Hydrogen-permeable Membrane Reactor Research Articles

Thermodynamic Analysis of Methylcyclohexane Dehydrogenation and Solar Energy Storage via Solar-Driven Hydrogen Permeation Membrane Reactor.

A novel methylcyclohexane (MCH) dehydrogenation system driven by solar energy with a hydrogen permeation membrane (HPM) reactor is proposed in this study. It is a promising method, via this novel system, to generate pure hydrogen and store intermittent solar energy. In this research, the thermodynamic analysis of MCH dehydrogenation via the HPM reactor was conducted based on numerical simulation. The conversion rates and thermodynamic efficiencies under different temperatures (150–350 °C), permeate pressures from 0.001 to 0.5 bar, and solar irradiation in the four seasons were studied and analyzed. Under a hydrogen partial pressure difference, HPM can separate hydrogen and shift the reaction equilibrium forward for a higher conversion rate of MCH, which can reach nearly 99.7% in this system. The first-law of thermodynamic efficiency, the solar-to-fuel efficiency, and the exergy efficiency are up to 95.58%, 38.65%, and 94.22%, respectively. This study exhibits the feasibility and potential of MCH dehydrogenation via the HPM reactor driven by solar energy and provides a novel approach for solar energy storage.

Innovative non–oxidative methane dehydroaromatization via solar membrane reactor

A novel solar–driven Non–Oxidative Methane Dehydroaromatization (NO–MDA) system integrated with membrane reactor is proposed in this study. NO–MDA driven by solar energy is a promising method to directly product benzene and pure hydrogen, in which solar thermal energy is converted into chemical energy. In this study, kinetic and thermodynamic analyses of NO–MDA via hydrogen permeation membrane (HPM) reactor were conducted based on numerical simulation. The partial pressure, conversion rate and thermodynamic efficiency under different temperatures (600–800 °C) and permeate pressures (0.01–1 bar) were studied and analyzed. Pure hydrogen and a near complete conversion rate (99.9%) are theoretically obtained due to the separation of hydrogen via HPM reactor, which shifts the reaction equilibrium forward for higher conversion rate. The first–law thermodynamic efficiency, the solar–to–fuel efficiency, and the exergy efficiency can reach as high as 85.89%, 33.72%, and 88.12%, respectively. This study exhibits the feasibility of efficient NO–MDA via HPM reactor driven by solar energy.

CFD Simulation of a Hydrogen-Permeable Membrane Reactor for CO2 Reforming of CH4: The Interplay of the Reaction and Hydrogen Permeation

A symmetric 2D CFD model of catalytic membrane reactor for dry reforming of methane (DRM) was built up. Nondimensionalization method was employed and the governing equations were simplified. Crucia...

Dual utilization of greenhouse gases to produce C2+ hydrocarbons and syngas in a hydrogen-permeable membrane reactor

The direct utilization of CH4 and CO2 to simultaneously produce C2+ hydrocarbons (C2 and aromatics) and syngas (CO and H2) on opposite sides of a mixed ionic-electronic conducting SrCe0.7Zr0.2Eu0.1O3-δ membrane reactor is demonstrated. On one side (interior) of the membrane reactor, direct non-oxidative methane conversion (DNMC) over an iron/silica catalyst produces C2+ hydrocarbons and H2. On the other side (outer surface) of the membrane, permeated hydrogen (driving the DNMC reaction) reacts with a CO2 sweep gas to form CO and water via the reverse water gas shift (RWGS) reaction. This novel single hydrogen-permeable membrane reactor simultaneously addresses both reduction of greenhouse gas (CO2 and CH4) emissions as well as production of value-added hydrocarbon products (C2+, CO, and H2) with in situ gas separation.

Experimental investigation of methane auto-thermal reforming in hydrogen-permeable membrane reactor for pure hydrogen production

An experimental investigation was investigated in order to assess the performance of the methane auto-thermal reforming (MATR) for hydrogen production over a nickel catalyst on an alumina support in both a traditional reactor (TR) and a membrane reactor (MR). The results show that the property of the reformer is dependent on the reformer temperature, the feed flow rate, the purge gas flow rate and the mole ratio of air-methane and steam-methane. The performance of the membrane reactor is better than the traditional reactor. The optimum conditions for high methane conversion and high hydrogen yield are air-methane and steam-methane mole ratio of 1 and 2, respectively. Under these conditions, a methane conversion of 96.13%, a hydrogen yield of 70.43% and hydrogen permeation rate of 81.61% can be achieved. Experimental results in terms of methane conversion, hydrogen yield and hydrogen permeation rate were compared with the traditional reactor and literature data.

Gas to Liquids: Natural Gas Conversion to Aromatic Fuels and Chemicals in a Hydrogen-Permeable Ceramic Hollow Fiber Membrane Reactor

The performance of a dense ceramic hydrogen-permeable membrane reactor for the nonoxidative methane dehydroaromatization (MDA), according to the equilibrium reaction 6CH4 ⇆ C6H6 + 9H2 with a 6 wt % Mo/HZSM-5 bifunctional catalyst was investigated. A U-shaped ceramic hollow fiber membrane of the composition La5.5W0.6Mo0.4O11.25−δ (LWM0.4) has been used for the in situ removal of H2 to overcome thermodynamic constraints. The yield of aromatics (benzene, toluene, naphthalene) in the MDA could be increased in the beginning of the aromatization reaction by ∼50%–70%, in comparison with the fixed-bed reactor, because 40%–60% of the H2 abstracted have been extracted at 700 °C with a weight hourly space velocity (WHSV) of 840 cm3 gcat–1 h–1. These advantages of the membrane reactor operation decrease with time on stream, since the removal of H2 boosts not only CH4 conversion and yield of aromatics, but also catalyst deactivation by deposition of carbonaceous deposits. However, the catalyst system could be regenera...

Methane Steam Reforming in Hydrogen-permeable Membrane Reactor for Pure Hydrogen Production

Steam reforming of methane over a ruthenium catalyst has been carried out at 500 °C in a membrane reactor equipped with a palladium membrane supported on a porous stainless steel tube. Hydrogen and carbon dioxide are mainly produced in the reaction, while hydrogen is selectively permeated through the membrane. Since equilibrium-shift takes place by hydrogen separation from the reaction mixture, the methane conversion significantly exceeds the equilibrium value, which is low at 500 °C. The selectivity to carbon monoxide by-produced in the reaction is lower than that expected from the equilibrium. Although the equilibrium conversion decreases with an increase in the reaction pressure, the conversion with the membrane reactor can increase because the hydrogen separation is promoted by the pressure increase. The catalytic activity is an important factor to produce a sufficiently high methane conversion and it is enhanced at a high reaction pressure.

Effective Suppression of Hydrogen Poisoning from a Ru-Based Catalyst in a Ag–Pd Membrane Reactor

Abstract Ammonia synthesis was performed using a hydrogen-permeable membrane reactor with a Ru/(MgO–CeO2) catalyst (Mg:Ce = 50:50 in molar ratio; Ru loading = 5 wt %). The catalytic activity with permeated hydrogen (atomic hydrogen) was 1.6 times higher than those of with non-permeated hydrogen (molecular hydrogen). Temperature-programmed reaction experiments, which were conducted by flowing hydrogen onto the catalysts, revealed that the ceria component of the MgO–CeO2 support became much more reductive by hybridization with magnesia. The partially reduced ceria promoted the dissociative adsorption of molecular nitrogen by donating the electrons of Ce3+ ions to Ru metal particles. Furthermore, hydrogen poisoning of the Ru metal catalysts was suppressed by supplying atomic hydrogen through a Ag–Pd hydrogen-permeable membrane under well-controlled conditions to accelerate the catalytic reaction.

Pure hydrogen production by methane steam reforming with hydrogen-permeable membrane reactor

Low temperature steam reforming of methane mainly to hydrogen and carbon dioxide (CH 4 + 2H 2O → 4H 2 + CO 2) has been performed at 773 and 823 K over a commercial nickel catalyst in an equilibrium-shift reactor with an 11-μm thick palladium membrane (Mem-L) on a stainless steel porous metal filter. The methane conversion with the reactor is significantly higher than its equilibrium value without membrane due to the equilibrium-shift combined with separation of pure hydrogen through the membrane. The methane conversion in a reactor with an 8-μm membrane (Mem-H) is similar to that with Mem-L, although the hydrogen permeance through Mem-H is almost double of that through Mem-L. The amount of hydrogen separated in the reaction with Mem-H is significantly large, showing that the hydrogen separation overwhelms the hydrogen production because of the insufficient catalytic activity.

A stable, novel catalyst improves hydrogen production in a membrane reactor

The dry reforming of methane as a source of H 2 was performed using a well-known catalyst, Rh/La 2O 3, together with a novel one, Rh/La 2O 3-SiO 2, in a hydrogen-permeable membrane reactor. The catalysts were characterized by XRD, TPR, FTIR, H 2 and CO chemisorption. In all lanthanum-based catalysts, the activity remained constant after 100 h on stream at 823 K. The basis of their high stability could be traced back to the strong metal-support interaction (TPR) in Rh/La 2O 3 catalysts. The La 2O 3-SiO 2 solids are also stable even though a weaker rhodium–lanthanum interaction (TPR) can be observed. The incorporation of the promoter (La 2O 3) to the silica support induces a parallel increase in the metal dispersion (CO adsorption). The effect of the operation variables upon the performance of the membrane reactor was also studied. The novel Rh (0.6%)/La 2O 3 (27%)-SiO 2 catalyst proved to be the best formulation. Operating the membrane reactor at 823 K, both methane and CO 2 conversions were 40% higher than the equilibrium values, producing 0.5 mol H 2/mol CH 4. This catalyst, tested at W/ F three times lower than Rh (0.6%)/La 2O 3, showed a similar performance. Both the increase of the sweep gas flow rate and the decrease of the permeation area significantly affected methane conversion and H 2 production. The presence of tiny amounts of graphite only detectable through LRS did not endanger membrane stability. The better performance of Rh (0.6%)/La 2O 3 (27%)-SiO 2 is related to the high dispersion.

Effect of catalytic activity on methane steam reforming in hydrogen-permeable membrane reactor

Steam reforming of methane, mainly to hydrogen and carbon dioxide, proceeds over nickel catalysts at 800 K in an equilibrium-shift reactor with a thin palladium membrane 11 μm-thick supported on a stainless steel porous metal filter. The methane conversion greatly exceeds its equilibrium conversion due to the hydrogen separation with the membrane. The catalytic activity affects the conversion much more than in the cases using an equilibrium reactor. The conversion in the membrane reactor decreases with an increase in the space velocity of the reaction mixture, mainly because of a decrease in the hydrogen separation ratio (rate of hydrogen separation/total production rate of hydrogen). The rate of hydrogen separation depends basically on the hydrogen permeability of the membrane, but an active catalyst also increases the rate; that is, the hydrogen production rate depends on the catalytic activity. Thus, the higher rate causes the higher partial pressure of hydrogen in the reactor, while the hydrogen flux through the membrane depends on the pressure.

Steam Reforming of Methanol on Ni/Al<SUB>2</SUB>O<SUB>3</SUB> Catalyst in a Pd-membrane Reactor

The application of the membrane reactor to steam reforming of methanol was studied as a hydrogen producing reaction. The activities, stabilities and selectivities of Cu/ZnO, Ni/Al 2 O 3 and Ru/Al 2 O 3 catalysts were tested using a conventional fixed-bed flow reactor. Ni/Al 2 O 3 catalyst showed the most stable activity at 723 K but relatively low hydrogen yield because of methanation. However, the hydrogen-permeable membrane reactor suppressed methanation and hydrogen yield was enhanced compared with the conventional reactor. The membrane reactor was more effective at higher temperatures and higher WIF.

Dehydrogenation of isobutane to isobutene in a palladium membrane reactor

The dehydrogenation of isobutane to isobutene was conducted in a comparatively low-temperature range (from 623 to 723 K) using a hydrogen-permeable membrane reactor. An Al 2O 3-supported platinum catalyst exhibited high activity compared with a commercial Cr 2O 3-Al 2O 3 catalyst in a conventional flow reactor. In the membrane reactor, however, the platinum catalyst gave a lower yield of isobutene than the Cr 2O 3-Al 2O 3 catalyst, although the isobutene yields on both of these catalysts were high compared with thermodynamic equilibrium values attained in a conventional reactor. The platinum catalyst deteriorated more rapidly in the membrane reactor, due to deposition of carbonaceous material. On the other hand, undesirable side reactions such as hydroisomerization and hydrogenolysis were suppressed in the membrane reactor due to the removal of hydrogen produced from the reaction side, leading to high selectivity for isobutene. The yield of isobutene in the membrane reactor increased by the addition of tin to Pt/Al 2O 3, due to the suppression of coke formation.

Dehydrogenation of isobutane to isobutene in a palladium membrane reactor

The dehydrogenation of isobutane to isobutene was conducted in a comparatively low-temperature range (from 623 to 723 K) using a hydrogen-permeable membrane reactor. An Al 2O 3-supported platinum catalyst exhibited high activity compared with a commercial Cr 2O 3-Al 2O 3 catalyst in a conventional flow reactor. In the membrane reactor, however, the platinum catalyst gave a lower yield of isobutene than the Cr 2O 3-Al 2O 3 catalyst, although the isobutene yields on both of these catalysts were high compared with thermodynamic equilibrium values attained in a conventional reactor. The platinum catalyst deteriorated more rapidly in the membrane reactor, due to deposition of carbonaceous material. On the other hand, undesirable side reactions such as hydroisomerization and hydrogenolysis were suppressed in the membrane reactor due to the removal of hydrogen produced from the reaction side, leading to high selectivity for isobutene. The yield of isobutene in the membrane reactor increased by the addition of tin to Pt/Al 2O 3, due to the suppression of coke formation.

Promotion of the conversion of propane to aromatics by use of a palladium membrane

The conversion of propane to aromatics on a gallium loaded H-ZSM-5 catalyst was studied using a hydrogen-permeable membrane reactor. The membrane used was composed of a thin palladium film (8.6μm) supported on the outer surface of a porous alumina cylinder. For the aromatization of propane, the yield of aromatics in this membrane reactor was higher than yields reported in conventional packed bed reactors. The high yield of aromatics was credited to the suppression of the formation of by-products, methane or ethane, probably due to the selective removal of hydrogen from the reaction system. It was found from a comparative study on the conversion of propene that dehydrogenation of propane to propene was efficiently promoted using the membrane reactor.

Steam reforming of methane in a hydrogen-permeable membrane reactor

Steam reforming of methane was carried out in a reactor incorporating a hydrogen-permeable membrane, which consisted of a thin palladium film supported on a porous glass cylinder. It was shown that the supported palladium membrane promoted the hydrogen production reaction more effectively than a porous Vycor glass membrane. The level of methane conversion exceeded the equilibrium attainable in a closed system in the temperature range of 623–773 K as a result of selective removal of hydrogen from the reaction system. Under the same conditions the porous Vycor glass membrane exhibited little effect on the shift of equilibrium. The difference between these two types of membranes is attributed to their hydrogen permeabilities. Although high reaction pressures are thermodynamically unfavorable for steam reforming, the level of methane conversion in the palladium membrane reactor increased with increasing pressure on the reaction side, as a result of accelerated hydrogen flow to the permeation side.