Oxidations employing platinum catalysts

Heyns, K., and Paulsen, H., Selective Catalytic Oxidation of Carbohydrates, Employing Platinum Catalysts, 17, 169-221... 

SELECTIVE CATALYTIC OXIDATION OF CARBOHYDRATES, EMPLOYING PLATINUM CATALYSTS... 

Abstract The faster kinetics of the alcohol oxidation reaction in alkaline direct alcohol fuel cells (ADAFCs), opening up the possibility of using less expensive metal catalysts, as silver, nickel, and palladium, makes the alkaline direct alcohol fuel cell a potentially low-cost technology compared to acid direct alcohol fuel cell technology, which employs platinum catalysts. In this work an overview of catalysts for ADAFCs, and of testing of ADAFCs, fuelled with methanol, ethanol, and ethylene glycol, formed by these materials, is presented. 

Catalytic oxidation ia the presence of metals is claimed as both nonspecific and specific for the 6-hydoxyl depending on the metals used and the conditions employed for the oxidation. Nonspecific oxidation is achieved with silver or copper and oxygen (243), and noble metals with bismuth and oxygen (244). Specific oxidation is claimed with platinum at pH 6—10 ia water ia the presence of oxygen (245). Related patents to water-soluble carboxylated derivatives of starch are Hoechst s on the oxidation of ethoxylated starch and another on the oxidation of sucrose to a tricarboxyhc acid. AH the oxidations are specific to primary hydroxyls and are with a platinum catalyst at pH near neutraUty ia the presence of oxygen (246,247). Polysaccharides as raw materials ia the detergent iadustry have been reviewed (248). 

Probably the most significant control technology breakthrough came m 1977, when Volvo released a computer-controlled, fuel-mjected vehicle equipped with a three-way catalyst. The new catalytic converters employed platinum, palladium, and rhodium to simultaneously reduce NO and oxidize CO and HC emissions under carefully controlled oxygen conditions. The new Bosch fuel injection system on the vehicle provided the precise air/fuel control necessary for the new catalyst to perform effectively. The combined fuel control and three-way catalyst system served as the foundation for emissions control on the next generation of vehicles. 

The discussion of the activation of bonds containing a group 15 element is continued in chapter five. D.K. Wicht and D.S. Glueck discuss the addition of phosphines, R2P-H, phosphites, (R0)2P(=0)H, and phosphine oxides R2P(=0)H to unsaturated substrates. Although the addition of P-H bonds can be sometimes achieved directly, the transition metal-catalyzed reaction is usually faster and may proceed with a different stereochemistry. As in hydrosilylations, palladium and platinum complexes are frequently employed as catalyst precursors for P-H additions to unsaturated hydrocarbons, but (chiral) lanthanide complexes were used with great success for the (enantioselective) addition to heteropolar double bond systems, such as aldehydes and imines whereby pharmaceutically valuable a-hydroxy or a-amino phosphonates were obtained efficiently. 

Some metallic catalysts in the form of gauzes are employed in certain processes, e.g. the oxidation of ammonia to nitrogen oxides over platinum, and for these heat transfer data have been published by London et al. [41,42]. 

Catalysts other than platinum catalysts have been considered for reforming. Included among these are certain metal oxides, e.g., chromia and molybdena. However, these catalysts are much less active than platinum and also less selective toward the reactions of most interest in reforming, at least under the conditions usually employed in commercial... 

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