燃料化学学报2017，Vol.45Issue(8)：939-949,11.
新型Br(o)nsted-Lewis酸性催化剂LaPW12O40/SiO2制备及其在催化酯化反应合成生物柴油中的应用
Preparation and application of a novel Br(o)nsted-Lewis acid catalyst LaPW12O40/SiO2 for the synthesis of biodiesel via esterification reaction
摘要
Abstract
In this study,H3PW12O40(Tungstophosphoric acid) was applied as matrix,and which was modified by La3+through conventional impregnation method,ultrasonic impregnation method and sol-gel method,obtained three solid acid catalysts:A-LaPW12 O40,B-LaPW12 O40/SiO2 and C-LaPW12 O40.These above catalysts were characterized by X-ray fluorescence spectrometer,specific surface area and porosity analyzer,X-ray diffraction,transmission electron microscopy,Fourier transform infrared spectoscopy,thermogravimetric analysis,N2/adsorption-desorption,NH3 temperature programmed desorption,pyridine adsorption IR spectra and X-ray photoelectron spectroscopy.The catalytic activities and stabilities of them were compared when they were used for the catalytic synthesis of biodiesel from the esterification reaction of oleic acid and methanol.Results shown that the B-LaPW12 O40/SiO2 has highest catalytic activity and stability.:the conversion of oleic acid can be high to 93％ when the molar ratio of methanol to oleic acid was 8 ∶1,mass ratio of catalyst to reactants was 2％,reaction temperature was 65 ℃ and reaction time was 1 h;the conversion of oleic acid maintained 86.4％ after B-LaPW12O40/SiO2 had been cycled six times.The high catalytic activity and stability of B-LaPW12 O40/SiO2 can be explained as follows:a SiO2 network was formed from the hydrolytic action of Si (OC2 H5) 4 (TEOS) under acidic conditions via Sol-Gel process.The H+of H3PW12O40 will bond with Si-OH in SiO2 network to form a (≡Si-OH2+) (H2PW12O40-) complex with strong electrostatic adsorption force,thus promoting the adsorption of La3+on the surface of SiO2,greatly.As a result,the pore structure of H3PW12O40 will be blockaged,the grow up of H3PW12O40 particles in the roasting process also will be inhibited.In addition,SiO2 may be existed in the form of dry gel in the B-LaPW12O40/SiO2 catalyst and acted as carrier.It will be favorable for the improvent of the surface area of B-LaPW12O40/SiO2 since SiO2 has high surface area,so the surface area of B-LaPW12O40/SiO2 has increased from the 1.4 m2/g of H3PW12O40 to the 31.3 m2/g.And more,LaPW12O40/SiO2 has been determined from the Py-FTIR spectra of pyridine adsorption analysis,which is a Br(o)nsted-Lewis solid acid.The formation of Lewis acid sites can help to reduce the deactivation of a solid acid catalyst:some H2O will be generated from the esterification reaction,and hydration will occur between Br(o)nsted acid site and H2 O,so the deactivation will occur.The formation of Lewis acid sites can be ascribed to the strong electrophilic action of La3+after it has been bonded with (≡ Si-OH2+) (H2PW12O40) to form LaPW12O40/SiO2.关键词
镧改性/磷钨杂多酸/溶胶-凝胶法/Br(o)nsted-Lewis固体酸/酯化反应Key words
lanthanum modification/tungstophosphoric acid/sol-gel method/Br(o)nsted-Lewis solid acid/esterification分类
化学工程引用本文复制引用
舒庆,唐国强,刘峰生,邹文强,贺江凡..新型Br(o)nsted-Lewis酸性催化剂LaPW12O40/SiO2制备及其在催化酯化反应合成生物柴油中的应用[J].燃料化学学报,2017,45(8):939-949,11.基金项目
The project was supported by the National Natural Science Foundation of China (21206062,21466013),Major project of Natural Science Foundation of Jiangxi Province for Youth (20143ACB21018),Program of Qingjiang Excellent Young Talents (Jiangxi University of Science and Technology).国家自然科学基金(21206062,21466013),江西省自然科学(青年)基金计划重大项目(20143ACB21018),江西理工大学清江青年英才支持计划资助 （21206062,21466013）
