RU2161600C1 - Propylene trimer and tetramer production process - Google Patents

Abstract

FIELD: petrochemical processes. SUBSTANCE: propylene oligomers for production of plasticizers, additives, detergents, nonionic surfactants, etc. are prepared by oligomerization of propylene in presence of solid phosphoric acid catalyst at elevated temperature and pressure followed by isolation of propylene dimer fraction, which is recycled into oligomerization stage. According to invention, in the oligomerization stage, C₈-olefin fraction in amounts 10 to 50% based on the weight of recycling propylene dimer fraction is added. C₇-C₈ fraction from propylene trimer and tetramer production process or C₈ fraction from production of alpha-olefins by oligomerization of ethylene are suitable to be added. EFFECT: increased yield of propylene tetramer fraction and decreased formation of paraffins. 2 cl, 1 tbl, 5 ex

Description

 The invention relates to the field of petrochemistry, in particular to the production of propylene oligomers, which are used to obtain plasticizers, additives, detergents, nonionic surfactants, etc.

A known method of oligomerization of olefins on a phosphoric acid catalyst at a temperature of 150-230 ^o C and high pressure (US patent N 4675463, MKI C 07 C 2/14, decl. 5.02.87, publ. 23.06.87). As a result of oligomerization under these conditions, a mixture is obtained containing 90% C ₅ -C ₁₂ olefins and ≈10% C ₅ -C ₈ paraffins. The formation of about 10% of paraffins, which are by-products, complicates the allocation of target products and reduces the technical and economic indicators of the process.

A known method of producing trimers and tetramers of propylene (RF patent N 2136642, MKI C 07 C 2/18, application. 21.08.98, publ. 10.09.99, Bull. N 25). Propylene oligomerization is carried out at elevated temperature and pressure with a recycle of the C ₆ dimer fraction and an additional supply of the C ₆ fraction of normal α-olefins in an amount of 5-20 wt.% Based on the C ₆ recycle fraction. This allows you to get up to 74.8 wt.% Trimers of propylene and reduce the yield of tetramers of propylene to 10.8 wt.%.

 The closest in technical essence is the method of producing trimers and tetramers of propylene (ed. St. USSR N 1641798, MKI C 07 C 2/18, decl. 18.02.88). The process is carried out by oligomerization of propylene in the presence of a solid phosphoric acid catalyst and 0.2-2 wt.% A mixture of branched and linear heptenes (calculated as propylene) under heating and pressure with the separation of the dimer fraction from the oligomerizate and returning it to the process. These conditions provide an increase in the yield of tetramers from 12.8 to 14.8%. The use of a mixture of branched and linear heptenes increases the yield of tetramers to a greater extent than trimers, and does not affect the content of paraffins in the oligomerizate. But the increase in the yield of propylene tetramers is not large enough.

 The objective of the invention is to increase the yield of the propylene tetramer fraction while reducing the formation of paraffin hydrocarbons.

To increase the yield of the propylene tetramer fraction and reduce the formation of paraffins in the process of propylene oligomerization, a method for producing propylene trimers and tetramers by oligomerization of propylene in the presence of a solid phosphoric acid catalyst at elevated temperature and pressure with the separation of the propylene dimer fraction from the oligomerizate and recycling it to oligomerization is proposed. oligomerization additionally serves C ₈ -containing fraction of olefinic hydrocarbons in an amount of 10-50 wt.% per recycle a new fraction of propylene dimers. It is possible to use the C ₇ -C ₈ fraction from the production of propylene trimers and tetramers and / or the C ₈ fraction from the production of α-olefins by ethylene oligomerization as a C ₈ -containing fraction of olefinic hydrocarbons.

The addition of a C ₈ -containing olefin fraction to the oligomerization process not only allows increasing the yield of the propylene tetramer fraction (C ₁₀ -C ₁₂ fractions), which are in greater commercial demand, but also decreasing the paraffin content in the oligomerizate on any phosphoric acid catalyst. Moreover, it was possible to achieve an increase in the yield of the propylene tetramer fraction with a decrease in the paraffin content only by adding precisely the C ₈ -containing olefin fraction (C ₇ -C ₈ fraction of the production of trimers and tetramers or C ₈ fraction of the ethylene oligomerization process or a mixture thereof). The addition of C ₈ olefins to raw materials to increase the yield of the tetrameric fraction of propylene and reduce the formation of paraffins, we have not found in the literature, which indicates compliance with the patentability criteria of "novelty" and "inventive step". The possibility of using propylene trimers and tetramers in the industrial process shows compliance with the criterion of "industrial applicability".

 All of the above is illustrated by the following examples.

 Example 1

In an industrial reactor, which is a shell-and-tube apparatus loaded with a phosphoric acid catalyst of grade C 84-5-01, propylene is oligomerized (GOST 25043-87, premium) in the presence of 5.1 wt.% Recycle fraction of propylene dimers, to which is added 10 wt.% Fractions of C ₇ -C ₈ production of examples and tetramers. The process is carried out at a temperature of 160-185 ^o C, a pressure of 50-52 atm, a volumetric feed rate of 1.0-1.5 hours ^-1 . The catalyst load is 3 tons. The composition of the obtained oligomerizate is analyzed by gas chromatography. The conditions and results of the experiment are shown in the table.

 Examples 2 and 3.

The experiments are carried out under the conditions of example 1, but various amounts of the C ₇ -C ₈ fraction of the production of trimers and tetramers of propylene are introduced into the composition of the raw material. The conditions and results of the experiments are shown in the table.

 Example 4

The experiment is carried out under the conditions of example 1, but the C ₈ fraction of the production of α-olefins of ethylene oligomerization is introduced into the composition of the feed. The conditions and results of the experiment are shown in the table.

 Example 5

The experiment is carried out under the conditions of example 1, but 15% of the C ₇ -C ₈ fraction from the production of trimers and tetramers and 15% of the C ₈ fraction from the production of α-olefins, calculated on a recycle fraction, are introduced into the raw material composition. The conditions and results of the experiment are shown in the table.

As can be seen from the above examples, the addition of a C ₈ -containing olefin fraction in the propylene oligomerization feedstock not only leads to an increase in the yield of the propylene tetramer fraction (C ₁₀ -C ₁₂ fraction), but also reduces the paraffin content in the oligomerizate.

Claims (2)

1. The method of producing trimers and tetramers of propylene by oligomerization of propylene in the presence of a solid phosphoric acid catalyst at elevated temperature and pressure, with the separation of the fraction of propylene dimers from the oligomerizate and its recycling for oligomerization, an additional supply of olefins, characterized in that C is additionally fed for oligomerization _8- containing fraction of olefinic hydrocarbons in an amount of 10 to 50 wt.% Calculated on the recycle fraction of propylene dimers. 2. The method according to claim 1, characterized in that as the C ₈ -containing fraction of olefinic hydrocarbons, a C ₇ -C ₈ fraction is used from the production of propylene trimers and tetramers and / or a C ₈ fraction from the production of α-olefins by ethylene oligomerization.

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