ACTIVATION OF WATER USED IN THE PREPARATION OF WHEAT GRAIN FOR VARIETAL MILLING

The purpose of the study is to change the properties of water in order to achieve the optimum impact on wheat grain in preparation for variety milling. The results of influence on the properties of drinking water by acoustic waves in the frequency range of 10-1000 Hz for 1 minute were determined. It is established that the optimal range of exposure is the interval of 80-100 Hz. At the same time water activation is achieved, leading to changes in its properties, such as specific water resistance, electric conductivity, content of dissolved salts, which positively affects the technological indicator - the amount of conductometric ash.

INFLUENCE OF THE TYPE OF WATER ACTIVATION ON THE CONTACT ZONE BETWEEN THE FILLER AND THE CEMENT STONE

Among the many ways to improve the preparation of concrete mix is to modify the properties of cement systems by mechanical, physical, chemical and combined effects. One of the directions of activation of the concrete mixture is the activation of its components, namely: electromagnetic, electrochemical and physics-chemical activation of mixing water. The most accessible and technological of them is the physics-chemical activation of water and aqueous solutions by certain organic substances used in ultra-low concentrations, followed by their use as a mixing fluid for building mixtures. The purpose of the study was to perform a comparative assessment of the effect of electromagnetic, electrochemical and physicochemical activation of water on the properties of cement paste and fine-grained concrete. To achieve this goal, the degree of influence ofelectromagnetic, electrochemical and physicochemical activation of water on the contraction and hardening time of cement paste, as well as the degree of influence of electromagnetic, electrochemical and physicochemical activation of water on compressive strength of fine concrete. It is established that the type of activation of kneading water affects the hardening time of the cement paste and the normal density. The shortest hardening times are set for cement paste, which is obtained on electrochemically activated alkaline water, and the longest with the use of physics-chemical activation. At the same time, the highest strength at the lowest contraction has concrete, which is obtained on physics-chemical activated water. This concrete has the highest rate of strength. Concretes obtained on «alkaline» water, after its electro-chemical activation, have a high rate of strength formation and its value, but high contraction, which leads to cracking of concrete.

Reaction Pathway for Coke-Free Methane Steam Reforming on a Ni/CeO2 Catalyst: Active Sites and Role of Metal-Support Interactions

<p>Methane steam reforming (MSR) plays a key role in the production of syngas and hydrogen from natural gas. The increasing interest in the use of hydrogen for fuel cell applications demands the development of catalysts with high activity at reduced operating temperatures. Ni-based catalysts are promising systems because of their high activity and low cost, but coke formation generally poses a severe problem. Studies of ambient-pressure X-ray photoelectron spectroscopy (AP-XPS) indicate that CH₄/H₂O gas mixtures react with Ni/CeO₂(111) surfaces to form OH, CH<i>_x</i> and CH<i>_x</i>O at 300 K. All these species are easy to form and desorb at temperatures below 700 K when the rate of the MSR process accelerates. Density functional theory (DFT) modeling of the reaction over ceria-supported small Ni nanoparticles predicts relatively low activation barriers between 0.3–0.7 eV for the complete dehydrogenation of methane to carbon and the barrierless activation of water at interfacial Ni sites. Hydroxyls resulting from water activation allow CO formation via a COH intermediate with a barrier of about 0.9 eV, which is much lower than that through a pathway involving lattice oxygen from ceria. Neither methane nor water activation are rate-determining steps, and the OH-assisted CO formation through the COH intermediate constitutes a low-barrier pathway that prevents carbon accumulation. The interaction between Ni and the ceria support and the low metal loading are crucial for the reaction to proceed in a coke-free and efficient way. These results could pave the way for further advances in the design of stable and highly active Ni-based catalysts for hydrogen production.</p>

Reaction Pathway for Coke-Free Methane Steam Reforming on a Ni/CeO2 Catalyst: Active Sites and Role of Metal-Support Interactions

<p>Methane steam reforming (MSR) plays a key role in the production of syngas and hydrogen from natural gas. The increasing interest in the use of hydrogen for fuel cell applications demands the development of catalysts with high activity at reduced operating temperatures. Ni-based catalysts are promising systems because of their high activity and low cost, but coke formation generally poses a severe problem. Studies of ambient-pressure X-ray photoelectron spectroscopy (AP-XPS) indicate that CH₄/H₂O gas mixtures react with Ni/CeO₂(111) surfaces to form OH, CH<i>_x</i> and CH<i>_x</i>O at 300 K. All these species are easy to form and desorb at temperatures below 700 K when the rate of the MSR process accelerates. Density functional theory (DFT) modeling of the reaction over ceria-supported small Ni nanoparticles predicts relatively low activation barriers between 0.3–0.7 eV for the complete dehydrogenation of methane to carbon and the barrierless activation of water at interfacial Ni sites. Hydroxyls resulting from water activation allow CO formation via a COH intermediate with a barrier of about 0.9 eV, which is much lower than that through a pathway involving lattice oxygen from ceria. Neither methane nor water activation are rate-determining steps, and the OH-assisted CO formation through the COH intermediate constitutes a low-barrier pathway that prevents carbon accumulation. The interaction between Ni and the ceria support and the low metal loading are crucial for the reaction to proceed in a coke-free and efficient way. These results could pave the way for further advances in the design of stable and highly active Ni-based catalysts for hydrogen production.</p>