RU2136642C1 - Method of preparing propylene trimers and tetramers - Google Patents

Abstract

FIELD: petrochemistry, more particularly manufacture of plasticizers, detergents and non-ionic surfactants. SUBSTANCE: described is method of preparing propylene trimers and tetramers by oligomerization of propylene in the presence of solid phosphoric acid catalyst at elevated temperature and pressure to isolate fraction of propylene dimers from oligomerizate and to direct it back for oligomerization, straight-chain C₆d olefins being fed for oligomerization in amount of 5-20 wt %. EFFECT: increased yield of propylene trimers and smaller amount of paraffins during propylene oligomerization process. 8 ex, 1 tbl

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, application. 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.

 The closest in technical essence is the method of producing trimers and tetramers of propylene (A.S.SSSR N 1641798, MKI C 07 C 2/18, decl. 18.02.88, N 4382664, publ. 15.04.91, N 14.). The process is carried out by oligomerization of propylene in the presence of a solid phosphoric acid catalyst and 0.2-2% wt.% Of 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 trimers from 36.8 to 39.3% and 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.

To increase the yield of propylene trimers 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 a fraction of propylene dimers from the oligomerizate and recycling it to oligomerization, is proposed. additionally, normal α-olefins C ₆ are fed in an amount of 5 to 20 wt.%.

The addition of normal α-olefins to the C ₆ oligomerization process not only allows increasing the yield of propylene trimers, which are in greater commercial demand, but also decreasing the paraffin content in the oligomerizate. Moreover, it was possible to achieve a decrease in the paraffin content only thanks to the addition of linear α-olefins. When using branched olefins, this effect is not observed. The addition of linear C ₆ α-olefins to raw materials to increase the yield of trimers 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 (comparisons). On a pilot installation in a reactor, which is a stainless steel tube with a diameter of 30 mm, loaded with a catalyst (polyphosphoric acid on silica gel) (TU 3840248-90) containing 55.2 wt.% P ₂ O ₅ , including 16.8 wt. .% in free form, conduct oligomerization of propylene (GOST 25043-87, premium) with the return to the process of the fraction of propylene dimers formed in this process, the content of dimers in the charge is 3.5 wt. % The process is carried out at 200 ^o C, 60 ATM, the volumetric feed rate of propylene 5 h ^-1 . Catalyst loading 50 ml. The propylene conversion is determined by the ratio of the gas and liquid phases after oligomerization, the composition of the obtained oligomerizate is analyzed by gas chromatography. The conditions and results of the experiment are shown in the table.

 Example 2 (comparisons). The experiments are carried out under the conditions of example 1, but as a catalyst using phosphoric acid catalyst brand C84-3. The conditions and results of the experiment are shown in the table.

Examples 3-5. The experiments are carried out under the conditions of example 1, but various amounts of linear α-olefin C ₆ (hexene-1) are introduced into the composition of the raw material. The experimental conditions and results are shown in the table.

Examples 6-8. The experiments are carried out under the conditions of example 2, but various amounts of a fraction of a linear α-olefin C ₆ (hexene-1) are introduced into the composition of the raw material. The conditions and results of the experiments are shown in the table.

As can be seen from the above examples, the addition of linear α-olefins C _{6 in the} propylene oligomerization feedstock allows not only to increase the yield of propylene dressers, but also to reduce the paraffin content in the oligomerizate.

Claims (1)

A 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 a fraction of propylene dimers from the oligomerizate and returning it to oligomerization, characterized in that normal C ₆ α-olefins are additionally fed to oligomerization in an amount of 5 - 20 wt.% Calculated on the return fraction.

Images