CN111068744A

CN111068744A - Supported catalyst precursor, preparation method thereof and production method of low-carbon olefin

Info

Publication number: CN111068744A
Application number: CN201811224383.5A
Authority: CN
Inventors: 晋超; 吴玉; 张荣俊; 侯朝鹏; 孙霞; 阎振楠; 夏国富
Original assignee: Sinopec Research Institute of Petroleum Processing; China Petroleum and Chemical Corp
Current assignee: Sinopec Research Institute of Petroleum Processing; China Petroleum and Chemical Corp
Priority date: 2018-10-19
Filing date: 2018-10-19
Publication date: 2020-04-28

Abstract

The invention provides a supported catalyst precursor and a preparation method thereof, the supported catalyst precursor comprises a carrier and an active metal oxide loaded on the carrier, wherein the carrier is a manganese oxide molecular sieve, and the active metal in the active metal oxide is a metal in a VIII group. The invention also provides a method for producing low-carbon olefin by using the supported catalyst precursor. The production method can improve the utilization rate of two greenhouse gases, namely carbon dioxide and methane, in the production process of the low-carbon olefin, so that the low-carbon olefin is converted into a product with a high added value, the emission of the greenhouse gases is reduced, the energy consumption of a system is reduced, and the resource and energy utilization rate of the whole process is obviously improved.

Description

Supported catalyst precursor, preparation method thereof and production method of low-carbon olefin

Technical Field

The invention relates to the field of olefin synthesis, in particular to a supported catalyst precursor, a preparation method thereof and a production method of low-carbon olefin.

Background

Olefins are important basic chemical materials in the production of chemical industry, and are also a mark for measuring the development level of the national petrochemical industry. The existing methods for preparing low-carbon olefins can be divided into three main categories according to raw materials: oil routes, natural gas routes, and coal routes. The method for preparing low-carbon olefin by adopting light oil cracking, namely a method for preparing low-carbon olefin by using a petroleum route, is adopted by most countries in the world and accounts for about 65 percent of the yield of olefin. The natural gas is used as a raw material, the technology for preparing the low-carbon olefin by an oxidative coupling method or a Bensen method is adopted, ethylene is mainly used in the product, and the yield of propylene is low. The research of preparing olefin by using coal-based synthesis gas through methanol is rapidly developed, and a plurality of sets of process devices are built in China.

The energy sources in China are rich in coal, more natural gas and lack of oil, and the indirect conversion of the coal or the natural gas into clean and efficient liquid fuel through Fischer-Tropsch synthesis is an important aspect of reasonably utilizing the resources and a main technical approach for relieving the contradiction between supply and demand of petroleum in China. In recent years, in the field of coal chemical industry in China, coal rapidly rises through methanol to olefin, and the direct preparation of olefin from coal through synthetic gas (FTO process) is another process for preparing olefin from coal. The process comprises the steps of firstly converting coal or natural gas into synthesis gas (carbon monoxide and hydrogen), and directly preparing the low-carbon olefin with the carbon atom number less than or equal to 4 through Fischer-Tropsch synthesis.

The technological process of preparing olefin by the currently commonly used FTO process is shown in figure 1, and comprises a coal water slurry preparation unit I ', a coal gasification unit II', a water gas conversion unit III ', a synthetic gas purification unit IV', a Fischer-Tropsch synthesis unit V 'and a low-carbon olefin separation unit VI' which are connected in sequence, wherein the specific process comprises the steps of preparing coal water slurry C 'from pulverized coal A' and water B 'in the coal water slurry preparation unit I', conveying the coal water slurry C 'into a coal gasification unit II', reacting with oxygen D 'to generate coal gasification crude synthetic gas E', adjusting the molar ratio of hydrogen and carbon monoxide of the coal gasification crude synthetic gas E 'through the water gas conversion unit III' to obtain converted crude synthetic gas F 'meeting the Fischer-Tropsch synthesis reaction requirement, removing acid gas and sulfide M' through the synthetic gas purification unit IV 'to obtain purified synthetic gas J', and conveying the obtained purified synthetic gas J 'into the Fischer-Tropsch synthesis unit V' to perform Fischer-, generating a Fischer-Tropsch reaction product N 'containing olefin, separating the low-carbon olefin K' from the Fischer-Tropsch reaction product N 'through a low-carbon olefin separation unit VI', discharging carbon dioxide H 'and methane G' generated by a Fischer-Tropsch synthesis unit V ', recycling one part of unreacted synthesis gas Y' to the Fischer-Tropsch synthesis unit V ', and discharging the other part of unreacted synthesis gas as purge gas Z' out of the system. The main problems of the process for preparing the low-carbon olefin are as follows: 1. the energy consumption is high, and the utilization rate of carbon atoms is low; 2. the emission of carbon dioxide is 5-6 times of that of the traditional petroleum route; 3. the Fischer-Tropsch synthesis product distribution is limited by an Anderson-Schulz-Flory rule (the molar distribution of chain growth decreasing according to indexes), and is limited by the generation of a large amount of methane and carbon dioxide caused by strong exothermicity of reaction, so that the overall energy efficiency of the process is low, and the industrial process of the Fischer-Tropsch synthesis process is seriously influenced. The coal gasification process uses a large amount of cooling water and discharged sewage to keep the water consumption high.

Therefore, there is still a need to optimize the fischer-tropsch synthesis process, reducing the system energy consumption and the emission of greenhouse gases.

It is noted that the information disclosed in the foregoing background section is only for enhancement of background understanding of the invention and therefore it may contain information that does not constitute prior art that is already known to a person of ordinary skill in the art.

Disclosure of Invention

The invention aims to provide a supported catalyst precursor and a production method of low-carbon olefin, which can effectively reduce the energy consumption of a system and the emission of greenhouse gases.

In order to achieve the purpose, the invention adopts the following technical scheme:

the invention provides a supported catalyst precursor, which comprises a carrier and an active metal oxide supported on the carrier, wherein the carrier is a manganese oxide molecular sieve, and the active metal in the active metal oxide is a metal in a VIII group.

According to one embodiment of the invention, the active metal is one or more of Fe, Ru, Pt, Co, Rh, Pd, Ir, preferably one or more of Fe, Ru, Co, more preferably Fe.

According to one embodiment of the invention, the active metal oxide is present in an amount of 0.2 to 40% by weight, preferably 0.3 to 30% by weight, calculated as metal element.

In another aspect, the present invention provides a process for preparing the above supported catalyst precursor, comprising:

and doping or loading the active metal on the carrier, and then sequentially drying and roasting to obtain the supported catalyst precursor.

According to one embodiment of the present invention, the temperature of the drying is 80-350 ℃, preferably 100-300 ℃; the drying time is 1 to 24 hours, preferably 2 to 12 hours.

According to one embodiment of the invention, the temperature of the roasting is between 250 ℃ and 900 ℃, preferably between 300 ℃ and 850 ℃, more preferably between 350 ℃ and 800 ℃; the calcination time is 0.5 to 12 hours, preferably 1 to 8 hours, and more preferably 2 to 6 hours.

In another aspect, the present invention provides a method for producing light olefins, comprising:

contacting methane with steam to carry out steam reforming reaction to obtain steam reforming synthesis gas;

contacting methane with carbon dioxide to carry out dry reforming reaction to obtain dry reforming syngas;

mixing at least part of the steam reforming synthesis gas and at least part of the dry weight integrated synthesis gas to prepare a Fischer-Tropsch synthesis reaction feed;

carrying out reduction activation on the supported catalyst to obtain a Fischer-Tropsch synthesis catalyst;

contacting the Fischer-Tropsch synthesis reaction feed with the Fischer-Tropsch synthesis catalyst to carry out Fischer-Tropsch synthesis reaction to obtain a Fischer-Tropsch synthesis product material flow; and

separating low carbon olefins, methane and carbon dioxide from the Fischer-Tropsch synthesis product stream.

According to one embodiment of the present invention, the steam reforming reaction is carried out in a fixed bed reactor at a reaction temperature of 700-: 0.5 to 4, preferably 1:1 to 3, based on the total amount of methane and steam, the hourly space velocity of the feed gas is preferably 10000-^-1Preferably 50000-100000 hours^-1。

According to one embodiment of the present invention, the dry reforming reaction is carried out in a fixed bed reactor at a reaction temperature of 600-: 0.5 to 5, preferably 1: 0.8 to 3, more preferably 1: 1-2, the gas hourly volume space velocity of the feed is 10000-100000 hours based on the total amount of methane and carbon dioxide^-1Preferably 50000-100000 hours^-1。

According to one embodiment of the invention, the Fischer-Tropsch synthesis reaction is carried out in a fluidized bed reactor and/or a fixed bed reactor, the reaction temperature is 200-¹Preferably 10000-^-1。

According to one embodiment of the invention, the molar ratio of hydrogen to carbon monoxide in the feed to the fischer-tropsch synthesis reaction is in the range of from 0.4 to 3: 1, preferably 0.6 to 2.5: 1, more preferably 0.8 to 2.2: 1, most preferably 1.5-2.2: 1.

according to one embodiment of the present invention, the reduction activation is performed under a hydrogen atmosphere, and the reduction temperature is 200-600 ℃, preferably 300-550 ℃, more preferably 350-500 ℃; the reduction time is 1 to 20 hours, preferably 2 to 10 hours, more preferably 5 to 8 hours; the hydrogen pressure is 0 to 2.5MPa, preferably 0.1 to 2 MPa.

According to an embodiment of the present invention, the method further comprises recycling the separated methane to the steam reforming reaction and/or the dry reforming reaction, and recycling the separated carbon dioxide to the dry reforming reaction.

The production method can improve the utilization rate of two greenhouse gases, namely carbon dioxide and methane, in the production process of the low-carbon olefin, so that the low-carbon olefin is converted into a product with a high added value, the emission of the greenhouse gases is reduced, the energy consumption of a system is reduced, and the resource and energy utilization rate of the whole process is obviously improved.

Drawings

FIG. 1 is a flow diagram of a typical process for the direct production of lower olefins from coal via synthesis gas in the prior art;

FIG. 2 is a process flow diagram of a process for producing lower olefins in accordance with one embodiment of the present invention;

wherein the reference numerals are as follows:

i': coal water slurry preparation unit II': a coal gasification unit III': water gas shift unit

IV': synthesis gas purification unit V': Fischer-Tropsch synthesis unit VI': low carbon olefin separation unit

A': pulverized coal B': water C': coal water slurry

D': oxygen E': coal gasification raw synthesis gas F': shifted raw synthesis gas

G': methane H': carbon dioxide K': low carbon olefin

M': acid gas and sulfide N': Fischer-Tropsch reaction product Y': unreacted synthesis gas

Z': purge gas J': purifying synthesis gas

I: a raw material gas separation unit II: steam reforming reaction unit III: dry reforming reaction unit

IV: Fischer-Tropsch synthesis reaction unit V: Fischer-Tropsch synthesis product separation unit A: raw material gas

B: methane C: water vapor D: carbon dioxide

E: steam reforming syngas F: dry weight integration gas G: Fischer-Tropsch synthesis reaction feed

H: Fischer-Tropsch synthesis product stream L: hydrogen and carbon monoxide K for recycle: low carbon olefin

M: methane N: carbon dioxide Z: purge gas

Detailed Description

The technical solution of the present invention is further explained below according to specific embodiments. The scope of protection of the invention is not limited to the following examples, which are set forth for illustrative purposes only and are not intended to limit the invention in any way.

In the present invention, anything or matters not mentioned is directly applicable to those known in the art without any change except those explicitly described. Moreover, any embodiment described herein may be freely combined with one or more other embodiments described herein, and the technical solutions or ideas thus formed are considered part of the original disclosure or original description of the present invention, and should not be considered as new matters not disclosed or contemplated herein, unless a person skilled in the art would consider such combination to be clearly unreasonable.

All features disclosed in this invention may be combined in any combination and such combinations are understood to be disclosed or described herein unless a person skilled in the art would consider such combinations to be clearly unreasonable. The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.

Any terms not directly defined herein should be understood to have meanings associated with them as commonly understood in the art of the present invention. The following terms as used throughout this specification should be understood to have the following meanings unless otherwise indicated.

According to a first aspect of the present invention there is provided a supported catalyst precursor comprising a support and an active metal oxide supported on the support.

In the supported catalyst precursor of the present invention, the support used is a manganese oxide molecular sieve, preferably an octahedral manganese oxide molecular sieve manganite (OMS-2).

The octahedral manganese oxide molecular sieve manganese potassium ore (OMS-2) is composed of MnO₆The chains are connected into the molecular sieve with a net tunnel structure on the plane through the interchain common edges and interchain common angle oxygen caps. Researches prove that the manganese oxide molecular sieve has strong hydrophobicity, moderate acidity and alkalinity and strong hydrothermal stability; with a pore channel of 0.46nm, and C₂-C₄The molecular dynamics diameters of the olefins are close, and the selectivity of the olefins can be improved by utilizing the selectivity effect; the variable valence state of Mn element in the molecular sieve can generate oxygen vacancy for stabilizing the loaded metal; in addition, the Mn, Ba and other framework elements of the manganese oxide molecular sieve can be replaced by other metal elements, and the characteristics enable the iron-manganese oxide molecular sieve OMS-2 to possibly become an excellent carrier material.

The inventors of the present invention have made extensive studies and found that a catalyst is obtained by supporting a group VIII metal component on an OMS-2 carrier. Compared with the prior art, the supported catalyst provided by the invention has the advantages that the product selectivity is improved, and the industrial popularization is facilitated.

The OMS-2 carrier can be prepared by a hydrothermal synthesis method, and specifically comprises the following steps:

(1) dissolving potassium permanganate in deionized water with a certain mass, heating and stirring to dissolve the potassium permanganate to form a potassium permanganate solution, adding a manganese sulfate solution with a certain mass into the potassium permanganate solution, uniformly stirring, transferring the mixed solution into a hydrothermal reaction kettle, and carrying out hydrothermal reaction at 180 ℃ for 24 hours.

(2) The resulting brown precipitate was washed with deionized water, dried at 120 ℃ overnight and calcined to produce pure phase octahedral manganese oxide molecular sieve OMS-2(JCPDS No. 29-1020).

In the hydrothermal synthesis method, after the slurry is formed, it is necessary to wash and dry the slurry appropriately, and the slurry is generally washed to be neutral, preferably at PH 7. After washing and drying, the product needs to be roasted, wherein the roasting temperature is 200-.

In the supported catalyst precursor of the present invention, the active metal is supported on the carrier in the form of an oxide, wherein the active metal is a group VIII metal, and the valence of the active metal in the oxide is the highest oxidation valence thereof.

More specifically, the active metal may be one or more of Fe, Ru, Pt, Co, Rh, Pd, Ir, preferably Fe, Ru and/or Co, more preferably Fe.

The supported catalyst precursor of the present invention contains the active metal oxide in an amount of 0.2 to 40% by weight, preferably 0.3 to 30% by weight, in terms of the metal element.

The supported catalyst precursor of the present invention can be obtained by in-situ doping or supporting an active metal on a carrier, followed by drying and calcination in this order.

The method for supporting the active metal according to the present invention may be a method conventionally used in the art, and for example, an impregnation method or a coprecipitation method may be used, and an impregnation method is preferred.

The impregnation method used in the invention is an isometric impregnation method or a saturation impregnation method, and specifically comprises the following steps: dissolving soluble salt of active metal in a solvent to obtain an impregnation solution; and immersing the support in the impregnation fluid.

The soluble salt of the active metal used in the preparation of the impregnation solution may be a nitrate or a hydrochloride (chloride).

The carrier is soaked in the soaking solution in one step or in multiple steps, and the multiple steps of soaking may be soaking the soluble salt of the active metal in the soaking solution and soaking the soaking solution onto the carrier twice or several times.

After OMS-2 is loaded with the active metal, it is dried, which may be a method conventionally used in the art, for example, a method of drying by heating. The drying temperature is 80-350 ℃, preferably 100-300 ℃; the drying time is 1 to 24 hours, preferably 2 to 12 hours.

After drying, the active metal-supporting carrier is calcined, and the calcination method may be a method conventionally used in the art as long as the active metal is converted into the corresponding oxide, for example, the calcination method is a calcination method in an air atmosphere, and the calcination conditions include: the roasting temperature is 250-900 ℃, preferably 300-850 ℃, and more preferably 350-800 ℃; the calcination time is 0.5 to 12 hours, preferably 1 to 8 hours, and more preferably 2 to 6 hours.

On the other hand, the invention also provides the application of the supported catalyst precursor in the reaction of preparing low-carbon olefin from synthesis gas.

After reduction and activation, the supported catalyst precursor still has higher CO conversion rate and selectivity of low-carbon olefin when used at a higher airspeed, and can overcome the defect that the catalyst used in the reaction for preparing the low-carbon olefin from the synthesis gas cannot be used at the higher airspeed.

In another aspect, the present invention further provides a method for producing light olefins, the method includes a contact reaction between syngas and the supported catalyst, and specifically includes the following steps:

s11, under the condition of steam reforming reaction, enabling methane to contact with steam to carry out steam reforming reaction to obtain steam reforming synthesis gas;

s21, under the condition of dry reforming reaction, enabling methane to contact with carbon dioxide for dry reforming reaction to obtain dry reforming synthesis gas;

s31, mixing at least part of steam reforming synthesis gas and at least part of dry weight integrated synthesis gas to prepare a Fischer-Tropsch synthesis reaction feed;

s41, carrying out reduction activation on the supported catalyst precursor to obtain a Fischer-Tropsch synthesis catalyst;

s51, contacting the Fischer-Tropsch synthesis reaction feed with a Fischer-Tropsch synthesis catalyst to carry out Fischer-Tropsch synthesis reaction to obtain a Fischer-Tropsch synthesis product material flow;

s61, separating the low-carbon olefin, the methane and the carbon dioxide from the Fischer-Tropsch synthesis product stream.

In step S11, the steam reforming reaction may be performed in a conventional reactor, preferably, a fixed bed reactor. The molar ratio of methane to water vapor may be 1: 0.5 to 4, preferably 1: 1-3. The methane may be contacted with the water vapor at a temperature of 700 ℃ to 950 ℃, preferably 800 ℃ to 900 ℃. The pressure in the reactor in which methane is contacted with steam may be 0.1 to 5MPa, preferably 1 to 3MPa, which is a gauge pressure. The hourly space velocity of the gas fed is preferably 10000-^-1Preferably 50000-100000 hours^-1。

In step S11, various steam reforming catalysts commonly used in the art and suitable for steam reforming reactions may be used. As an example, the steam reforming catalyst contains a carrier, which may be one or a combination of two or more of alumina, silica, zirconia, and silicon carbide, and an active component supported on the carrier. Preferably, the support is alumina, in particular gamma-Al₂O₃、θ-Al₂O₃、δ-Al₂O₃And α -Al₂O₃One or more than two of them. The active component can be a group VIII metal element, preferably a non-noble group VIII metal element, such as one or more of Fe, Co and Ni. More preferably, the active component is Ni. Negative of active ingredient on carrierThe loading may be conventionally selected. In general, the active component may be present in an amount of 1 to 30% by weight, preferably 5 to 25% by weight, more preferably 10 to 15% by weight, calculated as element, based on the total amount of the catalyst.

In step S21, the dry reforming reaction may be carried out in a conventional reactor, preferably a fixed bed reactor. The molar ratio of methane to carbon dioxide may be 1: 0.5 to 5, preferably 1: 0.8 to 3, more preferably 1: 1-2. The methane and carbon dioxide may be contacted at a temperature of 600-800 deg.C, preferably 650-750 deg.C. The pressure in the reactor in which the methane and carbon dioxide are contacted may be in the range of from 0.1 to 5MPa, preferably from 1 to 3MPa, as a gauge pressure. The gas hourly volume space velocity of the feed is 10000-100000 hours based on the total amount of the methane and the carbon dioxide^-1Preferably 50000-100000 hours^-1。

In step S21, various dry reforming catalysts commonly used in the art for dry reforming reactions can be used. As an example, a dry reforming catalyst contains a support and an active component supported on the support. The carrier may be one or a combination of two or more of alumina, silica, zirconia and silicon carbide. Preferably, the support is alumina, in particular gamma-Al₂O₃、θ-Al₂O₃、δ-Al₂O₃And α -Al₂O₃One or more than two of them. The active component can be a group VIII metal element, preferably a non-noble group VIII metal element, such as one or more of Fe, Co and Ni. More preferably, the active component is Ni. The amount of active ingredient supported on the carrier may be conventionally selected. In general, the active component may be present in an amount of 1 to 30% by weight, preferably 5 to 25% by weight, more preferably 10 to 15% by weight, calculated as element, based on the total amount of the catalyst.

In the process for producing low-carbon olefins of the present invention, the methane, which is one of the raw materials for steam reforming of methane and dry reforming of methane, may be methane of various sources, and is preferably methane separated from a raw material gas rich in methane. At this time, the method for producing lower olefins according to the present invention may further include a step S10 of separating methane from the feed gas containing methane in S10. The feed gas may be a common methane-rich mixture. Specifically, the raw material gas may be one or more selected from shale gas, coal bed gas, natural gas, refinery gas and coke oven gas.

The methane may be separated from the feed gas by conventional means, such as by pressure swing adsorption. As an example, methane is separated from a feed gas by a cryogenic condensation process. The cryocondensation method is a method for separating and purifying methane by using a difference in boiling point, and can determine whether to obtain methane from a gas phase or from a liquid phase according to the boiling point of each component in a raw material gas.

In the process for producing lower olefins according to the present invention, the content of elemental sulfur in methane, which is one of the raw materials for steam reforming and dry reforming, is generally 20ppm or less, preferably 10ppm or less, more preferably 5ppm or less, and still more preferably 1ppm or less, by mass.

In the method for producing the low-carbon olefin, the raw material utilization rate of the method can be further improved by controlling the amount of the methane fed to the step S11 and the step S21 according to the reaction property of steam reforming and dry reforming and the requirement of the Fischer-Tropsch synthesis reaction feed. Preferably, the weight ratio of the methane used in step S11 to the methane used in step S21 is 1: 0.5-2.5.

In step S31, at least a portion of the steam reformed syngas and at least a portion of the dry weight integrated syngas are mixed to prepare a fischer-tropsch synthesis reaction feed that meets the fischer-tropsch synthesis feed hydrogen to carbon ratio (i.e., the molar ratio of hydrogen to carbon monoxide). From the viewpoint of improving the selectivity of the low-carbon olefin, the molar ratio of hydrogen to carbon monoxide in the feed of the Fischer-Tropsch synthesis reaction is preferably 0.4-3: 1, preferably 0.6 to 2.5: 1, more preferably 0.8 to 2.2: 1, most preferably 1.5-2.2: 1.

in step S41, the supported catalyst precursor needs to be subjected to reduction activation to obtain a fischer-tropsch synthesis catalyst before being applied to a reaction for preparing low carbon olefins from synthesis gas, and the reduction activation can be performed in a pure hydrogen atmosphere, or in a mixed atmosphere of hydrogen and an inert gas, for example, in a mixed atmosphere of hydrogen and nitrogen and/or argon, and the hydrogen pressure is 0 to 2.5MPa, preferably 0.1 to 2 MPa. The temperature for reduction activation is 200-600 ℃, preferably 300-550 ℃, and more preferably 350-500 ℃; the time for the reduction activation is 1 to 20 hours, preferably 2 to 10 hours, more preferably 5 to 8 hours.

In step S51, the fischer-tropsch synthesis reaction may be performed under the conventional condition for producing low-carbon olefins, and may be performed in a fixed bed reactor, a fluidized bed reactor, or a combination of a fixed bed reactor and a fluidized bed reactor. Preferably, the hydrogen and carbon monoxide are contacted with the fischer-tropsch synthesis catalyst in a fixed bed reactor. Preferably, the Fischer-Tropsch synthesis reaction feed and the Fischer-Tropsch synthesis catalyst may be contacted at a temperature of from 200 ℃ to 400 ℃, preferably from 300 ℃ to 380 ℃. The pressure at which the Fischer-Tropsch synthesis reaction feed is contacted with the Fischer-Tropsch synthesis catalyst may be in the range 0.5 to 3MPa, preferably 1 to 2.5MPa, expressed as gauge pressure. When the hydrogen and the carbon monoxide are contacted with the Fischer-Tropsch synthesis catalyst in the fixed bed reactor, the volume space velocity of the feeding material of the Fischer-Tropsch synthesis reaction can be 5000-^-1Preferably 10000-^-1。

In step S61, light olefins, methane and carbon dioxide can be separated from the product stream of the fischer-tropsch synthesis by conventional methods. As an example, the Fischer-Tropsch synthesis product stream may be separated by cryocondensation to yield lower olefins, methane, and carbon dioxide, respectively.

In the method for producing low-carbon olefins, the separated methane can be recycled for steam reforming reaction and/or dry reforming reaction, namely, the methane separated from the Fischer-Tropsch synthesis product flow is sent to the step S11 and/or the step S21 to be used as the raw material of the steam reforming reaction and/or the dry reforming reaction. The separated carbon dioxide may also be recycled to the dry reforming reaction, i.e. the carbon dioxide separated from the product stream from the fischer-tropsch synthesis is fed to step S21 as a feed for the dry reforming reaction. According to the production method of the low-carbon olefin, the steam reforming and the dry reforming are combined for use, and the methane and the carbon dioxide separated from the Fischer-Tropsch synthesis product material flow are recycled, so that the utilization rate of the raw materials is effectively improved, and the emission of greenhouse gas carbon dioxide is obviously reduced.

From the viewpoint of further improving the utilization rate of the raw materials, it is preferable to further comprise separating unreacted hydrogen and/or carbon monoxide from the product stream of the Fischer-Tropsch synthesis, and feeding at least part of the hydrogen and/or at least part of the carbon monoxide to step S31 for formulating the feed for the Fischer-Tropsch synthesis reaction. Preferably, part of the hydrogen and/or part of the carbon monoxide separated from the product stream of the Fischer-Tropsch synthesis is recycled to step S31 for use in formulating the Fischer-Tropsch synthesis reaction feed, while the remainder of the hydrogen and/or carbon monoxide is vented as purge gas to the system. Generally, the amount of hydrogen and carbon monoxide used for recycle may be in the range of from 10 to 98%, preferably from 15 to 98%, based on the total amount of hydrogen and carbon monoxide separated from the Fischer-Tropsch synthesis product stream.

In the method for producing the low-carbon olefin, the step S11 and the step S21 can be simultaneously carried out, and the step S31 and the step S41 can be simultaneously carried out, so that the total reaction time is saved, and the production efficiency is improved.

After intensive research, the inventor of the invention finds that when the catalyst precursor is used for preparing the low-carbon olefin from the synthesis gas, compared with the prior art, the catalyst has the advantages of improved activity and product selectivity, high carbon monoxide conversion rate, high low-carbon olefin selectivity, mild reaction conditions, low energy consumption, high space velocity of the reaction, and contribution to industrial popularization.

The production method of the low-carbon olefin can be carried out by a low-carbon olefin production system which comprises a steam reforming reaction unit, a dry reforming reaction unit, a synthesis gas mixing unit, a Fischer-Tropsch synthesis reaction product separation unit and a circulation unit.

The steam reforming reaction unit is used for contacting methane with steam to carry out steam reforming reaction to obtain steam reforming synthesis gas. The steam reforming reaction unit may be provided with a conventional steam reforming reactor and corresponding feed, discharge and control means to enable the reforming reaction of methane with steam to produce a steam reformed synthesis gas having hydrogen and carbon monoxide as the main components.

And the dry reforming reaction unit is used for contacting methane and carbon dioxide to carry out dry reforming reaction to obtain dry reforming syngas. The dry reforming reaction unit may be provided with a conventional dry reforming reactor and corresponding feed, discharge and control means to enable the reforming reaction of methane with carbon dioxide to obtain a dry reformed gas having hydrogen and carbon monoxide as main components.

The synthesis gas mixing unit is used for mixing the steam reforming synthesis gas with the dry weight synthesis gas to prepare Fischer-Tropsch synthesis reaction feed, and the Fischer-Tropsch synthesis reaction feed is sent into the Fischer-Tropsch synthesis reaction unit. The synthesis gas mixing unit may be provided with a vessel for receiving and mixing the steam reformed synthesis gas and the dry integrated syngas, in which vessel the steam reformed synthesis gas is mixed with the dry integrated syngas to obtain the fischer-tropsch synthesis feed. The synthesis gas mixing unit can also adopt a pipeline mixer to directly mix the steam regenerated synthesis gas and the dry weight integrated synthesis gas in a conveying pipeline so as to obtain the Fischer-Tropsch synthesis reaction feed. The synthesis gas mixing unit can be provided with various common control devices for controlling the mixing proportion of the steam reforming synthesis gas and the dry weight integrated synthesis gas, so that the Fischer-Tropsch synthesis reaction feeding material meeting the hydrogen-carbon ratio of the Fischer-Tropsch synthesis reaction is obtained.

The Fischer-Tropsch synthesis reaction unit is provided with a Fischer-Tropsch synthesis reactor and is used for contacting Fischer-Tropsch synthesis reaction feed with a Fischer-Tropsch synthesis catalyst to obtain a Fischer-Tropsch synthesis product material flow containing low-carbon olefins. The Fischer-Tropsch synthesis reactor can be various common reactor forms, and specifically, the Fischer-Tropsch synthesis reactor can be a fixed bed reactor, a fluidized bed reactor or a combination of the fixed bed reactor and the fluidized bed reactor. Preferably, the Fischer-Tropsch synthesis reactor is a fluidized bed reactor.

The Fischer-Tropsch synthesis reaction unit is preferably further provided with a reduction activation subunit, and the reduction activation subunit is used for carrying out reduction activation on the supported catalyst precursor so as to convert the supported catalyst precursor into the Fischer-Tropsch synthesis catalyst with catalytic activity. The reductive activation subunit may be used to reductively activate the supported catalyst precursor to a fischer-tropsch synthesis catalyst by contacting the supported catalyst precursor with a reducing gas.

The reducing gas control means is for controlling the type of gas fed to the reduction activation reactor and the amount of gas fed thereto. Specifically, when the reduction activation subunit is operated, the reduction gas control device is configured to firstly input a reduction gas into the reduction activation reactor, so that the supported catalyst precursor is contacted with the reduction gas to carry out a pre-reduction reaction, and a pre-reduction catalyst is obtained. The reducing gas control means may employ conventional control elements such as various control valves for controlling the type of gas fed to the reduction activation reactor and the amount of gas fed thereto.

The reduction activation reactor and the Fischer-Tropsch synthesis reactor can be the same reactor, namely, the reduction activation of the supported catalyst precursor is carried out in the Fischer-Tropsch synthesis reactor.

The reduction activation reactor and the Fischer-Tropsch synthesis reactor also can be different reactors, namely the Fischer-Tropsch synthesis reactor and the reduction activation reactor are independent reactors. At this time, the reduction activation catalyst output port of the reduction activation reactor is set to be communicated with the catalyst input port of the fischer-tropsch synthesis reactor, so that the reduction activation catalyst output by the reduction activation reactor is sent into the fischer-tropsch synthesis reactor. The reduction activation catalyst output port of the reduction activation reactor and the catalyst input port of the Fischer-Tropsch synthesis reactor can be communicated by adopting a conveying pipeline, a control valve is arranged on the conveying pipeline, when the reduction activation reactor outputs the reduction activation catalyst, the control valve is opened, the reduction activation catalyst output port of the reduction activation reactor and the catalyst input port of the Fischer-Tropsch synthesis reactor are communicated, and the reduction activation catalyst is sent into the Fischer-Tropsch synthesis reactor.

In the low-carbon olefin production system, the circulating unit is used for circularly sending the methane separated by the Fischer-Tropsch synthesis reaction product separating unit into one or both of the steam reforming reaction unit and the dry reforming reaction unit, circularly sending the carbon dioxide separated by the Fischer-Tropsch synthesis reaction product separating unit into the dry reforming reaction unit, and circularly sending the hydrogen and/or the carbon monoxide separated by the Fischer-Tropsch synthesis reaction product separating unit into the Fischer-Tropsch synthesis reaction unit.

The circulation unit can be provided with a methane conveying pipeline which is respectively used for communicating the Fischer-Tropsch synthesis reaction product separation unit with the steam reforming reaction unit and the dry reforming reaction unit, and a control valve arranged on the methane conveying pipeline, so that the methane separated by the Fischer-Tropsch synthesis reaction product separation unit is respectively conveyed into the steam reforming reaction unit and the dry reforming reaction unit. The circulation unit can be provided with a carbon dioxide conveying pipeline for communicating the Fischer-Tropsch synthesis reaction product separation unit and the dry reforming reaction unit and a control valve arranged on the carbon dioxide conveying pipeline so as to convey the carbon dioxide output by the Fischer-Tropsch synthesis reaction product separation unit into the dry reforming reaction unit.

When the fischer-tropsch synthesis reaction product separation unit further separates hydrogen and carbon monoxide, the circulation unit is preferably provided with a conveying pipeline for communicating the fischer-tropsch synthesis reaction product separation unit and the fischer-tropsch synthesis reaction unit, and a control valve arranged on the conveying pipeline, so as to send the hydrogen and/or carbon monoxide separated by the fischer-tropsch synthesis reaction product separation unit into the fischer-tropsch synthesis reaction unit. Can send into during the ft synthesis reaction unit with hydrogen and carbon monoxide through same conveying pipeline, also can send into the ft synthesis reaction unit respectively with hydrogen and carbon monoxide through different conveying pipelines, can set up hydrogen conveying pipeline and corresponding control valve this moment respectively and carbon monoxide conveying pipeline and corresponding control valve.

Preferably, the system for producing low carbon olefins of the present invention further comprises a raw material gas separation unit, wherein the raw material gas separation unit is configured to separate methane from a raw material gas containing methane, and a methane output port of the raw material gas separation unit is respectively communicated with a methane raw material input port of the steam reforming reaction unit and a methane raw material input port of the dry reforming reaction unit, so as to respectively send the separated methane into the steam reforming reaction unit and the dry reforming reaction unit.

The feed gas separation unit may employ conventional separation methods to separate methane from the feed gas. In one embodiment, the feed gas separation unit employs a pressure swing adsorption process to separate methane from the feed gas. In a more preferred embodiment, the feed gas separation unit employs cryogenic condensation to separate methane from the feed gas. In this more preferred embodiment, a low-temperature condenser may be provided in the raw gas separation unit to condense the raw gas to separate methane from the raw gas. The low-temperature condenser may be a conventional condenser, and is not particularly limited.

Fig. 2 shows a preferred embodiment of the low carbon olefin production system according to the present invention, which is described in detail below with reference to fig. 2. As shown in fig. 2, the low carbon olefin production system includes a raw material gas separation unit I, a steam reforming reaction unit II, a dry reforming reaction unit III, a fischer-tropsch synthesis reaction unit IV, a fischer-tropsch synthesis product separation unit V, and a circulation unit.

And the raw material gas A enters a raw material gas separation unit I for separation to obtain methane B. And respectively feeding the methane B into the steam reforming reaction unit II and the dry reforming reaction unit III, and simultaneously feeding the steam C into the steam reforming reaction unit II so as to carry out reforming reaction on the methane and the steam to obtain the steam reforming synthesis gas E. And feeding carbon dioxide D into the dry reforming reaction unit III so as to carry out reforming reaction on methane and carbon dioxide to obtain dry reforming synthesis gas F. And (3) mixing the steam reforming synthesis gas E and the dry weight integrated synthesis gas F (preferably adopting a pipeline mixer) to prepare the Fischer-Tropsch synthesis reaction feed G according with the hydrogen-carbon ratio of the Fischer-Tropsch synthesis reaction. And (3) feeding the Fischer-Tropsch synthesis reaction feed G into a Fischer-Tropsch synthesis reaction unit IV, and contacting with a Fischer-Tropsch synthesis catalyst to carry out Fischer-Tropsch synthesis reaction. And the Fischer-Tropsch synthesis reactor in the Fischer-Tropsch synthesis reaction unit IV operates at the temperature of producing the low-carbon olefin. And the Fischer-Tropsch synthesis product material flow H output by the Fischer-Tropsch synthesis reaction unit IV enters a Fischer-Tropsch synthesis product separation unit V for separation to obtain the low-carbon olefin K, unreacted hydrogen, carbon monoxide, methane M and carbon dioxide N. Wherein, the low carbon olefin K is sent out of the system.

The separated hydrogen and carbon monoxide can be recycled for preparing the Fischer-Tropsch synthesis reaction feed, can also be discharged out of the system, and can also be recycled for preparing the Fischer-Tropsch synthesis reaction feed in a part of the system, and discharged out of the system in the other part of the system. Preferably, as shown in FIG. 2, the hydrogen and carbon monoxide L for recycle are mixed with the steam reforming synthesis gas E and the dry weight integrated synthesis gas F for formulating the Fischer-Tropsch synthesis reaction feed G; the remaining part of the hydrogen and carbon monoxide is discharged out of the system as purge gas Z.

The separated carbon dioxide N is sent to the dry reforming reaction unit III and recycled as one of the raw materials for the dry reforming reaction. The separated methane M is respectively sent into the steam reforming reaction unit II and the dry reforming reaction unit III to be used as one of the raw materials of the reforming reaction for recycling.

The present invention will be described in detail with reference to examples, but the scope of the present invention is not limited thereto.

Examples

In the following examples, preparations and comparative examples, the pressures were gauge pressures unless otherwise specified.

In the following examples, preparations and comparative examples, CO conversion (X)_CO)、CH₄Selectivity is

And C₂-C₄The selectivity of the hydrocarbon (among them,

is represented by C₂-C₄The selectivity of the olefin is high,

is represented by C₂-C₄Alkane selectivity) was calculated by the following formula:

wherein, V₁、V₂Respectively representing the volume of feed gas entering the reaction system and the volume of tail gas flowing out of the reaction system in a certain time period under a standard condition;

C_1,CO、C_2,COrespectively representing the molar contents of CO in raw gas entering a reaction system and tail gas flowing out of the reaction system;

n_conis the mole number of CO participating in the reaction;

to generate CH₄The number of moles of (a);

to generate C₂-C₄Moles of hydrocarbons.

In the following examples, preparations and comparative examples, the specific surface area, pore volume and average pore diameter were measured by nitrogen adsorption method, specifically, N was used₂Measuring an adsorption isotherm at a constant temperature of 77K, calculating a specific surface area and a pore volume according to a BET formula, and calculating an average pore size distribution according to a BJH method; the particle size distribution was determined using a laser particle sizer.

In the following examples, preparation examples and comparative examples, the kind and content of each metal element in the catalyst and the catalyst precursor were measured by the X-ray fluorescence spectrum analysis method specified in RIPP 132-92 (published in the protocols of petrochemical engineering analysis (RIPP Experimental method), Yankee, et al, science publishers, 1 st edition at 1990, p. 371-. When the catalyst was tested, a sample of the catalyst was stored under an argon atmosphere.

In the following examples, preparations and comparative examples, CO₂both-TPD and CO-TPD adopt Michmi chemisorptionThe instrument is detected on line by using an OMistar mass spectrometer as a detector, wherein CO is₂TPD recorded signals for the nuclear to cytoplasmic ratio of 44 by the mass spectrometer and CO-TPD recorded signals for the nuclear to cytoplasmic ratio of 28 by the mass spectrometer.

In the following examples, preparations and comparative examples, X-ray photoelectron spectroscopy was carried out on an ESCALB 250 type X-ray photoelectron spectrometer equipped with Thermo Avantage V5.926 software, manufactured by Thermo Scientific, with an excitation source of monochromated Al K α X rays, an energy of 1486.6eV, a power of 150W, a transmission energy for narrow scanning of 30eV, and a base vacuum of 6.5X 10 during analytical testing^-10mbar, electron binding energy was corrected for the C1s peak (284.6eV) of elemental carbon, data processed on Thermo Avantage software, and quantified in the analytical module using the sensitivity factor method.

Preparation example 1

(1) Preparation of doped Fe-OMS-2 catalyst precursor:

dissolving 3.17g of potassium permanganate in a certain amount of 40.55 deionized water, heating and stirring to dissolve the potassium permanganate to form a potassium permanganate solution a, and adding ferric nitrate into 3.64g of a 50% manganese nitrate solution to ensure that the ratio of Fe: and (3) uniformly stirring the mixture to obtain a solution b with the Mn molar ratio of 1:10, mixing the solution a and the solution b, transferring the mixed solution into a hydrothermal reaction kettle, and carrying out hydrothermal reaction for 24 hours at 180 ℃.

The resulting brown precipitate was washed with deionized water several times to a PH of 7, dried at 120 ℃ overnight and calcined at 400 ℃ for 4h to yield Fe-OMS-2 procatalyst a 1.

(2) Reduction of catalyst precursor

The catalyst precursor A1 was charged into a fluidized-bed reactor, into which H was passed₂And adjusting the pressure of the reactor to 0.1MPa and the space velocity of 20000h < -1 > to ensure that A1 is fully fluidized in the reactor, the temperature rise rate of the reactor at 10 ℃/min is increased to 300 ℃, and the temperature is kept for 4h to obtain the reduced catalyst.

(3) Preparation of lower olefins from synthesis gas

After the reduction activation, the temperature is raised to 340 ℃, the synthesis gas is introduced to start the reaction, and the space velocity is 10000h^-1The pressure is 1.5MPa, and the composition of the synthesis gas is H₂:CO:N₂56:28:16 (molar ratio, below)Same), the composition of the off-gas was analyzed by on-line gas chromatography. The results obtained after 50 hours of reaction are shown in Table 1.

Preparation example 2

(1) Preparation of doped Fe-OMS-2 catalyst precursor

An Fe-OMS-2 procatalyst a2 was prepared in the same manner as in preparation example 1, except that the amount of ferric nitrate added was varied, and the amount of ferric nitrate was increased so that n (Fe) and n (mn) in a2 were 1: 5.

(2) Reduction of catalyst precursor

The catalyst precursor a2 was reduced in the same manner as in preparation example 1.

(3) Preparation of lower olefins from synthesis gas

The catalyst precursor A2 was evaluated by synthesizing a lower olefin in the same manner as in preparation example 1, and the reaction data are shown in Table 1.

Preparation example 3

(1) Preparation of doped Fe-OMS-2 catalyst precursor

An Fe-OMS-2 procatalyst A3 was prepared in the same manner as in preparation example 1, except that the amount of ferric nitrate added was varied, and the amount of ferric nitrate was reduced so that n (Fe) and n (mn) in A3 were 1: 20.

(2) Reduction of catalyst precursor

The catalyst precursor a3 was reduced in the same manner as in preparation example 1.

(3) Preparation of lower olefins from synthesis gas

The catalyst precursor A3 was evaluated by synthesizing a lower olefin in the same manner as in preparation example 1, and the reaction data are shown in Table 1.

Preparation example 4

(1) Preparation of Supported Fe/OMS-2 catalyst precursor

OMS-2 support was prepared in the same manner as in preparation example 1, except that OMS-2 molecular sieve was prepared without doping Fe metal.

Using OMS-2 molecular sieve as carrier, loading Fe salt on OMS-2 carrier by impregnation method to make n (Fe): n (Mn) ═ 1:10 consistent with catalyst precursor A1, drying and roasting to obtain supported catalyst precursor A4.

(2) Reduction of catalyst precursor

The catalyst precursor a4 was reduced in the same manner as in preparation example 1.

(3) Preparation of lower olefins from synthesis gas

The catalyst precursor A4 was evaluated by synthesizing a lower olefin in the same manner as in preparation example 1, and the reaction data are shown in Table 1.

Preparation example 5

(1) Preparation of Supported Fe/OMS-2 catalyst precursor

Using OMS-2 molecular sieve as carrier, loading Fe salt on OMS-2 carrier by impregnation method to make n (Fe): n (Mn) ═ 1:5 consistent with catalyst precursor A2, drying and roasting to obtain supported catalyst precursor A5.

(2) Reduction of catalyst precursor

The catalyst precursor a5 was reduced in the same manner as in preparation example 1.

(3) Preparation of lower olefins from synthesis gas

The catalyst precursor A5 was evaluated by synthesizing a lower olefin in the same manner as in preparation example 1, and the reaction data are shown in Table 1.

Preparation example 6

(1) Preparation of Supported Fe/OMS-2 catalyst precursor

Using OMS-2 molecular sieve as carrier, loading Fe salt on OMS-2 carrier by impregnation method to make n (Fe): n (Mn) ═ 1:20 consistent with catalyst precursor A3, drying and roasting to obtain supported catalyst precursor A6.

(2) Reduction of catalyst precursor

The catalyst precursor a6 was reduced in the same manner as in preparation example 1.

(3) Preparation of lower olefins from synthesis gas

The catalyst precursor A6 was evaluated by synthesizing a lower olefin in the same manner as in preparation example 1, and the reaction data are shown in Table 1.

Comparative example 1

A catalyst precursor was prepared in the same manner as in preparation example 1, except that the catalyst precursor was prepared without adding the active component Fe, and only the support OMS-2 was prepared as the catalyst precursor D1.

The catalyst precursor D1 was reduced in the same manner as in preparation example 1.

The reaction for preparing lower olefins from synthesis gas under the same conditions as in preparation example 1 is shown in Table 1.

Table 1 evaluation test data

Note: O/P is C in gaseous hydrocarbon product₂-C₄Olefin (SC) of₂ ^＝-C₄ ^＝) With alkanes (SC)₂ ^o-C₄o) ratio.

The results show that when the catalyst provided by the invention is used in the reaction of preparing low-carbon olefin from synthesis gas, the conversion rate of carbon monoxide obtained in a fluidized bed reactor with high airspeed is high, the selectivity of the low-carbon olefin is high, the activity of the catalyst is stable, the reaction condition is mild, and the energy consumption is low.

Example 1

In this embodiment, the low-carbon olefin production system shown in fig. 2 includes a raw material gas separation unit I, a steam reforming reaction unit II, a dry reforming reaction unit III, a fischer-tropsch synthesis reaction unit IV, a fischer-tropsch synthesis product separation unit V, and a circulation unit. The specific process flow is as follows.

(1) And (2) sending shale gas with the flow rate of 220kmol/h and the pressure of 2.0MPa as a raw material gas A into a raw material gas separation unit I for low-temperature condensation separation, and removing sulfur, carbon and other impurities to obtain methane B with the sulfur mass content of less than 1 ppm.

And dividing the methane B into two parts by a flow divider, and respectively sending the two parts into a steam reforming reaction unit II and a dry reforming reaction unit III.

(2) Mixing the first stream of methane with medium-pressure steam C with the flow rate of 120kmol/h, the temperature of 370 ℃ and the pressure of 3MPa, and then mixing the mixtureThen enters a fixed bed reactor of a steam reforming reaction unit II to carry out reforming reaction to obtain steam reforming synthesis gas E. Wherein the molar ratio of methane to water vapor is 1: 3, the catalyst filled in the reactor is Ni/Al₂O₃(Ni content is 10% by weight, calculated as element, based on the total amount of the catalyst; Al)₂O₃Is α -Al₂O₃) The temperature in the catalyst bed layer is 900 ℃, the pressure in the reactor is 3MPa, and the gas-time volume space velocity based on the total amount of methane and water vapor is 50000h^-1。

(3) And mixing the second strand of methane with carbon dioxide D with the flow rate of 100kmol/h, the temperature of 370 ℃ and the pressure of 2MPa, raising the temperature of the mixture to 600 ℃, and then feeding the mixture into a fixed bed reactor of a dry reforming reaction unit III for reforming reaction to obtain dry integrated syngas F. Wherein the molar ratio of methane to carbon dioxide is 1:1, the catalyst filled in the reactor is Ni/Al₂O₃(Ni content is 10% by weight, calculated as element, based on the total amount of the catalyst; Al)₂O₃Is α -Al₂O₃) The temperature in the catalyst bed layer is 750 ℃, the pressure in the reactor is 2MPa, and the gas hourly volume space velocity is 80000h based on the total amount of methane and steam^-1。

(4) Mixing the steam reforming synthesis gas E and the dry weight integrated synthesis gas F to prepare a mixture with a hydrogen-carbon ratio of 2.1: 1 fischer-tropsch synthesis reaction feed G. The fischer-tropsch synthesis reaction feed G was fed into a fischer-tropsch synthesis reactor (a fluidized bed reactor) of the fischer-tropsch synthesis reaction unit IV, and contacted with a fischer-tropsch synthesis catalyst (obtained by reduction activation of the catalyst precursor prepared in preparation example 1) to perform a fischer-tropsch synthesis reaction. Wherein the temperature in the reactor is 340 ℃, the pressure in the reactor is 1MPa, and the gas hourly space velocity is 30000h based on the total amount of the synthesis gas^-1。

(5) And sending the Fischer-Tropsch synthesis product stream H output by the Fischer-Tropsch synthesis reaction unit IV into a Fischer-Tropsch synthesis product separation unit V for separation. The separation process comprises the following steps: firstly, carrying out gas-liquid separation to obtain low-carbon olefin K and a gas product; then, the gas product is subjected to cryogenic separation to remove carbon dioxide in the gas product; then, the gaseous product from which the carbon dioxide is separated is subjected to cryogenic separation to obtain methane, and unreacted hydrogen and carbon monoxide.

Discharging the low-carbon olefin K out of the system; the separated carbon dioxide N is circularly sent into a dry reforming reaction unit III; the separated methane M is respectively sent into a steam reforming reaction unit II and a dry reforming reaction unit III; and (3) circularly feeding a part of L of the separated hydrogen and carbon monoxide into a Fischer-Tropsch synthesis reaction unit IV, and discharging the rest of L out of the system as purge gas Z, wherein the amount of the circulated hydrogen and carbon monoxide L is 98% based on the total amount of the separated hydrogen and carbon monoxide.

The composition of the gaseous product stream exiting the reactor of the fischer-tropsch synthesis reaction unit was analyzed by an on-line gas chromatograph during the reaction and the results obtained after 50 hours of reaction are shown in table 2. The overall water consumption, carbon dioxide emissions, and energy efficiency of the system are listed in table 3.

Comparative example 1

The Fischer-Tropsch synthesis catalyst used in this comparative example was the same as the Fischer-Tropsch synthesis catalyst used in example 1.

The system shown in the figure 1 is adopted in the comparative example, and comprises a coal water slurry preparation unit I, a coal gasification unit II, a water gas shift unit III, a synthesis gas purification unit IV, a Fischer-Tropsch synthesis unit V and a low-carbon olefin separation unit VI which are sequentially connected. The specific process flow is as follows.

The coal water slurry C is prepared from pulverized coal A (pulverized coal (with the particle size of 10mm) obtained by crushing and screening solid raw material coal (brown coal produced by inner Mongolia)) in a coal water slurry preparation unit I at the flow rate of 360t/h and water B at the flow rate of 360t/h, and is conveyed into a coal gasification unit II to react with oxygen D under the conditions that the temperature is 1300 ℃ and the pressure is 3MPa to generate coal gasification crude synthesis gas E. Adjusting the molar ratio of hydrogen to carbon monoxide of the coal gasification crude synthesis gas E to be 2: and 1, removing acid gas and sulfide M through a synthesis gas purification unit IV to obtain purified synthesis gas, wherein the molar ratio of hydrogen to carbon monoxide is 2.1: 1. the purified synthesis gas obtained is conveyed into a Fischer-Tropsch synthesis unit V to carry out Fischer-Tropsch synthesis reaction in a fluidized bed reactor, and a Fischer-Tropsch reaction product N containing olefin is generated (the Fischer-Tropsch synthesis reaction conditions are the same as in example 1). And (3) separating the low-carbon olefin K from the Fischer-Tropsch reaction product N through a low-carbon olefin separation unit VI, discharging carbon dioxide H and methane G generated by a Fischer-Tropsch synthesis unit V, circulating a part of unreacted synthesis gas (the content is 98 percent based on the total amount of the separated synthesis gas) to the Fischer-Tropsch synthesis unit V, and discharging the other part of the unreacted synthesis gas as purge gas Z out of the system.

Comparative example 2

A low carbon olefin was produced in the same manner as in example 1, except that the dry reforming reaction unit III was not provided, and methane (including fresh methane and recycled methane) was entirely introduced into the steam reforming reaction unit II to carry out the reforming reaction.

Comparative example 3

A low carbon olefin was produced in the same manner as in example 1, except that the steam reforming reaction unit II was not provided, and methane (including fresh methane and recycled methane) was entirely fed into the dry reforming reaction unit III to undergo a reforming reaction.

Example 2

A low carbon olefin was produced by the same method as in example 1, except that the Fischer-Tropsch synthesis catalyst used was the Fischer-Tropsch synthesis catalyst produced in preparation example 2.

Example 3

A low carbon olefin was produced by the same method as in example 1, except that the Fischer-Tropsch synthesis catalyst used was the Fischer-Tropsch synthesis catalyst produced in production example 3.

Example 4

A low carbon olefin was produced by the same method as in example 1, except that the Fischer-Tropsch synthesis catalyst used was the Fischer-Tropsch synthesis catalyst produced in preparation example 4.

Example 5

In this example, the reaction system shown in fig. 2 was used, and the fischer-tropsch synthesis catalyst used was the fischer-tropsch synthesis catalyst prepared in preparation example 5. The specific process flow is as follows.

(1) And (2) taking the coke oven gas with the flow rate of 500kmol/h and the pressure of 3.0MPa as a raw material gas A, sending the raw material gas A into a raw material gas separation unit I for low-temperature condensation separation, and removing sulfur, carbon and other impurities to obtain methane B with the sulfur mass content of less than 1 ppm.

(2) Mixing the first stream of methane with medium-pressure steam C with the flow rate of 240kmol/h, the temperature of 370 ℃ and the pressure of 3MPa, raising the temperature of the mixture to 700 ℃, and then entering a fixed bed reactor of a steam reforming reaction unit II for reforming reaction to obtain steam reforming synthesis gas E. Wherein the molar ratio of methane to water vapor is 1:2, the catalyst filled in the reactor is Ni/Al₂O₃(Ni content is 10% by weight, calculated as element, based on the total amount of the catalyst; Al)₂O₃Is α -Al₂O₃) The temperature in the catalyst bed layer is 900 ℃, the pressure in the reactor is 3MPa, and the gas-time volume space velocity based on the total amount of methane and water vapor is 50000h^-1。

(3) And mixing the second strand of methane with carbon dioxide D with the flow rate of 200kmol/h, the temperature of 370 ℃ and the pressure of 2MPa, raising the temperature of the mixture to 600 ℃, and then feeding the mixture into a fixed bed reactor of a dry reforming reaction unit III for reforming reaction to obtain dry integrated syngas F. Wherein the molar ratio of methane to carbon dioxide is 1: 1.5, the catalyst filled in the reactor is Ni/Al₂O₃(Ni content is 10% by weight, calculated as element, based on the total amount of the catalyst; Al)₂O₃Is α -Al₂O₃) The temperature in the catalyst bed is 750 ℃, the pressure in the reactor is 2MPa, and the gas-time volume space velocity based on the total amount of methane and water vapor is 100000h^-1。

(4) Mixing the steam reforming synthesis gas E and the dry weight integrated synthesis gas F to prepare a mixture meeting the hydrogen-carbon ratio of 2.2: 1 fischer-tropsch synthesis reaction feed G. Feeding the Fischer-Tropsch synthesis reaction feed G into a Fischer-Tropsch synthesis reactor (a fluidized bed reactor) of a Fischer-Tropsch synthesis reaction unit IVThe Fischer-Tropsch synthesis reaction was carried out by contacting the catalyst precursor (obtained by reduction activation of the catalyst precursor prepared in preparation example 5). Wherein the temperature in the reactor is 340 ℃, the pressure in the reactor is 1.5MPa, the total amount of the synthetic gas is taken as a reference, and the gas hourly space velocity is 30000h^-1。

Discharging the low-carbon olefin K out of the system; the separated carbon dioxide N is circularly sent into a dry reforming reaction unit III; the separated methane M is respectively sent into a steam reforming reaction unit II and a dry reforming reaction unit III; and (3) circularly feeding a part of L of the separated hydrogen and carbon monoxide into a Fischer-Tropsch synthesis reaction unit IV, and discharging the rest of L out of the system as purge gas Z, wherein the amount of the circulated hydrogen and carbon monoxide L is 20% based on the total amount of the separated hydrogen and carbon monoxide.

During the reaction, the composition of the off-gas was analyzed by an on-line gas chromatograph, and the results obtained after 50 hours of the reaction are shown in table 2. The overall water consumption, carbon dioxide emissions and energy efficiency of the plant are listed in table 3.

Example 6

In this example, the reaction system shown in fig. 2 was used, and the fischer-tropsch synthesis catalyst used was the fischer-tropsch synthesis catalyst prepared in preparation example 6. The specific process flow is as follows.

(1) And (3) taking the coke oven gas with the flow rate of 150kmol/h and the pressure of 1MPa as a raw material gas A, sending the raw material gas A into a raw material gas separation unit I for low-temperature condensation separation, and removing sulfur, carbon and other impurities to obtain methane B with the sulfur mass content of less than 1 ppm.

(2) Mixing the first stream of methane with medium-pressure steam C with the flow rate of 300kmol/h, the temperature of 450 ℃ and the pressure of 3MPa, raising the temperature of the mixture to 700 ℃, and then entering a fixed bed reactor of a steam reforming reaction unit II for reforming reaction to obtain steam reforming synthesis gas E. Wherein the molar ratio of methane to water vapor is 1:1, the catalyst filled in the reactor is Ni/Al₂O₃(Ni content 15 wt% in terms of element, based on the total amount of the catalyst, Al₂O₃Is α -Al₂O₃) The temperature in the catalyst bed is 900 ℃, the pressure in the reactor is 1MPa, and the gas-time volume space velocity based on the total amount of methane and water vapor is 100000h^-1。

(3) And mixing the second strand of methane with carbon dioxide D with the flow rate of 150kmol/h, the temperature of 450 ℃ and the pressure of 3MPa, raising the temperature of the mixture to 700 ℃, and then feeding the mixture into a fixed bed reactor of a dry reforming reaction unit III for reforming reaction to obtain dry integrated syngas F. Wherein the molar ratio of methane to carbon dioxide is 1:1, the catalyst filled in the reactor is Ni/Al₂O₃(Ni content 12 wt% in terms of element, based on the total amount of the catalyst, Al₂O₃Is α -Al₂O₃) The temperature in the catalyst bed layer is 750 ℃, the pressure in the reactor is 2MPa, and the gas hourly volume space velocity is 80000h based on the total amount of methane and steam^-1。

(4) Mixing the steam reforming synthesis gas E and the dry weight integrated synthesis gas F to prepare a mixture meeting the hydrogen-carbon ratio of 1.5: 1 fischer-tropsch synthesis reaction feed G. The fischer-tropsch synthesis reaction feed G was fed into a fischer-tropsch synthesis reactor (a fluidized bed reactor) of the fischer-tropsch synthesis reaction unit IV, and contacted with a fischer-tropsch synthesis catalyst (obtained by reduction activation of the catalyst precursor prepared in preparation example 6) to perform a fischer-tropsch synthesis reaction. Wherein the temperature in the reactor is 360 ℃, the pressure in the reactor is 2.5MPa, the total amount of the synthetic gas is taken as a reference, and the gas hourly space velocity is 20000h^-1。

Discharging the low-carbon olefin K out of the system; the separated carbon dioxide N is circularly sent into a dry reforming reaction unit III; the separated methane M is respectively sent into a steam reforming reaction unit II and a dry reforming reaction unit III; and (3) circularly feeding a part of L of the separated hydrogen and carbon monoxide into a Fischer-Tropsch synthesis reaction unit IV, and discharging the rest of L out of the system as purge gas Z, wherein the amount of the circulated hydrogen and carbon monoxide L is 15% based on the total amount of the separated hydrogen and carbon monoxide.

TABLE 2

TABLE 3

	Water consumption (ton/ton)_{Low carbon olefin})	Carbon dioxide emission (ton/ton)_{Low carbon olefin})	Energy efficiency (%)
				Example 1	15	0.5	56
Comparative example 1	20	6.2	36
				Comparative example 2	21	4.2	41
Comparative example 3	19	0.6	46
				Example 2	17	2.3	49
Example 3	18	2.1	50
				Example 4	18	2.0	49
Example 5	17	1.2	48
				Example 6	17	1.8	47

Note: the energy efficiency is the sum of the calorific value of the low-carbon olefin finally discharged out of the device/the calorific value of the raw materials such as the coal-electricity water vapor catalyst solvent entering the device, namely the calorific value of the obtained low-carbon olefin/the comprehensive energy consumption required for producing the low-carbon olefin. Wherein, the comprehensive energy consumption comprises raw material heat value and public engineering energy consumption, and mainly comprises: the heat value of fuel coal and raw material coal, the electric energy consumed by a motor pump for the device process, the indirect energy consumption of circulating cooling water, boiler make-up water, process air, instrument air, fresh water and the like.

As can be seen from Table 3, the invention combines the methane steam reforming process and the methane dry reforming process to simultaneously utilize two greenhouse gases, namely carbon dioxide and methane, so that the greenhouse gases are converted into products with high added values, the greenhouse gas emission is reduced, and the resource and energy utilization rate of the whole process is obviously improved.

In conclusion, the production method can improve the utilization rate of two greenhouse gases, namely carbon dioxide and methane, in the production process of the low-carbon olefin, so that the low-carbon olefin is converted into a product with a high added value, the emission of the greenhouse gases is reduced, the energy consumption of a system is reduced, and the resource and energy utilization rate of the whole process is obviously improved.

It should be noted by those skilled in the art that the described embodiments of the present invention are merely exemplary and that various other substitutions, alterations, and modifications may be made within the scope of the present invention. Accordingly, the present invention is not limited to the above-described embodiments, but is only limited by the claims.

Claims

1. A supported catalyst precursor comprising a support and an active metal oxide supported on the support, wherein the support is a manganese oxide molecular sieve and the active metal in the active metal oxide is a group VIII metal.

2. A supported catalyst precursor according to claim 1, wherein the active metal is one or more of Fe, Ru, Pt, Co, Rh, Pd, Ir, preferably one or more of Fe, Ru, Co, more preferably Fe.

3. The supported catalyst precursor according to claim 1, wherein the active metal oxide is present in an amount of 0.2 to 40 wt.%, preferably 0.3 to 30 wt.%, calculated on the metal element.

4. A process for preparing the supported catalyst precursor of any of claims 1 to 3 comprising:

5. Process according to claim 4, wherein the temperature of the drying is between 80 and 350 ℃, preferably between 100 and 300 ℃; the drying time is 1 to 24 hours, preferably 2 to 12 hours.

6. A process according to claim 4, wherein the temperature of the calcination is from 250 ℃ to 900 ℃, preferably from 300 ℃ to 850 ℃, more preferably from 350 ℃ to 800 ℃; the calcination time is 0.5 to 12 hours, preferably 1 to 8 hours, and more preferably 2 to 6 hours.

7. A method for producing low-carbon olefins comprises the following steps:

subjecting the supported catalyst of any one of claims 1 to 3 to reductive activation to obtain a fischer-tropsch synthesis catalyst;

8. The production process according to claim 7, wherein the steam reforming reaction is carried out in a fixed bed reactor at a reaction temperature of 700-950 ℃, preferably 800-900 ℃, a reaction pressure of 0.1-5MPa, preferably 1-3MPa, and a molar ratio of methane to steam of 1: 0.5 to 4, preferably 1:1 to 3, based on the total amount of methane and steam, the hourly space velocity of the feed gas is preferably 10000-^-1Preferably 50000-100000 hours^-1。

9. The production process according to claim 7, wherein the dry reforming reaction is carried out in a fixed bed reactor at a reaction temperature of 600-800 ℃, preferably 650-750 ℃, a reaction pressure of 0.1-5MPa, preferably 1-3MPa, and a molar ratio of methane to carbon dioxide of 1: 0.5 to 5, preferably 1: 0.8 to 3, more preferably 1: 1-2, the gas hourly volume space velocity of the feed is 10000-100000 hours based on the total amount of methane and carbon dioxide^-1Preferably 50000-100000 hours^-1。

10. The production process according to claim 7, wherein the Fischer-Tropsch synthesis reaction is carried out in a fluidized bed reactor and/or a fixed bed reactor at a reaction temperature of 200-¹Preferably 10000-^-1。

11. The production process according to claim 7, wherein the Fischer-Tropsch synthesis reaction feed has a hydrogen to carbon monoxide molar ratio of from 0.4 to 3: 1, preferably 0.6 to 2.5: 1, more preferably 0.8 to 2.2: 1, most preferably 1.5-2.2: 1.

12. the production method according to claim 7, wherein the reduction activation is performed under a hydrogen atmosphere, and the reduction temperature is 200-600 ℃, preferably 300-550 ℃, more preferably 350-500 ℃; the reduction time is 1 to 20 hours, preferably 2 to 10 hours, more preferably 5 to 8 hours; the hydrogen pressure is 0 to 2.5MPa, preferably 0.1 to 2 MPa.

13. The production method according to claim 7, further comprising recycling the separated methane to the steam reforming reaction and/or the dry reforming reaction, and recycling the separated carbon dioxide to the dry reforming reaction.