Study On Preparation, Characterization And Adsorptive Performance Of Porous Glasses

Porous glasses were first synthesized in 1930s, it can work normally under rigorous experimental conditions because of good acid endurance, high temperature resistance and mechanical strength. Besides, porous glasses can be used in biological medicine, photo catalysis, and optical communications for its purity and light transmission. However, the deeply application of porous glasses is still in experimental stage and haven't been commercialized. Based on our experimental condition, this dissertation prepared high silicon (wt% of silicon dioxide>97%) glasses of steady properties through sol-gel process. Test and characterization of the productions are carried out by BET, XRD, SEM, EDS. Then the prepared porous glasses are used in high pressure adsorption of carbon dioxide and methane and adsorptive separation of CO₂/ N₂.The materials of the experiments are NaOH,H₃BO₃,Si(C₂H₅O)₄, the mass ratio is 0.039:0.179:0.782 , water and ethanol are used as solvent, nitric acid is catalyst, the preparations are carried out in 50℃water bath and pH=1. The transparent wet gel is obtained after 3 day's gelation, then dry gel is obtained after 3 day's aging under the same condition, afterwards, put the dry gel into pipe furnace and raise the temperature to 480℃to form ultra-fine powder of sodium borosilicate glass active precursor. The powder then melt to form uniformly colorless and transparent sodium borosilicate glass high temperature furnace at 1170℃, then split phase at 630℃for 24 hours, finally, porous glass is obtained after 12²4 hours'leaching in acid. Low acid concentration and leaching time will produce micropores glass and otherwise mesoporous glass. The ratio surface, pore diameter and pore volume of porous glass prepared at100℃in 0.2mol/L HCl solution and leaching for 3hours are respectively 267m2/g, 0.77nm, 0.13ml/g. The above parameters of mesoporous glass prepared at 100℃in 3mol/L and leaching for 12hours, 24hours are respectively 176m2/g,2⁴nm,0.125ml/g and 140m2/g,4nm,0.112ml/g.Alkali leaching and acid leaching at high temperature can lead to effective reaming. After leaching the porous glass into 0.5mol/L NaOH at room temperature, the pore diameter is expanded from 2nm to 4nm, and leaching in HCl at 140℃for 24hours, the pore diameter is expanded from 4nm to 4.5nm⁸nm. The result of SEM-EDS indicated that silicon dioxide content is up to 97%.The adsorbance of CH4 and CO₂ in porous glass at the pressure high to 6MPa are 2 mmol/g and 0.3 mmol/g. Micropores glass have good effect for CO₂ / N₂separation at atmospheric pressure, the separation factor can reach about 8.5, however, increase pore diameter or operation pressure will decrease the separation effect.