INFLUENCE OF MOLECULAR STRUCTURE OF HIGH OCTANE GASOLINE COMPONENTS AND FUEL ANTIOXIDANT ADDITIVES ON EFFICIENCY OF THEIR ACTION

DOI: 
10.6060/tcct.20165912.5375

Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2016. V. 59. N 12. P. 49-56

With the use of quantum-chemical calculations of the high-level theory by the method of B3LYP/6-31+G(d,p) in a solvent the geometrical and electronic structure of high-octane components (iso-paraffins and ethers), and anti-oxidant additives were studied. Their chemi-cal reactivity was assessed based on the analysis of bond lengths, valent and dihedral angles, charges, energy of frontier molecular orbitals. The comparison of the structural parameters and the effectiveness of the tested compounds in fuels was carried out. Isoparaffins (neohex-ane, isooctane, triptane) and ethers (methyl-tert-butyl ether, ethyl-tert-butyl ether, methyl-tert-amyl ether, ethyl-tert-amyl ether) were selected as high octane components of gasoline. Changes in the geometric and electronic structure of isoparaffins and ethers are shown. Re-ducing some bond angles and increasing in bond length for iso-paraffins (at increasing in detonation resistance of compound) and also reducing the length of bond, charge increase for ethers (at increasing in detonation resistance of compound) indicate a decline in com-pound reactivity. At the same time for compounds with lower reactivity the increase in deto-nation resistance is observed. Intensification of hydrocarbons oxidation process with oxygen occurs with an increase in a temperature and pressure in the combustion chamber, detona-tion occurs before pre-ignition of fuel combustion. Considered above iso-paraffins ethers are high-octane fuel components and at reducing the reactivity it is necessary to use a higher temperature for oxidation process intensification. It is shown that this research method of iso-paraffins and ethers molecules for assessment of the effectiveness of their action as a high-octane components, does not give a clear answer. Although most of the parameters in-dicate that the decrease in molecule reactivity results in the increase in octane number of the compound. For the calculations 2,6-di-tert-butyl-4-methylphenol (ionol), 2,2'-methylene-bis-(4-methyl-6-tretbutilfenol) (NG-2246), 4-(N, N-dimethylaminomethylene)-2,6-ditretbutilfenol (OMI), N-(2-ethylhexyl) -N'-phenyl-1,4-phenylenediamine (C-789) were chosen as antioxi-dant additives. At consideration of the parameters of geometric and electronic structure of the antioxidant additives it was revealed that for ionol, NG-2246, OMI the C-H bond break-age is possible in a tert-butyl fragment. Beside that for the NG-2246 the breakage of addi-tional C-H bond is possible as well. Probably it defines that this compound is more effective as an antioxidant since more numbers of oxidation chain terminations become possible. For compound C-789 dimensional structure of the molecule is more open: increased angles and bond lengths in the alkyl chain, decreased charges on the hydrogen atoms. The article shows that instead of considering the effectiveness of action of the compound according to the reac-tion mechanism only from static properties of the starting materials it is more informative to use comparison of the parameters of the geometric and electronic molecules structures, such as bond length, valent and dihedral angles, atomic charges.

Key words: antioxidant additives, iso-paraffins, esters, reactivity, bond length, valent and dihe-dral angles, atomic charges, motor fuel, antiknock ability

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2016, Т. 59, № 12, Стр. 49-56

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