Process Intensification of Immobilized Enzyme Reactors

The advantages of enzyme catalysis are high specificity and (enantio)selectivity, resulting in reactions with little or no by-products. The applications of enzymes in aqueous medium are well established and have been extended to organic synthesis more recently. The two limiting factors for large scale application of enzymes are continuous processing and process scale-up. Process intensification has the potential to overcome these challenges posed by conventional processing methods by incorporating a novel reactor design or by using alternate processing methods. Process intensified reactors like membrane reactors, microreactors, monolithic reactors and rotating disc reactors for enzyme catalyzed reactions will be discussed in this chapter. These reactors have shown an improved performance compared to the enzymatic reactors currently in use, and future opportunities include application for enzymatic catalysis on an industrial scale and advances in reactor design and process control.<br/

Investigating the effect of increasing cloth size and cloth number in a spinning mesh disc reactor (SMDR):A study on the reactor performance

The spinning mesh disc reactor (SMDR) is a rotating catalytic reactor with a potential to facilitate process intensification. In this study, the scale-up of a newly designed SMDR has been demonstrated by increasing (i) cloth size and (ii) cloth number for tributyrin hydrolysis and nitroaldol condensation reaction. The effect of spinning speed, cloth size and cloth number was investigated using design of experiments and the results show an increase in the cloth size or cloth number leads to a higher reaction rate. This is due to (i) an increased catalyst loading with increase in surface area and volume of the cloth stack and (ii) reduced film thickness with increasing shear forces and longer residence times improving the overall mass transfer. Addition of multiple cloths of increasing cloth sizes further improved the reaction rates at higher substrate concentration. A maximum reaction rate of 6.9 mM min−1 and 0.043 mmol min-1 was obtained for three 50 cm cloths for tributyrin hydrolysis and nitroaldol condensation reaction respectively. These results highlight the potential routes for the SMDR scale-up without a loss in the reaction efficiency for a range of catalytic reactions, thus allowing for a tuneable operation of the SMDR for industrial applications

Investigating the effect of increasing cloth size and cloth number in a spinning mesh disc reactor (SMDR):A study on the reactor performance

The spinning mesh disc reactor (SMDR) is a rotating catalytic reactor with a potential to facilitate process intensification. In this study, the scale-up of a newly designed SMDR has been demonstrated by increasing (i) cloth size and (ii) cloth number for tributyrin hydrolysis and nitroaldol condensation reaction. The effect of spinning speed, cloth size and cloth number was investigated using design of experiments and the results show an increase in the cloth size or cloth number leads to a higher reaction rate. This is due to (i) an increased catalyst loading with increase in surface area and volume of the cloth stack and (ii) reduced film thickness with increasing shear forces and longer residence times improving the overall mass transfer. Addition of multiple cloths of increasing cloth sizes further improved the reaction rates at higher substrate concentration. A maximum reaction rate of 6.9 mM min−1 and 0.043 mmol min-1 was obtained for three 50 cm cloths for tributyrin hydrolysis and nitroaldol condensation reaction respectively. These results highlight the potential routes for the SMDR scale-up without a loss in the reaction efficiency for a range of catalytic reactions, thus allowing for a tuneable operation of the SMDR for industrial applications

Kinetic resolution of 1-phenylethanol in the spinning mesh disc reactor: Investigating the reactor performance using immobilised lipase catalyst

The spinning mesh disc reactor (SMDR) is an innovative catalytic rotating reactor to aid process intensification. In this study, the application of the SMDR has been demonstrated for the enzymatic kinetic resolution of racemic 1-phenyethanol using amano lipase immobilised on wool as a catalyst. Physical characterisation of wool was carried out to confirm the presence of lipase. The reaction was tested for a range of solvents and temperatures for both free and immobilized lipase and the optimised reaction conditions were employed in the SMDR for different flowrates and spinning speeds. The SMDR showed better reaction efficiency compared to the batch reactor: the feed throughput was scaled-up from 10 ml to 250 ml and the productivity increased from 7.05 g l-1 h-1 in batch to 10.92 g l-1 h-1 in the SMDR. An increase in catalyst loading was achieved by adding more lipase cloths and the reaction rate increased from 0.16 mmol min-1 (one cloth) to 0.28 mmol min-1 (three cloths). These results show the first demonstration of novel reactor design for scale-up of enzymatic kinetic resolution using an inexpensive lipase. The SMDR thus shows potential for scale-up and continuous processing for versatile applications in the fine chemicals and pharmaceutical industry.<br/

Process Intensification of Catalysed Henry Reaction using Copper-Wool Catalyst in a Spinning Mesh Disc Reactor

The spinning mesh disc reactor (SMDR) is a novel process intensification technology which uses centrifugal force to drive reaction fluid over a mesh supported catalyst on a rotating disc. The potential of the SMDR for organic synthesis has been demonstrated for the first time for Henry reaction using copper immobilised on woollen cloth mesh. A new protocol for copper immobilisation on wool has been developed producing a superior catalyst to the homogeneous copper triflate system: copper heterogenised on wool afforded a higher batch conversion (85%) (cf. 57% for the homogeneous case) in the same timeframe. In the SMDR, the reaction was more efficient than either homogeneous or heterogeneous batch reaction: with further optimisation the conversion increased from 77% to 93% as the spinning speed of the disc increased from 250 to 450 RPM at a flowrate of 3 ml s-1. There was only a 3% reduction in conversion on re-use of copper wool over 3 cycles under similar experimental conditions indicating that this catalyst is robust. Pure wool was also found to have some catalytic activity for the Henry reaction, giving a maximum conversion of 85% at 450 RPM in the SMDR. However, it deactivated significantly with reuse and therefore cannot be considered a stable, robust catalyst. Overall, the results show that the copper immobilised wool in the SMDR can be used to improve the conversions for the Henry reaction and that there is therefore promise for the SMDR to be extended to other traditional solvent based reactions

Process Intensification of Immobilized Enzyme Reactors

The advantages of enzyme catalysis are high specificity and (enantio)selectivity, resulting in reactions with little or no by-products. The applications of enzymes in aqueous medium are well established and have been extended to organic synthesis more recently. The two limiting factors for large scale application of enzymes are continuous processing and process scale-up. Process intensification has the potential to overcome these challenges posed by conventional processing methods by incorporating a novel reactor design or by using alternate processing methods. Process intensified reactors like membrane reactors, microreactors, monolithic reactors and rotating disc reactors for enzyme catalyzed reactions will be discussed in this chapter. These reactors have shown an improved performance compared to the enzymatic reactors currently in use, and future opportunities include application for enzymatic catalysis on an industrial scale and advances in reactor design and process control.<br/

Simultaneous geraniol and citronellol transesterification using Pseudomonas fluorescens lipase for the production of fragrance, flavour and pharmaceutical esters: a kinetic study

Terpene esters are one of the most important and versatile compounds for the flavour, fragrance and pharmaceutical industries and are currently produced commercially using petrochemical-based starting materials and chemical catalysis routes. There is a current need in the industry to develop alternatives to the current production process due to an increased demand for natural products, environmental safety and sustainability. This paper for the first time demonstrates a kinetic study for the simultaneous transesterification of geraniol and citronellol using Pseudomonas Fluorescens lipase to produce geranyl and citronellyl esters. The study initially screened the influence of the molar ratio of alcohol to vinyl acetate for individual alcohol transesterification, revealing that increasing the molar ratio led to higher ester yields. The optimised conditions were determined as follows: a molar ratio of 1:4, temperature of 40 °C, agitation speed of 250 RPM, and an enzyme loading of 10 wt.% of alcohol. After 24 hours, the conversion rates reached 95% and 87% for geraniol and citronellol, respectively. These conditions were then applied to the simultaneous transesterification of citronellol and geraniol, with the best experimental condition being a molar ratio of 1:8. The kinetic study demonstrated that the simultaneous transesterification followed a ternary complex mechanism with vinyl acetate inhibition, which was consistent with the experimental data. A preliminary experiment involving the transesterification of rose oil resulted in a conversion rate of 32% for citronellol and 50% for geraniol after 30 hours of reaction time. Overall, this study showcases the potential of enzyme catalysts to selectively produce terpene esters from heterogeneous terpene alcohol mixtures and can be extended to terpene alcohols present in natural essential oils