FR2588266A1 - Improved process for sweetening petroleum cuts in a stationary bed - Google Patents

Abstract

Process for sweetening a hydrocarbon feedstock containing sulphur-containing products. The invention is characterised by the use of a supported catalyst treated with an anhydrous alcoholic solution containing an alkaline agent, the catalyst being based on a chelate of formula ML or M(LH2)X2 where M is a transition metal, X an anion and L originates from a tetradentate ligand based on a picolinic acid diamide or on one of its derivatives.

Description

The present invention relates to the softening, preferably in a fixed bed, of hydrocarbon feeds containing malodorous and corrosive sulfur products. In particular, it relates to the oxidation of mercaptans to disulphides by air in the presence of at least one catalyst based on at least one organo-metallic complex of particular nature deposited on support and operating under anhydrous conditions; the process according to the invention makes it possible in particular to avoid the conventional alkaline rejuvenation of the catalysts in the mercaptan oxidation reactions or at least to space considerably over time such alkaline rejuvinations.

The great application which is made industrially of the property possessed by the chelates of certain transition metals such as copper, cobalt, vanadium and nickel, is known to catalyze the conversion of mercaptans to disulfides in the presence of atmospheric oxygen. . This property is used, for example in the presence of sulfonated cobalt phthalocyanine, to soften, in the aqueous-alkaline liquid phase, liquefied gases, natural or cracked gasolines, naphthas, or solvents of any composition. such a method is described for example in US Patents. 2,966,453, US 2,882,224,
No. 2,988,500, according to which the alkaline solution containing, for example, a sulphonated cobalt phthalocyanine as catalyst, serves to extract the mercaptans from the fuel and to oxidise them to disulfides by means of an aqueous phase.

It is also possible to carry out this softening by using an oxidation catalyst attached to a support that is insoluble in sodium hydroxide and hydrocarbons. Such a process is described, for example, in French Patents 1,301,844 or US 2,988,500, according to which the hydrocarbon feedstock is brought into contact with a fixed bed of cobalt phthalocyanine on activated carbon, in the presence of air and a reagent. aqueous-alkaline.

Although these processes are widely used in the petroleum refining industry, they have the major disadvantage of consuming large amounts of aqueous soda solution which is found polluted during the softening operation by various products such as naphthenic acids, phenols, hydrogen sulphide, nitrogen products, etc. Recycling these polluted soda solutions is a difficult operation, and their removal poses ecological problems for the environment.

Another drawback related to the use of such processes is the rapid deactivation of the catalyst, which is compensated by frequent rejuvenations to the aqueous sodium hydroxide, and, less frequently, regeneration by washing with hot water allowing lead alkaline naphtenates and phenates which poison the catalyst. This is described, for example, in US Patents 3,148,156 and US 4,009,120. This rapid deactivation can be remedied by the use of activators such as nitrogenous bases (US Patents 4,100,057, US 4,168,245) or quaternary ammonium salts (US Patents 4,159,964, US 4,124,493, US Pat. US 4.1z397,
US 4,157,312 and US 4,206,079), but the use of these rozy activators found in the softened fillers strains the economy of these processes.

Another disadvantage of the use of such processes is related to the need to separate, at the outlet of the softening reactor, the hydrocarbon feedstock from the aqueous soda activating solution. It is also necessary to dry the softened load on a salt filter in order to minimize the water content in the hydrocarbons, and to eliminate the risk of settling in tanks and freezing in cold weather.

The catalyst used in the present invention leads to a procedure which avoids the above-mentioned disadvantages by considerably increasing the activity and stability of the supported softening catalysts.

This procedure consists, for example a) - to impregnate the metal chelate supported in an alcoholic medium
substantially anhydrous non-aqueous containing at least one alkaline agent,
or to post-treat the supported catalyst - with an alkaline solution
at least one alcohol.

b) - to percolate the charge containing the mercaptans on the catalyst
supported in the presence of air, as long as the mercaptans content
the reactor outlet did not reach the maximum value of the specified
cation required (usually 5 ppm for essences and 10 ppm
for kerosenes) and optionally subsequently, c) - to proceed with the regeneration of the supported catalyst by washing
with hot water or steam to remove impurities
accumulated on the support, then to reactivate the supported catalyst
thus washed with an alkaline solution of at least one alcohol.

The charge is then percolated again in the presence of air on the catalyst thus regenerated.

Such a procedure makes it possible to avoid the use of aqueous solutions of sodium hydroxide to reactivate the catalyst 9 and thus to eliminate the settling and drying operations related to the use of such aqueous sodium hydroxide solutions. It also makes it possible to reduce considerably
alkali consumption of the process, and thereby eliminate the problems of disposal and recycling of aqueous solutions of soda.

The chelate used in the present invention has the formula ML or M (LH2) X2 where M is a transition metal, X an anion, L from a tetradentate [LH2] ligand based on a diamine of picolinic acid or one of its derivatives substituted with compounds having at least two primary amine functions separated from each other by at least two carbon atoms.

dans laquelle R' et R", identiques ou différents représentent chacun un ou plusieurs atomes d'hydrogène ou groupes alkyle, aryle, aralkyle, alkylaryle comprenant de 1 à 20 atomes de carbone, ou des substituants halogène, amines, nitro, carboxylates, sulfonates situés sur l'une ou plusieurs des positions 3, 4 5 ou 6 du noyau pyridine.The diamides of picolinic acid or of one of its derivatives substituted with compounds having at least two primary amine functions separated from one another by at least two carbon atoms, thus constitute a tetradentate ligand FLH2J of general formula:

in which R 'and R ", which are identical or different, each represent one or more hydrogen atoms or alkyl, aryl, aralkyl or alkylaryl groups comprising from 1 to 20 carbon atoms, or halogen, amine, nitro, carboxylate or sulphonate substituents; located on one or more of the 3, 4 or 5 positions of the pyridine ring.

In this formula, R is a radical containing at least two carbon atoms chosen, for example, from one of the following groups - CH 2 -CH 2 -CH 2 -CH 2 -NH-CH 2 -CH 2 -CH 2 -CH 2 -CH 2

R1 = alkyl, aryl, NO2, halogen, NH2
SO3H, COOH ...

R2 R2 = alkyl, aryl, NO2, halogen, NH2,
SO3H, COOH ...

The tetradentate ligands of formula LH2 can be prepared by reacting two equivalents of the picolinic acid chloride or ester with a corresponding diamine equivalent, or, as described in the article by DJ BARNES, RL CHAPMAN, RS. VAGG and E. C. WALTON in Journal of Chemical and Engeneering Data, 1978, Vol. 23, p. 349, by reaction of picolinic acid with diamine in the presence of triphenylphosphite.

The chelates in question therefore have the formula ML or M (LH 2) X 2 in which M represents a transition metal (cobalt, copper, nickel, iron, manganese) and X an anion preferably halogen or halide, carboxylate, sulfate, nitrate, carbonate, acetylacetonate, etc ... They can be prepared directly by reaction of the metal salt with the tetradentate ligand LH2, for example according to the method described by RL CHAPMAN and RS VAGG in Inorganica Chimica Acta, 1979, Vol. 33, p. 227.

Nonlimiting examples of complexes that are particularly active for the softening of petroleum fractions include:
Co (BPB), Co (BPBH2) C12, Co (BPBH2) (OCOCH3) 2, Cu (BPB), Cu (BPBH2) C12,
Ni (BPB), Ni (BPBH 2) C 12, Fe (BPBH 2) C 13 where BPBH 2 represents the tetradentate ligand N, N'-bis (2'-pyridinecarboxamide) -1,2-benzene and BPB the same ligand in deprotonated form, the Cu (BPEN), Cu (BPENH 2) C 12 complexes
Co (BPENH 2) C 12, Fe (BPENH 2) Cl 2 where BPENH 2 represents the tetradentate N, N'-bis (2'-pyridine carboxamide) -1,2 ethane ligand, as well as the Co (DNAPH 2) C 12, Cu (DNAPH 2) complexes C12 and Mn (DPNAPH2) where DPNAPH2 represents the tetradentate ligand N, N '(dipicolyl) -1,8 naphthalenediamine.The complex Co (BPB) can be in the form Co (BPB) nL' where L 'is water or pyridine or any molecule of a complexed solvent used, n being equal for example to 1 or 2. Similarly, by way of examples,
Co (BPBH2) C12 can be in the form Co (BPBH2) C12, nH2O and Cu (BPBH2) C12 be present in the form Cu (BPBH2) C12, nH2O or
Ni (BPBH2) C12 be in the form Ni (BPBH2) C12, 2H2O or Cu (BPEN) be in the form Cu (BPEN) H2O etc.

The activation procedure according to the invention consists of impregnating the solid support with an alkaline metal chelate solution, or of post-treating a traditional supported catalyst with an alkaline solution of alcohol.

As the solid support of the chelates or complexes which can be used in the present invention, it is possible to use activated carbon preferably, but also any other suitable solid support such as silicas, aluminas, silica-aluminas, alumino silicates, zeolites, Activated earths are cation exchange resins, among which are exemplified Amberlite A.15 (RSO3H) or IRCSO (R-COOH).

The alcoholic alkaline activation solution may contain a base such as, for example, sodium hydroxide, potassium hydroxide, lithium hydroxide, ammonia dissolved in a primary or secondary alcohol such as, for example, ethanol, n-propanol, isopropanol, normal or branched butanols, pentanols, hexanols, ethyl-2-hexanol.

The impregnation temperature is between 20 and BOOC, preferably between 20 and 500C. The catalyst and its support impregnated with the alkaline alcohol chelate solution has an alkaline temperature of between 0.1 and 10% by weight, preferably between 1 and 5% by weight.

The softening is carried out by percolation of the petroleum fraction in the presence of oxygen or air on a fixed catalytic support bed containing, in supported form, the metal complex according to the invention.

No addition of alkali such as aqueous sodium hydroxide, potassium hydroxide or ammonia
is necessary after the impregnation or activation of the catalytic
supported by an alcoholic solution of alkali. The present process
thus allows, advantageously compared to conventional methods
avoid the use of a clarifier, a salt filter and a pump
with sodium hydroxide or any other alkaline compound.

In carrying out the softening reaction, the reaction temperature is not critical. It can be operated at room temperature, but it is also possible to operate at higher temperatures, without exceeding temperatures of the order of 120 C. On the other hand, the pressure required is generally between about 0.5 and 50 bar, and preferably between 1 and 30 bar approximately.

Air is the most appropriate oxidizing agent. Any other oxidizing agent such as oxygen in the pure state, is also usable, as well as any other gas or mixture of gases containing oxygen. The latter can be introduced into the reactor in stoichiometric quantities.

It is sometimes better to use it in excess.

When the softened charge at the outlet of the reactor has a mercaptan content exceeding that required by the specifications, the catalyst is regenerated by first washing with hot water (washing temperature between 60 and 1000C) or with water vapor, until colorless effluents are obtained, in order to rid the catalyst of the accumulated impurities contained in the charge. The catalyst thus washed is then re-impregnated with an alcoholic solution of alkali.

The following examples illustrate in a nonlimiting manner the implementation of the method according to the present invention.

Example 1 (comparative)
A cobalt complex is prepared by reacting cobalt acetate with N, N'-bis (2-pyridinecarboxamide) -1,2 benzene (BPBH2) in aqueous phase according to the method described by RL CHAPMAN and RSVAGG inorganica Chimica Acta , 1979, vol 33 p. 227. The complex obtained
Co (BPB) is dissolved in 90% ethanol and then drilled on activated charcoal.

The supported carbon catalyst thus obtained contains about 0.5% by weight of cobalt.

The charge to be softened is placed in a tank which feeds the reactor with an additional air. The reaction operating conditions are as follows: catalyst volume = 20 cm 3 - pressure = 1 atmosphere - temperature = 200 ° C. - hourly space velocity of the feedstock (VVH = 1 I / 1 catalyst / hour.

Once treated in the reactor, the effluent is separated from the air it contains in a separator. A residual mecaptan dosage is then carried out qualitatively by a "doctor test" (sodium lead and sulfur flower) and quantitatively by potentiometry every 24 hours.

The charge to be softened consists of kerosene (160-3000 ° C) containing 700 ppm of total sulfur and 150 ppm of mercaptan sulfur It is percolated in the presence of air directly on the supported catalyst not prepreged with sodium hydroxide.

The mercaptan content of the sweetened kerosene is less than 1 ppm for about 50 hours, then progressively increases to 10 ppm after 400 hours of walking. The service life of the catalyst can thus be evaluated at approximately 400 hours.

Example 2
The catalyst prepared according to Example 1, consisting of a catalyst Co (BPB) on charcoal containing approximately 0.5% by weight of cobalt is used.

The catalyst is treated by percolating it with a equivolume of ethanolic sodium hydroxide solution at 5% by weight for 1 hour at 600 ° C. The catalyst thus obtained is washed with pentane and dried. It contains 0.5% cobalt and 4% sodium hydroxide.

The softening is carried out under the same conditions as in Example 1 (200C, atmospheric pressure, 20 cm3 of catalyst, VVH = 1) and with the same charge to be softened (kerosene containing 150 ppm of mercaptan sulfur).

A softened kerosene containing less than 10 ppm of mercaptan sulfur is collected at the outlet for 1500 hours of walking. In this test 30 liters of kerosene were softened with 20 cm3 of catalyst. The life of the catalyst is 63 days of operation without the need to add sodium hydroxide.

This test shows that the impregnation of coal by the complex
Co (BPB) in ethanolic soda solution can quadruple the life of the catalyst compared to the same catalyst impregnated without sodium hydroxide.

After softening the kerosene for 1500 hours, the deactivated catalyst is washed with hot water at 800C until colorless effluents are obtained, and then re-impregnated with a equivolume of ethanolic sodium hydroxide solution at 5%. The same load of kerosene is then softened according to the conditions of example 1. The lifetime of the catalyst during which the softened filler has a mercaptan sulfur content of less than 10 ppm is 800 hours. .

Example 3 (comparative)
A catalyst supported by percolating on activated carbon is prepared a solution of sulfonated cobalt phthalocyanine in an aqueous solution containing 3% sodium hydroxide. The catalyst obtained contains 0.5% by weight of cobalt.

The softening of a kerosene is carried out under the same conditions and with the same charge as in example 1. After 200 hours, the mercaptan content of the sweetened kerosene exceeds 10 ppm.

Claims (9)

claims A process for softening a hydrocarbon feedstock containing sulfur-containing products in the presence of a supported catalyst, the method of pre-impregnating the supported catalyst in a substantially anhydrous alcoholic medium containing at least one alkaline agent, or to post treat the supported catalyst with an alkaline solution of at least one alcohol, the catalyst being based on at least one chelate of formula ML or M (LH2) X2 in which M is a transition metal, X an anion, L derived from a tetradentate [LH2] ligand based on a diamide of picolinic acid or a derivative thereof substituted with compounds having at least two primary amine functions separated from one another by at least two carbon atoms , [LH2l having the general formula ::  I

 in which R 'and R ", which are identical or different, each represent one or more hydrogen atoms or alkyl, aryl, aralkyl or alkylaryl groups comprising 1 to 20 carbon atoms or substituents of the halogen, nitro, amino, carboxylate or sulphonate type; in position 3, 4, 5 or 6 of the pyridine ring, R is a radical having at least two carbon atoms. 2. The process according to claim 1, wherein R is chosen from

NO2, halogen, NH2, SO3, COOH. SO3H, COOH, and R2 is alkyl, aryl or a group  where R 1 is an alkyl, aryl or a NO 2 radical, halogen, NH 2,

<tb> -CH2-CH2-NH-CH <SEP> 2-CH2 <tb> group <SEP> constituted <SEP> with <SEP> CH2-CH2, <SEP> CH2-CH2-CH2-, <SEP> -CH- (CH) 4-CH 3. A process according to one of claims 1 and 2 wherein M is selected from the group consisting of cobalt, nickel, iron, copper and manganese. 4. A process according to one of claims 1 to 3 wherein the alcoholic medium is an alcohol.  5. The method of claim 4 wherein the alcohol is a primary or secondary alcohol. 6. A process according to claim 5 wherein the alcohol is chosen from  the group consisting of methanol, ethanol, n-propanol, isopropanol, butanols, pentanols, hexanols and ethyl-2-hexanol. 7. A process according to one of claims 1 to 6 wherein the alkaline agent is selected from the group consisting of sodium hydroxide, potassium hydroxide, lithium hydroxide and ammonia. 8. A process according to one of claims 1 to 7 wherein the alkali content in the supported catalyst is between 0.1 and 10% by weight. 9. A process according to one of claims 1 to 8 wherein the regeneration of the catalyst is carried out by washing with hot water or steam and then treating with an alkaline solution of at least one alcohol.