Liquid phase oxidation of cyclohexane was carried out under mild reaction condition over copper pyrophosphate catalyst in CH3CN using hydrogen peroxide as an oxidant at the temperature between 25 and 80 °C. The copper pyrophosphate catalyst was characterized by means of XRD, FT-IR and water contact angle measurement. It was found that appropriate surface hydrophobicity is the key factor for the excellent performance of the catalyst. In addition, a significant improvement for the cyclohexane conversion in the presence of organic acid was observed.Liquid phase oxidation of cyclohexane was carried out over copper pyrophosphate catalyst using hydrogen peroxide as an oxidant in CH3CN at the temperature between 25 and 80 °C. It was found that appropriate surface hydrophobicity is the key factor for the excellent performance of the catalyst. Additionally, a significant improvement for the cyclohexane conversion in the presence of organic acid was observed.

It is reported that cyclic voltammetry (CV) is a strong tool to investigate catalytic reactions not only in homogeneous catalysis, but also in heterogeneous catalysis. The application of CV measurements in homogeneous catalysis is illustrated through investigation of NO removal (NO reduction and decomposition), which is an urgent task of today in environment catalysis. Results of our study indicate that both the area of redox peak and the symmetry of redox potentials of catalyst are important parameters in determining the catalytic activity, but each has his strong point in different reactions (NO reduction and decomposition). We suggest that CV is a powerful means to select catalysts for NOx removal.

Compound of La2−xSrxCuO4 (x ≥ 0.5) with T* phase structure were prepared by conventional citric method. The split peak at 2θ = ∼31° in XRD patterns and the broad absorption band at 680 cm−1 with a shoulder peak at 620 cm−1 in IR spectra suggested the formation of T* phase in La2−xSrxCuO4 compounds at x ≥ 0.5. The amount of sample with T* phase structure increased with the increase of Sr content as certified by XRD patterns. Catalytic performance of La2−xSrxCuO4 for NO decomposition was investigated, and it was found, by correlating the solid-state properties and the activity of NO decomposition, that the presence of T* phase structure enhanced the catalytic activity of La2−xSrxCuO4 in NO decomposition.

Catalytic reduction of NO by CO was studied over perovskite-like La2−xSrxCuO4 (x = 0.0, 0.5, 1.0) catalysts prepared by citrate method and calcined at 900 °C. The catalysts were characterized by O2-TPD, H2-TPR and cyclic voltammetry (CV) measurements. Results obtained from CV were in well agreement with those obtained from O2-TPD and H2-TPR, suggesting that CV is also a powerful means in the study of heterogeneous catalytic reaction carried out at high temperatures. In O2-TPD experiment, the desorption area of β oxygen, which was contributed by the oxygen adsorbed on the oxygen vacancy, increased with the increase of Sr content and was in the same order as the activity, indicating that the activity depended largely on the oxygen vacancy resulted by Sr addition. In H2-TPR measurements, the increasing area of the first reduction peak indicating that the oxygen vacancy resulted by Sr addition plays important role in this peak, since the Cu3+ content in La1.5Sro.5CuO4 and LaSrCuO4 is the same. And in the CV curves, the area of redox peak, which represents the amount of oxygen vacancy participating in the reaction, has close correlations with the activity of NO + CO reaction, while the symmetry of redox potentials does not contribute much to the activity. Overall, with the link of oxygen vacancy, CV was introduced and has obtained great success in explaining reaction in heterogeneous catalysis. Besides, from the result that none reductive peak was observed in the first CV curves of LaSrCuO4, it suggested that the first step of a catalytic reaction is reduction, corresponding to the oxidation of catalyst i.e., Mn+(Cu2+) → M(n+1)+(Cu3+).With the link of oxygen vacancy, CV was introduced and has obtained great success in explaining reaction in heterogeneous catalysis.

Perovskite-type oxide La0.4Sr.6Mn0.8Ni0.2O3 showed high activity for NO decomposition and thus was taken as the catalyst for investigation. Based on the ‘recycle’ mechanism of NO decomposition (NO2 acts as an intermediate of O2 formation) we reported recently, the kinetics of NO decomposition over La0.4Sr.6Mn0.8Ni0.2O3 was investigated. The NO decomposition rate was practically first-order for NO in the range 0.5–2.0 vol.% NO/He, while the reaction order varied from −0.24 to −0.08 for O2 (0–6 vol.% O2/He), depending on the temperature. The kinetics deduced from the ‘recycle’ mechanism accords well with that observed in practice by introducing the item K−6 (K−7)1/2PNO (PO2PO2)1/2, which reflects the reciprocity of O2 and NO in the reaction and is introduced in the kinetics for the first time. The rates and NO2 dissociation equilibrium constants calculated from the practical reaction certified that NO2 dissociation is indeed an important step of NO decomposition, and hence suggested that the ‘recycle’ mechanism is believable.The kinetic equation of NO decomposition over perovskite-type oxide is deduced. The reaction order for NO is 1 in the range 0.5–2.0 vol.% NO/He, while it varies from −0.24 to −0.08 for O2 (0–6 vol.% O2/He), depending on the temperature. The item K−6 (K−7)1/2PNO (PO2PO2)1/2, which reflects the reciprocity of O2 and NO in the reaction, is introduced in the kinetics for the first time.r=k3K1K2PNO2[L]1+K1PNO+(K−5K−6K−71/2/K1)PO21/2+K−6K−71/2PNOPO21/2

Effect of cerium ions on the activity of La1−xCexSrNiO4 (0 ≤ x ≤ 0.3) for NO decomposition was investigated both in the absence and presence of oxygen. The amount of Ce in the frame reached 30 at.% (x = 0.3) in the present case without destroying the matrix structure. The Ce-substituted samples showed high activity for NO decomposition not only in the absence of O2 but also in the presence of O2, and the specific activity reached 1.59 μmol s−1 m−2 even 6.0%O2 was fed to the reactant gas (La0.7Ce0.3SrNiO4, T = 1123 K), indicating that the Ce addition can enhance the oxygen forbearance of catalyst. In addition, a new highly active site, which facilitates oxygen mobilization and desorption, might be formed in the sample due to the Ce addition, which thus resulted in the high activity for NO decomposition.Ce added catalysts La1−xCexSrNiO4 (0 ≤ x ≤ 0.3) showed high activity for NO decomposition even in the presence of excess oxygen, due to the formation of the new highly active site: Ce3+-(O)-(Ni2+-[ ]-Ni3+).