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The dry reforming of glycerol (GDR) is one of the alternatives for syngas production by utilizing biodiesel byproduct glycerol and CO 2. The development of highly active and stable catalyst is significantly important to achieve GDR process, and the current work provides insights into Co and Fe-doping effects of mesoporous CeO 2 (CoFeCe) catalysts synthesized by the colloidal solution combustion method. The prepared catalysts presented the uniform mesoporous structure, the doping of Co and Fe metals resulted in stronger metal-support interaction. The GDR experimental data were compared with the non-stoichiometric thermodynamic equilibrium values. The conversions of glycerol and CO 2 were increased with increasing the reaction temperatures due to the endothermic GDR reaction, and the H 2 /CO produced in syngas was in the range of 0.7–1.4. Due to the improvement of Co and Fe metals in the mesoporous structure of CeO 2 catalyst, the 7CoFeCe catalyst exhibited excellent and stable GDR performance and no significant signs of deactivation were observed during 76 h test, and the results indicated that the enhanced interaction and high dispersion of Co and Fe in mesoporous CeO 2 catalyst could inhibit carbon formation and promote GDR reaction. [Display omitted] • Co and Fe co-doping on CeO 2 catalyst enhanced GDR reactions. • Increasing in Co-doping improved conversions of glycerol and CO 2 to syngas. • Co–Fe interaction and CeO 2 redox ability inhibited the formation of carbon. • Catalyst with CoFeCe of mole ratio 7: 5:10 exhibited high activity and stability. [ABSTRACT FROM AUTHOR]

In this work, two different types of catalysts with MgO support for aqueous phase reforming of glycerol were prepared by the sol-gel method and calcining method, respectively, and the active metals (nickel or/and cobalt) were added by the initial wet impregnation (IWI) method. It is found that the catalyst supported by gelatinous MgO presents better dispersion and the amount of hydrogen produced by the catalyst containing gelatinous MgO support is more than 1.5 times compared with other catalysts. For the Ni–Co bimetallic catalysts, the higher reaction temperature is beneficial to hydrogen yield, but decreases hydrogen selectivity. A high concentration of glycerol increases hydrogen yield and selectivity. Introducing CaO as an absorbent in aqueous phase reforming can improve WGS reaction and reduce methanation reaction through in-situ CO 2 removal and capture. The gelatinous Ni–Co/MgO catalyst presents superior activity and multi-cycle stability. [Display omitted] [ABSTRACT FROM AUTHOR]

Impurities are inevitable in crude glycerol, a by-product of biodiesel, which has a great influence on aqueous phase reforming (APR). This work investigates three impurities (CH 3 OH, CH 3 COOH, and KOH) in the aqueous phase reforming of glycerol (GAPR) using a mesoporous Ni–Cu/CeO 2 catalyst at three temperatures. The experiment results indicate that the increase of temperature is beneficial to the conversion of glycerol into gas products, but not favor to the proportion of H 2 in the gas phase. The presence of CH 3 OH almost has not affected the total gas volume, while CH 3 COOH and KOH decreased and increased the gas volume, respectively. The deactivation of the catalyst occurs under acidic conditions because the active phase Ni on the catalyst surface is lost in the hydrogen evolution reaction. KOH has the greatest influence on the gas phase composition, which greatly increases the H 2 production and the proportion of H 2. The results of liquid-phase solution analysis show that the addition of CH 3 COOH promoted the dehydration of glycerol, which is contrary to the results obtained by adding KOH. CH 3 OH, as the final product of glycerol dehydrogenation and decarbonization, is added to the initial solution, which will be conducive to the dehydration reaction. The addition of CaO can increase the H 2 production in the APR of glycerol solution containing impurities. • Mesoporous Ni–Cu/CeO 2 was successfully synthesized to APR of glycerol. • Effects of impurities of CH 3 OH, CH 3 COOH, and KOH on APR of glycerol were determined. • CH 3 COOH and KOH decreased and increased gas production from APR, respectively. • Deactivation of Mesoporous Ni–Cu/CeO 2 in APR occurred under acidic conditions. • Enhanced WGS and reduced methanation were achieved by in-situ CO 2 removal. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ni-based catalysts supported by mesoporous CeO 2 were successfully prepared for GDR. • Thermodynamic study of GDR was carried out to compare the experimental data. • 5Ni/CeO 2 presented the highest activity with glycerol conversion of 84.1% at 750℃. • Ni loading ratio of 5 could reduce the generation of filamentous carbon during GDR. In this paper, the mesoporous Ni/CeO 2 catalyst with high specific surface area was prepared by the colloidal solution combustion method and used for the production of syngas by glycerol dry reforming (GDR). The thermodynamic analysis was conducted by using a non-stoichiometric methodology based on the minimization of Gibbs's free energy. The characterization results show that the higher the Ni content, the weaker the interaction between Ni and the CeO 2 support. 5Ni/CeO 2 shows the most consistent Ni dispersion and uniform particle size, and it has the best catalytic activity in the GDR and the conversion of glycerol can reach 84.1 % at 750 °C. Besides, all catalysts exhibited excellent stability during the 10 h catalytic process. The temperature-programmed oxidation (TPO) results show that Ni loading ratio of 5 can reduce the production of filamentous carbon. Based on a kinetic model assuming a power law as a first-order reaction, the activation energy of the Ni-based catalyst for glycerol dry reforming was calculated. [ABSTRACT FROM AUTHOR]

A series of multifunctional catalysts were derived from lamellar montmorillonite (MMT) via ultrasound-assisted cation-exchange method. They were characterized by N 2 adsorption-desorption, X-ray diffraction (XRD), H 2 temperature-programmed reduction (H 2 -TPR), H 2 pulse chemisorption, inductively coupled plasma optical emission spectrometry (ICP-OES), and transmission electron microscopy (TEM). The characterization results show that metal-support interaction (MSI) together with Ni and Ca dispersion interrelates with confinement effect of montmorillonite. The CO 2 absorption capacity of CAT-5 (Ca/MMT molar ratio is 5) was still above 20.0% at the tenth cycle. The steam to glycerol molar ratio (S/G) and reaction temperature were investigated, and an S/G = 3 and a temperature of 600 °C were optimized. The hydrogen purity was significantly enhanced by the equilibrium shift of insitu CO 2 removal at 600 °C. CAT-5 presents the best performance considering the synchronized absorption capacity and catalytic activity. Compared with CAT-M, CAT-5 shows higher stability in the multiple reaction-decarbonation cycles, which is due to the elevated sintering resistance of CaO derived from the confinement effect of lamellar structure. [ABSTRACT FROM AUTHOR]

Hydrogen production from sorption enhanced aqueous phase reforming (APR) of biodiesel byproduct glycerol was studied by Ni-based monometallic and bimetallic catalysts supported on gelatinous MgO supports. Compared with Ni-based monometallic catalyst, the H 2 selectivity and glycerol conversion of the Cu–Ni bimetallic catalyst were found to be increased more than 3% and 30%, respectively. Meanwhile, higher reaction temperature was found to have higher H 2 yield with lower H 2 selectivity. The H 2 yield using the catalyst with gelatinous MgO support was 1.25 times higher than that of calcined support. Through in-situ CO 2 capture, the addition of CaO to the Cu–Ni bimetallic catalyst increased more than 58.3% and 14.4% of the H 2 yield and selectivity, respectively. An analysis about liquid product component indicate that the presence of CaO promote the further cleavage of the C–C bond, which further increased the conversion of glycerol. Furthermore, it was found that the presence of CaO could also improve the stability of the catalyst through the control experiments. [Display omitted] • Sorption enhanced APR to H 2 with in-situ CO 2 capture was studied. • Monometallic and bimetallic supported on MgO were developed. • Cu–Ni supported on gelatinous MgO exhibited good APR performance. • H2 yield by gelatinous MgO support was 1.25 times higher than that of calcined MgO. • Presence of CaO in APR improved conversion, selectivity, and stability. [ABSTRACT FROM AUTHOR]

This paper describes the synthesis of a series of Ni based Al-MCM-41 oxygen carriers with and without Ce promoter and their application in chemical looping steam reforming of glycerol. The Al-MCM-41 is derived from montmorillonite. The oxygen carriers were prepared by direct-synthesis and post-synthesis method. A variety of technologies including N 2 adsorption-desorption, X-ray diffraction (XRD), inductively coupled plasma optical emission spectroscopy (ICP-OES), H 2 temperature-programmed reduction (H 2 -TPR), and transmission electron microscopy (TEM) were conducted to characterize the fresh and used oxygen carriers. The results show the direct-synthesis oxygen carrier possesses excellent textual properties, such as high Ni loading, small particle size, large pore volume, and uniform pore size. The incorporation of Ce could effectively control particle size via strong metal support interaction, promote the homogeneous distribution of Ni, and enhance oxygen mobility capability and water gas shift reaction. And thus shorten ‘dead time’ during the fuel feed step. The CeNi/Al-MCM-41 displayed the superior activity and excellent long-term stability, which could be due to the strengthened anti-sintering and coke capability. [ABSTRACT FROM AUTHOR]

For the fixed-bed reactor configuration in the sorption-enhanced steam reforming process (SERP), solid mixture of catalyst and sorbent is stationary and alternatively exposed to reaction and regeneration conditions for multi-cycles by periodically switching the feed gases for enhanced hydrogen production with in-situ CO 2 removal. A NiO/NiAl 2 O 4 catalyst was synthesized by the co-precipitation method with rising pH technique and the crystalline spinel phase of NiAl 2 O 4 was formed under the calcination temperature of 900 °C. The catalyst was characterized by X-ray powder diffraction (XRD), scanning electron microscope (SEM), thermo-gravimetric analysis (TGA), and N 2 adsorption–desorption. The non-stoichiometric thermodynamic calculation was carried out to determine the effects of temperature and in-situ CO 2 removal on the enhancement of hydrogen production by SERP from glycerol at 425–700 °C. The multi-cycles on reaction and regeneration for hydrogen production by SERP from glycerol were performed by NiO/NiAl 2 O 4 catalyst and CaO based sorbent in a fixed-bed reactor. The results showed that hydrogen production by SERP can be clearly divided into three periods, and the experimental gaseous products were compared with non-stoichiometric thermodynamic calculations. It is obvious that H 2 purity was greatly increased, and CO 2 , CO and CH 4 concentrations were reduced by in-situ CO 2 removal during the pre-breakthrough period. It is found that enhanced hydrogen production was mainly depended on in-situ CO 2 removal. The operation durations for producing high-purity hydrogen of more than 90% were decreased with the increase of the cycles. It may due to the decrease in the reactivity of CaO based sorbent after multi-cycles reaction and regeneration. [ABSTRACT FROM AUTHOR]

Hydrogen production from chemical looping steam reforming (CLSR) of glycerol was studied by Ni-based oxygen carrier in a fixed-bed reactor. For the fixed-bed reactor configuration, solid Ni-based oxygen carrier is stationary and alternatively exposed to reducing and oxidizing conditions by periodically switching the feed gases. The Ni-based oxygen carrier was prepared by a liquid-state co-precipitation method with rising pH technique and the characterization was performed by X-ray powder diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM) and N 2 adsorption–desorption. Gaseous products and temperature variety during CLSR process by Ni-based oxygen carrier in a fixed-bed reactor were measured, and the thermodynamic equilibrium calculation was also carried out. The results showed that the Ni-based oxygen carrier synthesized has a dual function and can efficiently convert glycerol and steam to H 2 by redox reactions. The coexisting reactions of glycerol oxidization (or NiO reduction) and steam reforming occurred before the steady stage of hydrogen production in the fuel feed step, and the conversion of NiO to Ni was obtained. Alternating reduction and oxidation reactions enabled Ni-based oxygen carrier to produce H 2 with a concentration of 85% of the equilibrium value at 600 °C, and glycerol conversion was up to 99%. The increase of temperature related to the exothermic reactions by Ni-based oxygen carrier in CLSR process was observed in redox cycles. [ABSTRACT FROM AUTHOR]

The Ni-based multifunctional catalysts for the sorption-enhanced steam reforming process (SERP) with simultaneous in-situ CO 2 removal were synthesized by the co-precipitation method with rising pH technique, and the crystalline spinel phases of NiAl 2 O 4 and MgAl 2 O 4 in the catalysts were formed under the calcination temperature of 900 °C. The catalysts were characterized by X-ray powder diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), thermo-gravimetric analysis (TGA), and N 2 adsorption-desorption. Nonisothermal and isothermal CO 2 sorption experiments were carried out to evaluate the activity of catalysts for CO 2 removal. Desorption and optimum sorption temperatures for CO 2 removal were determined. Hydrogen production from SERP of glycerol over the multifunctional catalysts has been experimentally evaluated under 550 °C and steam to carbon (S/C) ratio of 3. The multifunctional catalyst with the composition of 41.21 wt% NiO, 28.02 wt% Al 2 O 3 and 30.77 wt% CaO presented satisfactory hydrogen purity in the multi-cycles of reforming and regeneration processes. Enhanced hydrogen production was mainly depended on in-situ CO 2 removal, and the operation durations for producing high purity hydrogen in the initial 30 min were relatively stable. The multifunctional catalyst possesses uniform distribution of Ni, Ca and Al, contributing significantly to the excellent CO 2 sorbent capacity and reforming activity. This multifunctional catalyst synthesized offers a new scheme other than the conventional mixture of sorbent and catalyst for SERP. [ABSTRACT FROM AUTHOR]

In this study, renewable hydrogen production was achieved by coupling of water splitting and glycerol oxidation reforming by chemical looping technology (CLWS-GOR) using the novel Ce–Ni modified Fe-based oxygen carriers (OCs). The OCs were developed by combining metal chelating sol-gel and isometric impregnation method, which exhibited anti-sintering characteristic and lattice oxygen migration ability in CLWS-GOR. The amount of hydrogen between 12.49 and 12.96 mmol in the steam stage was produced from all the OCs with different ratios of Fe, Ce and Ni. However, with the increase of Ce and Ni doping, the production of H 2 and CO in the fuel stage increased, as well as the probability of carbon deposits released in the subsequent steam stage. The H 2 /CO ratio in syngas were easily adjusted by steam to carbon molar ratio (S/C) in chemical looping steam reforming (CLSR), but the effects of steam introducing led to gradual deterioration of OCs. The results proved the OCs prepared by the combination method has high activity and stability for renewable hydrogen production from coupling of CLWS-GOR. [Display omitted] • Coupling of water splitting and glycerol oxidation reforming by chemical looping. • Ce–Ni modified Fe-based OCs were synthesized by combined method. • Pure H 2 was achieved from CLWS-GOR by reduced OCs. • WGS enhancement and the H 2 /CO ratio adjustment were achieved. [ABSTRACT FROM AUTHOR]

[Display omitted] • Mesoporous Ni-Cu/CeO 2 was successfully synthesized to APR of biodiesel byproduct glycerol. • 1Ni2Cu/CeO 2 presented superior activity and multi-cycle stability in APR. • Cu element in catalysts effectively improved WGS and inhibited CH 4 formation. • Enhanced WGS and reduced methanation were achieved by in-situ CO 2 removal. Aqueous phase reforming (APR), regarded as one method for inexpensive H 2 production, was widely studied due to lower temperature and unnecessary to vaporize water and fuels. In this study, the mesoporous CeO 2 , regarded as a metal oxide carrier, was first prepared by colloidal solution combustion, and then the Ni-Cu bimetallic supported on mesoporous CeO 2 was successfully synthesized to investigate the catalytic performance in APR of biodiesel byproduct glycerol. The results show that the Cu element in the catalysts can effectively improve water–gas shift (WGS) reaction and inhibit the formation of methane, which increases the H 2 production rate from 125.08 to 195.57 µmol⋅min−1⋅g cat−1. The higher reaction temperature is beneficial to the H 2 production rate, but not to H 2 selectivity. Kinetics analysis indicates that catalyst of 1Ni2Cu/CeO 2 + 0.2gCaO has the lowest apparent activation energy (29.86 kJ⋅mol−1). CaO is introduced as an absorbent to improve WGS reaction and reduce methanation reactions through in-situ CO 2 removal and capture. The reaction path and mechanism of APR of glycerol are also discussed in this paper. [ABSTRACT FROM AUTHOR]

[Display omitted] • Hydrogen was efficiently produced from CLSR of biodiesel byproduct glycerol. • Well-order mesoporous CeNiO/MCM-41 and CeNiO/SBA-15 were synthesized for CLSR. • High feeding conversion and H 2 selectivity was achieved by mesoporous OCs. • High loading NiO and CeO 2 on mesoporous OCs achieved excellent CLSR redox cycles. The selection of metal oxides and supports to improve catalytic activity and stability of oxygen carriers (OCs) is crucial for chemical looping steam reforming (CLSR) to hydrogen production. In this study, the Ni-based MCM-41 and SBA-15 OCs with and without CeO 2 promoter were prepared by direct synthesis and impregnation methods. The BET, XRD, TEM, ICP-AES, H 2 -TPR and DSC-TGA were used to analyze the synthesized OCs. Hydrogen production by CLSR using biodiesel byproduct glycerol was studied in a fixed-bed reactor with fuel and air stages. The DSC-TGA experiments were carried out to determine the thermal decomposition of biodiesel byproduct glycerol and the results indicated the exothermic and/or endothermic reactions as a result of secondary reactions and, the main degradation with the mass loss of 85.5 wt% occurred in the stages of 150–500 °C. The mesoporous OCs presented high specific surface area, large pore volume, and uniform pore size. It was found that the NiO and CeO 2 in the mesoporous OCs were first reduced by fuels and the reduced OCs was responsible of steam reforming and water gas shift (WGS) to hydrogen production, and hydrogen selectivity was up to 90% using CeNiO/SBA-15. The mesoporous OCs with Ce promoter greatly shortened 'dead time' (the reduce time of OCs), and effectively suppressed carbon deposited on OCs. High loading of NiO and CeO 2 on SBA-15 improved oxygen transfer and achieved excellent cyclic stability. These findings provide the fundamental understanding and principle of design on the conventional Ni-based OCs with room for further developments in chemical looping process. [ABSTRACT FROM AUTHOR]

[Display omitted] • CLWS coupled with glycerol decomposition was proposed to produce H 2 and syngas. • Fe-Ce-Ni based OCs were synthesized by improved metal chelating sol–gel method. • Pure H 2 was achieved at 750℃ from CLWS by reduced OCs. • High conversion of glycerol and selectivity of syngas obtained by re-oxidized OCs. • OCs with 100:10:3 of Fe-Ce-Ni molar ratio presented high activity and stability. In this study, chemical looping water splitting (CLWS) coupled with glycerol decomposition to simultaneously produce hydrogen and syngas was proposed using the iron-cerium-nickel (Fe-Ce-Ni) based oxygen carriers (OCs). The OCs containing large amounts of iron were synthesized by the metal chelating sol–gel method and characterized by BET, XRD and TEM. During the fuel stage, the OCs of oxidation state were first reduced by the glycerol and reactive gases from catalytic decomposition of glycerol producing syngas. Afterward in the subsequent steam stage, the previously reduced OCs were re-oxidized by the steam to generate pure hydrogen, which was also named the steam iron process (SIP). The prepared Fe-Ce-Ni based OCs demonstrated the remarkable redox behavior, and exerted an important catalytic function of the partial oxidation and decomposition of glycerol at 750 ℃. The OCs with 100:10:3 of Fe-Ce-Ni molar ratio presented the best capability of oxygen transfer and the highest yields of hydrogen and syngas, reaching the water splitting hydrogen production of 11.79 mmol/g per cycle on average and guaranteeing the high conversion of glycerol and selectivity of syngas. This could be ascribed to the preferable dispersion of Ce and Ni nanoparticle on the OCs. The results also proved the effectiveness of Ce and Ni doping Fe based OCs by the improved metal chelating sol–gel method to develop the catalysts with high activity and stability for co-production of hydrogen and syngas from CLWS coupled with glycerol decomposition. [ABSTRACT FROM AUTHOR]

The research describes the synthesis of nanocomposite Ni@ZrO 2 oxygen carriers (OCs) and lanthanide doping effect on maintaining the platelet-structure of the nanocomposite OCs. The prepared OCs were tested in chemical looping reforming of glycerol (CLR) process and sorption enhanced chemical looping reforming of glycerol (SE-CLR) process. A series of characterization techniques including N 2 adsorption-desorption, X-ray diffraction (XRD), inductively coupled plasma optical emission spectrometry (ICP-OES), high resolution transmission electron microscopy (HRTEM), H 2 temperature-programmed reduction (H 2 -TPR), H 2 pulse chemisorption and O 2 temperature-programmed desorption (O 2 -TPD) were used to investigate the physical properties of the fresh and used OCs. The results show that the platelet-stack structure of nanocomposite OCs could significantly improve the metal support interaction (MSI), thus enhancing the sintering resistance. The effect of lanthanide promotion on maintaining this platelet-stack structure increased with the lanthanide radius, namely, La 3+ > Ce 3+ > Pr 3+ > Yb 3+ . Additionally, the oxygen mobility was also enhanced because of the coordination of oxygen transfer channel size by doping small radius lanthanide ions. The CeNi@ZrO 2 showed a moderate ‘dead time’ of 220 s, a high H 2 selectivity of 94% and a nearly complete glycerol conversion throughout a 50-cycle CLR test. In a 50-cycle SE-CLR stability test, the CeNi@ZrO 2 CaO showed high H 2 purity of 96.3%, and an average CaCO 3 decomposition percentage of 53% without external heating was achieved. [ABSTRACT FROM AUTHOR]