US2029785A - Treatment of hydrocarbon oil - Google Patents

Description

Patented Feb. 4, 1936 UNITED STATES 2,029,785 TREATMENT OF HYDROCARBON on.

Jacque C. Morrell, Chicago, 111., assignor to Universal Oil Products Company, Chicago, Ill., a corporation of South Dakota No Drawing. Application February 18, 1932, Serial No., 593,87'7. Renewed April 8, 1935 4 Claims. (01. 196- 36) This invention relates more particularly to the refining treatment of the relatively low boiling cracked hydrocarbons produced by the thermal conversion of high boiling hydrocarbon oil mixtures into lower boiling hydrocarbons suitable for use as motor fuel.

In a more specific sense the invention is concerned with an improved process whereby relatively low boiling hydrocarbons may be treated and refined while in heated vaporous condition either as produced from the fractionators of the cracking plant or when the initially produced distillates or naphthas are redistilled to produce end point gasoline.

To produce marketable gasolines from cracked or pressure distillates it is practically always necessary to remove all or a major portion of the more highly unsaturated olefinic constituents and also the major portion of the more reactive sulfur compounds, since the former class, even in small percentages, accounts for the gum-forming tendencies of the gasolines and the latter produce the corrosive effects noted upon feed lines, valves, carburetors, et cetera, before the combustion of fuel, and produce oxides of sulfur which cause crankcase corrosion after combustion.

In one specific embodiment the invention comprises the treatment of hydrocarbon oils, particularly cracked hydrocarbon oils, While inheated vaporous condition, with reagent mixtures containing sulfuric and phosphoric acid.

The element phosphorus, owing to its variable valence, forms a considerable number of acids,

of which orthophosphoric acid (HsPOi) is by far the most common and generally used. This acid is miscible in substantially all proportions with sulfuric acid in various concentrations in which both acids may exist inwater. While the invention will be described principally in referenee to this most common acid of phosphorus, its scope is not limited thereto but comprises also the use of such other acids of phosphorus as may be suitable when mixed with sulfuric acid under various operating conditions. The following tabulation is appended to show the principal acids of phosphorus with their formulas and commoner properties, such as their melting and decomposing temperatures:

Acids of phosphorus M. P. O. V Decompfat O.

Orthophosphorous (H P03) 200 Hypophosphorous (HBPO2). 26. 6 Above M. P. Hypophosphonc (H4P2O 55 I 70 'm ent.

Acid mixtures of the character described may be employed for treating hydrocarbon oil vapors to produce substantially the same refining effects as are ordinarily produced when the condensed vapors are treated with sulfuric acid of commercial grade, neutralized and redistilled sired endpoint. By proper selection of the type of phosphorous acid (thus controlling to some extent the oxidizing or reducing effect) and its proper proportioning in respect to the amount and strength of sulfuric acid'used in the treating solutions, these effects may be produced upon hydrocarbon vapors over a considerable range of temperatures and pressures, such as, for example, between temperatures of 250 and 600 F. and pressures of from atmospheric to several hundred pounds persquare inch. These temperature and pressure ranges will cover in practically all cases the conditions under which vapors of approximate gasoline boiling point range are produced in straight run distilling, rerunning or cracking plants. The sulfuric acid apparently has the most pronounced effect upon the vapors, the phosporous acid acting to some degree as a diluent or spacing reagent, which moderates the intensity of the treating effect of the sulfuric acid, and prevents the decomposing and charring effects usually noted when attempts are made to treat hydrocarbon oil vapors H with it at elevated temperatures. Theadvantage inherent in thus using the phosphorous acid as a diluent for sulphuric acid appears in the lowervapor pressure of the acid, sothat the equivalent of dilute aqueous solutions of sulfuric acid may be usedwith substantially no tendency toward increase in concentration during treat- However, since the process may be employed under a wide variety of operating conditions as already stated, it may be advantageous or necessary in some cases to add water to themixture of acids and/or steam to the vapors undergoing treatment to prevent or retard evaporation of whatever water may be present in the solution. i

In applying the invention to practice, the optimum proportions and concentrations of sulfuric acid, phosphoric acid and water will be determined best by trial in a majority of instances,

since the exact treating effect to be expected-' when treating vapors of different composition from different sources is not accurately predictable from analytical data. I

The solutions may be applied to the vapors in any type of treating equipment capable of efiecting intimate contact between liquids and vapors, such types of equipment including vertical cylindrical treating towers containing various types of filling material such as coarse silica fragments, Raschig rings, crushed firebrick. et cetera, 60-.

with fire and steam to produce gasoline of dethrough some distributing means such as a spray or atomizer and then allow the liquid to flow downwardly countercurrent to the ascending stream of vapors. In some instances treatments may be conducted with the reagent and vapors flowing in the same direction, in which case any portions of the vapor which may condense will be subjected to liquid phase treatment. The use of a jet mixer is also satisfactory.

The spent reagents mixed with reaction products and some unconverted oil may be drawn from the bottom of the treater continuously or intermittently, the oil separated by gravity and the sludge acids subjected to any necessary regenerating steps to permit their cycling to the treater in lieu of fresh materials.

The invention is not limited to the use of any particular temperature and pressure ranges and, while it may be generally stated that temperatures of from 250 to 600 F. and pressures from atmospheric to several hundred pounds per square inch may be employed, it is further comprised' within the scope of the invention to vary pressure and temperature independently either by superheating vapors above the temperatures normal to the pressure under which they exist or to use pressures less than atmospheric so that correspondingly low temperatures are available with corresponding modification of the results obtained by the treatment. In all cases the strength of the treating reagent andthe conditions of operation will be chosen that are best suited to the efiicient treatment of the vapors in question. 7

The effects produced upon hydrocarbon oil vapors, particularly cracked vapors, are comparable to those produced by ordinary sulfuric acid treatments, and possess the added virtues of having a more selective action upon the diand triolefins in' vapor mixtures and of producing desulfurizing effects without removing unduly large percentages of mono-olefins, which are valuable in gasoline on account of their anti-knock character.

The process may be employed as a single treatment upon hydrocarbon oil vapors, or it may be used as one step in a series of treating steps, both vapor and liquid phase. For example, the vapors may be contacted with fullers earth, metal oxides. et cetera, prior to the use of the reagents described and treatment may be followed in turn by neutralizing treatments with caustic alkalis and ammonia or light final treatments upon the condensed vapors.

The corrosive effect of the treating mixtures may be overcome by the use of acid-resisting metals or suitable linings. For example, the treating towers may be lined with silicate mixtures and cements involving the use of water glass, fire clay, et'cetera, or they may be lined with various enameling compositions.

A single example of results selected from the many made possible by the use of the invention may be given as illustrative of the value of the process. In treating the vapors of approximate gasoline boiling point range arising from a cracking system operating on an approximately equal mixture of California heavy residuum and gas oil distillates as charging stock, a solution containing approximately 40% sulfuric acid, 50% phosphoric acid. and 10% water may be employed. The vapors from the high pressure fractionator may be reduced to a pressure of 50 pounds per square inch, at which their mean temperature is in the neighborhood of 325-350 F. These vapors may be passed upwardly through a filled tower containing coarse silica fragments with the solution flowing downwardly by gravity. By using an amount of reagent equal to approximately six pounds per barrel of finished gasoline and following the main treatment by neutralization of various acidic products with gaseous ammonia. the finally rectified gasoline after a light caustic wash may have the properties shown in the column headed ftreated gasoline as compared with a similar boiling range gasoline produced by simple fractionation of the vapors without chemical treatment:

Comparison of untreated and treated gasoline Untreated Treated Gravity A. P. I 53. 54.1 Endpoint F 418 412 Color-Saybolt 4 llus 30 Color after 4 hours exposure to sunlight... Yellow 25 Mgs. gum by copper dish method 260 25 Total sulfur percent 0. 45 0.14

oil of motor fuel boiling range and containing monoand diand tri-olefins to remove color and gum forming components and to reduce the sulphur content thereof, which comprises subjecting the hydrocarbon oil while entirely in vapor phase to the action of a mixture of sulphuric and phosphoric acids.

2. A process for refining cracked hydrocarbon oil of motor fuel boiling range and containing monoand diand tri-olefius to remove color and gum forming components and to reduce the sulphur content thereof, which comprises subjecting the hydrocarbon oil while entirely in vapor phase to the action of a solution containing sulphuric and phosphoric acids.

, 3. A process for refining cracked hydrocarbon oil of motor fuel boiling range and containing monoand diand tri-olefins to remove color and gum forming components and to reduce the sulphur content thereof, which comprises subjecting the hydrocarbon oil while entirely in vapor phase to the action of an aqueous solution containing sulphuric and phosphoric acids.

4. In the cracking of hydrocarbon oil wherein the cracked products evolved from the oil are fractionated to condense and separate fractions thereof heavier than gasoline. the method which comprises subjecting low boiling products uncondensed by the fractionation, while entirely in vapor phase, to the action of a mixture of sulphuric and phosphoric acids.

JACQUE o. MoRaELL.