| Pd-based composite membranes have attracted considerable interest due to their excellent separation and catalytic capability.They may be used in a variety of processes for hydrogen-related reactions in high temperature such as hydrogenation,dehydrogenation and methane reforming.The tubular substrates with outer surface are prone to be polluted and scraped,which easily influence characterization and gas permeable capability for them.In this thesis,Pd-based composite membranes were prepared on inner surface of porousα-Al2O3 tubular substrates by controlling Pd membranes deposition with electroless plating. Novel electroless plating with osmosis,using the bio-membrane as a semipermeable membrane,was introduced to prepare dense thin palladium membranes with fine particles and excellent gas permeablility.The preparation of Pd/TS-1 composite membranes supported onα-Al2O3 tubes,and the reaction mechanism of hydroxylation of benzene to phenol were investigated.The as-synthesized Pd/TS-1 composite membranes were characterized by scanning electron microscope(SEM),X-ray diffraction(XRD) and single gas permeation.1.Pd membranes were deposited on inner surface of alumina tubes mainly by circulating the plating solution through them.The morphology of substrate surface,time of plating solution staying in the tubes,sensitivation/activation and plating temperature,and depositon time are the key factors of the preparation of Pd membranes.To study various plating conditions,the microstructure of Pd membrane was controlled well.Uniform dense Pd-based membranes with the average pore size about 1～2μm were obtained successfully.2.Bio-membrane was added in the system of plating served as a semipermeable membrane.In contrast with conventional electroless plating,addition of the bio-membrane not only shrunk the Pd particle size,enhanced the interaction between Pd membrane and substrate,but also avoided the Pd-based membrane be polluted with plating solution remainder in the surface and pore site.The novel method enabled plating of denser Pd membranes which deposited on the supports with pore size of 0.8μm.H2 permeance of them up to 1.52×10-6 mol/m2·s·Pa and the ideal permselectivity reach 370 at 773K.Meanwhile, defect-free Pd membanes were deposited on the tubes with pore size of 0.2μm.H2 permeance of them up to 2.21×10-6 mol/m2·s·Pa and the ideal permselectivity over 2000 were obtained at 773K.The Pd membranes also were repaired by the novel electroless plating method. 3.To optimize the technological process,TS-1 zeolite films with desired morphology were obtained by controlling the seeding and synthesis conditions.Pd/TS-1/α-Al2O3 composite membranes were obtained.H2 permeance and selectivity of H2/N2 were 2.84×10-7mol/m2·s.Pa and 84 at 773K,respectively.4.To analyze the basic mechanism of hydroxylation of benzene to phenol,study at the thermodymacis and kinetics of the reacions,estimate reaction pathway and get the conclusion about key factors that restrict the catalytic reactions.
|
PDF Full Text Request