Continuous Production of Biorenewable, Polymer‐Grade Lactone Monomers through Sn‐β‐Catalyzed Baeyer–Villiger Oxidation with H₂O₂

Abstract

The Baeyer–Villiger oxidation is a key transformation for sustainable chemical synthesis, especially when H2O2 and solid materials are employed as oxidant and catalyst, respectively. 4‐substituted cycloketones, which are readily available from renewables, present excellent platforms for Baeyer–Villiger upgrading. Such substrates exhibit substantially higher levels of activity and produce lactones at higher levels of lactone selectivity at all values of substrate conversion, relative to non‐substituted cyclohexanone. For 4‐isopropyl cyclohexanone, which is readily available from β‐pinene, continuous upgrading was evaluated in a plug‐flow reactor. Excellent selectivity (85 % at 65 % conversion), stability, and productivity were observed over 56 h, with over 1000 turnovers (mol product per mol Sn) being achieved with no loss of activity. A maximum space–time yield that was almost twice that for non‐substituted cyclohexanone was also obtained for this substrate [1173 vs. 607 g(product) kg(catalyst)−1 cm−3 h−1]. The lactone produced is also shown to be of suitable quality for ring opening polymerization. In addition to demonstrating the viability of the Sn‐β/H2O2 system to produce renewable lactone monomers suitable for polymer applications, the substituted alkyl cyclohexanones studied also help to elucidate steric, electronic, and thermodynamic elements of this transformation in greater detail than previously achieved.

Porous metallosilicates for heterogeneous, liquid-phase catalysis: perspectives and pertaining challenges

“…These recent studies have highlighted several important factors that influence the stability of Sn-β during operation [ 118 – 121 ]. The most critical factor influencing stability of such materials is the choice of reaction solvent.…”

“…In contrast with conventional recyclability studies, our studies in this area employ a more rigorous evaluation of stability [117][118][119][120][121], by performing kinetic studies in continuous plug flow reactors. Such reactors (figure 22) provide several advantages over batch reactors, including (i) improved process and safety control, (ii) higher levels of mass and heat transfer, (iii) shorter reaction times, (iv) minimized reactor volumes, (iv) higher levels of scalability and (v) improved space-time yields.…”

Active Site Hydration Governs the Stability of Sn-Beta during Continuous Glucose Conversion

“…In this respect, the heterogeneous catalyst Sn-Beta (Sn- is of prime interest, having been shown to be highly active and selective for a range of processes such as i) fructose production via glucose-fructose isomerisation; [6][7][8][9][10] ii) the generation of renewable monomers such as alkyl lactates, 11,12 furanics 13,14 and methyl vinyl glycolate; [15][16] iii) the H2free reduction of carbonyl compounds via catalytic transfer hydrogenation; 17 and the Baeyer-Villiger oxidation of (renewable) ketones with H2O2 as oxidant. [18][19][20] Possessing an ability to operate continuously, without exhibiting excessive levels of deactivation, is one of the most important properties a promising heterogeneous catalyst must exhibit, in order to be suitable for industrialization. 21,22 As such, study and optimization of the stability of the catalyst under continuous conditions is paramount.…”

Kinetics study and process simulation of reactive distillation for the synthesis of ε‐caprolactone

“…ε‐CL is an important intermediate in organic synthesis, which is widely used in the field of organic chemistry. [ 1,2 ] It can be used to synthesize polycaprolactone and copolymerize with other esters. [ 3–5 ]…”