Modification of Cobalt Oxide Electrochemically Deposited on Stainless Steel Meshes with Co-Mn Thin Films Prepared by Magnetron Sputtering: Effect of Preparation Method and Application to Ethanol Oxidation

Magnetron sputtering is an advantageous method for preparing catalysts supported on stainless steel meshes. Such catalysts are particularly suitable for processes carried out at high space velocities. One of these is the catalytic total oxidation of volatile organic compounds (VOC), economically feasible and environmentally friendly method of VOC abatement. The reactive radio frequency (RF) magnetron sputtering of Mn and Co + Mn mixtures in an oxidation Ar + O2 atmosphere was applied to form additional thin oxide coatings on cobalt oxide layers prepared by electrochemical deposition and heating on stainless steel meshes. Time of the RF magnetron sputtering was changed to obtain MnOx and CoMnOx coatings of various thickness (0.1–0.3 µm). The properties of the supported CoOx–MnOx and CoOx–CoMnOx catalysts were characterized by scanning electron microscopy (SEM), powder X-ray diffraction (XRD), temperature programmed reduction (H2-TPR), Fourier-transform infrared (FTIR) and Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). The catalytic activity was investigated in the deep oxidation of ethanol, which was employed as a model VOC. According to the specific activities (amount of ethanol converted per unit mass of metal oxides per hour), the performance of CoOx–MnOx catalysts was higher than that of CoOx–CoMnOx ones. The catalysts with the smallest layer thickness (0.1 µm) showed the highest catalytic activity. Compared to the commercial pelletized Co–Mn–Al mixed oxide catalyst, the sputtered catalysts exhibited considerably higher (23–87 times) catalytic activity despite the more than 360–570 times lower content of the Co and Mn active components in the catalytic bed.

Ethanol Dehydrogenation to Acetaldehyde over Co@N-Doped Carbon

Cobalt and nitrogen co-doped carbon materials (Co@CN) have recently attracted significant attention as highly efficient noble-metal-free catalysts exhibiting a large application range. In a similar research interest, and taking into account the ever-increasing importance of bioethanol as a renewable raw material, here, we report the results on ethanol dehydrogenation to acetaldehyde over Co@NC catalysts. The catalyst samples were synthesized by a variety of affordable techniques, ensuring generation of various types of Co species incorporated in carbon, such as subnanosized cobalt sites and nano-sized particles of metallic cobalt and cobalt oxides. The catalytic activity was tested under both oxidative and non-oxidative gas-phase conditions at 200–450 °C using a fixed-bed flow reactor. The non-oxidative conditions proved to be much more preferable for the target reaction, competing, however, with ethanol dehydration to ethylene. Under specified reaction conditions, ethanol conversion achieved a level of 66% with 84% selectivity to acetaldehyde at 400 °C. The presence of molecular oxygen in the feed led mainly to deep oxidation of ethanol to COx, giving acetaldehyde in a comparatively low yield. The potential contribution of carbon itself and supported cobalt forms to the observed reaction pathways is discussed.

Near 100% ethene selectivity achieved by tailoring dual active sites to isolate dehydrogenation and oxidation

Prohibiting deep oxidation remains a challenging task in oxidative dehydrogenation of light alkane since the targeted alkene is more reactive than parent substrate. Here we tailor dual active sites to isolate dehydrogenation and oxidation instead of homogeneously active sites responsible for these two steps leading to consecutive oxidation of alkene. The introduction of HY zeolite with acid sites, three-dimensional pore structure and supercages gives rise to Ni2+ Lewis acid sites (LAS) and NiO nanoclusters confined in framework wherein catalytic dehydrogenation of ethane occurs on Ni2+ LAS resulting in the formation of ethene and hydrogen while NiO nanoclusters with decreased oxygen reactivity are responsible for selective oxidation of hydrogen rather than over-oxidizing ethene. Such tailored strategy achieves near 100% ethene selectivity and constitutes a promising basis for highly selective oxidation catalysis beyond oxidative dehydrogenation of light alkane.

SOME ISSUES OF THE MECHANISM OF DEEP OXIDATION OF ETHANOL ON THE SURFACE OF THE CATALYST OF A THERMOCATALYTIC SENSOR

In this work, the effect of the partial pressures of the starting materials and reaction products on the patterns of deep oxidation of ethanol on the surface of the catalyst of the thermocatalytic sensor was studied experimentally. At the same time, the regularities of the oxidation of combustible substances on selected catalysts have been established and the optimal conditions have been identified that ensure the flow of the process under study in the kinetic region. It is shown that the reaction on the sensor catalyst surface proceeds along two kinetically independent (basic) routes. Taking into account the above, a more detailed scheme of the heterogeneous catalytic oxidation of ethanol in the presence of a sensor catalyst is proposed.

Catalytic oxidation of CO in gases emitted by industrial processes and vehicle exhaust

A new type of catalysts not containing noble metal oxides have been developed and the possibilities of their application both for the complete neutralization of carbon monoxide in exhaust gases and the process of deep oxidation of volatile hydrocarbons are studied. It has been foundthatthe activity of catalysts based on vanadiumandphosphorus oxides supported on Al2O3, SiO2, TiO2by and their modification withof 1–3% oxides of Cu, Cr, Co, Zn enhanced the conversion of the deep oxidation process to 95–100% at the temperatures of 673–693K and volumetric velocities of 5000–10000 h–1. During the simultaneous oxidation of CO and C3H8at a CO conversion of 90%, the C3H8conversionwas 70%. It has been established that oxidation of CO and C1–C4 hydrocarbons, and especially propane, with the participation of synthesized catalytic series, occurs by stepwise and associative mechanisms. The oxidation of CO and C3H8required a high oxygen content of 1:20–25 mol. Besides utilizing carbon monoxide in exhaust gases from motor vehicles, these catalytic systems can be successfully used to neutralize industrial gases, especially those emitted from oil refineries and thermal power plants. Preliminary research has shown that these catalytic systems can operate for about 50000 hours without changing the activity.