CN113797854A

CN113797854A - Catalyst filling method for methane oxidative coupling reaction and method for preparing ethylene through methane oxidative coupling

Info

Publication number: CN113797854A
Application number: CN202010548690.XA
Authority: CN
Inventors: 武洁花; 赵清锐; 邵芸; 薛伟; 冯静; 张明森; 刘东兵
Original assignee: Sinopec Beijing Research Institute of Chemical Industry; China Petroleum and Chemical Corp
Current assignee: Sinopec Beijing Research Institute of Chemical Industry; China Petroleum and Chemical Corp
Priority date: 2020-06-16
Filing date: 2020-06-16
Publication date: 2021-12-17

Abstract

The invention relates to the technical field of methane oxidative coupling reaction, and discloses a catalyst filling method for methane oxidative coupling reaction and a method for preparing ethylene by methane oxidative coupling, which comprises the following steps: sequentially filling a catalyst I and a catalyst II in a reaction zone of the methane oxidative coupling reaction according to the flow direction of reaction materials; wherein the activation temperature of the catalyst I is not higher than 600 ℃, and the activation temperature of the catalyst II is not lower than 700 ℃. The method can start the reaction at a lower reaction initial temperature, and further can realize the continuous methane oxidation coupling reaction at a high temperature with low energy consumption by utilizing the heat release characteristic of the reaction, thereby reducing the energy consumption, effectively saving the energy and being beneficial to industrial popularization.

Description

Catalyst filling method for methane oxidative coupling reaction and method for preparing ethylene through methane oxidative coupling

Technical Field

The invention relates to the technical field of methane oxidative coupling reaction, in particular to a catalyst filling method for methane oxidative coupling reaction and a method for preparing ethylene by methane oxidative coupling.

Background

Ethylene is the most important basic organic chemical raw material, and its production has long been dependent on petroleum cracking routes, and the problems of environmental pollution and the like caused by the ethylene are becoming serious. In recent years, the price of crude oil is continuously rising to cause the price of ethylene cracking raw materials to rise, and the phenomenon of short supply and short demand of the ethylene cracking raw materials is also very prominent.

The most effective method for producing ethylene that is theoretically possible is oxidative coupling of methane, which is the most abundant component in natural gas and has the advantage of being inexpensive compared to other feedstocks.

At present, there are direct and indirect methods for the production of ethylene starting from natural gas. The direct method comprises oxidative coupling, chlorination coupling and direct dehydrogenation; the indirect method is to convert natural gas into synthesis gas and then prepare olefin from the synthesis gas, and comprises the methods of improving an F-T method, preparing olefin by methanol cracking and the like.

From natural gas, if a three-step method (POM/GTM/MTO) of preparing synthesis gas/synthesis gas and methanol to olefin by partial oxidation is adopted to prepare ethylene, not only are the reaction process steps numerous, but also oxygen atoms are inserted and then taken out, non-atomic economic reaction is realized, and the multi-step method is not an economical and reasonable choice from the aspects of technology, resource utilization, environmental protection and the like. Since the oxidative coupling of natural gas, i.e., methane, to produce ethylene (OCM) is the most direct method, OCM has been the focus of research by scientists in various countries in the world for decades.

The oxidative coupling of methane is an exothermic reaction at temperatures of 750 ℃ and 850 ℃ and even higher, and conventional catalysts are all capable of reacting at high temperatures.

For example, in OCM Catalyst system research, supported catalysts with silica as the carrier and sodium tungstate and manganese as the active components are one of the best performing systems (Li, S. (2003) 'Reaction Chemistry of W-Mn/SiO2Catalyst for the Oxidative Coupling of methane.' Journal of Natural Gas Chemistry (01): 1-9.).

Disclosure of Invention

The invention aims to overcome the defects of high energy consumption and low selectivity of hydrocarbon of carbon two or more in the methane oxidative coupling reaction in the prior art on the premise of keeping higher methane conversion rate.

In order to achieve the above object, a first aspect of the present invention provides a catalyst loading method for oxidative coupling of methane reaction, the method comprising: sequentially filling a catalyst I and a catalyst II in a reaction zone of the methane oxidative coupling reaction according to the flow direction of reaction materials; wherein the activation temperature of the catalyst I is not higher than 600 ℃, and the activation temperature of the catalyst II is not lower than 700 ℃.

The second aspect of the present invention provides a method for preparing ethylene by oxidative coupling of methane, which comprises: introducing methane and oxygen into a reaction zone containing catalyst I and catalyst II to carry out an oxidative coupling reaction of methane, wherein the catalyst in the reaction zone is packed by the method described in the first aspect.

The inventor of the invention provides a novel catalyst filling method for methane oxidative coupling reaction based on the current situation that the reaction temperature required by methane oxidative coupling reaction in the prior art is high, and a large amount of heat is required to reach the reaction temperature, so that higher operation cost is brought.

The method can start the reaction at a lower reaction initial temperature, and further can utilize the exothermic characteristic of the reaction to realize the continuous methane oxidation coupling reaction at a high temperature with low energy consumption, thereby reducing the energy consumption, effectively saving the energy and being beneficial to industrial popularization.

The method provided by the invention also has the advantage of improving the reaction efficiency.

Detailed Description

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.

The activation temperature indicates the temperature at which the catalyst starts to exert catalytic activity.

As previously mentioned, a first aspect of the present invention provides a catalyst loading method for oxidative coupling of methane, the method comprising: sequentially filling a catalyst I and a catalyst II in a reaction zone of the methane oxidative coupling reaction according to the flow direction of reaction materials; wherein the activation temperature of the catalyst I is not higher than 600 ℃, and the activation temperature of the catalyst II is not lower than 700 ℃.

The method can start reaction (namely low-temperature start) at the temperature of not higher than 600 ℃, and then the temperature in the reactor is raised to over 700 ℃ by utilizing the heat release of the reaction to reach the working temperature of the catalyst II (high-temperature catalyst), thereby effectively reducing the energy consumption of a reaction system and saving energy.

The low-temperature activation-high-temperature reaction catalytic reaction process is characterized in that after a reaction material enters a reactor, the reaction material is firstly contacted with a catalyst which can be activated at a relatively low temperature, the activation temperature of the low-temperature catalyst on the reaction is below 600 ℃, the reaction is carried out at a low temperature, the reaction is a strong exothermic reaction, the temperature of the reaction material is increased to above 700 ℃ or even above 750 ℃ and preferably above 750 ℃ and 900 ℃ to reach the working temperature of the high-temperature catalyst through the self heat release of the reaction and along with the flowing of the material when the reaction material is contacted with the high-temperature catalyst, and the reaction is completed at the reaction temperature of the high-temperature catalyst, so that the high-efficiency utilization of heat can be ensured, and the effect of reducing energy consumption is further realized.

Preferably, the activation temperature of the catalyst I is 400-600 ℃.

Preferably, the activation temperature of the catalyst II is 700-900 ℃.

Preferably, the catalyst I is all low-temperature activated catalysts which can be used for catalyzing the oxidative coupling reaction of methane and can start the reaction at the temperature of not higher than 600 ℃.

According to a preferred embodiment, the catalyst I contains at least one active element chosen from the lanthanides.

Preferably, the content of the active element is 85 to 99.9% by weight, calculated as element, based on the total weight of the catalyst I.

More preferably, the catalyst I contains lanthanum oxide. The lanthanum oxide of the present invention may be a nanowire or nanoparticle.

Particularly preferably, in order to realize higher conversion rate and product selectivity of methane, according to another preferred case, the catalyst I is lanthanum oxide doped with elements, and the hetero elements are at least one selected from calcium, magnesium, strontium, barium, samarium and lithium; in the catalyst I, the content of the hetero element calculated by the element is 0.1-15 wt%.

Preferably, the catalyst II is all high-temperature activated catalysts which can be used for catalyzing the oxidative coupling reaction of methane and can effectively catalyze the oxidative coupling reaction of methane at the temperature higher than 700 ℃.

According to another preferred embodiment, the catalyst II comprises a carrier and an active component supported on the carrier, wherein the active component comprises a manganese element, a tungsten element and an alkali metal element.

Preferably, the content of the manganese element is 0.2 to 10 weight percent, the content of the tungsten element is 0.5 to 20 weight percent, and the content of the alkali metal element is 0.1 to 5 weight percent based on the total weight of the catalyst II.

More preferably, in the catalyst II, the active component includes manganese element, tungsten element, and sodium element; the carrier is selected from at least one of silica, alumina, cristobalite, and cordierite.

Illustratively, the catalyst II contains manganese oxide, sodium tungstate and alkali metal compounds.

Preferably, the loading weight ratio of the catalyst I to the catalyst II is 1: 0.01-100; more preferably 1: 0.02-50; more preferably 1: 0.1-10.

As mentioned above, the second aspect of the present invention provides a method for preparing ethylene by oxidative coupling of methane, which comprises: introducing methane and oxygen into a reaction zone containing catalyst I and catalyst II to carry out an oxidative coupling reaction of methane, wherein the catalyst in the reaction zone is packed by the method described in the first aspect.

Preferably, the volume space velocity of the methane is 1000-50000h^-1(ii) a More preferably 5000-^-1。

Preferably, the molar ratio of the used methane to the used oxygen is 2-10: 1, more preferably 3 to 8: 1.

particularly preferably, the reaction temperature in the reaction unit filled with the catalyst I is 450-750 ℃.

Particularly preferably, the reaction temperature in the reaction unit filled with the catalyst II is 750-900 ℃, and more preferably 750-850 ℃.

The present invention will be described in detail below by way of examples. In the following examples, various raw materials used are commercially available ones unless otherwise specified.

The agilent gas chromatograph used below was model 7890A.

The following were used:

methane conversion ═ molar amount of methane consumed by the reaction/initial molar amount of methane × 100%

Ethylene selectivity is the molar amount of methane consumed by ethylene produced/total molar amount consumed of methane x 100%

Ethane selectivity is the molar amount of methane consumed by ethane produced/total molar amount consumed by methane x 100%

Propylene selectivity is the molar amount of methane consumed by propylene produced/total molar amount consumed by methane x 100%

Propane selectivity is the molar amount of methane consumed by the propane formed/total molar amount consumed of methane x 100%

Selectivity of hydrocarbons of two or more of ethylene, ethane, propylene and propane

The lanthanum oxide catalyst 1 used below is a catalyst self-made by a hydrothermal method in a laboratory, and the specific preparation method is as follows:

dissolving 9g of lanthanum nitrate hexahydrate in 500g of a mixed solution of deionized water and ethanol (the weight ratio of water to ethanol is 1:0.1), stirring and dissolving, adding 10 wt% of sodium hydroxide solution to adjust the pH value of the solution to 10.5, continuously stirring for 30min, transferring the solution to a stainless steel hot kettle lined with polytetrafluoroethylene, keeping the temperature at 160 ℃ for 12h, separating the solution at 8000rpm by using a centrifugal machine for 30min, washing for five times, washing with ethanol once to obtain a solid product, placing the solid product in an oven with the temperature of 80 ℃, drying for 12h, then placing the dried product in a muffle furnace, heating to 500 ℃ at the temperature of 2 ℃/min, and roasting for 2h to obtain the lanthanum oxide catalyst 1.

The lanthanum oxide catalyst 2 used below is a catalyst self-made by a hydrothermal method in a laboratory, and the specific preparation method is as follows:

the preparation method of lanthanum oxide is the same as that of lanthanum oxide catalyst 1, except that 0.055g of magnesium nitrate is weighed and added into 15g of deionized water, after stirring and dissolving, 1g of lanthanum oxide catalyst 1 is added into magnesium nitrate aqueous solution, stirring is carried out, the temperature is raised to 80 ℃, drying is carried out until the moisture is completely volatilized, the mixture is transferred to an oven, the temperature is 120 ℃ for 12 hours, then the mixture is placed in a muffle furnace, the temperature is raised to 600 ℃ at the rate of 1 ℃/min, the temperature is raised for 3 hours, and the temperature is lowered to room temperature, so that lanthanum oxide catalyst 2 is obtained.

The lanthanum oxide catalyst 3 used below is a catalyst self-made by a hydrothermal method in a laboratory, and the specific preparation method is as follows:

the preparation method of lanthanum oxide is the same as that of lanthanum oxide catalyst 1, except that 0.16g of barium nitrate is weighed and added into 20g of deionized water, after stirring and dissolving, 1g of lanthanum oxide catalyst 1 is added into barium nitrate aqueous solution, stirring is carried out, the temperature is raised to 80 ℃, drying is carried out until the water is completely volatilized, the mixture is transferred to an oven, the temperature is 140 ℃ for 10 hours, then the mixture is placed in a muffle furnace, the temperature is raised to 550 ℃ at the rate of 1 ℃/min for 3 hours, and the temperature is lowered to room temperature (25 ℃), so that lanthanum oxide catalyst 3 is obtained.

The lanthanum oxide catalyst 4 used below is a catalyst prepared by a roasting method in a laboratory, and the raw material lanthanum nitrate hexahydrate is purchased from Tianjin department chemical reagent GmbH, and the specific preparation method is as follows:

and (3) placing lanthanum nitrate hexahydrate in a muffle furnace, heating to 600 ℃ at the heating rate of 1 ℃/min under the atmosphere of carbon dioxide, keeping the temperature for 2 hours, and cooling to room temperature to obtain a lanthanum oxide catalyst 4.

Na used hereinafter₂WO₄the-Mn/carrier catalyst is prepared by a laboratory impregnation method, and the specific preparation method refers to the method reported in the journal of catalysis academic journal of 1998, volume 11, 19, 6, pages 526-529. And the different sodium tungstate content and manganese content are realized by adjusting the amount of the added precursor in the preparation process.

Example 1

0.2g of lanthanum oxide catalyst 1 and 0.4g of 5% by weight Na₂WO₄2% by weight Mn/SiO₂The catalysts are sequentially filled in a reactor, and methane and oxygen are introduced, wherein the flow rate of the methane is 99mL/min, and the flow rate of the oxygen is 33 mL/min; heating the reaction mass to 550 ℃, firstly contacting the lanthanum oxide catalyst 1, starting the reaction, raising the temperature to 750 ℃ after 60s, and then filling the heated mass with Na₂WO₄-Mn/SiO₂Bed of catalyst, material entering into filling with Na₂WO₄-Mn/SiO₂After the catalyst bed had been run for 10min, CH was determined by Agilent 7890A gas chromatograph₄Conversion and selectivity to hydrocarbons of two or more.

As a result: the methane conversion was 32.3% and the selectivity to hydrocarbons at and above 58.6%.

Example 2

0.1g of magnesium oxide-supported lanthanum oxide catalyst 2 (magnesium oxide-supported amount of 0.5% by weight) and 0.6g of 3.1% by weight Na₂WO₄2.5% by weight Mn/SiO₂The catalysts are sequentially filled in a reactor, and methane and oxygen are introduced, wherein the flow rate of methane is 150mL/min, and the flow rate of oxygen is 30 mL/min; heating the reaction mass to 500 ℃, firstly contacting the lanthanum oxide catalyst 2, starting the reaction, heating to 800 ℃ after 10s, and then filling Na into the heated mass₂WO₄-Mn/SiO₂Bed of catalyst, material entering into filling with Na₂WO₄-Mn/SiO₂After the catalyst bed had been run for 10min, CH was determined by Agilent 7890A gas chromatograph₄Conversion and selectivity to hydrocarbons of two or more.

As a result: the methane conversion was 28.3%, and the selectivity for hydrocarbons at and above carbon was 59%.

Example 3

0.2g of barium oxide-supported lanthanum oxide catalyst 3 (barium oxide supporting amount: 8% by weight) and 0.1g of 5% by weight Na were added₂WO₄-3 wt% of Mn/cristobalite catalyst is sequentially filled in a reactor, and methane and oxygen are introduced, wherein the flow rate of methane is 40mL/min, and the flow rate of oxygen is 10 mL/min; heating the reaction mass to 450 ℃, firstly contacting with the lanthanum oxide catalyst 3, starting the reaction, raising the temperature to 800 ℃ after 60s, and then filling Na into the heated mass₂WO₄Bed of-Mn/cristobalite catalyst, material entering the bed being packed with Na₂WO₄After 10min of the bed of-Mn/cristobalite catalyst, CH was determined by Agilent gas chromatograph₄Conversion and selectivity to hydrocarbons of two or more.

As a result: the methane conversion was 32.3% and the selectivity to hydrocarbons at and above 56.8%.

Example 4

This example was carried out in a similar manner to example 1, except that the catalyst I used in this example was different in kind and the same amount as that of the catalyst I used in example 1.

Specifically, catalyst I in this example is: lanthanum oxide catalyst 4.

As a result: the methane conversion was 37.4%, and the selectivity for hydrocarbons at and above carbon was 53%.

Example 5

This example was carried out in a similar manner to example 1, except that the amount of catalyst I and the amount of catalyst II used in this example were different from those in example 1, but the kind of catalyst I and the kind of catalyst II in this example were the same as those in example 1, respectively.

Specifically, in this example, catalyst I was used in an amount of 0.05g and catalyst II was used in an amount of 0.55 g.

As a result: the methane conversion was 39% and the selectivity for hydrocarbons at and above carbon was 44%.

Comparative example 1

The reaction procedure was similar to example 1, except that: the catalyst loading varied.

Specifically, 0.6g of 5 wt% Na₂WO₄2% by weight Mn/SiO₂The catalyst (same as in example 1) was filled in the reactor, and methane and oxygen were introduced at a methane flow rate of 99mL/min and an oxygen flow rate of 33 mL/min; heating the reaction material to 550 deg.C, reacting for 60s, heating the reaction material to 750 deg.C, reacting, measuring CH with Agilent gas chromatograph for 10min, and measuring CH content₄Conversion and selectivity to hydrocarbons of two or more.

As a result: the methane conversion was 32% and the selectivity for hydrocarbons at and above carbon was 43%.

From the above results, it can be seen that the comparative example was not loaded with a low temperature activated catalyst and the reaction mass required heating to 750 ℃ to react.

Therefore, the reaction materials can start to react when heated to 600 ℃ of 400-minus-one under the action of the low-temperature activated catalyst, and the reaction is exothermic, so that the temperature of the reaction materials in the reactor is raised to more than 750 ℃ under the action of the low-temperature activated catalyst, and the reaction temperature of the high-temperature catalyst can be reached without external heating, so that the reaction can be smoothly carried out.

The invention realizes the effective utilization of energy and solves the defect that the reaction can be started only by heating the materials to over 700 ℃ in the prior reaction.

The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including combinations of various technical features in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.

Claims

1. A method for loading a catalyst for use in oxidative coupling of methane, the method comprising: sequentially filling a catalyst I and a catalyst II in a reaction zone of the methane oxidative coupling reaction according to the flow direction of reaction materials; wherein the activation temperature of the catalyst I is not higher than 600 ℃, and the activation temperature of the catalyst II is not lower than 700 ℃.

2. The process as claimed in claim 1, wherein the activation temperature of the catalyst I is 400-600 ℃.

3. The process as claimed in claim 1 or 2, wherein the activation temperature of the catalyst II is 700-900 ℃.

4. The process according to any one of claims 1 to 3, wherein the catalyst I contains at least one active element selected from lanthanides;

5. The method of claim 4, wherein the catalyst I contains lanthanum oxide;

preferably, the catalyst I is lanthanum oxide doped with elements, and the hetero elements are at least one of calcium, magnesium, strontium, barium, samarium and lithium; in the catalyst I, the content of the hetero element calculated by the element is 0.1-15 wt%.

6. The method according to any one of claims 1 to 5, wherein the catalyst II comprises a carrier and active components loaded on the carrier, and the active components comprise manganese element, tungsten element and alkali metal element;

7. The process of claim 6, wherein in the catalyst II, the active components comprise manganese, tungsten and sodium; the carrier is selected from at least one of silica, alumina, cristobalite, and cordierite.

8. The process of any of claims 1-7, wherein the loading weight ratio of catalyst I and catalyst II is 1: 0.01-100; preferably 1: 0.02-50; more preferably 1: 0.1-10.

9. A method for preparing ethylene by oxidative coupling of methane is characterized by comprising the following steps: introducing methane and oxygen into a reaction zone containing a catalyst I and a catalyst II to perform an oxidative coupling reaction of methane, wherein the catalyst in the reaction zone is packed by the method of any one of claims 1 to 8.

10. The method as claimed in claim 9, wherein the volume space velocity of methane is 1000-^-1(ii) a Preferably 5000-^-1。

11. The process according to claim 9 or 10, wherein the methane and oxygen are used in a molar ratio of 2-10: 1, preferably 3 to 8: 1.

12. the process as claimed in any of claims 9 to 11, wherein the reaction temperature in the reaction unit charged with the catalyst I is 450-;

preferably, the reaction temperature in the reaction unit filled with the catalyst II is 750-900 ℃.