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
  • C10G27/12—Refining of hydrocarbon oils in the absence of hydrogen, by oxidation with oxygen or compounds generating oxygen with oxygen-generating compounds, e.g. per-compounds, chromic acid, chromates
• • 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
  • C10G53/00—Treatment of hydrocarbon oils, in the absence of hydrogen, by two or more refining processes
  • C10G53/02—Treatment of hydrocarbon oils, in the absence of hydrogen, by two or more refining processes plural serial stages only
  • C10G53/14—Treatment of hydrocarbon oils, in the absence of hydrogen, by two or more refining processes plural serial stages only including at least one oxidation step

Definitions

• This invention relates to a method of improving the storage stability of oils, in particular diesel fuels, and to apparatus for putting the method into effect.
• Oils are widely used industrially as fuels and as lubricants.
• a problem with some oils, particularly with some heavier oil fuels such as diesel fuels, gas oils and gas turbine fuels. Is the form ⁇ ation of sediments on storage, whether in tanks etc or when vehicles are left standing for a long period. Such sediments can cause blockages in fuel pipes, filters etc and fouling of engine components. It is believed that one important mechanism by which sediments are formed is reaction between trace compounds present in the oils to form solid or gummy products. Therefore even repeated filtration of the oils may not solve the problem of sediment formation.
• n is an integer 1 to 3 or more.
• Phenalenes, phenalanones, phenalenones and indoles are believed to be introduced into the oil, in the course of upgrading the oils by incorporation of catalytically cracked oils. This is increasingly being done with diesel and gas turbine fuels.
• oil as used herein includes all types of oils regard ⁇ less of their origin, which may be natural eg petroleum oils or shale oils, or may be wholly or partly synthetic, eg prepared from natural gas, from coal or by heating shale, or in any other way.
• gasoline gasolines
• naphthas paraffins (kerosine)
• fuel oils such as tractor fuels, diesel fuels, gas oils, gas turbine fuels, lubricating oils, cutting oils, hydraulic oils etc.
• a method for at least partly remov- ing potentially sediment-forming compounds from an oil comprises contacting the oil with a solution of an oxidising agent and an acid in an at least partly organic solvent, said oxidising agent, acid and solvent being wholly or substantially immiscible with the oil, then separating the oil and solvent phases.
• salts are insoluble or only sparingly soluble in oils such as diesel fuel but are soluble in organic solvents, and therefore are extracted into the organic solvent. These salts are also intensely blue in colour.
• Any oxidising agent which is known to oxidise phenalenes to phenalenones may be used. Inorganic oxidising agents are preferred, particularly transition metals in an oxidising oxidation state such as Ce IV, Mn VII (eg permanganate) or Cr VI (eg dichromate) . These latter two give a rapid reaction.
• Other suitable oxidising agents include I_, I0 font , BrO , and CIO . H Directory0 p may also be used but can give a slower reaction.
• Preferred acids are those which are known to form salts with the indolyl phenalenones or phenalanones condensation product.
• mineral acids such as hydrochloric or sulphuric acid/or percholoric acid may be used and give a rapid reaction.
• Preferred acids are organic sulphonic acids, such as alkyl or especially aryl sulphonic acids for example alkylphenylsulphonic acids such as p-toluene sulphonic acid.
• Carboxylic acids which may be a aliphatic or aromatic, such as acetic acid may be used but may give a slower reaction.
• Some acids are also oxidising agents, such as perchloric and nitric acids. Such oxidising acids may therefore in some cases be used in place of both the oxidising agent and the acid, or may be used in addition to either or both.
• oxidising acids may therefore in some cases be used in place of both the oxidising agent and the acid, or may be used in addition to either or both.
• Perchloric and nitric acids may for example be used as both an acid and oxidising agent or may be used together with an additional oxidising agent such as dichromate.
• the solvent is selected so as to be as immiscible as possible with the oil, and is a water-miscible organic solvent or an organic solvent-water mixture. It is desirable that the solvent has a different density to the oil so that the solvent and oil phases tend to separate spontaneously.
• the solvent may be more or less dense than the oil.
• Preferred solvents are therefore polar solvents such as alcohols, particularly lower alcohols (ie up to C_ alcohols), b especially methanol or ethanol, which are less dense than diesel fuel, or mixtures of these with water. If alcohols are used then the use of nitric acid is inadvisable because of the vigorous reaction that may take place between the two.
• the solvent is an organic solvent- water mixture, for example or methanol - or ethanol - water mixture
• the proportions of organic solvent and water in the solvent may be important. If too much water is present then the solvent may only separate with difficulty from the oil, or not at all. If too much organic solvent is present then if the preferred transition metal ion is used as an oxidising agent then it may be difficult to dissolve in the solvent.
• the concentration of oxidising agent and acid in the solution may be varied between wide limits. Typically if a transition metal oxidising agent such as potessium permanganate or dichromate is used, a concentration of 2-3 weight % in the solution is suitable, which is conveniently the solubility limit of these oxidising agents in a methanol - water mixture containing 70-80% by volume of methanol. Typically the concentration of acid should be 10% by weight or less. The method works rapidly at ambient temperatures (20 -30 C) and may be accelerated by gentle warming.
• a transition metal oxidising agent such as potessium permanganate or dichromate
• the relative volume ratios of oil to solution will vary from oil to oil depending inter alia upon the amount of phenalenones, phenalanones, phenalenes and indoles in the oil, and the way in which the method is put into effect as discussed below.
• A is the acid counter anion. It is clearly desirable to use an amount of the oxidising agent and acid in excess of the amount of the sediment - forming compounds believed to be present in the oil, so as to force the reaction rapidly to completion.
• a typical diesel fuel for example may contain 1-2 ppm of these compounds, and an acceptable upper limit of sediment formation on long term standing, bu a UK Ministry of Defense Standard is 2 mg sediment per lOOg of diesel fuel, ie 20 ppm.
• an apparatus for at least partly removing potentially sediment-forming compounds from an oil in which the oil may be contacted with a solution as defined above, then separating the oil and solvent phases.
• a quantity of the solution is added to a container of the oil, such as a storage tank, and the mixture simply left to stand.
• the mixture of oil plus solution is periodically agitated, especially immediately after addition of the solution, so as to encourage contact between the solution and the oil, preferably by breaking the solution up into small droplets thereby increasing the interfacial surface area.
• After a suitable period of standing the oil and solvent phases are separated. If the solution and the oil have different densities, spontaneous separation into phases will occur, with the solution forming an upper or lower layer which can be removed by simple drainage.
• Suitable apparatus for putting such a batch process into effect will be apparent to those skilled in the art. It may for example in its simplest form consist merely of a container of convenient volume optionally provided with agitator means, and having inlet and outlet means for introducing and removing the oil and the solution.
• the oil and the solvent are brought into contact as counter-currents which remain in moving contact for a suitable period of time.
• the streams are brought into contact in such a way that turbulence occurs and breaks up the streams into droplets, thereby increasing their interfacial surface area.
• Turbulence may optionally be increased by agitator means.
• the separation of the oil and solution may be achieved by known methods, for example if the oil and solution have different densities, separation can again be on this basis.
• SUBSTITUTE SHEET solution may be passed into a relatively static region where spontaneous separation into phases which can be separately drained off occurs.
• Suitable apparatus for putting such a continuous process into effect will be apparent to those skilled in the art. It may for example consist of a mixing chamber provided with inlet means for the oil and the solution and constructed so that the oil and solution may be brought into contact, connected to one or more separation chambers wherein the physical mixture of oil and solution may separate as a consequence of a difference in density, the separation chamber(s) being provided with separate outlet means for the oil and solution.
• the method is applied by a batch or continuous process it is desirable to test the treated oil for the presence of potentially sediment-forming compounds. This may for example be achieved using the test method described in PCT/AU90/00467.
• indoyl phenolene salts formed in the method of this invention have an intensely blue colour
• completeness of removal of sediment-forming compounds may be monitored by observing the colour of the solution phase that separates from the oil. This may be performed using a colourimetric instrument measuring absorbance in the solution phase in the 600-850 nm wavelength region, and the electrical output of this instrument may be electronically linked to the control system of the apparatus.
• a saturated aqueous solution of potassium dichromate and a 10 weight % solution of p-toluene sulphonic acid in methanol were prepared. 50 ml of the acid solution was mixed with 15 ml of the dichromate solution. This mixed solution was added to 500 ml of a straight run gas oil (known to be completely stable) which had been previously mixed with 10 volume % of a catalytically cracked oil (known to be unstable toward sedimentation) in a separating funnel. The combine solution and oil were shaken to form an unstable emulsion and then left to stand for 5-10 minutes. At the end of this time the methanolic solution had separated as a blue coloured upper phase. The lower oil phase was drained off and tested both by the method described in the above PCT and by a present standard test for sedimentation (eg the ASTM method D2274). Both tests showed the absence of sediment forming species to the above mentioned UK MOD Standard.
• Example 2 450 ml portions of a catalytically cracked North Sea gas oil were treated as follows: a) 25 ml of 5% p-toluene sulphonic acid in methanol and 24 ml of 2% aqueous potassium dichromate in methanol were added to the fuel and the mixture was shaken vigorously for 1 minute and then allowed to settle for approximately 30 to 40 minutes. The fuel portion was drawn off and washed with methanol (4 x 100 ml) to remove excess reacted material. The fuel layer was then drawn off, washed with water and allowed to settle. The portion was centrifuged to remove excess water and then stored in the dark for a 6 month period under ambient conditions before filterable and adherent insoluables were determined.
• Example 3 A continuous form of the method of the invention was carried out using two fuel blends made up of 5 and 10% light cycle oil in straight run distillate, these being typical concentrations of cracked material found in commercial blends.
• the blends were treated as follows: a) The fuel was mixed with 1% p-toluene sulphonic acid in methanol and in a ratio of 1:20 acid: fuel and saturated aqueous potassium dishromate was added in a ratio of 1:200 oxidant to fuel. The mixture was stirred vigorously, giving a contact time of approximately 30 minutes and then passed to a separate vessel to allow phase separation.
• the fuel phase was pumped to a further vessel for extraction with methanol in a ratio of 1-10 methanol to fuel, was separated and then the fuel phase treated with 1% potassium hydroxide in methanol in a ratio of 1:40 alkali to fuel.
• the treated fuel phase was given a final methanol rinse.
• the 5% blend was treated according to a) above and the 10% was treated using regime lacking the alkali rinse but in all other ways the same.
• the stability of each blend was determined using ASTM D4626 (storage at 43°C for 12 weeks) and filterable and adherent insolubles were measured. An untreated aliquot of each blend was also subjected to ASTM D4625 as a control. The results of the insolubles determinations is shown in Table II. 5% LCO blend Untreated
• an apparatus for performing the method by a continuous process comprises a mixing chamber 1 and a setting chamber 2;
• the mixing chamber 1 is cylindrical, vertically mounted and has an axially orientated vertical shaft 3 passing through and end-wall via an oil tight seal.
• the shaft 3 has radial blades 4, mounted thereon and on the interior wall of the mixing chamber are
• the mixing chamber 1 is provided with an inlet pipe 6 and an outlet pipe 7 communicating with the settling chamber 2 via control valve 8.
• the inlet 6 is connected via control valve 9 to oil inlet pipe 10 and to solution feed pipe 11.
• the control valve 9 is of a type that oil passing along inlet 10 cannot mix with solution passing along feed line 11 until both enter inlet 6.
• the settling chamber 2 is also cylindrical and vertically mounted and is provided with an oil outlet 12 near the bottom of the chamber 2, communicating with the control valve 13, a solution outlet 14 near the top of the chamber 2 communicates with the control valve 15 which in turn communicates with solution vent 16 and solution recycle pipe 17.
• the recycle pipe 17 communicates with solution feed 11 and with solution inlet pipe 19, the control valve 18 is of a type that allows solution to pass only from recycle pipe 17 into feed 11 and/or from inlet 19 into feed 11.
• the settling chamber 2 has a drain valve 20, and drain outlet 21 at it's lower end.
• a flow of diesel oil is passed into inlet 10, and a flow of a solution of an oxidising agent and an acid, for example having a composition as used in the laboratory example above, is passed into inlet 19, through valve 18 into feed 11.
• the flow of oil and solution and oil are allowed to flow via valve 9 and inlet 6 into mixing chamber
• valves 13 and 30 being closed.
• the emulsion 23 fills chamber 2 it separates as a consequence of the lower density of the solution into an upper solution phase 24, and an oil phase, free of solution 25.
• the purified oil 25 may be collected via outlet 12 and valve 13.
• the solution 24 may be collected via outlet 14, valve 15 and vent 16. Alternatively, if the ability of
• the rate of flow of oil and solution through the apparatus the degree of agitation in chamber 1 and the relative sizes of chambers 1 and 2 may be arranged so that the extent of contact between the solution and the oil is sufficient to remove sediment-forming compounds to an acceptable standard, whilst the flow through chamber 2 is slow enough to allow separation and coalescence of an upper solution phase 24 and a lower oil phase 25.
• the rate of flow may be controlled by electronic control of valves 8, 9, 13, 15 and 18 and of the oil and solution feed pumps (not shown).
• the apparatus also includes a colourimetric instrument 26 moni- toring the colour of the solution phase 24 so as to enable an assess ⁇ ment of inter alia whether the solution phase 24 can be recycled.
• the whole apparatus may be electronically, eg microprocessor, controlled. From time to time it may be necessary to drain the apparatus for cleaning etc and this may be done via valve 20 and outlet 21, and valve 9 and drain outlet 27.

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• Chemical & Material Sciences (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Fats And Perfumes (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
• Liquid Carbonaceous Fuels (AREA)
• Lubricants (AREA)

Applications Claiming Priority (2)

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• 1989
  • 1989-11-22 GB GB898926436A patent/GB8926436D0/en active Pending
• 1990
  • 1990-11-20 EP EP19900917003 patent/EP0502008A1/en not_active Withdrawn
  • 1990-11-20 JP JP2515812A patent/JPH05501578A/ja active Pending
  • 1990-11-20 DK DK90917003T patent/DK0502008T3/da active
  • 1990-11-20 WO PCT/GB1990/001786 patent/WO1991007475A1/en not_active Ceased
  • 1990-11-20 AU AU67408/90A patent/AU641707B2/en not_active Ceased

Non-Patent Citations (1)

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