Chemical Engineering Science, Vol.150, 1-15, 2016
A theoretical comparison of multifunctional catalyst for sorption-enhanced reforming process
This work presents the first side-by-side comparison of the two leading multifunctional catalyst designs reported in the literature today for sorption-enhance reforming processes. Two-dimensional unsteady state models were developed to compare the performance of a core-shell multifunctional catalyst, consisting of a calcium-based sorbent core enclosed in a porous shell of methane steam reforming or water-gas shift catalyst, against an equivalent case of a uniform-distributed multifunctional design in which catalyst and sorbent materials are uniformly distributed within the particle. Additionally, these two multifunctional catalyst designs were compared against the conventional two-pellet approach, where the capture and catalytic properties are distinguished into separate pellets. Both multifunctional catalyst designs (i.e. core-shell and uniform-distributed) had greater adsorbent utilization and higher H-2 outlet concentration up to breakthrough time than the conventional two pellet design. The uniform distributed multifunctional catalyst design had greater adsorbent utilization up to breakthrough conditions as compared to the core-shell design. This behavior may be attributed to the fact that for the uniform-distributed multifunctional, the active catalyst is constantly producing CO2 next to an adsorbent active site. For the core-shell multifunctional catalyst design, decreasing catalyst-shell thickness resulted in performance approaching the uniform-distributed case. For the case of exothermic water-gas shift reaction coupled with CO2 chemisorption, the core-shell design mitigated local bed hot-spot magnitudes by 40 K. (C) 2016 Elsevier Ltd. All rights reserved.