(575au) One Body Composite of Catalyst and CO2 Absorbent for Sorption Enhanced Reforming Process

Sorption enhanced reforming process (SERP) has characteristic to shift equilibrium of steam methane reforming (SMR) or water gas shift reaction (WGS) to favorable direction for hydrogen production by in-situ CO₂ removal using high temperature CO₂ absorbent (e.g. CaO) in the presence of SMR or WGS catalyst. In addition to the benefit of increased hydrogen yield, SERP may offer another beneficiary possibility of obtaining high purity of CO₂ from absorbent regeneration process. As an absorbent, metal oxides can be used because of reversible reaction characteristics between their oxide and carbonate with temperature change.

Despite of all the positive features of the SERP, there are several obstacles to overcome to materialize industrial level process. One of the major problems of SERP is poor thermal cyclic stability of CO₂ absorbent. To dates, numerous research results showed that the repetitive absorption and desorption of CO₂ cause sintering or agglomeration of the absorbent particles resulting in drastic reduction of CO₂ absorption capacity along with the increased cycle number. Since SERP utilize a CO₂ absorbent and reforming catalyst as mixture, the life time of CO₂ absorbent must be synchronized to that of the catalyst to avoid complex particle separation process. Solution to resolve these problems might be achieved by developing one-body composite, which possess catalytic and CO₂ absorbing features with enhanced cyclic stability.

Our group has come up with new synthesizing method to grant excellent cyclic stability to Ca-based high temperature absorbent. The result has been reported in previous AIChE meeting. This time, one body composite possessing catalytic feature possessing Ca-based CO₂ absorbents was synthesized and modified to achieve the cyclic stability. Ni precursor was added during absorbent preparation and its characterization was carried out by XRD, SEM and fixed bed SERP test. Even with catalyst addition, absortion/desorption test in thermal gravimetric analyzer using the one body composite at 700^oC with changing gas atmosphere showed stable CO₂ gain of 30 wt% over 50 cycles. In SERP test 3 to 10 wt % of Ni containing absorbents were tested and with more than 5 wt% of Ni, over 95% of hydrogen was obtained from product. With conventional SERP concept, to comply with 5 wt% of Ni in physical mixture of Ni catalyst and absorbent, more than 50 wt% of Ni catalyst must be added. Therefore, our new hybrid absorbent containing catalyst might provide minimizing reactor size upon commercialization of SERP without reducing feedstock injection rate.

Also, various catalyst metal precursors were used to prepare catalyst incorporated absorbents. The prepared catalyst-absorbent materials were tested in a fixed bed reactor to simulated SERP process and its results were compared with that of physical mixture of commercial catalyst and the CO₂ absorbent.