Ionic Liquids in Metal, Photo-, Electro-, and (Bio) Catalysis

Ionic liquids (ILs) have unique physicochemical properties that make them advantageous for catalysis, such as low vapor pressure, non-flammability, high thermal and chemical stabilities, and the ability to enhance the activity and stability of (bio)catalysts. ILs can improve the efficiency, selectivity, and sustainability of bio(transformations) by acting as activators of enzymes, selectively dissolving substrates and products, and reducing toxicity. They can also be recycled and reused multiple times without losing their effectiveness. ILs based on imidazolium cation are preferred for structural organization aspects, with a semiorganized layer surrounding the catalyst. ILs act as a container, providing a confined space that allows modulation of electronic and geometric effects, miscibility of reactants and products, and residence time of species. ILs can stabilize ionic and radical species and control the catalytic activity of dynamic processes. Supported IL phase (SILP) derivatives and polymeric ILs (PILs) are good options for molecular engineering of greener catalytic processes. The major factors governing metal, photo-, electro-, and biocatalysts in ILs are discussed in detail based on the vast literature available over the past two and a half decades. Catalytic reactions, ranging from hydrogenation and cross-coupling to oxidations, promoted by homogeneous and heterogeneous catalysts in both single and multiphase conditions, are extensively reviewed and discussed considering the knowledge accumulated until now.

Enhancement of the hydrophilic feruloyl glycerol synthesis using A-35 as a catalyst and its functional characteristics

Feruloyl glycerol (FG) is the hydrophilic ester of ferulic acid (FA), which has a high solubility in water and a strong ability to resist ultraviolet (UV) radiation. In this work, several solid acids were used as novel economical catalysts and FA was used as a cheap substrate for FG preparation. The effects of reaction variables on the esterification of FA with glycerol were investigated and optimized by response surface methodology (RSM). Results showed that a cheap solid acid cation exchange resin A-35 showed the best performance for esterification. The reaction conditions were optimized by RSM as follows: 15 : 1 (glycerol/FA) substrate molar ratio and 14% catalyst loading at 90 °C for 7 h. The maximum FG yield (98.50 ± 0.58%) was achieved under the optimized conditions. The activation energy of the esterification was 53.71 kJ mol^-1. The results of UV absorbance showed that FG had good anti-UV activity and photostability, which can be used as a potential antioxidant and UV absorber in food and sunscreen products.

Hydrophilic Glyceryl Ferulates Preparation Catalyzed by Free Lipase B from Candida antartica

Ferulic acid (FA), 4-hydroxyl-3-methoxy-2-benzylacrylic acid, has antioxidant, anticancer and ultraviolet absorption activities. However, the low hydrophilicity of FA has limited its application. Glyceryl ferulate (FG), which is an all-natural hydrophilic derivative of FA, can be used as an antioxidant and UV filter in food and cosmetic formulations. However, the applications of FG in these fields are limited due to its low content in nature. In this work, free liquid lipase was firstly used as a catalyst for FG preparation. Several different free liquid lipases (Candida antartica lipase-B, Candida antartica lipase-A, Thermomyces lanuginosus (Lipozyme TL 100L)) were screened and compared. The effects of the transesterification parameters (time, temperature, enzyme load and substrate ratio) were optimized and evaluated by response surface methodology. A reaction thermodynamic investigation was also performed. The results showed that, among the tested free lipases, the maximum FG yield (84.8±1.5%) was achieved using free Candida antartica lipase-B. Under the optimized conditions (an atmospheric system, an enzyme load of 11.1% and a 20:1 molar ratio of glycerol to EF at 70°C for 39.5 h), the FG yield and EF conversion were 84.8±1.5% and 95.7±1.2%, respectively. The activation energies of FG formation and EF conversion were 56.4 and 58.0kJ/mol, respectively.