Fuhang Mai,Kai Cui,Zhe Wen,Kai Wu,Fei Yan,Mengmeng Chen,Hong Chen,Yongdan Li
The conversion of guaiacol is examined at 300 °C in supercritical ethanol over a H2WO4 catalyst. Guaiacol is consumed completely, meanwhile, 16.7% aromatic ethers and 80.0% alkylphenols are obtained. Interestingly, tert-butylphenols are produced mainly with a high selectivity of 71.8%, and the overall selectivity of 2,6-di-tert-butylphenol and 2,6-di-tert-butyl-4-ethylphenol is as high as 63.7%. The experimental results indicate that catechol and 2-ethoxyphenol are the intermediates. Meanwhile, the WO3 sites play an important role in the conversion of guaiacol and the Brønsted acid sites on H2WO4 enhance the conversion and favour a high selectivity of the tert-butylphenols. The recycling tests show that the carbon deposition on the catalyst surface, the dehydration and partial reduction of the catalyst itself are responsible for the decay of the H2WO4 catalyst. Finally, the possible reaction pathways proposed involve the transetherification process and the alkylation process during guaiacol conversion.
Graphical Calcium requirements : Activated-carbon-supported calcium oxide was used as a catalyst for a clean and selective synthesis of nitrile-containing diaryl ethers. Transetherification was suppressed to 10 −3- -10 −4 scale. Activated-carbon-supported calcium oxide (CaO@AC) was prepared from AC and a suspension derived from CaO and ammonium carbonate. After calcination under nitrogen, high purity CaO@AC was obtained. The nature of non-aggregation and high purity of CaO@AC enabled a clean and selective synthesis protocol for nitrile-containing diaryl ethers. Various functional groups including methoxyl, amino, carboxyl, allyl and nitro were well-tolerated, and products were obtained in excellent yields and purities. Asymmetric substitutions could be achieved via simple adjustment of reaction conditions, and transetherification was greatly suppressed to 10 −3 –10 −4 scale. In addition, a mechanism for suppression in transetherification was proposed and discussed.
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