Chemie Ingenieur Technik最新文献

Copyright: © Max-Planck-Institut Magdeburg und Otto-von-Guericke-Universität Magdeburg

A comprehensive analysis of the flow in Schwarz-D triply periodic minimal surfaces (TPMS) structures based on CFD simulations is presented. The pressure drops and friction factor characteristics of the structure are investigated by employing both full-scale and representative elementary volume (REV)-scale CFD setups. The results are validated against experimental data from the literature. An analytical model is developed using hydraulic diameter, porosity, and permeability from the CFD simulation results. The findings contribute valuable insights into the optimization and application of Schwarz-D TPMS structures in engineering systems.

Coming to terms with climate change by understanding climate processes and their policy implications is essential not only for climate scientists and policymakers, but also for the general public, for industrial practitioners, and for engineers, including process system engineers. We have developed a simplified linear climate model (SLCM) to enable non-specialists to explore the essential physical and chemical processes caused by greenhouse gas emissions. Trading-off simplicity and accuracy, achieved by calibrating model parameters using established simple climate models, the SLCM allows (i) determining the climate impact of given past and future emissions, (ii) determining the amounts of CO₂ removal needed to compensate for any unavoidable emissions of CH₄ and N₂O from agriculture, and (iii) back-calculating emission pathways to meet specified global warming targets.

A stagnation-flow reactor was employed to investigate the decomposition of ammonia over a Ni/Al₂O₃ catalyst across a range of system pressures and ammonia mole fractions. The results indicate that the system pressure has a negligible impact on the light-off behavior and the concentration profiles of NH₃. A comparison of 1D modelling with 3D computational fluid dynamics (CFD) computations justifies the use of the simpler flow model. Good agreement between experiments and the 1D simulation is achieved for two different kinetic models from literature in the mainly diffusion-controlled regime. For lower temperatures, at which the process is kinetically controlled, the two mechanisms exhibit significant differences. The stagnation-flow reactor concept is shown to be a promising tool for understanding, developing, and validating the reaction kinetics of heterogeneous catalytic processes.

Power-to-methane (PtM) offers an efficient opportunity for surplus renewable energy storage, but heat management is a major challenge for conducting the highly exothermic methanation reaction. To address this challenge, this study presents the first successful demonstration of core-shell catalyst pellets in a pilot-scale reactor for CO₂ methanation. Experiments in a wall-cooled fixed-bed reactor are conducted with diluted and undiluted reactant feed under systematic variation of cooling temperature and inlet gas flow rate. The results show that core-shell catalyst pellets significantly reduce the hot-spot temperature while maintaining comparable reactant conversions to uncoated catalyst pellets at the same conditions. Additionally, core-shell catalyst pellets allow for undiluted reactant feed at comparably low hot-spot temperatures (approx. 600 °C).

The formation of hydrido rhodium(I) complexes of the type [HRh(CO)₃L] and [HRh(CO)₂L₂] from [Rh(acac)(CO)₂]/L (L: bulky monophosphite ligand) requires a ligand-to-rhodium ratio [L]/[Rh] > 10 to prevent the possible partial generation of [Rh₆(CO)₁₆] under typical hydroformylation conditions. Significant fractions of formed [Rh₆(CO)₁₆] at lower ratios of [L]/[Rh] can be reactivated towards the hydrido complexes after the addition of the monophosphite ligand in the presence of synthesis gas. It was also found that [Rh₆(CO)₁₆] can be transformed by treatment with an excess of monophosphite ligand under inert gas to form a mononuclear complex of the type [L`Rh(CO)L] with an ortho-metallated ligand.