空心微球基底的双壳层可控复盐催化剂歧化甲基氯硅烷机理研究

Dichlorodimethylsilane is the most important organosilicon monomer. Overstocking of by-products have caused a series of environmental and economic problems in producing dichlorodimethylsilane. All of the problems can be solved by disproportionation which could change wastes into precious resource. And the key is to discover the catalytic mechanism essentially. Previous study showed that the activity of NaAlCl4/carrier (ZSM-5,γ-Al2O3 and η-Al2O3) corelated with suface Lewis acids but not those in pores. So the following related problems, i.e. core-double shells catalysts based on hollow microspheres, cooperation between Lewis acid and activity, the fundamental reasons for activating Al-Cl bond should be further studied. Spectroscopy and surface analytical techniques with DFT theory should be used to clarify the structure-activity relationship; to recover the cooperation between Lewis acid and activity; to discover the effects of different components on the active sites NaAlCl4; to activate Al-Cl bond and make it electively react with CH3 of silane thus improving catalysts’ activity. The natural catalysis process being recovered in this project would provide basic data to understand the laws of core-double shells series hollow microspheres’ catalysts and disproportionation mechanism; and provide theoretical foundation to develop high performance catalysts.

二甲基二氯硅烷是有机硅材料的最重要单体，而现有直接法副产的大量废弃物带来了亟待解决的环保和经济问题。通过硅烷歧化可变废为宝并同时解决上述问题，而揭示该歧化的机理与本质则成为反应的关键。申请人发现NaAlCl4/载体（ZSM-5、γ-Al2O3和η-Al2O3）催化剂活性与表面（非孔道）L酸等密切相关。为此，申请人拟对中空微球表面覆壳制备的系列核双壳催化剂、L酸与活性的协同作用、Al-Cl键活化的本质原因进行深入研究。拟采用光谱学和表面分析技术结合DFT理论，阐明核双壳催化剂结构与活性的构效关系；探索与活性相关的L酸可控调节；揭示改性各组分对活化位NaAlCl4的本质影响，使Al-Cl键得以可控活化并定向进攻硅烷中的CH3，提高催化剂的活性。本项目所揭示的催化作用本质，将为理解相关基于中空微球的核双壳催化剂之作用规律与歧化机理提供基础数据，为发展相关高性能催化剂提供理论依据。

二甲基二氯硅烷是有机硅材料的最重要单体，而现有直接法副产的大量废弃物带来了亟待解决的环保和经济问题。通过硅烷歧化可变废为宝并同时解决其环保和经济问题，而揭示该歧化的机理与本质则成为反应的关键。通过该项目的研究，申请人主要讨论了ZSM-5、MIL-53(Al)和γ-Al2O3分别为核壳结构的催化剂，同时复盐中的金属Mt为Na和K的相关实验和理论探讨。研究结果表明在所有的核壳以及核壳空心微球催化剂中NaAlCl4/ZSM-5@γ-Al2O3空心微球催化剂效果最好（其最优条件为： Si：Al=50，NaAlCl4比例 8%，浸渍 2h，催化剂的用量 0.6g，反应物的配比 1:1，反应温度200℃时，二甲的产率为 73.80%）。相对于之前复盐负载之前的核壳载体的催化活性（实验结果表明在未覆上活性组分的复盐膜层之前制备的核壳载体具备歧化制备8.23%-24.4%二甲的能力），说明复盐负载后活性位变成了L酸的Al-Cl键。该键主要通过活化硅烷体系中的Si-CH3键，并定性进攻甲基从而实现歧化的整个过程并实现催化剂的选择性。理论计算的结果能说明MtAlCl4负载后大部分核壳催化剂上的活性位都大大提高了副反应速控步的活化能，并使得主、副反应活化能差异增大，从而使得副反应受到抑制，进而使得催化歧化生成二甲的可能性大大增强，从而使得催化剂的活性、选择性和定性进攻硅烷中的甲基得以实现。