liquefaction pathways of bituminous subbituminous coals andtheir

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concentration was determined by reference to a linear regression calibration curve derived from four standard solutions ranging from 0 to 10 ppm no. Samples which exceeded this range were diluted as needed to fall within the calibrated range. The agreement of the AA results with the concentrations determined from the weights of molybdate and buffer used in the Solution preparations is shown in Table 1, The last column of the Table lists the concentration determined by AA and the fifth column lists the concentration of Mo determined gravimetrically in each of the solutions used in this study. The agreement between the two determinations is very good: the gravimetric determination is always within two standard deviation units of the AA result and is often within one unit. There may be a small bias in one of the methods since the gravimetric determination is always lower than the AA determination, but the difference is considered insignificant for the purpose of these experiments. The standard deviations and relative standard deviations were derived from a series of control samples analyzed over the several days of the experiment. The magnitudes of the deviations are similar to those found for the AA technique itself. For example, the nominal 600 ppm controls gave a standard deviation of 27 ppm at both pH levels. This compares favorably with the precision of the AA technique of 42 ppm as determined in separate quality assurance experiments. Thus, the solutions themselves were stable with time and precipitation cannot account for the loss of Mo from solution. A false positive was never obtained for blank samples which were also analyzed routinely in single blind experiments. Results: Aqueous solutions of ammonium heptamolybdate containing up to 3000 ppm molybdenum were allowed to equilibrate with samples of the Argonne Premium Wyodak and Illinois No.6 coals. The loss of molybdate from solution was monitored by AA analyses of aliquots of the supernatant solution. The results obtained using the Wyodak coal at a pH of 2 are shown in v. Molybdate was adsorbed quickly and equilibration occurred within the first 24 hours. At the lowest initial concentration, 60 ppm, the adsorption of Mo was complete: the supernatant solution contained no detectable Mo after the first hour of contact. At 600 ppm, 90% of the Mo was adsorbed resulting in about 2 g of molybdenum being adsorbed per 100 g of as-received Wyodak coal. Increasing the solution concentration by a factor of 2.5 to 1500 ppm resulted in increased adsorption by a factor of about 2. A further doubling to 3000 pprn resulted in an even smaller incremental increase in adsorption, indicating that the amount of molybdate that can be adsorbed is limited. Inspection of the graphs in suggests that under these conditions the limiting value is in the neighborhood of 5%. Buffering the solution pH to 4 resulted in less molybdate adsorption, as can be seen in fiWe 2. Although increasing the initial Mo concentration from 60 through 600 to 3000 ppm resulted in increased amounts of Mo being adsorbed, the equilibrium values are noticeably lower at this higher pH. For the case at 3000 ppm, equilibration at a pH of 4 resulted in the coal adsorbing 3.4% of its weight in Mo; equilibration at a pH of 2 resulted in 4.3% adsorption by coal. Only at 60 pprn where both solutions were depleted in Mo was the amount adsorbed the same. Thus, lowering the PH of the medium effects a larger adsorption of molybdate from solution. 514
Different levels of adsorption occurred when a bituminous coal was used. Similar experiments using the Argonne Illinois N0.6 coal resulted in the data presented in Bigures 3 fi 4 . In contrast to the rather smooth trends discernible at all Mo concentrations for the Wyodak coal, the results for the Illinois coal contained appreciable scatter at the highest Mo concentration. Despite this scatter, some comparisons between the Wyodak and Illinois coals can be made by focusing on the results obtained at the 60 and 600 ppm concentrations. At these lower initial molybdenum concentrations, a rapid equilibration apparent within the first 24 hours was consistent with the rapid equilibration seen for the Wyodak coal. However, the amount of MO adsorbed was much smaller than was seen for the lower rank coal. At 60 ppm, the molybdenum adsorbed was barely above the detection limits at a pH of 2 and at the detection limits at a pH of 4. By contrast, the Wyodak coal adsorbed all of the available Mo under similar conditions. At an initial Mo concentration of 600 ppm, the amount of Mo adsorbed by the Illinois N0.6 coal is only 10% of that adsorbed by the Wyodak coal. Thus, on a weight basis, the Wyodak coal is 10 times more effective at adsorbing molybdenum anions than is the Illinois coal at a pH of 2. Substituting a pH 4 buffer (-4) for the pH 2 buffer ( a w e 9) effected an even greater decrease in lo adsorption for the Illinois N0.6 coal than it did for the Wyodak coal. At the 600 ppm level, the higher pH resulted in the coal adsorbing only 0.13% of its weight in molybdate instead of the 0.51% seen at the lower pH. Thus, the Illinois No.6 coal adsorbs less MO from solution than does the Wyodak coal and the amount adsorbed is more sensitive to the pH of the aqueous solution. DISCUSSION: The results obtained for these two coals appear to be consistent with an adsorption mechanism in which molybdate in solution is in equilibrium with surface-bound molybdate. The extent of surface adsorption is expected to depend on both the concentration of molybdenum in solution and the number of adsorption sites available on the coal surface. Because the coal surface develops more net positive charge at the lower pH, more anion binding sites are expected to become available. Thus, both increasing molybdate concentration and decreasing pH are expected to result in more molybdate being removed from solution. However, the nature of the molybdenum species in solution changes with changes in total concentration of molybdenum(V1) and PH.' For example, at a total Mo(V1) concentration of 50 ppm the predominate species is Mo(0H). at a pH of 2, but Moo,'- predominates at a pH of 4. At a total Mo(V1) concentration of 2000 ppm the predominate species is Mo.0,:- at a pH of 2, whereas HMo70,,'- predominates at a pH of 4. This rich chemistry provides alternate explanations to the observed adsorption trends. Each of these species as well as a number of other minor species may all adsorb with different equilibrium constants. Thus, the details of the adsorption mechanism are not clear. The adsorption sites on the coals are effected by the solution pH. These sites may reside in the organic portion, the mineral portion, or both portions of the coal. Organic functional groups play an important role in the electrokinetic behavior of coal-water suspensions' and the adsorption of molybdate by carbon supports can be related, in part, to the degree of surface oxidation.' Nitrogen heteroatoms, which become positively charged in acid, may also play an important role. It is interesting to note that an atomic MO to nitrogen ratio of 1 corresponds to a 5 515
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
Page 37 and 38: 0 0 0 0 0.000 0.005 0.010 0.015 0.0
Page 39: of these studies indicate that cont
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 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 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
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
Page 175 and 176:
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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