Reforming Of Glycerol Research Articles

Robust power-law kinetic model for the autothermal reforming of glycerol over metal oxide catalysts

The kinetics of autothermal reforming of glycerol in a tubular fixed-bed reactor using a nickel-based catalyst supported over Ce0.5Zr0.33Gd0.16O2−δ has been investigated for the first time for hydrogen production. The study was conducted using steam-to-glycerol ratio (6, 9, 12), oxygen-to-glycerol ratios (0.2, 0.5, 0.8) and weight of catalyst/glycerol molar ratio (W/FG0) of 5.05, 6.55 and 8.06 kgcatalyst h kmol G −1 at atmospheric pressure and reaction temperature in the range (723–873 K). An integral analysis combined with a real-valued genetic algorithm optimizer was used to estimate rate model parameters. This analysis resulted in a power law rate model with an apparent activation energy of 53.3 kJ mol−1 and reaction orders 0.16, 0.74 and − 0.49 with respect to glycerol, oxygen and steam partial pressures. The model predicted conversions and the experimentally obtained conversions exhibited close resemblance with an average absolute deviation of 7%.

K-Promoted Pt-Hydrotalcite Catalyst for Production of H2 by Aqueous Phase Reforming of Glycerol

The effect of potassium on the Pt supported hydrotalcite catalyst (Pt-KHT) was investigated in the aqueous phase reforming (APR) of glycerol for the efficient production of H2. Pt-KHT was prepared by the sequential incipient wetness impregnation method where impregnation of K was carried out first followed by incorporation of Pt. The catalyst was characterized by XRD, SEM, HRTEM, XPS, FTIR, TPR, and TPD. The TEM images of the catalyst showed highly dispersed Pt-species supported on hydrotalcite with needle-like structure. The addition of potassium (K+) increases the basicity of the Pt-KHT catalyst and enhances the production of hydrogen through APR of glycerol. The gaseous product formed over Pt-KHT at 250 °C was 99.4% which is higher than that obtained of Pt-HT catalyst, and an H2 selectivity of 67.4% was achieved over Pt-KHT after 3 h of reaction.

Production of renewable hydrogen through aqueous-phase reforming of glycerol over Ni/Al2O3[sbnd]MgO nano-catalyst

In this study, a series of Ni nano-catalysts supported on Al2O3 and MgO were prepared through the co-precipitation technique. Effects of the Al/Mg ratio on physicochemical characteristics of Ni/Al2O3MgO catalysts were examined. Moreover, catalytic performance was investigated in order to determine the optimum catalyst for H2 production in aqueous phase reforming (APR) of glycerol. It was revealed that, the APR activity of synthesized catalysts strongly depended on the aforementioned ratio. In addition, it was observed that, the catalytic activity of Ni/MgO and Ni/Al2O3 samples were both lower than that of the corresponding mixed oxide supports. Furthermore, it was shown that, amongst the compositionally different prepared mixed oxide materials, the respective catalytic activities increased through enhancing of the Al/Mg ratio. It was demonstrated that the Ni/Al2Mg1 catalyst possessed highest catalytic activity of 92% glycerol conversion and selectivity towards hydrogen production of 76%. Ultimately, it was concluded that, the APR activity lowered in the following order: Ni/Al2Mg1 > Ni/Al1Mg1 > Ni/Al1Mg2 > Ni/Al > Ni/Mg for the understudied synthesized materials.

Hydrogen production by glycerol reforming in a fixed-bed reactor

ABSTRACTHydrogen production from the steam-reforming reaction of glycerol was studied over charcoal as catalyst in a tubular fixed-bed reactor. The results showed that charcoal was a novel kind of catalyst, which not only had an active effect on the reforming process, but can decrease the cost of production. The optimum conditions were obtained at 800°C, S/C of 4, WHSV of 1.5 h−1. Hydrogen yield and potential hydrogen yield were up to 75.12% and 84.31%, as well as the carbon conversion reached 89.08% at the optimum conditions. The results of SEM and TGA indicated that there was polymerization and polycondensation of glycerol still in steam-reforming process.

Hydrogen production from glycerol reforming: conventional and green production

Abstract The use of biomass to produce transportation and related fuels is of increasing interest. In the traditional approach of converting oils and fats to fuels, transesterification processes yield a very large coproduction of glycerol. Initially, this coproduct was largely ignored and then considered as a useful feedstock for conversion to various chemicals. However, because of the intrinsic large production, any chemical feedstock role would consume only a fraction of the glycerol produced, so other options had to be considered. The reforming of glycerol was examined for syngas production, but more recently the use of photocatalytic decomposition to hydrogen (H2) is of major concern and several approaches have been proposed. The subject of this review is this greener photocatalytic route, especially involving the use of solar energy and visible light. Several different catalyst designs are considered, together with a very wide range of secured rates of H2 production spanning several orders of magnitude, depending on the catalytic system and the process conditions employed. H2 production is especially high when used in glycerol-water mixtures.

Hydrogen production by crude glycerol steam reforming over Ni–La–Ti mixed oxide catalysts

The production of H2-rich gaseous mixtures from steam reforming of crude glycerol was investigated on ternary Ni–La–Ti catalysts. Ni–La–Ti mixed oxides containing 15 wt% of Ni and a La/Ti atomic ratio of 1 were prepared by a coprecipitation method and characterized by a variety of physical and spectroscopic techniques. Samples were calcined in air at 700 °C or 850 °C for 2 h. Ni–La–Ti samples calcined at 700 °C (NiLaTi700) showed a well-defined NiO phase and an amorphous La–Ti mixed oxide, while those calcined at 850 °C (NiLaTi850), exhibited two well defined phases of NiO and LaTiO3 perovskite, respectively. NiO was completely reduced to metallic Ni on both solids under pure H2 at 650 °C and the resulting Ni0 phase remained as a separate phase under the steam reforming conditions. Standard catalytic tests for the steam reforming of glycerol were performed at 500 °C or 650 °C by feeding the fixed-bed tubular reactor with a crude glycerol:water solution containing 30 wt% glycerol. The best results were achieved on NiLaTi700 at 650 °C, obtaining H2 yields and H2/CO2 molar ratios close to the theoretical values predicted by the steam reforming reaction stoichiometry. A slight activity decay was observed on NiLaTi700 with the progress of the reaction, probably reflecting the formation of small amounts of coke.

Cd-doped SnO2/CdS heterostructures for efficient application in photocatalytic reforming of glycerol to produce hydrogen under visible light irradiation

A series of mixed oxide (CdySn(1-y)O2) were synthesized by Pechini method followed by ion exchange with sulfide ions and heat treatment in nitrogen atmosphere to reach Cd-doped SnO2 and binary (Cd-SnO2/CdS) and ternary (Cd-SnO2/CdO/CdS and SnO2/CdO/CdS) composites. These materials have demonstrated able to absorb visible light and some of them are actives in photocatalytic reforming reaction of glycerol aqueous solution to produce hydrogen. The materials obtained in each step of the synthesis were characterized using different techniques (XRD, Raman, DRS, SEM and EDX). The influence of the calcination temperature in the ion exchange step, as well as the cadmium content in the formation of oxides and composites were investigated. A type II heterostructure, Cd(7%)-SnO2/(CdS)0.3, was obtained when the start solution had the same amount of cadmium and tin and this composite has demonstrated the best photocatalytic activity in hydrogen production, around 290 μmol g−1 h−1. This value is very close to the obtained with commercial CdS, but with a great advantage, it has a lower content of cadmium, being less toxic.

Kinetics of hydrogen production by the autothermal reforming of crude glycerol over modified nickel supported catalyst

In this work, the kinetics of autothermal reforming (ATR) of synthetic crude glycerol (CG) to produce renewable hydrogen was studied over nickel catalyst supported on promoted cerium-zirconium carrier (5% Ni/CeZrCa) in a temperature range of 500–650°C, steam-to-carbon (S/C) range of 1.6–3.6, oxygen-to-carbon (O/C) range of 0.05–0.2 and weight hourly space range of 0–158.2gcatmin/mol C. Synthetic crude glycerol composed of pure glycerol, methanol, soap, free fatty acids and ashes was used in this work. A kinetic region free of heat and mass transfer limitations was established by varying catalyst particle size and inlet flow rate. The stability of the catalyst was also established in an extended period run for 15h time on stream experiment. The estimated activation energy of 93.7kJ/mol with reaction orders of 1, 0.5 and 2 for synthetic crude glycerol, steam and oxygen, respectively, were obtained for this reaction. The developed power law model was −rA=2.09×1011e(−937008.314T)PA1PB0.5PC2 with 95% predictability.

Sustainable Production of High-Purity Hydrogen by Sorption Enhanced Steam Reforming of Glycerol over CeO2-Promoted Ca9Al6O18–CaO/NiO Bifunctional Material

The present work investigates the sustainable production of high-purity hydrogen through sorption enhanced steam reforming of glycerol (SESRG) over Ca9Al6O18–CaO/xNiO (x = 15, 20, and 25 wt %) and Ca9Al6O18–CaO/20NiO–yCeO2 (y = 5, 10, and 15 wt %) bifunctional catalyst-sorbent materials. A wet mixing method involving limestone acidification coupled with two-step calcination was employed to prepare the bifunctional materials. Cyclic carbonation/calcination tests revealed that the bifunctional materials promoted with 10 and 15 wt % of CeO2 possessed an excellent CaO conversion (97% in both cases) and a remarkable cyclic stability (up to 15 cycles). This was mainly attributed to the thin shell-connected structure formed by the addition of CeO2 and the oxygen mobility characteristic of CeO2. The use of Ca9Al6O18–CaO/xNiO materials in five consecutive SESRG/regeneration cycles revealed that they suffered from fast deactivation mainly due to CaO sintering and coke deposition. Despite the high H2 purity obtained...

Preparation and characterization of metals supported on nanostructured TiO2 hollow spheres for production of hydrogen via photocatalytic reforming of glycerol

Nanostructured TiO2 hollow spheres (THS) were prepared via a simple hydrothermal method with titanium butoxide, ethanol, urea, and ammonium sulphate. The effects of Ti/ethanol, and reflux temperature on the morphological properties of the nanostructured THS were investigated. An impregnation method was subsequently employed to load metals such as Cu, Co, Cr, Ag, and Ni on the optimized THS, followed by calcination in H2/N2 at 450°C for 4h. The morphological properties of the prepared samples were characterized by Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and ultraviolet-visible spectroscopy (UV/vis). The SEM and TEM pictures showed that the Ti/ethanol ratio of 1:10 resulted in the formation of uniform hollow spheres. The XRD spectre revealed that phase transformation took place as the reflux temperature was increased, with pure anatase TiO2 hollow spheres being formed at 200°C. The BET surface areas of the calcined photocatalysts were in the range of 80.6–116m2/g−1. The UV/vis spectra of the photocatalysts showed that loading of transition metals reduced the band gap of the THS. The activities of the prepared catalysts were tested for hydrogen production via photocatalytic reforming of glycerol under solar irradiation. The improved hydrogen evolution from photocatalytic reforming of glycerol was attributed to: the high surface area which enhanced the adsorption of glycerol onto the surface of photocatalysts; high crystallinity and the reduced band gap which improved the solar light harvesting; the hollow chamber within the TiO2 spheres which produced multiple reflection of the light harvested, thus producing efficient electron/hole pair formation; and the detailed composition of the solids retarded the electron/hole recombination by trapping the electrons generated during the photo excitation of the photocatalysts, and thereby promoted their activity.

Packed bed reactor modeling of the catalytic auto-thermal reforming of synthetic crude glycerol

Modeling and simulation studies of synthetic crude glycerol auto-thermal reforming were performed in a catalytic packed bed reactor over a 5wt% Ni/CeZrCa catalyst. The numerical model comprised of two-dimensional material and energy balance equations and an in-house developed power law kinetic rate model. The model was validated against experimental data and a close agreement between the predicted and experimentally measured values was obtained with an average absolute deviation of <9%. Also, it was found that for the set of conditions and reactor dimensions used for this study, the effect of the axial dispersion term on the glycerol conversion was negligible. This effect is expected to be more pronounced at a larger scale and under actual operating conditions and therefore should not be neglected.

Hydrogenolysis of glycerol with in-situ produced H2 by aqueous-phase reforming of glycerol using Pt-modified Ir-ReOx/SiO2 catalyst

We found that Pt-modified Ir-ReOx/SiO2 acted as an effective catalyst for aqueous phase reforming (APR) and selective C-O hydrogenolysis of glycerol without external hydrogen sources at low temperature of 463K, and that 0.5wt% loaded Ir-ReOx/SiO2 (Pt(0.5)-Ir-ReOx/SiO2) provided 1,2-propanediol (1,2-PrD) and acetol in high total yield of 53% at 81% conversion. The initial activity (TOFinitial) over Pt(0.5)-Ir-ReOx/SiO2 at 463K was estimated to be 13h−1. Pt-Ir alloy and Ir-ReOx species in Pt-Ir-ReOx/SiO2 are main active species for APR and selective C-O hydrogenolysis, respectively, and the high yield can be achieved by balancing the APR and hydrogenolysis activities through the optimization of Pt and Ir-ReOx molar ratio.

Thermodynamic Analysis of Autothermal Reforming of Synthetic Crude Glycerol (SCG) for Hydrogen Production

This study presents the thermodynamic modelling of hydrogen production from autothermal reforming of synthetic crude glycerol using the Peng-Robinson Stryjek-Vera thermodynamic model and Gibbs free energy minimization approach. In order to simulate the typical crude glycerol, a solution was prepared by mixing glycerol, methanol, soap, and fatty acids. The equilibrium compositions of the reforming gas were obtained and the impacts of the operating temperature, steam to crude glycerol ratio (S/SCG), and oxygen to crude glycerol ratio (O/SCG) on hydrogen production were investigated. Under isothermal conditions, the result showed that maximum hydrogen production is favoured at conditions of high temperatures, high S/SCG, and low O/SCG ratio. However, under thermoneutral conditions where no external heat is supplied to the reformer, results indicate that high hydrogen yield is realised at conditions of high temperatures, high S/SCG and high O/SCG ratio. Furthermore, it was concluded that under thermoneutral condition, steam to SCG ratio of 3.6, oxygen to SCG ratio of 0.75, and adiabatic temperature of 927 K yields maximum hydrogen.

Synthesis of jet fuel rang cycloalkane from isophorone with glycerol as a renewable hydrogen source

For the first time, 1,​1,​3-​trimethyl-cyclohexane (a jet fuel range cycloalkane) was synthesized by coupling the aqueous phase reforming (APR) of glycerol and the hydrodeoxygenation (HDO) of isophorone which can be obtained from lignocellulose. Among the investigated catalysts, Pt/Al2O3 was found to be the most active for the production of 1,​1,​3-​trimethyl-cyclohexane with the hydrogen which was in-situ generated by the APR of glycerol. Over it, high carbon yield (67.0%) of 1,​1,​3-​trimethyl-cyclohexane can be achieved at 533K in the absence of external hydrogen. The excellent performance of Pt/Al2O3 catalyst can be explained because Pt is highly active for both APR and HDO reactions. Besides glycerol, many other lignocellulose derived polylols (such as ethylene glycol, xylitol and sorbitol) and methanol can also be used as renewable hydrogen source for the HDO of isophorone. As a potential application, the 1,​1,​3-​trimethyl-cyclohexane as obtained can be blended into the conventional jet fuels to improve their volumetric heat values.

Influence of MgO content as an additive on the performance of Ni/MgO[sbnd]SiO2 catalysts for the steam reforming of glycerol

Ni catalysts supported on MgOSiO2 were assessed in the steam reforming reaction of glycerol for the study of the H2 production and carbon deposition with different MgO contents as additives. The catalysts were prepared with commercial SiO2 by the aqueous impregnation method and characterized by energy dispersive X-ray spectroscopy, specific surface area, X-ray diffraction, thermogravimetric analysis, X-ray diffraction in situ with O2, temperature programmed reduction with H2, X-ray diffraction in situ with H2, temperature programmed desorption with H2 and scanning electron microscopy. The glycerol steam reforming reaction took place at 600 °C for 5 h, with a water/glycerol molar ratio of 12/1 at 5 mLh−1. N2 was used as the carrier gas. The characterization of the samples showed the interaction of Ni with the support increases with the MgO addition, due to the formation of a NiMg silicate hydrate and MgNiO2 solid solution; as a result, both metallic area and dispersion also increased. Catalytic results showed similar gaseous products yields (H2, CH4, CO and CO2) for mixed-matrix catalysts, however, a lower carbon deposition on 10 wt%Ni catalyst supported on 30 wt%MgOSiO2 was observed.

High purity hydrogen production from sorption enhanced chemical looping glycerol reforming: Application of NiO-based oxygen transfer materials and potassium promoted Li2ZrO3 as CO2 sorbent

Ni based oxygen transfer materials (OTMs) and Li2ZrO3 based sorbent have been synthesized for their potential use in a sorption enhanced chemical looping steam reforming (SE-CLSR) process. Ni based OTMs were firstly tested under chemical looping steam reforming (CLSR) process and the gaseous products with temperature variety during this process were measured and analyzed. Experimental results indicated that both of the OTMs exhibited good activities and stability during multiple glycerol reduction-air oxidation cycles towards H2 production. The desired maximum hydrogen selectivities of 87.9% and 84.7% were obtained for NiO/NiAl2O4 and NiO/ZrO2 for steam to carbon ratio of 3 at 550°C. The fuel feed step of reduction process could be divided into two periods with the OTMs possessing a dual function of oxygen carrier and catalyst. The decrease of conversions and selectivity for both OTMs was mainly due to the coke deposition, which reduced the catalytic effect in the reforming reaction as well as the oxygen transfer effect in the reduction reaction. Sorption enhanced chemical looping steam reforming (SE-CLSR) process for H2 production with in-situ CO2 removal was carried out with OTM/sorbent ratio of 1 and multi-cyclic reaction/regeneration processes under 550°C/850°C with a steam/carbon ratio of 3 was also achieved. H2 purity were both enhanced by the two OTMs and sorbent in SE-CLSR. Therefore, it is possible to utilize oxygen from NiO and steam to oxidize glycerol, while enhancing the water-gas-shift reaction by capturing CO2 at the same time.

Glycerol steam reforming over noble metal nanocatalysts

The precious metal nanocatalysts (Rh, Ru, Pt, Ir) prepared over promoted Al2O3 with MgO were evaluated in steam reforming of glycerol for the production of hydrogen. Different characterization techniques (TEM, SEM, BET, TPR, TPO and H2S chemisorption) were employed to determine the physicochemical properties of the prepared samples. The chemisorption of H2S showed the crystallite sizes of the active metals were in the range of 1.28–4.2nm. The catalytic results indicated that among the prepared catalysts, Rh and Pt possessed the highest activity in C3H8O3 steam reforming and Rh catalyst showed the highest stability with time on stream.

Bio-hydrogen production by APR of C2-C6 polyols on Pt/Al2O3: Dependence of H2 productivity on metal content

The effect of the platinum loading on the production of hydrogen by aqueous-phase reforming of ethylene glycol, glycerol, xylitol and sorbitol was studied on Pt/Al2O3 catalysts containing 0.30, 0.57, 1.50 and 2.77 Pt%. Catalytic runs were performed at a space velocity of 1.2h−1, 498K, 29.3bar and using a polyol(1.0%)/water feed. The total polyol conversion and the polyol conversion to gaseous products increased with surface Pt concentration (Pts, μmol Pt/gcat). Similarly, the yield and the productivity to hydrogen (Pr, molH2/gh) increased continuously with Pts in all the cases, but the Pr values diminished with the polyol chain length. Coke formation depended on Pts and the polyol size; the amount of carbon formed on the catalyst increased indeed with Pts and diminished with the polyol chain length. The metal fraction was severely sintered during the APR reaction, irrespective of the reactant size. Nevertheless, the magnitude of the Pt dispersion drop was not dependent on the amount of platinum on Pt/Al2O3 catalysts.

Aqueous-phase reforming of alcohols with three carbon atoms on carbon-supported Pt

Aqueous-phase reforming of propanol-1, propane-1,2-diol and glycerol was performed at 498K and 29.7bar in a continuous reactor with platinum supported on a polymer-derived carbon, as a catalyst. The number of hydroxyl groups of the reactant influenced the product distribution. An unexpectedly long stabilization period − more than 150h of time-on-stream − was found to be an important feature of the catalyst.

Cleaner hydrothermal hydrogenolysis of glycerol to 1,2-propanediol over Cu/oxide catalysts without addition of external hydrogen

The hydrogenolysis of glycerol is considered a sustainable process to produce 1,2-propanediol (1,2-PDO). However, the development of a cost-effective solid catalyst and a cleaner process minus the addition of external hydrogen remains a challenge. In the present work, a series of Cu/oxide (SiO2, MgO, Al2O3, and ZnO) catalysts were prepared and evaluated for the hydrothermal hydrogenolysis of glycerol. The relationships of structure-catalytic properties were probed by thermogravimetric analysis (TG), powder X-ray diffraction (XRD), nitrogen adsorption-desorption, temperature-programmed desorption of carbon dioxide (CO2-TPD), transmission electron microscopy (TEM), and X-ray photoelectron spectra (XPS). The catalytic activity of Cu/oxide catalysts was in the order of Cu/Al2O3<Cu/SiO2≈Cu/ZnO<Cu/MgO. The Cu/MgO catalysts were identified as highly active catalysts for the hydrothermal hydrogenolysis of glycerol under autogenic pressure without the addition of external hydrogen. When 1.0g Cu/MgO (Cu/MgO=0.5, molar ratio) catalyst and 50g 20wt% aqueous glycerol solution as the feedstock was loaded in a batch autoclave reactor, the conversion of glycerol reached 55% with a selectivity of 68% to 1,2-propanediol at 473K after 6h. Cu0 was identified as the active species both for the catalytic in situ aqueous-phase reforming of glycerol and for the hydrothermal hydrogenolysis of glycerol. The support basicity played a role in stabilizing the Cu nanoparticles on the support surface. During the catalytic reaction, part of Cu species leached from the MgO support into solvent and meanwhile part of Cu species on the support surface aggregated. The basicity and acidity of the solvent affected the behavior of the Cu/MgO catalysts. This work shows that hydrothermal hydrogenolysis process of glycerol is a facile process and the cost-effective Cu/MgO is worth further development for future industrial practice.