MXPA97005232A - Method to reduce odoriza depletion - Google Patents

Abstract

The present invention relates to a method for reducing odorant depletion during the transfer and storage of liquefied petroleum gas comprising the steps of: a) completely filling a transfer or storage vessel for liquefied petroleum gas with a passivating agent of so that all the inner surfaces of said container come in contact with said passivating agent, said passivating agent comprising one or more phosphate esters defined by the equation: [RX [mH2mO] n] k-PO (OH)) (3- k) wherein: R is an alkyl group containing from 4 to 18 carbon atoms or an alkylaryl group comprising an alkyl group selected from the group consisting of phenol, diphenol and mixtures thereof and an alkyl group containing 4 to Carbon atoms: X is selected from the group consisting of a carboxyl group (-COO-), oxygen (-O-), a group of secondary amines (-NH-) and mixtures thereof; m is an integer which t It has a value of about 2 to about 4, n is an integer that has a value of about 4 to about 20, and k is an integer that has a value of 1 to 2 and one or more fatty amines, polyamides and imidazolines , polyimidazolines, quaternary amines, quaternary polymers, dimer acids, trimer acids, polymeric acids, ethoxylated fatty amides, ethoxylated polyamides, ethoxylated alcohols or mixtures thereof and one or more solvents, b) draining said passivating agent from said container and c) evacuating said container prior to the introduction of said liquefied petroleum gas into said container.

Description

METHOD FOR REDUCING ODORIZING DEPLETION FIELD OF THE INVENTION The invention relates to a method for reducing odorant depletion during the transfer and storage of liquefied petroleum gas. BACKGROUND Liquefied petroleum gas (LP-gas), which consists mainly of propane with small amounts of lighter and heavier hydrocarbons, is commonly odorized with compounds based on ethyl mercaptan or other mercaptans so that it can be detected if the gas escapes. The propane distribution of the producer where the odorant is injected for the last consumer, may require propane to be transferred several times in and out of different transport and storage containers that are normally made of steel. Since about 1986, it has been recognized that mercaptan-based odorants may be depleted during transport and / or storage, a phenomenon sometimes referred to as "gradual odor disappearance". This depletion can occur by oxidation of the odorizing compound to a sulfide, or possibly through chemical adsorption in LP-gas transport or storage vessels with internal metal surface.

Attempts have been made to counteract the depletion of the odorant. For example, the Patent of E. U.A. Do not. No. 3,669,638 is directed to a method for delivering a constant dose of odorant wherein the odorants are added from a closed container through a permeable membrane for selected periods. The Patent of E. U.A. 3, 826,631 is directed to an odorant composition that includes an azeotropic mixture of an organic sulfur odorizer and at least one chemically inert, relatively odorless material capable of forming an azeotrope with minimal boiling point with the sulfur odorizer organic. COMPONENT OF THE I NVENTION According to the present invention, odorant depletion is reduced by passivating the internal surface of the LP-gas transport and storage vessels by the addition of passivating agents designed to create a protective film on the surface of the container. The term "passivation", as used herein, means temporarily returning the inner surface of a container less reactive to the odorant than a non-passivated container. The passivation of the inner surface of the containers can be achieved by a "filling treatment" method wherein the container is filled completely with the selected passivating agent and / or by an "additive treatment" method wherein an agent of Passivation that is dispersible, or more preferably soluble, in propane is added directly to the LP-gas together with the odorant in sufficient amounts to provide a concentration of passivation agents selected on a scale of up to about 250 ppm (v / v). The passivating agents, which may be water soluble or may be dispersible or soluble in LP-gas, comprise mixtures of corrosion inhibitors such as phosphate esters, fatty amines, polyamides, imidazolines, poly-imidazolines, quaternary amides, polyquaternary, dimer acids, trimer acids, polymeric acids, ethoxylated fatty amines, ethoxylated polyamides, ethoxylated alcohols and the like or mixtures thereof in one or solvents. Suitable solvents include, but are not limited to, water, glycol ether, heavy alcohols such as butane, hexanol, and the like, and aromatic solvents such as xylene, toluene, and the like. In a preferred embodiment, the passivating agents contain one or more phosphate esters and, in a more preferred embodiment, contain one or more phosphate ethers defined by the equation: [R-X- [CmH2mO) n] k-PO (OH)) (3.k) where; R is an alkyl group containing 4 to 18 carbon atoms or an alkylaryl group comprising an alkyl group selected from the group consisting of phenol, diphenol and mixtures thereof and an alkyl group containing from 4 to 18 carbon atoms; X is selected from the group consisting of a carboxyl group (-COO-), oxygen (-0-), a group of secondary amines (-NH-) and mixtures thereof; m is an integer having a value from about 2 to about 4; n is an integer that has a value of about 4 to about 20; and k is an integer having a value of 1 to 2 and one or more fatty amines, polyamides, and imidazolines, polyimidazolines, quaternary amines, polyquaternary acids, dimers acids, trimer acids, polymeric acids, ethoxylated fatty amides, ethoxylated polyamides, ethoxylated alcohols or mixtures thereof and one or more solvents. The treatment of LP-gas transport and / or storage vessels in the manner described herein, results in depletion of the odorant. In addition, passivating agents are not removed from the tank by the release of propane gas. These and other aspects and advantages of the present will be apparent from the following detailed description, which is given by way of illustration only. BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 represents the concentrations of ethyl mercaptan (ME) of passivation agents AN-1-76B, AN-1-76C, AN-1-76D, AN-1-76F and the target in the vapor phase in a tank of 794.50 liters, during a period of 26 weeks. FIGURE 2 represents the concentrations of ethyl mercaptan (ME) of passivating agents AN-1-76B, AN-1-76C, AN-1-76D, AN-1-76F and the target in the vapor phase in a tank of 381.36 liters during a period of 26 weeks. FIGURE 3 represents the concentrations of ethyl mercaptan (ME) of passivation agents AN-1-76B, AN-1-76C, AN-1-76D, AN-1-7éF and the white in the vapor phase in a tank of 79.45 liters during a period of 26 weeks. FIGURE 4 represents the concentrations of ethyl mercaptan (ME) of passivation agents AN-1-76B, AN-1-76C, AN-1-76D, AN-1-76F and the target in the vapor phase in a tank of 15.89 liters during a period of 26 weeks. FIGURE 5 represents the concentrations of ethyl mercaptan (ME) of passivation agents AN-1-76C in the liquid phase in a tank of 794.50 liters in a period of 26 weeks.

FIGURE 6 represents the concentrations of ethyl mercaptan (ME) of passivation agents AN-1-76C in the liquid phase in a tank of 381.36 liters in a period of 26 weeks.

FIGURE 7 represents the concentrations of ethyl mercaptan (ME) of passivation agents AN-1-76E in the liquid phase in a tank of 794.50 liters in a period of 26 weeks.

FIGURE RA 8 represents the concentrations of ethyl mercaptan (M E) of passivation agents AN-1 -76E in the liquid phase in a tank of 381 .36 liters over a period of 26 weeks. DETAILED DISCLAIMER In accordance with the present invention, odorant depletion is reduced by passivating the internal surface of the LP-gas transport and storage vessels by the addition of passivation agents designed to create a protective film on the surface of the container . The passivation of the internal surface of the containers can be achieved by a "filling treatment" method wherein the container is filled completely with the selected passivation agent and / or by a "additive treatment" method where it is added a passivating agent that is dispersible, or more preferably. soluble, in propane, directly to the LP-gas only with the odorant in sufficient quantities to provide a concentration of the passivation agent selected in the scale of up to about 250 ppm (v / v). The purpose of the film provided by the filling treatment method is to prevent the odorant from coming into contact with the surface of the tank where it can be exhausted by the adsorption processes or by oxidation by the metal oxides present on the surface. The purpose of the additive treatment is to keep the film that lines the surface of the container. The small amount of passivation agent added by this treatment method fills any part of the film that has been washed from the LP-gas or has been damaged for any other reason. The passivating agents may be water soluble or they may be dispersible or soluble in LP-gas, they comprise mixtures of corrosion inhibitors such as phosphate ethers, fatty amines, polyamines, imidazolines, poly-imidazolines, quaternary amines, polyquaternary acids, of dimers, trimer acids, polymeric acids, ethoxylated fatty amines, ethoxylated polyamines, ethoxylated alcohols and the like with mixtures thereof in one or more solvents. Suitable solvents include, but are not limited to, water, glycol ether, heavy alcohols such as butane, hexanol and the like and aromatic solvents such as xylene, toluene and the like. In a preferred embodiment, the passivating agents contain one or more phosphate esters and, in a more preferred embodiment, contain one or more phosphate esters defined by the equation: [R-X- [CmH2mO) n] k-PO (OH) (3.k) According to the above formula, R is either an alkyl group or an alkylaryl group. The alkyl group can be linear or branched and contain from 4 to 18 carbon atoms. When R is an alkylaryl group it has the same alkyl group as mentioned with the addition of an aryl group such as phenol, diphenol, other hydroxy-containing aryl radicals, alkylated hydroxyaryl group or mixtures thereof. Component X is selected from the group consisting of a carboxyl group (-COO-), oxygen (-O-), a secondary amine group (-NH-) and mixtures thereof. The variable m is an integer that has a value of about 2 to about 4. The n variable is an integer that has a value of about 4 to about 20. The variable k is an integer that has a value of 1 to 2 In the preferred embodiment, the passivating agents further contain one or more fatty amines, polyamides, imidazolines, poly-imidazolines, quaternary amines, polyquaternary amines, dimer acids, trimer acids, polymeric acids, ethoxylated fatty amines, ethoxylated polyamides, ethoxylated alcohols or mixtures thereof and one or more solvents. Suitable solvents include, but are not limited to, water, glycol ether, heavy alcohols such as butanol, hexanol and the like and aromatic solvents such as xylene, toluene and the like. Said compositions and their preparation are described in Co-pending patent application of E.U.A. 08 / 599,430 filed January 17, 1996, which is incorporated herein by reference. As demonstrated by the following tests, the treatment of LP gas transport and storage vessels in the manner described herein, reduces odorant depletion.

In addition, passivation agents are not removed from the LP gas storage or transport vessel by the release of propane gas. The passivation agents designated AN-1-76B, AN-1-76C, AN-1-76D, AN-1-76E and AN-1-76F and having the compositions set forth in Table 1 below were eated. TABLE 1 AN-1-76D Water Soluble Continue TABLE 1 AN-1-76B Soluble in Water AN-1-76C Dispersible in LP-gas Continuous TABLE 1 AN-1-76E Soluble in gas-LP AN-1-76F Dispersible in gas-LP The containers or tanks were prepared in the following manner. Forty-five tanks (45) were selected varying in volume from 79.45 to 794.50 Its. All tanks arrived sealed and under positive air pressure. The alteration to the weather was achieved by purging the tanks initially with 2.1 kg / cm2 of compressed air for 10 minutes, followed by storage outside the tanks with their es open for 90 days. For comparison purposes, tanks # 1, 11, 30 and 40 did not undergo this alteration process in the open. On the contrary, said tanks remained sealed as they were delivered. The purpose of the weathering was to simulate field conditions and generate or produce some iron oxide inside the tank, which is supposed to be the worst case scenario in terms of odorant depletion. However, with the limited sample it was not possible to demonstrate a difference in odorant depletion between altered and unaltered tanks. The tanks were organized into five identical groups of nine. A group was left untreated to serve as a target and four groups were treated with passivating agents described in Table 1. The allocation of tanks is shown in Table 2.

TABLE 2 Continue TABLE 2 The tanks were passivated by the filling treatment method, that is, the e was removed from each tank and the tank was completely filled with the selected passivation agent. The tank was then closed and the passivating agent was left in the tank for 10 minutes. During the 10 minute period, the tank was lifted and rolled so that the interior surfaces contacted the passivation agent. At the end of ten minutes, the tank was drained and the excess passivation agent was transferred to the next untreated tank and the procedure was repeated. When the passivation of the 9 tanks in the selected group was completed, the excess passivation agent was returned to the original drums. After four days, all tanks, both treated and white, were evacuated to 50.8 cm vacuum with a commercial pump to remove air and solvent vapors. All evacuated tanks, both treated and white, were filled with freshly odorized LP gas. The odorization followed the industry practice of 675 kg of ethyl mercaptan for 37,800 liters of LP gas. The odorant concentration (ethyl mercaptan) was then measured in the gas output of each tank. The concentrations of ethyl mercaptan in ppm (v / v) were measured using Sensidyne # 72 staining tubes according to the Gas Processors Associaton Test Method. The established accuracy of the staining tubes is +. 2.5% In order to increase the accuracy, each tank was sampled using two to four full loads of the sampling syringe and the concentration of ethyl mercaptan read directly from the tube was divided by the number of charges. Four charges were used except in the case where the concentration of ethyl mercaptan was clearly high, v.gr. , 30 ppm or higher, when only two charges were used. The target used for comparison was the weather-altered tank of similar size, since all the passivated tanks had been disturbed by the weather. It was expected that the concentration of ethyl mercaptan in the vapor phase would vary with temperature due to changes in relative volatility of ethyl mercaptan and propane, i.e., the values of k. A concentration of 8 ppm (v / v) was chosen as the original ethyl mercaptan concentration for all tanks. This number, which was appropriate for comparison purposes, does not represent the probable concentration of the start of the six-month trial, since the temperature at that time was low; on the contrary, it corresponded to the probable concentration at the end of the test when the temperatures were expected to reach 26.6 ° C, based on the known quantity of ethyl mercaptan injected into the LP gas in bulk at the beginning of the test.

In the first part of the test, some of the readings obtained with the same staining tubes were adjusted according to the ambient temperature. A correction factor provided by the pipe manufacturer would be used for external temperatures below 20 ° C. Figures 1-4 represent ethyl mercaptan for all passivation agents and white grouped by tank size. As shown in these Figures, for the four tank sizes: 794.50 liters: White loses the odorant in week 10.

Two passivation agents, AN-1 -76C and AN-1 -76D, retained significant amounts of odorant. These two passivation agents are clearly superior to the other two agents that lost the odorant at the end of the test. 381 .36 liters: White loses the odorant in week 6.

The two water-soluble passivation agents, AN-1 -76B and AN-1 -76D, retained significant amounts of odorant, the best being AN-1 -76D. The AN-1-76C dispersible in propane retained a low concentration of odorant, while AN-1-76F lost the odorant before the end of the test. 79.45 liters: White loses the odorant after 6 months. Two passivation agents, AN-1 -76C and AN-1 -76D retained approximately 50% of the original odorant concentration. . 89 liters: White loses the odorant at 6 weeks. All passivation agents work very well for this tank size. The concentration of ethyl mercaptan at the end of the test was greater than the final concentration. This can be explained by the fact that one each time the sampling in a tank of 15.89 liters acts, it significantly affects the volume of LP gas left in the tank, while for the tanks of larger size, the same volume was sampled. of gas during the time that the test had a much lower effect on the volume of non-vaporized liquid. Another smaller scale test was carried out using the passivation additive treatment method. For this test, tanks # 1, 2, 11 and 12, which were previously used as targets, were emptied and left out for 30 days with their valves open. To each tank was added 350 mm (v / v) of the passivation agent, based on an 80% fill of the tank. The same day, after being purged twice, the tanks were filled with LP gas. The passivation agents selected for this test were AN-1 -76C, which is dispersible in LP gas and AN-1-76E which was formulated to be completely soluble in LP gas. The tank allocation for this test is shown in Table 3.

TABLE 3 A Hewlett-Packard 5890 plus gas chromatograph (GC) with a flame ionization detector (DIF) and a sulfur chemiluminescence detector (DQLS, Antek Instruments, I nc.) Was used to collect the data. The CG column was supplied by Supelco, I nc. ASTM Method D5504-94 was used to establish the performance of the CG-DQLS system). The CG sampling system consisted of a needle valve, a gas sample valve and a liquid sample valve. These valves were connected in series with each other to the CG inlet port using a 0.158 cm Silicosteel pipe. To ensure reproducible results, it was necessary to passivate the internal surfaces of the sampling system by treating them with sulfur and minimizing connation with air (oxygen). The passivation procedure consisted of repeated injection of hexane and ethyl mercaptan gas and diethyl disulfide gas solutions through the GC column sampling system, until the peak areas for the two compounds were reproducible.

To protect the passivated surfaces, air diffusion in the sampling system was reduced by closing the needle valve during the change of the sample containers. Additionally, the sample lines were kept filled with a calibration gas when the system was not in use. The liquid propane from the test tanks was sampled using a 150 ml pressurized sample vessel known as a Welker unit. Noxidable steel and Quick connection hoses or fittings with Quick connection fittings were used to connect the Welker unit to the propane tanks or the CG sampling system. Before each use, the Welker unit was flushed with nitrogen without oxygen for about one minute to purge all residual propane in the sample and to protect the unit from air pollution. While collecting the LP gas sample, the liquid propane was allowed to flow through the samples for at least 30 seconds, thus protecting the sample from air pollution. An external normal method was used to convert the peak CG areas observed in LP gas samples to concentrations. The concentration of the odorant, ethyl mercaptan (M E), was measured in each tank and samples were taken from the trucks used to load the tanks with LP gas. Diethyl disulfide (DSDE) and one not known, tentatively identified as diethyl trisulfide (TSD) were detected by GC analyzes and measured together with ME. The performance of the system was monitored using a group of normal gas calibration (normal helium or gas) to calibrate the unit. The calibration gases were supplied to the CG sample valve (1 ml) at 3.09 kg / cm2. All samples of LP gas were supplied to the CG gas sample valve (1 ml) at 10.54 kg / cm2. For ideal gases, the weight of a gas in a fixed cycle filled at an inlet pressure of 3.09 kg / cm2, could be approximately one third of the pressure at 10.54 kg / cm2. Therefore, the concentration calculation based on CG peak areas and external normals required corrections due to pressure differences. The concentration was calculated according to the following formula: Concentration (ng / mg) =. { [Peak area (ng / 105 counts) / ml propane] x AF x WRf} in liquid propane where, the Response Factor Valued, WRf = [Rf (ng / 106 counts)] x the Pressure Factor / [Density, propane (1.8 mg / ml)]} Area Factor, FA = 36 / [(peak area for ME x WR, for ME) + (Sum of peak areas for DSDE and TSD x WRf for DSDE)]. Using the gas calibration data and from the graphs of CG areas against weight, ng, (ethyl mercaptan or other sulfur compounds), a response factor, Rf, was found expressing the tilt as counts of ng / 10s . The multiplication of the peak area of GC in propane with the value of Rf gave ng / ml of ethyl mercaptan present in propane. Dividing ng / ml of ethyl mercaptan with propane density (1.8 mg / ml) expressed results as ng / mg or ppm (w / w). The corrected concentrations were obtained by multiplying the product (ng / ml) with the pressure correction equal to a ratio of kg / cm2 of propane to kg / cm2 of helium. Figures 5-8 represent the concentrations of ethyl mercaptan for the two passivating agents used in this test. As shown in Figure 5-8, the four tanks contained significant amounts of odorant after three months. Based on the above tests, it is thought that the most effective method to reduce odorant depletion is a two-stage treatment. That is, the tank should be treated initially with a passivating agent by the filling treatment method and then treated with a propane-soluble passivating agent by the additive treatment method. A simple test was carried out in order to determine if the passivation agents would be carried out of the tank in the vapor phase. An outdoor commercial gas grill was connected to a previously passivated tank with an AN-1 -76C. The gas burned for about 8 hours a day for several weeks. At the end of that period, the grid was examined and no deposits were found in the gas burners. This test provides evidence that an internal scale would not occur when vaporized LP gas is used.

The above description was directed to particular embodiments of the invention for the purposes of illustration and explanation. However, it will be apparent to those skilled in the art that many modifications and changes in established compositions and methods will be possible without departing from the scope and spirit of the invention. The following claims are intended to be interpreted to cover all modifications and changes.

Claims (23)

1. CLAIMS 1. A method to reduce odorant depletion during the transfer and storage of liquefied petroleum gas comprising the steps of: (a) completely filling a transfer or storage vessel for liquefied petroleum gas with a passivating agent so that all the inner surfaces of said container come into contact with said passivating agent, said passivating agent comprising one or more phosphate esters defined by the equation: [RX- [CmH2mO) n] k-PO (OH)) (3. k) where; R is an alkyl group containing 4 to 18 carbon atoms or an alkylaryl group comprising an alkyl group selected from the group consisting of phenol, diphenol and mixtures thereof and an alkyl group containing from 4 to 18 carbon atoms; X is selected from the group consisting of a carboxyl group (-COO-), oxygen (-0-), a group of secondary amines (-NH-) and mixtures thereof; m is an integer that has a value of approximately 2 to around 4; n is an integer that has a value of about 4 to about 20; and k is an integer having a value of 1 to 2 and one or more fatty amines, polyamides, and imidazolines, polyimidazolines, quaternary amines, quaternary polymers, dimer acids, trimer acids, polymeric acids, ethoxylated fatty amides, ethoxylated polyamides , ethoxylated alcohols or mixtures thereof and one or more solvents; (b) draining said passivating agent from said container; and (c) evacuating said container prior to the introduction of said liquefied petroleum gas into said container.
2. 2. The method of claim 1, wherein said passivating agent comprises water glycol ether, morpholine or cyclohexylamine or mixtures of morpholine and cyclohexylamine, quaternized amines, imidazoline, polymeric acids, phosphate ester and ethoxylated polyamides.
3. The method of claim 2, wherein said passivating agent comprises from about 10 to about 3% by weight of water; from about 10 to about 30% by weight of glycol ether; from about 5 to about 15% by weight of morpholine or cyclohexylamine or a mixture of morpholine and cyclohexylamine; from about 10 to about 19% by weight of quaternary amines; from about 10 to about 25% by weight of imidazoline; from about 5 to about 15% by weight of polymeric acids; from about 10 to about 15% by weight of phosphate ester; and from about 5 to about 17% by weight of ethoxylated polyamides.
4. 4. The method of claim 3, wherein said passivating agent comprises about 20% water; about 20% glycol ether; about 5% by weight of morpholine or cyclohexylamine or a mixture of morpholine and cyclohexylamine; about 8% by weight of quaternary amines; about 15% by weight of imidazoline; about 10% by weight of polymeric acids; about 14% by weight of phosphate ester; and about 8% by weight of ethoxylated polyamides.
5. The method of claim 1, wherein said passivating agent comprises water, quaternary amines, phosphate esters, imidazoline and isopropanol.
6. The method of claim 5, wherein said passivating agent comprises from about 20 to about 35% by weight of water; from about 8 to about 15% by weight of quaternary amines; from about 20 to about 40% by weight of phosphate esters; from about 6 to about 26% by weight of imidazoline; and from about 5 to about 15% by weight of isopropanol.
7. The method of claim 6, wherein said passivating agent comprises about 30% by weight of water; about 10% by weight of quaternary amines; about 40% by weight of phosphate esters; about 10% by weight of imidazoline; and about 10% by weight of isopropanol.
8. The method of claim 1, wherein said passivating agent comprises aromatic solvent, imidazoline, phosphate ester and polymeric acids.
9. The method of claim 8, wherein said passivating agent comprises from about 25 to about 40% by weight of aromatic solvent; from about 25 to about 40% by weight of imidazoline; from about 7 to about 16% by weight of phosphate esters; and from about 16 to about 30% by weight of polymeric acids.
10. The method of claim 9, wherein said passivating agent comprises about 40% by weight of aromatic solvent; about 40% by weight of imidazoline; about 10% by weight of phosphate ester; and about 10% by weight of polymeric acids.
11. The method of claim 1, wherein said passivating agent comprises glycol ether, imidazoline, fatty acids and phosphate esters.
12. The method of claim 11, wherein said passivating agent comprises from about 15 to about 35% by weight of glycol ether; from about 38 to about 77% by weight of imidazoline; from about 3 to about 11% by weight of fatty acids; and from about 2 to about 15% by weight of phosphate esters.
13. The method of claim 12, wherein said passivating agent comprises; about 26% by weight of glycol ether; about 66% by weight of imidazoline; about 4% by weight of fatty acids; and about 4% by weight of phosphate esters.
14. 14. A method for reducing odorant depletion during transfer and storage of liquefied petroleum gas comprising the step of (a) adding a passivating agent that is dispersible or soluble in propane directly to said liquefied petroleum gas in a container of transport or storage together with said odorant in an amount sufficient to provide a concentration of said passivating agent in the scale of up to about 250 ppm (v / v), said passivating agent comprising one or more phosphate esters defined by the equation: [RX- [CmH2mO) n] k-PO (OH)) (3 .k) where; R is an alkyl group containing 4 to 18 carbon atoms or an alkylaryl group comprising an alkyl group selected from the group consisting of phenol, diphenol and mixtures thereof and an alkyl group containing from 4 to 18 carbon atoms; X is selected from the group consisting of a carboxyl group (-COO-), oxygen (-0-), a group of secondary amines (-N H-) and mixtures thereof; m is an integer that has a value from about 2 to about 4; n is an integer that has a value of about 4 to about 20; and k is an integer having a value of 1 to 2 and one or more fatty amines, polyamides, imidazolines, polyimidazolines, quaternary amines, quaternary polymers, dimer acids, trimer acids, polymeric acids, ethoxylated fatty amides, ethoxylated polyamides, ethoxylated alcohols or mixtures thereof and one or more solvents.
15. The method of claim 14, wherein said passivating agent comprises aromatic solvent, imidazoline phosphate ester and polymeric acids.
16. 16. The method of claim 15, wherein said passivating agent comprises from about 25 to about 40% by weight of aromatic solvent; from about 25 to about 40% by weight of imidazoline; from about 7 to about 16% by weight of phosphate esters; and from about 16 to about 30% by weight of polymeric acids.
17. The method of claim 16, wherein said passivating agent comprises: about 40% by weight of aromatic solvent; about 40% by weight of imidazoline; about 10% by weight of phosphate ester; and about 10% by weight of polymeric acids.
18. 18. The method of claim 14, wherein said passivating agent comprises glycol ether, imidazoline, fatty acids and phosphate esters.
19. The method of claim 18, wherein said passivating agent comprises from about 15 to about 35% by weight of glycol ether; from about 38 to about 77% by weight of imidazoline; from about 3 to about 11% by weight of fatty acids; and from about 2 to about 15% by weight of phosphate esters.
20. The method of claim 19, wherein said passivating agent comprises about 26% by weight of glycol ether; about 66% by weight of imidazoline; about 4% by weight of fatty acids; and about 4% by weight of phosphate esters.
21. 21. A method for reducing odorant depletion during the transfer and storage of liquefied petroleum gas comprising the steps of (a) completely filling a transfer or storage vessel for liquefied petroleum gas with a first passivation agent so that all inner surfaces of the container come into contact with said passivating agent; (b) draining said first passivating agent from said container; (c) evacuating said container; (d) filling said container with liquefied petroleum gas; (e) adding an odorant compound to said liquefied petroleum gas in said container; and (f) adding a second passivating agent that is dispersible or soluble in propane directly to said liquefied petroleum gas together with said odorant in an amount sufficient to provide a concentration of said second passivating agent in the scale of up to about 250 ppm. (v / v); said first and second passivation agents, comprising one or more phosphate esters defined by the equation: [R-X- [CmH2mO) n] k-PO (OH)) (3-k) where; R is an alkyl group containing 4 to 18 carbon atoms or an alkylaryl group comprising an alkyl group selected from the group consisting of phenol, diphenol and mixtures thereof and an alkyl group containing from 4 to 18 carbon atoms; X is selected from the group consisting of a carboxyl group (-COO-), oxygen (-0-), a group of secondary amines (-NH-) and mixtures thereof; m is an integer that has a value of approximately 2 to around 4; n is an integer that has a value of about 4 to about 20; and k is an integer having a value of 1 to 2 and one or more fatty amines, polyamides, imidazolines, polyimidazolines, quaternary amines, quaternary polymers, dimer acids, trimer acids, polymeric acids, ethoxylated fatty amides, ethoxylated polyamides, ethoxylated alcohols or mixtures thereof and one or more solvents.
22. 22. A method for reducing odorant depletion during the transfer and storage of liquefied petroleum gas comprising the steps of (a) completely filling a liquefied petroleum gas transfer or storage vessel with a passivating agent so that all surfaces interiors of said container come into contact with said passivating agent, said passivating agent comprising corrosion inhibitors selected from the group consisting of phosphate esters, fatty amines, polyamides, imidazolines, poly-imidazolines, quaternary amines, polyquaternary, dimer acids , trimer acids, polymeric acids, ethoxylated fatty amines, ethoxylated polyamides, ethoxylated alcohols or mixtures thereof and one or more solvents: (b) draining said passivating agent from said container; and (c) evacuating said container prior to the introduction of said liquefied petroleum gas into said container.
23. 23. A method for reducing odorant depletion during transfer and storage of liquefied petroleum gas comprising the steps of (a) completely filling a transfer or storage vessel for liquefied petroleum gas with a first passivating agent so that all the interior surfaces of the container come into contact with said passivating agent; (b) draining said first passivating agent from said container; (c) evacuating said container; (d) filling said container with liquefied petroleum gas; (e) adding an odorant compound to said liquefied petroleum gas in said container; and (f) adding a second passivating agent that is dispersible or soluble in propane directly to said liquefied petroleum gas together with said odorant in an amount sufficient to provide a concentration of said second passivating agent in the scale of up to about 250 ppm. (v / v); said first and second passivation agents, comprising corrosion inhibitors selected from the group consisting of phosphate esters, fatty amines, polyamides, imidazolines, poly-imidazolines, quaternary amines, polyquaternary amines, dimer acids, trimer acids, polymeric acids, amines ethoxylated fats, ethoxylated polyamides, ethoxylated alcohols or mixtures thereof and one or more solvents. RES UM EN The odorant depletion is reduced by passivating the internal surface of LP gas transport and storage containers by the addition of passivation agents comprising mixtures of corrosion inhibitors such as phosphate esters, fatty amines, polyamides, imidazolines, poly-imidazolines, quaternary amines, polyquaternary acids, dimer acids, trimer acids, polymeric acids, ethoxylated fatty amines, ethoxylated polyamides, ethoxylated alcohols or mixtures thereof and one or more solvents. In a preferred embodiment, the passivating agents contain one or more phosphate esters defined by the equation: [R-X- [CmH2mO) "] k-PO (OH)) (3-k) where; R is an alkyl group containing 4 to 18 carbon atoms or an alkylaryl group comprising an alkyl group selected from the group consisting of phenol, diphenol and mixtures thereof and an alkyl group containing from 4 to 18 carbon atoms; X is selected from the group consisting of a carboxyl group (-COO-), oxygen (-0-), a group of secondary amines (-N H-) and mixtures thereof; m is an integer having a value from about 2 to about 4; n is an integer that has a value of about 4 to about 20; and k is an integer having a value of 1 to 2 and one or more fatty amines, polyamides, imidazolines, polyimidazolines, quaternary amines, quaternary polymers, dimer acids, trimer acids, polymeric acids, ethoxylated fatty amides, ethoxylated polyamides, ethoxylated alcohols or mixtures thereof and one or more solvents.