Synthesis and properties of nanostructured adsorbents for gas separation and environmental applications.

摘要

With substantial progress in engineering of adsorption processes, synthesis of new adsorbents with improved properties has become most critical to the improvement of existing or development of new adsorption processes. This dissertation reports the development and understanding of two types of innovative technique for synthesis of nanostructured adsorbents with improved adsorption or mechanical properties. Sol-gel techniques were developed for fabrication of nanostructured {dollar}gamma{dollar}-alumina based adsorbents in both powder and granule forms. A novel microwave-heating method was studied for effective thermal dispersions of active species on internal pore surface of nanostructured supports. Adsorbents synthesized were characterized by various surface analysis and adsorption instruments for their pore structure, state of active species, structural stability and adsorption properties for CO, {dollar}rm Csb2Hsb4{dollar} and SO{dollar}sb2.{dollar}; The spherical {dollar}gamma{dollar}-alumina granular supports prepared by the sol-gel granulation process developed in this work were found to have: (1) desirable pore texture including large surface area (380 m{dollar}sp2{dollar}/g), large pore volume (0.5 cm{dollar}sp3{dollar}/g), narrow pore size distribution (20-60 A) and controllable average pore size (35 A); (2) promising-mechanical properties including high crushing strength (100 N per granule) and attrition resistance ({dollar}<{dollar}0.01 wt.%/h). The wet-impregnation and sol-solution mixing sol-gel methods were used to synthesize the {dollar}gamma{dollar}-alumina supported adsorbents containing one of the active species including Cu{dollar}sp+,{dollar} Ag{dollar}sp+,{dollar} CuO. The {dollar}gamma{dollar}-alumina adsorbents containing Cu{dollar}sp+{dollar} or Ag{dollar}sp+{dollar} ions can selectively adsorb CO or C{dollar}rm sb2Hsb4.{dollar} The {dollar}gamma{dollar}-alumina supported CuO adsorbents prepared in this work have higher monolayer coating amount (30 wt.%) and SO{dollar}sb2{dollar} sorption capacity (30 wt.%) than the similar adsorbents synthesized by the conventional methods because the sol-gel derived {dollar}gamma{dollar}-alumina support has a larger surface area. Besides, the {dollar}gamma{dollar}-alumina supported CuO adsorbents have a good thermal and chemical stability.; A novel microwave heating method was systematically studied in this work for adsorbents synthesis. The fundamental microwave heating properties of materials of interest to this work were investigated to elucidate the mechanism of the microwave heating process and to optimize the adsorbent synthesis. The DAY zeolite or {dollar}gamma{dollar}-{dollar}rm Alsb2Osb3{dollar} supported adsorbents containing CuO, Cu{dollar}sp+{dollar} or Ag{dollar}sp+{dollar} were synthesized by the microwave heating method. The results obtained in this work have demonstrated the feasibility of effective preparation of supported adsorbents by this novel method.