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The work of the ALTEREGO project started in three research work packages dealing with the development of the three technologies and led to two further ones focused on the application and demonstration for the pharmaceutical synthesis, and green fuels and bulk chemicals respectively.Project Image

Conceptual approach of the ALTEREGO project

In the first work package, tailored equipment was developed to efficiently perform the ultrasound-assisted processes in the application areas of advanced pharmaceutical synthesis and green fuels and bulk chemicals synthesis. Three types of multiphase processes were chosen as case studies: reactive solvent extraction, reactive synthesis and cooling crystallization, vapour-liquid systems. The work focused on enabling local positioning of the ultrasound energy at the interfaces (liquid/liquid, solid/liquid, gas/liquid), develop mechanistic understanding and models for the ultrasound-assisted operation of the above-cited processes, and - more recently - design an efficient ultrasound-assisted continuous reactor and demonstrate the developed technology for the specified processes. In the case of reactive solvent extraction, novel reactor types for efficient ultrasound transfer were explored. The new designs allowed reaching a threefold increase in yield for a specific solvent extraction reaction by the application of ultrasound. In the case of cooling and reactive crystallization, it has been found out that ultrasound clearly reduces nucleation induction time and metastable zone width as well as crystal size, but has limited effect on crystal shape. Breakage of crystals was observed only at low frequencies. Further, ultrasound effects on separation of binary systems involving methanol are shown to be insignificant. This is corroborated by the very limited mass transfer enhancement by ultrasound-assisted atomization. While ultrasound application can significantly improve reaction kinetics for enzymatically catalyzed reactions, it was shown that the combination of the chemical system and the form of enzyme immobilization play a vital role in the feasibility and effect of ultrasound application for enzymatic reactive distillation.

In the second work package, work was done i) to establish suitable equipment for the measurements of VLE, SLE and reaction under microwave and to determine experimentally the effect for a set of systems under investigation, ii) to identify suitable reaction-catalyst systems for the reactive distillation and the API synthesis reaction; as well as iii) to identify the mechanisms behind the MW effect on different phenomena which allows the modelling and subsequently the design of complex equipment. Within this work, a suitable setup to measure kinetics of reactions heated by conventional or MW has been established and validated. Comparisons of two different MW setup’s using two different MW equipment showing similar results reveals the validity of the obtained results for the reaction. For the investigated chemical system, the synthesis of DMC/EMC, the enhancement of kinetics of different homogenous catalysts by MW has been seen only at larger temperatures (T > 85 °C). No suitable heterogeneous catalysts have been found. The influence of MW on VLE has not been verified for the system under investigation and simulation studies revealed that no significant improvement for MW enhanced reactive distillation would be expected. The influence of MW on evaporative crystallization has been shown for the crystal shape and crystal size distribution, which are two important product parameters. In particular, it has been found that MW can induce faster solvent evaporation with concomitant enhancement of supersaturation that favors crystal nucleation instead of growth. As a result, smaller crystals with narrower size distribution are obtained compared to conventional evaporative crystallization. WP2 has focussed primarily on detailed kinetic investigations in order to compare conventional heating and microwave heating for three reaction types namely, esterification, and transesterification (relevant to reactive distillation) and a demethylation reaction relevant as an API study for the pharmaceutical industry. For each system, reactions were carried out in identical glassware under carefully controlled conditions. In all three reaction types, microwave effects have been observed, which are dependent on operating temperature, with positive microwave effects being observed at higher temperatures, but not at lower temperatures. As temperature increases, kinetic analysis indicates that the conventional systems behave consistently, while microwave reactions generally show enhanced reaction rates (of the magnitude 1.5-5). Microwave assisted crystallisation was also pursuit, and this demonstrated a positive impact in terms of reduction of process time (ca. 50% reduction) as well as improved size distribution of crystals. This is considered to be due to the faster response of microwave heating, compared to conventional heating, and the impact this has on unwanted nucleation.

In the third work package, the general objective was to develop prototype solutions for methanol synthesis from renewable feeds (CO2 and biomass) based on a novel microwave plasma technology. In this context, gas-phase CO2 hydrogenation to CO (CO2 + H2 à CO + H2O, i.e., reverse water gas shift (RWGS)) has been studied. Two relevant setups have been developed. In the case of RWGS, a bench-scale microwave plasma reactor based on a solid-state microwave generator MiniFlow 200SS and an electromagnetic surface wave launcher Surfatron, provided by SAIREM, has been designed and constructed. In the case of biomass gasification, a scalable containerized microwave plasma gasifier (10-20 kWth) based on a 6 kW magnetron has been built through funding from the Bill & Melinda Gates Foundation and it is further developed within ALTEREGO. Regarding RWGS, the results show that plasma treatment enables very high (superequilibrium) conversions, compared to the conventional thermal catalytic process, without the need of catalyst and without byproduct formation, which is highly desirable in terms of simplified downstream gas cleaning and minimization of recycle and purge streams. On the gasification side, biomass conversions as high as 85% were obtained at cold gas efficiencies (CGE) of ~40%. The product gas composition was found to be close to the equilibrium one at the reactor outlet temperature; this provides certainty that if the reactor becomes properly insulated to minimize heat losses, CGEs>80% will be possible to attain.

In the demonstration work package four, the overall objective was the implementation/validation of the ultrasound and microwave energy based technologies in a pharmaceutical environment. In addition to this, the technologies were evaluated economically and a roadmap for implementation was set up.

The demonstration work package five included the implementation/validation of all energy-based technologies in question in an academic lab/pilot environment. A technical-economic evaluation of the processes and comparison with the conventional processes currently applied in industry and the development of a roadmap for industrial implementation of the proposed technologies was done. Based on the results and the decision of the consortium, the prior case study of the reactive distillation on process for the transesterification of DMC with ethanol to yield DEC and EMC, was adapted towards an US-assisted enzymatically catalysed RD process to produce butyl butyrate by transesterification of butanol. 

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The ALTEREGO project, its results and achievements set the basis for future research and innovation.  Have a look at a follow-up project under Horizon 2020 (SPIRE-05-2015): ADREM – Adaptable Reactors for Resource- and Energy-Efficient Methane Valorisation –

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ALTEREGO Project Poster
ALTEREGO Project Final Report