DE1040162B - Process for removing mercaptans from acidic hydrocarbon distillates - Google Patents

Description

GERMAN

The invention relates to a method for removing mercaptans from acidic hydrocarbon distillates, such as heavy gasoline, luminous oil, heating oil and fuel oils from straight-run crude oil distillation or from thermal or catalytic cracking processes, with concentrated caustic alkali solutions, avoiding them unwanted color deterioration or the formation of oil-soluble color bodies.

So far, acidic, mercaptan-containing hydrocarbon distillates with alkaline solutions have been different Kind of been treated to remove the mercaptans. If low molecular weight mercaptans are present, as with low-boiling distillates, e.g. B. petrol can be removed by simple Washing with caustic alkali (caustic soda or caustic potash) can be effected. This is usually accompanied by an approximately 10-20% caustic soda solution used. The caustic alkali solution can be regenerated by steam treatment or by blowing air, whereby the mercaptans distilled off or converted into insoluble disulfides, which are separated from the caustic alkali solution can be.

In the case of higher-boiling starting products, especially luminous oil and heating oils, the removal is the Mercaptans due to their increased oil solubility or due to their higher molecular weight higher oil - water partition coefficients much more difficult. There are numerous methods of removal proposed and executed heavier mercaptans occurring in these higher-boiling distillates been. One has organic solvents or alkaline ones containing so-called "solubilizers" Solutions applied. Solutions of caustic alkali in methanol have a similar effect. Chemical Reagents which oxidize the mercaptans to disulfides in the presence of the oil are also used been. Among them are the well-known alkaline sodium plumbite or doctor solution, alkaline Hypochlorite solutions, etc. Attempts have been made to obtain mercaptans from petroleum distillates by treatment with anhydrous caustic alkali in the form of a dry powder or in solution or suspension in an organic solvent such as methanol. In this way of working however, severe color formation will result, especially if the treatment is increased Temperature, e.g. B about 66 ° C and higher. It turned out that there was color formation prevent under these conditions only by careful exclusion of oxygen or air can.

It has now been found that mercaptans are obtained from acidic hydrocarbon distillates, even from the boiling range of the heating oil distillates, without serious color

for removing mercaptans
from acidic hydrocarbon distillates

Applicant:

Standard Oil Company,
Chicago, 111. (V. St. A.)

Representative: Dr.-Ing. H. Ruschke, Berlin-Friedenau,

and Dipl.-Ing. K. Grentzenberg, Munich 27,

Pienzenauerstr. 2, patent attorneys

Jack H. Krause, Hammond, Ind.,

and Theodore B. Tom, Griffith, Ind. (V. St. A.),

have been named as inventors

education through treatment with a specific

^a 5 amount of air or oxygen in the presence of 1 to 15 percent by volume of an aqueous 50 to 60% potassium hydroxide solution at a temperature of 27 to 52 ° C (but high enough to avoid solidification of the caustic alkali) at atmospheric or superatmospheric pressure and in Presence of a special type of copper catalyst can be removed. It was discovered that under these conditions the mercaptans are converted into odorless disulfides without the formation of unpleasant color bodies. It has also been found that the oil purified in this way is satisfactory in terms of its burning properties when it is used in tube burners. The amount of oxygen used either in the form of air or commercially available oxygen is preferably about IV2 to 2V2 times the amount theoretically required to convert the mercaptans present into disulfides.

The oxidation of mercaptans with air or oxygen in the presence of a wide variety of catalysts (including copper and copper compounds), optionally in the presence of clays, has already been proposed, but without using aqueous caustic alkali (and a certain treatment temperature).
It has been found that the presence of a small amount of copper, e.g. B. 0.004 to 0.1 percent by weight, based on the potassium hydroxide solution, in the form of a catalytically active copper compound or a copper complex, such as colloidal copper oxide, is very much facilitated. That corresponds to about 0.01

EOS 640/423

up to 0.3% copper chloride, CuCl ₂ -2H ₂ O. With some catalysts, larger amounts of copper, e.g. Up to 0.5% by weight based on KOH can be used, but usually it is not necessary to exceed 0.1%. The copper is preferably added in the form of an aqueous solution of a copper salt, such as copper chloride, sulfate, nitrate or acetate. The copper salt solution can be added immediately to the potassium hydroxide solution when the latter is hot enough to avoid the formation of a black precipitate. If one uses the copper salt solution in this way, e.g. B. potassium hydroxide to be boiled, adds, a blue complex forms, which appears to be a colloidal copper compound; in this form and concentration the copper remains in the active state and does not precipitate from the treatment agent potassium hydroxide.

The copper catalyst can also be added to an intimate reaction mixture of KOH solution and oil be, in which case the oil forms the continuous phase of an emulsion, so that the Copper salt at its introduction is also distributed and in place of an inactive black precipitate forms an active catalyst. In this procedure, the KOH solution with the oil in mixed in a mixer, during or after which a water-soluble copper salt is introduced, oil and treating agents are then transferred to another mixer in which air or oxygen is introduced. However, if desired, the air can be in the oil and the KOH before the addition of the Copper catalyst are introduced, with air, oil, KOH and catalyst always in intimate contact be held until the mercaptans are substantially deposited.

The invention is illustrated by the drawings which form a part of this specification and are shown in FIG

1 shows, in the form of a diagram, a system suitable for carrying out the method;

Figures 2 and 3 are graphical representations of the data representing the results obtained in the process explain.

The following information illustrates the effect of copper catalyst concentration on speed the oxidation of mercaptan and the color of the oil. The oil used in these experiments was one Straight-run West Texas fuel oil with a color of about 17 Saybolt Universal and a Mercapto number of 69. The treatments were carried out at about 27 ° C with air and a volume percent of an aqueous, 55% KOH solution executed. The following results were obtained:

CuCl ₂ -2H ₂ O
Weight percent
in KO H solution Contact time
Minutes Mercaptan
number colour
Saybolt
Universal 0.3
0.2
0.1 6th
8th
10
15th
5
8th
10
15th
5
8th
10
15th 13.1
10.6
9.0
6.4
13.8
9.9
7.4
4.5
13.1
10.3
8.3
3.2 + 13
12th
11
8th
12th
12th
12th
9
12th
12th
12th
9

CuCl ₂ -2H ₂ O
Weight percent
in KO H solution Contact time
Minutes Mercaptan
number colour
Saybolt
Universal 0.05
0.01 8th
10
15th
8th
10
15th 17.3
13.5
10.3
23.7
19.6
13.1 12th
11
9
10
9
7th

The treatment process is explained in more detail with reference to FIG. 1, in which the reaction vessel is labeled A and the KOH concentrator used is labeled B. Separators C and D are provided for more complete removal of the caustic alkali from the oil, and E is a settling tank for removing the wash water from the treated oil. As can be seen from the drawing, the acidic oil is introduced through line 10 and the temperature is raised to a sufficient level by the heater 11, e.g. B. about 32 ° C, set. After flowing through the measuring device 12, the oil reaches the mixer 13, which can be provided with a sieve bottom. The air introduced through line 14 flows through measuring device 15 and is mixed with the oil in mixer 13, the suitable residence time being about 35 seconds. _{If H 2} S is present in the oil fed through line 10, a pre-wash with an alkaline solution, e.g. B. sodium hydroxide or sodium carbonate, be switched on to remove H, S.

Through line 16 an aqueous, 55 ^fl / o KOH solution is introduced into the mixer 13 entering the flow of air and oil. The resulting mixture flows through line 17 to reaction vessel A, where a partial separation of the KOH solution takes place.

Oil and unused air flow through line 18 to air separator 19, from which the air is discharged through line 20. Preferably, the reaction vessel A is pressurized, e.g. B. about 7 at; the pressure through valve 21 is reduced to about 1 atm in order to facilitate the separation of the air in the separator 19. The application of higher pressure increases the rate of oxidation and pressures in the range of 1.75 to 14 atm will suffice. When using oxygen, pressure is usually not required. From the separator 19, the oil flows through line 22 to the separator C, which is filled with glass wool, slag wool, sand, etc., which have a large surface for removing the colloidally suspended KOH solution from the oil. The separator can be a horizontal drum filled with glass wool, which is connected to the settling chamber 23, or it can be a filled vertical drum in which the oil preferably flows from top to bottom through the filling, with a separating chamber at the bottom. Because the demixer causes the KOH to be removed more quickly and more completely, it serves to prevent color development in the presence of the KOH solution.

From the separator C the oil flows through line 24 to the separator D of the second stage. The dwell time of the oil in the separators is best about 5 to 10 minutes. From the separator D , the oil flows through line 25 to the water mixer 26, the water being introduced through line 27 into the oil stream. Mixer 26 is provided with a sieve bottom, but it can be any suitable, effective mechanical

Mixer can be used in its place. The amount of water introduced is best about 5 to 10 per cent of the volume of oil. The water-oil mixture is passed through line 28 to settling tank E , from which the used water is drawn off through line 29. The washed oil flows through line 30 to water separator 31, from which the conditioned oil is withdrawn from the system through line 32. Used water from the separator is drawn off through line 33. If desired, a pre-wash of the oil with water can be included upstream of the mixer 26 for the purpose of recovering the potassium hydroxide dispersed in the oil.

Exhausted KOH is withdrawn from reaction vessel A through line 34 to settling vessel 35, where the potassium cresylates can collect in an upper layer. The separated KOH is withdrawn through line 36 and pump 37 and then flows through line 38 to concentrator B where it is heated by a submerged steam coil 39 to drive off the water that collects in the system, particularly as a by-product of the desulfurization reaction . Usually the concentration in B can be increased from about 51 to 55%. The water separated as vapor is fed through line 40 to compressor 41 and discharged from the system through line 42. The concentrated KOH flows through line 43 to condenser 44 and from there through line 45 to filters 46 for the KOH solution, which remove potassium carbonate and any other insoluble products that may collect in the reagent. The KO solution then flows through line 47 and pump 48 and finally line 16 back to the mixer 13. The refreshed KOH is added to the system through line 49 from time to time as needed. When working with the concentrator B under reduced pressure, e.g. B. about 0.35 at, the temperature can be kept below about 140 ° C, whereby the decomposition of the mercaptides to K ₂ S, which is undesirable because it settles and clogs the system, is largely avoided. the
Education would also require a loss of KOH.

The separated KOH solution is passed from the separators C and D through line 50 to the separating device 35. The cresylate layer from the separating device 35 is passed through line 51 to the separator 52, which can be a storage tank in which the aqueous KOH is able to separate out over a long period of time. This recovered KOH is routed regularly through line 53 to KO H line 36. If desired, the separator 52 can be enabled to raise the temperature of the cresylates, thereby facilitating the separation of the KOH. The precipitated potassium cresylates are discharged from the system through line 54.

The copper solution is introduced through line 55 and pump 56. A 10% solution of copper chloride or sulphate can be used for this purpose. The copper solution serving as a catalyst can be introduced into the system at various points, preferably it is added directly to the hot KOH in the concentrator B. A small amount of the added copper is precipitated from the caustic alkali solution as insoluble copper sulfide, CuS. The treated oil contains a trace of copper, but no more than 1 part per million. The influence of this small amount of copper on the color fastness of the oil can easily be reduced by adding a small amount of a metal deactivator, e.g. B. from 0.001 to 0.01% N, N'-disalicylidene-1,2-diaminopropane, are canceled.

y
K ₂ S - When carrying out the process according to the invention, it is important to keep the temperature in the range from about 27 to 52 ° C. if a product with a satisfactory color is to be obtained. It has been found that higher temperatures promote color formation and that the use of the copper catalyst appears to prevent color formation by directing the oxidation reaction towards the conversion of the mercaptans to disulfides. The cause of the color formation is not fully understood; it must probably be partly attributed to the oxidation of phenolic substances contained in oils with a high concentration of sulfur. This influence is evident from the data shown graphically in FIG. 2, which were obtained by treating an acidic West Texas heating oil with one volume percent KOH solution at 49 ° C. and air at a rate of 0.14 cbm per hour. The upper curve shows rapid color formation, ie decrease in the Saybolt Universal color values as the mercapto number of the oil decreases when it is treated with air and regenerated 55% KOH. The lower curve illustrates the improved results obtained with the same but 0.1 weight percent CuCl
KOH solution were obtained.

It should be emphasized that the highest rate of oxidation was achieved with a copper concentration of about 0.1 to 0.2% CuCl ₂ · 2H ₂ O. It should be further emphasized that the oil obtained under these conditions shows an improved color.

The following data show the influence of the temperature on the implementation, especially with regard to the mercapto number and color. Treatments were carried out using a straight run West Texas fuel oil with a color value of +16 and a 65 mercapto number. The treating agent was a 55% strength aqueous KOH solution containing 0.1% CuCl ₂ · 2H ₂ O, the ratio of solution to oil being 1% by volume. The oil and solution were vigorously stirred in the presence of air. The following results were obtained:

Containing 2 H ₂ O

temperature Mercaptan
number colour
Saybolt Time
Minutes about 27 32 + 9 15th about 38 3.8 + 9 15th about 49 3.5
0
3 + 9
-16
0 5
8th about 65.5 3 about 65.5 (inter
polished)

It is advisable to remove the oil from the caustic alkali solution after a contact time of about 25 to 40 minutes to separate to avoid color formation; it has been found that at over an hour of contact time the Saybolt color value decreased from 16 to 5 and less. One contact time is usually sufficient from 5 to 30 minutes, which largely depends on the temperature.

The ratio of caustic alkali solution to oil can be varied in the range from 1 to 10 or 15 percent by volume although it was found to be about 5 percent by volume in the case of the West Texas crude fuel oil delivered the best results. If only 1% KOH solution is used, the problem is separation The exhausted KOH solution is more difficult to remove from the oil than when using larger volumes of the solution. The effect of segregating the treated oil

Claims (1)

7 8 is especially in the case of a low KOH oil Ver mercaptane number to about one or practically zero Relatively valuable, as reduced from the following table, and process products with a good odor is visible: with a Saybolt color value from 15 to 17 and with With 55% KOH and air in the presence of S ^uter color fastness and excellent burning Copper catalyst treated fuel oil has ⁵ properties. FarbeSaybolt ^ ^{111 before} l ^'s e ^s the process can, of course, z. B. that Universally used caustic alkali subtracted through line 36 and α Untreated oil 17 ^only f ^{r 'scn} recycled caustic alkali solution in the ER- To remove "exhausted KOH heater 5 are introduced; this will cause the precipitation I fisung deposed. ... . 9 ^{lo emes} part of the copper through in the used etching Segregated substances containing 13 alkaline solutions are avoided. It Segregated and washed with water 16 ^{are, however,} further modifications within the framework of Invention possible. The in the subsequent If you get a separator with fresh glass wool or another filler material, the full capacity of copper in the form of an active compound in color removal or an active complex that achieves a colloidal: - working for several hours is obtained. The initial oxide can be. The working span of low performance can be shortened by pre-wetting the demixer patent spray: filling with a strong KOH solution. If ₂₀ 1. A method for removal of mercaptans two demixer are successively used. _from an acidic one, between 160 and 340 ° C, they can be alternately re-charged, especially 177 and 302 ° C, boiling coals are largely attenuated by this unfavorable effect at the beginning - hydrogen distillate without excessive color formation. The distillate was brought into intimate contact with an aqueous caustic alkali. Attempts to use the cheaper NaOH solution instead of KOH in the presence of a copper catalyst for desulphurising fuel oil distillates and these were unsuccessful. Compared to Na O Η solution, caustic alkali solution together with the secondary samples, KOH results in a faster conversion and a product that is sulphurised from the treated oil before the color develops. Which is separated, characterized in that a KOH solution also separates more easily from the oil, while the mixture of distillate is emulsified with 1 to 15 percent by volume of NaOH or, in the heavy oil, 50 to 60% aqueous potassium hydroxide solution and, on which it dissolves and, even in the subsequent aqueous potassium hydroxide solution, 0.004 to 0.1 percent by weight of the wash, is difficult to remove. Copper in the form of an oxidation catalyst. Fig. 3 explains the copper compound with an acidic superior effect of KOH, which is ineffective in comparison to NaOH-dissolving. The aeration 35 substance-containing gas at 27 to 52 ° C in intimate Be time to reduce the mercaptan number is brought to a stir, the catalytic NaOH solution of the same concentration considerably effective copper compound by adding a larger. The aeration time required to reduce the mercap water-soluble copper salt to the potassium hydroxide number from 80 to 60 was approximately 48 minutes before mixing it with the distillate or 25% NaOH and only 40 minutes with a mixture of the potassium hydroxide solution with the distillate KOH solution of the same concentration is generated, whereupon the used potassium hydroxide solution tration. and by-products of the implementation of the treated 3 further shows the effect of the concentration of the distillate separated off on the rate of mercaptan oxidation. 2. The method according to claim 1, characterized in that the oxidation is characterized as a function of 45 that in the reaction mixture of distillate, from the concentration at a certain mercap- 5 to 10 percent by volume of aqueous potassium hydroxide solution and t number cease entirely or at the same Value of the copper compound, with vigorous stirring, air can remain. So 40% KOH remained in one that is passed IV2 to 2 times that of the mercaptan number of about 22, while SOVcige the amount of mercaptan present in the distillate equi-KOH contains a reduction in the mercaptan number to about 7 50 valent oxygen until the Mercap allowed. These data were taken with a West Texas count of the distillate having dropped below about 5. 1 obtained fiz oil, which had a mercapt number of 80. 3. The method of claim 1 or 2. characterized inlet and with air and 1 volume percent caustic solution, the oil was directly by Absannnengebracht 0.1% CuCl ₂ · 2H _S O separation of the potassium hydroxide solution was washed with water contained. The treatment temperature was 29.5 ° C. and the speed of the air supply 0.14 cbm per 4. The method according to claim 1 or 2, characterized Hour. characterized in that the contact time between the smell of the present KOH-air distillate and potassium hydroxide solution is 5 to 60 minutes. Oxidation process treated oil turned out to be 5. Process according to claim 1 or 2, characterized satisfactory for market requirements if the 60 marked that the exhausted, of the beOxydation so far was continued until the mercap-traded distillate separated by potassium hydroxide solution t number was below 5. (The mercapt number is the number of distillation under reduced pressure and at Milligrams of mercaptan sulfur per 100 ecm of oil, which is normal for a temperature not exceeding 150 ° C generated by titration with a standard and then for the treatment of further Copper solution is determined.) When applying 65 quantities of acidic fuel oil distillate is used. about 5 percent by volume of caustic alkali solution (which is 55% ig 6. The method according to claim 1, 2 and 4 for loading and about 0.02 weight percent copper in the form of a treat of acidic hydrocarbon distillates contains active colloidal copper complex, with a high mercaptan sulfur content, thereby gedas But copper as an aqueous copper sulphate solution indicates that the treatment is carried out at pressures up to is performed), based on the treated oil, the 70 to 14 at have been made. 7. The method according to claim 1, 2 or 6, characterized in that the catalytically active Copper compound is a blue, colloidal copper oxide. 8. The method according to claim 1, 2 or 6, characterized in that the catalytically active Copper compound by adding copper sulfate to concentrated potassium hydroxide at one temperature which is high enough, e.g. B. below about 140 ° C to the noticeable formation of avoid black precipitation. Considered publications: U.S. Patent No. 2228 041. 1 sheet of drawings