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由可再生木质素基生物质油加氢脱氧制三苯(苯、甲苯及二甲苯)及燃油可减少对化石能源依赖、缓解环境问题,加氢脱氧催化剂的研究开发为众多学者密切关注.我们以低成本金属Ni为加氢脱氧活性组分,采用金属In对金属Ni催化剂进行改性,旨在增加以苯甲醚为模型反应物加氢脱氧中的三苯收率、降低金属Ni的C-C键氢解及甲烷化活性,提高反应过程中碳收率、降低耗氢量.采用等体积浸渍-程序升温还原法制备了Ni/SiO_2及Ni-In/SiO_2催化剂,研究了Ni/In比及Ni含量对In改性Ni/SiO_2催化剂结构和苯甲醚加氢脱氧性能的影响,利用H_2-TPR,H_2化学吸附,XRD,NH3-TPD,XPS,TEM及N2物理吸附-脱附等手段对催化剂及其前驱体进行了表征,采用石英管固定床反应器在300°C、常压、H_2/苯甲醚摩尔比25及苯甲醚重时空速0.4 h-1的反应条件下考察了催化剂苯甲醚加氢脱氧性能,分析了催化剂结构与性能之间的关系.H_2-TPR结果显示,金属In的加入抑制了催化剂前驱体中Ni物种的还原.XRD,H_2化学吸附,HAADF-STEM-EDS及XPS等结果表明,经450°C还原制备的Ni-In/SiO_2双金属催化剂中Ni和In接触紧密.In的加入明显降低了催化剂表面金属Ni的活性位数量;并且,Ni/In比越低Ni-In/SiO_2催化剂H_2化学吸附量越小.XPS结果还显示,Ni-In/SiO_2催化剂中存在金属In向Ni转移电子.上述结果说明,在Ni-In/SiO_2催化剂中金属Ni与In存在较强的相互作用.在苯甲醚加氢脱氧反应中,与Ni/SiO_2催化剂相比,Ni-In/SiO_2催化剂虽因表面Ni密度较低而具有较低苯甲醚转化率,但其苯环加氢、C-C键氢解及CO甲烷化活性较低,因而具有较高的三苯及环己烷选择性;并且,随Ni/In比的降低(即In含量的增加),Ni-In/SiO_2催化剂的加氢、氢解及甲烷化能力呈减弱趋势.随Ni质量含量提高,Ni-In/SiO_2双金属催化剂上苯甲醚转化率提高,但对三苯选择性及C-C键氢解能力影响不明显.经分析认为,与Ni/SiO_2相比,Ni-In/SiO_2催化剂较低的苯加氢及C-C键氢解活性与In对表面连续Ni位隔离作用及金属镍位电子云密度提高有关.在优化的反应条件下,Ni质量含量为40%、Ni/In比为40的Ni-In/SiO_2催化剂上三苯收率为60.4%,高于相同Ni质量含量Ni/SiO_2催化剂上三苯收率(51.6%).
The hydrodeoxygenation of triphenylbenzene (benzene, toluene and xylene) and fuels from renewable lignin-based biomass oils can reduce energy dependence on fossil fuels and alleviate environmental problems, and the research and development of hydrodeoxygenation catalysts are closely watched by many scholars. The low-cost metal Ni is used as the hydrodeoxygenation active component, and the metal In is used to modify the metal Ni catalyst so as to increase the yield of the benzene in the hydrodeoxygenation of the model reactant with anisole and reduce the CC of the metal Ni Key hydrogenolysis and methanation activity to increase the carbon yield during the reaction and reduce the consumption of hydrogen.The Ni / SiO 2 and Ni-In / SiO 2 catalysts were prepared by the same volume impregnation-temperature programmed reduction method, and the effects of Ni / In ratio and Ni content on the structure and the hydrodeoxygenation of anisole in the modified Ni / SiO_2 catalyst was investigated. The effects of H_2-TPR, H_2 chemisorption, XRD, NH3-TPD, XPS, TEM and N2 adsorption- The catalysts and their precursors were characterized by means of a quartz tube fixed bed reactor under the reaction conditions of 300 ° C, atmospheric pressure, H 2 / anisole molar ratio 25 and anisole weight hourly space velocity 0.4 h-1. Anisole hydrodeoxygenation performance, analysis of the catalyst structure and performance The results of H2-TPR showed that the addition of metal In inhibited the reduction of Ni species in the catalyst precursor.The results of XRD, H2 chemisorption, HAADF-STEM-EDS and XPS indicated that the reduction of Ni In / SiO 2 bimetallic catalyst, Ni and In are in close contact with each other, the addition of In significantly reduces the number of active sites of metal Ni on the surface of the catalyst, and the lower the Ni / In ratio, the smaller the amount of H 2 chemisorption on the Ni-In / SiO 2 catalyst. XPS results also show that there is metal In to Ni transfer electron in Ni-In / SiO_2 catalyst.The above results show that there is a strong interaction between Ni and In in Ni-In / SiO_2 catalyst.In the case of anisole hydrodeoxygenation Compared with the Ni / SiO 2 catalyst, the Ni-In / SiO 2 catalyst has a lower conversion of anisole because of its lower surface Ni density, but its benzene ring hydrogenation, CC bond hydrogenolysis and CO methanation activity Lower, and thus higher triphenyl and cyclohexane selectivity; and, with the Ni / In ratio decreased (ie, increased In content), Ni-In / SiO 2 catalyst hydrogenation, hydrogenolysis and methanation Showing a decreasing tendency.With the increase of Ni content, the conversion of anisole on the Ni-In / SiO_2 bimetallic catalyst increased, but the selectivity to triphenylbenzene CC bond hydrogenolysis ability is not obvious.Analysis shows that, compared with Ni / SiO_2, Ni-In / SiO_2 catalyst lower benzene hydrogenation and CC bond hydrogenolysis activity and In on the surface of the continuous Ni bit isolation and nickel The electron density increased.Under optimized reaction conditions, the yield of tribenzene on the Ni-In / SiO 2 catalyst with Ni mass content of 40% and Ni / In ratio of 40 was 60.4%, higher than that of Ni with the same Ni content / SiO 2 catalyst on the benzene yield (51.6%).