SIMULTANEOUS THERMAL-CRACKING AND OXIDATION OF PROPANE TO PROPYLENE AND ETHYLENE

Propane conversion by its simultaneous endothermic thermal clacking an d exothermic noncatalytic oxidative conversion to propylene and ethyle ne in the presence of steam and limited oxygen was investigated at var ious process conditions (temperature, 635-800 degrees C; C3H8/O-2 rati o in feed, 2.0-16.0; H2O/C3H8 ratio, 0.0-2.5; space velocity, 1, 170 - 7,150 h(-1); and sulfur additive/C3H8 ratio 10(-3) -10( - 5)). Influe nce of a sulfur additive (thiophene, CS2, or dimethyl sulfide) in the feed on process performance was also studied. The propylene/ethylene m ole ratio in the products is decreased with increasing the temperature but increased with the C3H8/O-2 and H2O/C3H8 ratios and space velocit y. Ar all the process conditions, the selectivity for CO2 a useful byp roduct is much mole than that for CO2. Because the thermal cracking of propane is carried our in the presence of limited O-2, not only the t otal conversion of propane but also the conversion of propane by its t hermal cracking alone is increased greatly. Hence this process occurs at a much lower temperature or contact time than that required for ach ieving the same conversion in the thermal cracking process. Since the endothermic thermal cracking and exothermic oxidative conversion react ions of propane occur simultaneously, both reactions are coupled to ma ke it highly energy-efficient, with a drastic reduction in external en ergy requirement and coke formation, and safe to operate. The overall process can be made almost thermoneutral, mildly exothermic, or mildly endothermic by manipulating the temperature and C3H8/O-2 ratio in the feed.