Chromium chloride catalyst

Darensbourg DJ, Yarbrough JC (2002) Mechanistic aspects of the copolymerization reaction of carbon dioxide and epoxides, using a chiral salen chromium chloride catalyst. J Am Chem Soc 124 6335-6342... 

Darensbourg, D. J. Yarbrough, J. C. Mechanistic Aspects of the Copolymerization Reaction of Carbon Dioxide and Epoxides, Using a Chiral Salen Chromium Chloride Catalyst. J. Am. Chem. Soc. 2002,124, 6335-6342. 

Twelve-membered rings have been obtained using coordination catalysts. The transJmns,ds-cyc. ododec2Lti ien.e has been prepared with a tetrabutyl titanate—diethylalurninum chloride catalyst (48,49) and with a chromium-based system (50). The trans,trans,trans-isom.e-i. has been prepared with a nickel system. 

Cobalt boride has been used for reducing unsaturated aldehydes to unsaturated alcohols improved results are obtained by addition of ferric chloride or chromium chloride (6S). It is a low-activity catalyst. 

Cr-ZSM-5 catalysts prepared by solid-state reaction from different chromium precursors (acetate, chloride, nitrate, sulphate and ammonium dichromate) were studied in the selective ammoxidation of ethylene to acetonitrile. Cr-ZSM-5 catalysts were characterized by chemical analysis, X-ray powder diffraction, FTIR (1500-400 cm 1), N2 physisorption (BET), 27A1 MAS NMR, UV-Visible spectroscopy, NH3-TPD and H2-TPR. For all samples, UV-Visible spectroscopy and H2-TPR results confirmed that both Cr(VI) ions and Cr(III) oxide coexist. TPD of ammonia showed that from the chromium incorporation, it results strong Lewis acid sites formation at the detriment of the initial Bronsted acid sites. The catalyst issued from chromium chloride showed higher activity and selectivity toward acetonitrile. This activity can be assigned to the nature of chromium species formed using this precursor. In general, C r6+ species seem to play a key role in the ammoxidation reaction but Cr203 oxide enhances the deep oxidation. 

Some chromium compounds (e.g., chromium chloride, chromic hydroxide, chromic phosphate) are used as catalysts for organic chemical reactions. 

Chromium(salen) catalysts are excellent reagents for the desymmetrization of OT to-epoxides. Thus, tfr-stilbene oxide is converted to the (3, 3 )-aminoalcohol in the presence of catalytic quantities of chromium-salen complex in methylene chloride solution open to the atmosphere. The addition of small quantities of triethylamine was found to dramatically increase enantioselectivities (by almost 25%). This catalytic system also promotes an efficient aminolytic kinetic resolution (AKR) of racemic epoxides with 2-type symmetry (Equation 18) <20040L2173, 1999TL7303>. W fo-Epoxides can be opened with aromatic amines in water in the presence of 1 mol% of an Sc(ni) catalyst ligated to 1.2mol% of a chiral bipyridine ligand <2005OL4593>. 

Metal cations can also affect the activity of Raney nickel catalysts. The presence of three to ten per cent of chromium or molybdenum in the Raney nickel alloy results in a general increase in the activity of the catalyst prepared from this alloy. Activation of nickel catalysts has also been accomplished by treating them with aqueous solutions of chromium chloride. Another effective promoter for Raney nickel is platinum which increases the activity of this catalyst for the... 

Hydroxymethylfurfural (HMF), a promising intermediate for chemical production [140], can be produced from glucose (Scheme 1) and fructose by dehydration. Conversion of fructose to HMF using l-H-3-methylimidazolium chloride as both catalyst and solvent was reported to result in 92% yield after only 45 min [141], The conversion of the more abundant substrate, glucose, often results in poor selectivity, but it was successfully converted with 70% yield using a chromium(II) chloride catalyst in [C2mim][Cl] [142, 143], The patented method includes monosaccharides, disaccharides and polysaccharides as substrates [143],... 

The supported chromium oxide catalysts can be prepared by impregnating a silica-alumina support with a solution of chromium ions or by coprecipitating the oxides. The preferred impregnating solutions contain dissolved Cr(N03)s.9H20 or CrOs in nitric acid because catalysts made from chromium chlorides or sulfates retain some of the anions after calcination. The solid mixture of chromium-silicon-aluminum compounds is calcined in dry air at 400-700° C or higher to obtain the desired oxide. This probably results in the reaction of surface hydroxy groups in the support material with CrOs to form chromate (IV) and dichromate (V) species ... 

Sasol reported the use of a chromium-based catalyst (Cr salt, 2,5-dimethylpyrrole ligand) for the trimerization of ethylene into 1-hexene (P= 5 MPa, T= 115 °C) [18, 19]. According to Sasol, the IL of choice is l-ethyl-2,3-dimethylimidazolium chloride/ AlEtj containing an excess of AlEtj. When compared to typical homogeneous catalytic systems, the activity and yield in 1-hexene are lower. 

Oxalic acid Oxalic acid dihydrate catalyst, nylon Manganese acetate (ous) catalyst, olefin isomerization Iron pentacarbonyl catalyst, olefin polymerization Acetylacetone Ammonium lactate Chromium carbonyl Chromium chloride (ic) Ethylacetoacetate... 

Because this chapter focuses on molecular transition metal complexes that catalyze the formation of polyolefins, an extensive description has not been included of the heterogeneous titanium systems of Ziegler and the supported chromium oxide catalysts that form HDPE. However, a brief description of these catalysts is warranted because of their commercial importance. The "Ziegler" catalysts are typically prepared by combining titanium chlorides with an aluminum-alkyl co-catalyst. The structural features of these catalysts have been studied extensively, but it remains challenging to understand the details of how polymer architecture is controlled by the surface-bound titanium. This chapter does, however, include an extensive discussion of how group(IV) complexes that are soluble, molecular species polymerize alkenes to form many different types of polyolefins. 

Darensbourg, D.J., Fitch, S.B., 2007. (Tetramethyl tetraaza annulene)chromium chloride a highly active catalyst for the alternating copolymerization of epoxides and carbon dioxide. Inorganic Chemistry 46, 5474—5476. 

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