CALCULATION OF ACTIVE FRACTIONS SIZES IN SUPPORTED NANOCRYSTALS
- Autores: Rakhimov T.K.1, Rakhmanova G.S.1
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Afiliações:
- the National University of Uzbekistan, Uzbekistan, Tashkent
- Edição: Volume 6, Nº 1 (2019)
- Páginas: 44-52
- Seção: Articles
- URL: https://journals.eco-vector.com/2313-223X/article/view/529717
- ID: 529717
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Resumo
Background. The paper is devoted to experimental verification of the possibility of the influence of minor difference between supported nanocatalysts within their carriers’ structure on their functional characteristics, in particular, on the calculated sizes of the active fractions. The oscillatory pattern of CO and hydrogen oxidation, observed in some cases in the presence of platinum metals’ containing nanoparticles, suggests the presence of dissipative structures. It’s known that systems possessed of high complexity (according to Von Neumann), in particular, autocatalytic hypercycles are capable of self-organization. Another sign of such systems’ presence may be a critical influence of minor changes in structure and/or composition on their characteristics. The possibility of such an effect has been verified experimentally: a series of palladium-containing nanocatalysts on activated carbon fibers, differing in particle size distribution, have been synthesized. Carbon fibers obtained from two different precursors were used. Samples from each batch were subjected to reductive treatment with hydrogen at a metered ratio. The boundary sizes of the active fractions are calculated, as well as the activity in the reaction of low-temperature oxidation of CO, at various depths of reduction. Since, for chemically sufficiently inert carbon fibers, a change in the nature of the precursor to the final nanosystems can be considered an insignificant influence factor, a significant effect of such an effect can be considered as confirmation of the hypothesis of the origin of self-organizing systems.Methods. All calculations were made by using MS Office Professional 2013. A series of palladium nanocatalysts on activated carbon fibers “Busofit Carbopon-Activ” with active surface of 1300 m2/g and Mtilon-M with an active surface of 2700 m2/g was prepared; sizes of nanoparticles varied by choosing modes of drying after application solutions with ions Pd2+. The initial reaction rate was measured by gas chromatography from CO concentrations’ decreasing.Results. The calculation of boundary sizes of nanosystems’ active fractions obtained using the Ball Painting Model showed that carbon fibers’ structure has a significant impact on these dimensions. In nanosystems on Carbopone in comparison with nanosystems on Mtilon-M, not only is the activity shifted towards particles with a smaller diameter, but also a significant narrowing of the size range within which nanoparticles retain activity. Recovery leads to a continuous narrowing of this interval, and therefore the total activity becomes lower with increasing content of the recovered phase. The catalysts applied to Mtilon-M are characterized by a wide size distribution, with unusually large particles showing activity.Despite the insignificant differences in the structure of the carrier, the characteristics of nanosystems differ significantly. This suggests that more likely are processes with the formation of autocatalytic hypercycles, otherwise one would expect that particles of the same size would be active regardless of the nature of the carrier.Conclusion. Minor changes in the structure of the carrier matrix lead to significant differences in the characteristics of nanocatalysts - the boundaries of the active fractions are mutually shifted, and the interval of the boundary sizes can be both wide enough and extremely narrow. This is consistent with the hypothesis of the formation of autocatalytic hypercycles, the level of complexity of which suggests that they are self-organizing.Implementation opportunities. High toxicity, lack of color and smell, low adsorption and chemical passivity of CO make it one of the most dangerous toxins. The removal of CO in practice is seriously difficult, and the use of nanocatalysts for life-support and respiration systems is practically non-alternative in this aspect. A reliable method of obtaining self-organizing high-performance nanosystems capable of removing CO under room conditions would be used to clean the atmosphere of closed living spaces - in cars, spaceships, submarines, in industrial workshops, and others. Considering that for almost all other gaseous toxins, with the exception of CO, robust removal systems have been developed, filling this gap will allow creating universal filters for life support systems.Social consequences. Work in this direction can be a solution to a number of social problems, including health safety while in traffic jams, especially for risk groups.Originality/value. Proof of hypercycles’ formation at a high level of complexity capable of further self-organization, and their careful study is of great theoretical importance for understanding the possibilities that open up for non-equilibrium dissipative systems - it is possible that they can be compared with questions about the origin of life and the evolution of hypercycles in nature. The study of the influence of the nature of carbon fiber precursor on the behavior of hypercycles seems rather unexpected, but nevertheless remains fruitful.
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Sobre autores
Tokhir Rakhimov
the National University of Uzbekistan, Uzbekistan, Tashkent
Email: tohir@mail.ru
Doctor of Science; Senior Researcher
Gulnara Rakhmanova
the National University of Uzbekistan, Uzbekistan, Tashkent
Email: gulshara@mail.ru
Researcher
Bibliografia
- Braun O.M., Medvedev V.K. Uspehi fizicheskih nauk [Physics-Uspekhi]. 1989. Vol. 157. № 4. Р. 631-666.
- Лиопо В.А., Никитин А.В., Струк В.А., Давлеткильдеев Н.А., Семиколенова Н.А. Размерные критерии наночастиц // Вестник Омского университета. 2005. № 2. С. 27-29.
- Jonesa M.G., Blonder R., Gardner G.E., Albe V. et al. Nanotechnology and nanoscale science: Educational challenges // International Journal of Science Education 35. 2013. № 9. Р. 1490-1512.
- Pradeep T. A textbook of nanoscience and nanotechnology. Tata McGraw-Hill Education. New Delhi, 2012. 220 p.
- Brinkley K.W. The Synthesis of Solid Supported Palladium Nanoparticles: Effective Catalysts for Batch and Continuous Cross Coupling Reactions. Virginia Commonwealth University. Richmond, VA, 2015. 136 p.
- Albanese A., Tang P.S., Chan W.C.W. The effect of nanoparticle size, shape, and surface chemistry on biological systems // Annual review of biomedical engineering. 2012. № 14. Р. 1-16.
- Zavodinskij V.G. Komp'juternoe modelirovanie nanochastic i nanosistem [Modeling Software for nanoparticles and nanosystems]. Moscow: Fizmatlit, 2013. 244 p.
- Valeeva A.A., Nazarova S.Z., Rempel' A.A. Fizika tverdogo tela [Physics of the Solid State]. 2016. 58. № 4. Р. 161-168.
- Gusev A.I., Rempel A.A. Nanocrystalline materials. Cambridge Int Science Publishing: Cambridge, 2004. P. 21-22.
- Рахимов Т.Х. Вычисление размеров активных фракций нанесенных нанокристаллов // Computational nanotechnology, 2015, №2. С. 6-16.
- Кутепов В.П., Фальк В.Н. Формы, языки представления, критерии и параметры сложности параллелизма // Программные продукты и системы. 2010. №3.
- Keuth H. The Philosophy of Karl Popper. Cambridge University Press, 2005.
- Wu Z., Overbury S.H. Catalysis by Materials with Well-Defined Structures. Academic Press, Elsevier Science. London, 2015. P. 51.
- Briot R., Auronx A., Jones D., Primet M. Effect of particle size on the reactivity of oxygen-absorbed platinum supported on alumina // Appl. Catalysis. 1990. Vol. 59. Р. 141-152.
- Rakhimov T.Kh., Mukhamediev M.G. Quantitative Criteria for the Comparative Size of the Nanoparticles // J. Chem. Eng. Chem. 2015. Res 2. № 6. Р. 663-670.
- Lundwall M.J. McClure S.M., Wang X., Wang Z.J., Chen M.S. The Structure-Sensitivity of n-Heptane Dehydrocyclization on Pt/ SiO2 Model Catalysts // The Journal of Physical Chemistry C. 2012. Vol. 116. № 34. Р. 18155-18159.
- Goodman D.W. Catalysis: from single crystals to the “real world” // Surface Sci. 1994. Vol. 299/300. Р. 837-848.
- АС СССР №1524767, C01B31/18. Способ получения катализатора для низкотемпературного окисления окиси углерода / Рахимов Т.Х., Мусаев У.Н., Хакимджанов Б.Ш. № 4664024. Заявл. 20.03.1989. Опубл. 01.10.1990.
- Рахимов Т.Х., Мухамедиев М.Г. Доступные методы биофизического анализа газовоздушной среды // Узб. Биол. журнал. 2014. № 5. C. 6-9.
- Авт. свид. 05375 РУз (программы для ЭВМ). Методика вычисления граничных размеров наночастиц / Рахимов Т.Х., Мухамедиев М.Г. № DGU 2018/0317. Заявл. 01.05.2018. Опубл. 31.05.2018.
- Рахимов Т.Х., Мухамедиев М.Г. Влияние состава наночастиц на граничные размеры их каталитической активности / Universum: Химия и биология: электрон. научн. журн. 2016. № 7 (25). С. 5.
- Hugo P., Jakubith M. Dynamisches Verhalten und Kinetic der Kohlenmonoxid-Oxidation am Platin-Katalisator // Chem.-Ing.-Techn. 1972. Bd 44. № 6. P. 383-387.
- Боресков Г.К. Катализ: Вопросы теории и практики. Избранные труды. Новосибирск: Наука, 1987. С. 33-50.
- Масленников К.Н. Химические волокна. М.: Химия, 1973. С. 72.
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