US1961204A

US1961204A - Process of kefining a benzenoid

Info

Publication number: US1961204A
Authority: US
Publication date: 1934-06-05
Anticipated expiration: 1951-06-05

Description

June 5, 1934.

G. G. DESY PROCESS OF REFINING A BENZENOID HYDROCARBON OIL Filed June 50, 1931 DI LUTE. ACID WITH WATER AGITATE OIL AND DILUTE ACID QH/e and area/77L I NEUTRALIZE on. .f

RESIDUE SPENT ALKALINE LIQUID DISTII. L.

REFINED OIL SOM/ENT NAPHTHIDI IN VEN TOR.

11.0 is by Patented June 5, 1934 PROCESS F REFINING A BENZENOID HYDROCARBON OIL Gustave G. Dsy, Pittsburgh, Pa., assigner to The Koppers Company of Delaware, a corporation of Delaware Application June 30, 1931, Serial No. 547,839

Claims. (Cl. 196-40) yThis invention relates to the reiining or puriiication of hydrocarbon oils and more particularly benzenoid hydrocarbons such as those de- .rived from coal gas. Crude hydrocarbon oils ordinarily contain impurities generally comprising unsaturated hydrocarbons which are dinicult to remove from the oils or from the various constituents of the :oils in the usual distillation operations. This reason of the fact that such impurities `are present Yin the oils in the form of compounds closely related to the desirable constituents of ,the oil with regard to Volatility and boiling point, Amaking separation of such impurities from the T more valuable constituents of the oils practically impossible by distillation alone.

It is therefore the common practice to treat the crude or partially refined oils at some time previous to ,final distillation thereof in such manner as t0 cause the conversion of materials originally present as impurities to products of higher boiling points by polymerization o r otherwise. The products of conversion thus obtained may either be Withdrawn from the oil inthe form of a sludge or may remain in the 011, to be separated from other constituents of the o il in the source of subsequent distillation operations.

According to the method most generally employed, the hydrocarbon oil is Washed with strong sulphuric acid, causing the formation of considerable amounts of sludge. The sludge and acid are then Withdrawn from the oil, which is then treated With a neutralizing agent such as a solution of caustic soda `and finally distilled.

This practice is extremely disadvantageous by reason of the fact that it produces large quantities of acid sludge, representing not only a great loss of acid but the production of a valueless material. The disposal of the sludge is a serious problem as is also the recovery of the acid and neither of these problems had been successfully solved until quite recently. Moreover, the practice recited above results in considerable washing losses and can be carried out continuously only with considerable difculty. Y

It has recently been proposed to accomplish the refining of hydrocarbon oils of the character described by Washing the oil with sulphuric acid to cause the conversion of impurities to products of higher boiling points, followed by dilution of the acid While in the presence of the oil, so that products of conversion temporarily removed from the oil are returned to the oil in 55 unobjectionable form, that is to say, capable of being separated by distillation in the usual manner.

The initial concentration of acid employed for the Washing of oil is of considerable importance in this process and it has been found that in the treatment of most oils and especially American oils recovered from coal gas by means of absorbent oils derived from petroleum, it is often necessary to employ slightly dilute acid in the initial stage in order to effect complete re-solution of the sludge constituents or products or" conversion of original impurities in the subsequent dilution stage.

It has been observed that in the treatment of oils of a certain class, for example, motor fuels distilled from unwashed light oil, and similar oils and more particularly Where exacting standards of purity must be met by the finished products, the use of acid of sufficient initial strength to accomplish the necessary refining frequently resuits in the formation of products of conversion which are wholly or in part incapable of re-solution in the oil in the dilution stage.

It is therefore an object of my invention to provide a process of refining hydrocarbon oils so vof this character in which the production of permanent acid sludge is substantially comparatively eliminated or avoided and according to which finished products may be obtained from the oils in a very high state of purity Without sacriicing other advantages of the general method of Washing referred to hereinabove.

My invention has for further objects such other operative advantages or improvements as may hereinafter be found to obtain.

I have observed that oils oi this class are generally deficient in benzenoid hydrocarbon constituents having boiling points of from 140 to 200 C. arranged corresponding to what is generally known as the solvent naphtha fraction. I have found that if the oil is built up= by the addition of constituents of this character, complete re-solution of the products of conversion may be obtained in the dilution stage.

My invention therefore contemplates the ad- 10o dition to hydrocarbon oil deficient in constituents having boiling points of from 140 to 200 C. of a suicient amount of such constituents to effect the substantially complete re-solution or the sludge or products of conversion.

My invention further contemplates a process in the course of which these constituents may subsequently be recovered and returned for use in the treatment of further quantities of the oil to be rened.

In order that my invention may be fully set forth and imderstood, I now describe a preferred manner in which it is carried out, and with particular reference to the washing of crude motor fuel.

The crude motor fuel upon which the following example is based is made by distilling unwashed light oil obtained from coke-oven gas to produce a distillate having the following distillation characteristics:

Volume distilled Temperature O'. First drop 8l 5% 85 10% 86 20% S7 .50% 89 40% 00 50% 92 00% 94 98 105 121 13G Dry point. 139

When this oil is washed with sulphuric acid' or, for example, 65 Baume, followed by dilution of the acid to 40 Baume in the presence of the oil, it is found that there remains after the dilution stage, a certain amount of sludge-like constituents which do not re-dissolve in the oil.

'Io this oil therefore before washing with acid, I add benzenoid hydrocarbon oil comprising constituents having boiling points between 140 and 200 C. It is not necessary that the added oil should consist entirely of such constituents, as other constituents having higher or lower boiling points may be present without harm. I may also employ benzenoid hydrocarbon oil comprising principally a single constituent such as a xylene, having a boilingpoint in the neighborhood of 140 C. or higher.

The amount of such added oil will be determined by the amount of similar constituents in the oil to be refined or more directly by the appearance or disappearance of insoluble sludge in the dilution stage in the washing process. That is to say, I employ a suicient amount of added oil, whatever the nature of the oil to be rened, to accomplish complete or substantially complete re-solution of the products of conversion of the original impurities.

In general, this will amount to from 5 to 10% by volume of the oil to be rened, although if the latter contains an unusually high percentage of impurities, or the process requires the use of extremely concentrated acid, even larger amounts of the supplementary oil may be added prior to the washing operation.

The oil is then agitated with sulphuric acid of requisite strength, for example, from 63 to 66 Baume, for a suitable period, for example, 30 minutes. To the mixture of the oil and acid is then added a considerable volume of water, for example, a suiiicient volume to dilute the acid to a concentration of around 40 Baume, and agitation is continued.

The initial treatment of the oil with acid accomplishes a polymerization or other conversion of the original impurities in the oil to products of higher boiling point which are capable of separation from the principal constituents of the oil by distillation in the usual manner. A portion or all of these products of conversion are absorbed by the strong acid, but in the subsequent dilution stage, re-dissolved in the oil, leaving a dilute acid of remarkable purity which is capable of use for many purposes, such as the removal of ammonia from coal gas, without further rening or purication.

The mixture of oil and dilute acid is then permitted to settle and the dilute acid is withdrawn. It will ordinarily be found to contain no sludge or at the most only slight amounts which have failed to re-dissolve in the oil for mechanical reasons, as will naturally be expected to happen to a certain extent in large-scale operations of this character.

The oil is then neutralized in the usual manner, for example, by agitating it with a solution of caustic soda, and also by water washing, if so desired.

The washed and neutralized oil is then distilled in the usual manner, the constituents comprising the bulk of the original oil to be refined being collected in one or more fractions, the boiling points of which will principally be below 140 C. The distillation is then completed, causing the production of oil similar to that added above and comprising constituents boiling between 140" C. and 200 C., while a residue is obtained which consists primarily of products of conversion of materials originally present in the oil as impurities of lower boiling points.

The disposal of this residue presents no problem and as a matter of fact the residue with its large content of polymerized hydrocarbons and similar substances is generally found to possess considerable value. On the other hand, if these saine products of conversion were permitted to be converted into the form of acid sludge, according to the method of the prior art, their disposal would present a very serious broblem, their value would be substantially nil and the acid with which they were mixed would be so impure as to be of substantially no value.

The solvent naphtha fraction collected in the distillation and comprising principally constituents boiling between 140 and 200 C. is then returned to be used in the treatment of further quantities of oil to be reiined. If, during the washing and distillation processes, mechanical or other losses of this material have been encountered, additional quantities may be supplied to make up for such losses in general. These losses should be very slight.

In the accompanying drawing, the single iigure illustrates a flow sheet of my process as described herein.

Under some conditions, as for example when the oil contains an unusually large amount of impurities and when the amount of solvent naphtha available is limited, if a .small amount of sludge appears, I may employ the method set forth and claimed in the copending application for Letters Patent of John W. Ingram, Se-

rial No. 541,117, filed May 29, 1931, in eombination with the several steps of my process.

According to this method, should any sludge remain after the dilution step, it is allowed to remain with the oil, and a fairly large volume 0f water, for example, 10% by volume of the oil, is added. Upon agitation, the sludge then goes into the form of an extremely nely divided dispensoid in the oil, which is unobjectionable because it can be separated from the oil in the usual course of distillation.

In some instances, it will not be necessary to return the solvent naphtha fraction from the distillation. For example, the rener may have at his disposal, in raddition to hydrocarbon oil Cil to be refined which is deficient in constituents having boiling points between 140 to 200 C., other oil which is well fortified in such constituents, in which event the advantages of my invention may be secured by blending or mixing the two oils prior to the washing process to such eX- tent as to effect the complete or substantially complete elimination of permanent acid sludge.

According to my process, it is possible to employ acids of higher strength than would otherwise be practicable without producing a permanent acid sludge and it is thus possible to obtain nished products capable of meeting eX- acting color standards and other criteria of purity.

It will be obvious to those skilled in the art that my invention is not limited to the specific example described hereinabove by way of illustration but may be variously practiced and carried out within the scope of the claims hereinafter made.

I claim as my invention:

1. In a process of rening a benzenoid hydrocarbon oil so deficient in hydrocarbon of higher boiling point constituent prior to distillation thereof as to cause unsatisfactory re-solution of sludge formed therein by an acid wash when the acid wash is followed by a dilution step with water to effect re-solution of the conversion products in the oil, the steps which comprise enriching said oil with respect to the deficient higher boiling point constituent by adding to the oil hydrocarbon of the deficient higher boiling point constituent, then treating the oil mixture with sulphuric acid to convert materials originally present in the oil as impurities to products of higher boiling point, and thereafter diluting the acid in the presence of the oil and thereby effecting re-solution in the oil of the products of conversion which would not undergo 11e-solution.

2. In a process of rening a benzenoid hydrocarbon oil so deficient in sufficient Iamounts of constituents having higher boiling points of from 140 C. to 200 C. as to cause, when subjected to the following process steps, an unsatisfactory resolution of the sludge in the oil when the sludge is diluted with the water, said process steps comprising; washing the oil to be refined with sulphuric acid of from 63 to 66 Baume, and then diluting the acid with water in the presence of the oil to effect re-solution of the sludge therein: the improvement which comprises, enriching the oil with respect to hydrocarbon of higher boiling point of from 140 C. to 200 C. by adding thereto solvent naphtha oil prior to the aforesaid washing of the oil with sulphuric acid, the amount of solvent naphtha oil added to the oil to be refined being such that substantially complete re-solution in the oil of products of conversion formed by said acid from materials originally present in the oils as impurities of lower boiling po-ints takes place in said dilution stage.

3. In a process of refining a benzenoid hydrocarbon oil so deficient in sufcient amounts of constituents having higher boiling points of from 140 C. to 200 C. as to cause, when subjected to the following process steps, an unsatisfactory re-solution of the sludge in the oil when the sludge is diluted with the water, said process steps comprising; washing the oil to be refined with sulphuric acid of from 63 to 66 Baume, and

then diluting the acid with water in the presence of the oil to effect re-solution of the sludge therein: the improvement which comprises, enriching the oil to be refined with respect to its content of constituents of higher boiling point of from 140 to 200 C. by adding thereto from 5 to 15% by volume of a benzenoid hydrocarbon oil comprising constituents having boiling points of from 140 C. to 200 C. prior to the aforesaid washing of the oil with the acid, and thereby effecting in said dilution stage substantially complete re-solution in the oil of products of conversion formed by said acid from materials originally present in the oils as impurities of lower boiling points.

4. In a process of refining a benzenoid hydrocarbon oil so deficient in sufficient amounts of constituents having higher boiling points of from 140 C. to 200 C. as to cause, when subjected to the following process steps, an unsatisfactory resolution of the sludge in the oil when the sludge is diluted with the water, said process steps comprising; washing the oil to be refined with sulphuric acid of from 63 to 66 Baume, and then diluting the acid with water in the presence of 100 the oil to effect re-solution of the sludge therein: the improvement which comprises, enriching the oil to be refined with respect to its content of constituents of higher boiling point by adding to the oil to be refined a benzenoid hydrocarbon 105 oil of higher boiling point comprising a Xylene prior to the aforesaid washing of the oil to be rened with an acid, the amount of enriching oil added being such as to effect in said dilution stage substantially complete re-solution in the oil of 110 products of conversion formed by said acid fro-m materials originally present in the oils as impurities of lower boiling points.

5. In a process of refining a benzenoid hydrocarbon oil so deficient in sufficient amounts of 115. constituents having higher boiling points of from 140 to 200 C. as to cause, when subjected to the following process steps, an unsatisfactory re-solution of the sludge in the oil when the sludge is diluted with the water, said process steps comprising; washing the oil to be refined with sulphuric acid of from 63 to 66 Baume, then diluting the acid with water in the presence of the oil to effect A.re-solution of the sludge therein, withdrawing the dilute acid from the oil, neutralizing 125 the oil, distilling the washed and neutralized oil to recover therefrom distillate comprising constituents boiling below 140 C., distillate comprising constituents boiling above 140 C. and still residue, and returning said latter distillate for adrnixture with further quantities of oil to be refined: the improvement which comprises, enriching the oil to be refined with respect to its content of constituents of higher boiling point by adding to the oil a benzenoid hydrocarbon oil 135 comprising constituents having boiling points of from 140 C. to 200 C. prior to the aforesaid washing of the oil to be refined with an acid, the amount of enriching oil adding being such as to effect in said dilution stage substantially complete re-solution in the oil of products of conversion formed by the acid from materials o-riginally present in the oils as impurities of lower boiling points.

GUs'rAvE G. DsY. 145