As an important bio-based chemical, methyl levulinate (ML) can be produced via enzymatic esterification of levulinic acid with methanol. A kinetic model is developed in this work based on the law of mass action and reaction reversibility, to investigate the effect of enzyme loading, alcohol/acid ratio and temperature on ML yield. Data analysis shows that newly developed binary regression is apparently more persuasive than the commonly used unitary regression. Kinetic study reveals: (1) rate constants of esterification/hydrolysis increase with increasing enzyme loading, while their ratio (equilibrium constant) remains invariant. (2) Methanol has no toxicity towards lipase, and hence, neither the rate constants of esterification/hydrolysis nor the equilibrium constant are affected by alcohol/acid ratio. (3) Both rate constants of esterification/hydrolysis and the equilibrium constant increase with temperature elevation, and their relationships agree with Arrhenius equation and Van't Hoff equation, respectively. (4) The esterification is endothermic and spontaneous. In total, the application of binary regression analysis for the developed model to study the enzymatic esterification kinetics is quite successful.
Jie Li,Shuaiheng Zhao,Zhen Li,Dan Liu,Yingnan Chi,Changwen Hu
Catalytic transformation of levulinic acid (LA) to γ-valerolactone (γ-GVL) is an important route for biomass upgradation. Because both Bro̷nsted and Lewis acidic sites are required in the cascade reaction, herein we fabricate a series of H3PW12O40@Zr-based metal–organic framework (HPW@MOF-808) by a facile impregnation method. The synthesized HPW@MOF-808 is active for the conversion of LA to γ-GVL using isopropanol as a hydrogen donor. Interestingly, with the increase in the HPW loading amount, the yield of γ-GVL increases first and then decreases, and 14%-HPW@MOF-808 gave the highest γ-GVL yield (86%). The excellent catalytic performance was ascribed to the synergistic effect between the accessible Lewis acidic Zr4+ sites in MOF-808 and Bro̷nsted acidic HPW sites. Based on the experimental results, a plausible reaction mechanism was proposed: the Zr4+ sites catalyze the transfer hydrogenation of carbonyl groups and the HPW clusters promote the esterification of LA with isopropanol and lactonization to afford γ-GVL. Moreover, HPW@MOF-808 is resistant to leaching and can be reused for five cycles without significant loss of its catalytic activity.
Highly efficient transformation of renewable biomass and its derivatives into high-value-added chemicals and biofuels over non-noble-metal catalysts is attractive but challenging. Herein, we developed non-noble CoNi alloy nanoparticles confined in N-doped porous carbon (CoNi@NC) via simple pyrolysis of the metal–organic framework (MOF) precursor at 900 °C under an inert atmosphere. The as-obtained CoNi@NC catalyst exhibited higher performance than monometallic Co@NC and Ni@NC catalysts in the reductive amination of levulinic acid (LA) with benzylamine to N-benzyl-5-methyl-2-pyrrolidinone (BMP) under mild conditions of 130 °C and 3 MPa H2 for 6 h, achieving a full conversion of LA and a ≥ 99% yield of BMP. Detailed characterizations substantiated that multifunctional support and the significant synergistic effect between Co and Ni markedly enhanced the catalytic performance. Furthermore, CoNi@NC manifested outstanding recyclability (reusable 20 cycles without loss of activity), which was attributed to the well-dispersed CoNi alloy nanoparticles confined in the N-doped porous carbon and the anchoring of N species to metal nanoparticles. Additionally, the resultant CoNi@NC catalyst can be successfully applied in the one-pot transformation of LA/esters with amines/nitroarenes/nitriles to the corresponding N-substituted pyrrolidones, as well as the reductive amination of other carbonyl compounds with benzylamine to form N-heterocyclic compounds. Moreover, CoNi@NC enabled us to catalyze the continuous reductive amination of LA with amines in a trickle-bed reactor, which is a more promising, efficient, highly atomically economic, and green synthetic methodology, and exhibited excellent stability during the reaction over 36 h.
危险品化学品经营许可证（带存储）