Study on catalytic performance and kinetics of high efficiency CeO2 catalyst prepared by freeze drying for the synthesis of dimethyl carbonate from CO2 and methanol

Abstract

• A high acid-base sites and oxygen vacancies of CeO 2 was prepared by freeze-drying. • The oxygen vacancies can be controlled by the oxygen content in the drying process. • The CeO 2 prepared by freeze drying achieves unprecedented DMC yield. • The optimal catalyst has good stability and has been recycled fifth times. • A new well-fitted kinetic model of sequential reaction was obtained. The synthesis of dimethyl carbonate (DMC) from CO 2 and methanol is an effective route of CO 2 utilization. In this work, CeO 2 nanorods prepared by hydrothermal synthesis using various drying methods were compared. Among them CeO 2 prepared by freeze drying (CeO 2 -FD) had the highest and unprecedented catalytic effects, with DMC yield of 873 mmol g -1 cat and methanol conversion of 51.6 % at 140 °C and 3.5 MPa for 4 h. All CeO 2 nanorods catalysts have been extensively characterized and the results showed that CeO 2 -FD had the largest specific surface area (90.7 m 2 g −1 ), pore volume, oxygen vacancy concentration (44.53%), and acid-base active site (189.4 vs 37.2 mmol g −1 ). The surface properties of CeO 2 nanoparticles were greatly affected by the lower absolute pressure and the use of water as a template agent in freeze-drying. For the first time, the kinetic model of sequential reaction with a dehydrating agent was deduced by Langmuir-Hinshelwood mechanism. The activation energy barrier was 20 ± 3.3 kJ mol −1 using the Arrhenius formula.