On improving performance of Fischer-Tropsch synthesis, model studies on catalyst, reactor and process.

摘要

The objective of this research is to improve the product quality and productivity of Fischer-Tropsch Synthesis (FTS) on cobalt catalysts for the production of diesel fuel. Model studies and designs are done on three different scales: catalyst, reactor and process. On the catalyst scale, in order to develop supported cobalt catalyst with both high activity and thermal and chemical stabilities, a structure sensitive deactivation kinetics incorporating with a population balance model (PBM) and an intrapellet mass and heat transfer model are formulated. The effect of particle size distribution and intrapellet diffusion on the catalyst performance is studied and optimization is carried out. Calculations suggest that an egg-shell catalyst with particle size around 9nm is optimal. The catalyst preparation process is also modeled by a PBM combined with a heterogeneous crystallization model. The effect of preparation conditions on metal loading profile as well as particle size distribution is studied. On the reactor scale, in order to overcome the negative role played by water, a flash reactor with a spatial patterned structure and a simplified recycle reactor is developed. Model study shows that the new reactors are effective to improve the catalyst performance and productivity. More complicated multiplicity is found for the flash reactor but it can be avoid by using the recycle reactor. On the process scale, processes integrating the FTS process with syngas regeneration process for both coal based- and natural gas based GTL applications are developed. The new processes are proven to improve the product quality as well as productivity dramatically. The coal based application can also improve the thermal efficiency while the natural gas based application decreases the thermal efficiency slightly.