Yunfei Zhi

Polypyrrole Nanofibers Supported Cr(III)(salen)Cl Catalyst: A Novel Polymer Supported Catalyst for Alternating Copolymerization of Cyclohexene Oxide with Carbon dioxide

Polypyrrole(PPy) supported Cr(III)(salen)Cl catalyst was prepared for alternating copolymerization of cyclohexene oxide and carbon dioxide. The supported catalyst and the copolymerization products were characterized by FTIR, XRD, XPS, ICP-MS, SEM, TEM, NMR, gel permeation chromatography, thermogravimetric analysis and differential scanning calorimetry. After the study, we concluded that the homogeneous Cr(III)(salen)Cl is successfully supported on the PPy, and its catalytic performance is much better than the homogeneous one. Moreover, the copolymerization product catalyzed by PPy-Cr(III)(salen)Cl exhibits higher molecular weight, narrower molecular weight distribution, superior thermal stability and selectivity.Graphical Abstract

Efficient alternating copolymerization of sulfur dioxide with cyclohexene oxide and a mechanistic understanding

The alternating copolymerization of sulfur dioxide with epoxides is rarely reported because of the low reactivity and polysulfite selectivity of the process. This work describes an efficient alternating copolymerization of sulfur dioxide with cyclohexene oxide using salenCrIIICl as the catalyst. The effect of temperature, time, and type of catalyst on the overall activity and selectivity was investigated in detail. The results proved that the reactivity and polysulfite selectivity of salenCrIIICl are better than those of amines and inorganic salts. The copolymer product poly(cyclohexene sulfite) was characterized by nuclear magnetic resonance spectroscopy, infrared spectroscopy, thermogravimetric analysis and gel permeation chromatography. We found that SO2 not only acts as reactant, but also acts as a co-catalyst to promote the copolymerization reaction in the presence of salenCrIIICl. On the basis of the copolymerization mechanism of CO2 and epoxide using a salen catalyst, and spectroscopic evidence, a mechanism to account for the results is proposed.

Effective and reusable microcrystalline cellulosic Salen complexes for epoxidation of alpha-pinene

Abstract 2,3-Epoxypinane, one of the alpha-pinene derivatives, has great economic value. Among the catalyst systems for the epoxidation of alpha-pinene, Salen transition metal complexes have shown exceptional catalytic activities, yet their reusability was a major problem. Herein, for the first time, we developed a heterogeneous microcrystalline cellulosic Salen complex using a facile method. Compared with some catalytic systems, the complex displayed superior catalytic activities in the epoxidation of alpha-pinene. Moreover, the key advantage is cellulose, the most abundant regenerable biopolymer in accordance with the requirements of green chemistry, which has been employed to synthesize a Salen complex. The reusability of the catalyst and different oxidant systems were also investigated in detail. The results demonstrated that the catalyst maintains excellent catalytic activity and selectivity after being used six times when using O2 and the co-oxidant. These interesting results unveil the potential of the cellulosic Salen complex for heterogeneous catalytic reactions.

Cellulosic Cr(salen) complex as an efficient and recyclable catalyst for copolymerization of SO2 with epoxide

The search for green catalytic processes for the synthesis of useful polymers and incorporating the waste SO2 in highly-selective pathways become extremely important in the coming years. Herein, cellulose was modified by ethylenediamine, and then synthesized Schiff base with 3,5-di-tert-butyl-2-hydroxybenzaldehyde to immobilize chromium chloride and formed a novel heterogeneous cellulosic Cr(salen)-type catalyst for the first time. The cellulosic Cr(salen)-type catalyst shows high efficiency and recyclability in copolymerization of cyclohexene oxide with SO2. The influence factors such as the molar ratio of the catalyst and cyclohexene oxide, reaction temperature, and reaction time were researched in detail to study the optimal conditions. The copolymer product was characterized by FTIR and 1H NMR for confirming the structure. The possible copolymer mechanism is given, and we believed that the novel cellulosic Cr(salen)-type complex will be used as an efficient catalyst in other chemical reactions.