US2428753A

US2428753A - Process for treating a hydrocarbon mixture which is contaminated by small amounts oforganic fluorine compounds

Info

Publication number: US2428753A
Application number: US619252A
Authority: US
Inventors: Carl B Linn
Original assignee: Universal Oil Products Co
Current assignee: Universal Oil Products Co
Priority date: 1945-09-28
Filing date: 1945-09-28
Publication date: 1947-10-07
Anticipated expiration: 1964-10-07

Description

Patented Oct. 7, 1947 PROCESS FOR TREATING A HYDRQCARBON MIXTURE WHICH- IS CONTAMINATED BY SMALL AMOUNTS F ORGANI/CFLUORINE .comrourms Carl B. Linn, Riverside, Ill; assignor Universal 0i] Products Company, Chicago, 111., a corporation of Delaware No Drawing. Application September 28, 1945, Serial No. 619.252

16 Claims. (01. 2605-676) This invention relates to a process for treating a hydrocarbon or hydrocarbon mixture which is contaminated by small amounts of organic fluorine compounds to remove fluorine therefrom.

More specifically, it relates to the treatment of hydrocarbons produced synthetically in the presence of an active fluoride catalyst to remove small amounts of organically combined fluorine present in compounds admixed with the hydrocarbon or hydrocarbon mixture.

The invention is particularly adapted to the a treatment of hydrocarbons produced by the alkvlation of isoparafllnic hydrocarbons with oleflnic hydrocarbons or with alkyl fluorides using active fluoride catalysts including hydrogen fluoride or fluoride mixtures comprising essentially hydrogen fluoride and boron fluoride. The process is also applicable to the removal of alkyl fluorides from propane and butane fractions. said fractions being recovered from the gaseousproducts discharged from an alkylation plant in which isobutane is alkylated by olefins present in a propane-propylene or butane-butylene fraction.

An obiect of this invention is to defluorinate a hydrocarbon or hydrocarbon mixture contaminated by relatively small amounts of organic fluorine compounds, part cularly alkyl fluor des.

Another obiect of this invention is to dehydrofluorinate an' isoparaflln alkylation product formed in the presence of an active fluoride catalyst.

A further obiect of this invention is to remove alkyl fluorides from hydrocarbon conversion products formed in the presence of an active fluoride catalyst.

A still further ob ect of this invention is to remove alkyl fluorides from a fraction of normally gaseous parafflnic hydrocarbons recovered from the produc s formed in the a kvlation of isohutane h olefins present in a C -C hydrocarbon fraction.

Another ob ect 01' this invention is to remove eth l fluor de from a propane fraction recovered from the products formed in the alkylation of is butane in the presence of hydrogen fluoride with a propa e-propvlene fraction containing a relatively small amount of ethylene.

One specific embodiment of the present invention comprises a process for treating hydroc rbon material contain ng as an impurity a relatively small percentage of organically combined fluorine to remove fluorine therefrom which comprises contactin said material with fluosulfonic acid at dehydrofluoriniting conditions of temperature 1 2 and pressure, and recovering the treated hydrocarbon material.

Another embodiment of the present invention comprises a process for treating hydrocarbons recovered from an alkylation process in which an isoparaflin is alkylated with an olefin in the Qpresence of an active fluoride catalyst, by treating said hydrocarbons with fluosulfon c acid at dehydrofluorinating conditions of temperature,

pressure and time, and recovering the treated hydrocarbons.

The alkylation of branched chain paraflinic hydrocarbons such as isobutane and isopentene with. oleflnic hydrocarbons, particularly the oleflnic hydrocarbons present in cracked gases, produces saturated liquid hydrocarbons utilizable as constituents of gasoline of high antiknock value. By this means relatively low boiling isoparafflnic hydrocarbons are alkylated with low boiling olefins and thereby converted into materials of higher boiling po nt and high antiknock values. The higher boiling hydrocarbons so formed from low boiling isoparaffins and olefins in the presence of an active fluoride catalvst including hydrogen fluoride or mixtures of hydrogen fluoride and boron fluor de, frequently contain small amounts of organic fluorine compounds which are not readily removable by washing with caustic and water or by fractional distillation.

These contaminating fluorine compounds which are thus present in alkylation hydrocarbon mixtures are frequently due to the interaction of hydrogen fluoride with olefins to form alkyl fluorides. Some alkyl fluorides are more stable than others in the presence of active fluoride catalysts. Thus, ethyl fluoride is more stable than some of the higher molecular weight alkyl fluorides in an alkylat on reaction mixture and is not converted completely into paraflinic alkvlation products but adm xes with the hydrocarbon products. Some higher boiling alk l fluorides and other organic fluorine compounds ma also remain in hydrocarbon alkvlation products. Because of its h gh stability, boiling 'point, and the fact that it forms w th propane an azeotrope boiling at -47 C., ethyl fluoride is found in the by the addition of hydrogen fluoride to this olefin of lowestmolecular weight.

Boron fluoride assists hydrogen fluoride in catalyzing the alkylation of an isoparaflln by ethylene and higher oleflns, but in these cases the alkylation product also contains small quantities of organic fluorides as do those formed in the presence of hydrogen fluoride from an isoparaflin and an olefin of higher molecular weight than ethylene.

Although the fluorine content of the hydrocarbon product of gasolineboiling range resulting from an alkylation treatment is rarely very high,

the presence of fluorine is undesirable both fromabout 0.001%, or less, by Weight of fluorine from a contaminated matc.ial containing 1.2% fluorine present as ethyl fluoride. These results are remarkableand unpredictable because I have also ing agent such as lead tetraethyl is added thereto.

not alkylated during the alkylation treatment of an isoparaflin with oleflns present in a C3 or a' C4 hydrocarbon fraction are recovered from alkylation products and marketed as bottled gas for use as domestic fuels and for various industrial uses. Such recovered propane and normal butane fractions are sometimes contaminated by ethyl fluoride and other organic fluorine compounds formed incidentally in the alkylation treatment and it is desirable that these propane and butane fractions be freed from fluorine compounds before being so utilized as fuel. I

It is much more diflicult to dehydrofluorinate ethyl fluoride than the other alkyl fluorides which may be encountered in products of the hydrogen fluoride alkylation process. It has been observed that alkylation plants which charge a propane-propylene feed stock to the alkylation reactor produce ethyl fluoride from the ethylene which sometimes contaminates the C3 feed stock. This ethyl fluoride tends to go through the plant unchanged and finally appears in the propane fraction recovered from the eilluent gases. The methods used heretofore for removing organic fluorine compounds from alk'ylate, such as passage through heated contactors containing bauxite or aluminum, do not cause sufficient dehydrofluorination of ethyl fluoride and consequently are ineffective for producing a propane fraction substantially free from fluorine. My process, however, does defluorinate not only the gasoline boiling range material but also propane and butane and makes it possible to produce substantially fluorine-free propane and butane fractions.

As indicated above, ethyl fluoride is more stable than the higher alkyl fluorides encountered in the products of the hydrogen fluoride alkylation process. Possibly one reason for this difierence in stability of the alkyl fluorides is the fact that ethyl fluoride is a primary alkyl fluoride, while the alkyl fluorides produced from propylene and higher oleflns are either secondary or tertiary alkyl fluorides. I have found that when propane which is contaminated by small amounts of ethyl fluoride is treated at about 25 C. with fluosulfonic acid, the fluorine content is reduced more than 997 to give a propane fraction containing only no harmful action on dry skin. .tothe touch and is without the intense blistering found that neitherhydrogen fluoride alone nor sulfuric acid alone nor a mixture of hydrogen fluoride and sulfuric acid will defluorinate to anything near this extent, that is, hydrogen fluoride alone or sulfuric acid alone had about 20% of the defluorinating activity of fluosulfonic acid while a mixture of sulfuric acid and hydrogen fluoride waslittle more than 40% as effective as fluosulfonic acid.

After prolonged use, the fluosulfonic acid may be regenerated by distillation but when only small percentages of fluorine are present in the charging stock, the cheapness of the fluosulfonic acid may permit it to be discarded after it has become contaminated too much for further use.

One method of preparing fluosulfonic acid, used .in the process of this invention, consists in treating fluorspar (CaFz) with fuming sulfuric acid (-60%-SO3) Fluosulfonic acid is a mobile liquid with a boiling point of 163 C. at 760 mm. pressure and has a faint pungent odor but substantially It feels greasy action of anhydrous hydrogen fluoride.

' According to the process of the present invention, hydrocarbon material contaminated by organicfluorine compounds is freed from a sub- .stantial proportion of such organically combined fluorine by treatment with fluosulfonic acid at a temperature of from about 50." to about 150 C.

and preferably at a temperatureof from about 0 to about 50 C. The proces s is carried out at atmospheric pressure or at a superatmospheric pressure sufficient to maintain the fluorine-containing hydrocarbon or hydrocarbon mixture in substantially liquidphase.

The treatment of the hydrocarbon or hydrocarbon mixture with fluosulfonic acid is effected use in treating an additional the latter is washed, dried, and distilled or otherwise treated to recover the desired hydrocarbon or hydrocarbons substantially free from fluorinecontaining compounds, while the used fluosulfonic acid is returned to the reactor for further quantity of the hydrocarbon charging stock.

Continuous treatment of a hydrocarbon containing organically combined fluorine is effected by passing said hydrocarbon and a proportioned amount of fluosulfonic acid through a baiiied mixer orother suitable type of contacting equipment in which the hydrocarbon and fluosulfonic acid are contactedat the aforementioned conditions of temperature and pressure for a time suflicient to effect the removal of substantially all of V the fluorine from the hydrocarbon material. Fromthis treating equipment the mixture of hydrocarbon-material and fluosulfonic acid is directed to a separator from which the hydrocarbon layer is removed and thenwashed, dried, and distilled or otherwise-treated to recover the desired hydrocarbons substantially free from fluorine-containing compounds. The used fluosulfonic acid is then withdrawn from the separator and a portion of it is recycled to further use in treating an additional quantity of the mentioned charging stock.

The following examples are given to show results obtained in the operation of the process. but they are not to be considered to unduly limit the broadscope of the invention.

Example I Several. runs were made in each of which 51 grams of a propane fraction containing small amounts of ethyl fluoride was contacted with 174 grams of fluosulfonic acid at 25 C. for 3 hours in a rotatable steel autoclave of 850 cc. capacity. After this treatment the rotation of the autoclave was stopped and the reaction mixture was permitted to stand at 25 C. for 14 hours.

The fluorine content of the propane fraction charged in each of these runs and the defluorination effect by the treatment with fluosulfonic acid are as follows:

Per cent by weight fluorine in propane (present g as ethyl fluoride) 1.21 1.53

Weight per cent fluorine I in propane product 0.0013 0.0053 0.0010

Per cent defluorination of propane charged 99.9 99.7 99.5

Example II Charge, grams:

Propane 102 102 Hydrogen fluoride 106 Sulfuric acid, 96% 183 Weight per cent fluorine in propane product 0.95 0.95 7 Per cent defluorination of propane charged 21 19 Example III A run similar to those referred to in Example II was made in which 102 grams of propane containing ethyl fluoride (0.209% by weight fluorine) was contacted at 25 C. with 115 grams of hydrogen fluoride and 27 grams of sulfuric acid of 96% concentration. The propane recovered from this treatment had a fluorine content of 0.12% by weight corresponding to 43% defluorination of the propane charged.

The nature of the present invention and the type of results obtained in the process are evident from the preceding specification and examples, although neither section should be construed to unduly limit the broad scope of the invention.

I claim as my invention:

1. A process for treating a saturated hydrocarbon material containing as an impurity a relatively small percentage of organically combined fluorine to remove fluorine therefrom which comprises contacting said hydrocarbon material with fluosulfonic acid'at defluorinating conditions of temperature and pressure, and recovering the treated hydrocarbon material.

2. A process for treating a paraffin hydrocarbon material containing as an impurity a relatively small percentage of an alkyl fluoride to remo e fluorine therefrom which comprises contacting said hydrocarbon material with fluosulfonic acid at defluorinating conditions of temperature and pressure, and recovering the treated hydrocarbon material.

3. A process for treating a hydrocarbon material containing as an impurity a relatively small percentage of organically combined fluorine and produce'dby catalytic alkylation of an isoparafilnic hydrocarbon with an oleflnic hydrocarbon in the presence of an active fluoride catalyst which comprises. treating said hydrocarbon material with fluosulfonic acid at defluorinating conditions of temperature and pressure, and recovering the treated hydrocarbon material.

4. A process for treating a hydrocarbon material containing as an impurity a relatively small hydrocarbon with an olefinic hydrocarbon of higher molecular Weight than ethylene in the presence of a hydrogen fluoride catalyst which comprises treating said hydrocarbon material with fluosulfonic acid at defluorinating conditions of temperature and pressure, and recovering the treated hydrocarbon material.

5. A process for treating a paraffin hydrocarbon material containing as an impurity a relatively small percentage of organically combined fluorine to remove fluorine therefrom which comprises contacting said hydrocarbon material with fluosulfonic acid at a temperature of from about 50 to about 150 C.. and recovering the treated hydrocarbon material.

6. A process for treating a paraffin hydrocarbon material containing as an impurity a relatively small percentage of organically combined fluorine to remove fluorine therefrom which comprises contacting said hydrocarbon material with fluosulfonic acid at a temperature of fromabout 50 to about 150 C. and at a pressure suflicient to maintain the hydrocarbon material in substantially liquid phase, and recovering the treated hydrocarbon material.

7. A process for treating a parafiin hydrocarbon material containing as an impurity a relatively small percentage of an alkyl fluoride to remove fluorine therefrom which comprises contacting said hydrocarbon material with fluosulfonic acid at a temperature of from about 50 to about 150 C., and recovering the treated hydrocarbon material. I

8. A process for treating a paraffin hydrocarbon material containing as an impurity a relatively small percentage of an alkyl fluoride to remove fluorine therefrom which comprises contacting said hydrocarbon material with fluosulfonic acid at a temperature of from about -50 to about 150 C. and at a pressure sufiicient to maintain the hydrocarbon material in substanorganically combinedfluorine to remove fluorine 10. A process for treating butane containing as an impurity a relatively small percentage of organically combined fluorine to remove fluorine therefrom which comprises contacting said butane withfiuosulfonic acid at de'fluorinating con.- ditions of temperature and pressure, and recovering the treated butane.

11. A process for treating a normally liquid pare. afiinic hydrocarbon mixture containing as an as an impurity a relatively small percentage of organically combined fluorine to remove fluorine therefrom which comprises contacting said propane with fluosulfonic acid at a temperature of from about -50 to about 150 C., and recovering the treated propane.

13. A process for treating butane containing as an impurity a relatively small percentage of organically combined fluorine to remove fluorine therefrom which comprises contacting said butane with fluosulfonic acid at a temperature of from about 50 to about 150 C., and recovering the treated butane.

14. A process for treating a normally liquid paraflinic hydrocarbon mixture containing as anlmpurity a relatively small percentage of organically combined fluorine to removefiuorine there-- from which comprisescontacting said normally,

liquid paraflinic hydrocarbon mixture with fluosulfonic acid at a temperature of from about to about C., and recovering the treated normally liquid paraflinic hydrocarbon mixture.

15. The process of claim 9 further characterized in that said impurity comprises ethyl fluoride.

16. The process of claim 12 further characterized in that said impurity comprises ethyl fluoride.

CARL B. LINN.

I REFERENCES CITED The following references are of record in the file of this patent:

' UNITED STATES PATENTS Number Name Date 1,950,878 Burk Mar. 13-, 1934 2,320,629 Matuszak June 1,1943 2,341,567 Moriarty Feb. 15, 1944 2,391,149 Frey Dec. 18, 1945 2,412,726 Frey Dec. 1'7, 1946