摘要
CO_(2)加氢过程中间体CO在分子水平上的吸附/脱附行为会显著影响产物选择性.本文采用浸渍法制备了Pt/Cd-TiO_(2)催化剂.通过X射线衍射(XRD)、H_(2)气程序升温还原(H_(2)-TPR)、拉曼光谱(Raman)、电子顺磁共振波谱(ESR)、透射电子显微镜(TEM)、X射线光电子能谱(XPS)、CO_(2)程序升温脱附(CO_(2)-TPD)和N_(2)气吸附-脱附实验等表征手段对Pt/Cd-TiO_(2)催化剂进行表征,并将其应用于CO_(2)加氢反应中.活性测试结果显示,Pt/TiO_(2)加氢产物中CO选择性是87.5%,CH_(4)选择性是12.5%.随着Cd^(2+)的引入,Pt/Cd-TiO_(2)的加氢产物中CO选择性提升至98.1%,CH_(4)选择性降低至1.9%.以Pt/Cd-TiO_(2)为催化剂,CO的生成温度降低至225℃(Pt/TiO_(2)是250℃).原位傅里叶变换红外光谱(FTIR)和X射线光电子能谱(XPS)分析结果表明,Cd^(2+)的引入能够降低Pt纳米颗粒(Pt NPs)表面的电子密度,Pt NPs表面电子密度的降低有利于吸附态CO(CO_(ads))脱附生成气态CO,同时抑制CO_(ads)加氢生成CH_(4).在CO甲烷化实验中,Cd^(2+)的引入使CH_(4)产量降低了约6.6倍,证明Cd^(2+)抑制了CO甲烷化生成CH_(4),这与Pt/Cd-TiO_(2)在CO_(2)加氢中CO选择性提升的结果一致.通过多种阳离子(Cd^(2+),Mn^(2+),Ba^(2+),K^(+),Na^(+))对Pt/TiO_(2)进行修饰,均能提升CO选择性,其中Pt/Cd-TiO_(2)表现出最高的CO选择性.
The adsorption/desorption of the key intermediate at the molecular level in CO_(2)hydrogenation deserves significant attention since the intermediate stability can greatly affect the products selectivity.In this paper,the Pt/Cd-TiO_(2)catalysts were synthetized by impregnation method.The Pt/Cd-TiO_(2)catalyst is characterized through X-Ray diffraction(XRD),H_(2)-temperature programmed reduction(H_(2)-TPR),Raman spectra,electron spin resonance(ESR),transmission electron microscope(TEM),X-ray photoelectron spectroscopy(XPS),CO_(2)temperature programmed desorption(CO_(2)-TPD),and N_(2) sorption experiments.With the introduction of Cd^(2+),CO selectivity increases to 98.1%and CH4 selectivity decreases to 1.9%over Pt/Cd-TiO_(2)compared to Pt/TiO_(2)(87.5%for CO and 12.5%for CH4)during CO_(2)hydrogenation.Additionally,CO was produced at 225℃over Pt/Cd-TiO_(2),which is 25℃lower than Pt/TiO_(2)catalyst(250℃).In situ FTIR and XPS measurements reveal that the Cd^(2+)could reduce the electron density of Pt nanoparticles(Pt NPs),and the reduced electron density of Pt NPs will contribute to the desorption of adsorbed CO ads into CO in the gas phase and inhibit the hydrogenation of CO ads to produce CH_(4).During CO methanation contrast experiments,CH_(4)evolution decreases by approximately 6.6 times with the introduction of Cd^(2+),indicating that Cd^(2+)hinders the reaction of CO with H to produce CH_(4),in accordance with the increased CO selectivity in CO_(2)hydrogenation over Pt/Cd-TiO_(2).The CO selectivity was all improved over Pt/TiO_(2)promoted with several cations(Cd^(2+),Mn^(2+),Ba^(2+),K^(+)and Na^(+)),and Pt/Cd-TiO_(2)exhibits the highest CO selectivity.This study sheds light on the enhanced CO evolution over Pt/Cd-TiO_(2)in CO_(2)hydrogenation and provides guidance for catalyst design.
作者
张明文
周杰
王兆宇
ZHANG Mingwen;ZHOU Jie;WANG Zhaoyu(Fujian Provincial Engineering Research Center for Food Flexible Packaging Technology,Fujian Polytechnic Normal University,Fuqing 350300,China;College of Chemical Engineering,Fuzhou University,Fuzhou 350000,China)
出处
《高等学校化学学报》
北大核心
2025年第9期95-103,共9页
Chemical Journal of Chinese Universities
基金
福建省科技计划面上项目(批准号:2024J01969)资助。
作者简介
联系人:王兆宇,男,博士,讲师,主要从事半导体材料的制备及其二氧化碳还原性能方面的研究.E-mail:1058238843@qq.com。
