KR102298756B1 - Preparation method for Propylene combining Adsorption separation with Olefin converstion process - Google Patents

Abstract

The present invention produces propylene by combining the propylene conversion reaction process as an adsorption separation process and an olefin conversion process using ethylene and butene as raw materials, thereby improving the efficiency of the catalytic reaction and process, and reducing the operating cost of the process. .

Description

Propylene manufacturing method combining adsorption separation and olefin conversion process {Preparation method for Propylene combining Adsorption separation with Olefin conversion process}

The present invention relates to a propylene manufacturing method combining adsorption separation and olefin conversion processes, and more particularly, a stream containing butene through an adsorption separation process using a stream containing ethylene and a stream containing butene as raw materials. It relates to a method for producing propylene by separating and injecting the separated stream into a propylene conversion process, and by combining the propylene conversion process and the adsorptive separation process, it reduces operating costs and increases production efficiency.

Most of the global petrochemical industry uses naphtha as a raw material due to the recent drop in naphtha price, instead of reducing the proportion of para-xylene production due to deterioration in profitability due to imbalance in supply and demand for para-xylene, which is used as a basic raw material for chemical fibers, etc. The production cost of light olefins used has decreased, and the profitability has greatly improved accordingly, and we are focusing on the production of light olefins, which are raw materials for synthetic resins, synthetic rubbers, and alcohol, and the production of various chemical products using them.

Light olefin refers to ethylene, butene, and propylene obtained through naphtha cracking, and is an essential raw material for the petrochemical industry in the manufacture of various chemical products. As the number of propylene increases, research on a production technology that can efficiently and economically meet the necessary demand for the propylene is continuously being conducted.

As a method for producing propylene, it can generally be obtained from a naphtha cracking process, and in particular, it is a selective Olefin Convsrsion Unit (OCU), which removes butadiene and C4 acetylenes through hydrogenation and then produces propylene through C4 isomerization and olefin metathesis using 2-butene and ethylene This is known

In the process, the C4 olefin mixture used in the metathesis reaction includes butadiene, isobutene, iso and normal butane, 1-butene and 2-butene, and the metathesis reaction produces propylene using 2-butene and ethylene among the raw materials. However, 1-butene contained in the raw material does not react with ethylene, but as hexene and pentene having a lower commercial value than propylene are produced, there is a loss of selectivity for propylene production, thereby reducing propylene production efficiency. .

On the other hand, in Korean Patent Laid-Open Publication No. 10-2007-0090886 among recently published studies, 2-butene was produced by hydroisomerizing a C4 olefin mixture using olefins and paraffins including n-butene and isobutylene in a fixed bed apparatus. There has been a report on increasing the catalytic efficiency by producing propylene through A technique for producing propylene by reacting a combination of There is a need for improvement in

In addition, in the conventional propylene manufacturing process, as materials other than the reaction are included, the scale of equipment such as a reactor and a distillation column is increased, and there is a need to improve operating cost and efficiency.

Therefore, the present invention purifies and pre-separates only butene from a raw material containing butane and butene through an adsorption separation process, and uses a butene-rich stream containing a large amount of butene separated in the above process to provide a propylene conversion reactor as an olefin conversion process. The present invention relates to a method for producing propylene through a propylene conversion process, and to provide a propylene production method capable of reducing operating costs and increasing production efficiency by combining a propylene conversion process and an adsorption separation process.

An object of the present invention is to pre-separate only butene from a raw material containing butene through an adsorption separation process, and use the butene-rich stream separated in the process to produce propylene through a propylene conversion reactor as an olefin conversion process, thereby improving process efficiency The height is to provide a method for producing propylene.

The present invention provides a method for producing propylene using a raw material containing ethylene and a raw material containing butene, in order to solve the above technical problem.

The propylene manufacturing method of the present invention is characterized in that it comprises the following steps.

(1) step of injecting the raw material containing ethylene (ethylene raw material) and the raw material containing butene (butene raw material) into an adsorption separation process to separate the butene-rich stream and the butene-poor stream;

(2) generating propylene by injecting the butene-rich stream separated in step (1) into a propylene conversion reactor;

(3) step of injecting the reaction product of step (2) into a primary distillation column to separate a fraction (C3+) having 3 or more carbon atoms in the lower portion of the primary distillation column; and

and injecting the fraction (C3+) having three or more carbon atoms separated in step (3) into a secondary distillation column to separate and recover propylene from the upper part of the secondary distillation column.

In the propylene manufacturing method described above, in the adsorption separation process of step (1), ethylene contained in the raw material containing ethylene (ethylene raw material) as a desorbent is injected into the adsorption separation process, and According to the relative adsorption power, the butene contained in the raw material (butene raw material) containing the butene is selectively adsorbed and separated.

The butene-rich stream separated from the adsorptive separation process means a stream having a butene content of 80% by weight or more among the fractions having 4 carbon atoms included in the stream among the streams separated in the adsorptive separation process, preferably preferably 90% by weight or more, more preferably 95% by weight or more.

For example, if there is a stream containing 40 wt% of ethylene, 5 wt% of butane, and 55 wt% of butene in the stream separated in the adsorption separation process, the butene content of butane and butene, which is a fraction having 4 carbon atoms, is about 91.7 with 55/60 As wt %, this stream corresponds to a butene-rich stream.

In addition, the stream lacking butene separated from the adsorptive separation process means a stream in which the butene content among the C4 fractions included in the stream separated in the adsorption separation process contains 20% by weight or less, preferably It means an oil fraction of 10% by weight or less, more preferably 5% by weight or less.

However, the criterion for the content of butene contained in the stream separated in the adsorption separation process is a value for separating the stream of butene, since the butene corresponds to an intermediate product of the recycle process of the adsorption separation according to the manufacturing method of the present invention. The standard is not limited to the content standard above.

The butene-deficient stream separated from the adsorption separation process is injected into an ethylene recovery tower and separated into a stream containing 2 or less carbon atoms (C2-) or 4 or more carbon atoms (C4+).

The fraction (C2-) having 2 or less carbon atoms separated in the ethylene recovery tower is recovered through an adsorption separation process, and the fraction (C4+) having 4 or more carbon atoms separated in the ethylene recovery tower is injected into the propylene conversion reactor.

A typical propylene conversion reactor uses a stream in which butadiene, isobutylene and 1-butene are removed as C4 fraction, and the composition of this raw material is 20-30 wt% of n-butane, 60-70 wt% of 2-butene, Other materials usually contain less than 5% by weight, and the C4 fraction of butane and butene is used as a raw material to be converted into propylene. At this time, unreacted butene is recovered and recycled, and propylene in the recycle stream. Butane, which does not participate in the conversion reaction, is also recycled together.

On the other hand, in the present invention, the adsorption separation process of step (1) is added, and in the process, only butene is adsorbed by using a zeolite (Molecular sieve) that selectively adsorbs only olefin (butene) to selectively select butene contained in the oil fraction. is separated and purified by desorbing the adsorbed butene using a stream (ethylene raw material) containing ethylene, which has a stronger relative adsorption strength than the butene for zeolite.

The reaction temperature in the adsorption separation process is 20 ~ 150 ℃, and 1 ~ 20kgf / cm ^{2 As the} reaction pressure, it is used.

Among the streams separated in the adsorption separation process, the butene-rich stream containing ethylene is injected into the propylene conversion reactor together with the fraction (C4+) having 4 or more carbon atoms separated in the ethylene recovery tower, and a conventional metal oxide catalyst By metathesis of the ethylene and butene contained in the stream using the, propylene is prepared.

The primary distillation column of step (3) separates a fraction (C2-) having two or less carbon atoms at the upper portion of the primary distillation column, and converts the fraction (C2-) having two or less carbon atoms to the propylene conversion reactor or the adsorption It may be recycled to any one or more selected during the separation process.

The stream (C3+) having three or more carbon atoms separated in the primary distillation column is injected into the secondary distillation column to prepare a propylene product from the secondary distillation column at the top, and the rest is separated from the bottom and the middle of the secondary distillation column, and the middle of the secondary distillation column The butene (unreacted butene) that has not been converted to propylene in the propylene conversion reactor is recovered.

The stream separated from the lower part of the secondary distillation column is injected into the third distillation column, and the butane (C4s) of four carbons is separated from the upper part of the third distillation column to produce LPG through a hydrogenation reactor or to be used as a raw material for naphtha crackers. , it is possible to solve the problem of accumulating C4 other than butene according to the repetition of the process, and to separate and process the by-product, a stream having 5 or more carbon atoms (C5+).

The present invention produces propylene by combining the adsorption separation process of pre-separation with a butene-rich stream with the propylene conversion reaction process as an olefin conversion process, thereby improving the efficiency of the catalytic reaction and propylene production process, and reducing the operating cost of the process have an effect

1 is a flowchart of the prior art.
2 is a flow chart for a preferred embodiment of the present invention.

The present invention uses a stream containing ethylene and a stream containing butene as raw materials to pre-separate and purify a stream containing butene in an adsorption separation process, and then prepare and separate propylene through a propylene conversion reactor. do.

Hereinafter, the present invention will be described in detail by way of examples, but the present invention is not limited thereto.

Example

Using a stream containing ethylene (ethylene raw material) and a stream containing butene (butene raw material) as raw materials, it is injected into the adsorption separation process before being introduced into the propylene conversion reactor.

The stream containing ethylene (ethylene raw material) as a raw material may be injected into at least one selected from the adsorption separation process, the propylene conversion reactor, or the upper part of the primary distillation column.

The butene-rich stream among the streams separated in the adsorption separation process is separated in the adsorption separation process of step (1) and contains ethylene. Among the butene-rich streams, according to the temperature and pressure conditions of the present invention, By adsorbing butene in the stream using zeolite, butane in the raw material is separated from butene, and the adsorbed butene is desorbed and purified using a stream containing ethylene as a desorbent.

The butene-rich stream is a stream in which the content of butene in the C4 fraction included in the stream separated in the adsorption separation process of step (1) is 90% by weight or more, and the stream lacking butene is adsorption in step (1) It is a stream in which the butene content in the C4 fraction included in the stream separated in the separation process is 10% by weight or less.

The separated butene-rich stream is injected into a propylene conversion reactor, and is converted to propylene through a metathesis reaction of ethylene and butene contained in the stream using a conventional metal oxide catalyst.

The stream lacking the butene is injected into an ethylene recovery tower and separated into a stream having two carbon atoms (C2-) and a stream having four or more carbon atoms (C4+), of which the stream having two carbon atoms (C2-) is recovered again by an adsorption separation process and the four or more streams (C4+) are injected into the propylene production reactor.

The product of the propylene conversion reactor is injected into a primary distillation column using the principle of a conventional distillation column, a stream (C3+) having 3 or more carbon atoms is separated from the bottom of the distillation column and injected into the secondary distillation column, and a stream having 2 or less carbon atoms at the top (C2-) is recycled to any one or more processes selected from the adsorption separation process or the propylene conversion reactor.

The stream (C3+) having 3 or more carbon atoms separated in the primary distillation column is injected into the secondary distillation column to prepare a propylene product from the top of the secondary distillation column, and to recover butene (unreacted butene) that has not been converted to propylene For this, unreacted butene is recovered from the middle of the secondary distillation column to a propylene conversion reactor, and the remaining fraction including butane is separated from the bottom of the secondary distillation column into a third distillation column and injected.

comparative example

The flow of butene of the above embodiment is used as a raw material, and it is directly injected into the propylene conversion reactor together with the flow containing ethylene, and converted using a conventional metal oxide catalyst. Subsequent processes are the same as in the above example. Typically, the conversion rate of the propylene conversion reactor is about 70%, and unreacted butene and ethylene unreacted in the propylene conversion reactor are recovered again in the primary distillation column for conversion reaction.

Examples and Comparative Examples

In general, the conversion rate of the propylene conversion reactor is about 60 to 70%, and ethylene and butene, which have not been reacted in the propylene conversion reactor, are recovered and reacted again in the first/second distillation column, respectively.

However, since butane and butene have similar boiling points, it is not easy to separate, so a large amount of butane is also recirculated during recovery, so this flow is accumulated and the recirculation flow rate is increased. Energy consumption also increases, in the case of an embodiment, most of the butane is removed through an adsorption separation process before being introduced into the propylene conversion reactor.

When simulating the Examples and Comparative Examples using Aspen, the results are summarized in Table 1.

In the case of the metathesis reaction (METATHESIS) in the propylene conversion reactor of Comparative Example, the conversion rate is low, and the butene is generally recycled (RECYCLE) in the secondary distillation column.

As the recirculated flow rate decreased, the flow rate flowing into the reactor decreased by about 30%, and thus the flow rate flowing into each distillation column was also reduced by up to 70%. The amount of heat required for separation in the first to third distillation column was also reduced by about 25% to 9.4 Gcal/hr in the comparative example, whereas the comparative example was 12.6 Gcal/hr.

Through the embodiment of the present invention, by increasing the concentration of butene in the flow injected into the propylene conversion reactor, the capacity in the propylene conversion reactor and the downstream process can be reduced, and thus the equipment, operation and catalyst costs can be reduced. And, due to the decrease in the flow of butane in the reactant, it is possible to obtain the effect of reducing the energy cost due to the decrease in the amount of heat in the pre-heater.

In addition, by separating butane and butene in the previous stage of the propylene conversion reactor of the present invention, the capacity of the facility process such as the reactor and the distillation column including the propylene conversion reactor to accommodate the butane contained in the raw material rather than the process of separating in the subsequent stage There is no need to increase the cost of installation and operation, and the effect of improving efficiency can be obtained.

Claims (6)

A method for producing propylene using an ethylene raw material containing ethylene and a butene raw material containing n-butane and 2-butene,
(1) step of injecting the ethylene raw material containing ethylene and the butene raw material containing n-butane and 2-butene into an adsorption separation process to separate the butene-rich stream and the butene-poor stream;
(2) generating propylene by injecting the butene-rich stream separated in step (1) into a propylene conversion reactor;
(3) step of injecting the reaction product of step (2) into a primary distillation column to separate a fraction having 3 or more carbon atoms in the lower portion of the primary distillation column; and
Propylene production combining adsorption separation and olefin conversion process comprising the step (4) of injecting the fraction having 3 or more carbon atoms separated in step (3) into a secondary distillation column to separate and recover propylene at the top of the secondary distillation column Way. According to claim 1,
A method for producing propylene combining adsorption separation and olefin conversion process, characterized in that in the adsorption separation process of step (1), ethylene contained in the raw material containing ethylene is used as a desorbent. According to claim 1,
The butene-poor stream is injected into an ethylene recovery tower to separate a fraction having 2 or less carbon atoms and a fraction having 4 or more carbon atoms, and the fraction having 2 or less carbon atoms is injected into the adsorption separation process, and the carbon number is 4 or more. A method for producing propylene combining adsorption separation and olefin conversion process, characterized in that the oil is injected into a propylene conversion reactor. According to claim 1,
The primary distillation column of step (3) separates a fraction having 2 or less carbon atoms in the upper portion of the primary distillation column, and converts the fraction having 2 or less carbon atoms to at least one selected from the propylene conversion reactor or the adsorption separation process. A method for producing propylene that combines adsorption separation and olefin conversion processes, characterized in that recovery. According to claim 1,
The butene-rich stream is a stream in which the content of butene in the C4 fraction containing ethylene separated in the adsorption separation process of step (1) is 90% by weight or more, and the stream lacking the butene is a stream in which the butene content is less than 90% by weight in the adsorption separation process of step (1). A method for producing propylene combining adsorption separation and olefin conversion process, characterized in that the stream having a butene content of 10 wt% or less in the C4 fraction containing ethylene separated in the process. According to claim 1,
In the adsorption separation process of step (1), the reaction temperature is 20 ~ 150 ℃, the reaction pressure is 1 ~ 20kgf / cm ^{2 A} method for producing propylene combining adsorption separation and olefin conversion process, characterized in that.

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