Performance of a mixed-conducting ceramic membrane reactor with high oxygen permeability for methane conversion

A mixed-conducting perovskite-type Ba0.5Sr0.5Co0.8Fe0.2O3-delta (BSCFO) ceramic membrane reactor with high oxygen permeability was applied for the activation of methane. The membrane reactor has intrinsic catalytic activities for methane conversion to ethane and ethylene. C-2 selectivity up to 40-70% was achieved, albeit that conversion rate were low, typically 0.5-3.5% at 800-900 degreesC with a 50% helium diluted methane inlet stream at a flow rate of 34 ml/min. Large amount of unreacted molecular oxygen was detected in the eluted gas and the oxygen permeation flux improved only slightly compared with that under non-reactive air/He experiments. The partial oxidation of methane to syngas in a BSCFO membrane reactor was also performed by packing LiLaNiO/gamma -Al2O3 with 10% Ni loading as the catalyst. At the initial stage, oxygen permeation flux, methane conversion and CO selectivity were closely related with the state of the catalyst. Less than 21 h was needed for the oxygen permeation flux to reach its steady state. 98.5% CH4 conversion, 93.0% CO selectivity and 10.45 ml/cm(2) min oxygen permeation flux were achieved under steady state at 850 degreesC. Methane conversion and oxygen permeation flux increased with increasing temperature, No fracture of the membrane reactor was observed during syngas production. However, H-2-TPR investigation demonstrated that the BSCFO was unstable under reducing atmosphere, yet the material was found to have excellent phase reversibility. A membrane reactor made from BSCFO was successfully operated for the POM reaction at 875 degreesC for more than 500h without failure, with a stable oxygen permeation flux of about 11.5 ml/cm(2) min. (C) 2001 Elsevier Science B.V. All rights reserved.

Novel porous metal/ceramic membrane materials

During the past 22 months, the preparation and application of novel porous metal/ceramic membrane materials have been extensively explored in the area of membrane science and catalysis. Thus, new preparation methods and new application concepts in membrane catalysis have been developed.

Synthesis and catalytic reactivity of MCM-22/ZSM-35 composites for olefin aromatization

A series of MCM-22/ZSM-35 composites has been hydrothermally synthesized and characterized by XRD, SEM, particle size distribution analysis, N-2 adsorption and NH3-TPD techniques. Pulse and continuous flow reactions were carried out to evaluate the catalytic performances of these composites in aromatization of olefins, respectively. It was found that MCM-22/ZSM-35 composites could be rapidly crystallized at 174 degrees C with an optimal gel composition of SiO2/Al2O3=25, Na2O/SiO2=0.11, HMI/SiO2=0.35, and H2O/SiO2=45 (molar ratio), of which the weight ratio of ZSM-35 zeolite in the composite relied on the crystallization time. The coexistence of MCM-22 and ZSM-35 in the composite (MCM-22/ZSM-35=45/55 wt/wt) was observed to exert a notable synergistic effect on the aromatization ability for butene conversion and FCC gasoline updating, possibly due to the intergrowth of some MCM-22 and ZSM-35 layers.