正丁烷氧化制顺酐流化床催化剂的性能

Catalytic Performance of Fluidized-Bed Catalyst for Oxidation of n-Butane to Maleic Anhydride

考察了前驱体制备过程中水合肼 /五氧化二钒摩尔比 (以下简记为n(N2 H4 ) /n(V2 O5) )对催化剂性能的影响 .由较高的n(N2 H4 ) /n(V2 O5) 比制得的催化剂 ,其 (VO) 2 P2 O7相含量较多 ,正丁烷转化率较高 .随着n(N2 H4 ) /n(V2 O5) 比的减小 ,δ VOPO4相的含量逐渐增多 ,正丁烷转化率随之升高 ;而顺酐选择性开始时升高 ,达到最大值后逐渐降低 .在n(N2 H4 ) /n(V2 O5) =0 34时制备的催化剂最佳 ,在丁烷浓度为 4 0 %、空速为 5 0 0h-1及反应温度为 4 2 0℃的反应条件下 ,顺酐收率可达 4 9 74 % .

The experiments of precursor preparation have been performed to investigate the effects of N2H4 . H2O/V2O5 mole ratio on catalytic performance of VPO catalyst for oxidation of n -butane to maleic anhydride (MA). For the catalyst samples prepared at higher mole ratio of N2H4 . H2O/V2O5, the quantity of (VO)(2)P2O7 (V4+) phase is considerably large, and the n -butane conversion is quite high. With the decrease of N2H4 . H2O/ V2O5 mole ratio in precursor preparation, the relative amount of delta-VOPO4,(V5+) phase increases progressively. The increase of V5+ phase strengthens the oxidation of the intermediate olefins, and then promotes the dehydrogenation of n -butane. Thus, the selectivity for MA increases at beginning, whereas the n -butane conversion increases continuously. When the V5+ phase reaches a given quantity, the overoxidation takes place, and the selectivity for MA begins to decrease. The yield of MA goes through a Maximum value at the optimal N2H4 . H2O/ V2.O5 mole ratio during the change of N2H4 . H2O/V2O5 mole ratio in precursor preparation from high to low. The catalyst sample prepared at N2H4 . H2O/V2O5 Mole ratio of 0.34 gave the maximum MA yield of 49.74% under the conditions of n -butane concentration of 4.0%, space velocity of 500 h(-1) and temperature of 420degreesC. The catalyst of fine particle bed in this study belongs to the particles of group A. The catalyst fluidizes easily and behaves a larger flexibility for operation.