WO2018180210A1

WO2018180210A1 - Film regeneration method

Info

Publication number: WO2018180210A1
Application number: PCT/JP2018/008118
Authority: WO
Inventors: 鈴木　貴博; 詩織大森; 貴笹沼; 英了三木
Original assignee: 日本ゼオン株式会社
Priority date: 2017-03-28
Filing date: 2018-03-02
Publication date: 2018-10-04
Also published as: JPWO2018180210A1

Abstract

A film regeneration method for regenerating a film that is suitable for use in separation of some hydrocarbons from a hydrocarbon mixture. More specifically, a film regeneration method which comprises: a step (A) wherein a hydrocarbon mixture is brought into contact with a zeolite film; and a step (B) wherein the zeolite film is exposed to an inert gas atmosphere and the temperature of the inert gas atmosphere is increased.

Description

Membrane regeneration method

The present invention relates to a membrane regeneration method, and more particularly to a membrane regeneration method for regenerating a membrane that can be suitably used when separating some hydrocarbons from a hydrocarbon mixture.

Conventionally, a membrane separation method has been used as a method for separating a specific component from a multi-component mixture with low energy. As the separation membrane, for example, a zeolite membrane formed by forming a zeolite on a support in the form of a membrane is used.

Here, generally, the performance of the zeolite membrane used for membrane separation is expressed by the permeation flux of the permeate and the separation factor. And the zeolite membrane used for membrane separation is calculated | required to raise a permeation | transmission flux and a separation factor.

Therefore, supply of regeneration gas containing heated air to zeolite membranes conventionally used for membrane separation of gas to be treated containing carbon dioxide and hydrocarbon combustible gas into permeate gas and non-permeate gas Thus, a film regeneration method for regeneration has been proposed (see, for example, Patent Document 1).

International Publication No. 2016/027713

However, in the above conventional membrane regeneration method using a regeneration gas containing heated air, the separation factor of the zeolite membrane for membrane separation of the hydrocarbon mixture could not be sufficiently increased.

Therefore, an object of the present invention is to provide a membrane regeneration method that can sufficiently increase the separation factor of a separation membrane for membrane separation of a hydrocarbon mixture.

The present inventors have intensively studied to achieve the above object. The present inventors have found that if the zeolite membrane used for membrane separation of the hydrocarbon mixture is regenerated using a specific regeneration gas, the separation factor of the zeolite membrane can be sufficiently increased, and the present invention has been completed. I let you.

That is, the present invention aims to advantageously solve the above problems, and the membrane separation method of the present invention comprises a step (A) of bringing a hydrocarbon mixture into contact with a zeolite membrane, and an inert gas. And (B) exposing the zeolite membrane to an atmosphere to raise the temperature of the inert gas atmosphere. In this way, the zeolite membrane brought into contact with the hydrocarbon mixture is exposed to an inert gas atmosphere, and the atmosphere is regenerated while raising the temperature, so that the separation factor of the zeolite membrane obtained through the step (B) is sufficient. Can be increased.

Here, in the membrane separation method of the present invention, it is preferable that the maximum temperature of the inert gas atmosphere in the step (B) is 100 ° C. or higher and 450 ° C. or lower. If the maximum temperature of the inert gas atmosphere to which the zeolite membrane is exposed during the step (B) is 100 ° C. or higher and 450 ° C. or lower, the separation factor of the zeolite membrane is more sufficiently suppressed while suppressing the loss of the zeolite membrane due to heat. Can be increased.

In the membrane separation method of the present invention, the inert gas is preferably nitrogen gas. If the atmosphere to which the zeolite membrane is exposed is nitrogen gas, the separation coefficient of the zeolite membrane can be further sufficiently increased by effectively regenerating the porosity of the zeolite membrane.

In the membrane separation method of the present invention, in the step (B), the zeolite membrane is exposed to the inert gas atmosphere before the temperature of the inert gas atmosphere is increased. It is preferable to further include a film pressurizing operation for pressurization. By performing such a membrane pressurizing step, the separation factor of the zeolite membrane can be further sufficiently increased.

According to the present invention, it is possible to provide a membrane regeneration method capable of sufficiently increasing the separation factor of a separation membrane for membrane separation of a hydrocarbon mixture.

It is a figure which shows an example of schematic structure of a membrane separator provided with the zeolite membrane reproducible by the membrane reproduction | regeneration method of this invention.

Hereinafter, embodiments of the present invention will be described in detail.
Here, the membrane regeneration method of the present invention can be used for regeneration of a zeolite membrane that can be suitably used for membrane separation of a hydrocarbon mixture. In particular, the membrane regeneration method of the present invention can remarkably improve the separation factor of a zeolite membrane when a new zeolite membrane brought into contact with a hydrocarbon mixture is treated for the first time.

(Membrane regeneration method)
The membrane regeneration method of the present invention is a method for regenerating a zeolite membrane that can be used for membrane separation of a hydrocarbon mixture. Such a membrane regeneration method includes a step (A) of bringing a hydrocarbon mixture into contact with a zeolite membrane, and a step (B) of exposing the zeolite membrane to an inert gas atmosphere to raise the temperature of the inert gas atmosphere. Including. In the membrane regeneration method of the present invention, after bringing the hydrocarbon mixture into contact with the zeolite membrane, the zeolite membrane is exposed to an inert gas atmosphere, and the membrane is regenerated while raising the temperature of the inert gas atmosphere. Therefore, the separation factor of the zeolite membrane can be sufficiently increased. As a result, it is possible to achieve good separation performance when the regenerated zeolite membrane is used for separation of a hydrocarbon mixture.

Here, the reason why it is possible to sufficiently increase the separation factor of the zeolite membrane by regenerating the zeolite membrane while raising the temperature in an inert gas atmosphere is not clear, but it is assumed that it is as follows. The That is, the zeolite membrane brought into contact with the hydrocarbon mixture retains the hydrocarbon component adsorbed or adhered to the membrane. Such a component can block or narrow the innumerable pores of a zeolite membrane that is originally porous. As a result, the permeation flux and the separation factor are reduced in the zeolite membrane after the operation of bringing the hydrocarbon mixture into contact, such as separating the hydrocarbon mixture. Here, the zeolite membrane is a membrane formed by growing zeolite crystals on a support. Generally, zeolite crystals include micropores having a pore diameter of 2 nm or less, and mesopores having a pore diameter of more than 2 nm and not more than 50 nm are formed at a crystal grain boundary formed between the plurality of crystals. The plural types of hydrocarbon compounds contained in the hydrocarbon mixture to be separated include those that are relatively easy to pass through the pores and those that are difficult to pass depending on their structure. And the separation factor is obtained due to the difference in pore permeability of each hydrocarbon compound. Here, when a zeolite membrane is used for separation of the hydrocarbon mixture, the pores may be blocked or narrowed with the passage of the separation time. For this reason, a separation factor falls by operation which makes a hydrocarbon mixture contact. However, in the membrane regeneration method of the present invention, the zeolite membrane is regenerated while raising the temperature in an inert gas atmosphere. Since it can be created well during regeneration, it is presumed that the separation factor of the zeolite membrane can be sufficiently increased compared to the zeolite membrane before the regeneration treatment.

<Hydrocarbon mixture>
Here, the hydrocarbon mixture that is the separation target of the zeolite membrane that can be regenerated by the membrane regeneration method of the present invention is a plurality of types of carbonized compounds that can separate some hydrocarbon compounds using the zeolite membrane. There is no particular limitation as long as it is a mixture of hydrogen compounds. Specifically, examples of the hydrocarbon mixture include a mixture containing a straight-chain hydrocarbon having the same number of carbon atoms, a branched hydrocarbon and / or a cyclic hydrocarbon. Among them, the hydrocarbon mixture is preferably a mixture containing as a main component a linear hydrocarbon having 4 carbon atoms and a branched hydrocarbon having 4 carbon atoms and / or a cyclic hydrocarbon having 4 carbon atoms, Alternatively, it is a mixture containing as a main component a linear hydrocarbon having 5 carbon atoms and a branched hydrocarbon having 5 carbon atoms and / or a cyclic hydrocarbon having 5 carbon atoms, and more preferably a carbon number Is a mixture containing as a main component a linear hydrocarbon having 5 and a branched hydrocarbon having 5 carbon atoms and / or a cyclic hydrocarbon having 5 carbon atoms.
In the present invention, “contains linear hydrocarbons and branched hydrocarbons and / or cyclic hydrocarbons as main components” means linear hydrocarbons and branched hydrocarbons in a hydrocarbon mixture. It refers to containing 50 mol% or more of hydrogen and / or cyclic hydrocarbons in total.

A mixture containing a linear hydrocarbon having 4 carbon atoms and a branched hydrocarbon and / or a cyclic hydrocarbon having 4 carbon atoms as main components (hereinafter referred to as “a hydrocarbon mixture having 4 carbon atoms”) As a straight chain hydrocarbon having 4 carbon atoms such as n-butane, 1-butene, 2-butene and butadiene, and a branched hydrocarbon having 4 carbon atoms such as isobutane and isobutene. And / or a mixture containing a cyclic hydrocarbon having 4 carbon atoms such as cyclobutane and cyclobutene. Specifically, the hydrocarbon mixture having 4 carbon atoms includes, for example, a C4 fraction produced as a by-product when pyrolyzing naphtha to produce ethylene, or after recovering at least a part of butadiene from the C4 fraction. Examples include remaining fractions.

Also, a mixture containing as a main component a linear hydrocarbon having 5 carbon atoms and a branched hydrocarbon and / or cyclic hydrocarbon having 5 carbon atoms (hereinafter referred to as “a hydrocarbon mixture having 5 carbon atoms”) And a linear hydrocarbon having 5 carbon atoms such as n-pentane, 1-pentene, 2-pentene, 1,3-pentadiene, isopentane, 2-methyl-1-butene, A mixture containing a branched hydrocarbon having 5 carbon atoms such as 2-methyl-2-butene, 3-methyl-1-butene and isoprene and / or a cyclic hydrocarbon having 5 carbon atoms such as cyclopentane and cyclopentene. Can be mentioned. Specifically, the hydrocarbon mixture having 5 carbon atoms includes, for example, a C5 fraction produced as a by-product when pyrolyzing naphtha to produce ethylene, or after recovering at least a portion of isoprene from the C5 fraction. Examples include remaining fractions.

<Zeolite membrane>
Further, examples of the zeolite membrane regenerated by the membrane regeneration method of the present invention include any zeolite membrane capable of separating a desired hydrocarbon compound from a hydrocarbon mixture. Specifically, although not particularly limited, the zeolite membrane includes a porous support and a porous separation layer provided on the porous support, and a porous separation layer is desired. And a separation membrane containing zeolite (aluminosilicate and / or silicalite) capable of separating the hydrocarbon compound. More specifically, for example, a porous support that is a zeolite membrane that can be suitably used for membrane separation of a hydrocarbon mixture having 4 carbon atoms or a hydrocarbon mixture having 5 carbon atoms, and a porous support on the porous support. And a separation membrane comprising an MFI-type zeolite (aluminosilicate having a MFI structure and / or silicalite).

Here, as the porous support, a porous body made of any material can be used as long as it is a porous body capable of supporting the porous separation layer. Among these, porous bodies made of porous ceramics such as alumina, mullite, zirconia, cordierite, etc .; glass such as shirasu porous glass; and porous sintered metals such as stainless steel are preferable. This is because a porous body made of porous ceramics or porous sintered metal is excellent in mechanical strength.
The shape of the porous support is not particularly limited, and can be any shape such as a flat film shape, a flat plate shape, a tube shape, and a honeycomb shape.

The porous separation layer can be formed, for example, by synthesizing zeolite having a desired structure such as MFI-type zeolite on a porous support or a porous support to which a zeolite seed crystal is attached. Specifically, the porous separation layer is obtained by immersing a porous support optionally attached with a zeolite seed crystal in an aqueous sol containing a silica source and a structure-directing agent, and synthesizing the zeolite by hydrothermal synthesis. Can be formed on a porous support.

In addition, the zeolite membrane obtained by forming the porous separation layer on the porous support is subjected to a calcination treatment for removing the structure-directing agent and a boiling washing treatment, followed by oxygen-containing conditions such as in an air atmosphere. It may have been subjected to a baking treatment in an atmosphere.

<Process (A)>
Here, in the step (A), the hydrocarbon mixture is brought into contact with the zeolite membrane. More specifically, step (A) can be a separation step for performing membrane separation or an exposure step for exposing the zeolite membrane to a hydrocarbon mixture gas. That is, the step (A) is a step that can be carried out by any specific operation without particular limitation as long as the hydrocarbon mixture can be brought into contact with the zeolite membrane. In step (A), the hydrocarbon component can be adsorbed or adhered to the zeolite membrane by bringing the hydrocarbon mixture into contact with the zeolite membrane.

In addition, when the step (A) is a separation step, a part of the hydrocarbon compound contained in the hydrocarbon mixture is separated by the zeolite membrane. Specifically, without particular limitation, in the step (A) that is the separation step, for example, carbonization including linear hydrocarbons, branched hydrocarbons and / or cyclic hydrocarbons having the same number of carbon atoms. For example, linear hydrocarbons can be efficiently separated and removed from the hydrogen mixture, thereby increasing the content of branched hydrocarbons and / or cyclic hydrocarbons in the hydrocarbon mixture. More specifically, in step (A), which is a separation step, a part of the components (for example, linear hydrocarbons) can be separated and removed from the hydrocarbon mixture by passing the hydrocarbon mixture through a zeolite membrane. it can.

The separation step using a zeolite membrane can be performed under any conditions, but is preferably performed under heating conditions. Specifically, the separation step is preferably performed under conditions of 20 ° C. or higher and 300 ° C. or lower, more preferably 25 ° C. or higher and 250 ° C. or lower, and further preferably 50 ° C. or higher and 200 ° C. or lower. The pressure conditions for performing the separation step are not particularly limited, but it is preferable that the differential pressure between the non-permeation side and the permeation side (pressure on the non-permeation side−pressure on the permeation side) be 10 kPa or more and 600 kPa or less, More preferably, it is 50 kPa or more and 300 kPa or less. In the present specification, the pressure is a gauge pressure.

On the other hand, when step (A) is an exposure step, for example, a hydrocarbon mixture containing linear hydrocarbons having the same number of carbon atoms and branched hydrocarbons and / or cyclic hydrocarbons is used as the zeolite membrane. It can be introduced on the non-permeable side and / or on the transmissive side. In step (A), which is the exposure step, the pressure of the hydrocarbon mixture-containing atmosphere to which the zeolite membrane is exposed is preferably, for example, 0 kPa or more and 600 kPa or less.

In addition, as the step (A), the place where the zeolite membrane is exposed to the hydrocarbon mixture is, for example, the case where the zeolite membrane is accommodated in the housing as in the case where the present step (A) is a separation step as described above. It may be in a place where the separation operation can be carried out, such as in the membrane separation module, or in a storage container for storing the zeolite membrane outside the membrane separation module.

<Process (B)>
In the step (B), the zeolite membrane is exposed to an inert gas atmosphere to raise the temperature of the inert gas atmosphere. Here, when the inert gas atmosphere to which the zeolite membrane is exposed in the step (B) is heated, the temperature of the atmosphere may be lowered during the execution of the step (B) or may not be lowered. May be. Among them, the zeolite membrane is exposed from the viewpoint of suppressing the destruction of the zeolite membrane due to a rapid temperature drop when the hydrocarbon mixture is subjected to membrane separation using the regenerated zeolite membrane that has undergone the step (B). It is preferable to lower the temperature of the inert gas atmosphere during the implementation of the step (B).

[Inert gas atmosphere]
Here, the inert gas atmosphere to which the zeolite membrane is exposed in the step (B) includes an atmosphere made of an inert gas such as nitrogen gas, argon gas, and helium gas. These inert gases can be used singly or in combination. Among these, nitrogen gas is preferable as the inert gas. If the inert gas atmosphere to which the zeolite membrane is exposed is a nitrogen gas atmosphere, the separation factor of the zeolite membrane can be further sufficiently increased by effectively regenerating the porosity of the zeolite membrane. This is because, when the zeolite membrane is regenerated while raising the temperature of the nitrogen gas atmosphere, micropores are created and the hydrocarbon compounds adhering to or adsorbing to the zeolite membrane carbonize, resulting in clogging of the mesopores. It is thought that it is to do. Therefore, the regenerated zeolite membrane obtained by performing the step (B) using a nitrogen gas atmosphere increases the permeability coefficient of the hydrocarbon compound that easily permeates the micropores, and the hydrocarbon compound that permeates the mesopores. The transmission coefficient can be reduced.

In addition, as the inert gas used for constituting the inert gas atmosphere to which the zeolite membrane can be exposed in the step (B), it is preferable to use an inert gas having a very low content of components other than the inert gas, It is more preferable that it is an inert gas consisting essentially of an inert gas, and it is even more preferable that no gas other than the inert gas is contained. Here, “consisting essentially of an inert gas” means that 99.9% by volume or more of the inert gas is the inert gas. The inert gas atmosphere can contain water vapor as a component other than the inert gas. However, when the inert gas atmosphere can contain water vapor, the dew point of the inert gas atmosphere is −20 ° C. or lower. Is preferably −30 ° C. or less, more preferably −40 ° C. or less, and particularly preferably −50 ° C. or less. In the present specification, the “dew point” refers to a dew point under atmospheric pressure determined from the amount of water measured using Fourier transform infrared spectroscopy (FT-IR).

Furthermore, the maximum temperature of the inert gas atmosphere to which the zeolite membrane is exposed during the step (B) is preferably 100 ° C. or higher, more preferably 150 ° C. or higher, and further preferably 200 ° C. or higher. Preferably, the temperature is 450 ° C. or lower, and more preferably 400 ° C. or lower. By making the maximum temperature of the inert gas atmosphere to which the zeolite membrane is exposed during the step (B) above the above lower limit, the separation factor of the regenerated zeolite membrane obtained through the step (B) can be sufficiently increased. it can. Moreover, it can suppress effectively that deterioration, such as a defect | deletion, arises in a zeolite membrane by making the maximum temperature of the inert gas atmosphere to which a zeolite membrane is exposed during a process (B) below the said upper limit. . The temperature of the inert gas atmosphere to which the zeolite membrane is exposed during the step (B) is preferably in the range of 10 ° C. or higher and 450 ° C. or lower, and preferably in the range of 20 ° C. or higher and 450 ° C. or lower. More preferred.
The pressure (gauge pressure) of the inert gas atmosphere to which the zeolite membrane is exposed is preferably 1 MPa or less, for example. This is because if the pressure is too high, the zeolite membrane may be damaged. Moreover, the pressure (gauge pressure) of the inert gas atmosphere to which the zeolite membrane is exposed is usually 10 kPa or more.

Here, the time for which the dew point is exposed to the inert gas atmosphere in the step (B) is not particularly limited and is preferably 5 hours or more, more preferably 10 hours or more, and 15 hours. More preferably, it is usually 500 hours or less. This is because the separation factor of the regenerated zeolite membrane obtained through the step (B) can be further sufficiently increased if the time for exposing the zeolite membrane to the inert gas atmosphere is equal to or more than the above lower limit value.
The time for exposing the zeolite membrane to the inert gas atmosphere at the highest temperature during the step (B) is not particularly limited, but is preferably 5 hours or longer, for example, 10 hours or longer. More preferably, it is more preferably 12 hours or more, more preferably 50 hours or less, and even more preferably 30 hours or less. If the time during which the inert gas atmosphere to which the zeolite membrane is exposed is kept at the maximum temperature is set to the lower limit value or more, the separation coefficient of the regenerated zeolite membrane obtained through the step (B) can be further sufficiently increased. Because. Further, if the time during which the atmosphere to which the zeolite membrane is exposed is kept at the maximum temperature is set to the upper limit value or less, the loss of the zeolite membrane due to heat can be efficiently suppressed.

As a method for exposing the zeolite membrane to an inert gas atmosphere, any method can be used as long as the atmosphere around the zeolite membrane can be changed to an inert gas atmosphere. Specifically, in the step (B), for example, the zeolite membrane may be exposed to an inert gas atmosphere by flowing an inert gas continuously or intermittently in a space in which the zeolite membrane is accommodated, or the zeolite membrane After the space in which the membrane is accommodated is replaced with an inert gas, the zeolite membrane may be exposed to an inert gas atmosphere by keeping the space airtight.
In addition, the place which exposes a zeolite membrane to inert gas atmosphere may be in a housing or a storage container similarly to the said process (A).

In addition, in raising the atmosphere to which the zeolite membrane is exposed during the step (B), the temperature rise may be started from the beginning of the step (B) or in the middle of the step (B). May be. When there is no temperature increase in the atmosphere to which the zeolite membrane is exposed in the initial stage of the step (B), the initial stage may correspond to a <membrane pressing operation> described later.

The temperature of the inert gas atmosphere is preferably raised to 100 ° C. or higher, more preferably raised to 150 ° C. or higher, further preferably raised to 200 ° C. or higher, and raised to 450 ° C. or lower. It is preferable to raise the temperature, and it is more preferable to raise the temperature to 400 ° C. or lower. This is because the separation factor of the regenerated zeolite membrane obtained through the step (B) can be further sufficiently increased by setting the temperature of the atmosphere after the temperature increase (temperature after the temperature increase) to the above lower limit value or more. Further, if the temperature of the atmosphere after the temperature rise (temperature after the temperature rise) is not more than the above upper limit value, it is possible to efficiently suppress the loss of the zeolite membrane due to heat.

The time for maintaining the temperature of the atmosphere at the temperature after the temperature rise after the temperature rise is not particularly limited, but is preferably, for example, 5 hours or more, more preferably 10 hours or more, and 12 hours. More preferably, the time is 50 hours or less, and more preferably 30 hours or less. This is because the separation coefficient of the regenerated zeolite membrane obtained through the step (B) can be further sufficiently increased by setting the time for maintaining the temperature at the temperature after raising the temperature to the above lower limit value or more. Moreover, it is because it can suppress efficiently that a zeolite membrane | film | coat lose | deletes with a heat | fever if the time which hold | maintains atmosphere after temperature rising is below the said upper limit.

In the step (B), the temperature of the heated atmosphere can be arbitrarily lowered to, for example, 30 ° C. or lower, preferably 25 ° C. or lower. If the temperature of the atmosphere to which the zeolite membrane is exposed is lowered to the above upper limit value or less, when the hydrocarbon mixture is subjected to membrane separation using the regenerated zeolite membrane obtained through the step (B), a rapid temperature drop occurs. This is because the destruction of the zeolite membrane can be suppressed.
Note that when the temperature of the atmosphere is lowered, the timing of ending the step (B) may be the same as the end of the temperature drop, or may be after an arbitrary time has elapsed after the temperature drop is ended.

<Membrane pressurization operation>
Furthermore, the membrane regeneration method of the present invention further includes a membrane pressurizing operation for pressurizing the zeolite membrane in a state where the zeolite membrane is exposed to an inert gas atmosphere in the initial stage of the step (B). Is preferred. By performing such a membrane pressurizing operation, the separation factor of the zeolite membrane obtained through the step (B) can be further sufficiently increased. The reason for this is not clear, but by pressing the zeolite membrane with the hydrocarbon mixture adsorbed or adhered, the hydrocarbon mixture can be "indented" closer to the inside of the porous structure of the zeolite membrane. It is guessed. The membrane pressurizing operation is not particularly limited as long as the zeolite membrane can be pressurized, and can be realized by any method. For example, in the membrane pressurizing operation, the zeolite membrane can be pressurized by filling the space containing the zeolite membrane with an inert gas and further increasing the pressure in the space. In addition, as described above, the place where the film pressurizing operation which is a part of the step (B) is performed may be in the housing or in the storage container.

Therefore, for example, in pressurizing the zeolite membrane in the membrane separation module, the zeolite membrane can be pressurized by applying a so-called “back pressure” to the zeolite membrane from the downstream side of the non-permeate side of the zeolite membrane. Alternatively, when the zeolite membrane in the membrane separation module is pressurized, the zeolite membrane can be pressurized by applying pressure to the zeolite membrane from the upstream side of the non-permeate side of the zeolite membrane. Among them, it is preferable to pressurize the zeolite membrane using a gas flow in a direction opposite to the flow direction in which the inert gas is supplied to the zeolite membrane in the step (B).

Under the condition that the pressure applied to each surface of the zeolite membrane can be different, such as when the zeolite membrane in the membrane separation module is pressurized, the differential pressure is preferably 1 MPa or less, and 700 kPa More preferably, it is more preferably 400 kPa or less, usually 10 kPa or more, and preferably 100 kPa or more. At this time, the pressure on the non-permeation side (that is, the side on which the hydrocarbon mixture is brought into contact) is preferably made higher than the pressure on the permeation side.
When the pressure applied to each surface of the zeolite membrane is the same, the pressure of the atmosphere to which the zeolite membrane is exposed during the membrane pressurizing operation is preferably 1 MPa or less, and 700 kPa or less. More preferably, it is more preferably 400 kPa or less, and usually 10 kPa or more.
By setting the differential pressure or pressure during the membrane pressurization operation to the upper limit value or less, it is possible to effectively suppress the zeolite membrane from being damaged by the pressure. Moreover, the separation factor of the zeolite membrane obtained through the step (B) can be further sufficiently increased by setting the differential pressure or pressure during the membrane pressurizing operation to the above lower limit value or more.

Here, prior to the membrane pressurization operation, after the step (A), at the beginning of the step (B), first, a discharge operation for discharging the hydrocarbon mixture and the like from the space in which the zeolite membrane is accommodated is performed. It is preferable to do. The discharge operation is not particularly limited, and can be realized by any specific operation as long as the atmosphere around the zeolite membrane can be replaced with the inert gas that can be used in the step (B), for example. .

Thus, at the beginning of the step (B), any hydrocarbon discharging operation, membrane pressurizing operation, or the like can be interposed. Here, between the step (A) and the step (B), the step of exposing to an atmosphere other than the hydrocarbon mixture or inert gas, such as the atmosphere or carbon dioxide atmosphere, and raising the temperature is not included.

Hereinafter, an example of a schematic configuration of a membrane separation apparatus including a zeolite membrane that can be regenerated by the membrane regeneration method of the present invention will be described. The membrane separation apparatus 100 includes a membrane separation module 30 having a zeolite membrane therein, a raw material supply mechanism 20 for supplying a hydrocarbon mixture to the membrane separation module 30, and an inert gas (N _{2 in the} illustrated example) as a membrane separation module. A gas supply mechanism 40 is provided for supplying a space containing 30 zeolite membranes. Then, the membrane separation apparatus 100 supplies the hydrocarbon mixture to the membrane separation module 30 using the raw material supply mechanism 20 and performs membrane separation, and then raises the temperature in an inert gas atmosphere supplied using the gas supply mechanism 40. However, the membrane separation module can be regenerated.

The membrane separation module 30 includes a housing 31 and a zeolite membrane 32 that is accommodated in the housing 31 and defines a non-permeation side region 33 and a permeation side region 34 in the housing 31. A non-permeate component outflow mechanism 60 that allows non-permeate components to flow out is provided on the downstream side of the non-permeate side region 33 of the membrane separation module 30. The non-permeable component outflow mechanism 60 includes a non-permeable component line 61, a back pressure valve 62, and a non-permeable component line valve 63. The non-permeable component line 61 is connected to a non-permeable component recovery device (not shown). Or may be connected to a hydrocarbon mixture reservoir 10 to form a circulation channel.

Further, a gas outflow line 71 for branching out the gas supplied from the gas supply mechanism branches and extends from the non-permeating component line 61, and a gas outflow line valve 72 is provided in the gas outflow line 71. . The gas outflow line 71 and the gas outflow line valve 72 constitute a gas outflow mechanism 70 that outflows the gas (N _{2 in the} illustrated example) supplied from the gas supply mechanism 40 and in contact with the zeolite membrane.

Further, a permeate component outflow mechanism 50 including a permeate component line for allowing permeate components to flow out is provided on the downstream side of the permeate side region 34 of the membrane separation module 30. The transmission component line is provided with a transmission component line valve (not shown). The permeation component line is connected to a permeation component recovery device (not shown) such as a cold trap.

The raw material supply mechanism 20 is provided with a raw material line 21 that connects the hydrocarbon mixture storage tank 10 and the non-permeate side region 33 of the membrane separation module 30, and the raw material line 21 is configured to remove the hydrocarbon mixture in the storage tank 10. A transfer device 22 for feeding to the permeate side region 33, a heater 23 provided in the raw material line 21 for heating the hydrocarbon mixture, and a raw material line valve 24 are provided.

According to the raw material supply mechanism 20, the hydrocarbon mixture fed through the transfer device 22 is heated by the heater 23 by operating the transfer device 22 and the heater 23 with the raw material line valve 24 opened. Then, it can be vaporized and supplied to the non-permeate side region 33 of the membrane separation module 30. Further, according to the raw material supply mechanism 20, the supply of the hydrocarbon mixture to the non-permeate side region 33 of the membrane separation module 30 can be stopped by closing the raw material line valve 24.

The gas supply mechanism 40 is connected to the raw material line 21 between the raw material line valve 24 and the membrane separation module 30 to connect an inert gas supply source (not shown) and the non-permeate side region 33 of the membrane separation module 30. The gas line 41 to connect, the gas line valve 42, and the heater 43 which is provided in the gas line 41 and heats inert gas is provided.

And according to the gas supply mechanism 40, by operating the heater 43 with the gas line valve 42 open, the gas is heated by the heater 43 and supplied to the non-permeate side region 33 of the membrane separation module 30. can do. Further, according to the gas supply mechanism 40, the gas supply to the non-permeate side region 33 of the membrane separation module 30 can be stopped by closing the gas line valve 42.

And according to the membrane separation apparatus 100 mentioned above, the raw material line valve 24, the non-permeate component line valve 63, and the permeate component line valve (not shown) are opened, the gas line valve 42 and the gas outflow line valve 72 are closed, and the raw material The hydrocarbon mixture can be flowed from the supply mechanism 20 to the membrane separation module 30 to separate the hydrocarbon mixture. Specifically, the vaporized hydrocarbon mixture is sent to the non-permeate side region 33 of the membrane separation module 30 through the transfer device 22 and the heater 23, and the permeated component permeated through the zeolite membrane 32 is transmitted to the permeated component outflow mechanism 50. The non-permeate component that has not permeated the zeolite membrane 32 can be recovered or circulated through the non-permeate component outflow mechanism 60.

Further, according to the membrane separation device 100 described above, the raw material line valve 24, the non-permeating component line valve 63 and the permeating component line valve (not shown) are closed, and the gas line valve 42 and the gas outflow line valve 72 are opened. Thus, the inert gas can flow from the gas supply mechanism 40 to the membrane separation module 30. Specifically, the inert gas heated by the heater 43 can be caused to flow into the housing 31 of the membrane separation module 30 so that the heated inert gas and the zeolite membrane 32 can be brought into contact with each other. Further, the inert gas after coming into contact with the zeolite membrane 32 can be discharged to an arbitrary processing apparatus via the gas outflow line 71.

The zeolite membrane 32 provided in such a membrane separation apparatus 100 can be regenerated by the membrane regeneration method of the present invention described above. Such a membrane separation device 100 can membrane-separate the hydrocarbon mixture using the obtained regenerated zeolite membrane 32.

EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these Examples.
In Examples and Comparative Examples, the separation factor improvement rate of the hydrocarbon mixture was measured and evaluated by the following method.

<Separation factor improvement rate>
In the examples and comparative examples, new zeolite membranes were used. Then, each of the examples, as comparative examples step (A), performs a separation process to obtain a permeate side samples S _1. Further, by using the reproduction completion zeolite membrane after a step (B), subjected to a separation step under the same conditions as step (A), to obtain a permeate side samples S _2. Then, using the permeation side samples S ₁ and S ₂ , a new product separation coefficient α _n and a regenerated membrane separation coefficient α _r were calculated according to the following formula (I). Furthermore, the separation factor improvement rate before and after the regeneration was calculated according to the following formula (II).
α _n or α _r = (Y _n / Y _iso ) / (X _n / X _iso ) (I)
Separation coefficient improvement rate (%) = (α _r −α _n ) / α _n × 100
In formula (I), X _n is the content ratio [mol%] of n-pentane in the raw material, X _iso is the content ratio [mol%] of isopentane in the raw material, and Y _n is a content of the permeate side samples S ₁ or in S ₂ of n- pentane _{[mol%], Y iso} are content of isopentane in the permeate side sample S ₁ or S ₂ [mol%].

Example 1
<Process (A)>
A structure separating agent is formed by forming a porous separation layer made of MFI-type zeolite on the outer surface of a cylindrical mullite porous support, followed by firing in an air atmosphere having a dew point of 2 ° C. at a temperature of 500 ° C. for 20 hours. Using the MFI-type zeolite membrane obtained by removing the membrane, a separation step as step (A) was performed using a membrane separation apparatus 100 as shown in FIG. The permeation component line of the membrane separation apparatus 100 was connected to a sampling cold trap, and the non-permeation component line 61 was connected to the storage tank 10 via a heat exchanger as a cooler.
The separation process using the membrane separation apparatus 100 shown in FIG. 1 was performed as follows.
Specifically, first, the storage tank 10 is filled with a hydrocarbon mixture of 5 carbon atoms composed of a mixed liquid of n-pentane and isopentane (a mixed liquid of n-pentane: 50 mol% and isopentane: 50 mol%). The deaeration operation was performed three times.
Next, the raw material line valve 24, the non-permeate component line valve 63, and the permeate component line valve (not shown) are closed, and the gas line valve 42 and the gas outflow line valve 72 are opened. Nitrogen gas (dew point: −50 ° C., introduced nitrogen gas purity: 99.99% by volume) was passed through 30 to bring the nitrogen gas into contact with the zeolite membrane 32. Specifically, nitrogen gas heated by the heater 43 is caused to flow into the housing 31 of the membrane separation module 30 and the temperature in the housing 31 is raised to 500 ° C. (maximum temperature), and then the maximum temperature 500 is reached. Nitrogen gas and the zeolite membrane 32 were contacted at 15 ° C. for 15 hours. Thereafter, the temperature in the housing 31 was lowered to 20 ° C., and the nitrogen gas and the zeolite membrane 32 were contacted at a temperature of 20 ° C. for 19 hours.
Thereafter, the raw material line valve 24 and the non-permeate component line valve 63 were opened, and the gas line valve 42 and the gas outflow line valve 72 were closed. Then, the hydrocarbon mixture was heated to 70 ° C. by the heater 23, supplied to the membrane separation module 30 in the gas phase, then condensed by the cooler, and the raw material circulation process to return to the storage tank 10 was started. . Then, after starting the material circulation treatment, the system is operated until the temperature in the system reaches a steady state. After the temperature in the system reaches a steady state, the back pressure valve 62 pressurizes the non-permeate side to 150 kPa (gauge pressure). At the same time, the permeation side (cold trap) was reduced to -100 kPa (gauge pressure). And after confirming that the temperature and pressure in the system were stable, the permeation component line valve (not shown) was opened, and membrane separation was started. That is, membrane separation was performed under the conditions of a temperature of 70 ° C. and a differential pressure of 250 kPa between the non-permeable side and the permeable side.
And after starting membrane separation, when 5 hours passed, discharge operation which discharges a raw material from the system as follows was performed. In the discharging operation, first, the raw material line valve 24 was closed and the gas line valve 42 was opened, and the hydrocarbon mixture in the line was pushed out to the storage tank 10 through the non-permeating component line valve 63. Then, nitrogen gas was supplied by the gas supply mechanism 40 until the pressure in 100 became 150 kPa, the pressure inside the system was increased, and a pressure release valve (not shown) was opened to release pressure from the storage tank 10. After the operation from the pressure increase to the pressure release was repeated four times, the non-permeate component line valve 63 was closed, the gas outflow line valve 72 was opened again, and supply of nitrogen gas (that is, nitrogen purge) was started.

<Membrane pressurization process>
Then, prior to the step (B) of regenerating the separation membrane, a membrane pressurizing step was performed as follows. First, after starting the nitrogen purge, the back pressure valve 62 was opened and a back pressure of 100 kPa (gauge pressure) was applied to the non-permeating side. At this time, the pressure on the permeation side (cold trap) was kept at −100 kPa (gauge pressure). That is, in the film pressurizing step, the differential pressure between the non-permeable side and the permeable side was set to 200 kPa. This state was maintained for 10 minutes.

<Process (B)>
Thereafter, in step (B), the nitrogen gas was heated while exposing the zeolite membrane 32 to nitrogen gas as an inert gas. Specifically, nitrogen gas (dew point: −50 ° C., introduced nitrogen gas purity: 99.99 vol%) from the gas supply mechanism 40 to the membrane separation module 30 with the gas line valve 42 and the gas outflow line valve 72 opened. ) And nitrogen gas and the zeolite membrane 32 were brought into contact with each other. Specifically, nitrogen gas heated by the heater 43 is caused to flow into the housing 31 of the membrane separation module 30 and the temperature in the housing 31 is raised to 250 ° C. (maximum temperature), and then the maximum temperature 250 is reached. Nitrogen gas and the zeolite membrane 32 were contacted at 15 ° C. for 15 hours. Thereafter, the temperature in the housing 31 was lowered to 20 ° C., and the nitrogen gas and the zeolite membrane 32 were contacted at a temperature of 20 ° C. for 19 hours (temperature lowering operation).
Then, using the regenerated zeolite membrane obtained through the step (B), the separation factor and the separation factor improvement rate were evaluated according to the above method. The results are shown in Table 1.

(Example 2)
A regenerated zeolite membrane was obtained in the same manner as in Example 1 except that the maximum temperature in the housing 31 in the step (B) was changed to 300 ° C. Using the obtained regenerated zeolite membrane, the separation factor and the improvement factor of the separation factor were evaluated according to the above method. The results are shown in Table 1.

(Comparative Example 1)
In step (B) of Example 1, the atmosphere to which the zeolite membrane was exposed was raised using air having a dew point of 20 ° C. instead of nitrogen gas, and the zeolite membrane was held at a maximum temperature of 250 ° C. for 10 hours. The temperature lowering operation was performed after interposing a drying operation in which the atmosphere exposed to was maintained at 250 ° C. as a nitrogen gas atmosphere for 5 hours. Except for these points, a regenerated zeolite membrane was obtained in the same manner as in Example 1. Using the obtained regenerated zeolite membrane, the separation factor and the improvement factor of the separation factor were evaluated according to the above method. The results are shown in Table 1.

From Table 1, it can be seen that in Examples 1 and 2, the separation factor improvement rate is remarkably improved. That is, in Examples 1 and 2, it can be seen that the separation factor of the regenerated zeolite membrane could be significantly improved over that of a new zeolite membrane.

DESCRIPTION OF SYMBOLS 10 Reservoir 20 Raw material supply mechanism 21 Raw material line 22 Transfer device 23 Heater 24 Raw material line valve 30 Membrane separation module 31 Housing 32 Zeolite membrane 33 Non-permeation side area 34 Permeation side area 40 Gas supply mechanism 41 Gas line 42 Gas line valve 43 Heater 50 Permeate component outflow mechanism 60 Non-permeate component outflow mechanism 61 Non-permeate component line 62 Back pressure valve 63 Non-permeate component line valve 70 Gas outflow mechanism 71 Gas outflow line 72 Gas outflow line valve 100 Membrane separation device

Claims

Contacting the hydrocarbon mixture with the zeolite membrane (A);
A step (B) of exposing the zeolite membrane to an inert gas atmosphere to raise the temperature of the inert gas atmosphere.
The film regeneration method according to claim 1, wherein a maximum temperature of the inert gas atmosphere in the step (B) is 100 ° C or higher and 450 ° C or lower.
The film regeneration method according to claim 1 or 2, wherein the inert gas is nitrogen gas.
The step (B) further includes a membrane pressurizing operation for pressurizing the zeolite membrane in a state where the zeolite membrane is exposed to the inert gas atmosphere before raising the temperature of the inert gas atmosphere. The film regeneration method according to any one of claims 1 to 3.