WO x /ZrO x functionalised periodic mesoporous organosilicas as water-tolerant catalysts for carboxylic acid esterification
WO x /ZrO x functionalised periodic mesoporous organosilicas as water-tolerant catalysts for carboxylic acid esterification
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WO x /ZrO x 功能化周期性介孔有机硅作为羧酸酯化的耐水催化剂
DOI：
10.1039/d2se01724e
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发表时间：
2023
影响因子：
5.6
通讯作者：
Dos Santos-Durndell V
中科院分区：
文献类型：
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作者：
Dos Santos-Durndell V
催化剂的疏水性是一种经常被忽视的性质，尽管它在水相反应和其中水是副产物的那些反应（例如缩合和酯化）中很重要。在这里，我们合成的WOx/ZrOx浸渍的周期性介孔有机硅（PMO）的不同的有机骨架含量，通过逐步取代的双（三乙氧基甲硅烷基）苯（BTSB）的正硅酸乙酯（TEOS），然后钨和锆共接枝。将苯基基团引入介孔SBA-15二氧化硅的骨架中赋予表面疏水性并调节固体酸性，同时保持母体二氧化硅的质地性质。所得的WOx/ZrOx/PMO催化剂对于C3-C16羧酸在甲醇中在60 °C下的酯化表现出优异的转换频率（TOF），其中TOF与脂肪酸链长成反比。与WOx/ZrOx/SBA-15相比，WOx/ZrOx/PMO的上级活性和稳定性（耐水性高达50摩尔%）归因于从孔内活性位点置换水，减轻逆酯水解反应。预计此类疏水性固体酸催化剂将广泛应用于水相合成，特别是生物精炼输出流的水相合成。
Catalyst hydrophobicity is an oft-neglected property despite its significance in aqueous phase reactions and those wherein water is a by-product, such as condensation and esterification. Here we synthesise WOx/ZrOx impregnated periodic mesoporous organosilicas (PMOs) of varying organic framework content, through the stepwise substitution of bis(triethoxysilyl)benzene (BTSB) for tetraethyl orthosilicate (TEOS), followed by tungsten and zirconium co-grafting. Incorporation of phenyl groups into the framework of mesoporous SBA-15 silica imparts surface hydrophobicity and tunes the solid acidity, while preserving the textural properties of the parent silica. The resulting WOx/ZrOx/PMO catalysts exhibit excellent turnover frequencies (TOFs) for the esterification of C3–C16 carboxylic acids in methanol at 60 °C, with TOFs inversely proportional to fatty acid chain length. The superior activity and stability (water tolerance up to 50 mol%) of WOx/ZrOx/PMO versus WOx/ZrOx/SBA-15 is attributed to the displacement of water from in-pore active sites, mitigating the reverse ester hydrolysis reaction. Such hydrophobic, solid acid catalysts are anticipated to find widespread application in aqueous phase synthesis, particularly of biorefinery output streams.