K/KCC-1 催化碳酸二甲酯和乙醇酯交换合成碳酸甲乙酯

Solid base catalysts (xK/KCC-1) with different K theoretical loading (x, x is the molar ratio of K to Si, x=0.3, 0.5, 0.7, 0.9, 1.1) were synthesized by equi-volumetic impregnation method using dendrite fibrous silica (KCC-1) prepared from hydrothermal synthesis as support and potassium acetate as precursor, and characterized by XRD, FTIR, BET, CO₂-TPD and SEM. xK/KCC-1 samples were then evaluated for their catalytic performance on the synthesis of methyl ethyl carbonate (EMC) via transesterification of dimethyl carbonate (DMC) and ethanol. The results indicated that xK/KCC-1 had two types of basic sites, the weak basic sites provided by K₂SiO₃ and the medium strong basic sites provided by K₂CO₃. With the increase in K theoretical loading, the weak basic sites gradually decreased, while the medium strong basic sites gradually increased, thus enhancing the reaction activity of transesterification. xK/KCC-1 with K theoretical loading ≤0.9 still maintained the dendritic fiber structure of KCC-1, allowing reactant molecules to diffuse well to the active sites. 0.9K/KCC-1 exhibited the highest catalytic activity. Under the optimal reaction conditions of reaction temperature 80 ℃, reaction time 5 h, molar ratio of ethanol to DMC (4.494 g) 4∶1, and 0.9K/KCC-1 dosage 5% of DMC mass, the conversion rate of DMC was 91.0%, and the EMC selectivity was 95.5%. Furthermore, 0.9K/KCC-1 showed good cyclic stability, with a DMC conversion of 86.7% and an EMC selectivity of 95.2% after 5 recycles.