Steam cracking of hydrocarbons 6. Effect of dibenzyl sulfide and dibenzyl disulfide on reaction kinetics and coking

The influence of aromatic sulfides on the kinetics and selectivity of hydrocarbon conversion by steam cracking and on pyrolytic coke formation was investigated in stainless steel tubular reactors with relatively large inner surface.The rate of decomposition of heptane (at 700 ‘C, 100 kPa, and a mass ratio of steam to feed 3:l) increased by 16 to 26 % , and the selectivity toward ethene decreased, if 0.1 to 1 .O % mass of dibenzyl sulfide, relative to heptane, was added. Addiiion of 1 % mass dibenzyl disulfide increased the decomposition rate of heptane by 8 % . Increasing amounts of the title compounds (0.1, 0.5% mass) in the feed decreased coking up to 70% in the pyrolysis of reformer raffinate at 820 OC, without steam. The decreased coking in turn caused an increased aromatic content in the liquid pyrolysis product mixtures. Based on the analytical results, obtained by capillary gas chromatography- mass spectrometry, reaction mechanisms are suggested.