Multiscale microkinetic modelling of carbon monoxide and methane oxidation over Pt/γ-Al2O3 catalyst

Although compared to conventional diesel and gasoline engines gas engines running on methane-based fuels emit less pollutants, slip of unburnt methane is a hurdle to be overcome. In this regard, particularly noble metal-based catalysts allow for an efficient methane conversion even at low temperatures. Since these catalysts can undergo modifications under the highly dynamic operation [1] affecting activity and stability, the present work aims at creating a multiscale microkinetic model that has a strong link to the structure of the active sites, which change according to the chemical environment they are exposed. A detailed surface reaction mechanism for platinum-catalysed abatement of exhaust gases by Koop et al. [2] was used as a basis for the further development. The model is validated using light-off experiments with a monolithic Pt/Al2O3 catalyst in stoichiometric model gas mixtures. Simulations were carried out using the DETCHEMCHANNEL software [3] and show a remarkable difference, especially regarding the predicted ignition temperature. This different behaviour could be associated to the activation energies of the key reactive steps that need further investigation, i.e. dissociative adsorption of CH4. Along with theoretical considerations, spatially resolved information from experiments are used to improve the model. [1] P. Lott, O. Deutschmann, “Lean-Burn Natural Gas Engines: Challenges and Concepts for an Efficient Exhaust Gas Aftertreatment System” Emiss. Control Sci. Technol. 7, 1-6 (2021). [2] J. Koop, O. Deutschmann, “Detailed surface reaction mechanism for Pt-catalyzed abatement of automotive exhaust gases”, Appl. Cat. B 91, 1 (2009) [3] O. Deutschmann, S. Tischer, C. Correa, D. Chatterjee, S. Kleditzsch, V.M. Janardhanan, N. Mladenov, H. D. Minh, H. Karadeniz, M. Hettel, V. Menon, A. Banerjee, H. Goßler, E. Daymo, DETCHEM Software package, 2.8 ed., www.detchem.com, Karlsruhe 2020

A New Approach to Research Data Management with a Focus on Traceability: Adacta

Traceability between samples, devices and data is of great importance to the catalysis community. Adacta is a new research data management (RDM) system designed to create a traceable digital twin of a testing environment, not only storing data, but also creating a readily retrievable time-accurate record of the critical components used to measure catalyst performance. Future developments include extending Adacta to interact with electronic laboratory notebooks and to spawn simulations directly using data and measurements stored in the database

Catalytic Biomass Gasification in Supercritical Water and Product Gas Upgrading

The gasification of biomass with supercritical water, also known as SCWG, is a sustainable method of hydrogen production. The process produces a mixture of hydrogen, carbon oxides, and hydrocarbons. Upgrading this mixture through steam or dry reforming of hydrocarbons to create synthesis gas and then extra hydrogen is a viable way to increase hydrogen production from biomass. This literature review discusses combining these two processes and recent experimental work on catalytic SCWG of biomass and its model compounds and steam/dry reforming of produced hydrocarbons. It focuses on catalysts used in these processes and their key criteria, such as activity, selectivity towards hydrogen and methane, and ability to inhibit carbon formation and deposition. A new criterion is proposed to evaluate catalyst performance in biomass SCWG and the need for further upgrading via reforming, based on the ratio of hydrogen bound in hydrocarbons to total hydrogen produced during SCWG. The review concludes that most catalysts used in biomass SCWG trap a large proportion of hydrogen in hydrocarbons, necessitating further processing of the product stream

Oxidative Coupling of Methane over Pt/Al2_{2}O3_{3} at High Temperature: Multiscale Modeling of the Catalytic Monolith

At high temperatures, the oxidative coupling of methane (OCM) is an attractive approach for catalytic conversion of methane into value-added chemicals. Experiments with a Pt/Al$_{2}$O$_{3}$-coated catalytic honeycomb monolith were conducted with varying CH$_{4}$/O$_{2}$ ratios, N$_{2}$ dilution at atmospheric pressure, and very short contact times. The reactor was modeled by a multiscale approach using a parabolic two-dimensional flow field description in the monolithic channels coupled with a heat balance of the monolithic structure, and multistep surface reaction mechanisms as well as elementary-step, gas phase reaction mechanisms. The contribution of heterogeneous and homogeneous reactions, both of which are important for the optimization of C2 products, is investigated using a combination of experimental and computational methods. The oxidation of methane, which takes place over the platinum catalyst, causes the adiabatic temperature increase required for the generation of CH$_{3}$ radicals in the gas phase, which are essential for the formation of C2 species. Lower CH$_{4}$/O$_{2}$ ratios result in higher C2 selectivity. However, the presence of OH radicals at high temperatures facilitates subsequent conversion of C2H2 at a CH$_{4}$/O$_{2}$ ratio of 1.4. Thereby, C2 species selectivity of 7% was achieved at CH$_{4}$/O$_{2}$ ratio of 1.6, with 35% N$_{2}$ dilution

Automating the Optimization of Catalytic Reaction Mechanism Parameters Using Basin-Hopping: A Proof of Concept

Parameter estimation is a crucial step for successful microkinetic modeling in catalysis. However, the large number of parameters to be optimized in order to match the experimental data is a bottleneck. In this regard, the global optimization algorithm Basin-Hopping is utilized to automate the typically time-extensive and error-prone task of manual fitting of kinetic parameters for a heterogeneous catalytic system. The stochastic approach of the Basin-Hopping algorithm to explore the kinetic parameter solution space coupled with local search methods makes it possible to screen the high-dimensional space for an optimal set of kinetic parameters giving the least residual between the simulated and the experimentally measured catalytic performance data. Our approach also ensures that only thermodynamically consistent solution candidates are explored at each optimization step. We utilize two example case studies in heterogeneous catalysis, namely, methane oxidation over a palladium catalyst and carbon monoxide methanation over a nickel catalyst, with corresponding detailed kinetic models to illustrate the applicability of the algorithm to efficiently fine-tune detailed kinetic models

CaRMeN: An Improved Computer-Aided Method for Developing Catalytic Reaction Mechanisms

The software tool CaRMeN (Catalytic Reaction Mechanism Network) was exemplarily used to analyze several surface reaction mechanisms for the combustion of H2, CO, and CH4 over Rh. This tool provides a way to archive and combine experimental and modeling information as well as computer simulations from a wide variety of sources. The tool facilitates rapid analysis of experiments, chemical models, and computer codes for reactor simulations, helping to support the development of chemical kinetic models and the analysis of experimental data. In a comparative study, experimental data from different reactor configurations (channel, annular, and stagnation flow reactors) were modeled and numerically simulated using four different catalytic reaction mechanisms from the literature. It is shown that the software greatly enhanced productivit

Reduction of CO2_{2} Emission from Off-Gases of Steel Industry by Dry Reforming of Methane

In a novel process, CO$_{2}$ and CH$_{4}$ from the off‐gases of the coke oven and blast furnace are used in homogeneous reforming of those greenhouse gases to valuable syngas, a mixture of H$_{2}$ and CO. Synthetic mixtures of the off‐gases from those large apparatuses of steel industry are fed to a high‐temperature, high‐pressure flow reactor at varying temperature, pressure, residence time, and mixing ratio of coke oven gas (COG) to blast furnace gas (BFG). In this study, a maximal reduction of 78.5 % CO$_{2}$ and a CH$_{4}$ conversion of 95 % could be achieved at 1350 °C, 5.5 bar, and a COG/BFG ratio of 0.6. Significant carbonaceous deposits were formed but did not block the reactor tube in the operational time window allowing cyclic operation of the process. These measurements were based on prior thermodynamic analysis and kinetic predictions using an elementary‐step reaction mechanism

Brown marmorated stink bug (Halyomorpha halys) feeding damage determines early drop in olive crops

The brown marmorated stink bug (BMSB), Halyomorpha halys Stål, is an invasive species and a polyphagous pest. BMSB feeding activity was suspected to be responsible for olive damage. To evaluate the effect of feeding damage from adults and nymphs of BMSB, 30 rearing sleeves were positioned in an olive grove, at an early stage of drupe development. The individuals were kept in the rearing sleeves for 48 h, and the number of olives in each sleeve was checked weekly, visually assessing signs of damage and measuring their volume. After the 48-hr exposure, the number of early dropped olives was significantly higher for rearing sleeves containing BMSB adults and nymphs compared with control, with visible signs of damage. The volume of olives still attached was significantly lower for rearing sleeves with adults. These results provide key evidence on BMSB damage in developing olives. If the numbers of BMSB keep increasing in Mediterranean regions (where most of the olive production occurs), actions should be taken to prevent economic losse

Prove di efficacia di alcuni insetticidi su Scaphoideus titanus in sperimentazione di semicampo

La sperimentazione è stata condotta negli anni 2022 e 2023 in serra su piante di vite in vaso con diversi insetticidi comunemente utilizzati nella gestione integrata e biologica della vite. L’attività residuale vs Scaphoideus titanus è stata valutata tramite l’inserimento degli insetti in manicotti di rete applicati a piante di vite trattate. In ogni manicotto-replica sono stati inseriti 5 insetti (stadi giovanili o adulti) in tre momenti successivi: il giorno del trattamento a vegetazione asciutta, dopo 3 e dopo 7 giorni per valutare la persistenza d’azione. I controlli di mortalità sono stati eseguiti dopo 1, 3 e 7 giorni dall’inserimento. I risultati indicano che i prodotti utilizzabili nelle strategie di controllo integrato, come Closer, Epik SL, Kaimo Sorbie, Trebon e Sivanto hanno una buona efficacia e persistenza nei confronti di S. titanus. Biopiren Plus, ammesso nella gestione biologica, ha dimostrato una buona attività abbattente dopo il trattamento ma bassa persistenza. Asset Five, Surround WP e Naturalis, non hanno mostrato significativa attività insetticida o di disturboThe trials were conducted in 2022 and 2023 in a greenhouse on potted vine plants, with various insecticides commonly used in IPM and organic management. The evaluation vs Scaphoideus titanus took place by inserting the insects into mesh sleeves applied to treated vine plants. 5 insects (young or adult stages) were inserted into each sleeve at three successive times: on the day of treatment with dry vegetation, after 3 and after 7 days to evaluate the persistence of action. Mortality assessments were performed 1, 3 and 7 days after insertion. Results indicate that products used in integrated control, such as Closer, Epik SL, Kaimo Sorbie, Trebon and Sivanto have good efficacy and persistence against S. titanus. Biopiren Plus, admitted into organic management, demonstrated good knockdown activity after treatment but low persistence. Asset Five, Surround WP and Naturalis, did not show significant activit

Long-term outcomes of the global tuberculosis and COVID-19 co-infection cohort

Background: Longitudinal cohort data of patients with tuberculosis (TB) and coronavirus disease 2019 (COVID-19) are lacking. In our global study, we describe long-term outcomes of patients affected by TB and COVID-19. Methods: We collected data from 174 centres in 31 countries on all patients affected by COVID-19 and TB between 1 March 2020 and 30 September 2022. Patients were followed-up until cure, death or end of cohort time. All patients had TB and COVID-19; for analysis purposes, deaths were attributed to TB, COVID-19 or both. Survival analysis was performed using Cox proportional risk-regression models, and the log-rank test was used to compare survival and mortality attributed to TB, COVID-19 or both. Results: Overall, 788 patients with COVID-19 and TB (active or sequelae) were recruited from 31 countries, and 10.8% (n=85) died during the observation period. Survival was significantly lower among patients whose death was attributed to TB and COVID-19 versus those dying because of either TB or COVID-19 alone (p<0.001). Significant adjusted risk factors for TB mortality were higher age (hazard ratio (HR) 1.05, 95% CI 1.03-1.07), HIV infection (HR 2.29, 95% CI 1.02-5.16) and invasive ventilation (HR 4.28, 95% CI 2.34-7.83). For COVID-19 mortality, the adjusted risks were higher age (HR 1.03, 95% CI 1.02-1.04), male sex (HR 2.21, 95% CI 1.24-3.91), oxygen requirement (HR 7.93, 95% CI 3.44-18.26) and invasive ventilation (HR 2.19, 95% CI 1.36-3.53). Conclusions: In our global cohort, death was the outcome in >10% of patients with TB and COVID-19. A range of demographic and clinical predictors are associated with adverse outcomes