount of converted tetralin were plotted against the value of hydrogen per tetralin (mol/mol) in Figure 4. The plots of the hydrogen-exchange ratio showed approximately a straight line and increased in proportion to hydrogen/tetralin values, while the plot of the amount of exchanged hydrogen showed some scatter. The amount of exchanged hydrogen showed a maximum, about 0.3 g at 30 or 50 g of tetralin, 60 kg/cm2. The plots of the amount of converted tetralin also showed a sure straight line and increased with an increase in hydrogen/ tetralin.
1 2 3 L Hydrogen /Tetrolin imol/mol)
Figure 4. Effects of hydrogen/tetralin molar ratio on hydrogenexchange ratio and amount of converted tetralin. Reaction temperature, 400 "C; reaction time, 120 min. 0,hydrogen-exchange ratio; 0 , amount of converted tetralin; A, amount of exchanged hydrogen (X1O-lg in scale of amount of converted tetralin).
--s
0
1 2 Hydrogen/Tetrolin
3
c
Imol/mol)
Figure 5. Effects of hydrogen/tetralin molar ratio on amounts of products. Reaction temperature, 400 O C ; reaction time, 120 min. A, naphthalene; 0,methylindan; V, butylbenzene.
The amounts of products formed were plotted against hydrogen/tetralin in Figure 5. 1-Methylindan showed a straight line and increased with an increase in hydrogen/tetralin. On the other hand, although 2.3 g of naphthalene was produced in the absence of hydrogen as shown in Table 111 and Figure 5, the amount of naphthalene formed was inhibited by the presence of hydrogen and showed the tendency to decrease slightly with an increase in a hydrogen/tetralin molar ratio (Figure 5). The amount of n-butylbenzene formed also increased with an increase in hydrogen/tetralin. These results mean that the hydrogen-exchangeratio, the amount of methylindan formed,
1758 Ind. Eng. Chem. Res., Vol. 30, No. 8, 1991 Table IV. Product Distribution and Hydrogen-Exchange Ratio of Tetralin in the Presence of Coal" product distrib? w t % run TL NP MI BB DL HER,% 9 10 11 12
97.52 93.40 81.47 76.93
2.50 6.47 16.72 19.55
0.00 0.06 1.13 2.19
0.00 0.06 0.62 1.18
0.00 0.02 0.06 0.15
0.05 0.60 3.60 10.10
Table V. Amount of Exchanged Hydrogen in Naphthalene" amt of exchanged hydrogen, g of H/mol run HER, % tetralinb naphthalene 16( 12d
10.90 10.10
1.33 1.29
1.85 1.00
'See Table 11. bTL, tetralin; NP, naphthalene; MI, methylindan; BB, butylbenzene; DL, decalin.
Naphthalene was isolated by liquid chromatography. *Tetralin was not isolated. The values of tetralin layers without naphthalene are shown. CTetralin,30 g; Hz,60 kg/cmz; 400 "C; 120 min. 60 kg/cm2; 400 "C; 300 min. dTetralin, 75 g; coal, 25 g; Hz,
and the amount of converted tetralin increase with an increase in hydrogen pressure. It is important that the gaseous hydrogen participates in the isomerization which does not accompany the income and the outgo of hydrogen. This may be one of the reactions that make it possible for hydrogen in tetralin to exchange with hydrogen molecule. McPherson et al. suggested that the fact that coal suppressed the formation of 1-methylindan necessitates a mechanism in which at least one step in the isomerization is multimolecular (McPherson et al., 1985). Penninger also showed by the kinetics derived from gas-phase work that gaseous hydrogen participated in the isomerization. Further, it has been shown that the enhancement of ring cracking becomes less significant with increasing concentration of the hydrocarbon and that the hydrogen-initiated ring cracking is gradually transferred into a hydrogendonor mechanism as the leading reaction scheme when the concentration of tetralin is increased (Penninger, 1982). A similar phenomenon was observed in our system. In Figures 4 and 5, the relationships between a hydrogen/ tetralin molar ratio and the amounts of 1-methylindan and n-butylbenzene formed or the hydrogen-exchange ratio approximately follow straight lines. This means that the increase of tetralin decreases the cracking products and the hydrogen exchange. Tetralin may be activated by collision with itself or a hydrogen molecule to produce one intermediate such as tetralyl radical in eq 3. However, if the intermediate is quenched by tetralin to form original tetralin, the conversion of tetralin and hydrogen exchange would be inhibited. The reaction of the intermediate with molecular hydrogen leads to hydrogen exchange in both the conversion and the reproduction of tetralin. Because molecular hydrogen promotes the conversion of tetralin, it would not quench the intermediate at least more rapidly than tetralin. Reactions of Tetralin with Tritiated Hydrogen Molecules in the Presence of Coal. The reactions of tetralin with tritiated hydrogen molecule in the presence of coal were investigated, and results are shown in Table IV. Although coal did not largely affect the formation of 1-methylindan, n-butylbenzene, or decalin at 300-400 "C, the amount of naphthalene formed remarkably increased, especially with a rise from 350 to 400 "C, compared with that in the absence of coal. It is suggested that the interaction between coal and tetralin is enhanced in the range of 350-400 "C. This is also observed in the changes of radioactivities in coal and tetralin as shown in Table 11. The radioactivity in tetralin remarkably increased with a rise from 350 to 400 "C while that in coal did not change greatly. In the reaction of coal with tritiated molecular hydrogen without solvent, the radioactivity in coal remarkably increased in the range of 350-400 "C (Kabe et al., 1990). When tetralin was added in the present work, it was considered that tritium initially introduced into coal would be rapidly transferred to tetralin in this temperature range. On the other hand, the hydrogen-exchange ratio of tetralin was much larger than that in the absence of coal
as shown in Table IV. This indicates that coal promotes the hydrogen-exchange reaction between molecular hydrogen and tetralin to introduce tritium into tetralin. King and Stock reported that the hydrogen exchange between coal and tetralin-d12 and naphthalene-d, was readily reversible at 400 "C and that the reactions were initiated by single-bond homolyses and by molecule-inducedhomolyses (King and Stock, 1982). Further, McMillen et al. reported that the hydrogen transfer from donor solvent to coal model compound proceeded by the radical hydrogentransfer mechanism (McMillen et al., 1987). Billmers et al. also reported that hydrogen migration between 9,lOdihydro positions in anthracene structures was consistent with a free-radical mechansim (Billmers et al., 1986). In these reports, the hydrogen-transfer processes are reversible and the hydrogen-exchange reaction can occur through these radical mechanisms. In our systems, since coal generates radicals more easily than tetralin, molecular hydrogens must be more easily activated on coal surface than tetralin. Tritium transferred into coal would readily exchange with hydrogen in tetralin through a radical mechanism. Hydrogen Exchange in Naphthalene. In the presence of coal, it has been reported that hydrogen in naphthalene, which was initially added, exchanges with gaseow hydrogen (Kabe et al., 1987b). In the present work, naphthalene formed from tetralin was isolated. In spite of the release of hydrogen, it contained tritium from the gas phase in the absence and presence of coal, as shown in Table V. Two data in the absence and presence of coal were chosen because the hydrogen-exchangeratios are very similar to each other. The amount of hydrogen exchanged per 1mol of naphthalene in the absence of coal was 1.85 g. Even in the presence of coal where a large amount of hydrogen was released, 1.00 g of hydrogen in naphthalene was exchangeable with gaseous hydrogen. It is suggested that when tetralin changes to naphthalene, hydrogen in tetralin will become very mobile and be able to exchange with molecular hydrogen. Skowronski et al. reported that, in the hydrogen exchange between tetralin-d12and hydrogen in coal at 400 "C, 1 h in a shaken autoclave system, protium was incorporated into Ha (66%),H, (23%), and H, (11%) positions in tetralin and that the Ha absorption of the recovered naphthalene in 'H NMR was approximately 7 times as intense as the H, absorption (Skowronski et al., 1984). Collin and Wilson showed from their INEPT and GASPE NMR study that, in the reaction of tetralin with deuterium and coal, the mixture of tetralins consists of molecules that were nondeuterated and monodeuterated at Haand/or H, positions while no evidence was found for any molecules that were dideuterated at Haand/or H, positions. In their NMR measurement, the intensity of the signal at the Ha position was larger than that at the H,position (Collin and Wilson, 1983). Franz and Camaioni, in a set of pyrolysis experiments with peresters of 1-tetralyl, 2-tetralyl, 1indanylmethyl, and 2-indanylmethyl, concluded that as
Ind. Eng. Chem. Res., Vol. 30, No. 8, 1991 1759 pyrolysis of the 1-tetralyl perester gave no detectable amount of methylindan, formation of 1-methylindan was primarily through the 2-tetralyl radical (Franz and Camaioni, 1980). These reports represent that the 1-tetralyl radical appears to be a more important intermediate than the 2-tetralyl radical in exchange with coal and that, in noncatalytic system without coal, the 2-tetralyl radical as well as the 1-tetralyl radical would become important. In the hydrogen exchange of naphthalene resulting from the dehydrogenation of tetralin, the 1-tetralyl radical would be also important in exchange with coal. In our system with coal, however, the 2-tetralyl radical may be formed competitively with the 1-tetralyl radical to lead to the hydrogen exchange at the &position of naphthalene since 1-methylindan was produced as a main product.
Conclusions Gaseous tritium was introduced into tetralin under coal liquefaction conditions even in the absence of coal. The hydrogen-exchange ratio, the amount of tetralin converted, and the amount of methylindan formed increased in proportion to a hydrogen/tetralin molar ratio. Coal catalyzed the hydrogen-exchange reaction between tetralin and molecular hydrogen. In the absence and presence of coal, gaseous tritium was introduced into naphthalene produced by the release of hydrogen in tetralin under coal liquefaction conditions. Although the possibility of the relationship between the hydrogen-exchange ratio and the conversion of tetralin was suggested a detailed mechanism of the hydrogen exchange still remains unclear and further investigations will be reported. Nomenclature Hadt(-): amount of hydrogen added from gas phase to organic layer Hex(-): amount of hydrogen exchanged between gas phase and organic layer, g H : amount of hydrogen in gas phase amount of hydrogen in organic layer H&: hydrogen-exchange ratio ROq: radioactivity in organic layer Ran: radioactivity in gas phase after the reaction
du:
Registry No. Tritium, 10028-17-8; tetralin, 119-64-2; naphthalene, 91-2G3; methylindan, 767-58-8; n-butylbenzene, 104-51-8 decalin, 91-17-8.
Literature Cited Benjamin, B. H.; Hagaman, E. W.; Raaen, V. F.; Collins, C. J. Pyrolysis of Tetralin. Fuel 1979,58, 386-390. Billmers, R.; Griffith, L. L.; Stein, S. E. Hydrogen Transfer between Anthracene Structure. J. Phys. Chem. 1986,90,517-523. Brower, K. R. Effects of Pressure and Isotopic Substitution on the Rate of Reaction of Coal with Tetralin. J. Org. Chem. 1982,47, 1889-1893. Collin, P. J.; Wilson, M. A. Use of INEPT and GASPE n.m.r. Pulse Sequences. Assignment of Position of Incorporation of Deuterium into Tetralin during Coal Hydrogenation. Fuel 1983, 62, 1243-1246. Cronauer, D. C.; Jewell, D. M.; Shah, Y. T.; Kueser, K. A. Hydrogen Transfer Cracking of Dibenzyl in Tetralin and Related Solvents. Ind. Eng. Chem. Fundam. 1978,17 (4), 291-297. Cronauer, D. C.; Jewell, D. M.; Shah, Y. T.; Modi, R. J.; Seshadri, K. S. Isomerization and Addition of Hydrogen Donor Solvents under Conditions of Coal Liquefaction. Ind. Eng. Chem. Fundam. 1979, 18 (4), 368-376. Cronauer, D. C.; McNeil, R. I.; Young, D. C.; Ruberto, R. G. Hydrogen/Deuterium Transfer in Coal Liquefaction. Fuel 1982,61, 610-619.
Franz, J. A. Carbon-13, Deuterium, and Proton NMR and GPC Study of Structural Evolution of a Subbituminous Coal during Treatment with Tetralin at 427 "C. Fuel 1979,58,405-412. Franz, J. A.; Camaioni, D. M. Fragmentations and Rearrangements of Free Radical Intermediates during Hydroliquefaction of Coals in Hydrogen Donor Media. Fuel 1980a, 59,803-805. Franz, J. A,; Camaioni, D. M. Radical Pathways of Coal Dissolution in Hydrogen Donor Media. 2. Scission and 1,2 Aryl Migration Reactions of Radicals Derived from Methylindans and Tetralin at 327-627 OC. J. Org. Chem. 1980b, 45, 5247-5255. Franz, J. A.; Camaioni, D. M.; Skiens, W. E. Application of Carbon-13, Hydrogen-2, Hydrogen-l NMR and GPC to the Study of Structural Evolution of Subbituminous Coal in Tetralin at 427 "C. Adu. Chem. Ser. 1981,192, 75-93. Hooper, R. J.; Battaerd, H. A.; Evans, D. G. Thermal Dissociation of Tetralin between 300 and 450 "C. Fuel 1979, 58, 132-138. Kabe, T.; Nitoh, 0.; Funatsu, E.; Yamamoto, K. Studies on Hydrogen Transfer Mechanisms in Coal Liquefaction by means of 3H and 14C Tracer Techniques. Fuel Process. Technol. 1986, 14, 91-101. Kabe, T.; Nitoh, 0.;Marumoto, M.; Kawakami, A.; Yamamoto, K. Liquefaction Mechanism of Wandoan Coal Using Tritium and C'l! Tracer Methods. 1. Liquefaction in 3H and 14CLabeled Solvent. Fuel 1987a, 66, 1321-1325. Kabe, T.; Nitoh, 0.;Funatsu, E.; Yamamoto, K. Liquefaction Mechanism of Wandoan Coal Using Tritium and "C Tracer Methods. 2. Liquefaction Using 3H Labeled Gaseous Hydrogen. Fuel 1987b, 66, 1326-1329. Kabe, T.; Nitoh, 0.;Kawakami, A.; Okuyama, S.; Yamamoto, K. Liquefaction Mechanism of Wandoan Coal Using Tritium and "C Tracer Methods. 3. Hydrocracking of Wandoan Coal Liquid. Fuel 1989,68, 178-184. Kabe, T.; Takaoka, H.; Ishihara, A.; Daita, Y. Estimation of Hydrogen Mobility in Coal Using A Tritium Tracer Method. Hydrogen Exchange Reaction of Coal with Tritiated Water. Chem. Lett. 1990, 1571-1574. King, H. H.; Stock, L. M. Aspects of the Chemistry of Donor Solvent Coal Dissolution. The Hydrogen-Deuterium Exchange Reactions of Tetralin-dlz with Illinois No. 6 Coal. Coal Products and Related Compounds. Fuel 1982,61, 257-264. McMillen, D. F.; Malhotra, R.; Chang, S.-J.; Ogier, W. C.; Nigenda, S. E.; Fleming, R. H. Mechanisms of Hydrogen Transfer and Bond Scission of Strongly Bonded Coal Structures in DonorSolvent Systems. Fuel 1987,66, 1611-1620. McPherson, W. P.; Foster, N. R.; Hastings, D. W.; Kalman, J. R.; Gilbert, T. D. Tetralin Decomposition in Short Contact Time Coal Liquefaction. Fuel 1985, 64, 457-460. Penninger, J. L. M. New Aspects of the Mechanism for the thermal Hydrocracking of Indan and Tetralin. Znt. J. Chem. Kinet. 1982, 14 ( 7 ) , 761-780. Poutsma, M. L.; Youngblood, E. L.; Oswald, G. E.; Cochran, H. D. Carbon-14 Tracer Study of the Fate of Tetralin under Simulated SRC-I Coal Liquefaction Conditions. Fuel 1982, 61, 314-320. Schweighardt, F. K.; Bockrath, B. C.; Friedel, R. A.; Retkofsky, H. L. Deuterium Magnetic Resonance Spectrometry as a Tracer Tool in Coal Liquefaction Processes. Anal. Chem. 1976,48,1254-1255. Skowronski, R. P.; Ratto, J. J.; Goldberg, I. B.; Heredy, L. A. Hydrogen Incorporation during Coal Liquefaction. Fuel 1984, 63, 440-448. Vlieger, J. J.; Kieboom, A. P. G.; Bekkum, H. Behavior of Tetralin in Coal Liquefaction. Examination in Long-Run Batch-Autoclave Experiments. Fuel 1984,63, 334-340. Wilson, M. A.; Collin, P. J.; Barron, P. F.; Vassollo, A. M. Deuterium as a Tracer in Coal Liquefaction. 1. The Incorporation of Deuterium into Liquid Products. Fuel Process. Technol. 1982, 5, 281-298. Wilson, M. A.; Vassollo, A. M.; Collin, P. J.; Bath, B. D. Deuterium as a Tracer in Coal Liquefaction. 2. Non-Catalytic Studies. Fuel Process. Technol. 1984,8, 213-229. Yen, Y. K.; Furlani, D. E.; Weller, S. W. Batch Autoclave Studies of Catalytic Hydrodesulfurization of Coal. Ind. Eng. Chem. Prod. Res. Deu. 1976,15 (l),24-28. Receiued for review September 19, 1990 Revised manuscript received March 11, 1991 Accepted March 26, 1991
