DE2335441A1 - PROCESS FOR DESORPTION OF ORGANIC, POLAR OR POLARIZABLE COMPOUNDS - Google Patents

Description

Schwedt, June 22, 1973

Applicant:

YEB Petrolchemieches Kombinat Schwedt, 133 Schwedt / Oder

Process for the desorption of organic, polar or polarizable compounds

The invention relates to a method for the desorption of organic, polar or polarizable compounds adsorbed on zeolitic molecular sieves. ,

The use of synthetic and natural aluminosilicates with molecular sieve properties for the adsorption of polar or polarizable organic compounds such as mercaptans, sulfides, aromatic and heterocyclic compounds Compounds from natural or synthetic hydrocarbon mixtures are known. To obtain this adsorbed compounds and to reuse the molecular sieves is a desorption of the adsorbed compounds necessary. Various desorption processes are known for this purpose. One can, for example, by heating the loaded molecular sieves achieve the desorption of the compounds. In this case, however, the adsorbed compounds are mostly cracked, what leads to cleavage products and contamination of the desorbate and the molecular sieve, another variant is the thermal .mix Desorption in the presence of oxygen. This process converts e.g. sulfur compounds into sulfur dioxide and oxidizes hydrocarbons, which however leads to structural changes of the molecular sieve and thus to one for the adsorption of the organic compounds Adsorptive capacity can come. The adsorbed compounds can also be displaced with a more strongly adsorbable

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Compound, such as lower hydrocarbons or COp, desorbed will. The desorption can be carried out in the liquid or gaseous phase. A complete desorption the adsorbed compounds do not succeed. In particular, thiophene homologues or polynuclear aromatics are under not desorbed under these conditions. By using higher temperatures, the desorption of the compounds becomes more complete. However, the desorption at higher temperatures than the adsorption process leads to a strong thermal load on the Molecular sieve and a major technical effort. The repeated heating and cooling of the molecular sieve calls Changes in the structure of the molecular sieve, which in turn cause a reduction in the adsorption capacity.

It is also known that monohydric and polyhydric alcohols are used for desorption. The desorption also takes place here completely at low temperatures. However, it is disadvantageous that the alcohols are also adsorbed very well by molecular sieves and it through the catalytic properties of the Molecular sieves can lead to undesirable side reactions.

The purpose of the invention is a complete desorption of organic, polar adsorbed on zeolitic molecular sieves or polarizable compounds, in which the desorbate and the molecular sieve are not contaminated and no structural change of the molecular sieve.

The invention is based on the object of using a suitable and easily accessible desorbent.

According to the invention, an aliphatic or aromatic nitrile, preferably acetonitrile, is used as the desorbent. Propionitrile, butyronitrile and benzonitrile, for example, are also embossed. The desorption can be in liquid or gaseous form Phase to be carried out. The use of pressure is also possible. The desorption is under static as well possible under dynamic conditions. The quality of the nitriles

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no great demands are made. Also mixtures of different Nitriles can be used.

In the process according to the invention, the natural or synthetic molecular sieve is first loaded in a known manner with adsorbable organic compounds. The molecular sieve can be loaded up to 100 % of the adsorption capacity. The non-adsorbed compounds are then removed from the intergrain volume and from the outer surface of the molecular sieve. This can be done, for example, by simply draining the operating contents of the adsorption apparatus or by purging with an inert gas, for example nitrogen. This is followed by desorption with the nitrile.

The desorption temperature can be selected within a wide range, which can only be determined by the melting and decomposition temperature of the Nitrile is limited. The desorption with aliphatic or aromatic nitriles can also be carried out in two stages «It is first desorbed in the liquid phase, with most of the adsorbed compounds Will get removed. In the second stage, a temperature is used at which the nitrile is in gaseous form and the remainder is desorbed. The use of pressure is also possible here.

In the case of desorption in the gas phase, it is also possible to use a mixture of an inert gas and the nitrile. The desorbate falls in liquid or gaseous form depending on its boiling point. The nitrile can be separated off from the desorbate in a known manner, for example by distillation.

The molecular sieve freed from the adsorbate is used to remove the nitrile with nitrogen or another poorly adsorbable Purging inert gas and is then available again for adsorption.

The process according to the invention can be applied to all types of zeolite. The molecular sieves can either be in powder form or processed into shaped bodies with binders

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By, the method according to the invention is a gentle one and. rapid desorption of those adsorbed by the molecular ie ti Connections are possible in which no structural changes occur on the molecular sieve and the molecular sieve and the desorbate not be contaminated · The nitriles are easily accessible. The invention will be explained in more detail below using six exemplary embodiments:

Example 1 ;

100 g of a 22 & ETonylmercaptan loaded molecular sieve of the type 5 A were stirred with 0.5 1 of acetonitrile in a reaction vessel at 7O ⁰ C for two hours. After filtering off the molecular sieve, the analysis of the acetonitrile shows a content of 21.5 g of Nonyimercaptan. Nitrogen is passed through the filtered molecular sieve in a drying tower until the emerging nitrogen is free of acetonitrile. The molecular sieve then takes up again 22 g of nonyl mercaptan from a benzene solution.

Example 2:

In a column there are 10g molecular sieve 13 X, loaded with a mixture of high-boiling sulfur compounds (breakthrough capacity 0.429 g S / 100 g molecular sieve). These are treated with propionitrile at 7O ⁰ C. The weight ratio of desorbent to adsorbent is 2.2: 1, the volume residence time of the desorbent is 112 seconds. It is then flushed with nitrogen until the emerging nitrogen is free of propionitrile. The breakthrough capacity of the molecular sieve when it is loaded again with a mixture of high-boiling sulfur compounds is again 0.430 g S / 100 g molecular sieve (which indicates the complete desorption of the sulfur compounds).

Example 3:

In an adsorption column there are 10 g molecular sieve 10 X (Ca-Porm, degree of exchange 80 10) , loaded with 1.9 g diethyl sulfide. At 15O ⁰ C is the molecular sieve benzonitrile

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directed. The volume residence time is 80 seconds. , the weight ratio of amount of desorbent: amount of adsorbent 4: 1. After flushing with nitrogen to remove the benzonitrile at 15O ⁰ C the molecular sieve resumes 1.9 g Diäthylsulfid.

Example 4t

In an adsorption column are 400 g of molecular sieve 10 X (Ca exchange level of 80%), loaded with high-boiling sulfur compounds (bp 180 -. 24O ⁰ C). The breakthrough capacity in dynamic adsorption is 0.484 g S / 100 g molecular sieve. Initially is carried out at 75 ⁰ C, a treatment with 0.5 1 of acetonitrile (640 Volumenverweilzeit lake) and then with 0.5 1 acetonitrile at 15O ⁰ C (see Volumenverweilzeit 600). After the desorbent has been expelled with nitrogen, the molecular sieve is available again for adsorption. It can again be loaded up to a breakthrough capacity of 0.484 g S / 100 g molecular sieve.

Example 5:

In an adsorption column are 150 g of molecular sieve 10 X (Mg-form), loaded with 23.4 g Benzol.- In 15O ⁰ C is passed over the molecular sieve acetonitrile. The volume residence time is 3 seconds and the weight ratio of the amount of desorbent to the amount of adsorbent is 1: 1. ! repeatedly flushing with nitrogen to displace the desorbent at 15O ⁰ C takes the molecular sieve to the appropriate loading capacity crowd benzene.

Example 6:

In an adsorption column there are 150 g molecular sieve 10 X (Ca-Porm, degree of exchange 80 #), loaded with high-boiling aromatic and unsaturated compounds from a petroleum fraction (breakthrough capacity 10.4 g aromatic hydrocarbons / 100 g molecular sieve). In a carrier gas stream of 70 1 N ₂ / h 150 g of acetonitrile was passed at a rate of 100 ml / h at 24O ⁰ C for the molecular sieve. The desorbent adhering to the molecular sieve is then rinsed off with nitrogen. The molecular sieve is then available again for a new adsorption.

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Claims (5)

Claims 1. Process for the desorption of organic sulfur compounds on zeolitic molecular sieves are adsorbed, characterized in that the Desorptionsmxttel an aliphatic or aromatic Nitrile or a mixture of several nitriles is used. 2. The method according to claim 1, characterized in that the desorption takes place with acetonitrile. 3. The method according to claim 1 and 2, characterized in that the desorption process is carried out at 20 to 400 ⁰ C, preferably at 60 to 25O ⁰ G, in the liquid or gaseous phase and with or without pressure. 4. The method according to claim 1 to 3, characterized in that the nitrile is used in a mixture with an inert gas. 5. The method according to claim 1 to 4, characterized in that the nitrile contains 0 to 2 % water. 409808/1037