Hydrotalcites Promoted by NaAlO2 as Strongly Basic Catalysts with Record Activity in Glycerol Carbonate Synthesis
Hydrotalcites Promoted by NaAlO2 as Strongly Basic Catalysts with Record Activity in Glycerol Carbonate Synthesis
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DOI：
10.1002/cctc.201701726
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发表时间：
2018-03-21
期刊：
影响因子：
4.5
通讯作者：
Debecker, Damien P.
中科院分区：
文献类型：
--
作者：
Ramesh, Sreerangappa;Devred, Francois;Debecker, Damien P.
用铝酸钠催化镁铝层状双氢氧化物制备了一种新型高碱性催化剂。由原始水滑石煅烧得到的镁铝混合氧化物在由甘油和碳酸二甲酯（DCM）合成碳酸甘油时活性较差。另一方面，纯铝酸钠在该反应中非常活跃，但它也具有很强的腐蚀性，使其处理出现问题。值得注意的是，用少量的铝酸钠促进水滑石足以达到高收率。在90℃、3wt%催化剂、DMC/甘油比例为2:1的条件下，在10wt% NaAlO2/水滑石催化剂上，30分钟后甘油转化率达到92%，对碳酸甘油的选择性几乎为100%。NaAlO2的加入对催化剂的结构和结晶度有较大的影响。高活性明显与铝酸钠的促进作用对碱度的提高有关。而原始水滑石只具有弱碱性位点，在NaAlO2的促进下，催化剂的碱性在数量和强度上都急剧增加。漫反射红外光谱与二氧化碳吸附测量相结合，揭示了表面碳酸盐的存在，这些碳酸盐来自强碱性位点。重要的是，我们的研究表明，这些基本催化剂是真正的多相、稳定和可重复使用的。
A new type of highly basic catalysts is obtained by promoting Mg-Al layered double hydroxides with sodium aluminate. The Mg-Al mixed oxides obtained by the calcination of pristine hydrotalcites are poorly active in the synthesis of glycerol carbonate from glycerol and dimethyl carbonate (DCM). Pure sodium aluminate on the other hand is highly active in this reaction, but it is also highly corrosive, making its handling problematic. Remarkably, promoting hydrotalcites with low amounts of sodium aluminate is sufficient to reach high yields. At 90 degrees C, with 3wt% catalyst and with a DMC/glycerol ratio of 2:1, a glycerol conversion of 92% was achieved after 30min over the 10wt% NaAlO2/hydrotalcite catalyst with almost 100% selectivity towards glycerol carbonate. The texture and the crystallinity of the catalysts were strongly affected by the addition of NaAlO2. The high activity was clearly correlated with the boost in basicity brought about by sodium aluminate promotion. Whereas pristine hydrotalcites possess only weak basic sites, the basicity of the catalysts increased drastically upon promotion with NaAlO2, both in amount and strength. Diffuse reflectance infrared spectroscopy coupled with CO2 adsorption measurements revealed the presence of surface carbonates arising from strongly basic sites. Importantly, our study demonstrates that these basic catalysts are truly heterogeneous, stable, and reusable.