15
Ind. Eng. Chem. Prod. Res. Dev. 1985, 2 4 , 15-19 Froment, 0. F.; Bischoff, K. B. Chem. Eng. Sci. 1061, 16, 189. Froment, G. F.; Blschoff, K. B. Chem. Eng. Sci. 1062, 77, 105. Hatcher, W. J.; Park, S. W.; Lin, C. C. 88th Natlonal Meeting of AIChE, Houston TX, April 1979, Paper 72a. Jacob, S. M.; Gross, B.; Voltz, S. E. and Weekman. V. W. AIChE J. 1076,
Voorhies, A. Ind. Eng. Chem. 1045, 3 7 , 318. Wojciechowski, B. W. Can. J. Chem. Eng. 1068, 4 6 , 48.
Received for review June 19, 1984 Accepted November 19, 1984
-- , 71-11 - .. 93
I
Lin, C . C.; Hatcher, W. J. ACS Symp. Ser. 1082, 796, 249. Lin, c. c.; Park, s. w.; Hatcher, w. J. Ind. Eng. Chem. process Des. D 1083, 22, 609.
~ V .
Presented at the National Meeting of the AIChE, Anaheim, CA, May 1984.
Hydrous Metal Oxide Ion Exchangers for Preparation of Catalysts for Direct Coal Liquefactiont Howard P. Stephens,* Robert G. Dosch, and Frances V. Stohl Sandia National Laboratories, Albuquerque, New Mexico 87 785
A group of hydrous oxide ion-exchange compounds which can be used to prepare hydrogenation catalysts by a novel synthesis route has been identified. These materials offer several advantages for catalyst formulation, including high surface area, dispersion of any metal or mixture of metals and promoters over a wide concentration range, and adjustment of substrate acidity as well as active metal oxidation state. Catalysts prepared by exchanging the sodium ion of sodium hydrous titanate for Ni, Mo, and Pd were tested for use in direct coal liquefaction. Results of hydrogenation experiments performed with the addition of the catalysts to a slurry of a bituminous coal in a coalderived solvent demonstrated that hydrous titanate catalysts with active metal loadings as low as 1% were equally effective for liquefying coal as a commercial Nl-Molalumina catalyst containing 15 % by weight active metals.
Introduction Interest in efficient conversion of coal to liquid fuels has encouraged exploration of catalytic materials for direct coal liquefaction. We have identified a group of hydrous oxide ion-exchange compounds of Ti, Zr, Nb, and Ta which can be used to prepare hydrogenation catalysts by a novel synthesis route involving exchange of active metals into these compounds. Hydrous oxide ion-exchange compounds have previously been investigated at Sandia National Laboratories for use in decontamination of aqueous nuclear waste (Dosch, 1978, 1981) and as precursors for ceramic materials (Hankey et al., 1981). A number of properties of the compounds suggested their use as substrates for catalyst preparation: (1)any metal or mixture of metals can be uniformly dispersed in the materials over a wide concentration range by a simple process; (2) the materials have high surface areas; (3) they exhibit good chemical stability; (4) solution chemistry or high-temperature reactions can be used to provide active metal oxidation state control; ( 5 ) acidity and basicity of the substrate can be modified by ion exchange; and (6) the catalysts can be prepared on transition metal supports (Ti, Nb, and Ta) known to undergo strong metal support interactions (Tauster et al., 1981). Although these properties suggested versatility of hydrous oxide ion exchangers for catalyst preparation, it was not known if Catalysts synthesized by exchanging ions of active metals into the material would exhibit hydrogenation activity. The purpose of the experiments reported here was to explore the hydrogenation activity of these materials for slurry phase catalysis of direct coal liquefaction. It is also possible that hydrous metal oxide ion This work supported by the U.S.Department of Energy at Sandia National Laboratories under Contract DEAC04-DP00789. 0196-4321/85/1224-0015$01.50/0
exchangers may be used to prepare multifunctional hydroprocessingcatalysts as well as catalysts for other processes such as oxidation, dehydrogenation, methanation, alkylation, and isomerization. The hydrous oxides investigated as active metal catalyst supports belong to a group of inorganic ion-exchange compounds represented by the empirical formula M(M’,O HJn where M is an exchangeable cation and M’ is Ti, N i , Zr, or Ta. Compounds in which M is a quaternary ammonium ion, for example the tetramethylammonium ion, are very soluble in water. Vapor pressure osmometry measurements on benzene extracts of these solutions give average molecular weights of 5000-15000 for the associated species. Thus, the solution chemistry, stoichiometry, and molecular weights of the compounds suggest empirical formulas such as [ (CH,),NTi,O,H], where n varies from 20 to 60. Upon dissolution in water, the tetramethylammoniumcompounds dissociate into ionic moieties, (CHJ4N+and Ti205H-,as indicated by the high electrical conductivities of the solutions. The anions can react with a solution of aqueous metal cations to form amorphous precipitates with combining ratios of one Ticontaining anion per unit charge on the cation. Although the structures of these precipitates have not been elucidated, they are thought to consist of a network formed by metal-oxygen and metal-hydroxide bridges which incorporate cations as illustrated in Figure 1. Details of the preparation of these compounds are described in the following section. Experimental Section Catalyst Preparation. The titanate system, the best characterized and least expensive of the hydrous oxides, was chosen for exploratory testing. Hydrous titanate catalysts were prepared by a technique which consists of synthesis of sodium hydrous titanate ion-exchange material 0 1985 American Chemical Society
16
Ind. Eng.
Chem. Prod. Res. Dev., Vol. 24, No. 0
0
I1
-TI
0
I1
-0
1 OH
Na+
I OH
I1
- 0-
-TI
I
OH
Na+
COMMERCIAL CATALVST
0
11
- TI - 0
1, 1985 NI HVDROUS TITANATE
TI -0--
NI++ OH
1
0035
A
I
-TI-O-TI-O-TI-O-TI-O-
I
0
I1
0
/I
O ' -5 0 0030 25
I
I
0
0
Figure 1. Conceptual structure of titanium hydrous metal oxide network containing sodium and nickel cations. Nb, Zr, and Ta form similar compounds.
followed by exchanging the sodium for active metal ions. Although sodium hydrous titanate can be prepared by a precipitation method in which an aqueous NaN03solution is added to an aqueous solution of tetramethylammonium hydrous titanate, a less expensive and more direct method was used. The synthesis involved three steps: (1)reaction of tetraisopropyl titanate with an alkali or alkaline earth metal hydroxide in alcohol solution to form a soluble intermediate Ti(OC3H7)4+ NaOH
CH,OH
soluble intermediate
(2) hydrolysis of the soluble intermediate in acetone/water mixtures to form the hydrous metal oxide exchange material acetone. H20
soluble intermediate
NaTi,O,H
(3) ion exchange of the alkali or alkaline earth metal for active metal ions in aqueous solution to form the catalyst
-
2NaTi2O5H+ Ni2+(aq)
2Na+ + Ni(Ti205H)2
For the tests described here, Ni, Mo, and Pd hydrous titanates with active metal loadings of 1%and 10% by weight were prepared. The procedure for the syntheses of the sodium hydrous titanate and the catalysts with a 10% loading is described in detail below. Sodium Hydrous Titanate. Tetraisopropyl titanate (569.2 g) was slowly added with continuous stirring (exothermic reaction) to 266.7 g of a 15 wt % solution of sodium hydroxide in methanol. The resulting solution was hydrolyzed by rapid addition to a solution of 200 mL of water in 2000 mL of acetone. After the slurry was homogenized by stirring, the precipitate was collected by filtering with a coarse glass frit and dried under vacuum overnight at ambient temperature. Recovery of the titanium and sodium was quantitative and the product contained 20-30% volatile constituents, predominantly water with minor amounts of alcohols. The amount of sodium hydrous titanate to be used for ion exchange was calculated from the ion-exchange capacity on a volatile-free basis (5.24 mequiv/g) and the volatile content of the material (28.9% for that used in the following steps). Nickel Hydrous Titanate. A 1.0 N solution of Ni(N03)2.6H20was prepared, the pH adjusted to 6, and 215 mL of this solution were diluted to 700 mL with water. Eighty grams of sodium hydrous titanate was added to the Ni2+solution. After the slurry was homogenized by stirring, it was filtered and washed with water to remove sodium nitrate and then acetone to minimize agglomeration during subsequent drying. The Ni-exchanged catalyst was dried overnight in vacuum at ambient temperature. Analysis of the catalyst gave Ni, Na, and volatile contents of 7.70%, 2.73%, and 26.02%, respectively, or 10.41% Ni and 3.69% Na on a volatile-free basis. Molybdenum Hydrous Titanate. Seven grams of molybdenum metal was dissolved in 50 mL of a 1:l mixture by volume of concentrated nitric and hydrochloric acids. After the Mo solution was diluted to 800 mL with water
10
100 PORE DIAMETER
1000
lib
Figure 2. Pore volume distribution for a 10% Ni hydrous titanate compared with a commercial Ni-Mo/alumina catalyst. BET surface areas were 219 m2/g for the titanate and 150 m2/g for the Ni-Mo/ alumina catalyst.
and the pH was adjusted to 2 with NaOH, it was filtered through a coarse glass frit and diluted further to 1000 mL with water. Seventy-five grams of sodium hydrous titanate powder was added to 866 mL of the Mo solution. The pH of the supernate was adjusted to a value of 4 to allow sorption of 99.8% of the Mo in the solution. The Moloaded catalyst was filtered, washed, and dried by the same procedure used for preparation of the Ni catalyst. The vacuum-driedcatalyst contained 8.18% Mo, 0.5% Na, and 23.01% volatiles or 10.6% Mo and 0.65% Na on a volatile-free basis. Palladium Hydrous Titanate. A solution containing 6.32 g of palladium was prepared by dissolving palladium metal in a solution of 17 mL of concentrated nitric acid and 0.2 mL of concentrated hydrochloric acid, and then diluted to 700 mL with water. Eighty grams of sodium hydrous titanate was added to this solution. The slurry was filtered, washed, and dried by the procedure used for the nickel preparation. The vacuum-dried material contained 7.62% Pd, 2.65% Na, and 26.78% volatiles or 10.41% Pd and 3.62% Na on a volatile-free basis. The typical sodium hydrous titanate product was an amorphous fluffy powder, as were the hydrous titanates of the other metals formed by exchange of the sodium ions. Drying the titanates at elevated temperature resulted in loss of volatiles. Approximately 90% of the volatiles were removed at 200 "C and greater than 95% were removed after heating to 400 OC. X-ray diffraction and scanning electron microscopy indicated that a transition from an amorphous to a crystalline form (rutile) occurs at approximately 600 "C. This was supported by differential thermal and thermogravimetric analysis studies, which showed a large exotherm with no corresponding weight change at the same temperature. Surface areas and pore volumes for various hydrous titanates have been measured by nitrogen BET and adsorption-desorption techniques. Surface areas for the materials ranged from 150 to 300 m2/g and the desorption pore volumes from 0.24 to 0.41 cm3/g. All of the titanates had bimodal pore volume distributions similar to the distribution illustrated for the 10% Ni titanate (total pore volume = 0.31) in Figure 2. For comparison, the unimodal pore volume distribution for a commercial Ni-Mo alumina catalyst is also shown. Materials, Apparatus, and Procedure. Twenty-eight liquefaction reactions were performed with Illinois No. 6 (Burning Star) coal, SRC-I1 heavy distillate solvent from the Ft. Lewis Pilot Plant (1:2 codsolvent, by weight) and high-purity hydrogen. Analyses of the coal and solvent are given in Table I. A 2.7% Ni, 13.2% Mo on alumina catalyst, currently used in integrated two-stage liquefaction
Ind. Eng. Chem. Prod. Res. Dev., Vol. 24, No. 1, 1985 Table I. Analyses of Coal and Coal-Derived Solvent Illinois No. 6 Coal. Burning Star Mine % % % %
Proximate Analysis moisture mineral matter volatile fired carbon
2.84 13.05 36.37 47.74 100.00
% % % % % % %
Ultimate Analysis (dmmf Basis) carbon 67.38 hydrogen 4.65 nitrogen 1.36 chlorine .04 sulfur 3.29 mineral matter 13.05 oxygen (difference) 10.23 100.00 Sulfur Forms
% pyritic sulfur % sulfate sulfur % organic sulfur (difference)
0.98 0.28 2.03
SRC-I1 Heavy Distillate % carbon % hydrogen % nitrogen
70 sulfur % oxygen (difference)
89.06 1.77 1.15 0.52 1.50 100.00
pilot plant studies (Schindler et al., 1983; Rao et al., 1983) was ground to -200 mesh and used as a reference for comparison of catalytic activity. Control experiments were also performed without catalyst addition. A randomized factorial experimental plan (3 X 2 with duplication) was used to test the effect of active metal and metal loading on liquefaction activity. For these experiments, Ni, Mo, and Pd titanates with metal loadings of 1% and lo%, by weight of titanate, were used. Catalyst weight added to the reactor was adjusted so that liquefaction reactions with the 1% titanates were performed with 4 x mol of active metal and reactions with the mol. To test the effects of 10% titanates with 4 X catalyst post-preparation treatments, which result in loss of volatiles and surface area, and oxidation or reduction of the Ni, experiments were performed in duplicate with the 10% Ni titanate heated for 2 h at six conditions-300, 450, and 700 "C in air and hydrogen. Reference experiments with the commercial catalyst were performed with the same number of moles of active metal (Ni + Mo) as the 10% loading experiments. All liquefaction reactions were performed in 40-cm3 batch microautoclaves described in detail elsewhere (Kottenstette, 1983). Four experiments could be performed simultaneously. After the reaction vessels were charged with 2.67 g of coal, 5.33 g of SRC-11, and catalyst (if used), they were pressurized to 800 psig with hydrogen. The reactors were then mounted on an agitation apparatus and heated to 425 "C for 30 min (time at temperature) in a fluidized sand bath while being agitated with a wrist action motion at 200 cycles/min during the heating period. Temperatures of the slurries and pressures of the gas phase were accurately monitored with thermocouples and strain-type pressure transducers, respectively, and were recorded by a digital data acquisition system during the course of the experiments. Following the heating period, the reaction vessels were quenched in water to ambient temperature, the resulting pressure was recorded, a gas sample was taken, and the product slurry was subsampled for analysis.
17
Liquefaction Product Analysis. Gas samples were analyzed for mole percentages of CO, COz,H2S,and C1-C4 hydrocarbons with a Hewlett-Packard 5710A gas chromatograph, which was calibrated with standard mixtures (Matheson Gas Products) of hydrocarbon gases in hydrogen. Hydrogen in the samples was obtained by difference as the remainder of the product gas mixture. The quantity of each gas produced was calculated from the mole percent in the gas sample and the post-reaction vessel temperature and pressure using an ideal gas law calculation. Hydrogen gas consumed during the reaction, obtained as the difference between the initial charge and hydrogen remaining after the reactor was quenched, was reported on a percent dry, mineral matter-free (dmmf) coal basis. Reaction product slurries were analyzed for the extent of hydrogenation and conversion of coal to lower molecular weight hydrocarbons. Quantitative analyses of the slurries for hydrogen content allowed calculation of the amount of hydrogen incorporated into product hydrocarbons. Extent of conversion of the coal to nongaseous product was analyzed by tetrahydrofuran (THF) solubility and highperformance liquid chromatography (HPLC), in terms of high molecular weight (mw), intermediate mw, and low mw product groups as follows. A 0.2-g subsample was mixed with about 50 mL of THF, filtered to obtain the weight of insoluble material, and brought to 100 mL with additional THF. Chromatograms of 5-FL aliquots of the filtrate were obtained with a Waters Assoc. Model 6000A solvent delivery system, a 100-8, microstyragel gel permeation column, and a Model 440 UV absorbancedetector. The UV absorbance response factors at 254 nm for the product groups were determined by using calibration samples prepared by dissolving known weights of high (-1000 g/mol), intermediate (-500 g/mol), and low (250 g/mol) mw coal-derived products obtained by preparative scale high-performanceliquid chromatographic (gel permeation) separation of whole liquid product from liquefaction reactions performed under similar conditions with the same coal and solvent. Chromatogram area measurements and response factors were used to calculate the percentages of high, intermediate, and low mw products for the THF soluble product. Conversion of coal to low mw product determined by this method is approximately equivalent to pentane-soluble product determined by Soxhlet extraction of the liquefaction slurry. Conversion data were calculated on a dmmf coal basis and included corrections for the conversion of the pyrite content of the coal to pyrrhotite and the loss of volatiles, if any, from the catalyst. Results and Discussion That the catalysts exhibited a true hydrogenation functionality was established by comparison of the hydrogen content of the hydrocarbon products to that of the reactants. The percentage change A%H in the dmmf coal basis hydrogen content of the products as compared to that of the reactants was calculated as the difference between the hydrogen content of the products (slurry and hydrocarbon gases) and that of the coal and solvent A% H = 100 X [(wt of H in hydrocarbon products) (wt in coal + solvent)]/(wt of dmmf coal) The results of these calculations for the hydrous titanate-catalyzed experiments and controls (no catalyst addition and commercial Ni-Mo/alumina catalyst) are shown in Table 11. As can be seen from Table 11, the products of the uncatalyzed experiments, as compared to the reactants, contained no additional hydrogen (A % H = -0.04 f 0.05), while the products of the catalyzed exper-
18
Ind. Eng. Chem. Prod. Res. Dev., Vol. 24, No. 1, 1985
Table 11. Percentage Change (A% H ) in the dmmf Coal Basis Hydrogen content of Hydrocarbon Products Compared to That of the Reactants (Coal and Solvent) for Experiments with Hydrous Titanate Catalysts and Controls A% H for hydrous titanate
loading 1%
Ni 0.98 0.67
cat. exvt Mo 1.33 1.02
10%
0.58 1.73
2.04 1.86
Ni-Mo /alumina (13.2% Mo, 2.7% Nil
Pd 1.55 1.77
Table IV. Hydrogen Consumptions from the Gas Phase (Weight Percent, dmmf Coal Basis) for Hydrous Titanate Catalysts and Controls Hydrous Titanate Catalyst Hydrogen Consumptions metal loading Ni Mo Pd 1Yo 1.25 1.38 1.59 1.19 1.45 1.73 10%
0.80 2.04 A % H for control expt 2.13 2.00
blank (no cat. addition)
-0.09
Table 111. Conversions to Low Molecular Weight Product (Weight Percent, dmmf Coal Basis) for Hydrous Titanate Catalysts and Controls Hvdrous Titanate Catalyst Conversions metal loading Ni Mo Pd 1% 39.8 41.8 45.3 43.1 45.0 47.3 20%
43.8 45.5
47.7 46.8
49.7 48.4
Conversions for Control Experiments Ni-Mo/alumina 43.4 (13.2% Mo, 2.7% Ni) 42.2 blank (no cat. addition)
26.0 27.7
iments contained up to an additional 2% dmmf coal basis hydrogen. Previous statistical analysis of experiments with oil-soluble catalysts (Kottenstette, 1983) has shown that hydrogen gas consumption and conversion to low mw product may be used as quantitative measures of catalyst activity for coal liquefaction. Table 111gives the conversions to low mw product and Table IV the hydrogen gas consumption for the controls and the experiments with the 1% and 10% Ni, Mo, and Pd titanates without postpreparation treatments. Absolute standard deviations were statistically determined to be 1.4% for conversion to low mw product and 0.13% for hydrogen gas consumption. As can be seen from Table 11, the ranking for metals effect with respect to both conversion to low mw product and hydrogen gas consumption is Pd > Mo > Ni and with respect to metals loading is 10% > 1%. Results of a two-way analysis of variance were used to make a quantitative comparison of performance. The effect of active metals (1% and 10% loadings averaged), were as follows: low mw product, Pd (47.7%) > Mo (45.3%) > Ni (43.0%); F = 10.8, P < 0.01; hydrogen consumption, Pd (1.86%) > Mo (1.65%) > Ni (1.35%);F = 22.4, P < 0.005, where F is the variance ratio and P is the probability of a chance occurrence of the result. These values may be compared with the results of experiments without catalyst addition (low mw product = 26.8% and hydrogen consumption = 0.69%) and experiments with the commercial catalyst (low mw product = 42.8% and hydrogen consumption = 1.88%). It was found that the 10% titanates averaged 3.2% greater conversion (F = 10.8, P < 0.01) and 0.37% greater hydrogen consumption ( F = 35.0, P < 0.005) than the 1%titanates. Only one post-preparation treatment of the 10% Ni hydrous titanates was found to have a significant effect on catalytic activity. Experiments with the titanate heated
1.93 1.82
1.90 2.22
Hydrogen Consumptions for Control Experiments Ni-Mo/alumina 1.94 1.81 (13.2% Mo, 2.7% Ni)
0.00
blank (no cat. addition)
1.50 1.45
0.77 0.61
to 700 "C in air produced a conversion of 33.6% to low mw product and had a hydrogen consumption of 0.71% which were significantly lower than the average of the values for the other treatments (45.2 f 1% and 1.5 f 0.2%). X-ray diffraction analysis of the post-preparation treated materials showed formation of NiTiO, for only the material heated to 700 "C in air. The NiTiO, formed probably could not be reduced to Ni under liquefaction conditions and therefore was not available for catalysis of hydrogenation reactions. This has been supported by preliminary oxygen chemisorption experiments which showed that the 700 "Clair treatment produced a catalyst that had less than half the active nickel of the other materials. The results of these tests may be interpreted in terms of the reaction mechanisms involved in coal liquefaction. It is currently believed that direct coal liquefaction proceeds primarily by a donor solvent mechanism (Whitehurst et al., 1980; Gorin, 1981) in which high molecular weight coal molecules are thermally fragmented into lower molecular weight free radicals, which subsequently abstract hydrogen from hydroaromatic solvent compounds. Dehydrogenated solvent species are rehydrogenated catalytically, either in situ or as a separate step of the process. Although the actual mechanism, involving myriad chemical species, is quite complex, it can be represented by three basic reactions-(1) bond fragmentation, (2) hydrogen transfer, and (3) solvent rehydrogenation R-CHZ-CH2-R ---* R-CHp + .CHzR (1) R-CHy
+ R'-CH2. + H2PA
4
R-CH3
+ R'CH3 + PA (2)
cat.
PA
+ H2(g)
F=
HzPA
(3)
where R and R' are large coal-derived molecule moieties and PA is a polynuclear aromatic compound (e.g., phenanthrene or pyrene). According to this mechanism, the net rate of conversion of coal from high to lower molecular weight compounds depends upon the relative rates of the above reaction steps. In addition, catalytic hydrogenation of polynuclear aromatic compounds is known to be reversible (Stephens and Chapman, 1983; Johnston, 1984) so that thermodynamic equilibrium can limit the hydrogen donor supply and thus impact the rate of the hydrogen transfer step. Two observations can be made regarding the experimental results: (1)the uncatalyzed control experiments had much lower conversions to low mw product and lower hydrogen consumptions than any of the catalyzed experiments; (2) in comparison, the differences between catalyzed experiments, with different active metals and load-
Ind. Eng. Chem. Prod. Res. Dev. 1985, 24, 19-27
ings, although statistically significant, were small. These observations can be explained in terms of the above reaction steps. The coal-derived solvent used for these experiments, SRC-I1 heavy distillate, was produced by a noncatalytic liquefaction process (Nowacki, 1979) and therefore contained a low concentration of hydroaromatic donor solvent components. Without a catalyst, a significant amount of gas-phase hydrogen cannot be transferred to dehydrogenated polynuclear hydroaromatics in order to replenish those consumed. Thus, for the uncatalyzed experiments, lack of hydrogen donors in the hydrogen transfer step severely limits the conversion of coal to low mw product. However, for the catalyzed experiments, hydrogen donors may be replenished in situ by reaction 3. With an adequate concentration of hydrogen donors, conversion of coal to low mw product in the presence of a catalyst is increased because the hydrogen transfer step is not rate limiting. The small differences in conversions between experiments with different catalysts and active metal loadings may be due to the consequences of either kinetic or thermodynamic constraints. The bond fragmentation step, not the catalytic hydrogenation step, may be rate limiting, or alternately, all of the catalysts may rapidly hydrogenate the donor solvent components to their thermodynamic concentration limits. Both effects would diminish the differences in the apparent activities of the catalysts. For example, although these experiments indicate that Pd hydrous titanate increases coal conversion only a few percent more than that of the Ni hydrous titanate, the rate of hydrogenation of solvent components to their thermodynamic concentration limits may be much greater with the Pd catalyst. Kinetic studies of catalytic hydrogenation of solvent alone or with much simpler model chemical systems (e.g., phenanthrene or pyrene) must be performed to quantify the differences in hydrogenation activity of the catalysts. These results indicate that catalysts prepared using hydrous metal oxide ion exchangers show promise for
19
applications to coal liquefaction and other hydrogenation processes. The hydrous titanate catalysts, even at low active metal loadings of 1%,are equally effective for conversion of coal to low molecular weight product as a commercial Ni-Mo/alumina catalyst containing 15% by weight active metals. Considering the versatility of these inorganic ion-exchange compounds for adjustment of substrate acidity and basicity, and addition of promoter elements, it is possible that these materials can be used to produce improved multifunctional catalysts for not only coal liquefaction but a variety of processes. Registry No. Ti(O-i-C3H7)4, 546-68-9;NaTizQ5H,60704-88-3; Ni(Tiz05H),,94090-50-3;Mo(Tiz05H)2,94090-51-4;Pd(TizQsH)z, 94090-52-5;Ni, 7440-02-0;Mo, 7439-98-7;Pd, 7440-05-3.
Literature Cited Dosch, R. G. Sandia National Laboratories Report SAND 78-0710, Albuquerque, NM, June 1978. Dosch, R. G. Sandia National Laboratories Report SAND 80-1212, Aibuquerque, NM, Jan 1981. Gorin, E. "Fundamentals of Coal Liquefaction", Chapter 27 in "Chemistry of Coal Utilization", 2nd Suppl. Vol., Elliot, M. A,, Ed.; Wiley: New York, 1981. Hankey, D. L.; Hammetter, W. F.; Dosch, R. G. 34th Pacific Coast Regional Meeting, American Ceramic Society, Oct 1981. Johnston, K. Fuel, 1984, 63(4), 463. Kotfenstette, R. J. Sandla National Laboratories Report SAND 82-2495, Albuquerque, NM, March 1983. Nowacki, P. "Coal Liquefaction Processes"; Noyes Data Corporation, Park Rage, NJ, 1979. Rao, A. K.; Pillai, R. S.; Lee, J. M.; Johnson, T. W. "Recent Advances in Two-Stage Coal Liquefaction at Wilsonville"; Eighth Annual EPRI Contractors' Conference on Coal Liquefaction, Palo Alto, CA, May 1983. Schindler, H. D.; Chen, J. M.; Potfs, J. D. "Integrated Two-Stage Liquefaction. Topical Technical Progress Report, Steady State Illinois No. 6 Program Period April 1, 1982 - July 6, 1982"; The Lummus Co., Report 1480449, Dist. Category UC-Sod, April 1983. Stephens, H. P.; Chapman, R. N. Am. Chem. Soc ., Div. Fuel Chem. Pfepr. 1983, 28(5),161. Tauster, S. J.; Fung, S.C.; Baker, T. K.; Horseiey, J. A. Science 1981, 211, 4487. Whitehurst, D. D.; Mitchell, T. 0.; Farcasiu, M. "Coal Liquefaction"; Academic Press: New York, 1980.
Received for review May 7, 1984 Revised manuscript received October 5, 1984 Accepted October 11, 1984
Characterization and Activity of Some Mixed Metal Oxide Catalysts Tetsuro Selyama, Noboru Yamazoe, and Kolchl Eguchl Department of Materiels Science and Technology, Graduate School of Engineering Sciences, Kyushu University, Kasugakoen, Kasuga-shi, Fukuoka 8 16, Japan
One of the most important factors which affect the catalytic activities of metal oxide catalysts in the oxidation process is the activation of oxygen. The properties of oxygen can be modified in mixed oxide catalysts, leading to promoter actions. This paper describe&three examples of catalysis for which lattice oxygen, adsorbed oxygen, or absorbed oxygen is responsible. Oxidation catalysis of heteropoly compounds is operated by the redox cycle of Keggin anions where the bridging oxygen participates in the reaction. The redox process in methacrolein oxidation is strongly affected by additives such as arsenic and copper. Adsorbed oxygen plays a major role in biacetyi formation from methyl ethyl ketone on spinel type oxides under the influence of acid-base properties of catalysts. Spinel type oxides, e.g., CuCo,O, and Co2Ni04,show excellent activity and selectivity for biacetyl formation. A large amount of absorbed oxygen is incorporated into the lattice defects of perovskite-type oxides. Partial substitution of Sr for La greatly affects the absorption behavior of oxygen as well as oxidation activity of LaCoO,.
Introduction Among many factors which affect the catalytic oxidation process, one of the most important ones is the activation of oxygen. Usually, two types of activated forms of oxygen 0198-4321/85/1224-0019$01.50/0
may be discerned, namely, lattice oxygen and adsorbed oxygen. However, we wish to add one more type, absorbed oxygen, which plays major roles in some oxide catalysts with defect structures. The three types of activated oxygen 0 1985 American Chemical Society
