Ethyl levulinate has shown great potential as a green fuel additive for gasoline, diesel, and biodiesel. One alternative for its synthesis is the direct heterogeneously catalyzed esterification of levulinic acid with ethanol. Most of the catalytic processes already reported for this system, however, rely on large residence times to deliver appreciable levulinic acid conversions. This work presents experimental and modeling results on the esterification kinetics of levulinic acid with ethanol assisted by supercritical carbon dioxide (scCO₂) and catalyzed by Amberlyst-15 in a fixed-volume batch reactor. We explore different molar ratios, catalyst amounts, temperatures, and scCO₂ loads. The presented reaction scheme leads to near-equilibrium levulinic acid conversions after less than 60 min at most of the evaluated conditions. To represent the phase-behavior of CO₂ + reactants and products, the Peng–Robinson equation of state with a quadratic mixing rule was used. We found that, at most of the experimental conditions, the reaction takes place in a two-phase system due to scCO₂; thus, a v-T flash algorithm was coupled to the kinetic model. The proposed kinetic modeling is one of the first attempts to simulate scCO₂-assisted reactions in heterogeneous catalytic systems in which the phase partition inside the reactor vessel is considered.

中文翻译：

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在间歇反应器中使用 Amberlyst-15 作为催化剂的 scCO2 辅助乙酰丙酸与乙醇的酯化的动力学建模

乙酰丙酸乙酯作为汽油、柴油和生物柴油的绿色燃料添加剂显示出巨大的潜力。其合成的一种替代方法是乙酰丙酸与乙醇的直接非均相催化酯化。然而，该系统已经报道的大多数催化过程依赖于较长的停留时间来实现可观的乙酰丙酸转化。这项工作展示了乙酰丙酸与乙醇在超临界二氧化碳 (scCO ₂ )辅助下并由 Amberlyst-15 在固定体积间歇式反应器中催化的酯化动力学的实验和建模结果。我们探索了不同的摩尔比、催化剂用量、温度和 scCO ₂负载。在大多数评估条件下，所提出的反应方案在不到 60 分钟后导致接近平衡的乙酰丙酸转化。为了表示 CO ₂ + 反应物和产物的相行为，使用具有二次混合规则的 Peng-Robinson 状态方程。我们发现，在大多数实验条件下，由于 scCO ₂，反应发生在两相系统中；因此，vT flash 算法与动力学模型相结合。所提出的动力学模型是在多相催化系统中模拟scCO ₂辅助反应的首次尝试之一，其中考虑了反应器容器内的相分配。