Structural and catalytic properties analysis of Ni-Ca-Al bi-functional materials derived from layered double hydroxide (LDH) precursors: Influence of Ca sources on performance of sorption enhanced steam methane reforming

Abstract

The sorption-enhanced steam methane reforming (SESMR) technology holds significant potential as a medium-term solution to address energy shortages. For SESMR, highly effective bi-functional material is the key requirement for economic operation. In this study, layered double hydroxide (LDH) precursors with calcium nitrate tetrahydrate and calcium chloride anhydrous as calcium sources were proposed for SESMR. LDH precursor facilitates the construct of the porous structure of catalytic-sorption bi-functional materials. The characterization results indicated that the strong interactions between metallic elements in bi-functional material with calcium nitrate as calcium source (NCABNs) result in the smallest particle size of Ni and the highest element dispersion, which are beneficial for the catalytic performance and CO₂ sorption performance. Additionally, the hydrogen yield of 95.83% in the pre-breakthrough stage and the menthane conversion rate of 99.38% further indicated the excellent catalytic performance and CO₂ sorption performance of NCABNs. Based on the analysis of thermogravimetric data, NCABNs was applied to conduct the SESMR-regeneration cyclic tests. The CO₂ sorption process was obviously observed in 10 cyclic tests with the CO₂ volume concentration in the pre-breakthrough stage fluctuated around 3 %. Moreover, the textural properties of NCABNs were still retained after the cyclic tests. The low coke graphitization in NCABNs was demonstrated by Raman data with an I_D/I_G of 1.4, which represents the coke can be easily removed by CO₂. The performance of the reported catalyst-sorbent system is encouraging for further studies for SESMR and other reforming techniques.