The Preparation Of Spherical Silica And The Study Of The Pore Structure

As the most popular pillar-stuffing,silica-gel plays a pivotal role in technology of chromatogram-Separation by its surface pore structure.It is very significative to prepare a king of globose silica-gel with symmetrical granularity and narrow distribution of aperture,and study on the pore structure. In this study,under the acidic condition,were given out by carbamide, formaldehyde and spherical SiO₂,which was prepared with tetraethoxysilane (TEOS)hydrolysis by PICA.In this research,we compared how different conditions affected products,and we found the best.After embedding the product and commercial silica-gel,changes of their pore structures and surface properties were studied by means of SEM observations,BET and mercury intrusion method.Experimental procedure were as follow:On one hand,the urea-formaldehyde SiO₂ spherules,under the acidic condition,were given out by carbamide,formaldehyde and SiO₂-hydrosol, which was prepared by PICA.By means of SEM observations,we researched the corresponding size and shape of urea-formaldehyde SiO₂ spherules in different conditions,involving quantity ratios of formaldehyde/carbamide,pH Values,reaction temneratures and reaction times.The results showed that the 5μm-average particle size of urea formaldehyde/SiO₂ can stably obtained in the condition of pH=1.5～2.5,N=1～3,T=15℃,t=10～20.On the other hand,using epoxy resin Epon 812,after compounding embedded solution A and embedded solution B,we investigated the influence of temperature on silica-gel embedding.The results showed that embedded solution of A and B could be affected by temperatures:A/B=1/4(15℃),and A/B=1/8(25℃)will be best.In above conditions,we embedded kromsil C-18 and macropore silica-gel,sliced up and observed by SEM.The results showed that the measure results of SEM observations and BET method were accordant, meanwhile,SEM method can offered lots of intuitionistic information by photos.Therefore,besides BET and mercury intrusion method,it is feasible to measure the size of pillar-stuffing pore.