Patent GB-943417-A (GB)
Title: Coke oven light oil purification
IPC: C10C1/20
Filed: 1960-07-20
Abstract: A process for purifying coke oven light oil contaminated with non-aromatic hydrocarbons and sulphur compounds comprises preheating the oil to at least 565 DEG  C., introducing it into contact with a chromia on alumina dehydrogenation catalyst prepared by impregnating porous activated alumina having a surface area of 100-200 sq. m/gm. with 5-40% wt. of the final catalyst of chromium oxide and thereafter adjusting the surface area to a significantly lower surface area of at least 50 sq. m/gm., effecting said contact in the range 599-632 DEG  C. in the presence of added compatible gas (i.e. hydrogen with or without normally gaseous hydrocarbons and/or gases inert under the reaction conditions, e.g. nitrogen) in an amount of 3.1-6.3 mols. of compatible gas per mol. of oil, said gas containing sufficient free hydrogen initially to give a partial pressure of at least 50% of the total pressure of said contact in which said total pressure is 28-70 kg/cm.2 gauge, introducing said light oil at a space rate of 0.1-1.4 vols. oil (as liquid)/vol. catalyst/hour, recovering and separating the effluent into products including a product substantially free of non-aromatic hydrocarbons and sulphur compounds. The light oil may first be vaporized in the presence of hydrogen containing gas at 121-315 DEG  C. at a total pressure of 31.5-65 kg/cm.2 gauge, the vaporized charge further heated and introduced to the dehydrogenation reaction at 593-599 DEG  C. Desirably, the effluent from the dehydrogenation is passed, with reduction of temperature and pressure, to a separation zone, where it is separated into a first fraction, containing substantially all products boiling below benzene, which is in turn passed to separation and purification zones, at least one gas stream comprising hydrogen being recovered, and a second fraction, containing products boiling in the range of benzene and higher, which fraction is subjected to a clay treatment to remove residual non-aromatic hydrocarbons and is then fractionally distilled to recover at least one fraction consisting of substantially pure aromatics. Preferably the liquid hourly space velocity provides a reaction time according to the formula 0 = 3600 MW.P/L.P.(1+G).T.R.  Where #q is the reaction time in seconds and lies in the range 60-180 seconds; MW is the average molecular weight of the liquid oil charge; P is the total absolute pressure; L is the liquid hourly space velocity of the oil charge; P is the density of the liquid oil charge; G is the gas to oil mol. ratio; T is the absolute temperature; and R is the gas constant. Preferably the reaction is effected at an average bed temperature within 5.5 DEG  C. of and no higher than the outlet temperature.ALSO:A dehydrogenation catalyst for the purification of coke oven light oils (see Division C5) is prepared by impregnating porous active alumina having a surface area of 100-200 m.2/g. with 5-40% weight based on the final catalyst, of chromium oxide, and thereafter adjusting the surface area to a significantly lower surface area of at least 50 m.2/g., for example by heat treatment.  Desirably a sterilizing agent such as 0,5-3,5% weight of swelling bentonite and/or an alkali metal content in amount of 0,15-0,5% weight, calculated as the oxide, may be incorporated with the alumina prior to compositing with the chromia. The starting alumina may be a gamma alumina or an alumina obtained from beta alumina trihydrate.  In an example a mixture of alumina trihydrate containing 0,35% Na2O, sodium bentonite, nitric acid and water was aged, extruded, and cut into pellets which were dried and heat treated in air, impregnated with a solution of CrO3, drained, dried, and calcined to obtain the catalyst.