Can Ultrasound or pH Influence Pd Distribution on the Surface of HAP to Improve Its Catalytic Properties in the Dry Reforming of Methane?

The influence of ultrasound and different pH pre-treatments during the metal doping/modification of a hydroxyapatite (HAP) support is investigated. HAP is first synthesised via a hard-template synthetic route using carbon nanorods followed by their full physiochemical characterisation. The HAP was found to be crystalline and comprised a mesoporous structure as observed via XRD and nitrogen adsorption with a BET surface area of 97.57 (±1.16) m2 g−1. Ultrasound-assisted ion exchange (IE) and incipient wetness impregnation (IW) methodologies were employed to decorate the surface of HAP with Pd0 and are compared to previous procedures. The influence of pH upon the distribution of Pd0 throughout the samples during the doping process is also studied. All the prepared samples were evaluated for their catalytic activity towards dry reforming of methane (DRM) and the reaction was monitored via a thermal conductivity detector, coupled with gas chromatography (GC-TCD). It was found that ultrasound-assisted IE significantly accelerated the process from 3 days to 3 h and with the Pd0 metal remaining highly distributed upon the HAP with minor changes in catalytic conversions. Moreover, the ultrasound-assisted IW method successfully improved the Pd0 distribution and catalytic performance. On the other hand, the dispersion of the metal was unaffected after pH treatments in IE with no catalytic improvements observed, in contrast to IW, where considerable increase in metal distribution and subsequently catalytic performance was observed

Active Mn species well dispersed on Ca 2+ enriched apatite for total oxidation of toluene

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Production of hydrogen by methane dry reforming over ruthenium-nickel based catalysts deposited on Al2O3, MgAl2O4, and YSZ

In this work, monometallic (1 wt% of Ru or 5 wt% of Ni) and bimetallic catalysts (1 wt% Ru-5 wt.% Ni) deposited on alumina (Al2O3), magnesium aluminate spinel (MgAl2O4), and yttriastabilized zirconia (YSZ) were prepared by wet impregnation. The synthesis method of MgAl2O4 was optimized and a well crystallized phase with high specific surface area was obtained by using wet impregnation, as a simple and low cost route, at 800 °C for 2 h. The catalytic activity was compared at atmospheric pressure and 750 °C toward methane dry reforming (DRM) reaction with a molar ratio CH4/CO2 ¼ 1/1 and a Weight Hourly Space Velocity (WHSV) of 60.000 mL g-1.h-1. Catalytic activity classification was obtained as the following: Ni/MgAl2O4 > Ru-Ni/ Al2O3 > Ru-Ni/MgAl2O4 > Ru-Ni/YSZ > Ni/Al2O3 > Ni/YSZ > Ru/Al2O3 > Ru/YSZ » Ru/MgAl2O4. Between the different catalysts, 5 wt% Ni/MgAl2O4 catalyst exhibited excellent catalytic activity for DRM. Furthermore, this catalyst was found to be very stable without any deactivation after 50 h under reacting mixture with a low carbon formation rate (3.58 mgC/gcat/h). Such superior activity and stability of MgAl2O4 supported Ni catalyst is consistent with characterization results from BET, XRD, TPR, CO-pulse chemisorption and CHNS analysis. It can be due to a strong interaction between Ni and MgAl2O4 leading to theincorporation of Ni into the spinel lattice and the formation of oxygen vacancies offering a benefit for DRM reaction. Furthermore, it seems that the addition of ruthenium onto Ni/MgAl2O4 decreases the interaction between Ni and the spinel leading to a decrease in the catalyst performance. On the other side, the addition of ruthenium on Ni/Al2O3 leads to an increase in the catalyst stability and efficiency by inhibiting the formation of poorly active phase NiAl2O4 already observed in TPR

Production of hydrogen by methane dry reforming: A study on the effect of cerium and lanthanum on Ni/MgAl2O4 catalyst performance

Hydrogen production from dry reforming of methane (DRM) was investigated on different Nickel based catalysts deposited on MgAl2O4. MgAl2O4 spinel was prepared using Alumina supplied from different manufacturers (Sigma Aldrich, Alfa Aesar and Degussa) with low and high specific surface area. Moreover, the influence of different parameters on the catalytic activity on methane dry reforming was studied such as the effect of Ni content, the effect of commercial alumina and the effect of doping nickel with cerium and lanthanum. During this study, the catalytic activity was compared at atmospheric pressure at 750 °C during 4h than 650 °C during 4h toward methane dry reforming (DRM) reaction with a molar ratio CH4/CO2 =1/1 and a Weight Hourly Space Velocity (WHSV) of 60.000 mL.g-1.h-1. The results showed that among the different catalysts 1.5Ce-Ni5/MgAl2O4, synthesized with alumina from Alfa Aesar, exhibited the best catalytic activity for DRM. Furthermore, this catalyst showed the best performance during a stability tes at 600 °C for 24 h under reacting mixture with a low carbon formation rate (2.71 mgC/gcat/h). Such superior activity is consistent with characterization results from BET, XRD, SEM, TPR and TPO analysis. Furthermore, it seems that the addition of Cerium on Ni/MgAl2O4 leads to an increase in catalyst efficiency. It can be due to an effective active oxygen transfer due to the redox properties of CeO2, leading to the formation of oxygen vacancies offering a benefit for DRM reaction