Ni/镁铝水滑石催化剂解聚木质素

Depolymerization of lignin over Ni/Mg-Al hydrotalcite catalyst

木质素是自然界具有芳香环结构单元的可再生资源,可将其解聚为单环芳香族为主体的高附加值化学品,符合我国的能源战略。以Ni/镁铝水滑石、Ni/石墨烯纳米片和Ni/碳纳米管为催化剂,比较分析了3种催化剂催化解聚碱木质素的转化率和选择性,并探究了木质素解聚可能的机理。结果表明:Ni/镁铝水滑石催化剂醇解木质素的性能最佳,转化率为77.1%、芳香族化合物的选择性为37.35%,芳香族产品以愈创木酚类化合物为主。3种催化剂活性组分均以氧化镍形式存在,但Ni/镁铝水滑石催化剂的载体中存在更多的氧空穴,导致其催化木质素的转化率最高;Ni/镁铝水滑石催化剂的载体的碱性点位更多,有利于木质素解聚后生成芳香族化合物,使木质素解聚的芳香族化合物的选择性远高于其他2种催化剂。

Because of the naturally aromatic ring structural units, lignin can be depolymerized to obtain high value-added chemical products, which is in line with China′s energy strategy. Ni/Mg-Al hydrotalcite, Ni/graphene nanosheets and Ni/carbon nanotubes were prepared and used as catalysts to depolymerize lignin. The conversion of alkali lignin and selectivity of monocyclic aromatic compounds were discussed, in addition, the possible mechanism of lignin was explored. The results show that Ni/Mg-Al hydrotalcite is the best catalyst for the alcoholysis of lignin. The corresponding conversion rate of lignin and the selectivity of aromatic compounds are 77.1% and 37.35%, respectively. The guaiacol chemicals are the main components of aromatic products. Moreover, the active components of three catalysts are confirmed in the form of nickel oxide. Attributed to abundant oxygen vacancies in the support of Mg-Al hydrotalcite, the conversion of lignin over Ni/Mg-Al hydrotalcite catalyst is better than the others. Furthermore, the basic sites of the Mg-Al hydrotalcite support facilitate the depolymerization of lignin into aromatic compounds, making Ni/Mg-Al hydrotalcite catalyst much more prominent in terms of selectivity of monocyclic aromatics.