Sermin G. Sunol

Development of titanium-dioxide-based aerogel catalyst with tunable nanoporosity and photocatalytic activity.

Nanostructured highly porous TiO(2)/WO(3)/Fe(3+) aerogel composite photocatalysts are prepared, characterized and tested for model photocatalytic reactions. The catalyst structure is tailored to capture environmental pollutants and enable their decomposition in situ under both ultraviolet (UV) and visible light through oxidation to smaller benign molecules. A novel and green method is utilized to prepare the unique surfactant-templated aerogel composite photocatalyst that has a highly accessible porous nanostructure with high surface area and tailored pore size distribution. The sol-gel process is combined with supercritical extraction and drying. Supercritical drying with heat treatment results in titanium dioxide with anatase crystal form. Templates used further enable retention and tuning of the nanopore structure and surface properties. The synthesized catalysts were characterized using SEM, FIB, XRD and porosimetry prior to post-evaluation in model reactions. The bandgap of the catalyst particles was also determined using diffuse reflectance. The resulting aerogel TiO(2)/WO(3)/Fe(3+) has similar photocatalytic capability compared to highly optimized commercial Degussa P25 under UV exposure and offers much superior photocatalytic capability under visible light exposure. The model reaction utilized employed methylene blue (MB) photooxidation under visible and UV light.

Stress formation during heating in supercritical drying

Silica aerogel preparation is analyzed and two different supercritical drying techniques, autoclave drying of the solvent and drying following carbon dioxide exchange of the solvent, are compared in terms of stress formation during the heating step. The model used is a partial differential equation that relates stress to thermal expansion and flow of pore liquid for a radially bounded cylindrical geometry and the model is modified to see the effect of condensation reactions that result in the contraction of the body. The finite element collocation method is used to solve the model for different drying techniques, at several heating rates, and shear moduli. The carbon dioxide exchange method is found to be more advantageous as far as the stress formation in the heating step of supercritical drying is concerned.

Recycling of Municipal Solid Waste Ash Through an Innovative Technology to Produce Commercial Zeolite Material of High Cation Exchange Capacity

Municipal solid waste ash (MSW ash) samples, obtained from a local incinerator in Florida, were converted via a chemical process into zeolite material. The conversion process was performed by applying a two step treatment. The ash samples were fused at 550C under alkaline conditions and then the fused ash samples were treated hydro-thermally at 60 C and 100C for different periods. This innovative technology involves adjusting the SiO2/Al2O3 ratio of the ash from 13.9 to 2.5 by adding sodium aluminates and by using a solid to liquid ratio of 10. The fusion step formed sodium silicate and sodium aluminum silicate phases. These phases acted as precursors to the formation of zeolite A. Zeolite A was successfully formed within the ash matrix when samples were fused and SiO2/Al2O3 was adjusted. The maximum cation exchange capacity, CEC, was measured by using ammonium acetate solution. The CEC of the produced zeolitic ash material has increased significantly from 17 meq/100g for non-treated ash up to 212 meq/100g for the treated ash. The cation exchange capacity of the produced zeolite ash material is close to that available from commercial zeolite materials which have a CEC of 245meq/100g. Zeolite A formation within the ash matrix increased the potential of using the ash as an adsorbent for industrial and environmental applications including ammonia removal from waste water or any other similar application that involves cation exchange.

A hierarchical approach to simultaneous design of products and processes

Abstract Product and process design involve algorithmic and heuristic processing of symbolic and numeric data. Therefore, for such a design task, a hybrid approach that interweaves numerical and heuristic paradigms is warranted. The increasing rigor in modeling along with the necessary knowledge feedback results in a generalized system architecture that forms the basis of this paper. The approach is implemented using KAPPA on a Sun SPARC 5 station. The superstructure developed using the heuristic method is optimized with respect to the choice of technology, operating conditions, the technology sequencing, and the stream flows using Mixed Integer (Non) Linear Programming (MI(N)LP). Product design involves relating product mix and processing conditions to various product characteristics. The multi-objective approach called for this type of problem is addressed through relative weighing of the objectives in the objective function. The lumped parameters used are derived from detailed distributed models using a two-tier approach. The first example used is porous matrix-polymer composite design through impregnation and surface treatment. A second example on catalyst design is also used. The rigorous models utilize a genetic algorithm for search in the discrete variable space. Learning from the rigorous models is used to update the process flowsheets as well as the knowledge bases.

Supercritical carbon dioxide aided catalyst design, its characterisation and behaviour in reacting environment

Abstract Gels of metal oxide catalysts (NiO/Al 2 O 3 gels), prepared by the sol-gel method, are dried using supercritical drying to obtain aerogel catalysts as porous powder. The supercritical drying is carried out at two temperatures and pressures of carbon dioxide. Also, volume of the autoclave is varied. A factorial design is applied to the experiments and effects of the variables are studied using Yates Algorithm. Gels are also dried in air and under vacuum in order to compare densities of xerogels with those of aerogels.