Process and reactor for production of carbon dihydrocarbons by oxidative coupling of methane and their use

Abstract

The invention relates to the technical field of oxidative coupling of methane, and discloses a method and a reactor for preparing C2 hydrocarbon through oxidative coupling of methane and application of the method and the reactor. The method comprises the following steps: a reaction gas containing CH4 and O2 is introduced into a reactor cavity for a methane oxidative coupling reaction, and a catalyst bed layer in the reactor cavity is filled with a mixture of a catalyst and an inert inhibitor; the inert inhibitor is selected from a substance with a function of inhibiting a non-catalytic combustion reaction. According to the method provided by the invention, a manner of mixed filling of the inert inhibitor and the catalyst is utilized, so that the adverse effect of the non-catalytic combustion reaction on the yield of C2 hydrocarbon and the conversion rate of methane in the oxidative coupling reaction of methane is effectively reduced, a relatively good reaction effect is obtained, and the method can stably operate for a relatively long time and has industrial application potential.

Description

Technical Field

[0001] The invention relates to the technical field of methane oxidative coupling, and in particular to a method and a reactor for preparing carbon dihydrocarbons through methane oxidative coupling and applications thereof. Background Art

[0002] The technology of preparing ethylene by oxidative coupling of methane is one of the direct conversion technologies of methane, and it has great potential application value in the field of petrochemicals. Due to the high stability of methane, it brings great challenges to the direct conversion technology of methane. Although the research on catalysts for the oxidative coupling of methane reaction has been carried out for decades, the industrial production of the oxidative coupling of methane reaction has not been achieved so far. The low selectivity of carbon dihydrocarbons is one of the main reasons restricting the industrialization of the oxidative coupling of methane reaction. The insufficient selectivity of carbon dihydrocarbons not only leads to a low yield of the target product, but also because more methane is converted into CO x (i.e. CO2 and CO) resulting in carbon emissions not meeting standards or heavy environmental pressure in production. Summary of the invention

[0003] The purpose of the present invention is to overcome the problems of insufficient selectivity of dihydrocarbons in the methane oxidative coupling reaction in the prior art, and to provide a method and a reactor for preparing dihydrocarbons by methane oxidative coupling and their applications. The method provided by the present invention effectively inhibits the occurrence of non-catalytic deep oxidation reaction by mixing and loading a catalyst and an inert inhibitor in a catalyst bed, thereby greatly improving the dihydrocarbon yield and methane conversion rate of the methane oxidative coupling reaction, and laying a foundation for industrial application.

[0004] In order to achieve the above object, the present invention provides a method for preparing carbon dihydrocarbons by methane oxidative coupling, the method comprising introducing a reaction gas containing CH4 and O2 into a reactor cavity to carry out a methane oxidative coupling reaction, wherein a mixture of a catalyst and an inert inhibitor is filled at a catalyst bed in the reactor cavity;

[0005] The inert inhibitor is selected from substances having the function of inhibiting non-catalytic combustion reactions.

[0006] A second aspect of the present invention provides the reactor defined in the first aspect.

[0007] The third aspect of the present invention provides the use of the method described in the first aspect and / or the reactor described in the second aspect in improving the selectivity of carbon dihydrocarbons in the methane oxidative coupling reaction.

[0008] Through the above technical solution, the present invention can at least achieve the following beneficial effects:

[0009] (1) The method provided by the present invention effectively inhibits non-catalytic combustion reactions by loading a mixture of catalysts and inert inhibitors in a reactor and further filling the voids in the reaction area with inhibitors having smaller particle sizes. It also reduces the adverse effects of free radical elimination reactions on the OCM reaction effect, thereby greatly improving the selectivity of dihydrocarbons and the methane conversion rate.

[0010] (2) The method provided by the present invention has the advantages of simple process, low equipment requirements, and good stability, which is conducive to industrial scale-up application. DETAILED DESCRIPTION

[0011] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0012] In the present invention, unless otherwise specified, "C2 hydrocarbons" and "C2 hydrocarbons (or C2 for short)" have the same meaning and can be used interchangeably, and refer to ethylene and / or ethane.

[0013] The inventors of the present invention cleverly discovered during the research process that in the methane oxidative coupling reaction, by adjusting the filling method of the catalyst and doping the catalyst with a substance that can inhibit non-catalytic combustion reactions and then loading it into the catalyst bed, the selectivity of C2 hydrocarbons can be effectively improved.

[0014] Based on the above findings, the first aspect of the present invention provides a method for preparing carbon dihydrocarbons by methane oxidative coupling, the method comprising introducing a reaction gas containing CH4 and O2 into a reactor cavity to carry out a methane oxidative coupling reaction, wherein a mixture of a catalyst and an inert inhibitor is filled at a catalyst bed in the reactor cavity;

[0015] The inert inhibitor is selected from substances having the function of inhibiting non-catalytic combustion reactions.

[0016] The inventors of the present invention have found through extensive research that when the loading amounts of the catalyst and the inert inhibitor form a specific ratio, a better effect of improving the selectivity of C2 hydrocarbons can be obtained.

[0017] According to a preferred embodiment of the present invention, the weight ratio of the catalyst to the inert inhibitor loaded in the catalyst bed is 2-8:1, preferably 4-6:1.

[0018] Preferably, the particle size ratio of the catalyst to the inert inhibitor is 4-12:1, preferably 4-10:1. For example, it can be 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, or any intermediate ratio within the range of any two of the above ratios.

[0019] It should be noted that the present invention has no particular restrictions on the shape of the inert inhibitor and the catalyst. For example, the catalyst can be a common regular shape such as a sphere, a cylinder, a cube, a sheet, or an irregular shape such as a clover, a star, or an irregular sphere. When the catalyst shape is a regular sphere, the catalyst particle size refers to its diameter, and when the catalyst shape is not a sphere, the catalyst particle size refers to its equivalent diameter. The equivalent diameter refers to a non-spherical particle converted into a sphere by a certain equivalent method, and the diameter of the converted sphere represents the particle size of the particle. Common equivalent methods include equal volume method, equal surface area method, equal projection area method, equal projection perimeter method, etc. The present invention has no particular restrictions on the specific selection of equivalent methods, and can be selected according to actual conditions and needs. In order to facilitate the screening of inert inhibitors and catalysts with suitable particle sizes, in the present invention, a sieve with the above ratio characteristics can be selected to screen the catalyst and the inert inhibitor respectively, so as to quickly obtain an inert inhibitor and catalyst with a suitable particle size ratio.

[0020] In the method provided by the present invention, there is no particular restriction on the specific selection of the inert inhibitor, and any substance having the function of inhibiting the non-catalytic combustion reaction in the methane oxidative coupling reaction can be applied to the present invention. In order to obtain a better reaction effect, according to a preferred embodiment of the present invention, the inert inhibitor is selected from SiO2.

[0021] Any type of SiO2 can be used as an inert inhibitor and is applicable to the present invention. According to some preferred embodiments of the present invention, the inert inhibitor can be quartz sand, and preferably the particle size of the quartz sand is 0.4-1.2 mm, preferably 0.6 mm-1.2 mm. For example, it can be 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1 mm, or any intermediate value in the range of any two of the above values.

[0022] According to a preferred embodiment of the present invention, the inert inhibitor is filled in gaps between catalyst particles and between the catalyst and the inner wall of the reactor chamber.

[0023] According to some preferred embodiments of the present invention, inert materials are also loaded at both ends of the catalyst bed to support the mixture of catalyst and inert inhibitor loaded in the catalyst bed. Inert materials refer to materials that do not participate in the methane oxidative coupling reaction. Any material having the above characteristics can be applied to the present invention, for example, the inert material can be aluminum oxide.

[0024] In the method provided by the present invention, any reactor commonly used in the art for methane oxidative coupling reaction can be used for the reaction. According to some preferred embodiments of the present invention, the material of the reactor cavity is at least one of quartz, alumina and stainless steel.

[0025] Preferably, the reactor cavity is made of quartz.

[0026] The inventors of the present invention also found in their research that when the methane oxidative coupling reaction is carried out under specific conditions, the method provided by the present invention can obtain better reaction results (such as higher C2 selectivity, higher C2 yield, etc.).

[0027] According to a preferred embodiment of the present invention, the volume ratio of CH4 to O2 in the reaction gas is 2-4:1, preferably 2.9-3.2:1. For example, it can be 2.9:1, 3:1, 3.1:1, 3.2:1, or any intermediate ratio within the range of any two of the above ratios.

[0028] According to a preferred embodiment of the present invention, the conditions for the methane oxidative coupling reaction include: a reaction temperature of 780-830°C; a reaction gas hourly space velocity of 8500-12000 mL·g -1 ·h -1 . Unit "mL·g -1 ·h -1 " means: the total amount (mL) of reaction gas (in terms of CH4 and O2) used at a time of 1 h relative to 1 g of the catalyst.

[0029] For example, the temperature of the methane oxidative coupling reaction may be 780° C., 790° C., 800° C., 810° C., 820° C., 830° C., or any intermediate value within the range formed by any two of the above values.

[0030] For example, the reaction gas hourly space velocity based on CH4 and O2 can be 8500 mL·g -1 ·h -1 , 9000mL·g -1 ·h -1 、9500mL·g -1 ·h -1 、10000mL·g-1 ·h -1 、10500mL·g -1 ·h -1 、11000mL·g -1 ·h -1 、11500mL·g -1 ·h -1 、12000mL·g -1 ·h -1 , or it can be any intermediate value in the range formed by any two of the above values.

[0031] Preferably, the reaction time of the methane oxidative coupling reaction is 1-40 h, for example, 1 h, 5 h, 10 h, 15 h, 20 h, 25 h, 28 h, 30 h, 31 h, 32 h, 33 h, 34 h, 35 h, 36 h, 37 h, 38 h, 39 h, 40 h, or any intermediate value in the range formed by any two of the above values.

[0032] The second aspect of the present invention provides a reactor as defined in the method described in the first aspect. It should be understood that the reactor is mainly characterized in that the catalyst in the reactor cavity is loaded in the manner described in the first aspect, and its specific features are as described above and will not be repeated here.

[0033] Since the method provided by the present invention and the reactor (in which the catalyst and the inert inhibitor are loaded in the catalyst bed in a specific manner) can effectively improve the yield of carbon dihydrocarbons in the methane oxidative coupling reaction, the third aspect of the present invention provides the method described in the first aspect and / or the use of the reactor described in the second aspect in improving the selectivity of carbon dihydrocarbons in the methane oxidative coupling reaction.

[0034] The present invention will be described in detail below by way of examples. It should be understood that the following examples are only used to further explain and illustrate the content of the present invention by way of example, and are not intended to limit the present invention.

[0035] The quartz sand used in the following examples was purchased from Sinopharm Chemical Reagent Co., Ltd., and the SiO2 carrier used in the catalyst preparation was purchased from Qingdao Ocean Chemical Plant. The chemicals used in the remaining examples were all commercial products purchased from regular chemical reagent suppliers without special instructions, and the purity was analytical grade.

[0036] In the following examples, unless otherwise specified, all pressures are gauge pressures; all operating temperatures are room temperature (25±5° C.).

[0037] In the following embodiments, unless otherwise specified, the reactor used includes a quartz reactor cavity with a length of 1000 mm, an inner diameter of 25 mm, and a cavity thickness of 2.5 mm. The catalyst and the inert inhibitor are loaded in the catalyst bed, wherein the inert inhibitor is loaded in the gaps between the catalysts and in the gaps between the catalyst and the inner wall of the reactor cavity, and alumina particles are loaded at both ends to form the filler in the catalyst bed.

[0038] The catalysts used in the following examples were prepared as follows:

[0039] According to the selection and content of the active components in Table 1, the precursor of the active component (the precursor of W and Na is sodium tungstate, and the precursor of Mn is manganese nitrate) is weighed and added to 1500g of deionized water, and the carrier is added, stirred for 2 hours, and dried at 120°C for 2.5 hours to obtain solid A, and then calcined at 850°C for 8 hours to obtain the catalyst powder. After the catalyst powder is mixed with sesbania powder and silica sol, it is extruded and cut to obtain solid B, and then calcined at 850°C for 8h to obtain the catalyst. The elemental composition of the catalyst is determined by X-ray fluorescence method, and the specific detection is carried out in accordance with GB / T 30905-2014.

[0040] Table 1

[0041]

[0042] Note: The content of each active component in the catalyst is the relative content calculated based on 100g of carrier.

[0043] Example 1

[0044] A mixture of catalyst and inert inhibitor was loaded into the catalyst bed according to the ratio in Table 2 (the catalyst loading amount was fixed at 10 g), and methane oxidative coupling reaction was carried out under the reaction conditions in Table 2 (the reaction pressure was the pressure brought by the reaction gas itself, which was about 0.01 MPa), and the products of each reaction were collected.

[0045] Table 2

[0046]

[0047]

[0048] Note: In Table 2, the loading ratio of catalyst and inhibitor refers to their weight ratio; the alkoxy ratio refers to the volume ratio of methane and oxygen in the reaction gas; the D1 catalyst bed is not loaded with inert inhibitor.

[0049] Test Example 1

[0050] The reaction products collected in Example 1 were detected by a gas chromatograph (Agilent, 7890A). The products were measured by a dual detection channel three-valve four-column system, in which the FID detector was connected to an alumina column to analyze CH4, C2H6, C2H4, C3H8, C3H6, C4H 10 、C4H8、C n H m The TCD detector is mainly used to detect CO, CO2, N2, O2, and CH4. According to the test results, the methane conversion rate, the selectivity of carbon dihydrocarbons, and the CO x (CO+CO2) selectivity. The results are shown in Table 3. In Table 3, "stable operation time" refers to the continuous operation time when the decrease in the selectivity of the two hydrocarbons in the reaction does not exceed 10%.

[0051] Methane conversion rate = amount of methane consumed by the reaction / initial amount of methane × 100%

[0052] Ethylene selectivity = amount of methane consumed by the generated ethylene / total methane consumption × 100%

[0053] Ethane selectivity = amount of methane consumed to produce ethane / total methane consumption × 100%

[0054] C2 selectivity = ethane selectivity + ethylene selectivity

[0055] CO x Selectivity = Amount of methane consumed by generated CO and CO2 / Total methane consumption × 100%

[0056] C2 hydrocarbon yield = methane conversion × (ethane selectivity + ethylene selectivity)

[0057] Table 3

[0058] serial number Methane conversion rate / % Selectivity of carbon dihydrocarbon / % <![CDATA[CO x Selectivity / %]]> C2Hydrocarbon Yield / % Stable running time / h A1 34.68 62.29 29.94 21.60 34 A2 33.79 61.25 30.97 20.70 35 A3 34.95 60.17 31.47 21.03 31 A4 30.80 60.14 32.88 18.52 30 A5 35.94 59.71 32.61 21.46 23 A6 36.40 53.17 38.42 19.35 18 A7 22.97 67.5 24.10 15.51 31 A8 20.31 69.12 10.33 14.04 33 D1 33.07 59.57 32.89 19.70 31

[0059] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for preparing carbon dihydrocarbons by methane oxidative coupling, the method comprising introducing a reaction gas containing CH4 and O2 into a reactor chamber to carry out a methane oxidative coupling reaction, characterized in that: in, The catalyst bed in the reactor cavity is filled with a mixture of catalyst and inert inhibitor; The inert inhibitor is selected from substances having the function of inhibiting non-catalytic combustion reactions.

2. The method according to claim 1, wherein: The weight ratio of the catalyst to the inert inhibitor loaded in the catalyst bed is 2-8:1, preferably 4-6:1; Preferably, the particle size ratio of the catalyst to the inert inhibitor is 4-12:1, preferably 4-10:

1.

3. The method according to claim 1 or 2, wherein: The inert inhibitor is selected from SiO2.

4. The method according to claim 3, wherein: The inert inhibitor is quartz sand, and preferably the particle size of the quartz sand is 0.4-1.2 mm.

5. The method according to any one of claims 1 to 4, wherein: The inert inhibitor is filled in gaps between catalyst particles and between the catalyst and the inner wall of the reactor chamber.

6. The method according to claim 1, wherein: The material of the reactor cavity is at least one of quartz, alumina and stainless steel.

7. The method according to claim 1, wherein: In the reaction gas, the volume ratio of CH4 to O2 is 2-4:1, preferably 2.9-3.2:

1.

8. The method according to claim 1, wherein: The conditions of the methane oxidative coupling reaction include: a reaction temperature of 780-830°C; a reaction gas hourly space velocity of 8500-12000 mL·g -1 ·h -1 ; Preferably, the reaction time of the methane oxidative coupling reaction is 1-40h.

9. The reactor defined in the process according to any one of claims 1 to 8.

10. The method according to any one of claims 1 to 8, and / or use of the reactor according to claim 9 in improving the selectivity of carbon dihydrocarbons in the oxidative coupling reaction of methane.

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