Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C7/00—Purification; Separation; Use of additives
  • C07C7/148—Purification; Separation; Use of additives by treatment giving rise to a chemical modification of at least one compound
  • C07C7/152—Purification; Separation; Use of additives by treatment giving rise to a chemical modification of at least one compound by forming adducts or complexes
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D9/00—Crystallisation
  • B01D9/0004—Crystallisation cooling by heat exchange
  • B01D9/0013—Crystallisation cooling by heat exchange by indirect heat exchange

Definitions

• This invention relates to an improved process for the refining of mineral oils. More particularly, the invention relates to a process for the extractive crystallization of petroleum oils, by means of urea.
• urea forms crystalline solid adducts with straight chain and slightly branched chain hydrocarbons but does not form solid compounds with naphthenes, highly branched compounds or aromatics.
• a method has been developed for refining petroleum fractions by resolution of the fractions into chemical types by forming the above solid compounds, removing the remaining liquid phase (known as the urea adduction rafiinate), decomposing the solid compounds and recovering from the product the liberated hydrocarbons (known as the urea adduction extract).
• the above object is accomplished by a process which comprises treating a mineral oil with a solution of urea in water or in a solvent comprising water, in the presence of biuret, under conditions such that a solid urea adduct is formed with components of the mineral oil and thereafter separating the solid urea adduct from the liquid phase.
• the amount of biuret employed constitutes 0.25%, based on the weight of urea present.
• the simplest method of providing biuret for use in the process of the present invention consists in promoting in the whole of the urea employed in the process, or preferably only in part of it, the formation of a sutficient proportion of biuret. This may be effected by heating the urea to temperatures between 140 and 170 C. It is known, that at these temperatures two molecules of urea give, with elimination of ammonia, one molecule of biuret, according to the equation:
• the urea solution employed is a solution of urea in a mixture of water and a water-soluble monohydric alcohol or ketone.
• the urea solution employed is a solution of urea in the ternary solvent described in copending U. S. patent application Serial No. 278,627, filed March 26, 1952. It is also preferred that the process of urea adduction be carried out in the manner described in said application.
• the urea adduct is formed as a suspension in a liquid phase comprising a solution of urea in the ternary solvent, the rafiinate being present as an emulsion in the urea solution.
• a particularly preferred ternary solvent for use in the process of the present invention comprises methanol, water and ethylene glycol. Suitable proportions are:
• urea crystals which could be termed nascent and which are of very small dimensions.
• the saturated urea solution is prepared in the presence of biuret.
• the crystals which form in the presence of the biuret are of even smaller size and react particularly easily with normal aliphatic hydrocarbons.
• the urea adducts are formed while the urea solution comprising biuret is in a supersaturated state.
• this may be achieved by cooling a saturated solution of urea containing biuret so as to obtain nascent urea crystals, then forming an emulsion from the supersaturated solution of urea and the hydrocarbon fraction. It is also possible to bring into contact the hydrocarbon fraction and the saturated urea solution and then to cause the nascent crystallization of urea by cooling.
• This may be efiiected in practice by delivering the urea solution to the contacting zone at a temperature above that of the mineral oil, While containing an excess of urea over that necessary to saturate the solution at the temperature of adduct formation.
• This method allows the urea crystals to react, from the time of their formation, with the hydrocarbon fraction and to attain a better heat economy since the cooling of the urea solution is efiected by the fresh charge of cool hydrocarbons which thus is warmed up.
• EXAMPLE 1 A solution of urea with a content of biuret was prepared using the ternary solvent glycol-methanol-water.
• the solution had the following composition (in per cent by weight):
• the urea containing 1 per cent of biuret was obtained by mixing 3 parts of commercial urea and 1 part of urea containing 4 per cent of biuret.
• Urea containing 4 per cent of biuret had been prepared by subjecting pure commercial urea to prolonged heating at 145 C.
• the saturation temperature of the above mentioned solution of urea is 38 C.
• the material treated was a fraction from the direct distillation of a crude Middle East oil with a boiling range of 140 to 320 C. and a temperature of incipient crystallization (cold test) of 20 C. (I. P. Standard Methods of Testing, 1951, page 102).
• the yield was 78% by weight of a raffinate suitable for use as an aviation gas-turbine fuel, the cold test of which conforms to the requirements laid down for trans-oceanic flights.
• a process for the extractive crystallization of mineral oils which comprises treating a mineral oil with a solution of urea in a solvent comprising water, in the presence of biuret in the proportion of 0.2 to 5% by weight relative to the urea content, whereby a solid urea adduct is formed with some components of said mineral oil, separating said solid urea adduct from the remaining components of said mineral oil, decomposing said urea adduct and recovering the liberated components of said mineral oil.
• said solution of urea is a solution of urea in a solvent comprising water and a water-soluble mono-hydric alcohol.
• a process for the extractive crystallization of mineral oils which comprises treating a mineral oil with a supersaturated solution of urea in a solvent comprising water, in the presence of biuret in the proportion of 0.2- 5% by weight relative to the urea content, whereby a solid urea adduct is formed with some components of said mineral oil, separating said solid urea adduct from the remaining components of said mineral oil, decomposing said urea aduct and recovering the liberated components of said mineral oil.
• a process for the extractive crystallization of distillation fractions of petroleum which comprises treating a distillation fraction of petroleum with a supersaturated solution of urea in a solvent comprising water, in the presence of biuret in the proportion of 0.2-5% by weight relative to the urea content, whereby a solid urea adduct is formed with some components of said distillation fraction, separating said solid urea adduct from the remaining components of said distillation fraction, decomposing said urea adduct and recovering the liberated components of said distillation fraction.
• a process for the extractive crystallization of mineral oils which comprises treating a mineral oil with a solution of urea in a solvent comprising water, in the presence of cyanuric acid in the proportion of 0.2 to 5% by weight relative to the urea content whereby a solid urea adduct is formed With some components of said mineral oil, separating said solid urea adduct from the remaining components of said mineral oil, decomposing said urea adduct and recovering the liberated compo nents of said mineral oil.
• a process for the extractive crystallization of mineral oils which comprises treating a mineral oil with a solution of urea in a solvent comprising water, in the presence of a compound selected from the group consisting of biuret and cyanuric acid, in the proportion of 0.2 to 5% by Weight relative to the urea content, whereby a solid urea adduct is formed with some components of said mineral oil, separating said solid urea adduct from the remaining components of said mineral oil, decomposing said urea adduct and recovering the liberated components of said mineral oil.
• a process for the extractive crystallization of mineral oils which comprises treating a mineral oil with a supersaturated solution of urea in a solvent essentially comprising, in admixture, water, a water-soluble oxygencontaining organic compound selected from the group consisting of ketones, mono-hydric alcohols and mixtures of ketones and mono-hydric alcohols and an alcoholic organic compound selected from the group consisting of polyhydric alcohols, mono-amino-alcohols and mixtures of poly-hydric alcohols and mono-amino-alcohols, in the presence of biuret in the proportion of 0.25% by weight relative to the urea content; forming an em sion of the oil-in-Water type; maintaining said emulsion under conditions such that a solid urea adduct is formed with components of said mineral oil; separating said solid urea adduct from the remaining components of said mineral oil; decomposing said urea adduct and recovering the liberated components of said mineral oil.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Water Supply & Treatment (AREA)
• Analytical Chemistry (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Engineering & Computer Science (AREA)
• General Chemical & Material Sciences (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Crystallography & Structural Chemistry (AREA)
• Production Of Liquid Hydrocarbon Mixture For Refining Petroleum (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

Applications Claiming Priority (1)

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Cited By (3)

Citations (2)

• 1951
  • 1951-05-17 FR FR1037205D patent/FR1037205A/fr not_active Expired
• 1952
  • 1952-05-08 US US28682952 patent/US2710855A/en not_active Expired - Lifetime
  • 1952-05-08 NL NL169384A patent/NL77413C/xx active
  • 1952-05-12 DE DEA15778A patent/DE1003893B/de active Pending

Patent Citations (2)

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