Patent Application
20150105594
This invention relates to halogenated alkene moieties.
Tetrachloropropenes are useful as precursors to fluorinated propenes used in manufacturing fluorinated blowing agents and refrigerants. Chlorinated organic compounds, including tetrachloropropenes, do however typically break down in prolonged contact with, singularly or in combination, heat, light, air, humidity or metals. Oxidation is a major mechanism of decomposition. U.S. Pat. No. 3,959,367 identifies the oxidation products of 1,1,2,3 tetrachloropropene as including primarily 1,1,1,3 tetrachloropropanone along with chloroacetyl chloride. Lab studies have shown the presence of tetrachloropropanone and increased acidity and phosgene levels upon storage of unstabilized 1,1,2,3 tetrachloropropene. EP0309958 describes stabilized C3 unsaturated organic chlorine compounds including dichlorinated propenes.
The inventors have discovered that tctrachloropropencs can be stabilized using an antioxidant, for example a phenolic antioxidant.
In one aspect, there is provided a composition comprising a chlorinated propene and a compound selected from the group of p-methoxyphenol and p-tert-amylphenol.
In some embodiments, the composition also includes an additional phenol compound selected from the group consisting of isopropyl-meta cresol (thymol), 4,4′-methylenebis(2,6-di-tert-butyl-phenol); 4,4′-bis(2,6-di-tert-butylphenol); 2,2-biphenyldiols, 4,4-biphenyldiols; derivatives of 2,2- and 4,4-biphenyldiols; 2,2′-methylenebis(4-ethyl-6-tert-butylphenol); 2,2′-methylenebis(4-methyl-6-tert-butylphenol); 4,4,-butylidenebis(3-methyl-6-tert-butylphenol); 4,4-isopropylidenebis(2,6-di-tert-butylphenol); 2,2′-methylenebis(4-methyl-6-nonylphenol); 2,2′-isobutylidenebis(4,6-dimethylphenol); 2,2′-methylenebis(4-methyl-6-cyclohexylphenol); 2,6-di-tert-butyl-4-methyl-phenol; 2,6-di-tert-butyl-4-ethylphenol; 2,4-dimethyl-6-tert-butylphenol; 2,6-di-tert-α-dimethylamino-p-cresol; 2,6-di-tert-butyl-4-(N,N′-dimethylaminomethyl)phenol; 4,4′-thiobis(2-methyl-6-tert-butylphenol); 4,4′-thiobis(3-methyl-6-tert-butylphenol); 2,2′-thiobis(4-methyl-6-tert-butylphenol; tocopherol; hydroquinone; tert-butyl hydroquinone; and derivatives of hydroquinone.
In some embodiments, the composition includes p-methoxyphenol, for example, from about 1 ppm to about 1000 ppm of p-methoxyphenol. In some embodiments, the composition is substantially free of p-tert-amylphenol.
In some embodiments, the composition includes p-tert-amylphenol, for example, from about 1 ppm to about 1000 ppm p-tert-amylphenol. In some embodiments, the composition is substantially free of p-methoxyphenol.
In some embodiments, the chlorinated propene is a tetrachloropropene, for example 1,1,2,3-tetrachloropropene or 2,3,3,3-tetrachloropropene or 1,1,3,3-tetrachloropropene or 1,3,3,3-tetrachloropropene or (cis or trans)-1,2,3,3-tetrachloropropene.
In some embodiments, the chlorinated propene is a trichloropropene, for example, 1,1,3-trichloropropene.
In some embodiments, the composition is substantially free of propanone and phosgene is <20 ppm.
In some embodiments, the temperature of the composition is from about 10 to about 200° C.
In some embodiments, the composition consists essentially of the chlorinated propene and the one or more phenolic compounds.
In some embodiments, the desired use is to react the stabilized chlorinated propene, for example, 1,1,2,3-tetrachloropropene to produce a fluorinated propene, for example 2,3,3,3-tetrafluoropropene, for example by reacting the composition with HF, such as in the presence of Cl2 and SbCl5. Accordingly in some of the embodiments, the composition further comprises HF. In some sub-embodiments thereof, the composition further comprises Cl2 and SbCl5. Embodiments thereof include those wherein the chlorinated propene is 1,1,2,3-tetrachloropropene.
In another aspect, there is provided an article comprising a container, for example a metal container, and a composition as described above contained within said container.
In some embodiments, the metal container is made of a metal, for example stainless steel or a MONEL® metal. In some embodiments, the MONEL® metal is in contact with the composition comprising the chlorinated propene.
In some embodiments, the container is a reaction vessel. In some embodiments, the container is a sealed container, for example, a sealed container is substantially free of oxygen and/or substantially free of water.
In some embodiments, the composition comprises p-methoxyphenol, for example, present in the composition in an amount from about 1 ppm to about 1000 ppm. In some embodiments, the composition comprises p-tert-amylphenol, for example, wherein the p-tert-amylphenol is present in the composition in an amount from about 1 ppm to about 1000 ppm.
In some embodiments the container is lined with a polymeric coating, for example a coating comprising a phenolic or epoxy resin. Embodiments thereof include those wherein the chlorinated propene is 1,1,2,3-tetrachloropropene and the lining serves to protect the chlorinated propene from possible exposure to a metal, for example carbon steel, that could lead to premature chemical breakdown of the chlorinated propene.
In one aspect, there is provided a method of making a fluorinated propene, the method comprising:
Embodiments of the method are those comprising reacting the chlorinated propene with HF. Embodiments of the method also include those comprising reacting the chlorinated propene with HF in the presence of chlorine and SbCl5.
In some embodiments, the chlorinated propene is a tetrachloropropene, for example, 1,1,2,3-tetrachloropropene or 2,3,3,3-tetrachloropropene.
In some embodiments, the fluorinated propene formed is a tetrafluoropropene, for example, 2,3,3,3 tetrafluoropropene.
In some embodiments, the composition is in contact with a metal vessel. In some embodiments, the metal vessel comprises a MONEL® metal.
In some embodiments, the antioxidants described herein can provide improved stability of tetrachloropropenes under a variety of conditions, for example storage conditions and/or processing conditions.
The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and from the claims.
A “chlorinated propene” is a compound according to the following formula:
C(H)3-x(Cl)x—C(H)1-y(Cl)y═C(H)2-z(Cl)z
Non-limiting examples of chlorinated propenes include those wherein at least one of y and z is other than zero, for example wherein y is 1 and/or z is 1 or 2. Other examples thereof include those wherein x is 0, 1, or 2.
Chlorinated propenes include: E-1-chloropropene, Z-1-chloropropene, 2-chloropropene, 3-chloropropene, 1,1-dichloropropene, E-1,2-dichloropropene, Z-1,2-dichloropropene, E-1,3-dichloropropene, Z-1,3-dichloropropene, 2,3-dichloropropene, 3,3-dichloropropene, 1,1,2-trichloropropene, 1,1,3-trichloropropene, E-1,2,3-trichloropropene, Z-1,2,3-trichloropropene, E-1,3,3-trichloropropene, Z-1,3,3-trichloropropene, 2,3,3-trichloropropene, 3,3,3-trichloropropene, 1,1,2,3-tetrachloropropene, 1,1,3,3-tetrachloropropene, E-1,2,3,3-tetrachloropropene, Z-1,2,3,3-tetrachloropropene, E-1,3,3,3-tetrachloropropene, Z-1,3,3,3-tetrachloropropene, 2,3,3,3-tctrachloropropene, 1,1,2,3,3-pentachloropropene, 1,1,3,3,3-pentachloropropene, E-1,2,3,3,3-pentachloropropene, Z-1,2,3,3,3-pentachloropropene, and hexachloropropene.
Oxidative degradation of components of a composition may be inhibited by including in the composition one or more compounds one or more compounds which have the property of inhibiting oxidation, or so-called “antioxidants”. The selection of a suitable antioxidant for a given process from the broad range which are commercially available or otherwise known in the art can be very challenging due to a variety of factors involved such as, for example, different chemical processing conditions. In general, since an anti-oxidant will be an impurity in the composition in which it is included, it is desirable to select an antioxidant which is effective at low concentrations. In addition, antioxidants themselves may be oxidized over time to darkly colored oxidation products, which can lead to undesirable product appearance, or undesirable inconsistencies and changes in product appearance. Thus, it is advantageous if a product composition can be found wherein the problem of such color formation is minimized, which may be because, for example, the antioxidant is effective at very low concentrations, minimal degradation of the antioxidant itself occurs, or such degradation products as are formed with the particular antioxidant in the particular composition are not highly colored (or a combination of such factors).
The inventors have discovered that chlorinated propene containing compositions can be stabilized by including an effective amount of p-methoxyphenol (“MEHQ”) or p-tert-amylphenol (“PTAP”) in the composition as phenolic antioxidants. In some preferred embodiments, PTAP is a preferred stabilizer for a composition comprising a chlorinated propene. Any chlorinated propene as described above, or any combination of such chlorinated propenes, may be used in the compositions described herein.
In some embodiments one or more additional phenolic compounds may be included in the composition, for example, one or more phenols selected from the group consisting of isopropyl-meta cresol (thymol), 4,4′-methylenebis(2,6-di-tert-butylphenol); 4,4′-bis(2,6-di-tert-butylphenol); 2,2-biphenyldiols, 4,4-biphenyldiols; derivatives of 2,2- and 4,4-biphenyldiols; 2,2′-methylenebis(4-ethyl-6-tert-butylphenol); 2,2′-methylenebis(4-methyl-6-tert-butylphenol); 4,4-butylidenebis(3-methyl-6-tert-butylphenol); 4,4,-isopropylidenebis(2,6-di-tert-butylphenol); 2,2′-methylenebis(4-methyl-6-nonylphenol); 2,2′-isobutylidenebis(4,6-dimethylphenol); 2,2′-methylenebis(4-methyl-6-cyclohexylphenol); 2,6-di-tert-butyl-4-methyl-phenol (BHT); 2,6-di-tert-butyl-4-ethylphenol; 2,4-dimethyl-6-tert-butylphenol; 2,6-di-tert-α-dimethylamino-p-cresol; 2,6-di-tert-butyl-4(N,N′-dimethylaminomethyl)phenol; 4,4′-thiobis(2-methyl-6-tert-butylphenol); 4,4′-thiobis(3-methyl-6-tert-butylphenol); 2,2′-thiobis(4-methyl-6-tert-buylphenol; tocopherol; hydroquinone; tert-butyl hydroquinone; or derivatives of hydroquinone.
Chlorinated propenes include compounds having one, two, three, four, five, or six chlorine atoms, referred to as mono-, di-, tri-, tetra-, penta-, or hexa-chloropropenes respectively. Examples of chlorinated propenes include monochloropropenes, such as E-1-chloropropene, Z-1-chloropropene, 2-chloropropene, and 3-chloropropene, dichloropropenes, such as 1,1-dichloropropene, E-1,2-dichloropropene, Z-1,2-dichloropropene, E-1,3-dichloropropene, Z-1,3-dichloropropene, 2,3-dichloropropene, and 3,3-dichloropropene, trichloropropenes, such as 1,1,2-trichloropropene, 1,1,3-trichloropropene, E-1,2,3-trichloropropene, Z-1,2,3-trichloropropene, E-1,3,3-trichloropropene, Z-1,3,3-trichloropropene, 2,3,3-trichloropropene, and 3,3,3-trichloropropene, tetrachloropropenes, such as 1,1,2,3-tetrachloropropene, 1,1,3,3-tetrachloropropene, E-1,2,3,3-tetrachloropropene, Z-1,2,3,3-tetrachloropropene, E-1,3,3,3-tetrachloropropene, Z-1,3,3,3-tetrachloropropene, and 2,3,3,3-tetrachloropropene, pentachloropropenes, such as 1,1,2,3,3-pentachloropropene, 1,1,3,3,3-pentachloropropene, E-1,2,3,3,3-pentachloropropene, and Z-1,2,3,3,3-pentachloropropene, and hexachloropropene, any of which, or mixtures of any of which, may be used in the compositions described herein. Preferred tetrachloropropenes for use in the compositions of the invention include 1,1,2,3-tetrachloropropene and 2,3,3,3-tetrachloropropene.
The phenolic antioxidants described herein can be used to stabilize the chlorinated propenes during storage of a chlorinated propene-containing composition, or when the chlorinated propene-containing composition is being used in a process. Examples of processes where stabilization may be useful include manufacturing processes (e.g., a process preparing the chlorinated propene or a chemical transformation converting the chlorinated propene to a different chemical entity).
The amount of phenolic antioxidant which is present in the composition can be a storage stabilizing amount, i.e., an amount sufficient to substantially inhibit the decomposition of the chlorinated propene. The time for storage may be a short period of a few weeks or a longer period of up to one or two years. For example, the phenolic antioxidant such as MEHQ or PTAP can be present in an amount of at least 1 part per million parts of the composition (ppm), at least 2 ppm, at least 3 ppm, at least 4 ppm, at least 5 ppm, at least 6 ppm, at least 7 ppm, at least 8 ppm, at least 9 ppm, at least 10 ppm, at least 11 ppm, at least 12 ppm, at least 13 ppm, at least 14 ppm, at least 15 ppm, at least 20 ppm, at least 25 ppm, at least 30 ppm, at least 40 ppm, at least 50 ppm, at least 60 ppm, at least 70 ppm, at least 80 ppm, at least 90 ppm, at least 100 ppm. Thus suitable amounts of MEHQ or PTAP for inclusion in such compositions include, for example, about 1 ppm, about 2 ppm, about 3 ppm, about 4 ppm, about 5 ppm, about 10 ppm, about 15 ppm, about 20 ppm, about 25 ppm, about 30 ppm, about 40 ppm, about 50 ppm, about 100 ppm, or wherein the MEHQ or PTAP is present in an amount which is in a range between any two of these amounts. The preferred concentration of MEHQ or PTAP is in the range from about 5 ppm to about 100 ppm, for example from about 5 ppm to about 50 ppm, or from about 10 ppm to about 20 ppm. The ppm values represent the amount by weight relative to the amount by weight of the stabilized chlorinated propenes. In cases where more than one phenolic antioxidant is present, it may suffice for the total amount of the phenolic antioxidants present to be present in the amounts indicated.
In some embodiments, the phenolic antioxidant present in a composition described herein can be present in an amount sufficient to stabilize the chlorinated propene during a product processing or purification process. For example, the amount of phenolic antioxidant such as such as MEHQ or PTAP can be present in an amount less than about 1000 ppm.
It is generally preferred that the chlorinated propene containing compositions described herein are substantially free of breakdown products, i.e., those products indicative of a destabilized chlorinated propene. For example, it is generally preferred that the amount of breakdown products be less than about 5000 ppm e.g. less than about 4000 ppm, less than about 2000 ppm, less than about 1000 ppm, less than about 500 ppm, less than about 200 ppm, less than about 100 ppm, less than about 50 ppm, less than about 10 ppm. Exemplary breakdown products include propanones (e.g., tetrachloropropanone), HCl, and phosgene.
In some embodiments the stability of a composition can be evaluated by observing the composition. For example, formation of color in the composition generally indicates a chemical reaction such as a breakdown of the chlorinated propene or oxidation of the antioxidant has occurred. Similarly the presence of a coating on the metal or lined surface in contact with the chlorinated propene or deposited particles within the composition may also indicate reactivity of the composition, for example with air or a material to which the composition is exposed (e.g., a metal). Preferred compositions are those which display no indication of breakdown or reactivity of the composition during storage conditions. Preferred compositions according to the invention include those wherein the MEHQ or PTAP is used to stabilize essentially pure chlorinated propenes during storage. Accordingly, examples of such a composition are those wherein composition consists essentially of the chlorinated propene and the one or more phenolic compounds used as stabilizing agents. For example, suitable compositions include compositions consisting essentially of one or more chlorinated propenes and an amount of MEHQ and/or PTAP which is effective to stabilize the chlorinated propene during the desired storage period, for example an amount in the range from about 5 ppm to about 100 ppm, for example from about 5 ppm to about 50 ppm, for example about 5 ppm to about 20 ppm, for example about 10 ppm. An example of such a composition is one consisting essentially of 1,1,2,3-tetrachloropropene and an amount from about 5 ppm to about 100 ppm, for example from about 5 ppm to about 50 ppm, for example about 5 ppm to about 20 ppm, for example about 10 ppm of PTAP or MEHQ.
The compositions described herein are preferably stable.
A composition described herein is generally stored in a container, such as a metal container or a metal container lined with a phenolic resin or a polypropylene container. The metal used for the container may be any metal having suitable physical characteristics (e.g. strength characteristics) and chemical characteristics (e.g. corrosion resistance). The metal selected should be one which will not react or be corroded by the composition stored in the container, particularly if the container is not lined and the composition is in contact with the walls of the container. Examples of suitable metals include stainless steels and alloys such as MONEL® metals.
Accordingly, the compositions described herein, can be in long term contact with a metal such as a MONEL® metal. MONEL® is a trademark for a series of stainless metal alloys, primarily composed of nickel (up to 67%) and copper, with some iron and other trace elements. The alloys are resistant to corrosion and acids, and some of the alloys can withstand a fire in pure oxygen. The alloys are commonly used in applications with highly corrosive conditions. Small additions of aluminum and titanium form an alloy with the same corrosion resistance but with much greater strength. Illustrative compositions of suitable alloys are shown in Table 1.
The compositions described herein can be in long term contact with a tank liner with a phenolic or epoxy resin liner such as Plasite 3070 (bake coating using an unmodified phenolic resin with superior resistance to acids and solvent available from Carboline Company described in the Product Data Sheet published August 2003 by Carboline Company), Plasite 7122 (cross-linked epoxy phenolic coating cured with an alkaline curing agent formulated with a wide range of chemical resistance available from Carboline Company described in the Product Data Sheet published May 2007 by Carboline Company), Plasite 9052 (water-resistant epoxy coating polymerized with a polyamine-type curing agent available from Carboline Company described in the Product Data Sheet published August 2003 by Carboline Company) or a non-baked liner such as Plasite 9122L (a cross linked epoxy-phenolic cured with a polyamine curing agent available from Carboline Company described in the Product Data Sheet published August 2003 by Carboline Company). In some embodiments, a composition described herein is stored in a sealed container. For example, a container including a composition described herein can be sealed, i.e. closed to the atmosphere. In some embodiments, the container is purged with an inert gas prior to sealing. In some instances, the container is removed of all or substantially all water and/or water vapor prior to sealing.
A composition can be stored for a variety of lengths of time, such as 1 day, 2 days, 3 days, 4 days, 5 days, 1 week, 2 weeks, 1 month, 2 months, 6 months, 1 year or longer. The storage conditions can vary. For example, the sample can be exposed to light or can be stored in a light blocking container. Storage temperatures will typically be at ambient conditions and generally range from about 0° C. to about 45° C. In some embodiments, the process of adding the stabilizer can be accomplished in a variety of methods. In one application, the stabilizer can be dissolved directly into the process vessel. A possible improvement would be to dissolve the stabilizer in a dedicated vessel and inject controlled quantities into a process vessel for stabilization. In yet another application, MEHQ or PTAP can be dissolved to a concentration of less than 0.045 Wt. %, less than 0.040 Wt. %, less than 0.035 Wt. %, less than 0.030 Wt. %, less than 0.025 Wt. %, less than 0.020 Wt. %, less than 0.015 Wt. %, less than 0.010 Wt. % in 1,1,2,3 tetrachloropropene. The mixture can be injected into the process at the point of producing purified 1,1,2,3-tetrachloropropene to provide chemical stability.
In some embodiments, the compositions described herein require stability during a reaction process, for example, conversion of a chlorinated propene to a fluorinated propene. However, in some embodiments, the conversion process may require very low stabilizer concentrations in order to prevent fouling or inactivation of the process catalyst. In some preferred embodiments, a composition including 1,1,2,3-tetrachloropropene or 2,3,3,3-tetrachloropropene can include 10 ppm or lesser amounts of PTAP or MEHQ in instances where the 1,1,2,3-tetrachloropropene or 2,3,3,3-tetrachloropropene will be used in a reaction to be converted to 2,3,3,3-tetrafluoropropene.
In some embodiments, the stabilizer concentration of the tetrachloropropene precursor to the tetrafluoropropene may need to be at higher concentrations ranging from greater than 10 ppm and as high as 1000 ppm in order to minimize phosgene formation In those instances, the stabilizer may need to be removed through contact with a caustic solid bed or various molecular sieves prior to feeding the tetrachloropropene to the production process. In some embodiments, the stabilized 1,1,2,3-tetrachloropropene could be fed into a hydrofluorination reactor with the desired intention of producing 2,3,3,3-tetrafluoropropane. A better option is to feed hydrofluoric acid (HF) and chlorine into a liquid phase hydrofluorination reactor with an antimony pentachloride (SbCl5) catalyst to produce the desired 2,3,3,3-tetrafluoropropene. Operating conditions could be less than 150 psig, or less than 100 psig, or less than 75 psig. Operating temperatures could be less than 300° F., or less than 250° F., or less than 210° F., or less than 200° F., or less than 190° F., or less than 180° F.
Duplicate samples containing 10 ppm MEHQ or 10 ppm PTAP or unstabilized product were stored in the dark at 25° C. or 55° C. for a period of 129 days. No metal coupons were present. Starting material from lab distillations, had between 200 ppm to 300 ppm acidity as HCl and 99.7% purity. No efforts were made during product sampling to exclude exposure to air. After the sample aliquots were placed into the storage sample bottles the headspace was purged with nitrogen prior to closure. Table I shows the analytical results.
The highest HCl values were seen in the unstabilized samples stored at the higher 55° C. temperature. The highest HCl value seen was 525 ppm as HCl. At ambient temperature, little difference in HCl values was seen for stabilized or unstabilized samples. Comparisons of phosgene values shown are not necessarily reliable due to delays in obtaining GC aliquots of the samples and actual analysis. Later studies showed that air contamination of the some of the samples may have caused some phosgene values to be artificially higher.
Color development varied among the samples. All unstabilized samples showed no color formation over the storage time, even at elevated temperature. PTAP stabilized samples stored at ambient temperature remained colorless over the storage time whereas MEHQ stabilized material started developing some color after 14 days of storage. At elevated temperature, both MEHQ and PTAP developed some color at 14 days storage but again PTAP showed less color than MEHQ.
The study was conducted for a total of 166 days using 1,1,2,3 tetrachloropropene with 99.9% purity. The container had been purged with nitrogen just before sample collection and the headspace was swept with nitrogen before closing the container. The MONEL® alloy 400 coupons used were scrubbed with a plastic scrubber and soap and water and then rinsed with de-ionized water. They were heated in a 100° C. oven for one hour and cooled in a desiccator prior to use. Duplicate samples of 0, 10 or 100 ppm PTAP or MEHQ stabilizer in 1,1,2,3 tetrachloropropene were stored at 25° C. with or without the presence of MONEL® metal coupons and with or without light. Starting acidity of stock solution was 48 ppm HCl. The samples were nitrogen padded prior to storage.
Visual color observations were made periodically over the storage period.
All unstabilized samples showed no color development. Of the stabilized samples, conditions of light and MONEL® metal present resulted in the least color development at 98 days storage. However, at 140 and 166 days storage, more samples with MONEL® metal present and no light present showed the least color development. All MEHQ samples developed color whereas overall PTAP stabilized material had one sample with no color development and less color than the MEHQ samples.
At the end of the 166 days storage, HCl values were measured to determine overall stability under the storage conditions.
The maximum acidity value seen for unstabilized samples was 130 ppm HCl. When light was present, the 100 ppm stabilizer concentrations for MEHQ and PTAP were required to suppress HCl formation as compared to unstabilized material. Under these conditions, PTAP at 100 ppm concentration would be the better choice to minimize color formation in the stored product. In the absence of light, 10 ppm MEHQ or 10 ppm PTAP did achieve lower HCl values than unstabilized material.
1,1,3,3-Tetrachloropropene compositions were subjected to a variety of storage conditions and evaluated for evidence of breakdown or reactivity of the composition. MEHQ and PTAP were used to stabilize the 1,1,3,3-tetrachloropropene containing compositions.
The 1,1,3,3 tetrachloropropene samples were stored in a lighted oven at 55° C. over a 90-day period. Stabilizer levels included unstabilized, 75 ppm MEHQ, 150 ppm MEHQ and 300 ppm MEHQ. Some samples also included MONEL® alloy 400 coupons, some using a nitrogen pad and some with air present. At various time points, the acidity (HCl content) of the samples was measured and the appearance of the MONEL® alloy coupons observed. The results of the experiments are shown in Table 3.
As little as 75 ppm MEHQ was sufficient to limit HCl levels for samples with no metal added over 90 days storage while the unstabilized material increased in HCl from 0.0124 to 0.0347% over the same period. Similar results were seen in the presence of MONEL® alloy with or without a nitrogen pad. Deposits were observed on the MONEL® alloy coupons over storage time. HCl was required to remove the deposits in samples containing MEHQ. In fact, the higher levels of MEHQ contributed to heavier and more difficult to remove deposits and a pinkish color in the solution. At longer storage time, visual metal corrosion was observed.
A similar storage stability study was conducted using lower concentrations of MEHQ at 10, 20 and 50 ppm and no metals present, the results of which are provided in Table 4 below. Samples with 20 ppm PTAP, 300 ppm PTAP and unstabilized material were also included in the study. MONEL® alloy 400 coupons were added to the 300 ppm PTAP stabilized sample.
No increases in HCl values were seen over the 90-day storage period, even for the 10 ppm MEHQ. In fact, the HCl values are lower than the starting materials except in the case of the unstabilized material. No coupon corrosion or solution color was observed for the 300 PTAP with MONEL® sample.
1,1,2,3-tetrachloropropene compositions were subjected to a variety of storage conditions and evaluated for evidence of breakdown or reactivity of the composition. MEHQ and PTAP were used to stabilize the 1,1,2,3-tetrachloropropene containing compositions.
Samples of 1,1,2,3 tetrachloropropene were stored in the absence of light at ambient temperature, approximately 25° C., over a 20-day period. Stabilizer levels included unstabilized, and various combinations of MEHQ and PTAP at the concentrations as shown in Table 5. No metals were in contact with the samples and no efforts were made to exclude air prior to scaling the sample bottles for storage.
The unstabilized sample showed a 30 times increase in acidity levels from the starting materials whereas the stabilized samples showed less than twice the increase over the storage time.
Other examples of the efficacy of MEHQ as a stabilizer for chlorinated propenes include very low increases in acidity when samples are stored in a refrigerator at 5° C. and in the absence of light. This is shown in Table 6. No metals were present in the samples.
Unstabilized samples stored under similar conditions are known to generate HCl much more rapidly that seen in the above stabilized samples.
All references cited herein are incorporated by reference. A number of embodiments of the invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, other embodiments are within the scope of the following claims.
This application claims the benefit of U.S. Provisional Application Ser. No. 60/911,214, filed Apr. 11, 2007, the entire disclosure of which is incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 60911214 | Apr 2007 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 13056749 | Jan 2011 | US |
| Child | 14172309 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 14172309 | Feb 2014 | US |
| Child | 14571975 | US |
