Siye Tang

The aim of this paper was to investigate the catalytic properties of palladium supported on chitosan catalysts. The effect of primitive chitosan and degraded chitosan on catalytic performance was compared. The structure, morphology, metal content and properties of the catalysts were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), inductively coupled plasma spectrometry (ICP), X-ray diffraction (XRD), Brunauer?Emmett?Teller (BET) method and X-ray photoelectron spectroscopy (XPS). The results showed that the catalytic performance of Pd/degraded chitosan was better than that of Pd/chitosan at a certain Pd load. Pd/degraded chitosan (degradation 4 h) catalyst exhibited excellent catalytic performance and stability. The acetylene conversion and ethylene selectivity, respectively, achieved 100 and 91 %. During 13.5 h, the acetylene conversion maintained 100 % and the ethylene selectivity decreased slightly from 88 to 71 %. Based on this study, it was demonstrated that Pd was successfully coordinated with chitosan; after degradation, the chitosan particles became smaller and had larger surface areas; these were conducive to improve the catalytic performance of Pd/degraded chitosan. Pd/degraded chitosan also had high selectivity at high conversion, greatly improving the characteristics of low selectivity at high conversion of traditional Pd-based catalysts.

Novel zinc–palladium–porphyrin bimetal metal–organic framework (MOF) nanosheets were directly synthesized by coordination chelation between Zn(II) and Pd(II) tetra(4-carboxyphenyl)porphin (TCPP(Pd)) using a solvothermal method. Furthermore, a serial of carbon nanosheets supported Pd–Zn intermetallics (Pd–Zn-ins/CNS) with different Pd: Zn atomic ratios were obtained by one-step carbonization under different temperature using the prepared Zn-TCPP(Pd) MOF nanosheets as precursor. In the carbonization process, Pd–Zn-ins went through the transformation from PdZn (650 °C) to Pd_3.9Zn_6.1 (~950 °C) then to Pd_3.9Zn_6.1/Pd (1000 °C) with the temperature increasing. The synthesized Pd–Zn-ins/CNS were further employed as catalysts for selective hydrogenation of acetylene. Pd_3.9Zn_6.1 showed the best catalytic performance compared with other Pd–Zn intermetallic forms.

A one-pot and green synthesis methodology was successfully designed to prepare nitrogen-doped carbon (NC) cohered Fe₃O₄ nanoparticles with rich oxygen vacancies (Fe₃O₄-OVs/NC). The preparation was achieved via cold-atmospheric-pressure air plasma using Fe₂O₃ nanoparticles as the only precursor, and pyridine as the carbon and nitrogen source. Systematic characterization results of the as-prepared Fe₃O₄-OVs/NC confirmed the transition from Fe₂O₃ to Fe₃O₄, along with the generation of oxygen vacancies, while preserving the original needle-like morphology of Fe₂O₃. Moreover, the results indicated the formation of the NC attaching to the surface of the formed Fe₃O₄ nanoparticles with a weight percent of ~13.6%. The synthesized nanocomposite was further employed as a heterogeneous Fenton catalyst to remove phenol from an aqueous solution. The material has shown excellent catalytic activity and stability, demonstrating a promising application for wastewater treatment.

The degradation reactions of chlorinated polypropylene (CPP) in toluene under ultrasonic irradiation were studied. The Mark–Houwink equation acquired from fractional precipitations was also suitable for estimating the molecular weight of degraded CPP. An objective standard was proposed for judging the solution behaviour of CPP in solvents by the study on the relative solubility of CPP before and after degradation. Then Hansen three-dimensional solubility parameters and the total parameter of CPP were obtained by optimization calculation in terms of the criterion proposed here. It was proved that the total parameter of CPP is creditable by the turbidity method. Compared to other standards, the result obtained from the proposed standard accorded well with the standard of complete miscibility suggested by Flory–Huggins for polymers and solvents as well as the objective reality. This standard may provide a reference for other polymers.