Anna M. Segarra (a) Jordi Llorca, Ausies , Francesc Medina,
a ) University Rovira i Virgili
Corresponding author email: email@example.com
Carboxylation reaction is thus a new, safe, eco-friendly and economic alternative way of valorizing CO2 for use in generating fine chemicals.
Some studies have reported on the heterogeneous carboxylation reaction because of the advantages of heterogeneous catalysts over their homogeneous counterparts. A recently published study reported that heterogeneous catalytic materials such as CeO2, SnO2 and pure and modified ZrO2 have catalyzed the direct synthesis of DMC directly from MeOH and CO2 in a batch reactor. However, the methanol conversion was around 1% [1-2]. Several studies have confirmed that the equilibrium of the reactions (Scheme 1) is largely shifted to the left and can reach equilibrium concentrations of alkyl carbonates of between 1% and 2% depending on the reaction temperature . Nevertheless, when was used CeO2-ZrO2 as catalyst, and when the H2O was removed from the reaction system using 2,2-dimethoxy propane as dehydrated agent, the methanol conversion improved from 0.81% to 4.2% .
The authors suggested that the presence of both acid and basic sites is an important factor in selective DMC synthesis. The mixed Mg-Al oxides (HTO) derived from the calcination of HTs are known to exhibit both weak acidic and weak basic properties . Silica lyogels (LGs)  are also appropriate materials for use as catalysts supports.
In this context, nonimmobilized and immobilized Mg-Al hydrotalcite-like materials on silica lyogel were prepared and activated by calcination to be tested as catalysts in the direct carboxylation reaction of methanol. The HTs supported on silica lyogel showed an important improvement and high stability in the direct synthesis reaction of DMC from CO2 and MeOH.
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