Stabilizing effect of α-Cr2O3 on highly active phases and catalytic performance of a chromium alumina catalyst in the process of isobutane dehydrogenation

he demand for C3-C5 olefins is constantly growing, that is why it is important to improve the performance of catalysts for dehydrogenation of light alkanes. The study regards the influence of the supports porous system, the contribution of α-Cr2O3 particles to the state of the active phase and the catalytic performance of the chromiaalumina catalysts in the isobutane dehydrogenation reaction. The catalysts were synthesized by impregnating the support with chromic acid. The supports and the catalysts were studied by the following techniques: lowtemperature nitrogen adsorption, temperature-programmed desorption and reduction; UV-Vis- and Ramanspectroscopy, X-ray phase and X-ray fluorescence analyses. It was found that crystals of α-Cr2O3 are formed on a support with 56 m2/g specific surface area and 7.1% (m/m) chromium content, that contributes to stabilization of the particles of highly active phases of amorphous Cr2O3 and polychromates and catalytic performance. Meanwhile, no α-Cr2O3 particles are formed on a support with a 103 m2/g specific surface area and 7.4% (m/m) chromium content. Therefore, in the course of 54 regeneration reactions cycles, the rates of isobutylene formation and isobutylene selectivity are significantly reduced due to agglomeration of amorphous Cr2O3 particles, formation of di-, tri- chromates, and migration of part of chromium into the support structure111610-11161

Synthetic Tuning of CoII-Doped Silica Nanoarchitecture Towards Electrochemical Sensing Ability

The present work introduces both synthesis of silica nanoparticles doped with CoII ions by means of differently modified microemulsion water-in-oil (w/o) and Stöber techniques and characterization of the hybrid nanoparticles (CoII@SiO2) by TEM, DLS, XRD, ICP-EOS, SAXS, UV-Vis, and UV-Vis/DR spectroscopy and electrochemical methods. The results reveal the lack of nanocrystalline dopants inside the hybrid nanoparticles, as well as no ligands, when CoII ions are added to the synthetic mixtures as CoII(bpy)3 complexes, thus pointing to coordination of CoII ions with Si-O- groups as main driving force of the doping. The UV-Vis/DR spectra of CoII@SiO2 in the range of d-d transitions indicate that Stöber synthesis in greater extent than the w/o one stabilizes tetrahedral CoII ions versus the octahedral ions. Both cobalt content and homogeneity of the CoII distribution within CoII@SiO2 are greatly influenced by the synthetic technique. The electrochemical behavior of CoII@SiO2 is manifested by one oxidation and two reduction steps, which provide the basis for electrochemical response on glyphosate and HP(O)(OEt)2 with the LOD = 0.1 μM and the linearity within 0.1–80 μM. The Stöber CoII@SiO2 are able to discriminate glyphosate from HP(O)(OEt)2, while the w/o nanoparticles are more efficient but nonselective sensors on the toxicants

Silica-Supported Assemblage of CuII Ions with Carbon Dots for Self-Boosting and Glutathione-Induced ROS Generation

The present work introduces coordinative binding of CuII ions with both amino-functionalized silica nanoparticles (SNs) and green-emitting carbon dots (CDs) as the pregrequisite for the CuII-assisted self-assembly of the CDs at the surface of the SNs. The produced composite SNs exhibit stable in time stimuli-responsive green fluorescence derived from the CuII-assisted assemblage of CDs. The fluorescence response of the composite SNs is sensitive to the complex formation with glutathione (GSH), enabling them to detect it with the lower limit of detection of 0.15 μM. The spin-trap-facilitated electron spin resonance technique indicated that the composite SNs are capable of self-boosting generation of ROS due to CuII→CuI reduction by carbon in low oxidation states as a part of the CDs. The intensity of the ESR signals is enhanced under the heating to 38 °C. The intensity is suppressed at the GSH concentration of 0.35 mM but is enhanced at 1.0 mM of glutathione, while it is suppressed once more at the highest intracellular concentration level of GSH (10 mM). These tendencies reveal the concentrations optimal for the scavenger or reductive potential of GSH. Flow cytometry and fluorescence and confocal microscopy methods revealed efficient cell internalization of SNs-NH2-CuII-CDs comparable with that of “free” CDs

Ex Situ Upgrading of Extra Heavy Oil: The Effect of Pore Shape of Co-Mo/γ-Al2O3 Catalysts

Co-Mo/γ-Al2O3 catalysts with different pore shapes were synthesized for the ex situ upgrading of extra heavy oils by hydrodesulfurization (HDS), hydrodemetallization (HDM), and hydrodeasphaltization (HDA). The catalysts were synthesized using aluminum oxides that were prepared by various methods. It was found that using the product obtained by the thermochemical activation of gibbsite leads to the formation of slit-shaped pores in aluminum oxide, while the application of the hydroxide deposition method by the precipitation of sodium aluminate and nitric acid gives cylindrical pores in aluminum oxide. Co-Mo catalysts synthesized using these two types of pores exhibit different catalytic activities. The catalyst synthesized on a carrier with cylindrical pores exhibited a higher catalytic activity in sulfur, heavy metals, and asphaltenes removal reactions that are synthesized on a carrier with slit-like pores. This is because the presence of cylindrical pores leads to a decrease in diffusion restrictions when removing large molecules of asphaltenes and sulfur-containing and metal-containing compounds

Ex Situ Upgrading of Extra Heavy Oil: The Effect of Pore Shape of Co-Mo/γ-Al₂O₃ Catalysts

Co-Mo/γ-Al2O3 catalysts with different pore shapes were synthesized for the ex situ upgrading of extra heavy oils by hydrodesulfurization (HDS), hydrodemetallization (HDM), and hydrodeasphaltization (HDA). The catalysts were synthesized using aluminum oxides that were prepared by various methods. It was found that using the product obtained by the thermochemical activation of gibbsite leads to the formation of slit-shaped pores in aluminum oxide, while the application of the hydroxide deposition method by the precipitation of sodium aluminate and nitric acid gives cylindrical pores in aluminum oxide. Co-Mo catalysts synthesized using these two types of pores exhibit different catalytic activities. The catalyst synthesized on a carrier with cylindrical pores exhibited a higher catalytic activity in sulfur, heavy metals, and asphaltenes removal reactions that are synthesized on a carrier with slit-like pores. This is because the presence of cylindrical pores leads to a decrease in diffusion restrictions when removing large molecules of asphaltenes and sulfur-containing and metal-containing compounds