Xianmei Xie

Fabrication of high-performance facilitated transport membranes for CO2 separation

At present, liquid membranes, ion-exchange membranes and fixed carrier membranes are the three popular facilitated transport membranes for CO2 separation. They possess their own advantages, as well as their respective deficiencies. In view of the characters of these three types of facilitated transport membrane, we report a method to combine their advantages and overcome their deficiencies. A new membrane was fabricated by establishing high-speed facilitated transport channels in the fixed carrier membrane. This membrane displays excellent CO2 separation performance and good stability. The results suggest that this is an effective way to fabricate high performance and high stability CO2 separation membranes. Furthermore, establishing high-speed facilitated transport channels in fixed carrier membranes will be a universal route to improve the performance of gas separation membranes.

A high performance PVAm–HT membrane containing high-speed facilitated transport channels for CO2 separation

A PVAm–HT membrane is fabricated by establishing a hydrotalcite (HT) channel in a polyvinylamine (PVAm) fixed carrier membrane. The flexible PVAm fixed carrier membrane material as a matrix membrane is beneficial to get high permeance. Simultaneously, the HT channels can be used as high-speed facilitated transport channels, in which the movable carbonate can actively meet CO2 and help to increase the CO2/N2 selectivity of membranes as in liquid membranes or in ion exchange membranes. Moreover, the unobstructed HT channels are conducive to transport CO2 rapidly and they can increase the chain spacing of polymers; these are beneficial to further enhance the permeance of membranes. In addition, the charged layers of HT provide necessary stability for movable carriers due to the electrostatic attraction. Thus, the PVAm–HT membrane obtains high permeance and high selectivity, as well as good stability. The CO2 permeance of the PVAm–HT membrane reaches 3187 GPU and the CO2/N2 selectivity of the PVAm–HT membrane reaches 296 at 0.11 MPa.

Organotemplate-free synthesis of hollow Beta zeolite supported Pt-based catalysts for low-temperature ethanol steam reforming

A novel platinum-encapsulated hollow Beta zeolite (Pt@HBS) catalyst was successfully fabricated through an organotemplate-free and seed-directed route, with carbon spheres as a hard template. Pt@HBS not only exhibited excellent catalytic performance, but could also maintain the catalytic reaction for more than 28 h without losing its activity.

A novel BEA-type zeolite core–shell multiple catalyst for hydrogen-rich gas production from ethanol steam reforming

BEA-type core–shell catalysts consisting of a core supporting Cu and Fe and a Ni-based shell were investigated for their ethanol steam reforming (ESR) activity. The effect of the nature of the core–shell double-support and the promotion achieved by adding Ni, Cu and Fe were studied. The catalysts were characterized by XRD, BET, SEM, TEM, H2-TPR, CH4-TPD, CO-TPD and XAFS analyses. Compared to zeolite Beta as support, the core–shell catalysts exhibited excellent performance in ethanol reforming, leading to high selectivity to hydrogen through a multiple reaction system. This result indicated that the special structural advantages of the core–shell support could give full play to the properties of active phases and provide a one-step production process for high-purity hydrogen. The Ni-base shell was twice as active for the catalytic reaction, resulting in greatly improved catalytic activity and selectivity to hydrogen; in addition, the decrease of by-products could be attributed to the function of the Cu and Fe phases, improving the steam acetaldehyde reforming, steam methane reforming and water gas shift reactions. Furthermore, in the investigation of the effects of the amount of the Cu and Fe phases, the best catalytic performance was reported by the 2.5Fe2.5Cu-SB@NB catalyst.

Synthesis and catalytic performance of hierarchically structured MOR zeolites by a dual-functional templating approach

Novel hierarchical MOR zeolites have been successfully synthesized via a one-step dual-functional templating strategy utilizing gemini organic surfactant (C18-2-8) through hydrothermal process. After a period of ∼96u202fh for crystallization, the hierarchy MOR zeolite with a larger BET (412.0u202fm2/g), abundant intracrystalline mesopores (average mesopore size distribution of 4.55u202fnm), and more accessible acid sites can be synthesized. The XRD study revealed a long range structural ordering of mesoporous and a good crystallinity of microporous structure. The results indicated that the surfactant acted as a dual-functional template for generating both micropores and mesopores simultaneously. Compared with conventional MOR zeolite, hierarchically structured MOR zeolite not only has higher activity and stability, but also can avoid side-reaction taking place in ethanol dehydration reactions. This hierarchical micro/mesostructured mordenite zeolite may be a candidate for practical industrial applications especially in those reactions where bulky molecules are involved.