碳四烃在改性HZSM-5分子筛上芳构化研究

STUDY OF THE AROMATIZATION OF C_4 HYDROCARBON MIXTURE OVER MODIFIED HZSM-5 ZEOLITE

研究了炼厂混合C_4烃在Zn、Ga、Cr、La改性的HZSM-5分子筛催化剂上的芳构化反应,采用TPD和IR测定了催化剂的表面酸性质。结果表明,用Zn(3%)和Zn(2%)Ga(1%)改性的HZSM-5分子筛具有较好的芳构化性能;各改性HZSM-5分子筛催化剂芳构化性能变化与表面酸性有关,总酸量下降,芳构化活性下降,强B酸中心减少,深度裂解反应减少;Zn的单组分和双组分改性的HZSM-5分子筛催化剂芳构化活性的增高与表面强L酸浓度增加和吡啶吸附IR谱中的1615cm^(-1)吸收峰出现有关。

HZSM-5 zeolites modified by Zn, Ga, Cr and La were studied by TPD and IR to characterize their surface acid properties, and the results were correlated with that of the aromatization of a C_4 hydrocarbon mixture (without i-butene) .The experiment results showed that Zn(3%) HZSM-5 and Zn(2%) Ga (1%) HZSM-5 zeolite catalysts possess higher activity of aromatization than others. With the decrease of total acidity, the activity of aromatization decrease.With the decrease of strong Bronsted acid sites, cracking reactions decrease. The high aromatization activity of one-component (Zn) and two-component (Zn-Ga and Zn-Cr) modified HZSM-5 catalysts may be corrolated to the 1615cm^(-1) peak in the absorption spectra of adsorbed pyridine and the increase of strong Lewis acid sites.