Performance of supported metal catalysts in the dimethyl carbonate production by direct synthesis using CO2 and methanol

Abstract

CO2 chemical transformation is an exciting way to reduce CO2 concentration in the atmosphere. The use of CO2 to produce dimethyl carbonate (DMC), a linear, biodegradable, low toxicity carbonate via direct synthesis, is one of the most promising routes from the environmental point of view. However, DMC direct synthesis presents obstacles such as unfavorable thermodynamics and catalytic deactivation due to the water produced as a by-product. Therefore, the development and optimization of a catalytic system that can overcome these obstacles are crucial. This study investigated the catalytic activity of iron nitrate (AC-Fe), copper nitrate (AC-Cu), magnesium nitrate (AC-Mg), and nickel nitrate (AC-Ni) impregnated in activated carbon for DMC direct synthesis. Catalysts were synthesized by the impregnation method and characterized by several techniques. Simulation results evidenced the major reaction steps and simplified models of a complex involving metallic catalysts and reactants. The optimization of the catalyst amount, pressure, temperature, and recyclability of the best catalyst under optimized conditions and in the presence of different dehydrating agents was also performed. Results showed that the AC-Fe catalyst is the most efficient in the DMC direct synthesis, with a yield of 23.5 % and a selectivity of 100 % (80 °C, 40 bar, and 24 h). Reaction optimization (120 °C, 40 bar, and 24 h) using (AC-Fe) as catalyst resulted in a DMC yield of approximately 30 %. The catalytic systems recycling proved that using the dehydrating agent right combination (molecular sieve) and catalyst (AC-Fe) can maintain selectivity at 100 %, slightly decreasing yield.