Zhang Junbo, Li Xiaolin, Xu Ming, Yang Yusen, Li Yinwen, Liu Ning, Meng Xiaoyu, Chen Lifang, Shi Shuxian, Wei Min
State Key Laboratory of Chemical Resource Engineering, Beijing Advanced Innovation Center for Soft Matter Science and Engineering, Beijing University of Chemical Technology, Beijing 100029, China.
College of Chemistry and Molecular Engineering and College of Engineering, BIC-ESAT, Peking University, Beijing 100871, China.
Sci Bull (Beijing). 2019 Dec 15;64(23):1764-1772. doi: 10.1016/j.scib.2019.10.003. Epub 2019 Oct 4.
Glycerol (GLY) aerobic oxidation in an aqueous solution is one of the most prospective pathways in biomass transformation, where the supported catalysts based on noble metals (mainly Au, Pd, Pt) are most commonly employed. Herein, Pt nanoparticles supported on rehydrated MgAl-hydrotalcite (denoted as re-MgAl-LDH-Pt) were prepared via impregnation-reduction method followed by an in situ rehydration process, which showed high activity and selectivity towards GLY oxidation to produce glyceric acid (GLYA) at room temperature. The metal-support interfacial structure and catalyst basicity were modulated by changing the Mg/Al molar ratio of the hydrotalcite precursor, and the optimal performance was achieved on re-MgAl-LDH-Pt with a GLY conversion of 87.6% and a GLYA yield of 58.6%, which exceeded the traditional activated carbon and oxide supports. A combinative study on structural characterizations (XANES, CO-FTIR spectra, and benzoic acid titration) proves that a higher Mg/Al molar ratio promotes the formation of positively charged Pt species at metal-support interface, which accelerates bond cleavage of α-C-H and improves catalytic activity. Moreover, a higher Mg/Al molar ratio provides a stronger basicity of support that contributes to the oxidation of terminal-hydroxyl and thus enhances the selectivity of GLYA. This catalyst with tunable metal-support interaction shows prospective applications toward transformation of biomass-based polyols.
水溶液中甘油（GLY）的好氧氧化是生物质转化中最具前景的途径之一，其中最常用的是基于贵金属（主要是Au、Pd、Pt）的负载型催化剂。在此，通过浸渍还原法并随后进行原位再水化过程制备了负载在再水化MgAl水滑石上的Pt纳米颗粒（表示为re-MgAl-LDH-Pt），该催化剂在室温下对GLY氧化生成甘油酸（GLYA）表现出高活性和选择性。通过改变水滑石前驱体的Mg/Al摩尔比来调节金属-载体界面结构和催化剂碱性，在re-MgAl-LDH-Pt上实现了最佳性能，GLY转化率为87.6%，GLYA产率为58.6%，超过了传统的活性炭和氧化物载体。对结构表征（XANES、CO-FTIR光谱和苯甲酸滴定）的综合研究证明，较高的Mg/Al摩尔比促进了金属-载体界面处带正电的Pt物种的形成，加速了α-C-H的键断裂并提高了催化活性。此外，较高的Mg/Al摩尔比提供了更强的载体碱性，有助于末端羟基的氧化，从而提高了GLYA的选择性。这种具有可调金属-载体相互作用的催化剂在生物质基多元醇的转化方面显示出潜在的应用前景。
