FR2878937A1 - METHOD FOR TREATING VISCOUS HYDROCARBON BY IN-SITU INERTING OF ASPHALTENES - Google Patents

Abstract

The present invention relates to a method of treating a viscous hydrocarbon containing asphaltenes, in which the following steps are carried out: - at least part of the asphaltenes is precipitated by adding a suitable solvent to the hydrocarbon, - adds polymerization products to the hydrocarbon suitable for encapsulating the precipitated asphaltenes so as to inert them.

Description

The present invention relates to the field of production and transport

  viscous effluents, especially so-called "heavy" crudes, for example because of their asphaltenes content.

  Processes are known for transporting viscous raw materials which consist in fluidifying the crude by heating, mixing with a fluidifying product, or pre-treatment for transport, for example aqueous emulsification. However, these techniques are expensive in energy, or implement complex processes requiring infra. important structures that penalize the exploitation of deposits.

  In the present description, slurry is a suspension or dispersion of solid particles in a liquid that can be circulated, in particular by pumping. This type of "slurry" flow is already commonly used in dredging estuaries, rivers, and in the mining industry. The interest is to transport a maximum of solid cuttings with the least possible pumping energy. In the oil sector, slurry transport is used to enrich fuels with coal particles and thereby increase their calorific value. The solids content can reach 60% by mass while keeping acceptable flow properties.

  The present invention is preferably applied to heavy crudes. It also applies to extra heavy crudes, bitumens, oil sands, or the like. It therefore consists in modifying the structural organization of the heavy crude which behaves like a viscous colloidal suspension, in order to obtain a suspension of particles of lower viscosity. The particles concerned by this transformation are, in the context of a preferred embodiment of the present invention, asphaltenes. Asphaltenes are the highest molecular weight molecules found in some petroleum crude oils. They are characterized by their strong polarity and the presence of polycondensed aromatic rings. The recovery of these particles deployed in the crude is largely responsible for the high viscosity of the heavy crudes. This recovery can be suppressed by keeping the asphaltenes in the form of solid particles encapsulated in the crude. This configuration change can be achieved by combining, in the crude, a precipitation and inerting asphaltenes, then dispersing asphaltenes encapsulated in the base liquid, in particular under strong mechanical agitation. A procedure, in no way limiting, has been developed and it has been verified that the change in morphology of the crude in suspension form which results, gives rise to a decrease in viscosity.

  Advantageously, according to the invention, the asphaltene particles in solid form are transported by the crude base liquid in which these asphaltenes are dispersed in such a way that the liquid obtained is more fluid than the original crude. Thus, the pumped transport in the pipes is facilitated up to the refining units. In these refining units, the "slurry" is either introduced as such into these treatment units, or after a phase of separation of suspended solid particles, asphaltenes, which can simplify downstream processes.

  Thus, the present invention relates to a method of treating a viscous hydrocarbon containing asphaltenes, wherein the following steps are carried out: at least a portion of the asphaltenes are precipitated by the addition in the hydrocarbon of a suitable solvent polymerization products suitable for encapsulating the precipitated asphaltenes so as to be inert with them are added to the hydrocarbon.

  Depending on the method, the asphaltenes can be precipitated with n-alkane.

  Polymerization products can be added to form a membrane around the asphaltene particles by interfacial polycondensation.

  Di or triamine, or mixture thereof, and an acyl dichloride may be added to form an aromatic polyamide on the surface of the asphaltene particles to form a membrane.

  Alkyd resins suitable for crosslinking can be added to the surface of the asphaltene particles.

  A siccative may be added as a crosslinking promoting agent. The invention also relates to the application of the method for obtaining a viscosity reduction of a viscous asphaltenic hydrocarbon.

  The method can be applied to the transport of a viscous asphaltenic hydrocarbon by pipe.

  The present invention will be better understood and its advantages will appear more clearly on reading the following examples of embodiments, which are in no way limiting, illustrated by the appended figures, of which: FIG. 1 shows the results of a embodiment of the invention, - Figure 2 shows the behavior in time of the method according to the invention.

  According to the invention, at least two polymerization modes can be described for encapsulating asphaltenes contained in a viscous hydrocarbon to inert them.

  The invention shows how the encapsulation of asphaltenes within a heavy crude can permanently reduce the viscosity of such oils.

  The invention is not limited to these two modes of encapsulation.

  The first embodiment of the invention is a polymerization which consists of an interfacial polycondensation. It is a matter of producing a synthesis of polymer material at the solid-liquid interface between the asphaltenes and their environment. This method relies on the selection of two suitable monomers, one soluble in the liquid phase and the other having high affinities with the asphaltenes. It is noted that the polymer obtained forms a membrane around the asphaltenes and must not be soluble in the liquid phase. The protocol of the preferred procedure involves the synthesis of aromatic polyamides obtained from the reaction between a di or triamine and an acyl dichloride. Due to its high polarity, di or triamine is preferentially located on the surface of asphaltenes. Acyl dichloride, on the other hand, is soluble in the surroundings of asphaltenes. The resulting polyamide is insoluble in the liquid phase and is formed on the surface of the asphaltene particles. It is part of the family of polyaramids whose aromatic structure is known to give them resistance to temperature, strong mechanical properties and good resistance to solvents and oxidizing agents [Odian: "Principles of Polymerization" 3rd ed., John Wiley & Sons, Inc., 1994.].

  The procedure developed allows to change the structural organization of the heavy crude, by passing it to a suspension of non-colloidal encapsulated particles of strongly viscosity, and durably reduced. This protocol is realized in situ; it does not require prior deasphalting crude with extraction, treatment and reincorporation of asphaltenes. The encapsulation method described merely requires the preliminary addition of a n-alkane in a controlled amount in order to precipitate the asphaltenes. The encapsulation reaction is then directly carried out on the precipitated asphaltenes without the need to filter them and then to disperse them. Once the polymer membrane is formed, the n-alkane is evaporated to be optionally recycled. In addition, some of the alkane may be left in place. Also, a light oil cut can be added to adjust the viscosity value.

  Example of Procedure The selected n-alkane is added according to the amount selected from the crude. After mechanical stirring for 20 minutes during which the aphalenes precipitate, di or triamine is introduced, according to the proportion chosen by mass relative to the amount of asphaltenes. Tributylamine is also added. Its purpose is to neutralize the hydrochloric acid which is evolved during the reaction between an amine group and an acyl chloride function. The mixture is stirred for one hour during which the di or triamine binds to the precipitated asphaltene particles. The acyl dichloride is then introduced in the molar proportion chosen with respect to the di or triamine. The encapsulation then occurs by the synthesis of the polyamide between the di or triamine and the acyl dichloride on the surface of the asphaltenes. The reaction is initiated by a gentle heating between 30 and 35 C, which is kept under reflux for one hour. The n-alkane is then evaporated. A suspension with a granular appearance is obtained, the particle size reaching several hundred microns.

  Test 1: Influence of the amount of n-alkane added Three samples were prepared for the encapsulation of asphaltenes of a heavy crude containing 17% by weight. The monomers selected to give rise to the interfacial polycondensation reaction are melamine (eg provided by Sigma-Aldrich) and sebacoyl dichloride (supplied by VWR). The triamine is introduced at a level of 5% by weight of the asphaltenes. The amount of acyl dichloride is set at 1.7 moles per 1 mole of melamine. The n-alkane chosen to precipitate the asphaltene particles is pentane. Its amount is known to influence both the particle size and the precipitation yield. This parameter is varied between 10, 15 and 20 ml / g of crude. In each case, after interfacial polycondensation reaction and evaporation of pentane, the samples are observed under optical microscopy and their viscosity is measured using an imposed stress rheometer. In this example, the size of the capsules changes with the amount of pentane, varying respectively for the samples prepared with 10, 15 and 20 ml / g of crude respectively 300, 700 and 50 gm.

  Figure 1 gives the viscosity V of the samples (in Pa $) as a function of the amount of pentane added Q (in ml / g). The results show that the encapsulated samples are less viscous than the original heavy crude and that there is an optimum content of n-alkane to better reduce the viscosity. This optimum (here between 10 and 15 mt / g) is to be calibrated according to the nature of the heavy crude, that is to say, the solvation state and the concentration of its asphaltenes.

  Test 2: Influence of the amount of monomers on the viscosity decrease of the encapsulated samples In order to observe the influence of the amount of monomers on the quality of the encapsulated products, four samples were prepared starting from 2.5; 5; 10 and 20% by weight of melamine with respect to asphaltenes. The amount of sebacoyl dichloride is always set at 1.7 moles per mole of melamine introduced. The tests use pentane as n-alkane with a content of 15 ml / g of crude. In each case, after interfacial polycondensation reaction and evaporation of pentane, the samples are observed under optical microscopy and their viscosity is measured using an imposed stress rheometer. The optical microscopy photographs make it possible to visualize the excess of polymer formed with the high concentrations of monomer, the polymer whose presence in excess results in a high viscosity. Table 1 indicates that the viscosity increases with the amount of monomers.

  To observe the temperature behavior of these samples, microscopic analyzes were repeated after heating at 80 C for 1 hour. All the results show that to obtain a good compromise between the level of the viscosity and the temperature resistance, the 5% content of melamine is preferred.

  2.5% monomers 5% monomers 10% monomers 20% monomers Viscosity 35 Pa.s 45 Pa.s 100 Pa.S 150 Pa. Tab.l: Viscosity at 20 C of the samples encapsulated by interfacial polycondensation with different amounts of monomers.

  Test 3: Time-holding of the samples encapsulated by interfacial polycondensation In order to check the durability of the crudes containing asphaltenes encapsulated by interfacial polycondensation, the viscosity of a sample was measured at different time intervals. This is the sample prepared from 5% by weight of melamine, 1.7 moles / mole of sebacoyl dichloride, and the precipitation of asphaltenes being obtained with pentane introduced at a level of 15 ml / g. of crude. The rheological measurements are presented in FIG. 2 which gives: [a viscosity V (in Pa. $) As a function of the shear rate t (s-). Curve 1 concerns the crude, curve 2 after encapsulation, curve 3 40 days later, and curve 4 after 66. The curves show the stability of the product over time.

  The second mode proposed for encapsulating the asphaltenes of a crude is to cause at their surface the crosslinking of alkyd resins. The alkyd resins are unsaturated polyesters (presence of double bonds) obtained from polyol and natural fatty acids. They are characterized by their vegetable oil content, called length in oil. The latter gives them a siccative power, that is to say an ability to polymerize in the presence of oxygen.

  This crosslinking process involves several physicochemical mechanisms depending on whether the double bonds involved are simple or conjugate [Marshall et al., Polymer, 28, 1093, 1987.], [Solomon, "The chemistry of organic film formers" Wiley-Intersciences, New York, 1967].

  It can appeal depending on the case to the addition of a siccatif whose role is to accelerate the crosslinking by promoting the supply of oxygen. These are most often metal oxides. As for the first interfacial polycondensation polymerization method described above, the procedure developed for this second method makes it possible to modify the structural organization of the heavy crude, making it pass to a suspension of encapsulated particles of strongly reduced viscosity and durably reduced. This protocol is realized in situ; it does not require prior deasphalting crude with extraction, treatment and reincorporation of asphaltenes. The encapsulation method described merely requires the preliminary addition of a n-alkane in a controlled amount in order to precipitate the asphaltenes. The alkyd resins will preferentially be placed on the surface of the asphaltenes. The crosslinking reaction then occurs directly on the precipitated asphaltenes. Once the membrane is formed, the n-alkane is evaporated to be optionally recycled. In addition, some of the alkane may be left in place. Also a light oil cut, or solvent, can be added to adjust the viscosity value.

  Example of Procedure The selected n-alkane is added according to the amount selected from the crude. After mechanical stirring for 15 minutes during which the asphaltenes precipitate, the alkyd resins, the optional siccative and a dispersant are introduced. Mechanical stirring is maintained under heating at 35 C for two hours. The n-alkane is finally evaporated. A suspension with a smooth appearance is obtained.

  Test 4: Influence of the quantity of alkyd resins on the viscosity decrease In order to observe the influence of the quantity of alkyd resins on the quality of the encapsulated products, three samples were prepared starting from 4, 6 and 8% in mass of Synolac 6883 (supplied by the company DSM) with respect to asphaltenes. The proportion of drying agent (Combi QS from Nuodex) is set at 4% by weight relative to the resin and the amount of dispersant (Montane 80 from Seppic) amounts to 1% by weight of the alkane added. The tests use pentane as n-alkane with a content of 10 mUg of crude. In each case, after crosslinking reaction and evaporation, the viscosity of the samples is measured using an imposed constraint rheometer. The results in Table 2 show that the lowest level of viscosity is obtained for 6% of resins.

  4% monomers 6% monomers 8% monomers Viscosity 75 Pa.s 50 Pa.s 70 Pa.S Tab.2: Viscosity at 20 C samples encapsulated by crosslinked alkyd resins.

  Test 5: Temperature resistance of the cross-linked samples In order to verify the temperature resistance of the crosslinked products, the viscosity of a sample was measured after heating at 50 ° C. and 80 ° C. for 1 hour. This is the sample prepared from 6% by weight Synolac 6883 alkyd resins (cf test 4). The rheological measurements are presented in Table 3 and show a good stability of the product. Despite the significant heat treatment, especially at 80 C, the viscosity of the crude is not reached.

  siccative test without heat treatment Pa s after 1 h at 50 C Pa s after 1 h at 50 Pa Pa Tab.3: Temperature resistance of the samples encapsulated by crosslinking of alkyd resins, viscosity measured at 20 ° C.

Trial 6: Influence of the drying agent.

  In order to observe the influence of adding the siccative, a sample was prepared from 6% Synolac resins without introducing siccatives. Its viscosity was measured after elaboration and after heating 50 and 80 C for 1 hour. The results show that the sample without drying agent has the same viscosity as the equivalent sample with drying agent (50 Pa. $). On the other hand, the sample without drying agent is much less resistant to the important heat treatment like that at 80 C (see Table 4).

  test without drying agents without heat treatment Not after 1 hour at 50 ° C. Pa.s after 1 h at 50 ° C. Tab.4: Temperature resistance of the samples encapsulated by crosslinking of alkyd resins, influence of the desiccant, viscosity measured at 20 ° C.

Claims (8)

  1) A method for treating a viscous hydrocarbon containing asphaltenes, in which the following steps are carried out: at least a portion of the asphaltenes are precipitated by the addition in the hydrocarbon of a suitable solvent; hydrocarbon polymerization products suitable for encapsulating the precipitated asphaltenes so as to inert them.   2) Method according to claim 1, wherein the asphaltenes are precipitated with n-alkane.   3) Method according to one of claims 1 or 2, wherein the polymerization products are added to form a membrane around the asphaltene particles by interfacial polycondensation.   4) The method of claim 3, wherein di or triamine, or mixture thereof, and an acyl dichloride are added to form an aromatic polyamide on the surface of the asphaltene particles.   5) Method according to one of claims 1 or 2, wherein one adds alkyd resins suitable for crosslinking to the asphaltene particle surfaces.   6) Method according to claim 5, wherein a drying agent is added as a crosslinking promoting agent.   7) Application of the method according to one of the preceding claims 5 to obtain a viscosity decrease of a viscous asphaltenic hydrocarbon.   8) Application of the method according to claim 7 for the transport of a viscous asphaltenic hydrocarbon by pipe.