DE1470487B - Process for the desulphurization of hydrocarbon mixtures - Google Patents

Description

The invention relates to the desulfurization of hydrocarbon mixtures, for example originate from petroleum, especially the desulphurisation of high-molecular petroleum fractions.

The presence of sulfur or sulfur-containing compounds in crude oils, distillates and Residue is usually extremely undesirable. These materials will have many valuable properties severely affected by the presence of sulfur compounds, so that their commercial value decreases.

So far, numerous methods have been used to either remove the undesired sulfur compounds remove or convert them to more harmless forms. So it is known the sulfur content of the To reduce petroleum by oxidative desulphurisation. Process of this type are z. B. in the Swiss patent specification 53,965 and in the USA patents 1972 102, 1971172, 1954 488, 1 862 952 and 1 803 964. Other methods involve extraction with a liquid solvent, such as sulfuric acid, sulfur dioxide, furfural and the like. Another type of procedure the sulfur compounds are adsorbed on suitable substances, e.g. B. activated Bauxite, activated carbon or activated clay, removed. Furthermore, the undesirable forms of the Sulfur compounds, ζ. Β. Mercaptans, through various chemical treatments, e.g. B. with plumbit, Hypochlorite and copper chloride, converted into less harmful forms such as disulfides and polysulfides will. The methods mentioned above are used in particular for the treatment of gasoline fractions. For high molecular weight feedstocks, a large portion of the material is in the form of Molecules that contain at least one sulfur atom, and especially in selective separation processes this portion would be removed so that the product yield would be low.

In another type of process, hydrocatalytic desulphurization, which has proven to be particularly advantageous For the treatment of middle distillate fractions, such as gas oils, the material is usually found with Hydrogen under pressure and at elevated temperature passed over a suitable catalyst, the Sulfur atoms in the form of hydrogen sulfide are removed from the sulfur-containing compounds. This type of process aims to break the carbon-sulfur bonds in the sulfur-containing compounds, whereby the sulfur is removed in the form of hydrogen sulfide and at the same time that as a result of the Hydrocarbon fragments remaining in the desulfurization reaction are hydrogenated. It turned out, however, that to achieve a substantial reduction in the sulfur content of high molecular weight material, for example of residual heating oils, severe conditions required for treatment with hydrogen and the life of the catalytic converter is shortened by the formation of deposits. Suitable hydrocatalytic Desulfurization processes are the so-called "hydrofining process", in which hydrogen is consumed, and the "autofining process" in which there is no net hydrogen consumption.

According to an older proposal by the patent owner, sulfur-containing hydrocarbons are oxidative desulphurized by subjecting them to a selective oxidation reaction in which the sulphurous Compounds are selectively attacked, causing the oxidized material to undergo thermal decomposition is subjected, through which the sulfur is removed in the form of sulfur-containing gas.

The invention relates to a multi-stage process for the desulfurization of hydrocarbon mixtures, which is characterized in that the starting material is in one stage of oxidative desulphurization and subsequent removal of the oxidized sulfur compounds by thermal decomposition at over 200 ^° C. and in another stage

ίο is subjected to a hydrocatalytic desulphurisation in this or the reverse order.
■ The process of the invention is particularly suitable for the desulfurization of petroleum fractions that consist at least partially of about 25O ⁰ C boiling material, such as crude oil and residues of atmospheric and vacuum distillation, the sulfur in amounts of 1%, or may contain more.
A number of oxidizing agents are suitable for the oxidation stage of oxidative desulfurization, e.g. B. organic and inorganic peroxides, hydroperoxides, organic and inorganic peracids, chlorine, nitrogen oxides, ozone and preferably - because of their low cost - molecular oxygen or air. In addition, the molecular oxygen in the air can be activated by suitable substances, for example by metals of groups Va and VIII of the periodic table or their salts or oxides, in particular platinum, palladium, nickel and vanadium. These activators can be applied to suitable carrier materials such as aluminum oxide, soda lime or activated carbon. In cases in which the carrier material has acidic and therefore cleavage properties, such as aluminum oxide, for example, these properties can be modified by treatment with an alkali metal, in particular sodium, or with an ammonium compound. The aforementioned activators improve the selective oxidation and furthermore increase the reaction rate, so that the selective oxidation can be carried out in a shorter time or at a lower temperature. The preferred conditions required for the selective oxidation depend both on the material to be treated and on the oxidizing agents used, but generally temperatures in the range from 80 to 180 ° C. with an amount of oxidizing agent containing 1 to 6 active oxygen atoms per sulfur atom Input material corresponds to the application for a period of ¹ J ₂ to 20 hours. With the use of molecular oxygen or air as an oxidant in the temperature range of 130 to 18O ⁰ C and treatment times of 2 to 20 hours are suitable ..
In the second stage of the oxidative desulfurization of the oxidized sulfur compounds are removed, by thermal decomposition, which is carried out at temperatures above 200 ⁰ C, preferably above 25O ⁰ C, in particular in the range of 300 to 400 ⁰ C, for such a long time that the release of practically all gaseous decomposition products is guaranteed. This time may be ₂ to 5 hours in the range of V and is preferably V2 to 2 hours. Under these conditions, the oxidized sulfur compounds are decomposed, the sulfur being released mainly as SO ₂ , but increasing amounts of _{H 2} S are also released at higher temperatures in the range of 300 ^° C. and above. The thermal decomposition can be more appropriate in the presence

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activating substances in the form of porous solids with acidic or basic properties will. Suitable for example are ferric oxide on aluminum oxide, bauxite, thorium oxide on pumice, Silica-alumina, soda-lime and sodium acid phosphate on charcoal. Preferably at thermal decomposition a small amount of an inert carrier gas, e.g. B. nitrogen, through the reaction mixture in order to avoid local overheating as well as the gaseous decomposition products remove.

The hydrocatalytic desulfurization can be carried out under relatively mild conditions. The catalyst can be used as a fixed bed, fluidized bed or fluidized bed. A fixed bed is preferably used under conditions such that regeneration of the catalyst is only necessary after relatively long operating times, for example at temperatures in the range from 260 to 482 ° C., preferably from 343 to 427 ° C., pressures in the range from 8 to 176 kg / cm ³ , preferably from 36 to 106 kg / cm ² , room flow rates in the range from 0.1 to 10 V / V / hour, preferably from 0.5 up to 4 V / V / hour, and hydrogen cycle rates from 90 to 900 m ³ / m ³ . Metals of group VIa or VIII or their oxides or sulfides, alone or as a mixture on a refractory oxide serving as a carrier, for example aluminum oxide, are suitable as catalysts. A particularly preferred catalyst is a mixture of cobalt and molybdenum on aluminum oxide which contains 1 to 10 percent by weight cobalt oxide (calculated as CoO) and 5 to 40 percent by weight molybdenum oxide (calculated as MoO ₃ ).

It has been shown that with successive use of an oxidative desulfurization and a hydrocatalytic desulphurisation the achieved degree of desulphurisation is significantly higher than when the starting material either twice in succession to oxidative desulfurization or twice one after the other is subjected to a hydrocatalytic desulfurization. This is better result furthermore regardless of the order in which the steps are carried out. It follows from this that the sulfur compounds, which are most easily attacked under oxidative and hydrocatalytic conditions are each different and that by using both processes a synergistic effect is achieved. It is of course appropriate that when carrying out the oxidative stage in the first place the all free oxygen removed from the hydrocarbons prior to the hydrocatalytic treatment will. This happens during the thermal decomposition as part of the oxidative stage. Likewise is any free hydrogen present in the first place when carrying out the hydrocatalytic stage to remove the oxidation stage. . ■. ■

2. Hydrocatalytic desulfurization with subsequent oxy-dative desulfurization;

3. two successive oxidative desulphurizations and

4. two successive hydrocatalytic desulphurizations.

Those used in each oxidative desulphurisation stage Conditions are given in Table 1 below.

Table 1
_1S oxidation

Residue 2 parts by weight

Boiling temperature. 250 ° C

Viscosity at 50 ° C 405 cSt

Toluene 2 parts by weight

Glacial acetic acid 1 part by weight

Hydrogen peroxide

(3O%, w / v) * ... amount accordingly 6 active sour

atoms per sulfur. atom

Temperature 98 ° C

Response time 25 minutes

Stripping time for toluene and

Acetic acid 25 minutes

Thermal treatment ..· ,

Temperature 370 ° C

Time 1 hour

Silicon dioxide catalyst -

Aluminum oxide (8 percent by weight)

*) Mixture of acetic acid and hydrogen peroxide was added to the mixture of toluene and residue.

example

With the ones described here. Comparative tests were made containing 4 percent by weight of sulfur Atmospheric distillation residue of Kuwait crude oil treated as follows:

. 1. Oxidative desulphurisation with subsequent hydrocatalytic desulphurisation: The conditions used in each hydrocatalytic desulfurization stage are below Table 2 named. .: u: _:

Table 2

Catalyst 2.0 weight percent

■■■■ - cobalt and

.. [. '.. 10.5 percent by weight

.. "! Molybdenum ^ uf '■' "'.'. ''. ' y-aluminum oxide

Temperature 393 ⁰ C

Pressure 71 kg / cm ²

Room flow rate 1.0 to 1.5 V / V / hour.

H ₂ amount 180 m ³ / m ³

The results are shown in Tables 3 to 6 below.

table

treatment In the oil
remaining amount,
Parts / 100 teaspoon oil sulfur
Quantity removed,
Parts / 100 parts oil Distant crowd
in ° / o. related to
untreated
Source material Untreated 4.0
2.8
1.6 1.2
1.2 Only oxidatively desulphurized
Then hydrocatalytically desulphurized - 2.4 30th
30th All in all 60

table

treatment In the oil
remaining amount,
Parts / 100 parts oil sulfur
Quantity removed,
Parts / 100 parts oil Distant crowd
in%, based on
untreated
Source material Untreated .7 4.0
2.8
1.6 1.2
1.2 Only hydrocatalytically desulphurized
Then oxidatively desulphurized - 2.4 30th
30th All in all 60

table

treatment In the oil
remaining amount,
Parts / 100 parts oil sulfur
Quantity removed,
Parts / 100 tea of oil Distant crowd
in%, based on
untreated
Source material Untreated 4.0
2.9
2.4 1.1
0.5 1. oxidative desulfurization
2. oxidative desulphurization - 1.6 27
13th All in all 40

table

treatment In the oil
remaining amount,
Parts / 100 teaspoon oil sulfur
Quantity removed,
Parts / 100 parts oil Distant crowd
in%, based on
untreated
Source material Untreated 4.0
2.8
2.2 1.2
0.6 1. Hydrocatalytic desulfurization
2. hydrocatalytic desulfurization - 1.8 30th
15th All in all 45

Claims (4)

Patent claims: 1. Multi-stage process for the desulfurization of hydrocarbon mixtures, characterized in that that the starting material in one stage of an oxidative desulfurization and a subsequent removal of the oxidized sulfur compounds by thermal decomposition at over 200 ° C and in another stage of a hydrocatalytic desulfurization in this or is subjected in reverse order. 2. The method according to claim 1, characterized in that petroleum fractions are subjected to the method which ^{contain at least partially above 250 0} C boiling material. 3. The method according to claims 1 and 2, characterized characterized in that petroleum fractions with 1 percent by weight or more sulfur are added to the process be subjected. 4. Process according to Claims 1 to 3, characterized in that in the oxidation stage with molecular oxygen or air is used as the oxidizing agent and with catalysts that Metals, metal salts or oxides of the elements of groups Va or VIII of the periodic table contained on a support and the hydrocatalytic desulfurization in the presence of catalysts is carried out, the metals, metal oxides or sulfides of the elements of groups VIa or VIII of the Periodic Table on a refractory oxide support.