US1969316A - Treatment of hydrocarbon oils - Google Patents

Description

Patented Aug. 7, 1934 TREATMENT OFHYDROCARBON 011s Jacqiie C. Morrell, Chicago, Ill., assignor to Universal Oil Products Company, Chicago, 111., a corporation of South Dakota No Drawing. Application December 19, 1931, Serial No. 582,152

3 Claims.

This invention relates to the treatment of hydrocarbon oils and more particularly is directed to the treatment of petroleum distillates, especially those resulting from the conversion of 5 relatively higher boiling hydrocarbons into lower I like,

,cracking process. I

boiling hydrocarbons by treatment at elevated temperatures, commonly referred to as cracked distillates, by subjecting the same while in vapor form to the action of solutions of acid sulphates alone or in direct combination with sulphuric acid. More particularly, the invention relates to the treatment of the said hydrocarbons while in the vapor form with solutions containing sulphuric acid and a salt of an alkaline earth metal such as the sulphates of calcium, barium, magnesium andstrontium. Presumably, these salts .are present as acid sulphates and it is desirable .that they always be present in the form of the acid sulphate, i. e. with excess sulphuric acid. Where an insuflicient quantity of the sulphate of the alkaline earth is dissolved to control the concentration of the sulphuric acid, the sulphates or acid sulphates of the alkali metals such as sodium, potassium and ammonium may be added in addition.

Petroleum distillates, especially cracked distillates, contain undesirable compounds, presumably of a highly unsaturated charactenwhich render them unstable with respect to color, gum forming properties and knock rating. Such distillates tend to deposit polymer or gum -like substances while in storage, causing a drop in color which may render the product unsaleable. The development of gums may also prevent proper operation of the motor by plugging or gumming up the fuel feed lines, carburetor, valves and other parts of the motor.

I Other objectionable compounds such as those of sulphur, nitrogen and the may be present in such distillates, and it is among the objects of this invention to remove or reduce to a minimum, the objectionable substances present in hydrocarbons and more particularly, in petroleum distillates. I

. One of the most important and most desirable developments in petroleum refining is the direct production of a marketable distillate from the Many attempts have been made to employ refining agents for this purpose, particularly directed towards the use of sulphuricacid which for the most part have been unsuccessful because they have failed to take into consideration the physical and chemical properties of sulphuric acid under the conditions of rein the United States, but heretofore, it has been most successfully applied as arefining agent to petroleum and its products while in the liquid state. 1 The following table taken from 1913 Edition of the Manufacture of Sulphuric Acid and Alkali by Lunge, a standard work on the subject, shows the relationship between the boiling point and con centration of sulphuric acid:

Table 1 msoi B. Pt. r.

From the above table it is evident that vat a given temperature and'at each temperature, the sulphuric acid exists at a definite concentration and that irrespective of the concentration ofthe sulphuric acid feed into a system ata given temperature, if it is more dilute than that indiecated by the concentration for the corresponding temperature it will concentrate to the givenconcentration. For example, if an approximately 8% solution of sulphuric acid is fed into a tower, the average temperature of which is approximately 360 R, neglecting the partial pressures of the steam and oil vapors, the sulphuric acid introduced will concentrate to approximately and under these temperatures, such a concentration of sulphuric acid will immediately attack and destroy the unsaturated hydrocarbons in the immediate vicinity, resulting in an offcolored overhead product of high gum content and in a charring of the derivatives of sulphuric acid in the hydrocarbons, plugging up the column and rendering the process inoperatiye. The

above indicates only approximately the conditions existing in the tower, but is sufficient to illustrate the trend and direction of the reaction and explain why previous attempts to refine in the manner described, have been unsuccessful. It is well known that concentrations of sulphuric acid which maybe even substantially non-reactive at ordinary temperatures are highly destructive in their reactions at elevated temperatures. Hence, while it is desirable to treat petroleum distillates in the vapor state in order to avoid the expense of redistilling the product, it isimperative that a method of treatment be provided which will enable one to definitely control the concentration and consequentlyth'e rate of reraction and kind of reaction at the elevated temperatures of treatment.

scribed.

In a specific aspect the invention comprises treating hydrocarbon vapors, especially cracked hydrocarbon vapors, with an aqueous solution containing dissolved therein sulphuric acid and a; sulphate of a an alkaline earth metal which is presumably present in the form of the acid sulphate. r v M In effecting the'operation of the invention, hydrocarbon vapors from any source, for example, direct from a cracking process, and in general from a distillation process, including vapors from atmospheric distillation or hydrocarbon vapors from rerun stills, may be passed counter-current or concurrent to the solution containing the acid sulphate and the sulphuric acid. The treating solution may be introduced in the form of a spray, atomized or otherwiseintroduced and employed in such manner as to give the most chicient contact of treating agent and vapors undergoing treatment. Under some conditions, the hydrocarbon vapors may be bubbled through a pool or pools of the treating agent preferably feeding in fresh reagent and withdrawing sludge continuously. In the countercurrentoperation the vapors may be withdrawn from the top of the treating tower and maybe condensed or fractionated and condensed, preferably subjecting the treated hydrocarbons to treatment with alkalis or combination washing and alkali to remove sulphur dioxide and possibly some' entrained treating agent. In the concurrent method of operation the vapors, reflux condensate and sludge may be passed through a separator, withdrawing the vaporsand condensing as described, and separatelywithdrawing the sludge and/orpro'ducts of reaction together with unused treating agent and reflux condensate if present. Steam may be introduced into the column duringlthetreathient in order to maintain an equilibriiiin between the dissolved substances in. the ivatfer, namely, the acid sulphate and sulphuric acid.

' The sludge may be used directly by recirculating to the treating column, The acid sulphates may be recovered 'by dilution and treatment of the slud e with water and subsequent purification and evaporation of the solution.

The process may constitute the solestep of the process in the refining of they hydrocarbons or may be combi'nedwith other treatments either applied before or after the process ofthis invention; For example, thevapors from the treating tower may be subsequently passed through a fllter or series of filterscontaining inert filter ing agents, adsorbents, solid alkalis, such as lime,

The: present invention accomplishes this aim in a new and novel man-'- ner which will be hereinafter more fully decaustic or mixtures of these and the like, catalytic materials such as metals and metallic oxides, solutions of alkalis, and the like. Preferably the vapors are fractionated before passing to the treating stage and may be fractionated after passing to the treating stage. Prior ,treatments of the hydrocarbons with other reagents, either in the vapor or liquid phase, or subsequent treatment of the condensed liquid may be applied.

For example, the condensed product may be sweetened by treatment with plumbite solutions, solutions of copper salts or other metallic salts alone or in combination with auxiliary chemical treatments with acids, and the like or with filtering agents such as fullers earth and like adsorbing agents. Sludges from the treating reagent may be reused or regenerated.

As specific examples of reagents used in the present invention where calcium sulphate is employed, an approximately 4% solution'in a 10% solution of the sulphuric acid may be employed. A solution containing approximately 18% of barium sulphate and approximately of sulphuric acid may be employed. Strontium sulphatefwill give a similar solution and magnesium sulphate Will dissolve to a greater extent. For some conditions of treatment the alkaline earth'metals, sulphates or equivalent salts do not dissolve-to a sufficient extent to permit the-requiredcon- 365 trol of the concentration of the sulphuricacid under the conditions of treatment.-

In order to obtain exact control of'the-solution, it is preferred in many cases to-ad'd-to'the sulphuricacid a sulphate or acid sulphate, p'ar- 1-10 ticularly a sulphate of-the-alkalimetals suchas sodium; potassium orammonium sulphate,-- in addition 'to the sulphates of the alkaline earth metals. Generally, the initial concentrations of sulphuric acid employed, vary from-30;to 60% 1'15 and the initial-concentrations of salts employed vary from -5 to 20%, theremainder being water.

As an example of results obtainableby the operation-of the process of my invention,- and of the operating conditions thereof, the 'follow 120 ing may-be cited; A California crack'eddistillate containing approximately 0.45 sulphuri's subjected 'to' treatment the vapor form at approximately 300 F; with a solution containing approximately 50 of calciumsulphate, 15% of ammonium acid sulphate and 25% of water." I The resultant product may have a'color of approximately '28which is stable on-exp'osure to sunlight, a g-umcontent of; sulphuric acid, 10%

ofapproxi-mately 15 "mgs. per'100fcc. and' 'a l iid Mixtures of 1. In a process for the refining of hydrocarbon oils, the improvement which comprises subjecting. the said hydrocarbon oils while 'inheated vaporous condition to reaction with an aqueous solution of sulphuric acid-in which has'been' dissolved atleast 4% of "a sulphate of an alkali lbo metal, the amount of acid originally contained in the solution exceeding the amount of the sulphate added thereto.

2. In a process for the refining of cracked hydrocarbon oils, the improvement which comprises subjecting the said cracked hydrocarbon oils in heated vaporous condition to reaction with an aqueous solution of sulphuric acid in which has been dissolved at least 4% of a sulphate of an alkaline earth metal and a sulphate of an alkali metal, the amount of acid originally con- J ACQUE C. MORREIL.