Mineral oils: processes and products – Refining – Organic acid or phenol contaminant removal
Patent
1997-02-27
2000-05-16
Myers, Helane
Mineral oils: processes and products
Refining
Organic acid or phenol contaminant removal
208189, C10G 1700
Patent
active
060632666
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a process for removing essentially naphthenic acids from a hydrocarbon oil, more specifically from a crude oil which has not previously been distilled into fractions, or from a crude oil in which only a naphtha fraction has been distilled.
It is well known that crude oil and crude oil fractions contain sulphur compounds, nitrogen compounds and other undesired compounds, and a large number of processes have been proposed for removing such compounds from crude oil fractions. Catalytic hydrogenation is a very commonly used method for removing i.a. sulphur and nitrogen content. Such hydrogenations of naphtha fractions are typically carried out at pressures of e.g. 10 to 30 bars and temperatures of 250 to 350.degree. C., whereas corresponding treatments of distillates are carried out at pressures of 20 to 80 bars and temperatures of 270.degree. C. to 400.degree. C., and treatments of residue oils are carried out at pressures of 100 to 150 bars and temperatures of 300.degree. C. to 450.degree. C. Such hydrogenation treatments also remove any naphthenic acids contained in the hydrocarbon fraction. The term naphthenic acids is used herein as a common designation for naphthenic, aromatic and paraffinic carboxylic acids.
It may often be strongly desired to remove particularly naphthenic acids from hydrocarbon oils, because they have a strong corrosive action on the process equipment. For that reason it would be desirable to eliminate the naphthenic acids as early as possible in the oil refining process.
It is has now been discovered that it is possible to carry out such removal of the naphthenic acids from a non-fractioned or only topped crude oil by a selective hydrogenation of the naphthenic acids under very mild conditions. Under such mild conditions, any substantial amount of desulphuration reactions, denitrification reactions and reactions leading to saturation of aromatics, is avoided, which results in a moderate hydrogen consumption.
Thus, the invention provides a process for removing essentially naphthenic acids from a hydrocarbon oil, in which process the hydrocarbon oil is hydrogenated at an elevated temperature over a catalyst of the kind used for hydrogenation of atmospheric residue oils, preferably a catalyst consisting of nickel-molybdenum or cobalt-molybdenum, deposited on alumina as a carrier material. The process is characterized by there being used as hydrocarbon oil: C. to 300.degree. C.
In both embodiments of the process of the invention it is preferred to carry out the hydrogenation at 20 to 30 bars and at a temperature of 200.degree. C. to 250.degree. C.
The hydrogenation is suitably effected in one or more parallel reactors having a fixed catalyst bed. As mentioned, the catalysts utilized in the process of the invention are such catalysts which have proved to be suitable for hydrogenation of atmospheric residue oils. It is important for a successful carrying out of the process that the carrier material of the catalyst is sufficiently porous to allow penetration of even the heaviest part of the crude oil into the catalyst pores. Therefore, the carrier material should have a porosity such that the final supported catalyst preferably has a porosity of the magnitude 10 to 12 nanometers (nm). Particularly useful catalysts comprise nickel-molybdenum or cobalt-molybdenum deposited on alumina as a carrier material. The oil flow through the catalyst is preferably 0.5 to 5.0 m.sup.3 oil per m.sup.3 catalyst per hour, most preferred 1.0 to 3.0 m.sup.3 oil per m.sup.3 catalyst per hour.
As a pretreatment of the crude oil it may be advantageous to carry out a conventional desalting of the crude oil with water.
The process of the invention allows a selective reduction of the content of naphthenic acids in the crude oil to less than about 5 to 6%, without simultaneous hydrogenation of sulphur compounds and nitrogen compounds which may be present. Concurrently with a strong reduction of the content of naphthenic acids, a certain reduction of the metal content in the crude oil
REFERENCES:
patent: 2921023 (1960-01-01), Holm
Grande Knut
Sorlie Carsten
Den norske stats oljeseskap a.s.
Myers Helane
LandOfFree
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