原位封装法制备Ni@ZSM-5催化剂及其在苯与甲醇烷基化反应中的性能

Preparation of Ni@ZSM-5 Catalysts by In-Situ Encapsulation and Its Performance in the Alkylation of Benzene With Methanol

使用原位封装法将金属Ni封装进ZSM-5纳米晶体中,通过调节金属含量成功制备了一系列封装NiO质量分数分别为0.2%、1.0%和4.0%的Ni@ZSM-5催化剂。利用X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)、N_(2)物理吸附-脱附(BET)、氨气程序升温脱附(NH_(3)-TPD)等手段对封装金属Ni后的催化剂进行表征,并详细考察金属Ni封装量的变化对苯与甲醇烷基化反应性能的影响。结果表明:金属Ni含量对催化剂粒径及形貌影响不大,总孔体积略有下降,比表面积、微孔体积、酸量上差别不大;金属Ni含量对催化剂稳定性有显著影响。在反应温度460℃、压力0.1 MPa下,发现封装质量分数1.0%NiO时,苯转化率可达到66%,比ZSM-5提高约10%,副产物乙苯初始选择性大幅度下降至仅0.25%,催化剂寿命为180 h。

In this study,Ni was encapsulated into ZSM-5 nanocrystals by in-situ encapsulation method,and a series of Ni@ZSM-5 catalysts with 0.2%,1.0%and 4.0%mass fractions of encapsulated NiO were successfully prepared by adjusting the metal content.The catalysts were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM),N_(2)-physical adsorption-desorption(BET)and ammonia programmed temperature desorption(NH_(3)-TPD),and the effect of Ni encapsulation amount on the alkylation of benzene with methanol was investigated in detail.The results show that the Ni content has little effects on the particle size and morphology of the catalysts,the total pore volume is decreased slightly,and little change occurs in the specific surface area,micropore volume and acid amount;the Ni content has a significant effect on the stability of the catalysts.At the reaction temperature of 460℃,pressure of 0.1 MPa,and 1.0%mass fraction of encapsulated NiO,the conversion rate of benzene can reach 66%,which is about 10%higher than that of ZSM-5.The initial selectivity of the by-product ethylbenzene is decreased significantly to only 0.25%,and the catalyst lifetime is 180 h.