The present disclosure relates to a process of preparing a fuel additive composition. BACKGROUND A number of automobile fuel additives have been developed over the past decade to improve the performance characteristics and efficiency of gasoline and other fuels. These include octane improvers, cetane improvers, gasoline and diesel deposit control additives, metal deactivators, oxygenates, antioxidants and corrosion inhibitors.

Recent advances in the design and construction of combustion engines have resulted in an increased use of silver and its alloys to help prevent carbon deposition in combustion engines. Silver is used as a material for fuel tank level sensors because of its resistance to corrosion caused due to water, salts and acids. However, it is susceptible to corrosion in the presence of elemental sulfur, hydrogen sulfides and volatile mercaptans which are present in the automotive fuels. This, however, has created difficulty in using silver and its alloys to make engine parts and fuel level sensors. However, this corrosion of silver and its alloys can be prevented by using silver corrosion inhibitors as fuel additives. These fuel additives form a very strong film over the silver metal surface and thus, prevent an attack of the sulfur species on the metal surface.

The most common fuel additives useful as silver corrosion inhibitors are alkyl disulfides and alkyl disulfide derivatives of thiadiazoles. However, the sulfur content in these derivatives of thiadiazoles is as high as above 35% in there neat form. Environmental regulations are changing towards use of fuel additives having low amounts of sulfur, nitrogen and other toxic elements.

The processes for the preparation of the fuel additive composition are complicated and expensive.

There is, therefore, felt a need to develop a simple process to prepare fuel additive compositions that is economical.

OBJECTS Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows.

It is an object of the present disclosure to ameliorate one or more problems of the prior art or to at least provide a useful alternative.

An object of the present disclosure is to provide a fuel additive composition that act as silver corrosion inhibitors.

Another object of the present disclosure is to provide a simple and economical process for preparing a fuel additive composition.

Other objects and advantages of the present disclosure will be more apparent from the following description, which is not intended to limit the scope of the present disclosure.

SUMMARY

The present disclosure provides a process for preparing a fuel additive composition. The process involves the following steps.

2-Mercaptobenzimidazole and a dialkylamine are mixed in at least one fluid medium selected from either group (a) consisting of toluene, xylene, and heavy aromatic naphtha, or group (b) consisting of methanol and acetonitrile, and the resultant mixture is stirred to obtain a first reaction mixture.

The dialkylamine is represented by Formula I,

Formula I

R is at least one selected from C1-C15 straight chain, branched chain and cyclic alkyl groups, C1-C15 straight chain, branched chain and cyclic hydroxyl-alkyl groups and Q-Qs substituted or unsubstituted aromatic, heteroaromatic, bridged ring and alkyl aromatic groups.

Formaldehyde is added to the first reaction mixture over a predetermined period of time

while stirring to obtain a second reaction mixture, and the second reaction mixture is stirred at a temperature in the range of 50 °C to 100 °C to obtain a slurry comprising a compound of formula I and the fluid medium.

Formula II R is at least one selected from Q-Cis straight chain, branched chain and cyclic alkyl groups, C ₁ -C15 straight chain, branched chain and cyclic hydroxyl-alkyl groups and C ₁ -C15 substituted or unsubstituted aromatic, heteroaromatic, bridged ring and alkyl aromatic groups.

The slurry is dehydrated to obtain the fuel additive composition when the fluid medium is selected from the group (a). Alternately, when the fluid medium is selected from the group (b), the slurry is subjected to further steps. These steps consists of (A) dehydrating the slurry followed by subjecting the dehydrated slurry to evaporation under reduced pressure of the fluid medium to obtain a compound of Formula II, and (B) mixing the compound of Formula II with at least one fluid medium selected from the group (a) to obtain the fuel additive composition. In accordance with the embodiments of the present disclosure, R is selected from the group consisting of ethyl, isopropyl, butyl, hexyl, octyl, 2-ethylhexyl, isobutyl, 2-hydroxyethyl, benzyl, and pyridin-2-ylmethyl.

In accordance with one embodiment of the present disclosure, 2-mercaptobenzimidazole is a substituted 2-mercaptobenzimidazole. At least one of the positions 4, 5, 6 and 7 on 2- mercaptobenzimidazole has a moiety independently selected from C ₁ -C15 straight chain, branched chain and cyclic alkyl groups, C ₁ -C15 straight chain, branched chain and cyclic hydroxyl-alkyl groups, and C ₁ -C15 substituted or unsubstituted aromatic, heteroaromatic, and alkyl aromatic groups.

The molar ratio of 2-mercaptobenzimidazole and diaikylamine (I) is in the range of 1: 1.8 to 1 :2.2.

The molar ratio of 2-mercaptobenzimidazole and formaldehyde is in the range of 1: 1.8 to 1 :2.2. Formaldehyde is in a form selected from the group consisting of aqueous solution of formaldehyde and paraformaldehyde.

The amount of formaldehyde in the aqueous solution of formaldehyde is in the range from 5 weight to 70 weight .

The predetermined period of time is in the range of 15 minutes to 300 minutes.

The second reaction mixture is stirred at a temperature in the range of 50 °C to 100 °C for a time period in the range of 3 hours to 36 hours.

The dehydration of the slurry is carried out by contacting the slurry with at least one dehydrating agent selected from the group consisting of sodium sulfate, molecular sieves, and silica.

The yield of compound of Formula II is in the range of 85 % to 99.5 , and the purity of compound of Formula II is in the range of 90 % to 99.5%.

The fuel additive composition comprises the compound of Formula II in the range of 30 weight% to 70 weight% of the total weight of the fuel additive composition. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING

The present disclosure will now be described with the help of the accompanying drawing, in which:

Figure 1 depicts a photograph showing inhibition of silver corrosion in gasoline containing 50 ppm sulfur, wherein 1 shows corrosion obtained for gasoline without corrosion inhibitor, 2-4 show corrosion inhibition using a standard corrosion inhibitor in different concentrations, and 5-7 show corrosion inhibition using fuel additive of the present disclosure in different concentrations; and

Figure 2 depicts a photograph showing inhibition of silver corrosion in diesel containing 50 ppm sulfur, wherein 1 shows corrosion obtained for diesel without corrosion inhibitor, 2-4 show corrosion inhibition using standard corrosion inhibitor in different concentrations, and 5-7 show corrosion inhibition using fuel additive of the present disclosure in different concentrations. DETAILED DESCRIPTION

Silver corrosion inhibitors in the state-of-the-art are toxic to the environment due to their high sulfur content. Further, the processes for their manufacturing are complicated and expensive. The present disclosure therefore envisages a simple and economic process for preparing fuel additive, useful as silver corrosion inhibitors.

The present disclosure provides a process for preparing a fuel additive composition. The process involves the following steps. 2-Mercaptobenzimidazole and a dialkylamine are mixed in at least one fluid medium selected from either group (a) consisting of toluene, xylene, and heavy aromatic naphtha, or group (b) consisting of methanol and acetonitrile, and the resultant mixture is stirred to obtain a first reaction mixture.

The dialkylamine is represented by Formula I, H R" ^R

Formula I

R is at least one selected from Q-Cis straight chain, branched chain and cyclic alkyl groups, Ci-Ci5 straight chain, branched chain and cyclic hydroxyl-alkyl groups and Q-Qs substituted or unsubstituted aromatic, heteroaromatic, bridged ring and alkyl aromatic groups. Formaldehyde is added to the first reaction mixture over a predetermined period of time while stirring to obtain a second reaction mixture, and the second reaction mixture is stirred at a temperature in the range of 50 °C to 100 °C to obtain a slurry comprising a compound of formula II and the fluid medium.

Formula II

R is at least one selected from C1-C ₁ 5 straight chain, branched chain and cyclic alkyl groups, C1-C15 straight chain, branched chain and cyclic hydroxyl-alkyl groups and Q-Qs substituted or unsubstituted aromatic, heteroaromatic, bridged ring and alkyl aromatic groups. The slurry is dehydrated to obtain the fuel additive composition when the fluid medium is selected from the group (a).

Alternately, the slurry is subjected to further steps when the fluid medium is selected from the group (b). The steps consists of (A) dehydrating the slurry followed by subjecting the dehydrated slurry to evaporation under reduced pressure of the fluid medium to obtain a compound of Formula II, and (B) mixing the compound of Formula II with at least one fluid medium selected from the group (a) to obtain the fuel additive composition.

In accordance with the embodiments of the present disclosure, R is selected from the group consisting of ethyl, isopropyl, butyl, hexyl, octyl, 2-ethylhexyl, isobutyl, 2-hydroxyethyl, benzyl, and pyridin-2-ylmethyl. In accordance with one embodiment of the present disclosure, 2-mercaptobenzimidazole is a substituted 2-mercaptobenzimidazole. At least one of the positions 4, 5, 6 and 7 on 2- mercaptobenzimidazole has a moiety independently selected from C1-C15 straight chain, branched chain and cyclic alkyl groups, C1-C15 straight chain, branched chain and cyclic hydroxyl-alkyl groups, and C1-C15 substituted or unsubstituted aromatic, heteroaromatic, and alkyl aromatic groups. Positions 4, 5, 6 and 7 on 2-mercaptobenzimidazole are shown in Formula III.

Formula-Ill

The molar ratio of 2-mercaptobenzimidazole and dialkylamine (I) is in the range of 1: 1.8 to

1 :2.2. In accordance with an embodiment of the present disclosure, the molar ratio of 2- mercaptobenzimidazole and dialkylamine (I) is 1 :2.

The molar ratio of 2-mercaptobenzimidazole and formaldehyde is in the range of 1: 1.8 to

1 :2.2.

In accordance with an embodiment of the present disclosure, the molar ratio of 2- mercaptobenzimidazole and formaldehyde is 1 :2.

Formaldehyde is in a form selected from the group consisting of aqueous solution of formaldehyde and paraformaldehyde.

The amount of formaldehyde in the aqueous solution of formaldehyde is in the range from 5 weight to 70 weight . The predetermined period of time is in the range of 15 minutes to 300 minutes.

The second reaction mixture is stirred at a temperature in the range of 50 °C to 100 °C for a time period in the range of 3 hours to 36 hours.

The dehydration of the slurry is carried out by contacting the slurry with at least one dehydrating agent selected from the group consisting of sodium sulfate, molecular sieves, and silica.

In accordance with preferred embodiment of the present disclosure, the dehydrating agent is sodium sulfate.

The yield of compound of Formula II is in the range of 85 % to 99.5 , and the purity of compound of Formula II is in the range of 90 % to 99.5%. The fuel additive composition comprises the compound of Formula II in the range of 30 weight to 70 weight of the total weight of the fuel additive composition.

The compound of Formula II is 13-bis(dialkylamino)methyl-lH-benzo[d]imidazole-2(3H)- thione. Non-limiting examples of compound of formula II present in the fuel additives of the present disclosure are as follows:

l,3-bis((diethylamino)methyl)-lH-benzo[d]imidazole-2(3H)-thi one (1)

l,3-bis((dibutylamino)methyl)-lH-benzo[d]imidazole-2(3H)-thi one (2)

l,3-bis((dihexylamino)methyl)-lH-benzo[d]imidazole-2(3H)-thi one (3) l,3-bis((dioctylamino)methyl)-lH-benzo[d]imidazole-2(3H)-thi one (4)

l,3-bis((diisopropylamino)methyl)-lH-benzo[d]imidazole-2( 3H)-thione (5)

l,3-bis((dibenzylamino)methyl)-lH-benzo[d]imidazole-2(3H)-th ione (6)

l,3-bis((bis(pyridin-2-ylmethyl)amino)methyl)-lH-benzo[d]imi dazole-2(3H)-thione (9)

The synthetic scheme for preparation of compound of formula II is represented in Scheme I. Scheme I: Synthetic scheme for compound of formula II

The synthesis of II proceeds via reaction of the secondary amine with formaldehyde to form a Schiff base by the elimination of a water molecule. The Schiff base thus formed, in turn, reacts with the 2-mercaptobenzimidazole (having acidic proton, N-H) to form the fuel additive.

The method of preparation of the fuel additive composition of the present disclosure is a simple process. In one embodiment all the steps of preparation are carried out in single pot.

All the compounds and reagents used for the preparation are cheap and easily available, and the product is obtained in high purity with high yield. Further, the manufacturing process is carried out using routine equipment. Therefore, the process of the present disclosure is economical. Further, these fuel additives are eco-friendly in terms of sulfur content.

The fuel additives of the present disclosure are found to have excellent silver corrosion inhibitory action. The present disclosure is further described in light of the following experiment which is set forth for illustration purpose only and not to be construed for limiting the scope of the disclosure. The following experiment can be scaled up to industrial/commercial scale and the results obtained can be extrapolated to industrial scale.

EXPERIMENTS Example 1: Synthesis of l,3-bis((dibenzylamino)methyl)-lH-benzo[d]imidazole-2(3H)- thione (6)

To a reaction vessel attached with a reflux condenser and a mechanical stirrer, 150 g (1 mole) of 2-mercapto-benzimidazole, 394 g (2 moles) of Ν,Ν-dibenzylamine and 569 g of heavy aromatic naphtha (HAN) were charged and the resultant mixture was stirred for 30 min to obtain a first reaction mixture. 162 g (2 moles) of formaldehyde (37% aqueous solution) was added in a drop wise manner over a period of 30 min (10°C exotherm was observed on the addition of formaldehyde) to obtain a second reaction mixture. The second reaction mixture was heated at a temperature of 60°C for 11 hours. The reaction progress was monitored using FTIR spectrophotometer.

After the completion of the reaction, a slurry containing l,3-bis((dibenzylamino)methyl)-lH- benzo[d]imidazole-2(3H)-thione (6) was obtained. The slurry was passed through sodium sulfate to get dry clear light yellow colored liquid product as a 50% active formulation in heavy aromatic naphtha (HAN). Yield = 98%, and Purity 98.5%.

Example 2: Synthesis of l,3-bis((dibenzylamino)methyl)-lH-benzo[d]imidazole-2(3H)- thione (6)

To a reaction vessel attached with a reflux condenser and a mechanical stirrer, 150 g (1 mole) of 2-mercapto-benzimidazole, 394 g (2 moles) of Ν,Ν-dibenzylamine and 605 g of toluene were charged and the resultant mixture was stirred for 30 min to obtain a first reaction mixture. To the first reaction mixture was added 162 g (2 moles) of formaldehyde (37% aqueous solution) in a drop wise manner over a period of 30 min (8 °C rise in temperature was observed on the addition of formaldehyde) to obtain a second reaction mixture. The second reaction mixture was heated at 60°C for 12 hours. The reaction progress was monitored using FTIR spectrophotometer.

After the completion of the reaction, a product slurry containing 1,3- bis((dibenzylamino)methyl)-lH-benzo[d]imidazole-2(3H)-thione (6) was obtained. This slurry was passed through sodium sulfate to get dry clear light yellow colored liquid product as a 50% active formulation in toluene. Yield = 98%, and Purity 98.2%.

Example 3: l,3-bis((bis(2-ethylhexyl)amino)methyl)-lH-benzo[d]imidazole -2(3H)-thione

(8)

To a reaction vessel attached with a reflux condenser and a mechanical stirrer, 150 g (1 mole) of 2-mercapto-benzimidazole, 482 g (2 moles) of bis(2-ethylhexyl)amine and 660 g of heavy aromatic naphtha (HAN) were charged and the resultant mixture was stirred for 30 min to obtain a first reaction mixture. To the first reaction mixture was added 162 g (2 moles) of formaldehyde (37% aqueous solution) in a drop wise manner over a period of 30 min (10°C exotherm was observed on the addition of formaldehyde) to obtain a second reaction mixture. The second reaction mixture was heated at 60°C for 11 hours. The reaction progress was monitored using FTIR spectrophotometer.

After the completion of the reaction, a slurry containing l,3-bis((bis(2- ethylhexyl)amino)methyl)-lH-benzo[d]imidazole-2(3H)-thione (8) was obtained. The slurry was passed through sodium sulfate to get dry clear light yellow colored liquid product as a 50% active formulation in heavy aromatic naphtha (HAN). Yield = 98%, and Purity = 98.9%.

Example 4: Synthesis of l,3-bis((dibutylamino)methyl)-lH-benzo[d]imidazole-2(3H)- thione (2)

To a reaction vessel attached with a reflux condenser and a mechanical stirrer, 150 g (1 mole) of 2-mercapto-benzimidazole, 258 g (2 moles) of Ν,Ν-dibutylamine and 435 g of heavy aromatic naphtha (HAN) were charged and the resultant mixture was stirred for 30 min to constitute a reaction first mixture. To the first reaction mixture was added 162 g (2 moles) of formaldehyde (37% aqueous solution) in a drop wise manner over a period of 30 min (10°C exotherm was observed on the addition of formaldehyde) to obtain a second reaction mixture. The second reaction mixture was heated at 60°C for 11 hours. The reaction progress was monitored using FTIR spectrophotometer.

After the completion of the reaction, a slurry containing l,3-bis((dibutylamino)methyl)-lH- benzo[d]imidazole-2(3H)-thione (2) was obtained. This slurry was passed through sodium sulfate to get dry clear light yellow colored liquid product as a 50% active formulation in heavy aromatic naphtha (HAN). Yield = 98%, Purity = 98.7%.

Example 5: Synthesis of l,3-bis((diisopropylamino)methyl)-lH-benzo[d]imidazole- 2(3H)-thione (5)

To a reaction vessel attached with a reflux condenser and a mechanical stirrer, 150 g (1 mole) of 2-mercapto-benzimidazole, 202 g (2 moles) of Ν,Ν-diisopropylamine and 380 g of heavy aromatic naphtha (HAN) were charged and the resultant mixture was stirred for 30 min to obtain a first reaction mixture. To the first reaction mixture was added 162 g (2 moles) of formaldehyde (37% aqueous solution) in a drop wise manner over a period of 30 min (10°C exotherm was observed on the addition of formaldehyde) to obtain a second reaction mixture. The second reaction mixture was heated at 60°C for 11 hours. The reaction progress was monitored using FTIR spectrophotometer.

After the completion of the reaction, a slurry containing l,3-bis((diisopropylamino)methyl)- lH-benzo[d]imidazole-2(3H)-thione (5) was obtained. This slurry was passed through sodium sulfate to get dry clear light yellow colored liquid product as a 50% active formulation in heavy aromatic naphtha (HAN). Yield = 96%, Purity = 98.7%.

Example 6: Synthesis of l,3-bis((dihexylamino)methyl)-lH-benzo[d]imidazole-2(3H)- thione (3)

To a reaction vessel attached with a reflux condenser and a mechanical stirrer, 150 g (1 mole) of 2-mercapto-benzimidazole, 370 g (2 moles) of Ν,Ν-dihexylamine and 550 g of heavy aromatic naphtha (HAN) were charged and the resultant mixture was stirred for 30 min to obtain a first reaction mixture. To the first reaction mixture was added 162 g (2 moles) of formaldehyde (37% aqueous solution) in a drop wise manner over a period of 30 min (10°C exotherm was observed on the addition of formaldehyde) to obtain a second reaction mixture. The second reaction mixture was heated at 60°C for 11 hours. The reaction progress was monitored using FTIR spectrophotometer.

After the completion of the reaction, a slurry containing l,3-bis((dihexylamino)methyl)-lH- benzo[d]imidazole-2(3H)-thione (3) was obtained. This slurry was passed through sodium sulfate to get dry clear light yellow colored liquid product as a 50% active formulation in Heavy Aromatic Naphtha (HAN). Yield = 97%, Purity = 98.2%.

Example 7: Synthesis of l,3-bis((dioctylamino)methyl)-lH-benzo[d]imidazole-2(3H)- thione (4)

To a reaction vessel attached with a reflux condenser and a mechanical stirrer, 150 g (1 mole) of 2-mercapto-benzimidazole, 482 g (2 moles) of Ν,Ν-dioctylamine and 660 g of heavy aromatic naphtha (HAN) were charged and the reaction mixture was stirred for 30 min to obtain a first reaction mixture. To the first reaction mixture was added 162 g (2 moles) of formaldehyde (37% aqueous solution) in a drop wise manner over a period of 30 min (10°C exotherm was observed on the addition of formaldehyde) to obtain a second reaction mixture. The second reaction mixture was heated at 60°C for 11 hours. The reaction progress was monitored using FTIR spectrophotometer.

After the completion of the reaction, a slurry containing l,3-bis((dioctylamino)methyl)-lH- benzo[d]imidazole-2(3H)-thione (4) was obtained. This slurry was passed through sodium sulfate to get dry clear light yellow colored liquid product as a 50% active formulation in heavy aromatic naphtha (HAN). Yield = 95%, Purity = 98.5%.

Example 8: Synthesis of l,3-bis(((pyridin-2-ylmethyl)amino)methyl)-lH- benzo[d]imidazole-2(3H)-thione (9)

To a reaction vessel attached with a reflux condenser and a mechanical stirrer, 150 g (1 mole) of 2-mercapto-benzimidazole, 398 g (2 moles) of Di-(2-picolyl) amine and 580 g of heavy aromatic naphtha (HAN) were and the resultant mixture was stirred for 30 min to obtain a first reaction mixture. To the first reaction mixture was added 162 g (2 moles) of formaldehyde (37% aqueous solution) in a drop wise manner over a period of 30 min (10°C exotherm was observed on the addition of formaldehyde) to obtain a second reaction mixture. The second reaction mixture was heated at 60°C for 11 hours. The reaction progress was monitored using FTIR spectrophotometer.

After the completion of the reaction, a slurry containing l,3-bis(((pyridin-2- ylmethyl)amino)methyl)-lH-benzo[d]imidazole-2(3H)-thione (9) was obtained. This slurry was passed through sodium sulfate to get dry clear light yellow colored liquid product as a 50% active formulation in Heavy Aromatic Naphtha (HAN). Yield = 95%, Purity = 98.6%.

Example 9: Synthesis of l,3-bis((dibenzylamino)methyl)-lH-benzo[d]imidazole-2(3H)- thione (6)

To a reaction vessel attached with a reflux condenser and a mechanical stirrer, 150 g (1 mole) of 2-mercapto-benzimidazole, 394 g (2 moles) of Ν,Ν-dibenzylamine and 500 mL methanol were charged and the resultant mixture was stirred for 30 min to obtain a first reaction mixture. To the first reaction mixture was added 60 g of paraformaldehyde in one lot (10°C exotherm was observed on the addition of paraformaldehyde) to obtain a second reaction mixture. The second reaction mixture was heated at 60°C for 11 hours. The reaction progress was monitored using FTIR spectrophotometer.

After the completion of the reaction, a slurry containing l,3-Bis((dibenzylamino)methyl)-lH- benzo[d]imidazole-2(3H)-thione (6) was obtained. This slurry was passed through sodium sulfate and methanol was removed under reduced pressure. Amber colored liquid obtained was dissolved in equal parts by weight with heavy aromatic naphtha (HAN) to get dry clear light yellow colored liquid product as a 50% active formulation. Yield = 95%, Purity = 98%.

Example 10: Silver corrosion inhibition in gasoline

The performance of silver corrosion inhibition was performed using ASTM D7671.

A silver strip was immersed in gasoline containing 50 ppm sulfur. The gasoline was maintained at 50 °C, and the experiment was conducted for 4 hours. This silver strip obtained under these conditions served as a blank sample.

One set of experiments was carried out using gasoline containing different concentrations of 2,5-bis(octyldithio)l,3,4-thidiazole, which served as a standard silver corrosion inhibitor. The concentrations of standard compound in gasoline were 4 ppm, 6 ppm and 8 ppm. Another set of experiments was carried out using gasoline containing different concentrations of the fuel additive containing l,3-bis((2-ethylhexyl)amino)methyl)-lH-benzo[d]imidazole- 2(3H)-thione (8) obtained in Example 3. The concentrations of the compound 8 in gasoline were 4 ppm, 6 ppm and 8 ppm.

The results are shown in Figure 1, wherein 1 is blank sample i.e. sample without use of any corrosion inhibitor. Samples 2, 3, and 4 are samples from experiments carried out using 4 ppm, 6 ppm and 8 ppm of compound of 2,5-bis(octyldithio)l,3,4-thidiazole, the standard silver corrosion inhibitor. Samples 5, 6, and 7 are samples from experiments carried out using the fuel additive obtained in Example 3 of present disclosure such that the gasoline contained4 ppm, 6 ppm and 8 ppm of compound 8 respectively. It was observed that the blank sample showed corrosion with ASTM rating of 4. The samples of standard compound solution of concentrations 4 ppm, 6 ppm and 8 ppm showed corrosion of ASTM rating 0. The samples of the fuel additive obtained in Example 3 with concentrations 4 ppm, 6 ppm and 8 ppm of the compound 8 also showed corrosion of ASTM rating 0, which indicated that the compound inhibits silver corrosion due to elemental sulfur.

Example 11: Silver corrosion inhibition in diesel

Testing of corrosion inhibition was carried out in a way similar to that of gasoline in Example 2. All conditions were same except for use of diesel in place of gasoline.

The results are shown in Figure 2, wherein 1 is blank sample, i.e. sample without use of any corrosion inhibitor. Samples 2, 3, and 4 are samples from experiments carried out using 4 ppm, 6 ppm and 8 ppm of compound of 2,5-bis(octyldithio)l,3,4-thidiazole, the standard silver corrosion inhibitor. Samples 5, 6, and 7 are samples from experiments carried out using fuel additive obtained in Example 3 such that diesel contained 4 ppm, 6 ppm and 8 ppm of compound 8. It was observed that the blank sample showed corrosion with ASTM rating of 4. The samples of standard compound solution of concentrations 4 ppm, 6 ppm and 8 ppm showed corrosion of ASTM rating 0. It was observed that the samples of solution of fuel additive obtained in Example 3, containing compound 8 in concentrations 4 ppm, 6 ppm and 8 ppm showed corrosion of ASTM rating 0, which indicated that the compound inhibits silver corrosion.

TECHNICAL ADVANCES AND ECONOMICAL SIGNIFICANCE

The present disclosure described herein above has several technical advantages including, but not limited to, the realization of silver corrosion inhibitors that:

- are eco-friendly due to their low sulfur content; - economical; and

- are manufactured by simple process. Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps. The use of the expression "at least" or "at least one" suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the disclosure to achieve one or more of the desired objects or results.

Any discussion of documents, acts, materials, devices, articles or the like that has been included in this specification is solely for the purpose of providing a context for the disclosure. It is not to be taken as an admission that any or all of these matters form a part of the prior art base or were common general knowledge in the field relevant to the disclosure as it existed anywhere before the priority date of this application.

The numerical values mentioned for the various physical parameters, dimensions or quantities are only approximations and it is envisaged that the values higher/lower than the numerical values assigned to the parameters, dimensions or quantities fall within the scope of the disclosure, unless there is a statement in the specification specific to the contrary.

While considerable emphasis has been placed herein on the components and component parts of the preferred embodiments, it will be appreciated that many embodiments can be made and that many changes can be made in the preferred embodiments without departing from the principles of the disclosure. These and other changes in the preferred embodiment as well as other embodiments of the disclosure will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation.