Oxidative Coupling Of Methane (OCM) In Catalytic Fixed-Bed Reactor And Membrane Reactor

Oxidative coupling of methane(OCM)to C2 hydrocarbons is a promising process among various schemes of methane conversion.Here,OCM was studied in fixed-bed reactor with different catalysts and in catalytic membrane reactors prepared from different materials.3wt%Li/MgO and Na-W-Mn/SiO2 with 1.9wt%Mn and 5wt%Na2W04 two types of catalysts were chosen for fixed-bed reactor to study OCM.The effects of various operating parameters,such as temperature,CH4/O2 feeding ratio,space velocity were studied to get an optimum condition.The best result which gave 37.15%methane conversion,53.14%C1 selectivity and 19.74%C2 yield were obtained over Na-W-Mn/SiO2-gel-p at 800?(FCH4=10 mL/min,Fair=24 mL/min).The different combinations of Li/MgO and Na-W-Mn/Si02 catalysts were also investigated.It was found that the two-stage catalyst bed form could improve the methane conversion and 21.11%C2 yield was obtained over Na-W-Mn/SiO2-gel-p?Li/MgO-p at 850? with the same gas flow as above.La0.7Sr0.3FeO3-?(LSF)hollow fiber membrane(OD 2mm,ID1.56mm)has good mechanical properties and its oxygen permeation flux increases with the rise of temperature from 650-950?.The LSF catalytic membrane reactors were prepared by coating the above catalysts on the inner face of membrane.Compared with fixed bed reactor,C2 selectivity in LSF catalytic membrane reactors increased at high temperature but methane conversion was very low and C2 yield was less than 4%.BaCe0.8Gd0.2O3(BCG)hollow fiber membrane(OD 1.52mm,ID 1mm)is not gas-tight but possesses catalytic activity to OCM.The BCG-Al2O3 tube membrane was prepared by coating the BCG material to the external surface of y-Al2O3 tube(OD 4.5mm,ID 3.4mm)which was pretreated with La(N03)3 aqueous solution.The BCG-Al2O3 membrane has low oxygen permeation flux and the results of OCM are not ideal.But the new type of membrane constructed with BCG hollow fiber and BCG-Al2O3 tube shows good catalytic and reactive performance for OCM.C2 yield could achieve 13.38%at 800 ?(FCH4 = 10 mL/min,FAr=25 mL/min in tube and Fair =300 mL/min in shell)in BCG-Al2O3-BCG membrane with length only 2.3 cm.