RU2068850C1 - Method for polymerization of olefin-containing raw materials - Google Patents

Abstract

FIELD: polymer production. SUBSTANCE: olefin-containing raw material is fed into the top section of a reactor with stationary layer of catalyst, which is orthophosphoric acid on carrier. When pressure rises more than twice as compared to recommended value (0.09-0.13 kg/sq.cm), the raw material feeding is reversed to be directed from below upwards. EFFECT: improved operation conditions. 1 tbl

Description

 The invention relates to oil refining and petrochemical synthesis, in particular to a method for the polymerization of olefin-containing raw materials to obtain polymer distillate raw materials for the production of additives.

When refining petroleum products according to the known method, the olefin-containing feed is fed to the upper part of the vertical shell-and-tube reactor (one or more) with a fixed layer of orthophosphoric catalyst. The process is carried out under a pressure of 3 8 MPa and at a temperature of 160 - 230 ^o C. The main product is a polymer fraction of a liquid fraction boiling in the range from 60 to 260 ^o C.

The disadvantage of this process is the uneven development of the catalyst and its compaction, ultimately leading to a decrease in the yield of polymer distillate and to an increased pressure drop in the reactor exceeding the requirements of the technology and to stop the apparatus [1]
The closest technical solution is a method of polymerization of a butane-butylene fraction in series reactors with a fixed catalyst bed orthophosphoric acid on a carrier [2]
The butane-butylene fraction is also fed to the top of the reactor in this known method.

 The introduction of olefin-containing raw materials into the lower part is not recommended due to the possible soaking of catalyst granules in the reaction tubes of the reactor and removal from the reactor, clogging of equipment, etc., which is undesirable.

 To improve the known method for the polymerization of the butane-butylene fraction, it is recommended that the head reactor be stopped for overload as the feed conversion decreases, and the reactor with the fresh catalyst should be connected last or the number of reactors in the circuit should be reduced to two or three, which reduces the total pressure drop in the reactor system and increase the life of the catalyst.

 However, the known method has the following disadvantages.

 The practice and operation of an industrial unit for the polymerization of butane-butylene fractions shows that the appearance of an increased pressure drop in the catalyst bed indicates only its compaction. Shutting down such a reactor and taking a catalyst for analysis to determine the activity of the latter almost always shows that the catalyst has sufficient activity to operate, and therefore disconnecting the reactor from the reactor system, if only this indicator of the catalyst is taken into account, is impractical.

 Reducing the number of reactors to two to three reduces the ratio of the total length of the reactors to their diameter and lowers the conversion of olefin-containing feed to polymer distillate.

 An object of the invention is to increase the yield of polymer distillate and better use of the catalyst by changing the place of introduction of the feed into the reactor (or in one of its sections) after the appearance of a certain increased pressure drop in it compared to the recommended value of this indicator for the process technology.

The problem is solved in that the polymerization of olefin-containing raw materials by feeding it to the top of series-connected reactors, monitor the pressure drop in each of them. After increasing the pressure drop in the reactor not less than twice the process recommended by the current technology (0.09 0.13 kg / cm ³ ), the olefin-containing feed is transferred to the lower part of the reactor (reversed).

 The operating experience of the experimental section of the reactor shows that only after the pressure drop in it is twice as high as in the first days of operation (the phosphoric acid catalyst is used for 40 to 100 days) the geometric shape of the catalyst changes, turning mainly into compounds from granules. These compounds from the granules of the catalyst, as it turned out, are strong enough, they are not crushed and are not moved by the stream of olefin-containing raw materials, the supply of which is transferred from the bottom up (reverses). As a result of this technique, the pressure drop in the reactor section is reduced, the catalyst consumption is increased, and the yield of polymer distillate is increased. However, single pellets, which are present in small quantities (2-4% of the total amount of catalyst) are held by conventional grids, which are installed both in the lower and upper parts of the reactor section.

 Example 1 (comparative known method [2]).

The polymerization of the butane-butylene fraction with a butylene content of 45 wt. carried out in a five-section vertical shell-and-tube reactor at an averaged temperature of 195 ^o C, a volumetric feed rate of the butane-butylene fraction 1 h ^-1 , an inlet pressure in the first section of the reactor 6.0 MPa and a pressure drop of 0.5 MPa (see table. 1, stage 1.1).

 Under these conditions, the yield of polymer distillate is 40 wt. per butane-butylene fraction.

During operation (see table 1, step 1.2), the pressure drop in the reactor increases, and in the fifth section it reaches 0.215 MPa and rises 2.87 times from the recommended value, and the yield of polymer distillate decreases to 34.3 wt. The total pressure drop in the reactor is 0.7 MPa. After 50 days from the start of operation, the 5th section of the reactor is turned off to overload the catalyst. In terms of the year, the yield of polymer distillate is 32.6
Example 2. The polymerization of the butane-butylene fraction is carried out under the conditions specified in example 1 (see table. 1, step 2.1). During operation after 36 days, the plant performance changes (see Table 1, step 2.2), the pressure drop in the fifth section of the reactor increases 2.7 times from the recommended value for the technology for the polymerization unit. In this regard, the supply of the butane-butylene fraction to the fifth section of the reactor is reversed from the bottom up (the re-ligation scheme was mounted in advance). With this scheme of operation of the fifth section of the reactor (see Table 1, step 2.3), the pressure drop after stabilization is reduced from 0.205 to 0.12 MPa, and the yield of polymer distillate increases to 37.8 wt. According to this scheme, the cycle of operation of the 5th section of the reactor is extended to 57 days, and the selection of polymer distillate at the end of this period is 35 wt. (see table 1, step 2.4). Unloading the catalyst from the reactor is easier than when the catalyst is operated according to the usual scheme, and its duration is reduced by two days. In terms of the year, the yield of polymer distillate is 34.0 wt.

 Example 3. The polymerization of the butane-butylene fraction is carried out under the conditions of example 1 (see table. 1, step 3.1). At the inlet of operation after 32 days, the installation indicators change (see table 1, step 3.2). The pressure drop in the fifth section of the reactor increases 2.05 times (from 0.09 to 0.154 MPa) from the recommended technology value for the polymerization unit. In this regard, the supply of the butane-butylene fraction in the fifth section of the reactor is reversed from the bottom up. With this scheme of operation of the fifth section of the reactor (see Table 1, step 3.3), the pressure drop after stabilization is reduced from 0.154 to 0.119 MPa, and the yield of polymer distillate increases from 37.7 to 37.9 wt. According to this scheme, the cycle of operation of the fifth section of the reactor is extended to 62 days, and the selection of polymer distillate at the end of this period is 35.1 (see table 1, step 3.4). The discharge of the catalyst from the reactor is easier than under the conditions of example 1, and the duration of the discharge of spent catalyst is 5 days. In terms of the year, the yield of polymer distillate is 35.2 wt.

 Example 4. The polymerization of the butane-butylene fraction is carried out under the conditions of example 1 (see tab. 1 step 4.1). During operation after 26 days, the installation indicators change (see table. 1, step 4.2). The pressure drop in the fifth section of the reactor increases 1.65 times (from 0.08 to 0.124 MPa) from the recommended technology value for the polymerization unit. The feed of the butane-butylene fraction is reversed from bottom to top. With this scheme of operation of the fifth section of the reactor (see Table 1, step 4.3), the pressure drop after stabilization is reduced from 0.124 to 0.110 MPa, and the yield of polymer distillate remains unchanged, which indicates the incompleteness of physicochemical changes in the catalyst granules, high activity the catalyst and the full use of its surface in the conversion of the butane-butylene fraction under the conditions of steps 4.2 4.3. The ongoing operation of the fifth section of the reactor (see Table 1, step 4.4) shows a decrease in the pressure drop in it almost to the initial one and the release of polymer distillate by the end of the operating cycle 33.6 Opening of the polymerization section after 42 days of operation shows that the remaining catalyst has a low activity and is partially fragmented. Pellet compounds are few and the catalyst unloading is easy. In terms of the year, the yield of polymer distillate in this example is 34.6 and is the lowest value compared to the same indicator in examples 2.3, but higher than in the known method of example 1.

 The use of this method of polymerization of olefin-containing raw materials with reversible input into the reactor provides the following advantages compared to existing methods: increased yield of polymer distillate, reduced catalyst consumption, facilitated catalyst discharge. TTT1

Claims (1)

The method of polymerization of olefin-containing raw materials in sequentially connected shell-and-tube reactors with a fixed catalyst layer of orthophosphoric acid by introducing olefin-containing raw materials into the upper part of the reactor and withdrawing reaction products from the lower part of each reactor, characterized in that after increasing the pressure in the shell-and-tube reactor more than doubled from the recommended values 0.09 0.13 kg / cm ² per 1 m of the height of the catalyst layer, the feed to the shell and tube reactor is reversed from the bottom up.

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