Production of hydrogen via steam reforming of biofuels on Ni/CeO2–Al2O3 catalysts promoted by noble metals

The catalytic activity of Ni/CeO₂–Al₂O₃ catalysts modified with noble metals (Pt, Ir, Pd and Ru) was investigated for the steam reform of ethanol and glycerol. The catalysts were characterized by the following techniques: Energy-dispersive X-ray, BET, X-ray diffraction, temperature-programmed reduction, UV–vis diffuse reflectance spectroscopy and X-ray absorption near edge structure (XANES). The results showed that the formation of inactive nickel aluminate was prevented by the presence of CeO₂ dispersed on alumina. The promoting effect of noble metals included a decrease in the reduction temperatures of NiO species interacting with the support, due to the hydrogen spillover effect. It was seen that the addition of noble metal stabilized the Ni sites in the reduced state along the reforming reaction, increasing the ethanol and glycerol conversions and decreasing the coke formation. The higher catalytic performance for the ethanol steam reforming at 600 °C and glycerol steam reforming was obtained for the NiPd and NiPt catalysts, respectively, which presented an effluent gaseous mixture with the highest H₂ yield with reasonably low amounts of CO.     

Current advances in syngas (CO + H2) production through bi-reforming of methane using various catalysts: A review

Today, bi - reforming of methane is considered as an emerging replacement for the generation of high-grade synthesis gas (H₂:CO = 2.0), and also as an encouraging renewable energy substitute for fossil fuel resources. For achieving high conversion levels of CH₄, H₂O, and CO₂ in this process, appropriate operation variables such as pressure, temperature and molar feed constitution are prerequisites for the high yield of synthesis gas. One of the biggest stumbling blocks for the methane reforming reaction is the sudden deactivation of catalysts, which is attributed to the sintering and coke formation on active sites. Consequently, it is worthwhile to choose promising catalysts that demonstrate excellent stability, high activity and selectivity during the production of syngas. This review describes the characterisation and synthesis of various catalysts used in the bi-reforming process, such as Ni-based catalysts with MgO, MgO–Al₂O₃, ZrO_2, CeO₂, SiO₂ as catalytic supports. In summary, the addition of a Ni/SBA-15 catalyst showed greater catalytic reactivity than nickel celites; however, both samples deactivated strongly on stream. Ce-promoted catalysts were more found to more favourable than Ni/MgAl₂O₄ catalyst alone in the bi-reforming reaction due to their inherent capability of removing amorphous coke from the catalyst surface. Also, Lanthanum promoted catalysts exhibited greater nickel dispersion than Ni/MgAl₂O₄ catalyst due to enhanced interaction between the metal and support. Furthermore, La₂O₃ addition was found to improve the selectivity, activity, sintering and coking resistance of Ni implanted within SiO₂. Non-noble metal-based carbide catalysts were considered to be active and stable catalysts for bi-reforming reactions. Interestingly, a five-fold increase in the coking resistance of the nickel catalyst with Al₂O₃ support was observed with incorporation of Cr, La₂O₃ and Ba for a continuous reaction time of 140 h. Bi-reforming for 200 h with Ni-γAl₂O₃ catalyst promoted 98.3% conversion of CH₄ and CO₂ conversion of around 82.4%. Addition of MgO to the Ni catalyst formed stable MgAl₂O₄ spinel phase at high temperatures and was quite effective in preventing coke formation due to enhancement in the basicity on the surface of catalyst. Additionally, the distribution of perovskite oxides over 20 wt % silicon carbide-modified with aluminium oxide supports promoted catalytic activity. NdCOO₃ catalysts were found to be promising candidates for longer bi-reforming operations.     

Ni/CeO2 catalysts with high CO2 methanation activity and high CH4 selectivity at low temperatures

CO₂ methanation was performed over 10 wt%Ni/CeO₂, 10 wt%Ni/α-Al₂O₃, 10 wt%Ni/TiO₂, and 10 wt%Ni/MgO, and the effect of support materials on CO₂ conversion and CH₄ selectivity was examined. Catalysts were prepared by a wet impregnation method, and characterized by BET, XRD, H₂-TPR and CO₂-TPD. Ni/CeO₂ showed high CO₂ conversion especially at low temperatures compared to Ni/α-Al₂O₃, and the selectivity to CH₄ was very close to 1. The surface coverage by CO₂-derived species on CeO₂ surface and the partial reduction of CeO₂ surface could result in the high CO₂ conversion over Ni/CeO₂. In addition, superior CO methanation activity over Ni/CeO₂ led to the high CH₄ selectivity.     

Hydrogen production by steam reforming of ethanol over Ni-based catalysts promoted with noble metals

The catalytic activity of Ni/La₂O₃-Al₂O₃ catalysts modified with noble metals (Pt and Pd) was investigated in the steam reforming of ethanol. The catalysts were characterized by ICP, S_BET, X-ray diffraction, temperature-programmed reduction, UV–vis diffuse reflectance spectroscopy and X-ray absorption fine structure (XANES). The results showed that the formation of inactive nickel aluminate was prevented by the presence of La₂O₃ dispersed on the alumina. The promoting effect of noble metals included a marked decrease in the reduction temperatures of NiO species interacting with the support, due to the hydrogen spillover effect, facilitating greatly the reduction of the promoted catalysts. It was seen that the addition of noble metal stabilized the Ni sites in the reduced state throughout the reaction, increasing ethanol conversion and decreasing coke formation, irrespective of the nature or loading of the noble metal.     

Oxidative steam reforming of ethanol over Ni/Al2O3 catalysts promoted by CeO2, ZrO2 and CeO2–ZrO2

Oxidative steam reforming of ethanol at low oxygen to ethanol ratios was investigated over nickel catalysts on Al₂O₃ supports that were either unpromoted or promoted with CeO₂, ZrO₂ and CeO₂–ZrO₂. The promoted catalysts showed greater activity and a higher hydrogen yield than the unpromoted catalyst. The characterization of the Ni-based catalysts promoted with CeO₂ and/or ZrO₂ showed that the variations induced in the Al₂O₃ by the addition of CeO₂ and/or ZrO₂ alter the catalyst's properties by enhancing Ni dispersion and reducing Ni particle size. The promoters, especially CeO₂–ZrO₂, improved catalytic activity by increasing the H₂ yield and the CO₂/CO and the H₂/CO values while decreasing coke formation. This results from the addition of ZrO₂ into CeO₂. This promoter highlights the advantages of oxygen storage capacity and of mobile oxygen vacancies that increase the number of surface oxygen species. The addition of oxygen facilitates the reaction by regenerating the surface oxygenation of the promoters and by oxidizing surface carbon species and carbon-containing products.     

Effect of La2O3 and CeO2 loadings on formation of nickel-phyllosilicate precursor during preparation of Ni/SBA-15 for hydrogen-rich gas production from ethanol steam reforming

The importance of La₂O₃ or both La₂O₃ and CeO₂ promoters on the formation of nickel phyllosilicate (Ni₃Si₄O₁₂H₂) as a precursor of Ni/SBA-15 for ethanol steam reforming (ESR) was investigated. The catalyst was made by a one-step modified conventional triblock copolymer synthesis method (pH-Adjustment with ammonium hydroxide). The prepared catalysts were characterized by N₂ adsorption/desorption isotherms, XRD, H₂-TPR, SEM-EDS and TGA-DSC techniques. The N₂ adsorption/desorption isotherms identified the mesoporous nature of the catalysts and the XRD patterns of the calcined catalysts confirmed the formation of nickel-phyllosilicate structure. The H₂-TPR analysis revealed that the La₂O₃ loading considerably increased the interaction between nickel and silica frame work of SBA-15 support. The ability of these catalysts for hydrogen production from ethanol steam reforming (ESR) was evaluated in a packed bed reactor at 650 °C. In the case of Ni/SBA-15 catalysts without and with La₂O₃ promoter, the ESR experiments experienced metal sintering and coke formation. Meanwhile, the catalytic activity of both La₂O₃ and CeO₂ promoted Ni/SBA-15 catalyst (Ni-La₂O₃-CeO₂/SBA-15) remained stable with time on stream in terms of GPR and hydrogen selectivity. The stable performance of this catalyst was explained by the strong interaction of nickel with SBA-15 promoted by La₂O₃ and the suppression of coke formation by CeO₂.     

Methanation of carbon dioxide over Ni/CeO2 catalysts: Effects of support CeO2 structure

The CeO₂, which were prepared by hard-template method, soft-template method, and precipitation method, were used as support to prepare Ni/CeO₂ catalysts (named as NCT, NCS, and NCP catalysts, respectively). The prepared catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and Brunauer–Emmett–Teller (BET). Hydrogen temperature-programmed reduction (H₂-TPR) was also used to study the reducibility of the support nickel precursors. Moreover, CO₂ catalytic hydrogenation methanation was used to investigate the catalytic properties of the prepared NCT, NCS, and NCP catalysts. H₂-TPR and XRD results showed that the NiO can be reduced by H₂ to produce metal Ni species, and the surface oxygen species existing on the surface of the support CeO₂ can also be reduced by H₂ to form surface oxygen vacancies. Low-angle XRD, TEM, and BET results indicated that the NCT and NCS catalysts had developed mesoporous structure and high specific surface area of 104.7 m² g^?1 and 53.6 m² g^?1, respectively. The NCT catalyst had the highest CO₂ methanation activity among the studied NCT, NCS, and NCP catalysts. The CO₂ conversion and CH₄ selectivity of the NCT catalyst can reach 91.1% and 100% at 360 °C and atmospheric pressure. The NCP catalyst, which had low specific surface area and low porosity, performed less CO₂ conversion and higher CH₄ selectivity than the NCT and NCS catalysts till 400 °C.     

Plasma-assisted CO2 reforming of methane over Ni-based catalysts: Promoting role of Ag and Sn secondary metals

Carbon dioxide (CO₂) and methane (CH₄) are the primary greenhouse gases (GHGs) that drive global climate change. CO₂ reforming of CH₄ or dry reforming of CH₄ (DRM) is used for the simultaneous conversion of CO₂ and CH₄ into syngas and higher hydrocarbons. In this study, DRM was investigated using Ag–Ni/Al₂O₃ packing and Sn–Ni/Al₂O₃ packing in a parallel plate dielectric barrier discharge (DBD) reactor. The performance of the DBD reactor was significantly enhanced when applying Ag–Ni/Al₂O₃ and Sn–Ni/Al₂O₃ due to the relatively high electrical conductivity of Ag and Sn as well as their anti-coke performances. Using Ag–Ni/Al₂O₃ consisting of 1.5 wt% Ag and 5 wt% Ni/Al₂O₃ as the catalyst in the DBD reactor, 19% CH₄ conversion, 21% CO₂ conversion, 60% H₂ selectivity, 81% CO selectivity, energy efficiency of 7.9% and 0.74% (by mole) coke formation were achieved. In addition, using Sn–Ni/Al₂O₃, consisting of 0.5 wt% Sn and 5 wt% Ni/Al₂O₃, 15% CH₄ conversion, 19% CO₂ conversion, 64% H₂ selectivity, 70% CO selectivity, energy efficiency of 6.0%, and 2.1% (by mole) coke formation were achieved. Sn enhanced the reactant conversions and energy efficiency, and resulted in a reduction in coke formation; these results are comparable to that achieved when using the noble metal Ag. The decrease in the formation of coke could be correlated to the increase in the CO selectivity of the catalyst. Good dispersion of the secondary metals on Ni was found to be an important factor for the observed increases in the catalyst surface area and catalytic activities. Furthermore, the stability of the catalytic reactions was investigated for 1800 min over the 0.5 wt% Ag-5 wt% Ni/Al₂O₃ and 0.5 wt% Sn-5 wt% Ni/Al₂O₃ catalysts. The results showed an increase in the reactant conversions with an increase in the reaction time.     

Cooperative effect of Pt and Cu on CeO2 for the CO-PROX reaction under CO2–H2O feed stream

Catalyst improvement for the preferential oxidation of CO (CO-PROX) is essential in developing efficient fuel cell technologies. Here, we investigate the promotion of the Cu/CeO₂ system with Pt, prepared by impregnation and alcohol-reduction methods, in the CO-PROX reaction under ideal and realistic feed compositions. The high Pt dispersion in PtCu/CeO₂ prepared by impregnation led to a CO conversion of 62% and CO₂ selectivity of 83% at 50 °C under a feed stream composed of H₂/CO/O₂, while monometallic Cu/CeO₂ and Pt/CeO₂ showed negligible activity at these conditions. By adding CO₂–H₂O to the feed stream, PtCu/CeO₂ catalysts prepared by both methods presented similar activity. The maximum CO conversion temperature was shifted to 100 °C. Under these conditions, Cu/CeO₂ was inactive, and Pt/CeO₂ showed identical conversion but lower CO₂ selectivity. In-situ XANES revealed that fast oxidation of Cu species at low temperatures is responsible for Cu/CeO₂ deactivation, while preferential adsorption of CO on Pt⁰ sites in PtCu/CeO₂ avoided deactivation. The use of deactivation-resistant Pt sites as complimentary sites for CO activation associated with improved oxygen mobility over Cu–CeO₂ surface proved to be an effective strategy for CO-PROX under H₂O/CO₂ feed stream at low temperatures.     

Effects of metal loading and support modification on the low-temperature steam reforming of ethanol (LTSRE) over the Ni–Sn/CeO2 catalysts

This article presents the effect of metal loading and support modification with MgO on low-temperature steam reforming of ethanol (LTSRE) over Ni–Sn/CeO₂ catalysts prepare by a single-pot solution combustion synthesis (SCS) method. Atmospheric pressure activity study of these catalysts (0.5 g) is performed at different temperatures (200–400 °C), H₂O:EtOH = 12: 1 mol ratio, and feed flow rate 0.1 ml/min. After 10 h TOS at 400 °C, NiSn(5)/CM12 catalyst with 5 wt.% total metal loading, optimal Sn (Ni:Sn = 14:1), and Ce:Mg = 1:2 mol ratio shows EtOH conversion 100% and H₂ selectivity 70% with low coke deposition. Physicochemical characterizations (XRD, Raman, FESEM, TEM, and N₂ adsorption-desorption) reveal that addition of MgO in CeO₂ and an optimal amount of Sn decrease both Ni and support particle sizes while oxygen storage capacity (OSC) of the support increases (by XPS). Alkaline characteristics of MgO reduces support's acidity and improves active metal-support interaction, as evaluated by NH₃-TPD and H₂-TPR.     

Autothermal reforming of ethanol on noble metal catalysts

Autothermal reforming of ethanol on zirconia-supported Rh and Pt mono- and bimetallic catalysts (0.5 wt-% total metal loading) was studied as a source of H₂-rich gas for fuel cells. The results were compared with those obtained on a commercial steam reforming catalyst (15 wt-% NiO/Al₂O₃). The Rh-containing catalysts exhibited the highest selectivity for H₂ production and were stable in 24 h experiments. The formation of carbonaceous deposits was lower on the noble metal catalysts than on the commercial NiO/Al₂O₃ catalyst. Thus, the Rh-containing catalysts are more suitable than the commercial NiO/Al₂O₃ catalysts for the ATR of ethanol.     

Promotion of CO2 methanation activity and CH4 selectivity at low temperatures over Ru/CeO2/Al2O3 catalysts

The effect of CeO₂ loading amount of Ru/CeO₂/Al₂O₃ on CO₂ methanation activity and CH₄ selectivity was studied. The CO₂ reaction rate was increased by adding CeO₂ to Ru/Al₂O₃, and the order of CO₂ reaction rate at 250 °C is Ru/30%CeO₂/Al₂O₃ > Ru/60%CeO₂/Al₂O₃ > Ru/CeO₂ > Ru/Al₂O₃. With a decrease in CeO₂ loading of Ru/CeO₂/Al₂O₃ from 98% to 30%, partial reduction of CeO₂ surface was promoted and the specific surface area was enlarged. Furthermore, it was observed using FTIR technique that intermediates of CO₂ methanation, such as formate and carbonate species, reacted with H₂ faster over Ru/30%CeO₂/Al₂O₃ and Ru/CeO₂ than over Ru/Al₂O₃. These could result in the high CO₂ reaction rate over CeO₂-containing catalysts. As for the selectivity to CH₄, Ru/30%CeO₂/Al₂O₃ exhibited high CH₄ selectivity compared with Ru/CeO₂, due to prompt CO conversion into CH₄ over Ru/30%CeO₂/Al₂O₃.     

Aqueous-phase reforming of n-BuOH over Ni/Al2O3 and Ni/CeO2 catalysts

The aqueous-phase reforming (APR) of n-butanol (n-BuOH) over Ni(20 wt%) loaded Al₂O₃ and CeO₂ catalysts has been studied in this paper. Over 100 h of run time, the Ni/Al₂O₃ catalyst showed significant deactivation compared to the Ni/CeO₂ catalyst, both in terms of production rates and the selectivity to H₂ and CO₂. The Ni/CeO₂ catalyst demonstrated higher selectivity for H₂ and CO₂, lower selectivity to alkanes, and a lower amount of C in the liquid phase compared to the Ni/Al₂O₃ sample. For the Ni/Al₂O₃ catalyst, the selectivity to CO increased with temperature, while the Ni/CeO₂ catalyst produced no CO. For the Ni/CeO₂ catalyst, the activation energies for H₂ and CO₂ production were 146 and 169 kJ mol⁻¹, while for the Ni/Al₂O₃ catalyst these activation energies were 158 and 175 kJ mol⁻¹, respectively. The difference of the active metal dispersion on Al₂O₃ and CeO₂ supports, as measured from H₂-pulse chemisorption was not significant. This indicates deposition of carbon on the catalyst as a likely cause of lower activity of the Ni/Al₂O₃ catalyst. It is unlikely that carbon would build up on the Ni/CeO₂ catalyst due to higher oxygen mobility in the Ni doped non-stoichiometric CeO₂ lattice. Based on the products formed, the proposed primary reaction pathway is the dehydrogenation of n-BuOH to butaldehyde followed by decarbonylation to propane. The propane then partially breaks down to hydrogen and carbon monoxide through steam reforming, while CO converts to CO₂ mostly through water gas shift. Ethane and methane are formed via Fischer-Tropsch reactions of CO/CO₂ with H₂.     

Study on the preparation of Ni–La–Ce oxide catalyst for steam reforming of ethanol

Two schemes for design and preparation of Ni–La–Ce oxide catalysts for steam reforming of ethanol were proposed in this work. The one via citrate complexing method was designed as NiO supported on ceria-lanthanum oxide (CL) solid solution, in which the strong interaction between NiO and CL solid solution was beneficial to inhibit the aggregation of NiO particles, and the abundant of oxygen vacancies existed in CL solid solution was in favor of carbon elimination from catalyst surface. The other was schemed as LaNiO₃ with perovskite structure loaded on CeO₂ support by using impregnation method, in which the particles of metal Ni derived from reduction of LaNiO₃ were highly dispersed, and the formation of La₂O₂CO₃ in the reaction process could act as the carbon scavenger. Both of the catalysts exhibited very good performance for steam reforming of ethanol (SRE), complete C₂H₅OH conversion was obtained with 70.3% of H₂ selectivity at 400 °C over the catalyst obtained from former method and complete C₂H₅OH conversion was achieved at 450 °C with 67% of H₂ selectivity over the catalyst from latter method. The catalyst made according to the citrate complexing method was more active for SRE and more selective for H₂ production. Both of the catalysts displayed very good anti-sintering ability which was tested at 650 °C and at a high space velocity of 180,000 ml g_cat⁻¹ h⁻¹ with reaction mixture of H₂O/C₂H₅OH = 3 in mole ratio. The results indicated that both of oxygen vacancy and La₂O₂CO₃ possessed the ability to remove the deposited carbon, and compared with La₂O₂CO₃ the oxygen vacancy could reduce one third more of the carbon deposited according to TG tests.     

Cu,Mg and Co effect on nickel-ceria supported catalysts for ethanol steam reforming reaction

Ethanol steam reforming is a promising reaction which produces hydrogen from bio and synthetic ethanol. In this study, the nano-structured Ni-based bimetallic supported catalysts containing Cu, Co and Mg were synthesized through impregnation method and characterized by XRD, BET, SEM, TPR and TPD analysis. The prepared catalysts were tested in steam reforming of ethanol in the S/C = 6, GHSV of 20,000 mL/(g_cat h) at the temperature range of 450–600 °C. Among the xNi/CeO₂ (x = 10, 13, 15 wt%) catalyst, the sample containing 13 wt% Ni with surface area of 64 m²/g showed the best performance with 89% ethanol conversion and 71% H₂ selectivity as well as low CO selectivity of 8% at 600 °C and The addition of Cu, Mg, and Co to catalyst structure were evaluated and it was found that the nature of second metal has a strong influence on the catalyst selectivity for H₂ production. Considering to results of TPR analysis, the 13Ni–4Cu/CeO₂ catalyst showed proper reduction which caused in better activity. On the other side based on TPD analysis, the more basic property of 13Ni–4Mg/CeO₂ bimetallic catalyst provided a better condition to methane steam reforming, leading to lower CH₄ selectivity and consequently more H₂ production. The 13Ni–4Cu/CeO₂ exhibited the highest activity and lowest selectivity towards ethanol conversion and CO production about 99% and 4%, while the 13Ni–4Mg/CeO₂ catalyst possessed the highest H₂ selectivity and lowest CH₄ selectivity about 74% and 1% respectively at 600 °C. The Ni–Cu and Ni–Mg bimetallic catalysts shows good stability with time on stream.     

Copper catalysts prepared via microwave-heated polyol process for preferential oxidation of CO in H2-rich streams

The purposes of this study were to prepare a copper catalyst by the microwave-heated polyol (MP) process and subsequently to evaluate the feasibility of the preferential oxidation of CO (CO-PROX) in excess H₂. A CeO₂-TD support was firstly prepared by the thermal decomposition from Ce(NO₃)₃·6H₂O precursor. For comparison, commercial ceria (CeO₂-C) and activated carbon (AC) selected as support materials. Experimental results of CO-PROX indicated that the highest catalytic activity is achieved when the Cu/CeO₂-TD used as catalysts. Correlating to the characteristic results, it is found that the CeO₂-TD support prepared by the thermal decomposition has a large surface area and high mesoporosity; these properties contribute to the easy adsorption of pollutants and the effective dispersion of metal particles. Further investigation of feed composition found that Cu/CeO₂-TD catalysts possess 100% CO conversion even existence of CO₂ and H₂O in H₂-rich streams at 150 °C. Besides, a decrease in CO conversion was clearly observed above 175 °C for Cu/CeO₂-TD catalysts due to the reverse water gas shift reaction tending to reform CO from CO₂ and H₂.     

Hydrogen production from oxidative steam reforming of ethanol over rhodium catalysts supported on Ce–La solid solution

The catalytic behaviors of Rh catalysts supported on Ce–La solid solution in H₂ production from the oxidative steam reforming (OSR) of ethanol were studied for the first time. 1%Rh/Ce_0.7La_0.3O_y exhibits 100% ethanol conversion at 573 K with H₂ yield rate 214 μmol g-cat⁻¹ s⁻¹, which is 150 K lower than that required for comparable performance with 1%Rh/CeO₂. La doping also enhanced the stability by accelerating CH₃COCH₃ conversion and gave low CO selectivity due to the high water gas shift activity. X-ray diffraction and Raman spectroscopy characterizations indicate the formation of Ce–La solid solutions and oxygen vacancies. H₂ temperature-programmed reduction and thermo-gravimetric measurement results confirmed that the redox properties of Rh/CeO₂ were greatly enhanced by La doping, which accelerated ethanol conversion, promoted H₂ yield, and maintained good long–term activity for the OSR reaction.     

Cooperative role of cobalt and gallium under the ethanol steam reforming on Co/CeGaOx

The performance of gallium promoted cobalt-ceria catalysts for ethanol steam reforming (ESR) was studied using H₂O/C₂H₅OH = 6/1 mol/mol at 500 °C. The catalysts were synthetized via cerium-gallium co-precipitation and wetness impregnation of cobalt. A detailed characterization by N₂-physisorption, XRD, H₂-TPR and TEM allowed the normalization of contact time and rationalization of the role of each catalysts component for ESR. The gallium promoted catalyst, Co/Ce₉₀Ga₁₀O_x, was more efficient for the ethanol conversion to H₂ and CO₂, and the production of oxygenated by-products (such as, acetaldehyde and acetone) than Co/CeO₂. The catalytic performance is explained assuming that: (i) bare ceria is able to dehydrogenate ethanol to ethylene; (ii) Ce–O–Ga interface catalyzes ethanol reforming; (iii) both Ce–O–Co and Ce–O–Ga interfaces takes part in acetone production; and (iv) cobalt sites further allow C–C scission. It is suggested that a cooperative role between Co and Ce–O–Ga sites enhance the H₂ and CO₂ yields under ESR conditions.     

Oxidative steam reforming of ethanol over Rh based catalysts in a micro-channel reactor

Oxidative steam reforming of ethanol (OSRE) was studied over Rh/CeO₂/Al₂O₃ catalysts in a micro-channel reactor. First, the catalyst support, Al₂O₃, was deposited on to the metallic substrate by washcoating and then the CeO₂ and active metal were sequentially impregnated. The effect of support composition as well as active metal composition on oxidative steam reforming of ethanol in a micro-channel reactor was studied at atmospheric pressure, with water to ethanol molar ratio of 6 and oxygen to ethanol molar ratio ranging from 0.5 to 1.5, over a temperature range of 350-550 °C. Ceria added to 1%Rh/Al₂O₃ showed higher activity and selectivity than 1%Rh/Al₂O₃ alone. Out of the various catalysts tested, 2%Rh/20%CeO₂/Al₂O₃ performed well in terms of activity, selectivity and stability. The OSRE performance was compared with that of SRE over 2%Rh/20%CeO₂/Al₂O₃ catalyst at identical operating conditions. Compared to SRE, the activity in OSRE was higher; however the selectivity to desired products was slightly lower. The H₂ yield obtained in OSRE was ∼112 m³ kg⁻¹ h⁻¹, as compared to ∼128 m³ kg⁻¹ h⁻¹ in SRE. The stability test performed on 2%Rh/20%CeO₂/Al₂O₃ at 500 °C for OSRE showed that the catalyst was stable for ∼40 h and then started to deactivate slowly. The comparison between packed bed reactor and micro-channel reactor showed that the micro-channel reactor can be used for OSRE to produce hydrogen without any diffusional effects in the catalyst layer.     

Combustion synthesis of copper catalysts for selective CO oxidation

Copper catalysts supported on ceria, zirconia and niobia were prepared by combustion method with urea, containing a CuO loading of 6 wt.%, and tested on selective oxidation of CO. The characterization of the samples by X-ray diffraction (XRD) presented the formation of solid solution on CuO–CeO₂ catalyst and a change in crystalline structure of the support with copper insertion on ZrO₂ and Nb₂O₅ catalysts. The analysis of temperature-programmed reduction (TPR) revealed different interaction degrees of copper with the supports, with reduction peaks between 222 and 390 °C. The temperature-programmed desorption of CO (TPD-CO) profiles showed formation of CO₂ and H₂ only for the ceria and zirconia catalysts. In relation to the catalytic tests, the CuO–CeO₂ catalyst presented the best performance, with CO conversion of 95% at 150 °C up to 45 h on stream, and CO₂ selectivity of 55%.