3A分子筛和Al2O3复合载体催化剂的催化特性

Catalytic performance of 3A molecular sieve and Al2O3 mixed carriers catalyst

摘要:

为探究3A分子筛和Al₂O₃复合载体催化剂的结构特征以及对甲苯的催化特性,采用等体积浸渍法制备Al₂O₃与3A分子筛不同掺混比的载体镍基催化剂,并对催化剂进行XRD、H₂-TPR、BET等特性分析,在固定床反应器中对催化剂催化甲苯的特性进行研究. 结果表明:催化剂中活性组分Ni主要以氧化镍NiO和镍铁合金Ni₃Fe的形式存在；Al₂O₃催化剂的比表面积和孔容随着Fe负载量的增加而减小,而不同掺混比催化剂的比表面积和孔容随着γ-Al₂O₃占比的增加而逐渐增大；甲苯的转化率随着反应温度的增加而逐渐增加,但是随着Fe负载量的增加而先增加后下降；对于不同掺混比的催化剂,随着γ-Al₂O₃占比的增加,催化剂的活性逐渐增强而后减弱,甲苯的转化率因此先增大后减小；当反应温度为700 ℃,水碳比为2,停留时间0.6 s,γ-Al₂O₃占比为60%时,甲苯转化率最高.

Abstract:

To research the structural characteristics of 3A molecular sieve and Al₂O₃ mixed carrier catalyst and the catalytic characteristics of catalyst for toluene, a series of nickel-based catalysts were prepared by equal volume impregnation, and γ-Al₂O₃ and 3A molecular sieve were mixed as carriers. The catalysts were characterized using XRD, H₂-TPR and BET, and the catalytic performance of nickel catalyst for toluene was investigated in a fixed-bed reactor. The results indicated that the active species Ni mainly exists as NiO and Ni₃Fe iron-nickel alloy in the catalysts. The specific surface area and pore volume of catalysts went down for the Al₂O3 catalysts, and then the toluene conversion rose with the increase of temperature, while the conversion rate of toluene increased firstly and then decreased as the load amount of Fe increased. For the mixing catalysts, the specific surface area and pore volume of catalysts increased, while the activity of catalysts and the conversion of toluene increased firstly and then decreased with the increase of γ-Al₂O3 proportion. It has the highest toluene conversion rate, when the reaction temperature is at 700 ℃, the water/carbon ratio is 2, and the residence time is 0.6 s, at same time the mixing ratio of γ-Al₂O3 is 60%.