Mass Spectrometric Research of Hydrogenated Molecules of Carbon As Products of Pyrolysis of Benzene and Pyridine Vapours
Total Page：16
File Type：pdf, Size：1020Kb
Chemical and Materials Engineering 1(4): 122-131, 2013 http://www.hrpub.org DOI: 10.13189/cme.2013.010404 Mass Spectrometric Research of Hydrogenated Molecules of Carbon as Products of Pyrolysis of Benzene and Pyridine Vapours Alexey Kharlamov1, Marina Bondarenko1,*, Ganna Kharlamova2 1Frantsevich Institute for Problems of Materials Science of NASU, Krzhyzhanovsky St. 3, 03680 Kiev, Ukraine 2Taras Shevchenko National University of Kiev, Volodymyrs'ka St. 64, 01601 Kiev, Ukraine *Corresponding Author: [email protected] Copyright © 2013 Horizon Research Publishing All rights reserved. Abstract Hydrogenated carbon molecules are to speak about creation on the basis of system of convertible synthesized by a method which essentially is distinct from reactions already known methods of preparation of fulleranes as this C60+30H2 C60H60 (1) method a preliminary stage of synthesis of carbon molecules accumulator of hydrogen with so huge (7.7mass. %) contents is excluded completely. Fulleranes and quasi-fulleranes as ⇌ of hydrogen. Though here it is necessary to note, that in nanodimentional particles were in common deposited by dodecahedrane С Н , which was synthesized by Paquette ethanol from benzene-xylene extracts from products of 20 20 [4] three years prior to opening of fullerene С (and 8 years pyrolysis of vapours of benzene and pyridine. The 60 prior to obtaining of first fullerane C H ), the ratio Н/C is dehydrogenation of the synthesized samples of fulleranes 60 36 the same (1/12) as in fullerene С Н . However of so and quasi-fulleranes is started at 30-50 °C and the evacuation 60 60 steadfast interest of the researchers this controllable of hydrogen proceeds up to 700 °C. At thermolysis of synthesized hydride of fullerene for some reason had not and nanopowders of fulleranes and quasi-fulleranes alongside has not. The reasonable explanation of so selective interest of with hydrogen are formed also hydrocarbons (methane, the researchers to hypothetical С Н , instead of to real propane and butane), which are usually detected at 60 60 С Н can be, probably, is connected to huge, global defullerenization (disclosing and partial fragmentation of 20 20 attention to such unique (Nobel dignity) object as fullerene fullerene cage) fulleranes, synthesized at hydrogenation of С . fullerenes or fullerite. The contents of hydrogen in some 60 In present time it is possible already to speak, that the quasi-fulleranes (C H , C H , C H ) and fulleranes 26 24 28 22 30 22 hopes of the researchers for creation of the storage of (C H , C H , C H ) reaches 5.4–6.9 mass%. The first 60 32 60 46 60 60 hydrogen on the basis of system fullerene (С ) - fullerane was detected by a mass spectrometric method the cluster 60 (С Н ) were not completely justified. The question, С Н , the thin structure of which spectrum completely 60 60 60 60 certainly, not that was not possible (all known methods of corresponds fullerane of equiatomic composition, С Н . 60 60 hydrogenation of fullerene [1, 2, 5-8] and fullerite [1, 8, 9]) Keywords Pyrolysis, Fulleranes, Quasi-Fulleranes, to synthesize fullerene of equiatomic (or even close to those) Quasi-Fullerenes, Hydrides, Benzene, Pyridine composition. Basically, fullerane С60Н60 in heterogeneous heterophases reactions of hydrogenation crystalline fullerene it was impossible to synthesize, where, as it is well known, limiting always is the diffusion stage, in particular, the diffusion of hydrogen atoms through a layer of the formed 1. Introduction product С60Нх. Even titanium hydride of stoichiometric composition (TiH2) it fails to obtain, at least, at Hydrides of fullerenes (or fulleranes [1]) as first hydrogenation of metal in one stage. Though, titanium is a derivatives of fullerene (obtained by Haufler [2] already after greatest hetter, in particular, of hydrogen. Fullerane with 5 years after opening by Kroto of a spheroidal molecule of greatest possible (it is possible also of composition С60Н60) carbon [3]) have attracted the special attention of the experts contents of hydrogen, which is formed at fullerite in the field of hydrogen power as, ostensibly, perspective and hydrogenation on a surface of the division of phases of effective accumulators of hydrogen. It was supposed, that in precursor and product, interferes further diffusion of atoms case of synthesis of equiatomic fullerane С60Н60 and of hydrogen to some more not reacted part of fullerite. To following its complete dehydrogenation it would be possible obtain homogeneous under the contents of hydrogen a Chemical and Materials Engineering 1(4): 122-131, 2013 123 product adequate equiatomic composition С60Н60, it is not 80 °С, bp 217.7 °С) and at the presence of the catalyst represented, basically, possible from the point of view of the (dihydro irridium bisphosphine complex) already at kinetics of heterogeneous reactions. The additional process temperature 225 °С is realized. of intensive mechanical dispergation of formed on a surface Unfortunately, the researches on study of processes of of division of phases of half-products is inevitable. However fulleranes dehydrogenation in comparison with a number of fullerite (or fullerane) is not titanium (or titanium hydride), the publications devoted to search and optimization of and at its mechanochemical milling the destruction of bonds methods of synthesis of fullerenes and fulleranes, are С–С (defullerenization) will be observed. Therefore for extremely not numerous. Though, just, joint study of kinetics more complete saturation fullerite by hydrogen process of of processes of dehydrogenation and defullerenization of the hydrogenation carried out at the increased temperatures samples of fulleranes, prepared by various methods (in and pressure [9], in particular, at temperatures is higher particular, by hydrogenation of fullerene or fullerite), is up 550 °C and super-high pressure (~2 GPa ) [1]. very important for comparison and understanding of However to avoid the destruction of molecules of mechanisms of dehydrogenation and destruction fulleranes. fullerene in so severe conditions of hydrogenation, naturally, In present time on the basis already of first experimental not it is possible: the process of partial defullerenization of results it is possible to speak, that the temperatures of a the closed carbon skeleton in С60 and С60Нх with formation beginning of fulleranes dehydrogenation and partial of the various size of unclosed hydrocarbon fragments destruction of fullerene skeleton significantly depend on a С<60Нх (for example, С58Hх, С56Hх) with the torn off bonds method of samples synthesis. So, in [10] temperature С–С is observed [1]. Deactivation of these carbon radicals (400 °C) of dehydrogenation of crystalline fullerane was due to instant formation bonds С-Н can create the illusion of established on measurement in the closed chamber of obtaining of highly hydrogenated fullerane (and even pressure of allocated gas. However it is necessary to note, fullerene of equiatomic composition [1]). This partially that the composition of volatile products of thermolysis of defullerenizated fullerane in the chemical relation is closest, fullerene hydride in [10] was not investigated. In [11] by a probably, to molecules of cycloalkanes (or thermogravimetric method was established, that the polycycloalkanes), the strength of bonds С–Н in which intensive loss of mass in fullerene hydride С60Н36 essentially approximately only twice is less than strength of bonds С–С. depends on a method of its obtaining. The reduction of mass Therefore calculated energy of activation of of samples С60Н36 prepared by reduction of fullerene by dehydrogenation of fullerane is so high (160 kJ/mol) [10]. dihydroanthracene or Burch method is began at temperatures However because of stress of bonds С-С in curved carbon 510 and 380 °C accordingly. Besides a mass of a sample skeleton of fragments С56Hх should decrease not only values С60Н36 (4.8 mass% of hydrogen) obtained in the melt is of strength of bonds С–С and С–Н, but also difference decreased on 6.8 mass%, whereas a mass of a sample С60Н36, between these values. Therefore at temperatures (> 400 °C) obtained in a solution by Burch reduction is decreased on 7.7 of appreciable dehydrogenation of fulleranes [11, 12] the mass%. As the loss of a mass in samples of fullerane С60Н36 allocation of alkanes (methane, propane and butane) as is significant (on 2-3 %) exceeds amount contained in it of products of destruction of a fullerene cage is indispensable hydrogen, the quite reasonable conclusion was made, that at observed also. thermolysis of fullerane there is an evacuation not only Hence, at realization any of convertible reactions in hydrogen, but also hydrocarbons as products of destruction system fullerene-fullerane the destruction of molecules of of molecules of precursor. Really, in [12] by method of mass precursor is fulfilled: at hydrogenatin the molecules of spectrometry was established, that in products of fullerene are collapsed, and at dehydrogenation – molecules temperature-programmed desorption (ТPD) deuterofullerite of fullerane. According to [10] the energy of activation of C60D19 are present, in particular, at temperatures 400 and fullerene hydrogenation only on 60 kJ / mol less than the 500 °C, also (except for deuterium) deuteromethane and energy of activation of fullerene dehydrogenation (160 kJ / deuteropropane. Thus the authors [12] all peaks which have mol). Moreover, and this main, appreciable allocation of so been found out in mass spectra with electron ionization (EI) necessary hydrogen owing to dehydrogenation of samples of of a gas phase above deuterofullerite C60D19, were explained fulleranes (for example, composition С60Н36), synthesized by due to the presence of only deuterium and fragments hydrogenation fullerene in solution by hydrogen at high deuterocarbons. It is impossible to consider this conclusion pressure is fulfilled at too high (> 500 °C) temperatures. Let's rather correct, as in volatile products of thermodesorption of emphasize, that the so high temperatures of dehydrogenation carbon materials [13, 14] and fullerene [14, 15] always are characteristic only for samples of fulleranes, obtained at contain also water, oxygen, CO and СО2.