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ISSN 2522-1841 (Online) AZERBAIJAN CHEMICAL JOURNAL No 4 2020 37
ISSN 0005-2531 (Print)
UDC 547.431.5: 621.892
IMPROVEMENT OF THERMAL OXIDATIVE CHARACTERISTICS OF DIESEL FUELS WITH ESTERS OF CYCLIC POLYATOMIC ALCOHOLS
L.M.Yusifova
Y.Mammadaliev Institute of Petrochemical Processes, NAS of Azerbaijan
Received 27.01.2020 Accepted 07.04.2020
A number of symmetric, asymmetric and complex esters of 2,2,5,5-tetramethylolcyclopentanol and 2,2,6,6-tetramethylolcyclohexanol were synthesized, their physicochemical, viscosity-temperature and thermo-oxidative properties were studied. With the addition of these esters to hydrotreated diesel fuels 0.004% it was possible to significantly improve the operational properties of fuels: to increase thermal oxidative stability, flash point and lower pour point. Proceeding from these results, the esters of cyclic polyatomic alcohols are recommended as complex additives to diesel fuels.
Keywords: esters of cyclic polyols, lubricating oils, diesel fuel, operational characteristics, complex additives.
doi.org/10.32737/0005-2531-2020-4-37-42 Introduction
To improve environmental characteristics the removal of sulfur- and nitrogen-containing heterocyclic compounds from diesel fuels (DF) is required, which leads to a decrease in oxidative stability, since sulfur and nitrogen compounds are natural antioxidants and contribute to the inhibition of the oxidation of DF. Following from this, the most effective and cost-effective way to protect DF from oxidative degradation is the use of various antioxidant additives.
Currently, extensive research is underway on the thermo-oxidative transformations of DF and the search for new effective antioxidants. It is required to select such compounds which stabilize a DF, at the same time without interacting with its components responsible for the main operational indicators.
At present, to increase thermal oxidative stability (TOS), antioxidant additives are used (added to the fuel in an amount (0.04-0.05)%), which are a composition of 2,6-di-tert-butyl-4-methylphenol (ionol), nitrogen- or a sulfur-containing derivative of shielded phenol, up to 100 mass% by weight of an organic solvent [1]; the composition of 2,2-methyl-bis (4-methyl-6-tert-butylphenol), an oil solution of alkenyl suc-cinimide, bis-(3.5-di-tert-butyl-2-hydroxybenzy-lidine) ethylenediamine etc. [2, 3]. However
these additives and their compositions at their application the operational properties of fuels is improve insufficiently. For instance, using ionol in an amount of 0.04%, the precipitate is 1 mg/100 ml of fuel. This figure currently does not meet the requirements of Euro-4 and Euro-5.
Therefore, the creation of new effective fuel additives is a very relevant scientific, practical and environmental problem. From this point of view, the synthesis of new esters of cyclic polyatomic alcohols of various structures and their study as additives to diesel fuels has is of certain scientific and practical significance.
Since the synthesized esters have symmetric, asymmetric, complex structures, five and six membered cyclic fragments, most polar ester groups should has is of a positive effect on the properties of fuels [4-6].
Experimental part
The starting cyclic polyatomic alcohols -
2.2.5.5-tetramethylolcyclopentanol (TMCP) and
2.2.6.6-tetramethylolcyclohexanol (TMCH) were synthesized by the aldol condensation of cyclopentanone and cyclohexanone with formaldehyde according to the Cannitzaro-Tishchenko reaction according to the following scheme:
он
CaO
HOH2C
+ Sonja + H20 -► HOH2C
-НСООН
СН2ОН СН2ОН
+5 сн2о + н2о
СаО
-5НСООН нОН2С
,СН2ОН СН,ОН
Symmetric esters were obtained by esteri- fonic acid (PTSA) taken in an amount of 1% of fication of TMCP and TMCH with caproic acid, the mass of the reaction mixture, until the retaken in a molar ratio of alcohol:acid of 1:5.5 in lease of reaction water is stopped [4,5]. the presence of a catalyst of ^ara-toluenesul-
OH
HOH2C. HOH,C
HOH2C, HOH2C
.CH2OH pTSA C5HnOCOH2C,
+5C5HnCOOH
CH,OH
-5H20
C5HnOCOH2C
OCOC5Hu
,CH2OCOC5Hu
CH2OCOC5Hn
OH
CH,OH
+5C,H,,COOH-
PTSA C5HnOCOH2C,
CH2OH
-5H,0
C5HnOCOH2C
ester 1
OCOC5H11
,СН2ОСОС5Нп СН2ОСОС5Нц
ester 2
Asymmetric esters were obtained in 2 were obtained, then in the second stage free stages: in the first, diesters with enanthic acid hydroxyl groups were esterified with caproic acid:
CH2OH + 2C7H15COOH-
PTSA C7H15OCOH2C
OH
чЛ/
,СН2ОСОС,Н15
-гиге
HOHJC CH2OH
.CH,OCOC,H,5
CHjOH + 3C5H„COOH-
С,Н15ОСОН2С.
-3H,0
- C5HnOCOH2C
CH,OCOC7H|5 CH2OCOC5Hn
ester 3
ester 4
The complex esters of TMCP and TMCH free hydroxyl group was esterified with pimelic were obtained in three stages: at the first stage, acid, and at the third stage, the free carboxyl group
tetraesters were obtained by esterification of alcohols with caproic acid, at the second stage, the
of the acid was esterified with hexyl alcohol:
OH
HOH2C CH2OH pTSA C5HnOCOH2C,
Jy^^fC, +4C5HnCOOH »■
HOHjC ^CH2OH 2 C5HnOCOH2C
CH^COCsHn CH2OCOC5Hn
C5HnOCOH2C, C5HnOCOH2C
,CH2OCOC5Hn
CH2OCOC5Hn
C5H„OCOH2C.
HOOC-(CH2)5-COOH ■
C5HnOCOH2C
OCO-(CH2)s-COOH
,CH2OCOCjHn
CH2OCOCsH,,
C5HnOCOH2C, C5IInOCOH2C
OCO-(CH2)5-COOH
,CH2OCOC5Hn
CH2OCOC5Hn
+ CfiH13OH ■
OCO-(CH2>5-OCOCsH13 pTSA C5HnOCOH2C J^ ^CH2OCOC5Hn
h,o
C5H,,OCOH2C
CH2OCOC5H,,
ester 5
HOH2C, HOH2C
I- 4C5HI1COOH -
C5HnOCOH2C, CsHnOCOH2C
,CH2OCOC5Hn CH2OCOC5Hn
,CH2OCOC5Hn
CH2OCOC5H|,
CsHnOCOH2C,
HOOC-(CH2)5-COOH ■
C.H,,OCOH2C
OCO-(CH2)5-COOH
,CH2OCOC5Hn
CH2OCOC5H„
C5HuOCOH2C. C5HnOCOH2C
Ç>CO-(CH2)5-COOH
.CH2OCOC5Hn PTSA CJHuOCOHJC.
+ C6HUOH
CH2OCOC5Hn
-h2o
C5H,,OCOH2C
The structure of the synthesized esters is proved by elemental analysis, IR spectroscopy and method NMR, as well as determination of acid and ether numbers.
Results and discussion
Physico-chemical properties of esters are given in Table 1.
The viscosity-temperature and thermo-oxidative properties of the synthesized esters were also determined (Tables 2, 3). The acid number is determined according to GOST 5895-79, thermo- oxidative stability (TOS) according to GOST 23797-79, volatility according to GOST 20354-74.
As can be seen from Table 2, the symmetric, asymmetric, and complex esters of TMCP in comparison with analogous esters of TMCH have low viscosity levels at 100C and 400C, low pour points, high flash points and viscosity index.
The results determining the thermo-oxidative stability of the esters also showed
OCO-CCHJs-OCOCjH^ ,CH2OCOC5Hn
CH2OCOCjHu
ester 6
that, according to all indicators, the TMCP esters have relatively better indicators than the TMCH esters: acid number 1.30-2.91 mg KOH/g versus 1.15-3.18, the precipitate is insoluble in isooctane 0.002-0.141% of the mass versus 0.004-0.180, volatility of 0.010-0.50% of the mass against 0.65-0.69% of the mass.
The synthesized esters of cyclic polyatomic alcohols were investigated as antioxidant additives wich improve the TOS of diesel fuels. By adding to diesel fuels in an amount of 0.10.004 mass % of these ethers, a number of compositions were prepared and settled on the optimal option - 0.004 mass %. Studied all the indicators of the compositions of diesel fuels, the results of which are given in Table 4.
The TOS of the prepared samples was determined in an LSART apparatus at 1500C for 4 hours (GOST 9144-79), flash point in a closed crucible in the TVZ-LAB-11 apparatus according to GOST 6350, ASTDM 93/SD 2719.
Table 1. Physico-chemical properties of synthesized esters
№ Esters Yield, mass % Boiling point, 0C at 0.27 kPa Refractive index, n20 D Density, p at 200C, kg/m3 Molecular mass, exp/cal Empirical formula
1 ^(CH2OCOC5Hu)2 \-OCOC5Hn ScH2ococ5Hn)2 80 238-240 1.4625 1012 691/694 C38H60O10
2 s (CH2OCOC5H11)2 ^ ^-OCOC5Hn %;CII2OCOC3IIn)2 90 270-272 1.0312 1457 710/712 C40H70O10
3 CH2OCOC5Hn / rn.nfYVjn,. N-OCOCjH,! -¿-CH2OCOCjH, ! \:h2ococ7h15 75.1 256-258 1.4590 999 742/746 C42H76O10
4 CH2OCOC;Hn .-L CH2OCOC7H15 ^ OCOC5ïr1i > /-CH2OCOC,H| ! ï2ir2OCOC7rrl; 83 290-297 1.0138 1465 766/765 C44H78O10
5 ^(CH2OCOC5H11)2 V-OCO-(CH2)5-OCOC6Hn V(CH2OCOC5Hn)2 78 1.4620 1050 820/825 C45H72O12
6 ^(CHaOCOCjHufe ^ OCO-(CH2)5-OCOC6H13 ^{CH2OCOCsHi i)2 80 1.4720 1118 838/840 C47H74O12
Table 2. The viscosity-temperature properties of the synthesized esters
Number of esters Viscosity, mm2/s, at temper. 0C Viscosity index Tem perature, 0C
100 40 -30 flash point pour point
1 7.90 34.20 26346 126 290 -53
2 10.28 42.23 26500 125 281 -47
3 8.61 36.28 26760 138 309 -50
4 10.47 44.51 24300 135 291 -44
5 17.90 56.23 - 136 320 -37
6 17.98 71.63 - 125 334 -31
Table 3. Thermo- oxidative stability of esters of TMCP and TMCH
Number of esters Viscosity at 1000C, mm2/s (after oxidation) Acid number, mg KOH/g (after oxidation) Precipitate insoluble in isooctane, mass % Corrosion, mg/cm2 Volatility, mass.%
AK-4 mx-15
1 8.82 1.30 0.002 0.120 0.025 0.010
2 11.40 1.15 0.004 0.015 0.018 0.65
3 9.60 1.40 0.003 0.130 0.030 0.018
4 11.56 1.36 0.010 0.022 0.035 0.50
5 19.23 2.91 0.141 0.110 0.133 0.50
6 19.80 3.18 0.180 0.100 0.130 0.69
Table 4. Test results for diesel fuel with the addition of esters
Indicators Samples of diesel fuels with ethers
DF I II III IV V VI
Density at 200C, kg/m3 at 15 0C 845.8 846.5 846.5 847.2 847.6 845.9 846.1
at 20 0C 844.6 846.0 846.2 845.4 847.2 844.3 844.6
Kinematic viscosity at 200C, 6.80 6.20 5.90 5.75 5.80 5.83 5.92
mm2/s
Pour point, 0C -18.2 -24.3 -22.6 -25.1 -21.8 -23.7 -22.4
Aromathydrocarbon content, % 17.6 17.3 17.1 17.8 18.0 18.2 17.9
Acidity, mg K0H/100 ml of fuel 0.0026 0.0026 0.0029 0.0030 0.0034 0.0030 0.0035
Thermo-oxidative stability, mg sediment/100 ml of fuel, (with
esters in the fuel 0.004%) 8.6 0.6 1.9 2.2 3.0 3.2 3.6
Test on a copper plate, 3 hours at 500C r e s i s t s
Coking ability of 10% residue, % 0.0025 0.0020 0.0023 0.0021 0.0023 0.0020 0.0025
In closed cup flash point, 0C 76 84 80 86 82 88 83
Fractional composition, 0C initial boiling point 50% distilled at temperature 206 275 202 275 204 270 200 277 203 272 210 280 213 281
96% distilled at temperature 350 352 354 352 356 360 362
End-boiling point 354 356 358 354 360 362 370
Mass fraction of sulfur, ppm 330 328 332 330 334 326 329
Cetane number 45 44.6 44.2 44.8 44.0 44.5 44.1
As a result of studies, it was found that the addition of ethers almost does not affect the fractional composition of diesel fuels, 96% are distilled in the range 350-3620C, the density of all samples is 845-847 kg/m3.
The addition of esters of TMCP and TMCH leads to an increase in the TOS of all samples of the tested fuels, what is determined by the amount of precipitate formed. As can be seen from Table 4, on adding 0.004% of esters of various structures to diesel fuel in six samples, it decreases from 8.6 to 0.6-3.6 mg/100 ml. The coke ability of the 10% residue also decreases: from 0.0025 to 0.0020%. The flash point in a closed cup raises from 76 to 880C, the pour point decreases from minus 18.20C to minus 25.10C. Among the given esters, the best indicators are symmetric and asymmetric esters of TMCP, which is directly related to the con-formational state of the cyclopentane ring [7]. In comparison with complex esters (esters 5, 6), symmetric and asymmetric esters of these alcohols have a certain advantage, which are explained by the fact that they have simple molecular structures and, during oxidation, form
labile and stable peroxide compounds with different thermal stability and initiating ability.
There is scientific information [8] that the effect of esters on the quality of fuels occurs according to a radical mechanism. It is also suggested that two types of peroxide compounds-labile and stable, with different thermal stability and initiating ability are formed under ester oxidation conditions [9]. Labile peroxide compounds represent a- and P-acyloxyhydroper-oxides and their products inside molecular isom-erization. They decompose with high speeds without the formation of free radicals.
Comparison of esters of cyclic polyatomic alcohols - TMCP and TMCH with known antiox-idant additives based on screened phenols (ionol) shows that these esters have significant advantages [2, 3]. In the case of adding 0.04% ionol, the precipitate makes up 1-1.5 mg/100 ml of fuel.
Conclusions
Relying on the results of the work performed, it was found that the addition of esters of cyclic polyatomic alcohols of various structures leads to significant increases in TOS, flash point, as well as lowering the pour point of diesel fuels.
Symmetric, asymmetric and complex esters of cyclic polyatomic alcohols - TMCP and TMCH can be recommended as complex additives to diesel fuels [10-11].
References
1. Pat. 2042709 RF. Additive to fuel. Gershanov F.B., Voronina O.A., Klinaeva E.V., Lyubimov N.V., Golubeva I.A. 1995.
2. Pat. 2372382 RF. Additive to increase the ther-mal-oxidative stability of hydrocarbon jet fuel and jet fuel. Varlamova N.I., Fedorov E.P., Vish-nyakova T.P., Yanovsky L.S., Golubeva I.A., Pustyrev O.G. 2009.
3. Moikin A.A. Prospects for the development of the production of additives to oils, diesel fuels. The world of petroleum products. 2006. № 1. P. 24-27.
4. Mamedyarov M.A., Gurbanov G.N., Yusifova L.M. Alkyl-substituted esters of cyclic polyols as a base and component of lubricating oils. The world of petroleum products. 2019. № 5. P. 27-31.
5. Mamedyarov M.A., Gurbanov G.N., Yusifova L.M. Synthesis and study of esters of 2,2,5,5-tetramethylolcyclopentanol as a base and compo-
nent of lubricating oils. Oil and gas technology. 2019. №3.P. 22-26.
6. Mamedyarov M.A., Gurbanov G.N., Yusifova L.M. Synthesis of complex oligoesters of cyclic polyols and investigation of them as high temperature lubricating oils. Proceedings of the Azerbaijan National Academy of Sciences. 2019. No 1. P. 48-52.
7. Iliel E. Fundamentals of stereochemistry. M.: BINOL. Laboratory of knowledge, 2014. 120 p.
8. Emanuel N.M., Zaikov G.E., Maisus Z.K. The role of the medium in radical chain reactions of oxidation of organic compounds. M.: Nauka, 1973. 279 p.
9. Denisov E.T., Kovalev G.I. Oxidation and stabilization of jet fuels. M.: Chemistry, 1983. 272 p.
10. Mitusova T.N., Polina E.V., Kalinina M.V. Modern diesel fuels and additives to them. M.: Tekhnika, 2002. 64 p.
11. Mitusova T.N., Khavkin V.A., Gulyaev L.A., Kalinina M.V., Vinogradov N.Ya. The current state of production of low-curing diesel fuels in Russian plants. The world of petroleum products. 2012. No 2. P. 6-8.
TSiKLiK СОХАТОМШ SPiRTLЭRlN EFiRLЭRi ЛЭ DiZEL YANACAQLARININ TERMOOKSiDLЭ§MЭ XASSЭLЭRiNiN YAX§ILA§DIRILMASI
L.M.Yusifova
2,2,5,5-tetrametiloltsiklopentanol vэ 2,2,6,6-tetrametiloltsikloheksanolun Ыг slra simmetrik, qeyri-simmetrik vэ кот-р1екБ efirlэri sintez о1ипти§, оп1апп fiziki-kimyэvi, бz1Шuk-temperatur vэ termooksidlэ§mэ хаББэЬп бyrэni1mi§dir Ви efirlэrin 0.004% miqdannda hidrotэmizlэnmi§ dize1 уапаса§та эlavэ edilmэsi ilэ yanacaq1ann istismar xassэlэri xeyli yax§l1a§ml§dlr: termooksidlэ§mэ stabilliyi, a1l§ma temperaturu artlr vэ donma temperaturu isэ a§agl du§ur. Ви nэticэlэrэ эsasэn, tsik1ik Qoxatom1u spirt1эrin efirlэri dizel yanacaglna kompleks эlavэlэr kimi tбvsiyэ olunur.
Адаг sбzlэr: tsiklikроНоПагт е/гПэп, зйНкй уа§1ап, dizel уапаса§1, istismar xassэbri, kompleks э^ЭЬГ
УЛУЧШЕНИЕ ТЕРМООКИСЛИТЕЛЬНОЙ ХАРАКТЕРИСТИКИ ДИЗЕЛЬНЫХ ТОПЛИВ ЭФИРАМИ
ЦИКЛИЧЕСКИХ МНОГОАТОМНЫХ СПИРТОВ
Л.М.Юсифова
Синтезирован ряд симметричных, несимметричных и комплексных эфиров 2,2,5,5-тетраметилолциклопента-нола и 2,2,6,6-тетраметилолциклогексанола, изучены их физико-химические, вязкостно-температурные и термоокислительные свойства. С добавлением этих эфиров к гидроочищенным дизельным топливам 0,004% удалось значительно улучшить эксплуатационные свойства топлив: повысить термоокислительную стабильность, температуру вспышки и снизить температуру застывания. Исходя из этих результатов эфиры циклических многоатомных спиртов рекомендованы в качестве комплексных добавок к дизельным топливам.
Ключевые слова: эфиры циклических полиолов, смазочные масла, дизельное топливо, эксплуатационные характеристики, комплексные добавки.
