Title of Invention

A PROCESS FOR EXTRACTION OF AROMATICS FROM HYDROCARBON STREAM

Abstract

A process for extraction of aromatics from petroleum hydrocarbon stream, said process comprising the step of contacting the petroleum hydrocarbon stream with a mixture of furfural and a co-solvent selected from aliphatic amide having less than 5 carbon atoms or mixture of aliphatic amides having less than 5 carbon atoms wherein the composition of amides in the solvent mixture is less than 30 vol% in a solvent dosage less than 250 vol% to facilitate phase separation and to increase raffmate yield, while maintaining the product qualityas measured by refractive index.

Full Text

FORM 2 THE PATENTS ACT, 1970 (39 of 1970) COMPLETE SPECIFICATION [See Section 10 ,rule 13 ] "A PROCESS FOR EXTRACTION OF AROMATICS FROM HYDROCARBON STREAM" INDIAN OIL CORPORATION LIMITED, a public limited company, G-9, Alf Yavar Jung Marg, Bandra (East), Mumbai 400 051. The following specification particularly describes and ascertains the nature of this invention and the manner in which it is to be performed. GRANTED 9 JAN 2001 25-11-2004 Field of the Invention The invention relates to extraction of aromatics from hydrocarbon oils using furfural-co-solvent mixture to improve the selectivity. Use of this furfural-co-solvent mixture as solvent produces same quality raffinate as those of neat furfural measured by the refractive index, but produces higher yield of raffinate at same solvent to feed treat ratio. Background and Prior Art references to the invention Solvent extraction is a process that separates hydrocarbon mixtures into two phases, a raffinate phase which contains substances of relatively high hydrogen to carbon ratio often called paraffinic type materials and an extract phase which contains substances of relatively low hydrogen to carbon ratio often called aromatic type materials. Therefore, it may be said that solvent extraction is possible because different liquid compoimds have different solution affinities for each other and some combinations are completely miscible while other combinations are almost immiscible. The ability to distinguish between high carbon to hydrogen aromatic type and low carbon to hydrogen paraffinic type materials is termed selectivity. The more fine the distinguishment is done, the higher is the selectivity of the solvent. Solvent extraction of hydrocarbon oils using polar solvents to remove aromatic constituents has long been a standard processing procedure in the Oil Industry. The use of furfural to selectively extract aromatic components from hydrocarbon oils is the subject of many patent, for instance, U.S. Pat. No.2,079,885, U.S. Pat. No.2,698,276, U.S. Pat. No.3,567,627 and U.S. Pat. No.4,571,295, which are incorporated by reference. In U.S. Pat. No.5,922,193, ethers or aldehydes is added to furfural to improve the solvent capacity for debottlenecking the extraction unit and claimed 2-3vol% increase in the raffinate yield during the process. In the prior art, U.S. Pat. No. 4,273,645 additives such as, sodium dodecylbenzene sulfonate or high molecular weight polyethylene oxide resin is added to improve the selectivity of furfural and claimed less than 3vol% increase in the raffinate yield at solvent dosage of 250vol%. Further, in the said prior art, the recovery and material balance of the additive employed is not disclosed. Objects of the invention The main object of the invention is to provide an improved process for the extraction of aromatic type material from hydrocarbon oil containing aromatic material by contacting the hydrocarbon oil with a solvent comprising furfural and a co-solvent. Another object of the present invention is to provide a method employing a co-solvent compnsmg one or more aliphatic amides or mixture of amides having an aliphatic carbon chain of less than 5 carbon atoms. Yet another object of the invention is to provide a method employing a co-solvent comprising aliphatic amides or mixtures of amides having aliphatic carbon chain of less than 3 carbon atoms. Still another object of the invention is to provide a furfural extraction process for lube oil based stock production from hydrocarbon oils employing a co-solvent and furfural in a continuous countercurrent extraction column. One more object of the invention is to provide a furftiral extraction process with a co-solvent to facilitate phase separation and to increase raffinate yield, while maintaining the product quality as measured by raffinate refractive index. Detailed description of the invention: Accordingly, the present invention provides a process for exfraction of aromatics from pefroleum hydrocarbon stream, said process comprising the step of contacting the petroleum hydrocarbon stream with a mixture of furfural and a co-solvent selected from aliphatic amide having less than 5 carbon atoms or mixture of aliphatic amides having less than 5 carbon atoms wherein the composition of amides in the solvent mixture is less than 30 vol% in a solvent dosage less than 250 vol% to facihtate phase separation and to increase raffinate yield, while maintaining the product quality as measured by refractive index. The present invention relates to an improved fiirfural exfraction process for lube oil base-stock production from hydrocarbon oils by the addition of a cosolvent preferably, an aliphatic amide or mixture of amides. Addition of the cosolvent to furfural, conducted in a continuous countercurrent exfraction column facilitates phase separation and increases raffinate yield while maintaining the same raffinate quality measured by raffinate refractive index. In this process, addition of a cosolvent, preferably an aliphatic amide or mixture of amides to fiirfural is done to facihtate phase separation and selectivity, wherein the raffinate yield increases by more than 3 vol% and preferably, more than 5 vol% at solvent dosage preferably less than 180 vol% and more preferably less than 150 vol%. The invention therefore, includes an improved method for the production of lubricant base oil from an aromatic containing hydrocarbon oil comprising contacting the hydrocarbon oil with a solvent comprising fiirfural and a co-solvent, preferably an aliphatic amide or mixture of amides having a aliphatic carbon chain less than five, and more preferably less than three under extraction conditions, producing a raffinate product with increased yield of more than 3vol% and preferably more than 5vol%. The invention further includes the cosolvent employed is recovered alongwith furfural and reused in the process. In an embodiment, the improved furfliral extraction process for hydrocarbon oils, which comprises contacting furfural extraction solvent in a unit with a cosolvent such as hereindescribed, to facilitate phase separation and to increase raffinate yield,_while maintaining the product quality as measured by raffinate refractive index. In another embodiment, the cosolvent is selected from an aliphatic amide or mixture of amides. In yet another embodiment, the amides are selected from aliphatic series with carbon number less than five and preferably less than three. In still another embodiment, the composition of amides in the solvent mixture is less than 30vol%, preferably less than 20vol% and more preferably less than 10vol%. In another embodiment, the yield of raffinate increases by more than 3 vol% and preferably more than 5vol%. In yet another embodiment, the solvent dosage is less than 250vol% preferably less than 180vol% and more preferably less than 150vol%. In another embodiment, the cosolvent-furfural solvent mixture shows improved stability. Feedstock The process is appUcable to hydrocarbon oils namely, vacuum gas oil, hydrotreated / hydrocracked oil and catalytic cracker bottom in the lubricant boiling range. The feedstocks may typically comprise hydrocarbons having initial boiling point of greater than 300°C and a final boiling point of about 600°C, preferably those fractions havmg a boiling range of about 370°C to565oC. These distillate lubricant stocks namely, light neutral, intemeutral and heavy neutral and are usually referred as solvent neutrals and are the distillate fi-actions of the vacuum tower. Solvent extraction Solvent extraction is conducted by contacting the lube distiljate with a selective solvent, furftiral in the present inverition. Since a feedstock contains aromatics usually ranging from at least about 25 vol%, specifically from 25 to 80vol% and more specifically from 30vol% to 60vol%, the feedstock is initially subjected to an extraction step. Extraction utilizes a solvent, which is selective for aromatics, such as furfural in the present invention, and removes the aromatics, which contribute to poor stability and viscosity index. The solvent extraction is conducted with a solvent to oil ratio in the range of from about 0.5:1 to 10:1, such as in the range from about 0.75:1 to 5:1, depending on the feedstock. The operating conditions for furfural extraction cover a temperature range of about 25°C to about 175°C, preferably from about 50°C to 150°C. The yield in terms of volume percent typically ranges from 30 to 80. The characteristics of the product of solvent extraction are very important, and consideration of the solvent extraction conditions coupled with the choice of feed is necessary to achieve a product with the desired viscosity and VT, maximum yield of high VI p/oduct is achieved by adjusting the extraction severity. The resulting rafFmate should have a VI of) at least about 85, preferably 90. The aromatic-reduced rafFmate should contain at most about 40vol% aromatics, preferably ranging from about 10 to 30vol%, even more preferably from 10 to 20vol%. The extractions may be preformed by conventional means, such as in a multistage countercurrent system, in a column with packing material or provided with perforated plates or in a column with a rotating shaft provided with discs. Solvent The process of the present invention involves the addition of a cosolvent preferably an aliphatic amide or mixture of amides to furfural to facilitate phase separation and selectivity. The process of the present invention involves the addition of small volumes of one or more cosolvents to furfural to increase raffmate yield. The properties of the cosolvent employed for the present invention are listed in Table 1. Tabic 1 Cosolvent Properties Generally, the co-solvent is added in an amount less than about 30vol% based on total solvent such as less than about 20vol% based on total solvent, less than about 10vol% based on total solvent and less than about 5vol% based on total solvent, depending on the feedstock. For example, a 10vol% co-solvent 90vol% furfural blend may be used in the extraction process of the present mvention when the feedstock is Arab mix hitemeutral distillate. Co-solvents used in the process of the present invention also have a boiling point in the range of from about 50°C to 225°C, preferably in the range of from about 75°C to 200°C. The addition of co-solvents, such as N-Methyl Acetamide to fiirfural improves its selectivity for exfraction of aromatics from lube distillates. Use of cosolvents in furfural extraction increases the raffinate yield at the same raffinate refractive index (RI). In essence, the invention includes an improved method for the production of lubricait, base oil from an aromatic containing hydrocarbon oil comprising contacting th? hydrocarbon oil, with a solvent comprising fiarfural and a cosolvent, preferably ai aliphatic amide or mixture of amides having a aliphatic carbon chain less than five am more-preferably less than three under extraction conditions, producing a raffinate produo with increased yield of more than 3vol% and preferably more than 5vol%. The invention further includes the cosolvent employed is recovered along with furfural and reused ii the process. The advantage of the present invention allows for retrofitting existing equiprnent. An additional advantage of the furfural/co-solvent mixture of the present invention is the lower operating cost as the cost of the co-solvent employed is lower than that of neat furfural. The addition of the co-solvent of the present invention also improves the stability of the resultant co-solvent-furfural blend compared to furfliral alone preventing degradation of flirfural, which results in lower furfural loss. Description of the preferred embodiment The following examples illustrate the process of the present invention. Arab mix Interneutral distillate having the properties as set forth below in Table 2, was used for each extraction example. Table 2 Properties of Inter-Ncutral Distillate For each furfural, with or without co-solvent, continuous countercurrent extraction was performed in a three meter height bench scale jacketed glass column extraction apparatus. The feed, Arab mix distillate was heated and pumped for example. 1.0kg hr from bottom of the extractor (feed inlet) and the solvent, furfural with or without cosolvent were heated and pumped for example, 1.5kg/hr at the top of the extractor (solvent inlet). The solvent rate was varied accordingly to the desired solvent to freed weight ratios of 1:1.5 and I; 1.8. (These ratios are typically referred to as 150% and 180% solvent dosage). The extractions were performed at column top temperature for example,110oC and column bottom temperature for example 70'C After the mixture of solvent and oil pumping started from their respective inlets, the raffinate phase from the top of t]ie__colum{i. (raffinate product phase outlet) and extract phase from the bottom of the column (extract product phase outlet) were drawn continuously. The interface between the lighter raffinate phase'and heavier extract phase flow. After steady state, say, after 1 to 2 hrs, indicated by constant interface level and constant raffinate and extract phases flow, the raffinate phase and the extract phase were collected simultaneously for a given period of time say, 30 to 40 minutes, in all three to four batches. The two phases collected were weighed to ensure material balance closure. The solvent was stripped from the extract and raffinate with nitrogen under vacuum. The stripped raffinate and extract phases were weighed and the raffinate yield was obtained. Final raffinate samples were analyzed for. Density, API gravity, and Refractive Index (Rl). The results from the continuous countercurrent extraction are shown below as Example 1 and Example 2 corresponding to two Solvent to Feed ratio's (S/F ratio) 1.5 and 1.8, respectively while the rest of the operating parameters are kept constant. Commercially, lube extraction units are operated to a Rl specification since for a particular lube crude and type of refining process, raffinate Rl correlates with the viscosity index (VI) of the dewaxed oil (DWO), with lower Rl corresponding to higher VI. Analysis of the data in Example 1 shows that for extraction conducted at solvent to feed treat ratio of 1.5 or solvent dosage of 150vol%, the cosolvent-fiirfriral blends are more effective than furfural alone, resulting in more than 3 vol% improvement in raffinate yield at same raffinate Rl. Similarly, the Example 2 shows an increase of more than 5vol% of raffinate yield at same Rl at solvent to feed treat ratio of 1.8 or solvent dosage of 180vol%. Example I Countercurrent extraction experimental conditions and Raffinate Properties Example 2 Countercurrent extraction experimental conditions and Raffinate Properties We Claim: 1. A process for extraction of aromatics from petroleum hydrocarbon stream, said process comprising the step of contacting the petroleum hydrocarbon stream with a mixture of furfural and a co-solvent selected from aliphatic amide having less than 5 carbon atoms or mixture of aliphatic amides having less than 5 carbon atoms wherein the composition of amides in the solvent mixture is less than 30 vol% in a solvent dosage less than 250 vol% to facilitate phase separation and to increase raffmate yield, while maintaining the product qualityas measured by refractive index. 2. A process as claimed in claim 1, wherein the aliphatic amides have less than 3 carbon atoms. 3. A process as claimed in claim 1, wherein the composition of amides in the solvent mixture is less than 20 vol% and preferably less than 10 vol%. 4. A process as claimed in claim 1, wherein the yield of raffinate increases by more than 3 vol% and preferably by more than 5 vol%. 5. A process as claimed in claim 1, wherein the solvent dosage is less than 180 vol% and preferably less than 150 vol%. 6. A process for exfraction of aromatics from pefroleum hydrocarbon stream substantially as herein described with reference to the foregoing examples. Dated this 6thday of January, 2001. G. Deepak Sriniwas OfK&S Partners Agent for the Applicants

Documents:

25-mum-2001-cancelled pages(25-11-2004).pdf

25-mum-2001-claim(granted)-(25-11-2004).doc

25-mum-2001-claims (granted) (25-11-2004).pdf

25-mum-2001-correspondence (07-03-2007).pdf

25-mum-2001-correspondence (ipo) (07-12-2004).pdf

25-MUM-2001-CORRESPONDENCE(30-1-2012).pdf

25-mum-2001-form 1(09-01-2001).pdf

25-mum-2001-form 1(24-04-2001).pdf

25-mum-2001-form 13(08-04-2004).pdf

25-MUM-2001-FORM 15(30-1-2012).pdf

25-mum-2001-form 19(18-08-2003).pdf

25-mum-2001-form 2(granted) (25-11-2004).pdf

25-mum-2001-form 2(granted)-(25-11-2004).doc

25-mum-2001-form 26(08-04-2004).pdf

25-mum-2001-form 3(24-04-2001).pdf

25-mum-2001-form 5(24-04-2001).pdf