Ulrich Krtschil

Sustainability through green processing – novel process windows intensify micro and milli process technologies

Drawing on sustainability for chemical production processes demands the prior integration of sustainability aspects during process development, when further environmental impacts and production costs become predefined. Micro and milli process technologies provide novel ways for process improvement combined with ecological and economic advantages. This is demonstrated by current developments in this area. In this context, the idea of “Novel Process Windows” is discussed referring to examples of actual research. A short overview on how to assess sustainability using established tools of evaluation is given as well. This is rounded up with a recent case study of the Kolbe–Schmitt synthesis, performed to disclose the key drivers of further green process development.

Agile Green Process Design for the Intensified Kolbe–Schmitt Synthesis by Accompanying (Simplified) Life Cycle Assessment

In order to investigate the potential for process intensification, various reaction conditions were applied to the Kolbe-Schmitt synthesis starting from resorcinol. Different CO₂ precursors such as aqueous potassium hydrogencarbonate, hydrogencarbonate-based ionic liquids, DIMCARB, or sc-CO₂, the application of microwave irradiation for fast volumetric heating of the reaction mixture, and the effect of harsh reaction conditions were investigated. The experiments, carried out in conventional batch-wise as well as in continuously operated microstructured reactors, aimed at the development of an environmentally benign process for the preparation of 2,4-dihydroxybenzoic acid. To provide decision support toward a green process design, a research-accompanying simplified life cycle assessment (SLCA) was performed throughout the whole investigation. Following this approach, it was found that convective heating methods such as oil bath or electrical heating were more beneficial than the application of microwave irradiation. Furthermore, the consideration of workup procedures was crucial for a holistic view on the environmental burdens.

Bridging sustainability and intensified flow processing within process design for sustainable future factories

Abstract A holistic, life cycle based evaluation approach was followed within the European collaborative project CoPIRIDE, in order to provide multi-criteria decision support for environmentally benign and cost efficient process design strategies in front of a scale-up of newly developed concepts. The approach is presented by means of three case studies, dealing on the one hand with different catalyst plate reuse options, and on the other hand with two process concepts for intensified processing of natural feedstocks by means of epoxidation and transesterification reactions. Key criteria for future sustainable production processes could be identified prior to the transfer of the experimental flow chemistry results to pilot scale processing.

Microstructured reactors for development and production in pharmaceutical and fine chemistry.

The true potential of microprocess technology for process intensification is not yet fully clear and needs to be actively explored, although more and more industrial case stories provide information. This paper uses a shortcut cost analysis to show the major cost portions for processes conducted by microstructured reactors. This leads to predicting novel chemical protocol conditions, which are tailored for microprocess technology and which are expected to highly intensify chemical processes. Some generic rules to approach this are termed new process windows, because they constitute a new approach to enabling chemistry. Using such process intensification together with scaled-out microstructured reactors, which is demonstrated by the example of gas-liquid microprocessing, paves the road to viable industrial microflow processes. Several such commercially oriented case studies are given. Without the use of new process windows conditions, microprocess technology will probably stick to niche applications.

Novel manufacturing techniques for microstructured reactors in industrial dimensions

Abstract The results of the development of novel manufacturing techniques for microstructured reactors in the framework of the European project CoPIRIDE are reported. The work was aimed at promoting the application of microstructured chemical reactors in the chemical industry. This can be achieved by completely new ways of production of microstructured plates, as manufactured by the roll embossing technique. This opens the door to mass manufacturing capability, which is a common enabler for cost reduction and resource efficiency. Roll embossing is especially suited for automated mass production, particularly on the larger scale. A modular reactor concept and a novel microreactor design for such microstructured plates were developed. The stacked plate reactors are joined either by laser welding or vacuum brazing. In this way, microstructured reactors can be manufactured for a wide range of throughputs, pressures, temperatures, for single and multi-phase reactions as well as for non-catalytic, homogeneously or heterogeneously catalyzed reactions. Within the project, the suitability of the novel techniques for the manufacture of microreactors with a reaction volume of up to 2 l, which is already the lower production scale of the fine chemical industry, was demonstrated. Three different reactor types could be successfully applied in pilot plants.

Selective hydrogenation of alkynes over ppm-level Pd/boehmite/Al2O3 beads in a continuous-flow reactor

A ppm-level Pd/boemite catalyst has been prepared over 3 mm alumina beads and used for the selective hydrogenation of alkynes in a continuous-flow reactor with two modes: closed-loop and flow-through. The flow rates of the alkyne solution and hydrogen gas are critical factors in the control of conversion and selectivity. In closed-loop mode, over 90% selectivity to alkene was achieved at over 90% conversion of phenylacetylene (PA) and 2-butyne-1,4-diol (ByD) in closed-loop mode, whereas diphenylacetylene (DPA) gave only 83% selectivity to (Z)-stilbene. The maximum outputs obtained for the hydrogenations of 22 mM PA, DPA and ByD at 60 °C, with 10 vol% H2 gas bubble at atmospheric pressure in the concurrent flow, were 37.8, 37.5 and 47.0 mmol min−1 g−1 Pd, respectively. In flow-through mode, the optimal H2 flow percentage in the concurrent flow was 44–45 vol%, while the optimal H2/ByD molar ratio was 1.6–1.7 for both concurrent flow rates of 0.4 and 0.7 mL min−1. 90% selectivity to 2-butene-1,4-diol was achieved at over 90% ByD conversion. The maximum output was 25.2 mmol min−1 g−1 Pd. Palladium leaching from the catalyst was evaluated in n-hexane and ethanol under the flow conditions over 100 hours of hydrogenation.