The obtaining of the anhydride products by oxidation of n-pentane on the VPO catalysts

Abstract

It was investigated VPMeO catalysts (Me=Fe, Mo, Te, W, Ni, Ti, La, Bi, Zr і Ag) in oxidation of n-pentane. On these catalytic samples the main products of reaction are maleic (MA), phthalic (PhA), citraconic (CA) anhydrides, carbon oxides and in-significant quantity of acetic and of acrylic acids. It was established that a change of physical-chemical properties of the VPMeO catalysts affects a course of reaction of n-pentane oxidation. It was determined that the introduction of additives into the basic VPO composition and its content influences a phase composition, a morphol-ogy, acidic properties of catalyst surface, a crystallization temperature of active component and a oxidation degree of vanadium in it. It was established that addi-tives in the VPO sample may be distributed in two ways: a) evenly, high disperse (Fe, Te, Ni, Ag ions), b) with formation of X-ray amorphous additive phosphate phase (Ti, Bi, La, W, Zr ions). Additives that decrease temperature of the active phase formation of a catalyst and increase temperature of its oxidation (Fe, Ti, Bi, Zr ions) positively influence the life of exploitation of catalytic pattern without losing its se-lectivity in the n-pentane oxidation. Additives that reduce the O 1s-electrons energy and increase an oxygen content (O/(V+P+Me)) on the VPO composition surface en-hance the specific rate of the hydrocarbon oxidation. A growth of phosphorous con-tent on the surface of synthesized compositions also contributes to the increase of the time of their stable work. The influence of ratio of Bronsted and Lewis acid cen-ters on surface of the VPМеO pattern on a selectivity of anhydrides production was established. The growth of acidic centers content on the surface of patterns increas-es the CA selectivity. The rise of quantity of Lewis centers favors the PhA formation while the MA selectivity reduces in the reaction products. According to experimental data the modification of the VPO catalyst is affect its physical-chemical and cata-lytic properties. The change of defined physical-chemical properties allows to regu-late a process of the n-pentane oxidation in the direction of formation of one of the anhydrides.