Band 2, Heft 5 - Special issue: CoPIRIDE / Issue editor: Patrick Löb

For the first time the anionic polymerization of 1,3-butadiene (Bd) is successfully transferred from semi-batch into a continuous microfluidic setup with comparable product properties. The molecular weight distribution described by the polydispersity index (PDI) is commonly used as a key criterion for product quality. The steady state and the local resolution of a continuous setup provide the opportunity to investigate the progress of the PDI during anionic polymerization. In this work, the influence of kinetics (statistics) and fluid dynamics (FD) on the PDI of the product is investigated. Therefore a dedicated setup was designed and erected to keep Bd in the liquid phase and provide a pulsation free constant liquid flow. With optimized parameter settings, a separation of initiation and propagation is obtained and the intrinsic kinetics of propagation are determined. To explain the experimental results, an ideal plug flow and an ideal laminar flow model are applied and compared to computational fluid dynamics (CFD) simulations. Finally, it is concluded which FD and statistical contributions lead to the very low PDI of 1.04 found in the experiments.

The profitability of biodiesel is nowadays limited by the price of raw materials, which require high purity standards to be employed in conventional production processes. To overcome this problem, the transesterification of triglycerides in alcohol supercritical conditions could be conveniently used: the non-catalytic nature of this process allows the use of recycled raw materials, which are cheaper. To this end, a pilot scale plant for the continuous production of biodiesel in supercritical conditions was designed, manufactured and operated. In this research paper, rapeseed oil and bioethanol were used as raw materials, and the investigated temperatures were between 200 and 340°C, the pressure between 150 and 240 bar, and the alcohol-to-oil ratio ranged between 9 and 100. The best fatty acid ethyl ester (FAEE) yields were obtained at 340°C, 240 bar and a molar ratio of 42, which is line with easier-to-control lab-scale tests in batch conditions found in the literature. This encourages widening of the operating conditions to further improve the maximum achievable yields for the rapeseed oil-ethanol system.

The synthesis of biodiesel has received attention as an alternative source of energy to decrease our dependence on petroleum-based fuels. The catalyzed processes present a series of limitations and drawbacks, among them the high energy required for complex purification and undesirable side reactions. Supercritical fluid (SCF) technology is being proved an efficient approach compared to traditional methods for preparing biodiesel. This review illustrates the advances, advantages, and drawbacks involved in the use of all current biodiesel production technologies.

This work studied the epoxidation of soybean oil with aqueous hydrogen peroxide and formic acid, in the presence of acidic ionic exchange resins as catalysts. Amberlyst 16 was found to actively and highly selectively promote this reaction, and it also had good resistance to thermal and physical degradation. These properties also allow this resin to be used in continuous processes. A detailed study was carried out to determine the best operating conditions for the epoxidation of soybean oil in semibatch reactors, and preliminary epoxidation runs were performed in a continuous packed bed tubular reactor.

Quasi-instantaneous exothermic reactions lead to the formation of unwanted hot spots even when carried out in conventional microstructured reactors (MSR) with tube diameter of 100–1000 μm. For this reason, alternative MSR designs are warranted to enable process intensification of fast reactions with characteristic reaction times <1 s. The continuous multi-injection MSR, where one of the reactants is successively added to the main flow of reactants along reactor length, may improve temperature control. The latter was studied first theoretically using numerical simulations and then experimentally with the cyclisation of pseudoionone to α- and β-ionones as a model reaction. The multi-injection MSR made of low temperature co-fired ceramics (LTCC) led to a yield of α-ionone and β-ionone >0.98 reaching a 500-fold process intensification as compared to the conventional semi-batch process. The temperature profiles monitored by quantitative infrared thermal imaging confirmed an 8-fold reduced temperature rise compared to adiabatic temperature rise, which was achieved by injecting the reactants at three different injection points.

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.

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.

The Fischer-Tropsch synthesis (FTS) for the conversion of carbon monoxide and hydrogen to higher hydrocarbons was investigated over a supported Cu/Co catalyst promoted by dielectric-barrier discharges (DBDs) at relatively low temperatures and ambient pressure. The effect of plasma power, operation pressure, and H 2 /CO molar ratio on the activity and selectivity of the catalyst in a DBD reactor were studied. The fresh and used catalyst samples were characterized by scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray, and X-ray diffraction. We also used DBDs in catalyst preparation as a technique to enhance metal distribution on the catalyst support. The present study reveals that plasma can promote the FTS over a Cu/Co-based catalyst at low temperatures and ambient pressure. The formation of methane was strongly suppressed in plasma. In contrast to conventional FTS, CO conversion was higher at low operating pressure than that at higher pressure in the DBD-promoted FTS, which indicates the presence of a new reaction path for FTS.

Atom-efficient multicomponent reactions (MCR) and step-efficient one-pot synthesis are developed for the synthesis of biaryl-substituted furocoumarins, furoquinolones, and furopyrimidines. Furocoumarin and furoquinolone derivatives are synthesized by a three-component reaction, followed by the Suzuki coupling reaction. Furopyrimidine derivatives are prepared by the Suzuki coupling and then the three-component reaction. The bromobenzaldehydes are the key bifunctional molecules for the multicomponent and Suzuki coupling reactions.

A highly viscous oil was used to create oil-in-water emulsions. Rheological properties of the dispersed phase, the emulsifier, and their combination were measured to study the flow behavior. The temperature dependence of the viscosity and the influence of different mixing orders on emulsion quality were examined. Furthermore, the stability of the produced emulsions was studied. Finally, the initial emulsification process was analyzed and optimizations were suggested.