Performance improvement of methanol steam reforming system with auxiliary heat recovery units

The thermal energy of a methanol steam reforming system is balanced with heat-up by a methanol burner, heat absorption by an evaporator, and an endothermic reforming reactor. As the thermal energy of a methanol steam reformer is delicately controlled, its thermal efficiency is significantly improved. In this study, three different system configurations are compared, namely, (1) a reference methanol steam reformer with an external evaporator, (2) a methanol steam reformer with an internal evaporator and type-1 auxiliary heat recovery unit (AHRU) with a heat source gas, and (3) a methanol steam reformer with an internal evaporator and type-2 AHRU with a heat source gas and reformed gas. These three configurations are analyzed, and the two heat recovery units are investigated. Results show that the internally evaporated methanol steam reformer efficiently converts the methanol to a hydrogen-rich mixture as exit gases are utilized to heat up the inlet methanol/water mixture.     

Characterization and activity test of commercial Ni/Al2O3, Cu/ZnO/Al2O3 and prepared Ni–Cu/Al2O3 catalysts for hydrogen production from methane and methanol fuels

In this study, methane and methanol steam reforming reactions over commercial Ni/Al₂O₃, commercial Cu/ZnO/Al₂O₃ and prepared Ni–Cu/Al₂O₃ catalysts were investigated. Methane and methanol steam reforming reactions catalysts were characterized using various techniques. The results of characterization showed that Cu particles increase the active particle size of Ni (19.3 nm) in Ni–Cu/Al₂O₃ catalyst with respect to the commercial Ni/Al₂O₃ (17.9). On the other hand, Ni improves Cu dispersion in the same catalyst (1.74%) in comparison with commercial Cu/ZnO/Al₂O₃ (0.21%). A comprehensive comparison between these two fuels is established in terms of reaction conditions, fuel conversion, H₂ selectivity, CO₂ and CO selectivity. The prepared catalyst showed low selectivity for CO in both fuels and it was more selective to H₂, with H₂ selectivities of 99% in methane and 89% in methanol reforming reactions. A significant objective is to develop catalysts which can operate at lower temperatures and resist deactivation. Methanol steam reforming is carried out at a much lower temperature than methane steam reforming in prepared and commercial catalyst (275–325 °C). However, methane steam reforming can be carried out at a relatively low temperature on Ni–Cu catalyst (600–650 °C) and at higher temperature in commercial methane reforming catalyst (700–800 °C). Commercial Ni/Al₂O₃ catalyst resulted in high coke formation (28.3% loss in mass) compared to prepared Ni–Cu/Al₂O₃ (8.9%) and commercial Cu/ZnO/Al₂O₃ catalysts (3.5%).     

Hydrogen production with a solar steam–methanol reformer and colloid nanocatalyst

In the present study a small steam–methanol reformer with a colloid nanocatalyst is utilized to produce hydrogen. Radiation from a focused continuous green light laser (514 nm wavelength) is used to provide the energy for steam–methanol reforming. Nanocatalyst particles, fabricated by using pulsed laser ablation technology, result in a highly active catalyst with high surface to volume ratio. A small novel reformer fabricated with a borosilicate capillary is employed to increase the local temperature of the reformer and thereby increase hydrogen production. The hydrogen production output efficiency is determined and a value of 5% is achieved. Experiments using concentrated solar simulator light as the radiation source are also carried out. The results show that hydrogen production by solar steam–methanol colloid nanocatalyst reforming is both feasible and promising.     

Steam reforming behavior of methanol using paper-structured catalysts: Experimental and computational fluid dynamic analysis

Copper–zinc oxide (Cu/ZnO) catalyst powders were impregnated into paper-structured composites (catalyst paper) using a papermaking process. The paper-structured catalyst was subjected to the methanol steam reforming (MSR) process and exhibited excellent performance compared with those achieved by pellet-type or powdered catalyst. The catalyst paper demonstrated a relatively stable gas flow as compared to catalyst pellets. Furthermore, the MSR process was simulated by computational fluid dynamic (CFD) analysis, and the heat conductivity influence of the catalyst layer was investigated. Higher heat conductivity contributed to both higher methanol conversion and lower carbon monoxide concentration; localization of heat and chemical species such as hydrogen and carbon dioxide were improved, resulting in suppression of reverse water–gas shift reaction. The CFD analysis was applied to the design of a catalyst layer in which a suitable shape was suggested, where carbon monoxide formation was further suppressed without a decrease in the methanol conversion.     

A novel passive feeding method for methanol steam reformers

This work presents a simple novel feeding method for a methanol steam reformer. Using a single heat source, a fixed ratio of water and methanol vapor can be fed into the reformer in a passive way. By adjusting the thermal resistances of the two separate heat paths, different amounts of heat, related to the stoichiometric ratio and heats of evaporation, are conducted to two separate evaporators to vaporize the liquid fuels. Compared with the conventional practice that feeding ratio of the two fuels are actively controlled with two pumps, no pump is needed in this novel feeding system. Thus, the controlling system can be simplified and the auxiliary power consumption can be minimized. Experiments were conducted to verify the feasibility of this novel fuel-feeding method. With increasing reaction temperature, the product composition varied from 61% H₂, 20% CO₂ and 0.7% CO to 72% H₂, 22% CO₂ and 2% CO.     

In situ hydrogen utilization in an internal reforming methanol fuel cell

In this work, we report on the catalytic properties of a novel ultrathin methanol reformer incorporated into the anode compartment of a High Temperature PEM Fuel Cell (HT-PEMFC). A highly active Cu-based methanol reforming catalyst (HiFuel R120, Johnson Matthey) was deposited on the gas diffusion layer of a carbon paper and the influence of anode flow distribution through the catalytic bed was studied in the temperature range of 160–220 °C. Inhibition by produced H₂ is higher in the case of through plane flow, especially in more concentrated methanol feeds. Higher methanol conversions were achieved with the in-plane flow distribution along the catalytic bed (>98% at 210 °C and without any deactivation for at least 100 h test), with a 50 cm² reformer (total thickness = 600 μm). The corresponding Internal Reforming Methanol Fuel Cell (IRMFC) operated efficiently for more than 72 h at 210 °C with a cell voltage of 642 mV at 0.2 A cm⁻², when 30% CH₃OH/45% H₂O/He (anode feed) and pure O₂ (cathode feed) were supplied.     

Improved charge transfer and morphology on Ti-modified Cu/γ-Al2O3/Al catalyst enhance the activity for methanol steam reforming

The metal-oxide interaction has been considered as an effective factor for catalytic performance in methanol steam reforming. In this work, Ti modified Cu/γ-Al₂O₃/Al catalyst was prepared by anodization technology. It is found that the addition of Ti can largely increase the surface area of the carrier and thus improve the dispersion of copper. The co-existence of Ti⁴⁺ and Ti³⁺ makes the charge transfer between Cu and Ti easier, which improves the redox performance of copper. The DFT calculations reveal that Ti also enhance the adsorption capacity of water and methanol on the surface of the catalysts. Besides, Ti also reduce the acid density on the carrier, inhibit methanol dehydration reaction and thereby reduce the selectivity of the DME. The optimal catalyst CuTi_1.9/γ-Al₂O₃/Al achieves nearly 100% conversion at 275 °C, while the methanol conversion of Cu/γ-Al₂O₃/Al is 82%. And the H₂ output of CuTi_1.9/γ-Al₂O₃/Al reached 69.17 mol/(kg_cat·h) at 300 °C.     

The influence of the support composition and structure (MХZr1-XO2-δ) of bimetallic catalysts on the activity in methanol steam reforming

Metal oxide-stabilized zirconia supports (M_xZr_1-xO₂-_δ) with different dopants (M = Y, La, Ce) were prepared by coprecipitation method. Bimetallic CuNi and RuRh catalysts supported on M_xZr_1-xO₂-_δ were prepared by the sequential wetness impregnation method, for use in hydrogen production by methanol steam reforming. The effect of the nature and quantity of the dopant cation (M = Y, Ce) on the catalytic performance of zirconia supported metal catalysts was investigated. The activity of NiCu/Y_xZr_1-xO_2-(x/2) (x = 0.1–0.3) samples increases with an increase in yttrium concentration due to the formation of oxygen vacancies. The dependence of the catalytic activity on the ceria concentration was not monotonous. The sample containing 10% of cerium oxide showed the highest activity. The performance of a NiCu/La_0·1Zr_0,9O_1.95 sample was compared with the performance of a Y and Ce containing samples with the same quantity of dopant cation (10%). The La doped catalyst was more active than the yttria-containing composites, but its selectivity was lower. The catalyst based on RuRh alloy differed with significantly higher activity and lower selectivity compared with NiCu samples. The selectivity of the process was not less than 99.5% for all catalysts even at the high temperatures. At the same time, the improved activity of the catalyst also results in an increase in carbon monoxide formation while the hydrogen selectivity decreases. The optimal characteristics, such as rather high hydrogen yield, good selectivity and stability were shown by the catalyst with Ce_0·1Zr_0·9O_2-δ support.     

Synergetic integration of a methanol steam reforming cell with a high temperature polymer electrolyte fuel cell

In this work an integrated unit, combining a methanol steam-reforming cell (MSR-C) and a high temperature polymer electrolyte membrane fuel cell (HT-PEMFC) was operated at the same temperature (453 K, 463 K and 473 K) allowing thermal integration and increasing the system efficiency of the combined system. A novel bipolar plate made of aluminium gold plated was built, featuring the fuel cell anode flow field in one side and the reformer flow field on the other. The combined unit (MSR-C/HT-PEMFC) was assembled using Celtec^® P2200N MEAs and commercial reforming catalyst CuO/ZnO/Al₂O₃ (BASF RP60). The water/methanol vaporisation originates oscillations in the vapour flowrate; reducing these oscillations increase the methanol conversion from 93% to 96%. The MSR-C/HT-PEMFC showed a remarkable high performance at 453 K. The integrated unit was operated during ca. 700 h at constant at 0.2 A cm^?2, fed alternately with hydrogen and reformate at 453 K and 463 K. Despite the high operating temperature, the HT-PEMFC showed a good stability, with an electric potential difference decreasing rate at 453 K of ca. 100 μV h^?1. Electrochemical impedance spectroscopy (EIS) analysis revealed an overall increase of the ohmic resistances and charge transfer resistances of the electrodes; this fact was assigned to phosphoric acid losses from the electrodes and membrane and catalyst particle size growth.     

Biogas steam reformer for hydrogen production: Evaluation of the reformer prototype and catalysts

This work aims to investigate a biogas steam reforming prototype performance for hydrogen production by mass spectrometry and gas chromatography analyses of catalysts and products of the reform. It was found that 7.4% Ni/NiAl₂O₄/γ-Al₂O₃ with aluminate layer and 3.1% Ru/γ-Al₂O₃ were effective as catalysts, given that they showed high CH₄ conversion, CO and H₂ selectivity, resistance to carbon deposition, and low activity loss. The effect of CH₄:CO₂ ratio revealed that both catalysts have the same behavior. An increase in CO₂ concentration resulted in a decrease in H₂/CO ratio from 2.9 to 2.4 for the Ni catalyst at 850 °C, and from 3 to 2.4 for the Ru catalyst at 700 °C. In conclusion, optimal performance has been achieved in a CH₄:CO₂ ratio of 1.5:1. H₂ yield was 60% for both catalysts at their respective operating temperature. Prototype dimensions and catalysts preparation and characterization are also presented.     

An investigation of a stratified catalyst bed for small-scale hydrogen production from methanol autothermal reforming

This research project explored a methanol reforming system using a stratified catalyst bed. Commercially available catalysts were used within a single reactor and the system was run autothermally (fuel, steam and oxidizer). The investigation explored the fuel conversion and reactor temperature profile at various O₂/CH₃OH ratios. The experiments showed that the stratified system had fairly high conversions at low O₂/CH₃OH ratios. Additionally, it showed high selectivity towards hydrogen, and low selectivity for carbon monoxide. The experimental results gathered show a promising use of stratified catalyst beds for small-scale reforming systems.     

Methanol steam reforming in a planar wash coated microreactor integrated with a micro-combustor

A numerical simulation of methanol steam reforming in a microreactor integrated with a methanol micro-combustor is presented. Typical Cu/ZnO/Al₂O₃ and Pt catalysts are considered for the steam reforming and combustor channels respectively. The channel widths are considered at 700 μm in the baseline case, and the reactor length is taken at 20 mm. Effects of Cu/ZnO catalyst thickness, gas hourly space velocities of both steam reforming and combustion channels, reactor geometry, separating substrate properties, as well as inlet composition of the steam reforming channel are investigated. Results indicate that increasing catalyst thickness will enhance hydrogen production by about 68% when the catalyst thickness is increased from 10 μm to 100 μm. Gas space velocity of the steam reforming channel shows an optimum value of 3000 h⁻¹ for hydrogen yield, and the optimum value for the space velocity of the combustor channel is calculated at 24,000 h⁻¹. Effects of inlet steam to carbon ratio on hydrogen yield, methanol conversion, and CO generation are also examined. In addition, effects of the separating substrate thickness and material are examined. Higher methanol conversion and hydrogen yield are obtained by choosing a thinner substrate, while no significant change is seen by changing the substrate material from steel to aluminum with considerably different thermal conductivities. The produced hydrogen from an assembly of such microreactor at optimal conditions will be sufficient to operate a low-power, portable fuel cell.