基于稻谷壳模板制备层状硅酸盐催化剂用于CO_(2)加氢反应

Preparation of Phyllosilicate Catalysts Using Rice Husk as Template for CO_(2) Hydrogenation

利用稻谷壳提供唯一硅源并作为硬模板制备了多孔型层状硅酸盐材料,通过原位还原技术还原层状硅酸盐中的过渡金属离子制得过渡金属基催化剂用于CO_(2)加氢反应。采用扫描电镜(SEM)、X射线粉末衍射仪(XRD)、氮气物理吸附、X射线荧光光谱仪(XRF)、热重分析(TGA)和氢气程序升温还原(H2-TPR)等对稻谷壳模板和所制备的层状硅酸盐催化剂进行了表征。结果表明:利用稻谷壳提供唯一硅源,在水热条件下与单一或混合过渡金属离子成功制得了层状过渡金属硅酸盐材料,制得的层状硅酸盐材料保留了稻谷壳的多层次空间结构。CO_(2)程序升温脱附(CO_(2)-TPD)验证了稻谷壳中的微量碱性金属(K和Ca)能够自掺杂硅酸盐材料,促进其对CO_(2)的吸附。此外,所制备的过渡金属催化剂均能有效催化CO_(2)加氢反应,其中层状硅酸镍的催化活性最高。采用原位红外表征技术探究了层状硅酸镍催化CO_(2)加氢的中间物种信息。结果表明,甲酸盐中间体(HCOO^(*))是生成CO和CH4产物的关键物种。

Herein,the layered transition metal silicates were prepared by using the rice husk as both silicon source and hard template,and the transition metal ions in the silicate can be in-situ reduced by H_(2) to prepare transition metal-based catalysts for CO_(2) hydrogenation reaction.The rice husk and the derived catalysts were systematically characterized by scanning electron microscopy(SEM),X-ray diffraction(XRD),nitrogen physical adsorption,X-ray fluorescence spectroscopy(XRF),thermalgravimetric analysis(TGA),H_(2) temperature-programmed reduction(H_(2)-TPR),and so forth.The results showed that the rice husks indeed provide the silicon source for the growth of phyllosilicate under hydrothermal conditions,while the obtained phyllosilicate retained the hierarchical porous structure of rice husks.CO_(2)-temperature-programmed desorption(CO_(2)-TPD)verified that the alkali metals(K,Ca)in rice husk could self-dope the resultant phyllosilicate and promote the CO_(2) adsorption capacity of the phyllosilicate.In addition,the prepared transition metal catalysts can effectively catalyze the CO_(2) hydrogenation,wherein the nickel silicate exhibited the highest catalytic activity.Besides,in-situ diffuse reflection Fourier transform infrared spectroscopy(DRIFTS)was used to explore the intermediates in CO_(2) hydrogenation over the nickel silicate catalyst.The results showed that formate(HCOO^(*))was the key species for the production of CO and CH_(4).