is an important intermediate in the chemical industry and is used, for example, in the production of various scent and flavor chemicals. Isoprenol is produced from aqueous formaldehyde and isobutene and is separated by distillation from mixtures containing formaldehyde, water, and isobutene in the process. As formaldehyde forms oligomers with both water and isoprenol, these mixtures are complex reacting systems, which are not easy to separate. Hence, for understanding and modeling the process, information on the vapor−liquid equilibria and the chemical equilibria in the system (formaldehyde + water + isoprenol) is essential. However, only very limited data on this system are available in the literature. Therefore, in the present work, vapor−liquid equilibria were measured in the following systems: system (water + isoprenol) at 20 and 90 kPa, system (formaldehyde + isoprenol) at 373 and 393 K, and system (formaldehyde + water + isoprenol) at 373 K. Furthermore, the chemical equilibria of the oligomerization reactions of formaldehyde and isoprenol were studied with 13 C-NMR spectroscopy at temperatures ranging from 283 to 353 K. The experimental data were used to extend a physico-chemical model of the system (formaldehyde + water) from the literature to include isoprenol.

Liquid lubricants play an important role in contact processes, e.g. they reduce friction and cool the contact zone. To gain better understanding of the influence of lubrication on the nanoscale, both dry and lubricated scratching processes in a model system are compared in the present work using molecular dynamics simulations. The entire range between total dewetting and total wetting is investigated by tuning the solid-fluid interaction energy. The investigated scratching process consists of three sequential movements: A cylindrical indenter penetrates an initially flat substrate, then scratches in lateral direction, and is finally retracted out of the contact with the substrate. The indenter is fully submersed in the fluid in the lubricated cases. The substrate, the indenter, and the fluid are described by suitably parametrized Lennard-Jones model potentials. The presence of the lubricant is found to have a significant influence on the friction and on the energy balance of the process. The thermodynamic properties of the lubricant are evaluated in detail. A correlation of the simulation results for the profiles of the temperature, density, and pressure of the fluid in the vicinity of the 1 chip is developed. The work done by the indenter is found to mainly dissipate and thereby heat up the substrate and eventually the fluid. Only a minor part of the work causes plastic deformation of the substrate.

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The elementary processes of friction in contact processes of two solid bodies occur on the nanoscale and are difficult to study experimentally. Therefore, molecular dynamics simulations are often used for their elucidation. In these studies, usually, only a single simulation is carried out for each scenario and the resulting observables are evaluated. In the present work, the reliability and reproducibility of measured observables from such nanoscopic contact process simulations is assessed by means of their statistical uncertainties. Therefore, the computer experiment is carried out not only once, but it is repeated eight times, with individual runs that only differ in the initial thermal motion. This set of replicas enables an assessment of observations for distinguishing reproducible physical phenomena from stochastic coincidence. In this way, a dry and a lubricated nanoscale scratching process were studied, in which a cylindrical indenter carried out two sequential movements: it first penetrates a substrate vertically and then scratches laterally, which causes elastic and plastic deformation of the substrate. In the lubricated case, the indenter was fully immersed in the fluid. Substrate, indenter, and fluid were described by suitably parametrised Lennard-Jones potentials. Various mechanical and thermodynamic process properties were monitored in all simulation runs. The results are compared and evaluated statistically.

An NMR spectroscopic method for measuring homogenous liquid phase reaction kinetics in systems that are used in reactive gas absorption processes is presented. In the kinetic experiment, carbon dioxide loaded and unloaded aqueous amine solutions are mixed such that no gas phase is involved. This