摘要
采用成核-晶化隔离法制备LiAl-CO_(3)-LDHs晶核,在LDHs晶核晶化的过程中引入葡萄糖分子作为碳源,构筑组成和结构可调的LDHs/C型杂化复合前体。通过高温处理,实现前体的结构拓扑转变及无定形碳组分的去除,得到高比表面积的LiAl复合金属氧化物型固体碱催化剂。采用XRD、FT-IR、BET、TEM、SEM、CO_(2)-TPD等表征手段对催化剂的组成、结构、织构性能、表面碱性进行了详细研究,并以苯甲醛和氰基乙酸乙酯间的Knoevenagel缩合反应为探针反应系统地研究了催化剂的碱催化性能。研究结果表明,LDHs/C杂化前体制备过程中葡萄糖与金属离子的摩尔比、水热晶化温度以及焙烧温度是影响催化剂活性的主要因素,晶化温度和焙烧温度的提升不利于碱性位的充分暴露。在150℃的水热晶化温度下,葡萄糖与Al 3+的摩尔比为3时的杂化复合前体经500℃焙烧得到的LiAl-MMO-150-3-500固体催化剂比表面积高达229 m 2·g^(-1),苯酚吸附测得催化剂的总碱量为855μmol·g^(-1),对苯甲醛的转化率高达88.21%。
A series of LiAl-CO 3-LDH/C hybrid composite precursors were prepared by a novel separate nucleation and aging steps we developed previously,glucose molecules were introduced as carbon source during the crystallization process of LDHs nuclei to fabricate LDHs/C hybrid composite precursor with controlled composition and structure.LiAl composite oxide based solid base catalyst with high specific surface area was obtained by topological transformation of precursors and removal of amorphous carbon components under high temperature treatment.Using XRD,FT-IR,BET,TEM,SEM,CO_(2)-TPD and other characterization methods,the composition,structure,texture properties and surface basicity of the catalyst were studied in detail.Knoevenagel condensation reaction of benzaldehyde and ethyl cyanoacetate was used as the probe reaction to investigate the alkali catalytic performance of the prepared catalyst.The results indicate that molar ratio of glucose to Al^(3+),hydrothermal temperature and calcination temperature are the main factors affecting the activity of catalysts,and higher hydrothermal temperature or calcination temperature has negative impact on the exposure of basic sites.The LiAl-MMO-150-3-500 catalyst,calcinated at 500℃with the molar ratio of glucose to Al^(3+)was 3 in the corresponding precursor,has a surface area of about 229 m^(2)·g^(-1),the total basic sites of about 855μmol·g^(-1) based on phenol adsorption method,and thus exhibits the highest catalytic performance with the conversion of benzaldehyde reach up to 88.21%under our experimental conditions.
作者
宋奕慧
雷志轶
范国利
杨兰
林彦军
李峰
SONG Yihui;LEI Zhiyi;FAN Guoli;YANG Lan;LIN Yanjun;LI Feng(State Key Laboratory of Chemical Resource Engineering,Beijing University of Chemical Technology,Beijing 100029,China;School of International Culture and Communication,Beijing City University,Beijing 100083,China;College of Chemical Engineering,Qinghai University,Xining 810016,Qinghai,China)
出处
《化工学报》
EI
CAS
CSCD
北大核心
2021年第6期3084-3094,F0002,共12页
CIESC Journal
基金
国家自然科学基金项目(21991102)。
