State Key Laboratory of Pulp and Paper Engineering, South China University of Technology, Guangzhou 510640, Guangdong, China; School of Chemical & Biomolecular Engineering and RBI at Georgia Tech, Georgia Institute of Technology, 500 10th Street N.W., Atlanta, GA 30332-0620, USA.
Guangdong Provincial Key Laboratory of Petrochemical Pollution Processes and Control, School of Environmental Science and Engineering, Guangdong University of Petrochemical Technology, Maoming 525000, Guangdong, China.
Int J Biol Macromol. 2021 Feb 1;169:274-281. doi: 10.1016/j.ijbiomac.2020.12.092. Epub 2020 Dec 17.
Upgrading of lignin derived bio-oil is an essential step for producing sustainable bio-based chemicals and fuel. Taken into account that α hydroxyl is the abundant functional group in lignin, high effective and selective catalytic alcoholysis for cleaving the C-OH linkages would be desirable. However, an in-depth understanding of the reaction mechanisms involved in the cleavage of C-C and C-O bonds over a novel catalyst is still needed. Herein, we report an efficient liquid-phase hydrogen transfer strategy for the selective hydrodeoxygenation of a non-phenolic lignin model compound, 3,4-dimethoxybenzyl (veratryl) alcohol, under mild conditions. By employing iso-propanol as solvent and H-donor, and palladium nanoparticles immobilized on nitrogen-doped carbon (Pd/CN) as efficient multifunctional catalyst, veratryl alcohol dehydroxylation exhibited almost 100% conversion along with very high selectivity for 1,2-dimethoxy-benzene (46%) and 3,4-dimethoxytoluene (54%). Compared with other Pd catalysis, the Pd/CN has excellent catalytic performances and exhibits higher selectivity for 3,4-dimethoxytoluene under incorporation with 1% HCOOH at 220 °C. The proportion of Pd (0) significantly increases in Pd/CN catalyst when introduced into N precursor because of its highly dispersed Pd NPs and preventing the reoxidation of Pd (0). The dehydrogenation reaction occurred through the hydrogen generation of a secondary alcohol. Then, the C-OH and C-C bonds of veratryl alcohol were selectively cleaved by catalytic transfer hydrogenolysis. The alcoholysis mechanism is supported by dispersion-corrected density functional theory computations.
木质素衍生生物油的升级是生产可持续生物基化学品和燃料的重要步骤。考虑到α-羟基是木质素中丰富的官能团，因此需要高效和选择性的催化醇解来裂解 C-O 键。然而，仍然需要深入了解新型催化剂上涉及 C-C 和 C-O 键裂解的反应机制。在此，我们报告了一种在温和条件下通过液相氢转移策略选择性加氢脱氧木质素模型化合物 3,4-二甲氧基苄基（藜芦基）醇的有效方法。通过使用异丙醇作为溶剂和氢供体，以及负载在氮掺杂碳（Pd/CN）上的钯纳米颗粒作为高效多功能催化剂，藜芦醇的去羟化反应几乎达到了 100%的转化率，同时对 1,2-二甲氧基苯（46%）和 3,4-二甲氧基甲苯（54%）具有很高的选择性。与其他钯催化相比，在 220°C 下加入 1% HCOOH 时，Pd/CN 具有出色的催化性能，对 3,4-二甲氧基甲苯表现出更高的选择性。由于其高度分散的 Pd NPs 和阻止 Pd（0）再氧化，Pd/CN 催化剂中 Pd（0）的比例显著增加。脱氢反应通过仲醇的氢气生成发生。然后，通过催化转移氢解选择性地裂解藜芦醇的 C-OH 和 C-C 键。醇解机理得到了修正色散密度泛函理论计算的支持。
