JPH04220492A - Preparation of white mineral oil of food grade quality - Google Patents

Abstract

The production of food grade quality white mineral oils from predominantly naphthenic or cycloparaffinic crude distillates heretofore have required acid treating using sulfuric acid followed by neutralization, water wash and possibly finishing step. Herein, however, three stages of hydroprocessing without any solvent extraction or acid treatment prior step are employed to produce the desired food grade quality white mineral oil having a trace of aromatic constituents therewithin. Specific steps are defined in the application in terms of the severity of the hydrogenation in the hydrotreating operation at each respective step; as well as the steps of separating gaseous constituents of the hydroprocessing product.

Description

[Detailed description of the invention]

001

FIELD OF THE INVENTION This invention relates to a process for producing white mineral oil of food grade quality. More particularly, the present invention relates to a process for producing white food grade mineral oil containing only trace amounts of aromatic hydrocarbons from naphthenic distillates as a feedstock.

002]

BACKGROUND OF THE INVENTION The prior art is replete with various references regarding methods of treating hydrocarbons. These range from techniques used during the Great Depression to modern hydrocarbon processing methods.

[003] There is an almost equal number of publications on the use of hydrogen in hydrogenation and hydroprocessing aspects. Two books published shortly after World War II, E. We
"The Text of Organic Chemistry" by rtheim
book of organic chemistry
), 2nd edition, Blakiston
Company), Philadelphia, Pennsylvania, 1947 and Unit Reactions in Organic Synthesis (
Unit Processes in Organic
Synthesis), edited by Groggins,
A3 edition, McGraw Hill
), New York, New York, 1947. As pointed out in these books, careful management of hydrogenation can give good results. This application contemplates the use of such careful management.

[004] The prior art has devised many methods to obtain food-grade quality white mineral oil, but they are always expensive and require acid treatment, neutralization, and removal of undesirable components to produce the final product. This method used an adsorption tower to obtain .

In particular, the prior art provides an economical way to produce food-grade quality white mineral oil without expensive and labor-intensive steps such as acid treatment, neutralization and adsorption of unwanted components from the product. I was unable to provide a specific method.

006]

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an economical method for producing food grade white mineral oil without going through the labor intensive processes of the prior art.

A particular object of the present invention is to provide an economical continuous flow process for producing food grade white mineral oil without going through the labor intensive processes of the prior art. These and other objects will become apparent upon consideration of the following description, and in particular upon reference to the accompanying drawings.

008

[Means for Solving the Problems] According to one aspect of the present invention,
Subjecting a naphthenic or cycloparaffinic feedstock to a three-step hydrotreatment without prior solvent extraction or acid treatment to obtain a desired final quality containing only trace amounts of aromatic hydrocarbons or aromatic carbon. A method is provided for producing food grade quality white mineral oil comprising:

According to another aspect of the invention, the naphthenic feedstock is first hydrogenated, the gaseous components formed during this hydrogenation reaction are separated, and then subjected to a second stage of hydrogen treatment or hydrogenation. , a method is provided in which the gaseous components produced by this second stage of hydrogenation are separated and then subjected to a third, less severe hydrotreatment step to produce the desired food grade white mineral oil.

The specific reaction conditions for each step will be described below.

FIG. 1 shows a conventional method for producing food grade white mineral oil. Here, the naphthenic distillate is extracted using a solvent such as phenol or N-methylpyrrolidine to produce a hydrocarbon oil containing about 4-7% aromatic carbon, which is then subjected to acid treatment. The bottoms fraction recovered from the acid treatment is then discharged as acid sludge, whereas the
The solvent extract containing a high concentration of aromatics from the stage solvent extraction is recovered as a bottom product. After acid treatment, the hydrocarbon oil containing traces of aromatic carbon or aromatic hydrocarbons enters line 15 leading from the acid treatment unit. A finishing step consisting of an adsorption tower 17 using clay or a hydrotreating tower 17 using hydrogen is used to reduce any remaining trace aromatic hydrocarbons and produce a satisfactory food grade white mineral oil in the outflow line 19. let

In contrast, the method of the present invention uses 15-
A naphthenic distillate containing aromatic carbon at a concentration of 25% by weight is hydrogenated to produce a hydrogenated product (in this case,
about 50-70% aromatic hydrocarbons are reduced resulting in an aromatic carbon content of 7-10% by weight). This is shown in FIG. 2, also labeled column 21 in stage 1. The term "naphthenic distillate" is synonymous with cycloparaffinic distillate. Typically, these distillates contain about 15-25% by weight aromatic carbon. These naphthenic distillates enter through line 23 in FIG. Hydrogen is shown in Figure 2
is supplied through line 25. Both feed components are mixed before entering stage 1, in the presence of a hydrogenation catalyst comprising a Group VIIIA metal component (preferably nickel) and a Group VIA metal component (preferably molybdenum). 550-750°F (preferably about 650-7
1200-2000 pounds per square inch gauge (psig) (preferably about 1500-18
Hydrogenation is carried out at a hydrogen partial pressure of 0.00 lb/in2 gauge). The hydrogenation product is then transferred to line 27
Leave Tower 21 through.

As a next step, the gaseous component of the hydrogenated product in line 27 is separated from the liquid component and passed through the overhead line 29.
flows out from The overhead line 29 carries away from the stripper 31 the gaseous products of the hydrogenation reaction carried out in the hydrogenation column designated 21 of stage 1, inter alia hydrogen sulfide and ammonia. After this process, the aromatic carbon content of the liquid component will be reduced to about 7-10% aromatic carbon in the liquid bottoms draw from the stripper in line 33. These liquid bottoms, which contain about half or less of the aromatic carbon of the initial feed in line 23, are then sent through line 35 to a second hydrogenation column 37. This liquid bottoms in line 35, the hydrogenation product from the first stage, is mixed with hydrogen through line 39. The second hydrogenation is carried out in the presence of a hydrogenation catalyst comprising a Group VIIIA metal component (preferably nickel) and a Group VIA metal component (preferably molybdenum).
0-3000 psig (preferably 2750-3000
psig) and a temperature of 575-750°F (preferably about 625-700°F). The entire reactor effluent then exits line 41 and enters stripper 43;
Again, the gaseous component of the reaction product of the second hydrogenation stage is separated from the liquid component and exits the second stripper 47 through line 45. These gaseous components include hydrogen sulfide and ammonia, among others. In line 49,
The liquid bottoms obtained from stripper 43 contain only about 1% aromatic carbon, and they are sent by line 51 and mixed with hydrogen in line 53 for final hydrogenation step 3. The less severe final hydrogenation of stage 3 is carried out in the hydrogenation column 55.

In the final step, the relatively less severe hydrogenation of stage 3, carried out in the third hydrogenation column, ie hydrotreating column 55, is carried out using a Group VIIIA metal component such as platinum, palladium or nickel (preferably at a hydrogen partial pressure of 2000-3000 psig (preferably 2500-3000 psig) and about 375-600°F (preferably 450- 550°F)
carried out at a temperature of

In all of these reactions, the use of relatively high hydrogen partial pressures and relatively low temperatures facilitates carrying out the hydrogenation without excessive cracking of the liquid stream to undesirable low boiling range materials. It is noteworthy that the aromatic content of the liquid stream provides a reduced desired reaction product.

In the illustrated embodiment, the liquid bottoms oil in line 57 contains only about 0.3% by weight or less aromatics, and this trace amount of aromatic hydrocarbons is food grade. It would be satisfactory as a white mineral oil. In particular, polynuclear aromatic hydrocarbons will account for less than 30 ppm of the final food grade white mineral oil.

During operation, the initial feedstock, naphthenic distillate, is fed and mixed with the desired partial pressure of incoming hydrogen to effect hydrogenation in stage 1. Similarly, the gas component is separated from the liquid component in the stripper, thereby causing the gas to exit as an overhead stream in line 29 and the bottoms to exit as a liquid stream 33 in line 3 of FIG.
5 to the second stage, that is, the hydrogen treatment tower 37. Again, the mixing of high partial pressure hydrogen with the liquid component causes a direct reaction at high temperature with a suitable catalyst, resulting in a reduction of aromatic carbon in line 41. After separating the gaseous components and discharging them to the overhead line 45, the liquid bottom oil 49 is
Although its aromatic carbon is reduced, the third hydrogenation stage 5
5. At the inlet of the third stage, it is mixed with hydrogen at the desired high partial pressure and the hydrogenation reaction is carried out in the third hydrotreating column 55. The result is that the final product exits the bottoms effluent line 57.

From the foregoing, it can be seen that the desired white mineral oil of food grade quality is produced in line 57 by a method that is substantially different from conventional production techniques for food grade white mineral oil.

Although the invention has been described in some detail, this description is merely exemplary and without departing from the spirit and scope of the invention (for which purpose, please refer to the claims). It will be understood that combinations and rearrangements of the parts are possible.

[Brief explanation of the drawing]

FIG. 1 is a flow diagram showing a conventional method for producing food grade white mineral oil.

FIG. 2 is a flow diagram showing the method for producing food grade white mineral oil of the present invention.

[Explanation of symbols]

17 Adsorption tower 21 Hydrogenation tower 23 Naphthenic distillate supply line 25, 39, 53 Hydrogen supply line 31, 43 Stripper 37 Second hydrogenation tower 55 Third hydrogenation tower 57 Bottom effluent line

Claims (9)

[Claims] 1. A process for producing white mineral oil of food grade quality comprising the steps of subjecting a naphthenic feedstock to continuous and progressive three-step hydrotreatment without solvent extraction or acid treatment. [Claim 2] Next step: a. subjecting the naphthenic feedstock to a first stage hydrotreatment to reduce the aromatic carbon content by about 50% without solvent extraction or acid treatment; b. separating gaseous components from the hydrogenated liquid product of step a; c. The product from step b, from which the gaseous components have been separated, is transferred to a second
reducing the aromatic carbon content to about 1% by subjecting it to a hydrogenation step; d. separating the gaseous product components of the hydrogenation product of step c; and e. Finally, subjecting said liquid, separated from its gaseous components, to a relatively less severe final hydrotreating step to produce a food-grade white mineral oil containing only trace amounts of aromatic hydrocarbons; How to make quality white mineral oil. [Claim 3] Next step: a. Hydrogenating a naphthenic, i.e. cycloparaffinic, distillate containing aromatic carbon in a concentration of 15-25% by weight to produce a hydrogenated product, the concentration of aromatic carbon being reduced by about 50%; b. separating the gaseous component of the hydrogenated product as overhead to produce a liquid bottoms oil containing about 1/2 of said concentration of aromatic carbon on a weight percent concentration; c.
After separating the gaseous components, the liquid oil drawn from the bottom of the column is transferred to a second
producing a second hydrogenation product through a hydrogenation step, wherein the concentration of aromatic carbon is reduced to about 1% of the liquid content; d. separating the gaseous component of the second hydrogenated product as overhead to produce a second liquid bottoms stream containing about 1% aromatic carbon; and e. Finally, subjecting said second liquid bottoms stream to a relatively less severe final hydrotreating step to produce a food-grade white mineral oil containing only trace amounts of aromatic hydrocarbons; How to make quality white mineral oil. 4. The first hydrogenation is carried out using a nickel molybdenum catalyst in a first hydrotreating column, and the gaseous components of the hydrotreated product include hydrogen sulfide and ammonia, and these gaseous components are 4. The method of claim 3, wherein the hydrogenation product effluent from the first column is separated by sending it to a stripper column apparatus. 5. The first hydrogenation is 1500-18
4. The process of claim 3, carried out at a hydrogen partial pressure in the range of 00 psig (pounds per square inch gauge) and a temperature in the range of 650-700<0>F. 6. The second hydrogenation is carried out in a second hydrogen treatment column using a nickel molybdenum catalyst,
4. The gaseous components of the hydrotreated product include hydrogen sulfide and ammonia, and wherein these gaseous components are separated by sending the second hydrotreated effluent from the second hydrotreated column to a second stripper column arrangement. Method 3. 7. The hydrogen partial pressure is 2750-3000p.
sig range, and the temperature is 625-700
7. The method of claim 6, wherein the range is .degree. 8. The process of claim 3, wherein said less severe final hydrogenation is carried out in a third hydrotreating column in the presence of a platinum reforming catalyst. 9. The relatively less severe final hydrogenation is conducted at a hydrogen partial pressure in the range of 2500-3000 psig and a temperature in the range of 450-550°F.
the method of.