Methanol Steam Research Articles

Post treatment and properties of PVA/SS composite nanofibers

Using deionized water as a solvent, the polyvinyl alcohol/silk sericin (PVA/SS) mixed solution was prepared, and the PVA/SS composite nanofiber membrane was spun by the electrostatic spinning method. The characteristics and properties of the PVA/SS composite nanofiber membrane untreated and treated with methanol and ethanol steam were analyzed by scanning electron microscope, infrared spectrum and X-ray diffraction. The results showed that the morphology of the PVA/SS composite nanofibers was fine in this experiment. The average diameter and standard deviation of diameter first increased, then decreased and at last increased with the increase of the SS content. The average diameter of nanofibers treated with methanol and ethanol steam was smaller than that without treatment. The infrared spectrum showed that the peak value of SS in the PVA/SS composite nanofibers treated with methanol steam and ethanol steam for 3 d changed. X-ray diffraction showed that the crystallization of the PVA/SS composite nanofiber membrane after being treated with methanol and ethanol vapor was changed. The results provide theoretical support for biomedical materials and tissue engineering scaffolds.

Direct synthesis of CuO–ZnO–CeO2 catalyst on Al2O3/cordierite monolith for methanol steam reforming

Methanol steam reforming (MSR) is a promising process for in-situ hydrogen production in vehicles. However, designing monolithic catalysts with high activity and selectivity as well as low pressure drop remains a challenge. In this work, CuO–ZnO–CeO2 catalysts were prepared directly on Al2O3/cordierite monolith through a sol-gel combustion method, and the effects of different combustion temperatures on the physicochemical properties and catalytic performance of the catalysts were investigated. It is demonstrated that the catalyst (CZC-400) prepared by combustion temperature at 400 °C is uniformly distributed on the Al2O3/cordierite monolith with smaller average catalyst particle size (4.2 nm) and higher specific surface area (23.7 m2 g−1). In the MSR, methanol conversion of CZC-400 reaches 100% at 260 °C without by-product CO. Furthermore, no significant change in the catalytic activity is observed during 32 h of the reaction. These results indicate that CZC-400 has the excellent catalytic activity and stability in the MSR.

Environmental sustainability improvement in chloromethanes production based on life cycle assessment

Chloromethanes (CMS), as major chlorine-consuming products and upstream raw material for emerging industries, play an irreplaceable role in the chemical industry and impose non-negligible environmental pressure during production. This study adopted the cradle-to-gate life cycle assessment approach to quantify the environmental performance of CMS production in China by using integrated data from five CMS enterprises, which underpin approximately 21 % of China's total CMS production capacity. An integrated and regionalized life cycle impact assessment method was employed to suit Chinese conditions and avoid spatial differences. The results indicate that fossil depletion is the dominant impact category, which was ascribed mainly to methanol production (37.0 %), electricity generation (27.3 %), and steam production (23.4 %). The coke oven gas-to-methanol process shows superiority in mitigating fossil consumption and CO 2 emission compared with the traditional coal-to-methanol process, with reduction ratios of 80.3 % and 83.2 %, respectively. Renewable energy power generation and pollution transfer in inter-regional power transmission also deserve attention. Green methanol, waste heat reuse, and advanced heat recovery technologies are recommended for further alleviation of the environmental burden. In addition, CMS-related industrial chains can improve industrial concentration and promote integrated development to achieve high-efficiency utilization of raw materials and energy.

A methanol autothermal reforming system for the enhanced hydrogen production: Process simulation and thermodynamic optimization

Methanol autothermal reforming is a potential way to produce hydrogen that can be used for vehicle power batteries like PEMFC. Combining a reformer with a combustor to produce substantial hydrogen is promising, but the challenge of heat transfer efficiency between the reformer and combustor must be considered. Furthermore, the complexity of the system structure is not conducive to its large-scale operation level. In this paper, a novel methanol autothermal reforming hydrogen production system without catalytic combustion was built and developed, aiming to produce hydrogen-rich gas with low CO concentration. Process simulation and thermodynamic optimization on the target system were detailedly performed using Aspen Plus software and parameter sensitivity analysis methods. In addition, a methanol autothermal reforming hydrogen production system using catalytic combustion was taken as the reference system. The results indicated that the novel system could achieve a self-sustaining operation by the coupled methanol partial oxidation and steam reforming. And the product gas contained very low CO concentration (<10 ppm) due to the combined effects of water-gas shifting and CO preferential oxidation reactions. It was verified that under the maximal exergy efficiency condition, the exergy efficiency of the novel system is not significantly improved compared with the reference system, but the hydrogen yield is increased by about 27.65%, the thermal efficiency is increased by about 17.51%, and the exergy loss when generating unit molar H2 is reduced by 20.53 kJ/mol; Under the condition of maximum hydrogen yield, the indicators of the novel system also perform better. Notably, the reformer is the main exergy loss source in the novel system, which provides a theoretical basis for further optimization of parameter configuration. This work will be beneficial to researchers who study the miniaturization design of the integrated system of methanol hydrogen production coupled vehicle power battery.

A Study of Thermoelectric Generation Coupled with Methanol Steam Reforming for Hydrogen Production

Waste heat recovery was considered as a promising candidate for energy conservation and emission reduction. Methanol steam reforming was considered to be an effective means for hydrogen production because of its advantages. In this work, a micro reactor was constructed and thermoelectric generation coupled with hydrogen production from methanol steam reforming was innovatively used to recycle waste heat, which was simulated by hot air from a hot air gun. The waste heat was converted into electricity and hydrogen at the same time. The characteristic of thermoelectric generation coupled with methanol steam reforming was investigated. It was experimentally verified that both the hydrogen production rate and methanol conversion increased with the increasing inlet temperature, but thermal efficiency increased firstly and then decreased with the increasing temperature. The methanol steam reforming could effectively maintain cold side temperature distribution of thermoelectric generation. In the case of the thermoelectric module (1), the highest temperature difference of 37 °C was determined and the maximum open circuit voltage of 2 V was observed. The highest methanol conversion of 64.26% was achieved at a space velocity of 0.98 h−1 when the temperature was 543 K, comprehensively considering the CO content and thermal efficiency.

Influence of ceria existence form on deactivation behavior of Cu-Ce/SBA-15 catalysts for methanol steam reforming

Methanol steam reforming (MSR) is promising in hydrogen production. Cu-SBA-15 and Cu–Ce/SBA-15-I suffer poor selectivity owing to sluggish steam activation on Cu0-SBA-15. And small Cu0 tend to sinter due to Ostwald ripening. Sintering can be avoided by modifying SBA-15 with Ce ion exchange, where Si–OH groups are replaced by Si–O–Ce. Ceria existence form varies from patches to small particles as exchange times increase. In Cu–Ce/SBA-15, ceria patches strongly interact with Cu, which promotes steam activation, hence the catalyst exhibit remarkable activity and selectivity. In Cu–3Ce/SBA-15, ceria patches grow into small ceria particles (<5 nm) after repeated ion exchange. Ceria particles tend to be over-reduced, thus accounting for carbonaceous deposits on excessive Ce3+. Such deactivation is reversible, and catalytic performance can resume after air exposure. This study reveals that deactivation behavior of MSR catalysts can be modified by existence and size effect of ceria, which is worth referring to in further MSR catalyst synthesis.

Methanol and dimethyl ether steam reforming: a thermodynamic analysis

Methanol and dimethyl ether steam reforming: a thermodynamic analysis

Comprehensive performance study on reflux solar methanol steam reforming reactor for hydrogen production

In this paper, a reflux solar methanol steam reforming reactor (SMSRR) system is proposed for efficient solar thermal hydrogen produced. A two-dimensional (2D) axisymmetric model is used to compare the comprehensive performance of three different SMSRRs: no reflux tube (SMSRR0), flow from the inside of the reflux tube to the outside (SMSRR1) and flow from the outside of the reflux tube to the inside (SMSRR2). The results showed that the reflux SMSRR uses the heat of the fluid at the outlet to further provide the reaction heat, which greatly reduces the outlet temperature, thereby improving the overall performance of the SMORE. By optimizing the diameter of the reflux tube and the operating conditions, the energy conversion rate can be increased by 19.5%, and the temperature distribution coefficients can be increased by 1.89% while the methanol conversion is increased by 6.43%, and the hydrogen yield is increased by 5.96%.

Electrically heated monolithic catalyst for in-situ hydrogen production by methanol steam reforming

Electrification of conventionally combustion-heated reactors has the potential to reduce CO2 emissions and provide a flexible and compact heat supply. In this paper, multi-segment helical FeCrAl substrates were arranged in tube-shell form with insulation by honeycomb ceramics to obtain the electrically heated monolithic catalyst (EHMC) substrate, followed by thermal treatment and catalyst deposition to obtain the EHMC. The start-up and catalytic performance of the EHMC at different reaction conditions were studied experimentally. The results showed that the desired temperature of 275 °C could be reached in 29 s with a uniform temperature distribution by supplying a current of 2 A in air atmosphere. Compared with the commercial granular catalyst under external heating condition, the EHMC showed better catalytic activity due to higher methanol conversion and similar CO concentration at low reaction temperature. Furthermore, when the methanol conversion was 90%, the GHSV of the EHMC was 5.54 times that of the commercial granular catalyst, indicating that the EHMC can operate at higher GHSV owing to the enhanced mass and heat transfer ability.

Theoretical insight into hydrogen production from methanol steam reforming on Pt(111)

Pt-based catalysts are widely used for hydrogen production from methanol steam reforming (MSR), but they show high CO selectivity. The reaction pathways of MSR on Pt(111) surface are systemically studied using density functional theory and kinetic Monte Carlo to reduce the selectivity of CO. The results show that CH3OH (g) → CH3OH* → CH2OH *→ CHOH * → CHO * → CO * → CO (g) is the main reaction pathway at 423–623 K and 0.1–10 atm with CH3OH: H2O of 3:1–1:1, and water is very difficult to dissociate. The difference between H2O* + * → OH* + H* and CH3OH* +*→ CH2OH * + H* is the key factor for MSR reaction on Pt(111) surface. The actual ratio of H2/(CO+CO2) is close to the theoretical ratio for MSR (2.91 vs. 3.00) when the energy barrier of H2O* + * → OH* + H* is smaller than that of CH3OH* +*→ CH2OH * + H* by 0.30 eV. The elimination of CO* is mainly from CO * + OH * → COOH*, and the ratio of CO/(CO+CO2) is 6.71%. These results may be useful for the design and optimization of Pt-based catalysts at low temperature for MSR reaction.

A Mechanistic Study of Methanol Steam Reforming on Ni2P Catalyst

Methanol steam reforming (MSR) is a promising technology for on-board hydrogen production in fuel cell applications. Although traditional Cu-based catalysts demonstrate high catalytic activity and selectivity towards CO2 relative to CO, which is produced via methanol decomposition, they suffer from poor thermal stability and rapid coke formation. Nickel phosphides have been widely investigated in recent years for many different catalytic reactions owing to their remarkable activity and selectivity, as well as their low cost. In this work, we present a mechanistic study of methanol decomposition and MSR pathways on Ni2P using density functional theory (DFT) calculations. DFT-predicted enthalpic barriers indicate that MSR may compete with methanol decomposition on Ni2P, in contrast to other transition metals (e.g., Pt, Pd, and Co) which primarily decompose methanol into CO. The formaldehyde intermediate (CH2O*) can react with co-adsorbed hydroxyl (OH*) from water dissociation to produce H2COOH* which then undergoes subsequent dehydrogenation steps to produce CO2 via H2COOH*→ HCOOH* → HCOO* → CO2. We also examined the conversion of CO into CO2 via the water–gas shift (WGS) reaction, but we ruled out this pathway because it exhibits high activation barriers on Ni2P. These findings suggest that Ni2P is a promising new catalyst for MSR.

Sustained release catalysis: Dynamic copper releasing from stoichiometric spinel CuAl2O4 during methanol steam reforming

Dynamic copper releasing from a stoichiometric CuAl2O4 catalyst in methanol steam reforming (MSR) is investigated via detailed characterizations of six samples that are collected after testing for different time (TOS). It reveals that Cu can be liberated from spinel structure under the MSR conditions, serving as the active species. The Cu releasing rate increases first and then decreases with TOS, and the released Cu atoms agglomerate into nano entities. Consequently, the number of these Cu nanoparticles increases quasi-linearly with TOS, suggesting at least part of newly released Cu do not coalesce with the former nanoparticles but form new entities anchored on the surfaces of remnant defective Cu-Al spinel, which retains a small portion of Cu2+ (5.8%) in spinel lattice even at a prolonged TOS of 300 h. The findings evidence the dynamic changes of both active Cu metal and local surface structures, which are essentially different from conventional catalysis.

The role of CO adsorption and CuO formation on the catalyst deactivation during the long-term performance evaluation of methanol steam reforming process for hydrogen production: Comparison of sono-coprecipitation and spray pyrolysis method

In this study, microreactors were coated with catalysts synthesized by two different methods and hydrogen was produced by methanol steam reforming. The structure of the catalysts was characterized by XRD, SEM and EDS analyses in the synthesis, activation and after long-term evaluation stages. The effect of CO adsorption and the structural changes of catalysts on the product stream and conversion were investigated and compared in detail. As a result, it was observed that the catalyst prepared by sono-coprecipitation (SCC) was more active although lost its performance much faster. Considering the performance graphs, SEM/EDS analyses and XRD results, it was revealed that the main reason for the performance decrease of the SPC-reactor (spray pyrolysis coating) was the increase of CO adsorption on the surface. Also, the formation of CuO structures and CO adsorption in the SCC-reactor were responsible for the faster performance decrease.

Computational fluid dynamics study of the effect of catalyst segmentation on the efficiency and performance of autothermal reformers for hydrogen production

Improvements in autothermal steam reforming reactors would be highly beneficial to the production of hydrogen. The design of the reactors may be optimized by reducing catalyst requirements while effectively increasing catalyst’s efficiency. The present study relates to a catalytic process of steam–methanol reforming for the production of hydrogen in an autothermal heterogeneous reaction system. Various catalyst segmentation methods are employed to maximize product yields and minimize the amount of the catalyst. Computations were carried out with respect to various factors pertaining to catalyst segments, such as length, number, thickness, and loading. The effects of various segmentation methods and key parameters on reaction and transport processes are investigated in terms of performance and efficiency. Design recommendations are made to improve overall reaction rates and yields. The results indicated that the factors pertaining to catalyst segments are fundamentally important. A desired level of reactor performance can be maintained through the use of catalyst segmentation, while reducing the amount of the reforming catalyst by half or more. However, to ensure the effectiveness of catalyst segmentation, the number of catalyst segments must be sufficiently large and the thermal conductivity of the walls must be sufficiently high. The thickness of catalyst segments can be tailored to avoid the limitations imposed by chemical kinetics. The parallel flow design is more effective than the counter flow design. The loading of the catalytically active material significantly affects the performance of the reactor.

Design and performance evaluation of flexible tubular microreactor for methanol steam reforming reaction

To obtain the flexible microreactor for potential application in constrained space, a novel flexible tubular microreactor was designed by using a corrugated shell and a high porosity porous copper fiber rod (PCFR) as catalyst support. The effect of placement position, bending direction, and bending angle on reaction performance of flexible tubular microreactor was investigated. Then, the stability of flexible tubular microreactor was further evaluated. The experimental results showed that the placement position and bending direction had a significant influence on the reaction performance of flexible tubular microreactor. Methanol conversion of flexible tubular microreactor with the vertical placement was 6.67% higher than that with horizontal placement. Higher methanol conversion and H2 flow rate were obtained when the microreactor bent along the vertical direction. The reaction performance of flexible tubular microreactor was found to decrease as the bending angle increased, and the methanol conversion decreased by around 14.07% with a bend of 90°. When the flexible tubular microreactor was horizontal placed with a bend of 60° in the vertical direction, the reaction performance of microreactor was not changed little after 20 cyclic bending. After continuous bending for 10 h, the methanol conversion and H2 flow rate of flexible tubular microreactor were 70.58% and 0.88 mol/h, showing good reaction performance.

Hydrogen generation from methanol steam reforming process of CuCrO2-CeO2 nanopowders catalyst

Hydrogen (H2) is under consideration as an alternative renewable energy transporter due to the energy crisis and climate change. In this research, CuCrO2-CeO2 nanopowders catalysts were synthesized through the glycine nitrate process and utilized in the SRM process. The prepared CuCrO2-CeO2 nanopowders were characterized by different characterization techniques. The nanosized CuCrO2-CeO2 nanopowders particles were confirmed by HRTEM to be around 10–15 nm in size. The specific surface area of the CuCrO2-CeO2 powders varied from 28.02 m2/g to 45.72 m2/g. The 50CuCrO2-50CeO2 powder was applied in the SRM process and exhibited the highest H2 production rate of 2059.65 ml STP min−1 g-cat−1 at 400 °C. Furthermore, the H2 production rate of the 50CuCrO2-50CeO2 nanopowders were increased by the added CeO2. The porous structure of the catalyst presents advantages in the SRM process, such as low cost, simplicity, and rapidity. As a result, the 50CuCrO2-50CeO2 nanopowders could have significant economic future.

Hydrogen production employing Cu/Zn-BTC metal-organic framework on cordierite honeycomb ceramic support in methanol steam reforming process within a microreactor

Three metal-organic frameworks Cu-BTC, Zn-BTC, and Cu/Zn-BTC were prepared and impregnated in nitrate solutions to obtain the precursors. After calcination, three metal-BTC-derived CuO/ZnO/CeO2/ZrO2 catalysts were obtained. The samples were characterized and the catalyst-coated cordierite honeycomb ceramics were used in a microreactor for methanol steam reforming at different reaction conditions. Results showed that the Cu/Zn-BTC-derived catalyst exhibited the most fine and uniform particles, the best reducibility, the largest specific surface area, and the optimal surface elemental state due to the difference in the formation mechanisms, resulting in its remarkable catalytic performance. The ceramic support coated with Cu/Zn-BTC-derived catalyst could achieve 100% methanol conversion rate and 0.336 mol/h H2 output at 260 °C in the microreactor. Stability tests demonstrated that the Cu/Zn-BTC-derived catalyst could maintain its excellent performance without deactivation within 30 h continuous reaction, which was connected with the Ce–Zr–O solid solution with high concentration of oxygen vacancies and surface oxygen.

Fabrication of high aspect ratio ceramic micro-channel in diamond wire sawing as catalyst support used in micro-reactor for hydrogen production

Ceramic is an ideal material for preparing micro-channel catalyst supports with their characteristics of high temperature resistance, corrosion resistance and mechanical strength. High aspect ratio micro-channel structure has the advantages of large specific surface area, strong mass and heat transfer performance and high material utilization. However, ceramic materials are hard and brittle, and it is difficult to fabricate micro-channel structures with aspect ratio more than 1.5:1 by traditional processing methods. In this paper, a cutting method of large diameter diamond wire sawing was proposed. The micro-channels with width of 520 μm and aspect ratio of more than 4:1 was successfully fabricated by this method. Furthermore, the integrity of the micro-channel structure processed by diamond wire sawing was analyzed. And than the effect of surface morphology in different processing parameters on the catalyst loading performance were studied. The catalyst loading strength of ceramic slices with different surface morphology was tested. Finally, the ceramic micro-channel array was used as the catalyst support in micro-reactor for hydrogen production via methanol steam reforming (MSR). The methanol conversion rate and H2 production rate could reach 87.8% and 74.6 mmol/h, respectively under GHSV 12600 ml/g·h at 300 °C. The experimental results show that the large-diameter diamond wire sawing technology can be used to process ceramic microchannels with high aspect ratio; using ceramic microchannel arrays as catalyst supports in hydrogen production can obtain better reaction performance; the feasibility of ceramic materials were broadened as microchannel catalyst supports.

Effects of fractal network channel on heat and mass transfer in methanol steam reforming

Hydrogen production by methanol steam reforming is one of the best choices for portable proton exchange membrane fuel cells (PEMFC). The channel is a dominant role in hydrogen production performance as the main reaction site. In this study, a fractal network channel architecture was designed and a three-dimensional (3D) numerical simulation was conducted in accordance with the Uniform Latin Hypercube design simulation scheme to explore the influence mechanism of branch grade (m), branch angle (θ), branch length ratio (α) and branch width ratio (β) on hydrogen production performance. Furthermore, four factors (m, θ, α, β) for the hydrogen production performance of fractal network channel were optimized by combining response surface method and non dominated sorting genetic algorithm II. The results showed that the hydrogen production performance is most sensitive to changes in β with the growth of the fractal network, followed by m, α, and θ. And the optimum parameter combination in terms of yield hydrogen is m of 3, θ of 134°, α of 0.88, and β of 0.85. The mechanism of the influence of fractal network structure parameters on the methanol reforming reaction as revealed in this study may provide a workable guideline for effective heat and mass transfer in new fractal reaction channel.

Mechanistic insights into methanol steam reforming over a ZnZr oxide catalyst with improved activity

Methanol steam reforming (MSR) holds great potential for mobile hydrogen production, but it still requires an active and stable catalyst. In this work, we report a high-performance ZnZr-0.5 composite oxide catalyst for this reaction, with a hydrogen production rate of 2.80 mol·gcat−1·h−1 and CO2 selectivity of 99.6% at a methanol space velocity of 22,762 mL·gcat−1·h−1. It also exhibits superior long-term durability in the TOS test for more than 100 h. Such good activity results from a synergistic effect of ZnO–ZrO2 dual sites. ZrO2 is capable of stabilizing and storing more CH3O∗ and HCOO∗ intermediates while ZnO is in charge of the dehydrogenation of these key intermediates. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and chemisorption results reveal that the MSR reaction experiences successively the hydrolysis of methyl formate and dehydrogenation of formate. More importantly, it is found that H2O significantly promotes the dehydrogenation of HCOO∗ intermediate by directly participating in this reaction from pulse chemisorption experiments.