The influence of dimethyl disulfide on naphtha steam cracking

A pilot unit for steam cracking equipped with a transfer line heat exchange r (TLE) that allows for the study of coke deposition in both the reactor an d the TLE is presented. The reactor and TLE are made of Incoloy 800HT. The duration of a coking run typically amounts to 32.4 ks. The influence of dif ferent dimethyl disulfide (DMDS) addition procedures, i.e., continuous addi tion, presulfidation and presulfidation followed by continuous addition, on CO production and on coke deposition in the reactor and in the TLE during naphtha cracking is investigated. Presulfidation reduces CO production. How ever, to obtain a low and stable CO production, continuous addition of sulf ur is required. The influence of sulfur addition on coke formation in the r eactor can strongly differ from its influence on coke formation in the TLE. In the reactor, as well as in the TLE, the observed influence of sulfur ad dition is complex and strongly depends on the technique used. The optimal o perating conditions for reducing CO production and minimizing coke formatio n consist of presulfidation followed by continuous dosing.