Energy & Fuels 1992,6, 826830
826
Using CO/Water To Hydroprocess Aromatic Containing Feeds Lillian A. Rankel Central Research Laboratory, Mobil Research and Development Corporation, P.O. Box 1025, Princeton, New Jersey 08543 Received April 6, 1992. Revised Manuscript Received August 10, 1992
An aromatic model feed containing 1-methylnaphthalene, quinoline, and dibenzothiophene has been used to demonstrate the potential of hydroprocessing over CoMo, NiMo, or NiW on alumina using the shift reaction (CO + H20) as a hydrogen source. At 8.7 MPa (1300psig), the shift reaction produced about 80% as much hydrogenation and 90% as much desulfurization as achieved with hydrogen at equivalent partial pressures. When a light cycle oil (LCO) was processed with the shift reaction at identical conditions, about 75% desulfurization of LCO occurred and 125-160 L of H2/L of oil was consumed with CoMo or NiMo on alumina. With LCO, NiW/alumina showed rapid aging but a NiW/zeolite catalyst showed good hydroprocessing activity and about 160 L of H2/L of oil consumption. When hydrogen was used with LCO, about 215 L of H2/L of oil was consumed for aromatics hydrogenation and desulfurization using these supported catalysts. The hydrogenation and desulfurization activities of these catalysts are ranked and potential applications for shift reaction hydroprocessing are discussed.
Introduction
-
There have been many reports suggesting advantages for using the water gas shift reaction (CO + H2O COZ + H2) as a source of hydrogen for coal sol~bilization,~-~ oil shale conversion,6 heavy oils c o n ~ e r s i o nolefin , ~ ~ ~ hydrocracking,g or model compound hydroproceasing.loJ1 However, little information was reported on hydroprocessing multicomponent model feeds or light cycle oil over Catalysts with the shift reaction (CO/water). Kumar, for instance, studied desulfurization of dibenzothiophene over a NiMo/ alumina catalyst with the shift reaction, and no comparisons with hydrogen were made.I0 Murahashi hydrogenated quinolines to tetrahydroquinolines with CO/water under water gas shift conditions using the rhodium carbonyl cluster Rhe(CO)l6.l1 Here, a multicomponent feed containing aromatics, nitrogen, and sulfur components was hydroprocessed with CO + HzO to compare the results of hydroprocessing with CO + H20 vs Hz. CoMo, NiMo, or NiW on alumina catalysts were used. Once hydroprocessing with CO + H2O was demonstrated with a model feed, an Arab Light FCC light cycle oil (LCO) was used with the shift reaction to determine whether a higher boiling, high sulfur multiringed aromatic feed with alkyl substituents could be (1) Fischer, F.; Schrader, H. Brennst-Chem 1921,2, 257-261. (2) Mills, A. Ind. Eng. Chem. 1969,61, 6-17. (3) Appell, H. R.;Wender, I. Presented at the 156th Meeting of the
American Chemical Society, Division of Fuel Chemistry, Atlantic City, Sept. 1968. (4) Newsome, S. Catal. Reo. Sci. Eng. 1980, 21(2), 275-318. (5) Ross, D. S.; Green, T. K.: Mansani, R.;Hum, G. P. Energy __ Fuel 1987, 1, 287-291. (6) Chong, S.; Heppner, R. A. Liq. Fuels Technol. 1983,1,67-88. (7) Stapp, P. R. US Patent 4,560,467, December 24, 1985.
(8)Patel, K. M.;Bekker, A. Y.; Murthy, A. K. S.;Gefri, F. J. US Patent
4,675,097, June 23, 1987. (9) Fujimoto, K.; Suzuki, N.; Tominaga, H.; Kunugi, T. Sekiyu Gakkaishi 1987,30, 124. (10) Kumar,M.;Akgerman,A.;Anthony,R. G. Ind.Eng. Chem.Process Des. Deu. 1984, 23, 88-93. (11) Murahashi, S.; Imada, Y.; Hirai, Y. Bull. Chem. SOC.Jpn. 1989, 62, 2968-2976.
hydroprocessed successfully. For the LCO, the above catalysts were tested as well as a NiW/zeolite material. Again, comparisons with hydrogen were made.
Experimental Section Analyses of the catalysts are given in Table I. CoMo, NiMo, and NiW/alumina or NiW/zeolite catalysts were evaluated for hydrogenation activity using either CO/water (water gas shift reaction) or hydrogen/nitrogen. A 3/s-in. stainless steel reactor was packed with 7.5 cm3 of 30/50 mesh sand, 7.5 cm3 catalyst, and topped with 6 cm3 of 30/50 sand and heated in a three-zone furnace. Catalysts were subjected to a standard presulfidingprocedure. Here, 1.8 L/h of 2% H2S in Hz at atmospheric pressure flowed over the catalyst in the trickle bed. The temperature was ramped from 25 to 400 "C (75-750 "F)over 3 h and then held at 400 OC for an additional 2 h. Immediately after sulfiding, the system was pressured with CO + HzO or Hz + Nz and run. CO, Nz,or Hz was fed into the top of the trickle bed reactor with individual flow controllers while water was delivered with a high-pressure syringe pump. Reaction conditions were 400 "C, 8.7 MPa (1300 psig), and -0.8 LHSV, and -1.0 WHSV based on hydrocarbon. This corresponded to a liquid hydrocarbon feed rate of 0.0057 L/h for all runs. Model feed or LCO was syringe pump co-fed with either carbon monoxide/water at 7.2 and 0.0052 L/h, respectively, or hydrogenlnitrogen at 5.7 and 9.0 LJh,respectively. For the comparison hydrogen co-feed experiments, the hydrogen flow rate corresponded to that which would exist at shift reaction equilibrium for the reaction conditions employed. This hydrogen flow of 0.0057 L/h corresponded to 1006 L of HdL of oil with a 0.0057L/h nitrogen coflow to provide the same hydrogen partial pressure as would exist at shift equilibrium. The shift reaction initially reached equilibrium during the runs discussed here. At equilibrium, the mole percent carbon dioxide should be 38.6% (water-free basis) under the reaction conditions of 400 "C and 8.7 MPa. At the start of some runs, higher than equilibrium values for COz concentration in the offgas likely occurred because of consumption of product hydrogen by the oil, driving the shift reaction to the right and producing higher than equilibrium amounts of CO2.
0887-0624/92/2506-0826$03.00/00 1992 American Chemical Society
Energy & Fuels, Vol. 6, No. 6, 1992 827
Hydroprocessing of Feeds Table I catalyst
""I
---
i
form Alumina-SupportedCatalyst
C o I M o I H z * N2
indicator Switch from CO + HzO lo Hz + N2 Seild Symbols A m Hz DaIa
NiMolHZ
CoMo 2.4% Co 8.4% Mo NiMo 3.0% Ni 9.4% Mo NiW 3.1% Ni 10.5% W
+
Nz
i
1/16-in.extrudate (sized to 12/30)
NiWlH2-
/
//-I
I
t
1/32-in.extrudate (used as is) 1/32-in.extrudate (used as is) Zeolite-SupportedCatalyst
NiW 4% Ni 14% W
1/16-in.extrudate (used as is) (50% zeolite, 50% alumina)
201 0
1
I
2
i
3
4
,
I
5
6
7
Days On Stream
Table 11. Model Feed dibutyl sulfide 1,2,4-trimethylbenzene quinoline l-methylnaphthalene dibenzothiophene hexadecane ~~~
Figure 1. l-Methylnaphthalene hydrogenation in the model feed.
3.4 30.0 4.6 26.0 11.5 24.5
0.75 S 0.50 N 2s
Arab Light Crude Light Cycle Oil (LCO) 87.7 carbon 9.6 hydrogen 0.06 nitrogen 3.1 sulfur Boiling Range, O C IBP-216 216-343 343-454 >454
alumina catalyst/gas CoMo/Hz + Nz COMO/CO+ H2O NiMo/CO + H2O NiW/CO + HzO
Chart I hydrogen produced from CO + HzO (L of Hz/L of oil) run start run end (-5 days) 1032 1032 1015 837 1068 854 819 854
Table 111. Hydroprocessing Model Feed at 8.7 MPa and 400 OC Co+Hzo Hz+Nt feed CoMo NiMo NiW CoMo time on stream (days) 4.0 3.7 4.1 5.2 gw, % Cd- + HzS 6.05 5.78 7.25 5.60 93.95 94.21 92.75 94.40 liquid, % liquid product carbon, % 86.18 88.46 89.32 88.47 87.87 hydrogen, % 9.86 10.70 10.41 10.52 10.99 nitrogen, % 0.47 0.063 0.07 0.13 O.OOO9 sulfur, % 2.75 0.16 0.36 0.098 0.023 ~~
5.6% 80.2% 12.9% 1.3%
All off-gaees were analyzedby a Carle RGAgas chromatograph. By monitoring the amount of carbon dioxide produced, the quantity of available hydrogen could be calculated for the shift reaction runs. Material balances were >98%. Thermogravimetric analyses (TGA) in the presence of HZor air were conducted on CoS2.0, NiS2.0, WSz.3, or MoS2.1 sulfides purchased from Alfa using previously described techniques.'* He gas was saturated with water at 25 OC for water reactivity TGA studies with the metal sulfides. Model Feed. The composition of the model feed is shown in Table I1 and was made with chemicals purchased from Aldrich. CoMo, NiMo, and NiW on alumina were evaluated for desulfurization, denitrogenation, and aromatics hydrogenation activity. Model feed products were identified and quantified using a 60-m column). Initial peak identifications were capillary GC (SP-2100 made by GUMS. Samples of liquid products were sent to Galbraith Labs., Knoxville, TN, for elemental analysis. For CoMo, separate runs were made using hydrogenhitrogen and carbon monoxide/water. NiMo and NiW runs used carbon monoxide/water for 4-5 days and then switched to hydrogen/ nitrogen for comparisons. Light Cycle Oils. An Arab Light crude derived FCC processed light cycle oil was used as the feed (Table I). CoMo, NiMo, or NiW on alumina and NiW on zeolite (Table 11) were evaluated for desulfurization, denitrogenation, hydrogenation activity, and boiling range conversion using either Co + H2O or HZ N2. Boiling range conversion was measured by using GC simulated distillation. GC/MS was used to determine changes in the LCO benzothiophenes as a result of processing. Only CoMo/alumina and NiW/zeolite were used in separate runs with Hz + NZor CO HzO. NiMo and NiW/alumina runs used CO + H2O for 3-5 days and then switched to H2 + Nz for comparisons.
+
+
(12) Rankel, L. A,; Rollmann,L. D. Fuel 1983, 62, 44-46.
~~~~
~~
~
deN, % des, % 1-MeN hydrog.
-
Ph-Ph Ph-cyclohexane Hz circulation, L of Hz/L of oil
Hz consumption
87.0 94.2 31 12 941
85.1 86.9 37 9
72.3 96.4 47 9
868
853
399
254
116
99.8
99.1 64
48 1032
392
Results Model Feed Hydroprocessing. The shift reaction reached equilibrium during the model feed runs at 400 O C and 8.7 MPa. At equilibrium, the mole percent carbon dioxide is 38.6%. At these conditions, initial hydrogen production corresponded to a circulation rate of 1032 L of Hz/L of oil for catalysts with molybdenum but aging caused a decrease in hydrogen production. By the end of the CO + HzO runs, all catalysts produced about 864 L of H2/L of oil HZcirculation rate (or -4800 scf/bbl; scf = standard cubic foot) (Chart 1.) At the temperature and pressure of these experiments, the available hydrogen
-
circulation is more than adequate for complete heteroatom removal and saturation of all aromatics in the model feed. Conversion of l-methylnaphthalene t o l-methyltetralin, 5-methyltetralinI and methyldecalins has been used to measure aromatics hydrogenation activity. All three alumina catalysts (CoMo,NiMo, and NiW) produce about 60 % hydrogenation of l-methylnaphthalene in the presence of Hz Nz (Figure 1 and Table 111). When CO HzO are used as the hydrogen source, 3040% of l-methylnaphthalene is hydrogenated. Hydrogenation activity
+
+
Rankel
828 Energy & Fuels, Vol. 6, No. 6, 1992 Chart 11. Runs with CO + HzO. Amount of Hz Consumption by Gas Production from CO + Hz aluminaL of Hz/L total L of HdL of oil used for of oil consumed supported ~
catalysts Co/Mo Ni/Mo NiIW
t
(daw) 0.1 3.0 0.04 3.7 0.04 4.1
CHa 124 147 152 119
27 17
C ~ H R C3Hs 16 4 32 6 5 11
forgas 144 185 158 130 21
17
byW 177 172 185 151 153 156
0 The incremental percent hydrogen gain times 116 L of Hz/L of oil, plus the N-loss times 111 L of H2/L of oil, plus S-loss times 18 L of H2/L of oil give an estimate of H consumption.
at -4 days on stream for these shift runs follows the order: NiW(-47%) > NiMo(-37%) > CoMo(-31%). In addition, mild aging of the catalysts occurs and hydrogenation activity decreases in the presence of CO + HzOduring 5-day runs. CoMo/Hzshowed no aging during this period. For all Catalysts and conditions, the distribution of 1and 5-methyltetralin was 31-33 % l-methyltetralin and 67-69 5% 5-methyltetralin. About 6 % of the hydrogenated l-methylnaphthalene is converted to decalins for the CoMo/hydrogen run. NiMo/CO + HzO yields about 1% decalins for the first day on stream but then only tetralins are produced. Both CoMo and NiW/shift reaction give only tetralins as hydrogenation products. All runs with CO + Hz0 provide 87-96 % desulfurization while those with Hz + Nz provide >99% (Table 111).The dibutyl sulfide is always completely desulfurized to butane and hydrogen sulfide while some of the dibenzothiophene remains unconverted. Some biphenyl from the desulfurization of dibenzothiophene is hydrogenated to produce phenylcyclohexane. After one day on stream, CO + HzO hydrogenate about 10% of the biphenyl to phenylcyclohexane while the HZ+ NZruns hydrogenate 20-40% of the biphenyl. About 50-70% denitrogenation of quinoline is found for all catalysts with CO + HzO while the hydrogen runs produced 100% denitrogenation. The hydrogen consumption for the CO + Hz0 runs is much higher for the CoMo and NiMo than for NiW on alumina. However, the hydrogen produced by the shift reaction is consumed not only by the model feed but also by reaction with CO to form light hydrocarbons (primarily CH4 and CZ'Sthat are typical products of Fischer-Tropsch synthesis)." It is estimated that Fischer-Tropsch consumes 178 L of HdL of oil hydrogen for CoMo, -125 L of H d L oil for NiMo, and 18L of HzL of oil for NiW runs while about 140-200 L of H2/L of oil is consumed by hydroprocessing the liquid (Chart 11). Evidence for Fischer-Tropsch synthesis comes from material balances and the identified products. When CO + HzO were used, 105-1 105% yields on a hydrocarbon basis were calculated while with Hz the material balances were 98-100 % and no CH4 was produced. At least one-third of the hydrogen generated from the shift reaction is consumed by the production of gas when CoMo or NiMo are used with the model feed. Despite Fischer-Tropsch side reactions, the available hydrogen exceeds the net consumption required for hydroprocessing the model feed. The increased hydrogen content of the liquid products is a measure of useful hydrogen consumption required for upgrading (Table 111). During the first few days on stream, NiW shift produced liquid product with equivalent hydrogen content when compared to CoMo/Hz. However, CoMo is more active catalytically for aromatics hydro-
-
genation than NiMo when the shift reaction is used. In all cases, hydroprocessing with CO + HzO produces less upgrading than with HZdirectly. Light Cycle Oil Hydroprocessing. The shift reaction initially reached equilibrium during most of the runs with LCO, corresponding to a hydrogen circulation rate of lo00 L of Hz/L of oil. However, the catalysts exhibited aging and shift equilibrium was not maintained for very long. With the LCO feed, the hydrogen circulation rate generated from CO + HzO was usually in the range 350-625 L of H d L of oil (about half that of the Hz runs). Activity for hydrogen production from the shift reaction with LCO follows this order: CoMo/Al,O, > NiMo/Al,O, = NiW/zeolite
>>
NiW/Al,O, After 1day on stream, hydrocarbon gas make (CI to C4) was less than 0.5% for all runs regardless of whether the shift reaction or hydrogen was used. Tables IV and V show run data for NiW/zeolite with CO + HzO or Hz + Nz. This is in contrast to the model feed runs where light hydrocarbons were formed primarily as a product of Fischer-Tropsch synthesis rather than through cracking reactions. As expected, boiling range conversion was less for all alumina supported catalysts than for NiW/zeolite (Chart 111). The highest percent hydrogen in the liquid product is obtained by using CoMo/AlzOa with HZ+ Nz. Here, an increase of about 1.5 w t % H content occurs which corresponds to a consumption of about 178 L of Hz/L of oil. Since the gas makes were always low, the incremental percent hydrogen gain times 115 L of H d L of oil, plus the N-loss times 111L of Hz/L of oil plus Moss times 18 L of H d L of oil give an estimate of the hydrogen consumption. NiW/zeolite with either Hz + Nz or CO + HzO produces about the same H-content liquid (Tables IV and V). Although NiW/zeolite consumed more hydrogen for the HZ+ Nz case because of higher desulfurization and denitrogenation levels, similar % H in liquid product is found (Chart IV). All catalysts with CO + H20 provide substantially leas desulfurization (Figure 2) than under HZ+ NZ(Chart VI. Mass spectral analyses of some of the products from light cycle oils showed that the water gas shift hydrogen did not hydrogenate the dibenzothiophenes contained in the LCO. This is in contrast to HZ+ Nz which did hydrogenate the dibenzothiophenes. Less denitrogenation occurs with the shift reaction compared to runs with HZfor all catalysts (Chart VI). Discussion Model Feed. An aromatic feed containing 2.8% sulfur can be hydroprocessed at 8.7 MPa over alumina supported CoMo, NiMo, or NiW with CO + HzO. The H content was raised from 9.9 to 10.7 % with 854 L of H d L of oil circulation (about 20 % below shift reaction equilibrium). Equivalent conditions with hydrogen produced higher levels of aromatics hydrogenation. With Hz + Nz, more l-methylnaphthalene was hydrogenated to 1-or B-methyltetralins and some further hydrogenation to methyldecalins occurred. The same level of desulfurization but more denitrogenation was found with HZ+ Nz vs CO + HzO. The hydrogen produced by the shift reaction for the model feed is consumed not only by addition to the model feed but also by reaction with CO to form light hydro-
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Hydroprocessing of Feeds
Energy & Fuels, Vol. 6, No. 6,1992 829
Table IV. LCO Processing over NiW/Zeolite with CO
run no. time on stream (days) liquid product, %
+ Water (8.7 MPa, 400 OC, 1 WHSV) CO + H2O
LCO feed
1 0.04
2 0.14
3 0.24
4 0.98
5 2.02
6 3.02
7 3.77
8 6.1
87.71 9.56 0.060 3.05
87.90 10.11 0.031 0.94 54.6 97.3
88.13 10.40 0.037 0.092 40.9 97.1
88.32 10.63 0.097 1.21 61.5
87.02 10.73 0.044 1.00 28.75 68.14
88.74 10.07 0.044 1.18 28.27 62.16
87.09 10.76 0.039 1.66 36.41 46.76
86.62 10.57 0.054 1.76 11.70 43.39
86.57 10.72 0.044 1.83 27.52 40.71
9.4 18.6 62.6 5.3 1.3 2.8 23.7
1.5 14.5 70.9 10.0 0.5 2.7 11.0 486
0.5 15.1 73.2 6.8 1.8 2.5 10.6 531
0.46 15.06 74.52 5.83 1.75 2.39 10.5 513
13.9 74.8 7.1 2.0 2.2 8.8 519
.30 10.37 74.93 11.93 0.59 1.88 5.37 455
0.29 12.85 76.53 6.87 1.86 1.61 7.99 532
0.16 12.06 76.45 7.70 2.47 1.16 7.01 413
C H N
S denitrogenation desulfurization boiling range, O C c4-
C5-216 216-343 343-454 >454 H2S net 454 HzS net 99.0 78.7 NiW/A12036 80.3 1.3 Hydrogen data obtained after running CO + H2O over catalyst for 7 days. * Ran 1 day with CO + HzO and then switched to H2 due to lack of HZproduction from the water gas shift reaction.
the net consumption by the model feed. Thus, lack of hydrogen availability alone does not account for lower hydrogenation activity when the shift reaction is used with a catalyst.
,
830 Energy & Fuels, Vol. 6, No. 6,1992 Chart VI. Donitrogemation Ranges NiW/zeolite COMO/&Oa NiMo/AlzOa
Hz + Nz 75-97
92-99 >40
CO + HzO
10-40 20-35 25-35
There are a number of factors that may reduce the hydrogenation activity of CO + H2O vs NZ+ Ha. At the top of the catalyst bed, 50 w t % water in hydrocarbon mixture enters the reactor with CO. As these reactants proceed down the catalyst bed, Hz, H2S, and C02 and Fischer-Tropsch gases are generated. Since the concentration of H2 is probably below equilibrium values a t the top of the catalyst bed, the CO + H2O runs would be equivalent to a smaller hydroprocessing catalyst bed or higher space velocity runs. In addition, the catalysts used here may not be completely sulfided. Atmospheric pressure TGA experiments showed that NiS1.e~and cd1.92 could be reduced to metals in flowing H2 above 450 OC a t atmospheric pressure.12 Air can oxidize Ni, Co, Mo, and W sulfides above 400 "C while water converts COSinto an oxide above 500 OC in the TGA. CO, C02, and water may also react with the metal sulfide catalysts during CO + H2O hydroprocessing a t 8.7 MPa to partially poison the catalysts. Since the H2 level may be below equilibrium at the top of the catalyst bed, the HzS concentration could also be lower there, accounting for less aromatic hydrogenation and HDN by CO + H2O vs Hz + N2.l6l7 Increased HDN activity has been observed when low levels of H2O (-0.5 wt %) are present during denitrogenation of model compounds.lB-18 However, oxygen compounds can mildly inhibit HDS.18 In the hydroproceasing with CO + H20, -50 wt % water is in the feed and about -20% water in the liquid product. With this quantity of water plus CO, COZ, HzS, and aromatics adsorption on the catalyst, many more experiments would be needed to determine whether water has a beneficial or negative effect on HDN, HDS, and aromatics hydrogenation. LCO Processing. Hydroprocessing a light cycle oil over CoMo/alumina, NiMo/alumina or NiW/zeolite with CO + HzO generated 350-625 L of H d L of oil (about 5070% of equilibrium due to catalyst aging). Changes in the Mo dispersion and crystallinity as well as coke formation could account for less hydrogen production than that observed in the model feed studies.lg The hydrogen consumption for the CO + HzO runs was 125-160 L of HdL of oil vs 196-231 L of H d L of oil for runs with hydrogen. NiW/alumina lost all hydroprocessing ability with CO HzO after 1 day on stream. The denitrogenation was poor for the water gas shift reaction runs, but 70-8096 desulfurization was obtained vs >90% for the hydrogen case. This decreased HDS and HDN activity can be accounted for by the smaller amounts of hydrogen generated by the shift reaction (350-625 L of Hz/L of oil for shift vs 1032 L of HdL of oil) for Ha + NZruns. Also, lower HDS may occur because dibenzothiophenes found in LCO have one or more methyl substituents which decreases their rate of hydrogenation relative to unsubstituted dibenzothiophene, making them more sensitive
+
(15)Rankel, L. A. Fuel. Sci. Technol. Int. 1991,9, 436-447. (16)Sattarfield, C. N.;Yang, S. H. J. Catal. 1981,81,335-346. (17)Satterfield,C.N.;Smith,C.M.; Ingalls, M. I d . Eng. Chem.Process Des. Deu. 1986,24,1OOO-1004. (18)Girgis, M. J.; Gates, B. C. I d . Eng. Chem. Res. 1991,30,20212058. (19)Laniecki, M.; Zmierczak, W. Zeolites 1991,11, 18-26.
I
Rankel
Hydroprocessor F~ 17~U;rrdedFwd
CO t H,O
t "2
480 I HJI Oil
Grnersted
Figure 3. Hydroprocessing using CO + water with generation of excess hydrogen.
to hydrogen partial pressure.20 Since the model feed has unsubstituted benzothiopheneand quinoline, steric effects would not be occurring for those studies. NiW/zeolite produced slightly more
