Steam Reforming Of Bioethanol Research Articles

Bio-ethanol steam reforming and autothermal reforming in 3-μm channels coated with RhPd/CeO2 for hydrogen generation

A silicon micromonolith of 7mm diameter and 0.2mm length containing 1.5 million regular channels with a diameter of 3.3μm was used for obtaining hydrogen through ethanol or bio-ethanol steam reforming (ESR) and oxidative steam reforming (OSR). The microchannels were coated with RhPd/CeO2 catalyst by a two-step method. First a CeO2 layer of ca. 100nm thickness was deposited from cerium methoxyethoxide over a SiO2 layer, which was previously grown over the silicon microchannels by oxidation. Then, noble metals were grafted over the CeO2 support from chloride precursors. The unit was successfully tested for hydrogen production, achieving hydrogen rates of 180 LH2 cmR−3 for the steam reforming of bio-ethanol at 873K, S/C=2 and 0.009s contact time. Reaction yields of 3.8 and 3.7mol hydrogen generated per mol ethanol in feed were measured for ESR and OSR, respectively. A performance comparison was performed with a conventional cordierite monolith with the same catalyst formulation. Results show for the silicon microreactor an outstanding improvement of the specific hydrogen production rate, operating at considerably reduced residence times, due to the increase in contact area per unit volume.

Cobalt hydrotalcites as catalysts for bioethanol steam reforming. The promoting effect of potassium on catalyst activity and long-term stability

Cobalt hydrotalcite-derived catalysts, doped with potassium, are active materials for the ethanol steam reforming reaction. Potassium addition reduces the acid sites number and strength. It acts as a promoter of the ethanol steam reforming (ESR); ethanol conversion is higher at lower temperature, as the amount of potassium at the surface of the catalyst increases. The catalysts are stable for long-term experiments (300h) under high loads of ethanol and bioethanol (0.036gEtOHmin−1, H2O:CH3CH2OH=4:1 molar). Moreover, they generate a low amount of carbon (0.0067gCgcatalyst−1h−1). The catalysts after reaction contain almost exclusively high spin Co2+ in cobalt oxide (or in (Co,Mg)O); only traces of metallic cobalt are identified by magnetometry, <0.1wt.% Co0, suggesting that oxidized cobalt is an active species in ESR.

Pd-based membrane reactors for producing ultra pure hydrogen: Oxidative reforming of bio-ethanol

A membrane reactor consisting of a dense self-supported Pd–Ag tube of wall thickness 60 μm has been filled with a Pt-based catalyst and used for producing pure hydrogen via oxidative steam reforming of bio-ethanol. The reformer feed stream consisted of water and ethanol with traces of glycerol and acetic acid in order to simulate a liquid waste of dairy industry after fermentation and concentration.The membrane reformer has been characterized through permeation and reaction tests performed at 400 and 450 °C with a reaction (lumen) pressure in the range 100–200 kPa. The hydrogen permeated through the membrane has been collected in the reactor shell by a sweep stream of nitrogen.Permeation tests verified the complete hydrogen selectivity of the thin wall tube membrane and measured permeability values at 400–450 °C of 1–2 mol m−1 s−1 Pa−0.5 accordingly to the literature.In the reaction tests, the capability of the membrane to promote the reaction conversion (shift effect) has been demonstrated. The gas chromatographic analysis of the retentate showed very low concentration of CO and the presence of methane as a main product of side-reactions. At 400 °C the pressure affects significantly the hydrogen production and the hydrogen yield moves from 0.4 to 1 when the pressure increases from 100 to 200 kPa. Significant increase of the hydrogen production has been attained at the higher temperature of 450 °C where maximum values of hydrogen yield (close to 3) have been measured with a lumen pressure of 200 kPa. Under these conditions, the technology of Pd-based membranes is effective for recovering hydrogen from a liquid waste.

New Catalysts based on Ni-Birnessite and Ni-Todorokite for the Efficient Production of Hydrogen by Bioethanol Steam Reforming

Catalytic steam reforming of bioethanol seems to be a promise option to produce renewable hydrogen; however efficient catalysts are still under development. Recently, manganese oxide based materials (MO) are the subject of intense research as low cost, efficient, and environmentally friendly catalysts. Among them MO with layer and tunnel structure have received significant attention due to their excellent catalytic activity. Specifically, we have explored the catalytic performance of two MO containing Ni (Birnessite and Todorokite). We find that both materials are highly active and selective to produce hydrogen by steam reforming of bioethanol. Their characterization by DRX, BET area, TPR, and TEM, has allowed to find that the excellent performance exhibited by these materials could be attributed to the especial structure of these MO, which would provide high-quality positions for the stabilization of the Ni metal particles.

Comparative Study of Ni-W /CeO2, Ni-W /y-Al2O3 and Ni-W /HT Catalysts for H2 Production by Steam Reforming of Bioethanol

Ni-W catalysts supported on CeO2,Al2O3 and hydrotalcite (HT) were studied in the steam reforming of ethanol at 500-650ºC. The CeO2 and HT were synthesized by impregnation and direct coprecipitation methods, respectively. Commercial Al2O3 was used. Nickel content was varied from 10, 15 and 30% with 1% W. The catalyst that presented the highest catalytic activity and selectivity to hydrogen was 10% Ni-W/HT. Conversion to ethanol was 100% and selectivities to H2, CH4, CO2 and CO were 75, 5.78, 0.37 and 18.85%, respectively, at a temperature of 500 ºC. Moreover, these catalysts showed good stability with respect to carbon deposition and low selectivity towards C2H4 production. These are desirable features for catalysts to be used in hydrogen production for fuel cell applications.

Bioethanol steam reforming on Ni-based modified mordenite. Effect of mesoporosity, acid sites and alkaline metals

Support plays an important role in the preparation of highly active and selective bioethanol steam reforming catalysts since it helps in the dispersion of metal particles and enhances its activity via metal-support interactions. The singular structure of zeolites makes these materials attractive to be used as supports for dispersing active metal phases. We have explored the activity, selectivity, and stability of Ni metal particles supported over a modified commercial Mordenite in the steam reforming of bioethanol. Commercial Mordenite has been previously modified in order to generate mesoporosity and produce good positions for the stabilisation of Ni metallic particles. The presence of mesoporosity has allowed preparing highly active catalysts for the steam reforming of bioethanol. The addition of alkaline metals (Na) has been also studied and it has been found that Na presence improves significantly the selectivity to hydrogen while decreases the coke deposition. A complete characterization of Ni-based modified Mordenite catalyst has been carried out (DRX, BET area, TPR and TEM) and interesting relationships between its catalytic performance and physico-chemical properties have been found.

Effect of crystalline modification of the support on the reduction and catalytic properties of Cu/ZrO2 catalysts in the steam reforming of bioethanol

A study was carried out on the steam reforming of bioethanol (15 vol.% ethanol in water) at 250–500 °C on copper catalysts supported on ZrO2 of the monoclinic (Z) and yttrium-stabilized tetragonal crystalline modifications (YSZ). Copper nanoparticles in such catalysts have similar reactivity regardless of the copper content and crystalline modification of the support. Cu/YSZ is highly selective relative to CO2, which may be related to enhanced mobility of oxygen in the support in the presence of Y2O3 stabilizing additive.

Selective production of hydrogen by steam reforming of bio-ethanol

Experimental results of catalytic activity, selectivity and coking phenomenon on co-precipitated cobalt catalysts with the ZnO–Al 2O 3 support in the steam reforming of ethanol (SRE) are reported. The influence of the cobalt active phase content (9–41 wt.%) and the reaction temperature (350–600 °C) was the point at issue. From the point of view of activity and selectivity, temperatures 420 °C and higher favoured steam reforming of ethanol on supported cobalt catalysts. At these temperatures the conversion of ethanol reached 100%, simultaneously the hydrogen yield achieved the level of above 5 mol of H 2 formed from 1 mol of EtOH introduced to the reaction, as well as the selectivity of carbon monoxide formation was depressed to 2–3%. However, taking into account possibility of coking of catalysts, the optimum temperature of the SRE is 420 °C. The catalyst containing 24 wt.% of cobalt was the most effective one. The obtained results are very important in the aspect of electricity generation in fuel cells feed with a reformate gas.

Catalytic Activity of Ceo2 Supported Pt-ni and Pt-co Catalysts in the Low Temperature Bio-ethanol Steam Reforming

Low temperature bio-ethanol steam reforming (ESR) can be considered a promising method to produce H2, owing the increase of thermal efficiency and reduction of capital costs. However, some detrimental effects such as lower H2 selectivity and catalyst deactivation can occur, making crucial the catalysts selection. The aim of this work is to study bimetallic Pt based catalysts for the low temperature ESR reaction in concentrated reaction mixture. Preliminary results concerning economic aspects are also reported.

Bioethanol steam reforming on Co/ITQ-18 catalyst: Effect of the crystalline structure of the delaminated zeolite ITQ-18

ITQ-18 delaminated zeolite has been used as Co support to synthesize steam reforming catalysts. The results obtained in the steam reforming of bioethanol indicate that a highly active and selective Co-based catalyst can be prepared using this delaminated zeolite as support. The high hydrogen selectivity exhibited by this catalyst, together with its good stability and low CH4 and CO production, can be related to the high surface area and singular crystalline structure of this delaminated zeolite formed by array of “cups” distributed along of sheets. This particular crystalline structure seems to supply good positions for the stabilization of the Co metal particles improving their dispersion and preventing their sintering during reaction stages.

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 Nm 3/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. Using data from PRO/II simulations, the findings for the processes developed around the two reaction schemes are compared, based on a range of quantitative and qualitative measures. Full heat integration is conducted for both schemes, with two different cases developed for the prereformer scheme. Ethanol-to-hydrogen processes based on catalytic reactions can only be brought into production when suitable reaction catalysts have been developed and proved. This is the major technical challenge which must be overcome to enable the processes investigated in this study to be implemented.

Autothermal reforming of ethanol in a Pd–Ag/Ni composite membrane reactor

The main objective of this project is to study the hydrogen production reaction from oxidative steam reforming of bio-ethanol in the pertinent characteristics of a palladium–silver alloy membrane reactor. The enhancements of hydrogen permeation and of H 2/N 2 permselectivity were studied in a Ni–Pd–Ag ternary alloy membrane, which was fabricated by successive electroless plating of palladium and silver on stainless steel (PSS) supports modified with nickel electroplating. XRD, SEM, and EDS were used to characterize the surface morphology of the membranes. Ethanol–water mixture ( n water/ n ethanol = 1 or 3) and oxygen ( n oxygen/ n ethanol = 0.2 or 0.7) were fed concurrently into the membrane reactor packed with Zn–Cu commercial catalyst (MDC-3). The reaction temperatures were set at temperatures of 593–723 K and pressures of 3–10 atm. The amount of oxygen added in the feed has a significant effect on the steam reforming reaction of ethanol. At high pressures, autothermal reaction of ethanol with no need for external heating to the composite membrane reactor to produce high purity hydrogen was easily processed.

Co/ZnO and Ni/ZnO catalysts for hydrogen production by bioethanol steam reforming. Influence of ZnO support morphology on the catalytic properties of Co and Ni active phases

Renewable hydrogen production from steam reforming of bioethanol is an interesting approach to produce sustainable hydrogen. However, simultaneous competitive reactions can occur, decreasing the hydrogen production yield. To overcome this problem, modifications in the steam reforming catalysts are being studied. Ni and Co active phases supported over modified ZnO have been widely studied in hydrogen production from steam reforming of bioethanol. However, the influence of the morphology and particle size of ZnO supports on the catalytic behaviour of the supported Ni and Co has not been reported. In the present work, we show how the morphology, shape, and size of ZnO support particles can control the impregnation process of the metal active centres, which manages the properties of active metallic particles. It has been found that nanorod particles of ZnO, obtained by calcination of Zn acetate, favour the metal-support interactions, decreasing the metallic particle sizes and avoiding metal (Co or Ni) sinterization during the calcination of metal precursors. Small metallic particle sizes lead to high values of active metal exposure surface, increasing the bioethanol conversion and hydrogen production.

Steam reforming of ethanol to hydrogen over nickel metal catalysts

In the present work acid-treated Ni catalyst was investigated for the steam reforming (SR) of bio-ethanol. Influential factors, such as reaction temperature, water-to-ethanol molar ratio and liquid hourly space velocity (LHSV), were investigated. The conversions were always complete at temperatures above 773 K, regardless of the changes of the reaction conditions. The yield to hydrogen increased with the increase in temperature and H2O/C2H5OH molar ratios. The hydrogen yield up to 84% was reached under conditions: 923 K, LHSV of 5.0 ml g−1 h−1, H2O/C2H5OH ratio of 10 over the acid-treated Ni catalyst. The effects of the influential factors on the side reactions and the distribution of byproducts were discussed. Copyright © 2010 John Wiley & Sons, Ltd.

Low temperature steam reforming of bio-ethanol over Ni%CuO-&lt;SUB align=right&gt;2O&lt;SUB align=right&gt;3 catalysts

Various loadings of Ni (5-20wt%) supported on CuO-Al2O3 mixed oxide catalysts has been explored for the low temperature steam reforming of bio-ethanol. It has been found that 10wt%Ni/CuO-Al2O3 catalyst showed relatively high ethanol conversion as well as selectivity towards H2 (∼74%) compared to other catalysts. The better performance of the 10wt%Ni/CuO-Al2O3 is explained based on the physico-chemical characteristics of the catalysts determined by BET – surface area, X-ray diffraction analysis (XRD), temperature programmed reduction (TPR), O2 pulse chemisorption, X-ray photoelectron spectroscopy (XPS), Fourier transformed infrared spectroscopy (FT-IR) and differential thermal/thermo gravimetric (DT/TGA) analyses.

Nano- and micro-powder of zirconia and ceria-supported cobalt catalysts for the steam reforming of bio-ethanol

The usefulness of nano- and micro-powders of ceria and zirconia as a support of the cobalt-based catalyst as well as additional modification of zirconia-supported cobalt catalysts with cerium for the production of hydrogen in the steam reforming of bio-ethanol (SRE) for fuel cell applications was studied. It was found that mainly different structural features of the nano- and micro-powder of ceria- and zirconia-supported cobalt catalysts are higher cobalt surface area and much smaller average sizes of cobalt crystallites for the catalysts with high-dispersed support. Similarly, the presence of high-dispersed ceria introduced to the zirconia-supported catalysts simultaneously with the deposition of cobalt increases their total and active surface area as well as decreases the size of cobalt crystallites, regardless of the initial dispersion of zirconia support. The results of the temperature-programmed reduction and the temperature-programmed desorption of hydrogen showed that small crystallites of the cobalt phase strongly interact with high-dispersed ceria. Ceria has a great influence on the effects of the SRE. For the nano-powder ceria-supported cobalt catalyst and for the nano-powder zirconia-supported catalysts with the cobalt–ceria active phase the yield of hydrogen formed from one molecule of ethanol supplied to the SRE process was the highest; even at the relatively low temperature of 420 °C it is close to 5.5 mol H 2/mol EtOH. At the same time there were achieved: complete conversion of ethanol, very close to that of water and 92%, 81–84%, 5–6% selectivities to hydrogen, carbon dioxide and carbon monoxide, respectively.

The effect of electrolyte wettability on reforming catalyst in direct ethanol MCFC

To overcome the poisoning of reforming catalyst contacted with the electrolyte without degradations of performance and long-term stability, we proposed on the development of support which has low wettability to electrolyte, but still keeps high activity on steam reforming of bio-ethanol. To perform the wettability measurement, a couple of supports (MgO and PbO) were pressed to form disc-shaped specimen with relatively low porosity, and subjected to an on-line optical contact angle measurement device at MCFC operating condition. The results of wettability of the supports indicated that PbO showed low wettability to the carbonates melts giving high contact angle. The microstructure of unreacted PbO layer might be contributed to its low wettability. The highest activity was achieved with Ni/MgO, while the lowest wettability was attained with PbO as a support. Ni/1MgO·1PbO seemed to be the most promising candidate for avoiding the reforming catalyst from poisoning.

Production of Hydrogen by Steam Reforming of Bio-Ethanol Over Nickel-Copper Bimetallic Catalysts

In the present study, nickel-copper bimetallic catalysts were investigated for the steam reforming of bio-ethanol. A comparison was made to the 10% nickel and the different content of copper supported on γ-Al2O3 promoted by MgO. Experimental results showed that the 10Ni5Cu/MgO/γ-Al2O3 catalyst was superior to other catalysts, especially in terms of the hydrogen-to-carbon monoxide ratio. Influential factors, such as reaction temperature, water-to-ethanol molar ratio, and liquid hourly space velocity (LHSV), were investigated using the 10Ni5Cu/MgO/γ-Al2O3 catalyst. The conversions were always completed at temperatures above 400°C, regardless of the changes of the reaction conditions. However, the yield to hydrogen increased with the increase in temperature and H2O/C2H5OH molar ratio. The hydrogen yield up to 71% was reached under these conditions: 550°C, LHSV of 5.0 h−1, and H2O/C2H5OH ratio of 10 over the 10Ni5Cu/MgO/γ-Al2O3 catalyst. The effects of the influential factors on the side reactions and the distribution of by-products were also discussed.

Effective and stable bioethanol steam reforming catalyst based on Ni and Co supported on all-silica delaminated ITQ-2 zeolite

Catalysts based on Ni and Co supported on pure silica ITQ-2 delaminated zeolite have been prepared and tested in the bioethanol steam reforming. Ni/ITQ-2 zeolite was found the most active material while ITQ-2 zeolite containing Co exhibited the highest hydrogen selectivity and the lowest CO selectivity. Deposition of coke occurs in both materials; however, deactivation was not detected during the experimentation time (72 h). The particular structure and physico-chemical characteristics of the ITQ-2 zeolite as support [absence of acid sites, high external surface area (>800 m 2 g −1)] could account for the high activity, selectivity and stability detected.

Efficiency analysis of a combined PEFC and bioethanol-solar-reforming system for individual houses

In this research, the development of a bioethanol reforming system for fuel cells (FBSR: fuel cell with bioethanol steam reforming) using sunlight as a heat source was investigated. The system was investigated using the experimental result of catalyst performance, and numerical analysis. If ethanol purity is high, the production method of the bioethanol used for the proposal system will not be limited. The overall efficiency of the production of electricity and heat power of this system was determined by examining its thermal output characteristic. The FBSR was introduced into standard individual houses in Sapporo, Japan, for analysis. The amount of hydrogen production, the production-of-electricity characteristic, and the thermal output characteristic were examined using meteorological data on representative days in March and August. Compared with the representative day in March (28.0 MJ day−1), the solar radiation of the representative day in August (37.0 MJ day−1) is large. However, the amount of solar radiation fluctuation of the representative day in August in this analysis is large compared with the representative day in March. It depends for the overall efficiency of the system on the amount of solar radiation fluctuation rather than the amount of solar radiation. As a result, the overall efficiency of the system, defined as the rate of power and heat output compared with the amount of solar heat collected, was calculated to be 47.4 and 41.9% on the representative days in March and August, respectively. Copyright © 2009 John Wiley & Sons, Ltd.