Kinetic investigation on butanol steam reforming over Ru/Al2O3 catalyst

Steam reforming of biomass-derived oxygenates is an attractive technique for the renewable production of hydrogen (H₂). In this work, steam reforming of n-butanol – a representative of bio-oxygenates – was studied over commercial 5% Ru/Al₂O₃ catalyst in a fixed-bed reactor. Kinetics of butanol reforming was investigated between temperatures 623 and 773 K at steam/carbon (S/C) ratio equal to 33.3 mol/mol. The W/F_A0 ratio (W: mass of catalyst, F_A0: molar flow rate of butanol in feed) was varied between 3.3 and 16.7 g h/mol. At T = 773 K, butanol conversion and H₂ yield were 93.4% and 0.61 mol/mol. Evaluation of the kinetic data showed that reaction order with respect to butanol was unity. The activation energy for the investigated reaction was 78 kJ/mol. Finally, a Langmuir-Hinshelwood model that assumed the surface reaction between the adsorbed reactants as rate-determining was used to describe the kinetic data.     

Renewable hydrogen production by steam reforming of butanol over multiwalled carbon nanotube-supported catalysts

The conversion of bio-oxygenates into hydrogen (H₂) via catalytic steam reforming is a green approach for H₂ generation. In the present work, butanol was chosen as renewable feedstock for producing H₂. Two catalysts supported on multiwalled carbon nanotubes, Ni/CNT and Co/CNT, were synthesized by the wetness impregnation method and used for butanol reforming. Trials were performed in a fixed-bed reactor in the 623–773 K range using S/C ratio equal to 33.3 mol/mol (here, S/C denotes steam to carbon ratio). The Ni/CNT catalyst exhibited higher reforming activity. The best catalytic performance for Ni/CNT was observed at T = 773 K. At this temperature, high values of butanol conversion (87.3%) and H₂ yield (0.75 mol/mol) were observed at W/F_A0 = 16.7 g h/mol (here, W is the catalyst mass and F_A0 is the molar flow rate of butanol at the inlet). The performance of Ni/CNT catalyst for steam reforming of synthetic bio-butanol was also investigated at T = 773 K and H₂ yield of 0.65 mol/mol was achieved.     

Novel zeolite-supported rhodium catalysts for ethanol steam reforming

Renewable bioethanol is an interesting hydrogen source for fuel cells through steam reforming, but its C–C bond promotes parallel reactions, mainly coke and by-products formation. In this way, good ethanol reforming catalysts are still needed, which explains current research and development efforts around the world. Most catalysts proposed for ethanol reforming are based on oxide-supported noble metals with surface area below 100 m² g⁻¹ and reaction temperatures above 500 °C. Novel Rh and Rh–K catalysts supported on NaY zeolite with surface area above 440 m² g⁻¹ are presented in this work. Reaction temperature was fixed at 300 °C and H₂O/EtOH molar ratio and reagent flow were varied. Ethanol conversion varied from 50 to 99%, with average increase of 50% due to K promoter, and hydrogen production yield achieved 68%.     

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.     

On the activity of bimetallic catalysts for ethanol steam reforming

The performance of CeO₂-supported Pt–Ni and Pt–Co catalysts in the low temperature-Ethanol Steam Reforming (ESR) reaction has been evaluated studying the effect of the preparation method (impregnation/coprecipitation) and parameters such as dilution ratio, temperature, water-to-ethanol feed ratio and Gas Hourly Space Velocity (GHSV). The results show that impregnated samples perform better. In particular, the Pt/Ni/CeO₂ catalyst starting from 350 °C leads to a products distribution very close to the equilibrium calculations, with a low CO content that is ideal for fuel cells devices. In addition, the Co-based catalysts appear attractive in terms of hydrogen yield and coking tendency.     

Hydrotalcites with vanadium,effective catalysts for steam reforming of toluene

The steam reforming of toluene has been studied on three catalysts with vanadium (0.9, 1.75, 3%) derived from hydrotalcites precursors (Mg/Al molar ratio 3) in the temperature range 400–500 °C. Catalysts were characterized by BET, XRD, SEM, TEM, FT-IR and then a correlation between physico-chemical characteristics and catalytic activity for toluene steam reforming has been done. The results showed that the catalyst with 3% V, with polyvanadate species, achieves the best catalytic activity, with a toluene conversion of 77.5%, at 500 °C, and a H₂ composition of 57%.     

Pathways of ethanol steam reforming over ceria-supported catalysts

Ceria-supported Pt, Ir and Co catalysts are prepared herein by the deposition–precipitation method and investigated for their suitability in the steam reforming of ethanol (SRE) at a temperature range of 250–500 °C. SRE is tested in a fixed-bed reactor under an H₂O/EtOH molar ratio of 13 and 20,000 h⁻¹ GHSV. Possible pathways are proposed according to the assigned temperature window to understand the different catalysts attributed to specific reaction pathways. The Pt/CeO₂ catalyst shows the best carbon–carbon bond-breaking ability and the lowest complete ethanol conversion temperature of 300 °C. Acetone steam reforming over the Ir/CeO₂ catalyst at 400 °C promotes a hydrogen yield of up to 5.3. Lower reaction temperatures for the water–gas shift and acetone steam reforming are in evidence for the Co/CeO₂ catalyst, whereas the carbon deposition causes its deactivation at temperature over 500 °C.     

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.     

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.     

Industrial scale steam reforming of bioethanol: A conceptual study

This study investigates the technical feasibility of using existing steam reforming and hydrogen separation technologies to produce hydrogen from bioethanol on an industrial scale (100,000 Nm³/h of hydrogen). Two separate reaction schemes for producing hydrogen from bioethanol are compared. One scheme utilises both a prereformer and steam reformer, and the other requires a steam reformer only.     

Perovskite-based catalysts for tar removal by steam reforming: Effect of the presence of hydrogen sulfide

One of the greatest problems in biomass gasification processes is the conditioning of the produced synthesis gas, which contains various contaminants, including tar and hydrogen sulfide. Nickel catalysts, designed for steam reforming of aliphatic hydrocarbons (natural gas and nafta), are usually deactivated by coke deposition and sulfur poisoning. In this work, nickel and/or manganese catalysts derived from perovskites were prepared by the citrate method and characterized by X-ray diffraction, N₂ physisorption and temperature programmed reduction. The catalysts were evaluated in the steam reforming of toluene, used as tar model compound, in the absence of H₂S at 700 °C and in the presence of 50 ppm H₂S at 800 °C. LaNi_0.5Mn_0.5O₃ catalyst showed higher activity and stability in the absence of H₂S. LaMnO₃ catalyst, although less active in the absence of H₂S, showed increased stability in the presence of H₂S, with conversion of about 60%. H₂ production was only observed in the absence of H₂S.     

Hydrogen production via sorption enhanced steam reforming of butanol: Thermodynamic analysis

Thermodynamic equilibrium for sorption enhanced steam reforming of butanol (SESRB) to hydrogen was investigated using Gibbs free energy minimization method. The optimal operation conditions for SESRB are at 800 K, the steam-to-butanol molar ratio of 10, the calcium oxide-to-butanol molar ratio of 8 and atmospheric pressure. Under the optimal conditions, complete conversion of butanol, 97.07% concentration of H₂ and 0.05% concentration of CO₂, and efficiency of 86.60% could be achieved and at which no coke tends to form. Under the same conditions in SRB, 58.18% concentration of H₂, 21.62% concentration of CO₂, and energy efficiency of 81.51% could be achieved. Butanol steam reforming with CO₂ adsorption has the higher H₂ content and efficiency, and lower CO₂ content than that without adsorption under the same reaction conditions. In addition, reaction conditions for coke-free and coke-formed regions are also discussed in butanol steam reforming with or without CO₂ separation.     

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.     

Hydrogen production by steam reforming of acetic acid: Comparison of conventional supported metal catalysts and metal-incorporated mesoporous smectite-like catalysts

The activities of various metal catalysts were tested in steam reforming of acetic acid for the production of H₂, using conventional metal oxides and transition metal-incorporated mesoporous smectite-like materials as supports. It has been found that Pt is superior to Ni, Co, and Fe among Al₂O₃ supported catalysts, Al₂O₃ is more effective than ZrO₂ and SiO₂ as support for Pt, Ni incorporated smectite (SM(Ni)) support is more effective than Fe and Co incorporated ones for Pt, and SM(Ni) is also active in the absence of Pt. The total activity for the conversion of acetic acid is in the order of Pt/Al₂O₃ > Pt/SM(Ni) > SM(Ni) but the ability of H₂ production is comparable among these catalysts. These catalysts (and the other ones) were observed to lose their activities during the reforming reactions. The activity of Pt/Al₂O₃ decreased during the whole course of reaction up to 10 h. In contrast, the activity of SM(Ni) also decreased within 2 h but it showed a stable activity in the following stage of reaction. The initial activity of the used Pt/SM(Ni) and SM(Ni) was able to be almost completely restored by thermal treatment with H₂ but less effectively for the used Pt/Al₂O₃. The catalyst deactivation was shown to occur by the formation and deposition of carbon materials on the catalysts (XRD, TEM, thermal analysis). The properties of carbon deposits formed on Pt/Al₂O₃ and SM(Ni) catalysts should be different and this may be responsible for the differences in the extent of deactivation and in the regeneration behavior between the two catalysts.     

Furfural steam reforming over Ni-based catalysts. Influence of Ni incorporation method

Catalytic steam reforming of biomass-derived compounds as furfural could be a promising option to produce renewable hydrogen; however efficient catalysts are still under study. Different commercial supports (SiO₂, Al₂O₃, ASA, MgO, MgAl₂O₃, ZnO, TiO₂, Natural Sepiolite) incorporating Ni by incipient wetness impregnation have been initially tested in the Steam Reforming of Furfural (SRF). Among them, Ni supported in natural sepiolite exhibited the best catalytic activity. In order to improve the catalytic performance of this sepiolite-based catalyst an alternative method for the incorporation of Ni was explored (precipitation). Precipitation method led to a Ni-based catalyst highly active and selective in the production of hydrogen. In addition, the production of undesired products (CO and acetone) decreased significantly. Characterization by BET area, XRD, TEM and TPR shows that precipitation method allows to synthesize a Ni-based catalyst with higher BET surface area and smaller metallic nickel particles. These particular physico-chemical properties seem to be the major responsible of the better catalytic performance exhibited by the material prepared by precipitation.     

Glycerol steam reforming over Ni catalysts supported on ceria and ceria-promoted alumina

In this paper glycerol steam reforming over Ni catalysts supported on bare CeO₂ and Al₂O₃, and CeO₂-promoted Al₂O₃ to produce H₂ was studied. The catalytic activity results for the NiAl5Ce and NiAl10Ce catalysts showed that the incorporation of low ceria loadings enhances the activity of the NiAl catalyst prepared using a similar composition to the commercial Ni/Al₂O₃ catalysts. The catalyst surface characterization revealed that the good behaviour of the NiAl5Ce and the NiAl10Ce catalysts depends on the stabilization of Ni° particles which is promoted by the formation of nickel–ceria interactions. The increase of ceria content reduced the capacity of the NiAl20Ce catalyst to convert intermediate oxygenated hydrocarbons into H₂.     

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.     

Nickel based monometallic and bimetallic catalysts for synthetic and real bio-oil steam reforming

Catalysts based on Ni supported on alumina were studied for steam reforming (SR) of a synthetic bio-oil/bio-glycerol mixture and a real bio-oil. Catalyst tests were carried out in a continuous fixed bed reactor at atmospheric pressure and steam to carbon (S/C) ratio of 5.0. In the case of experiments with the bio-oil/bio-glycerol mixture the initial temperature was 1073 K, then it was successively changed to 973 K and 1073 K again to assess catalyst deactivation. Experiments with the bio-oil sample were run at 1073 K. First, the effect of modifications to the alumina support with CeO₂ and La₂O₃ was studied in monometallic catalysts. Ni/CeO₂Al₂O₃ was identified as the catalyst more resistant to deactivation, likely due to its higher oxygen mobility, and selected for further tests. Then, bimetallic catalysts were produced by impregnation of noble metals (Pd, Pt or Rh) on the Ni catalyst supported on CeO₂Al₂O₃. Co-impregnation of Rh and Ni on the CeO₂Al₂O₃ support represented a further improvement in the catalytic activity and stability respect to the monometallic catalyst, leading to stable gas compositions close to thermodynamic equilibrium due to the favourable RhNi interactions. RhNi/CeO₂Al₂O₃ is therefore a promising catalyst to produce a hydrogen-rich gas from bio-oil SR.     

Production of hydrogen by ethanol steam reforming over catalysts from reverse microemulsion-derived nanocompounds

In the present work, hydrotalcite-like compound precursor for preparing mixed oxide catalyst was successfully synthesized by a novel method, which was a combination of the reverse microemulsion and coprecipitation methods. It was observed that the precursor obtained from the above method possessed superior characteristics for preparing mixed oxide catalyst used in ethanol steam reforming (ESR). Furthermore, for comparison, catalysts prepared from conventional coprecipitation and impregnation methods had been characterized together with the catalyst prepared from the new method. Besides ICP, BET, X-ray diffraction (XRD), temperature-programmed reduction (TPR), H₂-TPD, TG, and TEM analytic techniques, catalytic performance for ESR was also investigated. The results of XRD and TPR indicated that a solid solution phase existed in the catalysts obtained from reverse microemulsion and coprecipitation methods, while spinel phase together with solid solution were observed in the catalyst obtained from the impregnation method. The high BET surface area of the catalyst obtained from the reverse microemulsion method enhanced the dispersion and the surface area of nickel, which improved the catalyst performance. From TEM images, the aggregated Ni could be found in the catalyst obtained from the impregnation method, while the hydrotalcite-like compound precursors prepared from reverse microemulsion and coprecipitation methods produced homogeneously distributed active Ni metal species. The catalyst obtained from reverse microemulsion exhibited the best activity, stability, and least carbon deposition because of the formation of hydrotalcite-like compound precursor, uniform dispersion of active Ni metal species, and much more surface area supporting the active Ni metal sites.