阅读说明：本技术 一种由含乙苯的c8芳烃生产对二甲苯和乙苯的方法 (From C containing ethylbenzene8Method for producing paraxylene and ethylbenzene by aromatic hydrocarbon ) 是由 杨彦强 王德华 王辉国 马剑锋 王红超 李犇 刘宇斯 乔晓菲 高宁宁 于 2020-09-28 设计创作，主要内容包括：一种由含乙苯的C-8芳烃生产对二甲苯和乙苯的方法,包括将含乙苯的C-8芳烃送入乙苯液相吸附分离装置,经吸附分离得含乙苯的吸出液和吸余液,脱除吸出液和吸余液中的解吸剂,得到乙苯和吸余油,将吸余油送入对二甲苯吸附分离装置,不被吸附的组分作为抽余液排出吸附剂床层,用解吸剂冲洗吸附剂床层脱附其中的对二甲苯得抽出液,分别脱除抽出液和抽余液中的解吸剂,得对二甲苯和抽余油,将抽余油送入二甲苯异构化装置进行二甲苯异构化,将异构化产物进行分馏,分馏得到的C-7-芳烃排出装置,其余芳烃作为(2)步吸附分离装置的原料。该法可有效提高对二甲苯吸附分离效率,提高对二甲苯产量,并副产高纯乙苯。(From C containing ethylbenzene 8 A process for producing para-xylene and ethylbenzene from aromatic hydrocarbons comprises subjecting a C containing ethylbenzene 8 Sending aromatic hydrocarbon into an ethylbenzene liquid phase adsorption separation device, obtaining an absorption liquid containing ethylbenzene and an absorption residual liquid through adsorption separation, removing a desorbent in the absorption liquid and the absorption residual liquid to obtain ethylbenzene and absorption residual oil, sending the absorption residual oil into a paraxylene adsorption separation device, taking unadsorbed components as a raffinate to be discharged out of an adsorbent bed layer, flushing the adsorbent bed layer to remove paraxylene in the adsorbent bed layer by using the desorbent to obtain an extraction liquid, respectively removing the desorbent in the extraction liquid and the raffinate to obtain paraxylene and raffinate oil, sending the raffinate oil into a xylene isomerization device to carry out xylene isomerization, and sending the isomerized raffinate oil into a xylene isomerization device to carry out xylene isomerizationFractionating the product to obtain C 7 An aromatics take-off unit, the remaining aromatics being used as feed for the adsorption separation unit of step (2). The method can effectively improve the efficiency of paraxylene adsorption separation, improve the yield of paraxylene and produce a byproduct of high-purity ethylbenzene.)

1. From C containing ethylbenzene₈Method for producing paraxylene and ethylbenzene by aromatic hydrocarbonThe method comprises the following steps:

(1) adding C containing ethylbenzene₈Sending aromatic hydrocarbon into ethylbenzene liquid phase adsorption separation device, making ethylbenzene be adsorbed by adsorbent in ethylbenzene adsorbent bed layer, discharging non-adsorbed component out of adsorbent bed layer as raffinate, flushing adsorbent bed layer with desorbent to remove ethylbenzene to obtain extract, respectively removing desorbent from extract and raffinate to obtain ethylbenzene and raffinate oil,

(2) delivering the raffinate oil obtained in the step (1) into a paraxylene adsorption separation device, wherein paraxylene is adsorbed by an adsorbent in a paraxylene adsorbent bed layer, non-adsorbed components are taken as raffinate to be discharged from the adsorbent bed layer, a desorbent is used for flushing the adsorbent bed layer to desorb the paraxylene to obtain extract liquid, the desorbent in the extract liquid and the desorbent in the raffinate are respectively removed to obtain a paraxylene product and raffinate oil,

(3) sending the raffinate oil obtained in the step (2) into a xylene isomerization device, isomerizing xylene under the action of a xylene isomerization catalyst, fractionating an isomerized product, and fractionating to obtain C₇An aromatics take-off unit, the remaining aromatics being used as feed for the adsorption separation unit of step (2).

2. The method according to claim 1, wherein the ethylbenzene is separated by adsorption in step (1) by using a liquid phase simulated moving bed device, wherein the adsorption separation temperature is 70-180 ℃ and the pressure is 0.2-2.0 MPa.

3. The method according to claim 2, wherein the number of adsorbent beds in the liquid phase simulated moving bed apparatus in step (1) is 8 to 24.

4. The process according to claim 1, wherein the ethylbenzene adsorbent in step (1) comprises 95-99.5 mass% CsNaX zeolite and 0.5-5 mass% binder, wherein the Cs/Na molar ratio is 1.5-10.0, and the desorbent is toluene.

5. The process according to claim 1, wherein the ethylbenzene adsorbent in step (1) comprises 95-99.5 mass% of zeolite X having cation sites occupied by Ba or Ba and K, and 0.5-5 mass% of a binder, and the desorbent is benzene.

6. The process of claim 5, wherein the ethylbenzene adsorbent comprises Na₂The O content is less than 0.6 mass%, when the cation site of the X zeolite is occupied by Ba, the BaO content in the adsorbent is 35-45 mass%, and when the cation site of the X zeolite is occupied by Ba and K, the BaO content in the adsorbent is 25-35 mass%, and K is₂The O content is 7 to 10 mass%.

7. The process according to claim 4, characterized in that the desorbent has a water content of 1 to 15 ppm.

8. The process according to claim 5, characterized in that the water content in the desorbent is 50 to 100 ppm.

9. The process according to claim 4 or 5, wherein the ratio of the volumetric flow rate of the desorbent to the volumetric flow rate of the adsorbent feed for the adsorptive separation of ethylbenzene in step (1) is 0.6 to 5.0 or 0.6 to 3.0.

10. The method according to claim 1, wherein the paraxylene is separated by adsorption in step (2) by using a liquid phase simulated moving bed device, wherein the adsorption separation temperature is 110 to 200 ℃, and the pressure is 0.4 to 2.0 MPa.

11. The method according to claim 10, wherein the number of adsorbent bed layers of the simulated moving bed apparatus is 8 to 24.

12. The method according to claim 1, wherein the paraxylene adsorbent of the step (2) comprises 95 to 99.5 mass% of zeolite X having cation sites occupied by Ba or Ba and K and 0.5 to 5 mass% of a binder.

13. The process according to claim 1, wherein the desorbent for the adsorptive separation of paraxylene in step (2) is toluene or p-diethylbenzene.

14. The method according to claim 1, wherein the temperature of the xylene isomerization reaction in the step (3) is 210-360 ℃, the pressure is 0.1-4.0 MPa, and the mass space velocity of raffinate oil passing through the catalyst is 11-20 h^-1The hydrogen/hydrocarbon molar ratio is 0 to 0.9.

15. The process according to claim 1, wherein in the step (3), the isomerized product is fractionated, and C is fractionated₇-aromatic hydrocarbons and C₉+ aromatics removal unit, C₈And (3) taking the aromatic hydrocarbon as a raw material of the adsorption separation device in the step (2).

16. The process of claim 1, wherein step (2) further comprises adding a stream of C having a low ethylbenzene content to the raffinate obtained in step (1)₈An aromatic hydrocarbon component.

17. The process according to claim 16, characterized in that the C with low ethylbenzene content is added₈The mass ratio of the aromatic hydrocarbon component to the raffinate oil obtained in the step (1) is 0.1-0.8.

18. The process according to claim 1, wherein said ethylbenzene-containing C of step (1)₈The content of ethylbenzene in the aromatic hydrocarbon is 10-25 mass%.

19. The process according to claim 1 or 16, characterized in that the raffinate obtained in step (1) and additionally C having a low ethylbenzene content₈The ethylbenzene content in the aromatic hydrocarbon component is not more than 3 mass%.

20. The process according to claim 1, wherein the xylene isomerization catalyst in the step (3) comprises 15 to 90 mass% of ZSM-5 and/or ZSM-11 zeolite and 10 to 85 mass% of alumina.

21. The process according to claim 1, wherein the xylene isomerization catalyst in the step (3) comprises 15 to 90 mass% of ZSM-5 and/or ZSM-11 zeolite, 1 to 5 mass% of mordenite and 5 to 84 mass% of alumina.

Technical Field

The invention relates to a catalyst prepared from C containing ethylbenzene₈A method for producing paraxylene and ethylbenzene by aromatic hydrocarbon, in particular to a method for producing paraxylene and ethylbenzene by a liquid phase adsorption separation combined process.

Background

Para-xylene is an important chemical raw material for producing terephthalic acid and dimethyl terephthalate, and is used for synthesizing textile products and various plastic products.

The xylene is mainly derived from coal tar distillate, petroleum reformate, thermal cracking products and the like. The C rich in ethylbenzene and dimethylbenzene can be obtained by rectification₈A mixture of aromatic hydrocarbons. C₈The aromatic hydrocarbon comprises ethylbenzeneP-xylene, m-xylene and o-xylene. In the prior art, para-xylene is predominantly from C₈The aromatic hydrocarbon is obtained by separation, and m-xylene and o-xylene obtained by adsorption separation are required to be converted into p-xylene for producing more p-xylene, and the p-xylene is recycled to the adsorption separation device for separating the p-xylene.

Improvements to the above-described technology for adsorptive separation of paraxylene are important directions of research in the art, and not only relate to improvements in each unit step, but also relate to the whole system or a combination of multiple steps.

CN100506765C discloses a method for co-producing p-xylene and styrene by mixing C-xylene, ethylbenzene and xylene₉～C₁₀Feeding the hydrocarbon feed to a distillation column for separation of C by distillation₈Aromatic hydrocarbons and C₉～C₁₀Hydrocarbon, said C₈Aromatic hydrocarbon is introduced into an adsorption tower of a simulated moving bed to carry out C₈Separating out Paraxylene (PX) in aromatic hydrocarbon, introducing other components into ethylbenzene dehydrogenation reaction zone to make ethylbenzene generate styrene, separating out styrene from dehydrogenation product, contacting the rest unconverted ethylbenzene, m-xylene and o-xylene with isomerization catalyst to perform liquid phase isomerization reaction, and recycling the isomerization reaction product back to distillation column.

CN1886357B discloses a method for preparing paraxylene comprising an adsorption step and two isomerization steps, in which C containing ethylbenzene and xylenes is subjected to a simulated moving bed comprising at least 5 zones₈Dividing aromatic hydrocarbon into extract containing 90-95 wt% of p-xylene; intermediate raffinate rich in ethylbenzene, partial meta-xylene and partial ortho-xylene; a raffinate 2 comprising substantially m-xylene and o-xylene. The intermediate raffinate was isomerized in the gas phase to convert ethylbenzene therein to xylenes, and raffinate 2 was isomerized in the liquid phase at low temperature.

CN103373891B discloses a slave C₈A process for preparing p-xylene and ethylbenzene by adsorptive separation of arylhydrocarbon features that the raw material C is₈Separating aromatic hydrocarbon by liquid phase adsorption to obtain extract oil containing p-xylene and raffinate oil containing ethylbenzene, m-xylene and o-xylene, and separating the raffinate oil by gas phase pressure swing adsorption to obtain ethylbenzene; phase change of gasThe meta-xylene and ortho-xylene obtained by pressure adsorption are subjected to isomerization reaction under mild conditions.

CN103201240B discloses a preparation method of p-xylene₈After para-xylene is fractionated in aromatic hydrocarbon, the material poor in para-xylene is divided into two parts to be processed in a liquid phase isomerization unit and a gas phase isomerization unit which are connected in parallel; and in the examples it was demonstrated that such a mode of operation can reduce the energy consumption for the production of paraxylene.

Disclosure of Invention

The invention aims to provide a catalyst prepared from C containing ethylbenzene₈The process of producing p-xylene and ethyl benzene with arene includes the first adsorption and separation of material to obtain ethyl benzene, the subsequent separation in a p-xylene adsorption and separation device to obtain p-xylene, the isomerization of other xylene components, and the subsequent returning to the p-xylene adsorption and separation device to obtain high purity p-xylene and ethyl benzene.

The invention provides a catalyst prepared from C containing ethylbenzene₈A method for producing paraxylene and ethylbenzene by aromatic hydrocarbon comprises the following steps:

(1) adding C containing ethylbenzene₈Sending aromatic hydrocarbon into ethylbenzene liquid phase adsorption separation device, making ethylbenzene be adsorbed by adsorbent in ethylbenzene adsorbent bed layer, discharging non-adsorbed component out of adsorbent bed layer as raffinate, flushing adsorbent bed layer with desorbent to remove ethylbenzene to obtain extract, respectively removing desorbent from extract and raffinate to obtain ethylbenzene and raffinate oil,

(2) delivering the raffinate oil obtained in the step (1) into a paraxylene adsorption separation device, wherein paraxylene is adsorbed by an adsorbent in a paraxylene adsorbent bed layer, non-adsorbed components are taken as raffinate to be discharged from the adsorbent bed layer, a desorbent is used for flushing the adsorbent bed layer to desorb the paraxylene to obtain extract liquid, the desorbent in the extract liquid and the desorbent in the raffinate are respectively removed to obtain a paraxylene product and raffinate oil,

(3) sending the raffinate oil obtained in the step (2) into a xylene isomerization device, isomerizing xylene under the action of a xylene isomerization catalyst, fractionating an isomerized product, and fractionating to obtain C₇-aromatic hydrocarbonsAnd (3) discharging the aromatic hydrocarbon out of the device, and taking the rest aromatic hydrocarbon as the raw material of the adsorption separation device in the step (2).

The method comprises the steps of separating ethylbenzene from the raw material by arranging an ethylbenzene adsorption separation device to obtain a high-purity ethylbenzene product, and then separating the rest low-ethylbenzene content C₈Aromatic hydrocarbons are adsorbed and separated, the paraxylene in the aromatic hydrocarbons is separated, and the rest C₈The isomerization of the aromatic hydrocarbon can effectively improve the efficiency of the adsorption and separation of the paraxylene, improve the yield of the paraxylene and produce a byproduct of high-purity ethylbenzene.

Drawings

FIG. 1 is a prior art block diagram consisting of C₈A flow diagram of the production of para-xylene from aromatics.

FIG. 2 shows a schematic representation of the present invention consisting of₈A schematic flow diagram of the production of para-xylene and ethylbenzene from aromatics is shown.

Detailed Description

The method of the invention is used for adsorbing and separating C₈An ethylbenzene adsorption separation device is arranged in front of the aromatic hydrocarbon device to lead C containing ethylbenzene and xylene₈Separating ethylbenzene from xylene in aromatic hydrocarbon raw material by adsorption to obtain C with low ethylbenzene content₈And then carrying out liquid phase adsorption separation on the aromatic hydrocarbon to separate out p-xylene, sending the rest components into an isomerization device for isomerization reaction to generate p-xylene, and returning the isomerization product to the p-xylene adsorption separation device. The method reduces the content of ethylbenzene participating in circulation in a loop formed by adsorption separation of paraxylene and isomerization reaction, thereby enabling a paraxylene adsorption separation device to be more efficient and reducing the operation severity of the isomerization device. Compared with the prior art, the adsorbent, the isomerization catalyst and C are used under the condition of the same yield of p-xylene₈The aromatic hydrocarbon raw materials are all reduced, the scale of the added ethylbenzene adsorption separation device is smaller, only a small amount of ethylbenzene adsorbent is needed to be used, and a high-purity ethylbenzene product can be obtained.

In the method, the target product is preferably adsorbed and separated by adopting a liquid-phase simulated moving bed device in the steps (1) and (2), and the adsorbent is filled in an adsorption tower of the liquid-phase simulated moving bed device by a plurality of beds. In the adsorption separation process, four inlet and outlet materials of adsorption raw materials, desorbents, extract liquid and raffinate divide an adsorbent bed layer in the adsorption tower into four functional areas, the adsorbent bed layer between the desorbents and the extract liquid is a desorption area, the adsorbent bed layer between the extract liquid and the adsorption feed is a purification area, the adsorbent bed layer between the adsorption feed and the raffinate is an adsorption area, and the adsorbent bed layer between the raffinate and the desorbents is a buffer area.

In the step (1) of the invention, the liquid phase simulated moving bed device is preferably adopted to adsorb and separate the C containing the ethylbenzene₈The ethylbenzene in the aromatic hydrocarbon is preferably adsorbed and separated at the temperature of 70-180 ℃ and the pressure of 0.2-2.0 MPa.

(1) Step (a) said slave C₈Two schemes can be adopted for adsorbing and separating ethylbenzene from aromatic hydrocarbon.

The ethylbenzene adsorbent used in the first scheme comprises 95-99.5 mass% of CsNaX zeolite and 0.5-5 mass% of a binder, wherein the molar ratio of Cs/Na is 1.5-10.0, preferably 2-6, and the desorbent is toluene. The ethylbenzene adsorbent is prepared in detail in CN 106552582B.

In the first scheme, the number of the adsorbent beds of the liquid phase simulated moving bed device for adsorbing and separating ethylbenzene in the step (1) is preferably 8-24. The layer number proportion of adsorbent beds in a desorption zone, a purification zone, an adsorption zone and a buffer zone of the four functional zones for adsorption and separation is 16-26%: 37-47%: 20-30%: 7-17%. The water content in the desorbent is preferably not more than 15ppm, more preferably 1-15 ppm, and the ratio of the volume flow of the desorbent to the volume flow of the adsorption raw material for adsorbing and separating ethylbenzene is preferably 0.6-5.0.

The ethylbenzene adsorbent used in the second scheme comprises 95-99.5 mass% of X zeolite and 0.5-5 mass% of binder, wherein the cation position of the X zeolite is Ba or is occupied by Ba and K, and the desorbent is benzene.

Preferably, the ethylbenzene adsorbent contains Na₂The O content is less than 0.6 mass%. When the cation site of the X zeolite is occupied by Ba, the BaO content in the adsorbent is preferably 35-45 mass%, and when the cation site of the X zeolite is occupied by Ba and K, the BaO content in the adsorbent is preferably 25-35 mass%, and K is preferably K₂The O content is preferably 7 to 10 mass%.

In the second scheme, the number of the adsorbent beds of the liquid phase simulated moving bed device for adsorbing and separating ethylbenzene in the step (1) is preferably 8-24. The layer number proportion of adsorbent beds in a desorption zone, a purification zone, an adsorption zone and a buffer zone of the four functional zones for adsorption and separation is 16-26%: 37-47%: 20-30%: 7-17%. The water content in the desorbent is preferably 50 to 100ppm, more preferably 70 to 90ppm, and the ratio of the volume flow of the desorbent to the volume flow of the adsorption raw material for the adsorption separation of the ethylbenzene is preferably 0.6 to 3.0, more preferably 1.0 to 2.0.

In the step (2), the paraxylene is preferably adsorbed and separated by adopting a liquid phase simulated moving bed, the adsorption and separation temperature is preferably 110-200 ℃, and the pressure is preferably 0.4-2.0 MPa.

(2) The adsorbent used in the step of adsorption and separation preferably comprises 95-99.5 mass% of X zeolite and 0.5-5 mass% of binder, wherein the cation position of the X zeolite is occupied by Ba or Ba and K. The detailed preparation method can be seen in CN 101497022B.

The binder in the adsorbent of the present invention is preferably kaolin.

Preferably, the desorbent used in the adsorption separation in the step (2) is toluene or p-diethylbenzene.

(2) The number of the adsorbent bed layers of the liquid phase simulated moving bed adsorption tower used in the step is preferably 8-24, and the proportion of the number of the adsorbent bed layers of the four functional areas of desorption, purification, adsorption and buffer areas of adsorption and separation is 16-26%: 37-47%: 20-30%: 7-17%.

(2) And removing the desorbents in the extract and raffinate to obtain extract oil and raffinate oil, wherein the extract oil is a p-xylene product, and the raffinate oil is rich in o-xylene and m-xylene. Preferably, the desorbent in the extract and the raffinate are separated by a rectifying tower, the operating temperature and pressure of the rectifying tower are determined according to the boiling point of the desorbent, the desorbent is determined to be discharged from the top of the tower or from the bottom of the tower, and the desorbent obtained by rectification can be reused. Similarly, the desorbent in the absorption liquid and the absorption residual liquid can be respectively removed by the rectifying tower in the step (1), so as to obtain absorption oil and absorption residual oil, wherein the absorption oil is ethylbenzene.

Step (3) of the invention is to carry out xylene isomerization reaction on the raffinate oil obtained in step (2), and the xylene isomerization reaction is carried outThe temperature is preferably 210-360 ℃, the pressure is preferably 0.1-4.0 MPa, and the mass space velocity of raffinate oil passing through the catalyst is preferably 11-20 h^-1The hydrogen/hydrocarbon molar ratio is preferably 0 to 0.9, i.e., the isomerization may be carried out in the presence of hydrogen or in the absence of hydrogen, and when the isomerization is carried out in the presence of hydrogen, the hydrogen/hydrocarbon molar ratio is preferably 0.1 to 0.9.

The ethylbenzene content in the feed of the isomerization device is greatly reduced, the operation severity of isomerization can be reduced, the temperature is preferably 330-360 ℃, the pressure is preferably 0.1-2.0 MPa, and the hydrogen/hydrocarbon molar ratio is preferably 0.2-0.9 during gas phase reaction; during liquid phase reaction, the temperature is preferably 210-300 ℃, the pressure is preferably 1.5-4.0 MPa, and only hydrogen below the solubility limit needs to be introduced into the liquid phase feed.

Because the ethylbenzene content in the xylene isomerization reactant is reduced, the reaction condition is relatively mild, and benzene, toluene and C in the reaction product₉Less by-products such as aromatic hydrocarbon, reduced fractionation load after isomerization reaction, and removed C₇Aromatic hydrocarbons (7 or less carbon atoms) and C₉+ small amount of aromatic hydrocarbons, especially C₉The amount of + aromatic hydrocarbons is small and thus C removal can be dispensed with₉+ aromatics fractionation plant using only one fractionation column for C₇-aromatic hydrocarbons and C₈+ aromatic hydrocarbon, C₇Aromatic hydrocarbon discharge unit, C₈And the aromatic hydrocarbon is used as the raw material of the adsorption separation device in the step (2). The isomerized product may also be fractionated, preferably using two distillation columns, to obtain C₇-aromatic hydrocarbons and C₉+ aromatics removal unit, C₈And (3) taking the aromatic hydrocarbon as a raw material of the adsorption separation device in the step (2).

The xylene isomerization catalyst in the step (3) of the present invention preferably contains 15 to 90 mass% of ZSM-5 and/or ZSM-11 zeolite and 10 to 85 mass% of alumina.

Preferably, the xylene isomerization catalyst comprises 15 to 90 mass% of ZSM-5 and/or ZSM-11 zeolite, 1 to 5 mass% of mordenite and 5 to 84 mass% of alumina. The preparation method can be seen in CN 103418422B.

Optionally, in step (2) of the process of the present invention, a further stream of C with a low ethylbenzene content is added to the raffinate obtained in step (1)₈An aromatic hydrocarbon component.

Plus C with low ethylbenzene content₈The mass ratio of the aromatic hydrocarbon component to the raffinate oil obtained in the step (1) is preferably 0.1-0.8.

The invention comprises the residual oil absorbed in step (1) and the C with low ethylbenzene content added in step (2)₈The ethylbenzene content in the aromatic hydrocarbon component is preferably not more than 3 mass%, more preferably not more than 2 mass%. C of the low ethylbenzene content₈The aromatic hydrocarbon raw material can be one or more of materials of toluene disproportionation products, toluene disproportionation and transalkylation products and toluene methanol methylation products.

In the present invention, the ethylbenzene-containing C in the step (1) is₈The content of ethylbenzene in the aromatic hydrocarbon is preferably 10 to 30 mass%, more preferably 10 to 25 mass%. The C is rich in ethylbenzene and xylene₈The aromatic hydrocarbon raw material can be coal tar, reformate, transalkylation product and other C-containing₈One or more of the aromatic hydrocarbon compound materials.

The present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a prior art block diagram consisting of C₈A flow diagram of the production of para-xylene from aromatics. C containing ethylbenzene and xylene₈Aromatic hydrocarbon is mixed with the circulating material from the pipeline 8 through the pipeline 1, the mixture is sent to a paraxylene adsorption separation device 10 through the pipeline 2, extract rich in paraxylene is obtained through adsorption separation, desorbent in the extract is removed, extract oil with the purity of paraxylene of 99.5 mass percent or higher is obtained, the extract oil is discharged through the pipeline 3 and is a paraxylene product, and the obtained paraxylene-poor C is₈The aromatic hydrocarbon material is raffinate, and raffinate oil obtained after the desorbent is removed is sent to a gas phase xylene isomerization device 20 through a pipeline 4 for xylene isomerization, so that o-xylene and m-xylene are converted into p-xylene. The desorbent in the extract and raffinate obtained in the process is removed by a rectifying tower (not shown in figure 1). Alternatively, the vapor phase xylene isomerization process can convert ethylbenzene contained therein to form benzene and ethane or ethylbenzene to xylenes in close thermodynamic equilibrium in the presence of hydrogen supplied via line 11. The xylene isomerization product is sent to a fractionation device 30 through a pipeline 5, and is generally fractionated by two rectification towers, and is fractionated by a first rectification towerTo C₇The aromatic hydrocarbon feed is withdrawn via line 6 and the C obtained in the second fractionation column₉The + aromatic hydrocarbon feed is discharged via line 7, resulting in C₈The aromatic hydrocarbon is recycled to the pipeline 2 through the pipeline 8 and then enters the paraxylene adsorption separation device 10 through the pipeline 2. Optionally, adding a stream of C with low ethylbenzene content₈Aromatic hydrocarbon is added from line 9 to line 2, plus C₈The ethylbenzene content in the aromatic hydrocarbons is lower than that of C entering from line 1₈Ethylbenzene content in aromatics.

FIG. 2 shows a schematic representation of the present invention consisting of₈A schematic flow diagram of aromatic hydrocarbons to produce ethylbenzene and para-xylene. C containing ethylbenzene and xylene₈Aromatic hydrocarbon is sent to an adsorption tower of an ethylbenzene liquid phase adsorption separation device 140 through a pipeline 101, ethylbenzene in the ethylbenzene is adsorbed by an ethylbenzene adsorbent in an adsorbent bed layer, components which are not adsorbed are discharged from the adsorbent bed layer to be used as raffinate, a desorbent is used for flushing the adsorbent bed layer to desorb ethylbenzene in the adsorbent bed layer to obtain an absorbed liquid, the obtained absorbed liquid and the absorbed raffinate are respectively subjected to rectification removal of the desorbent in an arranged rectifying tower, the obtained absorbed oil is discharged through a pipeline 112, and the purity of the absorbed oil is greater than or equal to 99.85 mass percent and can also be greater than or equal to 99.9 mass percent of an ethylbenzene product. The resulting raffinate is discharged through a line 113 and sent to a paraxylene adsorption separation unit 110 (an adsorption column in the ethylbenzene liquid phase adsorption separation unit 140 and a rectifying column for removing the desorbent from the adsorption liquid and the raffinate, not shown) through a line 102.

The raffinate oil sent to the paraxylene adsorption separation device 110 is subjected to adsorption separation to obtain an extract rich in paraxylene, the desorbent in the extract is removed to obtain an extract with a paraxylene purity of 99.5 mass% or higher, the extract is discharged through a line 103 as a paraxylene product, and the paraxylene-poor C which is not adsorbed by the adsorbent is obtained₈The aromatic hydrocarbon material is raffinate, from which desorbent is removed, and raffinate oil obtained is sent to a xylene isomerization unit 120 through a pipeline 104 for xylene isomerization. The extract and raffinate obtained in the adsorption separation process are respectively rectified by a rectifying tower (not shown in figure 2) to remove the desorbent. Because the ethylbenzene content in the material of the paraxylene adsorption separation device 110 is low, the efficiency of the adsorption separation of paraxylene is improvedAnd the energy consumption is reduced.

The raffinate oil is sent to a xylene isomerization unit 120 via 104 for xylene isomerization, which converts ortho-xylene and meta-xylene into para-xylene. The xylene isomerization can be carried out by gas phase or liquid phase reaction. If a gas phase isomerization reaction is employed, an appropriate amount of hydrogen is optionally provided via line 111 to extend catalyst life. Due to the low ethylbenzene content in the reactant stream in line 104 to xylene isomerization unit 120, the isomerization reaction can be operated at lower reaction temperatures and mild hydrogen/hydrocarbon molar ratios, which can reduce xylene losses in the xylene isomerization reaction and lower operating costs.

The xylene isomerization product from the xylene isomerization unit 120 is sent via line 105 to a fractionation unit 130 for fractionation, preferably using a fractionation column, to fractionate the resulting C₇The aromatic hydrocarbon feed is withdrawn via line 106, C₉+ aromatic hydrocarbon discharged through line 107, C₈The aromatic hydrocarbons are recycled via line 108 back to line 102 and then via line 102 to para-xylene adsorptive separation unit 110. Optionally, adding a stream of C with low ethylbenzene content₈Aromatic hydrocarbon is added to line 102 via line 109 with the addition of C₈The ethylbenzene content of the aromatic hydrocarbons is lower than the C entering from line 101₈Ethylbenzene content in aromatics.

Since the xylene isomerization of the present invention generates less by-products, the fractionation device 130 can separate C using two distillation columns₇-aromatic hydrocarbons and C₉+ aromatic hydrocarbons, optionally without removal of C₉+ aromatics while C is separated using a fractionating column₇-aromatic hydrocarbons and C₈+ arene, with C₈The + aromatics are recycled via line 108 back to line 102 and then via line 102 to para-xylene adsorptive separation unit 110.

The invention is further illustrated below by way of examples, without being limited thereto.

Example 1

Adsorbent B, para-xylene or ethylbenzene, was prepared as in CN101497022B example 2.

(1) Preparation of small-grained X zeolite: a100 liter synthesis kettle was charged with 16.4 kg of sodium metaaluminate solution (containing Al)₂O₃17.3% by mass of Na₂O21.0 mass%), 11.0 kg of deionized water and 2.9 kg of sodium hydroxide, stirred to completely dissolve the solid alkali, and then 11.8 kg of sodium silicate solution (containing SiO) was added₂28.3% by mass of Na₂O8.8 percent by mass), stirring until the mixture is uniformly mixed, standing and aging at 25 ℃ for 20 hours to prepare the guiding agent.

Adding 255 kg of sodium silicate solution, 1001 kg of deionized water and 37 kg of sodium hydroxide into a 2000L kettle at 25 ℃, stirring to fully mix, adding 227 kg of sodium metaaluminate under stirring, adding 15 kg of guiding agent, continuously stirring until the mixture is uniformly mixed, heating to 100 ℃, standing and crystallizing for 4 hours. Washing the product with water until the pH value of the washing liquid is less than 10, filtering, and drying at 80 ℃ for 12 hours to obtain NaX type zeolite. Calculating the SiO of the zeolite from the unit cell constant₂/Al₂O₃The molar ratio is 2.19, and the average grain diameter of the crystal grains is 0.7 micron when observed by a scanning electron microscope.

(2) Rolling ball forming: 88 kg (dry basis weight, the same applies hereinafter) of the NaX zeolite prepared in step (1) was uniformly mixed with 9 kg of kaolin (containing 90% by weight of kaolinite, produced by Shanxi Bifen) and 3.4 kg of sesbania powder to form a mixed powder, and a suitable amount of aqueous solution of sodium carbonate having a concentration of 5.0% by weight was sprayed while rolling in a rotating disk to agglomerate the solid mixed powder into pellets, and the amount of the aqueous solution of sodium carbonate sprayed while rolling was 28% by weight of the solid mixed powder. Sieving small balls with the diameter of 0.35-0.80 mm, drying at 80 ℃ for 10 hours, and roasting at 540 ℃ in air flow for 4 hours.

(3) In-situ crystallization: mixing the above calcined pellets with a mixed solution of sodium hydroxide and sodium silicate containing Na at a liquid/solid volume ratio of 2.0: 1₂O4.3 mass% and SiO₂2.1 percent by mass, and standing the mixture for 4.0 hours at 96 ℃ to convert kaolin in the mixture into X zeolite by in-situ crystallization. The pellets obtained after the in-situ crystallization treatment were washed with deionized water until the pH of the washing solution was 9.0, dried at 80 ℃ for 12 hours, calcined at 500 ℃ for 2 hours, and measured to have a toluene adsorption capacity of 0.230 g/g, which corresponds to a content of zeolite X in the agglomerated pellets of 97.9 mass% and a binder content of 2.1 mass%.

(4) Ion exchange: carrying out ion exchange on the pellets subjected to in-situ crystallization and roasting by using a conventional column type continuous method, wherein the exchange liquid is 0.18moL/L barium nitrate solution, and the temperature is 92 ℃, the pressure is normal pressure and the volume space velocity of the exchange liquid is 4.0^-1The barium ion exchange was carried out for 10 hours under the conditions that the volume ratio of the barium nitrate solution to the pellets used was 40: 1. after the exchange, the adsorbent B was washed with 10 times the volume of the pellet of deionized water and dried in a nitrogen stream at 220 ℃ for 6 hours to obtain an adsorbent B, and the ignition loss was 4.5 mass% and Na% when the adsorbent B was calcined at 600 ℃ for 2 hours₂0.55 mass% of O and 39.5 mass% of BaO.

Example 2

Xylene isomerization catalyst C was prepared as in CN103418422B example 9.

Taking SiO₂/Al₂O₃ZSM-11 zeolite and mordenite (SiO) with molar ratio of 70₂/Al₂O₃The molar ratio is 11) and the proportion of the gamma-alumina powder is 58.5: 1.5: 40, adding 2 mass percent nitric acid aqueous solution accounting for 50 percent of the total mass of the powder, kneading and molding, drying at 120 ℃ for 2 hours, roasting at 600 ℃ for 3 hours, and then adding 3 mass percent NH₄And (3) carrying out ion exchange on the Cl aqueous solution at 90 ℃ for 3 hours, drying the solid at 60 ℃ for 6 hours, and roasting the solid in the air at 500 ℃ for 4 hours to obtain the composite carrier a.

Loading the composite carrier a into a reactor, heating to 500 ℃, introducing air containing water vapor for treating for 8 hours, wherein the volume space velocity of the air passing through the catalyst is 800 hours^-1And the water content in the air is 25 percent by volume, thus obtaining the composite carrier b.

And (3) carrying out liquid/solid volume ratio on the composite carrier b by using chloroplatinic acid solution, wherein the liquid/solid volume ratio is 2: 1 for 12 hours, the platinum content in the chloroplatinic acid solution was such that the platinum content in the composite carrier was 0.02 mass% (relative to the dry-based carrier). Drying the impregnated solid at 60 ℃ for 6 hours, and roasting the solid in the air at 500 ℃ for 4 hours to obtain the platinum-carrying catalyst C, wherein the platinum content is 0.02 mass percent based on the composite carrier, and the composite carrier contains 58.5 mass percent of HZSM-11 zeolite, 1.5 mass percent of hydrogen mordenite and 40 mass percent of gamma-alumina.

Example 3

Preparing an ethylbenzene adsorbent A.

Taking the agglomerated pellets prepared in the step (3) of example 1 and having a zeolite X content of 97.9 mass%, placing the agglomerated pellets in an exchange column, and reacting the agglomerated pellets with 0.5mol/L CsCl solution at 95 ℃ and 0.1MPa for 4.0h at an exchange liquid volume space velocity^-1After the exchange is finished, washing the ball by deionized water with the mass of 10 times that of the coalesced ball under the same condition, and then drying the ball in air at 230 ℃ for 4 hours to prepare the ethylbenzene adsorbent A, wherein the molar ratio of Cs/Na is 3.4: the ignition loss was 0.5 mass% when it was baked at 1,600 ℃ for 2 hours.

Comparative example 1

On a prior art process as shown in FIG. 1, a 1000 kiloton annually produced para-xylene is produced from C₈And (3) producing PX by using aromatic hydrocarbons.

C from line 1 rich in ethylbenzene and xylenes₈C of isomerization of aromatic hydrocarbons with xylene from line 8₈The mixed aromatics enter a paraxylene adsorption separation device 10 through a pipeline 2. The obtained extract oil is discharged from a pipeline 3 after being subjected to para-xylene adsorption separation to be a para-xylene product, the obtained raffinate oil enters a xylene isomerization reaction device 20 through a pipeline 4 to be subjected to gas phase isomerization reaction, hydrogen required by the reaction enters the xylene isomerization reaction device 20 through a pipeline 11, the reaction product enters a fractionating device 30 through a pipeline 5, the fractionating device 30 is provided with two rectifying towers, and C obtained by fractionating the top of the first rectifying tower is fractionated at the top of the first rectifying tower₇The aromatic hydrocarbon material is discharged through line 6, the bottom fraction enters a second fractionation column, C is obtained at the bottom of the column₉The aromatic hydrocarbons are discharged through line 7 and C is obtained at the top of the column₈The aromatic hydrocarbon is returned from a pipeline 8 and then enters a paraxylene adsorption separation device 10 from a pipeline 2. The main pipeline stream composition and flow are shown in table 1.

The p-xylene adsorption separation device 10 is a liquid-phase simulated moving bed adsorption separation device, the adsorbent filled in the adsorption tower is the p-xylene adsorbent B described in example 1, the loading amount is 1165 tons, the operating temperature is 170 ℃, the operating pressure is 0.8MPa, the desorbent is p-diethylbenzene, the number of adsorbent beds of the simulated moving bed is 24, the cycle period is 28 minutes, and the number of adsorbent beds of the desorption zone, the purification zone, the adsorption zone and the buffer zone is 5, 10, 6 and 3 respectively.

The catalyst loaded in the reactor of the xylene isomerization reaction device 20 is the isomerization catalyst C described in the example 2, the loading amount is 57.3 tons, the xylene isomerization reaction temperature is 370 ℃, the pressure is 0.6MPa, and the mass space velocity of the fed material of the reactor is 8h^-1The hydrogen/hydrocarbon molar ratio was 1.0.

The temperature at the bottom of the first fractionating tower is 161 ℃, the pressure is 0.04MPa, and the number of tower plates is 42.

The temperature at the bottom of the second fractionating tower is 195 ℃, the pressure is 0.04MPa, and the number of tower plates is 51.

TABLE 1

In the table, EB-ethylbenzene, PX-p-xylene, MX-m-xylene, OX-o-xylene are shown as example 4

According to the process of the invention illustrated in FIG. 2, the para-xylene is produced on an annual scale of 1000 kilotons₈Aromatics to produce PX and ethylbenzene.

C rich in ethylbenzene and xylene₈The aromatic hydrocarbon is sent to an adsorption tower in an ethylbenzene liquid phase adsorption separation device 140 through a pipeline 101, ethylbenzene in the ethylbenzene is adsorbed by an adsorbent in an ethylbenzene adsorbent bed layer, components which are not adsorbed are discharged from the adsorbent bed layer to be used as raffinate, a desorbent is used for flushing the adsorbent bed layer to desorb ethylbenzene in the adsorbent bed layer to obtain an absorbed liquid, the obtained absorbed liquid and the absorbed raffinate are respectively subjected to rectification removal of the desorbent in the distillation tower through an arranged rectification tower, and the obtained absorbed oil is discharged through a pipeline 112 to be an ethylbenzene product; the resulting raffinate is withdrawn via line 113 with C in the isomerate from line 108₈The aromatic hydrocarbon mixture enters a para-xylene adsorptive separation unit 110 via line 102. The obtained extract oil is discharged from a pipeline 103 after being subjected to paraxylene adsorption separation to obtain a paraxylene product, the obtained raffinate oil enters a xylene isomerization reaction device 120 through a pipeline 104 to be subjected to gas phase isomerization reaction, hydrogen required by the reaction enters the xylene isomerization reaction device 120 through a pipeline 111, the reaction product enters a fractionation device 130 through a pipeline 105, and the fractionation device 130 is provided with a fractionation deviceTwo rectifying towers, the top of the first fractionating tower fractionates to obtain C₇The aromatic hydrocarbon feed is discharged via line 106 and the bottoms fraction is fed to a second fractionation column, the C obtained at the bottom of the column₉+ aromatic hydrocarbons are discharged via line 107 and C is obtained overhead₈The aromatic hydrocarbon is returned via line 108 and then passed via line 102 to para-xylene adsorptive separation unit 110. The main pipeline stream composition and flow are shown in table 2.

The adsorbent filled in the reaction adsorption tower in the ethylbenzene liquid phase adsorption separation device 140 was the ethylbenzene adsorbent a described in example 3, the filling amount was 385 tons, the adsorption separation operation temperature was 110 ℃, the pressure was 0.6MPa, the desorbent was toluene, the water content in the desorbent was 5ppm, and the ratio of the desorbent volume flow rate to the adsorption feed volume flow rate in the adsorption tower was 1.2. The number of adsorbent bed layers of the simulated moving bed is 16, the cycle period is 28 minutes, and the number of adsorbent bed layers of the desorption zone, the purification zone, the adsorption zone and the buffer zone are respectively 3, 7, 4 and 2.

The p-xylene adsorption separation device 110 is a liquid-phase simulated moving bed adsorption separation device, the adsorbent filled in the adsorption tower is the p-xylene adsorbent B described in example 1, the loading amount is 990 tons, the operating temperature is 170 ℃, the operating pressure is 0.8MPa, the desorbent is p-diethylbenzene, the number of adsorbent bed layers of the simulated moving bed is 24, the cycle period is 28 minutes, and the number of adsorbent bed layers of the desorption zone, the purification zone, the adsorption zone and the buffer zone is 5, 10, 6 and 3 respectively.

The catalyst loaded in the reactor 120 of the xylene isomerization reaction device is the isomerization catalyst C described in the example 2, the loading amount is 35.3 tons, the temperature of the xylene isomerization reaction is 350 ℃, the pressure is 0.5MPa, and the mass space velocity of the reactor feeding is 12h^-1The hydrogen/hydrocarbon molar ratio was 0.8.

The first and second fractionators and the operating conditions were the same as in comparative example 1.

TABLE 2

The raw material consumption and adsorbent and catalyst loading of comparative example 1 and example 4 are shown in Table 3. As can be seen from table 3, for a paraxylene unit of 1000 kilotons/year, the process of example 4 has a 2.2% reduction in raw material consumption, a total reduction in the total charge of isomerization catalyst C of 22 tons and 38.4% reduction, and a reduction in the charge of paraxylene adsorbent B of 175 tons and 15% reduction, as compared with the process of comparative example 1, and the charge of ethylbenzene adsorbent increases 385 tons and produces 199.7 kilotons/year of ethylbenzene. The purity of ethylbenzene was 99.85 mass%, and the yield was 95 mass%.

TABLE 3

	Comparative example 1	Example 4
			High ethylbenzene C8Aromatic feedstock, kiloton/year	1262.4	1234.9
Total amount of isomerization catalyst C in ton	57.3	35.3
			Total package of p-xylene adsorbent B, ton	1165	990
Total package of ethylbenzene adsorbent A, ton	-	385
			Para-xylene production, kiloton/year	1000	1000
Ethylbenzene production, kiloton/year	-	199.7

Example 5

Production of 1000 kilotons of p-xylene annually by the method of example 4 from C₈Aromatics to produce PX and ethylbenzene. Except that the adsorbent loaded in the adsorption tower of the ethylbenzene liquid phase adsorption separation device 140 was the ethylbenzene adsorbent B described in example 1, the loading was 338 tons, the adsorption separation operation temperature was 135 ℃, the pressure was 0.6MPa, the desorbent was benzene, the water content in the desorbent was 80ppm, and the ratio of the desorbent volume flow to the adsorption feed volume flow in the adsorption tower was 1.5. The number of adsorbent bed layers of the simulated moving bed is 24, the cycle period is 28 minutes, and the number of adsorbent bed layers of the desorption zone, the purification zone, the adsorption zone and the buffer zone is 5, 10, 6 and 3 respectively. The purity of ethylbenzene was 99.86 mass%, and the yield was 97 mass%.

The composition and flow rate of the main pipeline streams are shown in Table 4, and the raw material consumption and the loading of the adsorbent and the catalyst are shown in Table 10.

TABLE 4

Comparative example 2

The procedure of comparative example 1 is as shown in FIG. 1, from C₈Aromatic hydrocarbon is used for producing PX, except that a stream of C with low ethylbenzene content is added from a pipeline 9₈Aromatic hydrocarbon with C entering from line 1₈The aromatics are mixed and enter a para-xylene adsorption separation unit 10 through a line 2. The main pipeline stream compositions and flow rates are shown in Table 5.

The operation of the para-xylene adsorption separation unit 10 was the same as in comparative example 1 except that the loading of the para-xylene adsorbent B was 1138 tons.

The operation of the xylene isomerization reaction apparatus 20 was the same as in comparative example 1 except that the loading of the catalyst C was 55.5 tons.

TABLE 5

Example 6

The method according to example 4 is represented by the scheme shown in FIG. 2, by C₈Aromatic hydrocarbons are used for producing PX and ethylbenzene, except that a stream of C with low ethylbenzene content is added from a pipeline 109₈The aromatic hydrocarbon is mixed with the raffinate from the line 113 and then introduced into the paraxylene adsorption separation apparatus 110 through the line 102. The main pipeline stream compositions and flow rates are shown in Table 6.

The operation of the ethylbenzene liquid phase adsorption separation unit 140 was the same as in example 4 except that the loading of adsorbent A was 242 tons.

The operation of the para-xylene adsorption separation device 110 is the same as in example 4.

The operation of the xylene isomerization reaction unit 120 was the same as in example 4 except that the loading of the catalyst C was 35.1 tons.

TABLE 6

The raw material consumption and adsorbent and catalyst loading of comparative example 2 and example 6 are shown in Table 7. As can be seen from Table 7, for a paraxylene unit of 1000 kilotons/year, the process of example 6 reduced the raw material consumption by 2.2%, the total charge of isomerization catalyst C by 20.4 tons and 36.7%, and the charge of paraxylene adsorbent B by 148 tons and 13.0%, respectively, and the charge of ethylbenzene adsorbent increased by 242 tons and produced 125.3 kilotons/year, as compared with the process of comparative example 2.

TABLE 7

Example 7

By the method of example 5 from C₈Aromatics to produce PX and ethylbenzene except that the water content of the desorbent was 40 ppm. The purity of the ethylbenzene obtained by separation was 99.85 mass%, the yield of ethylbenzene was 93.2 mass%, the composition and flow rate of the main line stream are shown in table 8, and the raw material consumption and the loading amounts of the adsorbent and the catalyst are shown in table 10.

TABLE 8

Example 8

By the method of example 5 from C₈Aromatics to produce PX and ethylbenzene except that the desorbent had a water content of 120 ppm. The purity of the ethylbenzene obtained by separation was 99.85 mass%, and the yield of ethylbenzene was 89 mass%. The composition and flow rate of the main pipeline streams are shown in Table 9, and the raw material consumption and the loading of the adsorbent and the catalyst are shown in Table 10.

TABLE 9

Watch 10

	Example 5	Example 7	Example 8
				High ethylbenzene C8Aromatic feedstock, kiloton/year	1234.9	1236.2	1236.5
Total amount of isomerization catalyst C in ton	35.3	35.3	35.3
				Total package of p-xylene adsorbent B, ton	990	990	990
Total loading of ethylbenzene adsorbent B, ton	338	338	338
				Para-xylene production, kiloton/year	1000	1000	1000
Ethylbenzene production, kiloton/year	203.9	196.0	192.8
				Purity and quality% of ethylbenzene product	99.86	99.85	99.85

Example 9

Preparing ethylbenzene adsorbent D.

The ethylbenzene adsorbent B obtained in example 1 was subjected to ion exchange in a tank system in the form of a 0.4mol/L potassium chloride solution at 95 ℃ under 0.1MPa for three times in a nitrogen stream at 205 ℃ in a liquid/solid volume ratio of 4.5 between the exchange liquid used each time and the ethylbenzene adsorbent B, to obtain an ethylbenzene adsorbent D, which was calcined at 600 ℃ for 2 hours to determine the weight loss of the ethylbenzene adsorbent D as 4.8 mass%, and Na as a result of drying in a nitrogen stream at 205 ℃ for 4 hours₂0.43 mass% of O, 28.2 mass% of BaO, and K₂O was 8.7 mass%.

Example 10

Production of 1000 kilotons of p-xylene annually by the method of example 4 from C₈Aromatics to produce PX and ethylbenzene. Except that the adsorbent packed in the adsorption tower of the ethylbenzene liquid phase adsorption separation device 140 was the ethylbenzene adsorbent D described in example 9, the loading was 298 tons, the adsorption separation operation temperature was 135 ℃, the pressure was 0.8MPa, the desorbent was benzene, the water content in the desorbent was 80ppm, and the ratio of the desorbent volume flow to the adsorption feed volume flow in the adsorption tower was 1.3. The number of adsorbent bed layers of the simulated moving bed is 16, the cycle period is 26 minutes, and the number of adsorbent bed layers of the desorption zone, the purification zone, the adsorption zone and the buffer zone is 3, 7, 4 and 2 respectively. The main pipeline stream compositions and flow rates are shown in Table 11. The purity of ethylbenzene was 99.86 mass%, and the yield was 97.4 mass%.

TABLE 11