Research On The Chemical Modification Of Materials With Silica Hydroxy And The Application In Environment

Silica-gel and mesoporous SBA-15 are both silica oxide material with abundance of suraface Si-OH.HSO₃-silica,SH-silica,TiO₂/SBA-15,Au-Ti₂O-SBA-15 were sybthesised by surface modification method,and these materials were applied in different catalysis rection。The phenyl and chloropropyl silica derived from chlorosilane were applied to synthesize HSO₃-functionalized silica by using H₂SO₄ or(NH₄)₂SO₃.The solid acid and their precursors were characterized by BET,IR,TOC.The surface coverage density of phenyl-silica and chloropropyl-silica were 1.40mmol/g and1.95mmol/g, while the acid exchanger capacities are 0.32mmol/g and 0.26mmol/g,respectively. The specific area of the samples decreased from 511m²/g to 406 m²/g and 432 m²/g. The solid acids were used in the synthesis of butyl acetate,and the results indicated that the catalysts can be reused for 5 times with high conversion.Thiol-functionalized silica has been prepared by cheaper chloropropyl trichlorosilane and NaSH successfully instead of expensive mercaptosilylating agent. The silica-SH and its precursor are characterized by BET,FT-IR,TOC and element analysis.Surface coverage density of silica-chloropropyl and silica-SH is 2.5mmol/g and1.56mmol/g,respectively.The silica-SH is used as sorbent to fix heavy metal ions,and the saturated adsorption capacity for Hg²⁺,Pd²⁺,Au³⁺were 47mg/L,87mg/g,120mg/g respectively,so it is an excellence material for fixation of mercury from wastewater and waste solid.Nanocrystalline anatase TiO₂ limited within the mesoporous channels of SBA-15 has been prepared by in-situ hydrolysis precipitation of Ti(SO₄)₂ solution and calcination subsequently.The as-synthesized samples were characterized by TEM, BET,XRD,SAXD,Raman,UV-Vis,XPS,XRF techniques,and the results indicated that nano-TiO₂ particles were restricted within the channel and dispersed uniformly without block the pores.The Raman and XPS data indicated that most TiO₂ particles are deposited on the support without forming Ti-O-Si bond.The activities of the samples were evaluated by the photo degradation of methyl orange under UV-light.The results showed that the TiO₂ contents and the size of particles on the support of SBA-15 affected the catalytic activity obviously,and the samples with TiO₂ particles size about 6～7nm showed the best catalytic activity.Little difference of the activity was observed between the fresh sample and the sample used for 5 times.TiO₂ and Mo₂O₃ were attach to the surface of SBA-15 by gas-phase surface modification using their chloride as precursors.The samples are characterized by BET, HRTEM,UV-Vis diffuse reflection absorption spectrum.The results indicated that Ti,Mo are in the channel of the SBA-15 without block it.The Au/Ti-SBA-15 are used to used in the oxidation of CO,and the results indicated that the catalysts in a wide range of temperature and the SBA-15 confined the growth of Au particles.