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Cobalt/bismuth, oxidation catalysts

Some remarks must be made about the role of oxygen coordination. Several authors have remarked that the coordination in catalytic oxides is of major importance. Mitchell and Trifiro (e.g. ref. 219) concluded that a bismuth molybdate catalyst is most active if the amount of tetrahedrally coordinated molybdenum is large in comparison with octahedrally coordinated molybdenum. However, V205 and Sb2Os are structures with specific octahedral coordination [142] and often the coordination is changed by reduction of the catalyst or by the support [203]. In a- and /3-cobalt molybdates the coordination differs, but the catalytic behaviour is really the same. The low temperature Bi2Mo06 (7 phase) has an octahedral coordination but is an effective catalyst. [Pg.247]

Shortly after the introduction of the bismuth molybdate catalysts, SOHIO developed and commercialized an even more selective catalyst, the uranium antimonate system (4). At about the same time, Distillers Company, Ltd. developed an oxidation catalyst which was a combination of tin and antimony oxides (5). These earlier catalyst systems have essentially been replaced on a commercial scale by multicomponent catalysts which were introduced in 1970 by SOHIO. As their name implies, these catalysts contain a number of elements, the most commonly reported being nickel, cobalt, iron, bismuth, molybdenum, potassium, manganese, and silica (6-8). [Pg.184]

The fust reaction takes place in the vapor phase, between 330 and 360°C, at low pressure (between 03 and 04.106 Pa absolute), in the presence of air and steam in a r-butanol/air/steam ratio of about 1 10 to 15/6 to 12, on a catalyst based on mixed oxides of molybdenum, cobalt, bismuth, iron, nickel, and additions of derivatives of alkaline metals, antimony, tellurium, phosphorus, tungsten, tin, manganese, etc. With residence times of 2 to 3 s, the molar yield of methacrolein exceeds 85 per cent for virtually total once-throngh conversion of r-butanoLThe main by-products formed are... [Pg.209]

Early catalysts for acrolein synthesis were based on cuprous oxide and other heavy metal oxides deposited on inert siHca or alumina supports (39). Later, catalysts more selective for the oxidation of propylene to acrolein and acrolein to acryHc acid were prepared from bismuth, cobalt, kon, nickel, tin salts, and molybdic, molybdic phosphoric, and molybdic siHcic acids. Preferred second-stage catalysts generally are complex oxides containing molybdenum and vanadium. Other components, such as tungsten, copper, tellurium, and arsenic oxides, have been incorporated to increase low temperature activity and productivity (39,45,46). [Pg.152]

The first-stage catalysts for the oxidation to methacrolein are based on complex mixed metal oxides of molybdenum, bismuth, and iron, often with the addition of cobalt, nickel, antimony, tungsten, and an alkaU metal. Process optimization continues to be in the form of incremental improvements in catalyst yield and lifetime. Typically, a dilute stream, 5—10% of isobutylene tert-huty alcohol) in steam (10%) and air, is passed over the catalyst at 300—420°C. Conversion is often nearly quantitative, with selectivities to methacrolein ranging from 85% to better than 95% (114—118). Often there is accompanying selectivity to methacrylic acid of an additional 2—5%. A patent by Mitsui Toatsu Chemicals reports selectivity to methacrolein of better than 97% at conversions of 98.7% for a yield of methacrolein of nearly 96% (119). [Pg.253]

The oxidation of propene to acrolein has been one of the most studied selective oxidation reaction. The catalysts used are usually pure bismuth molybdates owing to the fact that these phases are present in industrial catalysts and that they exhibit rather good catalytic properties (1). However the industrial catalysts also contain bivalent cation molybdates like cobalt, iron and nickel molybdates, the presence of which improves both the activity and the selectivity of the catdysts (2,3). This improvement of performances for a mixture of phases with respect to each phase component, designated synergy effect, has recently been attributed to a support effect of the bivalent cation molybdate on the bismuth molybdate (4) or to a synergy effect due to remote control (5) or to more or less strong interaction between phases (6). However, this was proposed only in view of kinetic data obtained on a prepared supported catalyst. [Pg.262]

Practically complete conversion of propylene and ammonia is achieved to produce acrylonitrile in 65-70% yield. Acetonitrile and HCN are the main byproducts. The Sohio process originally used oxides of Bi, Co, and Mo, and bismuth and cobalt molybdates.898,915,941,953 Other catalysts developed later (uranyl antimonate antimony oxide-iron oxide oxides of Fe, Ce, and Mo mixed oxides of Sb and Sn)898,915,939,953,955,956 produce fewer byproducts and ensure higher yields of acrylonitrile. [Pg.511]

Each c.c. of free space corresponds with 20 sq. cms. of catalyst surface. E. I. Orloff observed the oxidation of ammonia when mixed with air and passed over a heated copper gauze 4NH3-f-302 =2N2+6H20, with traces of nitrous and nitric acids—aniline, toluidine, and pyridine were oxidized in a similar way. W. W. Scott and W. D. Leech found that the conversion efficiency of cobalt oxide at 600°-800° is 79 3 per cent. This is augmented when about 3 per cent, of bismuth, or 10 to 12 per cent, of alumina, is used as... [Pg.213]

In the previous sections of this review, it has been shown that most effective catalysts for the selective oxidation of propylene contain at least two types of metal oxides—an amphoteric or low-valence oxide, such as bismuth, tin, iron, or cobalt, and an oxide of a high valence metal, such as molybdenum or antimony. Moreover, it has been suggested several times that each of these metal oxide components may give rise to an active site for example, propylene may adsorb on an active site associated with one of the metal oxide components, and oxygen may adsorb on an active site associated with another metal oxide component. This problem has been studied using spectroscopic, adsorption, and kinetic techniques. It now seems appropriate to consider some of these studies in detail, attempting to relate the solid structure of the catalyst to the active sites wherever possible. [Pg.210]

Catalysts based on transition metal molybdates, typically bismuth, cobalt and nickel molybdates [2-6], have received recent attention. Of the transition metal molybdates, those based on nickel, and in particular the stoichiometric NiMo04, have attracted the greatest interest. NiMo04 presents two polymorphic phases at atmospheric pressure a low temperature a phase, and a high temperature P phase [2,7]. Both phases are monoclinic with space group dim. These phases differ primarily in the coordination of molybdenum which is distorted octahedral in the a phase and distorted tetrahedral in the P phase. The P phase has been shown to be almost twice more selective in propene formation than the a phase for comparable conversion at the same temp>erature [2]. A similar effect has been noted for oxidative dehydrogenation of butane, with the P phase being approximately three times more selective in butene formation than the a phase [8]. The reason for the difference in selectivities is unknown, but the properties of the phases are known to be dependent on the precursors from which they are derived. Typically, nickel molybdates are prepared by calcination of precipitated precursors. [Pg.368]

A silver (or copper) catalyst suitable for the oxidation of methanol may also be prepared by heating silver or copper cyanide or a mixture of these in the presence of air to the point where puffing occurs. By incorporating a fervo- or ferri-cyanide, e.g., bismuth ferro-cyanide, bismuth ferri-cyanide, calcium cerium ferro-cyanide, cerium cobalt ferro-cyanide, vanadium or molybdenum ferro-cyanide with the starting material, an activated product may be obtained. The silver or copper cyanides are prepared by precipitating a soluble cyanide with silver nitrate or cupric chloride respectively.30... [Pg.147]

The catalyst systems employed are based on molybdenum and phosphorus. They also contain Various additives (oxides of bismuth, antimony, thorium, chromium, copper, zirconium, etc.) and occur in the form of complex phosphomolybdates, or preferably heteropolyacids deposited on an inert support (silicon carbide, a-alumina, diatomaceous earths, titanium dioxide, etc.). This makes them quite different from the catalysts used to produce acrylic acid, which do not offer sufficient activity in this case. With residence times of 2 to 5 s, once-through conversion is better than 90 to 95 per cent, and the molar yield of methacrylic acid is up to 85 to 90 per cent The main by-products formed are acetic add, acetone, acrylic add, CO, C02, etc. The major developments in this area were conducted by Asahi Glass, Daicel, Japan Catalytic Chemical, Japanese Gem, Mitsubishi Rayon, Nippon Kayaku, Standard Oil, Sumitomo Chemical, Toyo Soda, Ube, etc. A number of liquid phase processes, operating at about 30°C, in die presence of a catalyst based on silver or cobalt in alkaline medium, have been developed by ARCO (Atlantic Richfield Co,), Asahi, Sumitomo, Union Carbide, etc. [Pg.210]

Today the most cost-effective processes are those based on propylene as the starting material. There are three major variations of propylene processes, the Distillers process [21-23], the Sohio process [24], and the DuPont process [25,26]. All three processes are based on the ammonoxidation of propylene. The Distillers process is carried out in two stages. In the first, propylene is oxidized in air to form acrolein and water. These intermediate products are allowed to react in the second stage with ammonia in the presence of molybdenum oxide and air to form crude acrylonitrile. The pure monomer is recovered by a series of azeotropic distillations. The Sohio process is carried out in just one stage. Ammonoxidation of propylene takes place in air at 2-3 atmospheric pressure and 425-510°C. With catalysts, such as concentrated bismuth phosphomolybdate or other oxides of molybdenum and cobalt, the reaction takes place with over 50% yield in a reaction time of only about 15 s. In the DuPont version of this process, the ammonoxidation is brought about with nitric oxide at 500°C using silver on silica catalyst. The chemistry of acrylonitrile monomer has been reviewed by a number of authors [27-30]. [Pg.817]

The next major advance was the introduction of cobalt and nickel, which form divalent molybdates having the formulas C0M0O4 and NiMo04. The first disclosure of Co-Fe-Bi-Mo-0 catalysts was made by Nippon Kayaku Co., Japan for use in the selective oxidation of propylene to acrolein (16). The presence of the divalent transition-metal cation along with iron and bismuth molybdate produced a catalyst with significantly enhanced activity and selectivity. This discovery was... [Pg.247]

Various catalyst systems have been developed to increase the elRciency of the process and these use bismuth phosphomolybdate (as used in the Sohio process) and the mixture of oxides of cobalt, molybdenum, antimony and tin (as described in the Distiller s process). [Pg.150]


See other pages where Cobalt/bismuth, oxidation catalysts is mentioned: [Pg.42]    [Pg.190]    [Pg.262]    [Pg.212]    [Pg.407]    [Pg.42]    [Pg.49]    [Pg.615]    [Pg.221]    [Pg.426]    [Pg.120]    [Pg.563]    [Pg.159]    [Pg.115]    [Pg.17]    [Pg.124]    [Pg.20]    [Pg.331]    [Pg.3388]    [Pg.137]    [Pg.375]    [Pg.382]    [Pg.84]    [Pg.397]    [Pg.191]    [Pg.3387]    [Pg.702]    [Pg.343]    [Pg.41]   
See also in sourсe #XX -- [ Pg.432 ]




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Bismuth catalyst

Bismuth oxide catalysts

Bismuthic oxide

Bismuthous oxide

Cobalt catalyst

Cobalt catalysts catalyst

Cobalt oxidant

Cobalt oxide

Cobalt oxide catalyst

Cobalt oxidization

Cobaltous oxide catalysts

Oxidation cobalt

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