Coupling of exothermic and endothermic reactions in oxidative conversion of natural gas into ethylene/olefins over diluted SrO/La2O3/SA5205 catalyst

In the oxidative conversion of natural gas to ethylene/lower olefins over SrO (17.3 wt. %)/La2O3 (17.9 wt. %)/SA5205 catalyst diluted with inert solid particles (inerts/catalyst(w/w) = 2.0) in the presence of limited O-2, the exothermic oxidative conversion reactions of natural gas are coupled with the endothermic C2+ hydrocarbon thermal cracking reactions for avoiding hot spot formation and eliminating heat removal problems. Because of this, the process is operated in the most energy-efficient and safe manner. The influence of various process variables (viz. temperature, NG/O-2 and steam/NG ratios in feed, and space velocity) on the conversion of carbon and also of the individual hydrocarbons in natural gas, the selectivity for C-2-C-4 olefins, and also on the net heat of reactions in the process has been thoroughly investigated. By carrying out the process at 800-850 degrees C in the presence of steam (H2O/NG greater than or equal to 0.2) and using limited O-2 in the feed (NO/O-2 = 12-18), high selectivity for ethylene (about 60%) or C-2-C-4 olefins (above 80%) at the carbon conversion (> 15%) of practical interest could be achieved at high space velocity (greater than or equal to 34 000 cm(3) . g(-1)(catalyst) h(-1)], requiring no external energy and also without forming coke or tar-like products. The net heat of reactions can be controlled and the process can be made mildly exothermic or even close to thermoneutral by manipulating the O-2 concentration in the feed.