Continuous Flow Chemo-Enzymatic Baeyer–Villiger Oxidation with Superactive and Extra-Stable Enzyme/Carbon Nanotube Catalyst: An Efficient Upgrade from Batch to Flow

Abstract

Continuous flow chemo-enzymatic Baeyer−Villiger oxidation in the presence of exceptionally active Candida antarctica lipase B immobilized via simple physical adsorption on multiwalled carbon nanotubes has been investigated. The nanobiocatalyst was used to generate peracid in situ from ethyl acetate and 30 wt % aq. hydrogen peroxide as the primary oxidant. Application of the highly stable and active nanobiocatalyst in the Baeyer−Villiger oxidation of 2-methylcyclohexanone to 6-methyl-ε-caprolactone after 8 h at 40 °C led to a high product yield (87%) and selectivity (>99%). Environmentally friendly ethyl acetate was applied as both solvent and the peracid precursor. To determine the most favorable reaction conditions, a series of experiments using various parameters was performed. The main contribution of this work is that it describes the first application of the nanobiocatalyst in a chemo-enzymatic Baeyer−Villiger oxidation in a flow system. Since the process was performed in a flow reactor, many improvements were achieved. First of all, substantially shorter reaction times as well as a significant increase in the product yield were obtained as compared to the batch process. Since peracids are unstable, a large increase in the safety of the process was demonstrated under mild conditions in this work. In summary, this work shows a particularly efficient upgrade in the studied processes by transfer from a batch to a flow system.

Characterization and evaluation of immobilized enzymes for applications in flow reactors

“…The immobilization into the inner surface of wall-coated reactors usually aims at forming uniform monolayers by directed immobilization [12,16,17] or by the controlled formation of thin films [38,39]. However, when the inner reactor area is insufficient, surface coating with nanomaterials (i.e nanoparticles, nanosprings, nanotubes…) [40][41][42][43] and polymers [44] increases the enzyme loadings by 10-15 fold.…”

Outperformance in Acrylation: Supported D-Glucose-Based Ionic Liquid Phase on MWCNTs for Immobilized Lipase B from Candida antarctica as Catalytic System

“…Nowadays, the progress achievable by applying hydrophobic MWCNTs for the immobilization of CALB is indisputable [ 20 ]. For instance, our previous studies have proved the high stability of MWCNTs-CALB hybrids (pristine and polytetrafluoroethylene-modified MWCNTs) with a consecutive high activity and stability in organic synthesis in both batch and flow systems [ 25 , 26 , 27 , 28 , 29 ].…”

PTFE-Carbon Nanotubes and Lipase B from Candida antarctica—Long-Lasting Marriage for Ultra-Fast and Fully Selective Synthesis of Levulinate Esters

“…The scrupulous analysis of the up-to-date literature data—revealing medium yields of esters accompanied by rather moderate stability of the biocatalytic systems and extended esterification times—encouraged us to demonstrate the potential of the active solid carrier for CALB. In our previous studies, a highly active nanobiocatalyst from CALB non-covalently immobilized on multi-walled carbon nanotubes (MWCNTs) for the Baeyer–Villiger synthesis of lactones was presented [ 9 , 38 , 39 , 40 ]. The direct physical adsorption method was based on hydrophobic, electrostatic and hydrogen bonding interactions between MWCNTs and the enzyme.…”

“…The direct physical adsorption method was based on hydrophobic, electrostatic and hydrogen bonding interactions between MWCNTs and the enzyme. A particularly efficient upgrade of the process was achieved by transfer from a batch to a flow system [ 39 ]. Again, high activity and the enhanced stability of the same biocatalyst in the esterification of dicarboxylic acids for the production of diester plasticizers was further verified [ 40 ].…”