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Ind. Eng. Chem. Prod Res. Dev. 1984, 23, 215-219
Molten Salt Catalyzed Hydroliquefaction of Three Lithotypes of Yallourn Brown Coal. Characteristics of ZnCI, and/or SnCI, (and/or KCI) Containing Molten Salt Catalysts Masakatsu Nomura, Takeshl Yoshlda,+ and Zen-lchlro Morltat Department of Applled Chemistry, Faculty of Engineering, Osaka University, 2- 1 Yamadaoka, Sulta, Osaka 565, Japan
Three lithotypes of Yallourn brown coal, pale, medium light, and medium dark, are hydrogenated over ZnCI,, ZnCI,-KCI, SnCI,, SnCI,-KCI, ZnCI,-SnCI,, and ZnCI,-SnCI,-KCI molten salt catalysts, respectively, under the following conditions: 400 "C, 3 h, 100 kg/cm2 of H, melt/coal = 1 (wt/wt). With melt catalysts, conversions range from 66 to 77 wt % for pale, 50 to 65 wt % for medium light, and 41 to 65 wt % for medium dark. Pure ZnCI, affords the lowest conversion and oil yield among the molten salt catalyst systems, and the melt containing KCI is found to afford higher conversion than the corresponding KCI-free melt for each lithotype. These findings can be rationalized by referring to the moderate acidity of the molten salts and their reduced viscosities.
Introduction Recently, Victorian coal has been attracting a great deal of attention as a potential source of fossil fuel because of ita abundance and easy accessibility. In the Latrobe Valley open cut mining, there is seen a strate graphic banding which forms five primary lithotypes based on color and texture. Since lithotype is believed to influence liquefaction (Allardice et al., 1977), it is of a great use to hydrogenate brown coal according to this classification in order to obtain a better understanding of brown coal liquefaction. On the other hand, the authors have been extensively investigating coal liquefaction using different kinds of molten salt as catalysts (Ida et al., 1979; Nomura et al., 1982,1983). For some bituminous coals, KC1-containing ZnCl, or SnCl, melt was found to be effective in affording higher conversion and lower gas yield. The present paper deals with the hydroliquefaction of three lithotypes of Yallourn brown coal, pale, medium light, and medium dark, over the molten salt catalysts. Lewis acid types such as ZnCl,, ZnC12-KC1 (3:2 mole ratio), SnCl,, SnC1,-KCl (3:2), ZnC12-SnCl, (l:l),and ZnCl2-SnCl2-KC1 (3:3:4) melts are examined with an attempt to study their catalytic activities for the hydroliquefaction of oxygen-rich brown coal. Experimental Section Feedstock. Coals used here were three lithotypes of Yallourn brown coal from the State Electricity Commission of Victoria. Each lithotype was dried under 30 mmHg pressure at 100 "C for 24 h prior to pulverization. Then the dried coal was crushed, sieved to > medium light > medium dark, while the O/C ratio is reversed. From the change of these variables, pale seems quite different from the other two lithotypes which have a lot of similarity to each other. During brown coal hydroliquefaction, significant amounts of water are produced. However, in this study, no determination of water produced was undertaken. Here conversion was determined in terms of grams of [CO + C02 + (C,-C,) HS BS] per gram of (daf coal + Hz consumed). Taking into accounts the amounts of water produced, 100-BI should be real conversion. And when the SnC12-containingmelt was used, this value was relatively lower than that without SnCl,, because SnC1, is more difficult to remove from BI than ZnC1,. Hydroliquefaction of Three Lithotypes. A characteristic of brown coal liquefaction compared with that of bituminous coal is the high yields of CO and COz. Since humic acids are supposed to make a significant contribution to brown coal structure (Camier, 1979; Martin, 1975), C02is believed to derive from carboxylic groups of original coal and CO gas partly from carbonyl groups present in the coal and partly from the hydrogenation of C02.
+
+
Conversion of three lithotypes decreases in the order of pale, M-1 and M-d:66.2-77.1% with pale, 50.4-65.0% with M-1, and 41.2-65.690 with M-d in the presence of molten salt catalyst. According to the concentrations of humic acids and kerogen (Verheyer and John, 1981), the lithotypes are divided into two groups: (1)pale rich in humic acid, (2) medium light and medium dark rich in kerogen. Therefore the low level of humic acids but corresponding high kerogen levels of the latter two lithotypes could be correlated with the lower reactivity for hydroliquefaction even in the presence of the molten salt catalyst. Molten Salt Catalysis. In a previous paper (Nomura et al., 1983),we have pointed out that the addition of KC1 to ZnC1, or SnC12 caused the suppression of gaseous products from the hydroliquefaction of some bituminous coals accompanying the increasing yield of HS. From Table 11, the conversion of pale ranges from 77 % using ZnC12-SnC12-KC1 and ZnCl,-KCl melts to 71-74% using ZnC1,-SnC12, SnC2-KC1, and SnCl,, while the conversions using pure ZnC12 are relatively lower than the above values. It should be noted that HS yields from each lithotype are roughly similar to each other among five molten salt catalysts except pure ZnClz: pale 55-58%, M-1 30-3690, and M-d 33-35% except 27% of M-d over ZnC12-KC1 melt. Pure ZnC1, shows different behavior from other catalyst systems. This suggests that the acidity of molten salts can play an important role in molten salt catalyzed liquefaction because SnC1, acidity is lower than pure ZnC1, and the addition of KC1 reduces the melt acidity. Although it is quite difficult to evaluate the acidity of such a molten salt system, we tentatively assume that the ratio of isobutane/n-butane (Table 11) represents acid strength of the catalyst as suggested by Zielke et al. (1966). These values are as follows: ZnC12(1.5-2.5), ZnC12-SnC12 (0.7-l.l), ZnClZ-KC1 (0.6-0.91, SnC1, (0.5-0.61, ZnCl,-SnCl,-KCl (0.3-0.5), and SnC1,-KC1 (0.3-0.4). As expected, pure ZnC12shows the highest value and the catalytic behavior of molten salt for brown coal hydroliquefaction might be well correlated with the acidity estimated from the isobutaneln-butane ratio. However, it should be noted that ZnC12-SnC1, show relatively high HS yields and conversions of three lithotypes in spite of its higher isobutaneln-butane ratio [this suggests that not only the acid strength but also other properties of melt should be referred to (see later)]. Moderate acid strength of molten salt catalysts could be important in attaining a preferable liquefaction characterized by lower hydrogen consumption, higher HS yield, and higher conversion. Table I1 also indicates that the addition of KC1 to ZnC12, SnC12,and ZnC12-SnC12melts increases the amounts of BS compared with those of ZnCl,, SnCl,, and ZnCl,-SnCl, melts, respectively (the reverse is true with the amounts of C1-C4 hydrocarbons). This could be rationalized by referring to the decreasing acid strength of the melts caused by the addition of KC1 (Nakatsuji et al., 1980) because weak acid strength of the melts decreases both retrogressive reaction of BS to BI and hydrocracking of HS to C1-CI hydrocarbons. Analysis of HS Fraction. Elemental analyses and structural parameters of the HS fraction are listed in Table 111. With pale, H/C of resulting oils is in the range from 1.32 to 1.39 while they are 1.17-1.24 with M-d and M-1. Verheyer and John (1981) pointed out that progressively darker lithotypes may reflect increased aromaticity. Reduction in the H/C ratio of HS with medium light and medium dark is in accord with findings that these two lithotypes are less reactive than pale lithotype because the
Ind. Eng. Chem. Prod. Res. Dev., Vol. 23, No. 2, 1984 217 Table 11. Hydroliquefaction of Three Lithotypes gas
litho, cat.
co
noneb ZnC1, b , c ZnC1,-KClb SnC1, SnCl,-KCl ZnC1,-SnC1, ZnC1,-SnC1,-KCl
2.5% 1.4 1.4 0.9 0.9 0.9 1.0
noneb ZnC1,b ZnC1,-KC1 SnC1, SnCl,-KCL ZnCl,-SnCl, ZnC1,-SnC1,-KC1
4.3 2.0 1.8 1.6 1.5 1.6 2.0
none ZnC1,b ZnC1,-KCl SnCl, SnCl,-KCl ZnCl,-SnCl, ZnC1,-SnC1,-KC1
3.9 1.4 1.2 1.2 1.7 1.4 1.0
HSa
BS
8.6
0.3 2.5 0.9 0.6 0.4 1.1 0.5
28.6 48.0 56.8 56.8 55.3 55.6 58.3
2.6 1.0 3.3 2.3 5.0 3.1 4.5
52.7 66.2 76.5 70.9 71.4 73.6 77.1
69.7 94.0 97.1 (81.5) (81.9) (82.1) (82.5)
11.6 8.5 9.8 9.2 7.8 7.0 10.5
M-1 8.7 14.9 8.4 15.4 14.0 12.3 13.5
0.2 1.7 0.6 0.3 0.5 0.9 0.3
18.7 24.5 30.0 31.9 31.6 35.9 31.8
5.2 0.5 5.5 3.6 7.6 6.2 7.2
48.5 50.4 55.5 61.7 62.5 63.0 65.0
63.4 68.7 80.7 (69.3) (70.2) (70.7) (67.6)
6.9 7 .O 4.6 6.3 7.6 6.7 9.3
M-d 5.7 12.1 7.6 14.2 10.0 16.7 14.0
0.4 1.5 0.8 0.5 0.4 0.7 0.5
13.7 20.3 27.3 34.7 33.7 32.8 32.9
3.9 0.4 6.4 4.1 12.2 3.9 8.4
34.1 41.2 47.1 60.5 65.2 61.5 65.6
58.3 71.6 73.0 (74.2) (69.8) (63.3) (69.6)
CO, 9.7% 4.8 6.8 2.1 3.2 3.0 4.7
C,-C,
i-C,ln-C,
Pale 9.3% 11.0 8.2 8.8 7.0
11.0
conv, % 100 - BI,%
a HS contains a lighter fraction distilled. Hydrogen consumed; without catalyst, 1.2 wt % (pale), 1.5 (M-1), 2.4 (M-d); Another run was conducted as check ZnCl,, 4.1 (pale), 5.6 (M-I), 5.1 (M-d); ZnC1,-KCl, 3.2 (pale), 4.5 (M-1), 4.3 (M-d). experiment of reproducibility: (CO t CO,) 4.8%; ((2,-C,) 10.5, HS 46.4, BS 2.1, conv (%) 63.8.
Table 111. Elementary Analyses and Structural Parametersa of HS lithotype
C
H
N
none ZnC1, ZnC1,-KC1 SnC1, SnC1,-KCl ZnCl,-SnCl, ZnCl,-SnCl,-KCl
85.1% 89.0 88.0 88.7 88.2 89.2 87.8
none ZnC1, ZnC1,-KCl SnCl, SnC1,-KC1 ZnCl,-SnCl, ZnC1,-SnC1,-KCl
84.3 89.6 88.3 88.9 88.9 89.7 88.7
8.4 8.8 8.7 9.0 8.8 8.9 8.9
0.6 0.4 0.4 0.0 0.0 0.0 0.0
none ZnC1, ZnCl,-KCl SnC1, SnC1,-KCl ZnCl,-SnCl, ZnC1,-SnC1,-KCl
82.1 89.7 87.7 89.6 87.6 87.7 87.8
8.5 8.9 8.8 8.9 8.8 8.6 8.8
0.5 0.0 0.5 0.0 0.0 0.0 0.0
9.8% 9.9 10.1 10.1 10.1 9.8 10.0
0.3% 0.0 0.3 0.0 0.3 0.0 0.3
fa
u
1.1 1.6 1.2 1.4 1.0 1.9
1.39 1.34 1.37 1.36 1.38 1.32 1.36
0.47 0.50 0.49 0.49 0.50 0.51 0.49
0.43 0.41 0.42 0.42 0.40 0.44 0.41
0.81 0.83 0.79 0.79 0.76 0.70 0.77
200 230 260 230 240 250 250
M-1 6.7 1.2 2.6 2.1 2.3 1.4 2.4
1.20 1.19 1.17 1.21 1.19 1.19 1.20
0.62 0.61 0.60 0.59 0.60 0.61 0.59
0.39 0.36 0.42 0.38 0.37 0.38 0.37
0.84 0.74 0.76 0.75 0.78 0.73 0.76
240 240 240 210 260 230 240
1.24 1.20 1.20 1.19 1.20 1.17 1.20
0.59 0.60 0.58 0.59 0.58 0.60 0.59
0.42 0.35 0.41 0.37 0.40 0.39 0.39
0.84 0.77 0.75 0.73 0.76 0.77 0.77
200 230 2 30 280 280 250 240
M-d 8.9 1.4 3.0 1.5 3.6 3.7 3.4
a f a : aromaticity; u : the degree of substitution on aromatic rings; H,/C,: unsubstituted aromatic nuclei. Difference.
increasing degree of aromatic structure has resisted hydrogenation over the melt catalyst (Nakatsuji et al., 1978). For the oil from pale, the addition of KC1 to ZnClz, SnClZ,and ZnC12-SnClz results in incomplete elimination of nitrogen. From the oil of M-1 and M-d, nitrogen was removed completely over SnCl,, SnCl,-KCl, ZnC12-SnC1,, and ZnC12-SnC12-KC1. For oxygen contents of oil, ZnCl, is comparable to ZnC12-SnC1, in removing oxygen atoms of the oil from pale and M-1. This trend is not true with those of M-d. Effectiveness of ZnC1, and ZnC12-SnC1,melt
Haru/Car m o l w t
H/C
Ob
Pale 4.8%
hydrogenlcarbon ratio for the hypothetical
in eliminating heteroatoms could be rationalized b y referring to their strong acidities based on the i-C4/n-C4 ratio. For structural parameters, fa of oil from pale is lower than those of M-1 and M-d. Both M-1 and M-d are similar to each other in view of value of H,,/C,. Comparative gel-permeation chromatograms of HS fractions from noncatalyzed runs of each lithotype and those from the runs catalyzed by pure ZnC12 and ZnC1,KC1 melts are shown in Figure 1. A molecular-size-dis-
218
Ind. Eng. Chem. Prod. Res.
Dev., Vol. 23,No. 2,
1984
7
18
standards
I
1m 1 2 0 pale
178 128
17'
medium light
(phenanthrene, naphthkne)
medium dark
Figure 1. Gel permeation chromatogram of oils: column, Shodex AC-801 + AC-802; carrier, CHCl, 1 mL/min; detector, RI.
Table IV. Column Separation of HS from Pale aromatics cat.
saturate
mono
di
Poly
polar comp.a
none ZnC1, ZnCl,-KCl SnC1, SnC1,-KCl ZnCl,-SnCl, ZnC1,-SnC1,-KCl
8 . 3 wt % 11.6 8.4 11.6 11.0 8.3 10.6
6.1 11.9 17.5 16.1 15.8 15.4 12.8
2.6 8.1 7.9 8.2 6.3 11.0 16.4
3.5 10.2 10.1 11.6 8.5 12.5 9.2
8.1 6.2 12.9 9.2 13.7 8.4 9.3
a Wt % based on starting coal [obtained by multiplying the products of (recovery tribution ratio (%/loo)].
tribution curve of pale-HS from the run with ZnC12-KC1 shows the appearance of a broader shoulder at lower elution volumes than that from the run with pure ZnClz. A similar trend of the distribution curve was observed of HS from the runs of medium light and medium dark lithotypes; however, the shift to lower elution volumes of HS was much smaller, especially in the case of HS from medium light. Average-molecular-weight values of HS from pale lithotype over pure ZnC1, and ZnCl,-KCl (Table 11) are in good agreement with above observation by GPC analyses. Higher molecular weight over KC1-containing melts compared to that over KC1-free melt is observed for pale-HS over SnCl, system and medium light-HS over ZnC1,-SnClz system while roughly equal molecular weight of HS from M-d are observed over ZnCl, and SnC1, systems except ZnC1,-SnClz system. These findings suggest that for pale- and M-LHS, higher yields with ZnC12-KC1 than those over pure ZnC1, accompany their increased molecular weight. Table IV shows the distribution of five fractions, saturate, monoaromatics, diaromatics, polyaromatics, and polar compounds of HS from pale. It is evident that the addition of KC1 to ZnCl,, and SnC12,and ZnCl,-SnCl, increased polar compounds compared with corresponding KC1-free melts. Saturates range from 8.3 to 11.6%. The ZnCl,-KCl system yields the highest amounts of monoaromatics among catalysts examined here. Amounts of polar compounds increases in the following order: ZnC1, > (ZnCl,-SnCl,, SnCl,, ZnCl2-SnCl2-KC1) > (ZnCl,-KCl, SnCl,-KCl). I t is noted that this order parallels with the reverse of the order of the acid strength of melts. Eutectic Point and Viscosity of Molten Salt. As coal is heated without solvent, lower-eutectic-pointmelt sup-
%/loo) and HS yield (Table 11) by dis-
Table V. Eutectic Points and Viscosity of Melts melts ZnC1, ZnC1,-KCl SnC1, SnCl,-KCl ZnCl,-SnCl, ZnCl,-SnCl,-KCl a
eutectic viscosity, cP, pointy "C at 400 "C 313 203 255 180 191 152
240 7 3-4 3-4 7 2
These values were determined according t o DTA curves
of these melts. Therefore these values d o not necessarily
indicate their genuine eutectic points because binary or ternary melts have their lowest eutectic point where salts having constituents corresponding t o this lowest eutectic point partially start t o melt.
ported onto coal begins to melt both in the pore structure and over the surface of coal materials because brown coal does not show plastic state around these temperatures. Massive amounts of molten salt also act as a dispersant of coal particles. In this respect, eutectic points and viscosities of melts are vey important properties. The eutectic points and viscosities of melts are shown in Table V. The molten salt system except pure ZnC1, show 2-7 CPviscosity at 400 "C while that of pure ZnC12 is 240 cP, so low viscosity of the melt could be correlated with high conversion of brown coal. Because of its low viscosity, ZnCl2-SnClZ decreases the retrogressive reaction of BS to BI in spite of its relatively high acid strength, leading to high yield of HS and high conversion. Solubilization of hydrogen into melt is another factor affecting high conversion because this solubilization is supposed to be enhanced in less viscous melt and the resulting high hydrogen solubilization should affect the hydrogen transfer from melt to coal materials.
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Ind. Eng. Chem. Prod. Res. Dev. 1984, 23, 219-225
However, it is interesting to note that at moderate acid strength, melt having low viscosity attains higher conversion than that with pure ZnC12 in hydroliquefaction of brown coal without vehicle oil. Conclusion The hydroliquefaction of three lithotypes of Yallourn brown coal was investigated over molten salt catalysts (ZnC1, and/or SnC1, and/or KC1) in a batch autoclave at 400 “C and a cold pressure of 100 kg/cm2 for 3 h. Conversions of pale, medium light, and medium dark decrease in this order: 66.2-77.1%, 50.4-65.0%, and 41.2-65.690, respectively. It was found that hexane-solubleyields from three lithotypes catalyzed by pure ZnCl, are lower than those from the runs catalyzed by the other five molten salt systems. The acidity (evaluated by i-C4/n-C4ratio of gas produced) suggests that moderate acidity is effective in attaining high conversion and high yield of hexane solubles. However, this view has some limitation because ZnC1,SnC12 give high yields of HS in spite of its acidity comparable to pure ZnCIP. Viscosities (pure ZnC12,240 cP at 400 “C and other melts, 2.7 cP at 400 “C) seem to be correlated with degrees of hydroliquefaction. Therefore, both moderate acidity and reduced viscosity of the melts are supposed as major factors improving the hydroliquefaction of brown coal in the absence of organic solvents. Acknowledgment We are grateful to Dr. Paul Philp of CSIRO, Division of Fossil Fuels, Australia, for valuable discussion on brown
coal liquefaction using molten salt catalyst, and the State Electricity Commission of Victoria for providing the samples. Registry No. SnC12,7772-99-8; ZnC12,7646-85-7; KC1, 744740-7.
Literature Cited Allardlce, D. J.; George, A. M.; Hausser, D.; Neubert, K. H.; Smith, 0. C. “The Variation of Latrobe Valley Brown Coal Properties with Lithotype”. Victoria, State Electricity Commisslon, Brown Coal Res. Div. Rep. (1977), No. 342. Biackburn, D. T. “Floristic, Environmental, and Lithotype Correlations in the Yaiiourn Formation, Victoria”; paper presented at the Cainozoic Evolution of Continental South-Eastern Australia Conf., Canberra, Nov 1980. Camier, R. J. Ph.D. Thesis, Department of Chemical Engineering, University of Melbourne, Melbourne, Australia 1979. Ida, T.; Nomura, M.; Nakatsuji, Y.; Kikkawa, S. Fuel 1979, 58, 361. Martin, F. Fuel 1975, 54. 236. Morlta, 2.; IMa, T. Nlppon Klnzoku Gekkalshl 1980, 79, 655. Nakatsuji, Y.; Kubo, T.; Nomura, M.; Kikkawa, S. Bull. Chem. SOC. Jpn. 1978, 57, 618. Nakatsuji, Y.; Shigeta, K.; Nomura, M.; Kikkawa, S. Sekku Gakkaishl 1980, 2 3 , 420. Nomura, M.; Miyake, M.; Sakashita, H.; Kikkawa, S. Fuel 1982, 67, 18. Nomura, M.; Kimura, K.; Kikkawa, S. Fuel 1982, 6 2 , 1119. Sawatzky, H.; George, A. E.; Smiiey, G. T.; Montgomery, D. S. Fuel 1978, 55, 16. Verheyer, T. V.; John, R. B. Geochlm. Cosmochlm. Acta 1981, 45, 1899. YoshMa, M.; Ohnuki, T. I n “Shinjikken Kagaku Koza, Voi. I”; Japanese Chemical Society, Maruzen, 1975; p 436. Zieike, C. W.; Struck, R. T.; Evans, J. M.; Costanza, C. P.; Gorin, E. Ind. Eng. Chem. Process Des. D e v . 1968, 5, 158.
Received for review September 27, 1982 Revised manuscript received April 11, 1983 Accepted October 21, 1983
Decomposition of Alcohols over Zirconium and Titanium Phosphatest Soofln Cheng, Guang Zhl Peng, and Abraham Clearfleld’ Department of Chemistry, Texas A&M Unlverslv, College Station, Texas 77843
The catalytic properties of the layered compounds-zirconium phosphate, titanium phosphate, mixed zirconium titanium phosphate, and their organically pillared derivatives-toward methanol conversion have been examined. Dimethyl ether was found to be the precursor for hydrocarbon formation. However, strong acidities of the phosphate compounds seem to enhance methane formation. The phenyl-group bridged derivatives were found to have remarkably higher Catalytic activities and selectivities for the conversion of methanol to low molecular weight hydrocarbons. These pillared compounds were considered to provide pore structure for shapsselectiie products. Moreover, the phenyl pillars were suggested to be capable of stabilizing reaction intermediates.
Introduction The group 4 acid phosphates have layered structures and behave as ion exchangers (Clearfield and Alberti, 1982). Adjacent layers are arranged in such a way as to produce cavities between the layers (Clearfield and Smith, 1969; R o u p and Clearfield, 1977). A schematic view of a portion of the structure is shown in Figure 1. Exchange of cations apparently takes place by diffusion of the cations parallel to the layers as all the protons lie near the center of the interlayer space outlining the cavities. In the case of a+ The work reported in this paper was presented at the Symposium on New Catalytic Materials at the 186th National Meeting of the American Chemical Society, Washington, DC, August 1983.
Ol96-432lf84f 1223-O219$O1.5OfO
zirconium phosphate (a-ZrP), Zr(HP0,),-H20, the free space of the passageways leading into cavities is just sufficient to allow an unhydrated K+ to diffuse in unobstructed (Clearfield et al., 1969). Upon deh dration the a-ZrP, which has an interlayer spacing of 7.6 transforms to S.-ZFtP (dm2= 7.4 A), and at higher temperatures, 7-ZrP, interlayer spacing 7.1 A, is obtained (Clearfield and Pack, 1975). This interlayer distance is so small that the dehydration of cyclohexanol over zirconium phosphate was found to be catalyzed only by the surface acid groups and not those in the interior (Clearfield and Thakur, 1980; Thakur and Clearfield, 1981). Recently it was shown that the a-layered compounds could be pillared by organic phosphate and phosphonates (Dines et al., 1982). Produds of high, presumably internal,
l,
0 1984 American Chemical Society
