Reactor designs for ethylene production via ethane ODH: comparison of performance

L. RODRIGUEZ; D.E. ARDISSONE; E. LÓPEZ; M. N. PEDERNERA; D.O. BORIO

INDUSTRIAL & ENGINEERING CHEMICAL RESEARCH

AMER CHEMICAL SOC

Lugar: Washington; Año: 2011 vol. 50 p. 2690 - 2697

0888-5885

The implementation of ethane oxidative dehydrogenation (ODH) toward ethylene production in two differentreactor configurations is studied here by means of a mathematical model of the reactors. A conventional liquid-cooled multitubularreactor and a multitubular membrane reactor are considered for comparison. Both reactor designs use a Ni-Nb-O catalystwashcoated over raschig-rings inside the tubes; molten salts flow in the shell side of the conventional reactor whereas pure oxygen isassumed for the shell of themembrane reactor. Industrial-scale ethylene production is the aim. Results show that the variation of thebed density (different thickness of the catalytic washcoat over the pellets) shows opposite effects on both reactor designs. For theconventional reactor, the increase in bed density leads to more pronounced hot spots as well as to an undesired oxygen depletioninside the tubes. Conversely, for the membrane reactor, higher bed densities prevent oxygen accumulation along the tube lengthleading to lower oxygen partial pressures and, consequently, higher selectivities. In this way, higher ethylene production rates arefeasible. Although molten salts provides enhanced heat removal, the oxygen injection at only the tube mouth in the conventionalreactor leads to lower global selectivities and higher heat generation rates. In the membrane reactor design, the heat generation rateproves to be efficiently controlled by the permeation flow of oxygen through the membrane.