The experimental parameters controlling the rate and mechanism of the decomposition of compounds and the products formed, in a moving carrier gas stream were investigated. The parameters studied included the effects of pyrolysis temperature, sample size, sample weight, flow rate of the carrier gas, the method of introducing the sample into the pyrolysis unit.
An apparatus for pyrolysis-gas chromatography, using tho commonly used boat and furnace technique, was developed. Commercial grade sodium dodecylbenzene sulfonate was chosen for a model compound. The optimum conditions for the pyrolysis-gas chromatographic analysis of this material were established by the careful study of the experimental parameters.
The most serious limitations to this method of pyrolysis-gas chromatography appeared to be the strong dependence on the sample size and tho dependence on pyrolysis temperature, i.e., on the rate at which the sample was brought to the pyrolysis temperature. As the size of the sample was increased the amount of residue in the boat also increased. Also, although the majority of the sample was pyrolyzed at 580°C the amount of residue would decrease as the temperature was raised to a maximum of 710°C. A certain amount of residue always remained in the boat. The residue can be explained as the product of secondary reactions occurring between the initial pyrolysis intermediates (free radicals) and the unpyrolyzed portion of the sample.
In an attempt to eliminate these effects of secondary reactions a new technique of pyrolysis-gas chromatography by direct injection of solutions was developed. By handling the samples in dilute solution it was shown that a much smaller sample could be pyrolyzed such that the probability or secondary reactions was greatly reduced. Also the very small samples allow an apparent instantaneous heating of the samples to a given pyrolysis temperature. This approach offers a means of obtaining the simplest possible products from the pyrolysis of a compound, therefore offering a more accurate insight into the mechanism of the pyrolysis. These products then offer a means of establishing the structure of the original compound.
Using this technique a method was developed for analyzing aqueous solutions containing the alkylbenzene sulfonates. This method provides not only a measure of the total detergent present but also differentiates between the various alkyl groups found in the commercial products. The alkyl groups form the 1-alkenes which can be easily identified chromatographically. The conditions for this analysis along with curves showing the products obtained from the pyrolysis of samples with both straight and branched alkyl groups are given.
While the majority of the work done here was with aqueous solutions an attempt was made to determine the stability or some of the common organic solvents under such pyrolysis conditions. Those solvents studied were methylene chloride, chloroform, carbon tetrachloride, methanol, ethanol, and acetone. All of these solvents were round to be stable up to 500°C; however, at temperatures greater than this the decomposition of the solvents limits their use.
The technique of pyrolysis-gas chromatography by direct injection or solutions was also applied to certain amino acids in ethanol-water solutions. The results were again much more accurate than those found with the boat technique.
This technique was also shown to be useful in determining the structure of organic chelates bound to metal atoms. Solutions of copper II and chromium III acetyl-acetonates in chloroform were pyrolyzed and the product identified as acetylacetone. This offers a means of determining both the number and type of chelates bound to a given metal atom. / Ph. D.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/94544 |
| Date | January 1965 |
| Creators | Burke, Michael Francis |
| Contributors | Chemistry |
| Publisher | Virginia Polytechnic Institute |
| Source Sets | Virginia Tech Theses and Dissertation |
| Language | en_US |
| Detected Language | English |
| Type | Dissertation, Text |
| Format | 134 leaves, application/pdf, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
| Relation | OCLC# 20329946 |
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