Excess soluble alkalis to prepare highly efficient MgO with relative low surface oxygen content applied in DMC synthesis

Ju Liu,Fei Chen,Jianjun Guo,Wenbing Yang,Guangwen Xu,Fenglei Jia,Lei Shi

doi:10.1038/s41598-021-00323-5

Ju Liu, Fei Chen + Show 5 more

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https://doi.org/10.1038/s41598-021-00323-5

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Abstract

The activities of various MgO catalysts, which were prepared from different methods such as hydration synthesis, thermal decomposition, combustion, sol–gel and co-precipitation, were conducted in dimethyl carbonate (DMC) synthesis via transesterification of ethylene carbonate with methanol. MgO-P-Na2CO3-3.14 synthesized by the excess Na2CO3 precipitation compared the best catalytic activity and stability, which could be reused for seven times without obvious deactivation. The DMC yield was as high as 69.97% at 68 °C. The transesterification reaction could be separated into two steps, and the samples obtained by NaOH precipitant exhibited better ring-opening capability, while the catalysts acquired by Na2CO3 precipitant displayed superior transesterification ability. The structure-performance relationship was evaluated by multiple characterization methods. The results indicated that the as-synthesized catalyst derived from dried precursors with more crystalline magnesium carbonate was favorable for the promotion of DMC yield, and MgO-P-Na2CO3-3.14 with more Mg-O pairs, which were the active center for the transesterification of 2-hydroxyethyl methyl carbonate (HEMC) intermediate with methanol, resulted in more moderately basic sites left that was in accordance with the DMC yield variation. MgO-P-Na2CO3-3.14 with greater BET surface area and mesopore volume, relative low surface oxygen content and larger moderately basic sites amount compared the excellent activity in DMC synthesis.

Highlights

The activities of various magnesium oxide (MgO) catalysts, which were prepared from different methods such as hydration synthesis, thermal decomposition, combustion, sol–gel and co-precipitation, were conducted in dimethyl carbonate (DMC) synthesis via transesterification of ethylene carbonate with methanol
Jesús Gandara-Loe et al.[20] prepared six different layered double hydroxides (LDHs) catalysts derived from different interlayer anions (SiO44− or CO32−) and divalent cations (Mg2+, Zn2+ or Ni2+), proving that the catalysts containing Ni2+ exhibited better catalytic activity owing to their higher basicity, while the samples containing S iO44− displayed higher selectivity because of a lower acid sites amount
A series of MgO catalysts obtained by different preparation methods, such as hydration synthesis, thermal decomposition, combustion, sol–gel and co-precipitation, were prepared for DMC synthesis

Summary

Introduction

The activities of various MgO catalysts, which were prepared from different methods such as hydration synthesis, thermal decomposition, combustion, sol–gel and co-precipitation, were conducted in dimethyl carbonate (DMC) synthesis via transesterification of ethylene carbonate with methanol. Dimethyl carbonate (DMC), which is the simplest dialkyl c arbonates[1], is widely applied in the chemical industry owing to its unique physicochemical properties[2] It is an important intermediate for the synthesis of organic compounds and as an alkylating agent that can replace highly toxic dimethyl sulfate[3,4]. The resulting MgO catalysts were used for the synthesis of diethyl carbonate from ethyl carbamate and ethanol, demonstrating that sodium carbonate as the precipitant showed higher catalytic activity, which was attributed to a large amount of medium basic β sites. Sodium carbonate and a certain amount of sodium silicate were simultaneously reported as the precipitants to synthesize MgO for the removal of Congo red dye in aqueous solution, indicating that the capacity of adsorption was relevant to the surface base properties and the added amount of sodium s ilicate[30]

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