Synopsis of current research programs

Gas-to-Liquid Technology Research

Increasingly stringent environmental regulations have provided the impetus for renewed interest in the production of synthetic clean fuels (with low sulphur and aromatic content) from non-petroleum sources. Among others, the abundant natural gas reserve in the NW Shelf, provides strong incentive for a national development program on gas-to-liquid (GTL) technology. Production economics is, however, intricately tied to the availability of high performance catalyst and superior reactor operation. The main reaction involved in the process is the Fischer-Trospch synthesis. Within the past 2 decades, the group has built a strong international reputation in FTS (see Publications List) and this now serves as a springboard for current activities as described below.

Early transition metal carbides and nitrides which posssess Pt-like attributes are being prepared from the carburization and nitridation of precursor metal sulphides as an alternative system to conventional Co or Fe catalysts which suffer from poor CO hydrogenation activity. The carbide/nitride catalyst is relatively cheap and endowed with carbon-resilience and sulphur-resistant characteristics making it attractive for commercial exploitation. A design recipe which allows us to correlate carburization conditions (H2:hydrocarbon ratio, heating rate, carburization period, etc) to intrinsic catalyst properties, FT reaction metrics and longevity is being developed. A dedicated 8-port high throughput screening combinatorial reactor rig built in-house is employed for this catalyst development work.

Studies in slurry reactor system are being undertaken to obtain process parameters (feed H2:CO ratio, impeller speed, gas flow rate, solids recirculation, pressure, temperature, etc) for optimal reactor operation (product distribution, olefinity, catalyst attrition rate, etc).

Steam reforming and related hydrocarbon conversion processes

Studies in this area focus on the application bimetallic Co-Ni catalysts for hydrocarbon steam reforming. Catalysts were prepared by the incipient wetness impregnation method. We take advantage of the synergetic combination of exothermic hydrocarbon oxidation with endothermal steam reforming in the non-stationary operation mode to implement a thermally self-sustaining fluidised bed system. Carbon deposition is an inevitable accompaniment of hydrocarbon-mediated reactions, hence, we have proposed a new approach to optimal reformer operation via coupled coke-deactivation kinetic analyses. We therefore envisage the emergence of a practical control policy for reformer with deactivating catalysts.

The group is also investigating the production of olefins via oxidative dehydrogenation of light alkanes over composite oxide catalysts. We are particularly interested in relationship between surface acidity, type and concentration on olefin selectivity and the potential for multi-component feed processing.

Novel visible-light titania photocatalysts

Titania photocatalysis is highly rated as one of the most attractive options for the removal of recalcitrant organic pollutants in aqueous media. However, the requirement for UV irradiation to effect photogeneration of electron-hole pairs as active centres for subsequent redox steps imposes practical limitation on its application for municipal and industrial wastewater treatment and resource recovery. In order to harness solar energy utilization, the addition of transition metal dopants, alkali metals and rare-earth elements to titania sol-gel photocatalysts is being conducted with a view to optimizing light-harvesting characteristics and photoactivity as a function of preparation conditions.

Nanocrystalline perovskites

Perovskites, ABO3, (A=rare-earth element, B= transition metal) are an important class of catalytic materials due to possibility of tuning the crystallographic positions of the cations via partial substitution to permit a broad range of defects or excess oxygen to stabilize unstable oxidation states. They are normally synthesized via the ceramic route involving high temperature (>1273 K) calcination of a stoichiometric mixture of the rare earth and transition metal oxides. This method provides wide grain size distribution, phase inhomogeneity and significant loss in surface are due to sintering. Our investigation employs sol-gel technology and precipitation from homogeneous solution method to prepare relatively high surface area nanocrystalline perovskites for selective partial oxidation of hydrocarbons. The effect of different drying methods and calcination procedure on bulk and surface properties are also explored using a range of spectroscopic and electron microscopic tools.

Reaction Diagnosis and Kinetics

Catalyst development work is complemented with detailed kinetic analysis in many cases in order to systematically relate the surface characteristics to specific activity, selectivity. Reaction pathways are elucidated via steady-state rate, transient response, temperature-composition scanning and in-situ FTIR spectroscopy data. Corroboration is then carried out using mechanistic-based models.

Reactor Analysis and Operation

Work in this area revolves around the mathematical modeling and analysis of multifunctional reactor systems to understand inherent nonlinear behaviour and identify regions in parameter space for pathological operation. Examples include, packed bed catalytic membrane for H2S decomposition reactor, catalytic distillation and coupled endothermic-exothermic reactive systems. Computational fluid dynamic analysis is also employed to investigate the characteristics of gas-liquid-solid reactors for catalytic wet oxidation, photocatalysis and Fischer-Tropsch reactions.

However, in other circumstances, where it is not possible to depend on phenomenological models, artificial neural network and Monte Carlo methods have been effectively used to develop functional models for reactor simulation and optimization.