Metal phosphate-supported RuO x catalysts for N 2 O decomposition

Potassium promoted Gd0.06Co catalysts for highly efficient catalytic N2O decomposition in presence of impurity gases at low temperature

In order to enhance the catalytic performance of the Gd-modified Co₃O₄ catalyst (Gd_0.06Co) for the N₂O decomposition, alkali metal K was introduced as the promoter by impregnating the Gd_0.06Co powder with an aqueous solution of KNO₃ (with K/Co ratios 0.01-0.05). With the doping of K, the catalytic activity over Gd_0.06Co was significantly improved and the temperature of N₂O complete decomposition was decreased from 350 °C to 300 °C. Combining the results of XPS and O₂-TPD, the superior catalytic performance of the optimum catalyst K_0.025Gd_0.06Co was mainly owing to the synergistic effect of Gd and K, which weakened the Co-O bond and endowed the catalyst surface with much more amount of oxygen vacancies. Even under the coexist of the impurity gases, such as 5 vol% O₂, 100 ppmv NO and 2 vol% H₂O, the K_0.025Gd_0.06Co catalyst exhibited prominently better catalytic activity than Gd_0.06Co and K_0.025Co catalysts.

Vapour-Phase Selective O-Methylation of Catechol with Methanol over Metal Phosphate Catalysts

Guaiacol (2-methoxyphenol), an important fine chemical intermediate, is conventionally synthesized by liquid-phase processes with expensive, corrosive and toxic methylating agents such as dimethyl sulphate and dimethyl iodide. Recently, vapour-phase alkylation of catechol (1, 2-dihydroxybenzene) with methanol for the synthesis of guaiacol in the presence of heterogeneous catalysts has received more attention, as the route is economical and environmentally friendly. However, most of the investigated catalysts exhibited unsatisfactory catalytic performance for industrial applications. In this study, five metal phosphates M-P-O (M = La, Ce, Mg, Al, Zn) catalysts were synthesized and tested in the selective O-methylation of catechol with methanol. Among these catalysts, cerium phosphate (CP) showed the highest catalytic activity and guaiacol yield. Lanthanum phosphate (LP) was the second most active, which was still obviously better than magnesium phosphate (MP) and aluminium phosphate (ALP). Zinc phosphate (ZP) was not active in the reaction. Relevant samples were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), scanning electron microscopy (SEM), N2 adsorption-desorption, temperature programmed desorption of NH3 or CO2 (NH3-TPD, CO2-TPD). The suitable acid-base properties contribute to the superior catalytic performance of CP. Long-term stability and regeneration tests were also studied.