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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]

Chemical looping steam reforming (CLSR) of ethanol using oxygen carriers (OCs) for hydrogen production has been considered a highly efficient technology. In this study, NiO/MgAl 2 O 4 oxygen carriers (OCs) were employed for hydrogen production via CLSR with and without CaO sorbent for in-situ CO 2 removal (sorption enhanced chemical looping steam reforming, SE-CLSR). To find optimal reaction conditions of the CLSR process, including reforming temperatures, the catalyst mass, and the NiO loadings on hydrogen production performances were studied. The results reveal that the optimal temperature of OCs for hydrogen production is 650 °C. In addition, 96% hydrogen selectivity and a 'dead time' (the reduced time of OCs) less than 1 minute is obtained with the 1 g 20NiO/MgAl 2 O 4 catalysts. The superior catalytic activity of 20NiO/MgAl 2 O 4 is due to the maximal quantity of NiO loadings providing the most Ni active surface centers. High purity hydrogen is successfully produced via CLSR coupling with CaO sorbent in-situ CO 2 removal (SE-CLSR), and the breakthrough time of CaO is about 20 minutes under the condition that space velocity was 1.908 h−1. Stability CLSR experiments found that the hydrogen production and hydrogen selectivity decreased obviously from 207 mmol to 174 mmol and 95%–85% due to the inevitable OCs sintering and carbon deposition. Finally, stable hydrogen production with the purity of 89%∼87% and selectivity of 96%∼93% was obtained in the modified stability SE-CLSR experiments. [Display omitted] • High catalytic OCs were developed via the modified Pechi method. • 20NiO/MgAl 2 O 4 attained 96% H 2 selectivity and 1 minute 'dead time' in CLSR. • The breakthrough time of CaO was 20 minutes in SE-CLSR. • Stable H 2 yield with high purity was obtained in the long-term modified SE–CLR. [ABSTRACT FROM AUTHOR]

[Display omitted] • A coupled chemical looping conversion of glycerol, CO 2 and H 2 O is achevied. • High-purity H 2 and syngas are one-step produced by GO, GDR and WS using OC. • Co-Fe interaction in OC inhibits the formation of carbon. • FeCoCe OC achieve excellent oxygen storage and redox reactions. • OC with 7:5:10 of Co: Fe: Ce presents high activity and stability. A coupled chemical looping conversion of glycerol and CO 2 with thermochemical water splitting (WS) cycle is substantially researched due to its potential for one-step renewable H 2 and syngas production. The major challenge lies on having good controls of redox reactions of the oxygen carriers (OCs) used and its unusual sensitivity to the changes of the compositions, chemical states and structure, etc. Here, we develop the OCs that consists of Fe 2 O 3 -Co 3 O 4 supported on the mesoporous CeO 2 structure (Fe 2 O 3 -Co 3 O 4 /CeO 2), which simultaneously promote glycerol oxidization (GO), dry reforming of glycerol (GDR), and WS processes. The easy migration and activation of lattice oxygen by Fe 2 O 3 -Co 3 O 4 /CeO 2 greatly improved the GO and GDR to produce syngas at the first step, and the pure H 2 production by the reduced Fe 2 O 3 -Co 3 O 4 /CeO 2 achieved excellent WS and oxygen storage at 750℃. The low-content Fe dopant in the OC presented a beneficial effect on the anti-sintering performance, and increase of Co-doping indicated a high activity to WS as well as enhanced GDR. The Fe 2 O 3 -Co 3 O 4 /CeO 2 with 7:5:10 of Co: Fe: Ce molar ratio presented the highest glycerol and CO 2 conversions and the highest H 2 yield, also illustrated the excellent activity and stability in 40 consecutive redox cycles. [ABSTRACT FROM AUTHOR]

[Display omitted] • Integrated design of in-situ H 2 sorption/storage in WGS to H 2 production is proposed. • H 2 production from supercritical CO 2 , steam, air gasification of biomass is compared. • Energy analysis for H 2 production with in-situ H 2 sorption/storage is studied. The novel process on in-situ hydrogen sorption/storage during water gas shift (WGS) was proposed and the enhanced hydrogen production in supercritical CO 2 gasification (CG), air gasification (AG), and steam gasification (SG) from biomass was integrated. Pure hydrogen was obtained by regeneration from the material (Mg 2 Ni) used for in-situ H 2 absorption during WGS. The effects of temperature, pressure, steam-to-carbon (S/C) ratio, and the quantity of adsorbent for the enhanced hydrogen production with in-situ hydrogen sorption/storage were determined. When Mg 2 Ni was added as the in-situ H 2 adsorbent, the hydrogen conversion in WGS reaction was improved. The increase of temperature reduced the hydrogen yield. SG presented the highest hydrogen yield and AG showed the highest hydrogen conversion. The steam-to-carbon (S/C) had a positive effect on the hydrogen production for all the processes and the methanation reaction was greatly inhibited by AG. The energy efficiencies reached 22.98 %, 26.31 %, and 27.149.51 %, and the exergy efficiencies reached 61.66 %, 64.19 %, and 83.62 %, for CG, AG and SG, respectively. The system energy can be supplied by in-situ hydrogen sorption/storage and the energy requirement order was SG > CG > AG. [ABSTRACT FROM AUTHOR]

Under the high attention of the international community to CO 2 emissions, the capture utilization and storage (CCUS) and the CO 2 hydrogenation fuel production have become two popular directions, especially for the combination of the two processes. In this paper, the production of liquid fuels via the methanol synthesis pathway in an integrated CCUS system based on Aspen Plus models was studied. The NH 3 -CO 2 -H 2 O absorption was used to capture CO 2 and hydrogen was provided by water electrolysis using renewable energy sources. A two-stage reactor with a recirculating stream was specified for the process of CO 2 hydrogenation to synthesize methanol, and the liquid fuel dimethyl ether (DME) was reproduced by dehydrating methanol (Power-to-Liquid). The amount of absorbent used for the carbon capture process was determined and the yield differences due to the number of cycles in the intermediate methanol synthesis reaction were analyzed. It is possible to convert 4.15 t of CO 2 per tonne of DME produced at the mass material balance of the process. The optimization of the heat exchange network and the energy requirements for the total process were evaluated. It is calculated that the energy involved in producing 1 ton of DME in the process model is 176 GJ. The analysis of the overall process and the evaluation of models could provide options for the possibility of CCUS engineering application. [Display omitted] • An integral process model converts CO 2 to liquid fuels by methanol synthesis. • Treatment options are proposed for emissions that accumulate in the cycle of the process. • The model offers energy requirement assessment for possible engineering applications. [ABSTRACT FROM AUTHOR]

Abstract Hydrogen sorption and storage in a solid matrix can greatly improve its safety and efficiency when compared to the compressed gas or liquid hydrogen storage system, and kinetics mechanisms are of interest towards the development of such materials. In this study, the composites of Mg-Ni-Cu doped with singe-walled carbon nanotubes (Mg-Ni-Cu/CNTs) were synthetized. The activation performance, isothermal hydrogen sorption and desorption were systematically tested, and the experimental data were analyzed using the shrinking core model. The results show that three cycles of hydrogen sorption and desorption may be enough to fully activate Mg-Ni-Cu/CNTs and the stability can be kept for 150 cycles. A 10.1 wt% of Cu and 50.3 wt% of Ni in Mg-Ni-Cu/CNTs facilitates the hydrogen sorption and a reversible hydrogen capacity of ∼3.35 wt% can be achieved at 310 °C and 3.0 atm, and hydrogen capacity and kinetics shows significant decline during contact with 1.0 vol% CO impurity. Considering desorption at 600 °C, the kinetic profiles are about linear and desorption is completed within minutes. The gas-solid reaction processes for hydrogen sorption undergo three different rate-limiting stages, and hydrogen desorption can only be divided into two stages of surface chemical reaction and product layer diffusion. Highlights • MgNiCu/CNTs are active in H 2 sorption at 310 °C and 3.0H 2 pressure. • Cu, Ni and CNTs can facilitate H 2 sorption of Mg and increase stability. • H 2 sorption and kinetics are deteriorated during contact with CO impurity. • Kinetics mechanisms and rate-limiting steps were determined by SCM. [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]

Hydrogen production and reduction of Ni-based oxygen carriers (OCs) during chemical looping steam reforming (CLSR) of ethanol were studied in a fixed-bed reactor using four OCs with different supports including NiO/SBA-15, NiO/MCM-41, NiO/MMT and NiO/Al 2 O 3 . The OCs prepared were characterized by N 2 adsorption-desorption, TPR, TPO, XRD, TEM, FTIR and TGA-DSC. The results demonstrated that NiO component in all the OCs was first reduced by ethanol and the reduced OCs were responsible of catalytic steam reforming and water gas shift for hydrogen production. Mesoporous NiO/SBA-15 presented increasing conversion of NiO reduction and the highest selectivity of hydrogen production. The conversion of ethanol increased with reactions proceeding until the highest value is reached after about ∼300s, and the negative steam conversion obtained was resulted from H 2 O formation from ethanol oxidation by OCs. Compared with MMT and Al 2 O 3 supports, the oxidization of NiO with MCM-41 and SBA-15 supports was very fast and less carbon was formed and deposited. Enhancement in hydrogen production from CLSR process was achieved by in-situ CO 2 removal. Shrinking Core model (SCM) based on the constant pattern model for fixed-bed reactor indicated the rates of OCs reduction with ethanol were mainly controlled by surface chemical reaction and product layer diffusion. The reduction process was found to undergo three different rate-limiting stages, and the critical times for changes in the rate-limiting steps were determined. [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]

[Display omitted] • SECLSR proposed realizes CO 2 in-situ capture & utilization to H 2 and syngas. • Conversion of CO 2 from in-situ extraction of dolomite using MDR at 850 °C is feasible. • NiO/NiAl 2 O 4 of 15% NiO presented good activity and stability in SECLSR and MDR. • The process is no need for separating catalyst and sorbent for SECLSR. Hydrogen production from chemical looping steam reforming using an oxygen transport catalyst is definitely enhanced by CO 2 in-situ capture, which shifts the chemical equilibrium and reduces the energy demands. The utilization of CO 2 from this process as a reactant for chemicals and fuels could help to improve economic reasons and mitigate its impact on climate. In this study, we proposed a sorption-enhanced chemical looping steam reforming of glycerol to realize the synergetic capture and conversion of CO 2 in one integrated chemical looping hydrogen production process. The process is characterized to use the oxidized NiO/NiAl 2 O 4 as a steam reforming catalyst, the reduced NiO/NiAl 2 O 4 as a CO 2 -CH 4 dry reforming catalyst, and the inexpensive dolomite as a CO 2 sorbent. The surface carbon that would deactivate the catalyst is combusted by air after CO 2 -CH 4 dry reforming and the Ni on the catalyst is re-oxidized. The coupling of these different processes of chemical looping steam reforming, CO 2 in-situ capture, dolomite decomposition and CO 2 in-situ utilization, results in simultaneous generation of high purity hydrogen and syngas. The results demonstrated that hydrogen of above 92.5% was one-step generated and CO 2 was decreased to zero in the pre-CO 2 breakthrough periods. The reduced NiO/NiAl 2 O 4 catalysts favored the CO 2 -CH 4 dry reforming at 850 °C. The syngas of H 2 -to-CO molar ratios of 0.8–1.1 through the conversion of CO 2 from in-situ extraction of the absorbed CO 2 dolomite, was produced. The NiO/Al 2 O 4 with 15 wt% NiO gave the highest hydrogen and syngas yields, and maintained high performance for the proposed system. The catalysts and dolomite exhibited good stability with no obvious loss of activity in 10 cycles. [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]

The Ni-based oxygen carriers (OCs) with different supports including alloy Ni/Al 2 O 3 , lamellar Ni/MMT, mesoporous Ni/Al-MCM-41 and mesoporous Ni/SBA-15 were synthesized. The effect of support on hydrogen production from chemical looping steam reforming (CLSR) of ethanol was investigated in a fixed-bed reactor. The oxygen carriers were characterized by some techniques, including N 2 adsorption–desorption, XRD, TEM, ICP-OES, H 2 pulse chemisorption, H 2 -TPR, and TG-DTG. It was observed that Ni/SBA-15 exhibited most efficient confinement effect followed by Ni/Al-MCM-41, Ni/MMT and Ni/Al 2 O 3 via: 1) small nickel particle size and high dispersion as well as strengthened metal-support interaction; 2) sintering resistance due to spatial restriction of support; 3) anti-coke capability derived from small nickel particles and ordered diffusion routes for reactants and products. In addition, the silica supported OCs were conductive to promote water gas shift (WGS) reaction but the supports containing Al atoms were prone to coke deposition due to the formation of acid sites. The ‘dead time’ and oxygen transfer capacity reflected that the redox performance of oxygen carriers was listed in the following order: Ni/SBA-15, Ni/Al-MCM-41, Ni/MMT and Ni/Al 2 O 3 . Ni/Al-MCM-41 exhibited excellent activity in initial cycle of CLSR but the collapse of the Ni/Al-MCM-41 structure for its weak thermo stability leaded to the deactivation and sintering of active phase. The Ni/SBA-15 and lamellar Ni/MMT OCs exhibited superior activity and stability but the performance of Ni/Al 2 O 3 OCs was mediocre. [ABSTRACT FROM AUTHOR]

Hydrogen production by chemical looping steam reforming of ethanol using oxygen carriers was carried out in a fixed-bed reactor. NiO/montmorillonite prepared by ultrasound assisted cation exchange impregnation method was used as oxygen carriers. The synthesized NiO/montmorillonite was characterized by N 2 adsorption–desorption, inductively coupled plasma optical emission spectrometry (ICP-OES), X-ray diffraction (XRD), transmission electron microscopy (TEM), H 2 temperature-programmed reduction (H 2 -TPR), H 2 pulse chemisorption, temperature-programmed reduction (TPO) and thermal gravimetric analysis (TGA). The characterization results showed the particle size, metal-support interaction, nickel dispersion interrelated with cation exchange capability and confinement effect of montmorillonite’s lamellar structure. Activity and stability tests were conducted at 550 °C with a steam to carbon ratio of 4. The results showed that 20Ni–MMT possessed the best performance due to its strong sintering and coking resistance, and also presented the shortest ‘dead time’ due to its larger active surface area. Moreover, 20Ni–MMT exhibited the excellent coke elimination ability in the air feed step. [ABSTRACT FROM AUTHOR]

Chemical looping steam reforming of ethanol using x CeNi/SBA-15 oxygen carriers was carried out at 650 °C under atmospheric pressure in a fixed-bed reactor. The mesoporous support SBA-15 was synthesized via hydrothermal method and the x CeNi/SBA-15 oxygen carriers were prepared by encapsulating CeO 2 and NiO nanoparticles in SBA-15 using surfactant-assisted iso-volumetric impregnation method. Some techniques were conducted to characterize the oxygen carriers, including N 2 adsorption–desorption, XRD, TEM, H 2 -TPR, ICP-OES, and DSC-TGA. It was observed that all the oxygen carriers exhibited high specific surface area (>435 m 2 /g) and large pore volume (>0.64 cm 3 /g). Small NiO particle size (e.g. 3.2 nm for 12CeNi/SBA-15), high dispersion and strengthened metal-support interaction were achieved by the CeO 2 promotion. The ceria promoter not only inhibited the coke formation but facilitated the removal of coke deposition, and the coke deposition could be further eliminated in the air feed step, both of which resulted in long-term stability. Meanwhile, superior redox performance and shorter ‘dead time’ (e.g. 30 s for 12CeNi/SBA-15) were achieved on account of easier reducibility of NiO particles with increasing amount of CeO 2 . The oxygen carriers exhibited superior sinter resistance capacity and high activity and stability in CLSR process. The highest ethanol conversion (90.0%) and hydrogen selectivity (84.7%) were obtained for 12CeNi/SBA-15 even after 14 cycle stability test. [ABSTRACT FROM AUTHOR]

This paper proposes a novel system for continuous hydrogen production from waste plastic (WP) by fluidized-bed gasification (FBG) combined sorption-enhanced steam reforming process (SERP). The system was operated in successive processes of several sections: (a) gasifying a WP into a raw gas comprising CO, H 2 , CH 4 , total hydrocarbons (THC), and small amount of HCl contaminant, etc.; (b) passing the raw gas to hydrogen production through two moving-bed reactors by continuous SERP process over Ni-based catalyst mixed CaO sorbent for in-situ CO 2 capture and HCl removal; (c) simultaneously regenerating CaCO 3 formed and catalyst with carbons deposited in other moving-bed reactor at the regeneration condition selected; and (d) carrying the particles of catalyst and sorbent to continuous steam reforming and their regeneration between two moving-bed reactors by riser. Gradually expanding chamber design of FBG reactor suitable for different particles flow to prolong the residence times of gas and solid phases makes high carbon conversion and the maximum value is up to 83.6% at 880 °C during FBG stage. The combination of FBG and SERP has produced a stream of high-purity hydrogen at some certain conditions, and about 88.4 vol % of hydrogen (H 2 O- and N 2 -free basis) was obtained at 818 °C of FBG temperature with 706–583 °C of SERP temperature. Reduced Ni-based catalyst efficiently converted raw gas from FBG and steam to H 2 , and CaO sorbent in the moving-bed reactor are capable of reducing the HCl and CO 2 to low levels at all the temperatures tested. [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]

Integrating in-situ CO 2 removal at high temperature by solid sorbents during sorption-enhanced steam reforming process for high-purity hydrogen production has been considered to change the normal equilibrium limits of shift reactions and increase hydrocarbon conversion as well as reduce CO 2 emissions. However, a difficulty by integrating these reaction steps in a single and integrated process involves selecting suitable sorbents and reaction conditions under which all of the processes can be carried out. Due to the difficulty in application of solid sorbents in SERP, the improvement of their performance is crucial to make the process important for industrial applications. This study discussed the performances of CaO, MgO, hydrotalcite and Li 2 ZrO 3 based sorbents during sorption-enhanced steam reforming for high-purity hydrogen production, while different methods for enhancing these sorbents activities were summarized. The factors of reaction conditions such as temperature, pressure, the amount of water vapor etc. and related reaction mechanisms using these solid sorbents are identified. CaO has shown its potentials with its lost cost and high capacities. Nevertheless, the deactivation of CaO during multi-cycles carbonation-regeneration is challenging for continuous long-term operating conditions for hydrogen production from catalytic steam reforming. The potential and development of the multifunctional sorbent–catalyst materials having a dual function of catalytic steam reforming and in-situ CO 2 removal were discussed. [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, the Li2ZrO3based sorbentswith different compositions were synthesized by the solid-state reactionmethod from the mixtures of Li2CO3, K2CO3and ZrO2. CO2sorption propertiesof Li2ZrO3based sorbents were investigatedby analyzing the phases and microstructure changes with the help ofthermogravimetric analysis, X-ray diffraction and scanning electronmicroscopy. The thermodynamic calculations were carried out basedon the second law of thermodynamics. Li2CO3/K2CO3-doped Li2ZrO3sorbentwith the composition of 36.23 wt % Li2CO3, 55.12wt % ZrO2and 8.65 wt % K2CO3wasconsidered to achieve excellent capability for high temperature CO2sorption and presented the maximum sorption rate at 525 °Cand 0.15 atm of CO2partial pressure. The sorbent keptrather stable for multicycles sorption and regeneration, and maintainedits original capacity during 12 cycle processes. There were threedistinct phases in the nonisothermal CO2sorption processwhile the main CO2sorption occurred during the secondphase. An improved iterative Coats–Redfern method was usedto evaluate nonisothermal kinetics of the CO2sorptionprocess, and the kinetic parameters were derived by the MATLAB model.The Fn nth-order reaction model predictedaccurately the main phases and differences in the activation energiesand the frequency factors for different sorbents in the sorption phasescorroborated different mechanism integral functions and reaction orders. [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]

Highlights: [•] Ni–Cu–Al catalyst for hydrogen production was synthesized by rising pH technique. [•] Experimental data were analyzed with non-stoichiometric thermodynamic calculation. [•] Catalyst deactivation due to carbon deposits in glycerol steam reforming was found. [•] Carbon removal was analyzed by TGA experiment during medium temperature oxidation. [•] Reforming was tested by separability kinetics of rate law and catalyst deactivation. [Copyright &y& Elsevier]

Abstract: The objective of this review is to analyze potential technologies and their baseline performance of producing hydrogen from catalytic steam reforming of biodiesel byproduct glycerol. High oxygen content and high impurity level of biodiesel byproduct glycerol, as well as the complex intermediates and high coking potential in its thermal degradation, make the modeling, design, and operation of glycerol steam reforming a challenge. Thermal decomposition characterization of biodiesel byproduct glycerol was covered, and the recent developments and methods for high-purity hydrogen production from glycerol steam reforming were illustrated. The thermodynamics constraint of water gas shift reaction can be overcome by the sorption-enhanced steam reforming process, which integrated catalytic steam reforming, water gas shift reaction and in-situ CO2 removal at high temperatures in a single stage reactor. The effectiveness of both the enhanced H2 production and the use of CO2 sorbents have been demonstrated and discussed. The technical challenges to achieve a stable high-purity hydrogen production by the sorption-enhanced steam reforming process included extending operation time, selecting suitable sorbents, finding a way for continuous reaction-regeneration of catalyst and sorbent mixture and improving process efficiencies. The continuous sorption-enhanced steam reforming of glycerol was designed by a simultaneous flow concept of catalyst and sorbent for continuous reaction-regeneration using two slow moving-bed reactors for high-purity hydrogen production and CO2 capture, and in this process, catalyst and sorbent were run in nearly fresh state for H2 production. The sorption-enhanced chemical-looping reforming was also demonstrated. The paper discusses some issues and challenges, along with the possible solutions in order to help in efficient production of hydrogen from catalytic steam reforming of biodiesel byproduct glycerol. [Copyright &y& Elsevier]

In this study, the continuous sorption-enhanced steam reforming of glycerol to high-purity hydrogen production by a simultaneous flow concept of catalyst and sorbent for reaction and regeneration using two moving-bed reactors has been evaluated experimentally. A Ni-based catalyst (NiO/NiAl2O4) and a lime sorbent (CaO) were used for glycerol steam reforming with and without in-situ CO2 removal at 500 °C and 600 °C. The simultaneous regeneration of catalyst and sorbent was carried out with the mixture gas of N2 and steam at 900 °C. The product gases were measured by a GC gas analyzer. It is obvious that the amounts of CO2, CO and CH4 were reduced in the sorption-enhanced steam reforming of glycerol, and the H2 concentration is greatly increased in the pre-CO2 breakthrough periods within 10 min both 500 °C and 600 °C. The extended time of operation for high-purity hydrogen production and CO2 capture was obtained by the continuous sorption-enhanced steam reforming of glycerol. High-purity H2 products of 93.9% and 96.1% were produced at 500 °C and 600 °C and very small amounts of CO2, CH4 and CO were formed. The decay in activity during the continuous reaction-regeneration of catalyst and sorbent was not observed. [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]

Abstract: H2 production from glycerol steam reforming by the Ni–Cu–Al, Ni–Cu–Mg, Ni–Mg catalysts was evaluated experimentally in a continuous flow fixed-bed reactor under atmospheric pressure within a temperature range from 450 to 650 °C. The catalysts were synthesized by the co-precipitation methods, and characterized by the elemental analysis, BET, XRD and SEM. The GC and FTIR were applied to analyze the products from steam reforming of glycerol. The coke deposited on the catalysts was measured by TGA experiments during medium temperature oxidation. The results showed that glycerol conversion and H2 production were increased with increasing temperatures, and glycerol decomposition was favored over its steam reforming at low temperatures. The Ni–Cu–Al catalyst containing NiO of 29.2 wt%, CuO of 31.1 wt%, Al2O3 of 39.7 wt% performed high catalytic activity, and the H2 selectivity was found to be 92.9% and conversion of glycerol was up to 90.9% at 650 °C. The deactivation of catalysts due to the formation and deposition of coke was observed. An improved iterative Coats–Redfern method was used to evaluate the non-isothermal kinetic parameters of coke removal from catalysts, and the results showed the reaction order of n = 1 and 2 in the Fn nth order reaction model predicted accurately the main phase in the coke removal for the regeneration of Ni–Mg and Ni–Cu–Al catalysts, respectively. [Copyright &y& Elsevier]

Abstract: About 10wt.% of glycerol can be produced during the conversion of vegetable oils or animal fats into biodiesel fuel by the transesterification process. To make use of glycerol and increase its values, H2 production from catalytic steam reforming of glycerol by Ni–Mg–Al based catalysts was evaluated experimentally in a fixed-bed reactor under atmospheric pressure within a temperature range of 450–650°C. The thermodynamic analysis was conducted by using a non-stoichiometric methodology based on the minimization of Gibbs free energy. The Ni–Mg–Al based catalysts were synthesized by the co-precipitation method with rising pH technique. The synthesized catalysts were characterized by the elemental analysis, BET, XRD and SEM methods. All the metals in the catalyst remained in oxide forms and the catalysts had the specific surface areas from 98.542 to 126.777m2/g for different compositions. The results showed that glycerol conversion and H2 selectivity were increased with increasing temperatures from 450 to 650°C. The formations of CH4 and CO in the glycerol steam reforming were almost negligible. Carbon formation in glycerol steam reforming was serious in low temperatures. The catalyst containing NiO of 24.1wt.%, MgO of 26.1wt.% and Al2O3 of 49.8wt.% performed appreciable catalytic activity, and the H2 selectivity was found to be 78.5% and conversion of glycerol was up to 88.0% at 650°C. The effects of the operating conditions including temperature, the ratio of steam to carbon (S/C), glycerol inlet concentration and flow rate of carrier gas on glycerol steam reforming by the optimized catalyst were tested. Based on a kinetic model assuming the power law with a first reaction order, the activation energy and the frequency factor for glycerol steam reforming by the Ni–Mg–Al based catalysts were calculated. [Copyright &y& Elsevier]

Abstract: In this paper, the pyrolysis characteristics of sucrose biomass were investigated in a tubular reactor at different temperatures and also using a thermogravimetric analyzer at the heating rate of 10°Cmin−1 from room temperature to 1200°C. The gas products in the pyrolysis process were measured using an Agillent 6890N GC analyzer. The results showed that the temperature greatly affected the product yields. The pyrolysis gas consisted of a major amount of CO, CO2, H2, and CH4, and its yield increased greatly with increasing temperature. Tars occurred mainly at 200–300°C under isothermal measurements in tubular reactor. The amounts of solid residue and tars decreased with increasing temperature. The presence of CaO responsible for the pyrolysis phase was shown to increase the conversion of sucrose and capture the CO2 produced. The kinetic analysis indicated that the reaction order model (first order) predicted accurately the conversion of 0.102–0.901 during the isothermal pyrolysis of sucrose in tubular reactor, and Arrhenius parameters and prediction of the pyrolysis time were obtained from isothermal kinetic results. [Copyright &y& Elsevier]

Abstract: New porous heterostructured nanohybrid of MgO–TiO2–Al2O3/montmorillonite has been successfully synthesized by an inflating, intercalation, and reassembling method under the ultrasonic vibration. The synthesized material was characterized by TGA–DTG, XRD, TEM and elemental analysis. The results showed that the material had a specific surface area of 156m2 g−1 with an average pore diameter of 2.68nm and pore volume of 0.6627cm3 g−1, and that the MgO, TiO2 and Al2O3 nanoparticles were introduced in the montmorillonite by the heat treatment of 500°C. It was found that the intercalation and deposition of mixed oxides nanoparticles expanded the basal spacing of montmorillonite, and the crystallites of the nanohybrids were assembled to form a heterostructured composite. [Copyright &y& Elsevier]

Abstract: In this study, the adsorption and photocatalytic reduction of toxic mercury(II) from aqueous solutions at different pH values were investigated with the synthesized TiO2 nanoparticles. The synthesized materials were tested and characterized by TEM, XRD and BET methods. The results showed that high purity anatase TiO2 nanoparticles with an average diameter of 9.10nm were produced by the acid catalyzed sol–gel method at 500°C, and the specific surface areas of synthesized TiO2 nanoparticles were in excess of 200m2 g−1. The experimental results showed that the removal of mercury(II) in aqueous solutions were increased with an increase of pH in the range of 3.0–7.0, and the conversion of mercury(II) removal was more than 65% by TiO2 nanoparticles after 30min under UV illumination. Kinetics models of the adsorption and photocatalytic reduction were also studied by the experimental measurements. [Copyright &y& Elsevier]

Abstract: The adsorption and photocatalytic reduction of toxic Hg(II) in aqueous solutions were investigated at different temperatures using synthesized TiO2 nanoparticles and TiO2/montmorillonite. The synthesized materials were tested by TGA, BET, TEM and XRD methods. High-purity anatase TiO2 nanoparticles with an average diameter of 9.10nm were produced by the acid catalyzed sol–gel method at 500°C, and the specific surface area of synthesized TiO2 nanoparticles was in excess of 200m2 g−1. TiO2/montmorillonite was prepared by slurry reactions, resulting in average pore size of 3.10nm with TiO2 nanoparticles on the montmorillonite surface. TiO2/montmorillonite with a 22wt% TiO2 load exhibited a specific surface area of 239m2 g−1. Removal of Hg(II) in aqueous solutions at 25, 35 and 45°C in darkness and under UV illumination showed that the photocatalytic reduction of Hg(II) increased with increasing temperature, and a decline in adsorption was observed for a rise in temperature from 25 to 45°C, following the exothermicity of the adsorption process. The adsorption behavior of Hg(II) on TiO2 nanoparticles was well described by the Langmuir isotherm model, and the rates were simulated by the Elovich equation. A first-order reaction model was used to simulate the photocatalytic reduction reaction of Hg(II) in aqueous solutions, and a good fit was obtained with the experimental data. [Copyright &y& Elsevier]

Abstract: The gas–solid reaction and breakthrough curve of CO2 capture using calcium oxide sorbent at high temperature in a fixed-bed reactor are of great importance, and being influenced by a number of factors makes the characterization and prediction of these a difficult problem. In this study, the operating parameters on reaction between solid sorbent and CO2 gas at high temperature were investigated. The results of the breakthrough curves showed that calcium oxide sorbent in the fixed-bed reactor was capable of reducing the CO2 level to near zero level with the steam of 10vol%, and the sorbent in CaO mixed with MgO of 40wt% had extremely low capacity for CO2 capture at 550°C. Calcium oxide sorbent after reaction can be easily regenerated at 900°C by pure N2 flow. The experimental data were analyzed by shrinking core model, and the results showed reaction rates of both fresh and regeneration sorbents with CO2 were controlled by a combination of the surface chemical reaction and diffusion of product layer. [Copyright &y& Elsevier]

Abstract: Hydrogen production from steam reforming of glycerol in a fluidized bed reactor has been simulated using a CFD method by an additional transport equation with a kinetic term. The Eulerian–Eulerian two-fluid approach was adopted to simulate hydrodynamics of fluidization, and chemical reactions were modelled by laminar finite-rate model. The bed expansion and pressure drop were predicted for different inlet gas velocities. The results showed that the flow system exhibited a more heterogeneous structure, and the core-annulus structure of gas–solid flow led to back-mixing and internal circulation behaviour, and thus gave a poor velocity distribution. This suggests the bed should be agitated to maintain satisfactory fluidizing conditions. Glycerol conversion and H2 production were decreased with increasing inlet gas velocity. The increase in the value of steam to carbon molar ratio increases the conversion of glycerol and H2 selectivity. H2 concentrations in the bed were uneven and increased downstream and high concentrations of H2 production were also found on walls. The model demonstrated a relationship between hydrodynamics and hydrogen production, implying that the residence time and steam to carbon molar ratio are important parameters. The CFD simulation will provide helpful data to design and operate a bench scale catalytic fluidized bed reactor. [ABSTRACT FROM AUTHOR]

Abstract: Steam reforming of the crude glycerol by-product of a biodiesel production plant has been evaluated experimentally at atmospheric pressure, with and without in situ CO2 sorption, in a continuous flow fixed-bed reactor between 400°C and 700°C. The process outputs were compared to those using pure glycerol. Thermodynamic equilibrium calculations were used to assess the effect on the steam reforming process of the main crude impurities (methanol and four fatty acid methyl esters). The crude glycerol and steam conversions and the H2 purity reached 100%, 11% and 68%, respectively at 600°C. No CH4 was found at and above 600°C. Steam reforming of crude glycerol with in situ CO2 removal is shown to be an effective means of achieving hydrogen purity above 88% in pre-CO2 breakthrough conditions. [Copyright &y& Elsevier]

Abstract: The wet Flue Gas Desulfurization in the coal-fired power plants has been the most widely used because of its high SO2 removal efficiency, reliable and low utility consumption. The difficulty in the prediction of the SO2 removal from flue gas is that the performance of the system is related to a wide range of variables. In this paper, the SO2 was removed by absorbing and reacting SO2 with limestone slurry, and limestone scrubbing was accomplished in a spraying reactor. Experimental investigations for effects of different operating variables on the SO2 removal showed the reasonable process parameters such as the pH value of the liquid phase, droplet size of the spray and the flow rates of liquid and gas. The removal process was analyzed using the two-film theory of mass-transfer. Both the liquid and gas side resistances were important, and the absorption rate was controlled by a combination of both gas-film and liquid-film diffusion controls. A model of external mass-transfer with the effects of a chemical enhancement factor and sulfite concentration in the liquid phase was developed for the prediction of the SO2 removal efficiency, and the calculated values were in reasonable agreement with the experimental values. The study is considered as the one-dimensional prediction of SO2 removal and low-cost application of limestone slurry for commercial FGD technology. [Copyright &y& Elsevier]

Catalytic steam reforming of glycerol for H2 production has been evaluated experimentally in a continuous flow fixed-bed reactor. The experiments were carried out under atmospheric pressure within a temperature range of 400–700°C. A commercial Ni-based catalyst and a dolomite sorbent were used for the steam reforming reactions and in situ CO2 removal. The product gases were measured by on-line gas analysers. The results show that H2 productivity is greatly increased with increasing temperature and the formation of methane by-product becomes negligible above 500°C. The results suggest an optimal temperature of ∼500°C for the glycerol steam reforming with in situ CO2 removal using calcined dolomite as the sorbent, at which the CO2 breakthrough time is longest and the H2 purity is highest. The shrinking core model and the 1D-diffusion model describe well the CO2 removal under the conditions of this work. [Copyright &y& Elsevier]

Abstract: The pyrolysis of the crude glycerol from a biodiesel production plant was investigated by thermogravimetry coupled with Fourier transform infrared spectroscopy. The main gaseous products are discussed, and the thermogravimetric kinetics derived. There were four distinct phases in the pyrolysis process of the crude glycerol. The presence of water and methanol in the crude glycerol and responsible for the first decomposition phase, were shown to catalyse glycerol decomposition (second phase). Unlike the pure compound, crude glycerol decomposition below 500K leaves behind a large mass fraction of pyrolysis residues (ca. 15%), which eventually partially eliminate in two phases upon reaching significantly higher temperatures (700 and 970K, respectively). An improved iterative Coats–Redfern method was used to evaluate non-isothermal kinetic parameters in each phase. The latter were then utilised to model the decomposition behaviour in non-isothermal conditions. The power law model (first order) predicted accurately the main (second) and third phases in the pyrolysis of the crude glycerol. Differences of 10–30kJ/mol in activation energies between crude and pure glycerol in their main decomposition phase corroborated the catalytic effect of water and methanol in the crude pyrolysis. The 3-D diffusion model more accurately reproduced the fourth (last) phase, whereas the short initial decomposition phase was poorly simulated despite correlation coefficients ca. 0.95–0.96. The kinetics of the 3rd and 4th decomposition phases, attributed to fatty acid methyl esters cracking and pyrolysis tarry residues, were sensitive to the heating rate. [Copyright &y& Elsevier]

Abstract: Five catalysts were evaluated for removal of tar components in high temperature fuel gas cleaning. 1-Methylnaphthalene was chosen as a model of the tar components. The NiMo catalyst having the highest surface area exhibited the highest activity of tar removal among the five catalysts. The effects of reaction temperature and space velocity on tar removal were studied in the range of 250–650°C and 3000–9000h−1, respectively. A lumped kinetic model was developed to describe the removal process. A sequential method to estimate the rate constants in the lumped kinetic model was adopted, which greatly simplifies the data treatments. Kinetic constants and activation energies were determined by a nonlinear regression program. The results showed that the predicted yields were very close to the experimental ones. [Copyright &y& Elsevier]

Seven sorbents for alkali metal removal from high-temperature coal-derived gas were tested in a fixed-bed reactor at 840 °C. NaCl was used as an alkali metal model compound. It was found that five sorbents, including the second grade alumina, bauxite, kaoline, acidic white clay and activated Al2O3, present higher adsorption efficiency, and activated Al2O3 shows the highest capture capacity. In capturing time of 3 h, the adsorption efficiency and sodium content absorbed by activated Al2O3 are, respectively, up to 98.20% and 6.20 mg/g. The tests indicate the removal of alkali metal vapor with activated Al2O3 is a physical adsorption process in the absence of moisture. The adsorption kinetics of activated Al2O3 with NaCl indicates that there are critical times at which adsorption constants begin to change. The critical time is at about 4–5 h. [Copyright &y& Elsevier]

[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]

The evaluation of thermochemical characteristics and the development of kinetic model for pyrolysis of waste biomass are more challenging. In this study, the mass losses, intermediates evolved and products formed during pyrolysis of waste wood biomass were determined by coupling DSC/TGA-DTG/GC-MS/FTIR to improve the understanding of conversion processes and decomposition characteristics. The improved non-isothermal kinetics method was proposed by introducing the function of mechanisms, the activation energies and pre-exponential factors were estimated iteratively by regression to enhance modeling accuracy. The results indicated the gases of CO, CO 2 , CH 4 , H 2 and the liquids of N-containing organics, esters, ketons and carboxylic acids were the most dominated products evolved. The pyrolysis of waste wood biomass could be divided into three phases, and with the increase of heating rates, the caloric requirement for pyrolysis was greatly increased. The random nucleation and one-dimensional diffusion predicted accurately the main (second) and third phases in the pyrolysis of waste wood biomass and waste camphor presented lower activation energies than waste bamboo. [Display omitted] • Pyrolysis of waste wood is studied by DSC/TG-DTG/GC-MS/FTIR. • Mass loss and energy requirement of pyrolysis are determined by DSC/TGA-DTG. • Gases and liquids of pyrolysis are analyzed by FTIR, GC-MS. • Improved kinetics method is derived to enhance the accuracy of model. [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]

• Non-isothermal pyrolysis of bituminous coal were studied by coupling TG-MS/DSC. • Improved Coats-Redfern kinetics method to improve kinetics accuracy was developed. • Catalytic steam-assisted pyrolysis of bituminous coal by CaO was enhanced. • The addition of CaO and water feeding rates significantly promoted the H 2 production. The non-isothermal characteristics and pyrolysis kinetics of bituminous coal at different heating rates of 10, 20, and 30 ℃/min were studied by coupling TG-MS/DSC techniques. A fixed-bed reactor was used to investigate the coal-CaO-H 2 O reactions to understand hydrogen production and the effects of CaO under different water feeding rates. The pyrolysis phase, the maximum mass loss rate, the characteristic peak temperature, and the release of the main volatile gases were studied. Based on the improved Coats-Redfern method by introducing the function of Q (E/RT), the activation energies and pre-exponential factors of non-isothermal pyrolysis of bituminous coal were estimated iteratively by regression to enhance their accuracy. The values of E were calculated as 22, 22, 19 kJ/mol in the first stage, 67, 75, 78 kJ/mol in the second stage, 114, 96, 133 kJ/mol in the third stage at the heating rates of 10, 20, and 30 ℃/min. Finally, the concentration and selectivity of gaseous products from the pyrolysis of bituminous coal were studied. The concentrations of H 2 , CO, and CO 2 in the gas products increased with the addition of CaO and the increase of water feeding rate. Besides, the concentration of CH 4 increases with the increase of water feeding rate but decreases significantly with the addition of CaO. It is also worth noting that the pyrolysis process was enhanced by CaO addition to in-situ CO 2 captured and catalytic cracking reactions at the initial stage of the pyrolysis process. [ABSTRACT FROM AUTHOR]

In this study, a widely applicable hydrogen production system based on solid oxide electrolysis cells (SOEC) is proposed for industrial waste heat recovery. When the thermoneutral mode is employed to maintain the isothermal state of SOEC, the performances of a single SOEC and the system are comprehensively analyzed respectively. The results show that an increase in SOEC temperature leads to a rise in current density, power, hydrogen production, and inlet steam flow rate. Conversely, as the steam conversion rate rises, these parameter values decrease. A set of 3D performance maps are provided to illustrate parameter variations. The thermoneutral data of SOEC can be utilized in various systems, not limited to the proposed one. Increasing the steam conversion rate improves energy efficiency and energy consumption performance of the system, but decreases the inlet steam flow rate and production capacity. A temperature rise improves the inlet steam flow rate and production capacity but has a slight effect on energy efficiency and energy consumption performance. When the inlet steam flow rate is 50 kg/h and the temperature is 800 °C, the system achieves a maximum hydrogen production of 2.473 kmol/h. The proportion of waste heat supply to total energy consumption fluctuates between 15.5 % and 20.6 % across the operation conditions. It shows great potential for hydrogen production utilizing industrial waste heat. Meanwhile, the stack consumes almost all of the electrical energy. • A SOEC system is proposed that utilizes industrial waste heat. • The SOEC operates in the thermoneutral mode. • The performance maps illustrate parameter variations of a single cell. • The system can produce hydrogen, oxygen, and hot water. [ABSTRACT FROM AUTHOR]

• A life cycle analysis on recycling and secondary use of lithium-ion batteries. • Based on the recycling in China, the LCA of different methods has been established. • Compared to other recovery, the secondary use has the lowest environmental impact. • Secondary use has the greatest impact on assessment results in dynamic situations. With the rapid development of the global new energy vehicle industry, how to minimize the environmental impact of the recovery has become a common concern and urgent concern. China is a major production and consumption market for electric vehicles, there are no specific and extensive resource and environmental assessment system for batteries. In this paper, the retired Electric vehicles lithium-ion batteries (LIBs) was the research object, and a specific analysis of the recycling treatment and gradual use stages of power batteries were based on life cycle assessment. Different battery assessment scenarios were established according to the development of battery recycling in China. The results showed that the secondary use has the optimal performance compared to the full-component physical, pyrometallurgical and hydrometallurgy recycling. The results showed that direct recycling has a GWP of 0.037 kg-CO 2 eq·kg LIB-1, which is lower than others. Secondary use of LIB accounts for the most emission reductions with Global warming (GWP) as 12.134 kg-CO 2 eq·kg LIB-1. The secondary use has the greatest impact on the assessment results, especially in dynamic scenarios. Through a comprehensive comparison of different recycling technologies, the secondary use, increasing the recycling rate, reducing resource, energy consumption and pollution emissions. [ABSTRACT FROM AUTHOR]

This paper proposes novel microencapsulated phase change material slurries (MPCSs) as both the energy storage media and heat transfer fluids. The flow and heat transfer characteristics of MPCSs have been experimentally investigated. A series of experiments were conducted in laminar, transition and turbulent flow conditions for MPCSs in a circular tube under constant heat flux, respectively. The results of pressure drop measurements showed that transportation costs of slurries were close to pure water. The heat transfer experiments demonstrated that proposed MPCSs could enhance the heat transfer performance as the heat transfer fluids for thermal system applications in comparison with pure water. The average enhancement percentages of the Nusselt number were 23.9%, 20.5% and 9.1% for MPCS of 5 wt%, and enhancement of the Nusselt number was achieved when phase change material in the microcapsules were in solid, solid/liquid and liquid states, respectively. However, heat transfer enhancement of MPCS depends on the following combination factors: the slurry concentration, the flow rate, the pumping power and the heating rate. Importantly, the phase change process must be carefully controlled in the heat transfer test section with above combination factors in order to take advantages of MPCS over pure water. [ABSTRACT FROM AUTHOR]

• The performance of a scroll compressor under two operating conditions was assessed. • The optimal OCR values for the two conditions were found to be 3.5% and 5.5% respectively. • Optimal air injection pressures on the two conditions were 0.27 and 0.45 Mpa respectively. • An empirical formula for the heating capacity as a function of vapor injection coefficient and OCR was derived. Heat pump air conditioning (AC) based on a vapor injection scroll compressor has proven to be a promising solution to the current driving range limitations of electric vehicles (EV), especially in freezing climates. The lubricating oil inside the compressor is critical in promoting sealing and cooling, but it also exhibits a low performance under extreme working conditions. In addition, the effects of oil retention on compressor behavior and the optimal charge amount at low temperatures require further investigation. This paper adapts a second refrigerant calorimeter method to study the effects of different injection pressures on compressor performance. The results indicate that the mass flow rate, discharge temperature, compressor power consumption, and volume efficiency performance would increase significantly compared with the non-vapor injection (NV). The effects of oil circulation rate (OCR) on the performance of a vapor injection scroll compressor under two low-temperature operating conditions were also studied. The flow and heat transfer parameters were analyzed, and heating capacity was found to increase and decrease with enlarged OCR. The highest coefficient of heating performance (COP) was obtained at an OCR of 3.5% with a vapor injection pressure of 0.28 MPa. Compared with the non-vapor injection (NV) condition, the heating capacity and COP of the system at the same pressure of 0.28 MPa were increased by 6.2% and 1.8%, respectively. At extremely low temperatures, the heating capacity and COP were maximized at an OCR of 5.5% and an injection pressure of 0.45 MPa. Compared with that of NV, the heating capacity and COP of the heating system at the injection pressure were increased by 6.7% and 2.6%, respectively. The compressor discharge temperature decreased obviously with the increasing OCR. An empirical formula was devised to calculate the heating capacity for varying OCR. [ABSTRACT FROM AUTHOR]

Photovoltaic (PV) power generation coupled with proton exchange membrane (PEM) water electrolysis favors improving the solar energy utilization and producing green hydrogen. But few systems proposed focus on achieving all-day stable hydrogen production, which is important for the future large-scale hydrogen utilization. Herein, a PV-Battery-PEM water electrolysis system for hydrogen production was constructed. An energy management strategy (EMS) was proposed to achieve the goal of all-day stable hydrogen production, improve energy utilization efficiency and reduce light discard rate. The PV power generation system, battery system and PEM electrolyzer for hydrogen production system were first established by Matlab/Simulink platform. Then, the overall PV-Battery-PEM electrolyzer system for hydrogen production was constructed, and the effectiveness of EMS was verified. The energy efficiency of the system under different working conditions with and without battery for energy storage was analyzed. The results show that the proposed energy management strategy can meet the purpose of all-day stable hydrogen production. Under the same working conditions, the energy efficiency of the system with battery for energy storage increases by 2–4% compared with the system without battery for energy storage, which indicates that the addition of energy storage can improve the energy utilization and reduce the light discarding. [Display omitted] [ABSTRACT FROM AUTHOR]