PYROLYSIS OF THE LOWER PARAFFINS: V. THE CONVERSION OF THE GASEOUS PARAFFINS TO AROMATICS IN BAFFLED METAL TUBES AND THE CHEMICAL COMPOSITION OF THE PRODUCTS

The thermal conversion of propane to aromatics has been investigated by passing the gas through externally heated alloy steel tubes under conditions of turbulent flow. Recycling experiments carried out under pressure have shown that, when the gas flow is turbulent, high rates of conversion can be obtained at temperatures as low as 800–810 °C. Heat resistant chromium-nickel alloys of the 18:8 type have been found unsuitable for this purpose owing to the catalytic formation of carbon. Yields of 23.3 lb. of light oil per 1,000 cu. ft. of propane put through were obtained at 800 °C. together with 10 lb. of liquids boiling above 200 °C. The composition of the liquids obtained in these experiments has been determined by fractionation and chemical methods. The light oil obtained under the above conditions contains about 64% benzene, 14% toluene, 7.8% styrene and small amounts of cyclopentadiene, xylenes and higher aromatics. The liquids boiling above 200 °C. contain about 25% naphthalene and 12.5% anthracene together with smaller amounts of mono- and dimethyl naphthalenes, acenaphthene and phenanthrene.