Sustainable Hydrogen Production via Sorption Enhanced Reforming of Complex Biorefinery Side Streams in a Fixed Bed Adiabatic Reactor

In this work, sorption enhanced steam reforming is explored as a potential solution for the valorization of gaseous streams recovered from biorefinery hydrogenation processes. The hydrogen content of such streams limits the hydrocarbon conversion in conventional steam reforming due to thermodynamic and kinetic constraints. A previously developed 1D dynamic heterogeneous model of an adiabatic reactor was thus applied to evaluate the effect of H-2 dilution on the performance indicators of the sorption enhanced reforming process. The mathematical model analysis highlights that despite of CO2 capture by the sorbent favorably modifies the thermodynamics of syngas production, H-2 dilution worsens the performance of the sorption enhanced reforming of model H-2/CH4 streams with respect to pure CH4. Results show a drop of 17% for CH4 conversion and a reduction of 15.4% of the captured CO2 on passing from pure methane to a H-2/CH4 feed with a 40/60 molar ratio. However, on increasing the heat capacity of the bed, by replacing part of the sorbent with an inert heat carrier, better performances are calculated for the H-2/CH4 feed matching the pure CH4 case. The presence of C2+ hydrocarbons is assessed as well and the results show a significant improvement in the reformer's performance; in the case of a stream composed of H-2/CH4/C3H8 with a molar ratio 40/45/15, the total hydrocarbon conversion grows to 92.8%, CO2 capture ratio to 82.6%, and H-2 purity to 95.6%. The positive effect is associated with thermal factors that promote the reaction kinetics. Thus, the suitability of the sorption enhanced reforming technology to H-2-rich and C-poor streams is strictly composition dependent; by cofeeding of C2+ hydrocarbons, the process turns into a remarkable solution for converting gaseous streams in pure H-2.