liquefaction pathways of bituminous subbituminous coals andtheir

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i Temperature-Programmed Liquefaction of Coals Using Bimetallic Dispersed Catalysts from Organometallic Complexes Chunshan Song*, Derrick S. Parfitt, and Harold H. Schobert Fuel Science Program, 209 Academic Rojects Building, The Pennsylvania State University, University Park, PA 16802 Keywords: Bimetallic catalysts, coal, temperature-programmed liquefacion Introduction It has been recognized recently that dispersed catalysts are superior to supported catalysts for primary coal liquefaction. Most previous work involved dispersed molybdenum sulfide from a water-soluble salt [Derbyshire, 19881. Some organometallic compounds including metal carbonyls and naphthenates have also been tested as catalyst precursors [Suzuki et al.. 1987; Herrick et al.. 1990; Swanson. 19921. which often requires the addition of sulfur compounds [Yamada et al., 19851. There are some unique advantages of organometallic compounds as catalyst precursors. First. most organometallic compounds are soluble in hydrocarbon solvents and may be used as oil-soluble precursors. Second, as has been demonstrated by Hirschon and Wilson [1991, 19921. some organometallic compounds can be easily decomposed to metal sulfides at low temperatures. The present work is concerned with organometallic precursors which can directly produce metal sulfides upon thermal decomposition. Little work on bimetallic dispersed catalyst for coal liquefaction has appeared, although previous work on multicomponent catalysts has involved the mixture of two or more inorganic salts [Garg and Givens, 1984; Song et al., 1986, 1991; Sommerfeld et al.. 19921. Related to this work is a general observation from previous investigations that there could be synergistic effects between different metals. and an organometallic precursor may be better than an inorganic one. Our interest in the heteronuclear organometallic compounds was stimulated by the recent book on metal clusters published by Mingos and Wales [19901. It seemed to us that highly active catalysts might be prepared from some clusters containing metal-metal bonds. especially the “thiocubane” clusters containing two metals such as Fe or Co and Mo in a single molecule. Two different metals bound together in a single compound should have a more systematic spatial arrangement in the resulting catalytic phase upon thermal decomposition than if two separate compounds were used to introduce the two different metals to a catalytic system. The present work is an exploratory study of bimetallic dispersed metal sulfide catalysts for coal liquefaction. involving the synthesis of the orgnometallic thiocubane clusters that contain Mo and Co as well as sulfur in a single molecule, and liquefaction of coal impregnated with the precursors under non- programmed and temperature-programmed (TPL) conditions, where the programmed heat-up serves as a step for both catalyst activation and coal pretreatment or preconversion. The advantages of temperature-programmed conditions have been demonstrated in our recent work [Song et al.. 1992; Song and Schoben. 1992; Huang et al., 19921. 546
Experimental Catalyst Precursors and Coal Samples Three bimetallic thiocubanes were used as catalytic precursors: MO~CO~S~(S~CNE~~)~(CH~CN)~(CO)~ [MoCo-TCI]. Mo2Co~SqCp~(C0)2 [MOCO-TC~]. and Mo2Co2Sq(Cp")2(C0)2 [MoCO-TC~]. in which Et. Cp and Cp" represent ethyl group, cyclopentadiene, and pentamethylcyclopentadiene, respectively. These thiocubanes were synthesized in our laboratory based on the procedures of Brunner and Watcher [I9821 and Halbert et al. [1985]. For comparative examination, bimetallic metal sulfide complex, cobalt bis-tetrathiomolybdate trianion was also synthesized based on the procedure of Pan et al. [1985]. The trianionic compound, (PPh4)3Co(MoSq)2. is designated as MoCo-S. The U.S. Department of Energy Coal Samples (DECS. #9 and #12) were obtained from the Penn State/DOE Coal Sample Bank. The Montana subbituminous coal (DECS-9, PSOC-1546, < 60 mesh) has the following composition: 24.7% moisture, 4.8% ash. 33.5% volatile matter. and 37.1% fixed carbon on an as-received basis; 76.1% carbon, 5.1% hydrogen, 0.9% nitrogen, 0.3% organic sulfur, and 17.5% oxygen on a dmmf basis. The Pittsburgh #8 bituminous coal (DECS-12, PSOC-1549, < 60 mesh) has the following composition: 2.4% moisture, 10.0% ash, 35.2% volatile matter. and 52.4% fixed carbon on an as-received basis; 84.8% carbon, 5.7% hydrogen, 1.4% nitrogen. 0.7% organic sulfur, and 6.5% oxygen on a dmmf basis. The coals were dried for two hours at 100°C in a vacuum oven before use. Incipient Wetness Impregnation of Catalyst Precursors The catalytic precursors were dispersed on to the coal by the incipient wetness impregnation (IWI) method using organic solvents. IWI method was applied to coal in a previous work [Huang et al.. 19921. Because of the difference in the solubility of the organometallic precursors, several solvents including toluene, THF. CHC13 and acetonitrile were used for dissolving them. The organic solution of a precursor was intermittently added dropwise to the dried coal in a 100 mL beaker, in a fashion that the wet spots over the coal particles do not touch each other, followed by manual stirring with a glass rod until1 all signs of wetness disappeared. In order to keep the metal loading from different precursors at a constant level, we first estimated the incipient wetness volume prior to the catalyst impregnation with a given solvent, which means the total volume of the solvent needed to reach the point of incipient wetness: the point when the solution drops begin to remain on the external surface of the coal. The loading for the bimetallic thiocuhanes was 0.5-0.6 wt% of molybdenum on the basis of dmmf coal. The impregnated coal sample was dried at 100°C for 2 h in a vacuum oven. IWI method is often used for loading inorganic salts from their aqueous solution on to a catalyst support without [Solar et al., 19911. It should be noted that the IWI method used in our work is different from conventional one in that we only use certain amount of solution defined by the estimated incipent wetness volume to achieve a constant metal loading. Liquefaction under SSL and TPL Conditions All reactions were carried out in 25 mL tubing bomb microautoclaves in a temperature-controlled fluidized sandhath. Each reaction used approximately 3 g dried coal. 1-Methylnapthalene was used as the reaction solvent (3 g) unless otherwise mentioned. In several experiments tetralin was also used as a hydrogen-donor solvent (3 g) for comparison. The initial H2 pressure was 7 MPa at room temperature for all the runs. For catalyst screening. single-stage liquefaction (SSL) was performed, where the tubing bomb was rapidly heated to the prescribed temperatures (400-425. "C) for 30 minutes (plus a three minute heat-up period) followed by a rapid quench in cold water bath. Temperature-programmed liquefaction (TPL) had the tubing bomb rapidly heated up to a low temperature (275'C in all the catalytic runs, 200°C in the thermal 541
Page 1 and 2:
LIQUEFACTION PATHWAYS OF BITUMINOUS
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the conversion of A+P and O+G with
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Asphaltcncs PrCasphaltenCS Cwr%, da
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NEW DIRECTIONS TO PRECONVERSION PRO
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ecause of incorporation of the coal
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should be considered more. The step
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17 18 Run no. 0 cys I ToS-CyS TS-To
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INTRODUCTION Effects of Thermal and
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apid decline in modulus. The loss m
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-0.01- . 04 5 -0.03- E 6 -0.0s- c)
Page 21 and 22: Assessment of Small Particle Iron O
Page 23 and 24: yields are calculated by subtractin
Page 25 and 26: conversion is greater than the corr
Page 27 and 28: Table 3. Effect of Superfine Iron O
Page 29 and 30: EFFECT OF A CATALYST ON THE DISSOLU
Page 31 and 32: inherent volatility of Mo(CO), perm
Page 33 and 34: Analysis of the quantity and compos
Page 35 and 36: $ EO .- 0 m L 0 c 0 0 > 40 300 350
Page 37 and 38: 0 0 0 0 0.000 0.005 0.010 0.015 0.0
Page 39 and 40: of these studies indicate that cont
Page 41 and 42: Different levels of adsorption occu
Page 43 and 44: Nominal 2 Table 1. Concentration of
Page 45 and 46: - iF m 1.6 1.4 1.2 - - - 1- 0 0.8 -
Page 47 and 48: RESULTS AND DISCUSSION Swelling of
Page 49 and 50: . . % . . 9 'HF 0 0 0 *. . 0 . . 0
Page 51 and 52: 1.50 KQ 1.00 0.50 I / ' 02 525 I 1
Page 53 and 54: hydrogen atoms. The hydrogen atoms
Page 55 and 56: D to generate more D atoms. It is r
Page 57 and 58: 12. a. Poutsma, M. L.; Dyer, C. W.
Page 59 and 60: Figure 3. Minimum Steps to Explin D
Page 61 and 62: Apoaratus and Procedure Microflow R
Page 63 and 64: Model ComDound Test Figure 5 shows
Page 65 and 66: Figure 1. High resolution gas chrom
Page 67 and 68: Figure 5. Product distribution for
Page 69 and 70: THQ at somewhat higher temperatures
Page 71: areas of the particles and the SEM
Page 75 and 76: impregnating solvent. Table 3 shows
Page 77 and 78: of MoCo-TC2 at the level of 0.5 wt%
Page 79 and 80: Table 4. Effect of Temperature Prog
Page 81 and 82: In the past, chemical treatments in
Page 83 and 84: The effect of Corn20 preaatment on
Page 85 and 86: Reaction Time Figure 1 - Schematic
Page 87 and 88: DISSOLUTION OF THE ARGONNE PREMIUM
Page 89 and 90: A much more def~tive trend is seen
Page 91 and 92: EFFECT OF CHLOROBENZENE TREATMENT O
Page 93 and 94: same conditions and an extraction t
Page 95 and 96: ACKNOWLEDGEMENT The authors thank t
Page 97 and 98: THE STRUCTURAL &=RATION OF HUMINlTE
Page 99 and 100: to be originally derived from demet
Page 101 and 102: 145 30 I --/---Jh I , , I I , 250 2
Page 103 and 104: THE EFFECTS OF MOISTURE AND CATIONS
Page 105 and 106: 1 for the Zap lignite. These result
Page 107 and 108: content of the samples ion-exchange
Page 109 and 110: Table 1. F'yrolysis Results of Vacu
Page 111 and 112: 585 I
Page 113 and 114: EFFECT OF TEMPERATURE, SAMPLE SI2E
Page 115 and 116: of some of the thermobalance runs.
Page 117 and 118: 2. The mechanism of drying is a uni
Page 119 and 120: Influence of Drying and Oxidation 0
Page 121 and 122: "c gives W conversion mpared to the
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Table 1. Products dismbutions (dmmf
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- 50 45 40 E 35 2 30 E T) 25 ap 20
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Influence of Drying and Oxidation o
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FTIR . . of the L m To investigate
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CONCLUSIONS The characexizntion of
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A b S 0 r b a n C e A b s 0 r b a n
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An NMR Investigation of the Effd of
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for determining the area of the pea
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of the ronl roniponcnte nnd (2) the
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2w 180 160 9 140 120 P loo f 80 P O
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25 I 20 ' + 0 Drying lime, hours Fi
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substructure have been identified a
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Pyridine extraction showed that 60
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Figure 1. Reflected white-light pho
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Table 3. Pyridine Extraction Sample
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A bang-bang control strategy was us
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increased from 120°C to 135”C, r
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* wt% based on the amount of naphth
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Use of Biocatalysts for the Solubil
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Results Enzyme Modification with Di
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Conclusions Reducing enzymes can be
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Dynamics of the Extract Molecular-W
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where yi = (x-xi !/pi. The zero mom
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satisfactory agreement between theo
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0.8 0.6 0.4 0.2 “E \ bo Y, - 1 0
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The Use of Solid State C-13 NMR Spe
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differences lie in the fact that th
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I- z W 0 K W n PROTONATED AROMATIC
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ZAP WIO SIDE CHAINS IN PYRIDINE EXT
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ORGAFlIC VOLATILE MATER AND ITS SUL
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(Figure 1). They indicated that the
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Table 3. Elemental analysis of arom
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1- 700'C Figure 3. GClFID chromatog
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