US2416465A - Treatment of hydrocarbons with boron fluoride hydrate - Google Patents

Description

Patented Feb. 25, 1947 TREATMENT OF HYDROCABBONS BOBON FLUORIDE HYDBATE William N. Axe, Bartlesville. kla., assignor to Phillips Petroleum Company, a corporation of Delaware No Drawing.

This invention relates to the treatment of hydrocarbon oils with boron fluoride hydrate. More specifically this invention relates to the treatment of hydrocarbon stocks such as alkylate gasoline, hydrocodimer, straight run gasoline, natural gasoline. kerosene, cracked gasoline and coal-tar aromatics with a boron fluoride-water composi tion containing substantially one moi of boron fluoride per mol of water. Still more specifically the present invention relates to theremoval of sulfur compounds and unsaturated hydrocarbons from hydrocarbon oils by treatment of said hydrocarbons with boron fluoride hydrate.

One object of the present invention is'the re.- moval of deleterious constituents from the hydrocarbon distillates sublected'to treatment.

Another object of this invention is the improvement of octane number and lead response of gasoline distlllates by the removal of sulfur compounds.

A further object of the invention is the improvement of the stability of aviation gasoline blending stocks by the removal of residual unsaturation.

An additional object is the removal of basic nitrogen compounds from hydrocarbon oils.

Numerous other objects will be apparent to those skilled in the art upon reading the specification and claims.

The economic significance of the reduction of the sulfur content with the attendant reduction of tetraethyl lead consumption in motor fuels has long been recognized. More recently the deleterious effect of sulfur compounds on the rich-mixture rating of aviation gasoline has given added impetus to eflicient methods of sulfur removal from the various types of blending stocks.

Other than elemental sulfur, the classes of sulfur compounds that may be found in hydrocarbon oils are: hydrogen sulfide, mercaptans, alkyl disulfides, alkyl sulfides, and thiophene and its homologs. Hydrogen sulfide and methyl mercaptans are economically removed by means of caustic extraction. The addition of fatty acids to caustic solution is said to aid in the extraction of higher mercaptans. However, a satisfactory single processof the extraction type for removal of the various types of sulfur compounds in one operation without degrading the base stock, has not been developed heretofore. Strong sulfuric 'acid and liquid sulfur dioxide have been used for this purpose, but both reagents remove desirable aromatic constituents and leave a considerable proportion of sulfur unremoved.

Among the halides recommended for sulfur re- Application November l8, 1943, Serial No. 510,536 l 4 Claims. (71- 196-40) 2 I moval, aluminum chloride has been investigated most extensively. However, aluminum chloride performs best at relatively elevated temperatures where undesirable cracking reactions occur simultaneously with the desulfurization. At the boiling point of cleaners naphtha, aluminum chloride has been most effective toward high-boiling sulfides not ordinarily found in gasoline and least effective toward low-boiling sulfides and thiophene. Under optimum conditions, aluminum chloride may be expected to effect about 60-65 per cent removal of organically combined sulfur. I have found that a composition derived from the interaction of boron fluoride and water in a molal ratio ofabout 1:1 and hereinafter referred to as boron fluoride hydrate functions as a very efllcient desulfurization agent. I have alsovfound that residual unsaturation of such stocks can be simultaneously reduced to substantial saturation.

The unusual properties of boron fluoride hydrate as a treating agentfor hydrocarbon oils cannot be predicted on the basis of the properties of boron fluoride, but are unique to the acidic liquid composition of the empirical formula The unusual action of boron fluoride hydrate as a desulfurization agent-is reflected in its action on thiophene and homologs of thiophene. The

removal of this so-called residual sulfur has formerly yielded to partial removal only through the use of large volumes of concentrated sulfuric acid. I have found that, whereas dry BF: is without chemical action on pure thiophene, boron fluoride hydrate vigorously attacks this compound with the evolution of hydrogen sulfide.

I have also discovered that alkyl and aryl sul fides and mercaptans react with boron fluoride hydrate to form polar complex compounds insoluble in hydrocarbons, but miscible with excess boron fluoride hydrate.

- Alkyl disulfides, which in unsweetened gasoline comprise only an exceedingly minor proportion of the sulfur content, apparently do not undergo complex compound formation with the hydrate.

The acidic boron fluoride hydrate exerts practically no solvent action on aromatic hydrocarbons and is therefore particularly adaptable to the treatment of coal-tar hydrocarbons or petroleum distillates high in aromatic content. Since boron fluoride hydrate is an exceedingly active polymerization catalyst, a re-running operation following the desulfurization results in a substantially saturated stock.

The desulfurization procedure consists in agi boron fluoride hydrate and hydrogen sulfide. The

treated hydrocarbon may be re-run to improve color and remove dissolved heavy polymer as in the case of alkylates and cracked gasoline. However, in the case of natural gasoline and other saturated stocks, a re-distillation is usually not required.

The amount of treating agent "employed may .vary within wide limits depending on the type of hydrocarbon, the sulfur content and its degree of unsaturation. For hydrocarbon stocks such as natural gasoline, straight run gasoline'and the jlike. one per cent by volume based on the hydrocarbon is usually sufllcient. In the case'of thermally or catalytically cracked gasoline. treating agent to the extent of percent by volume may be required to produce a substantially sulfur-free and saturated product.

In a single stage contactor, I have found that ;a reaction time of minutes is sufllcient for most hydrocarbon stocks. In many instances much shorter contact times of about 5-10 minutes are adequate. The settling time involved in this process will depend on the degree of dispersion of the treating agent and the degree of unsaturation of the hydrocarbon being treated. Since the gravity of boron fluoride hydrate is approximately 1.75, settling times-comparable to those involved in sulfuric acid treating will be found satisfactory. j The desulfurization process is readily accomplished at atmospheric temperature. The reactions involved between the sulfur compounds and unsaturates with the treating agent are exothermic, hence in the case of highly volatile distillates conventional cooling methods may be desirable. In general, treating temperatures of from 70 to 135 F. have been found satisfactory although higher or lower temperatures may be employed in special cases. In the case of saturated stocks, the heat evolved from the desulfurization will not be of sufllcient magnitude to require a cooling procedure.

The following examples illustrate the operation and advantages of thepresent invention:

Example I A-selected hydrocarbon fraction derived from catalytically cracked naphtha was subjected to treatment with boron fluoride hydrate. A 1.4 gallon sample was agitated for 20 minutes with 10 4 fluoride hydrate equal to only 1 per cent of the hydrocarbon volume. 1

Before After W eight percent sulfur 0. 301 0. 066 Bromine i0 4. 3

Example III The hydrocarbon sample of the preceding examples was thoroughly saturated with anhydrous boron fluoride and the treated hydrocarbon was subsequently worked up in the mannerpreviously described. The analytical results indicated an efliciency of .sulfur removal comparable to results expected of aluminum chloride. Approximately 69 per cent of the sulfur was removed while the unsaturation was reduced by-about per cent. In Example I, however, the sulfur reduction amounted to 99 per cent while the unsaturates removal was substantially complete.

Example IV An extreme case of removal of olefinic material from hydrocarbon stocks is illustrated by the treatment of a 300 E. P. debutanized gas-plant gasoline with boron fluoride hydrate. The bromine number (grams of bromine absorbed per 100 7 grams of sample) of the unfractionated and untreated stock was about 50. Continuous treatment was carried out at 125 F, until 25 volumes of hydrocarbon charge had been treated per volume of boron fluoride hydrate. The treated stock was washed and distilled.

Bromine No.

Fractions Before After 80-ll0 F so 0 4 ll0300 F 45 3 0 Kettle product (23%) 40. 0

tillate by substantially completely removing unper cent of its volume of boron fluoride hydrate while maintaining the temperature at approximately 75 F. After settling, the two layers were separated and the hydrocarbon phase was washed with 5 per cent sodium carbonate solution followed by .water. The treated product was then re-run to the original end point. The results of the treatment are herewith listed:

Before After Weight percent sulfur 0. 301 0. 004 Bromine number i0 1 Rich mixture rating 8+0. 2 8+5. 2

Example II desirable impurities comprising sulfur compounds and unsaturated hydrocarbons, which comprises intimately contacting said distillate with at least one per cent by volume of a boronfluorlde hydrate substantially composed of one mol of water per mol of boron fluoride for a period of time and at a temperature suflicient to effect the removal of said impurities, separating the hydrate with dissolved impurities therein from said treated hydrocarbon distillate, and recovering said improved hydrocarbon distillate.

2. A process according to claim 1 in which the hydrate is contacted with the hydrocarbon distillate at a temperature between about and 135 F. and for a contact time between about 10 and 20 minutes.

3. A process for the desuliurization of hydrocarbon materials containing organic sulfur compounds of the class consisting of thiophene and 2,410,4es I of water for each mol of boron fluoride to effect substantially complete removal of said sulfur compounds, separating said hydrate containing said sulfur compounds and reaction products therewith, and recovering a substantially desuiturized hydrocarbon product.

4. A process for reducing thesulfur content and unsaturation of an aromatic hydrocarbon distillate containing undesirable proportions of sulfur compounds and unsaturated aliphatic compounds, which comprises intimately contacting said distillate with at least one per cent by volume of a boron-fluoride hydrate substantially composed of one mol of water per mol of boron fluoride, separating the hydrate with dissolved impurities therein from said treated aromatic distillate, and recovering the improved aromatic hydrocarbon distillate.

WILLIAM N. AXE.

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

UNITED STATES PATENTS Number Name Date 2,257,627 Vesterdal Sept. 30, 1941 2,099,835 Barlow et a] Nov. 23, 1937 2,203,470 Pier et a1 June 4, 1940 2,345,095 Bruner et a1 Mar. 28, 1944 2,348,637 Meinert May 9, 1944 2,375,675 Matuszak May 8, 1945 2,366,736 Linn et a1. Jan. 9, 1945 FOREIGN PATENTS Number Country Date 840,980 French Jan. 28, 1939 292,932 British May 23, 1929