Catalytic Esterification of Pentaerythritol over a Mesoporous Composite SnCl2@HZSM-5 Catalyst

Graphical Compared to SnCl 2 and HZSM-5, SnCl 2 @HZSM-5 was a mesoporous composite, which had the most amount of total and weak acidity, and the weakest acid strength. More total acid content is beneficial to increase pentaerythritol conversion, and the weak acid can improve the selectivity of PETS, and weak acid strength is beneficial to inhibit the formation of carbon deposits. Therefore, SnCl 2 @HZSM-5 showed the highest pentaerythritol conversion, PETS selectivity and catalytic stability. The mesoporous HZSM-5 and SnCl 2 @HZSM-5 mesoporous composite were prepared by two-step crystallization and wet impregnation method, respectively. The catalytic esterification performances of SnCl 2 , HZSM-5 and SnCl 2 @HZSM-5 were compared. SnCl 2 @HZSM-5 had the most amount of total and weak acidity, and the weakest acid strength. More total acid content was beneficial to increase pentaerythritol conversion, and the weak acid could improve the selectivity of PETS, and weak acid strength was beneficial to inhibit the formation of carbon deposits. Brönsted and Lewis acid sites were present simultaneously on the SnCl 2 @HZSM-5 catalyst. Moreover, some extra Brönsted acid sites were created on the SnCl 2 @HZSM-5 catalyst, because the interaction of SnCl 2 with HZSM-5 may result in the exchange of Sn 2+ with protons. Both acid sites could catalyze the esterification reaction, and the Brönsted acid site was more beneficial to increasing PETS selectivity. Therefore, SnCl 2 @HZSM-5 showed the highest pentaerythritol conversion, PETS selectivity and catalytic stability. The generation of coke and the leaching of Sn were the main cause of catalyst deactivation. Under the optimized process conditions: 105 °C, 4.7 molar ratio of stearic acid and pentaerythritol, 1.2 wt % catalyst amount and 2.5 wt % SnCl 2 loading, after 3 h reaction time, the pentaerythritol conversion, PETS selectivity and yield was 99.3 %, 97.2 % and 96.5 %, respectively.