Lewis酸型固体酸催化剂Ce-Ag-PW的制备、表征及催化酯化反应合成生物柴油性能研究  

Preparation,characterization of Lewis acidic solid acid catalyst Ce-Ag-PW and its catalytic application in biodiesel production via esterification

作　　者：李兴鹏 舒庆[1] LI Xingpeng;SHU Qing(Faculty of Materials Metallurgy and Chemistry,Jiangxi University of Science and Technology,Ganzhou 341000,China)

机构地区：[1]江西理工大学材料冶金化学学部,江西赣州341000

出　　处：《有色金属科学与工程》2020年第2期42-50,共9页Nonferrous Metals Science and Engineering

基　　金：国家自然科学基金项目资助(21466013,21766009)。

摘　　要：通过超声浸渍法,经Ce^3+和Ag^+协同改性磷钨杂多酸(HPW)制备了一种以Lewis酸性活性位为主的固体酸催化剂Ce-Ag-PW。采用X射线衍射(XRD)、傅里叶变换红外光谱(FT-IR)、扫描电镜(SEM)、透射电镜(TEM)、热重(TG)、NH3程序升温脱附(NH3-TPD)、吡啶吸附红外光谱(Py-IR)和X射线光电子能谱(XPS)等表征手段对其物理化学性能进行了表征分析。并以Ce-Ag-PW为经甲醇和油酸酯化反应来合成生物柴油的催化剂,对其的催化活性和稳定性进行了研究。结果表明,Ce-AgPW具有高催化活性和稳定性,以其为催化剂,当甲醇与油酸的物质的量比为14∶1,催化剂用量为反应物总质量的2%,反应温度为65°C,反应6 h后,油酸的转化率即高达91%。固体酸催化剂在经过4次循环使用后,油酸的转化率仍可达到80.5%。Ce-Ag-PW的高催化活性和稳定性可归因于Ag^+可置换HPW中的质子,以及Ce^3+的强吸电子作用,使其由Bronsted酸型催化剂转化为以Lewis酸型为主的催化剂。由于Bronsted酸位易与酯化反应过程中生成的水发生水合反应而失活,因而Lewis酸位的形成有助于减少催化剂的失活现象发生。因此,当通过油酸与甲醇酯化反应合成生物柴油时,Ce-Ag-PW是一种具有高催化活性和稳定性的以Lewis酸性活性位为主的固体酸催化剂。A solid acid catalyst Ce-Ag-PW with Lewis acidic active site as the main active sitewas prepared from the synergistic modification of phosphotungstic heteropoly acid(HPW)by Ce^3+ and Ag^+ through ultrasonic impregnation.Physicochemical properties of the obtained catalyst were characterized by X-ray diffraction(XRD),Fourier-transform infrared spectroscopy(FT-IR),scanning electron microscopy(SEM),transmission electron microscopy(TEM),thermogravimetry(TG),NH3 temperature programmed desorption(NH3-TPD)pyridine adsorption Fourier-transform infrared(Py-IR)and X-ray photoelectron spectroscopy(XPS).The catalytic activity and stability of Ce-Ag-PW were studied from the biodiesel production via the esterification of oleic acid and methanol.Results showed that Ce-Ag-PW had high catalytic activity and stability.The conversion of oleic acid reached 91% after 6 h with Ce-Ag-PW as catalyst when the molar ratio of methanol to oleic acid was 14:1,the amount of catalyst was 2% of the total mass of the reactant and the reaction temperature was 65℃.The conversion of oleic acid could still reach 80.5%after the Ce-Ag-PW catalyst was used for four cycles.The high catalytic activity and stability of Ce-Ag-PW can be attributed to the replacement of the protons in HPW by Ag+and the strong electron-withdrawing effect exerted by Ce^3+,which transforms it from Bronsted acid catalyst to Lewis acid catalyst.Since the Bronsted acid site is easily deactivated due to the hydration reaction between it and the water generated from the esterification reaction,the formation of Lewis acid sites helps reduce catalyst deactivation.Therefore,Ce-Ag-PW solid acid catalyst based on Lewis acidic active sites has high catalytic activity and stability in the catalytic synthesis of biodiesel by the esterification reaction of oleic acid and methanol.

关 键 词：生物柴油 杂多酸 Ce^3+和Ag^+协同改性 固体酸 酯化反应 

分 类 号：O621.33[理学—有机化学]