Nicolas von Solms

Application of the perturbed chain SAFT equation of state to complex polymer systems using simplified mixing rules

Abstract A simplified perturbed-chain statistical associating fluid theory (PC-SAFT) equation of state is applied to polymer systems that include a variety of non-associating (esters, cyclic hydrocarbons), polar (ketones) as well as associating (amines, alcohols) solvents. The solvent pure-component parameters that are not available in the literature are estimated by correlating vapor-pressure and liquid-density data. The performance of the simplified PC-SAFT is compared to the original PC-SAFT equation of state for polymer systems of varying complexity. It is shown that the applied simplification is not at the expense of the accuracy of equation of state, while the computational time and complexity are significantly reduced, especially for associating systems. With no binary interaction parameter, simplified PC-SAFT is successfully able to predict vapor–liquid equilibria of polymers with non-associating solvents. In the case of associating solvents, a small binary interaction parameter k ij is usually needed for the satisfactory correlation of the experimental data.

Erratum to: Transport properties of natural gas through polyethylene nanocomposites at high temperature and pressure

High density polyethylene (HDPE)/clay nanocomposites containing nanoclay concentrations of 1, 2.5, and 5 wt% were prepared by a melt blending process. The effects of various types of nanoclays and their concentrations on permeability, solubility, and diffusivity of natural gas in the nanocomposites were investigated. The results were compared with HDPE typically used in the production of liners for the petroleum industry. Four different nanoclays—Cloisite 10A, 15A, 30B and Nanomer 1.44P—were studied in the presence of CH4 and a CO2/CH4 mixture in the temperature range 30–70 °C and pressure range 50–100 bar. The permeability and diffusivity of the gases were considerably reduced by the incorporation of nanoclay into the polymer matrix. Addition of 5 wt% loading of Nanomer 1.44P reduced the permeability by 46% and the diffusion coefficient by 43%. Increasing the pressure from 50 to 100 bar at constant temperature had little influence on the permeability, whereas increasing the temperature from 30 to 70 °C significantly increased the permeability of the gas. Additionally, the effect of crystallinity on permeability, solubility, and diffusivity was investigated. Thus, the permeability of the CO2/CH4 mixture in Nanomer 1.44P nanocomposite was reduced by 47% and diffusion coefficient by 35% at 5 wt% loading, 50 °C, and 100 bar, compared with pure HDPE.

Antifreeze activity enhancement by site directed mutagenesis on an antifreeze protein from the beetle Rhagium mordax

The ice binding motifs of insect antifreeze proteins (AFPs) mainly consist of repetitive TxT motifs aligned on a flat face of the protein. However, these motifs often contain non‐threonines that disrupt the TxT pattern. We substituted two such disruptive amino acids located in the ice binding face of an AFP from Rhagium mordax with threonine. Furthermore, a mutant with an extra ice facing TxT motif was constructed. These mutants showed enhanced antifreeze activity compared to the wild type at low concentrations. However, extrapolating the data indicates that the wild type will become the most active at concentrations above 270 μmol.

Systematic identification of crystallization kinetics within a generic modelling framework

Abstract A systematic development of constitutive models within a generic modelling framework has been developed for use in design, analysis and simulation of crystallization operations. The framework contains a tool for model identification connected with a generic crystallizer modelling tool-box, a tool for data handling and translation as well as model application features. Through this framework it is possible, for a wide range of crystallization processes, to generate the necessary problem-system specific models; to identify the parameters for constitutive models; and to handle or translate raw crystallization data. Application of the systematic framework is highlighted through a sucrose crystallization case study, for which the parameters for nucleation and crystal growth are first estimated from the available measured data and are then applied to study the crystallization operation.

Compositional Simulation of In-Situ Combustion EOR: A Study of Process Characteristics

DTU Orbit (15/04/2019) Compositional Simulation of In-Situ Combustion EOR: A Study of Process Characteristics In order to facilitate the study of the influence of reservoir process characteristics in In-Situ combustion modeling and advance the work of Kristensen et al. in this domain; a fully compositional In-situ combustion (ISC) model of Virtual Kinetic Cell (VKC; single-cell model) for laboratory scale combustion simulation is used. Preceding research work primarily focused on a kinetic model that was based on six components and incorporated four chemical reactions. However, modeling of a thermal process as complex as In-situ combustion requires in-depth understanding of detailed reaction kinetics and multidisciplinary process data. This paper extends the understanding of previous research done in this domain by performing the process simulations to study further the impact of oxidation reactions and combustion reactions of crude oils along with their saturate, aromatic, resin, and asphaltene (SARA) fractions. This incorporates fourteen pseudo components and fourteen reactions (distributed amongst thermal cracking, low temperature oxidation and high temperature oxidation). The paper presents a set of derivative plots indicating that reservoir process characterization in terms of thermal behavior of oil can be well construed in terms of thermo-oxidative sensitivity of SARA fractions. It can be interpreted from the results that operating parameters like air injection rate, oxygen feed concentration and activation energy have significant influence on oil recovery; an increase in air injection rate can lead to cooling of the combustion front and thus decrease oil recovery, while increase in oxygen feed assists combustion and contributes towards improved oil recovery. The critical properties of the pseudo components are not determined experimentally, thus extending significance to fluid characterization. The composition plays a key role e.g. due to asphaltenes being most resistant toward oxidation and saturates being the easiest oxidizable ones.

Inhibition of Gas Hydrate Formation by Low-dosage, Environmentally Benign Inhibitors

Publisher Summary Gas hydrates are crystalline compounds formed when water and suitably sized gas molecules are combined at high pressure and low temperature. They consist of polyhedral cavities formed from networks of hydrogen-bonded water molecules in which small gas molecules can enter. Depending on the type of gas molecules present gas hydrates form different structures, known as structure I (sI), structure II (sII) and in special cases structure H (sH). The gases that form hydrates are normally small molecules, many of which are encountered in natural gas. Traditionally the formation of hydrates has been prevented by addition of thermodynamic hydrate inhibitors such as methanol and glycol. However the amounts needed to avoid hydrate formation may reach 50 wt% in the water rich phase. Since water production from fields can be quite severe, especially in cases where water injection has been used to enhance the oil recovery, large amounts of hydrate inhibitor are required.

Efficient Ionic Liquid–based platform for Multi-Enzymatic Conversion of Carbon Dioxide to Methanol

Low yields commonly obtained during enzymatic conversion of CO2 to methanol are attributed to low CO2 solubility in water. In this study, four selected ionic liquids with high CO2 solubility were separately added to the multi-enzyme reaction mixture and the yields were compared to the pure aqueous system (control). In an aqueous 20% [CH][Glu] system, yield increased ca. 3.5-fold compared to the control (ca. 5-fold if NADH regeneration was incorporated). Molecular dynamics simulation revealed that CO2 remains for longer in a productive conformation in the enzyme in the presence of [CH][Glu], which explains the marked increase of yield that was also confirmed by isothermal titration calorimetry – lower energy (ΔG) binding of CO2 to FDH. The results suggest that the accessibility of CO2 to the enzyme active site depends on the absence/presence and nature of the ionic liquid, and that the enzyme conformation determines CO2 retention and hence final conversion.

PROPANE GAS HYDRATE NUCLEATION KINETICS: EXPERIMENTAL INVESTIGATION AND CORRELATION

In this work the nucleation kinetics of propane gas hydrate has been investigated experimentally using a stirred batch reactor. The experiments have been performed isothermally recording the pressure as a function of time. Experiments were conducted at different stirring rates, but in the same supersaturation region. The experiments showed that the gas dissolution rate rather than the induction time of propane hydrate is influenced by a change in the stirring rate. This was especially valid at high stirring rates when the water surface was severely disturbed. Addition of polyvinylpyrrolidone to the aqueous phase was found to reduce the gas dissolution rate slightly, however the induction times were prolonged quite substantially. The induction time data were correlated using a newly developed induction time model based on crystallization theory also capable of taking into account the presence of additives. In most cases reasonable agreement between the data and the model could be obtained. The results revealed that especially the effective surface energy between propane hydrate and water is likely to change when the stirring rate varies from very high to low. The prolongation of induction times according to the model is likely to be due to a change in the nuclei-substrate contact angle.