Abstract
The Ca–Al and Ca–Al–X (X = F−, Cl− and Br−) catalysts were prepared via thermal decomposition of Ca–Al layered double hydroxides (LDHs), and tested for methanolysis of propylene carbonate (PC) to produce dimethyl carbonate (DMC). The catalytic performance of these catalysts increased in the order of Ca–Al–Br− < Ca–Al < Ca–Al–Cl− < Ca–Al–F−, which was consistent with the strong basicity of these materials. The recyclability test results showed that the addition of Al and halogens (F−, Cl− and Br−) not only stabilized the CaO but also improved the recyclability of the catalysts. Particularly, the Ca–Al–F− catalyst exerted the highest stability after 10 recycles. These catalysts have an important value for the exploitation of DMC synthesis by transesterification of PC with methanol.
Highlights
A series of Ca–Al mixed oxide catalysts were synthetized by thermal decomposition of Ca–Al–X (X 1⁄4 FÀ, ClÀ and BrÀ) layered double hydroxides (LDHs), and were tested for the transesteri cation of propylene carbonate (PC) with methanol
The Dimethyl carbonate (DMC) synthesis from transesteri cation of methanol with PC can be depicted in Scheme 1
MDMC is the mass of formed DMC, MDMC is the molecular weight of DMC, mPC1 is the mass of PC in the feeds, mPC2 is the mass of PC in the products, and MPC is the molecular weight of PC
Summary
Dimethyl carbonate (DMC), as a green organic ne chemical intermediate, is widely used in carbonylation, methylation and methoxylation reactions.[1,2] Several ways are developed for DMC synthesis, such as oxidative carbonylation of methanol,[3,4,5] transesteri cation of methanol with cyclic carbonate,[6,7,8,9] alcoholysis of urea[10,11,12] and direct synthesis from carbon dioxide and methanol.[13,14,15,16] As compared to other routes, DMC synthesis by transesteri cation of propylene carbonate (PC) with methanol under mild conditions is a promising and environmentally benign route, which has earned much attention of researchers.[17,18]. It is well known that the basicity of the catalysts plays an important role in the transesteri cation of PC with methanol.[20] It is possible to modulate the basicity of the catalysts by modi cation of halogen anions. A series of Ca–Al mixed oxide catalysts were synthetized by thermal decomposition of Ca–Al–X (X 1⁄4 FÀ, ClÀ and BrÀ) layered double hydroxides (LDHs), and were tested for the transesteri cation of PC with methanol. The effect of Al on the stabilization of the active CaO component and the in uence of the halogen anions (FÀ, ClÀ and BrÀ) on the basicity of the Ca– Al mixed oxide catalysts were investigated. This work has meaningful and practical applicative values for the stabilization and basicity regulation of CaO catalyst, and provides a new idea for the stabilization of the catalyst applied to the transesteri cation
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