US2872304A

US2872304A - Odorized gas and method for odorizing the same

Info

Publication number: US2872304A
Application number: US400098A
Authority: US
Inventors: John L Eaton; George E Hinds
Original assignee: Pennsalt Chemical Corp
Current assignee: Pennwalt Corp
Priority date: 1953-12-23
Filing date: 1953-12-23
Publication date: 1959-02-03
Anticipated expiration: 1976-02-03

Description

2,8 7 2,304 Patented Feb; 3, 1959 ODORIZED GAS AND METHOD FOR ODORIZING THE SAME "John L. Eaton, Whitemarsh, Pa.;-andGeorgeEi Hihds,

Houston, Tex., assignors, by mesne assignments, to 'Pennsalt Chemicals Corporationpa corporation of Pennsylvania I NoDrawing. Application December 235-1953 Serial No. 400,098

18 Claims. (Cl. 48-195) This invention relatesto alkyl 'thioethers containing at least one tertiary alkyl. group, and relates also to the use of these compounds as gas odorants.

Natural gas, thepropane and'butane fractions of liqui- 'fied petroleum gases, and-some types of 'manufactured Igases possess practically no inherent odor, and odorization of these gases, so that they will be detectable at low concentrations'in the atmosphere, has been' practiced for many years. :In the gas industry, it is standard practice to add a controlled amount of a strongly odorifer'ous material to act as a warning'agent in the case of a gas leak, and many states have laws requiring that gas be odorized to a specifiedminimum level as a safety measure. "Adequate odorization is not only a safety measure but] results also in substantial economies since pipe line leaks, which may amount in the aggregate to considerable gas loss, may be promptly detected and repaired. Also, these leaks would not be detected if the gas were not odorized.

Gas odorants in current use belong to the general category either of'merc'aptahs 'or organic sulfides. Odor'ants in either category may be pure compounds ormixtures, and may be used in concentrated form or diluted with relatively inodorous materials. Mercaptans have a higher odor intensity but are easily oxidized by traces of oxygen in a pipe line to relatively inodorous disulfides. Organic sulfides are of lower odor intensity than mercaptans, but arestable to pipe line oxidative conditions so" that, if

added to the gas in sufiicient amountrthe odor Will'be' transmitted unimpaired over'long distances.

An odorant of acceptable quality'should be harmless and neither toxic nor nauseating, non-corrosive,-'chemically inactive, insoluble in water, inexpensive and readily available, burn completely without harmfulor odorous products of combustion, be stable and not adsorbed'by mains or meters, and should possess a. penetrating odor similar to the artificial gas smell.

In accordance with the present invention, alkyl thioethers containing a'tertiary alkylgroup are used as sulfidetype odorants, possessing the oxidation stability common to thioethers and possessing ahigher odor intensity than other alkyl thioethers.

Among the compounds whichareuseful asfodorants in accordance with the invention maybe mentioned tertiary butyl, methyl, ethyl, propyl, and isopropyl sulfides, and tertiary amyl, methyl, ethyl, propyl, and isopropyl sulfides. Other compounds of this type may also be employed, the alkyl chain length being limited only by the vapor pressure of the compounds, i. e., the compounds must have a vapor pressure sufficiently high-that thecornpound may be vaporized into the gas stream in a pipe line in amount suificient for adequate odorization. It is also essential that a tertiary carbon atom be directly linked to the sulfur atom.

In practice, odorization is usually effected by means of an injection type o dorizer in which-the odorant is pumped into the gas stream and vaporized,"or a metered portion of gas is passed over a wick and saturated with the odor- .ant. @These are conventional 'expedients in-the art, and any othertype-of'odorizing equipment may'alsobe'empl'oyed. The odorant is generally added-tothe gas-in a pipe line at the rate of about 0.2 pound to 3.0 pounds fofodorant per million cubic feet of gas with the preferredrate being about 1.5 pounds ofodorantpermillibn cubic feet of gas.

The invention will be further illustrated by reference to the following specific examples:

EXAMPLE 1 Preparation of tertiary butyl ethyl sulfide A two gallon autoclave was charged with 1261 grams (14 mols) of tertiary butyl'mercap'tan, 950 grams (14.72 mols) of ethyl chloride and 616 grams (-15.4mols)' of sodium hydroxide dissolved in 2308 grams of Water,-this 'being'the calculated amount of water to yield a saturated salt solution if the reaction goes to completion. The reagents were chilled before charging and the autoclave was rapidly closed after chargin was completed. The autoclave was then heated, with continuous agitation, to a temperature of 150 C. in'45 minutes, maintained at a temperature of 150 C; for 15 minutes, rapidly cooled, and discharged, using conventional precautions to avoid loss of volatile components.

After distillingofi unreactedethylchloride, theoil layer was steam distilled, dried azeotropically," and fractionally-distilled. Ethyl chloride and mercaptan heads were removed and 1511 grams of as a cutboiling at 119 to 119.5 C.

EXAMPLE 2 Preparation of tertiary bzztyl isopropyl sulfide A two gallon autoclave was charged with 910 grams of tertiary butyl mercaptan, 800 grams of isopropylchloride, and a solution of 450 grams of sodium hydroxide in 2850 grams of water. The autoclave was heated to a temperature of 126 C;'in 40 minutes and was held at--a temperature of 125 to 135 C. for minutes, during which time the pressure varied between and 100 p. s. i.-g. The autoclave was cooled to a temperature'of 25 C. and discharged. 1,580 grams of crude oil layer were recovered having a specific gravity of 0.840.

The Engler distillation of this layer was as follows:

product were obtained C. C. IBP 37.0 60 55 1 39.0 70 64 5 40 80 "'98 10 42 132 20 43.5 30 45 FBP 141 40 48 Re'cov 97 50 50.5

' 1,163 grams of neutral crude product were fractionally distilled. After removin un'reaeted isopropyl chloride arid tertiary butyl mercaptan, 142.5 grams of tertiary biityl isopropylsulfide wererecovered, boiling at l 3 2 C.*'-and having a specific gravity of 0.815.

EXAMPLE '3 Preparation of tertiary amyl ethyl sulfide A two gallon-autoclave was charged withl050""g'r'an1s (10.1 mols) of tertiary amyl mercaptan, 450 grains (11.2 mols) or sodium hydroxide, and 660 grams (10.2 mols) of ethyl'chloride in 2000 g'rams'of water. The' auto clave was then-heated, while subjecting the'mixture to agitation. The temperature was-maintained"at"l30to C. for two hours, during which time the pressure varied from 80 to 100 p: s. ifig. The autoclave w'as cooled to 24 C. (pressure 5 p. s. i. g), vented, and discharged. 1,482 grams of oil layer, and 2,646 grams of saline solution were obtained. Titration of the water layer indicated that 77.5% of the total sodium hydroxide 'had been consumed. The crude oil layer had a specific gravity of 0.831 and the Engler distillation of this layer was as follows:

1110.5 grams of crude product were fractionally distilled, and after distilling off the unreacted mercaptan and ethyl chloride, 465 grams of tertiary amyl ethyl sulfide were recovered as a clear colorless liquid boiling at 146 to 148.5" C. and having a specific gravity of 0.840.

EXAMPLE 4 A room test procedure was used to estimate odor thresholds of various materials. The test consisted of the vaporization of successive increments of a dilute ethanolic solution of the odorant to be evaluated into a nitrogen stream which was passed at a uniform rate into an electric fan which circulated the odor throughout a closed room, the exact time of each injection being recorded. This room had a volume of 1233 cubic feet. A panel or six observers was seated at random in the room prior to the start of the test, in clear view of a clock. At the end of the test, each observer independently recorded the earliest time at which odor had become apparent to him. The odorant concentration in the room at any given time was calculated from the known injection schedule of the odorant solution and thus the threshold concentration for each observer was determined.

As shown by the following table, tertiary butyl ethyl sulfide was rated as stronger than mixed lower alkyl ethyl sulfides by three of the five observers, with one observer considering the intensities equal and one considering the tertiary butyl ethyl sulfide as weaker. Four out of the six observers considered tertiary butyl methyl sulfide as equal to the corresponding ethyl sulfide, with one rating the methyl homologue stronger and onerating it weaker:

I One observer falls to detect at indicated level. 1 Two observers fall to detect at indicated level.

Comparisons between tert-BuSET, tert-AmSET, and mixed amylmethyl sulfides were made, using an apparatus which presents, to the nose of the observer, a definitely known concentration of odorant in gas-air' mixture. The tests, as originally conducted, were duplicated two days later, but with the order of presentation of the odorants reversed, to cancel out any efiect the order of presentation may have on the observations.

Threshold, lbs/10 C. F.

Odorant Observer A Observer B order as order order as order listed reversed listed reversed tert-BuSET 0. 55 0.3 0. 4 0. 2 tert-AmSET 1. 5 0.65 0.2 0. 3 Mixed AmSMe 2. 7 1. 1 2. 4 0. 4

It will be obvious to those skilled in the art that many modifications may be made within the scope of the present invention without departing from the spirit thereof, and the invention includes all such modifications.

We claim:

1. A method of odorizing a gas which comprises mixing the gas to be odorized with a compound having the structure in which R is selected from the group consisting of tertbutyl and tert-amyl radicals and R is selected from the group consisting of methyl, ethyl, propyl, and isopropyl radicals.

2. A method of odorizing a gas which comprises mixing the gas to be odorized with a compound having the structure in which R is a tert-butyl radical and R is selected from the group consisting of methyl, ethyl, propyl, and isopropyl radicals.

3. A method of odorizing a gas which comprises mixing the gas to be odorized with a compound having the structure in which R is a tert-amyl radical and R is selected from the group consisting of methyl, ethyl, propyl and isopropyl radicals.

4. A method of odorizing a gas which comprises mixing the gas to be odorized with a compound having the structure in which R is selected from the group consisting of tertbutyl and tert-amyl radicals.

5. A method of odorizing a gas which comprises mixing the gas to be odorized with a compound having the structure R-S-CH in which R is selected from the group consisting of tertbutyl and tert-amyl radicals.

6. A method of odorizing a gas which comprises mixing the gas to be odorized with a compound having the structure in which R is selected from the group consisting of tertbutyl and tert-amyl radicals.

7. A method of odorizing a gas which comprises mixing the gas to be odorized with a compound having the structure in which R is selected from the group consisting of tertbutyl and tert-amyl radicals.

8. A method of odorizing a gas which comprises mixing the gas to be odorized with tert-butyl ethyl sulfide.

9. A method of odorizing a gas which comprises mixing the gas to be odorized with tert-butyl methyl sulfide.

10. A method of odorizing a gas which comprises mixing the gas to be odorized with tert-butyl isopropyl suifide.

11. A method of odorizing a gas which comprises mixing the gas to be odorized with tert-butyl propyl sulfide.

12. A method of odorizing a gas which comprises mixing the gas tobe odorized with tert-amyl ethyl sulfide.

13. A method of odorizing a gas which comprises mixing the gas to be odorized with an alkyl thioether having a tertiary carbon atom linked to the sulfur atom and having a vapor pressure sufficiently high that the compound may be vaporized into a gas stream in a pipe line in amount sutficient for adequate odorization.

14. A method of odorizing a gas which comprises mixing the said gas with an alkyl thioether having a tertiary carbon atom linked to the sulphur atom and having a vapor pressure sufficiently high that the compound may be vaporized into the said gas, the said thioether being present at a concentration of 0.2 to 3 pounds per million cubic feet of gas.

15. An odorized gas comprising a major proportion of a member of the class consisting of natural gas, man ufactured gas and mixtures thereof, and a minor proportion of an alkyl thioether having a tertiary carbon atom linked to the sulphur atom, said thioether being present at a concentration of 0.2 to 3 pounds per million cubic feet of gas.

16. An odorized gas comprising a major proportion of a member of the class consisting of natural gas, manufactured gas, and mixtures thereof, and a minor proportion of an organic sulfide having the structure in which R is selected from the group consisting of tertbutyl and tert-amyl radicals and R is selected from the group consisting of methyl, ethyl, propyl, and isopropyl radicals, said organic sulfide being present at a concentration of 0.2 to 3 pounds per million cubic feet of gas.

17. An odorized gas comprising a major proportion of a member of the class consisting of natural gas, manufactured gas and mixtures thereof, and a minor proportion of an organic sulfide having the structure in which R is a tert-butyl'radical and R is selected from the group consisting of methyl, ethyl, propyl, and isopropyl radicals, said organic sulfide being present at a concentration of 0.2 to 3 pounds per million cubic feet of gas.

18. An odorized gas comprising a major proportion of a member of the class consisting of natural gas, manufactured gas and mixtures thereof, and a minor proportion of an organic sulfide having the structure RSR in which R is a tert-amyl radical and R is selected from the group consisting of methyl, ethyl, propyl and isopropyl radicals, said organic sulfide being present in the gas mixture at a concentration of 0.2 to 3 pounds per million cubic feet of gas.

References Cited in the file of this patent UNITED STATES PATENTS Bureau of Mines, page 17.

Claims

1. A METHOD OF ORDORIZING A GAS WHICH COMPRISING MIXING THE GAS TO BE ODORIZED WITH A COMPOUND HAVING THE STRUCTURE.