MOLYBDENUM
Catalysts
P
Molybdenum is a transition element with an electronic structure favorable to catalytic activity. It forms catalysts effective in reactions of these types : oxidation, hydrogenation, dehydrogenation, isomerization, cyclization, chlorination, dehydration and condensation, polymerization, and alkylation. The principal commercial applications of molybdenum catalyats today are the reforming of straight-run naphthas, desulfurization and upgrading of petroleum stocks, hydrogenation of coal and shale oils, oxidation of aromatics to acids, oxidation of alcohols to aldehydes, and chlorination of aromatic compounds. Applications to other processes are under investigation.
BENJAMIN H. DANZIGER Climax Molybdenum Co., 500 F$th Ave., New York 36, N. Y .
M
OLYBDENUM is one of the most widely used catalytic elements. In 1955, it is estimated that nearly 1,200,000 pounds of molybdenum will be consumed in the manufacture of catalysts. A recent digest of the literature through 1947 (26) summarizes some 535 articles and 1755 patents on molybdenum catalysts. As a transition element, molybdenum has the incomplete inner shell of electrons needed for catalytic activity. Ease of transition from one to another of its six valence states allows it to function readily as an electron acceptor or donor. It forms a variety of compounds in all valence states with varying catalytic activities and selectivities. Most of these compounds are resistant to common catalyst poisons. MOLYBDENUM-CATALYZED REACTIONS
Molybdenum compounds are used commercially to catalyze #even types of chemical reactions: 1. Oxidation 2. Hydrogenation 3. Dehydrogenation 4. Isomerization 5. Cyclization 6. Chlorination 7. Condensation
Molybdenum catalysts have also been investigated in a number of other reactions. Most promising results have been obtained in dehydration, polymerization, and alkylation. Oxidation. Molybdic oxide catalysts are ueed for the partial oxidation of alcohols to aldehydes and ketones. The chief commercial application of these catalysts is in the conversion of methanol to formaldehyde. Specific compositions of commercial catalysts have not been reported, but unsupported catalysts of molybdic oxide and iron oxide, with or without promoters, appear to be the most widely used. This type of catalyst has proved to be extremely selective. Yields are almost quantitative; one process is reported to give an ultimate conversion of 95%, Similar yields are given for a mixed catalyst of molybdic oxide and tungstic oxide (8). The catalysts have good selectivity only when molybdenum is in the sexivalent state. To prevent reduction of molybdic oxide, large excesses of air are used. Inspection of the patent literature shows that the percentage of methanol in air generally favored is in the range of 5 to 10% by volume. Reaction temperatures of 225' to 500' C. are reported. Pressures are atmospheric. Addition of molybdic oxide t o standard vanadium pentoxide
August 1955
catalysts improves the vapor-phase oxidation of benzene to maleic acid or anhydride ( I S ) . As in other oxidation reactions over molybdenum catalysts, large excesses of air are used. A reaction temperature of 430" C. is reported (16). A similar oxidation of naphthalene to phthalic anhydride gave yields of 82% in the laboratory. Maleic acid and anhydride have also been prepared by the direct oxidation of aliphatic hydrocarbons over a molybdic oxide catalyst coprecipitated with either cobalt or nickel oxide ($2). Oxides of boron, phosphorus, or vanadium are suggested as promoters. A cobalt molybdate catalyst promoted with boric acid converted butane to maleic anhydride a t an operating temperature of 475 O C. The conversion rate was 46% with an ultimate yield of 60%. The product was pure white, did not discolor on aging, and contained no measurable maleic or fumaric acid. Similar results were obtained when 2-butene was used as the feed. Furfural can also be oxidized to maleic acid and anhydride with a promoted vanadium pentoxide-molybdic oxide catalyst (SO). At a temperature of 270" C. and extremely high ratios of air to furfural, the yield of product was 71%. After the catalyst had been used 2 months, the yield increased to SO%, and after 300 days t o 81 %. Hydrogenation. Molybdenum catalysts, especially those containing sulfur, are particularly effective in hydrogenation reactions. These catalysts may be made directly from molybdenum sulfides or thiomolybdates. Oxides, molybdates, and molybdites are also commonly used. Where sulfur-bearing compounds are present in the feed stock, the oxygen-containing catalysts may be sulfurized during the initial stages of the reaction. This may explain the rapid rise in catalytic activity of a cobalt molybdate catalyst in the first stages of desulfurizing a petroleum fraction by hydrogenation. The original valence of molybdenum may be misleading, as reduction may occur during hydrogenation,, Often reduction of the catalyst with hydrogen is considered an essential pretreatment. The hydrogenation reactions catalyzed by molybdenum compounds fall essentially into the following categories: 1. Rupture of the carbon-sulfur or carbon-nitrogen bond Rupture of the carbon-carbon bond 3. Partial hydrogenation or complete rupture of the carbonoxygen bond 4. Hydrogenation of unsaturated compounds 5. Hydrogenation of nitro compounds t o amines 2.
The effect of molybdenum catalysts in rupturing the carbonsulfur bond in both cyclic and straight-chain compounds has
INDUSTRIAL AND ENGINEERING CHEMISTRY
1495
ENGINEERING, .DESIGN, AND EQUIPMENT been known for a number of years. Recently this type of hydrogenation reaction has found large scale application because of the demand for low-sulfur petroleum products, the necessity of using high-sulfur crudes, the product losses occurring when noncatalytic processes are used, and the availability of low-cost byproduct hydrogen from catalytic reforming processes. 2.0
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1. Cobalt molybdate 2. Zinc molybdate 3. Aluminum mol bdate 4. Copper molybdiate 5 . Iron molybdate
Rupture of the carbon-carbon bond occurs in destructive hydrogenation and has been of particular interest in the production of gasoline from coal and shale oil. The conventional coal process is composed of two steps. The first is the conversion of the pulverized coal to a soluble oil. I n this step depolymerization and a mild hydrogenation take place. I n the second stage the heavy oil is hydrogenated under severe pressures with the subsequent cracking of the carbon-carbon bond. A4mmonium molybdate impregnated in the coal has been investigated as a catalyst for the liquefaction step. Figure 1 summarizes results with a coal from Rock Springs, Wyo. ( S I ) . At 400" C. and hydrogen pressures of 2000 pounds per square inch gage and above, over 90% of the coal was converted to benzene-soluble oils in 30 t o 40 minutes. The rate of wnversion varies with the coal treated. Figure 2 shows that a molybdenum catalyst gave more rapid liquefaction of Rock Springs coal than a tin catalyst. However, with Velva lignite from Ward County, N. D., the rates of conversion were about equal (6).
1.E
8
A number of other molybdates exhibit definite catalytic effecta ( 6 ) . The order of activity is reported as:
U
.4
0.09
0
A
.2
I Velva Lignite + Mo A Velva Lignite Sn o Both, no added
0.00
0
20 30 40 Time, minutes (including 5 minutes for reaction during heating to 4OOOC.) 10
50
Figure 1. Hydrogenation of coal over molybdenum oxide at 400' C. and varying pressures
Five new desulfurization processes have been announced in the past 5 years. All use cobalt molybdate catalysts, which generally contain about 10% molybdenum oxide and less than 1% cobalt oxide supported on alumina. They are extremely resistant to poisoning by sulfur. Mixed oxides of cobalt and molybdenum have shown lower activity than the cobalt molybdate, an indication that some chemical compound exists in the commercial catalysts. Four of these new processes are vapor-phase systems using a fixed catalyst bed. The fifth process uses a moving bed and a liquid-phase system. Stocks containing 3 to 4y0 by weight of sulfur have been processed. Sulfur compounds such as thiophenes, thiophanes. thioethers, mercaptans (thiols), and organic sulfides are hydrogenated t o hydrogen sulfide and hydrocarbons. Products containing as little B S O.Olyo sulfur can be obtained. Nitrogen is also remoyed as ammonia and gum-forming diolefins are selectively hydrogenated (9). Liquid recoveries are almost 100% by weight and over 1 0 0 ~ o by volume. Stocks ranging from naphthas to crudes have been treated. The usual operating temperatures are about 400" C.; above 500 O C. catalyst activity declines rapidly. Pressures vary from about 100 to 850 pounds per square inch gage, depending on the process used ( I 1). The addition of an alkali salt t o the catalyst reduces the desulfurization activity (1.6). However, it reduces the accompanying hydrogenation of olefins to a much greater extent and may therefore be advantageous where hydrogenation of the double bond is undesirable.
1496
Rock Springs + Mo Rock Springs + Sn
+
i0.07 8
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0.05
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0.01
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1,000
2,000
3,000
4,000
5,000
Pressure, p.s.i.g.
Figure 2. Hydrogenation of coal and lignite over molybdenum and tin catalysts at $00" C. and varying pressures
Molybdenum catalysts have been studied extensively for the second-stage reaction, which is carried out at temperatures of 400 t o 500 O C. and pressures over 5000 pounds per square inch gage. One catalyst reported was prepared by treating bentonite clay with hydrofluoric acid, impregnating it with ammonium thiomolybdate, chromic acid, and zinc oxide, and mixing it with sulfur. The approximate composition was molybdenum lo%, chromium 2%, zinc 3.5y0,and sulfur 7%.
INDUSTRIAL AND ENGINEERING CHEMISTRY
vola47, N ~ a.
~
MOLYBDENUM Addition of 1% molybdenum to activated alumina previously treated with hydrofluoric acid nearly doubled the yield of gasoline (6). One of the more interesting recent proposals has been the use of a one-stage rather than a two-stage process. Recent laboratory work by the Bureau of Mines (6) indicates that a t temperatures about 500" C. and hydrogen pressures around 8000 pounds per square inch gage, coal can be converted rapidly to a distillable oil containing a high percentage of gasoline. Coal was neutralized with sulfuric acid and impregnated with ammonium molybdate equivalent to 1% molybdenum. Sixty parts of oil were added as a vehicle to 40 parts of coal. At 538" C. and 8800 pounds per square inch gage, 82y0 of the feed was converted to oil per pass, Thirty per cent of the oil was gasoline. Small percentagee of molybdic oxide on silica and alumina are also effective in the destructive hydrogenation of heavy residual petroleum fractions. Two per cent molybdic oxide was considered the optimum concentration. Operating temperatures were 400" to 500" C. and pressures were about 1000 pounds per square inch gage (26). Molybdenum oxides and sulfides catalyze the hydrogenation of organic oxygen compounds by rupture of the carbon-oxygen bond-for instance, phthalic acid and anhydride can be converted to toluene a t 375" C. and 3000 pounds per square inch gage in the presence of excess hydrogen. A reduced molybdenum oxide on a clay support is used as the catalyst (19). At 270" to 280" C and 1200 pounds per square inch gage phthalic anhydride was converted to xylene with a yield 70'% of theoretical. In this case a molybdenum disulfide catalyst was used ( 3 7 ) . Molybdenum sulfide on charcoal catalyzes the partial hydrogenation of carbonyl compounds to the corresponding alcohols
The postwar demand for high-octane gasolines has greatly extended the use of this general type of process. Commerical reforming with molybdenum catalysts requires temperatures of 475" to 550" C. and pressures of 100 to 400 pounds per square inch gage. Hydrogen pressure maintains the dehydrogenation activity of the molybdenum catalyst and appears to aid in the removal of decomposition products from the catalyst. Another theory is that the hydrogen maintains the molybdenum in the more active reduced form.
(82).
Below 450" C. naphthalene can be hydrogenated almost entirely to tetrahydronaphthalene over a molybdenum catalyst (83). At higher tempera tures the tetrahydronaphthalene decomposes into benzene hydrocarbons. A high pressure of hydrogen is necessary to avoid carbon formation. Hydrogenation of the benzene ring is not as easily catalyzed. Molybdenum sulfide catalyzes the hydrogenation of benzene a t about 430" to 440" C. and a hydrogen pressure of 1200 to 1300 pounds per square inch gage, but both the rate of reaction and the ultimate yield are low (1). Basic information on the hydrogenation of olefins and diolefins is scarce, although it is known that diolefins are selectively hydrogenated in the desulfurization and upgrading of petroleum fractions previously described. At about 100 to 200 C. molybdenum disulfide on alumina has a remarkable activity for hydrogenation of certain polyolefins to mono-olefins in the liquid phase, but is virtually inactive for hydrogenation of mono-olefins or of the benzene ring ($9) The selective hydrogenation of a catalytically cracked recycle stock has also been accomplished. The catalyst used was of the hydroforming type, 10% molybdic oxide on alumina. The optimum operating conditions were 480" C. and 700 to 750 pounds per square inch gage The hydrogen was obtained from the simultaneous hydroforming of a naphtha stock ($4 j. Aromatic nitro compounds can be converted to amines by the use of molybdenum catalysts. As in the case of other hydrogenation reactions, the sulfides and mixed cobalt-molybdenum oxides are considered most effective. Nitrobenzene has been converted to aniline and nitroxylene to xylidine a t temperatures of 200" to 320" C. and wide ranges of pressures. In o nitrobenzene v a s converted to aniline one study 85 to 1 0 0 ~ of
0
100
200
300
400
500
600
Pressure, p.s.i. g.
Figure 3. Thermodynamic equilibria between methyl cyclohexane and toluene a t varying temperatures and pressures
---
Without added hydro en
A t infinite hydrogen jilution
Catalytic reforming involves principally the following reactions:
O
($1 ).
Dehydrogenation, Isomerization, and Cyclization. A t the beginning of World War I1 the increased demand for T N T and highoctane aviation gasoline required new sources of aromatic compounds. To supply this demand a commercial catalytic reforming process using molybdic oxide on alumina was introduced. August
1955
1. Dehydrogenation of cyclohexane and ita homologs to aromatics 2. Dehydrocyclization of aliphatics containing a t least six carbon atoms in a straight chain to form aromatics 3. Dehydroisomerization of cyclopentane homologs to aromatics 4. Isomerization of normal paraffins
Steiner ( 3 3 ) concluded that the active catalyst sites for these basic reactions were largely identical. Because normal naphtha feeds contain a wide variety of compounds, all four of these reactions take place simultaneously. In addition, secondary reactions occur, such as cracking, polymerization, dehydrogenation of paraffins and naphthenes to olefins, hydrogenation of aromatics and olefins, isomerization of olefins and naphthenes, and dehydrocyclization of olefins. In order to understand these complex reactions better, considerable work has been done on individual pure compounds. For example, from Figure 3 it is evident that a t low pressures the equilibrium favors the dehydrogenation of methylcyclohexane to toluene even a t temperatures as low as 300" C. (18). With higher pressures the temperatures required for substantial conversion increase. As molybdenum catalysts are relatively inactive for dehydrogenation a t low pressurm, high pressures and
I W D U S T R I,A L A N D E N G I N E E R I N G C H E M I S T R Y
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ENGINEERING, DESIGN, AND EQUIPMENT high temperatures are required. At the same pressures, temperatures of 50" to 75' C. higher are required for the dehydrocyclization of n-heptane to toluene. At atmospheric pressures, the initial activity of molybdenum catalysts for dehydrocycliaation is high but decreases rapidly. At 300 pounds per square inch gage the initial activity is somewhat lower but decreases much more slowly. 100
70
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Figure 5 indicates, the most practical operating pressure for the isomerization of n-pentane is 250 to 500 pounds per square inch gage. Another dehydrogenation reaction using molybdenum catalysts is the production of nitriles from a variety of organic compounds. Alkyl- and alkenyl-substituted aromatics, substituted saturated and unsaturated cyclic compounds, olefin oxides, and alcohols are reported amenable to the treatment (IO). Ammonia is generally used as the source of nitrogen. An example of this reaction is the conversion of toluene to benzonitrile. The tempemture range is considered critical; under different conditions it varies from about 400" to 550" C. Pressures are close to atmospheric. Yields of 60 to 85y0 are reported. I n one case a large excess of air was used, but in another case reduced molybdenum oxides were satisfactory. The most commonly used catalyst is composed of about 10% molybdic oxide on alumina. Chlorination. Molybdenum catalysts have not generally been considered for chlorination reactions. I n one commercial process benzene is chlorinated in the liquid phase in the presence of molybdenum chlorides (27). At atmospheric pressure and moderate.temperatures monochlorobenzene, o- and p-dichlorobenzene, and small amounts of m-dichlorobenzene are recovered. A similar catalyst has also been reported to be uniquely effective in the difficult chlorination of phthalic anhydride to tetrachlorophthalic anhydride (4). The molybdenum was introduced as a metal powder but under the conditions of the reaction was converted to chloride. The effective temperature range was 200' to 270 ' C.
Conversion to Gaseous Hydrocarbons per Pass
0
1
2
3
4
5
6
loo
I
7
Temperature 440'C Hydrogen /Pentane (mole) 0.7
Mole Ratio of Hydrogen to Pentane
Figure 4. Isomerization of n-pentane over molybdic oxide A t 460° C., 500 pounds per square inch gage, and varying ratios of hydrogen t o pentane
The dehydroisomerization of cyclopentane homologs islthermodynamically similar to the dehydrogenation of cyclohexane and its homologs, At atmospheric pressure and 490" C. in the presence of hydrogen, methylcyclopentane over molybdic oxide on alumina gave initially a high concentration of aromatics in the liquid product. However, after 5 hours, extensive cracking took place. At 150 to 300 pounds per square inch gage activity of the catalyst was both increased and sustained over longer periods. Cracking was greatly reduced. Benzene constituted 65 to 70% of the aromatics, and higher homologs and polycyclics the remainder. It thus appears that the ring-expansion step leads to more side reactions than the simple dehydrogenation of cyclohexane. Nevertheless, with molybdenum reforming catalysts dehydroisomerization is an effective auxiliary source of aromatics. Under conditions of catalytic reforming the equilibrium favors the production of a high percentage of branched-chain isomers from n-paraffins. As isomers of pentanes and higher paraffins have much higher octane ratings than the corresponding straightchain compounds, this type of reaction is significant. With molybdic oxide on alumina, n-pentane gave about Soy0 isopentane a t mole ratios of hydrogen to hydrocarbons greater than 3 t O 1. In another series of tests the effect of varying this ratio was studied (8). Figure 4 shows that almost quantitative yields of isopentane can be obtained at a mole ratio of about 0.5. As
1498
Total Conversion
P .-m
r"
10
I
I
I
I
J
0
250
500
750
1000
Pressure, p.s.i.g.
Figure 5. Isomerization of n-pentane over molybdic oxide at various pressures
Dehydration and Condensation. Metal molybdites such as those of zinc, nickel, and cobalt are catalysts for intra- and intermolecular dehydration processes. Reactions of the following types have been suggested: synthesis of nitriles from amides or ammonium salts, preparation of heterocyclic nitrogen compounds, cleavage of tetrahydrofuran, formation of hydrocarbons from monohydric alcohols, and formation of cyclic ethers from poly-
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 47, No. 8
hydric alcohols. Temperatures of 90" t o 450" C. have been suggested (3). Another composition, molybdic oxide on magnesia, catalyzes the dehydration of isopropyl alcohol ( 1 7 ) . A number of other intermolecular dehydrations, or condensation reactions, have also been investigated-for example, thiophenes can be formed from sulfur dioxide and hydrocarbons with molybdenum oxide or sulfide catalysts. At 600" C. 10% molybdic oxide on alumina gave yields of 30 to 43y0 thiophenes (35). Similarly, alkyl ketones were condensed into unsaturated carbonyl compounds and trialkylbenzene by passing their vapors over an alumina-sup-
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. FACTORS AFFECTING PERFORMANCE OF MOLYBDENUM CATALYSTS
The activity and selectivity of molybdenum catalysts can often be significantly improved by changes in one or more of the following variables: 1. 2. 3. 4. 5. 6.
Molybdenum compound used Oxidation state Support Promoter Composition Method of manufacture
Molybdenum Compounds. Molybdenum oxides and sulfides and molybdates salts thus far have received most attention as catalysts However, molybdenum forms an unusually large number of, other compounds that have been studied less thoroughly. Among those of interest for catalyst use are: halides, oxyhalides, and halide salts; heteropolymolybdates; complexes with polyfunctional organic acids; permolybdates; refractory borides, carbides, nitrides, and silicides. Oxidation State. The importance of the specific oxidation state of molybdenum was not fully appreciated by some of the earlier investigators. As molybdenum has six oxidation states, there is a tendency for oxidation or reduction of the catalyst t o take place under operating conditions. This frequently has a substantial effect on catalytic properties. As noted earlier, the selectivity of molybdenum oxidation
August 1955
ultimate isopentane yields of over 90%. T o prove that dispersion on the carrier was not the significant difference, molybdic oxide was supported on activated charcoal. Conversion rates were very low and ultimate yields were below 50%. The authors proposed that the alumina-silica support supplies the acid conditions necessary for promoting reactions which proceed by the carbonium ion mechanism.
Table I. Effect of Catalyst Composition on Isomerization of n-Pentane" Catalyst composition, wt. % Molybdic oxide Alumina Silica Activated charcoal Isopentane conversion per pass, wt. % Ultimate yield, wt. % Liquid products Isopentane only
100 0
0 100
99 1
0
0
0 0
0 0
2.0
2.4 34.2
20 11
42 36
15.0 6.4 75b 20b 0 89.0 0
85.0
4.6 0
5b 0
4.2 45.3 49.6
87.6 48 85.3 48
90.6 90.0 90.6 88.2
a Duration, 4 hours: pressure, 500 pounds per square inch gage; temperature. 460' C. b Coprecipitated.
Promoter. A large number of promoters improve the performance of molybdenum catalysts. Compounds of vanadium iron, cobalt, and nickel are especially important.
INDUSTRIAL AND ENGINEERING CHEMISTRY
1499
ENGINEERING, DESIGN. AND EQUIPMENT A thorough investigation of the effect of various promoterr on the decomposition of hexane a t 500’ C. using a molybdic oxide catalyst was made by Griffith ( 2 0 ) . Copper, iron, and lead were used in the metallic form and barium, chromium, and aluminum in the form of oxides. As Figure 6 indicates, all the promoters show an optimum concentration relatively independent of the particular element used. The optimum concentration of the metals is only half that of the oxide promoters. The rate of increase in activity and the maximum activity reached depend to some extent on the particular promoter. Griffith concluded from the shape of the curves that the results were not due to compound formation, and that, with all true promoters, the addition of a second promoter gave no benefit unless the concentration of the first promoter was below the optimum. Composition. Mixed catalysts of molybdenum and other elements are often more active than molybdenum alone-for example, in oxidation reactions molybdenum is commonly used with vanadium or iron oxides. Third components such as cobalt and titanium oxides are sometimes added. For desulfurization the addition of cobalt oxide is especially effective. Method of Manufacture. Actual manufacture of molybdenum catalysts, like that of most other catalysts, remains more of a n art than a science. Physical characteristics of the catalyst, such as surface area, particle size, pore size, and crystal structure are frequently of extreme importance in determining activity and selectivity. Generally ammonium molybdate is used a~ a starting material for the preparation of oxide or sulfide catalysts. Acidification of an ammonium molybdate solution with hydrochloric acid precipita,tes molybdic oxide in an active form. Coprecipitation is used to prepare both supported and mixed catalysts. However, supported oxide catalysts are usually prepared by the impregnation of the carrier with ammonium molybdate. Heating the catalyst to 400” to 500” C. drives off the ammonia and leaves a finely dispersed trioxide. Molybdenum sulfide catalysts are prepared b y the acidification of ammonium thiomolybdate or by the reaction of molybdic oxide and hydrogen sulfide a t elevated temperatures. Ciapetta and Plank ( l a ) in a recent publication give 23 references for the preparation of molybdenum catalysts. FUTURE POSSIBILITIES
I n recent years the importance of molybdenum as a catalytic raw material has increased substantially. World consumption has increased from around 200,000 pounds of contained molybdenum in 1953 to an estimated 1,200,000 pounds in 1955. Expansion of present uses and the introduction of new processes now in the pilot plant stage should continue this increase. Still, only a small percentage of the possible compositions based on molybdenum have been thoroughly investigated as specific catalysts. Even fewer have been tested for any large number of reactions or over any appreciable range of operating conditions. The increased work now being done on the theoretical aspects of catalysis makes possible more basic and systematic studies of molybdenum catalysts. Such studies should help eliminate unlikely compositions and encourage active investigation of promising molybdenum catalysts previously neglected.
1500
LITERATURE CITED
(1) dndo, Singo, J . SOC.Chem. Ind. Japan, 42, 391-3 (1939). (2) Arnold, H. R. (to E. I. du Pont de Nemours & Co.), U. S. Patent 2,439.880 (Ami1 20. 19481. (3) Arnold, H.R., ind Carnahan, J. E. ;to E. I. du Pont de Nemours & Co.), Ibid., 2,591,493 (April 1, 1952). (4) Blume, P. W.,and Thomas, G. A (to Niagara Alkali Co.). Ihid., 2,429,985(Nov. 4, 1947). (5) Bur. Mines, “Synthetic Liquid Fuels, Oil from Coal,” Rept. of Invest. 5043 (Aoril 1954). (6) Byrns, A. C., Bradley, W. E.,‘and Lee, 41. W.. IND. ENG.CHEM., 35, 1160-7 (1943). (7) Carnahan, J. E. (to E. I. du Pont de Nemours & Co.), U. S. Patent 2,634,260(Auril 7, 1953) (8) Clark, A., Matuszak, M. P., Carter, N. C., and Cromeans, J. S., IND. ENQ.CHEM..45,803-6 (1953). (9) Danriger, B. H.,and Kline, C. H.. Chem. Eng. News, 33, 26872 (1955). (10) Denton, W. I., Bishop. R. B., Caldwell, H. P., and Chapman, H.D., IND.ENQ.CHEM.,42, 796-800 (1950). (1 1) Desulfurization Symposium, Petroleum Refiner, 32, No. 12, 81-92 (19531. (12) Emmett,‘P. H’., “Catalysts,” Vol. 1, pp. 331-2,Reinhold, New York, 1954. (13) “Encyclopedia of Chemical Technology,” Vol. 8, pp. 690-1, Interscience Encyclopedia, New York. 1952. (14) Engel, W.F. (to N. V. de Bataafsche Petroleum Maatschappij), Dutch Patent 72,052 (April 15,1953). (15) Fawcett, F. S.,and Hawk, B. W. (to E. I. du Pont de Nemours & Co.),U.S. Patent 2,5’72,019 (Oct. 23,1951). 1 Fukuda, Tosao, J . Chem. SOC. Japan, Ind. Chem. Sect., 54, 111-13 (1951). Gershbein, L. L., Pines. H., and Ipatieff, V. N., J . Am. Chem. SOC.,69, 2888-93 (1947). Greensfelder, B. S., Archibald. R. C., and Fuller, D. L.. Chem. Eng. Progr., 43, 561-8 (1947). Griffith, R. H. (to Gas Light and Coke Co.), Brit. Patent 577,816 (June 3, 1946). Griffith, R. H.,“Mechanism of Contact Catalysis,” pp. 74-7, Oxford University Press, London, 1936. Griffitts, F. A,, and Brown, 0. W., J . Phys. Chem., 42, 107-11 (1938). Hartig, M. J. P. (to E. I. du Pont de Nemours & Co.), U. S. Patent 2,625,519(Jan. 13, 1953). Ipatieff, V. N., “Catalytic Reaction at High Temperature and Pressure,” p. 378, Macmillan, New York, 1936. Johnson, F. B. (to Standard Oil Development Co.), U. 5. Patent 2,502,958 (April 4, 1950). Keely, W. M., IND. ENC.CHEM.,46, 1846 (1954). Killeffer, D. H., and Lins, A., “Molybdenum Compounds, Their Chemistry and Technology,” pp. 201-398. Interscience, New York, 1952. Lee, J. A., Chem. Eng., 54, No. 11, 118-20 (1947). Linn, C.B., and Ipatieff, V. h’. (to Universal Oil Products Co.), U.S. Patent 2,429,361 (Oct. 21, 1947). Moore, R. J., Trimble, R. A., and Greensfelder, B. S,, J . Am. Chem. floc., 74, 373 (1952). Nielsen, E. R. (to Quaker Oats Co.), U. S. Patent 2,421,428 (June 3, 1947). Pelipetz, M. G., Salmon, J. R., Bayer. J , and Clark, E. L., IND.ENG.CHEM.,45, 806-9 (1953). Standard Oil Development Co., Brit. Patent 667,617 (March 5, 1952). Steiner, H.. Discussion Faraday SOC.,1950,No. 8,264-70. Stewart, M.M., and Moore, F. J. (to Texas Co.), U. 5. Patent 2,446,619 (Aug. 10, 1948). Texaco Development Corp., Brit. Patent 627,247(Aug. 4,1949). Woertr, B. B., Henderson, L. M., and Ridgway, C. M. (to Pure Oil Co.), U. S. Patent 2,589,523(March 18,1952). Yura, Shoro, and Hara, Hiroo, Japan Patent 174,870 (June 8, 1948). RECEIVEDfor review January 19, 1955.
INDUSTRIAL AND ENGINEERING CHEMISTRY
A C C ~ P T EJune D 3, 1955.
Vol. 47, No. 8
