The detection of an inorganic hydrocarbon formation in silicate melts by means of a direct-coupled-evolved-gas-analysis-system (DEGAS)

In an attempt to determine the volatile components in various industrial, laboratory and natural glasses, the gas release from the silicate melts in high vacuum — high temperature extraction experiments were analyzed by simultaneous TG and mass spectrometry. In the temperature range from 800 to 1200°C molecular fragments with m/z=13, 15, 27, 28, 29, were detected, which are possible fragments of hydrocarbon molecules. Similar behaviour could be demonstrated by analysis of glass samples synthesized in the laboratory. The formation of hydrocarbons during the heating process was successfully controlled by the carbon concentrations in the batches, through appropriate additions of carbon bearing reagents — graphite, Al- and Ca-carbides, di- and polysaccharides, or Na-acetate. Based on the degassing profiles (DP) it is possible to deduce a mechanism for the formation of hydrocarbons, e.g. of methane in systems containing graphite or carbides and hydroxideions:C+4(OH)−⇒CH4+2O2−+O2The oxygen formed during this process is dissolved in the melt and escaped again in the form of oxygen bubbles with a further temperature increase. With the DP of laboratory prepared melts, it was possible to give an interpretation of the observed degassing maxima of m/z 13, 15, 27, 28, 29, on the one hand, by the formation of molecular fragments of CH4 and C2H6 and, on the other hand, by the carbon isotopic relations, e.g. m/z 13=12CH+ or 13C+; m/z 28=12C2H4+ or 12C13CH3+.