Sorption-enhanced steam reforming of toluene using multifunctional perovskite phase transition sorbents in a chemical looping scheme

Abstract Sorption-enhanced steam reforming (SESR) of toluene (SESRT) using catalytic CO₂ sorbents is a promising route to convert the aromatic tar byproducts formed in lignocellulosic biomass gasification into hydrogen (H₂) or H₂-rich syngas. Commonly used sorbents such as CaO are effective in capturing CO₂ initially but are prone to lose their sorption capacity over repeated cycles due to sintering at high temperatures. Herein, we present a demonstration of SESRT using A- and B-site doped Sr_1−x A’ _x Fe_1−y B’ _y O_3−δ (A’ = Ba, Ca; B’ = Co) perovskites in a chemical looping scheme. We found that surface impregnation of 5–10 mol% Ni on the perovskite was effective in improving toluene conversion. However, upon cycling, the impregnated Ni tends to migrate into the bulk and lose activity. This prompted the adoption of a dual bed configuration using a pre-bed of NiO/γ–Al₂O₃ catalyst upstream of the sorbent. A comparison is made between isothermal operation and a more traditional temperature-swing mode, where for the latter, an average sorption capacity of ∼38% was witnessed over five SESR cycles with H₂-rich product syngas evidenced by a ratio of H₂: CO _x > 4.0. XRD analysis of fresh and cycled samples of Sr_0.25Ba_0.75Fe_0.375Co_0.625O_3-δ reveal that this material is an effective phase transition sorbent—capable of cyclically capturing and releasing CO₂ without irreversible phase changes occurring.