Selective catalytic tailoring of the H unit in herbaceous lignin for methyl p-hydroxycinnamate production over metal-based ionic liquids,Green Chemistry

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Selective catalytic tailoring of the H unit in herbaceous lignin for methyl p-hydroxycinnamate production over metal-based ionic liquids
Green Chemistry ( IF 9.3 ) Pub Date : 2018-06-21 , DOI: 10.1039/c8gc01252k
Zhangmin Li _{1,

2,

3,

4,

5} , Zhenping Cai _{1,

2,

3,

4,

5} , Qiang Zeng _{1,

2,

3,

4,

5} , Tian Zhang _{1,

2,

3,

4,

5} , Liam John France _{1,

2,

3,

4,

5} , Changhua Song _{1,

2,

3,

4,

5} , Yaqin Zhang _{5,

6,

7,

8,

9} , Hongyan He _{5,

6,

7,

8,

9} , Lilong Jiang _{5,

10,

11,

12,

13} , Jinxing Long _{1,

2,

3,

4,

5} , Xuehui Li _{1,

2,

3,

4,

5}

Affiliation

Selective valorization of lignin to achieve high value and commodity chemicals is attracting increasing attention. In this work, an efficient and reusable metal-based ionic liquid (MBIL) was developed for the selective tailoring of p-coumaric acid ester (pCA), a typical p-hydroxyphenyl (H) unit, into methyl p-hydroxycinnamate (MPC). Under optimized conditions and in the presence of catalyst [Bmim][FeCl₄], a volatile aromatic product of 10.5 wt% was obtained, of which, 70.5% separated as pure MPC with an isolated yield of 71.1 mg g⁻¹. FT-IR, ¹³C NMR, ANO and 2D HSQC demonstrated that the H unit was preferentially tailored from lignin, of which, 86.0 wt% of the H structure unit is cut off from lignin, with 70.6% being selectively converted to MPC. Further investigation demonstrated that MBIL prefers to tailor ester bonds compared to ether bonds using model compounds, and the superior catalytic ester bond cleavage performance exhibited by [Bmim][FeCl₄] can be ascribed to the relatively narrow energy gap between the lignin ester bond and [FeCl₄]⁻ anion and to the comparatively low absolute binding energy between the cation and anion through DFT calculations.

中文翻译：

草本木质素中H单元的选择性催化修饰，用于在金属基离子液体上生产对羟基肉桂酸甲酯

木质素的选择性增值以实现高价值和商品化学品正受到越来越多的关注。在这项工作中，一种有效的和可重复使用的金属系离子性液体（MBIL）中的混合物中选择性的剪裁开发p香豆酸酯（p CA），一个典型的p -羟基苯基（H）单元，成甲基p -hydroxycinnamate（MPC ）。在优化的条件下，在催化剂[Bmim] [FeCl ₄ ]的存在下，获得了10.5 wt％的挥发性芳烃产物，其中70.5％的化合物以纯MPC的形式分离，分离产率为71.1 mg g ^-1。红外，¹³13 C NMR，ANO和2D HSQC证明H单元优先由木质素改造而成，其中86.0 wt％的H结构单元被木质素切断，其中70.6％被选择性转化为MPC。进一步的研究表明，与使用模型化合物的醚键相比，MBIL更倾向于定制酯键，并且[Bmim] [FeCl ₄ ]表现出的优异的催化酯键裂解性能可归因于木质素酯键与[FeCl ₄ ] ^-阴离子和通过DFT计算得到的阳离子和阴离子之间相对较低的绝对结合能。

更新日期：2018-08-13

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