Continuous Liquid-Phase Upgrading of Dihydroxyacetone to Lactic Acid over Metal Phosphate Catalysts
Continuous Liquid-Phase Upgrading of Dihydroxyacetone to Lactic Acid over Metal Phosphate Catalysts
复制标题
DOI：
10.1021/acscatal.0c03761
复制
发表时间：
2020-10-16
期刊：
影响因子：
12.9
通讯作者：
Sievers, Carsten
中科院分区：
文献类型：
--
作者：
Innocenti, Giada;Papadopoulos, Eleni;Sievers, Carsten
使用固定床反应器研究了布朗斯台德酸性和路易斯酸性磷酸 La、Nb 和 Zr 磷酸盐（LaPO、NbPO 和 ZrPO）在二羟基丙酮 (DHA) 水相转化为乳酸 (LA) 过程中的性能。彻底研究了传质现象，并从每种催化剂的固有动力学常数中解卷积了传质系数，以便能够对两者进行定量评估。发现 NbPO 的传质受到限制。尽管存在这一限制，NbPO 的 LA 产率最高，为 36%。 ZrPO 上的反应不受传输限制，可以对内在动力学进行严格的分析。该分析表明，DHA 转化为丙酮醛 (PVA) 遵循二聚中间体的二级反应机制，这巩固了文献中的先前报告。此外，还观察到 LA 产量与碳平衡中碳缺失（碳损失）之间的相关性。最后，NbPO 和 ZrPO 在 150 摄氏度下运行长达 10 小时，表现出稳定的性能。反应 15 小时后，PVA 产率增加，但以 NbPO 的 LA 为代价。这是由于产生 LA 所需的活性位点失活所致，这些活性位点与产生 PVA 的位点不同。这一假设得到了用 C-13 魔角旋转核磁共振和衰减全反射红外光谱对废催化剂进行表征的支持。
The performance of Bronsted- and Lewis-acidic La, Nb, and Zr phosphates (LaPO, NbPO, and ZrPO) during the aqueous phase conversion of dihydroxyacetone (DHA) to lactic acid (LA) is investigated using a fixed-bed reactor. Mass-transfer phenomena are thoroughly investigated, and the mass-transfer coefficient is deconvoluted from the intrinsic kinetic constant for each catalyst to enable the quantitative assessment of both. NbPO is found to be mass-transfer-limited. Despite this limitation, NbPO shows the highest yield of LA at 36%. The reaction over ZrPO is not transport-limited, allowing for a rigorous analysis of intrinsic kinetics. This analysis shows that the conversion of DHA into pyruvaldehyde (PVA) follows a second-order reaction mechanism via a dimeric intermediate, which consolidates previous reports in the literature. Additionally, a correlation between LA production and the carbon missing from the carbon balance (carbon loss) is observed. Finally, NbPO and ZrPO show stable performance up to 10 h on stream at 150 degrees C. After 15 h of reaction, the PVA yield increases at the expense of LA with NbPO. This is ascribed to the deactivation of the active sites necessary to produce LA, which are different from the sites that produce PVA. This hypothesis is supported by the characterization of the spent catalyst with C-13 magic-angle spinning nuclear magnetic resonance and attenuated total reflectance infrared spectroscopy.