Chunshan Lu

Aqueous system for the improved hydrogenation of phenol and its derivatives

The hydrogenation of phenol to cyclohexanol under mild conditions (∼340 K) was achieved over Raney Ni catalyst in the aqueous phase. The adsorption–desorption properties of the reactants (phenol and H2) and the products (cyclohexanone and cyclohexanol) on the Raney Ni catalyst are different in the aqueous phase and the organic phase. The hydrogenation rate of phenol is improved because the Raney Ni catalyst adsorbs more H2 and phenol in water than in methanol. Meanwhile, the higher uptakes of H2 and the lower desorption rates for cyclohexanone on the Raney Ni catalyst in the aqueous system result in the further hydrogenation of cyclohexanone to cyclohexanol.

A phosphorus–carbon framework over activated carbon supported palladium nanoparticles for the chemoselective hydrogenation of para-chloronitrobenzene

A novel Pd–P–C framework structure was fabricated by supporting Pd on a P-doped carbon layer coated with activated carbon. A P-doped carbon layer was generated via calcination of sodium hypophosphite and ethanediol under inert gas atmosphere. The catalysts were characterized by Brunauer–Emmett–Teller (BET) analysis, X-ray diffraction (XRD), transmission electron microscopy (TEM), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) and were evaluated in the selective hydrogenation of p-CNB to p-CAN. The results indicate that the carbon layer generated via calcination of ethanediol presents a higher disordered structure and then the P-doped carbon layer becomes more ordered due to the formation of a P–C framework. Some electrons were transferred from C atoms adjacent to the P atoms to P atoms, which favors the formation of stable Pd–P species such as the Pd15P2 phase. Pd in the Pd–P–C framework structure possesses electron-rich properties resulting from electron transfer from C atoms to Pd atoms via P atoms, which induces the formation of electron-rich hydrogen (H−) when hydrogen was absorbed on the Pd particles. The produced electron-rich H− might prefer the nucleophilic attack on the nitro group rather than the electrophilic attack on the C–Cl bond. We suggest that it is responsible for the superior selectivity of up to 99.9% to p-CAN for the hydrogenation of p-CNB. The catalytic performance of the Pd particles supported on the P-doped carbon layer remains unchanged after five cycles indicating excellent stability.

N-Heterocyclic carbene catalyzed direct carbonylation of dimethylamine

N-Heterocyclic carbene (NHC) catalyzed direct carbonylation of dimethylamine leading to the formation of DMF was successfully accomplished under metal-free conditions. The catalytic efficiency was investigated and the turnover numbers can reach as high as >300. The possible mechanism was also proposed.

Cu–Pd/γ-Al2O3 catalyzed the coupling of multi-step reactions: direct synthesis of benzimidazole derivatives

The coupling of multi-step reactions catalyzed by a heterogeneous catalyst is an important path to accomplish some unconventional chemical transformations. Since the starting materials generated from previous steps were adsorbed on the catalyst, the activation energy of following steps was largely decreased, and thus the reaction conditions were more mild and environmental friendly. Catalyzed by a multifunctional Cu–Pd/γ-Al2O3 catalyst, the transfer hydrogenation and successive cyclization coupling reaction from o-nitroaniline and alcohol to afford benzimidazole derivatives in high yield was realized. The catalyst could be reused several times without loss of activity. The synergies of reforming hydrogenation of Cu–Pd bimetal and support acidity of γ-Al2O3 were responsible for this catalytic transformation.

Preparation of supported core–shell structured Pd@PdxSy/C catalysts for use in selective reductive alkylation reaction

Supported noble-metal sulphide catalysts have attracted extensive scientific interest for their good selectivity in selective hydrogenation. However, the application of noble-metal catalysts is limited due to their lower activity, leading to harsh reaction conditions and poor conversion during hydrogenation reactions. In this study, Pd/C was sulphidized by H2S to prepare a series of core–shell structured Pd@PdxSy/C catalysts, which were characterized by BET, EDS, XPS, XRD and CO chemisorption to investigate the influences of sulphidation temperature, sulphidation time and sulphidation atmosphere on the structure of the resulting catalysts. The sulphidation of Pd/C at low temperatures resulted in a core–shell structured catalyst, Pd@PdxSy/C; with increasing sulphidation temperature, the size of Pd0 as the core decreased, and the thickness of palladium sulphides as the shell increased correspondingly. When the sulphidation temperature reached 150 °C, the resulting catalyst transformed to a complete palladium sulphide catalyst, PdxSy/C. The structure of Pd@PdxSy/C sulphidized at 30 °C was independent of sulphidation time and sulphidation atmosphere. The sulphidized catalysts were applied to the reductive alkylation of PADPA and MIBK to DBPPD. The sulphidized catalysts presented a much higher selectivity for DBPPD compared with Pd/C, and Pd@PdxSy/C showed higher activity than PdxSy/C; moreover, the greater amount of PdxSy content in the resulting catalyst led to a lower activity.

Mesoporous carbon nitride as a basic catalyst in dehydrochlorination of 1,1,2-trichloroethane into 1,1-dichloroethene

1,1-Dichloroethene has many applications in industrial production and it holds great promise in developing a vapor phase catalytic dehydrochlorination process. We synthesized a carbon nitride material by dissolving dicyandiamide in N,N-dimethylformamide (DMF) as a precursor and using SBA-15 as a template. A carbon nitride material with a mesoporous structure and textured pores has been obtained and then characterized by N2-adsorption measurements, XRD, HRTEM, EDS and FT-IR. A mesoporous carbon nitride material with a surface area of 350 m2 g−1 and pore volume of 0.72 cm3 g−1 was fabricated, which also possessed triazine N heterocycles with extra amino groups. It is an outstanding heterogeneous base catalyst in the selective catalytic dehydrochlorination of 1,1,2-trichloroethane into 1,1-dichloroethene reaction with a maximum 1,1,2-trichloroethane conversion of 23.96% and maximum 1,1-dichloroethene selectivity of 100%. A total of 110 h stability experiment of the catalyst was provided and the selectivity stayed above 99% all through the experiment and the conversion remained no less than 15% for 35 h.

Thermal oxidation to regenerate sulfone poisoned Pd-based catalyst: effect of the valence of sulfur

Sulfur deactivation is a serious problem which largely limits the industrial application of noble metals as catalysts. Here we report a thermal oxidation method to regenerate sulfone poisoned Pd/C catalyst applied in the hydrogenation of sodium-m-nitrobenzene sulfonate (SNS). It was found that the initial activity of Pd/C catalyst could be substantially recovered after treating it in air at temperatures as low as 100 °C. And the catalyst could be reused for at least 20 times without the significant loss of activity. The properties of deactivated and regenerated catalysts were studied in detail by BET measurement, X-ray photoelectron spectroscopy (XPS), temperature programmed desorption (TPD), and Fourier transform infrared spectroscopy (FT-IR). The results indicated that the main surface sulfur species found on deactivated and regenerated Pd surfaces were Sn and sulfate (SO4), respectively. The change of the valence of sulfur species was found to be the key factor influencing the catalytic activity of the Pd-based catalyst.

Ir/C and Brφnsted acid functionalized ionic liquids: an efficient catalytic system for hydrogenation of nitrobenzene to p-aminophenol

In this study, we found that the phenylhydroxylamine intermediate could desorb more easily from an Ir surface than from a Pt surface, which is beneficial for inhibiting the over-hydrogenation of phenylhydroxylamine to aniline. On the other hand, the Brφnsted acid functionalized ionic liquids with sulfonic acid and bisulfate anions were acidic enough to catalyze the Bamberger rearrangement to form p-aminophenol from phenylhydroxylamine. On this basis, a new catalytic system constructed by Ir/C and Brφnsted acid functionalized ionic liquid was applied, for the first time, to the one-pot hydrogenation of nitrobenzene to p-aminophenol. Our results indicate that the PAP selectivity of Ir/C and [SO3H-bmim][HSO4] Brφnsted functionalized ionic liquid was far more than that of the traditional Pt/C and sulfuric acid catalyst system. Furthermore, the dually functionalized ionic liquid ([HSO3-b-N-Bu3][HSO4]) can be used simultaneously as an acid catalyst and also as a surfactant, due to its higher lipophilicity. Therefore, our new catalytic system has unique advantages in the hydrogenation of nitrobenzene to p-aminophenol.