Hydrogen production by steam methane reforming in a membrane reactor equipped with a Pd composite membrane deposited on a porous stainless steel

With the aim of producing hydrogen at low cost and with a high conversion efficiency, steam methane reforming (SMR) was carried out under moderate operating conditions in a Pd-based composite membrane reactor packed with a commercial Ru/Al₂O₃ catalyst. A Pd-based composite membrane with a thickness of 4–5 μm was prepared on a tubular stainless steel support (diameter of 12.7 mm, length of 450 mm) using electroless plating (ELP). The Pd-based composite membrane had a hydrogen permeance of 2.4 × 10^?3 mol m^?1 s^?1 Pa^?0.5 and an H₂/N₂ selectivity of 618 at a temperature of 823 K and a pressure difference of 10.1 kPa. The SMR test was conducted at 823 K with a steam-to-carbon ratio of 3.0 and gas hourly space velocity of 1000 h^?1; increasing the pressure difference resulted in enhanced methane conversion, which reached 82% at a pressure difference of 912 kPa. To propose a guideline for membrane design, a process simulation was conducted for conversion enhancement as a function of pressure difference using Aspen HYSYS^®. A stability test for SMR was conducted for ～120 h; the methane conversion, hydrogen production rate, and gas composition were monitored. During the SMR test, the carbon monoxide concentration in the total reformed stream was <1%, indicating that a series of water gas shift reactors was not needed in our membrane reactor system.     

Ethanol steam reforming reaction in a porous stainless steel supported palladium membrane reactor

In this experimental work, the ethanol steam reforming reaction is performed in a porous stainless steel supported palladium membrane reactor with the aim of investigating the influence of the membrane characteristics as well as of the reaction pressure. The membrane is prepared by electroless plating technique with the palladium layer around 25 μm deposited onto a stainless steel tubular macroporous support. The experimental campaign is directed both towards permeation and reaction tests. Firstly, pure He and H₂ are supplied separately between 350 and 400 °C in the MR in permeator modality for calculating the ideal selectivity αH₂/He. Thus, the MR is packed with 3 g of a commercial Co/Al₂O₃ catalyst and reaction tests are performed at 400 °C, by varying the reaction pressure from 3.0 to 8.0 bar. Experimental results in terms of ethanol conversions as well as recovery and purity of hydrogen are given and compared with some results in the same research field from the open literature.As best result of this work, 100% ethanol conversion is reached at 400 °C and 8 bar, recovering a hydrogen-rich stream consisting of more than 50% over the total hydrogen produced from reaction, having a purity around 65%.     

Co-current and counter-current modes for methanol steam reforming membrane reactor

In this simulation study, methanol steam reforming reaction to produce synthesis gas has been studied in a membrane reactor when shell side and lumen side streams are in co-current mode or in counter-current mode. The simulation results for both co-current and counter-current modes are presented in terms of methanol conversion and molar fraction versus temperature, pressure, _H2O/_CH3OH${\mathrm{H}}_2\mathrm{O}/{\mathrm{CH}}_3\mathrm{OH}$ molar feed flow rate ratio and axial co-ordinate.     

Techno-economic assessment of solar steam reforming of methane in a membrane reactor using molten salts as heat transfer fluid

This paper reports the results obtained in a techno-economic analysis of the Steam Methane Reforming (SMR) technology aided with solar heat, developed and demonstrated in the European FCH JU project CoMETHy: a compact membrane reformer heated with molten salt up to 550 °C allowed to simultaneously carry out methane steam reforming, water-gas-shift reaction and hydrogen separation. This reactor can be integrated with new generation Concentrating Solar Thermal (CST) systems to supply the process heat. Experimental validation of the technology has been successfully achieved in a pilot scale plant and the results recently published. In this paper, we introduce a fully-integrated scheme and operation strategies of a plant on the 1500 Nm³/h hydrogen production scale. Then, techno-economic analysis of this new solar-driven process is presented to evaluate its competitiveness. Considering a plant capacity of 1500 Nm³/h (pure hydrogen production) and today's costs for the methane feed and the CST technology, obtained Hydrogen Production Cost (HPC) are in the range of 2.8–3.3 €/kg for a “solar-hybrid” system with high capacity factor (8000 h/year operation) and 4.7 €/kg for a “solar-only” case, while HPC≅1.7 €/kg can be obtained with the conventional route under equivalent assumptions. However, a sensitivity analysis shows that the expected drop of the cost of the CST technology will bring the HPC around 2.4 €/kg for the “solar-hybrid” case and close to 3.4 €/kg for the “solar-only” case, thus making the cost of solar reforming closer to conventional SMR with CO₂ capture and with wind/solar electrolysis in the future. In the “solar-hybrid” case total CO₂ production can be reduced by 13–29% with 58–70% of produced CO₂ recovered as pure stream (at 1.3 bar); in the “solar-only” case total CO₂ production can be reduced by 52% and 100% of produced CO₂ recovered as pure stream (at 1.3 bar). However, compared to the conventional route, CO₂ avoidance costs are still relatively high (≥137 €/ton_CO2) and process optimization measures required. Therefore, optimization measures have been outlined to increase the overall process efficiency and further reduce the HPC.     

Methanol and ethanol steam reforming in membrane reactors: An experimental study

In this work a comparison between methanol steam reforming (MSR) reaction and ethanol steam reforming (ESR) reaction to produce hydrogen in membrane reactors (MRs) is discussed from an experimental point of view.     

Steam reforming of simulated pre-reformed naphtha in a PdAu membrane reactor

Process intensification in a membrane reactor is an efficient and compact way to produce hydrogen. A methane-rich gas mixture that simulated the composition of pre-reformed naphtha (PRN; with a steam-to-carbon ratio of 2.7) was reformed at temperatures of 550 °C–625 °C and pressures up to 40 barg. The reactor contained commercial steam reforming catalyst and a 14.8 cm long, 2.6 μm thick Pd-1.8Au (wt. %) membrane on a porous alumina support. Methane conversions approaching 90% were obtained in the membrane reactor at a gas-hourly space velocity of 676 h^?1, compared to ≤30% conversion at the same conditions in conventional reactor mode (CM) without withdrawing hydrogen through the membrane. The results were compared to steam methane reforming (SMR) in the membrane reactor at similar conditions. The nitrogen leak through the membrane increased slowly during the testing, because of both pinhole formation and some leakage through the end seals.     

Compartment model for steam reforming of methane in a membrane-assisted bubbling fluidized-bed reactor

A compartment model was developed to describe the flow pattern of gas within the dense zone of a membrane-assisted fluidized-bed reactor (MAFBR), in the bubbling mode of operation for steam reforming of methane both with (adiabatic) and without (isothermal) entering oxygen. Considering such a flow pattern and using the experimental data reported elsewhere [Roy S, Pruden BB, Adris AM, Grace JR, Lim CJ. Fluidized-bed steam methane reforming with oxygen input. Chem Eng Sci 1999; 54:2095–2102.], the parameters of the developed model (i.e., number of compartments for the bubble and emulsion phases) were determined and fair agreements were obtained between model predictions and experimental data. The developed model was utilized to describe the behavior of an industrial scale adiabatic and isothermal MAFBR. Moreover, the influences of various operating and design parameters such as steam-to-methane ratio (SMR), oxygen-to-methane ratio (OMR), operating temperature and pressure, and the number of hydrogen membrane tubes on the performance capability of the MAFBR were investigated. Furthermore, the performance capability of the MAFBR was optimized subject to the various operating and design constraints, including 1 ≤ SMR ≤ 4 and 500 ≤ T ≤ 1250 K, in the bubbling regime.     

Influence of the pre-reformer in steam reforming of dodecane using a Pd alloy membrane reactor

Dodecane, one of the main components in kerosene, was used as a model material to investigate reactions in a palladium membrane reactor for steam reforming of kerosene. The influence of pre-reforming on the performance of the membrane reactor was investigated. A decrease in hydrogen yield caused by coke formation was suppressed through pre-reforming by lowering the concentration of olefins, aromatics and unreacted dodecane in the feed to the membrane reactor. In addition, the proportion of total hydrogen production that permeated the membrane was clearly higher with pre-reforming compared with that without pre-reforming. Pre-reforming prevented deactivation of both the catalyst and the membrane, resulting in efficient separation of hydrogen from the reaction field and therefore achieving a higher hydrogen yield.     

Methane steam reforming operation and thermal stability of new porous metal supported tubular palladium composite membranes

In 2009 cooperation between Plansee SE, Austria (PSE), Karlsruhe Institute of Technology, Germany (KIT) and the Engineering Division of Linde AG, Germany (LE) was set up with the aim to develop new tubular palladium composite membranes and a membrane reformer system for small scale on-site hydrogen production.     

Catalytic reforming of natural gas for hydrogen production in a pilot fluidized-bed membrane reactor: Mapping of operating and feed conditions

A fluidized-bed membrane reformer was operated in two independent laboratories to map various operating conditions, to investigate the effects of changing the composition of the natural gas feed stream and to verify earlier experimental trials. Two feed natural gases were tested, containing either 95.5 or 90.1 mol% of methane (3.6 or 9.9 mol% of other gaseous higher hydrocarbons). Experimental tests investigated the influence of total membrane area, reactor pressure, permeate pressure and natural gas feed rates. A permeate-H₂-to reactor natural gas feed molar ratio >2.3 was achieved with six two-sided membrane panels under steam reforming conditions and a pressure differential across the membranes of 785 kPa. The total cumulative reforming time reached 395 h, while hydrogen purity exceeded 99.99% during all tests.     

Pd–Ag membrane reactor for steam reforming reactions: A comparison between different fuels

The simulation of a dense Pd-based membrane reactor for carrying out the methane, the methanol and the ethanol steam reforming (SR) reactions for pure hydrogen production is performed. The same simulation is also performed in a traditional reactor.     

Steam reforming of heptane in a fluidized bed membrane reactor

n-Heptane served as a model compound to study steam reforming of naphtha as an alternative feedstock to natural gas for production of pure hydrogen in a fluidized bed membrane reactor. Selective removal of hydrogen using Pd₇₇Ag₂₃ membrane panels shifted the equilibrium-limited reactions to greater conversion of the hydrocarbons and lower yields of methane, an intermediate product. Experiments were conducted with no membranes, with one membrane panel, and with six panels along the height of the reactor to understand the performance improvement due to hydrogen removal in a reactor where catalyst particles were fluidized. Results indicate that a fluidized bed membrane reactor (FBMR) can provide a compact reformer for pure hydrogen production from a liquid hydrocarbon feedstock at moderate temperatures (475-550 °C). Under the experimental conditions investigated, the maximum achieved yield of pure hydrogen was 14.7 moles of pure hydrogen per mole of heptane fed.     

Evaluation of silica membrane reactor performance for hydrogen production via methanol steam reforming: Modeling study

The aim of this work is to analyze the potential application of microporous silica membrane reactor carrying out methanol steam reforming reaction for hydrogen production. As a further study, a comparison with dense Pd–Ag membrane reactor and a traditional reactor, working at the same operating conditions of silica membrane reactor, is realized.     

Effect of palladium addition on catalytic activity in steam methane reforming over Ni-YSZ porous membrane

This study investigated the additive effects of palladium, and the deposition method of palladium on Ni-YSZ porous membrane in steam methane reforming. Pd–Ni-YSZ porous membrane prepared by the wet impregnation method showed superior catalytic activity, where the methane conversion reached 94.6% at 650 °C, with H₂ yield above 3.9. The palladium particles were well dispersed, and the Pd–Ni-YSZ porous membrane exhibited high adsorption capacity for water. The addition of palladium and the deposition method of palladium are very important for the steam methane reforming reaction.     

Methane steam reforming using a membrane reactor equipped with a Pd-based composite membrane for effective hydrogen production

Herein, a methane steam reforming (MSR) reaction was carried out using a Pd composite membrane reactor packed with a commercial Ru/Al₂O₃ catalyst under mild operating conditions, to produce hydrogen with CO₂ capture. The Pd composite membrane was fabricated on a tubular stainless steel support by the electroless plating (ELP) method. The membrane exhibited a hydrogen permeance of 2.26 × 10^?3 mol m² s^?1 Pa^?0.5, H₂/N₂ selectivity of 145 at 773 K, and pressure difference of 20.3 kPa. The MSR reaction, which was carried out at steam to carbon ratio (S/C) = 3.0, gas hourly space velocity (GHSV) = 1700 h^?1, and 773 K, showed that methane conversion increased with the pressure difference and reached 79.5% at ΔP = 506 kPa. This value was ～1.9 time higher than the equilibrium value at 773 K and 101 kPa. Comparing with the previous studies which introduced sweeping gas for low hydrogen partial pressure in the permeate stream, very high pressure difference (2500–2900 kPa) for increase of hydrogen recovery and very low GHSV (<150) for increase hydraulic retention time (HRT), our result was worthy of notice. The gas composition monitored during the long-term stability test showed that the permeate side was composed of 97.8 vol% H₂, and the retentate side contained 67.8 vol% CO₂ with 22.2 vol% CH₄. When energy was recovered by CH₄ combustion in the retentate streams, pre-combustion carbon capture was accomplished using the Pd-based composite membrane reactor.     

Steam reforming of propane in a fluidized bed membrane reactor for hydrogen production

Steam reforming of propane was carried out in a fluidized bed membrane reactor to investigate a feedstock other than natural gas for production of pure hydrogen. Close to equilibrium conditions were achieved inside the reactor with fluidized catalyst due to the very fast steam reforming reactions. Use of hydrogen permselective Pd₇₇Ag₂₃ membrane panels to extract pure hydrogen shifted the reaction towards complete conversion of the hydrocarbons, including methane, the key intermediate product. Irreversible propane steam reforming is limited by the reversibility of the steam reforming of this methane. To assess the performance improvement due to pure hydrogen withdrawal, experiments were conducted with one and six membrane panels installed along the height of the reactor. The results indicate that a compact reformer can be achieved for pure hydrogen production for a light hydrocarbon feedstock like propane, at moderate operating temperatures of 475–550 °C, with increased hydrogen yield.     

Production of enriched methane by a molten-salt concentrated solar power plant coupled with a steam reforming process: An LCA study

Enriched Methane is a gas mixture consisting of methane and a certain amount of hydrogen (10–30%vol) that finds out several applications such as fuel of Internal Combustion Engines (ICEs). To produce EM, a steam reforming reactor whose heat duty is supplied by a molten-salt stream heated up by a concentrating solar power (CSP) plant can be used, in order to generate the hydrogen steam by solar energy. In fact, molten salts at temperatures up to 550 °C can allow to reach the necessary thermal level inside the reactor to promote steam reforming reaction.     

Comparative study of propane steam reforming in vanadium based catalytic membrane reactor with nickel-based catalysts

The performance of catalytic membrane reactor with Pd-coated V membrane was examined for steam reforming of propane. The long term reforming experiment confirmed the stability of the V membrane with high hydrogen selectivity and permeability. The effect of types of hydrogen permeable membranes on the performance of the catalytic membrane reactor was studied by comparing Pd-coated V, Pd–23Ag, and Pd–10Ag membranes. The types of hydrogen separation membranes (i.e. hydrogen removal rates) did not have a marked effect on the propane conversion rates, while the product compositions were largely influenced by the hydrogen removal rate. Varying metal oxide supports of Ni-catalysts resulted in significant differences in the product compositions. Further, the evaluation of various catalyst-support systems (9wt%Ni–1wt%M/CeO₂, M = Co, Pt, Ag, Ru) revealed that hydrogen yield was the highest when 1wt%Ag was added to Ni/CeO₂. However, it was also found that excessive secondary metal additions can have negative impact on the catalytic behaviour of parent catalysts.