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Abstract

Studies have been made of vapour-phase reactions of styrene both in the absence and presence of oxygen at subatmospheric pressures and at temperatures ranging from 180-580°C. Special attention has been paid to the influence of polymerising liquid styrene on the vapour-phase oxidation of this compound.

In the Introduction, the liquid-phase polymerisation of styrene and related monomers is discussed in detail. The limited amount of work which has been carried out on the vapour-phase polymerisation of styrene is also described. Finally a review is given of the vapour-phase oxidation of aromatic hydrocarbons with special reference to the behaviour of styrene.

The Experimental Section describes the apparatus and procedures used in this work, Reactions were followed by virtue of the accompanying pressure and temperature changes, which were measured with a strain-gauge pressure transducer and a microthermocouple respectively. The principal reaction products were identified and determined by gas chromatography.

In the Results Section, it is shown that no appreciable polymerisation of styrene takes place in the vapour—phase at pressures below atmospheric. Furthermore, the presence of 1-5% oxygen does not significantly enhance such polymerisation. Styrene remains stable in the absence of oxygen up to temperatures of ca. 550°C. However, in the presence of 1-5% oxygen, decomposition occurs at temperatures as low as 320°C.

Studies of the vapour-phase oxidation of styrene have shown that no cool flame region is observed and that only slow oxidation takes place at temperatures below 465°C. At higher temperatures, ignition occurs.

Experiments carried out at ca. 570°C in which polymerising liquid styrene was introduced into a reacting styrene-air vapour mixture, have shown that the liquid monomer facilitates ignition. At higher initial pressures, however, temperature measurements indicate that a cooling effect takes place when the relatively cold monomer is introduced into the vapour mixture. This cooling effect tends to ‘mask’ the influence of polymerising liquid styrene in promoting ignition.

Finally, in the Discussion, the significance and implications of the experimental results are considered and deductions are made as to the probable mechanisms involved in the vapour-phase reactions of styrene.

Publication Type:	Thesis (Doctoral)
Subjects:	Q Science > QD Chemistry
Departments:	School of Science & Technology > School of Science & Technology Doctoral Theses Doctoral Theses

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