Method for treating regenerated catalyst by using MTO byproduct oxygen-containing compound

Abstract

The invention discloses a method for treating a regenerated catalyst by using an MTO byproduct oxygen-containing compound, and the method specifically comprises the following steps: (1) placing an incompletely regenerated SAPO-34 molecular sieve catalyst in a fluidized bed reactor, heating to 450-700 DEG C in a nitrogen atmosphere, and carrying out nitrogen purging under a heat preservation condition; and (2) after nitrogen purging, vaporizing the MTO byproduct oxygen-containing compound, introducing the vaporized MTO byproduct oxygen-containing compound into the fluidized bed reactor, carrying out carbon pre-deposition reaction on the vaporized MTO byproduct oxygen-containing compound and the incompletely regenerated SAPO-34 molecular sieve catalyst, stopping feeding after the reaction, and purging and cooling with nitrogen to obtain the carbon pre-deposited incompletely regenerated SAPO-34 molecular sieve catalyst. The method is simple in process, high in operability and high in conversion rate, the byproduct oxygen-containing compound generated in the methanol-to-olefin reaction can be effectively utilized, and the treatment cost of the byproduct oxygen-containing compound and the pollution to the environment are reduced.

Description

Technical Field

[0001] The invention relates to the technical field of methanol to olefins, and in particular to a method for treating a regenerated catalyst by using oxygen-containing compounds produced as byproducts of MTO. Background Art

[0002] Low-carbon olefins mainly include ethylene, propylene and butene, which are three very important basic chemical raw materials. Low-carbon olefins are mainly obtained through naphtha cracking, and my country's dependence on foreign oil is high, and energy security issues have attracted great attention from the industry. In this context, continuously promoting technological progress and high-quality development of coal-to-methanol-to-olefins is of great significance for saving precious oil resources, meeting the growing demand for petrochemical product consumption, and ensuring national energy security. Methanol-to-olefins has now developed into one of the important process technologies for producing olefins in my country.

[0003] The methanol to olefins process refers to a production process that uses methanol as raw material to produce low-carbon olefins, mainly ethylene and propylene. Due to the presence of various side reactions in the methanol to olefins reaction mechanism, these by-products mainly include oxygen-containing compounds such as ketones, aldehydes, ethers and alcohols. These oxygen-containing compounds will gradually accumulate in the water system, and the concentration is highest in the concentrated water in the stripping tower. The existing technology is to return this part of oxygen-containing compounds and unreacted methanol and / or dimethyl ether directly to the reactor for refining, but refining will cause the sewage stripping tower plate and feed distributor to be blocked, which will cause production fluctuations and affect the long-term stable operation of the device.

[0004] SAPO-34 molecular sieve catalyst has excellent activity and olefin selectivity in the methanol to olefin reaction. The prior art (CN109865530A) shows that an incompletely regenerated catalyst with a certain amount of carbon deposition has good catalytic activity in the methanol to olefin reaction, which can greatly improve the selectivity of the initial low-carbon olefins and ensure the highest selectivity of the catalyst for low-carbon olefins, thereby improving the overall selectivity of low-carbon olefins. Therefore, if the by-product oxygen-containing compounds produced in the methanol to olefin process can be used to pre-carbonize the incompletely regenerated SAPO-34 molecular sieve catalyst, the by-product oxygen-containing compounds produced in the methanol to olefin reaction can be effectively utilized, thereby reducing the processing cost of the by-product oxygen-containing compounds and the pollution to the environment. However, there is no relevant report on the use of by-product oxygen-containing compounds produced in the methanol to olefin reaction to pre-carbonize the incompletely regenerated SAPO-34 molecular sieve catalyst. Summary of the invention

[0005] The purpose of the present invention is to provide a method for treating the by-product oxygen-containing compounds of MTO to regenerate the catalyst, which has the advantages of simple process, strong operability, high conversion rate, and can effectively utilize the by-product oxygen-containing compounds produced in the methanol to olefins reaction, thereby reducing the treatment cost of the by-product oxygen-containing compounds and the pollution to the environment.

[0006] In order to achieve the above object, the present invention adopts the following technical scheme: A method of treating a regenerated catalyst using oxygen-containing compounds produced as a byproduct of MTO, the specific method is: (1) An incompletely regenerated SAPO-34 molecular sieve catalyst is placed in a fluidized bed reactor, heated to 450-700°C under a nitrogen atmosphere, and then purged with nitrogen under insulation conditions.

[0007] (2) After nitrogen purging, the MTO by-product oxygen-containing compounds are vaporized and introduced into a fluidized bed reactor to react with the incompletely regenerated SAPO-34 molecular sieve catalyst for pre-carbon deposition. After the reaction, the feed is stopped and the temperature is cooled by nitrogen purging to obtain the pre-carbon deposited incompletely regenerated SAPO-34 molecular sieve catalyst. The MTO by-product oxygen-containing compounds are aqueous solutions of oxygen-containing compounds such as ketones, aldehydes, ethers and alcohols in the MTO process, which can be derived from different separation sections (such as quenching towers, stripping towers, etc.). The MTO by-product oxygen-containing compounds are products well known in the art, which mainly include alcohols, ketones, acids, aldehydes and ethers. In the present invention, the MTO by-product oxygen-containing compounds are vaporized and introduced into a fluidized bed reactor to react with the incompletely regenerated SAPO-34 molecular sieve catalyst for pre-carbon deposition under specific conditions, which not only increases the carbon content of the incompletely regenerated SAPO-34 molecular sieve catalyst, but also generates less CO and CO2, while reducing the treatment cost of the MTO by-product oxygen-containing compounds and the pollution to the environment.

[0008] Preferably, in step (1), the carbon content of the incompletely regenerated SAPO-34 molecular sieve catalyst is 0.5-3%. If the carbon content of the incompletely regenerated SAPO-34 molecular sieve catalyst is too high or too low, it will affect the carbon deposition amount and thus the catalytic effect. If the carbon content is too high, it will also cause more CO and CO2 to be generated during the pre-carbon deposition process, which will increase the subsequent removal cost of CO and CO2. Therefore, in the present invention, the carbon content of the incompletely regenerated SAPO-34 molecular sieve catalyst is limited to 0.5-3%.

[0009] Preferably, in step (1), the temperature is raised to 480-650° C. in a nitrogen atmosphere and then nitrogen purging is performed under insulation conditions.

[0010] Preferably, in step (2), the mass percentage of oxygen-containing compounds in the MTO by-product oxygen-containing compounds is controlled to be 10-30%, and the rest is water.

[0011] Preferably, in step (2), the carbon content of the pre-carbonized incompletely regenerated SAPO-34 molecular sieve catalyst is controlled at 1-5%. In the pre-carbonized incompletely regenerated SAPO-34 molecular sieve catalyst, a carbon content that is too high or too low will affect the catalytic performance of the catalyst.

[0012] Therefore, the present invention has the following beneficial effects: after the specific MTO by-product oxygen-containing compounds are vaporized, they are introduced into a fluidized bed reactor, and a pre-carbon deposition reaction is carried out with an incompletely regenerated SAPO-34 molecular sieve catalyst under specific conditions, thereby effectively utilizing the by-product oxygen-containing compounds produced in the methanol to olefins reaction, reducing the processing cost of the by-product oxygen-containing compounds and the pollution to the environment. The present invention is further described below through specific implementation modes.

[0013] In the following examples and comparative examples, the carbon content of the pre-carbonized incompletely regenerated SAPO-34 molecular sieve catalyst is calculated by the following formula: Carbon content ω = (m 250℃ -m 900℃ ) / m 250℃ ×100%; where ω is the carbon content of the catalyst in mass percentage, m 250℃ is the mass of the catalyst after the temperature rises from room temperature to 250°C in air atmosphere, m 900℃ It is the mass of the catalyst after heating to 900°C in air atmosphere.

[0014] Example 1 (1) An incompletely regenerated SAPO-34 molecular sieve catalyst with a carbon content of 2.89% was placed in the constant temperature zone in the middle of a fluidized bed reactor, heated to 500°C under a nitrogen atmosphere, and then purged with nitrogen for 1 hour under insulation conditions.

[0015] (2) After nitrogen purging, the MTO by-product oxygenated compounds with a mass percentage of 20% oxygenated compounds (from the MTO by-product concentrated water of Tianjin Bohai Chemical Development Co., Ltd.: the oxygenated compounds are ketones (mainly acetone) 65.6%, alcohols 31.8%, aldehydes 1.4%, and the remaining 1.2%) were vaporized and introduced into a fluidized bed reactor for a pre-carbon deposition reaction with an incompletely regenerated SAPO-34 molecular sieve catalyst. The reaction temperature was 550°C and the mass space velocity of the MTO by-product oxygenated compounds was 2.0 h -1 , reaction time 2min, after the reaction, stop feeding and cool down with nitrogen purge, thus obtaining pre-carbon deposited incompletely regenerated SAPO-34 molecular sieve catalyst.

[0016] The carbon content of the pre-carbonized incompletely regenerated SAPO-34 molecular sieve catalyst was measured to be 4.32wt%. The composition of the gas product was analyzed online by gas chromatography, and the conversion rate of oxygen-containing compounds was 99.3wt%, the CO selectivity was 7.65wt%, and the CO2 selectivity was 9.78wt%.

[0017] Comparative Example 1 Comparative Example 1 is different from Example 1 in that the mass percentage of oxygen-containing compounds in the MTO byproduct oxygen-containing compounds is 5%, and the rest is the same as Example 1. The carbon content of the pre-carbonized incompletely regenerated SAPO-34 molecular sieve catalyst is measured to be 2.93wt%. The gas product composition is analyzed online by gas chromatography, and the conversion rate of oxygen-containing compounds is 9.2wt%, the CO selectivity is 10.52wt%, and the CO2 selectivity is 10.61wt%.

[0018] Comparative Example 2 Comparative Example 2 is different from Example 1 in that the mass percentage of oxygen-containing compounds in the MTO byproduct oxygen-containing compounds is 35%, and the rest is the same as Example 1. The carbon content of the pre-carbonized incompletely regenerated SAPO-34 molecular sieve catalyst is measured to be 4.58wt%. The gas product composition is analyzed online by gas chromatography, and the oxygen-containing compound conversion rate is 99.2wt%, the CO selectivity is 15.32wt%, and the CO2 selectivity is 17.64wt%.

[0019] Comparative Example 3 Comparative Example 3 is different from Example 1 in that the temperature is raised to 400°C under a nitrogen atmosphere, and the rest is the same as Example 1. The carbon content of the pre-carbonized incompletely regenerated SAPO-34 molecular sieve catalyst is measured to be 6.72wt%. The gas product composition is analyzed online by gas chromatography, and the conversion rate of oxygen-containing compounds is 79.3wt%, the CO selectivity is 16.62wt%, and the CO2 selectivity is 13.94 wt%.

[0020] Comparative Example 4 Comparative Example 4 is different from Example 1 in that the temperature is raised to 750°C under a nitrogen atmosphere, and the rest is the same as Example 1. The carbon content of the pre-carbonized incompletely regenerated SAPO-34 molecular sieve catalyst is measured to be 4.87wt%. The composition of the gas product is analyzed online by gas chromatography, and the conversion rate of oxygen-containing compounds is 99.5wt%, the CO selectivity is 18.88wt%, and the CO2 selectivity is 16.71wt%.

[0021] Comparative Example 5 Compared with Example 1, Comparative Example 5 has the following differences: the carbon content of the incompletely regenerated SAPO-34 molecular sieve catalyst is 3.5%, and the rest is the same as Example 1. The carbon content of the SAPO-34 molecular sieve catalyst after pre-carbon deposition is measured to be 4.26wt%. The composition of the gas product is analyzed online by gas chromatography, and the conversion rate of oxygen-containing compounds is 80.5wt%, the CO selectivity is 16.55wt%, and the CO2 selectivity is 18.92wt%.

[0022] Example 2 (1) An incompletely regenerated SAPO-34 molecular sieve catalyst with a carbon content of 0.5% was placed in the constant temperature zone in the middle of a fluidized bed reactor, heated to 620°C under a nitrogen atmosphere, and then purged with nitrogen for 1 hour under insulation conditions.

[0023] (2) After nitrogen purging, the MTO by-product oxygenated compounds with a mass percentage of oxygenated compounds of 28% (from the MTO by-product concentrated water of Tianjin Bohai Chemical Development Co., Ltd.: the oxygenated compounds are ketones (mainly acetone) 65.6%, alcohols 31.8%, aldehydes 1.4%, and the remaining 1.2%) were vaporized and introduced into the fluidized bed reactor for pre-carbon deposition reaction with the incompletely regenerated SAPO-34 molecular sieve catalyst. The mass space velocity of the MTO by-product oxygenated compounds was 2.0h -1 , reaction time 2min, after the reaction, stop feeding and cool down with nitrogen purge, thus obtaining pre-carbon deposited incompletely regenerated SAPO-34 molecular sieve catalyst.

[0024] The carbon content of the pre-carbonized incompletely regenerated SAPO-34 molecular sieve catalyst was measured to be 2.98wt%. The composition of the gas product was analyzed online by gas chromatography, and the conversion rate of oxygen-containing compounds was 99.5wt%, the CO selectivity was 9.38wt%, and the CO2 selectivity was 7.71wt%.

[0025] Example 3 (1) An incompletely regenerated SAPO-34 molecular sieve catalyst with a carbon content of 2.91% was placed in the constant temperature zone in the middle of a fluidized bed reactor, heated to 550°C under a nitrogen atmosphere, and then purged with nitrogen for 1 hour under insulation conditions.

[0026] (2) After nitrogen purging, the MTO by-product oxygenated compounds with a mass percentage of oxygenated compounds of 12% (from the MTO by-product concentrated water of Tianjin Bohai Chemical Development Co., Ltd.: the oxygenated compounds are ketones (mainly acetone) 65.6%, alcohols 31.8%, aldehydes 1.4%, and the remaining others 1.2%) were vaporized and introduced into the fluidized bed reactor for pre-carbon deposition reaction with the incompletely regenerated SAPO-34 molecular sieve catalyst. The mass space velocity of the MTO by-product oxygenated compounds was 2.0h -1 , reaction time 2min, after the reaction, stop feeding and cool down with nitrogen purge, thus obtaining pre-carbon deposited incompletely regenerated SAPO-34 molecular sieve catalyst.

[0027] The carbon content of the pre-carbonized incompletely regenerated SAPO-34 molecular sieve catalyst was measured to be 3.84wt%. The composition of the gas product was analyzed online by gas chromatography, and the conversion rate of oxygen-containing compounds was 99.2wt%, the CO selectivity was 9.19wt%, and the CO2 selectivity was 8.85wt%.

[0028] It can be seen from the above embodiments and comparative examples that the oxygen-containing compound conversion rates of Embodiment 1, Embodiment 2 and Embodiment 3 are all above 99.2%, and the CO selectivity and CO2 selectivity are both low, resulting in less CO and CO2, which is beneficial to reducing the subsequent CO and CO2 removal costs. However, Comparative Examples 1 to 5 cannot have both a high oxygen-containing compound conversion rate and a low CO and CO2 selectivity, resulting in a higher treatment cost.

[0029] The above-described embodiment is only a preferred solution of the present invention and does not limit the present invention in any form. There are other variations and modifications without exceeding the technical solution described in the claims.

Claims

1. A method for treating a regenerated catalyst using oxygen-containing compounds produced as a by-product of MTO, characterized in that: The specific method is: (1) placing the partially regenerated SAPO-34 molecular sieve catalyst in the constant temperature zone in the middle of the fluidized bed reactor, heating it to 500-700°C under a nitrogen atmosphere, and then purging it with nitrogen under insulation conditions; (2) After nitrogen purging, the oxygen-containing byproduct of MTO is vaporized and then introduced into a fluidized bed reactor for a pre-carbon deposition reaction with an incompletely regenerated SAPO-34 molecular sieve catalyst. After the reaction, the feed is stopped and the temperature is cooled by nitrogen purging to obtain a pre-carbon deposited incompletely regenerated SAPO-34 molecular sieve catalyst.

2. A method for treating a regenerated catalyst using oxygen-containing compounds produced as a byproduct of MTO according to claim 1, characterized in that: In step (1), the carbon content of the incompletely regenerated SAPO-34 molecular sieve catalyst is 0.5-3%.

3. The method of treating a regenerated catalyst using oxygen-containing compounds produced as a byproduct of MTO according to claim 1, characterized in that: In step (1), the temperature is raised to 480-650° C. in a nitrogen atmosphere and then nitrogen purging is performed under insulation conditions.

4. The method of claim 1, wherein the method comprises: In step (2), the mass percentage of oxygen-containing compounds in the MTO by-product oxygen-containing compounds is controlled to be 10-30%, and the rest is water.

5. A method for treating a regenerated catalyst using oxygen-containing compounds produced as a byproduct of MTO according to claim 1 or 4, characterized in that: In step (2), the carbon content in the pre-carbon-deposited incompletely regenerated SAPO-34 molecular sieve catalyst is controlled at 1-5%.