Combustion synthesized copper-ion substituted FeAl2O4 (Cu0.1Fe0.9Al2O4): A superior catalyst for methanol steam reforming compared to its impregnated analogue

Abstract

A series of copper ion substituted MAl2O4 (M= Mg, Mn, Fe and Zn) spinels is prepared by a single step solution combustion synthesis (SCS) and tested for methanol steam reforming (MSR). The copper ion substituted Cu0.1Fe0.9Al2O4 appears to be the most active, showing ~98% methanol conversion at 300 °C with ~5% CO selectivity at GHSV= 30000 h-1 and H2O:CH3OH= 1.1. The analogous impregnated catalyst, CuO (10 at.%)/FeAl2O4, is found to be much less active. These materials are characterized by XRD, H2-TPR, BET, HRTEM, XPS and XANES analyses. Spinel phase formation is highly facilitated upon Cu-ion substitution, and Cu loading beyond 10 at.% leads to the formation of CuO as an additional phase. The ionic substitution of copper in FeAl2O4 leads to the highly crystalline SCS catalyst containing Cu 2+ ion sites that are shown to be more active than the dispersed CuO nano-crystallites on the FeAl2O4 impregnated catalyst, despite its lower surface area. The as prepared SCS catalyst contains also a portion of copper as Cu 1+ that increases when subjected to reforming atmosphere. The MSR activity of the SCS catalyst decreases with time-on-stream due to the sintering of catalyst crystallites as established from XPS and HRTEM analyses.

Local crystal structure and physical properties change of p-type transparent conducting oxide: CuCrO2 upon Ti-substitution

“…Although the formal valence state of Cu ions does not cross over to 2þ, as the absorption edge for CuO, an oxide of copper with a 2þ valence state is at least 5 eV higher than the pure Cu -metal. 33 However, we observe a slight shift ($0.7 eV each) towards higher energy with increasing Ticontent. This slight change in absorption energy, though not an indication of any significant oxidation of Cu ions, suggests that subtle changes in the electronic structure of CuCrO 2 take place with Ti addition.…”

Effect of Fe‐Containing Supports Prepared by a Novel Sol–Gel Method in the CO Methanation Reaction: CO Elimination and Synthetic Natural Gas Production

“…The small shoulder observed at 850 °C is related to the reduction of nickel aluminate spinel. From Figure b, the TPR curve of the Fe 1 Al 3 O x support reveals a peak, which is attributed to the reduction of the FeAl 2 O 4 spinel . The reduction peak related to nickel oxide starts at a temperature of about 430 °C and reached a maximum at around 690 °C.…”

Review of Recent Studies on Solution Combustion Synthesis of Nanostructured Catalysts

“…Their microstructure analysis revealed that copper ionic substitution facilitates the spinel formation during combustion and leads to the SCS catalyst with significantly high crystallinity. The catalysts with the Cu 2+ ion sites proved to be more active than the dispersed CuO nanocrystallites on the FeAl 2 O 4 impregnated catalyst, although they had lower specific surface area …”