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首页> 外文期刊>Applied Catalysis, A. General: An International Journal Devoted to Catalytic Science and Its Applications >Trifluoromethanesulfonic acid immobilized on zirconium oxide obtained by the sol-gel method as catalyst in paraben synthesis
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Trifluoromethanesulfonic acid immobilized on zirconium oxide obtained by the sol-gel method as catalyst in paraben synthesis

机译：溶胶-凝胶法制得的固定在氧化锆上的三氟甲磺酸作为对羟基苯甲酸酯合成的催化剂

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摘要

The parabens, alkylic esters of p-hydroxybenzoic acid, were synthesized using trifluoromethanesulfonic acid immobilized on zirconium oxide (zirconia) as catalyst. The oxide was obtained by the sol-gel method, using urea as a pore-forming agent. After removing urea by extraction with water, the solid was dried and then calcined at 100,205,310 and 425 °C for 24 h. Afterward, it was impregnated with trifluoromethanesulfonic acid in toluene at reflux and leached to remove the weakly adsorbed acid. Mesoporous materials were obtained, whose mean pore diameter increased with the temperature of the thermal treatment of the support, while the specific surface area and the amount of acid bonded to the support decreased. The samples are crystalline from 400 °C and are thermally stable up to 250 °C. The catalysts have strong acidity and the number of acid sites decreased with the acid content in the support. The catalytic activity in the synthesis of propyl paraben, expressed as moles of ester formed at 5 h/mol acid in the catalyst, decreased when samples obtained from supports thermally treated at higher temperature were used. The activity also slightly diminished for the synthesis of different parabens in the order propyl > ethyl > methyl ester.
机译：对羟基苯甲酸酯，对羟基苯甲酸的烷基酯，是使用固定在氧化锆（氧化锆）上的三氟甲磺酸作为催化剂合成的。使用尿素作为成孔剂，通过溶胶-凝胶法得到氧化物。通过用水萃取除去尿素后，将固体干燥，然后在100,205,310和425°C下煅烧24小时。之后，将其在回流下用三氟甲磺酸浸渍在甲苯中，并沥滤以除去弱吸附的酸。获得了介孔材料，其平均孔径随着载体的热处理温度而增加，而比表面积和与载体结合的酸的量减少。样品在400°C时为晶体，在高达250°C的温度下均具有热稳定性。催化剂具有强酸度，并且随着载体中酸含量的增加，酸位的数目减少。当使用从高温下热处理过的载体获得的样品时，对羟基苯甲酸丙酯的合成催化活性（表示为催化剂在5 h / mol酸中形成的酯的摩尔数）降低。对于不同对羟基苯甲酸酯的合成，活性也略有降低，顺序为丙基>乙基>甲基酯。

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