ISSN:
1573-9171
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
Notes:
Summary 1. An investigation has been made of the effect of pressures of up to 20,000 arm on the porosity characteristics adsorption activity, and catalytic properties of silica gel. 2. It has been shown that the greatest reduction (by 50%) in the limiting sorptive capacity of the pores (sum of the capacities of the micro and connective pores of the coarsely porous silica gel) occurs during compression to 5000 atm, but no simultaneous change in specific surface occurs. The greatest reduction in the limiting sorptive capacity of the pores of the finely porous silica gel occurs over the range 5000-10,000 atm. The reduction in the limiting sorptive capacity of the pores is therefore attained by a lower compression for the coarsely porous silica gel.The explanation of this is that the coarsely porous silica gel, unlike the finely porous material, has a greater volume of connective pores. Mechanical action, therefore, primarily destroys the connective pores, whereas thermal action destroys the fine pores. In general, the limiting sorptive capacity of the coarsely porous silica gel compressed at 5000-10,000 atm does not differ, from that of the finely porous material, i.e., the coarsely porous material is converted by pressure into finely porous material. When the compression is further increased to 20,000 atm, the limiting sorptive capacity, of the pores of the samples of finely and coarsely porous silica gels remains practically the same as that of the samples, compressed at 10,000 atm. 3. Compression at 20,000 atm results in reduction of the specific surface of coarsely porous silica gel from 350 to 260 sq.m/g, and that of the finely porous silica gel from 680 to 290 sq.m/g, i.e., by 26% and 57%, respectively. 4. The productivity of samples compressed at 5000 atm is higher, and of those compressed at 20,000 atm lower, than that of the uncompressed sample. The greater the compression, the lower the specific activity. 5. The selectivity of samples compressed at 5000 atm differs little from that of the uncompressed sample, but samples compressed at higher pressures have greatly reduced selectivity. it is possible that samples that have been subjected to higher compression, i.e. have a more severely destroyed porous structure, more readily sinter together, and so become deactivated. 6. It has been shown that the chromatographic activity of silica gel compressed at 20,000 atms about 25% less than that of the uncompressed sample.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01178863
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