Preparation And Modification Of Silica Using Residue Of Huadian Oil Shale

With the shortage of petroleum,oil shale,a kind of new altermative energy,is becoming more and more important for people.The main utilization way of oil shale is retorting and burning for electricity.Because it contain a series of mineral composition,the production rate of residue is very high.This residue,an environmental pollution,is harmful for people's health.Therefore the comprehensive utilization of the waste material has important practical meanings.Silica white is a kind of powdery or ultrafine particle silicon dioxide,which is an important inorganic fine chemical Si-based material.Based on the high SiO₂ content,the optimal technology for silica white with residue of oil shale was studied.In addition,the surface modification of silica white production was studied and the good performance hydrophobic silica had been produced.Residues test samples obtained from semicoke of Huadian oil shale-retored solid heat carrier,semicoke of Huadian oil shale-retored Fushun Furnaces and fly ash of Huadian oil shale-fired circulating fluidized bed(CFB).SiO₂ in the residue was changed to Na₂SiO₃ through alkali-dissolved reaction.The effect of the granularity of raw material,the activation temperature,the activation time,dosage of alkaline,concentration of NaOH and reaction time on the leaching rate of SiO₂ were discussed.The results indicated that the optimum calcinating temperature of semicoke of Huadian oil shale-retored solid heat carrier is 850℃and calcinations were not required for the other raw materials.The optimum concentration of NaOH for three materials were 25%.The ratio of liquid to solid of semicoke of Huadian oil shale-retored solid heat carrier and semicoke of Huadian oil shale-retored Fushun Furnaces was 4:1 and the reaction time was 3h.The optimum of ratio of liquid to solid of fly ash of Huadian oil shale-fired circulating fluidized bed was 3:1 and the reaction time was 2.5h.The optimum granularity of semicoke of Huadian oil shale-retored solid heat carrier and semicoke of Huadian oil shale-retored Fushun Furnaces was 0.1mm and the granularity of fly ash of Huadian oil shale-fired circulating fluidized bed wasn't need to investigate.The leaching rates of SiO₂ is respectively 81.3%,72.4%and 61.5%for the materials of semicoke of Huadian oil shale-retored solid heat carrier,semicoke of Huadian oil shale-retored Fushun Furnaces and fly ash of Huadian oil shale-fired circulating fluidized bed.Silica white was prepared with homo-precipitation method,used the Na₂SiO₃ extract as one major raw material and ethyl acetate as hide reagent.The effect of SiO₂ concentration,the quantity of ethyl acetate,reaction temperature and reaction time on the particle size and yield of silica white were discussed.The results indicated that while the concentration of SiO₂ was 0.052g/ml,the molar ratio of ethyl acetate to SiO₂ was 0.9 and the reaction temperature was 40℃,the powder silica white was spherical approximately,the average particle size is about 150nm and the specific suface are is about 162m²/g.In addition,chemical analyses,thermo gravimetry(TG),infrared spectrum(IR),scanning electron microscope(SEM) and X-ray diffraction(XRD) were employed to test and analyze the product.The product could be comparable with the relevant national standards.It provides a new way for the development and utilization of residue of oil shale.Surfactant and silane coupling agent were used to modified the production silica. Modification effect was identified by the change of hydroxyl number on surface of slica white.The results indicated that,when the modifier was cationic surfactant,the best modification result was gained.The hydrophobic rate of silica white could reach to 82～84%. Nonninic surfactant took the second place.The hydrophobic rate of silica white was about 80%.when the modifier was silane coupling agent,modification effect was the poorest. According to the result of IR,TG and ¹H nuclear magnetism resonance(¹HNMR),silica white has been modificated.The hydrophobic rate of silica white could over 90%and good performance hydrophobic silica could be produced.