CN118389171A - Naphtha directional adsorption separation method - Google Patents
Naphtha directional adsorption separation method Download PDFInfo
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- CN118389171A CN118389171A CN202410498488.9A CN202410498488A CN118389171A CN 118389171 A CN118389171 A CN 118389171A CN 202410498488 A CN202410498488 A CN 202410498488A CN 118389171 A CN118389171 A CN 118389171A
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Abstract
The invention provides a naphtha directional adsorption separation method, and relates to the technical field of petrochemical industry. The invention adopts a double-desorbing agent process flow, utilizes stronger adsorption force of high-carbon alkane (n-dodecane, n-tetradecane or n-hexadecane) and the adsorbent, solves the problems of incomplete desorption of the low-carbon alkane desorbing agent, low separation yield and the like, and thereby remarkably improves the separation efficiency of the process. Meanwhile, the high-carbon alkane on the adsorbent is replaced by the low-carbon alkane (n-pentane or n-hexane), so that the high-carbon alkane is prevented from remaining on the adsorbent and influencing the recycling of the adsorbent. The invention adopts the double-desorbing agent process flow, which not only ensures high separation efficiency, but also improves the utilization rate of the adsorbent. The invention can efficiently separate normal paraffins in naphtha, and is used as a raw material for preparing ethylene (propylene) by high-quality pyrolysis; the separated raffinate oil rich in isoparaffin, naphthene and arene can be used as a high-quality raw material for preparing arene by catalytic reforming.
Description
Technical Field
The invention relates to the technical field of petrochemical industry, in particular to a naphtha directional adsorption separation method.
Background
Naphtha refers to the light fraction of crude oil from the temperature at which atmospheric distillation begins (i.e., the initial point of distillation) to 200 ℃ (or 180 ℃) and has a hydrocarbon composition with a carbon number distribution between C4 and C10. In a typical naphtha composition, n-paraffins account for 30%, isoparaffins account for 30%, naphthenes account for 30%, and aromatics account for 10%. Conventional petroleum processing schemes employ strategies for fraction management, i.e., cutting mixtures in crude oil into products of different distillation ranges according to the distillation characteristics of the materials, and then imparting corresponding uses according to the nature of the products. Resources are often not utilized most reasonably in this management mode. For example, naphtha is mainly used in the oil refining industry in two ways, but from the perspective of reaction engineering analysis, the molecular composition of naphtha raw materials has obvious malposition and low-efficiency conversion conditions: (1) The catalyst is used as an ethylene raw material for preparing by steam cracking, and accounts for more than 65% of the composition of the ethylene raw material at present, but aromatic hydrocarbon and naphthene in naphtha are difficult to crack by ring opening and are easy to coke; (2) Used as raw materials for catalytic reforming to produce aromatic hydrocarbon products, but paraffin in naphtha (the content can be more than 50 percent) is difficult to cyclize and dehydrogenate to produce aromatic hydrocarbon in the catalytic reforming reaction process, and cracking to produce byproducts.
At present, molecular sieves are used as adsorbents to separate normal paraffins from non-normal hydrocarbons (isoparaffins, naphthenes and aromatics) in naphtha, oil products rich in normal paraffins are used as high-quality raw materials for preparing ethylene by steam cracking, and oil products rich in non-normal hydrocarbons are used as high-quality raw materials for catalytic reforming. Much research work has been carried out by foreign UOP corporation, exxonMobil corporation.
In the existing simulated moving bed adsorption separation process, n-pentane or n-hexane is generally adopted as a desorbent, for example, china patent CN102585887A discloses an adsorption separation method of naphtha, and the naphtha is introduced into a simulated moving bed adsorption separation device filled with a 5A molecular sieve under the condition of keeping a liquid phase; obtaining a desorption effluent and an adsorption effluent by a liquid-solid adsorption separation continuous process by taking n-pentane or n-hexane as a desorption agent; and the desorption effluent and the adsorption effluent are respectively recovered by a desorption agent to obtain desorption oil rich in normal paraffins and adsorption oil rich in non-normal paraffins. However, the adsorption performance of n-pentane and n-alkane in naphtha on a molecular sieve is similar, and the problems of incomplete desorption, low separation yield and the like exist.
Disclosure of Invention
In view of the above, the present invention aims to provide a naphtha directional adsorption separation method. The invention can realize the efficient adsorption separation of naphtha.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a naphtha directional adsorption separation method, which comprises the following steps:
Adsorbing the liquid naphtha by using a molecular sieve adsorbent to obtain a raffinate effluent;
Carrying out first desorption on the adsorbed molecular sieve adsorbent by adopting a first desorption agent to obtain desorption effluent;
Performing second desorption on the molecular sieve adsorbent subjected to the first desorption by adopting a second desorption agent, and repeating the adsorption process of the obtained molecular sieve adsorbent;
Recovering the desorption effluent by a desorption agent to obtain desorption oil rich in normal alkane components; recovering the residual adsorption effluent by a desorbent to obtain residual adsorption oil rich in isoparaffin, naphthene and aromatic components;
The first desorbing agent is n-dodecane, n-tetradecane or n-hexadecane; the second desorbing agent is n-pentane or n-hexane.
Preferably, the liquid naphtha is straight run naphtha, hydrocracked naphtha or hydrocracked naphtha.
Preferably, the molecular sieve adsorbent is one or more of 5A, ZSM-5, UZM-35 and beta molecular sieve, and the silicon-aluminum ratio of the molecular sieve adsorbent is 40-200.
Preferably, the temperature of the adsorption, first desorption and second desorption are independently 100 to 190 ℃.
The invention provides a naphtha continuous directional adsorption separation method, which comprises the following steps:
providing a simulated moving bed adsorption separation device, wherein the simulated moving bed adsorption separation device comprises an adsorption zone and a desorption zone which are arranged in series, the adsorption zone and the desorption zone are respectively provided with a plurality of separation columns filled with molecular sieve adsorbents, and the inlet and the outlet of each separation column are provided with program-controlled valves;
introducing liquid naphtha into a first separation column of the adsorption zone for adsorption, and allowing the adsorbed raffinate oil to flow out of a simulated moving bed adsorption separation device, and sequentially cooling and recovering desorbent to obtain desolventized raffinate oil rich in isoparaffins, naphthenes and aromatic hydrocarbons;
Simultaneously, a second desorption agent is introduced into the next separation column of the liquid naphtha inlet to carry out second desorption, and the first desorption agent in the column is replaced; introducing a first desorbing agent into a first separation column of the desorption zone to carry out first desorption, and replacing normal alkane adsorbed by a molecular sieve adsorbent in the column; the desorption oil generated by the first desorption and the second desorption flows out of the simulated moving bed adsorption separation device and is sequentially cooled and recovered by the desorption agent to obtain desorption oil rich in normal paraffins; the first desorbing agent is n-dodecane, n-tetradecane or n-hexadecane; the second desorbing agent is n-pentane or n-hexane;
And switching the liquid naphtha inlet, the second desorbent inlet and the first desorbent inlet through a program-controlled valve of the simulated moving bed adsorption separation device, moving a separation column forward, and repeating the adsorption and desorption process.
Preferably, the separation columns are respectively filled in cylindrical tower sections, and the single column height-to-diameter ratio of the separation columns is 2-20: 1.
Preferably, the bed temperature of the simulated moving bed adsorption separation device is 100-190 ℃.
Preferably, the liquid naphtha feed space velocity is from 0.05 to 1.5h -1 and the first and second desorbents feed space velocities are independently from 0.05 to 10h -1.
Preferably, the feed space velocity of the first desorbent and the second desorbent are equal.
Preferably, the switching time is 700-900 s.
The invention provides a naphtha directional adsorption separation method, which comprises the following steps: adsorbing the liquid naphtha by using a molecular sieve adsorbent to obtain a raffinate effluent; carrying out first desorption on the adsorbed molecular sieve adsorbent by adopting a first desorption agent to obtain desorption effluent; performing second desorption on the molecular sieve adsorbent subjected to the first desorption by adopting a second desorption agent, and repeating the adsorption process of the obtained molecular sieve adsorbent; recovering the desorption effluent by a desorption agent to obtain desorption oil rich in normal alkane components; recovering the residual adsorption effluent by a desorbent to obtain residual adsorption oil rich in isoparaffin, naphthene and aromatic components; the first desorbing agent is n-dodecane, n-tetradecane or n-hexadecane; the second desorbing agent is n-pentane or n-hexane. Compared with the prior art (for example, patent CN 102585887A) which adopts n-pentane or n-hexane as a desorbing agent, the invention has the following beneficial effects:
the invention combines the advantages and disadvantages of low-carbon alkane and high-carbon alkane, adopts a double-desorbing agent process flow, utilizes stronger adsorption force of the high-carbon alkane (n-dodecane, n-tetradecane or n-hexadecane) and the adsorbent, solves the problems of incomplete desorption, low separation yield and the like existing in the similar adsorption performance of the low-carbon alkane desorbing agent and the n-alkane in naphtha on the molecular sieve, and obviously improves the separation efficiency of the process. Meanwhile, the high-carbon alkane on the adsorbent is replaced by the low-carbon alkane (n-pentane or n-hexane), so that the high-carbon alkane is prevented from remaining on the adsorbent and influencing the recycling of the adsorbent. The invention adopts the double-desorbing agent process flow, which not only ensures high separation efficiency, but also improves the utilization rate of the adsorbent. The invention can efficiently separate normal paraffins in naphtha, and is used as a raw material for preparing ethylene (propylene) by high-quality pyrolysis; the separated raffinate oil rich in isoparaffin, naphthene and aromatic hydrocarbon can be used as a high-quality catalytic reforming aromatic hydrocarbon raw material, so that the dual-objective optimization of the yield of ethylene (propylene) and aromatic hydrocarbon by taking naphtha as a raw material is realized, the utilization efficiency of naphtha resources is obviously improved, the requirements of the ethylene and aromatic hydrocarbon industry on the naphtha raw material are fully met, and the dual-objective optimization of the yield of low-carbon olefin and aromatic hydrocarbon by taking naphtha as the raw material is realized.
The invention also provides a naphtha directional adsorption separation method, which adopts a simulated moving bed double-desorbent process flow, and has the advantages of continuous operation, high yield, high product yield, high molecular sieve utilization rate and directional separation of normal alkane components in naphtha.
Drawings
FIG. 1 is a flow chart of a naphtha continuous directional adsorption separation process in an embodiment of the invention, wherein the naphtha is 1-naphtha storage tank in FIG. 1; 2-a first desorbent tank; 3-a second desorbent reservoir; 4-a residual oil absorbing storage tank; 5-desorbing the oil storage tank; 6-program control valve; 7-a separation column; 8-a condenser; 9-pump.
Detailed Description
The invention provides a naphtha directional adsorption separation method, which comprises the following steps:
Adsorbing the liquid naphtha by using a molecular sieve adsorbent to obtain a raffinate effluent;
Carrying out first desorption on the adsorbed molecular sieve adsorbent by adopting a first desorption agent to obtain desorption effluent;
Performing second desorption on the molecular sieve adsorbent subjected to the first desorption by adopting a second desorption agent, and repeating the adsorption process of the obtained molecular sieve adsorbent;
Recovering the desorption effluent by a desorption agent to obtain desorption oil rich in normal alkane components; recovering the residual adsorption effluent by a desorbent to obtain residual adsorption oil rich in isoparaffin, naphthene and aromatic components;
The first desorbing agent is n-dodecane, n-tetradecane or n-hexadecane; the second desorbing agent is n-pentane or n-hexane.
In the present invention, all preparation materials/components are commercially available products well known to those skilled in the art unless specified otherwise.
The invention adopts molecular sieve adsorbent to adsorb liquid naphtha to obtain raffinate effluent. In the present invention, the liquid naphtha is preferably straight run naphtha, hydrocracked naphtha or hydrocracked naphtha. In the present invention, the molecular sieve adsorbent is preferably one or more of 5A, ZSM-5, UZM-35 and beta molecular sieves, and the silicon to aluminum ratio of the molecular sieve adsorbent is preferably 40 to 200, more preferably 50 to 150. The source of the molecular sieve adsorbent is not particularly limited, and the molecular sieve adsorbent is prepared by adopting commercial products or adopting a preparation method well known to a person skilled in the art. In the present invention, the temperature of the adsorption is preferably 100 to 190 ℃, more preferably 150 to 180 ℃, and even more preferably 170 ℃. In the adsorption process, normal paraffins (C4-C10) in naphtha are adsorbed in molecular sieve pore channels.
The invention adopts a first desorption agent to carry out first desorption on the adsorbed molecular sieve adsorbent to obtain desorption effluent. In the present invention, the first desorbent is n-dodecane, n-tetradecane or n-hexadecane. In the present invention, the temperature of the first desorption is preferably 100 to 190 ℃, more preferably 150 to 180 ℃, and even more preferably 170 ℃. In the first desorption process, the first desorbent displaces the normal alkane adsorbed in the molecular sieve to form desorption effluent. The invention utilizes stronger adsorption force of high-carbon alkane and adsorbent to more thoroughly desorb normal alkane, solves the problems of incomplete desorption, low separation yield and the like of the low-carbon alkane desorbing agent and the normal alkane in naphtha, which are similar to the adsorption performance of the normal alkane on the molecular sieve, thereby obviously improving the separation efficiency of the process.
The invention adopts the second desorption agent to carry out the second desorption on the molecular sieve adsorbent after the first desorption, and the obtained adsorbent repeatedly carries out the adsorption process. In the present invention, the second desorbing agent is n-pentane or n-hexane, and the temperature of the second desorbing agent is preferably 100 to 190 ℃, more preferably 150 to 180 ℃, and even more preferably 170 ℃. In the second desorption process, the second desorbent displaces the first desorbent in the adsorbent. When the high-carbon alkane as the first desorbent is adopted, the high-carbon alkane and the adsorbent have strong binding force, and the separation efficiency of normal alkane is improved, but the re-adsorption performance of the adsorbent on naphtha is affected, so that the utilization rate of the adsorbent is low. In the repeated adsorption process, the second desorbent in the adsorbent is replaced, and the second desorbent flows out along with the residual oil.
After desorption effluent and residual adsorption effluent are obtained, the desorption effluent is recycled by a desorption agent to obtain desorption oil rich in normal alkane components; and recovering the residual adsorption effluent by a desorbent to obtain the residual adsorption oil rich in isoparaffin, naphthene and aromatic components. The method of recovering the desorbent is not particularly limited, and the corresponding method known to those skilled in the art, such as rectification, can be adopted.
The invention separates normal paraffins from naphtha based on molecular management, can be used as a high-quality raw material for preparing ethylene (propylene) by cracking, separates isoparaffin, naphthene and arene from naphtha, can be used as a high-quality raw material for preparing arene by catalytic reforming, realizes the double-target optimization of the yield of ethylene (propylene) and arene by taking naphtha as raw materials, obviously improves the utilization efficiency of naphtha resources, fully meets the requirements of the ethylene and arene industry on the naphtha raw materials, and realizes the double-target optimization of the yield of light olefins and arene by taking naphtha as raw materials.
The invention provides a naphtha continuous directional adsorption separation method, which comprises the following steps:
Providing a simulated moving bed adsorption separation device, wherein the simulated moving bed adsorption separation device comprises an adsorption zone and a desorption zone which are arranged in series, the adsorption zone and the desorption zone are provided with a plurality of separation columns filled with molecular sieve adsorbents, and the inlet and the outlet of each separation column are provided with program-controlled valves;
introducing liquid naphtha into a first separation column of the adsorption zone for adsorption, and allowing the adsorbed raffinate oil to flow out of a simulated moving bed adsorption separation device, and sequentially cooling and recovering desorbent to obtain desolventized raffinate oil rich in isoparaffins, naphthenes and aromatic hydrocarbons;
Simultaneously, a second desorption agent is introduced into the next separation column of the liquid naphtha inlet to carry out second desorption, and the first desorption agent in the column is replaced; introducing a first desorbing agent into a first separation column of the desorption zone to carry out first desorption, and replacing normal alkane adsorbed by a molecular sieve adsorbent in the column; the desorption oil generated by the first desorption and the second desorption flows out of the simulated moving bed adsorption separation device and is sequentially cooled and recovered by the desorption agent to obtain desorption oil rich in normal paraffins; the first desorbing agent is n-dodecane, n-tetradecane or n-hexadecane; the second desorbing agent is n-pentane or n-hexane;
And switching the liquid naphtha inlet, the second desorbent inlet and the first desorbent inlet through a program-controlled valve of the simulated moving bed adsorption separation device, moving a separation column forward, and repeating the adsorption and desorption process.
The simulated moving bed adsorption separation device is not particularly required, and the simulated moving bed adsorption separation device well known to the person skilled in the art can be adopted.
In the invention, the separation columns are preferably respectively filled in cylindrical tower sections, and the height-to-diameter ratio of the single column of the separation columns is preferably 2-20: 1, more preferably 10:1.
In the present invention, the molecular sieve adsorbent is preferably the same as the above technical solution, and will not be described herein.
In the present invention, the bed temperature of the simulated moving bed adsorption separation device is preferably 100 to 190 ℃, more preferably 150 to 180 ℃, and even more preferably 170 ℃.
In the present invention, the liquid naphtha feed space velocity is preferably 0.05 to 1.5h -1, more preferably 0.17 to 0.34h -1, the first and second desorbents feed space velocities are preferably independently 0.05 to 10h -1, more preferably 0.68 to 1.37h -1, and the switching time is preferably 700 to 900s. In the embodiment of the present invention, the feeding airspeed of the first desorbent and the feeding airspeed of the second desorbent are more preferably equal, and the switching time is preferably the same.
In the present invention, the temperature of cooling the raffinate oil and the desorbent oil is preferably 10 to 30 ℃, and the raffinate oil and the desorbent oil are condensed and liquefied after the cooling.
In the present invention, in order to enhance the purity of the raffinate oil, it is preferable to introduce the obtained raffinate oil as a raw material into the simulated moving bed adsorption separation apparatus again, perform adsorption separation according to the above-described method, and recover the raffinate oil by a desorbent to obtain a total raffinate oil rich in high concentrations of isoparaffins, naphthenes and aromatics.
FIG. 1 is a flow chart of a naphtha continuous directional adsorption separation process (namely a simulated moving bed adsorption separation process) in an embodiment of the invention, wherein a simulated moving bed adsorption separation device is divided into four areas of an area I, an area II, an area III and an area IV. The method for carrying out naphtha continuous directional adsorption separation according to the flow shown in fig. 1 comprises the following steps: heating the bed temperature of the simulated moving bed adsorption separation device to 100-190 ℃, introducing naphtha in a naphtha storage tank 1, a first desorbent in a first desorbent storage tank 2 and a second desorbent in a second desorbent storage tank 3 into a raw material inlet (F) and a desorbent inlet (D/E) of the simulated moving bed adsorption separation device filled with molecular sieve adsorbents respectively, adsorbing normal paraffins in the naphtha in a molecular sieve pore canal of a first separation column in an adsorption zone (III), allowing the adsorbed residual oil to flow out of the simulated moving bed adsorption separation device, condensing and liquefying by a condenser 8, collecting by an residual oil storage tank 4, and obtaining desolventized residual oil rich in isoparaffins, naphthenes and aromatic hydrocarbons after passing through a desorbent recovery tower; simultaneously, the second desorbent is introduced into the next separation column of the naphtha inlet to replace the first desorbent in the adsorption column; at this time, the first desorbent is substituted in the desorption zone (zone I) of the simulated moving bed to extract the normal paraffins adsorbed in the molecular sieve and is carried out by a desorption oil outlet (G), condensed and liquefied by a condenser 8, collected by a desorption oil storage tank 5, and then passed through a desorption agent recovery tower to obtain desorption oil rich in normal paraffins. And then the naphtha inlet, the second desorbent inlet and the first desorbent inlet are all moved forwards by a separation column through a program-controlled valve 6, and the adsorption and desorption process is repeated. After the adsorption of the III areas is finished, the III areas are adsorbed to the IV areas, and the II areas are desorbed; then adsorbing in zone I, and desorbing in zone III; the circulation is carried out according to the method, so that the adsorption column capable of adsorbing is ensured.
The invention adopts a program-controlled valve simulated moving bed adsorption separation device, and realizes continuous directional adsorption separation of naphtha by a liquid-solid adsorption separation continuous process and double desorbents.
In order to further illustrate the present invention, the naphtha directional adsorption separation process provided by the present invention is described in detail below with reference to examples, but they should not be construed as limiting the scope of the present invention.
Example 1
Referring to the process flow of fig. 1, the process flow of this embodiment is as follows:
Respectively introducing liquid naphtha and n-dodecane as a desorbent into a separation column III region and a separation column I region filled with a ZSM-5 molecular sieve (with a silicon-aluminum ratio of 50), adsorbing normal paraffins in the naphtha into micro-pore channels of a bed molecular sieve in the III region, allowing the adsorbed and treated raffinate oil to flow out of the separation column III region of the simulated moving bed, cooling, condensing the raffinate oil to obtain raffinate oil rich in isoparaffins, naphthenes and aromatic hydrocarbons, and sending the raffinate oil into a catalytic reforming device to obtain reformate such as benzene, toluene and xylene;
Meanwhile, the desorbent n-dodecane is desorbed in the simulated moving bed separation column I area, the desorbent carrying n-alkane flows out of the simulated moving bed separation column I area, the n-alkane is condensed and liquefied to obtain the desorbed oil rich in the n-alkane, and the desorbent n-pentane is substituted for the n-dodecane in the adsorption column in the next separation column at the naphtha raw material inlet of the simulated moving bed separation column III area;
then the inlet and outlet positions of the simulated moving bed are synchronously moved forward to the position of a separation column through a program control valve, and the adsorption separation principle is the same as that described above.
Comprises 30% of normal alkane, 5kg of straight run liquid naphtha with the distillation range of 40-180 ℃ and a simulated moving bed molecular sieve bed with the passing temperature of 170 ℃, 3.4kg of ZSM-5 molecular sieve is filled in the bed, the height of the bed is 30cm, and the height-diameter ratio is 10:1, the feeding airspeed of naphtha is 0.34h -1, the feeding airspeed of desorbent n-dodecane is 1.37h -1, the feeding airspeed of desorbent n-pentane is 1.37h -1, the switching time is 900 seconds, the residual intermediate oil and the desorbed oil are obtained after condensation, the residual intermediate oil and the desorbed oil are subjected to the recovery (rectification recovery) process of the desorbent to obtain the desolventized residual intermediate oil and the desolventized desorbed oil, wherein the total mass concentration of isoparaffin, naphthene and arene in the residual intermediate oil is 88%, and the mass concentration of n-alkane in the desolventized desorbed oil is 99%.
And (3) introducing the desolventized residual intermediate oil serving as a raw material into a simulated moving bed for re-adsorption separation, and performing a desorbent recovery process (rectification recovery), wherein the total mass concentration of isoparaffin, naphthene and aromatic hydrocarbon in the obtained desolventized residual oil is 94%.
Because the simulated moving bed layer is composed of a plurality of single columns connected end to end, naphtha and desorbent need to pass through all the single column beds in one switching period to complete separation. Therefore, for the simulated moving bed process, the molecular sieve bed utilization rate is 100%. For the simulated moving bed process in this example, the annual naphtha throughput was 2000kg/a.
Example 2
The process flow of this embodiment is shown in fig. 1.
Comprises 30% of normal alkane, 5kg of straight run liquid naphtha with the distillation range of 40-180 ℃ and a simulated moving bed molecular sieve bed with the passing temperature of 150 ℃, 3.4kg of ZSM-5 molecular sieve (with the silicon-aluminum ratio of 50) is filled in the bed, the height of the bed is 30cm, and the height-diameter ratio is 10:1, the feeding airspeed of naphtha is 0.17h -1, the feeding airspeed of desorbent n-tetradecane is 0.68h -1, the feeding airspeed of desorbent n-hexane is 0.68h -1, the switching time is 900 seconds, the residual intermediate oil and the desorbed oil are obtained after condensation, and the residual intermediate oil and the desorbed oil are subjected to the recovery process of the desorbent to obtain the desolventized residual intermediate oil and the desolventized desorbed oil. Wherein the total mass concentration of isoparaffin, cycloparaffin and arene in the desolventizing residual intermediate oil is 85%, and the mass concentration of normal paraffin in the desolventizing desorption oil is 95%.
And (3) introducing the desolventized residual intermediate oil serving as a raw material into a simulated moving bed for re-adsorption separation, and recovering the desorbent to obtain the desolventized residual oil with the total mass concentration of isoparaffin, naphthene and aromatic hydrocarbon of 92%.
Example 3
The process flow of this embodiment is shown in fig. 1.
Comprises 25% of normal alkane, 5kg of straight run liquid naphtha with the distillation range of 44-180 ℃ and a simulated moving bed molecular sieve bed with the passing temperature of 170 ℃, 3.4kg of ZSM-5 molecular sieve (with the silicon-aluminum ratio of 50) is filled in the bed, the height of the bed is 30cm, and the height-diameter ratio is 10:1, the feeding airspeed of naphtha is 0.17h -1, the feeding airspeed of desorbent n-dodecane is 0.86h -1, the feeding airspeed of desorbent n-pentane is 0.86h -1, the switching time is 700 seconds, the residual intermediate oil and the desorbed oil are obtained after condensation, and the residual intermediate oil and the desorbed oil are subjected to desolventizing and residual intermediate oil and desolventizing and desorbed oil obtained after the recovery process of the desorbent. Wherein the total mass concentration of isoparaffin, cycloparaffin and arene in the desolventizing residual intermediate oil is 88%, and the mass concentration of normal paraffin in the desolventizing desorption oil is 97%.
And (3) introducing the desolventized residual intermediate oil serving as a raw material into a simulated moving bed for re-adsorption separation, and recovering the desorbent to obtain the desolventized residual oil with the total mass concentration of isoparaffin, naphthene and aromatic hydrocarbon of 96%.
Example 4
The process flow of this embodiment is shown in fig. 1.
Comprises 30% of normal alkane, 5kg of straight run liquid naphtha with the distillation range of 50-190 ℃ and a simulated moving bed molecular sieve bed with the passing temperature of 170 ℃, 3.4kg of ZSM-5 molecular sieve (with the silicon-aluminum ratio of 50) is filled in the bed, the height of the bed is 30cm, and the height-diameter ratio is 10:1, the feeding airspeed of naphtha is 0.34h -1, the feeding airspeed of desorbent n-dodecane is 1.37h -1, the feeding airspeed of desorbent n-hexane is 1.37h -1, the switching time is 900 seconds, the residual intermediate oil and the desorbed oil are obtained after condensation, and the residual intermediate oil and the desorbed oil are subjected to desolventizing and residual intermediate oil and desolventizing and desorbed oil obtained after the recovery process of the desorbent. Wherein the total mass concentration of isoparaffin, cycloparaffin and arene in the desolventizing residual intermediate oil is 88 percent, and the mass concentration of normal paraffin in the desolventizing desorption oil is 95 percent.
And (3) introducing the desolventized residual intermediate oil serving as a raw material into a simulated moving bed for re-adsorption separation, and recovering the desorbent to obtain the desolventized residual oil with the total mass concentration of isoparaffin, naphthene and aromatic hydrocarbon of 92%.
Example 5
The process flow of this embodiment is shown in fig. 1.
Comprises 35% of normal alkane, 5kg of straight run liquid naphtha with the distillation range of 50-190 ℃ and a simulated moving bed molecular sieve bed with the passing temperature of 180 ℃, 3.4kg of ZSM-5 molecular sieve (with the silicon-aluminum ratio of 50) is filled in the bed, the height of the bed is 30cm, and the height-diameter ratio is 10:1, the feeding airspeed of naphtha is 0.34h -1, the feeding airspeed of desorbent n-hexadecane is 1.37h -1, the feeding airspeed of desorbent n-pentane is 1.37h -1, the switching time is 900 seconds, the residual intermediate oil and the desorbed oil are obtained after condensation, and the residual intermediate oil and the desorbed oil are subjected to the recovery process of the desorbent to obtain the desolventized residual intermediate oil and the desolventized desorbed oil. Wherein the total mass concentration of isoparaffin, cycloparaffin and arene in the desolventizing residual intermediate oil is 87%, and the mass concentration of normal paraffin in the desolventizing desorption oil is 98%.
And (3) introducing the desolventized residual intermediate oil serving as a raw material into a simulated moving bed for re-adsorption separation, and recovering the desorbent to obtain the desolventized residual oil with the total mass concentration of isoparaffin, naphthene and aromatic hydrocarbon of 93%.
Comparative example 1
Contains 30% of normal alkane, 5kg of straight run liquid naphtha with the distillation range of 40-180 ℃ and passes through a fixed bed molecular sieve bed layer with the temperature of 300 ℃, 3.4kg of ZSM-5 molecular sieve (with the silicon-aluminum ratio of 50) is filled in the bed layer, and a desorption oil product rich in alkane and a raffinate oil product rich in non-alkane are obtained, and the purity of the product is equivalent to that of the product obtained by a simulated moving bed process. The annual treatment capacity of naphtha in the fixed bed process is 972kg/a, and the utilization rate of a molecular sieve bed layer is about 95 percent (the actual adsorption capacity of the molecular sieve divided by the theoretical adsorption capacity).
The result shows that the annual treatment capacity of naphtha is only 49% of that of the simulated moving bed process by adopting the fixed bed adsorption separation process, and the utilization rate of the fixed bed molecular sieve bed is lower than that of the simulated moving bed process.
Comparative example 2
Comprises 30% of normal alkane, 5kg of straight run liquid naphtha with the distillation range of 40-180 ℃ and a simulated moving bed molecular sieve bed with the passing temperature of 170 ℃, 3.4kg of ZSM-5 molecular sieve (with the silicon-aluminum ratio of 50) is filled in the bed, the height of the bed is 30cm, and the height-diameter ratio is 10:1, the feeding airspeed of naphtha is 0.34h -1, only n-pentane is used as a desorbing agent, the feeding airspeed of the desorbing agent n-pentane is 1.37h -1, the switching time is 900 seconds, the residual-absorption intermediate oil and the desorbed oil are obtained after condensation, and the residual-absorption intermediate oil and the desorbed oil are subjected to the desolventizing and residual-absorption intermediate oil and the desolventizing and desorbed oil obtained after the recovery process of the desorbing agent. Wherein the total mass concentration of isoparaffin, naphthene and arene in the residual intermediate oil is 76%, and the mass concentration of normal paraffin in the desolventized desorption oil is 84%.
And (3) introducing the desolventized residual intermediate oil serving as a raw material into a simulated moving bed for re-adsorption separation, and recovering the desorbent to obtain the desolventized residual oil with the total mass concentration of isoparaffin, naphthene and aromatic hydrocarbon of 82%.
The result shows that when the desorbent only adopts n-pentane, the total mass concentration of isoparaffin, naphthene and arene in the obtained residual oil and the mass concentration of n-paraffin in the desorbed oil are smaller than those obtained by using the double-desorbent process because the adsorption performance of n-paraffin in naphtha and n-pentane on the molecular sieve are similar.
The foregoing is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. It should be noted that modifications and adaptations to the present invention may occur to one skilled in the art without departing from the principles of the present invention and are intended to be comprehended within the scope of the present invention.
Claims (10)
1. A naphtha directional adsorption separation method, which is characterized by comprising the following steps:
Adsorbing the liquid naphtha by using a molecular sieve adsorbent to obtain a raffinate effluent;
Carrying out first desorption on the adsorbed molecular sieve adsorbent by adopting a first desorption agent to obtain desorption effluent;
Performing second desorption on the molecular sieve adsorbent subjected to the first desorption by adopting a second desorption agent, and repeating the adsorption process of the obtained molecular sieve adsorbent;
Recovering the desorption effluent by a desorption agent to obtain desorption oil rich in normal alkane components; recovering the residual adsorption effluent by a desorbent to obtain residual adsorption oil rich in isoparaffin, naphthene and aromatic components;
The first desorbing agent is n-dodecane, n-tetradecane or n-hexadecane; the second desorbing agent is n-pentane or n-hexane.
2. The naphtha directional adsorptive separation process of claim 1, wherein the liquid naphtha is straight run naphtha, hydrocracked naphtha, or hydrocracked naphtha.
3. The directional adsorptive separation process of claim 1, wherein said molecular sieve adsorbent is one or more of 5A, ZSM-5, UZM-35 and beta molecular sieves, said molecular sieve adsorbent having a silica to alumina ratio of 40-200.
4. The naphtha directional adsorptive separation process of claim 1, wherein the temperatures of the adsorption, first desorption, and second desorption are independently 100-190 ℃.
5. The naphtha continuous directional adsorption separation method is characterized by comprising the following steps of:
providing a simulated moving bed adsorption separation device, wherein the simulated moving bed adsorption separation device comprises an adsorption zone and a desorption zone which are arranged in series, the adsorption zone and the desorption zone are respectively provided with a plurality of separation columns filled with molecular sieve adsorbents, and the inlet and the outlet of each separation column are provided with program-controlled valves;
introducing liquid naphtha into a first separation column of the adsorption zone for adsorption, and allowing the adsorbed raffinate oil to flow out of a simulated moving bed adsorption separation device, and sequentially cooling and recovering desorbent to obtain desolventized raffinate oil rich in isoparaffins, naphthenes and aromatic hydrocarbons;
Simultaneously, a second desorption agent is introduced into the next separation column of the liquid naphtha inlet to carry out second desorption, and the first desorption agent in the column is replaced; introducing a first desorbing agent into a first separation column of the desorption zone to carry out first desorption, and replacing normal alkane adsorbed by a molecular sieve adsorbent in the column; the desorption oil generated by the first desorption and the second desorption flows out of the simulated moving bed adsorption separation device and is sequentially cooled and recovered by the desorption agent to obtain desorption oil rich in normal paraffins; the first desorbing agent is n-dodecane, n-tetradecane or n-hexadecane; the second desorbing agent is n-pentane or n-hexane;
And switching the liquid naphtha inlet, the second desorbent inlet and the first desorbent inlet through a program-controlled valve of the simulated moving bed adsorption separation device, moving a separation column forward, and repeating the adsorption and desorption process.
6. The method for continuous directional adsorption separation of naphtha according to claim 5, wherein the separation columns are respectively filled in column sections, and the ratio of the height to the diameter of a single column of the separation columns is 2-20: 1.
7. The method for continuous and directional adsorption separation of naphtha according to claim 5, wherein the bed temperature of the simulated moving bed adsorption separation device is 100-190 ℃.
8. The naphtha continuous directional adsorptive separation process of claim 5, wherein the liquid naphtha feed space velocity is from 0.05 to 1.5h -1 and the first and second desorbents feed space velocities are independently from 0.05 to 10h -1.
9. The naphtha sequential directional adsorption separation process of claim 8, wherein the feed space velocities of the first and second desorbents are equal.
10. The naphtha continuous directional adsorption separation method according to claim 5 or 8, wherein the switching time is 700 to 900s.
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