Innovative valorization of naturally abundant and renewable lignocellulosic biomass is of great importance in the pursuit of a sustainable future and biobased economy. Ionic liquids (ILs) as an important kind of green solvents and functional fluids have attracted significant attention for the catalytic transformation of lignocellulosic feedstocks into a diverse range of products. Taking advantage of some unique properties of ILs with different functions, the catalytic transformation processes can be carried out more efficiently and potentially with lower environmental impacts. Also, a new product portfolio may be derived from catalytic systems with ILs as media. This review focuses on the catalytic chemical conversion of lignocellulose and its primary ingredients (i.e., cellulose, hemicellulose, and lignin) into value-added chemicals and fuel products using ILs as the reaction media. An outlook is provided at the end of this review to highlight the challenges and opportunities associated with this interes...

Catalytic Transformation of Lignocellulose into Chemicals and Fuel Products in Ionic Liquids

Lignocellulosic biomass is the most abundant organic carbon source and has received a great deal of interest as renewable and sustainable feedstock for the production of potential biofuels and value-added chemicals with a wide range of designed catalytic systems. However, those natural polymeric materials are composed of short-chain monomers (typically C6 and C5 sugars) and complex lignin molecules containing plenty of oxygen, resulting in products during the downstream processing having low-grade fuel properties or limited applications in organic syntheses. Accordingly, approaches to increase the carbon-chain length or carbon atom number have been developed as crucial catalytic routes for upgrading biomass into energy-intensive fuels and chemicals. The primary focus of this review is to systematically describe the recent examples on the selective synthesis of long-chain oxygenates via different C-C coupling catalytic processes, such as Aldol condensation, hydroalkylation/alkylation, oligomerization, keto...

Carbon-Increasing Catalytic Strategies for Upgrading Biomass into Energy-Intensive Fuels and Chemicals

Application of deep eutectic solvents in biomass pretreatment and conversion

Cellulose, lignin and lignocellulose are important bioresources in the nature. Their effective and environmentally friendly utilization not only reduces dependence on fossil resources but also protects the environment. Recently, a class of novel eco-friendly solvents, ionic liquids, is employed to dissolve and process these bioresources. In this mini-review, we summarized the recent advances of processing and valorization of cellulose, lignin and lignocellulose in ionic liquids. It is expected that this up-to-date survey provides a comprehensive information of this field, and accelerates the development and utilization of the renewable plant biomass resources.

Processing and valorization of cellulose, lignin and lignocellulose using ionic liquids

Bring on the subs! Biorefining will be realized by using two different approaches: the production of new biobased molecular targets or sustainable access to traditional base and commodity chemicals. Awakening of 5-hydroxymethylfurfural (HMF) can be expected with different probabilities, depending on the approach chosen to create a sustainable future.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/cssc.201900592

When Will 5-Hydroxymethylfurfural, the "Sleeping Giant" of Sustainable Chemistry, Awaken?

Conversion of lignin model compounds under mild conditions in pseudo-homogeneous systems

Aromatics play essential and unique roles in the areas ranging from synthetic chemistry to the manufacturing industry. Production of aromatics from biomass is of great fundamental interest and practical importance to ease the burden of fossil resources. This work delineates a one-step route for the synthesis of renewable aromatics from various biobased furanics and dienophiles by acidic ionic liquids at mild conditions. [Bmim]HSO4 was used as a catalyst and solvent for the direct conversion of 2,5-dimethylfuran and acrylic acid into p-xylene and 2,5-dimethylbenzoic acid; up to 89% aromatic selectivity was achieved at 87% conversion of 2,5-dimethylfuran at room temperature and atmospheric pressure, and totally 84% selectivity of p-xylene can be obtained with a subsequent decarboxylation reaction. The reaction mechanism study supplemented with isotopic tracing and DFT calculations revealed the lowest-energy pathway for the two main products. Various starting materials were studied for further extensions of ...

One-Step Conversion of Biomass-Derived Furanics into Aromatics by Brønsted Acid Ionic Liquids at Room Temperature

Water electrolysis is an advanced and sustainable energy conversion technology used to generate H2 . However, the low efficiency of the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) hampers the overall water-splitting catalytic performance. Here, a hybrid catalyst was constructed from N-doped CoS2 nanoparticles on N,S-co-doped graphene nanosheets (N-CoS2 /G) using a facile method, and the catalyst exhibited excellent bifunctional activity. Introduction of N atoms not only promoted the adsorption of reaction intermediates, but also bridged the CoS2 nanoparticles and graphene to improve electron transfer. Moreover, using thiourea as both N- and S-source ensured synthesis of much smaller-sized nanoparticles with more surface active sites. Surprisingly, the N-CoS2 /G exhibited superior catalytic activity with a low overpotential of 260 mV for the OER and 109 mV for the HER at a current density of 10 mA cm-2 . The assembled N-CoS2 /G : N-CoS2 /G electrolyzer substantially expedited overall water splitting with a voltage requirement of 1.58 V to reach 10 mA cm-2 , which is superior to most reported Co-based bifunctional catalysts and other non-precious-metal catalysts. This work provides a new strategy towards advanced bifunctional catalysts for water electrolysis.

Nitrogen-Incorporated Cobalt Sulfide/Graphene Hybrid Catalysts for Overall Water Splitting

Dual anions engineering on nickel cobalt-based catalyst for optimal hydrogen evolution electrocatalysis.

Exploring highly efficient electrocatalysts for both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) is of great significance for addressing energy and environmental crises. Vacancy engineering has been regarded as a promising way to optimize the catalytic activity of electrocatalysts. Herein, we put forward a conceptually new dual Ni,S vacancy engineering on 2D NiPS3 nanosheet (denoted as V-NiPS3 ) by a simple ball-milling treatment with ultrasonication. This material presents an ideal model for exploring the role of dual vacancies in improving the catalytic activity for overall water splitting. Structural analyses make clear that the formation of dual Ni,S vacancies regulates the electronic structure and catalytic active sites of NiPS3 nanosheet, leading to the superior HER/OER performance. Smaller overpotentials of 124 mV and 290 mV can be achieved at a current density of 10 mA cm-2 for HER and OER, respectively. The OER performance of V-NiPS3 is the best value among all state-of-the-art NiPS3 catalysts. In addition, the assembled two-electrode cell incorporating V-NiPS3 exhibits enhanced catalytic performance with a low cell voltage of 1.60 V at 10 mA cm-2 . This work offers a promising avenue to improve the electrocatalytic performance of the catalysts by engineering dual vacancies for large-scale water splitting.

Lu Chen

Papers

Conversion of lignin model compounds under mild conditions in pseudo-homogeneous systems

One-Step Conversion of Biomass-Derived Furanics into Aromatics by Brønsted Acid Ionic Liquids at Room Temperature

Nitrogen-Incorporated Cobalt Sulfide/Graphene Hybrid Catalysts for Overall Water Splitting

Dual anions engineering on nickel cobalt-based catalyst for optimal hydrogen evolution electrocatalysis.

Dual Vacancies Confined in Nickel Phosphosulfide Nanosheets Enabling Robust Overall Water Splitting