Membrane Reactor Concepts for Power-to-Fuel Processes

This thesis concerns the development of membrane reactor concepts in the context of Power-to-Fuel processes. Standing on the disciplines of Process Engineering and Chemical Reaction Engineering, this thesis carries out work at the process level and the equipment level, respectively. Dimethyl carbonate and methyl formate are selected as two representative esters for their potential as electrofuels. At the process level, available production pathways are screened with respect to their technical maturities and their compliance with green chemistry principles. The selected pathways are conceptually designed starting from CO2 and H2, which also act as the background of membrane reactor development. The process simulations and techno-economical assessments adopt the same boundary conditions and assumptions to ensure comparability across pathways. It can be expected that these pathways can be technically realistic, energy efficient, and economically viable in the near future. It is thus with enough confidence to believe that esters will sit alongside alcohols, ethers, and hydrocarbons as a new member of the Power-to-Fuel family. To guide membrane selection and matching, mapping relationships among reaction, membrane, and reactor concept are constructed to present an overview of possible combinations before detailed designs. Theoretical calculations are then performed to quantify the potential of each combination by correlating equilibrium constant, conversion, and the Damköhler (Da) number as well as the Péclet (Pe) number. The correlation is exemplified by the reverse water gas shift and dry reforming of methane. At the equipment level, various novel membrane reactor concepts are designed for the two reactions based on CFD simulations by receiving boundary conditions from process analysis. The trade-off among conversion, productivity, and membrane permeation is the core design aspect of the membrane reactors. The conversion enhancement is directly related to the percentage of species permeation. Concentration polarization is a phenomenon that adversely affects the species permeation and has to be minimized to fully exploit the membrane potential. Compact designs by increasing the ratio of membrane area to reactor volume are simple but effective approaches to increase conversions but maintain high productivity. A methodological framework that starts from process analysis, over theoretical calculation, to CFD simulation can be condensed from this work. The communications among these methodologies make them an integrated part and can be applied to other processes and reactor concepts of interes