Ind. Eng. Chem. Process Des. Dev. 1083,
to apply a distribution of activation energies such as those used by Anthony and Howard (1976) in coal pyrolysis experiments and later by Campbell and co-workers (1980) in oil shale pyrolysis. To that end additional work is in progress to compare this technique with more traditional approaches. Acknowledgment The author would like to thank Brad Perry for his invaluable assistance in separating the petroleum fractions and carrying out the experimental TGA work. Literature Cited Anthony, D. B.; Howard, J. B. AIChE J . 1078, 22(4), 625-656. Bestougeff, M. A.; Gendrel, P. Prepr. Div. Pet. Chem., Am. Chem. SOC. 1084, 9(2), 8-51, Campbell, J. H.; Kosklnas, 0.H.; Stout, N. D. Fuel 1078, 5 7 . 372-376. Campbell, J. H.; Gallegos. 0.; &egg. M. Fuel 1080, 5 9 , 727-732. Collett, G. W.; Rand, B. T h e m h l m . Acta 1980, 4 1 , 153-165. Cotte, E. A.; Calderon. J. L. R e v . Dlv. Pet. Chem., Am. Chem. SOC. 1081, 26(2), 538-547. Cronauer, D. C.; Jewell, D. M.; Shah, Y. T.; Keuser, K. A. Ind. Eng. Chem. Fundem. 1078. 17, 291-297.
22, 619-625
619
Drushel, H. V. Prepr. Div. Pet. Chem., Am. Chem. Soc. 1972, 17(4), F92F101. Flynn, J. H.; Wall, L. A. J . Res. Net/. Bur. Stand., A . Phys. Chem. 1088, 70A (a), 487-523. Friedman, H. L. J . Pokm. Sci., Part C 1085, No. 6, 183-195. Levlnter, M. E.; Medvedeva, M. I.; Panchenkov, G. M.; Aseev, Y. G.; Nedosh Ivln, Y. N.; Finkelshteln. 0.B., Galhkbarov, M. F. Khim. i Tekh. Top/. i Masel 1068, No. 9, 31-35. Moschopedls, S. E.; Parkash, S.; Spelght, J. G. Fuel 1978, 5 7 , 431-343. Rajeshwar, K. Thermochm. Acta 1081, 4 5 , 253-263. RRchle, R. 0.S.; Roche, R. S.; Steedman, W. Fuel 1079, 58, 523-530. Schucker, R. C.; Keweshan, C. F. Prepr. Dlv. FueiChem.. Am. Chem. Soc. 1980, 25(3), 155-165. Sekhar, M. V. C.; Ternan, M. Fuel 1079, 58. 92-98. Shih, S. M.; Sohn, H. Y. Ind. Eng. Chem. Process Des. Dev. 1080, 19, 420-426. Voge, H. H.; oood,G. M. J . Am. Chem. SOC. 1040, 71, 593-597.
Received for review July 21, 1982 Revised manuscript received January 27, 1983 Accepted February 15, 1983 Presented before the Division of Fuel Chemistry, 183rd National Meeting of the American Chemical Society, Las Vegas, NV, Apr 2, 1982.
Characterization and Catalytic Activity of Coal Mineral Matter. 3. Hydrodenitrogenat ion of n -Butylamine Klndtoken Hwal-Der Llut and Charles E. Hamrln, Jr." Department of Chemlcal Engineering and Institute for Mining and Minerals Research, University of Kentucky, Lexington, Kentucky 40506
Catalytic activity of coal mineral matter was tested for hydrodenitrogenation (HDN) of pyrrole, pyrrolidine, and particularly n-butylamine. Reaction was carried out in a pulse reactor at 673 K and 239 kPa. Activity of mineral matter, obtained by low-temperature ashing, from nine U.S. coals, ranged from 1.3 to 52% based on the mean conversion of the HDN of n-butylamine. The activity ranking was Kentucky No. 11 > KY Homestead > Illinois No. 6 > Bruceton 2 Elkhorn No. 1 2 Pittsburgh Seam > Kentucky No. 9 2 Clearfield >> Beulah Lignite. The correlation between activity and surface area was the only one found of statistical significance at the 95% confidence level. Additional results from mixtures of feldspar and LTA showed that the activities based on equal surface area increased with increasing feldspar content. The catalytic poisoning effects of bassanite on HDN as well as the effect of acid, KCI, and H 2 0 pretreatments on the catalytic activii were also determined. The reaction network of HDN was discussed and a denitrogenation mechanism for n -butylamine was proposed.
Introduction Catalytic activity of naturally occurring minerals has been reported since the 1930's. Clays, such as bentonite and montmorillonite, and natural zeolites have been studied extensively. Mineral matter in coal also has catalytic activity. Yavorsky et al. (1972) first pointed out that coal mineral matter behaved as a catalyst during coal liquefaction. Reactions catalyzed by coal mineral matter in liquefaction were reported as hydrocracking, hydrogen transfer, hydrogenation, isomerization, and hydrodesulfurization (HDS). Recently, the catalytic activity of coal mineral matter was tested for the HDS of thiophene, a model organic sulfur-coal compound. It was reported that at 748 K, thiophene conversion with mineral matter from western 'Halcon Catalyst Industries, 33 Industrial Ave., Little Ferry, NJ 07643. 0196-4305/83/1122-0619$01.50/0
Kentucky coal was 12% of that obtained with a commercial cobalt-molybdate HDS catalyst (Morooka and Hamrin, 1978). Other systematic studies for the catalytic HDS activity of coal mineral matter using low-temperature ash (LTA) and pyrite were also reported (Vaidyanathan, 1977; Guin et al., 1979; Garg and Givens, 1982; Johannes and Hamrin, 1983). Hydrodenitrogenation (HDN) is another important reaction in the liquefaction process. Little information on the catalytic HDN activity of coal minerals has been reported. Very recently, Sakata and Hamrin (1983a) reported the HDN activity of mineral matter from two Kentucky coals and compared then with some standard clay samples (Sakata and Hamrin, 1983b). The purpose of this study was to test the HDN activity of coal mineral matter prepared from a series of typical US.coal samples. Then, the HDN activity was correlated with the chemical composition and physical properties of the coal mineral matter. The reactants chosen were pyr0 1983 American Chemical Society
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Ind. Eng. Chem. Process Des. Dev., Vol. 22, No. 4, 1983
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role, pyrrolidine, and n-butylamine because they are representative of the reaction progression from unsaturated ring compound to saturated ring compound to straight chain amine for nitrogen removal from coal. In a previous paper, the characterization of the coal mineral matter samples used in this HDN study was reported in detail (Liu et al., 1983). Experimental Section Apparatus and Procedure. A pulse reactor was used to study the catalytic activity of the coal mineral matter. A flow sheet of the reactor system is illustrated in Figure 1. The same hydrogen as used in the reaction system was fed through the gas chromatograph as a carrier gas. Pulses (1pL) of n-butylamine, pyrrolidine, and pyrrole were injected into a heated injection port (423 K) directly above the reactor. The reactor, made from a 4.57 mm i.d. stainless steel tube, was packed with catalyst and immersed vertically in a fluidized sand bath manufactured by Techne Incorporated. Temperature was controlled to within k0.3 K. The reactor temperature was measured with a sheathed chromel-alumel thermocouple placed on the top surface of the catalyst bed which was supported on a plug of quartz wool. Hydrogen was split into two streams; one flowed through the reactor and to the sampling column at 1.167 mL (STP)/s; the other one flowed directly to the reference column at 0.5 mL (STP)/s. The chromatographic column was packed with a 20% bis(2-methoxyethyl) adipate on 60/80 mesh chromasorb W supplied by Supelco, Inc. This column separated nbutane, 1-butene, trans-2-butene, cis-2-butene, and 1,3butadiene in this order at 308 K and 239 Wa. A primary standard mixture containing all five straighbchain C4gases in He was used to calibrate the gas chromatograph. Detection of unreacted n-butylamine was not attempted. The chromatograph used was a keyboard-controlled 5830 A model with a 18850 GC terminal supplied by HewlettPackard Co. The shut-off valve was designed to allow hydrogen bypass of the gas chromatograph sampling column when the three-way valve was opened to vent during the hydrogen pretreatment of catalyst. Helium was passed over the catalyst during the heat-up and cool-down periods. Catalysts. Mineral matter was obtained by low-temperature ashing of nine US. coals in an oxygen plasma. The low-temperature ash samples were die-pressed under a pressure of 180 MN/m2 for 2 min and ground in an agate mortar and pestle. The crushed particles were then screened, and the -24 +42 mesh fraction was collected. All the catalysts were pretreated with hydrogen a t 723 K for 4 h before activity testing. Hydrogen flow rate for catalyst pretreatment was 15 mL (STP)/s. All LTA samples were characterized by surface area, X-ray diffraction (XRD), and X-ray fluorescence (XRF)
a
Liu e t al. (1983).
32.0 30.3 26.1 21.0 18.0 17.7 17.6 16.0 12.8
4.1 1.8 5.1 3.9 5.9 3.4 ND 3.6 3.8 4.0 f 1.2
Not determined.
before and after this H2pretreatment. Weight losses due to this pretreatment and the results of characterization were reported earlier (Liu et al., 1983). For each run the initial weight of catalyst used was 500 mg (taken after pretreatment) which made a 30-40 mm long bed. Weight losses for the activity run are summarized in Table I. Materials. Ultrahigh-purity hydrogen and helium were used with Oxisorb units to remove trace quantities of water and oxygen. High-purity pyrrole, pyrrolidine, and n-butylamine were Aldrich reagent grade and were used without further purification. Acid, Water, and KCl Treatment. A train of Soxhlet extraction vessels was used to acid-treat low temperature ash samples of 0.5 X loT3to 3.0 X kg. Samples were weighed out to f 1 X lo-' kg and placed in ceramic extraction thimbles. The thimbles were weighed before each extraction in order to determine their net weight gain between each test. This net gain is added to the net figures for kilograms out. The acid solution was prepared from 37% HC1 Fisher Reagent and double-distilled water and titrated to the phenolphthalein endpoint (pH 8.20). The thimbles were placed inside the Soxhlet apparatus and approximately 150 mL of 5% HC1 solution was added to the flasks. The extractors were wrapped with heavy aluminum foil in order to minimize heat losses from the extractors. The hot plates were turned on, and the time at which the solution boiled was recorded as time zero. The particular acid solution used boiled at 372 K. The samples were exposed to the boiling acid for 2 , 4 , or 6 h, after which they were removed from the extractor and the acid solution collected. The solid samples were removed from the extraction thimbles using a Buchner funnel and Fisher ashless filter paper (ash content maximum 1.6 X kg). The samples were washed with approximately 100 mL of double-distilled H20and vacuum dried in an oven at 383 K for about 16 h. The samples were then low-temperature ashed to remove the filter paper and reweighed to determine the final mass. This mass was adjusted to include the residual amount left in the extraction thimble during the process. The results are averaged for the three time periods and no trend with time was found for the LTAs. Results and Discussion Reactivities of Nitrogen-Containing Compounds. Little or no reaction (< 0.1 mol % conversion) for pyrrole and pyrrolidine was found at 673 K; therefore, n-butylamine was selected as a model coal-nitrogen compound. The difference in reactivity among these compounds can be explained by the weak hydrogenation ability of LTA, since the removal of ring nitrogen requires hydrogen saturation of the ring before rupture. This is followed by
Ind. Eng. Chem. Process Des. Dev., Vol. 22, No. 4, 1983 621
c
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Figure 2. Catalytic ranking of LTAs by HDN of n-butylamine.
nitrogen removal from a straight chain amine in the form of NH3. Ranking of Catalytic Activity for HDN. The ranking of mineral matter from nine US.coals, using the mean conversion of the first ten pulses, is shown in Figure 2 based on the HDN of n-butylamine at 673 K. Four groupings of the coals are possible: very active including KY No. 11, KY Homestead, and Illinois No. 6 with a range of conversion from 52.0 to 40.6%, respectively. An active group of Bruceton, Elkhorn No. 1, and Pittsburgh Seam (Ireland Mine) is next with overlapping standard deviations and a mean of 32% conversion. Kentucky No. 9 and Clearfield represent a slightly active group with conversions of 16.5 and 14.2%, respectively. Finally, lignite is basically inactive with 1.3%. The conversions of the very active group of LTAs are quite impressive when compared to a commercial catalyst (Harshaw Ni-4301, 6% Ni and 19% W as oxides on silica-alumina, 230 m2/g) which gave a mean conversion of 37.8% under comparable conditions. It must be emphasized, however, that this catalyst was not presulfided and was most likely developed for the ring saturation and/or rupture steps which are considered rate-limiting in commercial applications. The C4 product was pure n-butane and more cracking products were also found. In earlier studies (Sakata and Hamrin, 1983a,b) at 723 K using a pulse reactor, the following order of n-butyl HDN conversions was found LTA No. 11,42%;Fe203/A1203,39%; A1203,29%; CoMo/A1203 (Harshaw CoMo-402T), 2070, LTA No. 9, 16%; and SO2, 8%. Another interesting finding of that study was that A1203was the only catalyst capable of converting pyrrole and pyrrollidine to any significant degree, namely 28% and 23%, respectively, compared to
