Synthesis And Performance Of Highly Dispersed Fe³⁺ Activity Site Heterogeneous Catalysts

Diphenylmethane(DPM)is a very significantly and commonly used organic compound as pharmaceutical intermediates and fine chemicals,which is mainly synthesized via Friedel-Crafts benzylation of benzene with benzyl chloride(BC).However,the traditional homogeneous acid catalysts widely used in industry deviate from the development demands of green chemistry and clean technology.Hence,it is highly desirable to design high-efficiency heterogeneous catalysts,which are non-toxic,reproducible and friendly to environment,to replace these catalysts.Especially,much work has been focused on the iron functionalized mesoporous catalysts because of their structural advantages and excellent Fe3+activity site.In this thesis,Fe2O3/SiO2 and Fe2O3/C-SiO2 nanocomposites prepared by various methods were used as the catalysts for the benzylation of benzene,and the relationships between structure and catalytic performance were evaluated.The main conclusions areas follows:(1)Using sol-gel method,Fe2O3/SiO2 mesoporous composites with shell-core structure were synthesized by ethyl orthosilicate(TEOS)as silica raw and ferric citrate as iron raw.and the catalytic activity was investigated under different reaction conditions.The results showed that appropriate additive ferric citrate could be of benefit to expand pore channels and form dispersed Fe2O3 nanopaticles coated by silica shell.However;excessive Fe2O3 could block or collapse the nanochannels,leading to decline of the specific surface area and catalytic efficient.And also,the suitably increase of reaction temperature.time and catalyst could improve the conversion of benzyl chloride and selectivity of diphenylmethane.0.5g Fe/MS-8 exhibited an excellent activity with 100%conversion of BC and selectivity to DPM within 45min at 75?.and reused three time cycles.(2)Ordered mesoporous hybrid materials(MCS)and MCS supported iron were synthesized by triconsituent co-assembly method,with triblock copolymer F127 as a structure-directing agent.resol polymer as carbon source.TEOS as silica source and ferric nitrate as iron source.Characterization results revealed that MCS and catalysts with low content of iron(Fe/MCS-0.10?0.15)possessed ordered two-dimensional hexagonal mesoporous structure,wherein Fe2O3 and ?-Fe0 components were well dispersed.When the iron content was too much to seriously affect the self-assembly process,the order mesostructure was destroyed.The catalytic activity of Fe/MCS-y depends on amount and degree of disperse of Fe2O3 oxide sites.The conversion of BC rapidly improved along with the increase of iron content.Fe/MCS-0.25 could completely transform benzyl chloride,but only reach 87%DPM selectivity due to the coacervates and collapsed channels.(3)The Fe2O3/C-SiO2 functionalized mesoporous materials were obtained by using MCS prepared via one-step soft-templating route as supports,and calcined after impregnation of ferric nitrate solution.The well-defined mesostructure of MCS carriers was maintained by a impregnation method.The particle size and disperse of iron oxide is effected by calcined temperature and the amount of Fe introduction,which also effect the specific surface area.pore diameter and catalytic performance.Fe/MCS-0.5-600 samples with 0.5g ferric nitrate addition and calcined at 600? achieved 100%conversion of BC and 96.4%selectivity of DPM owe to the highly dispersed Fe2O3 nanopaticles.