A Kinetic Model Considering Catalyst Deactivation for Methanol-to-Dimethyl Ether on a Biomass-Derived Zr/P-Carbon Catalyst

A Zr-loaded P-containing biomass-derived activated carbon (ACPZr) has been tested for methanol dehydration between 450 and 550 °C. At earlier stages, methanol conversion was complete, and the reaction product was mainly dimethyl ether (DME), although coke, methane, hydrogen and CO were also observed to a lesser extent. The catalyst was slowly deactivated with time-on-stream (TOS), but maintained a high selectivity to DME (>80%), with a higher yield to this product than 20% for more than 24 h at 500 °C. A kinetic model was developed for methanol dehydration reaction, which included the effect of the inhibition of water and the deactivation of the catalyst by coke. The study of stoichiometric rates pointed out that coke could be produced through a formaldehyde intermediate, which might, alternatively, decompose into CO and H2. On the other hand, the presence of 10% water in the feed did not affect the rate of coke formation, but produced a reduction of 50% in the DME yield, suggesting a reversible competitive adsorption of water. A Langmuir–Hinshelwood reaction mechanism was used to develop a kinetic model that considered the deactivation of the catalyst. Activation energy values of 65 and 51 kJ/mol were obtained for DME and methane production in the temperature range from 450 °C to 550 °C. On the other hand, coke formation as a function of time on stream (TOS) was also modelled and used as the input for the deactivation function of the model, which allowed for the successful prediction of the DME, CH4 and CO yields in the whole evaluated TOS interval.

Martensitic Phase Transition in Yttrium-Stabilized ZrO2 Nanopowders by Adsorption of Water

The present study was aimed at revealing the influence of the mechanical stress induced by water molecules adsorption on the composition of crystalline phases in the ZrO2–3mol%Y2O3-nanoparticles. Three basic methods have been used to determine the phase transition: neutron diffraction, Raman microspectroscopic scanning, and X-ray diffraction. The fact of phase-structural β → α transformation and the simultaneous presence of two polymorphic structural modifications (β is the phase of the tetragonal syngony and α of monoclinic syngony in nanosized particles (9nm)) under normal physical conditions was established by these methods. Satisfactory consistency was achieved between the results obtained using different techniques.

Basics of the Development of Microwave Intensification of Upstream on the Example of Escherichia coli

Introduction. E. coli strains are the main microorganisms used for the production of a number of important biopharmaceutical products. There are no natural sources of microwave radiation on Earth, as it is absorbed by the upper atmosphere. No one doubts the importance of studying the biological effect of microwave radiation. The number of publications devoted to this problem is growing every year, and new ideas for the use of microwaves in drug production technology are emerging.Aim. Reveal the main effects of microwave irradiation and develop a technology for microwave intensification of E. coli culture growth.Materials and methods. This study presents the results of atomic force microscopy, refractometry, NMR relaxometry, turbidimetry, and lumimetry, demonstrating the possibility of microwave intensification of the cultivation process.Results and discussion. It was found that microwave irradiation leads to changes in the mobility of protons and the adsorption of water molecules on biopolymers and cells. These are the main links in the mechanism of "non-thermal" microwave action. A single microwave irradiation, depending on a number of parameters, can decrease or increase the growth of biomass. Studies of the bioluminescence of the E. coli strain with the lux-operon have shown that the optimal processing conditions do not negatively affect the luciferase production and metabolic activity of cells. Conclusion. The intensification procedure using microwave radiation can be considered a promising method and can provide new ideas for various applications in biotechnology.

Martensitic Phase Transition in Yttrium-Stabilized ZrO2 Nanopowders by Adsorption of Water

The present study was aimed at revealing the influence of the mechanical stress induced by water molecules adsorption on the composition of crystalline phases in the ZrO2–3mol%Y2O3-nanoparticles. Three basic methods have been used to determine the phase transition: neutron diffraction, Raman microspectroscopic scanning, and X-ray diffraction. The fact of phase-structural β → α transformation and the simultaneous presence of two polymorphic structural modifications (β is the phase of the tetragonal syngony and α of monoclinic syngony in nanosized particles (9nm)) under normal physical conditions was established by these methods. Satisfactory consistency was achieved between the results obtained using different techniques.

Evaluation of ZIF-8 and ZIF-90 as Heat Storage Materials by Using Water, Methanol and Ethanol as Working Fluids

The increasing demand for heating/cooling is of grave concern due to the ever-increasing population. One method that addresses this issue and uses renewable energy is Thermochemical Energy Storage (TCES), which is based on the reversible chemical reactions and/or sorption processes of gases in solids or liquids. Zeolitic imidazolate frameworks (ZIFs), composed of transition metal ions (Zn, Co, etc.) and imidazolate linkers, have gained significant interest recently as porous adsorbents in low temperature sorption-based TES (sun/waste heat). In this study, we examined two different sodalite-type ZIF structures (ZIF-8 and ZIF-90) for their potential heat storage applications, based on the adsorption of water, methanol and ethanol as adsorbates. Both ZIF structures were analysed using PXRD, TGA, SEM and N2 physisorption while the % adsorbate uptake and desorption enthalpy was evaluated using TGA and DSC analysis, respectively. Among the studied adsorbent–adsorbate pairs, ZIF-90-water showed the highest desorption enthalpy, the fastest sorption kinetics and, therefore, the best potential for use in heat storage/reallocation applications. This was due to its significantly smaller particle size and higher specific surface area, and the presence of mesoporosity as well as polar groups in ZIF-90 when compared to ZIF-8.

Adsorption of Binary Solvents on Chiral Stationary Phases with Grafted Macrocyclic Antibiotics

A study is performed of the adsorption of water–methanol and water–acetonitrile mixtures on chiral stationary phases (CSPs) Chirobiotic R, Chirobiotic T, and Nautilus-E with grafted macrocyclic antibiotics ristocetin A, teicoplanin, and eremomycin, respectively. The patterns of adsorption on the indicated CSPs are qualitatively the same, and differ only by quantitative indicators. Adsorption isotherms of excess water from binary solvents have adsorption azeotrope points and show the preferred absorption of water in the range of pure organic component to an azeotrope point in the range of 60–75 mol % for H2О–МеОН and 80–90 mol % for H2O–MeCN systems. It is shown that the thickness of the adsorption phase in the first case is less than one nominal molecular layer (0.10–0.13 nm). For H2O–MeCN, it is 3–4 molecular layers (0.88–1.05 nm). Activity coefficients are calculated for the components of solutions in surface layers. The coefficients indicate the systems deviate considerably from the properties of an ideal adsorption solution. Reasons for this behavior are discussed.

Water Splitting on Multifaceted SrTiO3 Nanocrystals: Computational Study

Recent experimental findings suggest that strontium titanate SrTiO3 (STO) photocatalytic activity for water splitting could be improved by creating multifaceted nanoparticles. To understand the underlying mechanisms and energetics, the model for faceted nanoparticles was created. The multifaceted nanoparticles’ surface is considered by us as a combination of flat and “stepped” facets. Ab initio calculations of the adsorption of water and oxygen evolution reaction (OER) intermediates were performed. Our findings suggest that the “slope” part of the step showed a natural similarity to the flat surface, whereas the “ridge” part exhibited significantly different adsorption configurations. On the “slope” region, both molecular and dissociative adsorption modes were possible, whereas on the “ridge”, only dissociative adsorption was observed. Water adsorption energies on the “ridge” ( −1.50 eV) were significantly higher than on the “slope” ( −0.76 eV molecular; −0.83 eV dissociative) or flat surface ( −0.79 eV molecular; −1.09 eV dissociative).

METHYLENE BLUE REMOVAL THROUGH ADSORPTION OF WATER HYACINTH USING COBALT NANOPARTICLES SUPPORTED ON ACTIVE CARBON

In this research, active carbon-based catalyst synthesis and characterization were investigated for different applications in catalysis. The active carbon-based catalyst was combined with metal oxides to dye methylene blue (MB) removal. Water hyacinth is one of the major problems that facing society and especially in Egypt. One of the implications of industrial activities is environmental pollution. One of the major pollutants is dyes that are used in the production of textiles, paper, and clothes. The waste of those dyes discharged into water supplies without treatment, or ineffective treatment will harmfully impact the environment. In this research, the treatment is implemented using active carbon-based catalysts using embedded nanoparticles. That will lead to a huge increase in the surface area of the adsorbent to increase the adsorbent efficiency. The activated carbon was derived from water hyacinths that grow in the Nile River. Water hyacinth has many good uses as it can absorb heavy metals like lead and dyes. Water hyacinth was converted into activated carbon through carbonization. Different dyes were used with different contact times in fixed conditions.