Supported boria catalysts

Beckmann rearangement of cyclohexemone oxime to e-caprolactam is catalyzed by sulfuric acid in the industrial process. Several attempts have been reported to substitute sulfuric acid by suitable solid acids,but it is rather difficult to obtain high yields. Recendy, it was reported the silica-supported boria catalyst prepared by vapor phase decomposition method was very efficient (oxime conversion 98%, lactam selectivity 96 % at 523K), with slight deactivation with reaction time. (see Section 3.1.11) ... 

It follows from all the above considerations that the acidic character of the surface is necessary for the esterification reaction. This view is supported by the parallel found by some workers [405,406] between the rate of esterification and that of other typical acid-catalysed reactions. A linear correlation was established between the rate of acetic acid—ethanol esterification and that of deisopropylation of isopropylbenzene on a series of silica—alumina, alumina—boria and alumina catalysts [406] a similar relation was found between the rate coefficient of the same esterification reaction and the cracking activity of a series of silica—alumina catalysts prepared in a different way [405]. 

Alumina is one of the most widely used catalyst supports in the petroleum industry because it is robust, porous, relatively inexpensive, and—what is especially important—it is capable of contributing acid-catalyzed activity that can be tailored to suit the requirements of a diverse array of catalytic processes. These include reforming (52, 55), hydrotreating (84, 55), and paraffin isomerization (56-55). Since pure alumina is relatively inactive for the skeletal isomerization reactions that are necessary in such processes, its acid activity is promoted through the addition of catalyst components such as fluoride, chloride, phosphate, silica, or boria. After a discussion of pure alumina itself, we will review pertinent studies of surface acidity and catalytic activity of the promoted aluminas. 

The acid function of the catalyst is supplied by the support. Among the supports mentioned in the literature are silica-alumina, silica-zirconia, silica-magnesia, alumina-boria, silica-titania, acid-treated clays, acidic metal phosphates, alumina, and other such solid acids. The acidic properties of these amorphous catalysts can be further activated by the addition of small proportions of acidic halides such as HF, BF3, SiFit, and the like (3.). Zeolites such as the faujasites and mordenites are also important supports for hydrocracking catalysts (2). 

Ray et al.29 used V205/Cr2 03 catalysts supported on A1203 for the ammoxidation of xylenes. The maximum yields increased from 40% for o-xylene to 70% for m-xylene and, using a catalyst with boria addition, to 89% for p-xylene. From t.p.r. and e.s.r. measurements the authors conclude that a new compound VCr04 is present which is responsible for the catalytic activity. 

Beside adsorption techniques, an 85% control efficiency of dioxins/furans can be achieved by the employment of the DeDiox system. The catalysts used are mostly composed of Ti, V and W oxides. Additionally, Pt and Au oxides supported on silica-boria-alumina were also found to be effective at 200" C. ... 

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