Classifications

• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
  • C10G27/00—Refining of hydrocarbon oils in the absence of hydrogen, by oxidation
  • C10G27/04—Refining of hydrocarbon oils in the absence of hydrogen, by oxidation with oxygen or compounds generating oxygen

Definitions

• This invention relates to the" conversion of mercaptans or mercaptides into disulfides by free oxygen in a twophase system, one phase of which is formed by a hydrocarbon'oil, particularly a light distillate such as gasoline and kerosine, and the other by an aqueous alkaline solution, particularly an aqueous alkali metal hydroxide solution.
• the quantity of oxygen required to oxidize the mercaptans in a two-phase system can be considerably decreased by the simultaneous use of a comparatively small quantity of a peroxide. Even when a quantity of peroxide is used which as such supplies only a small fraction of the excess of oxygen otherwise required, the quantity of oxygen can be reduced to the quantity which is theoretically necessary, without retarding thereby the conversion of the mercaptans (mercaptides) into disulfides.
• the simultaneous use of a small quantity of peroxide renders it therefore possible to decrease considerably the required quantity of oxygen and accordingly the pressure to be applied, so that the previous drawbacks accompanying the use of larger quantities of oxygen and of higher pressures are avoided.
• oil can be treated per unit of time.
• mercaptans will be used in a generic sense to denote boththe neutral substance as well as the mercaptide ions as the substance exists in aqueous alkaline solutions.
• the desired activation of the effect of oxygen is generally accomplished by using a quantity of peroxide amount to l0% 40%, particularly l5%'25%, of the stoichiometrical quantity with respect to the mercaptans 3 to be converted, calculated for conversion to disulfides;
• Organic peroxides can in most cases be dissolved di rectly in the hydrocarbon oil to be treated in the quantities mentioned.
• Hydrogen peroxide can' only be dissolved in hydrocarbon oils with difiiculty and may conveniently be mixed with the hydrocarbon oil in the form of an alcoholic solution or it may be injected in the hydrocarbon oil in the form of a concentrated solu-- oxygen or air may, for instance, first be passed through I an ozonizer and then dissolved in the hydrocarbon oil.
• peroxides of various types are-
• suitable peroxides are the suitable.
• peroxides in the hydrocarbon oil to be treated by treating the hydrocarbon oil at a suitable temperature, for instance, C.-l25 C. and, more particularly C.- C., with oxygen, whereupon the hydrocarbon oil is brought into contact with an aqueous alkali metal hydroxide solution in the presence of oxygen, pref-
• the initially formed peroxides then activate the oxygen which is used for converting mercaptans into disulfides.
• the present process for converting mercaptans into disulfides is generally put into practice at temperatures of from 0 C. to 70 C., although, if desired, temperatures outside this range may be used.
• the preferred temperature range is from 10 C. to 45 C.
• the oxygen required for the process may be supplied to the two-phase system to be treated, either as such or in the form of a mixture of oxygen with another gas which is inert under the operation conditions.
• a mixture of oxygen with another gas which is inert under the operation conditions.
• air is particularly suitable.
• the oxygen may be either dissolved in the hydrocarbon oil in advance or injected into the hydrocarbon oil while the latter is in contact with the aqueous alkali metal hydroxide solution.
• the quantity of oxygen is at least so large that, together with the oxygen which may be supplied by the peroxide, it is theoretically sufiicient for converting the total quantity of the mercaptans present in the hydrocarbon oil into disulfides.
• the required quantity of oxygen exclusive of the oxygen.
• the process for removing mercaptans from gasoline or kerosine with a mercaptan sulfur content not exceeding 0.040.05% by weight and the gasoline or kerosine is at equilibrium with the atmosphere the quantity of oxygen present in the gasoline or kerosine will generally suffice to bring about the desired oxidation.
• the process for removing mercaptans from gasoline and kerosine is frequently employed shortly after the gasoline or kerosine has been produced from the crude oil and has been subjected to other pretreatments, if any, so that it is not saturated with air. It is then often necessary for air or another oxygen-containing gas to be dissolved in the hydrocarbon oil before or during con tact between the latter and the aqueous alkali metal hydroxide solution.
• the process is carried out under atmospheric pressure. If the process is applied for removing mercaptans from hydrocarbon oils with a relatively high mercaptan content, for instance a mercaptan sulfur content of 0.06% by weight or higher, and air is used as oxygencontaining gas, it may indeed be advisable to operate under somewhat increased pressure so as to dissolve a sufiicient quantity of oxygen in the hydrocarbon oil, but the pressure increase may then be considerably less than in the case Where no peroxides are used for activating the effect of oxygen.
• a relatively high mercaptan content for instance a mercaptan sulfur content of 0.06% by weight or higher
• air oxygencontaining gas
• aqueous sodium and potassium hydroxide solutions of widely differing concentrations are suitable as alkali metal hydroxide solution. It is preferred to make the concentration 2-normal or higher, since higher caustic alkali concentrations promote extraction of the mercaptans and accelerate oxidation to disulfides in the aqueous alkali metal hydroxide solution.
• suitable solutizers may be dissolved therein.
• suitable solutizers in aqueous alkali metal hydroxide solutions are: aminoand hydroxyalkyl amines, in which the alkyl groups contain 2-3 carbon atoms, glycols, amino glycols and diamino alcohols with 3-5 carbon atoms, diamino-, dihydroxyor amino hydroxy dialkyl ethers or -thio others in which the alkyl groups have 2-3 carbon atoms, alkali salts, in particular potassium salts, of fatty acids with 3-5 carbon atoms (e. g.
• aqueous solutions of an alkali metal hydroxide and a phenolate which may or may not be substituted by alkyl groups with a total of not more than 3 carbon atoms and does not contain any other substituents) and which contain at most 54% by volume of water and at least 2 mol/liter of free alkali metal hydroxide.
• the ratio of the quantity of hydrocarbon oil to the quantity of the aqueous alkali metal hydroxide solution may vary between wide limits.
• the ratio of the volume of the aqueous alkali metal hydroxide solution to the volume of the hydrocarbon oil generally lies between 0.5 and 5.
• the process is applied for removing mercaptans from a hydrocarbon oil by bringing the latter into contact with an aqueous alkali metal hydroxide solution in the presence of oxygen and a peroxide
• the desired result may, in general, be obtained by treating the hydrocarbon oil with a quantity of the aqueous alkali metal hydroxide solution which is considerably smaller than the quantity of hydrocarbon oil.
• a quantity of the aqueous alkali metal hydroxide solution from 5% to 50% by volume and more particularly from 10% to 20% by volume, calculated on the hydrocarbon oil, is very suitable.
• the process is used for regenerating an alkali metal hydroxide solution containing mercaptides by treating this solution in the presence of a. hydrocarbon oil, preferably a light hydrocarbon oil, with oxygen and a peroxide, it is preferred to take the ratio of the volume of the aqueous alkali metal hydroxide solution to the volume of the hydrocarbon oil between 0.2 and 5, more particularly between 0.5 and 2.
• a. hydrocarbon oil preferably a light hydrocarbon oil
• the hydrocarbon oil may be supplied to the aqueous alkali metal hydroxide solution in such a manner that the oil is in contact with the aqueous solution for a sufficiently long time, and the continuously discharged hydrocarbon oil passed into a separate settling vessel, in which the entrained aqueous solution separates out and is recycled to the process.
• the process may be applied for removing mercaptans from hydrocarbon oils, particularly light hydrocarbon oils (i. e. hydrocarbon oils with a boiling point or end boiling point of not more than 350 C.), especially gasoline and kerosine of different origin including gasoline or kerosine obtained by straight distillation from crude oils and gasoline and kerosinc obtained from heavy base materials by cracking.
• hydrocarbon oils particularly light hydrocarbon oils (i. e. hydrocarbon oils with a boiling point or end boiling point of not more than 350 C.)
• gasoline and kerosine of different origin including gasoline or kerosine obtained by straight distillation from crude oils and gasoline and kerosinc obtained from heavy base materials by cracking.
• the so-called reformed gasolines may also be freed from mercaptans according to the present process.
• an anti-oxidant e. g.
• an aryl amine or an alkyl phenol the alkyl groups of which contain a total of 4 carbon atoms or more to inhibit the formation of gum from the unsaturated components of the oil.
• a quantity from 0.0001% to 0.01 by weight of such an anti-oxidant will sutlice.
• the hydrocarbon oil no longer contains peroxides at the end of the treatment. This is apparently due to the fact that the peroxide is completely decomposed during contact of the hydrocarbon oil with the aqueous alkali metal hydroxide solution. use of a peroxide does not impair the stability to gum formation of the hydrocarbon oil.
• hydrocarbon oils may further be desirable to remove from the hydrocarbon oils any acids present such as hydrogen sulfide, which are stronger than the mercaptans, by means of a diluted aqueous alkali metal hydroxide solution before oxidizing the, mercaptans in the manner indicated.
• a pretreatment with diluted caustic alkali solution has the further advantage of aromatic mercaptans, which on the one hand possess a considerably stronger acidic character than aliphatic mercaptans, and on the other are more difficult to oxidize than aliphatic mercaptans, being removed, at any rate in a considerable quantity, from the hydrocarbon oil to be treated according to the manner indicated.
• a pre-treatmentwith diluted caustic alkali solution is especially suitable for such products. It is preferable to: carry out this pro-treatment before the cracked products come Further the into contact with oxygen or an oxygen-containing gas so as to prevent the formation of gum.
• the disulfides formed during oxidation pass again into the hydrocarbon oil and for this reason the process is primarily suitable for treating hydrocarbon oils with a low mercaptan content, i. e. lower than 0.05% by weight and preferably lower than 0.02% by weight, calculated as mercaptan sulfur.
• the quantity of disulfides returned into hydrocarbon oil is also small.
• a low content of organic disulfides does not appreciably affect the lead susceptibility of gasoline.
• the greater proportion of the mercaptans may be first removed by one of the hitherto usual methods and then the remainder of the original quantity of mercaptans oxidized according to the process of the invention.
• the pro-treatment for removing the greater proportion of the mercaptans may, for instance, be effected by extracting (without oxidation) the hydrocarbon oil with an aqueous alkali metal hydroxide solution containing a solutizer.
• the present process provides a very simple method by which hydrocarbon oils, particularly gasoline or kerosine, can be freed from mercaptans in a short period, which in many cases varies between 2 and 20 minutes. If the hydrocarbon oil contains mercaptans which are diflicult to oxidize, it may be necessary to keep the oil and the aqueous alkali metal hydroxide solution in contact with each other in the manner described for a somewhat longer period. With a sufiiciently intensive contact between the hydrocarbon oil to be treated and the aqueous alkali metal hydroxide solution, it is, however, also possible in the latter case to free hydrocarbon oil from mercaptans to such an extent that the oil gives a negative doctor test within one hour.
• the invention will be illustrated by the following examples.
• EXAMPLE I A number of tests was carried out whereby a gasoline as a percentage by weight. In the third column of Table I the quantity of the peroxide absorbed by the gasoline is expressed as a percentage of the stoichiometrical quantity with respect to the mercaptan content of the initial gasoline. For purposes of comparison two tests were made without the addition of peroxide.
• the fifth column of Table I shows the total content of oxygen available, i. e. the sum of the quantity of atmospheric oxygen and the oxygen which can be supplied by the peroxide. This total quantity of oxygen is also shown as a percentage of thestoichiometrical quantity with respect to the mercaptan content of the gasoline.
• the sixth column of Table I shows the feed rate of the gasoline expressed in liters per hours.
• the seventh column of Table I relates to the average contact time, expressed in seconds, of the gasoline with the aqueous solution of potassium hydroxide and cresolate.
• Co represents the mercaptan sulfur content of the initial gasoline and Cr, the mercaptan sulfur content of the gasoline after treating it for t seconds.
• aqueous alkali metal hydroxide solution use was made of a solution having the following composition: 34% by weight of water, 33 by weight of potassium hydroxide, 33% by weight of cresol (this percentage is actually calculated as cresol, although the cresol is in effect combined witha part of the potassium hydroxide to form potassium cresolate)
• a 1% solution of cumene hydroperoxide in a sample of the same gasoline which was to be treated was injected into the latter gasoline, in'a quantity which is shown for-each of the tests under consideration in the second column of Table I, by indicating the peroxide content absorbed by the gasoline, expressed It will be seen from the results of tests 1 and 2 that without the simultaneous use of a peroxide the theoretical quantity of oxygen gives a factor A of not more than 4.5 against a factor A of 10.0 when the double quantity of oxygen is used, This corresponds to an average increase in A 10 (delta A 10 of 0055x10 for each 1% excess of free oxygen over the stoich
• test results are shown by a comparison of the results of tests 3 and 4. While maintaining the same percentage of peroxide (8% of stoichiometrical quantity), a 10% excess of free oxygen (110 vs. 100), resulted in an average increase in A 10 per 1% excess of free oxygen, of 0.07 X lO Finally, the result of test 7 demonstrates that a considerable value for factor A is obtained by using a quantity of curnene hydroperoxide amounting to 15% of the stoichiometrical quantity. In test 7 the total quantity of oxygen was 102% of the stoichiometrical quantity.
• EXAMPLE II The tests of this example were carried out in a manner similar to that of Example I except that a gasoline was used with a boiling range of from about 80 C. to 200 C. and which was obtained by thermal cracking.
• a gasoline was used with a boiling range of from about 80 C. to 200 C. and which was obtained by thermal cracking.
• a solution was used which consisted of 34% by weight of water, 33% by weight of potassium hydroxide and 33% by weight of cresol.
• Table 11 The results of the tests of this example are shown in Table 11 arranged in exactly the same way as Table I.
• a process for converting mercaptans into disulfides by means of oxygen in a two-phase system, one phase of which is formed by a hydrocarbon oil, and the other by an aqueous alkali metal hydroxide solution which comprises carrying out the conversion in the presence of a peroxide in a quantity of 10% to 40% of the stoichiometrical quantity with respect to the mercaptans to be converted and of free oxygen in a quantity of no more than 130% of the stoichiometrical quantity with respect to said mercaptans.
• a process according to claim oxide is cumene hydroperoxide.
• a process according to claim oxide is tertiary butyl hydroperoxide.
• a process according to claim oxide is hydrogen peroxide.
• a process according to claim oxide is benzoyl peroxide.
• a method of sweetening hydrocarbon oils contaminated with mercaptans which comprises oxidizing said mercaptans by means of no more than of the stoichiometrical amount of free oxygen in the presence of an aqueous alkali metal hydroxide solution and of a catalytic amount of peroxide.

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• Oil, Petroleum & Natural Gas (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Production Of Liquid Hydrocarbon Mixture For Refining Petroleum (AREA)

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Citations (7)

• 0
  • NL NL80085D patent/NL80085C/xx active
  • BE BE527750D patent/BE527750A/xx unknown
• 1954
  • 1954-03-22 US US417917A patent/US2744054A/en not_active Expired - Lifetime
  • 1954-03-31 GB GB9411/54A patent/GB769208A/en not_active Expired
  • 1954-04-01 DE DEN8703A patent/DE951951C/de not_active Expired
  • 1954-04-02 FR FR1099653D patent/FR1099653A/fr not_active Expired

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