Conversion And Comprehensive Utilization Of Organic Silicon High-boiling Residues

The"Direct Process"is a main way to produce silane monomers,during which a range of silane mixture with boiling point greater than dimethyldichlorosilane are gener-ated,called high-boiling residues（HBR）.With a substantial growth of China’s organic silicon capacity and emission reduction required,conversion and comprehensive utiliza-tion of HBR had been attracting more and more attention.In this paper,the author put forward a set of comprehensive utilization plan,providing useful references for future re-search.Firstly,immobilized Lewis Acid catalysts were used in the pyrolysis reaction under atmospheric pressure.After immobilized on the support,performance between AlCl₃ and ZnCl₂ were compared by an liquid-solid phase reaction,conclude that the AlCl₃ catalyst was better than ZnCl₂,its selectivity to dimethyldichlorosilane（DMCS）was 9.78%more than the latter.The effects of catalyst supports on reaction performance were studied.It showed that the MCM-41 support was the most durable,also hold the highest conversion,up to 18.22%.However catalyst immobolized on SiO₂ support was much cheaper,the HBR conversion was 9.57%and selectivity to DMCS was 53.71%.The best immobiliza-tion ratio of AlCl₃/SiO₂ catalyst was AlCl₃:SiO₂（wt/wt）=0.8:1,reaction at reflux tem-perature of HBR for 3 hours,under which the HBR conversion and DMCS yield were9.72%and 5.65%respectively.Replaced by gas-solid phase catalytic reaction,the yield of DMCS was only 4.01%,as a result of equipment limitations.Secondly,the ammonia propyl silica gel（APS）catalyst was synthesized based on stober method,which was microspheres without hole.Its thermal stability was good un-der experimental temperature.The optimum operating parameters of pyrolysis using APS catalyst were obtained through an orthogonal test,the best mole ratio of TEOS and KH-550 was 4,reaction temperature was 140℃,reaction time was 2 hours and catalyst amount was 10%on the total mass of HBR.At this point,the HBR conversion and DMCS yield were as high as 80.48%and 30.60%respectively but the space-time yield of DMCS was 1.53g/g（cat.）·h only.However reduce the reaction time to 1 hour and the catalyst amount to 2.5%,the space-time yield increased to 8.74g/g（cat.）·h.During batch reaction,the catalyst capacity of APS was higher than the industrial process using organic amine catalysts.Finally,HBR hydrolyzation was proposed in order to deal with components couldn’t be cracked.Hydrolysed HBR was used as filler for LDPE,which maximum filling rate was 34.83%on the total mass of material.Without aid agent,the influence of HBR filler on material properties was similar to unmodified inorganic fillers,but the extent was lesser.The composite’s tensile strength and impact strength were reduced by 24.36%and71.97%maximum,while flexural strength was improve by 19.58%maximum.Compared with pure LDPE the composite’s temperature resistance,weather resistance and combus-tion properties were also improved.With characteristics of process simpled and operation easied,the conversion and comprehensive utilization methods showed promising potential for industrial application.In addition,this work provided a clear target for future research.