Hydrogen production from glycerin by steam reforming over nickel catalysts

Increasing biodiesel production has resulted in a glut of glycerin that has led to a precipitous drop in market prices. In this study, the use of glycerin as a biorenewable substrate for hydrogen production, using a steam reforming process, has been evaluated. Production of hydrogen from glycerin is environmentally friendly because it adds value to this byproduct generated from biodiesel plants. The study focuses on nickel-based catalysts with MgO, CeO₂, and TiO₂ supports. Catalysts were characterized with thermogravimetric analysis and X-ray diffraction techniques. Maximum hydrogen yield was obtained at 650 °C with MgO supported catalysts, which corresponds to 4 mol of H₂ out of 7 mol of stoichiometric maximum.     

Hydrogen production via steam reforming of ethylene glycol over Attapulgite supported nickel catalysts

Steam reforming of ethylene glycol was investigated over Ni-based catalysts supported on Attapulgite (ATP; originating from Jiangsu (JS), Anhui, and Gansu (GS) provinces in China). N₂ adsorption–desorption, XRD, FTIR, H₂-TPR, NH₃-TPD, SEM, and TEM-EDS measurements were performed to analyze the catalyst properties. The results revealed that Ni/ATP_GS had the largest particle size (17.9 nm) and the highest reductive degree (98.0%). Consequently, Ni/ATP_GS showed the highest ethylene glycol conversion (97.2%) during the first 4 h of reaction. However, this catalyst showed the lowest H₂ yield (71.2%), possibly owing to large Ni particle sizes as well as ample surface acidic sites and acidity, leading to a high selectivity toward CH₄ (20.8%) and C₂H₄ (2.2%). In contrast, Ni/ATP_JS presented the highest H₂ yield (89.8%) owing to it having the smallest Ni particle sizes and lowest amount of surface acidic sites. Additionally, this catalyst showed the highest stability over 8 h of reaction. An examination of the spent catalysts revealed that Ni/ATP_JS possessed excellent antisintering and coking properties.     

Hydrogen production via the glycerol steam reforming reaction over nickel supported on alumina and lanthana-alumina catalysts

In the present work, a comparative study of Ni catalysts supported on commercially available alumina and lanthana-alumina carriers was undertaken for the glycerol steam reforming reaction (GSR). The supports and/or catalysts were characterized by PZC, BET, ICP, XRD, NH₃-TPD, CO₂-TPD, TPR and SEM. Carbon deposited on the catalytic surface was characterized by SEM, TPO and Raman. Concerning the Ni/LaAl sample it can be concluded that the presence of lanthana by: (a) facilitating the active species dispersion, (b) strengthening the interactions between nickel species and support, (c) increasing of the basic sites' population and redistributing the acid ones in terms of strength and density, provides a catalyst with improved performance for the GSR reaction, in terms of activity, H₂ production and long term stability. TPO and Raman indicate that the carbon on the Ni/LaAl catalyst was mostly amorphous and was deposited mainly on the support surface. For the Ni/Al catalyst, graphitic carbon was prevalent and likely covered its active sites.     

Hydrogen production from catalytic steam reforming of glycerol over various supported nickel catalysts

Supported Ni catalysts have been investigated for hydrogen production from steam reforming of glycerol. Ni loaded on Al₂O₃, La₂O₃, ZrO₂, SiO₂ and MgO were prepared by the wet-impregnation method. The catalysts were characterized by nitrogen adsorption–desorption, X-ray diffraction and scanning electron microscopy. The characterization results revealed that large surface area, high dispersion of active phase on support, and small crystalline sizes are attributes of active catalyst in steam reforming of glycerol to hydrogen. Also, higher basicity of catalyst can limit the carbon deposition and enhance the catalyst stability. Consequently, Ni/Al₂O₃ exhibited the highest H₂ selectivity (71.8%) due to small Al₂O₃ crystallites and large surface area. Response Surface Methodology (RSM) could accurately predict the experimental results with R-square = 0.868 with only 4.5% error. The highest H₂ selectivity of 86.0% was achieved at optimum conditions: temperature = 692 °C, feed flow rate = 1 ml/min, and water glycerol molar ratio (WGMR) 9.5:1. Also, the optimization results revealed WGMR imparted the greatest effect on H₂ selectivity among the reaction parameters.     

Toluene steam reforming over nickel based catalysts

Steam reforming of toluene (SRT) has been studied initially in eight nickel-based catalysts where nickel (10 wt%) was incorporated in different supports (olivine, Al2O3, MgO, LDH, ZrO₂, CeO₂ and natural sepiolite) by the incipient wetness impregnation method. Among them, nickel catalyst based on sepiolite exhibited a promising catalytic performance, with a high conversion of toluene (16%), high selectivity to hydrogen (68.4%) and low production of undesired by-products (CO, CH₄, ethylene and benzene) at low temperature (500 °C). On the other hand, the incorporation of Ni in the sepiolitic material by precipitation (PP) has been considered as alternative method to the incipient wetness impregnation method (IWI). PP method allowed to prepare a Ni-based catalyst with a very high activity (conversion of toluene ~100%), high selectivity to hydrogen (73%) and lower production of undesirable by-products (5% CO, 2% CH₄ and 0% C₆H₆) at 575 °C. In addition, catalytic deactivation due to coke deposition and nickel sinterization was clearly lower for the catalyst synthesized by PP. Characterization by different physicochemical techniques (XRD, TEM, BET surface area, ICP-OES, TPR and EA) showed that PP method allowed to obtain a sepiolite-based catalyst containing Ni with larger external surface area and smaller, highly dispersed and easily reducible Ni metal particles. The results here discussed show that the Ni incorporation method has a clear influence in the preparation of nickel catalyst supported on sepiolite with improved catalytic performance in the steam reforming of toluene.     

Hydrogen production from glycerol steam reforming over Co-based catalysts supported on La2O3, AlZnOx and AlLaOx

A comparative study of 10 wt% Co-based catalysts supported on La₂O₃, AlZnO_x and AlLaO_x was performed for glycerol steam reforming (GSR). The catalysts physicochemical characterization was done through several techniques. All catalysts were screened in terms of catalytic activity and time-on-stream stability for GSR. The catalytic activity experiments aimed to assess the effect of temperature (400–700 °C) on the glycerol conversion and yield of gaseous products (H₂, CO₂, CO and CH₄). Additionally, catalytic stability experiments were conducted at 625 °C to investigate deactivation of the catalysts, in which a drop in the activity was observed, especially for Co/La₂O₃. The glycerol conversion into gaseous products as a function of the time-on-stream was more affected for all catalysts in comparison to total glycerol conversion, being this effect assigned to the increase in the formation of liquid products and to the formation of coke. CoAlLaO_x was observed to be more carbon-resistant, followed by CoAlZnO_x, through the measurement of the quantity of carbonaceous species formed during the GSR experiments. A NiAlLaO_x catalyst was also prepared and assessed in terms of catalytic stability for GSR; a stable behavior was observed throughout all experiment in relation to glycerol conversion into gaseous products and H₂ yield.     

La-doped supported Ni catalysts for steam reforming of methane

Ni-La/α-Al₂O₃ catalysts at different Ni/La ratio of respectively 7/3, 8/2 and 9/1 to obtain a material with total loading of 10 wt% as used in industrial methane steam reforming field are prepared with incipient wetness impregnation method. Various techniques including TGA-DTA, XRF, XRD, particles size, H₂-RTP and BET are used to characterize materials and their catalytic performance is evaluated during the steam reforming reaction at different temperatures ranging from 500 to 800 °C. Only NiO and α-Al₂O₃ phases are evidenced by DRX indicating probably the presence of small lanthanum crystallites in high dispersion state. Addition of La may cause strong change at the surface of NiO sites. Substitute Ni by La leads to smaller and well dispersed NiO particles sizes with strong metal support interaction (SMSI). TPR analysis reveals the reduction of Ni species with high Ni-La-Al interactions particularly well observed with 3 wt%La catalyst. The small Ni particles sizes highly dispersed on the support enhance the dissociative adsorption of CH_x species. The highest H₂ yield is obtained with 7Ni-3La/Al catalyst reaching 94% at 800 °C.     

Hydrogen production from a model bio-oil/bio-glycerol mixture through steam reforming using Zeolite L supported catalysts

Zeolite L featuring different size and shape (nanocrystals and discs), with and without alkaline metal exchange (Cs or Na), was used as catalyst support in bio-oil/bio-glycerol mixture Steam Reforming (SR). Zeolites were modified with CeO₂ to improve support properties before the impregnation of nickel. Then, prepared catalysts were tested in SR of a multi-component synthetic bio-oil/bio-glycerol mixture at 1073 and 973 K, under atmospheric pressure and using a Steam to Carbon (S/C) ratio of 5.0. Activity tests showed that catalysts deactivated during the experiments at 973 K. In addition, the sodium exchange produced the sintering of the Zeolite L crystals. Thus, Na containing catalysts produced low conversions and hydrogen yields lower than 30%. On the other hand, Cs containing catalysts resulted in slightly lower hydrogen yields than the supports without this metallic cation. Regarding the morphology of the zeolites, the ones with disc shape were the most active for bio-oil SR purposes producing hydrogen yields close to 80% in the first reaction stage at 1073 K and hydrogen yields close to the 50% at the last reaction stage at 1073 K.     

Exergy analysis of hydrogen production via steam methane reforming

The performance of hydrogen production via steam methane reforming (SMR) is evaluated using exergy analysis, with emphasis on exergy flows, destruction, waste, and efficiencies. A steam methane reformer model was developed using a chemical equilibrium model with detailed heat integration. A base-case system was evaluated using operating parameters from published literature. Reformer operating parameters were varied to illustrate their influence on system performance. The calculated thermal and exergy efficiencies of the base-case system are lower than those reported in literature. The majority of the exergy destruction occurs due to the high irreversibility of chemical reactions and heat transfer. A significant amount of exergy is wasted in the exhaust stream. The variation of reformer operating parameters illustrated an inverse relationship between hydrogen yield and the amount of methane required by the system. The results of this investigation demonstrate the utility of exergy analysis and provide guidance for where research and development in hydrogen production via SMR should be focused.     

Hydrogen production by steam reforming of liquefied natural gas (LNG) over nickel catalysts supported on cationic surfactant-templated mesoporous aluminas

Two types of mesoporous γ-aluminas (denoted as A-A and A-S) are prepared by a hydrothermal method under different basic conditions using cationic surfactant (cetyltrimethylammonium bromide, CTAB) as a templating agent. A-A and A-S are synthesized in a medium of ammonia solution and sodium hydroxide solution, respectively. Ni/γ-Al₂O₃ catalysts (Ni/A-A and Ni/A-S) are then prepared by an impregnation method, and are applied to hydrogen production by steam reforming of liquefied natural gas (LNG). The effect of a mesoporous γ-Al₂O₃ support on the catalytic performance of Ni/γ-Al₂O₃ is investigated. The identity of basic solution strongly affects the physical properties of the A-A and A-S supports. The high surface-area of the mesoporous γ-aluminas and the strong metal–support interaction of supported catalysts greatly enhance the dispersion of nickel species on the catalyst surface. The well-developed mesopores of the Ni/A-A and Ni/A-S catalysts prohibit the polymerization of carbon species on the catalyst surface during the reaction. In the steam reforming of LNG, both Ni/A-A and Ni/A-S catalysts give better catalytic performance than the nickel catalyst supported on commercial γ-Al₂O₃ (Ni/A-C). In addition, the Ni/A-A catalyst is superior to the Ni/A-S catalyst. The relatively strong metal–support interaction of Ni/A-A catalyst effectively suppresses the sintering of metallic nickel and the carbon deposition in the steam reforming of LNG. The large pores of the Ni/A-A catalyst also play an important role in enhancing internal mass transfer during the reaction.     

Evaluation of the economic impact of hydrogen production by methane decomposition with steam reforming of methane process

There has been considerable interest in the development of more efficient processes to generate hydrogen. Currently, steam methane reforming (SMR) is the most widely applied route for producing hydrogen from natural gas. Researchers worldwide have been working to invent more efficient routes to produce hydrogen. One of the routes is thermocatalytic decomposition of methane (TCDM) - a process that decomposes methane thermally to produce hydrogen from natural gas. TCDM has not yet been commercialized. However, the aim of this work was to conduct an economic and environmental analysis to determine whether the TCDM process is competitive with the more popular SMR process. The results indicate that the TCDM process has a lower carbon footprint. Further research on TCDM catalysts could make this process economically competitive with steam methane reforming.     

Catalytic steam reforming of complex gasified biomass tar model toward hydrogen over dolomite promoted nickel catalysts

The complex mixture of gasified tar model (phenol, toluene, naphthalene, and pyrene) was steam reformed for hydrogen production over 10 wt% nickel based catalysts. The catalysts were prepared by co-impregnation method with dolomite promoter and various oxide supports (Al₂O₃, La₂O₃, CeO₂, and ZrO₂). Steam reforming was carried out at 700 °C at atmospheric pressure with steam to carbon molar ratio of 1 and gas hourly space velocity of 20 L/h·g_cat. The catalysts were characterised for reducibility, basicity, crystalline, and total surface area properties. Dolomite promoter strengthened the metal-support interaction and basicity of catalyst. The Ni/dolomite/La₂O₃ (NiDLa) catalyst with mesoporous structure (26.42mn), high reducibility (104.42%), and strong basicity (5.56 mmol/g) showed superior catalytic performance in terms of carbon conversion to gas (77.7%), H₂ yield (66.2%) and H₂/CO molar ratio (1.6). In addition, the lowest amount of filamentous coke was deposited on the spent NiDLa after 5 h.     

Modelling of one-dimensional heterogeneous catalytic steam methane reforming over various catalysts in an adiabatic packed bed reactor

Kinetic data relevant to steam methane reforming (SMR) are often applied to catalysts and conditions for which they have not been derived. In this work, kinetic rates for the two SMR and water gas shift reactions were derived for 12 commonly used reforming catalysts based on conversion data obtained from the literature. Subsequently, these rates were tested in dynamic operation, steady-state, and equilibrium using a 1-D reactor model developed in-house with gPROMS model builder. Modelling outputs were further validated independently at equilibrium using the software chemical equilibrium with applications (CEA), and the literature. The effect of variables such as temperature, pressure, steam to carbon ratio (S/C), and gas mass flux (G_s) on the performance of the SMR process was then studied in terms of fuel and steam conversion (%), H₂ purity (%), H₂ yield (wt. % of CH₄) and selectivity of the carbon-based products. A comparative study was then performed for the 12 catalysts. Some catalysts showed better activity owing to their fast kinetics when they are tested in mild industrial conditions, while others performed better in more severe industrial conditions, substantiating that the choice of a catalyst ought to depend on the operating conditions.     

Ni supported on MgO modified attapulgite as catalysts for hydrogen production from glycerol steam reforming

A series of Mg-modified Ni/Attapulgite (ATP) catalysts have been prepared by impregnation method for glycerol steam reforming to produce hydrogen. The physicochemical properties of catalysts were characterized using various techniques including N₂ physical adsorption analysis, XRD, H₂-TPR, SEM, TEM and NH₃-TPD. The results of N₂ physical adsorption indicated MgO modified Ni-based catalysts had unique mesostructure, resulting in the high metal dispersion and interaction between active metal and support as proven by XRD, TEM and H₂-TPR. Results of glycerin reforming experiments showed that Ni/10MgO/ATP catalyst had the highest activity than that of the other catalysts. Ni/10MgO/ATP catalyst had the smallest Ni average crystal size (10.1 nm) and the highest surface area (110.31 m²/g). These excellent properties made it show the enhanced glycerol conversion (94.71%) and a higher H₂ yield (88.45%) and the longest stability (30 h) during glycerol steam reforming (GSR) at 600 °C, W/G = 3, and WHSV = 1 h^?1. The used catalysts after 60 h of glycerin reforming experiments were also investigated by XRD, SEM, TEM, Roman and TG-DTG. The results indicated that the addition of Mg significantly inhibited the sintering of nickel grains and the formation of amorphous carbon. Therefore, Ni/10MgO/ATP catalyst increased the activity of the catalyst and extended the life of the catalyst.     

Ni supported on the CaO modified attapulgite as catalysts for hydrogen production from glycerol steam reforming

The Ni catalyst supported on CaO-modified attapulgite (CaO-ATP) were synthesized by wet impregnation method at a constant Ni metal loading (10 wt%). The catalyst was tested by carrying out a glycerin steam reforming reaction under the following conditions: 400–800 °C, W/G is 3, GHSV is 1 h⁻¹. Ni–CaO-ATP exhibited the highest hydrogen yield (85.30%) and glycerol conversion (93.71%) at 600 °C. The catalysts were characterized by N₂ adsorption/desorption, BET, XRD, H₂-TPR, TG and SEM. The results show that ATP has good resistance to carbon deposition. As an attapulgite modifier of Ni–CaO-ATP, CaO promotes the dispersion of the active component nickel species, which would promote the water gas shift reaction, leading to the improving of hydrogen yield. In addition, the addition of Ca would further enhance the inhibition of carbon deposition and prolong the life of the Ni–CaO-ATP catalyst.     

Enhancing the catalytic performance of Co substituted NiAl2O4 spinel by ultrasonic spray pyrolysis method for steam and dry reforming of methane

(Ni,Co)Al₂O₄ mesoporous spinel particles with a high specific surface area were synthesized in a single-step by ultrasonic spray pyrolysis at 1000 °C. After reduction, a uniform metal distribution was obtained on the support, which was used as a catalyst for dry and steam reforming of methane. Substituting Ni with Co resulted in a substantial increase in the specific surface area from 118 m²/g to 182 m²/g as a result of different decomposition paths that occurs for Ni and Co salts in the pyrolysis reactions. Results show that partial substitution of Ni with Co, between 20 and 50%, significantly increased the methane conversion values and improved the stability of the catalysts in the time on stream experiments. It also shows that partial substitution substantially improved the catalyst resistance against carbon deposition in the dry reforming process. The complete replacement of the cobalt with nickel in spinel structure caused a significant drop in catalytic properties.     

Hydrogen production by steam reforming of liquefied natural gas over a nickel catalyst supported on mesoporous alumina xerogel

Mesoporous alumina xerogel (A-SG) is prepared by a sol–gel method for use as a support for a nickel catalyst. The Ni/A-SG catalyst is then prepared by an impregnation method, and is applied to hydrogen production by steam reforming of liquefied natural gas (LNG). The effect of the mesoporous alumina xerogel support on the catalytic performance of Ni/A-SG catalyst is investigated. For the purpose of comparison, a nickel catalyst supported on commercial alumina (A-C) is also prepared by an impregnation method (Ni/A-C). Both the hydroxyl-rich surface and the electron-deficient sites of the A-SG support enhance the dispersion of the nickel species on the support during the calcination step. The formation of the surface nickel aluminate phase in the Ni/A-SG catalyst remarkably increases the reducibility and stability of the catalyst. Furthermore, the high-surface area and the well-developed mesoporosity of the Ni/A-SG catalyst enhance the gasification of surface hydrocarbons that are adsorbed in the reaction. In the steam reforming of LNG, the Ni/A-SG catalyst exhibits a better catalytic performance than the Ni/A-C catalyst in terms of LNG conversion and hydrogen production. Moreover, the Ni/A-SG catalyst shows strong resistance toward catalyst deactivation.     

Hydrogen production over Rh/Ce-MCM-41 catalysts via ethanol steam reforming

1 wt%Rh/Ce-MCM-41 catalysts were synthesized using Ce-MCM-41 as support where Si/Ce molar ratio varied from 10 to 30 and 50. During hydrogen reduction process, metallic Rh particles were formed on the Ce-MCM-41 at around 130 °C with an average particle size 6.8 nm. These catalysts were tested in the ethanol steam reforming (ESR) under atmospheric pressure between 225 and 425 °C. Compared to Rh/MCM-41 catalyst, cerium introduction would significantly enhance both the catalytic activity and hydrogen yield by approximately 2–3 times. However, the amount and the method of Ce incorporation in the framework of MCM-41 could greatly impact the catalytic performance of the Rh/Ce-MCM-41 catalysts. The ethanol conversion at 425 °C over the Rh/Ce-MCM-41 catalysts increased from 90.0% to 95.1% and 99.9%, as the Si/Ce molar ratio increases from 10 to 30 and 50. However, product selectivity is almost independent of the cerium content. The direct hydrothermal method of introducing Ce into the framework of MCM-41 is much superior to the impregnation route in the ESR reaction. After 6 h of reaction, the catalysts remain the mesostructure and the chemical state of cerium ions unchanged. Trace coke with graphite-like structure deposited on the surface does not modify the catalytic performance.     

Hydrogen production from methane autothermal reforming over CaTiO3, BaTiO3 and SrTiO3 supported nickel catalysts

Nickel supported on perovskite supports were investigated in the autothermal reforming of methane. The catalysts were prepared by incipient wetness impregnation and characterized by energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), N₂ physisorption, H₂ temperature programmed reduction (H₂-TPR), H₂ chemisorption, dehydrogenation of cyclohexane model reaction and Raman spectroscopy. The alumina supported catalyst exhibited highest initial conversion and selectivity to H₂, however it deactivated. All catalysts with perovskite support were very stable, with Ni/CaTiO₃ and Ni/BaTiO₃ converting over 70% of the methane. Due to carbon formation, Ni/SrTiO₃ conversion was only 50%. Turnover frequency was higher on perovskite supported catalysts. Deactivated Ni/Al₂O₃ favored total oxidation of methane instead of methane reforming, however the selectivity of catalysts supported on perovskites remained stable.