Promotional Effect of Cu and Influence of Surface Ni–Cu Alloy for Enhanced H₂ Yields from CH₄ Decomposition over Cu-Modified Ni Supported on MCM-41 Catalyst

Abstract

Catalysts based on MCM-41 decorated with 35–70 nm diameter Ni particles were tested for the production of hydrogen by catalytic decomposition of methane (CDM). About 122 N m3 (molNi)−1 hydrogen yield was achieved over a catalyst comprised of optimized Ni loading of 50 wt % Ni/MCM-41. The H2 yield increased dramatically to 204 N m3 (molNi)−1, upon modification with 10 wt % Cu. The presence of Cu, in contact to Ni, appeared to reduce the sintering and coking of the active Ni sites, which enhanced the longevity of the catalyst. Raman analysis of the catalysts recovered after CDM experiments revealed that doping of Cu to Ni/MCM-41 enhanced the graphitic carbon deposition over the catalyst. All of the samples (Ni and Ni–Cu-modified MCM-41) were characterized by H2 chemisorption, SEM/TEM, XPS, XRD, H2-TPR, N2O titration, and Raman spectroscopy to examine the bulk and surface properties of the catalysts.

Screening of Ni-Cu bimetallic catalysts for hydrogen and carbon nanofilaments production via catalytic decomposition of methane

“…In this regard, bimetallic catalysts based on the doping with low contents of noble (Ni-Cu, Ni-Pt, Ni-Pd), ferrous (Ni-Co, Ni-Fe) and refractory metals (Ni-Mo) were explored [8][9][10][11][12][13][14][15][16]. Among them, Cu doping involving the formation of the Ni (x) Cu (1-x) alloy stands out for enhancing the catalyst stability and activity at high temperature in addition to improving its reducibility and modifying the crystalline structure of the resulting carbon nanofilaments [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31].…”

“…Ni dispersion and sintering related challenges have also been addressed playing with the catalytic support [31][32][33] or the preparation method, which influence the formation of Nibased alloys when a dopant is involved in the catalyst preparation. Conventional supports for…”

“…Ni supported catalysts include metal oxides (SiO 2 , Al 2 O 3 , TiO 2 , MgO, and ZrO 2 ) [29,34,35], carbon materials [25,27,35] or zeolites and mesoporous silica [28,31,36] among the most used due to their thermal and chemical stability. A suitable support improves the CDM reaction influencing in the Ni crystal size and its dispersion, the support/metal interaction and the carbon diffusion mechanism [37][38][39].…”

“…A suitable support improves the CDM reaction influencing in the Ni crystal size and its dispersion, the support/metal interaction and the carbon diffusion mechanism [37][38][39]. The support particle size and textural configuration also influenced the Ni (x) Cu (1-x) alloy dispersion [28,31]. As for the reported Ni (x) Cu (1-x) alloy catalysts preparation methods (sol-gel, impregnation, co-precipitation and fusion) [4, 18, 21-23, 30, 40, 41], these showed in most cases a heterogeneous particle dispersion and a low metal size control.…”

Co-, Cu- and Fe-Doped Ni/Al2O3 Catalysts for the Catalytic Decomposition of Methane into Hydrogen and Carbon Nanofibers

“…It was reported that Cu doping improved the reducibility of the Ni-based catalyst (Cu is easier to reduce than Ni) and enhanced its stability and activity in the CDM at high temperature [23][24][25][26][27][28][29][30][31][32][33][34]. The Ni-Cu alloy is formed over a wide composition range and at temperatures above 354 • C [35].…”