Low Space Velocity Research Articles

Bisphenol F Synthesis from Formaldehyde and Phenol over Zeolite Y Extrudate Catalysts in a Catalyst Basket Reactor and a Fixed-Bed Reactor

The objective of this study was to evaluate the applicability of zeolite Y as a catalyst for producing bisphenol F (BPF) from phenol and formaldehyde. Catalyst extrudates were prepared by extrusion after adding pseudoboehmite sol (PS) and Ludox (Lu) as alumina and silica binders, respectively. The compressive strength of the catalyst extrudates increased with the addition of Ludox. However, the formaldehyde conversion decreased as more Ludox was used as a binder, resulting in a decrease in the yield of BPF. This decrease is attributed to the reduction in the total amount of acid sites caused by the addition of Ludox. In this study, the Y_PS5_Lu5 catalyst was selected as the most suitable for BPF synthesis. In the BPF synthesis over the Y_PS5_Lu5 catalyst in a catalyst basket reactor, the optimum reaction temperature was determined to be 110 °C. The effect of stirring speed on the yield of BPF was found to be negligible in the range of 200 rpm to 350 rpm. The spent catalyst was able to recover a specific surface area and reaction activity similar to those of a fresh catalyst through regeneration in an air atmosphere at 500 °C. When the Y_PS5_Lu5 extruded catalyst was used in a continuous reaction in a fixed-bed reactor, there was no noticeable deactivation of the catalyst at low space velocities of the reactants. However, when the space velocity was increased to 18.0 h−1, catalyst deactivation was clearly observed. This suggests that periodic regeneration of the catalyst is inevitable in a continuous reaction using the Y_PS5_Lu5 extruded catalyst.

Catalytic cycle network: Boosting CO2 hydrogenation to propane

The utilization of CO2 hydrogenation to manufacture high-value chemicals is a viable strategy for achieving carbon neutrality. However, the reaction mechanisms still need to be further developed to improve catalytic efficiency. In this context, we report a bifunctional ZnZrOx/SSZ-13 catalyst, the conversion of CO2 reached 44.7 %, while the selectivity for CO was maintained at 16.7 %, and remarkably, the selectivity and yield for propane increased to 70.3 % and 26.1 %, respectively. A “catalytic cycle network” that involve H2O generated in situ by tandem reaction is suggested, and its mechanism confirmed through in situ DRIFTS spectroscopy, density functional theory (DFT) calculations, studies on water diffusion, and empirical evidence. This innovative mechanism, which departs from traditional tandem catalysis, signals a paradigm shift in the field of catalytic chemistry. At low space velocities, water generated during the reaction contributes by mass transfer diffusion to promote the tandem reactions. This phenomenon establishes a positive feedback loop in which “reaction-produced H2O promotes the reaction” and integrates with tandem reactions to form a “catalytic cycle network”. Such complex, multi-level interactions significantly improve the hydrogenation of CO2. Subsequent studies of the structure-activity relationship between zeolite properties and bifunctional catalyst performance reveal a synergistic effect of zeolite acidity and hydrophobicity on reaction performance, which together determine the efficiency of the reaction. These findings provide a solid foundation for the design of effective catalysts for CO2 hydrogenation and have the potential to transform the field, thereby making a significant contribution to sustainable chemical synthesis.

Study on Novel SCR Catalysts for Denitration of High Concentrated Nitrogen Oxides and Their Reaction Mechanisms

With the rapid development of industrialization, the emission of nitrogen oxides (NOx) has become a global environmental issue. Uranium is the primary fuel used in nuclear power generation. However, the production of uranium, typically based on the uranyl nitrate method, usually generates large amounts of nitrogen oxides, particularly NO2, with concentrations in the exhaust gas exceeding 10,000 ppm. High concentrations of nitrogen dioxide are also produced during silver electrolysis processing and the treatment of waste electrolyte solutions. Traditional V-W/TiO2 NH3-SCR catalysts typically exhibit high catalytic activity at temperatures ranging from 300 to 400 °C, under conditions of low NOx concentrations and high gas hourly space velocity. However, their performance is not satisfying when reducing high concentrations of NO2. This study aims to optimize the traditional V-W/TiO2 catalysts to enhance their catalytic activity under conditions of high NO2 concentrations (10,000 ppm) and a wide temperature range (200–400 °C). On the basis of 3 wt% Mo/TiO2, various loadings of V2O5 were selected, and their catalytic activities were tested. Subsequently, the optimal ratios of active component vanadium and additive molybdenum were explored. Simultaneously, doping with WO3 for modification was selected in the V-Mo/TiO2 catalyst, followed by activity testing under the same conditions. The results show that: the NOx conversion rates of all five catalysts increase with temperature at range of 200–400 °C. Excessive loading of MoO3 decreased the catalytic performance, with 5 wt% being the optimal loading. The addition of WO3 significantly enhanced the low-temperature activity of the catalysts. When the loadings of WO3 and MoO3 were both 3 wt%, the catalyst exhibited the best denitrification performance, achieving a NOx conversion rate of 98.8% at 250 °C. This catalyst demonstrates excellent catalytic activity in reducing very high concentration (10,000 ppm) NO2, at a wider temperature range, expanding the temperature range by 50% compared to conventional SCR catalysts. Characterization techniques including BET, XRD, XPS, H2-TPR, and NH3-TPD were employed to further study the evolution of the catalyst, and the promotional mechanisms are explored. The results revealed that the proportion of chemisorbed oxygen (Oα) increased in the WO3-modified catalyst, exhibiting lower V reduction temperatures, which are favorable for low-temperature denitrification activity. NH3-TPD experiments showed that compared to MoOx species, surface WOx species could provide more acidic sites, resulting in stronger surface acidity of the catalyst.

An investigation of monolithic nickel-based catalyst for clean hydrogen production with CCS technology: The effect of structure

At present, hydrogen is recognised as a carbon-free energy carrier, but its major production via the steam methane reforming (SMR) process requires further decarbonisation as a considerable amount of carbon dioxide is simultaneously emitted. Carbon capture and storage (CCS) techniques can be integrated with typical SMR to produce clean hydrogen. Previously, a novel structured catalyst (Ni/SiC-M) was developed, and it was highly active for SMR under low operating temperature and high gas space velocity. By integrating CCS techniques, this structured catalyst is promising to produce clean hydrogen, however, there is a lack of knowledge about the catalytic performance when CCS is applied, especially the effect of structure. In this work, the feasibility of producing cleaner hydrogen with monolithic catalysts (Ni/SiC-M) coupled with sorbent particles was discussed. Different modified structures were applied for performance evaluation with a fixed bed reactor, to better understand the relationship between the structure and the activity. The results showed that sorbent particles can adsorb most of the generated carbon dioxide, leading to a higher hydrogen purity; the limitation of internal mass transfer caused by high pressure drops can result in a decrease in catalytic activity, but the impact was limited. The pore size could be the key factor to influence the performance of structured catalysts.

Capacity of Ca-based slags for carbon capture

Efficiency in reutilization of Ca-based waste for carbon capture has gained high interest. Besides, the CO2 capture mechanism will be influenced by several operating parameters. Observation of carbonation by Ca-based slags (desulfurization slag/De-S, electric arc furnace/EAF slag, and bottom ash/BA) in this study indicated that De-S had the highest Ca(OH)2 content (73%) and largest surface area which led to the best slag utilization. This slag was further applied in the test under various operating conditions including temperature, space velocity, and the content of gas impurity (H2O and SO2). Higher temperature and lower space velocity promoted efficient carbonation. De-S endured the presence of ≤5% water vapor content in the simulated gas. Higher SO2 content in the simulated gas initiated the formation of CaSO4 and declined the CO2 capture capacity. Discussion in this study was complemented by the characterization of slags before and after carbonation process along with reaction kinetics analysis.

Extraordinary synergy on 3D hierarchical porous Co-Cu nanocomposite for catalytic elimination of VOCs at low temperature and high space velocity

It is still a challenge to develop hierarchically nanostructured catalysts with simple approaches to enhance the low-temperature catalytic activity. Herein, a set of mesoporous Co-Cu binary metal oxides with different morphologies were successfully prepared via a facile ammonium bicarbonate precipitation method without any templates or surfactants, which were further applied for catalytic removal of carcinogenic toluene. Among the catalysts with different ratios, the CoCu0.2 composite oxide presented the best performance, where the temperature required for 90% conversion of toluene was only 237°C at the high weight hour space velocity (WHSV) of 240,000 mL/(gcat·hr). Meanwhile, compared to the related Co-Cu composite oxides prepared by using different precipitants (NaOH and H2C2O4), the NH4HCO3-derived CoCu0.2 sample exhibited better catalytic efficiency in toluene oxidation, while the T90 were 22 and 28°C lower than those samples prepared by NaOH and H2C2O4 routes, respectively. Based on various characterizations, it could be deduced that the excellent performance was related to the small crystal size (6.7 nm), large specific surface area (77.0 m2/g), hollow hierarchical nanostructure with abundant high valence Co ions and adsorbed oxygen species. In situ DRIFTS further revealed that the possible reaction pathway for the toluene oxidation over CoCu0.2 catalyst followed the route of absorbed toluene → benzyl alcohol → benzaldehyde → benzoic acid → carbonate → CO2 and H2O. In addition, CoCu0.2 sample could keep stable with long-time operation and occur little inactivation under humid condition (5 vol.% water), which revealed that the NH4HCO3-derived CoCu0.2 nanocatalyst possessed great potential in industrial applications for VOCs abatement.

Understanding catalytic hydrotreating of hydrothermal liquefaction nitrogen-rich biocrude in a two-stage continuous hydrotreater

Hydrothermal liquefaction biocrude from non-lignocellulosic feedstocks often shows properties, such as a high presence of inorganics, oxygen and especially a high nitrogen content, which are challenging in view of hydroprocessing for the production of drop-in biofuels. In particular, nitrogen removal requires severe conditions, that might compromise continuous operations and affect the yield of the different hydrocarbon fractions. This work demonstrates the possibility of successful long-time continuous operations for microalgae biocrude, a feed with a high content of metals and nitrogen, thanks to a multi-stage approach with different sulfided catalysts. Whereas hydrodeoxygenation was achieved at relatively mild conditions, nitrogen removal was challenging. By using a number of advanced characterization techniques, among which FTICR-MS, it was possible to unveil how nitrogen removal takes place at different reaction severities, in terms of temperature, WHSV and pressure. High nitrogen removal needs high temperature (∼400 °C) and low space velocities and is associated with a high H2 consumption. This causes also a remarkable change in the boiling point distribution, which is shifted to products in the gasoline range, while the yields of middle distillates are marginally affected by hydrotreating severity. This seems to be a consequence of the denitrogenation mechanism, promoting the fragmentation of larger molecules in the heavy fractions of biocrude.

Continuous flow upgrading of lignin pyrolysis oils to drop-in bio-hydrocarbon fuels over noble metal catalysts

Although there are many studies on the noble metal-based catalysts for the hydrodeoxygenation (HDO) of lignin model compounds such as phenols, HDO studies on lignin biomass pyrolysis oil are relatively scarce. Owing to its complex composition (i.e., a mixture of phenolic monomers and oligomers), the activity and stability of the catalysts for the HDO of pyrolysis oil are significantly different from those for the model compounds. In this study, the catalytic performances of typical HDO catalysts, that is, Ru, Pd, Ru-Re supported on carbon, and the effects of process parameters such as solvent, temperature, and space velocity were investigated for the real lignin pyrolysis oils in a continuous-flow trickle bed reactor system for the first time. We demonstrated that proper tuning of catalyst composition and process parameters allows for producing the deoxygenated hydrocarbon mixtures which can be used for gasoline, jet fuel, and diesel fuels. Specifically, activated carbon promoted the HDO of lignin oil more effectively than acidic supports like HZSM-5 and TiO2 due to the weak adsorption of phenolic molecules. Among the different metals, Ru-Re supported on carbon exhibited the highest deoxygenation activity due to the synergy of the two metals. Tetrahydrofuran was the best solvent for lignin oil processing due to its high solubility and inertness to other side reactions (e.g., excess alkylation with ethanol solvent). The use of low space velocity of 0.2 h−1 and intermediate temperature of 350 °C resulted in the highest yield of the upgrade oil (∼25 wt%) simultaneously with the high level of deoxygenation (O/C < 0.04), mainly consisting of branched cycloalkanes. The causes of the catalyst deactivation and regeneration process are also discussed to provide practical significance.

Carbon capture from low CO2 concentration stream through ternary alkali metal nitrates promotion of MgO sorbents at intermediate temperature and low space velocity

Many MgO sorbents exhibit high CO2 uptake in the presence of high concentration CO2 and aided by high space velocity, which unfortunately leads to low CO2 capture efficiency from the gas stream. This study investigates the effect of Li/Na/K ratio on sorption performance in dilute CO2 streams (15% CO2) using alkali metal nitrates-promoted MgO sorbents at a low space velocity of 20 ml/g·min in fixed bed reactor. Study shows that the ratio of Li/Na/K in ternary alkali nitrate salt mixture significantly affects the induction periods for the second phase CO2 sorption, which is a key contributor to high CO2 uptake. High LiNO3 content in ternary mixture leads to long induction period, and therefore lower CO2 capacity during the 4 h period. Conversely, high ratios of NaNO3 and KNO3 leads to shorter induction periods. Among the samples, MgO with 9 mol% (Li0.18Na0.52K0.3) exhibits the highest CO2 sorption capacity of 5.56 mmol/g at 240°C in 4 h (20.6% CO2 capture efficiency) and 3.18 mmol/g after 5 cycles (10.8% CO2 capture efficiency). Comparative studies show that optimal temperatures for CO2 sorption are higher when using pure CO2 (280 to 320°C) than when using 15% CO2 (240°C) due to the thermodynamic equilibrium. CO2-TPD results indicate that CO2 desorption proceeds in two phases similar to CO2 sorption, and the presence of alkali salt in MgO also promotes the decomposition of bulk carbonate to CO2. It is shown that molten salt migration and agglomeration of MgO particles are likely the factors that lead to decline in CO2 uptake over the sorption-desorption cycles.

Catalytic conversion of bioethanol over cobalt and nickel‐doped HZSM‐5 zeolite catalysts

AbstractThis study focuses on the use of H‐ZSM‐5 catalyst modified with transition metals for the conversion of ethanol into liquid fuel hydrocarbons. The HZSM‐5 catalyst was synthesized hydrothermally, and the transition metal (0.5 wt%) was incorporated by the incipient wetness impregnation method. The synthesized catalysts were tested in a fixed‐bed reactor at varying weight hourly space velocities (WHSVs) and temperatures to investigate their effects on the selectivity of the liquid hydrocarbon product. The pure and metal‐doped catalysts were characterized using XRD, FTIR, SEM–EDX, PSD, BET, N2 adsorption–desorption, and NH3‐TPD. The metal species were evenly dispersed on the catalyst support without affecting the porous framework significantly. The modification did not alter the morphology of the catalyst; however, the particle size was altered slightly. The pore distribution plot confirms the hierarchical porous framework of the catalyst. This unique feature facilitates internal diffusion and accelerates mass transfer, improving the selectivity and distribution of the liquid product. The catalytic evaluation showed ethanol conversion of more than 97% for all catalysts tested. A low space velocity (5 h−1) favored gaseous (C1‐C4) hydrocarbons, but more liquid products (C5+) were generated at 12 h−1 (at 350 and 400 °C), with metal‐doped catalysts showing higher selectivity (&gt; 79%). In comparison with the unmodified catalysts, the metal‐doped catalysts enhanced the production of aromatics (benzene), with Ni/HZSM‐5 showing higher selectivity (&gt; 4%). This study showed that the synthesized catalysts are active in the selective production of liquid hydrocarbon and improve the transformation of ethanol to fuel‐range hydrocarbons.

Modeling and comprehensive analysis of hydrogen production in a newly designed steam methane reformer with membrane system

The use of a hydrogen perm-selective membrane in the conventional steam methane reformer (SMR) is a promising technology for producing ultra-pure hydrogen under moderate operating conditions. A detailed computational fluid dynamics (CFD) analysis is performed on a membrane SMR unit for an on-site hydrogen refueling station (HRS) to get the optimum operating conditions. The developed model was validated with experimental results. The obtained results predicted that the high temperature of the process gas inlet, the high operating pressure, and the low gas hourly space velocity (GHSV) were advantageous. However, these factors must be carefully adjusted to achieve optimal efficiency. Furthermore, the simulation with a counter-current sweep gas flow configuration gave better results than a co-current operation. The estimated optimal conditions for improved CH4 conversion and H2 recovery were 4500 h−1 GHSV, 500 K inlet temperature, and the 8.5 bar operating pressure, representing CH4 conversion and H2 recovery of approximately 94.7% and 95.8%, respectively.

One-pot lower olefins production from CO2 hydrogenation

In this work the one-pot conversion of CO2 into lower olefins is investigated over a physical mixture of a methanol synthesis catalyst and a methanol-to-olefins (MTO) zeolite. First, the feasibility of the single reactions is tested at CO2 to olefins conditions, i.e., high temperature and high H2/CO2 pressure, providing insights on the reaction mechanism and catalyst stability. The effects of the operating conditions are then analyzed over the individual samples, starting from CO2/H2 mixtures in the case of the methanol synthesis catalyst and from methanol in CO2/H2 in the case of the zeolite. The In2O3-ZrO2 catalyst exhibits very good selectivity to methanol and high activity, reaching thermodynamic equilibrium above 380 °C. The zeolite sample showed high activity as well and the presence of high H2 partial pressure consistently increases the zeolite lifetime at high temperatures, but also the paraffin selectivity at the expense of the olefins, especially at low space velocity. It is therefore clear that a trade-off should be identified when testing the bi-functional catalytic samples in order to guarantee high methanol formation and good olefins production in the one-pot process. Finally, a comparison between methanol-mediated and modified Fischer-Tropsch (MFT) routes is presented, highlighting strengths and weaknesses of each reaction pathway. In particular, CO must be reduced in the methanol-mediated route, while methane and C5+ hydrocarbons formation is the main issue for the MFT reaction.

Reactive Separations of CO/CO2 mixtures over Ru–Co Single Atom Alloys

Reactive separations of CO/CO2 mixtures are a promising pathway to lower the energy requirement of CO2 hydrogenation to chemicals and fuels, with applications in the U.S. Navy’s seawater-to-fuel process. With the CO/CO2 feedstock, a challenge is activating CO to produce heavier hydrocarbons while preventing CO2 methanation, requiring low-temperature Fischer-Tropsch synthesis (FTS) catalysts. In this work, we demonstrate that a Ru–Co single atom alloy (SAA) catalyst produces C5+ hydrocarbons at a rate of 11.7 μmol/s/g-cobalt (hexane basis) in a 50/50 CO/CO2 stream with ≤1% CO2 conversion. The reaction operates at a relatively low temperature (200 °C) and high gas hourly space velocity (GHSV: 84,000 mL/g/h) that is compatible with the upstream reverse water-gas shift reaction. Detailed experiments, catalyst characterizations, and density functional theory (DFT) calculations have been conducted to understand the active phase, the role of the Ru dopant, and catalyst restructuring that occurs at elevated temperatures (>200 °C). Ru dopants are found to promote the reduction of Co species, enabling catalytic activity for CO hydrogenation without pre-reduction, but may not enhance the FTS activity or desired C5+ hydrocarbon selectivity.

Thermal effect optimization endows a selective and stable PdCu single atom alloy catalyst for acetylene hydrogenation

AbstractHere, we proposed a universal approach to solve a seesaw relationship between thermal effect control and conversion efficiency in strong exothermic acetylene hydrogenation by constructing Pd‐based single atom alloy (SAA), in which Cu was chosen as host atom and heat transfer agent. Lower desorption energy of *C2H4 intermediate on isolated Pd atoms greatly improved ethylene selectivity. Notably, this excellent performance was well maintained, even at extremely low space velocity, implying the thermal effect was effectively controlled. On one hand, the heat generation rate over single active site was largely decreased. On another hand, host Cu atoms with proper continuity degree endowed the SAA with attractive lattice heat capacity and phonon scattering rate, which ensured the instant heat transfer from Pd atoms to the surroundings. The optimized performance (conversion 90.7% and selectivity 95.8%) was stably operated for 270 h under GHSV = 2400 h−1.

Formation of nitrous oxide over Pt-Pd oxidation catalysts: Secondary emissions by interaction of hydrocarbons and nitric oxide

The interaction of hydrocarbons (HC) and nitric oxide (NO) over noble metal catalysts for exhaust gas after-treatment of lean-operated combustion engines can lead to secondary emissions, namely the formation of nitrous oxide (N2O), which is a strong greenhouse gas calling for N2O reduction concepts. By means of a series of light-off tests over state-of-the-art Pt-Pd oxidation catalysts, this study identifies the most critical catalyst operation regimes that should be avoided in order to minimize N2O levels. Especially unsaturated HCs react with NO to form significant amounts of N2O between 150 °C and 350 °C; an increasing HC/NOx ratio generally promotes N2O formation, whereas the NO oxidation reaction is increasingly inhibited. Since low space velocities and fast catalyst heating allow for minimizing N2O levels, active heating of catalytic converters during cold start and phases of low exhaust gas temperatures may efficiently reduce the formation of N2O in real-world applications.

Parametric Analysis and Optimization of Vanillin Hydrodeoxygenation Over a Sulfided Ni-Mo/δ-Al2O3 Catalyst Under Continuous-Flow Conditions

A fundamental understanding of the process parameters affecting the catalytic hydrodeoxygenation (HDO) of bio-oils is of significance for enabling further progression and improvement of industrial biofuel upgrading methods. Herein, a novel demonstration and evaluation of the effect of temperature, pressure, and weight hourly space velocity in the continuous HDO of vanillin to cresol over a Ni-Mo/δ-Al2O3 catalyst are presented. Response surface methodology was used as a statistical experimental design method, and the application of central composite design enabled the generation of a statistically significant simulation model and a true optimization parametric study. The distribution of Ni and Mo on δ-Al2O3 was confirmed using scanning electron microscopy with energy dispersive X-ray analysis (SEM-EDX). No gradients with EDX mapping could be identified, and the elemental analysis showed well-dispersion of the metals. The mesoporous character of the catalyst-support system was unraveled using N2 physisorption. Experiments were conducted within the parametric range of 250–350 °C, 3–9 bar, and 15–35 h−1. Both temperature and pressure were found to have statistically significant linear and quadratic effects on the selectivity for cresol. The parametric interaction of temperature with pressure and space velocity also had a significant effect on the resulting response. The optimal temperature range becomes more critical at lower space velocities. Optimal selectivity for cresol was established at 314 °C, 5 bar, and 35 h−1. The fitting quality of the generated regression model was statistically confirmed and experimentally validated to describe the specified HDO process within the 95% two-sided confidence interval.

Non-ideal characteristics in a micro packed-bed reactor: A coupled reaction-transport CFD analysis for propane dehydrogenation

Kinetic experiments can be significantly influenced by fluidic effects and transport limitations within reactors, particularly for strongly exo- and endo-thermic reactions. This paper describes the influence non-uniform physical fields, e.g. temperature, velcocity and species concentration, on the determination of kinetic parameters for endothermic systems with propane dehydrogenation (PDH) as a model process, which was analyzed using computational fluid dynamics (CFD) method based on the porous media model. Propane conversions calculated from 3-D porous media model at various conditions have discrepancies from the reported experimental data and 1-D numerical regression. This is due to the application of kinetic parameters obtained from 1-D plug flow assumption to the 3-D model with inhomogeneous temperature distributions. In the kinetic analysis, it is found that the low space velocity may lead to backward diffusion but can be a preference to minimize the temperature gradients within the catalyst bed. On the other hand, the commonly used higher space velocity may enlarge the temperature inhomogeneity. The sensitivity of temperature distribution with various reaction conditions is further analyzed. In addition, with respect to the packed bed properties, a high thermal conductivity and low loading of catalysts can reduce the non-uniformity of temperature distribution. Therefore, it is proposed that a mixed packing scheme with lower catalyst concentration and higher thermal conductivity could effectively suppress temperature gradients in kinetic analysis. This study exemplifies the necessity to consider the non-ideal distribution of physical fields for the kinetic study of reactions with strong thermal effects.

Experimental optimization analysis on operating conditions of CO removal process from hydrogen-rich reformate

The catalytic effects of CO preferential oxidation and methanation catalysts for deep CO removal under different operating conditions (temperature, space velocity, water content, etc.) are systematically studied from the aspects of CO content, CO selectivity, and hydrogen loss index. Results indicate that the 3 wt% Ru/Al2O3 preferential oxidation catalysts reduce CO content to below 10 ppm with a high hydrogen consumption of 11.6–15.7%. And methanation catalysts with 0.7 wt% Ru/Al2O3 also exhibit excellent CO removal performance at 220–240 °C without hydrogen loss. Besides, NiClx/CeO2 methanation catalysts possess the characteristics of high space velocity, high activity, and high water-gas resistance, and can maintain the CO content at close to 20 ppm. Based on these experimental results, the coupling scheme of combining NiClx/CeO2 methanation catalysts (low cost and high reaction space velocity) with 0.7 wt% Ru/Al2O3 methanation catalysts (high activity) to reduce CO content to below10 ppm is proposed.

Parametric study for N2O conversion and reduction using cobalt‐oxide‐based catalysts

AbstractNitrous oxide is a highly reactive gas with several well‐known environmental impacts. Its presence in the atmosphere can decrease the stratospheric ozone levels, cause an increase in the greenhouse gas emissions, and contribute to acid‐rain formation. Therefore, in this article, the potential and performance of different types of cobalt oxide (Co3O4) catalysts in N2O decomposition and conversion was studied. For this, the catalytic activity of these materials was tested in a differential fixed‐bed reactor, operated under steady state conditions. The results obtained in this study show reduced CoO achieved 100% N2O conversion at 250°C; that CoO has a great performance (&gt;95%) in the absence of oxygen and humidity, regardless of the W/F; even at low space velocities (0.1 g−s/ml) and in the absence of humidity the N2O conversion efficiency is still very high (100%); 10%La/CoO has a higher catalytic activity than 10% Ba/CoO, 10% Na/CoO, and 10% W/CoO. The highest catalytic activity (&gt;90%) was reported in samples with 50%La/CoO, even in the presence of 5% H2O and 15% O2.

Model-Based Analysis for Ethylene Carbonate Hydrogenation Operation in Industrial-Type Tubular Reactors

Hydrogenation of ethylene carbonate (EC) to co-produce methanol (MeOH) and ethylene glycol (EG) offers an atomically economic route for CO2 utilization. Herein, aided with bench and pilot plant data, we established engineering a kinetics model and multiscale reactor models for heterogeneous EC hydrogenation using representative industrial-type reactors. Model-based analysis indicates that single-stage adiabatic reactors, despite a moderate temperature rise of 12 K, suffer from a narrow operational window delimited by EC condensation at lower temperatures and intense secondary EG hydrogenation at higher temperatures. Boiling water cooled multi-tubular reactors feature near-isothermal operation and exhibit better operability, especially under high pressure and low space velocity. Conduction oil-cooled reactors show U-type axial temperature profiles, rendering even wider operational windows regarding coolant temperatures than the water-cooled reactor. The revelation of operational characteristics of EC hydrogenation under industrial conditions will guide further improvement in reactor design and process optimization.