1981 Volume 28 Issue 5 Pages 183-195
The pyrolysis of the silica gels which are surface-treated with (A)n-butanol, (B) iso-butanol, (C) see-butanol and (D) d-sec butanol was investigated by means of the quadru-pole mass spectra (QPMS) or the gas chromatograph-quadru-pole mass spectra (GC-QPMS). These silica gels were confirmed from their infrared absorption spectra and microanalysis to be sufficiently surface-treated. The pyrolysis has been observed in the following three temperature ranges, i.e., (i) in the vicinity of 150°C, (ii) in the range of 200°-300°C and (iii) 300°-500°C. From the amount of vapors evolved it is shown that this amount was the most appreciable in the range or (iii) and had the maximum at 450°C for (A), at 400°C for (B) and at 375°C for (C) respectively. The behavior of the pyrolysis of (D) was nearly same as the one of (C). The followings were noticed from the analysis of the mass spectra of vapors evolved in these temperature ranges; (1) physisorbed water or unreacted alcohol was released in the temperature range of (i); (2) the water released in the temperature range of (ii) and (iii) was regarded as the one formed by the condensation of unreacted silanols; (3) the principal constituent of the vapors evolved in the temperature range of (ii) was the alcohol used. which was formed by the hydrolysis of the surface groups; (4) the vapors evolved in the temperature range of (iii) still include the respective alcohol, but its amount is small and decrease appreciably with increasing temperature. The principal constituent is 1-butene for (A), iso-buten for (B) and 2-butene for (C), respectively and also the vapors include the small amount of both ethylene with a minute amount of methane and pro-pylene. Accordingly, the pyrolysis of surface groups is considered to take place in these temperature ranges; (5) since the same trend of pyrolysis curves and the same constituents of vapors evolved were observed for both (C) and (D), it would be considered to be no effect of the asymmetry of surface groups on the pyrolysis; (6) these results could be reasonably explained through the mechanism where the reaction, ?? proceed on the primary reaction of their pyrolysis and the alkyl radical, R thus formed could decompose into olefines, (7) the increase of either methan, ethylene or propylene and the decrease of 2-butene were observed in the products of pyrolysis for (C) and (D) at higher temperature than 650°C and furthermore the formation of 1, 3-butadiene was newly observed. This indicates that the reactions between 2-butene and methyl radical which are formed on the primary step proceeds as the secondary reaction of pyrolysis. 1) Studies on the Pyrolysis of the Esterified Silica Gels through the Gas chromatograph-Quadrupole Mass Spectrometer 11. Silica Gels surface-treated with Butanols.
