Hourly Space Research Articles

Experimental study of the design and performance optimisation of a self-heating methanol on-board reforming reactor for hydrogen production

There is an increasing research on efficient and compact on-board reformer, based on which a serpentine plate type self-heating reformer integrating preheating, reforming and combustion has been designed and fabricated, which can be disassembled and assembled flexibly. In this paper, experiments on the self-heating reformer have been carried out to optimise the differential structure of different chambers. It can be found that: the combustion chamber needs to be partitioned and the resistance loss is small and stable for a long time when the number of partitions is 3. The combustion chamber with O2/CH3OH = 1.5 has the highest wall temperature of 240 °C. Hydrogen yield can be increased to more than two times after optimising the evaporation chamber. The catalyst in the reforming chamber must be uniformly distributed, and the methanol conversion rate is stable at 75 % with a mass of 110 g and Weight Hourly Space Velocity (WHSV) = 8 h−1. The optimum operating conditions of the reactor is WHSV = 8 h−1 with air flow rate of 25 L/min, at which the reactor starts up within 20 min, the hydrogen yield stabilises within 40 min, and the hydrogen yield is 9.8 L/min and remains stable for 120 min.

Predicting Methanol Space-Time Yield from CO? Hydrogenation Using Machine Learning: Statistical Evaluation of Penalized Regression Techniques

This study investigates the effectiveness of machine learning techniques, specifically penalized regression models Ridge Regression, Lasso Regression, and Elastic Net Regression in predicting methanol space-time yield (STY) from CO? hydrogenation data. Using a dataset derived from Cu-based catalyst research, the study implemented a comprehensive preprocessing approach, including data cleaning, imputation, outlier removal, and normalization. The models were rigorously evaluated through 10-fold cross-validation and tested on unseen data. Ridge Regression outperformed the other models, achieving the lowest Root Mean Squared Error (RMSE) of 0.7706, Mean Absolute Error (MAE) of 0.5627, and Mean Squared Error (MSE) of 0.5938. In comparison, Lasso and Elastic Net Regression models exhibited higher error metrics. Feature importance analysis revealed that Gas Hourly Space Velocity (GHSV) and Molar Masses of Support significantly influence catalytic activity. These findings suggest that Ridge Regression is a promising tool for accurately predicting methanol production, providing valuable insights for optimizing catalytic processes and advancing sustainable practices in chemical engineering.

Effect of crystalline TiO2 on V2O5WO3/TiO2 as tunable low-temperature shift De-NOx catalyst

Based on the crystalline size of anatase TiO2, a series of tunable low-temperature shift V2O5-WO3/TiO2 (VW/Ti) catalysts for NH3 selective catalytic reduction (NH3-SCR) of NOx were prepared by impregnation process. These catalysts contained a loading amount of 2 wt% WO3 and either 2 or 5 wt% V2O5. The tunable low-temperature shift De-NOx performance of the VW/Ti catalysts was significantly enhanced and dramatically decreased after heat treatment of TiO2 from 100 °C to 700 °C (Ti100 ∼ Ti700). Nearly 100 % De-NOx efficiency was achieved at a gas hourly space velocity (GHSV) of 60,000 h−1. A notable shift from higher to lower temperatures was observed from V2W2/Ti100 to V2W2/Ti600; however, the activity was lost for V2W2/Ti650 to V2W2/Ti700. When the V2O5 loading increased from 2 wt% to 5 wt%, the V5W2/Ti600 showed the highest De-NOx efficiency at 225 °C, demonstrating a remarkable synergistic effect compared to the V2W2/Ti100 catalyst, which achieved maximum efficiency at 375 °C. The De-NOx performance and low-temperature shift effect of these catalysts were elucidated by considering TiO2 crystalline size, the synergistic effect between V2O5 content and TiO2, and the V4+/V5+ oxidation state of V2O5 in the catalyst. Additionally, the high crystalline TiO2-based V2W2/Ti600 catalyst prepared in this study is expected to effectively decompose NOx at low temperatures, in contrast to the low crystalline TiO2-based V2W2/Ti100 catalyst.

Dynamic Reconstruction of Yttrium Oxide-Stabilized Cobalt-Loaded Carbon-Based Catalysts During Thermal Ammonia Decomposition.

Hydrogen production from the decomposition of ammonia is considered an effective approach for addressing challenges associated with hydrogen storage and transportation. However, their relatively high energy consumption and low efficiency hinder practical multi-scenario applications. In this study, Y2O3-stabilized catalysts with Co-loaded onto porous nitrogen-doped carbon (Y2O3-Co/NC) are synthesized by pyrolysis of Y(NO3)3-modified ZIF-67 under an inert atmosphere, followed by annealing in a reducing environment. The introduction of Y2O3 enhanced the recombination and desorption of N atoms and facilitated the gradual dehydrogenation of NHx on the catalyst surface, resulting in improved catalytic activity for the thermal decomposition of ammonia. Benefitting from the electron-donating properties of Y2O3 and N-doped carbon, the optimized catalyst achieved a remarkable NH3 conversion efficiency of 92.3% at a high gas hourly space velocity of 20000 cm3· ·h-1 with an encouraging H2 production rate of 20.6 mmol· ·min-1 at 550°C. Moreover, the synthesized catalyst undergoes a fast-dynamic reconstruction process, resulting in exceptionally stable catalytic activity during the thermal decomposition of ammonia, rendering it a promising candidate for carbon-free energy thermocatalytic conversion technology.

Superhydrophobic Surface Modification of a Co-Ru/SiO2 Catalyst for Enhanced Fischer-Tropsch Synthesis

Commercial silica support pellets were impregnated and calcined to contain cobalt oxide and ruthenium oxide for Fischer-Tropsch synthesis (FTS). The precatalyst pellets were split evenly into two groups, the control precatalyst (c-precat) and silylated precatalyst (s-precat), which were treated with 1H,1H, 2H, 2H-perfluorooctyltriethoxysilane (PFOS) in toluene. The samples of powderized s-precat were superhydrophobic, as determined by the water droplet contact angle (>150°) and sliding angle (<1°). Thermal analysis revealed the PFOS groups to be thermally stable up to 400 °C and temperature programmed reduction (TPR) studies showed that H2 reduction of the cobalt oxide to cobalt was enhanced at lower temperatures relative to the untreated c-precat. The two active catalysts were examined for their FTS performance in a tubular fixed-bed reactor after in situ reduction at 400 °C for 16 h in flowing H2 to give the active catalysts c-cat and s-cat. The FTS runs were performed under identical conditions (255 °C, 2.1 MPa, H2/CO = 2.0, gas hourly space velocity (GHSV) 510 h–1) for 5 days. Each catalyst was examined in three runs (n = 3) and the mean values with error data are reported. S-cat showed a higher selectivity for C5+ products (64 vs. 54%) and lower selectivity for CH4 (11 vs. 17%), CO2 (2 % vs. 4 %), and olefins (8% vs. 15%) than c-cat. S-cat also showed higher CO conversion, at 37% compared to 26%, leading to a 64% increase in the C5+ productivity measured as g C5+ products per g catalyst per hour. An analysis of the temperature differential between the catalyst bed and external furnace temperature showed that s-cat was substantially more active (DTinitial = 29 °C) and stable over the 5-day run (DTfinal = 22 °C), whereas the attenuated activity of c-cat (DTinitial = 16 °C) decayed steadily over 3 days until it was barely active (DTfinal < 5 °C). A post-run surface analysis of s-cat revealed no change in the water contact angle or sliding angle, indicating that the FTS operation did not degrade the PFOS surface treatment.

Roles of Catalysts and Feedstock in Optimizing the Performance of Heavy Fraction Conversion Processes: Fluid Catalytic Cracking and Ebullated Bed Vacuum Residue Hydrocracking

Petroleum refining has been, is still, and is expected to remain in the next decades the main source of energy required to drive transport for mankind. The demand for automotive and aviation fuels has urged refiners to search for ways to extract more light oil products per barrel of crude oil. The heavy oil conversion processes of ebullated bed vacuum residue hydrocracking (EBVRHC) and fluid catalytic cracking (FCC) can assist refiners in their aim to produce more transportation fuels and feeds for petrochemistry from a ton of petroleum. However, a good understanding of the roles of feed quality and catalyst characteristics is needed to optimize the performance of both heavy oil conversion processes. Three knowledge discovery database techniques—intercriteria and regression analyses, and artificial neural networks—were used to evaluate the performance of commercial FCC and EBVRHC in processing 19 different heavy oils. Seven diverse FCC catalysts were assessed using a cascade and parallel fresh catalyst addition system in an EBVRHC unit. It was found that the vacuum residue conversion in the EBVRHC depended on feed reactivity, which, calculated on the basis of pilot plant tests, varied by 16.4%; the content of vacuum residue (VR) in the mixed EBVRHC unit feed (each 10% fluctuation in VR content leads to an alteration in VR conversion of 1.6%); the reaction temperature (a 1 °C deviation in reaction temperature is associated with a 0.8% shift in VR conversion); and the liquid hourly space velocity (0.01 h-1 change of LHSV leads to 0.85% conversion alteration). The vacuum gas oil conversion in the FCC unit was determined to correlate with feed crackability, which, calculated on the basis of pilot plant tests, varied by 8.2%, and the catalyst ΔCoke (each 0.03% ΔCoke increase reduces FCC conversion by 1%), which was unveiled to depend on FCC feed density and equilibrium FCC micro-activity. The developed correlations can be used to optimize the performance of FCC and EBVRHC units by selecting the appropriate feed slate and catalyst.

Ortho to para hydrogen conversion over bimetallic iron and cobalt catalysts

The catalytic conversion of ortho-hydrogen (o-H2) to para-hydrogen (p-H2) serves as a crucial step in the storage of liquid hydrogen. A variety of iron-cobalt bimetallic catalysts (FCO) were synthesized using a precipitation method, incorporating diverse levels of Co doping into Fe-based catalysts. The effects of Co doping on the crystal structure, porosity, and magnetism of FCO catalysts were studied by XRD, N2 physical adsorption, FTIR, XPS, and VSM analyses. The efficiency of ortho-para hydrogen conversion over FCO at 77 K was evaluated. It was found that the catalyst’s lag coefficient was significantly improved by Co doping, leading to an increase of magnetic moment. The catalyst of FCO-5 with a Fe/(Fe + Co) molar ratio of 0.5 exhibited the highest activity in ortho-para hydrogen conversion. The corresponding conversion rate, outlet p-H2 content, and the reaction rate constant were 99.2%, 49.7% and 291.7 mol·L−1·s−1, respectively, under a gas hourly space velocity of 5400 h−1.

Tandem Pt/TiO2 and Fe3C catalysts for direct transformation of CO2 to light hydrocarbons under high space velocity

CO2 hydrogenation to hydrocarbons under high space velocity is crucial for industrial applications, but traditional Fe-based catalysts often suffer from the low activity and poor stability. Herein, we report a new tandem catalyst system combining Pt/TiO2 catalysts with Fe3C catalysts for the direct conversion of CO2 into C2-C4 hydrocarbons under high space velocity. The Pt/TiO2 component promotes *CO intermediate production with an enhanced Reverse Water-Gas Shift (RWGS) reaction efficiency, providing a highly reactive species for the Fe3C catalyst to achieve Fischer-Tropsch synthesis (FTS). By maximizing the contact interface between the Pt/TiO2 and Fe-based components through a granule mixing configuration, we achieve significant enhancements in both CO2 conversion rate (24.0 %) and C2-C4 hydrocarbons selectivity (51.1 %) under the gaseous hourly space velocity (GHSV) of 100000 mL gcat−1h−1. Besides, excellent stability is achieved by the tandem catalysts with continuous catalysis for up to 80 h without significant decrease in activity. Through modulation of the reduction states of iron oxide, we effectively tune the composition of Fe-based catalyst, thereby tailoring the product distribution. Through this work, we not only offer a promising avenue for reducing CO2 for efficient CO2 utilization but also highlight the importance of catalyst design in advancing sustainable chemical synthesis.

Innovative pressurized diesel reforming for sustainable hydrogen production using advanced PtRu-CGO catalyst

This study suggests a novel approach for producing hydrogen through the pressurized reforming of commercial diesel, leveraging the PtRu-CGO catalyst. Foundational experiments were performed with PtRu-CGO powder catalysts at conditions up to 9 bar and 800 °C, achieving complete fuel conversion and stable performance with an average hydrogen concentration of approximately 58.7 mol%. Additionally, the structured catalysts developed herein also could maintain high efficiency and durability under a gas hourly space velocity (GHSV) of 10,000 h−1. Notably, at 6 bar, the system exhibited an extraordinary efficiency of around 75 % over 300 h of continuous operation. These results underscore the practicality of pressurized diesel reforming for hydrogen production with the PtRu-CGO catalyst, highlighting its potential in the development and optimization of hydrogen energy systems and aiding the shift towards a hydrogen-based economy.

Innovative In/H-SSZ-39 Catalysts: An Exploration in NOx Reduction via CH4-SCR

Nitrogen oxides (NOx), pivotal atmospheric pollutants, significantly threaten the environment and human health. The CH4-SCR process, leveraging the abundance and accessibility have methane, emerges as a promising avenue for NOx abatement. Previous studies have demonstrated that zeolite support with twelve-membered ring (12-MR) and five-membered ring (5-MR) structures are susceptible to framework collapse in the presence of H2O, leading to catalyst deactivation. Consequently, there is a necessity to explore novel zeolites with enhanced hydrothermal stability for application in CH4-SCR processes. This research introduced for the first time an investigation into a novel In/H-SSZ-39 catalyst, which was synthesized via ion exchange and meticulously optimized for preparation conditions, including calcination temperature and In ions concentration, and reaction conditions, including CH4/NO ratio, O2 concentration, H2O content, and Gas Hourly Space Velocity (GHSV). Furthermore, long-term operation tests and stability tests were conducted on the In/H-SSZ-39 catalyst. In addition, a series of characterizations were conducted to delve into the reasons behind how preparation conditions influence catalytic activity, as well as to investigate the changes in physicochemical properties during the reaction process.

Engineering In-Co3O4/H-SSZ-39(OA) Catalyst for CH4-SCR of NOx: Mild Oxalic Acid (OA) Leaching and Co3O4 Modification.

Zeolite-based catalysts efficiently catalyze the selective catalytic reduction of NOx with methane (CH4-SCR) for the environmentally friendly removal of nitrogen oxides, but suffer severe deactivation in high-temperature SO2- and H2O-containing flue gas. In this work, SSZ-39 zeolite (AEI topology) with high hydrothermal stability is reported for preparing CH4-SCR catalysts. Mild acid leaching with oxalic acid (OA) not only modulates the Si/Al ratio of commercial SSZ-39 to a suitable value, but also removes some extra-framework Al atoms, introducing a small number of mesopores into the zeolite that alleviate diffusion limitation. Additional Co3O4 modification during indium exchange further enhances the catalytic activity of the resulting In-Co3O4/H-SSZ-39(OA). The optimized sample exhibits remarkable performance in CH4-SCR under a gas hourly space velocity (GHSV) of 24,000 h-1 and in the presence of 5 vol% H2O. Even under harsh SO2- and H2O-containing high-temperature conditions, it shows satisfactory stability. Catalysts containing Co3O4 components demonstrate much higher CH4 conversion. The strong mutual interaction between Co3O4 and Brønsted acid sites, confirmed by the temperature-programmed desorption of NO (NO-TPD), enables more stable NxOy species to be retained in In-Co3O4/H-SSZ-39(OA) to supply further reactions at high temperatures.

Mechanistic insights on the preparation of 5-methyl-2-hexanone by hydrogenation of 5-methyl-3-hexen-2-one using Pd/Al2O3 catalysts

5-methyl-2-hexanone is used as a versatile polymerization solvent for industrial preparation processes of bulk and fine chemicals. An efficient catalyst, Pd/γ-Al2O3, is reported for the preparation of 5-methyl-2-hexanone by selective hydrogenation of 5-methyl-3-hexen-2-one. The catalyst exhibits remarkable activity and selectivity even at atmospheric pressure and low temperature (1 atm, 80 °C). The influence weight of reaction conditions on the reaction process was obtained through the Artificial Neural Network model, which were reaction pressure, reaction temperature and liquid hourly space velocity in order. The reaction kinetics and mechanism of 5-methyl-2-hexanone preparation by hydrogenation over Pd/γ-Al2O3 catalyst were investigated. The hydrogenation reaction pathway of 5-methyl-3-hexen-2-one was obtained by using Density functional theory calculations, and the mechanism of selective hydrogenation of CC double bonds and CO double bonds was revealed. A kinetic model based on the LHHW model assumption was also proposed and compared with experimental results demonstrating good predictability.

Nickel nanocatalyst on lanthanum aluminate: Optimizing preparation and evaluating performance in glycerol dry reforming for syngas production

In this study, mesoporous nanocrystalline Ni/La-Al catalysts with varying nickel (Ni) loadings (5, 10, 15, and 20 wt.%) were synthesized using a solid-state method for the glycerol dry reforming (GDR) reaction. The effects of different Ni loadings and the addition of steam on the structural and catalytic performance of the catalysts were investigated. Characterization techniques, including Brunauer-Emmett-Teller (BET) surface area analysis, temperature-programmed reduction (TPR), temperature-programmed oxidation (TPO), and X-ray diffraction (XRD) were employed to analyze the catalysts' properties. Results showed that increasing Ni loading to 10 wt.% improves the catalytic properties. However, by increasing the Ni loading, a decrease in catalytic properties due to increasing particle size, creating NiO bulk phase and surface pore blockage is obvious. A series of experiments were performed to investigate the effect of steam usage on catalytic properties. TPO analysis revealed that steam addition reduces the carbon deposition and shifts oxidation peaks to lower temperatures; consequently, the activity and stability of the catalyst will be enhanced. Although the 5 - 7.5 vol.% of steam in the feed composition significantly stabilizes the catalyst, it is possible to produce H2-rich synthesis gas, and conversely, increasing the temperature reduces the H2/CO ratio. Various examinations were conducted under different conditions, including varying gas hourly space velocity (GHSV), carbon-to-glycerol ratio (CGR), and temperature, to obtain more comprehensive data on the catalysts.

Design of dual-channel Swiss-roll reactor for high-performance hydrogen production from ethanol steam reforming through waste heat valorization

Steam reforming is one of the most economical and efficient methods for hydrogen production. However, one of its glaring issues is the heat supply, which is used to maintain the reactions. Among reactors for hydrogen production, Swiss-roll reactors have exhibited exceptional performance in sustaining the heat required for reactions. Furthermore, heat supply via waste heat recovery has been an attractive industrial prospect for improving the sustainability of hydrogen production. This study proposes a design of a novel Swiss-roll reactor with dual channels to harvest waste heat from the flue gas to sustain the steam reforming reactions. Ethanol is used as a feedstock due to its environmentally benign properties. Numerical simulations are conducted to establish the reactor's catalytic reactions and heat transfer phenomena under the variations of gas hourly space velocity (GHSV), steam-to-ethanol (S/E) ratio, and inlet flue gas temperature. Heat recovery improves at higher GHSVs and lower S/E ratios at the cost of less efficient hydrogen production, while high inlet flue gas temperature improves heat recovery and hydrogen production. The novel reactor design can fulfill complete ethanol conversion maintained by heat recovered from waste flue gas, achieving 86.6 % hydrogen production efficiency and 72.7 % heat recovery under optimal operating conditions.

Room temperature thermocatalytic removal of formaldehyde in air using a copper manganite spinel-supported palladium catalyst with ultralow noble metal content

The room temperature (RT)-catalytic oxidation of gaseous formaldehyde (FA) in the dark is regarded as one of the most viable technical options for its removal from indoor air. Herein, the copper manganite spinel (CuMn2O4) supported palladium (Pd) catalysts are firstly synthesized for the thermocatalytic oxidation of FA in air. In particular, 0.05% Pd-CuMn2O4-R (‘R’ denotes high-temperature reduction pre-treatment using hydrogen) achieves 100% conversion (XFA) of 50 ppm FA at RT (gas hourly space velocity of 4342 h−1). The performance of 0.05% Pd-CuMn2O4-R against FA, if assessed in terms of the reaction kinetic rate (r at 10% XFA), is estimated as 3.01E−02 mmol g−1h−1. The lowering of XFA with the increases in FA concentration, flow rate, and relative humidity indicates the detrimental effects of such variables on the catalytic activity. FA oxidation kinetics predominantly follows the Mars van Krevelen mechanism. In-situ diffuse reflectance infrared Fourier transform spectroscopy shows that FA oxidation proceeds through multiple reaction intermediates (e.g., dioxymethylene and formate). The density functional theory simulations indicate that the catalytic oxidation efficacy of FA over CuMn2O4 increases by the synergy between Pd loading and surface reduction. The present study represents the first report on the synthesis of CuMn2O4-supported Pd catalysts and their application for the RT oxidative removal of FA in air under dark conditions. The findings of the present work offer valuable insights into the construction of efficient and cost-effective catalysts with ultra-low noble metal content for the RT oxidative removal of VOCs in indoor environment.

Asymmetric Ru-In atomic pairs promote highly active and stable acetylene hydrochlorination

Ru single-atom catalysts have great potential to replace toxic mercuric chloride in acetylene hydrochlorination. However, long-term catalytic stability remains a grand challenge due to the aggregation of Ru atoms caused by over-chlorination. Herein, we synthesize an asymmetric Ru-In atomic pair with vinyl chloride monomer yield (>99.5%) and stability (>600 h) at a gas hourly space velocity of 180 h−1, far surpassing those of the Ru single-atom counterparts. A combination of experimental and theoretical techniques reveals that there is a strong d-p orbital interaction between Ru and In atoms, which not only enables the selective adsorption of acetylene and hydrogen chloride at different atomic sites but also optimizes the electron configuration of Ru. As a result, the intrinsic energy barrier for vinyl chloride generation is lowered, and the thermodynamics of the chlorination process at the Ru site is switched from exothermal to endothermal due to the change of orbital couplings. This work provides a strategy to prevent the deactivation and depletion of active Ru centers during acetylene hydrochlorination.

Efficient solar-driven ammonia decomposition using economical K-Co3Mo3N catalyst at low temperatures

Solar-driven ammonia decomposition suffers from either using expensive ruthenium catalysts or requiring a high operating temperature (>550 °C). Here, we report that this limitation can be overcome by using a K-modified Co3Mo3N catalyst constructed by a single-step nitridation of CoMoO4 and plentiful K2CO3. The optimal 0.864 %K-Co3Mo3N catalyst presents a conversion of 86.5 % and a hydrogen production rate of 347.5 mmol gcat−1⋅h−1 under conditions of 500 °C and a gas hourly space velocity of 6000 mL gcat−1⋅h−1, which is comparable to most of the reported Ru-based catalysts. Based on the results from density functional theory calculations, the step of desorbed N2 is with the highest energy barrier. The overall energy barrier computed is 0.54 eV, which is consistent with the experimentally measured activation energy. Further, a remarkable solar-to-fuel efficiency of 14.4 % is achieved. This work highlights the enhancement effect of K on Co3Mo3N for efficient solar-driven NH3 decomposition at low temperatures.

High-quality utilization of raw coke oven gas for hydrogen production based on CO2 adsorption-enhanced reforming

To realize the high-quality utilization of raw coke oven gas (RCOG), the adsorption-enhanced steam reforming process was purposed for hydrogen production, coupled with the sensible heat recovery and the conversion of the high-energy components (such as tar). For this process, the hydrogen production performance and energy utilization efficiency were focused via reforming experiment and process simulation. Using the prepared bifunctional catalyst (Ni/Ce–CaO–Ca12Al14O33), the enhanced reforming experiment was conducted based on orthogonal design and Taguchi method. Compared to S/C ratio (the mole ratio of steam to carbon in the simulated RCOG) and WHSV (weight hourly space velocity), reforming temperature shows a higher sensitivity to hydrogen production. At 800 °C, the produced H2 amount can achieve 3.86 times of that in the initial RCOG and the H2 concentration in the produced gas can reach 88.38 %, when the S/C ratio was 15 and the WHSV was 0.0847 h−1. Based on the established process model, the energy consumption of RCOG enhanced reforming system was discussed. Compared to traditional hydrogen production technologies, this novel process exhibits a lower energy consumption, just about 62.5 MJ/kg H2, and also shows a higher energy conversion efficiency.

Transforming CO2 into Synthetic Fuels: Modeling, Simulation, and Optimization Analysis of Methanol Production from Industrial Wastes

Carbon capture and utilization (CCU) has emerged in recent years as a promising decarbonization solution for hard-to-abate industries. Compared to carbon capture and storage (CCS), CCU aims not for the storage of carbon dioxide (CO2) but for its use in the production of synthetic fuels, such as synthetic methanol (MeOH). Synthetic MeOH is produced through CO2 hydrogenation, utilizing green hydrogen (H2). Efficient use of CO2 and H2 feedstocks is essential to maximize the carbon reduction potential and energy efficiency of the process. This study performed an optimization analysis on a small-scale, containerized, and portable CO2 hydrogenation unit with a 5 kg MeOH/h production capacity goal, focusing on carbon conversion efficiency (CCE), MeOH yield, H2 consumption, and MeOH purity. The analysis was conducted using Aspen Plus V12. A single-pass model was used first to evaluate an initial reactor design. The reactor was then re-designed according to the results of the gas hourly space velocity (GHSV). The model was then expanded to include a recycling loop and the final reactor design was validated, aiming to maximize overall efficiency. The effects of the operational parameters including the reactor inlet temperature, reactor pressure, thermal fluid temperature, and condensation temperature were examined. The model was then further expanded to include the MeOH distillation process, and the effect of the distillation temperature was examined. The final product of the analysis was a fully-defined and optimized unit, achieving an 87.97% CCE and an 84.99% MeOH yield, consuming 1.11 kg H2/h for the production of 5.01 kg MeOH/h of 99.86 wt% purity. This study can provide valuable information and guidelines for designing small-scale, containerized, and portable CO2 hydrogenation units, which can serve as alternative solutions to address issues of H2 production and transportation related to large-scale installations.

Modulating adsorption-oxidation dual sites and confinement structure of interlayered MnO2/defective rGO nanoreactor for efficient and stable catalytic ozonation of CH3SH

The design of catalyst structure and adsorption-oxidation sites is of great significance for catalytic ozonation to eliminate sulfur-containing volatile organic compounds (S-VOCs). Herein, a well-defined 2D/2D interlayered DrGO/MnO2-Vo consisting of oxygen vacancy-rich (Vo) MnO2 and defective reduced graphene oxide (DrGO) was successfully synthesized by face-to-face electrostatic self-assembly method. DrGO/MnO2-Vo with delimited void space could be employed as confined nanoreactor to boost reactive oxygen species (ROS) yields and improve mass transfer, thus achieving excellent methyl mercaptan (CH3SH) removal efficiency (82.4 %). The experimental results revealed that the DrGO/MnO2-Vo catalyst could still remove ∼74 % of CH3SH after running for 60 h at 25 ℃ with an initial concentration of 80 ppm CH3SH, 2 mg/L ozone, and a gas hourly space velocity (GHSV) of 60,000 mL/(h⋅g). The essence of the outstanding stability and durability of DrGO/MnO2-Vo lied in its role as an active dual-site catalyst, in which CH3SH was preferentially enriched on DrGO nanosheets and subsequently oxidized by ROS generated by ozone decomposition on the oxygen vacancies of MnO2 nanosheets. Additionally, the cycling redox of Mn2+/Mn3+→Mn4+→Mn2+/Mn3+ could regenerate oxygen vacancies of MnO2. This research offered novel perspectives on tackling the control issues related to S-VOCs.