Pingping Jiang

An α-MnO2 nanotube used as a novel catalyst in ozonation: performance and the mechanism

As a common monocomponent metal oxide, an α-MnO2 nanotube was synthesized by a simple hydrothermal method and developed as an ozonation catalyst for the first time. α-MnO2 nanotubes revealed excellent catalytic activity and stability for degradation of phenol in water. The strong interaction between ozone and α-MnO2 in water was observed and confirmed as a critical step of catalysis. The IR analysis and the influence of phosphate showed that the surface hydroxyl groups and chemisorbed water acted as the active sites in promoting active oxygen species, while Lewis acid sites were confirmed as reactive centers for catalytic ozonation in the aqueous phase. The ˙OH, O2˙−, *O2 and *O were not mainly involved in the catalytic ozonation of phenol based on the corresponding experimental results. According to the X-ray photoelectron spectroscopy (XPS) results, in the presence of α-MnO2, electrons from the surface Mn(III) were responsible for the catalysis and the oxidation of lattice oxygen enhanced the reversion of Mn(IV) to Mn(III). The balance between Mn(III)/Mn(IV) and O(–II)/O(0) was the primary factor for the catalytic performance of α-MnO2.

Synthesis of novel dicationic basic ionic liquids and its catalytic activities for biodiesel production

Biodiesel produced by transesterification of vegetable oils or animal fats is a potential alternative fuel to diesel, given the limited resources of fossil fuel and its environmental concerns. Three novel dicationic basic ionic liquids (DBILs) have been prepared for synthesis of biodiesel from soybean oil. Among them, 1, 2-bis (3-methylimidazolium-1-yl) ethylene imidazolide performed best and the yield of biodiesel reached 99.6%, which was related to the basicity and miscibility properties of the IL.

A polyhedral oligomeric silsesquioxane (POSS)-bridged oxo-molybdenum Schiff base complex with enhanced heterogeneous catalytic activity in epoxidation

We have generated a new heterogeneous catalyst by bridging an oxo-molybdenum Schiff base on a polyhedral oligomeric silsesquioxane (POSS) via covalent attachment. The resulting POSS-bridged oxo-molybdenum Schiff base complex catalyst was fully characterized by 1H NMR, XRD, FT-IR, SEM, TGA, and contact angle analysis, and its catalytic potential was studied for the epoxidation of alkenes using aqueous tert-butyl hydroperoxide (TBHP) as the oxidant. The catalyst was found to be highly efficient and showed higher catalytic reactivity than the corresponding homogeneous analogues with added benefits of facile recovery and recycling of the heterogeneous catalyst. The POSS-bridged oxo-molybdenum Schiff base complex was successfully reused for four runs without significant loss in activity. The unique three dimensional network catalyst structure and the hydrophobic properties of the POSS units in the catalyst are revealed to be responsible for the catalysts excellent performance in epoxidation reactions.

An insight into the kinetics and interface sensitivity for catalytic ozonation: the case of nano-sized NiFe2O4

In this paper, the kinetics and interface sensitivity of nano-sized magnetic NiFe2O4 in incomplete catalytic ozonation were investigated in detail. By analyzing the kinetics of heterogeneous reactions, it was found that both the degradation of phenol and the decomposition of molecular ozone appeared to follow a first order kinetics model and the presence of nano-NiFe2O4 significantly enhanced these processes. The kinetics equations and reaction rate constants were determined according to experimental results. In light of the IR spectra, the Lewis acid sites were further confirmed as reactive centers for catalytic ozonation in the aqueous phase, and the reason for deactivation of the NiFe2O4 nanocatalyst during incomplete ozonation of organic compounds was determined. The catalytic activity of the NiFe2O4 nanocatalyst could be completely recovered by calcination and ozonation methods, which makes it an attractive nanomaterial with prospective applications in water treatment. According to the interface sensitivity of ozone in water, a strong interaction between ozone and NiFe2O4 was observed and the role of water was revisited. Water molecules were clarified as two different types: one is chemisorbed water on the catalyst surface and the other is bulk water in aqueous solution. Both bulk and chemisorbed water molecules should be weak competitors compared with ozone, and the chemisorbed water on the catalyst surface was proposed not as an inhibitor but an accelerator for catalytic activity.

Heteropolyanion-based polymeric hybrids: highly efficient and recyclable catalysts for oxidation of alcohols with H2O2

New heteropolyanion-based polymeric hybrids prepared by the anion-exchange of newly task-specific designed ionic copolymers with Keggin heteropolyacids are revealed to be highly efficient, conveniently recoverable, and steadily reusable catalysts for the oxidation of alcohols with H2O2.

A high-surface-area mesoporous sulfated nano-titania solid superacid catalyst with exposed (101) facets for esterification: facile preparation and catalytic performance

In this paper, a high-surface-area mesoporous sulfated nano-titania exposed with (101) facets was prepared by a simple hydrothermal method without any template followed by surface sulfate modification. The physicochemical properties of the as-prepared catalyst were well characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), Raman spectroscopy (Raman), Fourier transform infrared spectroscopy (FTIR), N2 adsorption–desorption isotherms, temperature programmed desorption of NH3 (NH3-TPD), X-ray photoelectron spectroscopy (XPS) and pyridine adsorption infrared spectroscopy. The BET surface area of sulfated nano-titania with exposed (101) facets was 121 m2 g−1. Well dispersed bidentate sulfate groups were linked to the exposed (101) facets of anatase nano-titania. Acid sites with moderate- and superacidic strength formed in the sulfated titania catalyst. Also, the as-prepared sulfated sample possessed both Lewis and Bronsted acid sites. The catalytic activity of sulfated nano-titania with exposed (101) facets was evaluated using the esterification reaction between acetic acid and n-butanol. It was found that the yield of butyl acetate increased to about 92.2% in the presence of the catalyst. Compared with the exposed (001) facets, the exposed (101) facets showed better catalytic activity of sulfated TiO2 in esterification. The effects of different reaction conditions were discussed in detail. Additionally, the as-prepared sulfated sample could be efficiently recycled and regenerated by simple soaking in sulfuric acid followed by calcination.

A novel method to reduce the influence of by-product water on the catalytic performance of PdCl2/Cu-HMS catalysts for the synthesis of diethyl carbonate

A novel method to synthesise diethyl carbonate is introduced by the coupling reaction, the hydrolysis of diethyl ether (DEE) and oxidative carbonylation of ethanol, which reduces the influence of by-product water and satisfies the energy coupling for the reaction system.