Zinc-chromium oxide

Copper—cadmium and zinc—chromium oxides seem to provide most selectivity (38—42). Copper chromite catalysts are not selective. Reduction of red oil-grade oleic acid has been accompHshed in 60—70% yield and with high selectivity with Cr—Zn—Cd, Cr—Zn—Cd—Al, or Zn—Cd—A1 oxides (43). The reduction may be a homogeneously catalyzed reaction as the result of the formation of copper or cadmium soaps (44). 

Old processes use a zinc-chromium oxide catalyst at a high-pressure range of approximately 270-420 atmospheres for methanol production. 

Such reactions comprise practically all those in which hydrogen is linked to carbon to produce of necessity hydroxy compounds, which are of industrial importance, e.g., the manufacture of methanol and higher alcohols from carbon monoxide and hydrogen in presence of catalysts, such as zinc-chromium oxides. 

TABLE 9.2 The Effect of Temperature on Hydrogenation of Nitrocyclohexane over Silver-Zinc-Chromium Oxide"... 

The hydrogenation of an unsaturated ester to an unsaturated alcohol may be possible over zinc-chromium oxide as catalyst, although the catalyst is known to be much less active for the usual ester hydrogenations than copper-chromium oxide. Ethyl or butyl (eq. 10.25) oleates were hydrogenated to octadecenol in yields of over 60% with a zinc-chromium oxide at 280-300°C and 20 MPa H2.16 The butyl ester was much preferred to the ethyl ester, since it was difficult to separate the ethyl ester from the alcohol product because of their similar boiling points. 

Heterogeneity of the surfaces of oxide catalysts such as chromium oxide, zinc oxide, and zinc-chromium oxide has been postulated by H. S. Taylor (75) on the basis of adsorption studies. In the author s view, Taylor s experimental observations may be also explained without assuming a heterogeneous character of the oxide surfaces. 

We have investigated a series of the dehydrogenating catalysts for this reaction. Our attention was focused on two of them. Further study of 2,3-butanediol dehydrogenation and oxidative dehydrogenation to butadione was performed using zinc-chromium oxide catalysts and vanadium-magnesium oxide catalysts as well. 

Figure 1. Dehydrogenation of acetoin (to the left, pale dots) and of 2,3-butanediol (to the right) on zinc- chromium oxide catalyst, LHSV=1.6 h" 2, acetoin (as initial material) 3, butadione 1, butanediol (as initial material) 2, acetoin (formed as intermediate from butanediol) 3,butadione.

Zinc-chromium oxide catalysts were prepared by co-precipitation from aqueous solutions of corresponding nitrates with aqueous ammonia. The precipitated hydroxo-compounds mixed with ZnO were dried at 120°C and the slightly wet product was then molded by squeezing out through orifices with diameter of 4 mm [6]. 

Zinc-chromium oxide and massive amounts of finely divided Ni (W4 or W6 Raney Ni) in ethanol are effective , but saturation of a benzene ring occurs preferentially. 

ZINC CHROMIUM OXIDES (12018-19-8 14018-95-2 13530-65-9) An oxidizer. Reacts with reducing agents, alcohols, combustible materials, ethers, hydrazines, organic substances, metal powders. 

Zinc chromium oxide (ZrCr04) Zinc hydroxychromate Zinc tetraoxychromate Zinc tetraoxychromate 76A Zinc tetraoxychromate 780B Zinc tetroxychromate Zinc yellow Zincro ZTO. Used as a yellow pigment in paints, varnishes, oil colors, linoleum, rubber etc. [hydrate] fine yellow powder slightly soluble in H2O. Landers-Segal Color. 

Zinc chromium oxide (ZrCrO+74) 4141 Zinc vitriol (heptahydrate) 4160... 

Olefinic bonds also undergo, hydrogenation in the presence of copper-chromium oxide catalyst but usually require a temperature above 150-200°C. The latter catalyst is useful if it is desired to reduce certain other groups in the molecule at the same time. Zinc chromium oxide is even less active for hydrogenating an ethylenic linkage. 

These observations, when extended to other oxides or mixtures of oxides, gave in part confirmatory data and, in one case, that of manganese-chromium oxide, data which significantly differed from those obtained with zinc oxide. Thus, with chromium oxide gel with a surface area of 189.5 sq. meters/g. the quantities of gas involved in the desorption-readsorption phenomena between 56 and 302° C. amounted to 9 cc. or nearly 5% of the total surface. With a zinc chromium oxide of 21 sq. meters/g. the area involved in desorption-readsorption phenomena was 13% of the total surface between 0 and 302° C. With manganese-chromium oxide, on the other hand, no readsorption of gas was observed when the sample was cooled in hydrogen from 218 to 0° C. 

When, however, desorption does occur in the ascending portion of the curve BC, there should, on cooling down from C, no longer be a horizontal section CE but continuously increasing values of the adsorption CG, measuring, in excess of the values over the horizontal section, the quantity of gas which was desorbed during the measurements made in passing upwards in temperature from B to C. It is this behavior which is shown by zinc oxide, chromium oxide gel, and zinc-chromium oxide. 

Synonyms Basic zinc chromate Buttercup yellow Chromic acid, zinc salt Chromium zinc oxide Cl 77955 Citron yellow Pigment yellow 36 Pure zinc chrome Pure zinc yellow Zinc chromate (VI) hydroxide Zinc chrome Zinc chrome yellow Zinc chromium oxide Zinc... 

Zinc chromate (VI) hydroxide Zinc chrome Zinc chrome yellow Zinc chromium oxide. See Zinc chromate... 

Chromium, tris (2,4-pentanedionato-0,0>. See Chromic acetylacetonate Chromium yellow. See Lead chromate Chromium zinc oxide. See Zinc chromium oxide Zinc chromate Chromocene. See Bis (cyclopentadienyl) chromium... 

Zinc chromite. See Zinc chromium oxide Zinc chromium oxide... 

Zinc chromium oxide. See Zinc chromate Zinc citrate... 

ZMB ZMBI. See Zinc 2-mercaptobenzimidazole ZMBT. See Zinc 2-mercaptobenzothiazole ZMMBI. See Zinc 2-mercaptotoluimidazole ZN-7. See Zirconium boride ZN89. See Zinc rosinate Zn-0312 T1/4". See Zinc chromium oxide Zn-0401 E 3/16". See Zinc oxide Zn-0602 T1/8". See Zinc chromium oxide ZnMB. See Zinc 2-mercaptobenzothiazole Zoco 100, Zoco 103, Zoco 104, Zoco 112 USP, Zoco 124 Zoco 600, Zoco 603, Zoco 604, Zoco 624. See Zinc oxide... 

Zinc chromium oxide catalyst, moderating Ferric acetylacetonate catalyst, mold lubricants Ethyl acid phosphate 2-Ethylhexyl phosphate Stearyl acid phosphate... 

The earlier zinc-chromium oxide catalysts require reaction temperatures of about400°C, and hence pressures of300 atm and above are commonly used. For very large-scale operation (500 tonnes/day or more), the compression/reaction system is very similar to that described for ammonia synthesis. However, large methanol plants are not required in less well-developed areas. The characteristics of compressors are such that smaller high-pressure plants must use reciprocating machinery, which is costlier to instal and maintain. 

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