Ind. Eng. Chem. Process
Des. Dev. 1983, 22, 401-409
Nomenclature
C = conversion factor between partial pressure and concentration, mol/m3, Pa E = eddy diffusivity, m2/s H = height of an increment, m H,, = total bed height, m I = increment index J = gas component index, J = Hz, CO, CO2, CH4,HZS, H20, 0 2
40 1
conversion rate of C02in the shift reaction rpi,i = Hz, CO, COZ, CHI, H20,HzS;pyrolysis yield of component i, mol/kg of shale V = volumetric gas flow, m3/s uo = superficial gas velocity, m/s u = gas velocity, m/s y = dispersion parameter, dimensionless L i t e r a t u r e Cited Berggren, J.C.; Bjerle, I.; Eklund, H.; Karlsson, H.; Svensson, 0. Chem. Eng. Scl. 1980, 35, 448. BJerle, I.; Eklund, H.; Svensson, 0. I d . Eng. Chem. Process Des. Dev. 1980, 19, 345. Bjerle, I.;Eklund, H.; Llnn6, M.; Svensson. 0. I d . Eng. Chem. Process Des. D e v . 1982, 21, 141. Eklund, H.; Llnder, 0.; Svensson, 0. “A Klnetlc Study of the Heterogeneous Shlfi Reactlon over Shale Char and Kerogen Free Ash”; Report, Lund Instltute of Technology, Dept of Chemical Engineering, 1980. Qeldart, D. Powder Techno/. 1973, 7, 285. Kato, K.; Wen, C. Y. Chem. Eng. Scl. 1969, 24, 1351. Park, D.; Levensplel. 0.: FitzgeraM, T. J. Fuel 1981, 60, 295.
kl, k4 = constants, l / s k2: k3, k5,k6’ = constants, 1/Pa k3 = constant, 1/Pa0.= k6 = constant, 1/Pa0.05 k7 = constant, mol/kg, s, Pa2 k8 = constant, dimensionless K H Kco KCO,K H = constants, 1/Pa P, $Azo, P&, PCO, $H2 = partial pressure, Pa R = production rate, mol/s rc = reaction rate of fixed carbon, mol/kg, s reo, = reaction rate of C02 in ri, i = 1-3 reaction rate of f i e d
Received for review January 28, 1982 Accepted August 27, 1982
Hydrocracking Polycyclic Hydrocarbons over a Dual-Functional Zeolite (Faujasite)-Based Catalyst Henry W. Haynes, Jr.’ Chemlcal Englneerlng Department, Unlverslty of Wyomlng, Laramle, Wyoming 82071
Jon F. Parcher and Norman E. Helmer Department of Chemlshy, Unlverslty of Mlsslsslppl, Unlverslty, Mlssisslppl 38677
Mixtures of two-, three-, and four-ring (naphthalene, phenanthrene, and pyrene) structures were hydrocracked over a nickel-tungsten sulfide uttrastable zeolite Y catalyst. The hydrocracking of tetralin and phenanthrene proceeds by elimination of butanes to form CBand Clo hydrocarbons primarily. Isomerization of saturated six-member rings to methyl-substituted five-member rings is also prominent. The presence of 1-cyclohexyl-2-phenylethane in the products from phenanthrene hydrocracking suggests an akematlve reaction path for the hydrocracking of structures containing adjacent saturated rings. Pyrene hydrocracking proceeds primarily by elimination of propane followed by butanes ellmination, Le., CIB -, C,, Clo Ce. The C13intermediates are mostly h drogenated phenalenes. The zeolite-based catalyst was very active in hydrocracking pyrene (critical diameter = 9 ) and smaller molecules. The perhydropyrene component of the feed mixture was relatively inert, but it could not be established whether this was due to a molecular sieve effect or intrinsic chemical kinetics factors.
--
Introduction
In the production of liquid transportation fuels from coal by any of the several “direct” liquefaction routes, catalytic hydrocracking will play an important role. A question arises concerning the effectiveness of zeolite-based hydrocracking catalysts for processing the higher molecular weight and inherently larger molecules typically found in coal liquids. Consider, for example, the critical diameters of some hydrocarbon species which are common to coal liquids (Table I) and contrast these molecular dimensions to the effective pore opening of the zeolite faujasite which is about 8-9 A. Certainly one would expect the larger molecules to be strongly hindered if not totally excluded from the internal catalytic sites of the zeolite crystal. It has been suggested that the initial seat of catalytic activity might be the external surface of the zeolite crystal and that the cracked fragments produced at the surface
Ay
Table I. Approximate Critical Diameters of Some Condensed-Ring Aromaticsa molecule crit diam, it benzene naphthalene, anthracene phenanthrene pyrene coronene
6.7 7.3 7.9 9.0 11.4
a Calculations assume the molecule is planar with bond lengths: C-C = 1.395 it, C-H = 1.084 A , and Van der Waals radius of H atom = 1.2 A .
are rapidly converted to low molecular weight gaseous species upon entering the zeolite voids (Thomas and Barmby, 1968). In support of this view, the patent literature makes reference to poor midbarrel range selectivities when feedstocks containing a substantial amount of ma-
0196-43Q5l83/1122-Q4Q7$Q1.5QlQ @ 1983 American Chemlcal Society
402
Ind. Eng. Chem. Process Des. Dev., Vol. 22, No. 3, 1983
terial boiling above about 375-425 OC are cracked over zeolites (Kelley et al., 1973; Ward, 1974a;Hass et al., 1974). Some commerical midbarrel hydrocracking processes use nonzeolitic catalysts (Ward, 1974b). Several investigators have suggested reducing the zeolite crystallite size (and therefore increasing the external surface area per unit volume) as a means of enhancing activity toward high molecular weight feedstocks (Maher and Schemer, 1970; Schwartz, 1973a, 1973b; Young, 1975). Others propose opening up the pore structure by steaming or chemically dealuminating (Ward, 1973, 1974a,b). As alternatives to zeolite-based catalysts for hydrocracking high molecular weight feedstocks, amorphous silica-aluminas having controlled pore sizes have been developed (Vaughan et al., 1974; Manton and Davidtz, 1979). Granquist and co-workers have developed catalysts based upon small nonporous two-dimensional crystalline aluminosilicates, and these are claimed to have high activity relative to zeolite catalysts most probably as a consequence of decreased pore diffusion limitations (Granquist, 1966; Wright et d.,1972; Capell and Granquist, 1966; Hoffman and Granquist, 1974). Active hydrocracking catalysts are prepared by depositing transition metals on these layered clay-type materials (Jaffe, 1970; Csicsery and Kittrell, 1971, 1972; Swift and Black, 1974). In a similar vein, synthetic crystalline flake-like materials having the chemical and structural characteristics of chrysotile have been found to possess high catalytic activity (Robson, 1973; Arey and Sawyer, 1975). In surveying the literature, one finds very few examples in which heavy coal-derived liquids or model coal liquids compounds have been processed over zeolite catalysts. The most informative work seems to be an investigation by Nace (1970). A series of fused-ring naphthenes was cracked over Rare Earth X zeolite and an amorphous silica-alumina. A decrease in the REHX/Si-A1 relative activity with increasing molecular size was attributed to pore diffusion resistance of the zeolite. Beecher and coworkers (1968) hydrocracked decalin over a Pd-loaded hydrogen mordenite and observed an enhanced activity resulting from partial dealumination of the zeolite. This was believed due in part to a lowered diffusion resistance. In the present study a series of two-,three- and four-ring polycyclic hydrocarbon feeds is prepared and each is hydrocracked over a nickel-tungsten ultrastable zeolite Y catalyst in a laboratory trickle bed reactor. A detailed workup of the reaction products is made possible by utilization of high-resolution capillary gas chromatography and capillary GC/MS. Experimental Section The hydrocracking studies were conducted in a benchscale hydrocracking unit which consists of a fixed-bed reactor heated by an electrical resistance furnance, a high-pressure syringe feed pump, hydrogen compression facilities, two high-pressureaccumulators,a wet test meter, and a gas collection bag. A schematic is presented in Figure 1. The reactor consists of a 0.5-in.heavy wall (0.048 in.) type 316 stainless steel tube packed with catalyst in the central zone (- 15 cm) and 10-20 mesh glass chips in the fore and aft zones. A thermocouple well extends through the bed, and the bed temperature profile can be monitored by means of a movable thermocouple. The tubular furnace is provided with external connections for shunts which can be used to adjust the temperature profie. Hydrogen flow is set by a precision metering valve and monitored by a differential pressure cell connected across a 75-cm capillary with 0.023 cm inside diameter. The capillary pressure is held constant at a pressure 1720 kPa
..
.WTM 8,s
Compressor II
b a l e d L,".
BPR C
co cv DPC
MV
PCO
PO PR
RD
Figure Table 11. Calculated Dry Catalyst Composition ",),WO, NiNH,-USY Al,O,.H,O
2.91w t % 23.66 wt % 13.42 wt %
' Ni2+/Almole ratio =
0.042 NH,+/Al mole ratio = 0.260 Na+]Al mole ratio = 0.01 0.312
(250 psi) above the reactor pressure by a pressure regulator, and reactor pressure is controlled by a back-pressure regulator. The valving arrangement associated with the high-pressure accumulators allows switching from one collector to another without disturbing the system. The product gases are vented through a dry ice-acetone cold trap, a wet test meter, and into a butyl rubber gas bag. The contents of this bag are analyzed immediately upon completion of an experiment. Catalyst Preparation. The starting point for our catalyst preparation is Linde LZ-Y82 (formerly 33-200) powder. According to company literature, LZ-Y82 is an ammonium-exchanged form of a thermally stabilized, partially decationized Linde type Y zeolite. The value given for the unit cell size indicates that LZ-Y82 is an ammonium form of ultrastable zeolite Y, i.e., NH4-USY. The NH4-USY as received was dried for 2 h at 210 "C under vacuum, and 101.64 g (dry weight) was slurried in approximately 250 mL of distilled water in a 1000-mL beaker. A nickel nitrate solution was prepared by adding 12.5359 g of Ni(NOs)2.6H20(Aldrich, 19.7% Ni by analysis) to approximately 250 mL of distilled water. The nickel solution was added slowly to the zeolite slurry with vigorous stirring. After 4.5 h of stirring at room temperature the slurry was filtered and the filter cake was washed with a total of 500 mL of distilled water. The filtrate and washings were collected and analyzed for nickel ion by precipitation with dimethylglyoxime solution. The nickel on catalyst was calculated by difference. The filter cake, NiNH4-USY,was dried and ground to a fine powder in a mortar and pestle. Exactly 10.9681 g of ammonium tungstate, (NH4),W04, (Aldrich, 69.7 wt % W by analysis) was dissolved in about 250 mL of distilled water. This solution was added to 95.7 g of the vacuum-dried NiNH4-USY in four successive impregnations at incipient wetness. A 34.2778 g portion of the W-impregnated NiNH4-USY zeolite powder was mixed with 94.7 g of Conoco Catapal SB (both weights after vacuum drying at 200 "C for 2 h) and the powder was tabletted with approximately 0.5 wt % graphite as a lubricant. The final dry catalyst composition calculated from analysis of the spent nickel solution, recorded weights, and literature provided by Linde, is presented in Table 11.
Ind. Eng. Chem. Process Des. Dev., Vol. 22, No. 3, 1983 403
Table 111. Hydrogenated Phenanthrene Feed Composition" mol component formula wt % 2.3 perhydrophenanthrene isomers
Table IV. Hydrogenated Pyrene Feed Composition" mol
component perhydrophenanthrene
~~~~
unidentified my m-octahydrophenanthrene sy m-octahydrophenanthrene sy m-octahydroanthracene
a
unidentified tetrahydrophenanthrene unidentified dihydrophenanthrene phenanthrene Av mol wt = 184.20;wt % C = 91.29;wt
1.1 10.1 32.4 19.7 0.6 7.7 0.3 11.0 14.8 % H = 8.71.
Prior to charging the reactor, the catalyst was ground and sieved to 10-20 mesh size and calcined in air at 400 "C for 16 h. The catalyst was then presulfided in situ with 5% CSz in cyclohexane at 1820 kPa (250 psi), 300 "C, 2.0 g/(h g) sulfiding feed and 0.25 L (STP) Hz/cm3liquid feed. The temperature was increased gradually (67 "C/h) and held at maximum temperature (300 "C) for 1 h. Feed Preparation. Two prehydrogenated feedstocks were prepared for this investigation. These consisted of a mixture of hydrogenated pyrenes and a mixture of hydrogenated phenanthrenes. Conditions in the batchwise hydrogenations were selected to keep carbon-carbon bond breakage at a minimum. Our reasons for prehydrogenating the hydrocracking feedstocks were threefold. First, the large heat effect which accompanies the hydrogenation of hydrogen-deficient feedstocks is minimized, thus making it possible to more closely approach isothermal conditions in the hydrocracking experiments. Second, the hydrogenated feedstock is a more realistic choice than pure phenanthrene or pure pyrene from the standpoint of commercial hydrocracker operations. (Commerical hydrwracker feedstocks are nonnally hydrotreated to remove catalyst poisons prior to hydrocracking and some feed hydrogenation is also accomplished.) A third reason for hydrogenating the feedstock was to make the feed more pumpable. The mixture of hydrocarbons was a liquid at room temperature; thus the need for cumbersome heated transfer lines was avoided. The third feedstock employed in this investigation was pure tetralin (Aldrich, 99%). Pure phenanthrene (Aldrich, 98%) or pure pyrene (Aldrich, 99+ 90) were hydrogenated batchwise in a highpressure autoclave with an alumina-supported nickel catalyst (15 wt % Ni). In each case several batches were prepared and combined to make the required amount of feedstock. The preparation of a typical batch of feedstock proceeded as follows. Approximately 40 g of catalyst was reduced in flowing hydrogen at 400 "C for 5 h. After cooling to room temperature, the catalyst was submerged in hydrogenated product oil to prevent direct exposure of the catalyst surface to air. The catalyst and approximately 300 g of phenanthrene (or pyrene) were charged to a 1-L stirred autoclave, and after the system was purged with hydrogen, the hydrogen pressure was set at 10440 kPa (1500 psi). The reactor feed and purge valves were closed and the reactor was heated to a reaction temperature of 300 "C. Additional hydrogen was added as needed to maintain a total pressure of approximately 13890 kPa (2000 psi). Analyses of the prehydrogenated hydrocracking feeds by gas chromatography revealed the compositions of Tables I11 and IV. With the exception of trace quantities of biphenyl, all components of the hydrogenated phenanthrene feed are three-ring species in various states of saturation. Note the presence of considerable quantities
unidentified unidentified perhydropyrene isomers
unidentified
C14H14 C13H16
C14HZ0
C,,H,
decahydrop yrene-A
CMH26 C16HZO
hexahydropyrene-A
C16H'20 C16H26
WL
decahydropyrene-B unidentified a
formula
hexahydropyrene-B Av mol wt = 213.99;wt
C16H16
wt % 0.5 0.3 0.4 39.7 1.1 6.3 39.9 1.2 3.2 6.6
% C = 89.62;wt % H = 10.38.
Table V. Identification of Hydrogenated Pyrenes Perhydropyrene
Decahydropyrene-A (1,2,3,3a,4,5,9,1O,lOa,lObDecahydropyrene)
Decahydropyrene-B (1,2,3,3a,4,5,5a,6,7,8Decahydropyrene)
Tetrahydropyrene (4,5,9,10-Tetrahydropyrene)
w n
Hexahydropyrene-A (1,2,3,3a,4,5Hexahydropyrene)
Hexahydropyrene-B (1,2,3,6,7,8Hexahydropyrene)
I
n Dihydropyrene (4,s-Dihydropyrene)
Pyrene
of sym-octahydroanthracene in the mixture of Table 111. A small amount of cracking occurred during the preparation of the hydrogenated pyrene feedstock, but the total cracked products were only of the order of 1% of the feed mixture. The various hydrogenated pyrenes are identified in Table V. Analytical. Both the gas and liquid products were analyzed on a Hewlett-Packard 5840 gas chromatograph with dual flame ionization detectors. The gas analysis column was a 6 f t X in. 0.d. stainless steel tube packed with 80/100 mesh Chromosorb 102. The nitrogen carrier gas flow was set at 20 cm3/min, and the column was temperature programmed from 100 to 150 "C at a rate of 5
404
Ind. Eng. Chem. Process Des. Dev., Vol. 22, No. 3, 1983
Table VI. Run CCCOP. Run Summary and Product Yields (5.75 g of Approximately 25%NiWH-USY) WIN SUMMARY YIELD PERIOD N O YIELD PERIOD LENGTH HRS EFFECTIVE ISOTHERMALTEMPERATURE C PRESSURE KPA LIQUID FEED RATE CC/HR LIQUID SPACE VELOCITY GM/HR/GM SPACETIME (GM/HR/GM) 1 APPROX H2 TREAT RATE L(STP)/HR APPROX H2 TREAT RATE L(STP)/GM EXIT GAS RATE L(STP)/HR CUMULATIVEHRS ON CATALYST CUMULATIVEGMS OIL/GM CATALYST LIQUID MATERIAL BALANCE WT% CARBONMATERIAL BALANCE WT%
1
2
3
4
12.00 375
7.00 361
5.75 376
4.83
4 .00
10480 3.1 0.54 1.80
I0510
lMlO
380 lO5lO
344 I0510
9 2.8 6.9 18.5 9.9 72.8 95.8
6.2 1.13 0.89 12 1.9 11.4 38 .O 28.1 90.0 95.0
6.2 1.11 0.90 10 1.6 9.4 52.1 51.7 94.3 99.6
12.3 2.22 0.45 IO
12.3 2.23 0.45 10
91.3 1.12 10.1 87.2 14.0 22.8 34.8 0.1 87
96.2 0.55 5.0 22.6 71.2 83.4 95.8 41.6 5.0
100.0 0.70 6.3 33. I 72.5 73.2 137.4 9.9 0.0
5
6
7
8
9
10
II
12
13
14
15'
16'
6.00
7.00 369
4.00 398
3.00 398
15380
6.30 370
l05lO 12.3 2.22 0.45
10510 20.8 3.76 0.27 10 0.5 7.6
7.00 370 7 w 6.2 1.12
7.00 375 10490 6.2 1.11 0.90 10 1.6 10.1 147.8
7.00 371 10440 6.2 LO4 0.96
136.3 94.7 95.7
10 1.6 9.1 132.8 175.7 91.2 95.9
2.50 369 10440 20.6 3.71 0.27 13 0.6 12.8 139.5 191.3 92.6 93.9
3.00 369
6.2 1.11 0.90 12 I .9
7.50 372 10510 6.2 1.12 0.90 12 1.9 11.4 110.7 151.3 86.7 93.7
89.9 96.9
20 10 1 I62 8 2197 886 958
60.2 0.38 3.4 17.5 40.0 85.9 57.4 23.3 41.1
93.1 0.54 4.8 24.4 67.4 80.5 95.2 35.7 7.8
39.0 0.31 2.8 11.6 25.8 91.1 34.5 16.5 61.9
18.4 0.20 I .8 5.1 11.6 96.7 13.4 9.5 82.3
98.5 0.60 5.4 28.0 71.9 77.4 1l1.5 29.6 I .8
99.5" 0.64 5.8 36.2 69.5 69.5 105.4 1.6 0.0
344
8.4 60.4 66.4 93.5 93.4
11.9 68.2 83.3 96.5 96.8
10510 6.2 1.12 0.90 12 I .9 12.4 76.2 94.2 93.1 94.8
72.3 0.48 4.3 22.1 47.7 82.2 65.4
14.7 0.17 1.6 2.9 10.5 98.7 10.8 8.6 86.2
32.9 0.29 2.6 7.6 23.8 95.0 25.6 18.9 68.0
0.8
0.8
10
105.8
0.8 7.5 94.5 119.6
88.8
92.0
93.7
93.7
93.2 0.53 4.7 23.2 69.7 81.6 98.1 35.8 7.6
80.7 0.46 4.2 21.4
11.8 86.7
1m.o
13960 6.4 1.15 0.87 12 1 .8
0.W
10.0 12'2.6 164.3 84.3 95.5
m3.8
l05lO 12.3 2.06 0.49 I1 09 11 6 1698
12
m)3 939 957
CORRECTEDYIELDS BASED ON LIQUID FEED /GM
29.3 29.3
Y.0 82.8 73.5 35.5 21 .o
100.0 0.80 7.2 41.1 66.0 66.0 134.6 3.5 0.0
26.6" 0.15 1.3 4.8 93.7 96.6 l8,4 84.7 0.0
'TETRALIN RUN5 "CONVERSION TO C9.. MOLE%
Table VII. Run CCCO2. Product Yields by Weight Yldd hrW Ne. CIH4 C2H6
C3H8
UHIO UHIO CW12 C5Hl2 C6H14 C6H12 C6H6 C6H12 C7H16 OH14 C7H14 C7H8 C8H16 C8H10 C9H18 C9HI 6 C9H12 ClOH14 C9HlO ClOHl8 CloH14 ClOHl8 ClOHlZ CloHl8 C11H16 CloH12 ClOH8 CllH14 CllHlO C12H16 ClZHlO C13HI8 CI4H24 CI4HZO CI4H20 CI4H20 C13H16 CI4H18 Cl4Hl4 Cl4Hl8 C14H18 CI4HIB CI4H14 Cl4H14 Cl4HlO
Methane Ehne Propane ihtane n-Butane !.Pentane n-Pentane Hexonas Methyl+opmtane Benzene Cyclohexane Heptanes Dimethyl clopentancn Methvlcvzohexone Toluene Alkyicyclohexonea 8 cyclopentanes Alkvlbenrenes
1 1.31 5.05 29.46 24.74 26.68 7.64 4.20 0.79 Tr Tr I .07 0.00 0.00 0.00 Tr 0.00 0.00
0 .00 0.00 Alkylbenzener lndan n.Butylbenzene trans-Decolin Methylindons cis.Decolin
Tetralin Naphthalene Dimethylindons 8 Methyltetralinr Methylnophlhalenes Alkyltetralins 8 indans Biphenyl
0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Tr 0.00 0.00
0.00 0.00 0.00 0.00
0 .00 Butyltetrolins 2.Cyclohexyl. 1-phenylethane
0.00 0.00
0.00 0.00 arym-Octahydrophenanthrene Methylbenzindanr rym-~tohydroanthracene
rym-Octohydrophenanthrene Tetrahydrophenanthrene
Phenanthrene
TOTAL5 'Tetralin Runs
0.54 0.00 3.43 0.47 3.01 0.69 0.00 0.64
1 Tr 0.44 4.22 5.89 11.76 4.75
0.54 3.16 4.40 7.18 0.75 1.16 4.89 2.89 3.85 10.12 3.60 1.11 0.31
3.00 0.67 1.89 1 3.76 0.88 4.80 0.00 1.46 5.80 0.53 3.32 Tr 0.62 Tr 1 .i4 0.79 1.52 0.00 1.37
a
0.27 0.80 6.40 9.82 15.81 8.16 1 .04 5.19 7.24 9.22 I .92 1.43 6.82 3.12 8.09 7.87 6.14 0.00
0.00 I .95 0.00
0.26 0.00
0.00
0.60
1.59
2.30
0.00 2.03 0.00
.w om
0.00
4 0.27 0.29 4.04 6.37 11.16 4.25 1.33 2.25 2.40 5.32 0.83 0.37 2.09 1.72 3.48 4.39 2.73 0.00 0.00 0.71
0.00 0.92
0.00 0.65 0.47 0.00 Tr 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
0.00
0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 l10.05 104.98 106.34
4.80 0.00
0.78
a
0.27 Tr
0.58 0.69 1.22 0.40 TI Tr 0.48 1.11 Tr
0.00 0 .OO 0.45
b Tr 0.18 1.44 1.91
7 0.25 0.48 4.39
3.88
12.22 4.68 0.80 3.01 4.14
1.36 Tr 1.15
I .3l 3.1 1
0.00 0.00 0.00
5.84
8.39 0.60 0.82 4.57 3.14 4.90
0.84
1.32 1.35 1.15 1.12
0.00 0.00 0.00
0.00 0.00 0.00
0.00 0.40 0.00 0.41
0.00 0.91 0.00 0.87
0.00
0.00
0.00
0.00
0.83 0.00 1, 3.53
1.70 0.00 0.00 8.30
0.00
0.00
0.63 Tr
0.00
1.72 6.57 0.66 2.19 0.25
0.39 0.00
0.00 0.00
0.88 0.69
6.81 0.60 3.22 Tr 0.47 0.00 0.75 4.33 8.03 0.90 5.73 0.70 3.77
6.73 6.88 2.87 6.47 0.78 14.30
12.55 2.86 10.37 0.82 12.27
0.00
0.00
0.00
1.90 1.65 1.44 0.35 0.00 Tr
19.42 5.23 14.56 4.31 1.83 3.77
8.28 5.79 6.36 0.73 0.39 0.00
104.31
101.M
102.59
0.30 0.00
0.00
OC/min. The sample was introduced by means of an automatic sampling valve. Preliminary work demonstrated that the detector response was linear over the range of concentrations encountered. The liquid products were coUected in a cold sample bottle, immediately capped, and stored in a freezer. They were then diluted with cold carbon disulfide in the ratio 20 to 1 prior to analysis. When solids were present the entire liquid product was dissolved in carbon disulfide to ensure that a representative sample was available for analysis. The diluted liquid samples were analyzed on a 60-m SP-WOO coated glass capillary column (J & W Scientific, Inc.). From 3 to 5 p L was injected with a typical split at the injection port of 40 to 1. T h e column flow rate (nitrogen) was approximately0.65 cm3/min. The column oven was run isothermal at 50 "C for the first 10 min after injection and then programmed at a rate of 5 OC/min to
1.49
0.00 8.85
8.99 4.06 0.00 0.00 1 .84 2.17
0.00
I
9
0.38 0.68
0.32 0.51 4.01 4.52 8.19
4.92 5.51 9.94 3.79 0.87 2.63 2.60 6.12 0.89
3.00 0.79 2.31 2.1 1 5.24 0.46 Tr 1.91 1.30 4.39 2.82 2.88
0.50 2.42 1.39 5.59 3.94 4.73 0.32 Tr 2.05
0.00 0.00 0.87 0.00 I .21
0.31 1 .64
le
0.28 0.67 5.40 6.22 11.86 4.44 0.70 2.88 3.55 7.87 0.90 0.92 3.69 2.44
6.28 7.89 5.12
0.64 Tr 2.73 0.71 1.78
12 Tr 0.36 2.78 3.09 5.16 1.80 0.42 1.33 1 .I8 3.57 Tr
0 0.37 Tr 1.15 1.25 2.11 0.71 Tr
0.58 0.53 1.37 Tr
14 0.30 0.75 6.06 7.43 13.46 5.59 0.83
3.50 4.61 8.87 0.78
0.00
0.00
1.18
0.89 0.90 2.84
0.32
5.17
0.35 0.92
3.04
1.29 1.89
0.57 0.73
0.00
0.00 0.00
1.55
0.42
0.00
0.00
0.00 0.00 0.00 0.00
Tr 0.00 0.48
0.92 0.00 0.65
0.48 0.00 0.33
0.00
3.50
Tr
0.42
1.82 4.15 11.42 4.34 13.94 0.58 Tr 33.93 2.14 2.56 Tr
0.00
0.00
3.49
0.57 4.72
0.00
5.93
Tr
2.16
0.95
0.00
0.00
0.00
0.00
0.00 0.00
0.00 0.00
0.00
3.20 0.00
1.
4.77 0.50 1.62 Tr 0.52 0.25
0.79 I .28 2.43
0.00 1.69
0.00 0.62 0.00 0.31 Tr
0.40 0.00 0.00 0.00 104.74
1 .38 4.08 0.51 2.69 Tr 0.44 0.00 0.89 1.m 2.26 Tr
2.20 0.00 0.49 0.00 Tr Tr Tr 0.00 0.00 0.00 104.84
0.00
0.00 0.00 0.00 0.00 0.00 0.00 0.00
0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
0.00 6.40
8.84 2.05 7.36
Tr 3.16 0.32 0.90 Tr 0.40 Tr
1 .Y 2.17 0.33 I .82 Tr
0 .OO 6 .04
0.27 Tr 1, 0.00
6.71 2.87 7.69
0.50
0.30 1 .& 0.68 4.26 Tr
.w
.m
1b' 0.34 Tr 1.03 1.25 1.98 0.53 Tr 0.43 1.19 5.24 0.69 Tr 0.64
0.94
0.00 1 .20 0.00
0.45 1 5.05 4.67 0.76 0.74 2.85 4.54 0.31 0.30 0.55 1.07 Tr Tr 0.50 1.21 2.84 2.97 7.38 5.46 I .04 0.60 5.98 5.23 0.67 0.45 6.80 2.30 0.68 1.89 2.89 Tr 5.77 I.96 Tr 2.01 Tr 1.64 0.00 I.06 1.07 0.00 104.19 1W.4.5
15. 0.30 0.70 6.49 14.83 13.92 7.54 0.76 5.71 12.48 16.59 2 1.55 4.74 2.54 7.74 2.19 4.05
1.11 0.45 0.70 0.71 Tr 5.18
6.90 8.60 5.45 1.15 0.30 3.17
0.57 2.41 0.26 5.40
4.41
0.83 3.84
11 0.37 1.26 9.46 13.52 16.52 9.92 1.54 6.63 7.21 8.39 1.?s 1 .Bo 5.69 2.95 7.65 5.42 5.13 0.00
0.00 0.00
0.00
0.00 0.00
0.00 0.00 0.00 0.00 0.00 Tr
0.00 0.00 0.00 0.00 0.00 0.00
0.00 0.00
om
0.00 0.00 0.00 0.00
0.00 0.00 0.00 0.00
0.88
0.00
14.01 1.69 1 .w 6.91 IS.% 7.53 5.54 5.22 11.73 1.40 4.57 0.00 2.31 . ~. 0.98 0.00 0.30 3.10 107.17 102.77 101.76
0.30
0.00 0.00
0.00 0.00
0.00
0.00
0.00
0.37 Tr 0.30
0.00
0.00
0.00 0.00
0.00
0.88 13 27
Tr
0.00 0.00
0.00
0.00
0.00 105.42
0.00
0.00
1M.76
101.34
0.00 0.00
250 "C, where it was again held isothermal for a period of time sufficient to ensure that all the high-boiling compounds had eluted. For a quantitative analysis it was necessary to divide each peak area by an FID response factor (Dietz, 1967) calculated from FID = 1.1 FID = 1.3 - NJ30
N, I6 N,
>6
(1)
where N , = carbon number. As many as 200 peaks were resolved in an analysis of typical products from pyrene or phenanthrene hydrocracking. Identification of these peaks was primarily by GC/MS (Hewlett-Packard 5985) analyses of selected product samples. A 50-m methyl silicone coated fused silica capillary column was used in the GC/MS work. Operating conditions were similar to those chosen for the
Ind. E% CkeFR. Process Des. Dev., Vol. 22, No. 3, 1983 405 Table VIII. Run TMLOQ. Run Summary and Product Yields (5.75 g Approximately 25%NiWH-USY) RUN SUMMARY YIELD PERIOD NO. YIELD PERIOD LENGTH, HRS EFFECTIVE ISOTHERMAL TEMPERATURE,C PRESSURE, KPA LIQUID FEED RATE, CC/HR LIQUIDSPACE VELOCITY. GM/HR/GM SPACE TIME, (GM/HR/GM).I APPROX. HZTREAT RATE, L(STP)/HR APPROX. HZTREAT RATE. L(STP)/GM EXIT GAS RATE, L(STP)/HR CUMULATIVE HRS O N CATALYST CUMULATIVE GMS OIL/GM CATALYST LOUID MATERIAL 8ALANCE WT%
2
1
10.17 372 10650
3.1 0.55 1.82
4.93 372 l05lO 6.1 1.08 0.92 IO 1.6 11.3 32.5 24.5 68.4 77.7
i.: ~~
10.0 l7,4 11.4 55.4 84.5
3 5.00 343 10680
6.1 1.09 0.91 IO 1.6 8.4 41.9 34.9 107.1 109.4
4 2.72 371 10440 12.4 2.21 0.45 I5
1.2 11.4 50.7 48.4 72.9
n.1
5
6.50 393 10510 6.2 1.10 0.91 IO 1.6 7.4 61.1 62.1 82.5
91.3
6
7
8.
9'
10'
11'
12'
13.
6.00 427
13.93 369
3.50 416
3.50 344
11.00 375
IC580 3.1
4.00 368 10440 12.6 2.10 0.48
9.75 369
lOsB0
13.22 368 10510 3.1
10550
10580
10580
10580
6.2 1.03 0.97
12.3 2.06 0.49
6.2 1.10 0.91 IO 1.6 8.3 72.9 74.0 68.2 93.7
0.55 1.82 10
3.2 9.6 90.3 85.1
67.2 87.7
0.51
1.94 10
12
3.4 9.9 114.1 92.9 68.6 1m.2
1.0 13.1 126.1
99.3"
25.7.. 0.12 1.1
107.1
96.2 98.6
10
1.7 10.4 136.4 119.4 93.2 96.5
15
12.3 2.W 0.49 13
1.3 12.6 148.2 138.0 92.5 98.2
16.7 155.0 151.9 97.0 97.6
99.3" 0.52
10.2.' 0.05
4.7 34.9 69.8 69.8
0.5 2.0 97.9 98.5 11.0 91.3 0.0
3.1 0.52 1.94
1.1
3,4 10.8 169.5 162.2 85.8 100.3
10
CORRECTED YIELDS BASED ON LIQUID FEED CONVERSIONTOCIS., MOLE% HYDROGEN CONSUMPTION,L(STP)/GM HYDROGEN CONSUMPTION,W % GASYlELD(CI-CI), W % NAPHTHAYIELD(C5-ClO). W % LlQUlDYlELD(CS+).WT% CS.C8YIELD, MOLE% cP.Cl2 YIELD, MOLE% C13+ YIELD, MOLE%
60.7 0.26 2.3 17.2 33.3 85.2
99.1 0.94 8.5 83.5 24.1 24.9 67.3 0.0 0.9
17.8 0.09 0.8 3.5
21.3
10.9 97.3 21.3 3.9
M.I
86.5
56.5
26.4 0.04 0.3 5.6 14.8 94.7 22.0 10.5 80.6
68.6 0.26 2.3 17.3 44.4 85.0
78.7 21.9 40.8
97.8 0.88 7.9 78.1 27.3 29.8 70.9 1 .2
2.5
63.5 0.46 4.1 30.8 31.6 73.3 65.9 9.0 41.7
0.92 8.3 70.1 38.2 38.2 59.9 1.5 0.0
5.6 92.8 95.5 22.8 80.8 0.0
45.0,. 0.23 2.1 10.6 88.5
91.5 36.9 67.9 0.0
106.5 2.0 0.0
96.7.' 0.66 5.9 39.1 66.9 66.9 99.3
3.8 0.0
'TETIUIIN RUNS "CONVERSION TO C9-,MOLE%
Table IX. Run TMLOP. Product Yields by Weight C O I I M I D CloWcI Y l i W BASEDON LlOUID m D . W K
nold krldNe. ClH4 Methane Elhane QH6 WHB UHlO UHlO CSHI2 C5HlZ -14
w 1 2
W 6 w 1 2
OH16 on14 OH14
Propane i.Butane n.0utane i.Pentane n.Penlone Hexaner M.*lylyclopontane Benzene Cvclohoxane Hbloner
C8n10
Alkylyclohexanes 8 yclopantoner Alkylbmrener
OH18 OH16 m 1 2
C9HIO ClOHl4 ClOH18 ClOHl4 ClOHl8
ClOHlZ ClOHl8
Alkylbanrnes Indan n-0utylbanrene trona-kalln Methylindona clr-kolln
CllH16
ClOH12 ClOH8
Tetrolin
CllHI4 CI2H16
Dinwthyllndanr 8 Methyltetralinr Alkyltelralim L indanr kahydrabonrlndan Iromer. * I 0 4 Tetrahydroocnaphthene
CI~HZZ
C12HI4 Cl2Hl4 Cl4H24 C13H16 C13H16
.
knhlhnlm. ._r
Tetrahydrobanrindan isomer 11 I2 Hexahydrophonalene #I 15
c16H28
Cl4H20 C13H12 Cl4H16 Cl4Hl4 C16H26 C16H20 Cl6H20 C16H20 C16Hl4 C16H16
C16H16 C16H16 c16H12
C16HIO
28.28
19.03 10.07 5.22 2.52
0.44 0.29 4.59 0.00 0.00 Tr 0.56
OH8
CHI6
0.69 4.70 30.85
Dlhydrophenolene. #I23
0.00 0.35 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
Tetrohydropyrene Hexahydropyrene.A Hexohydropyrene-8 Dihydropyrene Pyrene
C17H12 TOTALS *Tetrolin Runs
1.95
0.56 2.48 1.74 1.07 3.27 1.65 0.95 0.58 1.44 1.40 0.00 0.54 0.68 Tr
2.00 0.00
Tr
Tr 0.25
Tr 1.05
1.34 1.20 0.76 1.26
Tr
2.53 1.50 1.23 1.23
Tr
Tr 0.u
6.94 4.22 4.90 4.48 0.43 3.53 5.16 2.46 0.86 0.76
0.89 1.48 0.27 0.83 0.00 1.15 0.89 0.36 1.42 0.30 0.00 Tr Tr
0.44 0.00 0.00
0.00 0.00 0.38 0.00
0.00
Tr
0.00 0.00 0.00
1.95
0.00 0.86
Tr
0.00
1.40 0.29 0.34 0.33 0.61
0.00 0.27
0.00 0.00 0.00 0.00 0.00 0 ..m ..
0.66 0.39 ..
0.00 0.00 0.00
2.89 1.01
0.w
2.15 0.61 0.75 25.88 0.73 1.20
0.00
Pecj?ydropyrme bcahydrapyrene-A kahydropyrene-8
TI
0.79 7.15 4.93 4.09 3.76 0.33 2.16 3.57 0.92
0.00 0.46 0.00 0.32 0.00 0.w
0.00 Tr
0.00 0.00 0.00 0.00 108.49
0.33
0.25
0.69 2.12 3.20 0.41 2.31 1.46 0.67 102.31
Tr Tr
0.00 0.46 0.00 2.02 0.00 0.00 0.77 0.00 0.00 52.66 4.70 7.00 0.44 0.75 4.91 7.51 TI
2.03 2.41 0.00 100.82
GC analyses and the chromatograms were practically identical in appearance. The principal source of mass spectral data was tables published by the American Petroleum Institute, Project 44. Additional information was found in the literature (Kikkawa et al., 1976), and Profeasor Shaichi Kikkawa of Osaka University, Osaka,Japan, graciously provided mass spectral data pertaining to the hydrogenated pyrenes. Mass spectral data pertaining to the CI3 hydrocarbons were obtained from synthetically prepared materials. The GC/MS peak identification was complemented by a boiling point vs. retention time correlation, and when samples of a particular pure component could be obtained, the corresponding peak was identified by comparison of its retention time with that of the unknown peak.
1.66 0.38 0.35 0.00 1.21 0.81
3.51
0.53 1.26 0.94 0.00 0.46 0.71 0.97
2.15 2.96 3.10 3.26 0.40 0.80 1.79 2.26
TI
0.44 0.30 6.59
0.00
Tr
0.00 0.00
0.00 0.34
0.44
0.00
2.28 0.00
Tr
Tr 1.80 0.00
0.00
0.00 Tr
1.66 0.00 0.49
1.73 0.00 0.95
0.w
0.00
0.26 0.31 0.00 0.53 0.34 2.69 0.00 0.00
0.25 0.28 0.00
0.00 3.58 0.00
0.00 22." Tr
0.32 Tr
0.36 0.83 1.24 Tr
2.15 3.98 0.90 101.29
000 0.00
0.00
TF
0.w
0.47 0.00
0.29
0.00 0.00 0.00 om
Tr TI
0.00 0.00
Tr 0.29
0.00 0.00 0.00 Tr
1.16 1.68
1 .80
Tr
0.00
0.00 0.00
0.00
Tr
Tr
0.00 1.68 0.00 0.00 30.26 0.92 1.05
Tr 0.00
0.68
0.76 0.00 0.00
2.21
1.21 0.40 1.10 1 .m 5.5s Tr Tr 0.85
0.47 2.39 TI
0.57 0.00
.
1.62
I .29 0.25
0.00 0.00 Tr 0.00 0.00 Tr 0.00 0.00 0.00 0.00 0.00
19s
Tr 1.18
Tr
0.00 0.00
0.42
0.38
3.05 0.00 0.00
0.00
0.00 1.46 0.00 3.29
Tr
Tr
Tr
26.72 21.43 10.60 4.26 4.61 0.94 5.45 0.30
0.00
0.w
5.12 7.01 0.00 100.34
0.89 0.45 3.16 0.29 1.66 0.00
0.57 2.84 18.54
Tr 0.00
0.00
0.00 42.98 1.72 2.87 0.27 1.37 4.78 7.08
3.15 1 .58 2.64 Tr Tr
2.66 3.68 11.39 7.30 5.81 4.91 0.53 3.58 4.17 2.10 0.78 0.55 2.13 1.46 2.16 2.17 2.16 0.25 0.86 0.97 0.00
0.00 0.47 0.00 1.37 0.00
1.88 0.00
I .56 6.94 34.46 17.32 17.82 9.20 3.17
Tr
2.20 1.14 1.36 1.58
6.62 2.37 12.75
0.51
0:oo
0.00 45.91 3.47 2.48 0.00 000 0.00 0.00
0.00
0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
0.00 0.00 0.00
0.36 0.27 2.11 3.13 4.68 1.67 Tr
1.18
2.54 9.46 0.44 Tr
1.26 0.88 2.87 0.99
0.49 1.19 7.16 11.23 14.86 6.66 0.91 4.92 7.21 23.68 1.16 0.56
2.90
2.01
1.51 12.14 0.00 6.30
0.97
0.W
Tr
6.04 2.00 3.30 3.46 11.46 3.64 11.36 0.40 0.55
20.02 1.88 2.18
0.00 0.00 0.00
0.00 1.11
0.00 0.00 0.00 0.35
0.00 0.00 0.00 0.00 0.38 0.00 0.00 0.00 0.00 0.00
0.G Tr 0.28
0.46 0.77 0.39 Tr
0.40 0.62 3.28 Tr 0.00 Tr Tr 1.15 0.00 0.51
0.00 0.00 0.50 0.36 0.60 1.19 1.77 2.18 4.28 0.85 0.00 n.44 1.76 0.60 0.00 0.00
0.00 3.21 0.00 0.00 0.00 0.00
0.00
0.00 0.00
0.00
0.00
0.00
0.00 0.00
0.00
0.00 0.00 0.00
0.00
0.00
0.00 0.00 0.00 0.00 0.00 0.00
0.00 0.00 0.00 0.00 0.00 0.00
0.00 0.00 0.00 0.00 0.00
o m om
0.00 0.00 0.00
0.00 0.00 0.00 0.00
0.00 0.00 0.00 0.00 0.00
0.00
0.00
0.00 0.00
0.00 0.00
0.00 0.00
0.00 0.00 0.00
0.00 0.00 0.00 0.00 0.00
0.00 0.00 0.00 0.00 0.00
0.00 0.00
0.00
0.00
0.00
0.00
0.91 0.40
0.00
0.00
o m
0.00 0.00 0.00
0.00 0.00 0.00
107.88
104.13
108.28
0.00 0.00 101.08
0.00 0.00
0.00
0.00 0.00
102.10
104.71
100.46
Tr
Tr 0.00 0.00 0.00
0.00
0.00 0.00
0.38
1 .w
0.00 0.00
0.00
0.00
0.35
7.59 16.30 13.80 8.31 1.04 7.02 10.77 15.68 2.17 1.28 3.41 1.94 7.78 0.52 3.18 0.00 0.00 0.44 0.00 0.00 0.00
om
0.00
0.00 0.00 0.00 0.00
0.00 0.00
0.00
0.00 0.00 105.91
Results Two series of runs designated CCCOS and TMLOP were successfully completed at the conditions of Tables VI and VIII, respectively. The corresponding product yield s u m maries are provided in Tables VI1 and IX. More detailed product yields are available (Haynes, 1981). Some of the compounds in these tables are not named, and in most cases the component was not present in large enough concentrations to obtain good mass spectral data. The molecular formula assigned to these components corresponds to the largest mass number observed in the mass spectrum. Run CCCOB was brought on stream with the hydrogenated phenanthrene feedstock of Table I11 and the feed was
'
408
Ind. Eng. Chem. Process Des. Dev., Vol. 22, No. 3, 1983
switched to pure tetralin immediately after the fourteenth yield period (CCCO2-14). The total run duration was 172 h of continuous operation. Operability was generally good for this series of runs. The carbon material balances average slightly below 100%, but all are above 90% and most fall in the range of 95-100%. We consider these material balances to be quite acceptable in view of the losses that always occur during transfer of samples despite efforts to mimimize these losses. The hydrogenated pyrene mixture of Table IV was the first feed to the TMLO2 series which was terminated after 175 h of continuous operation. The feedstock was switched to pure tetralin immediately after the seventh yield period. Operability was not as good for the first seven yield periods of run TMLO2 as was experienced with the CCCO2 series. There was a tendency for plugs to develop in the product lines between the reactor and the product accumulators. Normally these could be eliminated by applying external heat to the suspected plug location, but sometimes it was necessary to drop the pressure downstream of the plug to force material through the line. The carbon material balances were relatively poor also during the first seven yield periods. The high material balance of TML02-3 resulted after the product accumulator was heated, suggesting that material was adhering to the walls of the vessel. Thereafter the accumulator vessels were maintained at an elevated temperature. In contrast to the experience early in run TMLO2, operability was exellent once the feed was switched to tetralin. The carbon material balances for yield periods TML02-8 through TML02-13 are excellent. The temperatures recorded in Tables VI and VI11 are the effective isothermal temperatures (EIT) which are defied as the temperature assumed constant throughout the reactor which would produce the same hydrocracking conversion as observed experimentally. In fact, the reactor did not operate isothermally with temperature spreads of 5 OC typical and on occasions a temperature difference of about 20 "C was observed. A first-order rate model was assumed in calculating the EIT. More details are provided by Haynes (1981). All product yields were corrected to force a 100% carbon material balance. The correction procedure assumes that the gain or loas of carbon material balance is not associated with any particular component, or grouping of components, of the reaction mixture. Relative Reaction Rates. Several factors contributed to make a precise evaluation of the reaction kinetics impossible. The data were limited in extent, and in some cases of poor quality as reflected in the carbon material balance. The deviations from isothermal operation were sometimes substantial. The catalyst deactivated throughout the course of the run. Finally, the contacting efficiency in short laboratory trickle bed reactors can be quite poor, as discussed by Satterfield (1975). Although it is not possible to make a quantitive statement about catalyst activity, it is clear from an inspection of the conversions in Tables VI and VI11 that the catalyst is very active for all three feedstocks. Plots of hydrocracking fiit-order rate constants calculated from runs at a set of base conditions are provided in Figures 2 and 3. The results for phenanthrene hydrocracking reveal an initial decline in activity followed by a leveling off and then an increase toward the end of the sequence of runs. The increase in activity follows a period of operation at higher pressure (CCCOB-11) when some of the deactivated reaction sites may have been rejuvenated. For the phenanthrene and pyrene-based feedstocks the values of ko are
8.0,
::
2.0
t
0 0
50 I00 150 200 CUMULATIVE GMS OIL/GM CATALYST
2 0
Figure 2. Deactivation during the run series CCCOP.
1
0
I 20
I
I
I
I
I
I
40 60 80 I00 120 140 CUMULATIVE GM5 OIL/GM CATALYST
I 160
I,
0
Figure 3. Deactivation during the run series TMLOP.
obtained by extrapolating these plots to zero grams of oil on catalyst. No runs were made with tetralin on fresh catalyst, so initial activities could not be obtained directly. An estimate of the tetralin to pyrene relative activity can be obtained at the point where the switch in feeds was accomplished after TMLO2-7. From Figure 3 it is apparent that this ratio is about 5. (Simii estimates of the relative tetralin to phenanthrene activities after CCCO2-14 are inaccurate since the conversion approaches 100% in both CCCO2-14 and CCCO2-15.) Assuming the relative tetralin to pyrene activities to remain constant at about 5, it is apparent that the initial pseudo-first-order rate constants decreased in the order tetralin ( ~ 1 5>) phenanthrene (=6) > pyrene ( ~ 3 ) Since . no abrupt changes in activity with molecular size are apparent, it seems improbable that there are any molecular sieve effects. Products of Tetralin Hydrocracking. The predominant tetralin hydrocracking products are benzene, n-butane, isobutane, propane, isopentane, toluene, and methylcyclopentane. In addition, there are sizeable quantities of n-butylbenzene,methylindans, and indan. Naphthalene and decalin are also present. The product distribution is plotted by carbon number at several levels of conversion in Figure 4. A t low conversion levels the major cracked products are C6 hydrocarbons and a comparable quantity of butanes. This observation coupled with the presence of large amounts of n-butylbenzene indicates that the major reaction path is ring opening followed by dealkylation of the butylbenzene. Flinn et al., (19601, observed a similar tetralin hydrocracking pattern over a NiW/SiAl (amorphous) catalyst. Isomerization would be expected to accompany the ring opening as the carbonium ion rearranges to a secondary position and then attacks the aromatic ring. Thus, the presence of indan structures is not surprising, and indeed
Ind. Eng. Chem. Process Des. Dev., Vol. 22, No. 3, 1983 407 140
I20
c I
180
I OTML02-12 0 TML02- IO OTMLO2-II ATML02-8
A
0 TMLO2 - 3 0 TMLOZ-4 0 TMLO2 - 2 A TMLO2 - 6
J
Y
5 2
E
80
60
40
Figure 4. Product yields by carbon number for tetralin hydrocracking.
20
0 I20
I
0 ccco2-5 0 CCCOZ-6 0 ccco2-4 A CCCO2-3
CARBON NUMBER
Figure 5. Product yields by carbon number for phenanthrene hydrocracking.
Qader (1973), Yamadaya et al. (1977), and others have made similar observations. The cyclopentanes are expected from the paring reactions of alkylcyclohexanes (Langlois and Sullivan, 1970). Generally speaking, the product distribution observed for tetralin hydrocracking is similar to the product distributions reported in studies of tetralin hydrocracking over dual-functional, nonzeolite catalysts. Products of Hydrogenated Phenanthrene Hydrocracking. The product yields from hydrocracking the mixture of hydrogenated phenanthrenes are plotted by carbon number in Figure 5. In this figure we see peaks a t carbon numbers 10,6, and 4, indicating that the major reaction path is similar to that obsd. in tetralin hydrocracking, i.e., ring opening followed by dealkylation. Substantial quantities of butyltetralins and tetralin are present in the products. The methylbenzindans are presumably formed in an isomerization reaction similar to that observed with tetralin. One interesting observation is the presence of 2-cyclohexyl-1-phenylethane in the product mixture. This compound was also found in the products from phenanthrene hydrocracking over molten salts (Nakatsuji et al., 1978), and it was suggested that the precursor is asym-octahydrophenanthrene which is also present in our reaction mixture. Ring opening a t the 12, 13-position forms a secondary carbonium ion and would therefore be favored over ring opening a t the 10,ll-position which must form a primary carbonium ion. Biphenyl is present in our products, but in very small yields. It was also present in the feed, and ita origin is believed to be the hydrogenation
2
3
4
5
6 7 8 9 IO I / CARBON NUMBER
12
13
14 15
16
Figure 6. Product yields by carbon number for pyrene hydrocracking.
of dibenzothiophene present as an impurity in the phenanthrene obtained from the supplier. This may also have been the source of biphenyl in an earlier report from our laboratory (Wu and Haynes, 1975). In sharp contrast to the investigation of Sullivan et al. (1964),we observed copious quantities of butanes in the products. This has been true in other phenanthrene hydrocracking studies from our laboratory (Wu and Haynes, 1975; Huang et al., 1977). To explain the absence of light paraffins in their own investigation of phenanthrene hydrocracking over a nickel sulfide/silica-alumina catalyst, Sullivan et al. proposed a complex mechanism involving transfer of a butyl group to another reactant molecule followed by simultaneous ring closure and hydrogenation to form a tetracyclic compound which cracked to form two cyclic products. The only products larger than CI4that we observed were some methyl-substituted CI6species in trace amounts. While Sullivan’s results were much different from our own, strong similarities exist between our product distribution and the distribution of phenanthrene hydrocracking products obtained by Nakatsuji et al. (1978) over molten salt catalysts. We have no explanation for the discrepancy between our results and Sullivan’s, but the similarity with Nakatsuji’s results provides further evidence that no molecular sieve effects are operative. Products of Hydrogenated Pyrene Hydrocracking. Hydrocracking of the prehydrogenated pyrene feedstock produced results that are somewhat different from the tetralin and phenanthrene hydrocracking results. The distribution of products contains significant amounts of propane and CI3hydrocarbons. It appears that a major hydrocracking path involves splitting out propane to form a C13species. This is perhaps best illustrated in a comparison of Figure 6 with Figures 4 and 5. At low conversion levels butanes tend to dominate light alkanes produced from tetralin and phenanthrene hydrocracking. However, the propane production equals or exceeds butane production during pyrene hydrocracking, and furthermore, the distribution of products by carbon number indicates a peak at CI3. The propane/butanes ratio tends to increase at the higher conversion levels possibly as a consequence of CI3hydrocracking to Clo hydrocarbons, the most notable of which is tetralin. It would appear that the major re-
408
Ind. Eng. Chem. Process Des. Dev., Vol. 22, No. 3, 1983
Figure 8. Hydrogenated pyrenes yields as a function of conversion.
PRECENT CONVERSION TO C i s
Figure 7. Hydrogenated pyrenes yields as a function of conversion.
Scheme I
CH3-CH2-CH
(
CH2 = CH-CH3
I I
CH -CH -CH 3 2 3
- - CH:
= CH-CH3
action path is in accord with: C16 C13 Clo Cg. It is of interest to observe the distribution of hydrogenated pyrenes as reaction proceeds (Figures 7 and 8). Clearly the various hydrogenated species appear to be trying to establish a chemical equilibrium. Of the major components of the feed, Decahydropyrene-B appears to be the most reactive. One can postulate a carbonium ion mechanism by which this species might crack. The essential features are given in Scheme I. A similiar mechanism could explain another elimination of propane to form a C , hydrocarbon. For example, see Scheme II. The CI3 hydrocarbons present in greatest abundance were found to be phenalene type structures (Table M)in accord with the proposed mechanism. It has been reported (Qader, 1973) that the hydrocracking of pyrene over amorphous dual-functional catalysts involves phenanthrene type intermediates; however, we see no evidence to support such a reaction path in our system. The identification of the C13hydrocarbons was accomplished by comparing the mass spectra obtained from chromatographic separation of the product mixture with
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Ind. Eng. Chem. Process Des. Dev., Vol. 22, No. 3, 1983 409
effective in processing cyclic hydrocarbons as the molecular size is increased. Clearly we have established that faujasitebased hydrocracking catalysts have excellent activities toward molecules having the pyrene structure (critical diameter = 9.0 A) and smaller. The products obtained from hydrocracking two- and three-ring molecules over the NiWH/USY catalyst are similar to products obtained when these same compounds are hydrocracking over dual-functional amorphous hydrocracking catalysts and molten salt (Lewis acid) catalysts. There are no qu-antitative data for the hydrocracking of pyrene over amorphous catalysts for comparison with the present study. On the other hand, there is an indication that a molecular sieve effect may be influencing the product distribution obtained from hydrocracking the hydrogenated pyrene feedstock. As compared with all other components of the feed mixture, the perhydropyrene isomers were relatively inert to hydrocracking. See Figures 7 and 8. Naphthenic hydrocarbons are generally quite reactive in a hydrocracking environment because the secondary and tertiary carbon atoms form relatively stable carbonium ions. As an example, Flinn et al. (1960) obtained much higher conversions of decalin as compared with tetralin when these two pure compounds were hydrocracked over a sultided Ni/Si-Al catalyst at comparable conditions. It seems possible then that the inertness of the perhydropyrene component of the feed mixture may be due to some factor other than chemical reactivity. A possible explanation is the molecular exclusion effect. As discussed by Pauling (1960), the saturated C-C bond length (1.54 A) is slightly larger than the aromatic C-C bond length (1.40 A). Thus the critical diameter of the perhydropyrene molecule may be slightly larger than that of pyrene depending upon the configuration of the molecule. When diffusion is in the configurational zone, differences of the order of tenths of an Angstrom unit in molecular size can have drastic influences on the zeolite diffusivity. Unfortunately, an alternative explanation may be responsible for the refractory nature of perhydropyrene. As compared with the naphthenic species, aromatic compounds generally adsorb more strongly on zeolites. It is possible, therefore, that when a mixture of aromatic and naphthenic compounds is present, the aromatics win in the competition for surface sites. Thus, the exclusion of perhydropyrene from the active sites may be a competitive surface phenomenon rather than a molecular sieve effect. Acknowledgment Funds for this project were provided by the US. Department of Energy under Contract No. DE-AS2277ET10651. Mr. Damon Tat-Man Lai and Mr. Chu-Chi
Chen assisted with the experimental work. Registry No. Tetralin, 119-64-2; perhydrophenanthrene, 5743-97-5;asym-octahydrophenanthrene, 16306-39-1;sym-octahydrophenanthrene, 5325-97-3; sym-octahydroanthracene, 1079-71-6; tetrahydrophenanthrene, 73493-69-3; dihydrophenanthrene,26856-35-9;phenanthrene,8541-8; perhydropyrene, 2435-85-0;decahydropyrene-A, 55821-21-1;decahydropyrene-B, 14698-02-3; tetrahydropyrene, 781-17-9; hexahydropyrene-A, 5385-37-5;hexahydropyrene-B, 1732-13-4;dihydropyrene, 662898-4; pyrene, 129-00-0; nickel sulfide, 11113-75-0;tungsten sulfide, 12627-71-3.
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Received for review April 28, 1982 Accepted October 4, 1982
