Zengxi Li

Degradation of poly(ethylene terephthalate) using ionic liquids

The degradation of poly(ethylene terephthalate) (PET) was successfully achieved using ionic liquids. The products were separated according to their solubilities in boiling water. Average molecular weights of the main product were determined by gel permeation chromatography (GPC). The physicochemical properties of the product have been characterized by scanning electron microscopy equipped with an energy dispersive X-ray analyzer (SEM/EDX), X-ray diffractometer, infrared spectrometric analyzer, differential scanning calorimeter, and thermogravimetric analysis instrument. The influences of experimental parameters, such as the reaction time, reaction temperature, and addition of different catalysts on the solubility of PET were investigated. A study on the recycling of the ionic liquid shows that ionic liquid could be used repeatedly. Moreover, the solubility of PET in the recycled ionic liquid is higher than that in fresh ionic liquid. Further study shows that the increase of solubility in the recycled ionic liquid is attributable to the presence of a minor amount of water. A mechanism of the degradation of PET in 1-butyl-3-methylimidazolium chloride ([bmim]Cl) was proposed. In addition, the kinetics of this reaction was investigated. Results show that this degradation process is a first-order kinetic reaction and the activation energy is 232.79 kJ mol−1.

Coagulation of Chitin and Cellulose from 1‐Ethyl‐3‐methylimidazolium Acetate Ionic‐Liquid Solutions Using Carbon Dioxide

Chemisorption of carbon dioxide by 1-ethyl-3-methylimidazolium acetate ([C2 mim][OAc]) provides a route to coagulate chitin and cellulose from [C2 mim][OAc] solutions without the use of high-boiling antisolvents (e.g., water or ethanol). The use of CO2 chemisorption as an alternative coagulating process has the potential to provide an economical and energy-efficient method for recycling the ionic liquid.

Effective catalysis of poly(ethylene terephthalate) (PET) degradation by metallic acetate ionic liquids

Poly(ethylene terephthalate) (PET) is widely used for beverage bottles, electrical and electronic instruments, household wares, and so on. As a consequence of dramatically increasing consumption, recycling of post-consumer PET products has become an important environmental opportunity for sustainable usage in society. In this paper, we investigated the use of chlorine-free metallic acetate ionic liquids (ILs) as catalysts for the degradation of PET because of their lower toxicity, corrosivity, and cost. 1,3-Diethylimidazolium triaceticzincate ([deim][Zn(OAc)3]) behaved as the best in this group. The synthesized ILs and the major product, characterized by a variety of techniques and factors affecting glycolysis, were examined. Under optimum conditions, conversion of PET reached 98.05 %, and the selectivity of the bis(hydroxyethyl) terephthalate (BHET) monomer was 70.94 %. A probable mechanism for the glycolysis of PET catalyzed by [deim][Zn(OAc)3] was given. In our opinion, catalysis accounted for the synergic effect of the cation and anion of the IL.

Catalytic hydrorefining of tar to liquid fuel over multi-metals (W-Mo-Ni) catalysts

In the perspective of fossil fuel depletion, the importance of renewable and substitute fuels is remarkable. In this study, clean liquid-fuel was obtained from tar through catalytic hydrorefining method. Hydrorefining catalysts were prepared by impregnation, containing tungsten-nickel (W-Ni), molybdenum-nickel (Mo-Ni), tungsten-molybdenum-nickel (W-Mo-Ni), and tungsten-molybdenum-cobalt (W-Mo-Co). γ-alumina was used as catalysts supporter. The clean liquid fuel product was analyzed by Fourier transform infrared spectroscopy, gas chromatography-mass spectrometry, elemental analyzer, octane number for gasoline fraction and cetane-number for diesel fraction, and Engler distillation range. The rules of sulfur and nitrogen content were also investigated. The overall product yield was up to 97%, and the sulfur and nitrogen content was less than 70 ppm. The W-Mo-Ni/γ-Al2O3 catalyst showed high performance in catalytic hydrofinishing and good stabilization under required conditions.

Polymer dots grafted TiO2 nanohybrids as high performance visible light photocatalysts

As a new member of carbon dots (CDs), Polymer dots (PDs) prepared by hydrothermal treatment of polymers, usually consist of the carbon core and the connected partially degraded polymer chains. This type of CDs might possess aqueous solubility, non-toxicity, excellent stability against photo-bleaching and high visible light activity. In this research, PDs were prepared by a moderate hydrothermal treatment of polyvinyl alcohol, and PDs grafted TiO2 (PDs-TiO2) nanohybrids with TiOC bonds were prepared by a facile in-situ hydrothermal treatment of PDs and Ti (SO4)2. Under visible light irradiation, the PDs-TiO2 demonstrate excellent photocatalytic activity for methyl orange degradation, and the photocatalytic rate constant of PDs-TiO2 is 3.6 and 9.5 times higher than that of pure TiO2 and commercial P25, respectively. In addition, the PDs-TiO2 exhibit good recycle stability under UV-Vis light irradiation. The interfacial TiOC bonds and the π-conjugated structures in PDs-TiO2 can act as the pathways to quickly transfer the excited electrons between PDs and TiO2, therefore contribute to the excellent photocatalytic activity.

Effect of Structural and Lattice Oxygen Changes on the Properties of CuO/CeO2 Catalysts for High-Temperature Water-Gas Shift of H-2-rich Coal-Derived Synthesis Gas

Abstract A series of CeO2-based Cu catalysts was synthesized by the co-precipitation method. BET, N2O decomposition, XRD, TEM, EDS, Raman spectroscopy, H2-TPR, and XPS were used to characterize the catalysts. The catalytic activity was tested in terms of CO conversion and H2 selectivity in a H2-rich coal-derived synthesis gas. The effects of the copper content and the calcination temperature on the catalytic activity were investigated. A strong surface structure-activity relationship in the water-gas shift (WGS) reaction was observed for all the catalyst samples. With increasing CuO loading, the portion of finely dispersed CuO nanoparticles decreased. By contrast, increasing calcination temperature reduced the BET surface area and reducibility, as induced by CuO agglomeration, resulting in a negative effect on H2 production. The distinctive dependence of the WGS activity on the surface lattice oxygen and active oxygen vacancy of the examined solids was observed and investigated for all the CuO/CeO2 catalysts.

An ionic liquid catalyzed probase method for one-pot synthesis of α,β-unsaturated esters from esters and aldehydes under mild conditions

A one-pot synthesis of α,β-unsaturated esters from unactivated esters and aldehydes using strong bases, such as sodium alkoxide and potassium tert-butoxide, was reported. However, the ionic liquid (IL) catalyzed probase method for producing α,β-unsaturated esters was not reported until now. In this work, a series of ILs with fluoride anions were firstly prepared and used as catalysts in combination with the probase N,O-bis(trimethylsilyl) acetamide (BSA) for the α,β-unsaturated esters synthesis. This process could also be promoted through the introduction of another IL with Lewis acid sites. The yield and selectivity of the product could reach up to 84.2% and 95.0%, respectively, when [Bmim]F was used in combination with [Bmim]Cl/AlCl3 (the molar fraction of AlCl3 is 0.67). The mechanism investigation through GC-MS indicates that BSA would convert into onium amide, which acted as a strong base for α-H abstraction, with the catalysis of [Bmim]F. Meanwhile, [Bmim]Cl/AlCl3 played an important role in the condensation step between enolates and aldehydes. On the basis of mechanism insights, kinetic and thermodynamic studies were also carried out for a better understanding of this new route.

Study on the hydrotreatment of C9 aromatics over supported multi-metal catalysts on gamma-Al2O3

With the dramatic increasing of economy, the conflict between the lack of petroleum resource and sharply increasing demand for gasoline and diesel has restricted the continuous development of economy and energy of our world. The catalytic conversion of C9 aromatics into clean fuel was studied in our laboratory using hydrotreating catalysts which were prepared by new synthesis technologies that combine vacuum-impregnation and temperature-programmed calcinations. Characterization results indicate that these catalysts have a high surface area, and the activity sites dispersed well on the supporter. Hydrogenation performance of reaction conditions was carried out in two-stage fixed beds. Products of gasoline (<180 °C) and diesel (180–360 °C) fractions were separated from intermediate products via distillation, and the analysis results demonstrate that S/N content, density, and viscosity decreased. However, the H/C molar ratio increased. The main reactions of isomerization, disproportionation, and dealkylation occurred during the conversion of C9 aromatics and the activity order accorded the mechanism of carbenium ion reaction. This study indicates that C9 aromatics could be considerably upgraded through catalytic hydroprocessing to high-quality fuel in the presence of high-performance catalysts and appropriate reaction conditions. Thus, they are promising catalytic technologies and materials. Furthermore, the products could substitute gasoline and diesel partly.

N-Nitro-1H-pyrrole-2-carboxamide.

In the title compound, C5H5N3O3, the nitro group is twisted with respect to the amide group, with C—N—N—O torsion angles of 29.0 (2) and −153.66 (14)°. In the crystal, molecules are linked through intermolecular N—H⋯O and C—H⋯O hydrogen bonds, forming supramolecular chains along the a axis. These chains stack in parallel and form distinct layer motifs in the (001) plane.