Dehydrogenation Of Methylcyclohexane Research Articles

A multipass catalytic reactor insert for continuous hydrogen generation from methylcyclohexane

Herein we describe a multipass Catalytic Static Mixer (CSM) for implementation in on-demand hydrogen generation. The insert is a 3D printed metal scaffold with a catalyst coating containing a multitude of channels and a hollow core for a heater rod. This next generation of CSMs offers higher throughput and increased residence times for applications involving liquid-gas or gas only flow. We have implemented this CSM as an insert in a continuous flow tubular reactor for the dehydrogenation of Liquid Organic Hydrogen Carriers (LOHCs). The catalyst coating is comprised of 5 wt.% Pt/Al2O3 and is used for the dehydrogenation of methylcyclohexane (MCH) to generate hydrogen gas as the model system. This experimental study investigates the thermal profiles of the reactor and validates the potential of the CSM technology in hydrogen generation from LOHCs.

Nix/TiO2 catalysts for enhancing the selectivity of methylcyclohexane dehydrogenation

The dehydrogenation of methylcyclohexane (MCH) is a widely used hydrogen storage technology, but nowadays, precious metal catalysts such Pt are used for this reaction and non-precious metal catalysts suffer from low selectivity and instability problems. Two catalysts, Ni20/TiO2 and Ni20/Al2O3, were prepared through the improved co-precipitation method and their dehydrogenation performance of MCH was compared. It was found that the application of TiO2 carrier could significantly reduce the acidity of the catalysts, and the nickel particles could be stably dispersed on the carriers, which could effectively improve the selectivity of the target product (toluene). In addition, the influences of different Ni contents, reaction temperatures, and weight hourly space velocity (WHSV) on the performance of the catalysts were also evaluated, and the results showed that the catalyst with 17.16 % Ni content exhibited high activity with up to 86.48 % conversion of MCH and 96.51 % selectivity of toluene, under atmospheric pressure condition with the reaction temperature of 375 °C and WHSV of 1.9 h−1, while 96.03 % and only 42.64 %, respectively, for the Ni20/Al2O3 catalyst. In addition, the catalyst exhibited excellent anti-coking ability, indicating that it has a promising future for industrial applications.

Active and stable Pt-Ga2O3/Al2O3 catalyst for dehydrogenation of methylcyclohexane

Methylcyclohexane (MCH) is considered as one of the most promising liquid organic hydrogen carriers (LOHCs) in terms of hydrogen storage and delivery. However, the dehydrogenation process of MCH is relatively difficult, which requires catalyst having high activity and stability. In this work, a catalyst of Pt/Al2O3 by doping Ga2O3 was prepared and tested in the dehydrogenation of MCH, resulting in both high activity and stability. After 176 h of the reaction, the conversion of MCH is no significant decrease, and the toluene (TOL) selectivity was greater than 99%. The characterization results of the catalyst evidenced that the excellent performance of the catalyst is due to the introduction of Ga2O3, which prevents the growth of Pt species and results more positively charged Pt species. These Pt species can weaken the strength of the adsorption between Pt and dehydrogenation products, making dehydrogenation products more easily to be desorbed, which achieving high activity and stability. The catalyst shows great potential for industrial application in the future. This work provides theoretical guidance for designing highly stable dehydrogenation catalysts.

Insights into size effects of Pt/Al2O3 catalysts on hydrogen production from methylcyclohexane dehydrogenation

A volcano trend is observed for the intrinsic activity of Pt/Al2O3 catalysts in methylcyclohexane dehydrogenation.

Fabrication of Carbon Nanotubes Derived from Waste Tire Pyrolytic Carbon and Their Application in the Dehydrogenation of Methylcyclohexane to Produce Hydrogen

The accumulation of waste tires has resulted in very urgent environmental problems. Pyrolysis has been regarded as a green eco-friendly technology to deal with waste tires, and it is vital to make use of the pyrolysis carbon. Herein, we propose a new way to utilize pyrolysis carbon, to prepare carbon nanotubes with the help of ferrocene. The optimal preparation processes were determined by optimizing the parameters including the solvent, temperature, time, etc. The results of scanning electron microscopy and transmission electron microscopy evidenced the successful formation of carbon nanotubes. Meanwhile, the Brunauer–Emmett–Teller (BET) method and N2-adsorption showed that the yielded carbon nanotubes featured a large surface area and abundant pore structure in comparison with the pyrolytic carbon. Finally, the as-prepared carbon nanotubes were applied as the supports for Pt-based catalysts for the dehydrogenation of methylcyclohexane to produce hydrogen. The results showed that the Pt/carbon-nanotubes catalyst exhibited the highest conversion of methylcyclohexane (28.6%), stability, and hydrogen evolution rate (336.9 mmol/gPt/min) compared to the resulting Pt/commercial-activated-carbon (13.6% and 160.2 mmol/gPt/min) and Pt/pyrolytic-carbon catalysts (0.19% and 2.23 mmol/gPt/min).

Effect of Pt particle size on methylcyclohexane dehydrogenation over Pt/Al2O3 catalysts

A rational design of highly active and durable Pt catalysts for methylcyclohexane (MCH) dehydrogenation is essential for the utilization of liquid organic hydrogen carriers. Herein, a series of Pt/Al2O3 catalysts supported with a particle size of Pt ranging from 0.78 to 2.02 nm were synthesized and the effect of the particle size of Pt on the activity and stability of the catalyst for the MCH dehydrogenation were studied. The Pt loaded on Al2O3 with an actual average particle size of about 1.57 nm (Pt/Al2O3-1.57) has the highest activity and stability when compared to other Pt/Al2O3 catalysts. The hydrogen evolution rate of Pt/Al2O3-1.57 reaches about 656.12 mmol·gPt-1·min−1 while its apparent activation energy (38.05 KJ·mol−1) and deactivation rate (0.11 %/min) are the lowest. Both the poisoning experiment and the catalyst characterization demonstrate that the competition between the number of active sites and the strength of toluene adsorption explain why the particle size of Pt affects the MCH dehydrogenation. Additionally, the Pt/Al2O3-1.57 catalyst also maintains an excellent performance after three cycles of regeneration.

Palladium-Containing Catalysts Based on Functionalized Carbon Nanofibers for the Dehydrogenation of Methylcyclohexane

Palladium-Containing Catalysts Based on Functionalized Carbon Nanofibers for the Dehydrogenation of Methylcyclohexane

The origin of extraordinary selectivity in dehydrogenation of methylcyclohexane over Ni-Sn-based catalysts

High-loaded nickel catalysts (HLNCs) modified with Sn were synthesized and tested in dehydrogenation of methylcyclohexane (MCH) as a liquid organic hydrogen carrier. The catalyst composition and its reduction temperature were optimized that enabled to achieve the dehydrogenation selectivity of 99.0 % at a MCH conversion of 92 % and WHSV of 6.0 h−1, while the 99.9 % selectivity was reached at the conversion of 60.4 %, and WHSV of 18.5 h−1. Further, stability of the high selectivity of Sn-modified HLNCs was demonstrated in the long-run (100 h) catalyst test. The genesis of the HLNCs during their modification with Sn and reductive activation in hydrogen was studied. It was shown that the activation at temperatures above 450 °C resulted in a uniform distribution of Sn with the predominant formation of solid NiSn solutions having a crystal lattice of metallic nickel. The formation of the solid solutions provided a decrease in the adsorptive properties relating to the reaction product, toluene, which, in turn, led to an increase in the selectivity of MCH dehydrogenation.

Dehydrogenation of cycloalkanes over Pt/SBA-15 for endothermic cooling

Dehydrogenation of cyclohexane, methylcyclohexane, and decalin was studied on Pt/SBA-15 between 773 and 873 K for application to engine cooling in hypersonic aircraft. While the reactions were unstable at 1 bar, the reactions showed no evidence for deactivation at pressures of 20 and 60 bar for at least 4 h. Selectivities for dehydrogenation of cyclohexane to benzene and methylcyclohexane to toluene were greater than 90% in all cases. The reaction of decalin proceeded sequentially, forming primarily tetralin at low reactor space times and naphthalene at higher space times. The reaction of 50% mixtures of n-dodecane and decalin at 773 K showed negligible conversion of n-dodecane but the reaction of decalin was similar to what was observed for a pure decalin feed. Heat measurements gave endothermicities that were in good agreement with standard reaction enthalpies.

A first principles study on the catalytic performance of methylcyclohexane dehydrogenation on a monoatomic catalyst

SummaryThis research explores how methylcyclohexane (MCH) interacts with individual metal atoms M (M= Pt, Pd, and Cu) based on density functional theory (DFT) total energy calculations. We analyzed the adsorption energies of MCH on these metal atoms to understand their stability and reactivity. The results show that MCH prefers to attach to single Pt atoms, which exhibited the strongest adsorption energy. Compared with Pt(111) surfaces, the adsorption energies on Pt atoms were slightly higher, indicating enhanced stability at the nanoscale. Adsorption on Pd and Cu atoms resulted in lower adsorption energies than on Pt. We also focused on the initial step of dehydrogenation, where we studied the removal of one hydrogen atom (H1) from MCH. The presence of a single metal atom significantly lowered the energy required for breaking the C1–H1 bond, with Pt showing the lowest energy barrier compared with Pd and Cu due to the excessive of charge transfer. We analyzed the electronic properties and charge transfer during dehydrogenation, revealing the influence of the metal atom's electronic structure on catalytic behavior. Overall, this research provides valuable insights into how MCH interacts with monoatomic metal catalysts, emphasizing the role of the metal atom's electronic configuration in determining reactivity.

Perfect Conversion of Methylcyclohexane Dehydrogenation under Superheated Liquid-Film Conditions

Perfect Conversion of Methylcyclohexane Dehydrogenation under Superheated Liquid-Film Conditions

Dehydrogenation of methylcyclohexane using solid oxide fuel cell – A smart energy conversion

Dehydrogenation of methylcyclohexane (MCH), a hydrogen carrier, is investigated using a solid oxide fuel cell (SOFC). When an SOFC is operated with a cell temperature of 420 °C and a current density of 16 mA cm−2, toluene and benzene, the products of MCH’s dehydrogenation reaction, are observed, with a molar ratio of 94:6. When the cell is operated at 490 °C and 90 mA cm−2, in addition of toluene and benzene, 1,4-dioxane is formed at a molar ratio of >86%, indicating an oxidative dehydrogenation reaction of MCH. These findings indicate that an SOFC successfully extracts electrons directly from MCH and generates electricity by utilizing the SOFC’s oxygen ion conduction function. The energy required for this process is expected to be less than that required for conventional MCH dehydrogenation. Furthermore, we reveal that SOFCs can be applied to the oxygen displacement reaction of benzene rings.

Boosting methylcyclohexane dehydrogenation over Pt-based structured catalysts by internal electric heating

Boosting methylcyclohexane dehydrogenation over Pt-based structured catalysts by internal electric heating

Effect of CeO2 redox properties on the catalytic activity of Pt-CeOx over irreducible SiO2 support for methylcyclohexane (MCH) dehydrogenation

A highly reducible CeO2 surface was prepared on a SiO2 support to investigate the effect of redox properties of CeO2 on the catalytic activity of Pt/CeO2-SiO2 for MCH dehydrogenation. Characterization of the Pt/CeO2-SiO2 catalyst revealed a significantly higher Pt dispersion than Pt/micro-sized CeO2 and Pt/SiO2. The well-dispersed Pt particles averaging 1.1 nm in size (Pt/CeO2-SiO2) were primarily attributed to the high surface concentration of oxygen vacancies, which provided abundant defect sites that stabilized the Pt particles from sintering. Hydrogen released from MCH dehydrogenation was approximately 5–6 times greater with high selectivity towards toluene products for Pt/CeO2-SiO2 compared to its counterparts. The excellent catalytic activity of Pt/CeO2-SiO2 was attributed to the presence of rich oxygen vacancies on the CeO2 surface, which was significantly reduced under MCH dehydrogenation conditions, resulting in faster toluene desorption.

Supported metal clusters: Nix/CuZnAl catalysts effectively improve the performance of hydrogen evolution from methylcyclohexane dehydrogenation

BackgroundRecently, with the emphasis on hydrogen as alternative clean energy, it is necessary to identify a safe and efficient technique. As a hydrogen storage technique, the liquid organic hydrogen carrier (LOHC) technique has the advantages of high hydrogen storage density, high safety, and low technical cost. MethodsA series of Nix/CuZnAl catalysts were synthesized using co-precipitation and ultrasonic-assisted incipient wetness impregnation methods. Combining XRF, XRD, Uv-vis, H2-TPR, XPS, TEM, and SEM techniques, we show the morphology of the active site during the reaction, and further explore the effects of the formation of the metal cluster NiCuZn. Significant findingsThe multi-metal oxide phase in the sample disappeared after reduction and was transformed into the metal cluster NiCuAl. During the formation of the metal cluster NiCuAl on the catalyst surface, electron transfer towards Ni occurred and the reduction temperature of Ni was lowered, which contributed to the electronic effect and synergy. In this work, The Ni10/CuZnAl catalyst shows the best dehydrogenation activity and selectivity, the catalytic effect was 15–20 times that of the CuZnAl catalyst, and the hydrogen evolution rate reached 77.31 ± 1.25 mmol/gcat/h. Moreover, based on the characterization analysis, the work speculates that the active atom H simultaneously dissociates and desorbs on the Cu and Ni surfaces of the metal cluster. In addition, as a possible active center, with a strong metal-support interaction, the metal cluster NiCuZn promotes the dehydrogenation reaction.

Nickel single atoms/cerium oxide hybrid for hydrogen production via solar-heating catalytic dehydrogenation of methyl Cyclohexane

Methylcyclohexane (MCH)-toluene-hydrogen cycle can realize the recycling of matter and energy, owning a wide foreground in industrial application. The MCH dehydrogenation process is highly endothermic, and a heating temperature is needed to stimulate this reaction. The combination of thermal catalytic reactor and solar-to-heat system can realize solar-heating catalytic MCH dehydrogenation reaction. Whereas, such a highly desirable advanced system has not yet been reported. In this study, a hybrid of single-atom nickel anchored on cerium oxide nanosheets (Ni SA/CeO2 NS) has been constructed successfully. The hybrid exhibits remarkable thermal catalytic activity in MCH dehydrogenation, owning an H2 generation rate of 2756 mmol g−1 h−1 at 400 °C. The stepwise MCH dehydrogenation mechanism on the hybrid is investigated via density functional theory calculations. Moreover, we have developed a novel type of solar-to-heat device based on Ti2O3 thin film/Cu. Based on this device and the Ni SA/CeO2 NS hybrid, a solar-heating catalysis mode has been developed, with the H2 generation rates of 404 and 2604 mmol g−1 h−1 from MCH dehydrogenation under 1 and 2 kW m−2, respectively. This strategy provides the possibility to realize scalable MCH dehydrogenation under solar irradiation without secondary energy input.

膜工学研究を振り返って– 膜を創る

Last time, the author described the study of membrane fouling and the transport equation for membrane permeation. This time, the author would like to introduce his research on creating membranes. Polymer membranes and inorganic membranes have been developed. The polymer membranes are negatively and positively charged ultrafiltration membranes, which are polysulfone membranes with sulfonic acid groups and quaternary ammonium groups. The charged membranes have a complex separation mechanism, that is combination of separation by membrane pores and by charge repulsion between the membrane and solute. It was possible to separate not only salts but also various substances such as amino acids, peptides, and proteins. The transport equations of charged membranes were also studied. Inorganic membranes are mainly silica membranes produced by chemical vapor deposition, and zeolite membranes have also been produced, but they will not be introduced here. The author started with low–temperature deposition using ozone, and finally deposited membranes at high temperature (600 ℃) using various silica sources, and was able to obtain high–performance membranes. Since the advantages of inorganic membranes can be applied to membrane reactors, membrane reactors have been applied to steam reforming of methane, dehydrogenation of cyclohexane and methylcyclohexane, and thermal decomposition of hydrogen sulfide. In particular, the cyclohexane dehydrogenation membrane reactor operated continuously for 1,054 hours, and a small membrane reactor equipped with six 50 cm membranes was also developed.

Low-Pt-Based Sn Alloy for the Dehydrogenation of Methylcyclohexane to Toluene: A Density Functional Theory Study

Spin-polarized van der Waals corrected density functional theory calculations were applied to Sn–Pt alloys with Pt content ≤ 50% (referred to as low Pt alloys) to evaluate their catalytic activity towards the dehydrogenation of methylcyclohexane (MCH), with the formation of toluene as product. The calculated adsorption energies of MCH, its intermediates and toluene showed that these molecules bind on the considered Sn–Pt alloys. Sn–Pt alloys had the lowest dehydrogenation energetics, indicating that the activity of this catalytic material is superior to that of a pristine Pt catalyst. Desorption of the intermediate species was feasible for all Sn–Pt alloy configurations considered. The catalytic dehydrogenation reaction energetics for the various Sn–Pt alloy configurations were more favourable than that achieved with pristine Pt surfaces. The current study should motivate experimental realization of Sn–Pt alloys for the catalytic dehydrogenation reaction of MCH.

Improved catalytic stability of Pt/TiO2 catalysts for methylcyclohexane dehydrogenation via selenium addition

To improve the catalytic activity of Pt catalysts for methylcyclohexane (MCH) dehydrogenation, which is utilized for hydrogen transportation, the effects of the addition of Se on the performance of Pt/TiO2 catalysts were investigated. In Se/Pt/TiO2 catalysts, even a small amount of Se addition (Se/Pt = 0.01) improved the catalyst stability. Se was highly dispersed on the Pt/TiO2 surface, without volatilizing in a reducing atmosphere at temperatures below 450 °C, and did not form an alloy with Pt. The analysis of adsorption-desorption characteristics revealed that the addition of Se promoted the desorption of products, including the main product, toluene. Moreover, an electron donation effect from Se to Pt was observed by FT-IR measurement after the reduction. The desorption characteristic caused by the electron donation effect suppressed the deterioration of the catalyst and allowed stable catalytic activity toward the MCH dehydrogenation reaction.

Acid site introduced by Al3+penta and boron in Pt/Al2O3 catalyst for dehydrogenation of methylcyclohexane

A series of catalysts with different acid strengths were obtained by constructing unsaturated pentacoordinate (Al3+penta) sites in Al2O3 and loading with boron. The effects of support properties and the addition of boron on the strength and type of catalyst acid were investigated, and their influence on the dehydrogenation performance of methylcyclohexane (MCH) was discussed. In Pt-B/Al2O3-600 catalysts containing Al3+penta sites, the strongly acidic L acid sites gradually decreased and the weakly acidic [L + B] acid sites gradually increased with increasing boron loading, indicating coverage of the Al3+penta site by boron. In Pt-B/Al2O3-750 catalysts without Al3+penta sites, strongly acidic L acid sites gradually decrease with increasing boron loading and weakly acidic [L + B] acid sites remains essentially unchanged. For Pt-B/Al2O3-600 catalysts, the effect of boron on the interaction of Pt with Al2O3 is minimized when the loading of boron is between 0 and 1 wt% and the MCH dehydrogenation performance increases with the number of weak acid sites. At a boron loading of 1 wt%, the abundance of weak acid sites maintains the dispersion of Pt and allows a suitable interaction between Pt and Al2O3, thus enhancing the dehydrogenation performance of MCH.