Nanoarchitectonics of Ni/CeO2 Catalysts: The Effect of Pretreatment on the Low-Temperature Steam Reforming of Glycerol

Abstract

CeO2 nanosphere-supported nickel catalysts were prepared by the wetness impregnation method and employed for hydrogen production from glycerol steam reforming. The dried catalyst precursors were either reduced by H2 after thermal calcination or reduced by H2 directly without calcination. The catalysts that were reduced by H2 without calcination achieved a 95% glycerol conversion at a reaction temperature of only 475 °C, and the catalytic stability was up to 35 h. However, the reaction temperature required of catalysts reduced by H2 with calcination was 500 °C, and the catalysts was rapidly inactivated after 25 h of reaction. A series of physicochemical characterization revealed that direct H2 reduction without calcination enhanced the concentration of oxygen vacancies. Thus, the nickel dispersion was improved, the nickel nanoparticle size was reduced, and the reduction of nickel was increased. Moreover, the high concentration of oxygen vacancy not only contributed to the increase of H2 yield, but also effectively reduced the amount of carbon deposition. The increased active nickel surface area and oxygen vacancies synergistically resulted in the superior catalytic performance for the catalyst that was directly reduced by H2 without calcination. The simple, direct hydrogen reduction method remarkably boosts catalytic performance. This strategy can be extended to other supports with redox properties and applied to heterogeneous catalytic reactions involving resistance to sintering and carbon deposition.

The influence of calcination temperature on crystallographic and chemical characteristics of NiO-CeO2 powder for PCFC anodes

“…There are a few broad CeO2 diffraction peaks that can be observed in the calcined NiO-CeO2 at 300 °C. Since there are no crystalline NiO particle peaks, it is most likely that NiO NPs are either are either highly dispersed, or their size are too small for detection [18]. However, at 600 °C calcination, the CeO2 peaks appeared to be more distinct and intense [19].…”

CeO2-supported Ni and Co catalysts prepared by a solution combustion method for H2production from glycerol: the effect of fuel/oxidizer ratio and oxygen excess

“…The excellent stability of Ni/CeO 2 has been related to accelerated carbon removal from the metal surface due to the mobility of oxygen ions and formation of oxygen vacancies in the support. 46 Recent studies of Ni/CeO 2 systems in reforming processes are related to controlling the functional properties of catalysts through changing the morphology, 32,33,36 preparation methods, 24,28,34,35 active component content, 24 promoters, 26,47 and additives. 27,48,49…”

“…Ni-containing catalysts are known to have a high capability for C-C, C-H and O-H bond cleavage 10 and can be easily dispersed on a range of supports. A number of nickel catalysts supported on Al 2 O 3 , [11][12][13][14][15][16][17][18][19][20] CeO 2 , 17,[20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37] MgO, 21,22,30 TiO 2 , 21,22,38 SiO 2 , 13,[38][39][40] and ZrO 2 (ref. 13, 38, and 41-44) have been studied in reforming processes of several renewable feeds, including methanol, 9 ethanol, [14][15][16][17]24,26,27,[32]…”

“…13, 38, and 41-44) have been studied in reforming processes of several renewable feeds, including methanol, 9 ethanol, [14][15][16][17]24,26,27,[32][33][34]37,39,41 and glycerol. [11][12][13][20][21][22][23]25,[28][29][30][31]35,36,38,40,[42][43][44] Al 2 O 3 and CeO 2 as supports are considered effective in terms of high H 2 production and lower coke formation. 17 However, according to ref.…”

“…45 The excellent stability of Ni/CeO 2 has been related to accelerated carbon removal from the metal surface due to the mobility of oxygen ions and formation of oxygen vacancies in the support. 46 Recent studies of Ni/CeO 2 systems in reforming processes are related to controlling the functional properties of catalysts through changing the morphology, 32,33,36 preparation methods, 24,28,34,35 active component content, 24 promoters, 26,47 and additives. 27,48,49 Although Co-based catalysts supported on CeO 2 have not been studied for glycerol reforming as extensively as nickelbased catalysts, 50 they have also been reported to demonstrate excellent ethanol steam reforming activity.…”