氨辅助浸渍法制备抗烧结Ni/SiO2催化剂及其甲烷二氧化碳重整反应的性能  

Preparation of sinter-resistant Ni/SiO2 catalysts using ammonia-assisted impregnation method and its performance in CO2 reforming of methane

作　　者：万吉纯 朱孔涛 翁维正[1] 楚沙沙 郑燕萍[1] 黄传敬[1] 万惠霖[1] WAN Jichun;ZHU Kongtao;WENG Weizheng;CHU Shasha;ZHENG Yanping;HUANG Chuanjing;WAN Huilin(State Key Laboratory of Physical Chemistry of Solid Surfaces,National Engineering Laboratory for Green Chemical Productions of Alcohols-Ethers-Esters,College of Chemistry and Chemical Engineering,Xiamen University,Xiamen 361005,China)

机构地区：[1]厦门大学化学化工学院固体表面物理化学国家重点实验室醇醚酯化工清洁生产国家工程实验室

出　　处：《厦门大学学报（自然科学版）》2019年第5期651-660,共10页Journal of Xiamen University：Natural Science

基　　金：国家自然科学基金(21473144);教育部创新研究团队项目(IRT_14R31)

摘　　要：以硝酸镍为前驱盐、商品SiO2为载体,采用氨水辅助浸渍法通过改变n(NH3)/n(Ni)制备了系列Ni/SiO2催化剂,并将其应用于甲烷二氧化碳重整(DRM)制合成气反应.实验结果表明:在浸渍过程中加入氨水可显著改善Ni/SiO2催化剂的DRM反应活性、稳定性和抗积碳性;随着氨水添加量的增加,催化剂活性相分散度提高,当浸渍液中n(NH3)/n(Ni)≥6时,经800℃焙烧后催化剂上NiO物种的平均粒径小于5 nm.通过改变氨水、SiO2、前驱盐的浸渍顺序,发现只有用硝酸镍与一定浓度的氨水配成的混合溶液浸渍SiO2才能获得具有良好分散度的Ni/SiO2催化剂.氨水与Ni形成的镍氨络合物能够避免在浸渍过程中生成Ni(OH)2沉淀,进而有利于Ni物种在SiO2表面均匀分散.氨水所形成的碱性环境还可使载体表面Si—O物种部分溶解或“软化”,进而促进Ni物种与载体表面相互作用,在后续的焙烧过程中生成与SiO2具有较强相互作用的Ni物种以及表面镍硅酸盐物种.这些物种具有良好的抗烧结性能,可防止Ni物种在高温下团聚,并在600℃以上通H 2还原后得到分散性良好且具有较强抗烧结性能的金属Ni颗粒.Ni/SiO2 catalysts were prepared with ammonia-assisted impregnation method using Ni(NO3)2·6H 2O as precursors and commercial SiO2 as support through changing the n(NH3)/n(Ni).The catalysts were applied to CO2 reforming of methane(DRM)to syngas reaction.It is found that addition of ammonia in the impregnation step can significantly improve the activity and stability as well as coke resistance ability of the Ni/SiO2 catalysts for the DRM reaction;dispersion of the active phase in the catalysts increases with the increase of the amount of ammonia addition.When n(NH3)/n(Ni)in the impregnation solution is higher than 6,the NiO species with average particle size of less than 5 nm can be achieved after calcination in air at 800℃.It is also found that highly dispersed Ni/SiO2 catalysts can only be obtained when SiO2 is impregnated with a solution containing both nickel nitrate and ammonia after changing the dipping sequence of NH3·H2O,SiO2 and precursor salt.The formation of nickel-ammonia complex plays an important role in preventing the formation of Ni(OH)2 precipitation in the impregnation step,thus facilitating the uniform dispersion of Ni species on the surface of SiO2.The alkaline environment caused by ammonia can also partially dissolve or“soften”the Si—O species on the surface of the support,and thereby facilitates the formation of the Ni species with strong interaction with SiO2 as well as Ni-silicate species by the interaction/reaction of Ni and surface of the SiO2 in the calcintion step.Formation of these species with high sinter-resistant property prevents Ni from sintering at high temperature.These species will further transform to well-dispersed and sinter-resistant Ni particles on SiO2 after reduction by H2 at temperature above 600℃.

关 键 词：Ni/SiO2 氨水辅助浸渍 抗烧结 镍硅酸盐 甲烷二氧化碳重整 

分 类 号：O643.361[理学—物理化学]