DE2709020C3 - Process for the treatment of an acidic mercaptan-containing hydrocarbon distillate - Google Patents

Description

The invention relates to an improved process for sweetening acidic hydrocarbon distillates by oxidizing mercaptans in the distillate to disulfides with oxygen in the presence of a phthalocyanine catalyst on a carbon carrier and a basic one Medium.

The sweetening of sour hydrocarbons is known in earth refining technology. There are abundant methods of treating petroleum distillates such as sour Gasoline, cracked gasoline, straight-run gasoline, jet fuels, kerosene, and fuel oil.

One method of sweetening hydrocarbon distillates with a fixed catalyst layer is in US-PS 29 88 500 described, wherein a catalyst made of cobalt phthalocyanine sulfonate on a Coal carrier is used. A mixture of acid kerosene, aqueous sodium hydroxide solution and air is poured over the Catalyst sent to convert mercaptan sulfur to a sufficient extent to allow the recovered Kerosene product is doctor sweet. The treatment reaction is carried out in the presence of an alkaline reagent. The patent teaches that any suitable alkaline reagent can be used and that the preferred reagents are sodium hydroxide and potassium hydroxide. Others considered possible The reagents are aqueous solutions of lithium hydroxide, rubidium hydroxide and cesium hydroxide.

The sweetening process with a fixed catalyst layer has been carried out with success around the world. In particular, the common practice of using aqueous sodium hydroxide solutions as the basic medium required for the oxidation of mercaptans to disulfides has posed the problem of caustic removal. The alkali solution used in a plant with a fixed catalyst layer eventually becomes unsuitable for further use because various toxins or catalyst poisons generated by the oxidation reaction are accumulated in the alkali. Thus, for a number of reasons, the alkali commonly used in a fixed catalyst bed sweetening process must be discarded. While sodium hydroxide is a very cheap chemical to buy, it is a relatively expensive chemical to dispose of

of pollution problems.

Also unpleasant for the refiner is the danger that some of the alkali solution will somehow find its way can find in the final product. For some uses, such as jet fuel, may be in the product neither sodium hydroxide nor water will be tolerated. Laborious measures must be used to ensure that the kerosene product intended for use as jet fuel does not contain water or NaOH Kerosene spill from the fixed catalyst layer treatment process washed with water to remove sodium hydroxide solution therefrom. The kerosene washed with water can then be passed over a layer of salt, so that a Salt solution forms which is left behind. Finally, the kerosene is carried through a layer of clay or sand sent to remove the last traces of water or saline solution that are still in the product may be present. While such measures are effective, they add to the cost of treatment and the capital expenditure.

Other problems encountered with the fixed catalyst layer sweetening process were occasional clogging of the catalyst layer due to the formation of soaps. A number of hydrocarbon distillates contain naphthenic acids, and the naphthenic acids react with aqueous sodium hydroxide with the formation of a soap that forms a gel with the hydrocarbon, which in turn forms the carbon layer clogged It was necessary to remove these naphthenic acids with alkaline pre-washes so that the The fixed catalyst bed sweetener charge was essentially free of naphthenic acids.

A replacement has now been found for the sodium hydroxide solution currently used in fixed catalyst bed treatment processes.

The invention relates to a process for treating an acidic mercaptan-containing hydrocarbon distillate by guiding the distillate and an oxidizing agent over a fixed layer of a phthalocyanine catalyst on a carbon support in an alkaline medium, which is characterized in that a tetraalkylguanidine is used as the alkaline medium.

In addition to eliminating some of the problems caused by sodium hydroxide solutions known to be used, according to US Pat Invention found that a surprising advantage by using tetraalkylguanidine as the basic Medium is reached. This benefit is a surprising unexpected increase on the obvious catalytic activity of the sweetener with a fixed catalyst layer. The usage of Tetraalkylguanidine allows significantly improved mercaptan conversion in a sweetening process with a fixed catalyst layer. The use of tetraalkylguanidines is also advantageous because because the guanidines stay in the hydrocarbon phase and go into the storage containers that are used for the Hydrocarbons are used. The guanidines suppress the discoloring degradation during storage and can also act as corrosion inhibitors. In addition, the guanidines do not change the color of the hydrocarbon product, and this is stated in the Contrasted with some of the phenylenediamines which give the product a red color.

An excellent method of performing hydrocarbon treatment with a fixed catalyst bed is described in US-PS 29 88 500. All things described in this patent specification can be used to good effect in the practice of the invention provided that the alkaline reagent replaced by a tetraalkylguanidine.

The tetraalkylguanidine is preferably tetramethylguanidine. Instead of four methyl groups it can but also contain four ethyl groups, propyl groups or butyl groups; there can also be guanidines are used that contain alkyl groups of different chain lengths. Tetramethylguanidine is preferred, as it is easily available and cheap. Another advantage of tetramethylguanidine is that it has light and heavy naphthenic acids and phenols can react without the formation of soapy salts. The reaction product of guanidine and naphthenic acids is Iösmüi in a hydrocarbon medium, so that it does not clog the catalyst layer. This is in contrast to the reaction product of Naphthenic acids with sodium hydroxide in aqueous solution, which forms soaps and gels, which the Completely clog the catalyst layer and render it ineffective. There are also emulsion problems switched off because sodium salts do not occur.

Because of the variety of feed materials to be treated, it may be desirable be to use heavier alkylguanidines. Generally the guanidine in the hydrocarbon is jo the longer the alkyl groups, the more soluble. Experiments have shown that selost is the easiest Tetraalkylguanidines do a very effective sweetening job with only very low concentrations. afford, and that they are completely soluble in the hydrocarbon oil to be treated, such as a kerosene.

The tetraalkylguanidine is preferably added continuously to the hydrocarbon to be treated It can be used in an aqueous or alcoholic solution, periodically over a stationary catalyst bed is pumped in order to wet its surface with basic solution.

The catalyst used is a phthalocyanine. The monosulfonated derivatives of cobalt phthalocyanine are particularly preferred. The sulfonation of the cobalt phthalocyanine renders the material sufficiently soluble in various solvents to allow a stationary layer of carbon to be impregnated with the catalyst. The monosulfonate derivative is preferred because the more sulfonated derivatives are more soluble in the hydrocarbons being treated, which enables the catalyst from Catalyst Table I.
Inorganic bases

layer is leached.

In order to evaluate the effectiveness of the tetraalkylguanidine in the method according to the invention, a Series of Experiments Conducted A kerosene, which was very difficult to sweeten, was used as a Dezugbeschikkungsmaierial used The kerosene contained 180 ppm by weight of mercaptan sulfur.

The test procedure is to mix 2 g of catalyst with 5 ml of the alkaline reagent to be tested was moistened plus 100 ml of feed to a 300 ml capped flask. The flask was then placed in an automatic shaker. The temperature was increased nicr ·. measured but all tests were at ambient temperature carried out in a room that was kept at about 25 ° C, so that temperature changes shouldn't matter. The contents of the flasks were sampled at regular intervals and the mercaptan sulfur content of the hydrocarbon was determined

In addition, a number of blank samples were also tested, ie tests were carried out with charcoal without a metal phthalocyanine catalyst and with a conventional alkaline reagent (sodium hydroxide solution). The same carbon material, a biochar, was used throughout the test. The catalyst was made by impregnating the carbon with a cobalt phthalocyanine monosulfonate. The catalyst was prepared by dissolving 0.15 g of cobalt phthalocyanine sulfonate in 100 cm ^{3 of} methanol was, ie a quarter of the alcohol was mixed with the phthalocyanine and then decanted, now the next quarter of the cobalt phthalocyanine remaining at the bottom of the flask was added by rubbing the cobalt compound! This was repeated a third and fourth time to make sure that all of the active material was dissolved in the alcohol. The alcohol was then placed in a container with 15 g (100 cm ³ ) charcoal, stirred gently, and allowed to stand overnight. The material was then drained of alcohol and the charcoal was dried under a water aspirator vacuum. The filtrate was only pale blue in color, but did not contain a substantial amount of cobalt, so that the catalyst contained 1% by weight of the cobalt phthalocyanine sulfonate. This catalyst was divided into several portions of 2 g to carry out the activity tests. The bases used and the results of the test are shown in the table below.

Weight%
catalyst

ml base
base

1.0
0

1.0 1.0

1.0

1.0

20th 20th 20th water 20th *) aqueous **) alcohol ***) NH ₄ OH ****) alcohol NaOH liquid NaOH riges lish NH4OH Weight ppm R SH

Knriset / ung

test

Shaking time 180 (Min.) 167 0 164 5 164 1-j 164 30th - 60 90 120

180 158 152 146 137

180 5 2 1

180

78 53 30 26 25

180

44 38 33 22

*) I n NaOH in H ₂ O.

**) 1 η NaOCHj solution, produced by reacting sodium metal with methyl alcohol. ***) 1 η NH ₄ OH in HjO. ****) 1 η NH. (OH solution, produced using chemically pure aqueous NH4OH and methyl alcohol.

A dash indicates that the mercaptan content is not has been tested. The results reported for Test 3; H. for the use of aqueous NaOH solution, can be considered the standard activity for a conventional fixed catalyst bed process.

hea be.

A number of organic bases were also tested The results are shown in Table II below

Table II test 1.0 8th 1.0 180 180 9 1.0 Organic bases 7th 20th 20th 31 71 20th *) alcoholic **) alcoholic 27 53 ***) alcoholic Weight% Diethylamine Diethylenetriamine 22nd 42 Tetramethylguanidiii catalyst Cirwrirh * " nnm -P ^ TT 19th 36 ml base base 180 8th Shaking time 7th (Min.) 5 0 3 5 3 15th 30th 60 90 120

*) I η diethylamine solution, prepared using the pure base and methyl alcohol. **) 1 η diethylenetriamine, made using the pure Bi each and methyl alcohol. ***) 1 η tetramethylguanidine solution, prepared using the pure base and methyl alcohol.

It can be seen that the Basic Reagpns method is a more effective sweetening method Invention of a way to treat even difficult 65 as aqueous sodium hydroxide solutions or various organic

/.u sweetening kerosene without using an aqueous one Sodium hydroxide solution supplies. In addition, results in that used in the method according to the invention

see bases suggested after.

the state of the art

Claims (3)

Patent claims: 1. Process for the treatment of an acidic mercaptan-containing hydrocarbon distillate by guiding the distillate and an oxidizing agent over a fixed layer of a phthalocyanine catalyst on a carbon carrier in one alkaline medium, characterized in that a tetraalkylguanidine is used as the alkaline medium. 2. The method according to claim 1, characterized in that one is used as an alkaline medium alcoholic solution of tetraalkylguanidine is used 3. The method according to claim 1 and 2, characterized in that the tetraalkylguanidine in an amount of 1 to 500 ppm by weight, based on the weight of the acidic hydrocarbon distillate, is used.