Catalytic membrane nano reactor with Cu/ZnO in situ immobilized in membrane pores for methanol dehydrogenation to formaldehyde

A catalytic membrane nano reactor (CMNR) with deep-permeation nanocomposite structure (DPNS) has been fabricated by flowing synthesis for methanol dehydrogenation to formaldehyde. In this structure, Cu/ZnO nanoparticles are in situ immobilized in the pores of Ti membrane substrate with thickness 1 mm, pore size 10 μm and porosity 45%. The characterization by XRD , TGA , XPS, SEM and TEM indicates that the Cu/ZnO nanoparticles with mean size of 82 nm was successfully embedded into the membrane pores, and well distributed along the thickness direction of the membrane. The ICP measurement results demonstrate that the immobilization amount of 20 mg of Cu/ZnO nanoparticles per gram of Ti membrane substrate can be obtained. The prepared Cu/ZnO/Ti CMNR was built in the technological apparatus for catalytic dehydrogenation of methanol. For one sheet of membrane setting up, the conversion efficiency of methanol 7.5%, the mass specific activity 183 mmol MeOH ·h -1 ·g cat -1 , the pressure drop 2.7 kPa with gas permeating the membrane have been measured, under mass ratio of Cu to ZnO 0.05 in the membrane, reaction temperature 360 °C, the gas flux 8 m 3 ·m -2 ·h -1 through the membrane. The selectivity of formaldehyde is up to 98% and increases with increasing reaction temperature, the highest mass specific activity of 318 mmol MeOH ·h -1 ·g cat -1 can be achieved with mass ratio of Cu to ZnO 0.12 at 360 °C. For three sheets of CMNRs setting up in serials, over 18% of conversion efficiency has been achieved with gas pressure drop 6.8 kPa. If 70 sheets of CMNRs are packed in serials to build a reactor with 70 mm thickness, which will produce the gas pressure drop 162 kPa, the conversion efficiency of 99% would be expected according to a simple simulation based on the experimental measurement.