") ,_J ; .' ; J ) Articles Indian Journal of Chemical Technology Vol. 9, September 2002, pp. 393-396

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Preparation and performance of new base fuel an!io.xid�I1� based on hindered phenol and heterocyclic amine

- \ . . _ . . " I r . \ b I -\ - :\ a* r :J -Jl$ar\Desai\ iA NjMlsra\ & . K B 1Nal\ - I

'(Department of Chemistry, Faculty of Scie-;ce, M . S. University of B aroda, Baroda 390 002; India

v - hGujarat Al kalies and Chemicals Li mited, P O-Petrochemicals 39 1 346, Baroda, I�a

Received 14 September 2001; revised received 20 June 2002; accepted 22 Jllly 2002

U-PhenyV4-<3',5'-di-tert-butyl-4'-hydroxybenzYI) viperazine was prepared and its synthesis, spectral characteri­sation and thermal stability are reported along with its characteristic as antioxidant in base fuel. The effectiveness of the synthesized antioxidant was compared with that of the commercially available antioxidant. The newly synthe­sizeaantI6xTdarii was round to possess excellent thermal stability and comparable antioxidant activity. -. \

Lubricants and lubricating oi ls are the most i mportant class of materials that require antioxidant protection because most of them function at h igh temperature where number of physical and chemical changes in­volve a complex pattern of thermolytic and oxidative reactions. To avoid or delay the oxidation of oil at h igh temperature, antioxidants are added, out of which, phenolic and amine antioxidants are pre­ferred I . 2,6-Di-tert-butyl-4-methyl phenol (BHT) and derivatives of 1 ,4-diamino benzene are widely used as antioxidants for gasoline. Substi tuted phenolic com­pounds in combination with ester, amine and poly­amines are also used as fuel additive for the preven­tion and control of engine deposite2-4. The oil soluble organo molybdenum compounds in combination with phenolic or amenic antioxidant have been used to im­prove the dispersancy retention capabi l ity of crank­case lubricants5. Many types of heterocycl ic com­pounds including triazine, triazole and oxazolines have been used as antioxidant in turbine aviation oils6. A sulphurised olefi n with th iadiazole derivative is used as antioxidant in lubricating oil as extreme pres­sure additive7. Pyrazol ines and their derivatives are used for long-term storage of liquid fuels as well as metal deactivating additives for light fuels due to their action as multifunctional inhibitors8, Carbazole and other heterocycl ic aromatic amines are useful as addi­tive in gasoline9. Heterocyclic compounds are more stable at higher temperature than other amines and

*For correspondence (E-mai l : j igarndesa i@rediffmai l .com)

) amides, so that l ifeti me of the o i l can be improved with them6. B HT is used as a potent antioxidant in hydraul ic fluid. However B HT suffers from major drawback, h igh volatility and low melting point. It has been reported that volat i l i ty can be minimised by re­placing the methyl group at the position para to hy­droxyl group in BHT by long aliphatic group 10. Most of the amine antioxidants are coloured and produce colour during oxidation, l imiting their use to applica­tion where discolouration can be tolerated I I .

Considering these factors and i n continuation of search for new antioxidants I 2- 1 5, synthesis of new an­tioxidant based on hindered phenol in combination with heterocyclic amine and evaluation of antioxidant activity in base fuel has been reported. The antioxi­dant act ivi ty of newly synthesized antioxidant was compared with commercial sample UOP-S. The structure of B HT was modified by replacing one of the hydrogens of methyl group ,at the position para to hydroxy group by another active moiety. This resulted in getting an antioxidant with less volat i l i ty and high melting point.

2,6-Di-tert-butyl phenol [A] on chloromethylation using paraformaldehyde and dry HCI gas gave 2,6-di­tert-butyl-4-chloromethyl phenol [B] 1 6 which on con­densation with N-phenyl piperazine yielded I -phenyl-4-(3',5' -di-tert-butyl-4'-hydroxybenzyl) piperazine [C]. Compound [C] could also be synthesized by the application of Mannich reaction on 2,6-di- tert-butyl phenol using formalin and N-phenyl piperazine in ethanol. Structure of the synthesized compound has

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been established on the basis of elemental analysis, IR, NMR and mass spectral studies.

Antioxidant activity of synthesized compound [C] was evaluated in base fuels MS & FCC gasol ine and compared with commercially used sample UOP-5 at Indian Oil Corporation Limited [IOCL] using stan­dard test method for oxidation stabi li ty of aviation fuels (Potential residue method) ASTM-D873-94. This method is used for the determination of tendency of aviation reciprocating, turbine, and jet engine fuels to form gum and deposit under accelerated aging con­dition. These results can be used to indicate storage stabi l i ty of fuels. Amount of potential gum formed indicates the effectiveness of antioxidant added to i t .

Experimental Procedure

Materials 2,6-Di-tert-butyl phenol, N-phenyl piperazine ob­

tained from Lancaster (Strasbourg, France). Para for­maldehyde and formalin used were from BDH (Eng­land) make. Organic solvents used were from Spec­trochem (Mumbai, India). Hydrochloric acid (98%) received from Qual igens (Mumbai, India).

Analysis Elemental analysis was performed using Perkin­

Elmer-2400 (Norwalk, CT) C, H, N and S analyser. IR spectrum was recorded on Shimadzu - IR 408 (Ja­pan) spectrophotometer as KBr pel let. NMR spectrum was recorded on Brukers-200 MHz (Wissenbourg­France) spectrophotometer using CDCl3 as solvent and TMS as internal standard. S ignal positions (8 val­ues) were measured relative to the TMS signal (8 0). Mass spectrum was recorded on Fil l i sinnigan MAT-1 020B instrument. Thermal analysis and melting points were determined using T A instrument DSC 29 1 0 (USA). 2,6-Di-tert-butyl-4-chloromethyl phenol [B) was synthesized from 2,6-di-tert-butyl phenol ac­cording to the reported method 1 6.

Synthesis of l-phenyl-4-(3',S'-di-tert-butyl-4'-hydroxybenzyl) piperazine [C]

Method 1: Condensation of [BI with N-phenyl pi­perazine-To a mixture of 2,6-di-tert-butyl-4-chloromethyl phenol [B) (0. 1 mol) in dry benzene (25 mL), N-phenyl piperazine (0. 1 mol) was added slowly fol lowed by triethyl amine (0. 1 5 mol). The reaction mixture was refluxed for 6 h. Excess of ben­zene was removed by disti llation . Benzene layer was washed with di l . HCI fol lowed by distilled water.

394

Indian J. Chern. Technol . , September 2002

Product obtained by removing benzene was crystal­l i sed from hexane. Y ield 90%, m.p. = 1 2 1 °e.

Method 2: Mannich reaction on 2,6-di-tert-butyl phenol - N-Phenyl piperazine (0. 1 mol) was added to the mixture contain ing 2,6-di-tert-butyl phenol (0. 1 mol) and formal in 30% (0.4 mol) in ethanol (25 mL). The mixture was refluxed for 5 h and poured in ice cold water. The product obtained was fi ltered, dried and crystal l i sed from hexane. Yield 94%, m.p. 1 2 1 °e.

Spectral characterisation

The compound [C] i s white crystal l ine solid. Ele­mental analysis (%) calculated for M.F. C2sH36N20, C: 78 .90, H: 9.40, N: 7 .36; Found: C: 79.29, H: 9 .75, N: 7 .24. IR ( KBr, cm- I ) : 3622(YOH phenol), 3070(YCH aromatic ring), 1 48 1 - 1 470 (Yc=c tetra substituted aro­matic), 1 375 (YCH methyl) . I H NMR 8 (ppm): 1 .44 (s, 1 8H, 2xC (CH3h, 2 .70-3 . 1 9 (m, 4H, CH2-CH2), 3 .59 (s, 2H ,CH2-N), 5 .20 (s, 1 H, OH), 6.9-7.3 (m, 7H, ArH). MS (mlz): 380 [M+, 1 00], 2 1 9 [380- 1 6 1 (C6HSN (CH2h. (CH2h.N+)], 1 32 [ 1 6 1 -29 (CH2=NH)], 1 04 [ 1 32-28 (CH2=CH:J] ' 77 [ 1 04-27 (HCN»). Thermal decomposition temperature was found to be 252.2°e.

Evaluation of antioxidant activity by potential resi­due method

Base fuel was mixed with specific concentration of antioxidant and was kept in a weighed glass sample container. This glass sample container was placed in a bomb and oxygen was introduced in order to flush out air present original ly . Charged bomb was then placed in an oxidation bath for 4 h 17 at 1 00°e. After com­plete oxidation, bomb was removed, cooled and amount of soluble and i nsoluble gum formed during oxidation was measured. Temperature and pressure condition used in this method was according to the ASTM D-873-94 method. An effective antioxidant should protect oxidation and hence gum formation should be less.

The synthesized antioxidant [C) and commercial antioxidant UOP-5 are tested in base fuel (MS) at two different concentration 1 0 ppm and 20 ppm and in base fuel (FCC gasoline) at 20 ppm. Results obtained are l isted in Tables 1 & 2 .

Results and Discussion Synthetic route for the preparation of I -Phenyl-4-

(3', 5'-di-tert-butyl -4'-hydroxybenzy I) plperaZll1e

Desai el al. : Preparation and performance of new base fuel antioxidant

from 2,6-di -tert-buty l-4-ch loromethyl phenol and from 2,6-di-tert-butyl phenol is shown in Scheme 1 .

Dry 110 gas Acetic Acid (lieIlO)"

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J ?II Dry Ilwull<

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Scheme 1

From the Tables I & 2, i t has been shown that i n the absence of antiox idant, the degradation of base fuel ( M S ) and base fuel (FCC gasol ine) are very fast, this i s probably because gasol ine and fuel s contain unsaturated hydrocarbon that oxidise eas i ly on storage forming free radicals. Th i s degradation leads to the formation of soluble and insoluble gu m .

The amount of potential g u m formation in t h e ab­sence of anti ox idant in base fuel (MS) is 4.8 mg/ l OO mL, whi le potential gum formation i n base fuel ( FCC gasol ine) is 8 .6 mg/ l OO mL. However, with the commercial ly ava i lable antiox idant UOP-S the potential gum formation in base fuel (MS) i s 3.4 mg/ I OO mL at 1 0 and 20 ppm level . This value in base fuel ( FCC gasoli ne) i s 6 .2 mg/ 1 00 mL at 20 ppm leve l . These values of potential gum suggest that UOP-S can resist the oxidation of base fuels and hence i t is an effective antioxidant for base fue l .

Wi th the synthesized antioxidant [C], the potential gum formation values are qui te comparable with that of base fuel with UOP-S. The potential gurr. formation

values in base fuel (MS) with antioxidant [C] at 1 0 ppm level is 3 . 8 mg/ l 00 mL and at 20 ppm level i s 3 .6 mgl l 00 mL. The potential gum formation value in base fuel (FCC gasol ine) wi th [C] at 20 ppm l evel is found to be 7 .2 mg/ I 00 mL. Above results i ndicate that compound [C] prevents the oxidation of base fu­els and can act as an effect ive antioxidant for base fuels . Here activ i ty is due to the presence of h indered phenol ic group in combination with h indered amino group, which exhibit the effect of auto synergism i .e . presence of two chemically different antioxidant functional i ty in the same molecule .

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Table I -Activity evaluation in base fuel (MS)

Samples Potential gum, mg/ l 00 mL

B ase Fuel (MS) 4.8

Base fue l + UOP-5 ( 1 0 ppm) 3.4

Base fuel + C ( 1 0 ppm) 3 .8

Base fuel + UOP-5 (20 ppm) 3.4

Base fuel + C (20 ppm) 3 .6

Base fuel (MS) = Reformate 40%, SR Naptha 30% and FCC gasol i ne 30% by volume.

Table 2-Activity evaluation in base fuel (FCC gasol ine)

Samples

B ase fuel (FCC gasol ine)

Base fuel + UOP-5 (20 pplll) Base fuel + C ( 20 pplll)

Potential gum, mg/ l 00 mL

8.6

6.2

7.2

The new antioxidant has good thermal stab i l i ty and excel lent stabi l is ing property . The newly synthesized antioxidant is white in colour and does not i mpart any c1 i scolouration to base fuel at processing temperature. Based on the above facts it can be concl uded that th is antioxidant i s a su i table antiox idant for base fuel and its performance is comparable w i th commercial sam­ple UOP-S .

Acknowledgement The authors are thankfu l to Dr. A. K. Bhatnagar

and Dr Sari n, Indian Oi l Corporation Limi ted, for evaluating antioxidan t activ i ty . One of the authors (J.D . ) thanks Gujarat Alkalies and Chemicals Limited for the award of J . R . F and for all other necessary fa­c i l it ies.

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