Effect of CaO, Al2O3, and MgO Supports of Ni Catalysts on the Formation of Graphite-like Carbon Species during the Boudouard Reaction and Methane Cracking.

The investigation of the course of the Boudouard reaction and methane cracking was performed over nickel catalysts based on oxides of calcium, aluminum, and magnesium. The catalytic samples were synthesized by the impregnation method. The physicochemical characteristics of the catalysts were determined using atomic adsorption spectroscopy (AAS), Brunauer-Emmett-Teller method analysis (BET), temperature-programmed desorption of ammonia and carbon dioxide (NH3- and CO2-TPD), and temperature-programmed reduction (TPR). Qualitative and quantitative identification of formed carbon deposits after the processes were carried out using total organic carbon analysis (TOC), temperature-programmed oxidation (TPO), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The selected temperatures for the Boudouard reaction and methane cracking (450 and 700 °C, respectively) were found to be optimal for the successful formation of graphite-like carbon species over these catalysts. It was revealed that the activity of catalytic systems during each reaction is directly related to the number of weakly interacted nickel particles with catalyst support. Results of the given research provide insight into the mechanism of carbon deposit formation and the role of the catalyst support in this process, as well as the mechanism of the Boudouard reaction.

Influence of Lanthanum Precursor on the Activity of Nickel Catalysts in the Mixed-Methane Reforming Process.

This work investigated the influence of the catalytic support precursor on the activity of nickel catalysts 20%Ni/5%La2O3-95%Al2O3 in the mixed methane reforming process. The activity tests were carried out at a temperature of 750 °C. The research showed that the catalyst prepared from the precursor containing chloride exhibited very low conversions of methane and carbon dioxide. The poisoned catalyst system before and after the calcination process was subjected to Temperature Programmed Surface Reaction tests to determine whether the thermal treatment causes a decrease in the amount of chlorine in the system. To determine the decomposition temperature of the LaCl3 precursor and the nickel chloride NiCl2 compound, the samples were analyzed by Thermogravimetry. Finally, the catalytic samples were tested by Time-of-Flight Secondary Ion Mass Spectrometry analysis to confirm the presence of nickel-chlorine bonds on the surface of the catalytic system.

Effect of Ruthenium and Cerium Oxide (IV) Promotors on the Removal of Carbon Deposit Formed during the Mixed Methane Reforming Process.

This work investigates the effect of the addition of Ru and CeO2 on the process of gasification of carbon deposits formed on the surface of a nickel catalyst during the mixed methane reforming process. Activity studies of the mixed methane reforming process were carried out on (Ru)-Ni/CeO2-Al2O3 catalysts at the temperature of 650-750 °C. The ruthenium-promoted catalyst exhibited the highest activity. Carbonized post-reaction catalyst samples were tested with the TOC technique to investigate the carbonization state of the samples. The bimetallic catalyst had the lowest amount of carbon deposit (1.5%) after reaction at 750 °C. The reactivity of the carbon species was assessed in mixtures of oxygen, hydrogen, carbon dioxide, and water. Regardless of the gasifying agent used, the carbon deposit was removed from the surface of the catalytic system. The overall mechanism of mixed methane reforming over Ru and CeO2 was shown.

The Formation of Cr-Al Spinel under a Reductive Atmosphere.

In the present work, for the first time, the possibility of formation of CrAl2O4 was shown from the equimolar mixture of co-precipitated Al2O3 and Cr2O3 oxides under a reductive environment. The crystallographic properties of the formed compound were calculated using the DICVOL procedure. It was determined that it has a cubic crystal structure with space group Fd-3m and a unit cell parameter equal to 8.22(3) Å. The formed CrAl2O4 is not stable under ambient conditions and easily undergoes oxidation to α-Al2O3 and α-Cr2O3. The overall sequence of the phase transformations of co-precipitated oxides leading to the formation of spinel structure is proposed.