Catalysts antimony-vanadium

The relative ratios for the formation of m-tolunitrile from m-xylene, ki/kx was nearly the same for both a vanadium and a chromium-vanadium catalyst, but it was higher for an antimony-vanadium catalyst. The increase of kx/kx, which indicates an increase of the degree of single methyl group adsorption for m-xylene, seems to be ascribable to the strength of adsorption and the surface structure of an antimony-vanadium catalyst. 

The data on the rate of reaction of o-, m-, and p-xylene over vanadium oxide catalyst and of m-xylene over mixed vanadium oxide catalysts (chromium-vanadium and antimony-vanadium) were correlated with the reaction scheme below by the following rate expressions, which are based on the Langmuir-Hinshelwood mechanisms where the adsorption of m-xylene is strong. 

When a chromium-vanadium oxide and an antimony-vanadium oxide catalyst were used, the atomic ratio of chromium or antimony to vanadium was unity. 

The oxidation states of antimony, vanadium, and molybdenum in a "MoVSbNbO" propane-to-acrylic acid catalyst were probed by XANES... 

Like the original uranium-antimony oxide catalyst, the titanium substituted catalysts were able to operate only a short time without regeneration. Otherewise, the catalyst became overreduced, the USb3O2 Q type phase decomposed, and selectivity suffered. The addition of small amounts of molybdenum or vanadium prevented over-reduction enabling the catalyst to operate without regeneration. 

Antimonate-Based Catalysts. In addition to the bismuth-molybdenum oxide catalyst system, several other mixed metal oxides have been identified as effective catalysts for propylene ammoxidation to acrylonitrile. Several were used commercially at various times. In particular, the iron-antimony oxide catalyst is currently used commercially by Nitto Chemical (now Dia-Nitrix Co. Ltd., Japan) and its licensees around the world, although the catalyst was originally discovered and patented by SOHIO (20,21) and by UCB (22). Nitto Chemical improved the basic iron-antimony oxide catalyst with the addition of several elements that promote activity and selectivity to acrylonitrile. Key among these additives are tellurium, copper, molybdenum, vanadium, and tvmgsten (23-25). 

Park, M., Vislovskiy, V., Chang, J., et al. (2003). Dehydrogenation of ethylbenzene with carbon dioxide promotional effect of antimony in supported vanadium-antimony oxide catalyst, Catal. Today, 87, pp. 205-212. 

Chang, J., Hong, D., Vislovskiy, V, et al. (2007). An overview on the dehydrogenation of aUcylbenzenes with carbon dioxide over supported vanadium-antimony oxide catalysts, Catal. Surv. Asia, 11, pp. 59-69. 

Chang JS, Vislovskiy VP, Park MS, Hong DY, Yoo JS, Park SE (2003) Utilization of carbon dioxide as soft oxidant in the dehydrogenation of ethylbenzene over supported vanadium-antimony oxide catalysts. Green Chem 5 587-590... 

The oxidation of methacrolein to methacrylic acid is most often performed over a phosphomolybdic acid-based catalyst, usually with copper, vanadium, and a heavy alkaU metal added. Arsenic and antimony are other common dopants. Conversions of methacrolein range from 85—95%, with selectivities to methacrylic acid of 85—95%. Although numerous catalyst improvements have been reported since the 1980s (120—123), the highest claimed yield of methacryhc acid (86%) is still that described in a 1981 patent to Air Products (124). 

A study of the vanadium catalyzed dehydrogenation reaction showed antimony interacts with vanadium and decreases its dehydrogenation activity. Cracking catalyst was contaminated with vanadium in the laboratory, A portion of this contaminated catalyst was then treated with an antimony containing compound to passivate vanadium. The catalysts were evaluated by cracking gas oil. The yield of hydrogen for passivated catalyst averaged fifteen percent less than for the unpassivated catalyst. 

Metals passivation is an area of active research and development, and several passivation systems have been commercialized. Commercialized systems include addition of elements and combinations of elements to FCC catalysts, such as antimony, antimony plus phosphorus (6,. 14), antimony plus phosphorous plus tin, antimony plus tin, tin (19-21), and bismuth (22, 23). Other commercialized systems include process changes or catalyst changes such as the use of steam or light hydrocarbons as diluents in the reactor (24) and vanadium traps (25). Antimony has been used successfully in conjunction with these systems. Another metals passivation additive, containing ingredients that are proprietary, has also been introduced commercially (26) ... 

The combination of antimony and tin reduces the yield of hydrogen and coke, and increases the yield of gasoline when compared with the use of antimony alone. The resistance of the catalyst to deactivation by vanadium may also be improved. The combination of antimony and tin helped maintain catalyst activity for several commercial cases. With comparable feedstock and process conditions, the conversion increased up to three percent, the yield of gasoline increased up to 2.4 percent, and the yield of coke decreased up to 0.5 weight percent. 

In this process HCN is produced when methanol reacts with ammonia and oxygen in the presence of an oxide catalyst that contains iron, antimony, phosphorous and vanadium. The reaction occurs in the vapor phase in a fluidized bed reactor with an oxygen-to-methanol molar ratio in the gas phase that is less than 1.6. The process and the catalyst are described in patents that were issued to Nitto Chemical (now Mitsubishi Rayon) during the late 1990 s (European Patent 864,532 Japanese patents 10-167,721, 10-251,012, 11-043,323 US Patent 5,976,482). 

Brazdil, J.F. Cavalcanti, A.P. Padolewski, J.P. Method for Preparing Vanadium Antimony Oxide Based Oxidation and Ammoxidation Catalysts US Patent 5,693,587, Dec 2, 1997 [assigned to The Standard Oil Company of Ohio (Sohio/BP)]. 

Unless otherwise noted, catalysts were prepared by coprecipitating the hydrous oxides of uranium, antimony, and a tetravalent metal from a hydrocholoric acid solution of their salts by the addition of ammonium hydroxide. The precipitates were washed, oven dried, then calcined at 910 C overnight or at 930 C for two hours to form crystalline phases. Attrition resistant catalysts, containing 50% by weight silica binder, were prepared by slurrying the washed precipitate with silica-sol prior to drying. In some cases, small amounts of molybdenum or vanadium were added by impregnating the oven dried material with ammonium paramolybdate or ammonium metavanadate solution. The details of these preparations may be found elsewhere (5-8). 

Addition of promoters to neutralize poisons. Sulfur poisoning of nickel is reduced in the presence of copper chromite, since copper and chromium ions preferentially form sulfides. Another example is heavy metals poisoning of cracking catalyst, in which iron, nickel, and vanadium are alloyed with antimony added to the feed and deposited on the catalyst. 

The synthesis of acrylonitrile from propane, as an alternative route to the industrial process which employs the olefin as the raw material, is carried out on catalysts which are based on vanadium and antimony mixed oxides. The catalyst contains a large excess of antimony with respect to the stoichiometric requirement for the formation of VSb04, and the... 

This catalytic system, as well as systems based on Mo/V/Te/Nb mixed oxides which have been developed by Mitsubishi (65), also represent an example of catalyst characterized by multifunctional properties. The rutile structure is the matrix to host vanadium ions as solid solutions, while the antimony oxide is present as a dispersed microcrystalline oxide. Vanadium is the component which is more active in paraffin conversion, while the high selectivity to the desired product is due to the presence of dispersed, separate phase, antimony oxide. 

Sohio Issued several patents claiming catalysts based on vanadium, antimony and some promoters which are able to ammoxidize propane with a completely heterogeneous mechanism (66). These catalysts can be considered intrinsically multifunctional since both dehydrogenation and nitrogen insertion functions are present (67,68). The main problem with this type of catalyst is the low rate of the subsequent ammoxidation of intermediate propylene. Indeed, propylene is always present as a by-product. 

The most studied systems for oxidative propane upgrading are vanadium [2], vanadium-antimony [3], vanadium-molybdenum [4], and vanadium-phosphorus [5] based catalysts. Another family of light paraffin oxidation catalysts are molybdenum based systems, e.g. nickel-molybdates [6], cobalt-molybdates [7] and various metal-molybdates [8-9]. Recently, we investigated binary molybdates of the formula AM0O4 where A = Ni, Co, Mg, Mn, and/or Zn and some ternary Ni-Co-molybdates promoted with P, Bi, Fe, Cr, V, Ce, K or Cs [10-11]. A good representative of these systems is the composition Nio.5Coo.5Mo04 which was recently selected for an in depth kinetic study [12] and whose mechanistic aspects are now further illuminated here. 

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