US1973500A - Treatment of hydrocarbon oils - Google Patents

Description

Patented Sept. 11, 1934 UNITED STATES PATENT OFFICE TREATMENT OF HYDROCARBON OILS No Drawing. Application January 11, 1932,

Serial No. 586,077

3 Claims. v(Cl. 196-36) This invention relates to the treatment of hydrocarbon oils, and refers more particularly to the treatment of lower boiling motor fuel fractions produced in the conversion of high boil- 5 ing hydrocarbon mixtures at elevated tempera-,

ducing the percentages of highly unsaturated" gum-forming components and the sulfur content respectively of hydrocarbons to a point consistent with the requirements of commercial speciiications, the process disclosed being one of wide 15. application.

Various attempts have been made from time to time to improve upon the established and generally utilized method for the production of salable motor fuels from the raw distillates produced. in cracking operations, this method consisting of regulated treatments with chemicals chief of which is sulfuric acid of commercial grade, followed by neutralizing and redistillation. to any desired end point. However, none of the 26 treatments thus far proposed for producing treating efiects upon such distillates in heated vaporous condition has been commercially economical. The present invention accomplishes these ends by a new and novel process which will be 30 hereinafter fully disclosed.

In one specific embodiment the invention comprises treatment of hydrocarbon oil vapors, particularly cracked hydrocarbon oil vapors, with oxidizing gases in the presence of suitable catalytic and/or adsorbent contact materials in a primary stage and the further treatment of the vapors with sulfuric acid solutions containing dissolved salts or other equivalent diluent or spacing materials.

so To produce the oxidation reactions characteristic of the first stage of the treatment any oxygen-containing gas mixture, such as air, or such gases ascxygen or ozone may be employed alone, or in admixture with diluent or relatively inert gases such as steam, carbon dioxide, nitrogen, et cetera, or diiferent oxidizing gases may be used in combinations suitable for producing desired eifects. While in the majority of instances air is sufilciently active for producing the treating effects characteristic of .this stage, the effect of the oxygen contained therein may be augmented by the addition of oxygen to produce a mixture containing an excess over the percentage normal to the atmosphere or air may be oz'onized by the '55 usual method of subjecting it to the action of electrical discharges. In any event the amount and character of oxidizing gas employed will be so regulated that the reactions produced are at all times within the control of the operator.

To further assist in controlling the rate and character of the oxidation processes various contacting materials may be employed, these being classifiable broadly as follows:

1. Metals,

2. Metal oxides,

3. Salts of metals, and

4. Adsorbent materials usually of a non-metallic or siliceous character.

As metals which may be used as contact materials to assist in the oxidation reactions may be mentioned such metals as iron, aluminum, zinc, tin, nickel, cobalt, copper, lead, mercury, calcium, barium, strontium, cadmium, molybdenum, tungsten, chromium, vanadium, et cetera, such metals being utilizable either singly or in suitable combinations or alloys although not with equivalent efliciencies.

As oxides, the corresponding oxygen compounds of the metals disclosed in the previous paragraph may be employed, and at times the oxides corresponding to the difierent degrees of valence of the metals may be utilized to advantage. For example, either ferrous or ferric oxide may be employed or the various oxides of chromium. In some instances mixtures of metals and oxides may be employed, which mixtures correspond to either a low degree of oxidation or a partially reduced oxide.

Under the heading of' metal salts are employed preferably those that are not materially effected by contact with the mixture of oxygen-containing gases or the oil vapors. While in most cases it may be suilicient to use, the commoner salts of metals such as sulfates, chlorides, nitrates,

classes, each mixture producing characteristic results.

Various contact materials of the adsorbent character mentioned above as class 4 may be employed, such materials including fullers earth, bentonite, bauxite, zeolites, activated carbons.

support or as spacing means. Thus, in some cases solutions of metallic salts may be incorporated with the adsorbent material, the solvent being driven off by heating, the salt brought to'the oxide condition by calcination and reduced to metal by means of hydrogen or other reducing gases,'though the operation may also stop at the production of the salt or the oxide.

In place of materials of a distinctly adsorbent character, relatively. inert spacing materials may be used such as fire-clay, pumice, silica fragments, et cetera.

To summarize, the effect of the reactions of the first stage is generally to oxidize and/or cause the polymerization of highly unsaturated hydrocarbons and sulphur compounds so that high molecular weight aggregates may be produced, these reactions being continued by the treatments of the second stage to be presently described so that the net result is the elimination of the undesirable constituents to any desired extent. It will be evident that owing to the wide- 1y varying composition and complicated chemical nature of the hydrocarbon oil mixtures which may be subjected to the treatment that the exact nature of the treatingreactions will vary markedly, and in some cases they may be of an extremely complex character.

In the second stage of the process the vapors after the preliminary oxidizing treatment are further subjected to the action of what may be termed spaced sulfuric acid solutions to complete the treatment. Such treating solutions are made by using soluble compounds,'particularly sulfates and acid sulfates, in solution with sulfuric. acid. The treating effect of these solutions may be considered to be substantially equivalent to the effect which would be produced by the use of aqueous sulfuric acid -solutions of similar concentrations, though it is manifestly impossible to maintain such dilute solutions under the conditions of temperature and pressure under which vapors of gasoline boiling point range exist. When attempts are made to use such dilute aqueous solutions the acid is rapidly concentrated by the evaporation of the water to a strength which in practically all cases produces heavy treating effects accompanied by charring and carbonization of the hydrocarbons. By using dissolved compounds of a substantially neutral character and having a low vapor pressure, the concentration of sulfuric acid solutions may be maintained at a concentration low enough to produce desirable treating effects without undue side reactions and unnecessarily high losses. v

While the sulfates and acid sulfates of the alkali, alkaline earth and heavy metals may be advantageously employed in solutions of the type described, other compounds such as neutral, acidic or basic organic materials may be used as described in a number of my copending applications. I v

To summarize, the net effect of the two-stage treatment is the controllable elimination of high- 1y unsaturated olefinic constituents responsible for the gum formation and the reduction of the total. sulphur content to a percentage meeting commercial specifications.

The two stages of the treatment may be conwhich supports the solid contact materials on a perforated false bottom.

In the second stage of the treatment, the sulfuric acid solutions may be introduced at the top of a treating tower filled with baffling or spacing material and allowed to flow downwardly countercurrent to the ascending stream of vapors. Sludge materials and heavy hydrocarbon oil mixtures accumulating as liquids in the bottom of such a treater may be removed and separated, the spent treating reagents being either wasted or regenerated in suitable steps and continuously returned to the treater in lieu of fresh solution.

It will be obvious to those conversant with the types of treatment described that the use of filtering or settling devices may be necessary in case the treated vapors contain suspended or entrained particles of liquids or solids and that if necessary they may be subjected to further treating steps such as, for example, neutralization with ammonia or alkaline solutions.

As a characteristic example of results obtainable by the application of the process of the iiivention to the treatment of cracked vapors, an example may be chosen in which the vapors arise from the fractionator of a cracking plant operating upon heavy California distillates as charging oil.

Such vapors at the temperature and pressure normal to the primary fractionator of the plant, to-wit, 520 F. and 225 pounds per square inch may be passed in the primary oxidizing stage over a mixture of lime and ferric oxide mixed with fairly coarse fullers earth to assist in extending the contact surfaces. Air may be added to. the vapors prior to their passage through the oxide bed in amounts approximating twenty cubic feet per barrel of fractionated and condensed gasoline from the process.

, After this preliminary oxidizing treatment the vapors may be further acted upon by an aqueous solution of sulfuric acid andsodium acid sulfate by flowing the solution downwardly in a filled treating tower countercurrent to the ascending vapors. The composition of the treating solution may be approximately as follows by weight: sulfuric acid, 50%; sodium acid sulfate, 25%; water, 25%. By using this solution in the proper amount to constitute a treatment equivalent to the use of five pounds of sulfuric acid per barrel of finished gasoine and reducing the pressure and temperature somewhat, the degree of refinement of the gasoline produced by fractionating the vapors to a desired end point may be brought to a point consistent with the commercial requirements in finished gasoline with perhaps a light caustic wash as a final treatment.

The following tabulation indicates a triple comparison between (1) the gasoline produced by simple fractionation without vapor phase treatment of any kind, (2) gasoline produced by a vapor phase treatment with sulfuric acid containing sodium acid sulfate, and (3) combination vapor phase treatment with mild oxidation in the first stage as described, followed by treatment and final fractionation:

54.7 54.9' 55.0 420 41s 415 M b d" h thud 393 i g-gllm YCODDGI 18 me Totalsuliur 0.45 0.3 cm

Thus, it is pointed out that while distillation to end point gasoline is not effective in producing a product of good color, low gums and low sulfur, and the sulfuric acid reagent alone causes insufficient reduction in sulfur and gums, the com- I bination of oxidation and sulfuric acid treatment in vapor phase produces all of the desired results. This may be explained by the removal of oxidation products of sulfurin the flnal treatment which otherwise would not be removed. The invention may be applied equally as well to very high sulfur stocks, such as those from California, Oregon Basin, Venezuela, Mexico and the like.

The oxidizing step is of a relatively simple character and presents no special difilculties so that its use in combination with the spaced sulpoints within the motor fuel range, the improveresulting from the cracking of hydrocarbon oil and comprising a mixture of saturated and unsaturated hydrocarbons of diiferent boiling points within the motor fuel range, the improvement which comprises subjecting said overhead products in heated vaporous condition first to the action of a free oxygen-containing gas in the presence of a solid contact agent and thereafter while still in heated vaporous condition subjecting said overhead products to the action-of an aqueous solution of sulfuric acid containing a dissolved salt. v

2. In the art of refining the overhead products resulting from the cracking of hydrocarbon oil and comprising a mixture of saturated and unsaturated hydrocarbons of difierent boiling points within the motor fuel range, the improvement which comprises subjecting said overhead products in heated vaporous condition first to the action of a free oxygen-containing gas in the presence of a solid contactagent and thereafter while still in heated vaporous condition subjecting said overhead products to the action of an aqueous solution of sulfuric acid containing a dissolved salt of an alkali metal.

3. In the art of refining the overhead products resulting from the cracking of hydrocarbon oil and comprising a mixture of saturated and unsaturated hydrocarbons of, diiferent boiling ment which comprises subjecting said overhead products in heated vaporous condition first to the action of airin the presence of a metal oxide and thereafter subjecting said overhead products while still in heated vaporous condition to 3 the action of an aqueous solution of sulfuric acid containing a dissolved salt of an alkali metal.

JACQUE C. MORRELL.