US2079035A - Process of refining petroleum - Google Patents

Description

Patented May 4, 1937 UNITED STATES PATENT OFFICE PROCESS OF REFINING PETROLEUIVI No Drawing.

Application September 10, 1935,

Serial No. 39,938

8' Claims.

This invention relates to the refining of petro- :leum, and has-to do particularly with the refining of the relatively viscous petroleum fractions to produce lubricating oil of good quality.

IOne object of the invention is to provide a process. of refining petroleum lubricant stocks which is applicable generally to the treatment of any petroleum lubricant stock, including crude petroleumdistillation residuessuch as long residuum or heavier residues, and in general any petroleum lubricant oil stock which contains fractions of good lubricating oil value but which also contains asphaltic matter and/or wax and naphthenic substances, to produce therefrom a refined lubricating oil of high quality having highviscosity index, low carbon residue, and desired pour point.

It is a further object of the invention to provide a new solvent refining agent for extracting naphthenic substances and a process for refining petroleum stocks by means of this agent, this solvent refining process being applicable to pctroleum lubricant oil stocks generally but being 1 preferably used in the refining of stocks which already have been treated to remove wax or asphaltic matter, or both,

Viscosity index is ainumerical index, referred to an arbitrary scale, as proposed by Dean and Davis, Chemical and Metallurgical Engineering, 36-618 (1929), and refers to the rate at which the viscosity of the oil decreases with increase in temperature. Pennsylvania base lubricants of present manufacture have a viscosity index of around 95 to 100, coastal naphthenic base lubricants have viscosity indices of about to 20, and various. Mid-Continent mixed base lubricants range in between these values. It is possible for the viscosity index to be numerically less than 0 or more than 100. The higher index numbers indicate a greater resistance to loss of viscosity with rise of temperature. In the present terminology of the art, the rapidly thinning constituents are spoken of as naphthenic, and the more slowly thinning constituents are spoken of as parafiinic. In this sense only, and not in a rigorous chemical sense, the terms naphthenic and paraffinic are used herein.

The viscosity-gravity constant, proposed by Hill and Coates, Ind. & Eng. Chem. 1928, page 641 is also a valuable indication of the paraifinic nature of an oil fraction as v-g-c value indicates increasing freedom from constituents highly naphthenic with decrease in numerical value of the constant. The v-g-c or viscosity-gravityconstant for present day lubricants of Pennsylvania origin is around 0.800 to 0.830 with lubricants from other sources ranging up to 0.900.

Carbon residue is the amount of weighed resi due left when a given weight of oil is burned 'under certain specified conditions fully set forth in Bureau of Mines Technical Paper 323B, Method 500.12, commonly knownas the Conradson carbon residue test. The result is expressed in per cent of residue and is indicative of carbonforming and decomposition tendencies of the oil when heated, an oil having a lower percentage of residue being one more able to endure under conditions of field performance.

Pour point, as referred to herein, shall mean,

cially directed to the use of a particular solvent of that general class.

This invention has for an object the use of is used to extract naphthenic constituents of low, viscosity index; etc., from the oil, and is espe benzylamine as a solvent refining reagent capable of improving lubricating oils by separating from the petroleum lubricant stock constituents having undesirable characteristics; e. g. naphthenic substituents. Benzylamine is the amine corresponding with benzyl alcohol, having the structural formula Zia.

That is, it is a primary amine with the amine group in the side chain. Chemically, it partakes more of the nature of methylamine than of that of aniline. This compound has been found to be possessed of a particularly high solvent power when used in the treatment of oils, which makes it particularly suitable for treating stocks of a more highly parafiinic nature, such as from Mid- Continent stocks and Pennsylvania stocks. The boiling point of the compound is 184 C., which is sufliciently low to permit of its efiicient removal from the oil.

The treatment oi petroleum lubricant oil stock,

containing both parafiinic and naphthenic con-,

stituents, with the solvent (benzylamine) comprises intimately mixing the petroleum stock and the benzylamine. I have found that the benzylamine extracts or dissolves out naphthenic constituents from the petroleum stock undergoing treatment, and must be used in relative proportion sufficient to effect the removal of such constituents. The benzylamine must be used in proportions suflicient to establish two liquid phases; viz., a solvent phase consisting mainly of benzylamine and containing the extracted naphthenic substances and an oily phase consisting mainly of the oil and containing some benzylamine. The extraction of the petroleum stock with the benzylamine, as just described, can be eifected either in batch or continuous operation as desired. After the extraction is complete, the two phases, which consist of two superimposed liquid layers, are separated by drawing off the layers separately. Solvent may be recovered from the solvent layer by distillation and traces of solvent may be removed from the oily phase, as for instance by treatment with finely divided clay, to produce refined lubricating oil.

As an example of the eificacy of benzylamine as a refining agent for petroleum lubricating oil stock the following example is presented in which one volume of adewaxed and deasphaltized residuum from Mid-Continent crude was treated at 20 F. with five volumes of benzylamine in a The above results indicate a very substantial improvement in viscosity index and carbon residue, and may be taken as typical of the capabilitles of this solvent refining reagent on oils of a high parafiinic nature, as it will be noted that the oil treated had already been deasphaltized.

A satisfactory degree of improvement can be obtained ordinarily by treatment of one volume of oil with from one to seven and preferably from three to five volumes of benzylamine. The temperature of the solvent refining operation will ordinarily range from about 20 F. or 30 F. to 125 F., depending upon the stock which is treated, preferably between about 50 F. and 100 F.

I have found that benzylamine can readily and conveniently be employed to produce refined lubricating oils of especially high viscosity index as compared with the viscosity index which can readily be obtained by certain solvent refining agents of the prior art, for example, I have obtained by single batch extraction a dewaxed and deasphalted residuum from Mid-Continent crude with benzylamine a refined lubricating oil having a viscosity index of practically 100, while similar extraction of the same stock with many of the solvents commonly used commercially will produce refined oils of considerably lower viscosity indices. Also I have found that benzylamine is possessed of a relatively high solvent power which renders it capable of effective use on stocks in which the so-called naphthenic constituents of low viscosity index are present in relatively less amount.

As an example of the effectiveness of benzylamine when applied to stocks already highly parafiinic, I may cite the following example, in

which this solvent was applied to a Bradford long residuum:

Bradford (Pa) long residuum Gravity S. U. V. Carbon A. P. I. 210 F. residue Dewaxed residuum 27. 4 76. 2 0. 816 1.6 Same after batch extraction with 5 vols. benzylamine at F 29. 1 95. l 0. 798 1.0

two liquid phases; viz., a solvent phase consisting mainly of benzylamine andan oilyphase consisting mainly of the parafiinic part of oil and containing some benzylamine, removing the oily phase from the solvent phase, and removing the remainder of the benzylamine from the oily phase to obtain a refined lubricating oil.

2. The method of refining petroleum lubricant oil stock containing naphthenic substances which comprises extracting the said stock with liquid benzylamine to separate naphthenic substances therefrom, separating benzylamine and extracted matter from the said stock, and freeing the remaining oil of such benzylamine as it may contain to produce a refined lubricating oil.

3. The method of refining petroleum lubricant oil stock containing naphthenic constituents which comprises intimately mixing the oil stock with an agent comprising benzylamine in suflicient proportion relative to the stock to produce two phases, namely, a solvent phase consisting mainly of solvent and extracted naphthenic substances and an oily phase consisting mainly of the oil and containing some benzylamine, separating the two phases, and removing solvent from the oily phase to obtain a refined lubricating oil.

4. The method of refining petroleum lubricant oil stock to remove naphthenic constituents therefrom which comprises treating the petroleum stock with benzylamine at temperatures of from 20 F. to 125 F. and in the proportion of from one to seven volumes of benzylamine to one volume of stock, thereby producing two liquid phases, separating the respective phases, and removing the refined lubricating oil from the phase which contains same.

5. The method of refining petroleum lubricant oil stock containing naphthenic constituents to remove said naphthenic constituents therefrom which comprises the steps of intimately admixing the oil stock with benzylamine at a temperature of from 50 F. to F. and in the relative proportions of from three to five volumes of benzylamine to one volume of oil sufiicient to produce two liquid phases, namely a solvent phase consisting mainly of benzylamine and extracted naphthenic substances and an oily phase consisting mainly of the oil and containing benzylamine, removing the oily phase from the solvent phase, recovering benzylamine from the solvent phase and from the oily phase recovering lubricating oil having a viscosity index not substantially lower than the general order of 100 and carbon residue not greater than 1.0.

6. A process for separating mineral oil containing parafiinic and non-parafiinic fractions therein from the raflinate phase containing the into more paraffinic and less paraffinic fractions undissolved fractions and separating the benzylwhich comprises commingling said oil with benamine from said fractions.

zylamine to cause phase separation and separat- 8. A process for the separation of oil into frac- 5 ing the benzylamine and dissolved fractions from tions which comprises commingling said oil with 5 the remaining undissolved more paraffinic fracbenzylamine below the temperature of complete tions. miscibility to cause separation of extract and 7. A process for separating oil into fractions raflinate phases, and separating the extract phase which comprises commingling said oil with bencontaining benzylamine and oil fractions dis- 10 zylamine to cause separation of rafiinate and exsolved therein from the raffinate phase contain- 10 tract phases, separating the extract phase coning the undissolved fractions. taining benzylamine and oil fractions dissolved THEODOR A. PE'I'RY.