CA2587634A1 - Method for treating viscous hydrocarbon by in situ inerting of asphaltenes - Google Patents

Abstract

The present invention relates to a method of treating a hydrocarbon viscous mixture containing asphaltenes, in which the steps are carried out following: at least part of the asphaltenes are precipitated by the addition in the hydrocarbon of a suitable solvent; the hydrocarbon is added polymerization products suitable for encapsulating the precipitated asphaltenes of way to inerter them.

Description

WO 2006/06148

2 PCT / FR2005 / 002943 METHOD OF TREATING A HYDROCARBON
VISCOUS BY INTEGRATION IN SITU ASPHALTENES

The present invention relates to the field of production and transport of viscous effluents, in particular so-called "heavy" crudes, for example because of their asphaltenes content.

Methods of transporting viscous crudes which consist of fluidizing the crude by heating, mixing with a fluidifying product, or pre-transport treatment, for example aqueous emulsification.
However these techniques are expensive in energy, or implement complex processes requiring significant infrastructures that penalize exploitation of deposits.

In the present description, "slurry" is a suspension, or a dispersion of solid particles in a liquid which can be circulation, especially by pumping. This type of flow in "slurry" is already commonly used during dredging operations of estuaries, rivers, as well as in the mining industry. The interest is to carry a maximum of solid cuttings with the least possible pumping energy. With regard to concerned the oil sector, "slurry" transport is used to enrich two fuels fuels with coal particles and increase this way their calorific value. The solid content can reach 60% by mass all keeping the flow properties acceptable.

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

Advantageously, according to the invention, the particles are transported of asphaltenes in solid form, by the base liquid of the crude in which these

3 Asphaltenes are dispersed in such a way that the resulting liquid 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 introduced as such into these treatment units, or after a phase solid particles in suspension, the asphaltenes, which can simplify downstream processes.

Thus, the present invention relates to a method of treating a viscous hydrocarbon containing asphaltenes, in which the following steps:

at least a part of the asphaltenes is precipitated by the addition in the hydrocarbon of a suitable solvent, polymers are added to the hydrocarbon which are suitable for encapsulate the precipitated asphaltenes so as to inert them.

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

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

We can add di or triamine, or their mixture, and a dichloride of acyl to form an aromatic polyamide on the surface of particles 2o asphaltenes, 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.

4 The invention also relates to the application of the method for obtaining a viscosity decrease of a viscous asphaltenic hydrocarbon.

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

The present invention will be better understood and its advantages appear more clearly on reading the following examples of realization, in no way limiting, illustrated by the figures below annexed, among:

FIG. 1 shows the results of an embodiment according to the invention, FIG. 2 shows the behavior over time of the method according to the invention.

According to the invention, at least two modes of polymerization to encapsulate 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 interfacial polycondensation. It's about making a synthesis of polymer material at the solid-liquid interface between the asphaltenes and their environment. This method is based on the selection of two monomers appropriate, one soluble in the liquid phase and the other affinities with asphaltenes. It is noted that the polymer obtained forms a membrane around asphaltenes and should not be soluble in the phase

5 liquid. The protocol of the preferred procedure implements the synthesis of aromatic polyamides obtained from the reaction between a di or triamine and acyl dichloride. Due to its strong polarity, di or triamine himself preferentially located on the surface of asphaltenes. Acyl dichloride, in however, is soluble in the surrounding environment of asphaltenes. The polyamide obtained is insoluble in the liquid phase and is formed at the surface of asphaltene particles. He is part of the family of polyaramids whose aromatic structure is known to give them a 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 operating procedure developed makes it possible to modify the organization of heavy crude, by moving it to a suspension of particles encapsulated non-colloidal viscosity strongly, and durably, reduced.
This protocol is performed in situ; it does not require prior deasphalting 2o crude with extraction, treatment and reincorporation of asphaltenes. The encapsulation method described simply requires that the addition of a n-alkane in a controlled quantity in order to precipitate the asphaltenes. The encapsulation reaction is then directly implemented asphaltenes precipitated without the need to filter them, then to the

6 disperse. Once the polymer membrane has been formed, the n-alkane is evaporated to possibly recycled. In addition, some of the alkane may be left in place. Also, a light oil cut can be added for adjust the value of the viscosity.

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

Test 1: Influence of the amount of n-alkane added Three samples were prepared for encapsulation of asphaltenes a heavy crude that contains 17% by mass. The monomers chosen for

7 give rise to 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 mass of asphaltenes. The amount of acyl dichloride is set at 1.7 moles for 1 mole melamine. The n-alkane chosen to precipitate the asphaltene particles is pentane. Its quantity is known to influence both the size of particles and precipitation yield. This parameter is varied between 10, 15 and 20 ml / g of crude. In each case, after polycondensation reaction interface and evaporation of pentane, the samples are observed in optical microscopy and their viscosity is measured using a rheometer at imposed constraint. In this example, the capsule size changes with the amount of pentane, varying respectively for prepared samples with 10, 15 and 20 ml / g of crude respectively of 300, 700 and 50 μm.

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

Test 2: Influence of the amount of monomers on the decrease of viscosity of the encapsulated samples

8 In order to observe the influence of the quantity of monomers on the quality encapsulated products, four samples were prepared from 2.5;
5;
and 20% by weight of melamine relative to asphaltenes. The quantity of Sebacoyl dichloride is always fixed at 1.7 moles per mole of melamine 5 introduced. The tests use pentane as n-alkane with as content 15 ml / g of crude. In each case, after reaction of interfacial polycondensation and evaporation of pentane, the samples are observed under optical microscopy and their viscosity is measured using a constrained rheometer. Optical microscopy snapshots To visualize the excess of polymer formed with the important concentrations in monomer, the polymer whose presence in excess causes a high viscosity.
Table 1 indicates that the viscosity increases with the amount of monomers.
To observe the temperature behavior of these samples, the analyzes microscopic were repeated after heating at 80 C for 1 hour.

The overall results show that to obtain a good compromise between the level of the viscosity and the temperature resistance, the content of 5%
melamine is preferred.

2.5% monointers 5% inonomers 10% mononaers 20% naonomers Viscosity 35 Pa.s 45 Pa.s 100 Pa.S 150 Pa.s Tab.1: Viscosity at 20 C of the polycondensation-encapsulated samples inteifaciale with different amounts of rononzères.

Test 3: Resistance in time of the samples encapsulated by interfacial polycondensation

9 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. It is the sample prepared from 5% by weight of melamine, 1.7 mol / mol of sebacoyl dichloride, and the precipitation of asphaltenes being obtained with pentane introduced at a level of 15 ml / g of crude. Rheological measurements are shown in Figure 2 which gives the viscosity V (in Pa.s) depending of shear rate t (s 1). Curve 1 relates to the crude, curve 2 after encapsulation, curve 3 40 days after, and curve 4 after 66 days. The curves show the stability of the product over time.

The second mode proposed for encapsulating the asphaltenes of a crude is to cause on their surface the crosslinking of alkyd resins. Resins alkyds are unsaturated polyesters (presence of double bonds) obtained at from polyol and natural fatty acids. They are characterized by their content in vegetable oil, called length in oil. The latter gives them a drying power, that is to say an ability to polymerize in the presence oxygen.
This crosslinking process involves several physicochemical mechanisms depending on whether the double bonds involved are simple or conjugate [Marshall 2o et al., Polymer, 28, 1093, 1987.], [Solomon, "The chemistry of organic film trainers "Wiley-Intersciences, New York, 19671.

It can appeal as appropriate to the addition of a desiccant whose role is to accelerate the crosslinking by promoting the supply of oxygen. These are the most often metal oxides. As for the first mode of interfacial polycondensation polymerization described above, the procedure developed for this second method allows to modify the structural organization of heavy crude, moving it to a suspension of 5 encapsulated particles of strongly reduced viscosity and durably reduced. This protocol is performed in situ; it does not require the deasphalting crude with extraction, treatment and reincorporation of asphaltenes. The encapsulation method described simply requires that the addition of a n-alkane in a controlled quantity in order to precipitate the

Asphaltenes. The alkyd resins will preferentially be placed at the area asphaltenes. The crosslinking reaction then occurs directly on precipitated asphaltenes. Once the membrane is formed, the n-alkane is evaporated for possible recycling. In addition, some of the alkane can to be left in place. Also a light petroleum cut, or a solvent, can be added to adjust the viscosity value.

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

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

4% monomonomers 6% monomers 8% monomers Viscosity 75 Pa.s 50 Pa.s 70 Pa.S

Tab.2: Viscosity at 20 C of the samples encapsulated by alkyd resins crosslinked.
Test 5: Temperature resistance of crosslinked samples In order to check the temperature resistance of the crosslinked products, the viscosity of a sample was measured after heating at 50 and 80 C
for 1 hour. This is the sample prepared from 6% by mass of Synolac 6883 alkyd resins (see test 4). Rheological measurements are presented in Table 3 and show good stability of the product. Despite the important heat treatment, especially at 80 ° C., the viscosity of the crude oil is not not reached.

12 without heat treatment after 1 hour at 50 ° C. after 1 hour at 50 ° C.
try with siccative 50 Pa.s 60 Pa.s 80 Pa.s Tab.3: Temperature resistance of the samples encapsulated by cross-linking of alkyd resins, viscosity measured at 20 C.

Trial 6: Influence of the drying agent.

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

without heat treatment after 1h at 50 ° C after 1h at 50 ° C
test without drying agent 50 Pa.s 60 Pa.s 180 Pa.s Tab.4: Temperature resistance of the samples encapsulated by crosslinking alkyd resins, influence of siccatif, viscosity measured at 20 C.

Claims (8)

1) Method of treating a viscous hydrocarbon containing asphaltenes, in which the following steps are carried out:

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