Cu/Mg比对K3PO4/HTLcs催化剂酸碱性及甲苯甲醇侧链烷基化性能的影响

Effect of KPO/HTLcs catalysts with different Cu/Mg ratio on the acid-base distribution and catalytic performance for side chain alkylation of toluene with methanol

通过共沉淀法制备出具有不同Cu/Mg物质的量比的三金属类水滑石材料(HTLcs)作为载体,通过等体积浸渍法负载K3PO4进行改性,得到负载型的催化剂,并对其在甲苯甲醇侧链烷基化反应中的催化活性进行考察;利用XRD、BET、FT-IR、NH3-TPD、CO2-TPD等手段对催化剂的物化性质进行表征。研究发现,在催化剂载体中引入第三组分过渡金属Cu,会明显降低催化剂强碱性位的含量,进一步调整载体中的Cu/Mg物质的量比后,催化剂的酸碱性位分布及催化性能都有明显的变化。催化剂中弱酸性位与中强碱性位的协同作用有利于乙苯及苯乙烯的生成。当n(Cu)∶n(Mg)=1∶1时(cat-11),乙苯及苯乙烯的总产率最高为65.64%,其中乙苯选择性为52.51%,苯乙烯的选择性最高可达24.44%(cat-02:n(Cu)∶n(Mg)=0∶2)。

Calcined trimetal hydrotalcite-like compounds as catalyst support with different Cu/Mg molar ratios were prepared by co-precipitation method, and modified with the K3PO4 through incipient-wetness impregnation to obtain a series of supported catalysts.The catalytic performance for the side chain alkylation of toluene with methanol was examined. The catalyst physico-chemical properties were characterized by X-ray diffraction(XRD), N2 physical adsorption and desorption(BET), Fourier Infrared(FT-IR) and programmed temperature desorption(NH3-TPD and CO2-TPD). It was found that the presence of the transition metal Cu on the catalyst support would significantly reduce the content of strong base sites on the catalyst. Further adjusting the Cu/Mg molar ratio on the catalyst support, the acid-base site distribution and catalytic performance of catalysts both changed obviously. It was worth noting that the synergistic effect between the weak acid sites and middle base sites were beneficial to the production of ethyl benzene and styrene. The highest yield of styrene and ethyl benzene(65.64%) was obtained at cat-11(the molar ratio of Cu/Mg was 1∶1), where the selectivity of ethyl benzene was 52.51%. The highest selectivity of styrene reached 24.44% at cat-02(the molar ratio of Cu/Mg was 0∶2).