Reverse Flow Catalytic Membrane Reactors for Energy Efficient Syngas Production

Natural gas is becoming an increasingly important energy source, due to the increasing energy demands and declining oil reserves, whereas large volumes of natural gas are still widely available at remote locations. In view of the existing infrastructure for liquid fuels, natural gas is most efficiently used in the transport sector by converting it to liquid fuels via the Gas-To-Liquid process. In this process natural gas is converted with pure O2, obtained from cryogenic air distillation, to syngas, which is converted to higher hydrocarbons in the Fischer-Tropsch process. Although numerous syngas production technologies have been commercialised, so far the Gas-To-Liquid process has not found widespread application yet, mainly because of the enormous investment costs related to the air separation and syngas production units. To decrease these investment costs, two areas of possible cost reduction have been identified: improved recuperative heat exchange, which also reduces the pure O2 consumption, and an alternative air separation. Out of the numerous alternative reactor concepts that have been proposed in the literature for the syngas production unit, the most interesting concepts appear to be the reverse flow reactor with its integrated recuperative heat exchange and the porous membrane reactor with its distributive feeding of O2 avoiding premixed feeds and hot spots. To combine the advantages of these concepts and eliminate their disadvantages, a reverse flow catalytic membrane reactor with porous membranes is proposed, in which recuperative heat exchange and the partial oxidation reaction are integrated into a single apparatus. To eliminate the investments costs associated with cryogenic air distillation, membrane reactors with alternative air separation via perovskite membranes have been proposed in the literature. However, due to the presence of a large amount of inert N2, additional preheating of the feeds with the corresponding additional external recuperative heat exchange equipment is required, which increases the investment costs substantially. To reduce these investment costs, again the reverse flow concept can be used. Therefore, also a reverse flow catalytic membrane reactor with perovskite membranes is proposed, in which recuperative heat exchange, air separation and the partial oxidation reaction are integrated into a single apparatus. In this thesis the reverse flow catalytic membrane reactor concept with porous or perovskite membranes are developed on basis of a combined theoretical and experimental study. Finally, this chapter concludes with an outline of the thesis. General Introduction 15