Energy & Fuels 1990, 4 , 236-242
236
alyst system revealed a wide distribution of particle sizes, with many particles between 10 and 100 nm. Energy dispersive X-ray analysis confirmed that the small particles observed in the STEM contained iron, while the matrix as well as the activated carbon blank contained no detectable iron. A typical micrograph is shown in Figure 6, exhibiting the iron-bearing particles (small, dark spots) on the more transparent background of the larger activated carbon particle.
Conclusions It has been shown that an Fe(C0)5 catalyst precursor can produce pyrrhotite particles in the size range 10-20 nm in the coprocessing of Illinois No. 6 coal and Maya ATB residuum. This crystallite size was measured by X-ray diffraction line broadening, and further investigation using Mossbauer spectroscopy and transmission electron microscopy confirmed this measurement. It is believed that this is the first quantitative measurement of the
dispersion of a liquefaction catalyst produced from an Fe(CO), precursor. The initial decomposition of the Fe(CO)5yielded not only pyrrhotite but also very highly dispersed Fe3C and iron oxide/oxyhydroxide. These species were eventually converted to Fel-xS after long reaction times. The crystallite size of the pyrrhotite increased after 1h at reaction temperature (425 "C) due to sintering of the small crystallites. Sintering is not so great a problem with this disposable catalyst since its activity need only be maintained for the short time it passes through the reactor.
Acknowledgment. We gratefully acknowledge the contributions of Cole van Ormer and J. R. Blachere for the transmission electron microscopy, the donation of Maya crude by CITGO, and funding support from the U.S. Department of Energy under Grant DE-FC22-88PC8806. Registry No. Fe, 7439-89-6; Fe(C0I5, 13463-40-6; Fe&, 12011-67-5; pyrrhotite, 12305-96-3.
Distribution and Characterization of Phenolics in Distillates Derived from Two-Stage Coal Liquefaction Richard E. Pauls, Mark E. Bambacht, Cherlynlavaughn Bradley, Stuart E. Scheppele, and Donald C. Cronauer" Amoco Research Center, P.O. Box 301 1, Naperville, Illinois 60566 Received J a n u a r y 18, 1990
The nature and distribution of the phenolic fractions isolated from 175-425 "C coal-derived distillates have been quantified. These products were from liquefaction runs made at the Advanced Coal Liquefaction R & D Facility a t Wilsonville, AL. The concentrations of moderate to low boiling phenolics were determined by isolating an acidic concentrate by extraction with sodium hydroxide, freeing the phenolics by acid addition, and analyzing the fraction by gas chromatography/mass spectrometry and high-resolution mass spectrometry. The phenolics derived from both Illinois No. 6 and Wyodak coals are primarily found in the 175-315 "C boiling range. They chiefly consist of four types of ring structures: phenols, indanols, naphthols, and biphenylols/acenaphthols. Most of these compounds are alkyl substituted with short chains. Longer chains appear to be branched. During liquefaction, the recycling of mineral matter plus uncoverted coal along with the solvent shows catalytic activity for deoxygenation; however, this activity is not selective toward individual phenolic species. With the introduction of a catalyst to the first-stage reactor, additional deoxygenation occurs, and there is a trend toward selectively reducing nonhindered phenolics.
Introduction Coal-derived liquids contain a complex array of aromatic and heteroaromatic compounds. Hydroxyaromatics (phenolics) constitute a major oxygen-containing class found in these liquids.' They are derived from phenolics in the coal and by cleavage of aryl-alkyl ether linkages during liquefaction.2 The amount and distribution of phenolic species in coal and coal-derived liquids have been shown to affect coal degradation and reactivity? upgrading to fuels,4 and ~ t a b i l i t y . Furthermore, ~ most phenolics are (1) Zhou, P.; Dermer, 0. C.; Crynes, B. L. In Coal Science; Gorbaty, M. L., Larsen, J. W., Wender, I., Eds.: Academic Press: New York, 1984; Vol. 3, pp 253-300. (2) Aczel, T.; Williams, R. B.; Brown, R. A.; Pancirov, R. J. In Analytical Methods for Coal and Coal Products: Karr.. C... Ed.: Academic Press: New York, 1978; Vol. 1, pp 449-540. (3) McClennen, W. H.; Meuzelaar, H. L. C.; Metcalf, G. S.; Hill, G. R. Fuel 1983,62, 1422. (4) Sullivan, R. F. Prepr. Pap.-Am. Chem. Soc., Diu. Fuel Chem. 1986, 31, 280.
Table I. Elemental Analyses of Coals (wt '70)" IL No. 6 Wyodak carbon hydrogen nitrogen oxygen (by difference) sulfur ash
67.25 5.24 0.88 17.48 1.04 8.08
Moisture free.
poor solvents for coal liquefaction because of their tendancy to react with coal-derived compounds to produce higher molecular weight compounds. This process is referred to as adduction. In contrast, m-cresol has a positive effect on coal conversion and has a lower tendency for Therefore, knowledge regarding the types (5) Renauld, M.; Chantel, P. D.; Kaliaguine, S. Can. J . Chem. Eng. 1986, 63, 187.
0887-0624/90/2504-0236$02.50/0
70.03 4.90 1.24 8.55 3.76 11.48
0 1990 American Chemical Society
Phenolics
Energy & Fuels, Vol. 4, No. 3, 1990 237
in Distillates from C o a l L i q u e f a c t i o n
HYDROGEN GRS RECYCLE FLRRE LIQUID SOUR 420
MRKE-UP
HZ
CORL
D
REACTOR I
L
-
HP SEPRRRTOR
_C
I
HYDROGEN
OVHO
T 104 L T SOLVENT RECOVERY COLUHN
PRSTING SOLVENT SRHPLE REACTOR I1
V I 0 7 2 PRODUCT PRODUC7
t
*
1
HP SEPRRRTOR
RTMOS FLRSH
VRCUUM FLRSH
{
HYDROGEN VENT GRSES
C
F L R R E LIQUID
C GRS
CSOUR 9 0
RESID
I
CSD
I
RSH-CONCENTRRTE
Figure 1. Schematic of Wilsonville close-coupled, integrated, two-stage liquefaction mode with interstage vapor/liquid separation between reactors.
Table 11. Summary of Wilsonville Runs run no. coal first stage second stage "ashy recycle"
250D
250H IL No. 6 IL No. 6 thermal thermal catalytic catalytic no Yes
251E
251-IIB IL No. 6 Wyodak catalytic thermal catalytic catalytic Yes Yes
251-IIIB Wyodak catalytic catalytic Yes
and amounts of phenolics is of considerable importance in the study of coal liquefaction. A number of workers have previously applied chromatographic and spectroscopic techniques to characterize phenolics in coal In the current study, we have expanded on these techniques to provide detailed characterization of phenolic fractions isolated from 175-425 "C coal-derived distillates from the Advanced Coal Liquefaction Facility at Wilsonville, AL.
Wilsonville Configurations The coal-derived liquids were obtained from the Advanced Coal Liquefaction R & D Facility a t Wilsonville, AL. The samples were from lined-out runs in which the unit was operating in the close-coupled, integrated, twostage liquefaction (cc-ITSL) mode with interstage vapor/liquid (V/L) separation between the two reactors.12-14 The products from five Wilsonville runs were characterized, three from the liquefaction of Illinois No. 6 bituminous coal and two from Wyodak subbituminous coal. The elemental analyses of the two coals are given in Table I. (6) McNeil, R. I., Cronauer, D. C. Fuel Process. Technol. 1984,9,43. (7) Cronauer, D. C.; McNeil, R. I.; Galya, L. G.; Danner, D. A. Prepr. Pap.-Am. Chem. SOC., Diu.Fuel Chem. 1984,29(5), 130. (8) White, C. M.; Li, N. C. Anal. Chem. 1982, 54, 1564. (9) Scheppele, S. E.; Benson, P. A,; Greenwood, G. J.; Grindstaff, Q. G.; Aczel, T.; Beier, B. F. In Chemistry of Asphaltenes; Bunger, J. W., Li, N. C., Eds.; Advances in Chemical Series 195; American Chemical Society: Washington, DC, 1981; pp 53-82. (10) Parees, D. M.; Kamzelski, A. Z. J. Chromatogr. Sci. 1982,20,441. (11)Later, D. W.; Lee, M. L.; Bartle, K. D.; Kong, R. C.; Vassilaros, D. L. Anal. Chem. 1981,53, 1612. (12) Lamb, C. W.; Nalitham, R. V.; Johnson, T. W. Prepr. Pap.-Am. Chem. Soc., Diu. Fuel Chem. 1986, 31(4), 240. (13) 'Technical Progress Report: Run 250 with Illinois No. 6 Coal"; Document No. DOE/PC/50041, 1986 (prepared by Catalytic, Inc.). (14) "Technical Progress Report: Run 251, Part I with Illinois No. 6 Coal and Part I1 & 111 with Wyodak Coal"; Document No. DOE/PC/ 50041-88, 1987 (prepared by Catalytic, Inc.).
Table 111. Oxygen Content and Phenolic Extraction Results of Product Streams from Illinois No. 6 Runs
run 250D run 250H run 251E
T-104 T-104 V-1078 OVHD BTMS ATM (A) Oxygen Content, wt '70 4.77 2.15 0.95 3.53 2.29 0.61 1.26 0.98 0.56
V-1072 VAC 0.95 1.41 0.48
(B)NaOH Extractables, wt '70 run 250D run 250H run 251E
21.3 18.5 4.8
15.2 10.0 2.9
2.7 2.0 2.5
2.3 1.2 0.0
A summary of the five runs is given in Table 11. Four liquid products from each run with Illinois No. 6 coal was examined in this study. These consisted of (1)first-stage V/L separator distillates (T-104 OVHD and T-104 BTMS), (2) atmospheric flash distillates (V-10781, and (3) vacuum flash distillates (V-1072). In addition, selected feed solvent samples were analyzed to check the phenolic material balance. The oxygen content of these streams and their extraction results are given in Table 111. A schematic of run 250D is given in Figure 1, and process details have been reported.12-14 Pilot plant operation was continuous with the recycle solvent consisting of a blend of vacuum overheads (V-1072), residue from the Kerr McGee ROSE critical solvent deashing (CSD) unit, and recycled slurry product from the second reactor in selected runs. These latter runs are designated "ashy recycle" due to the recycling of unconverted coal and mineral matter.14 In the case of the Wyodak coal liquefaction runs, bottoms from the T-104 fractionation unit was also included as recycle. Only an indirect comparison between the Illinois No. 6 and the Wyodak coals can be made due to process changes. Iron oxide was fed at a level of 0.8 lb/100 lb MAF coal in both of the Wyodak runs because it has been reported that the addition of pyrite to the feed slurry promotes the liquefaction of subbituminous ~ 0 a l . l ~Thus, strictly (15) Anderson, E. P.; Alexander, B. F.; Wright, C. H.; Freel, J. Fuel 1985, 64, 1564.
238 Energy & Fuels, Vol. 4, No. 3, 1990
Pauls et al.
Table IV. Summary of GC/MS and GC Conditions
GC/MS column oven program head pressure split ratio injection volume mass resolution source temperature scan rate electron energy
60-m DB-1 50 "C for 4 min, 6 "C/min to 300 "C 20 psig 80:1
3 rL
3000
a -
GC 60-m DB-1 60-250 "C a t 2 OC/min 30 psig 50:1 3 rL
0 Blend of overheads of Run 251-110
fj
0 Blend of T104 OVHD and T104 BTMS 1250DI 0 Blend of R u n 250D First Reactor Product
,
230 "C 0.5 s/decade 70 eV
C
m
b 0
2
speaking, the thermal/catalytic r u n with Wyodak coal does not have a noncatalytic first reactor. Both runs used the "ashy recycle" configuration, so iron was also present in the recycle stream.
Experimental Section Extraction. Analyses were performed using either the as-
received stream sample or a 'phenolic concentrate". This concentrate was obtained by extracting the coal liquid sample with aqueous NaOH at a weight ratio of 1/2. In all cases a 10 wt % NaOH solution was employed. The organic phenolic-free phase is referred to as the raffinate. The concentration of phenols in the sample was taken as the weight gain of the aqueous layer. The aqueous phase was separated and acidified with 20 wt % H2S04 to release a phenolic Concentrate. After phase separation, the aqueous layer was extracted with methylene chloride to obtain additional phenolics. This latter step normally resulted in little additional product. As a check, several samples of previously extracted coal liquid were reextracted with aqueous NaOH, but a t a 1/20 weight ratio. The additional extracted material was typically less than 5 wt % of the original value. When a specific sample was too viscous for extraction, toluene was added to make phase separation easier. Analysis of Phenolic Concentrates. Phenolic concentrates and aqueous phases were analyzed by combined gas chromatography/mass spectrometry (GC/MS) employing a Varian 3500 GC and a VG ZAB-2F mass spectrometer. Table IV contains a summary of GC/MS conditions. Concentrates were dissolved in methylene chloride prior to injection. Phenolic concentrates were also examined directly by gas chromatography. A cleanup of the sample by liquid chromatography was performed in selected cases. These were performed on a column system consisting of a precolumn (Brownlee cyano, 5-pm particles, 30 x 4.6mm) and an analytical column (Alltech cyano, 8-pm particles, 150 X 10 mm). Refractive index detection was employed. Samples were diluted with heptane so that a 2-mL injection volume delivered approximately 50 mg of phenols. Insoluble material was removed by filtration with 0.45-pm disposable filters. The column system was initially equilibrated with heptane at a flow rate of 5 mL/min. After 4 min the mobile phase was switched to 10% methyl tert-butyl ether in heptane. This fraction contained the phenolics. After passage of 50 mL of this mobile phase, the column was backflushed to remove strongly retained material. Gas chromatographic separation of the phenol-containing fraction was performed employing conditions specified in Table IV. Determination of Extraction Efficiency. A solution containing weighed amounts of a coal liquid and phenol-d, was prepared and extracted with sodium hydroxide as described above. The coal liquid was derived from liquefaction of Martin Lake (Texas) lignite at the Wilsonville facility.16 It was a blend of T-104 OVHD and T-104 BTMS. After acidification and back-extraction with methylene chloride, three fractions were obtained: a phenolic concentrate, a raffinate, and an aqueous phase. The aqueous phase was continuously extracted with ethyl acetate to recover organics. The ethyl acetate phase was examined by GC/MS to determine unrecovered phenolics. (16) "Technical Progress Report: Run 255 with Martin Lake, Texas Lignite Coal"; in preparation by Southern Company Services, Inc.; DOE Contract No. DE-AC22-82PC50041.
100 200 300 400 500 Average vapor temperature of distillate cut, O C
Figure 2. Oxygen distribution in the V/L separator distillate
liquids. Known amounts of p-xylene-dIo were added to the original coal liquid, the phenolic concentrate, and the raffinate. A sample of each was introduced into the ion source of an MS-50 mass spectrometer via the all-glass inlet system. Temperatures of the inlet system, transfer line and ion source were 300-325 "C. Low-voltage electron impact spectra (LVEIMS) were obtained at a resolving power of about 18000 using an electron energy that produced a m / z 106 to m / t 91 ratio from p-xylene of about 20:l and a trap current of 100 pA. Homologues of the aromatic compound types present in the three fractions were identified from the experimental masses in the LVEIMS using an error tolerance for formula acceptability of 10 ppm." Relative sensitivities were calculated from the sensitivity of phenol-d, relative to the sensitivity of p-xylene-d,, assuming unit relative mole sensitivites.
Results Distribution of Phenolics. The distribution of extractable phenolics and the concentration of elemental oxygen i n narrow-boiling-range distillate cuts from the liquefaction of both Illinois No. 6 and Wyodak coals follow the same trends. Figure 2 illustrates the elemental oxygen distributions in the blended overheads from run 251-IIB, the blend of T-104 OVHD and T-104 BTMS from r u n 250D, and the total first-reactor product from 250D. The NaOH extractables of the narrow-boiling c u t s were found t o have t h e s a m e distribution as the elemental oxygen. Most of the phenolics were concentrated i n the boiling range of 175-315 "C with a maximum at 230 "C. The 315 '"C upper limit corresponds roughly with the boiling points of 1-and 2-naphthols. In the 230 "C cut of the distillate liquids from the first-stage thermal reactor for both coals, NaOH extractables accounted for 40% of the sample. Less than 5 % NaOH extractables were observed in the c u t s boiling above 315 "C. Experiments were performed to ensure that phenolics could be quantitatively recovered using the described sod i u m hydroxide extraction procedure. We had two concerns regarding the recovery of phenolics. The first concern was the molecular weight dependance of the extraction of phenolics from the coal liquid with aqueous sodium hydroxide. The second was a concern over losses of lighter phenolics to the aqueous phase obtained after acidification. To address these concerns, mass-balance studies were performed. The phenolic distribution i n a coal liquid derived f r o m M a r t i n L a k e lignite was o b t a i n e d b y L V E I M S . After extraction, t h e a m o u n t s of phenolics in the phenolic concentrate and the raffinate were also determined b y LVEIMS. T h e phenolics left in the aqueous (17) Scheppele,S. E.; Chung, K. C.; Hwang, C. S. Int. J . Mass Spec-
trom. Ion Phys. 1983, 49,
143.
Phenolics i n Distillates from Coal Liquefaction
Energy & Fuels, Vol. 4, No. 3, 1990 239
Table V. Extraction Efficiencv of Maior Phenolic Classes
Table VIII. Distribution of Phenolics in V-1078 Streamso
wt % recovered a t alkyl carbon no.'
phenols indanols naphthols
normalized '70 a t alkyl carbon no.
c,
c,
c,
c,
c,
Cs+b
42c 83 83
7OC 78 100
82= 75 71
85 60 73
78 38 63
44 30 38
'Weight percent in phenolic concentrate. Weighted average of all C5+ species detected. cAqueous phase contains remaining wt % of homologue. Table VI. Distribution of Phenols in T-104 OVHD
co
run 250D run 250H run 251E
C1
c2
c3
15 18 5.1
44 45 30
35 31 38
6.0 6.3 26
Table VII. Distribution of Phenolics in T-104 BTMS" normalized % a t alkyl carbon no. cl
phenols indanols naphthols phenols indanols naphthols phenols indanols naphthols biphenylols
0.2 7.0 1.1
Run 1.7 16.4 2.3
c2
c3
250D 7.8 20.7 9.1 3.4 2.8
11.3 0.8
Run 250H 2.9 11.2 26.3 14.4 7.9 1.0 2.2 0.5
5.0 0.8 0.2
Run 251E 1.2 3.5 11.4 12.1 12.7 2.5 2.1 0.7 0.5 2.8 0.8
c4
cS
c6
14.3
6.5
1.3
12.8
2.2
15.3
3.5
0.1 0.1
0.8
0.1
Additional material, not reported in the table, was also present in the extracts and accounts for the remainder of the sample.
phase after back-extraction were determined by GC/MS. Table V contains a summary of the amount of the major classes of phenolics recovered in the phenolic concentrate. The low recovery of phenol (42%) is due to its high solubility in water. For most of the other species, recovery of up to the C3 alkylated species was greater than 70%. The extraction efficiency falls off with increasing ring and alkyl carbon numbers. These nonextracted phenolics remain with the raffinate. The distribution of components in the phenolic concentrates was obtained by combined gas chromatography/mass spectrometry (GC/MS). The areas of the total ion chromatogram were normalized to provide a distribution of the phenolics. Some non-phenolic material was also carried along. Tables VI-VI11 contain a summary of the GC/MS results of the distillate concentrate samples of the Illinois No. 6 coal runs. Figure 3 shows the GC/MS total ion chromatograms of two of the four streams from run 250D; those of the other runs were similar. Emphasis was directed toward the products from the Illinois No. 6 runs with subsequent characterization of only the primary products of the Wyodak runs. These data are given in Table IX. Illinois No. 6 Coal Derived Products. The phenolic concentrates from the T-104 OVHD samples of the Illinois No. 6 runs consisted of phenols containing fewer than four alkyl carbons. Table VI contains a summary of these results. The distribution of phenols in the T-104 OVHD from runs 250D and 250H were fairly similar with C1-and C,-alkylated phenols accounting for over 75% of the total. However, the concentrate from run 251E contained significantly higher amounts of C3-alkylated homologues
cz
c3
phenols indanols biphenylols
2.2 3.2 0.2
Run 250D 12.3 22.2 25.6 7.4 5.8 1.6 0.2
phenols indanols naphthols
2.0 3.6
Run 250H 11.8 21.0 28.0 8.5 3.5 0.9
phenols indanols naphthols biphenylols
1.7 2.3
Run 251E 11.2 21.7 21.9 6.3 4.4 1.3 1.1 1.7
0.2
0.8
normalized % a t alkvl carbon no.
co
c1
c4
c5
15.9
3.4
13.7
1.3
13.4
2.2
C6
0.2
0.3
"Additional material, not reported in the table, was also present in the extracts and accounts for the remainder of the sample.
Table IX. Distribution of Phenolics in Wyodak Coal Runs' normalized % a t alkvl carbon no.
phenols indanols naphthols biphenylols
4.3 8.2 0.4
Overhead 15.9 23.2 19.0 8.7 6.6 1.9 1.1 0.2 0.1
phenols indanols naphthols biphen ylols
0.6 7.1 1.5
Bottom Slurry 4.4 9.7 11.3 10.9 9.6 3.6 2.9 3.2 4.5 0.8 0.3 0.6
7.7 0.2
1.5
6.7 1.9 1.0
0.2
0.2
'Additional material, not reported in the table, was present also present in the extracts and accounts for the remaining material.
T-104 Overhead
1
I I
m C +-
VI078 Distillate
.-m
._ +-
-mm
= 5 0
0 500
1000
Scan number
Figure 3. Total ion chromatograms of T-104 OVHD and V-1078 atmospheric flash distillate run 250D products. See text for details of analysis.
compared to the other two runs (26% vs 6%). As will be discussed, this latter difference may have been due to a difference in the selectivity of the catalyst in the first stage. The flash conditions in the vapor/liquid separator were
Pauls et al.
240 Energy & Fuels, Vol. 4 , No. 3, 1990
ITT II c1
Run250H
c,
0 lobo
C
0 loo,
I
15bO
Scan number
Figure 5. Total ion chromatogram of T-104 BTMS from run
250H.
loo 1
lndanols
I
I I/ 0
600
700
800
900
Scan number
Figure 4. Total ion chromatograms of T-104 OVHD from runs
250H and 251E.
similar enough that there would be essentially no difference in the distribution of phenolics. Figure 4 contains GC/MS chromatograms of the T-104 OVHD from runs 250H and 251E. The results for the T-104 BTMS are reported in Table VII. Comparison of Tables VI and VI1 reveals that the T-104 BTMS contain a more complex array of species than the T-104 OVHD. In run 250D, indanols and naphthols were present as well as phenols. McClennen et al.3 have also reported the presence of high levels of indanols in coal-derived materials. Separate NMR experiments indicated that the hydroxyl group of the indanols is on the aromatic ring. The carbon number distribution of alkyl carbons on the phenols maximized a t C3 with the maximum alkyl carbon number being 6. The principal indanol species were methylindanols which accounted for 16% of the total phenolics in run 250D. Small amounts of naphthol, methylnaphthols, and C2-alkylatednaphthols were also present. In addition, LVEIMS analysis of this stream indicated the presence of some dioxygenated species. These were not observed by GC/MS. A similar distribution of components was found in run 250H. Figure 5 shows the total ion chromatogram of the phenolic concentrate from run 250H. Figure 6 shows single ion traces illustrating the distribution of indanols and naphthols in this sample. These plots indicate the elution ranges of the various substituted compounds. Additional components were found in the T-104 BTMS from run 251E. In this sample the alkyl carbon number of the phenols had a maximum of 4. High levels of C1- and C,-alkylated indanols were found, and naphthols having up to four alkyl carbons were present. Roughly 5% of the normalized area was accounted for by biphenylols or possibly acenaphthols, but these species were not observed in the other two runs. The carbon number distribution of the phenolics from run 251E is consistent with the higher boiling point of these products compared to the other runs. The phenolic concentrates from V-1078 (see Table VIII) atmospheric flash distillate were similar in composition but
co
Naphthols > W
a
504
Co
lo00
1500
Scan number
Figure 6. Single ion traces of indanols and naphthols in T-104 BTMS from run 250H.
lower in amount than those of the T-104 BTMS (see Table VII). The concentrate from run 250D consisted primarily of C,-C,-alkylated phenols and unsubstituted through Cz-alkylated indanols. No naphthols were detected and only 0.4% of the concentrate consisted of biphenylols. Naphthols are apparently much easier to deoxygenate than other phenolics. Similar results were noted for run 250H although no biphenylols were observed in this concentrate. As in the cases of T-104 OVHD and BTMS, the composition of the concentrate from 251E was different from that of the thermal catalytic runs. The final set of concentrates examined by GC/MS were V-1072 samples (data not given). These concentrates were high in boiling point, and they were contaminated with varying levels of hydrocarbons. The concentrate from 250D contained 47% phenols, 34% indanols, and 3.3% biphenylols. In addition, the concentrate contained 13% non-phenolic material. The concentrates from 250H and 251E were similar and also contained appreciable amounts of non-phenolic contaminants, especially pyrenes. The distribution of hindered and unhindered C1- and C2-alkylatedphenols was determined for the T-104 OVHD from runs 250D, 250H, and 251E. The Cz-alkylated phe-
Energy & Fuels, Vol. 4 , No. 3, 1990 241
Phenolics i n Distillates from Coal Liquefaction Table X. Distribution of Hindered and Unhindered C, and C2 Phenols in T-104 OVHD % of C2phenols
run 250D run 250H run 251E
most hindered
moderately hindered
unhindered
3.8 3.7 6.7
40.5 41.0 44.9
55.7 55.3 48.4
o-cresolltotal cresols, %
24 25 39
Table XI. Distribution of Mono- and Disubstituted C2 Phenols in T-104 OVHD w t % of C2phenols dimethylphenols’ ethylphenols* 3,5-dimethyl + 3-ethylphenols
250D 41.0 28.0 31.0
250H 40.8 27.2 32.0
0 All dimethylphenols except 3,5-dimethylphenol. phenols except 3-ethylphenol.
251E 45.7 25.1 29.2 *All ethyl-
nols were divided into three groups: highly hindered (2,6-dimethylphenol),moderately hindered (2-ethylphenol, and 2,3-, 2,4-, and 2,5-dimethylphenols), and unhindered phenols (3- and 4-ethylphenol and 3,4- and 3,5-dimethylphenols). In addition, the ratio of o-cresol (hindered) to total cresols was obtained. These data are presented in Table X. The catalytic effect of the recycle mineral matter (and unconverted coal) is nonselective; i.e., there was no difference in the distribution of hindered phenols in runs 250D and 250H, while the first-stage Amocat 1A catalyst is more specific for removing unhindered phenol. The levels of remaining “most hindered” and “moderately hindered” C2-alkylated phenols were equal in the run 250D and 250H products, and they were higher in the run 251E product (see Table X). In addition, the ratio of o-cresol to total cresols followed the same trend, namely, 24%, 2590, and 39%, respectively. Thus the first-stage catalyst is more selective for reducing less hindered phenols. This effect may even be more pronounced for larger phenolic species. This selectivity toward unhindered phenols may explain the higher levels of C3-alkylated phenols in the T-104 OVHD from run 251E. The level of extractable phenols was lower in this run than in runs 250D and 250H, Le., 4.8% compared to 21.3% and 18.5%, respectively. It appears that the C1- and C2-alkylphenols reacted faster in the catalytic-catalytic mode, and as a result, run 251E was enriched with C,-alkylated phenols. This greater reactivity suggests that the lighter phenols are less hindered (substituted at the 2- or 6-position) than the heavier phenols. Many of the phenols contained multiple alkyl groups on the aromatic ring. Table XI contains a distribution of substitution patterns for the C2-alkylated phenols in the T-104 OVHD from runs 250D, 250H, and 251E. The C2 substituted homologues were selected because pure samples of all nine isomers are available and their GC retention times could be determined. Unfortunately, on our GC column, 3,5-dimethylphenol and 3-ethylphenol could not be resolved. Thus, in Table XI the C,-alkylated phenols are divided into three groups: (1) all dimethylphenols except the 3,5 isomer, (2) all ethylphenols except the 3 isomer, and (3) 3,5-dimethylphenol and 3-ethylphenol. The data indicate that greater than 4090 of the C,-alkylated phenols contain dimethyl groups. The distributions for the products from runs 250D and 250H were nearly identical, while a greater proportion of the 251E phenols appear to have multiple substitution. Again, this is consistent with the first-stage catalyst being selective
for the removal of less hindered phenolics. Wyodak Coal Derived Products. Only blended samples derived from the Wyodak coal were examined. The oxygen content of a blend of products from run 251-IIIB was 0.81% oxygen while that from run 251-IIB was 2.60%. Therefore, only the phenolic products from the thermal/catalytic Wyodak run were characterized. These data are presented in Table IX. The recoverable phenolics in the overhead stream of the V/L stream of run 251-IIB (thermal/catalytic) were primarily phenols with a high degree of alkyl substitution. The number of alkyl carbons appeared to be somewhat larger than that of the Illinois No. 6 products. Substituted indanols and naphthols were also present. The phenolics remaining in the underflow stream included phenols, indanols, naphthols, biphenylols, and minor amounts of several other oxygenates. Small amounts of hydrocarbons were also present in the phenolic concentrate.
Discussion Sizable recoveries of relatively low molecular weight phenolics were obtained from the liquefaction of both Illinois No. 6 bituminous and Wyodak subbituminous coals. These phenolics primarily had boiling points in the range of 175-315 “C. This is similar to the results reported by Gray et a1.18 in an examination of products from the liquefaction of Pittsburgh seam coal using the SRC-I1 process. GC/MS results indicate that major components of the phenolic concentrates derived from both coals are phenols, indanols, naphthols, and biphenylols. Both LVEIMS and NMR revealed the presence of small amounts of dihydroxy compounds. Indanols account for 20-3090 of the extracts. These jndanols have the hydroxyl group on the aromatic ring, as shown by NMR. They should donate hydrogen, perhaps a t a low level compared to tetralin-type hydroaromatics. However, the resulting indanol radical has a high potential to adduct, thereby being lost and also increasing the molecular weights of the products. Essentially all of the phenolics are alkyl substituted. Alkyl groups containing up to four carbons were most abundant. A 13C NMR examination of the phenolic concentrate of the run 250D/T-104 BTMS indicated that about 57% of the carbons are aromatic. Of the aromatic carbons, about 34% are unsubstituted, about 8% are hydroxyl substituted, and 15% are alkyl substituted or bridgehead carbons. Therefore, only one to two of the aromatic carbons per ring are substituted. From the GC analysis, the C2 phenol fraction contained a t least 40% disubstitution. Based upon the NMR spectra, aliphatic substituents containing three or more carbons are likely to be branched. The catalytic activity of the ”ashy recycle” mode (recycle of unconverted coal plus mineral matter) was confirmed by noting sizable reductions in the oxygen content and in the percent extractables from that of operation with recycle of liquids plus residue as solvent (run 250D vs run 250H). Specifically, with Illinois No. 6 coal there was a reduction in the oxygen content from 4.8 to 3.5 wt % in the T-104 OVHD. This catalytic activity is not selective for individual types of phenolics. However, the first-stage catalyst (CoMo on alumina) is selective as indicated by a higher level of hindered phenolics being present in run 251E products. Because of this selectivity toward nonhindered (18) Gray J. A.; Holder, G. D. “Selected Physical, Chemical and ThermodynamicProperties of Narrow Boiling Range Coal Liquids for the SRC-I1 Process, Supplemental Property Data”; Report No. DOE/ET/ 10104-44, April 1982.
Energy & Fuels 1990, 4 , 242-248
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species, it is anticipated that the more highly substituted and larger ring phenolics will be more difficult to hydrogenate by using this or a similar catalyst. Therefore their relative concentration will increase with further conversion.
Conclusions A study of the extraction and characterization of phenolics from coal-derived products from the Wilsonville facility was performed. Phenolics were separated from first-stage vapor condensates by aqueous sodium hydroxide extraction. For Illinois No. 6 coal with a thermal/catalytic mode, approximately 18 wt % of the liquid product was extracted with NaOH. For the Wyodak subbituminous coal, approximately 21 w t % of the liquid product was extracted. These phenolics consist of phenols, indanols, naphthols, and biphenylols/acenaphthols. Homologues containing one through four alkyl carbons predominate. Phenolics derived from both Illinois No. 6 and Wyodak coals have boiling points primarily in the range of 175-315
"C. The "ashy recycle" mode at Wilsonville (namely, the recycle of some unconverted coal plus mineral matter with the solvent) exhibits a catalytic effect for increased deoxygenation over that occurring with recycle of only solvent plus residue. The use of Amocat-1A catalyst in the first-stage Wilsonville reactor results in further deoxygenation. This catalyst is somewhat specific in that it more easily reduces less hindered phenolics.
Acknowledgment. We are grateful to E. J. Bernier and T. L. Marker for their work on this project. We are also grateful to R. E. Lumpkin, B. A. Fleming, A. Basu, R. W. Dunlap, and E. G. Wollaston for their discussions, P. L. Baldwin for her extraction work, and W. H. Weber, J. M. Lee, and others at the Wilsonville facility who helped in obtaining the samples and operating data. We also acknowledge the funding of the Wilsonville facility by the Department of Energy, The Electrical Research Institute, and Amoco Oil Company.
Coal Solubilization. Promotion of the C-Alkylation Reaction by n -Butyllithium and Potassium tert -Butoxide Kuntal Chatterjee,tp*Mikio Miyake,s and Leon M. Stock*>+ Department of Chemistry, The University of Chicago, Chicago, Illinois 60637, and Department of Applied Chemistry, Osaka University, Osaka 565, J a p a n Received January 26, 1990. Revised Manuscript Received March 16, 1990
A new base-catalyzed C-alkylation reaction that employs a mixture of n-butyllithium and potassium tert-butoxide in refluxing heptane to produce coal anions that are subsequently treated with n-alkyl halides a t 0 OC has been developed and applied. Almost quantitative pyridine solubilization was achieved by C-octylation of a Lower Kittanning coal, PSOC 1197. C-Octylation was less successful for the solubilization of bituminous Illinois No. 6 coal, APCSP 3, and subbituminous Wyodak coal, APCSP 2, which gave 35 and 33% soluble material, respectively. Their 0-methyl derivatives yielded 43 and 20% soluble material in the same reaction. The observations are in accord with the concept of Ouchi and his associates that higher rank coals, although more aromatic in character, have a lower degree of polymerization than low-rank coals. In this situation relatively mild chemical reactions, such as C-alkylation, that lead to modest changes in molecular dimensions can disrupt intermolecular forces and accomplish solubilization of the high-rank coals.
Introduction Most chemical reactions that have been investigated for the transformation of coal to soluble products disrupt strong covalent linkages.'S2 More recently, interest has been directed to the application of simple alkylation reactions that can alter the nonbonded intermolecular interactions that contribute to the binding of large coal molecules in the solid state.2 These strategies are based on the idea that the introduction of an 0-alkyl group can eliminate hydrogen-bonding interactions and the introduction Of a group can disrupt polarization forces. Whereas, 0-alkylation does not generally enhance the solubility of either high- or low-rank to a significant C-alkylation is 'The University of Chicago. *Link Foundation Fellow, 1989-1990. Osaka University.
0887-0624/90/2504-0242$02.50/0
effective for some high-rank coals?-1o Indeed, C-octylation with sodium amide in liquid ammonia converts at least one low volatile bituminous coal from the Lower Kittanning (1) Davidson, R. M. Coal Sci. 1982, 1, 84. (2) Stock, L. M. Coal. Sci. 1982, 1, 161. (3) Mallya, N.; Stock, L. M. Fuel 1986, 65, 736. (4) Ignasiak, B.; Carson, D.; Gawlak, M. Fuel 1979, 58, 833. (5) Gawlak, M.; Carson, B.; Strausz, 0. P. Preprints of Papers, In-
ternational Conference on Coal Science, Maastricht, The Netherlands, 1987; P 57. (6) Lazarov, L.; Marinov, S. P.; Stefanova, M.; Angelova, G. Preprints of Papers, International Conference on Coal Science, Maastricht, The Netherlands. 1987: D 745. (7) Lazarov, L.;'Marinov, S. P. Fuel 1987, 66, 185. (8) Chambers, R. R.; Jr.; Hagaman, E. W.; Woody, M. C. Polynuclear Aromatic Hvdrocarbons: Ebert, L, Ed,: Advances in Chemistrv 217: American Chemical Society: Washington, DC, 1987; Chapter -15, p 255. (9) Miyake, M.; Stock, L. M. Energy Fuels 1988, 2, 815. (10) Chambers, R. R., Jr.; Hagaman, E. W.; Woody, M. C. Preprints of Papers, International Conference on Coal Science, Maastricht, The Netherlands, 1987; p 741.
0 1990 -4merican Chemical Society
