MUST: MicroflUidics for Structure-reactivity relationships aided by Thermodynamics & kinetics

• Applicant: Privatdozent Dr.-Ing. Christoph Held
• Subject Area: Chemical and Thermal Process Engineering
• Term: since 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 446436621

The relationships between the structure of chemicals (reactants or products) and their reactivity (kinetics and thermodynamics) is a research area that crosslinks thermodynamics, kinetics, organic chemistry and chemical engineering. This project will investigate this research area by German and French specialists. The concept of Linear Free Energy Relationships (LFER), including Taft equation, is a powerful structure-reactivity tool that accounts for steric, polar and resonance effects on a series of chemical reactions. Taft equation shows that there is a relationship between the structure of reactants (i.e., the substituent near to the reaction center) and their reactivities within a reaction series. It is state-of-the art to apply this to chemical reactions (e.g. esterification), and it is claimed that the developed parameters are valid independent of the reaction conditions. However, mainly esterification and hydrolysis reactions were used in one kind of solvent, which in principle limits the general validity of the relationships. Thus, generalizing LFER concepts to vast number of solvents or solvent mixtures and even to multiphase reaction systems requires intrinsic kinetic profiles in the absence of concentration and temperature gradients, expressed in terms of thermodynamic activities. This will be developed in this project.The redeveloped Taft-based method will be mainly applied to three chemical reaction systems that involve lignocellulosic-derived platform molecules: 1) glucose solvolysis to levulinate ester using different alcohol solvents, 2) esterification-hydrolysis of levulinic acid-levulinate ester and 3) hydrogenation of levulinic acid or levulinate ester to gamma-valerolactone by H2 and solid catalyst. For these systems, we will vary the reactants, i.e., different alcohols for 1) and 2), and different levulinate esters for 3). System 2) will prove the validity of the LFER concept to enzyme catalysis. The goal is to use the redeveloped method to study and predict the -R substituent effect in the reactant and the solvent effect on kinetic profiles.Reaching the goal requires different research expertise. The use of microfluidic technologies will allow performing kinetic experiments avoiding transport limitations. Activities of the reactants and products will be predicted based on the experimental kinetic profiles and the equation of state ‘ePC-SAFT’. This will ultimately allow predicting reaction properties (standard enthalpies, standard Gibbs energies) as well as intrinsic activity-based reaction kinetic constants. Furthermore, ePC SAFT will be used to predict the required phase behavior of the reaction systems (e.g. H2 solubility in reaction medium); all predictions (phase behavior and reaction characteristics) will be validated by experiments.The association of both methods –LFER & ePC-SAFT– will mean a significant new understanding and a new dimension in designing chemical syntheses.

• DFG Programme: Research Grants
• International Connection: France
• Partner Organisation: Agence Nationale de la Recherche / The French National Research Agency
• Cooperation Partners: Professor Julien Legros; Professor Dr. Sébastien Leveneur