Chemical Looping-Steam Reforming of Biogas and Methane over Lanthanum-Based Perovskite for Improved Production of Syngas and Hydrogen

Abstract

Biogas is a renewable energy resource that can be effectively utilized for hydrogen (H 2 ) generation. Chemical looping-steam reforming (CL-SR) of biogas produces syngas and pure H 2 in a two-stage redox process using an oxygen carrier (OC). The objective of this study was to evaluate the applicability of the lanthanum-based perovskite OC for CL-SR of biogas and methane. La 0.95 Ce 0.05 Ni 0.2 Fe 0.8 O 3 perovskite was used for reforming biogas and methane in a fixed-bed reactor. Several key features of this OC were studied using nitrogen adsorption−desorption (Brunauer−Emmet−Teller method), scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The perovskite and porous structure of the OC were evident from the outcome of SEM and XRD techniques. The presence of lattice oxygen was evident in the XPS spectra. The availability of lattice oxygen facilitated partial oxidation of methane and produced optimal syngas and H 2 . In a fixed bed, the material (2 g) was reduced in the 750−850 °C range using methane (flow of 20−40 mL/min). At 850 °C, the syngas ratio (H 2 /CO) was 2.3 mol/mol, while the values of H 2 and CO yields were 67.6 and 49.5%, respectively. Upon reduction with biogas, the yield values improved to 79 (H 2 ) and 62% (CO). The subsequent oxidation step using steam resulted in a H 2 -rich product. The chosen La-based perovskite OC was stable for 20 redox cycles, and the average values of the syngas ratio and yields of H 2 and CO were 1.5, 60, and 52%. The purity of H 2 during the oxidation step over 20 cycles was 95%. Thus, the chosen OC was attractive for the CL-SR process.

Review and Outlook of Confined Ni Catalysts for the Dry Reforming of Methane Reaction

“…Perovskites with the chemical formula of ABO 3 or A 2 BO 4 are widely investigated catalysts for DRM because of their excellent oxygen carrier property at high temperatures. − This is good for carbon gasification. Besides, Ni nanoparticles can be exsolved from Ni-containing perovskites during high-temperature hydrogen reduction treatment, showing the pseudo-confined properties by the effect of the lattice confinement and strong metal–support interaction. , …”

“…Because of the abilities of breaking the C–H bond and activating CO 2 by the Ni atom, a Ni-based catalyst is the most active for DRM. − As such, Ni nanoparticles that are supported on carriers, encapsulated in shell materials, derived from perovskites, etc. are developed for DRM. − However, DRM is endothermic, which means that it can only occur at high temperatures. Under the condition, Ni nanoparticles tend to be sintered by Ostwald ripening and carbon is favored to be deposited by methane cracking. − …”