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以Pb_1 _(3x)Bi_(2xφx)MoO_4为例,研究了白钨矿A_1~(2+)_(3x)A_(2x)~(3+)φ+xMoO_4型催化剂的热处理方法对丙烯氨氧化制丙烯腈催化活性的关系。利用DTA及XRD研究温度对PbMoO_4晶体生长的影响以确定焙烧温度。阳离子空位x=0.04对催化性能最佳,丙烯转化率76%,丙烯睛收得率51%。没有空位的PbMoO_4(x=0)基本上没有催化活性。研究了焙烧温度、时间和气氛对30X催化剂比表面和表面总酸度的影响,并与催化性能相关联,从而优化了此催化体系的焙烧条件。在空气气氛中650℃停留25min获得的催化剂(比表面约为43m~2/g,表面总酸度0.33mmol/g)用于氨氧化反应,丙烯转化率大于99.5%,丙烯睛收得率约86%。
Taking the Pb_1_ (3x) Bi_ (2xφx) MoO_4 as an example, the effects of the heat treatment method on the catalyst A_1_2 + 3x_ (2x) -3x + xMoO_4 for the ammoxidation of propylene Preparation of acrylonitrile catalytic activity. The effect of temperature on the growth of PbMoO_4 crystal was studied by DTA and XRD to determine the calcination temperature. Cationic vacancies x = 0.04 for the best catalytic performance, propylene conversion 76%, acrylonitrile yield 51%. PbMoO_4 (x = 0) with no vacancy has essentially no catalytic activity. The effects of calcination temperature, time and atmosphere on the specific surface area and total surface acidity of 30X catalyst were investigated and correlated with the catalytic performance to optimize the calcination conditions of this catalytic system. The catalyst (surface area about 43m ~ 2 / g, surface total acidity 0.33mmol / g) obtained in an air atmosphere at 650 ℃ for 25min was used for ammoxidation. The propylene conversion was over 99.5% and the acrylonitrile yield was about 86 %.