Space Velocity Values Research Articles

Highly-efficient hydrogen production through the electrification of OB-SiC nickel structured catalyst: Methane steam reforming and ammonia cracking as case studies

The aim of this work is the preparation and the electrification of Ni_CeO2_Al2O3/OBSiC (Oxygen Bonded SIlicon Carbide) based foams used in two different endothermic reactions for H2 production: methane steam reforming and ammonia cracking. In particular, the heating of the catalytic foams occurs by the Joule effect, and to guarantee a uniform temperature profile in both the axial and radial direction, two different heating resistances were used. In addition, the high tortuosity together with the very high thermal conductivity of the OBSIC carrier, allow to overcome the heat and mass transfer limitations achieving a better control of the reaction behavior.Wet impregnation method was adopted for the Ni and Ce deposition, while the final catalysts was characterized through Hg penetration technique, Scanning Electron Microscope (SEM), N2 adsorption @77 K for the specific surface areas (SSA) determination and X-ray diffraction (XRD). The methane steam reforming and ammonia cracking tests were both carried out, in the same reactor, but at different space velocity values (WHSV). The results obtained are exciting, not only in terms of equilibrium approach and hydrogen production, but also in terms of energy consumption as kWh/Nm3 of H2 produced. In particular, in the case of methane steam reforming the results showed an energy consumption E [kWh/Nm3 H2] equal to 1.21 obtained at WHSV equal to 6.2 h−1, very close to the theoretical limit of 0.98 kW h/Nm3 H2. Also, for ammonia cracking, the energy consumption was very promising considering the scale of our reactor, with 1.5 kW h/Nm3 H2 obtained at a WHSV of 2.27 h−1, considering the theoretical limit equal to 0.71 kW h/Nm3 H2.

Experimental study and comprehensive kinetic modeling of the direct dimethyl ether synthesis on Cu/ZnO/ZrO2 and H-FER-20

In the direct dimethyl ether (DME) synthesis, the combination of Cu/ZnO/ZrO2 (CZZ) and H-FER-20 (FER) has shown high selectivity and productivity for a broad range of CO2/COX ratio. Aiming to understand the behavior of the studied catalyst system under distinct operating conditions, we developed a new 9-parameter kinetic model. The parameters were estimated based on 815 steady-state experiments carried out at several values of pressure (30–54 bar), temperature (190–250 ℃), space-velocity (0.79–4.34 s−1) and inlet gas composition. This broad database was used in the development and validation of a new 9-parameter kinetic model for the direct DME synthesis. The model adequately simulates experiments in several process conditions, with 95% of the simulated points presenting a deviation lower than 20% with respect to the experimental results for outlet DME molar percentage. In addition, it correctly predicts the trends with respect to variations in H2 inlet fraction, which is of high relevance for processes using fluctuating renewable power sources for H2 production. In comparison to state-of-the-art models with more parameters, the new model is significantly more accurate. It benefits from the broad range of validity and elevated number of experimental points, which makes it a reliable model that can be applied for process optimization and scale-up.

CO2 hydrogenation over Ru hydrotalcite-derived catalysts

The hydrogenation of CO2 over Ru catalysts is structure sensitive, the selectivity of the process can be driven either to the production of CH4 or CO depending on Ru particles and support features. Herein, Ru-based MgAl-HT (HT=hydrotalcite) derived catalysts with different Ru loadings (0.5, 1.0 and 2.0 wt%) and promoted with La3+ were prepared, characterized, and tested for CO2 methanation at high Gas Hourly Space Velocity values (480 L/gcat h) feeding a CO2/H2/N2 = 1/4/1 v/v mixture. The MgAlOx mixed oxide obtained after calcination at 600 °C and reduction provided weak, medium and mainly strong basic sites, able to activate the CO2 molecule, and hosted very small Ru nanoparticles (1–3 nm). However, the catalysts displayed a low activity in the low temperature range and a poor selectivity to CH4. The addition of La3+, despite contributing to the basicity, did not have any significant effect on performance. In a comparison between Ru- and Ni-HT-derived catalysts, tested under similar reaction conditions, Ni largely overperformed Ru.

Effect of the surface composition of MnOX-CeOX 3D-printed monolithic catalysts toward total oxidation of toluene.

Successful fabrication of Mn-based 3D-printed monoliths by stereolithography (SLA) is reported for the first-time in this work. The catalytic performances, as function of the surface composition, of the developed monoliths were evaluated by the total oxidation of toluene. The monolith with a surface composition of Mn0.7Ce0.3 showed the highest catalytic efficiency (98%) with a T90 value of 322 °C and acceptable catalytic stability after a second reaction cycle. By changing space velocity values, the T90 value can decrease to 311 °C. Microstructural and surface characterizations confirm the formation of Mn2O3 and Ce species on Mn sites and the homogeneous dispersion of Mn and Ce species on the surface of the 3D-printed monoliths. For comparison purposes, a single MnOX and CeOX monoliths were also synthesized and tested by toluene total oxidation, which confirms the cooperative effect between the oxygen storage capacity of Ce and the redox ability of Mn species observed in Mn0.7Ce0.3 monolith catalyst, giving rise to the highest catalytic activity. These results pointed out the promising catalytic properties of the developed Mn-based 3D-printed monolith catalysts for the total oxidation of volatile organic compounds at a low cost, which is an interesting alternative to mitigating atmospheric emissions.

Syngas to FCC-like gasoline range hydrocarbons with upgraded light olefin selectivity catalyzed by readily synthesized Fe-MOF

The global trend toward sustainability is due to the growing demand for synthetic chemicals and fuels relying on fossil crude oil with the associated concerns of climate change. The Fischer-Tropsch synthesis (FTS) process is a key sustainable pathway for supplying light olefins, gasoline, and other petrochemicals using green hydrogen and energy. Here we report a simple, green, cost-effective synthesis strategy to prepare an iron-based metal–organic framework (Fe-BTC MOF) at room temperature with a remarkable porous structure analogous to the commercially available Basolite F300. The catalyst shows a 97% syngas conversion to gasoline-range hydrocarbons (C5-C12) at high temperatures, with a selectivity of 48.3%, yield of 28%, low methane selectivity (15.5%) and low C13+ selectivity (1%). In addition, the catalyst is 29% selective to light olefin (C2-C4=), yielding 17%, besides an olefin/paraffin ratio (O/P) of 4.3 with 81% olefin selectivity of the C2-C4 fraction. The resulting gasoline is equivalent to gasoline produced by Fluid Catalytic Cracking (FCC) of crude oil. The highest C5-C12 selectivity reached 63.6%, yielding 12% at 29% CO conversion. The Fe-BTC/C catalyst showed excellent stability for time on stream >100 h and a high gas hourly space velocity (GHSV) value of 20000 mL g-1cat h−1 with an Fe-time yield of 165 µmolCO g-1Fe s−1. The prepared Fe-BTC catalyst, with a 2-fold larger pore volume than the previously prepared Fe-MIL-88B catalyst, has a higher olefin production capability by 2-fold, 7-fold higher O/P for the light fraction and 2.3-fold higher C5+ selectivity. The sustainable synthesis of catalysts with improved porous structure may significantly foster FTS technology for being economically practical to be scaled up and commercialized for national fuel and olefin production projects.

SiC-based structured catalysts for a high-efficiency electrified dry reforming of methane

The process of dry reforming of methane (DRM) can allow the conversion of methane and carbon dioxide, the two main greenhouse gases (GHG), into syngas which can be either used as feedstock for chemicals production or it can undergo through separation step for H2 recovery. However, the heat required for the reaction is obtained by combustion of fossil fuels, so CO2 footprint of the process is significant. Another problematic aspect of the process concerns the heat transfer to the catalytic volume: for allowing the catalytic bed to reach and maintain the reaction temperature, the heating medium outside the tubes containing the catalyst must have a temperature higher than 1000 °C. A process intensification could be performed by combining two innovative technologies: (i) the use of electrification for the energy supply (microwave heating and direct electrification) and (ii) the adoption of structured catalysts with high thermal conductivity.This work proposed the study of electrified DRM process using two Ni-based structured catalysts prepared starting by different carriers, a Silicon carbide (SiC) honeycomb monolith and a Si–SiC open-cell foam. The electrification of the DRM process has been realized by using either microwave heating or electrification through Joule (or ohmic) heating, and the experimental tests have been performed at different space velocity values. The configuration of the carriers has been carefully chosen in order to enhance the heat and mass transport phenomena, allowing to assure a flat temperature profile along the entire catalytic bed.The results have shown that the SiC monolith is more suitable than the Si–SiC foam for a microwave-assisted catalytic test. In fact, the higher fraction of void in the foam determines a lower heat absorption, and a consequently higher energy consumption (8.29 kWh/Nm3 H2 and 4.2 kWh/Nm3 H2, for the foam and the monolith respectively). Moreover, the monolith-based catalyst approached the thermodynamic equilibrium values in terms of CH4 conversion in all the investigated temperature range, while in the same tests the foam-based catalyst reached these values only at the higher temperatures. Conversely, the foam-based catalyst has shown the best performance in the electrification tests through Joule heating: the CH4 conversion approached the equilibrium values in the investigated temperature range and, more important, the energy consumption value was of 2.6 kWh/Nm3 H2, very close to the theoretical one (1.90 kWh/Nm3 H2) and equal to about ¼ of that obtained with microwaves.

Fabrication of highly active and stable Ni/CeO2-nanorods wash-coated on ceramic NZP structured catalysts for scaled-up CO2 methanation

The production of synthetic natural gas from CO2 methanation using green H2 produced via water electrolysis is a promising pathway regarding both the curtailment of excess power by variable renewables and the mitigation of CO2 emissions. Several catalytic systems have been employed for thermocatalytic CO2 methanation in lab-scale, with Ni-based catalysts being amongst the most cost-effective and active materials. In this regard, we have recently demonstrated the remarkable low-temperature CO2 methanation activity of a nickel catalyst supported on ceria nanorods, ascribed to the augmented metal-support synergy. Herein, we report on a scaled-up process of CO2 methanation, involving; i) fabrication of a highly porous NZP-type ceramic substrate of Ba1+xZr4P6–2xSi2xO24 in the form of extruded pellets, ii) wash-coating of Ni/CeO2-nanorods catalyst on NZP pellets, iii) design and testing of scaled-up experiments under a scaling factor of 80:1 and 65:1 in terms of mass and volume of catalysts compared to lab-scale experiments, respectively. The as-synthesized catalyst exhibited remarkable performance under variable reaction conditions and stable behavior after 75 h. Remarkably, the structured catalyst attained a methane formation rate of 277 NL gNi−1 h−1, being higher to numerous values reported in relevant works. Equally importantly, it was disclosed that increased values of space velocity led to high temperature gradient in the catalytic bed, thereby favoring the generation of CO. Intriguingly, the morphological and structural characteristics of the used catalyst remained unaltered even after various on/off reaction cycles and the stability test, which is a promising finding toward scaling-up the process at higher technology readiness levels using real feed streams.

In-situ preparation of zinc sulfide adsorbent using local materials for elemental mercury immobilization and recovery from zinc smelting flue gas

Exploiting a cheap and readily available adsorbent for elemental mercury (Hg0) immobilization from zinc smelting flue gas has become an urgent requirement to ensure the sustainable development of zinc smelting industry. Herein, a novel protocol of using intermediate products derived from zinc smelting process to synthesize porous ZnS adsorbent is proposed in this study to provide a practicable support for efficient capture of Hg0. The as-prepared ZnS-300℃-120 min adsorbent exhibits an outstanding performance for Hg0 capture. Approximately 100% of Hg0 can be entrapped even under the extreme conditions of high gaseous hourly space velocity (GHSV) values and wide temperature ranges. Additionally, its saturated adsorption capacity and average adsorption rate reach 3.6 mg/g and 1.3 μg/g/min, respectively, much higher than common adsorbents. The in-situ Raman spectra and XPS spectra results confirm that the unsaturated short-chain Sn2- is dominant adsorption site. The active Sn2- site would be formed on the surface of ZnS during the calcination process. The formed Sn2- ligand would promptly and selectively react with Hg0 to form stable HgS, consequently achieving the efficient immobilization of Hg0. After Hg0 capture, the spent ZnS adsorbent can be safely disposal of by thermal desorption, simultaneously realizing the recycling of zinc and mercury resource. The purposefully synthesized ZnS adsorbent can provide a practical and yet easy-to-adopt strategy for mercury pollution control of zinc smelting industry, while opening a new path to recycle valuable metal from smelting waste.

Characterization and catalytic activity of soft-templated NiO-CeO2 mixed oxides for CO and CO2 co-methanation

Nanosized NiO, CeO2 and NiO-CeO2 mixed oxides with different Ni/Ce molar ratios were prepared by the soft template method. All the samples were characterized by different techniques as to their chemical composition, structure, morphology and texture. On the catalysts submitted to the same reduction pretreatment adopted for the activity tests the surface basic properties and specific metal surface area were also determined. NiO and CeO2 nanocrystals of about 4 nm in size were obtained, regardless of the Ni/Ce molar ratio. The Raman and X-ray photoelectron spectroscopy results proved the formation of defective sites at the NiO-CeO2 interface, where Ni species are in strong interaction with the support. The microcalorimetric and Fourier transform infrared analyses of the reduced samples highlighted that, unlike metallic nickel, CeO2 is able to effectively adsorb CO2, forming carbonates and hydrogen carbonates. After reduction in H2 at 400 °C for 1 h, the catalytic performance was studied in the CO and CO2 co-methanation reaction. Catalytic tests were performed at atmospheric pressure and 300 °C, using CO/CO2/H2 molar compositions of 1/1/7 or 1/1/5, and space velocities equal to 72000 or 450000 cm3·h−1·gcat−1. Whereas CO was almost completely hydrogenated in any investigated experimental conditions, CO2 conversion was strongly affected by both the CO/CO2/H2 ratio and the space velocity. The faster and definitely preferred CO hydrogenation was explained in the light of the different mechanisms of CO and CO2 methanation. On a selected sample, the influence of the reaction temperature and of a higher number of space velocity values, as well as the stability, were also studied. Provided that the Ni content is optimized, the NiCe system investigated was very promising, being highly active for the COx co-methanation reaction in a wide range of operating conditions and stable (up to 50 h) also when submitted to thermal stress.

Analysis of Membership Probability in Nearby Young Moving Groups with Gaia DR2

Abstract We analyze the membership probability of young stars belonging to nearby moving groups with Gaia DR2 data. The sample of 1429 stars was identified from “The Catalog of Suspected Nearby Young Moving Group Stars.” Good-quality parallax and proper motion values were retrieved for 890 stars from the Gaia DR2 database. The analysis for membership probability is performed in the framework of the LACEwING algorithm. From the analysis it is confirmed that 279 stars do not belong to any of the known moving groups. We estimated the U, V, W space velocity values for 250 moving group members, which were found to be more accurate than previous values listed in the literature. The velocity ellipses of all the moving groups are well constrained within the “good box,” a widely used criterion to identify moving group members. The age of moving group members are uniformly estimated from the analysis of the Gaia color–magnitude diagram with MIST isochrones. We found a spread in the age distribution of stars belonging to some moving groups, which needs to be understood from further studies.

Effect of manganese and/or ceria loading on V2O5–MoO3/TiO2 NH3 selective catalytic reduction catalyst

The effect of manganese and/or ceria loading of V2O5–MoO3/TiO2 catalysts was investigated for selective catalytic reduction (SCR) of NOx by NH3. The manganese and/or ceria loaded V2O5–MoO3/TiO2 catalysts were prepared by the wetness impregnation method. The physicochemical characteristics of the catalysts were thoroughly characterized. The catalytic performance of 1.5 wt% V2O5–3 wt% MoO3/TiO2 (V1.5Mo3/Ti) is greatly enhanced by addition of 2.5 wt% MnOx and 3.0 wt% CeO2 (V1.5Mo3Mn2.5Ce3/Ti) below 450 °C. Compared with the V1.5Mo3/Ti catalyst with NOx conversion of 75% at 275 °C, V1.5Mo3Mn2.5Ce3/Ti exhibits higher NOx conversion of 84% with good resistance to SO2 and H2O at a gas hourly space velocity value of 150000 h−1. The active manganese, cerium, molybdenum, and vanadium oxide species are highly dispersed on the catalyst surface and some synergistic effects exist among these species. Addition of MnOx significantly enhances the redox ability of the cerium, vanadium, and molybdenum species. Addition of Ce increases the acidity of the catalyst. More active oxygen species, including surface chemisorbed oxygen, form with addition of Mn and/or Ce. Because of the synergistic effects, appropriate proportions of manganese in different valence states exist in the catalysts. In summary, the good redox ability and the strong acidity contribute to the high NH3-SCR activity and N2 selectivity of the V1.5Mo3Mn2.5Ce3/Ti catalyst in a wide temperature range. And the V1.5Mo3Mn2.5Ce3/Ti catalyst shows good resistance to H2O and SO2 in long-time catalytic testing, which can be ascribed to the highly sulfated species adsorbed on the catalyst.

A two-step process for sewage sludge treatment: Hydrothermal treatment of sludge and catalytic hydrothermal gasification of its derived liquid

The worldwide increase in amount of sewage sludge has recently attracted considerable interest in developing an efficient and economical sludge disposal method. A sewage sludge treatment process combining the hydrothermal treatment (HT) of sludge and the catalytic hydrothermal gasification (CHTG) of its derived liquid (HT&CHTG-Process) is proposed in this paper. Liquid hourly space velocity (LHSV) value of 25–100 h−1 and liquid flow rate of 10–40 mL/min were employed with a self-designed CHTG experimental setup. During the first stage of the HT-Process, approximately 56% of the carbon in the sludge was transferred into the derived liquid at 300 °C. During the second stage of the CHTG-Process, the derived liquid was gasified into CH4, H2, and CO2 using a Ni/carbon catalyst, and the carbon conversion reached 88% at 350 °C and 20 MPa with a LHSV of 25 h−1. Using the integrated HT&CHGT-Process, approximately 0.78 Nm3 of CH4, 0.62 Nm3 of H2 and 0.31 Nm3 of CO2 were generated from 1 kg of carbon in the sewage sludge. The combined process was expected to be an efficient method for sewage sludge treatment due to its mild conditions (≤350 °C and ≤20 MPa) and high yield of fuel gases.

Hydrodesulfurization Properties of Dibenzothiophene over NiMo Catalysts Supported on Cubic Fm3m Mesoporous Structure and High-Framework Aluminum-Modified AlKIT-5

The AlKIT-5 sample with Fm3m symmetry order structure and different Si/Al ratios was first synthesized by chemical grafting method. The 27Al NMR result of the AlKIT-5 sample proves that most aluminum species have been incorporated into the silicon framework. The oxidized supports and catalysts were characterized by XRD, N2 adsorption, 27Al MAS NMR, SEM, TEM, Py-FTIR, and Raman spectroscopy, and the series of sulfided catalysts were investigated by XPS and HRTEM. The corresponding NiMo catalysts were obtained by impregnation method, and the hydrodesulfurization activity for dibenzothiophene (DBT) was tested in a high-pressure microreactor under different weight hourly space velocity (WHSV, 10–100 h–1) values. All of the catalysts based on KIT-5 mesoporous material support showed better HDS efficiencies than that of the NiMo/AlMCM-41 catalyst, benefiting from the interconnected large pore structure. The NiMo/AK-10 catalyst exhibited the best HDS activity (99.2%) when the WHSV was 10 h–1, which resulted from...

Hydrogen production from supercritical water reforming of acetic acid, acetol, 1-butanol and glucose over Ni-based catalyst

Supercritical water reforming (SCWR) of four main constituents of bio-oil aqueous phase (acetic acid, acetol, 1-butanol and glucose) to produce hydrogen was studied in a tubular fixed-bed reactor using commercial Ni/Al2O3-SiO2 catalyst. The process was carried out under different operating conditions at 240 bar (500–800 °C, 5.0–22.5 wt.% of organic compounds and values of weight-hourly space velocity (WSHV) of 2.5–22.5 gorg-comp h−1 gcat−1). The data were reported as reaction rates, expressed as turnover frequencies (TOF), and the Arrhenius parameters (pre-exponential factor and apparent activation energy) were obtained. The process performance was compared to that without using any catalyst and that regarding equilibrium condition. Hydrogen yields were very close to those values predicted by equilibrium within the operating window tested in this study.

Mn-Ce-V-WOx/TiO2 SCR Catalysts: Catalytic Activity, Stability and Interaction among Catalytic Oxides

A series of Mn-Ce-V-WOx/TiO2 composite oxide catalysts with different molar ratios (active components/TiO2 = 0.1, 0.2, 0.3, 0.6) have been prepared by wet impregnation method and tested in selective catalytic reduction (SCR) of NO by NH3 in a wide temperature range. These catalysts were also characterized by X-ray diffraction (XRD), Transmission Electron Microscope (TEM), in situ Fourier Transform infrared spectroscopy (in situ FTIR), H2-Temperature programmed reduction (H2-TPR) and X-ray photoelectron spectroscopy (XPS). The results show the catalyst with a molar ratio of active components/TiO2 = 0.2 exhibits highest NO conversion value between 150 °C to 400 °C and good resistance to H2O and SO2 at 250 °C with a gas hourly space velocity (GHSV) value of 40,000 h−1. Different oxides are well dispersed and interact with each other. NH3 and NO are strongly adsorbed on the catalyst surface and the adsorption of the reactant gas leads to a redox cycle with the valence state change among the surface oxides. The adsorption of SO2 on Mn4+ and Ce4+ results in good H2O and SO2 resistance of the catalyst, but the effect of Mn and Ce are more than superior water and sulfur resistance. The diversity of valence states of the four active components and their high oxidation-reduction performance are the main reasons for the high NO conversion in this system.

Facile one-pot synthesis of Ni@HSS as a novel yolk-shell structure catalyst for dry reforming of methane

A novel yolk-shell Ni@HSS catalyst with Ni nanoparticles highly dispersed in the inner surface of hollow silica spheres(Ni@HSS) was designed and prepared via a facile one-pot micro-emulsion method for its application in reactions pertaining to the dry reforming of methane (DRM). The small size of Ni particles, as well as the strong metal-support interaction and confinement effect of the porous silica shell give rise to excellent catalytic activity and stability. Ni@HSS showed significantly enhanced methane and carbon dioxide conversions that both nearly reached the thermodynamic equilibrium at a large gas hourly space velocity value and a prolonged stability over 55 h without carbon deposition.

Reaction characteristics of dimethyl ether (DME) steam reforming catalysts for hydrogen production

The purpose of this study was to develop new catalysts for dimethyl ether (DME) steam reforming (SR) in the absence of a carrier gas for hydrogen fuel cell vehicles and to find the optimal reaction conditions for said process. The steam reforming catalysts were prepared by impregnation of Cu, the active material, with Ce and Ni additives using mordenite (MOR) and alumina as supports. The prepared catalysts were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray (EDX), X-ray diffraction (XRD), and inductively coupled plasma – optical emission spectrometer (ICP-OES). The catalysts were prepared in honeycomb and pellet form. The hydrogen yield with the pellet Cu10MOR10/γ-Al2O3 catalyst was 80% at 400 °C, higher than that obtained with the honeycomb catalyst under the same experimental conditions (50%). The ratio of H2O/DME, one of the most important parameters among the experimental conditions, afforded the best hydrogen yield at a value of 6, higher than the theoretical ratio of 3. Space velocity (SV) values in the range of 340–510 h−1 afforded hydrogen yields of ∼80%. The hydrogen yield was similar at temperatures in the range of 300–550 °C although, at 400–450 °C, higher DME conversions and lower CH4 production were observed. The addition of Ni to the catalyst resulted in the inhibition of the deposition of hydrocarbons, and the Ce additive was found to increase the DME conversion. Finally, it was found that the best catalyst for DME steam reforming was Cu10Ce4MOR10/γ-Al2O3. The optimum reaction conditions for H2 production were determined as SV = 340 h−1, H2O/DME ratio = 6, the pellet-type catalyst, and a catalytic reaction temperature range of 400–450 °C.

CFD analysis of Pd-Ag membrane reactor performance during ethylbenzene dehydrogenation process

In this study, the catalytic dehydrogenation of ethylbenzene (EB) to styrene production was investigated in a tubular Pd-Ag membrane reactor (MR) in presence of a commercial iron oxide catalyst. To this purpose, a 2D-axisymmetric, isothermal model based on computational fluid dynamic (CFD) method is presented to investigate the Pd-Ag MR performance during EB dehydrogenation process for styrene and hydrogen production. The proposed CFD model provides the local information of velocity, pressure and component concentration for the driving force analysis. After investigation of mesh independency of CFD model, the validation of model results was carried out by experimental data and a good agreement between model results and experimental data was achieved. It was found that the efficient removal of hydrogen in the Pd-Ag MR could significantly increase the EB conversion. Moreover, using CFD simulation runs, effects of operating parameters such as reaction temperature, pressure and gas hour space velocity (GHSV) values on the Pd-Ag MR performance with two various flow patterns was evaluated in terms of EB conversion and COx-free hydrogen recovery. It can be concluded that the EB conversion realized in Pd-Ag MR with countercurrent flow is higher than the ones achieved for Pd-Ag MR with cocurrent flow and also for traditional reactor (TR) during EB dehydrogenation reaction, in all the studied cases. In particular, under the optimal reaction conditions, 40% enhancement in EB conversion can be obtained in the Pd-Ag MR with countercurrent flow with respect to TR.

CO2 methanation on hard-templated NiO[sbnd]CeO2 mixed oxides

Mesostructured NiOCeO2 mixed oxides, with Ni loadings in the range 5–35 wt% (gNi/gCeO2), were synthesized by the hard template procedure using SBA-15 as the template. A hard-templated CeO2 was also prepared and used as the support for depositing Ni (5–35 wt%) by impregnation. Two NiOAl2O3 catalysts were synthesized for comparison, by impregnating nickel on a commercial γ-alumina. All the samples were characterized by different techniques as to their chemical composition, structure, morphology, texture, and redox features. The catalytic performance was investigated in the CO2 methanation reaction after mild reduction pretreatment (H2 at 400 °C for 1 h). Catalytic testing was performed under atmospheric pressure, 300 °C, 72,000 cm3 h−1 gcat−1, and stoichiometric H2/CO2 molar ratio. High catalytic activity, with CH4 selectivity values ≥ 93 mol%, was obtained with the NiOCeO2 mixed oxides (CO2 conversions up to 76 mol%). When γ-Al2O3 was used as the support, catalysts with low activity (CO2 conversion ≤ 20 mol%) were obtained. On selected samples, additional catalytic runs were also performed for reaction times up to 30 h or with a higher space velocity value. The catalytic results were explained by taking into account the role of the nickel-ceria interactions both during the reduction of NiO and in the reactants activation.

Performance Study on Microchannel Coated Catalytic Plate Reactor Using Electrophoresis Technique for Medium Temperature Shift (MTS) Reaction

The medium temperature shift (MTS) microreactor has been proposed in order to decrease the CO content of reformate for fuel cell applications. The Ni–K/CeO2 catalyst is synthesized and coated on stainless-steel plates by electrophoretic deposition (EPD) and then evaluated at 300–390 °C. The morphology of the catalyst layers are analyzed by X-ray diffractometry (XRD), scanning electron microscopy (SEM), and three-dimensional (3D) optical microscopy. The FT-IR analysis and conductivity measurements are used for slurry characteristics of different polyethylenimine (PEI) contents. The activity of the catalytic plates inside the microreactor is tested at different gas hourly space velocity (GHSV) values and H2O/CO molar ratio of 3. The CO conversion is raised by increasing the coating time from 1 min to 3 min, and it has an optimum at 140 V for applied voltage (between 30 V and 180 V). Also, it is found that the CO conversion is optimal at a PEI content of 0.3 wt %. Generally, the optimum conditions are achiev...