Rapid chemical recycling of waste polyester plastics catalyzed by recyclable catalyst

Waste plastics are serious environmental threats due to their low degradability and low recycling rate.Rapid and efficient waste plastics recycling technologies are urgently demanded for a sustainable future.Herein,we report a rapid,closed-loop,and streamlined process to convert polyesters such as poly(ethylene terephthalate)(PET)back to its purified monomers.Using trifluoromethanesulfonic acid or metal triflates as the recyclable catalyst,polyesters such as PET can be completely depolymerized by simple carboxylic acids within 1 h.By coupling this acidolysis with a subsequent hydrogenolysis process,the consumed carboxylic acid was recovered and the closed-loop of PET depolymerization could be established.All catalysts and depolymerization agents are fully recycled while only PET and hydrogen are consumed.

Efficient and recyclable Rh-catalytic system with involvement of phosphine-functionalized phosphonium-based ionic liquids for tandem hydroformylation—acetalization

The phosphine-functionalized phosphonium-based ionic liquids(dppm-Q, dppe-Q, dppp-Q and dppb-Q) as the bi-functional ligands enable the efficient one-pot tandem hydroformylationeacetalization. It was found that, in dppm-Q, dppe-Q, dppp-Q and dppb-Q, the incorporated phosphino-fragments were responsible for Rh-catalyzed hydroformylation and the phosphoniums were in charge of the subsequent acetalization as the Lewis acid catalysts. Moreover, the diphosphonium-based ionic liquid of dppb-DQ could be applied as a co-solvent to immobilize the Rh/dppb-Q catalytic system with the advantages of the improved catalytic performance, the available catalyst recyclability, and the wide generality for the substrates.

Efficient Knoevenagel condensation catalyzed by imidazole-based halogenfree deep eutectic solvent at room temperature

For the first time,we employed the halogen-free deep eutectic solvent(DES)into the Knoevenagel condensation between aromatic aldehydes and active methylene compounds at room temperature.The DESs[3Im:PTSA]and[4Im:PTSA]were prepared by imidazole(Im)and p-tol-uenesulfonic acid(PTSA),which were experimentally screened from a series of organic acids with imidazole.a,b-Unsaturated carbonyl compounds were obtained in good to excellent yields under solvent-free conditions with fast reaction rate.These two DESs can be reused for multiple times with no loss of catalytic activity.

Efficient and recyclable palladium enriched magnetic nanocatalyst for reduction of toxic environmental pollutants

In this paper,highly stable,powerful,and recyclable magnetic nanoparticles tethered Nheterocyclic carbene-palladium(Ⅱ)((CH_(3))_(3)-NHC-Pd@Fe_(3)O_(4))as magnetic nanocatalyst was successfully synthesized from a simplistic multistep synthesis under aerobic conditions through easily available low-cost chemicals.Newly synthesized(CH_(3))_(3)-NHC-Pd@Fe_(3)O_(4) magnetic nanocatalyst was characterized from various analytical tools and catalytic potential of the(CH_(3))_(3)-NHC-Pd@Fe_3 O_4 magnetic nanocatalyst was studied for the catalytic reduction of toxic 4-nitrophenol(4-NP),hexavalent chromium(Cr(Ⅵ)),Methylene Blue(MB)and Methyl Orange(MO)at room temperature in aqueous media.UV-Visible spectroscopy was employed to monitor the reduction reactions.New(CH_(3))_(3)-NHC-Pd@Fe_(3)O_(4) magnetic nanocatalyst exhibited excellent catalytic activity for the reduction of toxic environmental pollutants.Moreover,(CH_(3))_(3)-NHC-Pd@Fe_(3)O_(4) magnetic nanocatalyst could be easily and rapidly separated from the reaction mixture with the help of an external magnet and recycled minimum five times in reduction of 4-NP,MB,MO and four times in Cr(Ⅵ)without significant loss of catalytic potential and remains stable even after reuse.

Heterogeneously supported pseudo-single atom Pt as sustainable hydrosilylation catalyst

The identification of highly active heterogeneous catalysts to replace their homogeneous counterparts remains a challenge in the case of organic catalysts, especially polymers, in highly viscous reaction systems. In this work, we designed and synthesized a novel, solid-supported, and heterogeneous pseudo-single atom Pt catalyst with high activity and recyclability. Superparamagnetic Fe3O4-SiO2 core--shell nanoparticles （NPs） were used as the substrate. The functionalization of the SiO2 shell with silane coupling agents containing vinyl groups allows stabilizing Pt on the SiO2 surface through complexation. The as-prepared pseudosingle atom Pt displays high activity in the hydrosilylation of allyl-terminated polyether with polymethylhydrosiloxane and could be easily collected by applying a magnetic field. The Pt/vinyl/SiO2/Fe3O4 catalyst can be reused for up to four reaction cycles without appreciable decrease in activity. This work demonstrates a novel strategy for the design of pseudo-single atom noble metal catalysts for processes in high-viscosity media.

A pH-responsive TiO_2-based Pickering emulsion system for in situ catalyst recycling

Developing methods for efficient product/catalyst separation and catalyst recycling is meaningful in multi-phase catalytic reactions. Here, we reported a p H-responsive emulsion system stabilized by interfacially active TiO2 nanoparticles for achieving in situ product/catalyst separation and catalyst recycling. In this system, emulsification and demulsification process could be easily engineered through tuning the p H values. The emulsion droplets were destroyed completely at a p H value of 3–4, and the solid catalyst distributed in the aqueous phase could be used to the next reaction cycle after removal of the organic product and adjusting the p H to 7–8. Such a p H triggered switchable Pickering emulsion catalytic system not only shows good recyclability of the solid catalyst but also high catalytic efficiency,and could be recycled more than 10 cycles.

A green access to supported cinchona alkaloid amide catalysts for heterogeneous enantioselective allylsilylation of aldehydes and process intensity evaluation in batch and flow

We report herein a new class of polystyrene-supported cinchona alkaloid amide catalysts for enantioselective allylation of various aldehydes using allyltrichlorosilane under both batch and continuous flow conditions.The supported catalyst was synthesized using an environmentally benign coupling agent with a surfactant in aqueous media.Under batch conditions,consistently high yields and enantioselectivity were obtained for the allylation of aliphatic aldehydes with recycling and reuse of the catalyst for more than 10 runs.Subsequently,this catalytic system was successfully implemented into a packed bed flow reactor with similar efficiency and enantiose-lectivity.While flow is a viable option,the batch methodology has better potential for application at a larger-scale setting upon the comparison of space-time yield and catalyst loadings.With the sustainable synthesis and great recyclability of our polymeric catalyst,this methodology holds great potential for the large-scale delivery of valuable enantiopure homoallylic alcohols.

Polymer-Supported Chiral Monodentate Phosphoramidites in Palladium-Catalyzed Allylic Alkylation Reactions

A new and simple method for immobilization of monodentate chiral ligand on the cheap resin has been developed. A series of resin-immobilized phosphoramidite ligands based on BINOL and TADDOL backbones have been synthesized and characterized with gel-phase NMR. The immobilized ligands have been applied to the Pd-catalyzed asymmetric allylic alkylation of 1,3-diphenyl-2-propenyl acetate. Among four ligands, the supported bulky monodentate phosphoramidite ligand based on TADDOL backbone afforded the chiral product with ee up to 65%; moreover, this ligand could be recycled for 3 times without substantial decrease of the conversion and ee.