Recycling : Reduce, Reuse and Recycle

Liquid fuels produced from biomass via Fischer-Tropsch (FT) synthesis have great potential to produce high-performance, environmentally friendly clean and high-quality transportation fuels; mainly due to the absence of aromatic compounds, SOx and NOx. Currently, there are three main aspects for consideration regarding the FT synthesis processes. Firstly, there exists the FT synthesis reaction mechanism, the details of which are still not fully understood. Furthermore, from the outlook of chemical engineering, there is the design and scale-up of the commercial FT synthesis plant in which studies of the comprehensive mathematical modelling of the reactor hydrodynamics, reaction kinetics mechanisms as well as optimization study play significant roles. In fact, to reach the ideal performance of the FT synthesis process, a precise comprehensive mathematical modelling along with chemical reaction kinetics mechanisms that can describe the product distribution of FT synthesis is essential. This research has been focused on production of biodiesel (ultra-clean transportation fuels) from biomass via Fischer-Tropsch synthesis process at the presence of supported cobalt catalyst (37%Co/SiO2). The aim was to

develop a comprehensive mathematical model of a catalytic fixed-bed reactor along with comprehensive chemical kinetics model of Fischer-Tropsch synthesis reaction mechanism in order to investigate the conversion, as well as productivity and selectivity of gasoline, diesel and wax based on required application as this process can play a major role in solving the world's current energy problems and is crucial to industrial practice, being a prerequisite for industrial process design, optimization and simulation. Therefore, a novel kinetic mechanism along with comprehensive novel mathematical model of the fixedbed catalytic FT synthesis reactor was established. The results indicated that the novel developed kinetic model based on a combination of alkyl/alkenyl mechanism for FT reactions (for production of n-paraffins and α-olefins compounds) along with formate mechanism for WGS reaction can provide the most accurate predictions. In order to enhance the performance of the FT synthesis process, first the parametric studies were performed to numerically investigate the effects of operating conditions on the catalytic performance of the fixed bed FT synthesis reactor over 37%Co/SiO2. The reaction temperature, total pressure, space velocity and H2/CO molar ratio were tested to see how effective they are. Those parameters that have the most significant

effects were then included in the multi-objective optimization process in MATLAB programming software using advance Non-dominated Sorting Genetic Algorithm (NSGA–II) to optimize the productivities and conversion. My advance codes and optimization process gave rise to a set of trade-off optimal solutions known as Pareto-optimal solutions. As a result, the Paretofront solutions were established in order to be used as a dynamic database for the specific requirement. Different operating conditions from the obtained database were selected which privileged the optimization of a particular output for example increasing the production of bio-diesel fuel, increasing the conversion rate of bio-syngas species (CO and H2), decreasing of CO2 emissions and decreasing the production of undesired CH4 and lighter hydrocarbon compounds.