Effect of calcium addition on catalytic ethanol steam reforming of Ni/Al2O3: II. Acidity/basicity, water adsorption and catalytic activity

Steam reforming of biomass tar model compound at relatively low steam-to-carbon condition over CaO-doped nickel–iron alloy supported over iron–alumina catalysts

“…6, the low temperature Unlike the low temperature CO 2 desorption peak, the moderate temperature desorption peak exist at similar temperature range for all the Ni/Ca-Fe-Al catalysts. According to literature [39,58], this moderate temperature CO 2 desorption peak is generally observed because of the presence of over-saturated CaO species. This CaO species adsorbs CO 2 much stronger than those Ca ions dispersed in the Al 2 O 3 matrix.…”

“…All the profiles for Ni/Ca-Fe-Al catalysts in Fig. 6 shows two-stage CO 2 desorption peaks, with the first peak being a low temperature intense CO 2 desorption peak ranging from 100 to 350 • C. These peaks can be assigned to low-strength basic sites, such as bicarbonates that result from the interactions between CO 2 and weak basic surface hydroxyl groups [39]. Secondly, broad CO 2 desorption peak was observed at a moderate temperature range of 400-600 • C. This latter peak is probably due to high-strength basic sites such as unidentate carbonates [58].…”

“…Catalysts with basic properties tend to decrease the rate of coke formation in many reforming reactions, such as steam reforming of toluene [18,30], CO 2 reforming of methane [35][36][37], steam reforming of methane [37], steam reforming of ethanol [38,39], which in turn leads to reduced catalyst deactivation over time and helps to increase the stability of the catalyst. Furthermore, calcium oxide (CaO) is widely known to be a CO 2 sorbent, assisting the production of hydrogen-rich gas [40,41] in biomass gasification for hydrogen production.…”

“…In steam reforming of ethanol, the addition of CaO to Ni catalyst could prevent the formation of crystalline carbon which is more difficult to be removed, resulting in higher catalyst stability. Moreover, it was reported that Ca addition promoted water adsorption and provided abundance of adsorbed OH groups on Ni catalyst which could facilitate the C C break, resulting in higher ethanol conversion [38,39]. It has been reported [44][45][46][47][48] that the surface properties of Ni/Al 2 O 3 systems could be improved by introduction of alkaline earth metal oxides (MgO and CaO) due to the increase of steam-carbon reaction and the neutralization of the acidity of the support to suppress cracking and polymerization reactions.…”

Catalytic steam reforming of volatiles released via pyrolysis of wood sawdust for hydrogen-rich gas production on Fe–Zn/Al2O3 nanocatalysts

“…For example, a mixture of MgO or CaO with alumina support could strongly enhance the interaction between support and surface atoms of metal particles, which could strongly stabilize the metal particles to block their sintering and also enhance the metal activity due to the electron transfer between support and surface [13][14][15][16][17].…”