Novel Synthesis of Immobilized Brønsted‐ Acidic Ionic Liquid: Application in Lignin Depolymerization

Abstract

Designing of efficient catalyst for the valorization of lignin is a topic of long neglect due to intrinsic properties of lignin. We show designing of an efficient, stable and recyclable Immobilized‐Brønsted acidic ionic liquid (I‐BAIL), which was further used as a solid acid catalyst for the depolymerization of lignin. The synthesized I‐BAIL catalyst with sulfonic acid (–SO3H) groups was found to be stable until 250 °C and has 42.2 wt.% loading of BAIL anchored on silica framework. The detailed characterization (elemental, Thermogravimetric analysis, Fourier transformation‐Infrared, Nuclear magnetic resonance) of catalyst disclosed formation of strong covalent bond between Si and carbon of BAIL, which in turn is responsible for achieving a stable catalyst. The catalyst could successfully depolymerize range of lignin substrates with high molecular weight (60000 Dalton) at 200 °C in 1 h to achieve 90% yield of tetrahydrofuran soluble products with good mass balance. The formation of products and correlation of products with lignin was achieved with the help of Nuclear magnetic resonance, gel permeation chromatography, gas chromatography, gas chromatography‐mass spectrometry, high performance liquid chromatography etc.

Preparation of magnetic silica supported Brønsted acidic ionic liquids for the depolymerization of lignin to aromatic monomers

“…To overcome these shortcomings, researchers have proposed to graft ILs on the surface of organic polymers or inorganic materials to prepare immobilized ILs. Singh et al 25 designed an immobilized BAIL with a sulfonic acid group for the depolymerization of lignin and achieved a 90% yield of THF soluble products. The immobilized ILs combine the characteristics of ILs and carrier materials and have the advantages of high catalytic activity and high specific surface area, but still face the challenges in separating and recycling for the homogeneous reactions.…”

Determination of Alpha-, Beta- and Gamma- Cellulose in Bagasse and Wheat Straw: Lignin Recovery, Characterization and Depolymerization

“…We have screened a series of reaction conditions to have maximum amounts of low molecular weight aromatic products using an I-BAIL catalyst. Under the optimized reaction conditions, the autogenerated pressure (32 bar) due to methanol and water (5:1 v/v) reaction medium, was noted (Sandip K. Singh and Dhepe, 2018c). Lignin-derived from WS showed (Fig.…”

“…We have investigated several methods including solid acids (Deepa and Dhepe, 2015), solid bases, (Chaudhary and Dhepe, 2017), homogenous ionic liquids (ILs) (Sandip K. Singh and Dhepe, 2016a;2019) and heterogeneous ionic liquid (Sandip K. Singh and Dhepe, 2018c), to convert the various types of lignin to a large fraction of aromatic monomers. These catalysts have been screened and correlated with lignin conversion using a wide range of reaction and THF are 2.8, 4.4, and 4.0, respectively.…”

“…, solid bases,(Chaudhary and Dhepe, 2017), homogenous ionic liquids (ILs) (Sandip K Singh and Dhepe, 2016a;2019). and heterogeneous ionic liquid (Sandip K Singh and Dhepe, 2018c),. to convert the various types of lignin to a large fraction of aromatic monomers.…”

Production of 4-Ethylphenol from Lignin Depolymerization in a Novel Surfactant-Free Microemulsion Reactor

“…Mass Balance Calculation. According to the reported literature, 25 the main process for mass balance calculation was carried out according to the following steps: 0.5 wt % lignin, 0.25 mmol IL, and 10 g of microemulsion were added to a 50 mL autoclave. The autoclave was then purged three times and pressurized to 1.0 MPa with nitrogen, and the reaction was carried out at 180 °C for 4 h at the rate of 600 rpm.…”