Method for bio-oxidative desulfurization of liquid hydrocarbon fuels and product thereof

Abstract

Disclosed herein is a method for producing ultra-low-sulfur content hydrocarbon fuel and product thereof. The method comprises selective biocatalytic oxidation of sulfur containing compounds present in the fuels employing enzyme lipase as biocatalyst in presence of controlled and incremental amount of hydrogen peroxide and carboxylic acid without using water or any co-factor for the reactivity of said enzymes.

Description

FIELD OF THE INVENTION[0001]This invention, in general, relates to the field of hydrocarbon fuel, in particular to the method for desulfurization of the liquid hydrocarbon fuel and product thereof. More specifically but without restriction to the particular embodiments hereinafter described in accordance with the best mode of practice, this invention provides a method for selective biocatalytic oxidation of sulfur containing compounds present in fossil fuels employing enzyme lipase as a biocatalyst.BACKGROUND OF THE INVENTION[0002]Sulfur compounds are widely distributed in petroleum distillates of all boiling ranges. In gasoline, the principal sulfur compounds are mercaptans, aliphatic sulfides, disulfides, five and six membered ring cyclic sulfides, while diesel fuel is rich in benzothiophenes and alkyl substituted benzothiophenes. The removal of sulfur from fuels is necessary for both industrial and environmental reasons. Sulfur in fuels poisons catalytic converters, corrodes the ...

AI Technical Summary

Benefits of technology

The present invention provides a method for producing ultra-low-sulfur fuel oils using bio-oxidative desulfurization of fossil fuel using a selective catalyst, lipase enzyme. The method selectively removes sulfur content from the fuel by oxidizing thiophenes and organosulfides to their respective sulfoxides and sulfones, without apparently changing non-sulfur-bearing components of the fuel. The method is pH independent and does not require water or co-factors for reactivity. The invention also provides a method for producing ultra-low-sulfur fuel oils using controlled and incremental amounts of hydrogen peroxide and carboxylic acid to oxidize thiophenes and organosulfides to their respective sulfoxides and sulfones, and a microbial source enzyme that is recoverable and reusable. The method is effective in removing even the most refractory organic sulfur compounds, such as dibenzothiophene and related sulfur-bearing organic sulfides. The invention also provides an industrial and environmental friendly hydrocarbon fuel with ultra-low-sulfur content.

Problems solved by technology

Sulfur in fuels poisons catalytic converters, corrodes the parts of internal combustion engines and refinery equipment because of the formation of oxy-acids of sulfur.

However, more active catalysts and recent developments in fixed bed hydro treating technology have reduced the time spent in the reactor, thus lowering the required reactor volume and operating costs but it is limited in treating benzothiophene and dibenzothiophene especially DBTs having alkyl substitutions on their 4 and / or 6 positions.

The 4,6 disubstituted compounds do not adsorb on the active sites of the catalyst due to steric limitations.

But the usage of such oxidants is known to be very non-selective and slow.

The use of large amount of hydrogen peroxide make it environment reactive and moreover, safety-related issues are also an area of concern.

Chemical oxidation route as described above are known to be very non-selective and slow.

The use of large amount of hydrogen peroxide makes it environment reactive and moreover, safety-related issues are also an area of concern.

Although this process is effective, it is energy-intensive and requires aqueous medium for reaction.

Microbial desulfurization, however, requires a vast amount of water during the desulfurization process to sustain microbial activity (intrinsic mass transfer issue).

Beside this, microorganisms for desulfurization also degrade some aliphatic or aromatic fractions of fuels causing the decrease of fuel yield.

The method reported in prior art for biocatalytic oxidation of organosulfur compounds require considerable amount of water in diesel mixture for reaction leading to stable emulsion formation and poor recovery of water soluble products.

Moreover, some of the enzyme requires costly co-factors (co-enzymes) and are pH sensitive.

The major drawback of these co-factor dependent enzymatic desulfurization reactions is that co-factors are gradually destroyed due to undesired side reactions.

These co-factors (co-enzymes) are very expensive.