Patent Application
20080015121
The present invention may allow a variety of quaternary ammonium compounds to be prepared in good yield without olefin formation occurring and with excellent conversion. These compounds show significant steric hindrance, which may serve to inhibit formation of hydrates that include, for example, hydrocarbons having a variety of carbon chain lengths. The compounds may further serve the same purpose with respect to materials that may form non-hydrocarbon hydrates, such as carbon dioxide, nitrogen and hydrogen sulfide.
While it is hypothesized that the reaction to prepare the sterically hindered quaternary ammonium compounds occurs in at least three discrete events, it is emphasized that the method may be carried out as a single step, thereby simplifying and facilitating production. Without wishing to be bound by any mechanism or theory thereof, it is hypothesized that these events include, first, the amine acting as a base which effects epoxidation of the halohydrin and also forms an amine hydrohalide. Second, the amine hydrohalide salt exists in equilibrium with the protonated epoxide and the amine. Third, the protonated epoxide reacts with the amine to form the quaternary ammonium compound. It is further hypothesized that all three reactions are favored by the hydroxyl functionality of the solvent.
The starting materials for the inventive method include, first, the halohydrin. This compound is defined herein as a type of chemical compound or functional group in which one carbon atom has a substituent of the halogen group in a carbon-carbon saturated covalent bond, and the other carbon atom has a hydroxyl substituent. These compounds adhere to the general formula
wherein X is chlorine, fluorine, bromine or iodine; and wherein RA, RB, RC and RD are independently selected from hydrogen, hydrocarbon substituents containing from 1 to 20 carbon atoms, and heteroatoms selected from oxygen, nitrogen, phosphorus and combinations thereof.
Thus, simple halohydrins would include, for example, 1-halo-2-hydroxyl ethane (X—CH2CH2—OH), and 1-halo-2,3-hydroxyl propane (X—CH2—CH2CH2OH), wherein X is the halogen. Halohydrins may be, in general, formed from an alkene in a halohydrin formation reaction, or from an epoxide by reaction with a hydrohalic acid. Those skilled in the art will be aware of means and methods to prepare these materials without further direction herein, and alternatively such materials may be, in some instances, purchased commercially.
The second starting material is the solvent having hydroxyl functionality. This solvent may be selected from the group consisting of water; alcohols containing from 1 to 10 carbon atoms; glycols; and mixtures thereof. Of these, methanol, ethanol, water, and mixtures thereof may, in some non-limiting embodiments, be particularly preferred for reasons of economy and yield. In other non-limiting embodiments, glycols, longer-chain alcohols, or mixtures of any of these with one another or with water, methanol, and/or ethanol, may be effectively employed. Among suitable and commercially available glycols are, for example, ethylene glycol and propylene glycol.
The third starting material is a sterically hindered tertiary amine. This tertiary amine is, in some non-limiting embodiments, a tertiary amine conforming to the general formula
wherein R2, R3 and R4 each independently have from 3 to 12 carbon atoms, may be linear or branched, and may have one or more carbon-to-carbon double bonds. In some non-limiting embodiments the R2, R3 and R4 groups each independently have from 3 to 5 carbon atoms. Amines having 3 carbon atoms for each group may be selected from the group consisting of tripropylamine and triallylamine (also called triprop-2-enylamine). Amines having 4 carbon atoms for each group include tributylamine, triisobutylamine (i.e., tri-2-methylpropylamine), trimethyl-allylamine (i.e., tri-2-methylprop-2-enylamine), tribut-2-enylamine, and tribut-3-enylamine. Amines having 5 carbon atoms for each group include tripentylamine, triisopentylamine (i.e., tri-3-methylbutylamine), tri-3-methylbut-2-enylamine, and tri-3-methylbut-3-enylamine. Mixtures of any of the above may also be employed. In some non-limiting embodiments the sterically hindered tertiary amine may be selected from the group consisting of tripropylamine, tributylamine, triisobutylamine, and mixtures thereof. In other non-limiting embodiments, tributylamine and triisobutylamine are selected, and in still other non-limiting embodiments, tributylamine is selected.
The proportions of the starting materials may be conveniently calculated based on the molar ratio of the halohydrin to the amine. While a wide range of ratios may be employed, it will be obvious to those skilled in the art that controlling the molar ratios within certain ranges will help to optimize conversions, i.e., yields. In one non-limiting embodiment the mole ratio of halohydrin to amine may be from about 2:1 to about 1:2. In another non-limiting embodiment a mole ratio of from about 1.5:1 to about 1:1.5 may be employed. In yet another non-limiting embodiment, a ratio of from about 1.15:1 to about 1:1.15 may be employed.
Once a mole ratio of halohydrin to amine is selected, the amount of hydroxyl functionality containing solvent may be estimated as a weight percentage of the total mass contained in the reaction vessel. The solvent may, in some non-limiting embodiments, range from about 1 to about 99 percent by weight. In other non-limiting embodiments it may be in the range of from about 2 to about 80 percent by weight. In certain particularly desirable but non-limiting embodiments, a solvent in the range of from about 5 to about 50 percent by weight may result in a product that is not excessively dilute and yet still exhibits a relatively high rate of conversion to the quaternary ammonium compound, within a reasonable time.
The reaction conditions are, in some non-limiting embodiments, based upon a combination of temperature and pressure sufficient to yield the sterically hindered quaternary ammonium compound. In certain non-limiting embodiments, the reaction parameters are also selected to ensure that the desired final product is prepared within a commercially desirable time period and/or to result in a commercially desirable yield. In order for the reaction to proceed to the desired end product, it is necessary for most or all of the solvent to remain in liquid form to ensure a liquid phase reaction, and desirable to employ a temperature and/or pressure that is somewhat above ambient in order to expedite the reaction. In some non-limiting embodiments the reaction is desirably carried out at a temperature of at least about 60° C. (about 140° F.), and in other non-limiting embodiments the temperature is desirably at least about 80° C. (about 176° F.). In still other non-limiting embodiments the temperature is desirably at least about 100° C. (about 212° F.). Thus, it will be seen that, in the case of relatively low boiling solvents, e.g., methanol, pressures above ambient may be required in order to ensure maintenance of a liquid state during the reaction, while higher boiling solvents, e.g., glycols, may be employed at elevated temperatures without the need for greater-than-ambient pressure.
Contacting of the starting materials may be done in any way and in any type of vessel that results in formation of the desired final product, i.e., the sterically hindered quaternary ammonium compound. Because the end product includes anionic halide, laboratory or production vessels that are resistant to corrosion from halide are generally preferred. For example, reaction vessels made of glass or metal alloys, including those specifically designed to be resistant to halide corrosion such as hastalloy, may be particularly useful.
Introduction of the solvent, halohydrin and sterically hindered tertiary amine into the reaction vessel may be concurrent or in any order or combination of orders. However, those skilled in the art will keep in mind that if contact of any one starting material is significantly delayed relative to the other starting materials, side reactions, that may significantly reduce or even circumvent production of the desired final product, may occur. Simple mixing or stirring, using any conventional means known in the laboratory or production facility to maximize contact, may be employed. Production may be carried out via either batch or continuous methods.
Inclusion of a catalyst with the starting materials may also be considered. One effective type of catalyst is a second amine compound that acts as a base to heighten promotion of the ring closure of the halohydrin to form the epoxide, but which, due to either steric or electronic reasons, does not react significantly with the protonated epoxide to, itself, form a quaternary ammonium compound. For example, amines such as diazabicyclo[2.2.2]octane, diazabicyclo[5.4.0]-undecene, and mixtures thereof may, in some non-limiting embodiments, be effective for this purpose. However, it has been found that the inventive method's generalized reaction will, in some non-limiting embodiments, proceed effectively and at high yield even without a catalyst.
In many non-limiting embodiments, the method described herein results in yields, i.e., conversions, of at least about 50 percent of theoretical, and in other non-limiting embodiments the yields are at least about 80 percent. In yet other non-limiting embodiments, the yields may be at least about 90 percent of theoretical. Where smaller and structurally simpler tertiary amines are employed, yields tend to be higher than for larger and more complex tertiary amines.
The compounds thus formed are sterically hindered quaternary ammonium compounds. In some embodiments it may be desirable to employ a mixture of two or more halohydrins, in order to produce a mixture of two or more sterically hindered quaternary ammonium compounds. This approach might be selected where, for example, a single quaternary ammonium compound results in a more crystalline or otherwise less-easily-dispersed final product. In one non-limiting embodiment, a mixture of dodecyl alcohol and tetradecyl alcohol may be reacted with epichlorohydrin to produce a mixed chlorohydrin product. This mixed product is then used in the method of the present invention to result in a mixture of two sterically hindered quaternary ammonium compounds conforming to Formula 1, which may alternatively be denominated as C27H58ClNO2 and C29H63ClNO2. In other non-limiting embodiments the chlorine atom in these compounds may be replaced with bromine, fluorine or iodine.
The sterically hindered quaternary ammonium compounds formed by the method previously described are useful for any purpose for which quaternary ammonium compounds are known to be useful, such as surface active agents, dispersing agents, foaming agents, and corrosion inhibitors. Of particular application, however, is their notable efficacy in inhibiting formation of hydrates in susceptible fluids. In this use the quaternary ammonium compounds may be introduced into a wellbore, reservoir, or any associated or other oilfield tubulars, such as flowlines, pipelines, transfer lines, tubing, and the like, by way of equipment or methods known to those skilled in the oilfield arts. For example, the compounds may be injected by way of coiled tubing.
In amount the quaternary ammonium compounds useful in the invention for hydrate control may range, in some non-limiting embodiments, from about 0.01 to about 2.0 volume percent, based on the water or other aqueous fluid (for example, brine) that is present. In other non-limiting embodiments such may range from about 0.5 to about 1.5 volume percent. In other applications, such as when the sterically hindered quaternary ammonium compounds are used as corrosion inhibitors, surfactants, and the like, it is more typical to employ much smaller amounts, ranging from about 1 to about 5,000 ppm, and in some non-limiting embodiments amounts from about 10 to about 1,000 ppm may be desirable.
The description hereinabove is intended to be general and is not intended to be inclusive of all possible embodiments of the invention. Similarly, the examples hereinbelow are provided to be illustrative only and are not intended to define or limit the invention in any way. Those skilled in the art will be fully aware that selections of solvents and combinations of solvents, sterically hindered tertiary amines and combinations thereof, and halohydrins and combinations thereof; reaction conditions; reaction vessels; reaction protocols; hydrocarbon streams and reservoirs; and the like; may be varied within the scope of the claims appended hereto.
About 4.00 g methanol; 2.00 g water; 8.02 g of a mixture of the chlorohydrin products of the reaction of epichlorohydrin with ALFOL™-1214, which is a mixture of dodecyl alcohol and tetradecyl alcohol; and 5.58 g tributylamine; were combined in a 4 ounce (about 0.1134 kg) vial. The chlorohydrin products mixture includes two compounds, of which each conformed to the general formula
wherein X is chlorine, fluorine, bromine or iodine; and wherein RA, RB, and RC are hydrogen and RD is CH2O(CH2)nCH3, and wherein n is 11 (representing one compound) and 13 (representing a second compound). The vial was loosely capped with aluminum foil and then shaken manually for about 1 minute to thoroughly mix the constituents. The vial was then placed in a stainless steel pressure bomb. The bomb was sealed and pressurized to 150 psi (about 1034 kPa) with nitrogen. It was then placed in an oven at 120° C. (about 248° F.) for 20 hours. The bomb was then removed from the oven and allowed to cool to room temperature. Then the pressure was slowly vented. The bomb was opened and the vial removed. It was found to contain a mixture of sterically hindered quaternary ammonium compounds as a yellow solution including methanol and water. These compounds were characterized as conforming to Formula 1, with one compound having as R1 a C12H25 moiety, and the other having as R1 a C14H29 moiety, and with R2, R3 and R4 in both compounds being n-butyl. Thus, the final compounds could be alternatively characterized as C27H58ClNO2 and C29H63ClNO2, respectively.
Four 33 ml test cells, each having a sapphire glass window and containing a number of ball bearings, were selected. Into each of these test cells was charged an aqueous phase consisting of 3.0 g of an 11.0 weight percent NaCl solution and 9.0 ml of a 75 volume percent natural gas condensate from the Gulf of Mexico. A gas composition that was an 85/15 mole/mole mixture of methane and propane was also added as compressed gas to obtain a pressure of 1500 psi (about 10340 kPa). This combination of materials simulated the production composition that is frequently encountered in gas wells and particularly in subsea operations, where brine, natural gas mixtures, and liquid hydrocarbons come into contact.
The four cells were then prepared for comparative testing. Cell A included, in an amount of 1.2 volume percent based on the brine, a sterically hindered quaternary ammonium compound that is known in the art to be useful for inhibiting hydrate formation and that was commercially manufactured by a more complex method than that of the present invention. This cell was, thus, the “control.” Cell B was a “blank,” i.e., it included no gas hydrate inhibitor. Cell C and Cell D were duplicates of the same sterically hindered quaternary ammonium compound of the invention, used as the hydrate inhibitor. This quaternary ammonium compound had been previously prepared according to the method, materials and proportions used in Example 1. It was added to each of Cells C and D as a 70 volume percent by weight dilution that included 30 volume percent methanol.
The test cells' contents were pressurized initially at 1500 psi (about 10340 kPa) using compressed gas at ambient temperature, then underwent a “shock” cool-down (i.e., a rapid cool-down) to 40° F. (about 4.4° C.) in a refrigerated bath. They were then shut-in (i.e., allowed to sit without movement) for a time, followed by gentle rocking to an angle of approximately 30° from horizontal. These conditions were intended to simulate the overall conditions to which a typical production composition would likely be subjected, including extended quiescence under low temperature and high pressure, followed by rocking-like movement through pipelines and flowlines. At various points in time the test cells' contents were inspected visually to determine whether gas hydrates were forming or had formed. The ball bearings, called simply “balls” hereinbelow, simulated the effect of fluid flow in a pipeline, breaking viscosity somewhat and providing for gentle agitation of the cells' contents. The following table, designated as Table 1, shows the results of the tests.
It will be seen from the table that the quaternary ammonium compound of the invention (Cells C and D) was fully as effective as the control (Cell A) at inhibiting hydrate formation, and that both of the hydrate inhibitors were much more effective than using no inhibitor at all (Cell B).
A mixture of sterically hindered quaternary ammonium compounds characterized as C27H58ClNO2 and C29H63ClNO2, in a 30 weight percent solution in methanol, is injected along with water into a hydrocarbon fluid present in a reservoir. The mixture of compounds is added such that it is present in the injected water in an amount ranging from about 0.9 to about 1.1 percent by volume.
