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在气相氧浓度10%条件下,研究了催化剂中各组元含量及助剂K、P、Nb对催化活性的影响。结果表明,在一定浸涂量下,V含量有一最佳值(4.38%),K含量达0.3%(mol)时,催化剂活性处于最佳值。XRD分析表明:由于助剂的存在,催化剂结构中V_2O_(4.33)的晶胞尺寸发生了畸变。经计算,沿001面,V_2O_(4.33)的C轴缩短了0.018nm。IR测试表明,由于助剂的作用使V=O键振动频率发生改变,说明助剂对V=O键有诱导作用。在空速3.000h~(-1),氧浓度10%,邻二甲苯60g/m~3,床层最高温度450℃条件下,苯酐重量收率可达117.4%。
Under the conditions of 10% gas phase oxygen concentration, the effects of various components and K, P, Nb promoters on the catalytic activity were investigated. The results showed that the best catalyst activity was obtained when the content of V was an optimum value (4.38% ) and the content of K was 0.3% (mol) under a certain amount of dip coating. XRD analysis shows that due to the presence of additives, the unit cell size of V 2 O 4 (4.33) in the catalyst structure is distorted. It is calculated that along the 001 surface, the C axis of V 2 O 4 (4.33) is shortened by 0.018 nm. IR test showed that the vibration frequency of V = O bond changed due to the effect of auxiliaries, indicating that the promoter has an induction effect on V = O bond. Under the conditions of airspeed of 3.000h ~ (-1), oxygen concentration of 10%, o-xylene of 60g / m ~ 3 and bed temperature of 450 ℃, the yield of phthalic anhydride reached 117.4%.