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A series of novel polyacrylonitrile fiber catalysts modified with different ratio of quaternary ammonium salt (QA) to tertiary amine (TA) were screened for heterogeneously catalyzed aza-Michael addition in water. The best catalyst was found to be PANPQ-1F with a QA:TA ratio of 1:1, which can lead to high yield, excellent selectivity of solvent and great recyclability under optimized conditions. The special microenvironment of hydrophilic inner layer and hydrophobic surface layer of PANPQ-1F is conducive to the leaving of the product and the high conversion of the reaction. Based on the fact that appropriate microenvironment combined with the catalytic sites promoted the reaction, cooperative effect of QA and TA in the microenvironment of PANPQ-1F catalyst was proposed. [ABSTRACT FROM AUTHOR]

Multifunctional NiCoTi metal oxide catalysts (denoted herein as NiCoTi-x, where x is the molar ratio Ni + Co:Ti) were successfully prepared by thermal treatment of NiCoTi layered double hydroxide (LDH) precursors. The NiCoTi-x catalysts were then applied to the hydrogenation of 5-hydroxymethylfurfural (HMF) to 2,5-dimethylfuran (DMF). The Ni:Co:Ti molar ratio in the catalysts was found to strongly influence both catalyst activity and product selectivity. A NiCoTi-8 catalyst, containing Ni, Co and Ti in a 4:4:1 molar ratio (i.e. Ni + Co/Ti = 8), displayed outstanding performance for HMF hydrogenation at 200 °C and 1.5 MPa, evidenced by a 90.7% HMF conversion and 95.8% selectivity to DMF. A ternary metal oxide catalyst derived from a layered double hydroxide was proposed for the efficient and selective hydrogenation of 5-hydroxymethylfurfural to 2,5-methylfuran. [ABSTRACT FROM AUTHOR]

Abstract: The l-lysine functionalized polyacrylonitrile fiber (PANLF) was prepared by grafting the l-lysine into a commercially available polyacrylonitrile fiber and showed highly catalytic activity for Knoevenagel condensation reaction. With low temperature (45 °C) and short reaction time (1 h), the fiber catalyst was well applicable to Knoevenagel condensation of a wide range of aldehydes and the yields could reach up to 99%. Interestingly, only in water could the reaction take place smoothly (with a yield of 88%) and a polar micro-environment promoted reaction process had been proposed to explain this phenomenon. Besides, the fiber catalyst has advantages of easy preparation, high functional degree, strong mechanical strength and thermal stability, etc. And it can be reused at least 5 times without further treatment and performed well in scaled-up experiment (amplified 50 times) and flow chemistry experiment (no loss of catalytic activity after 48 h), which indicates its potential application in industry application.Graphical Abstract: [ABSTRACT FROM AUTHOR]

The reaction of secondary amines with CS under mild conditions using reduced graphene oxide (rGO) as a green catalyst was reported, which provided an efficient access to the one-pot synthesis of bis(aminothiocarbonyl)disulfides. The rGO can be recycled at least four times without any loss of catalytic activity. A plausible mechanism was proposed. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]