Hydrogenation Reactor Research Articles

Continuous-Flow Hydrogenation of Nitroaromatics in Microreactor with Mesoporous Pd@SBA-15

The hydrogenation of nitroaromatics to prepare aromatic amines plays a crucial role in the chemical industry. Traditional hydrogenation has the risk of hydrogen leakage from the equipment, and its catalyst has the disadvantage of being easily deactivated and difficult to recover. In this study, we designed an efficient and stable mesoporous catalyst, Pd@SBA-15, which was constructed by impregnating the nanopores of the mesoporous material SBA-15 with palladium nanoparticles. The catalyst was then filled in a micro-packed-bed reactor (MPBR) for continuous flow hydrogenation. The designed continuous flow hydrogenation system has two distinctive features. First, we used mesoporous Pd@SBA-15 instead of the traditional bulk Pd/C as the hydrogenation catalyst, which is more suitable for exposing the active sites of metal Pd and reducing the agglomeration of nanometals. The highly ordered porous structure enhances hydrogen adsorption and thus hydrogenation efficiency. Secondly, the continuous flow system allows for precise detection and control of the reaction process. The highly efficient catalysts do not require complex post-treatment recovery, which continues to operate for 24 h with barely any reduction in activity. Due to the high catalytic activity, the designed mesoporous Pd@SBA-15 showed excellent catalytic performance as a hydrogenation catalyst in a continuous flow system with 99% conversion of nitroaromatics in 1 min. This work provides insights into the rational design of hydrogenation systems in the chemical industry.

Preparation of ZSM-22 zeolite and its application in hydroisomerization dewaxing of lubricating oils

Hydroisomerization dewaxing is an advantageous process to improve lubricating oil quality. The bifunctional catalyst used in the hydrogenation isomerization reaction provides the isomerization function with the acidic site supported by molecular sieve, and the precious metals such as Pt and Pd provide the hydrogenation function for the metal site, which has the advantages of high activity, low production cost, and mature synthesis process. The ZSM-22 zeolite was hydrothermal synthesized using 1,6-diamino hexane (DAH) as templates in the presence of the seed, XRD, N2 adsorption-desorption and NH3-TPD Cha adsorption-desorption times. Finally, the hydroisomerization dewaxing performance of the Pt/ZSM-22 and Pt-Pd/ZSM-22 bifunctional catalysts were investigated on a high-pressure fixed-bed hydrogenation reactor. The results show that the hydroisomerization dewaxing performance of the Pt-Pd/ZSM-22 catalyst is better.

Carbon capture and utilization: More than hiding CO2 for some time

Carbon capture and utilization: More than hiding CO2 for some time

Effects of normalizing temperature on microstructure and high-temperature properties of 2.25Cr-1Mo-0.25V bainitic steel

In 2.2Cr-1Mo-0.25V bainitic steels, the effect of the initial microstructure on carbide precipitation has not yet been elucidated. Therefore, in this work, the effect of normalizing temperature on the microstructure evolution and corresponding high-temperature strength change of bainitic steels was investigated by transmission electron microscopy (TEM) and scanning electron microscopy (SEM) using extra-thick hydrogenation reactor steel as the assessed material, and the precipitation strengthening mechanism was discussed. When the normalizing temperature increased from 900 °C to 990 °C, the high-temperature yield strength increased from 451 to 475 MPa and the average absorbed Charpy impact energy at −30 °C decreased from 93 to 41 J. Therefore, the optimal normalizing temperature was 960 °C. The volume fraction of MC carbides with almost no change in average diameter increased from 0.21% to 0.44%, and the dispersed strengthening of carbide was significantly enhanced. The increase in normalizing temperature increased the solid solution of alloying elements within the bainite matrix, which increased the precipitation of MC carbides during the tempering process. In addition, the lamellar M-A constituents in the initial microstructure decomposed to form MC carbides.

CFD Simulation of a Hybrid Solar/Electric Reactor for Hydrogen and Carbon Production from Methane Cracking

Methane pyrolysis is a transitional technology for environmentally benign hydrogen production with zero greenhouse gas emissions, especially when concentrated solar energy is the heating source for supplying high-temperature process heat. This study is focused on solar methane pyrolysis as an attractive decarbonization process to produce both hydrogen gas and solid carbon with zero CO2 emissions. Direct normal irradiance (DNI) variations arising from inherent solar resource variability (clouds, fog, day-night cycle, etc.) generally hinder continuity and stability of the solar process. Therefore, a novel hybrid solar/electric reactor was designed at PROMES-CNRS laboratory to cope with DNI variations. Such a design features electric heating when the DNI is low and can potentially boost the thermochemical performance of the process when coupled solar/electric heating is applied thanks to an enlarged heated zone. Computational fluid dynamics (CFD) simulations through ANSYS Fluent were performed to investigate the performance of this reactor under different operating conditions. More particularly, the influence of various process parameters including temperature, gas residence time, methane dilution, and hybridization on the methane conversion was assessed. The model combined fluid flow hydrodynamics and heat and mass transfer coupled with gas-phase pyrolysis reactions. Increasing the heating temperature was found to boost methane conversion (91% at 1473 K against ~100% at 1573 K for a coupled solar-electric heating). The increase of inlet gas flow rate Q0 lowered methane conversion since it affected the gas space-time (91% at Q0 = 0.42 NL/min vs. 67% at Q0 = 0.84 NL/min). A coupled heating also resulted in significantly better performance than with only electric heating, because it broadened the hot zone (91% vs. 75% methane conversion for coupled heating and only electric heating, respectively). The model was further validated with experimental results of methane pyrolysis. This study demonstrates the potential of the hybrid reactor for solar-driven methane pyrolysis as a promising route toward clean hydrogen and carbon production and further highlights the role of key parameters to improve the process performance.

A high activity mesoporous Pt@KIT-6 nanocomposite for selective hydrogenation of halogenated nitroarenes in a continuous-flow microreactor.

In this study, we designed a Pt@KIT-6 nanocomposite prepared by impregnating platinum nanoparticles on the nanopores of the KIT-6 mesoporous material. This Pt@KIT-6 nanocomposite was used as a catalyst in a micro fixed bed reactor (MFBR) for the continuous-flow hydrogenation of halogenated nitroarenes, which demonstrates three advantages. First, the Pt@KIT-6 nanocomposite has a stable mesoporous nanostructure, which effectively enhances the active site and hydrogen adsorption capacity. The uniformly distributed pore structure and large specific surface area were confirmed by electron microscopy and N2 physisorption, respectively. In addition, the aggregation of the loaded metal was avoided, which facilitated the maintenance of high activity and selectivity. The conversion and selectivity reached 99% within 5.0 minutes at room temperature (20 °C). Furthermore, the continuous-flow microreactor allows precise control and timely transfer of the reaction system, reducing the impact of haloid acids. The activity and selectivity of the Pt@KIT-6 nanocomposite showed virtually no degradation after 24 hours of continuous operation of the entire continuous-flow system. Overall, the Pt@KIT-6 nanocomposite showed good catalysis for the hydrogenation of halogenated nitroarenes in the continuous-flow microreactor. This work provides insights into the rational design of a highly active and selective catalyst for selective hydrogenation systems.

Micropacked‐bed Reactor for Continuous Hydrogenation of Aromatic Dinitro Compounds

AbstractDue to the intricacy aromatic dinitro compound hydrogenation processes, it is difficult to attain high conversion and selectivity using merely modified catalysts in batch reactors. The micropacked‐bed reactor (μPBR) offers efficient heat and mass transfer, a precise and controllable reaction process, and a high level of safety. In this work, the hydrogenation of 2,4‐dinitroanisole was selected as the model reaction, and a variety of catalysts were utilized in the continuous flow system based on μPBR for hydrogenation of 2,4‐dinitroanisole. During 960 minutes of operation, the synthesis of 2,4‐diaminoanisole was carried out using a Pd (OH)2/C catalyst and the optimal process condition, yielding 100 % conversion, 99.5 % selectivity, and the favorable durability. For the hydrogenation of relevant aromatic dinitro compounds, the continuous flow system demonstrates exceptional performance.

Catalytic hydrogenation of p-nitroanisole over Raney nickel for p-aminoanisole synthesis: Intrinsic kinetics studies

The understanding of intrinsic kinetics was crucial in guiding reactor design. However, the intrinsic kinetics of catalytic hydrogenation of p-nitroanisole (PNA) to p-aminoanisole remains obscure. In this work, the kinetic characteristics were experimentally and theoretically investigated under various experimental conditions. From the power law analysis of the initial reaction rate, the reaction order was found to be from 0.34 (at 343 K) to 0.53 (at 353 K) for hydrogen and 0.31∼ 0.34 for PNA (at concentrations less than 90 g·L−1), while the reaction was considered to be zero-order under higher PNA concentration (>90 g·L−1). The data was also used to fit Eley-Rideal and Langmuir-Hinshelwood-Hougen-Watson (LHHW) models. It was found that the rate-controlling step was the adsorption of dual-site dissociative H2 based on LHHW model. The accuracy of the screened model was verified by correlation, between the predicted data and experimental data. This study could provide significant guidance for the hydrogenation reaction and reactor.

Photochemical reactor for selective hydrogenation of asphaltene molecules at room temperature in absence of a catalyst

Photochemical reactor for selective hydrogenation of asphaltene molecules at room temperature in absence of a catalyst

Experimental analysis of hydrogen storage performance of a LaNi5–H2 reactor with phase change materials

Energy storage, especially thermal energy storage, has an important place in terms of efficient use of energy. Systems in which phase change materials (PCMs) are used are among the thermal energy storage (TES) options, thanks to their advantages such as energy storage at almost constant temperature. The use of PCM as a TES material in the metal hydride (MH) reactor is an influential method to store the heat released by the exothermic reaction occurring in the hydrogen charging process and to recover this heat with the endothermic reaction occurring in the hydrogen discharge process. In the present study, hydrogen charge and discharge processes in a LaNi5–H2 reactor were experimentally investigated and compared with and without PCM. Therefore, a hybrid system was designed by integrating PCM around the cylindrical MH reactor filled with LaNi5 alloy. The hydration process was carried out at both constant pressure and variable pressure. The temperature changes on the reactor surface and inside the PCM were measured over time. In experiments to determine the change in the amount of hydrogen stored in MH reactors over time, it was determined that the hydrogen storage pressure and reactor design significantly affect the hydrogen charge-discharge rate. Considering the use of MH reactors in transportation vehicles such as automobiles and submarines, designing a hybrid MH-PCM storage system is promising for the development of hydrogen storage technologies and transportation technologies.

Performance evaluation of adaptive based model predictive control for ethylene glycol production from dimethyl oxide hydrogenation

Abstract Advance process control is a proven control and optimization technology delivering measurable and sustainable improvements in production yield, coupled with the added value of energy savings. In this work, an adaptive based model predictive control (aMPC) is developed and implemented to control the hydrogenation of dimethyl oxide to ethylene glycol (EG) in a plug flow reactor. The aMPC is compared with 3 other control schemes; proportional-integral (PI), decoupled PI (dPI) and linear model predictive control. The aim is to determine the reliability of aMPC in controlling the production rate and reactor temperature for an optimized hydrogenation reactor. The aspects compared include set point tracking, disturbance rejection and robustness test. The analysis concludes that the aMPC offers the best overall performance compared to the other control schemes.

Effects of Simulated PWHT on the Microstructure and Mechanical Properties of 2.25Cr1Mo0.25V Steel for a Hydrogenation Reactor

The effect of post-welding heat treatment (PWHT) on the microstructure and mechanical properties of large-thickness 2.25Cr1Mo0.25V steel was investigated through simulated post-welding heat treatment (SPWHT). The results showed that an increase in the SPWHT time decreased the toughness, hardness, and strength of the steel. After Min.SPWHT, the high-temperature tensile strength decreased more significantly, and the damage of Min.SPWHT to the high-temperature tensile strength reached approximately 80% of the Max.SPWHT. The microstructure of the tested steel before and after SPWHT consisted of granular bainite and lath bainite. After SPWHT, intergranular carbides were precipitated as coarsened carbides, carbide clusters, and chains of carbides; alloy element segregation occurred, and the segregation of Mo was the most serious, followed by Cr, and V. The precipitation behavior of the carbides and the increase in the effective grain size caused by the widening of the bainite–ferrite lath worked together and resulted in the decline of the impact toughness; the reduction in the solid solution and precipitation strengthening effects were the main factors in the strength reduction of the tested steel. In the high-temperature tensile tests, defects first appeared around the coarse carbides and carbide clusters. Controlling the size of the intergranular large-size carbides and the degree of cluster precipitation in the NT state structure may be a means of obtaining higher strength of the base metal subjected to PWHT.

The potential for hydrogen ironmaking in New Zealand

Globally, iron and steel production is responsible for approximately 6.3% of global man-made carbon dioxide emissions, because coal is used as both the combustion fuel and chemical reductant. Hydrogen reduction of iron ore offers a potential alternative ‘near-zero-CO2’ route, if renewable electrical power is used for both hydrogen electrolysis and reactor heating. This paper discusses key technoeconomic considerations for establishing a hydrogen direct reduced iron (H2-DRI) plant in New Zealand. The location and availability of firm renewable electricity generation is described, the experimental feasibility of reducing locally-sourced titanomagnetite ironsand in hydrogen is shown, and a high-level process flow diagram for a counter-flow electrically heated H2-DRI process is developed. The minimum hydrogen composition of the reactor off-gas is 46%, necessitating the inclusion of a hydrogen recycle loop to maximise chemical utilisation of hydrogen and minimize costs. A total electrical energy requirement of 3.24 MWh per tonne of H2-DRI is obtained for the base-case process considered here. Overall, a maximum input electricity cost of no more than US$80 per MWh at the plant is required to be cost-competitive with existing carbothermic DRI processes. Production cost savings could be achieved through realistic future improvements in electrolyser efficiency (∼ US$5 per tonne of H2-DRI) and heat exchanger (∼US$3 per tonne). We conclude that commercial H2-DRI production in New Zealand is entirely feasible, but will ultimately depend upon the price paid for firm electrical power at the plant.

Synthesis of a Cu/Zn-BTC@LTA derivatived Cu–ZnO@LTA membrane reactor for CO2 hydrogenation

Methanol (MeOH) formation from CO2 hydrogenation has attracted increasing interest for CO2 reduction and utilization. However, CO2 conversion to methanol production is greatly blocked because of the thermodynamical restriction and catalyst inactivation caused by by-product water. In this work, we develop a Cu/Zn-BTC@LTA derivatived Cu–ZnO@LTA catalytic membrane reactor (CMR) for methanol production via CO2 hydrogenation. Through the successive separation of the by-product steam from the reactor by using a water-selective LTA membrane, the thermodynamic restriction is broken to promote CO2 transformation and methanol production. At 533 K and 3.00 MPa, a high CO2 conversion (49.1%) as well as methanol selectivity (90.2%) is obtained in the catalytic membrane reactor, which are much higher than the corresponding CO2 conversion (26.2%) and methanol selectivity (50.6%) obtained in the catalytic fixed bed reactor (CFBR). Further, catalyst deactivation induced by water can be effectively repressed in the catalytic membrane reactor, which is helpful to keep a high stability of the catalyst.

A low temperature SOFC as a self-promoted reactor for CO2 catalytic hydrogenation

Low temperature operation of Solid Oxide Fuel Cells (SOFC) typically provides limited and insufficient power for practical applications. The present work demonstrates how this limited power can be utilized effectively for the promotion of a catalytic reaction taking place on a catalyst electrode with minimal energy consumption and environmental impact. A novel design of a low-temperature SOFC reactor is reported and utilized for the electrochemical promotion of CO2 hydrogenation, a reaction of both environmental and industrial importance. The power demand for the enhancement of the catalytic reaction rates is produced in situ by the cell during the parallel oxidation of hydrogen which acts both as a reactant and as a fuel. The results of the present study pave the way for the utilization of Electrochemical Promotion of Catalysis (EPOC) in a wireless configuration, using exclusively the internal power of low temperature, low pressure, SOFCs.

Synthesis of Cu–ZnO–Pt@HZSM-5 catalytic membrane reactor for CO2 hydrogenation to dimethyl ether

CO2 hydrogenation to dimethyl ether (DME) has drawn increasing interest in science and industry. However, the conversion of CO2 to DME is challenging due to the limitation of thermodynamic equilibrium and the water-induced degradation of the catalysts in a catalytic fixed bed reactor (CFBR). In this study, a novel reaction-separation coupling Cu–ZnO–Pt@HZSM-5 catalytic membrane reactor (CMR) was fabricated for CO2 hydrogenation to DME. Owing to continuous separation of the by-product steam by using an HZSM-5 membrane, the limitation of thermodynamic equilibrium can be broken effectively, thus leading to a substantially enhanced CO2 conversion (from 24.9% in the CFBR to 41.1% in the CMR) and DME selectivity (from 53.7% in the CFBR to 100% in the CMR). Further, water-induced degradation of the catalyst can be restrained because of water removal, thus keeping a high catalytic activity for a long time.

Designing PEM Electrolysis-Based Hydrogen Reactors In The Area of Baron Beach Of Yogyakarta, Indonesia

This study aimed to design a PEM electrolysis-based hydrogen reactor and the potential for hydrogen production at Baron Beach, Gunung Kidul, Yogyakarta. Based on the calculation done at the initial process, the electrical energy potentially generated from renewable energy, such as wind, waves, and solar, reached 10.7 MW. This study also investigated the effect of reactor operating temperature on reactor efficiency and hydrogen production. A numerical thermodynamic approach was applied in the design process. The model, validated by laboratory experiments by other institutions, was in good agreement with previous research with an error value of 13%. The temperature range was dynamically limited from 30 to 80°C. The optimum operating conditions occurred when the temperature was set at 80 °C with a reactor efficiency, a water consumption rate, and a hydrogen production capacity of 76.3%, 2.817 kg/hour, and 250.42 kg/hour, respectively. The raw material, namely seawater, was processed using the reverse osmosis method. Ten reactors (with 13 cells per reactor) were installed in parallel.

Techno-economic Analysis of Biogas Conversion to Liquid Hydrocarbon Fuels through Production of Lean-Hydrogen Syngas

Large-scale biogas plants are a viable source of CH4 and CO2 to be converted efficiently into high-value products. Specifically, production of liquid hydrocarbons can enhance the availability of green fuels while achieving significant CO2 reductions on site. In this study, the production of liquid hydrocarbons is simulated by dry reforming of biogas into lean-hydrogen syngas, further converted in CO hydrogenation and oligomerization reactors. The process was modeled by using CHEMCAD based on published experimental results with the projected feed composition. A high molar feed ratio of CO2/CH4 (>1.7) was set for the reformer to minimize steam requirement while avoiding carbon formation and reaching an optimal H2 to CO molar ratio (0.7). Two options were techno-economically evaluated based on a biogas plant with a capacity of 5000 N m3/h that produces between 13.8 and 15.7 million liters per year of blending stock for transportation fuels. The economics of the process depends mainly on the cost and availability of the biogas. The minimum selling price of the liquid fuels is $1.47/L and $1.37/L for options 1 (once-through conversion of syngas to liquid fuels) and 2 (recycle of tail gas from oligomerization reactor), respectively, and can be significantly reduced in case the biogas throughput is increased to >20 000 N m3/h. Recycling of the tail gas (option 2) yielded higher productivity, resulting in higher carbon yield (77.9% on the basis of methane) and energy efficiency (67.1%). The economic viability of the process can be improved by implementing CO2 tax or other incentives to reduce capital investment. It provides a potential route for efficient conversion of biogas into liquid hydrocarbons to meet the increased demand for renewable fuels as blending stock in the transportation sector while improving the sustainability of the plant.

Computational Fluid Dynamics Study of a Pharmaceutical Full-Scale Hydrogenation Reactor

The pharmaceutical industry has been quite successful in developing new hydrogenation processes, and the chemistry of hydrogenation is currently well understood. However, it is a complex process to scale and optimize due to its high exothermicity, use of expensive catalysts and solvents, and its mass transfer requirements. Therefore, the aim of this work is to develop a CFD model to be able to describe the mass transfer, hydrodynamics, and mixing with respect to changes in rotational speed for a full-scale pharmaceutical hydrogenation reactor. In the first stage, a simple CFD model is used to predict the development of the surface vortex, and it is validated against literature data. In the second stage, the CFD model is tested on a full-scale configuration equipped with a Rushton turbine and a bottom kicker to study the formation of the surface vortex. Simulation results show the ability to predict the development of the surface vortex. These results are used to estimate the liquid height and mixing time as a function of several rotational speeds, allowing us to propose novel process correlations for this particular configuration. Although modelling the complete hydrogenation process would be challenging, this work is seen as a first step towards developing models that demonstrate the use of CFD at such large reactor scales.

Creep rupture behavior of 2.25Cr1Mo0.25V steel and weld for hydrogenation reactors under different stress levels

Abstract In the present research work, the 2.25Cr1Mo0.25V steel plates with a thickness of 112 mm were welded using the multi-pass submerged automatic arc welding process. The creep specimens were prepared from the base metal (BM) and weld metal (WM) in the welded joint after heat treatment process. The uniaxial creep tests were performed to investigate the creep deformation and rupture behaviors at 550°C under different applied stress levels. The microstructure and fracture surface morphology of crept BM and WM samples were also characterized using the scanning electron microscope with energy-dispersive X-ray spectroscopy. The results showed that typical three-stage creep deformation curves are observed in both BM and WM specimens, and the BM exhibits a faster deformation rate than the WM. Both the creep rupture time and uniaxial creep ductility are found to be increased with a decrease in applied stress. Furthermore, the relationship between the minimum creep rate and time to rupture of both BM and WM samples was obtained, and it can be described using a unified Monkman–Grant equation. In addition, it is found that the creep fractures of the BM and WM are a transgranular ductile failure. The creep damages of both materials are mainly associated with the microstructural degradations, that is, the initiation and coalescence of creep cavities at second phase particles such as carbide and inclusion particles along the loading direction.