Enhanced direct deoxygenation of anisole to benzene on SiO2-supported NiGa alloy and intermetallic compound
Enhanced direct deoxygenation of anisole to benzene on SiO2-supported NiGa alloy and intermetallic compound
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SiO2负载NiGa合金和金属间化合物增强苯甲醚直接脱氧制苯
DOI：
10.1016/j.apcatb.2019.02.073
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发表时间：
2019
期刊：
影响因子：
--
通讯作者：
Chen Jixiang
中科院分区：
文献类型：
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作者：
Zheng Ying;Zhao Ning;Chen Jixiang
本文采用浸渍法制备了Ni/SiO2和NixGa/SiO2（Ni/Ga原子比x = 6和3）催化剂，并在0.1 MPa和300 °C下进行了苯甲醚气相加氢脱氧反应。在Ni 6 Ga/SiO2和Ni 3Ga/SiO2中分别形成了Ni-Ga合金和Ni 3Ga金属间化合物（IMC），其中Ga原子破坏了相邻的Ni原子，减少了Ni原子的聚集和H2的吸收。此外，从Ga到Ni的电荷转移增加了Ni的电子密度，并且在NixGa/SiO2上发生氢溢出。与Ni/SiO2相比，NixGa/SiO2不仅提高了催化剂的加氢脱氧活性，而且提高了催化剂对苯的选择性。在苯甲醚转化率接近31%时，Ni/SiO2、Ni 6 Ga/SiO2和Ni 3Ga/SiO2催化剂上苯的选择性分别为75.2%、83.0%和92.6%。反应活性评价、苯甲醚-TPD和TPSR结果表明，NixGa/SiO2催化剂上的CAr单键OCH 3键（CAr代表苯环上的碳）直接断裂成苯的反应比Ni/SiO2催化剂上的更优先.同位素示踪实验表明，Ni_3Ga颗粒与载体之间的界面处溢出的氢参与了反应。我们认为，Ni和Ga之间的协同作用促进了CAr单键O键的直接断裂。此外，NixGa/SiO2催化剂对苯加氢和C单键-C键氢解反应的催化活性低于Ni/SiO2催化剂，有利于提高苯的选择性。NixGa/SiO2催化剂上的甲醇主要分解为CO和H2，甲烷化反应几乎不发生，而Ni/SiO2催化剂上的甲醇主要转化为甲烷. Ni_xGa/SiO_2（尤其是Ni_3Ga/SiO_2）催化剂的苯加氢、C单键-C键氢解和甲烷化活性较低是由于Ga在合金和IMC中的几何效应和电子效应所致。研究结果对合理设计高苯收率、低氢耗的催化剂具有重要意义。
Herein, Ni/SiO2and bimetallic NixGa/SiO2(Ni/Ga atomic ratio x = 6 and 3) catalysts were prepared by the impregnation method followed by reduction at 550 °C and tested in the vapor hydrodeoxygenation of anisole at 0.1 MPa and 300 °C. Ni-Ga alloy and Ni3Ga intermetallic compound (IMC) formed in Ni6Ga/SiO2and Ni3Ga/SiO2, respectively, where the Ga atoms break contiguous Ni ones reducing the ensembles of Ni atoms and the H2uptakes. Also, a charge transfer from Ga to Ni increased the electron density of Ni, and hydrogen spill-over occurred on NixGa/SiO2. In contrast to Ni/SiO2, NixGa/SiO2improved not only the hydrodeoxygenation activity but also the selectivity to benzene. At the similar anisole conversion (˜31%), the selectivity to benzene was 75.2%, 83.0% and 92.6% on Ni/SiO2, Ni6Ga/SiO2and Ni3Ga/SiO2, respectively. Reactivity evaluation, anisole-TPD and TPSR results show that the direct CArsingle bondOCH3bond cleavage (CArrepresents the carbon in benzene ring) to benzene was more preferential on NixGa/SiO2than on Ni/SiO2. Isotope tracing experiment indicates that the spilt-over hydrogen at the interface between the Ni3Ga particles and support participated in the reaction. We suggest that the synergetic effect between Ni and Ga facilitated the direct CArsingle bondO bond cleavage. Moreover, NixGa/SiO2were less active for benzene hydrogenation and Csingle bondC bond hydrogenolysis than Ni/SiO2, contributing to higher selectivity to benzene. Significantly, methanol, derived from the direct the CArsingle bondOCH3bond cleavage, dominatingly decomposed to CO and H2and methanation scarcely occurred on NixGa/SiO2, however, it was mainly converted to methane on Ni/SiO2. Low activities for benzene hydrogenation, Csingle bondC bond hydrogenolysis and methanation on NixGa/SiO2(especially Ni3Ga/SiO2) are attributed to the geometric and electronic effects of Ga in alloy and IMC. The finding is significant in rationally designing the catalyst with high benzene yield and low H2consumption.