SUPPRESSION OF COKE FORMATION IN THE STEAM CRACKING OF ALKANES - ETHANE AND PROPANE

The effects of a H2PtCl6 additive on the rate of formation of coke dep osits on quartz and Incoloy surfaces were investigated in the steam cr acking of ethane and propane in a continuous-flow thermogravimetric an alyzer (TGA). The TGA operating conditions were 1 atm pressure, 820-84 5 degrees C temperature range, about 1.5 s reaction time, and steam to hydrocarbon molar ratio of about 2. Specific coke formation rates con sistently decreased in the presence of the additive for both ethane an d propane pyrolysis. For example, in ethane pyrolysis the specific cok e formation rate on the quartz surface at 830 degrees C decreased from 0.34 mu g/cm(2).min in the absence of the additive to 0.089 mu g/cm(2 ).min in the presence of the additive, representing an improvement by a factor of about 4 in coking rates. On the Incoloy surface, coke form ation decreased from 0.98 to 0.38 mu g/cm(2).min. For the case of prop ane pyrolysis at 830 degrees C, the coke formation rate decreased from 0.51 to 0.33 mu g/cm(2).min on the quartz surface and from 1.9 to 1.0 mu g/cm(2).min on the Incoloy surface.