Patent Application
20190071612
Additives to hydrocarbon liquids.
Pseudoplastic, or shear-thinning fluids have a lower apparent viscosity at higher shear rates. An example of a shear-thinning fluid is a solution of large, polymeric molecules in a solvent with smaller molecules. It is generally supposed that the large molecular chains tumble at random and affect large volumes of fluid under low shear, but that they gradually align themselves in the direction of increasing shear and produce less resistance.
Friction reducers (aka drag reducers) are commonly used in pipelines. Typically, friction reducers comprise large polymer chains dissolved in the surrounding fluid which is made up of smaller molecules. However, it would be useful to have more molecules suitable as friction reducers. Also, large molecular chains are commonly broken up by shear, resulting in changes of properties with prolonged shear. It is desirable for molecules to not change significantly in response to prolonged shear. This property of not changing in response to shear, especially as relates to lack of change in viscosity, is known as shear stability. Shear thinning, where the shear thinning is a temporary change in viscosity due to shear that does not change as the shear persists and is reversed when the shear ends, is not considered to be a violation of shear stability.
These properties of friction reduction and shear stability are also useful for lubrication.
Bitumen is commonly diluted with a lower viscosity solvent (known as a diluent) in order to be transported in pipelines. It would be useful to further reduce the viscosity of the diluted bitumen with a relatively low concentration additive.
International published patent applications WO2013040718 and WO2014146191 are hereby incorporated by reference. These international applications disclose how to make the materials described below, for use as gelling agents in downhole fluids. In those documents, it was disclosed that a molecule referred to as “TB” in the terminology of those documents, and corresponding to the label “BTA4” in the terminology used in this document, was shear thinning when added to cyclohexane. However, no friction reduction was mentioned.
There is provided a method of reducing friction of a hydrocarbon fluid in a motor or a pipeline. A compound is added to the hydrocarbon fluid. The compound may comprise an aromatic core of one or more aromatic rings, and two or more amide branches distributed about the aromatic core, each of the two or more amide branches having one or more organic groups is added to the hydrocarbon fluid.
In various embodiments, there may be included any one or more of the following features. The method may be applied to reduce the friction of the hydrocarbon fluid in a pipeline. The method may be applied to reduce the friction of the hydrocarbon fluid in a motor. The compound is added to the hydrocarbon fluid before injecting the hydrocarbon fluid into the pipeline or motor before injecting the hydrocarbon fluid into the pipeline or motor. The compound may be added to a portion of the hydrocarbon fluid before injecting the portion of the hydrocarbon fluid into the pipeline or motor.
There is also provided a method of reducing friction of a diluted bitumen, for example in a pipeline. A compound is added to the diluted bitumen. The compound may comprise an aromatic core of one or more aromatic rings, and two or more amide branches distributed about the aromatic core, each of the two or more amide branches having one or more organic groups.
These and other aspects of the device and method are set out in the claims.
Embodiments will now be described with reference to the figures, in which like reference characters denote like elements, by way of example, and in which:
Immaterial modifications may be made to the embodiments described here without departing from what is covered by the claims.
International published patent applications WO2013040718 and WO2014146191 disclose a class of compounds for use as gelling agents in downhole fluids. As further disclosed below, some of these molecules have been tested and found to be useful as friction reducers, and one has been tested and found to reduce the viscosity of diluted bitumen. It is expected that all other members of the class of molecules that act as gelling agents also act as friction reducers to some extent, and that other members of the class of molecules reduce the viscosity of diluted bitumen. The class includes pyromellitamides and benzamides. In the case of the benzamides, there is a C—N bond between the aromatic core and the amides.
The Class of Molecules
Pyromellitamides have the general base structure (1) shown below:
A suitable member of the disclosed class of molecules, as disclosed in international published patent applications WO2013040718 and WO2014146191, may have the general formula of:
with R1, R2, R3, R4, R5, R6, R7, and R8 each being a hydrogen or an organic group. The description below of variations of the organic groups applies to the organic groups discussed for all embodiments disclosed in this document. R5, R6, R7, and R8 may each be hydrogens (example non organic group) and one or more or all of R1, R2, R3, and R4 may each be an alkyl group (an example of an organic group). In some cases, R1═R2═R3═R4. R1, R2, R3, and R4 may each have 6 carbon atoms, for example 6-10 or 6-24 carbon atoms. Each alkyl group may be one or more of straight chain, branched, aromatic, or cyclic. However, preferably each alkyl group is straight chain, for example if R5, R6, R7, and R8 are each hydrogens, and R1, R2, R3, and R4 are each straight chain alkyl groups with 6-10 carbon atoms. In one example, R1, R2, R3, R4, R5, R6, R7, and R8 are each hydrogen or a C7-24 alkyl group. The organic groups may include functional groups such as esters. Some specific pyromellitamides disclosed as tested as gelling agents in international published patent applications WO2013040718 and WO2014146191 include compounds where R5, R6, R7, and R8 are each hydrogens, and R1═R2═R3═R4, and R1 equals n-pentyl (from 1-pentylamine used in amide synthesis), R1═CH(Me)CH2CH3 (from 2-aminobutane used in amide synthesis), R1═CH(Me)CH2CH2CH2CH2CH3 (from 2-aminoheptane used in amide synthesis), R1═CH(Me)CH2CH2CHMe2 (from 2-amino-5-methylhexane used in amide synthesis), and R1═CH2CH(Et)CH2CH2CH2CH3 (from 2-ethylaminohexane used in amide synthesis). Also disclosed as tested as gelling agents in those applications were tetracyclohexyl, tetrabenzyl, tetraallyl, tetra n-butyl and tetra t-butyl pyromellitamides.
Also as disclosed in international patent application WO2014146191, in some cases one or more, for example each, of the amide branches are connected to the aromatic core via a carbon-nitrogen bond. The molecules may have three or four amide branches. Each organic group may be an alkyl group, such as for example a C6-24 straight chain alkyl group.
In some embodiments of the class of molecules disclosed in the WO2014146191 patent application, the gelling agent has the form of compounds (3) or (4) below, in which R independently represent hydrocarbon or a hydrocarbon group with 1-29 carbon atoms, and R1 independently represents a hydrocarbon group with 1-29 carbon atoms. Further examples of these and other suitable gelling agents are disclosed in U.S. Pat. No. 6,645,577, which describes gel forming compounds. An example of one such compound (5) is detailed below.
In some embodiments of the class of molecules disclosed in the WO2014146191 patent application, one or more of the amide branches is connected to the aromatic core via a carbon-carbon bond and one or more of the amide branches are connected to the aromatic core via a carbon-nitrogen bond. Examples of such structures with varying proportions of N—C and C—C connections include the form of compounds (6)-(8) below:
In the examples of (6)-(8) above, R1, R2 and R3, or Y1, Y2 and Y3, or Z1, Z2 and Z3 independently of one another are C1-C20alkyl unsubstituted or substituted by one or more hydroxy; C2-C20alkenyl unsubstituted or substituted by one or more hydroxy; C2-C20alkyl interrupted by oxygen or sulfur; C3-C12cycloalkyl unsubstituted or substituted by one or more C1-C20alkyl; (C3-C12cycloalkyl)-C1-C10alkyl unsubstituted or substituted by one or more C1-C20alkyl; bis [C3-C12cycloalkyl]-C1-C10alkyl unsubstituted or substituted by one or more C1-C20alkyl; a bicyclic or tricyclic hydrocarbon radical with 5 to 20 carbon atoms unsubstituted or substituted by one or more C1-C20alkyl; phenyl unsubstituted or substituted by one or more radicals selected from C1-C20alkyl, C1-C20alkoxy, C1-C20alkylamino, di(C1-C20alkyl)amino, hydroxy and nitro; phenyl-C1-C20alkyl unsubstituted or substituted by one or more radicals selected from C1-C20alkyl, C3-C12cycloalkyl, phenyl, C1-C20alkoxy and hydroxy; phenylethenyl unsubstituted or substituted by one or more C1-C20alkyl; biphenyl-(C1-C10alkyl) unsubstituted or substituted by one or more C1-C20alkyl; naphthyl unsubstituted or substituted by one or more C1-C20alkyl; naphthyl-C1-C20alkyl unsubstituted or substituted by one or more C1-C20alkyl; naphthoxymethyl unsubstituted or substituted by one or more C1-C2alkyl; biphenylenyl, flourenyl, anthryl; a 5- to 6-membered heterocylic radical unsubstituted or substituted by one or more C1-C20alkyl; a C1-C20 hydrocarbon radical containing one or more halogen; or tri(C1-C10alkyl)silyl(C1-C10alkyl); with the proviso that at least one of the radicals R1, R2 and R3, or Y1, Y2 and Y3, or Z1, Z2 and Z3 is branched C3-C20alkyl unsubstituted or substituted by one or more hydroxy; C2-C20alkyl interrupted by oxygen or sulfur; C3-C12cycloalkyl unsubstituted or substituted by one or more C1-C20alkyl; (C3-C12cycloalkyl)-C1-C10alkyl unsubstituted or substituted by one or more C1-C20alkyl; a bicyclic or tricyclic hydrocarbon radical with 5 to 20 carbon atoms unsubstituted or substituted by one or more C1-C20alkyl; phenyl unsubstituted or substituted by one or more radicals selected from C1-C20alkyl, C1-C20alkoxy, C1-C20alkylamino, di(C1-C20alkyl)amino, hydroxy and nitro; phenyl-C1-C20alkyl unsubstituted or substituted by one or more radicals selected from C1-C20alkyl, C3-C12cycloalkyl, phenyl, C1-C20alkoxy and hydroxy; biphenyl-(C1-C10alkyl) unsubstituted or substituted by one or more C1-C20alkyl; naphthyl-C1-C20alkyl unsubstituted or substituted by one or more C1-C20alkyl; or tri(C1-C10alkyl)silyl(C1-C10alkyl).
Further examples of (6)-(8) and other members of the class of molecules are disclosed in U.S. Pat. No. 7,790,793, which describes gelling agents for the preparation of gel sticks and that improve the gel stability of water and organic solvent based systems.
As shown above the class of molecules may have benzene as an aromatic core. However, other aromatic cores may be used. For example, naphthalene may be used as an aromatic core. Aromatic cores may be flat.
As shown above, each amide branch may have one organic group or side chain. However, in some cases one or more of the amide branches have two organic groups. For example, the amide branch connects to the aromatic core via a carbon-nitrogen bond, the nitrogen has an alkyl group and the carbonyl carbon has an organic group. Other examples may be used. One or more amide branches may have two organic groups on the amide nitrogen, so long as at least one, two, or more amide branches have an amide nitrogen with a free hydrogen for hydrogen bonding. In other cases each amide branch nitrogen has one hydrogen atom for maximum facilitation of hydrogen-bonding and gel formation.
Non-alkyl organic side chains may be used. Organic groups with five or less carbon atoms may be used.
A Subclass of the Above Class of Molecules, and Friction Reducing Results
An exemplary pyromellitamide may have a structure as represented by the general formula of:
with R1, R2, R3, R4, each being an organic group. The description below of variations of the organic groups applies to the organic groups discussed for all embodiments disclosed in this document and one or more or all of R1, R2, R3, and R4 may each be an alkyl group (an example of an organic group). In some cases, R1═R2═R3═R4. R1, R2, R3, and R4 may each have 6 carbon atoms, for example 6-10 or 6-24 carbon atoms. Each alkyl group may be one or more of straight chain, branched, aromatic, or cyclic. However, preferably each alkyl group is straight chain, and R1, R2, R3, and R4 may each be straight chain alkyl groups with 6-10 carbon atoms.
BTA6 is N,N′,N″,N′″-tetrahexylbenzene-1,2,4,5-tetracarboxamide (TH) and corresponds to the above formula with R1═R2═R3═R4=hexyl. BTA8 is N,N′,N″,N′″-tetraoctylbenzene-1,2,4,5-tetracarboxamide (TO) and corresponds to the above formula with R1═R2═R3═R4=octyl. BTA6 and BTA8 have been tested for friction reduction in a flow loop and give the results shown below.
As shown in
Other pyromellitamides or benzamides described in WO2013040718 and WO2014146191 are predicted to provide some degree of shear stability and friction reduction though not necessarily the same as for BTA6 (hexyl) and BTA8 (octyl). Thus, at least the following versions of the BTA are soundly predicted to provide a level of friction reduction: butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl (BTA10), undecyl and dodecyl (BTA12).
It has also been found that, out of BTA6 and BTA8 which are the molecules that have been tested for friction in a flow loop, BTA8 works best in fluid that have carbon numbers around C12-C16, whereas BTA6 is best for C6-C10. It is therefore expected that there is a general relationship between the carbon numbers of the fluid and the optimal chain lengths (BTA numbers). Thus it is expected that longer chain molecules such as BTA14, BTA16 and BTA18 may work better in some of the heavier oils, which have larger carbon numbers.
In addition, combinations are soundly predicted to work, for example where different amides on the aromatic core have branches with different alkyls attached. Odd numbered chains are expected to work as well as even numbered, but are more expensive.
Thus, friction reduction in hydrocarbons can be achieved by the addition of pyromellitamides or benzamides described in WO2013040718 and WO2014146191, at levels of, for example, between 500-1000 ppm in a hydrocarbon liquid. This can reduce the friction of the oil by 60-75%. A narrower exemplary additive amount is 500-800 ppm. Where not stated otherwise, ppm is defined by mass (mg/kg). The amounts are exemplary only and the most useful range of amounts is predicted to be greater than this on the basis of the results, with performance varying somewhat based on the amount.
Due to its non-polymeric nature the pyromellitamide will be shear stable when exposed to shear. The pyromellitamide forms hydrogen bonded polymer chains. The shear will break up the chains but they have the ability to reform an infinite number of times.
Applications for this molecule include hydrocarbon transmission in pipelines to reduce friction. A pipeline also exposes oil to shear over the long distances in which the oil travels, making shear stability useful. The molecule may also be used as an additive to gasoline to reduce friction, for example for use in two stroke motors.
Shear Thinning Effect
When added to hydrocarbon fluids, the tested compounds reduce friction. This is believed to be due to a shear thinning effect. The shear thinning effect has been tested for BTA8 and BTA10 additives and is expected to apply also to other molecules of the class. The additive will increase the viscosity of the fluid slightly (around 10-20 cP at typical concentrations tested). When shear is applied the viscosity of the sample will decrease but for most fluids never drops below that of the base fluid. This is the case for all fluids tested except the bitumen blends, which are further described below.
Without modification, a hydrocarbon fluid is typically Newtonian, i.e., the viscosity does not vary with shear. By measuring shear stress across a range of shear rates (and fitting to a power law curve) is it possible to calculate the constant n, known as the “power-law index” or “flow behavior index,” which for a Newtonian fluid=1.
For a non-Newtonian fluid, the viscosity is dependent on the shear rate. Fluids can be shear thickening (e.g., corn starch in water) or also shear thinning such as hydrocarbon fluid with added pyromellitamide. For a shear thinning fluid, n<1.
By measuring n values of hydrocarbon fluids with and without added pyromellitamide, we find that it does alter the behavior from Newtonian to non-Newtonian. From our flow loop data, we know that the shear-thinning fluids that we have tested display vastly reduced friction so we therefore deduce that this would be the case for all the pyromellitamide containing fluids that display n<1. The table below displays these experimentally determined values. In the table, ppm is measured by mass. In the table, “Blank” means no pyromellitamide was added.
It is believed that the shear thinning effect of the additives results from hydrogen bonded polymer chains.
The pyromellitamides are believed to reduce the friction of a liquid against a solid by creating laminar flow against the solid. That laminar flow is created in a boundary layer where the fluid at the boundary (touching the solid) moves very slowly and the fluid above the boundary slips by very quickly. This creates the reduced friction we see in a pipe and increased flow.
Generally, as the flow velocity of the bulk fluid increases there is more turbulent flow which will limit the amount of fluid that can be forced down the pipe. It is believed that the hydrogen bonded polymer chain that the BTA forms helps maintain the laminar flow by preventing and limiting the effect of any turbulent flow.
Lubrication of two surfaces occurs in the same way as flow in a pipe. The pyromellitamide creates hydrogen bonded polymer chains within the fluid, these chains orient along the axis of flow and/or break due to shear and reform and allow the liquid to easily slide over itself to reduce friction between two surfaces, while turbulence is reduced.
It is expected that the shear thinning and friction reduction effects found for tested hydrocarbons will also work for other hydrocarbons. For example, it is believed that the lubrication provided for other hydrocarbons as disclosed in this document would also work for other fuels, which are commonly moved by pipeline.
In order to add the molecules to a hydrocarbon and get them to disperse quickly, they may be initially dissolved in a smaller quantity of the hydrocarbon, and then the smaller quantity of the hydrocarbon added to a larger quantity of the hydrocarbon. In an example, in order to make a 500 ppm mixture of a BTA6 additive with gasoline, the BTA6 additive was dissolved in gasoline, and then the gasoline with the dissolved BTA6 was added to a gas tank in a 10:1 dilution to get the final 500 ppm concentration. This mixture has been found to achieve a friction reduction of 70-75%, and was tested as the fuel for a leaf blower, which ran with no apparent problems with the additive present.
It is believed that molecules in this class can be used in gasoline for lubrication, replacing current lubrication molecules (which include metals in a lot of cases) but are environmentally inert and combust in the engine.
Bitumen
It has also been found that BTA10 reduces the viscosity of diluted bitumen. This is different from other hydrocarbon fluids tested in which there is a friction reduction with increased viscosity. It is believed that this viscosity reduction results from a different mechanism than the shear thinning effect, though the shear thinning effect is also present in bitumen, as shown in Table 1 above.
Bitumen asphaltenes are believed to be stacks of plate-like sheets formed of aromatic/naphthalenic ring structures. The viscosity of a solution, in particular a dilute solution (a dilbit), depends on the shape of the asphaltene particles and the amount of hydrogen bonding that occurs between the sheets. At high temperature hydrogen bonds holding the sheets together to form the stacks are believed to be broken resulting in a change in both size and shape of the asphaltenes. Dissociation of the asphaltene is believed to continue until the limiting moiety, the unit sheet, is reached. Consequently viscosity falls as the temperature increases. Hydrogen bonding of the stacks is believed to be broken by a stronger affinity of BTA10 to the hydrogen bonds of the individual sheets than the stacks.
It is thought that the BTA10 is acting as a breaker by interrupting the hydrogen bonding of the stacks. So we see a characteristic similar to heating the bitumen up. The diluent is important because it does not cause the BTA10 to form its own stacks, i.e., gel the diluent. So the BTA10 is left to attack the bitumen stacks and “break” the hydrogen bonding. It is believed that different molecules of the class of molecules described in this application would also work instead of BTA10.
To add the additive to the diluted bitumen, for example the additive could be dissolved in the diluted bitumen; or the additive could be dissolved in a smaller sample of diluted bitumen which is then added to the diluted bitumen; or the additive could be dissolved in the diluent before it is added to the bitumen to form diluted bitumen; or the additive could be dissolved in a smaller sample of diluent that is added to the rest of the diluent before it is added to the bitumen to form diluted bitumen; or the additive could be dissolved in a smaller sample of diluent that is added to the diluted bitumen. An exemplary method of reducing the viscosity of diluted bitumen is shown in
The additive could also be added to bitumen without diluent, for example by first heating the bitumen to allow mixing. The above described mechanism should also be effective in lowering the viscosity of undiluted bitumen.
In the claims, the word “comprising” is used in its inclusive sense and does not exclude other elements being present. The indefinite articles “a” and “an” before a claim feature do not exclude more than one of the feature being present. Each one of the individual features described here may be used in one or more embodiments and is not, by virtue only of being described here, to be construed as essential to all embodiments as defined by the claims.
| Number | Date | Country | |
|---|---|---|---|
| 62552099 | Aug 2017 | US |
