Copper catalysts basic properties

Takaya and co-workers (256) disclosed that chiral copper alkoxide complexes catalyze the transesterification and kinetic resolution of chiral acetate esters. Selec-tivities are very poor (E values of 1.1-1.5) but it was noted that the Lewis acid BINAP CuOTf was not an effective catalyst. The observation thatp-chlorophcnyl-BINAP-CuOf-Bu complex gave faster rates than BINAP-CuOt-Bu suggests that both the Lewis acidic and Lewis basic properties of the copper alkoxide are required for optimal reactivity. 

Co. surface area = 300 m2/g ) with aqueous solutions of Cu, Cr, Mg, Ca, Sr, and Ba in Nitrate. All the catalysts have Cu to Si02 weight ratio of 14/86. For promoted catalyst, the Cr to Cu molar ratio was varied from 1/4 0 to 1/4, and the alkaline earth metal to Cu molar ratio was kept at 1/10. The impregnated catalysts were dried at 100 °C overnight, calcined at 450 for 3 h and then reduced in a stream of 10% H2 in Ar at 300 °C for 2 h. The copper surface areas of catalysts were determined by the N20 decomposition method described elsewhere [4-5J. The basic properties of the catalysts were determined by temperature-programmed desorption ( TPD ) of adsorbed carbon dioxide. Ethanol was used as reactant for dehydrogenation reaction which was performed in a microreactor at 300°C and 1 atm. 

Decarboxylation of -a-phenylcinnamic acid is effected by refluxing the acid in quinoline in the presence of a trace of copper chromite catalyst both the basic properties and boiling point (237°C) of quinoline make it a particularly favorable solvent. Z-Stilbene, a liquid at room temperature, can be characterized by trans addition of bromine to give the crystalline -dibromide. A little meso-dibromide derived from -stilbene in the crude hydrocarbon starting material is easily separated by virtue of its sparing solubility. 

From this study the following reaction scheme describing the transformation of ethylamine to the main product DMEA and by-products was established. From a kinetic point of view, steps 2 and 3 are the rate determining reactions. It follows that the DMEA selectivity is increased by modifying the acido-basicity of copper chromite used as a catalyst. In fact, the change of the catalyst basicity can decrease the MEA condensation to form DEA without modification of the hydro-dehydrogenating properties of the catalyst which are necessary for the methylation of ethylamine with methanol (steps 1 and 3). 

Decarboxylation Reactions. Taking advantage of its basic properties, quinoline is generally useful as a solvent for decarboxylation reactions. It is especially suitable because its relatively high boiling point facilitates the decarboxylation. Examples include the decarboxylation of 3-methyl-2-furoic acid (10) to 3-methylfuran (11) (eq 6), /w-nitrocinnamic acid (12) to m-nitrost)frene (13) (eq and a-phenylcinnamic acid (14) to cis-stilbene (15) (eq 8). Copper catalysts such as copper or copper chromite are used to effect the decarboxylations. 

The vapor-phase dehydration of glycerol to hydroxyacetone was also studied by Sato et al. on copper catalysts at 205°C. They found that the acid-base property of the support material affected the selectivity basic MgO, CeOg, and ZnO supports showed low hydroxyacetone selectivity, while acidic supports, such as AlgOg, Zr02, FeaOa, and SiOg, effectively promoted hydroxyacetone selectivity. 

Formation of the mixed cement-containing systems within the range of low copper concentrations with addition of alkali metal dopants as well as catalytical properties of these systems in the ethane oxidative chlorination process have been investigated. Based on the obtained data the efficient and stable copper-cement catalyst has been worked out. This catalyst will assist in the development of a new technology of the vinyl chloride production from ethane. The basic peirameters of the ethane oxychlorination process have been determined at 623-673K, time-on-stream 3-5s and reactant ratio of C2H6 HCI 02 = 1 2 1 the conversion of ethane is more than 90% and the total selectivity to ethylene and vinyl chloride is 85-90%. 

This type of reaction requires a complex, multifunctional catalyst with acid and hydrogenating properties. In a previous work we showed that these properties and hence the activity and the selectivity of the catalyst depended very much on the support and on the various promoters of copper which was chosen as a basic metallic element (1, 2). Furthermore the stability of the catalysts also depends largely on their composition and of certain products of the reaction such as water and ammonia (3). We have therefore studied the modifications of the bulk and surface compositions as well as those of the adsorption properties of supported (alumina or graphite) or promoted (barium) copper-chromium... 

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