CN113509957A

CN113509957A - Method for improving cycle stability and service life of catalyst for methanol-to-olefin reaction

Info

Publication number: CN113509957A
Application number: CN202110783971.8A
Authority: CN
Inventors: 戴卫理; 王畅; 杨柳; 李兰冬; 武光军; 关乃佳
Original assignee: Nankai University
Current assignee: Nankai University
Priority date: 2021-07-12
Filing date: 2021-07-12
Publication date: 2021-10-19
Anticipated expiration: 2041-07-12
Also published as: CN113509957B

Abstract

The invention discloses a method for improving the cycle stability and the service life of a catalyst for a reaction of preparing olefin from methanol. Putting a molecular sieve catalyst sample in a quartz tube of a fixed bed reactor, pretreating at 450 ℃, then reducing the temperature to 400 ℃, introducing ethylene or butylene gas, and purging ethylene/butylene adsorbed on the surface of the sample by inert gas to obtain the pre-deposited carbon catalyst. And (3) carrying out methanol-to-olefin reaction on the pre-deposited carbon catalyst, feeding methanol and water together in the reaction process or introducing steam to treat the catalyst before the reaction, introducing a product into a gas chromatography for real-time monitoring, carrying out regeneration treatment after the catalyst is deactivated, carrying out the methanol-to-olefin reaction again, and introducing ethylene/butylene for pre-deposition before each circulation. The method for improving the circulation stability and the service life of the methanol-to-olefin reaction catalyst has the characteristics of easiness in operation, wide application range and the like, and is suitable for large-scale industrial methanol-to-olefin production.

Description

Method for improving cycle stability and service life of catalyst for methanol-to-olefin reaction

Technical Field

The invention belongs to the field of molecular sieve catalysis and organic synthesis, and particularly relates to a method for improving the cycle stability and the service life of a catalyst for a reaction for preparing olefin from methanol.

Background

The demand for lower olefins (ethylene, propylene) as very important chemical raw materials is increasing. At present, the route of preparing olefin (MTO) from coal-based methanol can realize the diversified development of olefin production raw materials, thereby obviously reducing the external dependence of petroleum in China, and is also beneficial to improving the energy structure in China, further ensuring the energy safety in China, and is more and more valued by people. For the methanol-to-olefin route, the search for a suitable catalyst is the focus of research.

In the current technology of preparing olefin from methanol, the demand of propylene in chemical production is increased year by year, and the propylene is more than ethylene and becomes the chemical raw material with the fastest demand increase. Increasing the propylene to ethylene ratio in methanol to olefins has become a focus of research. Chinese patent (CN111423302) reports a method and equipment for preparing olefin from methanol, wherein hydrocarbon streams of C4 and C5 in the process of preparing olefin from methanol are contacted with a completely regenerated catalyst, and then the reaction of preparing olefin from methanol is circularly carried out, so that the yield of low-carbon olefin (ethylene and propylene) is improved. Chinese patent (CN101955406) reports a method for producing propylene and coproducing ethylene. The method comprises the steps of introducing gaseous materials containing ethylene and methanol into a reactor, and reacting the gaseous materials with a solid acid catalyst to obtain a propylene product and an ethylene product. The ethylene product can be continuously introduced into the reactor for cyclic conversion after being separated. Chinese patent (CN109865530) reports a method for partially regenerating a methanol to olefin catalyst. The method comprises the steps of placing the deactivated methanol-to-olefin catalyst in a regenerator for partial regeneration reaction, and then introducing water vapor into the regenerator to serve as regeneration gas. The regenerated catalyst is used for the reaction of preparing the olefin from the methanol, so that the selectivity of the low-carbon olefin is improved.

The above technologies mainly aim at improving the olefin selectivity of methanol-to-olefin, but the stability of the industrial catalyst in the long-term cyclic regeneration process still lacks corresponding research. Taking SAPO-34 molecular sieve for preparing olefin from methanol as an example, due to the specific pore channel structure of the molecular sieve, the pore channels are blocked by carbon deposition generated by continuous reaction after the reaction for a period of time, so that the catalyst is quickly deactivated. Although carbon deposition blocking the pore channels of the catalyst can be burnt off after high-temperature roasting treatment so as to recycle the catalyst, the stability of the catalyst is reduced after multiple cycles, and frequent regeneration can cause partial structural damage of the molecular sieve catalyst, thereby affecting the long-term stability of the molecular sieve catalyst. The method of co-feeding methanol and water is commonly adopted in industry to improve the one-way life of the catalyst and prolong the reaction time, but the long-time contact of water vapor and the catalyst under high temperature condition is easy to cause partial collapse of the catalyst framework, and the long-term recycling of the catalyst is also influenced.

Based on this, the current research direction is mainly to change the pore diameter morphology of the catalyst, modify metals, and the like. Chinese patents CN106925340A, CN101318667 and the like modify the molecular sieve by metals, thereby improving the selectivity of methanol conversion and the service life of the catalyst. Chinese patent (CN 106698467A) synthesizes a nano SAPO-34, and the service life of the catalyst is improved by controlling the aperture of the molecular sieve. Most of the technologies modify molecular sieves, so compared with industrial catalysts, the synthesis cost is high, and the large-scale industrial production is not facilitated. In addition, the technology also mainly improves the single pass life and activity of the molecular sieve catalyst, but the stability and the life of the molecular sieve catalyst in a long-term cyclic regeneration process are not involved, which is a technical problem in the field.

Disclosure of Invention

In order to solve the technical problems and improve the long-term circulation stability and the service life of the molecular sieve catalyst in the industrial process of preparing the olefin from the methanol, the invention innovatively provides a method for combining pre-deposited carbon and water vapor treatment, and provides a method for improving the circulation stability and the service life of the molecular sieve catalyst in the process of preparing the olefin from the methanol.

The technology of the invention is based on the industrial catalyst for preparing olefin from methanol, and improves the long-term circulation stability and the service life of the catalyst. The introduction of ethylene/butylene can form larger organic molecular naphthalene species in the molecular sieve cage, occupy certain acid sites, protect the structure of the catalyst, prevent the collapse of the molecular sieve framework caused by the introduction of subsequent water vapor, and improve the stability of the catalyst. Higher methanol conversion and olefin selectivity can still be maintained after the regeneration cycle. In addition, the method of pre-depositing carbon and then treating water vapor protects the catalyst framework, and simultaneously, the introduction of the water vapor improves the service life of the catalyst and the selectivity of the reaction product. The method for combining the pre-deposited carbon and the co-fed water can effectively improve the service life and the utilization rate of the catalyst in the industrial reaction of preparing the olefin from the methanol, and reduce the cost of the reaction of preparing the olefin from the methanol.

The technical purpose of the invention is realized by the following technical scheme: a method for improving the cycle stability and the service life of a methanol-to-olefin reaction catalyst is characterized by comprising the following steps:

step 1, placing 0.2-0.6g of molecular sieve catalyst sample in a constant temperature area in the middle of a quartz tube of a fixed bed reactor, heating to 450 ℃ in a nitrogen atmosphere, stabilizing for 0.5-1.0h, and then cooling to 400 ℃;

introducing ethylene or butylene gas at the temperature of 2.350-550 ℃, wherein the contact time of ethylene/butylene and the catalyst is 5-15min, and preparing a pre-carbon deposition catalyst after the ethylene/butylene is adsorbed on the surface by nitrogen purging for 5 min;

step 3, introducing the methanol solution doped with a certain amount of water into a fixed bed preheating chamber by using a sample injection pump, mixing the methanol solution with carrier gas, and introducing the mixture into a catalyst bed layer, wherein the reaction temperature is 350-550 ℃, the reaction pressure is normal pressure, and the mass space velocity (WHSV) of the methanol is 1.0-3.0h^-1(ii) a The product is analyzed on line by gas chromatography;

step 4, stopping introducing the methanol solution after the reaction is inactivated; raising the temperature to 550 ℃, and introducing 20% oxygen/nitrogen for high-temperature treatment to burn off carbon deposition;

and 5, carrying out catalytic circulation reaction according to the step 2 and the step 3.

The invention also provides a method for improving the cycle stability and the service life of the catalyst for the reaction of preparing the olefin from the methanol, which is characterized by further comprising the following steps:

step 3, introducing water by using a sample injection pump, gasifying the water by using a fixed bed upper layer vaporizing chamber, and then introducing the water into a reactor, wherein the contact time of water vapor and the pre-deposited carbon catalyst obtained in the step 2 is 1-30h, so as to prepare a pre-deposited carbon and water vapor treatment catalyst;

step 4, introducing the methanol into a fixed bed gasification chamber by using a sample injection pump for gasification, mixing with nitrogen, and introducing into a catalyst bed layer of the reactor, wherein the reaction temperature is 350-^-1(ii) a The product was analyzed on-line by gas chromatography.

Further, in step 1, the catalyst comprises methanol-to-hydrocarbon molecular sieve catalyst, specifically SAPO-34, H-ZSM-5 and H-SSZ-13.

Further, in the step 2, the reaction temperature is 400 ℃, and the reaction pressure is normal pressure; the flow rate of nitrogen is 20 ml/min; the flow rate of ethylene/butene was 10-30 ml/min.

Further, the water accounts for 20-50% of the methanol solution by volume;

furthermore, the invention is characterized in that the contact time of the water vapor and the methanol is 1-30 h: compared with the prior art, the invention has the beneficial effects that:

(1) the technical method provided by the invention does not relate to the change of the catalyst, can directly utilize the existing industrial catalyst, and is easy to popularize and use industrially.

(2) The technical method provided by the invention is simple, does not need to adjust the existing industrial device for preparing the olefin from the methanol, and is easy to upgrade the existing industrial technology.

(3) The technology provided by the invention can effectively improve the one-way service life and long-term circulation stability of the catalyst and reduce the production cost of the low-carbon olefin.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings:

FIG. 1 is a graph showing the evaluation of methanol conversion activity of the three catalysts of the example.

Figure 2 is a graph of the activity of the three catalysts of the example after 20 cycles of methanol conversion.

FIG. 3 is a graph showing the evaluation of methanol conversion activity of the four catalysts of the example.

FIG. 4 is a graph showing the evaluation of methanol conversion activity of the catalysts of example five and example six.

FIG. 5 is a flow diagram of an example three catalyst methanol conversion;

FIG. 6 is a BET plot of the four catalysts of the examples.

Detailed Description

The following describes in detail specific embodiments of the present invention. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation.

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.

Technical terms in the present invention are defined in the following, and terms not defined are understood in the ordinary sense in the art.

The present invention will be described in more detail and fully hereinafter with reference to specific examples. The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses.

Example one

The embodiment provides a method for improving the cycle stability and the service life of a methanol-to-olefin reaction catalyst, which is characterized by comprising the following steps of:

Example two

The embodiment provides a method for improving the cycle stability and the service life of a catalyst for a reaction of preparing olefins from methanol, which specifically comprises the following steps:

step 1, placing a 0.4g SAPO-34 molecular sieve catalyst sample in a constant temperature area in the middle of a quartz tube of a fixed bed reactor, heating to 450 ℃ in a nitrogen atmosphere, stabilizing for 1h, and then cooling to 400 ℃;

step 2, introducing ethylene gas at 400 ℃, leading the ethylene to contact with the catalyst for 5min, and blowing off the ethylene adsorbed on the surface by nitrogen

After 5min, preparing a pre-deposited carbon catalyst;

step 3, introducing the methanol solution doped with 20 Vol% of water into a fixed bed preheating chamber by using a sample injection pump, mixing the solution with carrier gas, and introducing the mixture into a catalyst bed layer, wherein the reaction temperature is 400 ℃, the reaction pressure is normal pressure, and the mass space velocity (WHSV) of the methanol is 1.0h^-1(ii) a The product is analyzed on line by gas chromatography;

step 5, pre-depositing carbon again at 400 ℃; and (4) after the pre-carbon deposition is finished, the methanol-water co-feeding is carried out again to prepare the olefin.

For ease of illustration in the legend, fresh SAPO-34 is designated as SAPO-34-F, and the pre-carbon deposited catalyst is designated as SAPO-34-P; respectively introducing pure methanol solution or methanol solution of 20 Vol% water through a sample injection pump, and marking as SAPO-34-P + H₂O and SAPO-34-F + H₂And O, analyzing the product on line by using a gas chromatography, and obtaining an activity evaluation chart shown as a first figure and an activity evaluation chart shown as a second figure after 20 cycles.

EXAMPLE III

Introducing water by using a sample injection pump, gasifying the water by using a fixed bed upper layer vaporizing chamber, and then introducing the water into a reactor, wherein the contact time of water vapor and the pre-deposited carbon catalyst obtained in the step 2 is 1-30h, so as to prepare a pre-deposited carbon and water vapor treatment catalyst;

introducing methanol into a fixed bed gasification chamber by using a sample injection pump for gasification, mixing with nitrogen, and introducing into a catalyst bed layer of a reactor, wherein the reaction temperature is 350-; the product was analyzed on-line by gas chromatography.

Example four

Introducing steam after the fresh SAPO-34 is pre-deposited with carbon, wherein the contact time of the steam and the catalyst is 30 h. The prepared catalyst is placed in a constant temperature area in the middle of a quartz tube of a fixed bed reactor, and is heated to 450 ℃ and stabilized for 1h under the nitrogen atmosphere. Reducing the temperature to 400 ℃ to carry out the reaction of preparing olefin from methanol.The mass space velocity of the methanol is 2.5h^-1. The activity evaluation graph is shown in FIG. three.

EXAMPLE five

The implementation method is the same as the second embodiment, the catalyst is changed into H-ZSM-5, the carbon pre-deposition time is not changed, and the water vapor treatment time is 30H. The mass space velocity of the methanol is 3.75h^-1. The activity evaluation graph is shown in FIG. four.

EXAMPLE six

The implementation method is the same as the second embodiment, the catalyst is changed into SSZ-13, the pre-carbon deposition time is not changed, and the water vapor treatment time is 30 h. The mass space velocity of the methanol is 1.25h^-1. The activity evaluation graph is shown in FIG. four.

Although the present invention has been provided in detail with reference to the accompanying drawings, it is to be understood that such description is merely illustrative and not restrictive of the application of the present invention. The scope of the invention is defined by the appended claims and may include various modifications, adaptations and equivalents of the invention without departing from its scope and spirit.

Claims

1. A method for improving the cycle stability and the service life of a methanol-to-olefin reaction catalyst is characterized by comprising the following steps:

2. A method for improving the cycle stability and the service life of a methanol-to-olefin reaction catalyst is characterized by further comprising the following steps:

3. The method for improving the cycle stability and the service life of the methanol-to-olefin reaction catalyst according to claim 1 or 2, wherein in the step 1, the catalyst comprises methanol-to-hydrocarbon molecular sieve catalysts, specifically SAPO-34, H-ZSM-5 and H-SSZ-13.

4. The method for improving the circulation stability of the catalyst for the methanol-to-olefin reaction according to claim 1 or 2, wherein in the step 2, the reaction temperature is 400 ℃, and the reaction pressure is normal pressure; the flow rate of nitrogen is 20 ml/min; the flow rate of ethylene/butene was 10-30 ml/min.

5. The method for improving the cycle stability and the service life of the methanol-to-olefin reaction catalyst according to claim 1, wherein the water accounts for 20 to 50 percent of the volume of the methanol solution.

6. The method of claim 2, wherein the contact time of the water vapor and the methanol is 1-30 h.