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US 2005/0224395 Al

PRODCUTION OF POLYMER/FOOD GRADESOLVENTS FROM PARAFFIN RICH LOW VALUE

STREAMS EMPLOYING HYDRO PROCESSING

FIELD OF THE INVENTION[0001] The present invention relates to the process for thepreparation of Polymer/Food grade hydrocarbon solvents ofnaphtha range essent ially free from ole fins less than 2 0 ppmof aromatics and less than 1 ppm of sulfur from paraffinicrich low value streams such as raffinate from the solventextraction units in crude oil refineries employed for recoveryof aromatics from reformate by hydrogenation in the presence of a nickel based catalyst.

BACKGROUND OF THE INVENTION

[0002] Petroleum naphtha is a widely used solvent both inindustry and laboratories. Different grades of naphtha solvents are available for various applications. These solventsare normally used as

[0003] a an ingredient in the finished product,

[0004] b) solvent s for extract ion of vegetable oil (fromoil seeds), minerals, pharmaceuticals,

[0005] c) solvents for reactants e.g. in polymerizationreactor and

[0006] d) solvents for cleanup and maintenance operations.

[0007] These solvents are manufactured from low boilingrefinery streams like naphtha and find their applications inagriculture, food and pharmaceuticals, petrochemicals,printing, paint and coating, chemical industries etc.

[0008] Though, there does not exist any universally

accepted nomenclature for hydrocarbon solvents, mostmanufacturers group their solvents according to boilingpoint and composition. Distillation range is also one of themain criteria. Solvent grades with narrow and wide boilingranges, also referred to as Special Boiling Point Spirits(SBPS) are generally found in the boiling range of 45-160C. White spirit is the name given to solvents in the boilingrange of 150-220 C. Composition is another importantparameter for characterizing the solvents. Depending uponthe type of compounds present in the solvents, they arenamed such as aromatic solvents, Isoparaffinic solvents. Formost of the polymers and resins, solvent power is found inthe following order:

[0009] Aromatics>Naphthenes>n-Paraffins>i-Paraffins

[0010] Aromatics are known to have maximum solubilizing power. However, from toxicological and performancepoint of view, benzene-free and very low aromatic contentsolvents are required in applications e.g. Oil seed extraction,polyolefins manufacture, printing inks and adhesives.Evaporation rate, appearance, color and odor are some of theother important characteristics of solvents. When the solvents consist mainly of a single hydrocarbon, they arenamed after the same e.g. Hexane, Isohexane, Heptane etc.

[0011] In an extract ion processes, the function of thesolvent is to extract selectively some particular ingredientfrom a mixed product or raw material e.g. vegetable oils,pharmaceuticals, cleaning degreasing etc. For food processing and pharmaceutical applications, criteria must be

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strictly qualified with respect to present of compoundshaving toxicological properties. In chemical process, thefunction of the solvent is to act as an inert reaction mediumor catalyst carrier e.g. in polyolefins manufacture. In these

and other process, apart from benzene and other aromaticscontent, strict specifications are maintained with respect toolefins, Sulfur also.

[0012] The product form Hydrocracking unit are very lowin aromatics. Therefore, fractionation of hydrocracker naphtha into suitable boiling ranges is often done to producedearomatised solvents. But hydrocracker naphtha is a premium product and has other preferred uses e.g. feedstock forreforming, ethylene cracking etc. The S content in Hydrocracker naphtha quite often exceeds 1 ppm due to recombination of H 2 S and ole fins into mercaptans . This amount ofsulfur is unacceptable in Food Grade and Polymer Gradesolvents. Catalytic hydrogenation of Straight Run Naphthastreams is another option. However, the sulfur present inthese streams require prior desulfurisation and the higherpressure process employing sulfided catalysts are uneconomical. Patents describe processes for hydrogenation ofbenzene in heterogeneous reactor either in liquid phase (U.S.Pat. No. 4,327,234: Hydrogenation process using supportednickel catalyst) or in gas phase (U.S. Pat. No. 5,771,86:Process for hydrogenating benzene in hydrocarbon oils) aswell as in homogeneous reactor (U.S. Pat. No. 5,668,293:Catalyst and a benzene hydrogenation process using saidcatalyst). Patents also describe proceses for benzene hydrogenation through catalytic distillation (U.S. Pat. No. 6,084,141: Hydrogenation process comprising a catalytic distillation zone comprising a reaction zone with distribution ofhydrogen, U.S. Pat. No. 6,048,450: Process for the selectivereduction to the content of benzene and light unsaturatedcompounds in a hydrocarbon cut). However, all these pro

cesses are meant for meeting benzene specifications in MSwhere benzene is required to be reduced to 1 vol % only tomeet the most stringent Euro-IV standard. In addition tohydrogenation of benzene in fuels, patents describe processes for production of cyclohexane also through hydrogenation of Benzene (U.S. Pat. No. 5,589,600: Preparationof cyclohexene by partial hydrogenation of benzene).

[0013] Solvent extraction is another method used for theproduction of dearomatised solvents. A patent (IN 168536)describes such a process of Separation of benzene and C5-6non-aromatic hydrocarbons from naphtha fractions by countercurrent extraction for recovery of food-grade n-hexane.

[0014] However, for very low aromatics concentration insolvents, solvent extraction would be prohibitively expen

sive. Moreover, solvent extracted paraffins have relativelylower solvent power in comparison to hydrogenated solvents, as the naphthenes from saturation partly compensatefor the solvent power of the aromatics. Moreover, solventextracted solvents may not be able to mee t the specificationsfor Bromine member (olefins).

[0015] Adsorptive dearomatisation using silica gel, alumina and activated carbon has not so far been attractive forlarge scale commercial production due to requirements forcontinuous regeneration. Acidic clays also been used forproduction of solvents. But they only remove olefins, notaromatics. Two patents (IN 184574 IN 179409) describemethods to produce Food Grade Hexane through adsorptionand clay treatment.

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