12
I n d . E n g . C h e m . Res. 1987, 26, 12-18
Catalytic Coprocessing: Effect of Catalyst Type and Sequencing Christine W. Curtis,* Kan-Joe Tsai, and James A. Guin Chemical Engineering Department, A u b u r n Uniuersity, Auburn, Alabama 36849
The importance of catalyst accessibility, loading, and type in coprocessing coal with heavy residua
was evaluated by examining the changes in the product slate and the production of upgraded products. A commercial hydrotreating catalyst (NiMo/A1203),bulk metal sulfides (FeS2 and MoS2), a homogeneous catalyst (H2S),and four oil-soluble metal salts of organic acids were used. The more accessible NiMo/A1203powder promoted higher conversion and more upgrading than did the less accessible extrudates. The oil-soluble catalyst precursors showed higher levels of activity for coal conversion and oil production in the coprocessing reaction than did either NiMo/A1203 or pyrite a t equivalent loading. The product slates from catalyst sequencing in two-stage coprocessing were examined and compared to the results obtained from single-stage processing at comparable conditions. consumption. Two-stage processing is described in a patent by Rosenthal and Dahlberg (1982) in which oxides of cobalt-molybdenum, nickel-molybdenum, and nickeltungsten were used for hydrocracking coal in heavy oil in the second stage. Chevron (Shinn et al., 1984) has developed a coal-oil two-stage reaction process which is similar to that used for coal liquefaction. They stated that the advantages of corefining include increased yields, process stability, coal feed flexibility, ability to process residua with high-metals content, and efficient hydrogen utilization. A process patented by Gatsis (1982) converts coal to liquid products and reduces the residuum asphaltene content by solvent extraction in a heavy hydrocarbonaceous liquid using a finely divided unsupported metal catalyst. A review of coprocessing by Monnier (1984) discusses the work of several other groups which are mentioned in the following. Russian workers have used coal impregnated with (0.2 wt %) Mo6+and (0.75%) Fe3+ to achieve a coal conversion of 82%. Japanese workers have performed pilot studies investigating the solvolysis of coal in asphalt and residual oils. Two-stage processing has been performed in which coal is dissolved at 390 "C in the first stage and then hydrocracked over a catalyst in the second stage at 400 "C. A number of different catalysts have been used including oxides of nickel-molybdenum, cobalt-molybdenum, and nickel-tungsten on y-alumina. The NiMo/A1203 gave the best results although zeolites and other commercial catalysts also performed well. The concept of two-stage processing has also been widely used in coal liquefaction (Tarrer et al., 1981; Garg et al., 1979, 1980a,b; Schindler et al., 1981; Lebowitz et al., 1981; Rosenthal et al., 1982; Curtis et al., 1983; Neuworth and Moroni, 1984) and as mentioned above has in several instances been applied to coprocessing (Shinn et al., 1984; Monnier, 1984; Aldridge and Bearden, 1978). Japanese workers have attempted to improve the product slate from coprocessing by adding additives to the first stage (Monnier, 1984). Calcium carbonate increased the liquid yield, and various disposable catalysts such as iron oxides, hydroxides, and sulfides showed positive effects on coal dissolution. Two-stage processing using the combination of a disposable catalyst in the first stage and a commercial hydrotreating catalyst in the second stage has been shown to be beneficial in improving the product slate from coal liquefaction (Curtis et al., 1983). One advantage of twostage coal liquefaction is that it increases the efficiency of upgrading by removing some of the heteroatoms in the first stage to prevent downstream catalyst poisoning. Other
In coprocessing petroleum residua and coal, two goals are paramount: (1) the conversion of coal to liquefied products and (2) the upgrading of heavy fractions from liquefied coal and petroleum residua to high-quality products. These two goals are not necessarily synonymous since in certain coal/solvent systems, coal can be converted without producing high-quality products; likewise, highquality pentane-soluble products can be achieved at fairly low coal conversions (Curtis et al., 1986~).Because of the compositional differences in these materials, the use of several catalysts or combinations of catalysts may be desirable for promoting the desired reactions. Catalytic two-stage processing may provide a means of achieving both goals by increasing the overall efficiency of the process. The initial work in catalytic coprocessing was performed by Boomer and Saddington in which petroleum solvents were used to coprocess lignite, subbituminous, and bituminous coals from Alberta in the presence of molybdic oxide (Monnier, 1984). Moschopedis and co-workers have performed extensive work in catalytic coprocessing reactions using CoMo/A1203and Fez03catalysts (Moschopedis et al., 1980; Monnier, 1984). Their results indicate that the coal conversion to toluene solubles is improved with the addition of a CoMo/A1203 catalyst and that the product slate is dependent upon coal and solvent type as well as processing conditions. A process for catalytic hydrocracking of coal-oil mixtures has been developed by HRI in which coal and heavy vacuum residuum are catalytically coprocessed in the presence of a CoMo/Alz03catalyst. Coprocessing reduced the amount of benzene-insoluble materials in the products as well as the sulfur content of the liquid boiling above 204 "C. The synergistic effects of the coprocessing allowed operation at lower severity than coal liquefaction (Monnier, 1984). Oil-soluble coprocessing catalysts, phosphomolybdic acid and naphthenates of molybdenum, vanadium, and chromium, have been described as catalysts for coprocessing by Exxon. Aldridge and Bearden (1981) used molybdenum naphthenate as a catalyst for coprocessing Athabasca bitumen and Wyodak coal. By using molybdenum naphthenate, they increased the liquid yield by 20% and decreased the coke formation. Aldridge and Bearden (1978) also described a two-stage process in which bitumen is first hydrocracked and then hydrogenated with Wyodak coal using a phosphomolybdic acid catalyst in both stages. Compared to a single-stage process using a molybdenum catalyst, the two-stage process produced more residual oils boiling above 540 "C, more char, and lower hydrogen 0888-5885/87/2626-0012$01.50/0
0
1987 American Chemical Society
Ind. Eng. Chem. Res. Vol. 26, No. 1, 1987 13 Table I. Analyses of Feedstocks West Texas elemental analysis, w t % carbon hydrogen nitrogen sulfur
H/C
chem and phys properties ash, wt 70 Mr aromaticity refractive index, 20 "C viscosity, 40 " C , P specific gravity OAPI Conradson C residue, w t % product distribution, wt 70 oil asphaltenes
MayaTLR
VSR
85.3 10.8 0.51 4.19 1.51
86.1 10.4 0.44 3.33 1.47
0.082 668 0.37 1.56 317 1.000 10.0 15.87
0.012 922 0.35 1.58 7075 1.014 8.05 17.33
79.2 20.5
88.7 11.3
advantages include increasing the efficiency of the hydrogen distribution among the various competing reactions, thereby producing a liquid of higher quality. Two-stage processing provides more flexibility for adjusting process parameters and catalyst types and combinations for attaining the desired end product. Recent work has shown that the two goals of coprocessing, which are coal conversion and oil production, are difficult to achieve in the absence of a catalyst (Curtis et al., 1986~).Catalytic coprocessing offers a possible means of achieving both goals simultaneously. The objective of this present work was to evaluate the effectiveness of different catalysts in combined upgrading of coal and petroleum by examining the changes in the product slate. In addition, two-stage coprocessing with catalyst sequencing in the first and second stages was explored with the goal of maximizing the amount of coal converted and the production of high-quality product. The quality of the products obtained from the coprocessing reactions was determined by their solubility in a solvent extraction procedure detailed later. The solubility analysis provided information on the degree of upgrading of heavy insoluble materials to lighter, more soluble materials. The solubility analysis, rather than distillation, was used to establish the efficiency of the catalyst or processing scheme because it provided more reproducible results for small quantities of materials (ca. < l o 8). Experimental Section Materials and Procedures. The solvents used in this study were Maya topped long resid (TLR) and West Texas vacuum short resid (VSR), supplied by Cities Service Research and Development Company. Illinois No. 6 hvC bituminous coal from the Burning Star mine was supplied by the Advanced Coal Liquefaction Research and Development Facility, Wilsonville, AL. Analyses of these materials are given in Tables I and 11. The catalysts used were (1)a mineralogical iron pyrite (FeS2,obtained from Juan Montal, Spain) ground to -200 mesh, (2) Shell 324 NiMo/Alz03 presulfided extrudates, and (3) metal salts of organic acids: molybdenum and nickel octoates and cobalt and molybdenum naphthenates obtained from Shepherd Chemical. The properties from Shell 324 NiMo/Al2O3 catalysts are given in Table 111. The NiMo/A1203catalyst was presulfided in 5% HzS in H2 at elevated temperatures (200,315,371 OC) in a tube furnace until breakthrough of HzS was observed. The catalysts were transferred to a vacuum desiccator and stored until
Table 11. Analysis of Illinois No. 6 Coal from B u r n i n g Star Mine proximate analysis, wt 70 35.8 volatile matter 50.9 fixed carbon 10.3 ash 3.0 moisture ultimate analysis, wt % 68.42 carbon 4.42 hydrogen 1.37 nitrogen 3.20 sulfur 0.08 chlorine 10.62 ash 11.89 oxygen (by difference) 0.78 H/C atomic ratio ~~~
~
~
~
Table 111. Properties of Shell 324 NiMo/A1203 0.66 attrition index 99.5 LOI, wt % 53.9 metal content, wt % compacted bulk density, nickel 2.72 lb/ft3 crush strength, lb 17.5 molybdenum 13.16
use. The reactions were performed in 50-cm3stainless steel tubing bomb reactors with a valve for introduction of hydrogen. These reactors have been described in detail by Curtis et al. (1983). H2 was consumed during the reactions, causing the pressure to decrease during the reaction. The amount of that decrease was dependent upon the reaction conditions, the amount and type of catalyst, and the amount of hydrocarbon gases produced during the reaction. H2 consumption was determined by P-V-T and gas chromatographicmethods. The reaction products were analyzed by solvent fractionation described previously (Curtis et al., 1983) in which the reaction products were sequentially extracted with pentane, benzene, and methylene chloride/methanol. The products obtained were defined as oil, pentane soluble; asphaltenes, pentane insoluble, benzene soluble; preasphaltenes, benzene insoluble, methylene chloride/methanol soluble; and insoluble organic matter (IOM), methylene chloride/ methanol insoluble. The IOM is composed of unreacted coal and coke formed during the reaction and is ash free. Since the initial amounts of pentane solubles charged to the reactor varied according to the residuum used, the percentage of pentane insolubles rendered soluble was defined as oil production. Oil production is the pentane solubles after the reaction minus the pentane solubles before the reaction divided by the pentane insolubles present in both the residuum and the coal, expressed on a percentage basis. All reactions were at least duplicated. Average standard deviations for the catalyst loading experiments were 0.20, 0.90, 0.40, 0.21, 0.27, 0.94, 2.2, and 1.7 absolute percentage units for gas, oil, asphaltenes, preasphaltenes, IOM, coal conversion, oil production, and H2 consumption, respectively; these standard deviations are representative of all experiments performed, e.g., catalyst loading, catalyst type, and single- and two-stage reactions. Catalyst Loading Experiments. In reactions using West Texas VSR and Illinois No. 6 coal, the catalyst loading was varied from 0 to 33 wt 9'0 of the coal and solvent charge. Powdered and 1.6-mm extrudates of presulfided Shell 324 NiMo/A1203were used. The reaction conditions were 425 "C, 30 min, 6 g of solvent, and 3 g of coal, and 8.72 MPa of cold Hz pressure yielding a Hz pressure of 20 MPa at the reaction temperature. For comparison, reactions using hydrotreated West Texas VSR and Illinois No. 6 coal were also performed at different
14 Ind. Eng. Chem. Res. Vol. 26, No. 1, 1987
powdered catalyst loadings. Hydrotreated West Texas VSR was used to evaluate the effect of removing coke producers from the residuum prior to coprocessing. The solvent was hydrotreated in the presence of H2 (20 MPa at the reaction temperature) and Shell 324 NiMo/A1203 catalyst at 425 "C for 30 min and then extracted with THF to remove the catalyst and IOM. The THF was evaporated and the extract was used as a solvent in the catalyst loading experiments. The reaction products from the catalyst loading experiments were analyzed by solvent fractionation, and hydrogen consumption was determined. Coke on the extrudates was determined by first washing in methylene chloride/methanol in an ultrasonic bath followed by oxidation for 60 h in air at 370 "C. The amount of material removed from the catalyst during oxidation was defined as coke, after being corrected for changes in the catalyst from sulfide to oxide. Catalyst Type. Coprocessing experiments were performed with several different types of catalysts by using the reaction conditions of 425 "C, 30 min, 6 g of solvent, 3 g of coal, and 8.72 MPa of cold H2 pressure. More than 97% of the material was recovered from the reactor. For most experiments, pyrite and Shell 324 NiMo/A1203 were used at 1-g loadings. For material balance calculations, pyrite was assumed to react completely with H2 to form FeS and H2S (Stohl, 1983). The reactions using oil-soluble metal salts of organic acids were performed at a lower catalyst loading (0.002 g of active metal/g of coal). For comparison, reactions were also performed at this lower catalyst loading using Shell 324 NiMo/A120s,MoS2, and pyrite. Single- and Two-Stage Reactions. The reaction conditions for single-stage processing were 60 min, 425 "C, 8.72 MPa of cold H2 charge, 6 g of solvent, 3 g of coal, and 2 g of catalyst. Catalysts used were pyrite, NiMo/A1,03, and H2S generated in situ from the reaction of CS2 with H2. The two-stage experiments were performed as two sequential 30-min reactions with 1 g of catalyst in each stage and with the other reaction conditions being the same as the single-stage reactions. Approximately 1 min each was required for heating up and cooling down the reactor between stages. The gas was vented after the first stage, the reactor was then opened, and the second stage catalyst was added. The first-stage catalyst was not removed and was present in the second-stage reaction. After repressurization with H2,a second reaction was performed. The total gases were measured by adding the weight of the gases produced in each stage.
Results and Discussion The effect of catalyst loading and particle size on the product slate from coprocessing West Texas VSR with Illinois No. 6 coal was examined. Three sets of catalytic reactions were performed (1)with presulfided 1.6-mm NiMo/A1203extrudates, (2) with presulfided NiMo/A1203 powder and, (3) with presulfided NiMo/A1203 powder using prehydrotreated West Texas VSR as solvent. For both the powdered catalysts and the extrudates, increased catalyst loading resulted in increased pentanesoluble oil yields as shown by product distributions for the three sets of reactions in Figures 1-3. The extrudates (Figure 1)gave much lower oil yields and smaller changes in the heavier fractions than did the powdered catalyst (Figure 2). Since the extrudates in Figure 1 and the powder in Figure 2 were prepared in different batches, their activity levels could have been different; therefore, the extrudates in Figure 1 were ground and used in reactions at 1 and 2-g catalyst loading levels. The oil yield increased at both loadings. The difference in oil yield
b
6
a
I
I
20
3.0
ae z z
40-
0 ZJ V 0 L
a 30.
-0
0.5
I O
Catalyst Loading lg)
Figure 1. Product distribution from coprocessing reactions using different loadings of NiMo/Al,O, extrudates (filled symbols) and ground extrudates (open symbols).
L
a
40t I O
'
O L 0 025
'
0 5
I
10
I
I 5
20
2 5
30
C a t a l y s t L o a d i n g (9)
Figure 2. Product distribution from coprocessing reactions using different loadings of powdered NiMo/A1,OB.
between the extrudates and the powder in Figure 1 is caused by the diffusional restrictions of the extrudates, while the difference in the oil yield between the ground catalysts in Figures 1and 2 is due to differences in catalyst activity as well as to small changes in the residuum due to sampling. This difference in the residuum can be observed by comparing the yield differences in the thermal reactions. Reactions using naphthalene hydrogenation as activity tests also indicated that the catalyst produced for
Ind. Eng. Chem. Res. Vol. 26, No. 1, 1987 15 Table IV. Coke Deposition on Catalyst Surface" catalyst loading, g 0.5 1.0 2.0 3.0 coke deposited on extrudate surface, w t % 14.1 14.7 13.4 16.0 coal conversion assuming coke originates 50.7 51.5 51.1 43.2 from coal, % coal conversion assuming coke originates 53.4 56.8 61.0 61.1 from solvent, % "Reaction conditions: 6 g of residuum, 3 g of coal, 8.72 MPa of H2 cold, 425 "C, 30 min.
the experiments in Figure 2 was more active than those in Figure 1. Therefore, increased accessibility as well as the level of catalyst activity is important in achieving upgraded reaction products in coprocessing. The presence of diffusional restrictions in coal liquefaction reactions has been observed by Curtis et al. (1986a) and Gollakota et al. (1985) and coprocessing reactions by Curtis et al. (1985). The powdered catalysts affected the heavier asphaltene, preasphaltene, and IOM fractions to a greater extent than did the extrudates. In Figure 2, a rise in the asphaltene level is observed at low catalyst loadings of 0.25 and 0.50 g. A corresponding decrease in the IOM level was observed. As the catalyst loading increased above 0.5 g, the asphaltene and IOM lines came closer together and crossed, giving higher IOM values and less asphaltenes than in the original material. The increase in IOM is reflected directly as a decrease in the calculated coal conversion. As shown in Table IV, this increase in IOM was probably due to the deposition of coke materials on the catalyst surface, which was a transient phenomenon since each batch experiment began with fresh catalyst having no coke deposits. The weight percent of the coke deposits shown in Table IV has been corrected for the weight change resulting from the oxidation of the metal sulfides. For each loading level the weight percent coke present was very similar. Therefore, the amount of IOM deposited on the catalyst increased as the amount of catalyst in the reactor increased. Depending on whether the coke originated from the coal or the solvent, different values of the apparent coal conversion can be calculated as given in Table IV. As the catalyst loading increased, the amount of coke formed was greater and had a greater effect on the amount of coal conversion obtained from the two cases. In a mixed system of this type (coal petroleum), it is not possible to discern the exact source of the IOM, including coke, and thus, the true amount of coal converted to soluble form is between the two values listed in Table IV. In the remainder of this paper, the coal conversion is calculated assuming that all IOM, including coke on the catalyst, originates from coal. This assumption results in a conservative (minimum) value for the amount of coal converted to soluble products. As shown in Table V, the trend of hydrogen consumption followed that of oil yield, increasing with increased catalyst loading and being higher for the powder than the extrudates. Comparing the prehydrotreated solvent to the original solvent showed that hydrogen consumption was lower in the pretreated solvent when a catalyst was present.
+
H y d r o f r i i f i d W e 6 1 Texas VSR 60
-
0 qa8
-
0 O 011 il
r
B
0 aiphalten8s VQraaspha1tan~~
50-
0 IOU
In
c
Q oil charged
a u
z
40-
L
R
30-
20-
10
0
0 5
I O
20
30
Catalyst Loading (g)
Figure 3. Product distribution from coprocessing reactions with prehydrotreated solvent using different loadings of powdered NiMo/Al,O,.
This lower consumption indicates that prehydrotreated solvent did not uptake as much hydrogen as the original solvent. Although the opposite trend is noted in the thermal reaction, the values for hydrogen consumption are within experimental error and, therefore, do not show a deviation from the expected result. The heavier product fractions from the reaction using the prehydrotreated solvent showed the same trends as that with the untreated solvent; i.e., the asphaltenes decreased and the IOM increased with increased catalyst loading. Effect of Catalyst Type on Coprocessing. Several different types of catalysts were examined for their activity in coprocessing: pyrite, NiMo on 7-AlZO3,Mo and Ni octoates, Co and Mo naphthenates, and HzS. Several of these catalysts were also tested for the upgrading of petroleum residua. The catalytic activity of pyrite and powdered NiMo/Al2O3was compared for the upgrading of West Texas VSR. In addition, coprocessing reactions were performed with West Texas VSR and Maya TLR in conjunction with Illinois No. 6 coal. In Table VI, the upgrading of West Texas VSR is compared among the thermal reaction and the reactions using pyrite and powdered NiMo/A1203. The original solubility distribution obtained prior to reaction is given as a reference. Comparing the thermal products to the solubility analysis of the original residuum shows that gases, IOM, and small amount of asphaltenes were produced and oil was decreased. When pyrite was added, the asphaltenes were
Table V. Effect of Catalyst Loading on Hydrogen Consumptiona reaction none 7.1 Illinois No. 6 coal + West Texas VSR + powdered N ~ M o / A ~ ~ O ~ ~ ~ Illinois No. 6 coal + West Texas VSR + 1.6 mm NiMo/Al,O, extrudatesbc 4.1 Illinois No. 6 coal + hydrotreated West Texas VSR + powdered NiMo/Al2OBbC 8.0 "Reaction conditions: 6 g of residuum, 3 g of coal, 30 min, 8.72 MPa of H, cold, 425 "C. coal).c CMultiplyby 6.3 X lo4 to obtain scf/bbl. d N P = not performed.
0.01
5.9 NPd NP
catalyst loading, g 0.25 0.5 1.0 11.7 12.1 15.2 NP 8.5 12.2 NP 9.5 11.6
2.0 19.0 14.9 16.8
3.0
19.7 16.6 NP
units of (g of H2 X 103)/(gof solvent + maf
16 Ind. Eng. Chem. Res. Vol. 26, No. 1, 1987 Table VI. Effect of Catalyst on Upgrading of West Texas VSR" catalyst none pyrite NiMo/Al,O, solvent VSR West VSR West VSR West Texas Texas Texas production fraction, Wt
70
gas oil asphaltenes preasphaltenes IOM Hz consumptionbc
3.5 79.1 15.0 0.1 2.3 2.2
1.9 95.3 0.6 1.2 1.0 3.9d
3.9 86.6 3.1 2.8 3.6 14.7
"Reaction conditions: 6 g of residuum, 1 g of catalyst, 30 min, 8.72 MPa of H2 cold, 425 "C. *In units of (g of H2 X 103)/g of solvent.' 'Multiply by 6.3 X lo4 to obtain scf/bbl. dNot including hydrogen consumed to convert FeS, to FeS.
virtually eliminated from the residuum, producing primarily oil; only small amounts of gases, preasphaltenes, and IOM were produced. In contrast, the NiMo/Alz03did not increase the oil fraction but did reduce the asphaltene fraction by -80%, producing gas, preasphaltenes, and IOM in almost equal amounts. The selectivity of these two catalysts for different upgrading reactions is apparent, with pyrite being more effective than NiMo/A1203in producing pentane-soluble materials from the residuum. This is an intriguing finding in view of the wide application of the latter catalysts in resid hydroprocessing. The properties of the pentane-soluble oil produced may have been different with the two catalysts but were not measured in this work. The effect of pyrite and NiMo/A1203 in coprocessing West Texas VSR and Illinois No. 6 coal is presented in Table VII. Four different reactions with equivalent reaction conditions are compared: (1)thermal reaction; (2) two reactions with pyrite, one with prehydrotreated residuum and the other with original residuum; and (3) reaction with ground NiMo/A1203. For calculational purposes in the reactions with pyrite, the pyrite was considered to be reduced to FeS and the amount of H, required for H2S formation was subtracted from the experimental hydrogen consumption, giving the value reported for hydrogen consumption in the table. The amount of oil produced by the catalysts was in the order NiMo/A1203 > pyrite > thermal. On the basis of the selectivityof pyrite for oil observed in the upgrading of the West Texas VSR (Table VI), prehydrotreatment of the residuum with pyrite and H2 could produce a solvent which would improve the final product slate. However, comparing the second and third columns in Table VII, little improvement in the coprocessing product slate was observed when using the pretreated solvent compared to the original. It appears that the primary effect of pyrite was in the upgrading of the residuum asphaltenes to oil but not in the production Table VII. Effect of Catalyst catalyst solvent product fraction, wt 70 gas oil asphaltenes preasphaltenes IOM coal conversion,c % oil production, % H, consumptionde
of oil from coal. Thus, most of the pentane-soluble oil produced from the coprocessing reaction using the original West Texas VSR and pyrite (column 2, Table VII) was most probably from the residuum and not from coal. In the pyrite pretreatment case (column 3, Table VII), most of the upgrading of the residuum occurred prior to the coprocessing reaction, leaving little residuum material for further upgrading. Therefore, little change in the product slate was observed between the original and hydrotreated materials. Since accessibility of the catalyst surface to the coprocessing reactants has been shown to be highly important in producing a quality product, oil-soluble metal salts of organic acids were used to provide catalysts during reaction which have both a high degree of accessibility and active metals necessary for upgrading reactions. These oil-soluble catalysts are believed to be converted to catalytic species at the high temperatures and pressures typical of coprocessing. These catalysts are introduced as metal salts of organic acids, but the active catalyst is thought to be a noncolloidal metal-containing salt and probably a metal sulfide (Kottenstette, 1983). Due to their activity, they were used at much lower levels (0.002 g of active metal/g of coal) than the previously described catalytic experiments. For comparison, reactions were performed using Shell 324 NiMo/A1203and two metal sulfide catalysts at this same loading. As shown in Table VIII, coal conversion was substantially higher in the reactions using the metal naphthenates and the octoates than the pyrite and NiMo/Alz03. Higher oil productions were also observed with all of the oil-soluble catalysts. The two molybdenum catalysts showed the highest levels of activity, with molybdenum naphthenate being the more active. The oilsoluble catalysts produced 3-6 % more asphaltenes and nearly equivalent amounts of preasphaltenes as the other catalysts. The product slates and coal conversions obtained from the reactions using the bulk metal sulfide catalysts were very similar to the thermal case. Although NiMo/Al,03 was somewhat more active, it was not as effective as the oil-solublecatalysts at the low concentration level. Single- and Two-Stage Processing. Previous work performed in our laboratories demonstrated the feasibility of a two-stage liquefaction process utilizing an inexpensive disposable catalyst in the first stage coupled with a second-stage hydrotreating catalyst (Curtis et al., 1983). The product slate was improved, and more pentane-soluble materials were produced from the two-stage process when pyrite was used as the first-stage catalyst. The improvement was greater with pyrite than with other first-stage catalysts or with a thermal first stage. In this work, the enhancement of the coprocessing product through a combination of a first stage with a pyrite additive and a second stage with a pyrite additive or a
on the Comocessina Reactions" Using West Texas VSR none pyrite pyrite West Texas VSR West Texas VSR hydrotreated* West Texas VSR 4.2 58.6 15.2 8.2 13.8 55.5 -2.1 7.1
3.3 67.1 19.6 6.2 3.8 87.6 18.8 8.5'
3.0 68.3 16.6 6.6 5.5 82.3 2.25 6.g
NiMo/A1,03 West Texas VSR 4.3 72.9 13.4 3.0
6.4 79.3 33.1 15.2
"Reaction conditions: 6 g of residuum, 3 g of coal, 1 g of ground catalyst, 30 min, 8.72 MPa of H2cold, 425 O C . *The solvent was hydrotreated in the presence of pyrite. 'Assuming all IOM, including coke in the catalyst, originates from coal. units of (g of H2X 103)/(g of solvent + maf coal).' eMultiply by 6.3 X lo4 to obtain scf/bbl. fNot including hydrogen consumed to convert FeS, to FeS.
Ind. Eng. Chem. Res. Vol. 26, No. 1, 1987 17 Table VIII. Effect of Catalysts o n Coprocessing" octoate Mo Ni product fraction, wt % 4.8 4.7 gas oil 62.9 62.0 17.2 asphaltenes 19.6 preasphaltenes 7.0 7.3 8.7 IOM 5.8 80.6 71.7 coal conversion,b % oil production, 70 17.1 16.5 H, consumptioncd 9.6 6.8
naphthenate Mo Co 4.1 65.6 19.1 6.7 4.5 85.1 25.3 9.9
4.0 60.2 16.5 9.1 10.2 66.7 12.6 6.4
NiMo/Al,Og
MoSz
FeS,
thermal
4.8 60.2 13.6 8.5 12.8 57.5 12.0 6.3
4.2 58.0 13.9 8.4 15.5 50.1 6.9 5.1
4.0 58.4 13.8 8.8 15.0 51.8 7.9 4.9
4.3 57.7 13.4 9.3 15.3 50.5 5.9 3.9
Reaction conditions: 6 g of residuum, 3 g of coal, 0.002 g of active metal/g of maf coal, 30 min, 8.72 MPa of H2 cold, 425 " C . Assuming all IOM including coke in the catalyst originates from coal. C I nunits of (g of H2 X 103)/(g of solvent + maf coal).d dMultiply by 6.3 X lo4 to obtain scfibbl. (I
Table IX. Single-Stage Coprocessing Using West Texas VSR" catalysts pyrite + Shell 324 Shell 324 NiMol NiMo/ thermal H2S pyrite A1203 Al,03 product fractions, wt % gas 5.9 6.2 3.5 3.8 5.1 oil 56.lC 56.7c 71.2d 75.4c 81.4c asphaltenes 16.6 16.8 17.0 12.8 6.2 preasphaltenes 8.4 7.1 5.3 2.9 2.6 IOM 13.0 13.2 3.0 5.1 4.7 coal conversion,' 58.2 57.4 89.2 83.7 85.0 %
oil production, % H2consumptionfg
-8.3 8.7
-6.9 6.0
23.9 12.9
39.3 17.2
54.3 21.4
"Reaction conditions: 6 g of residuum, 3 g of coal, 2 g of catalyst, 8.72 MPa of H, cold, 425 " C , 60 min. gram of ground pyrite and 1 g of ground NiMo/A1,03 were used. CPercentoil in original charge = 59.5%. dPercent oil in original charge = 62.1%. e Assuming all IOM including coke on the catalyst originates from coal. /In units of (g of H, X 103)/(g of solvent + maf coal).# gMultiply by 6.3 X lo4 to obtain scf/bbl.
second stage with a commercial hydrotreating catalyst was explored. The efficiency of the two-stage reactions compared to the single stage was measured by the products obtained from the solubility extraction and by the amount of H2 consumed. Single-stage reactions were performed in which pyrite, NiMo/A1203,and H2S were used individually and in combination as shown in Table IX. Two-stage reactions were then performed by using the same catalysts and under nearly identical reaction conditions as described in the Experimental Section. The results from the two-stage reactions are given in Table X. The single-stage 1-h reactions showed similar product distributions to those observed in the shorter residence time experiments. In every case, though, the coal conversion, oil production, and H2 consumption were slightly higher with longer processing time. This result is in accordance with that obtained from a parametric evaluation of coprocessing (Curtis et al., 1985). Again the reaction using pyrite produced the highest coal conversion, although the conversion obtained by using NiMo/A1203 was also above 80%. The percent oil production obtained with the different catalysts was in the order of NiMo/A1203> pyrite + NiMo/A1203> pyrite > H2S > thermal, with the values ranging from +54.3% to -8.3%. Negative oil production values indicate the occurrence of regressive reactions. Under thermal conditions, a small portion of the pentane-soluble fraction of the residuum forms asphaltenes and gases (Curtis et al., 1986b).
Table
X. Two-Stage Coprocessing Using West Texas VSR"
first-stage catalystb second-stage catalyst product fractions, W t 70 gas oil asphaltenes preasphaltenes IOM coal conversion: % oil production, 70 H, consumptionde
none none
pyrite pyrite NiMo/Al,O, pyrite NiMo/A120, NiMo/A1203
6.8 59.2 16.9 6.0 11.1 64.3 -0.38 8.8
4.0 70.4 18.1 5.1 2.4 92.2 26.8 12.1
6.0 76.9 10.5 2.2 4.3 85.9 43.0 17.9
6.6 83.2 3.2 2.1 4.9 84.1 58.5 23.5
"Reaction conditions: 6 g of residuum, 3 g of coal, 1 g of firststage catalyst, 1 g of second-stage catalyst, 8.72 MPa of H2 cold, 425 "C, 30 min/stage. *The first-stage catalyst also remained in the reaction during the second stage. Assumes all IOM, including coke on catalyst, originates from coal. units of (g of Hz X 103)/(g of solvent + maf coal).' eMultiply by 6.3 X lo4 to obtain scf/ bbl.
Since pyrite is a reacting mineral rather than a true catalyst at liquefaction conditions, the form of the active species is open to speculation. It is possible that the H2S produced during the reduction of the FeS2is functioning as a homogeneous catalyst. To test the catalytic activity of H2S alone, H2S was generated in situ from the reaction of CS2and H2. The amount of CS2added was equivalent to that needed to produce the same amount of H2S as would be produced from the reduction of FeS2to FeS. The amount of Hz consumed in the reaction forming H2S was subtracted from the total experimental hydrogen consumption to give the amount of H2 consumed by the coal and solvent reported herein. The product slate from the in situ H2S generation did not vary significantly from that of the thermal reaction. In two-stage processing, four sets of experiments given in Table X were performed: thermal for both the first and second stages; pyrite in both stages; pyrite in the first stage wtih NiMo/A1203in the second stage; and NiMo/A1203 in both stages. The highest amount of coal conversion achieved, 92.270,occurred in the experiments using pyrite in both stages, which corresponds to the high coal conversions obtained by using pyrite in the single-stage reactions. The two-stage reactions using the catalyst sequences pyrite-NiMo/A1203 and NiMo/A1203-NiMo/ A1203also produced high coal conversions, 85.9% and 84.1% , respectively. The oil production from the two-stage coprocessing reactions showed the same order of catalytic activity as did the single-stage experiments. Two-stage coprocessing using the catalyst sequences of pyriteNiMo/A1203and NiMo/A1203-NiMo/A1203both achieved high levels of oil production, 43.0% and 58.5%, respectively.
I n d . Eng. Chem. Res. 1987,26, 18-22
18
Curtis, C. W.; Guin, J. A.; Tarrer, A. R.; Huang, W. J. Fuel Proc. Technol. 1983, 7, 277-291. Curtis, C. W.; Tsai, K. J.; Guin, J. A. Ind. Eng. Chem. Process Des. Deu. 1985, 24, 1259. Curtis, C. W.; Guin, J. A.; Kamajian, B. L.; Moody, T. Fuel Proc. Technol. 1986a, 12, 111. Curtis, C. W.; Guin, J. A.; Pass, M. C.; Tsai, K. J. Fuel Sci. Technol. Int. 1986b, in press. Curtis, C. W.; Tsai, K. J.; Guin, J. A. Fuel Proc. Technol. 1986c, in press. Garg, D.; Tarrer, A. R.; Guin, J. A.; Curtis, C. W. Fuel Proc. Technol. 1979, 2, 189. Garg, D.; Tarrer, A. R.; Guin, J. A.; Curtis, C. W.; Clinton, J. H. Fuel Proc. Technol. 1980a, 3, 245. Garg, D.; Tarrer, A. R.; Guin, J. A.; Clinton, J. H.; Curtis, C. W.; Paranjape, S. M. Fuel Proc. Technol. 1980b, 3, 263. Gatsis, J. G. US Patent 4 338 183, 1982. Gollakota, S. V.; Guin, J. A.; Curtis, C. W. Ind. Eng. Chem. Process Des. Dev. 1985, 24, 1148. Kottenstette, R. J. Sandia Report SAND82-2495, March 1983. Lebowitz, H.; Kulik, C.; Weber, W.; Johnson, T. W. Presented at the 74th AIChE Annual Meeting, New Orleans, LA, Nov 1981. Monnier, J. CANMET Report 84-53, March 1984. Moschopedis, S. E.; Hawkins, R. W.; Fryer, J. F.; Speight, J. G. Fuel 1980, 59, 647. Neuworth, M. B.; Moroni, E. C. Fuel Proc. Technol. 1984, 8 , 231. Rosenthal, J. W.; Dahlberg, A. J. US Patent 4 330 390, 1982. Rosenthal, J. W.; Dahlberg, A. J.; Kuehler, C. W.; Cash, D. R.; Freedman, W. Fuel 1982, 61, 1045. Schindler, H. D.; Chen, J. M.; Peluso, M.; Moroni, E. C.; Potts, J. D.; Presented a t the 74th AIChE Annual Meeting, New Orleans, LA, Nov 1981. Shinn, J. H.; Dahlberg, A. J.; Kuehler, C. W.; Rosenthal, J. W. Presented a t the EPRI Coal Liquefaction Contractor’s Meeting, May 1984. Stohl, F. V. Fuel 1983, 62, 122. Tarrer, A. R.; Curtis, C. W.; Guin, J. A.; Huang, W. J.; Lee, J. M. EPRI Report AP-1827, 1981.
Summary
Highly effective and accessible catalysts are required to achieve high levels of oil production from the coprocessing of coal and heavy residua. Powdered hydrotreating catalyst at the higher loading and oil-soluble metal salts of organic acids catalyst precursors achieved the highest levels of activity for coal conversion and oil production. On a weight of active metal basis, the catalysts from the oilsoluble salts were the most effective in achieving both high levels of coal conversion and oil production. Pyrite was effective in achieving upgrading of asphaltenes from residuum and in achieving coal conversion in both singleand two-stage processing. Two-stage catalytic coprocessing using the first- and second-stage catalyst sequences of pyrite-NiMo/Alp03 and NiMo/A1203-NiMo/A1203 achieved the dual goals of coal conversion and oil production; however, the NiMo/A1,03-NiMo/A1203 sequence was much more effective in oil production. The products from the two-stage reactions were slightly more upgraded than those from the single-stage reaction.
Acknowledgment We gratefully acknowledge the support of this work by the US Department of Energy and Cities Service Research and Development Company under Contract DEFG2282PC50793. The provision of petroleum crudes and residua from Cities Service Research and Development Company and coal from the Wilsonville Advanced Coal Liquefaction Research and Development Facility is also gratefully acknowledged.
Literature Cited
Received f o r review February 10, 1986 Revised manuscript received July 16, 1986 Accepted August 26, 1986
Aldridge, C. L.; Bearden, R. US Patent 4 111787, 1978. Aldridge, C. L.; Bearden, R. US Patent 4 298454, 1981.
The Cup-and-Cap Reactor: A Device To Eliminate Induction Times in Mechanically Agitated Slurry Reactors Operated with Fine Catalyst Particles Ricardo J. Grau,t Albert0 E. Cassano,§and Miguel A. BaltanBs*S INTEC,’ Guemes 3450, 3000 S a n t a Fe, Argentina
A new three-phase mechanically agitated batch laboratory reactor is presented, featuring a cupand-cap holder for powdered catalyst. The apparatus allows precise determination of minute catalyst loadings, accurate control, and stability of process operating conditions, in situ preactivation of the catalyst at any pressure and temperature without external devices for injection or introduction of solids, and zero induction time determinations of reaction rates. The catalytic hydrogenation of vegetable oil derivatives and the evaluation of mass-transfer coefficients are exemplified. Introduction The accurate determination of initial reaction times is a basic requirement for interpretation and data treatment of experimental results in time-dependent heterogeneous catalytic processes. Unfortunately, an “induction time” Instituto de Desarrollo Tecnoltgico para la Industria Quimica. Universidad Nacional de! Litoral (UNL) and Consejo Nacional d e Investigaciones Cientificas y TBcnicas (CONICET). Research Assistant from CONICET. $Member of CONICET’s Scientific and Technological Research Staff and Professor at UNL.
*
0888-5885/87/2626-0018$01.50/0
is all too often observed for hydrotreating processes and, as a general rule, for hydrogenation of vegetable oils and fats (List et al., 1974; Cordova and Harriott, 1975; Coenen, 1976; Drozdowski and Zajac, 1980). Hydrogenation processes for margarine and shortening production operate at 393-473 K and 140-1300 kPa under hydrogen pressure, in batch three-phase reactors. The hydrogenation catalysts consist of very fine particles of prereduced supported metal or metal oxides imbedded onto a protective, saturated-fat coating, which dissolves under process conditions into the oil to yield a catalyst slurry with 0.04-0.40% of solids. 0 1987 American Chemical Society
