liquefaction pathways of bituminous subbituminous coals andtheir

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liquefaction yields with tar yield. However, the gas yields in liquefaction show an irregular variation with pH and with cation type. For example, the CO, yield is high for the partially barium exchanged Zap lignite, and is significantly reduced for the completely barium exchanged sample. The Wyodak subbituminous coal shows the opposite trend. For the ion-exchanged Zap lignite, the decrease of the CO, yield in liquefaction can be explained by the loss of some organic components, which contain COP-forming functions, during the barium exchange at high pH. Some of these variations could be due to catalysis of secondary gas-phase or gas-solid reactions. For CO evolution in pyrolysis, the demineralized samples show the major evolution at temperatures between 400 and 800 OC. CO evolution also occurs in a similar temperature range for fresh and ion-exchanged samples. However, the evolution is depressed at temperatures lower than about 750 OC, but elevated above this temperature by comparing with that of the demineralized samples. It was also noted that the fraction of CO evolving before 750 OC increases with increasing tar yield, as shown in Fig. 3a for the Zap lignite. This observation is significant. The higher CO evolution at temperatures lower than 750 OC for demineralized samples could be due to more oxygen functions evolving as CO without crosslinking. For ion- exchanged samples, the depressed CO evolution at lower temperatures is probably caused by oxygen retention through crosslinking between oxygen functions, and the CO evolved at 750 OC or above, is likely from the decomposition of the metal carboxylate groups which can produce carbonates as a decomposition product. The raw and cation exchanged samples have a sharp evolution peak in the TG-FTIR analysis, as shown in Figs. 1 and 2. This occurs in the same temperature range as the decomposition of carbonates and could be the result of catalytic gasification of the CO, produced to CO. The correlation of the total CO evolution in coal pyrolysis with pyrolytic tar and liquefaction yields was studied, as shown in Fig. 3b for the Zap lignite. The data shows that both tar and liquefaction yields increase with decreasing total (pyrolysis) CO yield. Therefore, both the relative amount of CO evolved before 750 OC and the total CO evolution are indicators of the extent of crosslinking. Figures 1 to 2 also show that CO, H,O, and low temperature CO evolve in a similar temperature range. This might imply that these products are derived from a consecutive mechanism. The CO, evolution curve does not show as much shape variation with changes in cation content. However, the yield is basically a decreasing function of tar yield. In previous work, the relationship between CO, evolution and crosslinking events has been noted (13-15). This has been explained by the mechanism that elimination of CO, would create aryl radicals to enhance crosslinking. The CH, yield also showed a trend opposite to that of the tar yield for the ion- exchanged samples. This has been generally reported in coal pyrolysis studies. By reincorporation into the solid matrix by more stable bonds, the tar precursors can yield volatiles only by cracking off of small side groups, hence the increased CH, yields with decreasing tar yields. One aspect of the H,O evolution data revealed in Figs. 1 and 2 merits further comment. For samples which contain acidic functions in the salt form, including fresh and barium exchanged samples, there is always a water evolution peak present at around 200 OC. This 200 OC peak is obscure for demineralized samples. It is very likely that this peak is due to the evolution of moisture which is ionically bonded on the salt structure. For vacuum dried samples, it can be seen that the moisture content increases with the amount of barium in the samples, as shown in Table 3. This indicates that the acidic functions in the salt forms attract polar water molecules. These attracted water molecules cannot be removed by vacuum drying, but only by raising the temperature of the sample. Analysis Of Carboxyl and Phenolic Groups by Barium Titration - In theory, all of the carboxyl groups of demineralized samples can be exchanged with barium at pH 8. Consequently, it follows that one could determine the concentration of carboxyl groups in coal by knowing the amount of barium ion exchanged at pH 8. The chemical composition of ash formed by combustion Of the barium exchanged sample is predominantly BaO. Therefore, from the ash 580
content of the samples ion-exchanged at pH 8, one can estimate the concentration of carboxyl groups in the coal. Similarly, the total concentration of carboxyl and phenolic groups can be determined by the ash content of the sample ion-exchanged at pH 12.6. The concentration of phenolic groups can be obtained from the difference of the above two measurements. The concentrations of carboxyl and phenolic groups determined in this manner for Zap and Wyodak are shown in Table 4. The results shown in Table 4 are similar to those determined by Schafer (10, 16) for Australian low-rank coals, using barium titration methods. However, our FT-IR results indicate that not all of these groups can be exchanged and that the cations can interact with additional sites in the coal. This will be the subject of a separate publication. Pyrolysis and Liquefaction of Moisturlzed Coal Samples - Remoisturization of vacuum dried Zap and Wyodak was done in the attempt to understand if moisture uptake for low rank coals is a reversible process and to see if moisture influences the role of the cations. The remoisturized samples were analyzed by programmed pyrolysis with TG-FTIR. Preliminary results show that the moisture content can reach that of the raw samples by remoisturization for Zap, but not for Wyodak. The results for the Zap lignite are shown in Table 3. Furthermore, the chemical structure of the coal samples seems to have been changed by remoisturization, since different CO evolution behaviors were observed. A comparison of the CO, evolution behavior for raw ancfremoisturized coal samples is given in Fig. 4. The detailed liquefaction and pyrolysis results are presented in Ref. 11. In almost every case, the asphaltene yield was increased with moisturization except for the pH 8 Zap, in which case the asphaltene yield was slightly reduced. Interestingly enough, the oil yield was reduced for most of the modified samples with moisturization, except for the demineralized Zap and the pH 12.6 Wyodak. The indication from the above results is that moisturization favors the formation of the larger molecular weight asphaltenes in liquefaction, while the formation of the smaller molecular weight oils is less favored. It is usually shown that the trends for improved liquefaction yields parallel those for improved tar yields In pyrolysis. However, it was found in this study that the influences of moisturization on the yields of pyrolytic tars and liquefaction toluene soluble yields are different in that moisturization does not appear to have a significant effect on pyrolysis tar yields. This indicates that moisture plays different roles for the formation of tars in pyrolysis and coal liquids in liquefaction. A possible explanation for the difference is that most of the moisture is depleted early in the pyrolysis process, whereas the moisture is retained in the reactor during liquefaction and can exist in a liquid phase. This aspect requires further investigation. The resuits also show that the moist samples have higher gas yields in liquefaction than the vacuum dried samples. The increase in gas yield is mainly from CO, and CO (especially CO,), whereas the yields of hydrocarbon gases decrease with moisturization. One possible explanation for this result is that moisture may react with side chain structures in coal, which are the sources for the formation of oils and hydrocarbon gases during liquefaction, to form oxygen functions. The subsequent reaction of these oxygen functions produces more CO, CO and asphaltenes in the liquefaction of moist coals. CONCLUSIONS The conclusions from this study are as follows: The tar yields and liquefaction yields are reduced for all three cations tested (K', Ca", Ba+ +) and are lower for the fully exchanged coals. The ability of cations to act as initial crosslinks is an important aspect of their role in retrogressive reactions. The previously observed correlation between pyrolysis tar and liquefaction yields for coals and modified coals appears to hold for the vacuum-dried cation-exchanged coals, but not always for the re-moisturized coals. 581
Page 1 and 2:
LIQUEFACTION PATHWAYS OF BITUMINOUS
Page 3 and 4:
the conversion of A+P and O+G with
Page 5 and 6:
Asphaltcncs PrCasphaltenCS Cwr%, da
Page 7 and 8:
NEW DIRECTIONS TO PRECONVERSION PRO
Page 9 and 10:
ecause of incorporation of the coal
Page 11 and 12:
should be considered more. The step
Page 13 and 14:
17 18 Run no. 0 cys I ToS-CyS TS-To
Page 15 and 16:
INTRODUCTION Effects of Thermal and
Page 17 and 18:
apid decline in modulus. The loss m
Page 19 and 20:
-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
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0 0 0 0 0.000 0.005 0.010 0.015 0.0
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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
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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 and 72: areas of the particles and the SEM
Page 73 and 74: Experimental Catalyst Precursors an
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: 1 for the Zap lignite. These result
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
Page 123 and 124: Table 1. Products dismbutions (dmmf
Page 125 and 126: - 50 45 40 E 35 2 30 E T) 25 ap 20
Page 127 and 128: Influence of Drying and Oxidation o
Page 129 and 130: FTIR . . of the L m To investigate
Page 131 and 132: CONCLUSIONS The characexizntion of
Page 133 and 134: A b S 0 r b a n C e A b s 0 r b a n
Page 135 and 136: An NMR Investigation of the Effd of
Page 137 and 138: for determining the area of the pea
Page 139 and 140: of the ronl roniponcnte nnd (2) the
Page 141 and 142: 2w 180 160 9 140 120 P loo f 80 P O
Page 143 and 144: 25 I 20 ' + 0 Drying lime, hours Fi
Page 145 and 146: substructure have been identified a
Page 147 and 148: Pyridine extraction showed that 60
Page 149 and 150: Figure 1. Reflected white-light pho
Page 151 and 152: Table 3. Pyridine Extraction Sample
Page 153 and 154: A bang-bang control strategy was us
Page 155 and 156: increased from 120°C to 135”C, r
Page 157 and 158:
* wt% based on the amount of naphth
Page 159 and 160:
Use of Biocatalysts for the Solubil
Page 161 and 162:
Results Enzyme Modification with Di
Page 163 and 164:
Conclusions Reducing enzymes can be
Page 165 and 166:
Dynamics of the Extract Molecular-W
Page 167 and 168:
where yi = (x-xi !/pi. The zero mom
Page 169 and 170:
satisfactory agreement between theo
Page 171 and 172:
0.8 0.6 0.4 0.2 “E \ bo Y, - 1 0
Page 173 and 174:
The Use of Solid State C-13 NMR Spe
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differences lie in the fact that th
Page 177 and 178:
I- z W 0 K W n PROTONATED AROMATIC
Page 179 and 180:
ZAP WIO SIDE CHAINS IN PYRIDINE EXT
Page 181 and 182:
ORGAFlIC VOLATILE MATER AND ITS SUL
Page 183 and 184:
(Figure 1). They indicated that the
Page 185 and 186:
Table 3. Elemental analysis of arom
Page 187:
1- 700'C Figure 3. GClFID chromatog
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