US1876702A - Refining hydrocarbon oil - Google Patents

Description

Patented Sept. 13, 1932 UNITED. STATE-s ROBERT I. LEWIS, 0F WILMINGTON, CALIFORNIA, 'ASSIGNOR TO SHELL DEVELOPMENT PATENT FifcE COMPANY, or SAN r'nA vcrsco, CALIFORNIA, A CORPORATION or ELAWARE" nnrnvme rrrnnoojeinaon OIL No Drawing.

This invention relates to the refining of hydrocarbon oils, 'especially'petroleum oils, with sulfuricacid, and more particularly to such refining at temperatures belownormal.

It is an-object of this, invention to reduce the losses of material, desirable as motor fuel, in the refining of hydrocarbon oils, especially in the refining with sulfuric acid, and more particularly in the refining with sulfuric acid at temperatures below atmospheric.

, Further objects of this inventionwill appear from the following description in which I have set forth the preferred method of my invention. It is to be understood that the appended claims are to be accorded the scope and range of equivalents consistent with the prior art. 7

Principally my invention consists in subjecting the hydrocarbon oils after a refining treatment with sulfuric acid at low temperature, to an additional treatment with a relatively small amount of acid at normal temperature.

In the following I will describe my invention particularly in relation to the refining of pressure distillate, the distillate resulting from cracking processes, which contains the gasoline fractions formed by the conversion of heavier oils during the cracking. It is to be understood thatI do not liimt my inven tion to the treatment of pressure distillate, as treatments according to the principle of my invention can advantageously be applied to many other hydrocarbon oils.

The pressure distillate from many cracking stocks is high in sulfur bearing compounds, which are very detrimental in a motor fuel, and have to be removed from the gasoline fractions, before these are marketable.

- According to the specifications of the United States Government for motor gasoline the sulfur content may not be more than 0.1 of

1%. The removal of sulfur compounds is frequently done by a treatment with strong sulfuric acid of B. or stronger, followed by redistilling. The sulfur compounds are partially removed in the heavy sludge formed, while a portion remains in the acid treated distillate. The compounds in this last mentioned portion have been polymerized to such Application filed September .26, i928. Serial No. 308,583.-

an extent that the increase in their boiling however,causes heavy losses of desirable gasoline hydrocarbons, presentin the pressure distillate. The reaction between the acid and the hydrocarbons is not fully understood, but

' it is assumed that the losses are caused partly. by evaporation due to the heat generated by s 55 Be. at normaltemperature, around F.,

thereaction of the acid on the oil, partly by dissolution in the sludge formed, partly by polymerization into tarlike heavy bodies, settling outas sludge, and partly byp oly'merization into. heavier polymerized hydrocarbons. An increase in specific gravity and rise of boiling point, takes place whereby the gasoline hydrocarbons become less volatileto such an extent that they can not be used as gasoline, and are lost as such. I

To reduce the losses in gasoline material caused by this treatment it has recently been proposed, to treat the pressure distillatewith strong sulfuric acid at temperatures below normal, approximately at 2010 F. At these temperatures the action of the sulfuric acid on the oil is probably one of solution rather than of polymerization. Also the sulfur compounds are apparently to a lesserextent polymerized by the acid and more dissolved; This cold treatment has many advantages as it nearly eliminates the loss by evaporation, and greatly reduces the other losses of hydrocarbons. However, I have found that this cold treat- "ment hasa marked disadvantage, namely that normal temperature, the decreased further reduction during the rerunning leaves the sulfur content ofthe finished gasolineafter.

in the rerun bottoms and not distill over with the gasoline vapors in the rerunning.

The reduction of the sulfur content is one of the main objects of the treatment with sulfuric acid, and therefore, the fact that a larger part of the sulfur compounds remains in the gasoline on rerunning, is important and impairs the advantages of the cold treatment.

I have discovered that this disadvantage can be overcome by treating the pressure distillate after the cold treatment and before re running with a limited amount of strong sulfuric acid of 55 B. or stronger at normal temperature. This probably polymerizes the sulfur compounds left by the cold treatment sufiiciently to cause'them to remain in the rerun bottoms. The amount of acid used for this additional treatment is too small to cause any material vaporization loss, and hardly any sludge is formed, as the materials whichv are apt to form sludge have substantially been removed by the previous cold treatment. The gasoline obtained after this additional treat-- ment and rerunning shows a very markedly lower sulfur content than the gasoline obtained by the cold treatment and rerunning only. Another advantage of my invention is that the color stability of the cracked gasoline is also decidedly improved, and compares very favorably with that of straight run gasoline.

As an illustration of the operation of the process,I may state, that when treating pressure distillate containing 0.7 of sulfur with about 12 lbs. per barrel of strong sulfuric acid of 66 B. at normal temperature the sulfur content of the gasoline recovered after rerunning was 0.4%, and after the cold treatment and rerunning the sulfur content was about the same, though the losses in material were substantially reduced. When I treated the pressure distillate according to my invention, using the same total amount of strong acid, 12 lbs. per barrel, but dividing this in a cold treatment at 20 F. with about 9.5 lbs. acid and a subsequent treatment at atmospheric temperature around 60 F. with about 2.5 lbs. acid of the same strength the sulfur content was reduced to 0.22%. The color of thecold treated gasoline when finished was 27 and after 4 weeks of dark storage had dropped to 25; that of the gasoline treated according to my invention was at first 30 and in the dark after 4 weeks dropped only to 28, aconsiderable improvement. These figures and conditions are not tobe taken as a limitation of the scope of the invention but as an illustration of the beneficial results of my process in a given case.

If in the application of my process it would not be desired to reduce the sulfur content further than was done before with the other treatments, or in the above figures, only to 0.4%, instead of to 0.22%, then much less acid is needed in my process to obtain the same results. Treating the same pressure distillate as in the case referred to above, a reduction of the sulfur content to 0.4% was obtained with only 8 lbs. of acid, divided again in about the same proportions, at low temperature, and subsequently at atmospheric temperature.

I claim as my invention:

1. The process of preparing a. gasoline of reduced sulfur content comprising: treating pressure distillate with concentrated sulfuric acid at about 20 F, and subsequently before redistilling further treating the distillate at atmospheric temperature with sulfuric acid of the same concentration and of an amount equal to about one-fourth of that used in the cold acid treatment, and redistilling the treated pressure distillate.

2. The process of preparing a gasoline of reduced sulfurcontent by treatment with concentrated sulfuricacid comprising: treating the'gasoline distillate with four-fifths of the acid at a temperature of about 20 F., and subsequently before redistillation treating the distillate with the remaining acid at an atmos pheric temperature of about 60 F., and redistilling.

3. The process to reduce the sulfur content and improve the color of a cracked gasoline comprising: treating the pressure distillate with about 9 pounds per barrel of 66 B. sulfuric acid at a temperature of about 20 F., andsubsequently before redistilling treating the distillate with about 2 pounds per barrel of 66 B. sulfuric acid at atmospheric temperature of around 60 F., and redistilling the treated pressure distillate.

In testimony whereof, I have hereunto set my hand.

. R. I. LEWIS.