不同镁铝比LDHs对苯甲醚合成反应催化效果的研究

采用共沉淀法合成了一系列不同镁铝比的类水滑型层状金属氢氧化物(LDHs)，通过XRD、SEM、FT-IR、NH₃-TPD、CO₂-TPD、TG和ICP-OES方法对MgAl-LDHs和焙烧产物进行表征，并用于催化苯酚与碳酸二甲酯(DMC)气相合成苯甲醚。结果表明，共沉淀法合成的MgAl-LDHs在Mg/Al比为2~4时具有良好的类水滑石结构，主要以球形层片聚集体的形态存在，其层间距、平均孔径和碱酸比在Mg/Al比为2~4之间逐渐增加；所制备的MgAl-LDHs样品均显示出良好的反应活性，并发现苯甲醚的选择性随催化剂酸碱比先增加后减小，当镁铝比为4时，其酸碱比为0.32，此时苯甲醚选择性最高为88.93 %。此外，还考察了反应温度和质量空速对苯甲醚催化效果的影响。

Catalytic synthesis of anisole over LDHs with different Mg/Al ratios

A series of layered hydroxides(LDHs)with different Mg/Al ratios were synthesized by coprecipitation method.MgAl LDHs and their calcined products were characterized by XRD, SEM, FT-IR, NH₃-TPD, CO₂- TPD, TG and ICP-OES, and were used to catalyze the vapor phase synthesis of anisole from phenol and dimethyl carbonate(DMC).The results show that MgAl LDHs synthesized by coprecipitation method have good hydrotalcite like structure when Mg/Al ratio is 2 to 4, mainly in the form of spherical lamellar aggregates.The interlayer spacing, average pore size and alkali acid ratio increase gradually when Mg/Al ratio is from 2 to 4.It is found that the selectivity of anisole first increases and then decreases with the acid-base ratio of the catalyst.The highest anisole selectivity of 88.93 % is achieved when the Mg/Al ratio is 4 and the acid/base ratio is 0.32.In addition, the effect of reaction temperature and mass space velocity on the catalytic performance are also investigated.