阅读说明：本技术 连续转化下脱氢芳构化催化剂的再生 (Regeneration of dehydroaromatization catalyst under continuous conversion ) 是由 阿米特·库马尔 斯里尼瓦萨拉奥·加朱拉 齐亚德·科塔瓦里托蒂 埃斯瓦拉·拉奥·穆帕拉胡 于 2019-08-21 设计创作，主要内容包括：本发明提供了连续转化下脱氢芳构化催化剂的再生。一种用于甲烷的脱氢芳构化的方法,包括：将甲烷和二氧化碳引入芳构化反应器；在700至850℃的温度下在脱氢芳构化催化剂存在下将一部分甲烷转化为芳香烃；在700至800℃的再生温度下用氢气再生脱氢芳构化催化剂；并重复引入、转化和再生；其中,在每2至5个再生循环后,将再生温度提高5至15℃。(The present invention provides for the regeneration of a dehydroaromatization catalyst under continuous conversion. A process for dehydroaromatization of methane comprising: introducing methane and carbon dioxide into an aromatization reactor; converting a portion of the methane to aromatic hydrocarbons at a temperature of 700 to 850 ℃ in the presence of a dehydroaromatization catalyst; regenerating the dehydroaromatization catalyst with hydrogen at a regeneration temperature of 700 to 800 ℃; and repeating the introducing, converting and regenerating; wherein the regeneration temperature is increased by 5 to 15 ℃ after every 2 to 5 regeneration cycles.)

1. A process for dehydroaromatization of methane comprising:

introducing a feed stream of methane and carbon dioxide into an aromatization reactor;

converting a portion of the methane to aromatics in the presence of a dehydroaromatization catalyst, preferably a Mo-HZSM-5 catalyst;

regenerating the dehydroaromatization catalyst with hydrogen at a regeneration temperature of 700 to 800 ℃;

repeating said introducing, said converting and said regenerating; and

periodically increasing the regeneration temperature by 5 to 15 ℃.

2. The process of claim 1, wherein the catalyst is regenerated with only hydrogen.

3. The process according to any of the preceding claims, wherein the reaction temperature is increased after a reduction of the conversion percentage of 5 to 20%, preferably 8 to 15%, or 10 to 15%.

4. The process according to any of the preceding claims, wherein the reaction temperature is increased after every 2 to 8 regeneration cycles, preferably after 2 to 5 regeneration cycles, or after 3 to 5 regeneration cycles.

5. A process according to any one of the preceding claims, wherein the conversion is initially carried out at a temperature of 700 to 780 ℃, preferably 730 to 770 ℃, or 745 to 755 ℃.

6. The process of any one of the preceding claims, wherein the feed stream comprises greater than 90 vol% methane and 0.05 to 3 vol% (preferably 0.05 to 2 vol%) carbon dioxide, based on 100 vol% of the feed stream.

7. The process according to any one of the preceding claims, wherein the aromatization reactor is a fixed bed reactor.

8. The method according to any one of the preceding claims,

wherein the dehydroaromatization catalyst is carburized prior to use in the aromatization reactor;

wherein the reaction temperature is increased after the percent conversion has decreased by greater than or equal to 5%, preferably greater than or equal to 8%;

wherein the conversion is initially carried out at a temperature greater than or equal to 745 ℃; and is

Wherein the feed stream comprises 0.05 to 3 vol%, preferably 0.05 to 2 vol% carbon dioxide based on 100 vol% of the feed stream.

9. The method of claim 8, wherein the feed stream comprises 0.05 to 2 vol% carbon dioxide based on 100 vol% of the feed stream.

Technical Field

The present application relates to a process for converting methane to aromatic products using a dehydroaromatization catalyst.

Background

Aromatic hydrocarbons, such as benzene, toluene, ethylbenzene, xylenes, and polycyclic aromatic hydrocarbons, such as naphthalene, are important commercial chemicals in the petrochemical industry.

Since methane is one of the most abundant organic compounds on earth, one method of producing aromatics is through Dehydroaromatization (DHA) of methane. For example, methane is the major component of natural gas; a large amount of methane exists in marine sediments in the form of hydrates and coal gangue (coal scale) in the form of coal bed methane; and it may also be derived from biomass, e.g. biogas.

Dehydroaromatization of methane is becoming increasingly important. Catalyst-based dehydroaromatization of methane is a promising process for the production of valuable aromatics and hydrogen from natural gas.

Catalyst deactivation due to coking (coke formation) is one of the major drawbacks of dehydroaromatization of methane. Coking can reduce the activity of the catalyst. The balance of dehydroaromatization of methane is also low due to coking on the catalyst. Coking is most prone at high temperatures, particularly at 700 ℃ and above. Coking can be of two types, hard coke and soft coke. Hard coke is mainly referred to as graphite type coke. The soft coke may be a polycyclic aromatic hydrocarbon deposit.

US 2013/0090506 to Ogawa proposes a process for producing aromatic hydrocarbons. When aromatic hydrocarbons are produced by a contact reaction of lower hydrocarbons with a catalyst, the aromatic hydrocarbons can be stably produced for a long period of time while maintaining a high aromatic hydrocarbon yield. The process may include a regeneration process for regenerating the catalyst, and the process may be repeated.

CN 104326854 of Cheng et al proposes a methane oxygen-free aromatization reaction technique using a catalyst for pre-carbonization. By utilizing the technology, a catalyst pre-carbonization coupling device is arranged in a regeneration continuous circulation reaction system in the reaction of preparing aromatic hydrocarbon from methane.

US 2013/0012747 to Ma et al proposes a process for the production of aromatic compounds. The method includes a reaction process of inducing a contact reaction between a lower hydrocarbon and a catalyst to obtain an aromatic hydrocarbon and hydrogen, and a regeneration process of regenerating the catalyst by contacting hydrogen with the catalyst used in the reaction process. The reaction process and the regeneration process are repeated to produce aromatic hydrocarbons and hydrogen. During the reaction, carbon monoxide is added to the lower hydrocarbon. The reaction temperature is preferably not lower than 820 ℃.

US 6,239,057 to Ichikawa et al proposes a catalyst for converting lower carbon number aliphatic hydrocarbons to higher carbon number hydrocarbons. A catalyst has been developed for producing higher carbon number hydrocarbons such as benzene from lower carbon number hydrocarbons such as methane. The catalyst comprises a porous support, such as ZSM-5, having rhenium dispersed thereon, and a promoter metal, such as iron, cobalt, vanadium, manganese, molybdenum, tungsten, and mixtures thereof. Method for producing a catalyst and a catalyst in CO or CO₂A process for converting lower carbon number aliphatic hydrocarbons to higher carbon number hydrocarbons in the presence of a catalyst.

Hard coke can be removed at lower temperatures (400 to 550 ℃) in dilute oxygen and soft coke can be removed by pure hydrogen at higher temperatures (700 to 850 ℃). As used herein, the term "coke" is used to denote a carbonaceous solid material that is essentially a solid that is not readily volatile under the reaction conditions.

Disclosure of Invention

Disclosed herein is a process for dehydroaromatization of methane.

A process for dehydroaromatization of methane comprising: introducing a feed stream of methane and carbon dioxide into an aromatization reactor; converting a portion of the methane to aromatic hydrocarbons in the presence of a dehydroaromatization catalyst, in particular a Mo-HZSM-5 catalyst; regenerating the dehydroaromatization catalyst with hydrogen at a regeneration temperature of 700 to 800 ℃; repeatedly introducing, converting and regenerating; and periodically increasing the regeneration temperature by 5 to 15 ℃.

Drawings

Fig. 1 is a graph of methane conversion over time according to the methods disclosed herein.

Fig. 2 is a graph of methane conversion over time according to the process disclosed herein compared to a process conducted at constant temperature.

Detailed Description

The invention solves the problem of reduced catalyst activity caused by coking in the methane dehydrogenation aromatization reaction. The use of hydrogen to decarbonise the catalyst and restore the catalyst activity is disclosed. It has been found herein that regeneration of coked catalyst with a hydrogen-containing gas stream (e.g., comprising at least 100% by volume (vol%) hydrogen), wherein the reaction (and regeneration) temperature is increased after several regeneration cycles, improves the overall process and feasibility of catalyst regeneration. For example, the performance is improved when dehydroaromatization of methane is carried out until the percent conversion of methane is reduced from the initial value by, for example, 10 to 15%. Once conversion is reduced, methane and CO₂The flow will stop and the catalyst is regenerated with hydrogen. The reaction temperature is increased after a predetermined number of regeneration cycles or after the percent conversion is reduced. For example, the reaction temperature is increased after the percent conversion is reduced by 5 to 20%, preferably 8 to 15%, or 10 to 15%, or after 2 to 8, preferably 2 to 5 regeneration cycles. In other words, the percent conversion achieved after the percent conversion is reduced from the initial percent, and then the percent conversion is increased from the regeneration temperature. This process may continue until a temperature of 800 ℃ is reached. Above 800 ℃, graphite coking may form.

Methane dehydroaromatization comprises contacting a dehydroaromatization catalyst with a methane feed at an initial reaction temperature of 700 to 780 ℃. Methane is supplied to the catalyst together with carbon dioxide and converted into aromatics. The feed stream may comprise from 85 to 100 vol%, preferably from 90 to 100 vol%, or from 90 to 96 vol% methane, based on the total volume of the feed stream. The feed stream can comprise 0 to 10 vol% (e.g., greater than 0 to 10 vol%), preferably 5 to 10 vol%, or 0 to 4 vol% (e.g., greater than 0 to 4 vol%) carbon dioxide, based on the total volume of the feed stream. The catalyst is regenerated after a set period of time or after the percent conversion is reduced. The time may be up to 120 minutes (min), for example, 15min to 60min, or 15min to 30 min. The reduction in percent conversion may be greater than or equal to 15 percent from the initial percent conversion, e.g., 10 to 20 percent or 10 to 15 percent.

Regeneration may be performed, for example, at the same temperature as dehydroaromatization. Hydrogen is introduced into the catalyst to react and remove coke from the catalyst. Regeneration may also be performed over a set period of time or may be based on measurements of the effluent stream from the reactor. The time may be up to 120 minutes, for example, 30 minutes to 90 minutes, or 30 minutes to 60 minutes, or 45 to 60 minutes. If the cycle time is based on a measurement of the effluent stream, regeneration is stopped when the amount of methane is less than or equal to 0.2%, e.g., a 0 to 1% or 0 to 0.2% reduction.

The hydrogen stream can comprise greater than or equal to 90 vol%, preferably greater than or equal to 95 vol%, or greater than or equal to 99 vol% hydrogen, or pure hydrogen (e.g., 100 vol% hydrogen). The hydrogen stream may be fed directly to the methane dehydroaromatization reactor for the first regeneration of the catalyst. The hydrogen stream may be at a concentration of greater than 1000ml g^-1h^-1Preferably 1000 to 4000ml g^-1h^-1Or 2500 to 3500ml g^-1h^-1Is introduced at a Gas Hourly Space Velocity (GHSV).

Alternatively, hydrogen may be supplied from the product stream of the methane dehydroaromatization reaction. In particular, the product stream of the methane dehydroaromatization reaction may be further processed to separate pure hydrogen from the remainder of the product. The hydrogen separated from the product stream can be greater than 90 vol% hydrogen. Hydrogen separated from the product stream of the methane dehydroaromatization reaction having no more than 0.1 to 3% residual methane may be used as the hydrogen stream for catalyst regeneration to save the cost of supplying an additional hydrogen stream.

After regeneration, another cycle of methane dehydroaromatization may be performed by discontinuing the introduction of the hydrogen stream into the reactor and reintroducing the feed stream. After 2 to 8 regeneration cycles, the reaction temperature can be increased. For example, the reaction temperature is increased after the catalyst activity decreases by greater than or equal to 10% (preferably by greater than or equal to 12% or by greater than or equal to 15%) and then hydrogen regeneration and at the start of dehydroaromatization. The increase in temperature may be from 5 to 20 ℃, preferably from 5 to 15 ℃, or from 8 to 12 ℃.

For example, the first, second and third cycles may include dehydroaromatization at a pressure of 5 to 100MPa, a reaction temperature of 750 ℃ for 15 to 60 minutes followed by regeneration at 750 ℃ for a time of 30 to 90 minutes. The fourth, fifth, sixth and seventh cycles may include dehydroaromatization at a pressure of 5 to 100MPa, a reaction temperature of 760 ℃ for 15 to 60 minutes followed by regeneration at 760 ℃ for a time of 30 to 90 minutes. The eighth through twelfth cycles may include dehydroaromatization at a pressure of 5 to 100MPa, a reaction temperature of 770 ℃ for 15 to 60 minutes followed by regeneration at 770 ℃ for a time of 30 to 90 minutes. The thirteenth and fourteenth cycles may include dehydroaromatization at a pressure of 5 to 100MPa, a reaction temperature of 780 ℃ for 15 to 60 minutes followed by regeneration at 780 ℃ for a time of 30 to 90 minutes. The circulation may be continued until a temperature of 800 c or higher is reached. Temperatures in excess of 800 c are preferred to continue to rise to temperatures of 800 c, since graphite coking can form.

It has been found that increasing the reaction temperature can increase the catalyst conversion efficiency by maintaining the percent conversion for a longer period of time. From fig. 2 and the reaction data, it is believed that catalyst stability will be greatly (e.g., 5-fold) increased.

The aromatic stream produced by the dehydroaromatization reaction comprises at least one of benzene, toluene, naphthalene, or xylene. The aromatic compound may comprise at least one of benzene or toluene. The aromatic stream may further comprise minor amounts, for example, less than 5 vol% (e.g., 1 to 5 vol%) in total of one or more of ethane, ethylene, propylene, or propane. Desirably, the aromatics stream contains substantially benzene (e.g., greater than or equal to 80 vol% of the aromatics can be benzene).

The aromatic compound may be produced under reaction conditions including a temperature of 700 to 800 ℃, preferably 750 to 800 ℃. The pressure may be from 5 megapascals (MPa) to 150MPa, preferably from 30MPa to 100MPa, or from 40MPa to 60 MPa. The production rate may be greater than or equal toEqual to 250 ml per gram per hour (ml g)^-1h^-1) Preferably 250 to 350ml g^-1h^-1Or 275 to 325ml g^-1h^-1Gas Hourly Space Velocity (GHSV).

A zeolite catalyst may be used in the methane dehydroaromatization reaction. The aromatization catalyst may comprise the catalytic metal in an amount in the range of from 2 weight percent (wt%) to 7 wt%, or from 3 wt% to 6 wt%, based on the weight of the inorganic support. The catalytic metal may comprise at least one of chromium, cobalt, gallium, iron, magnesium, molybdenum, vanadium or zinc, preferably the catalyst comprises molybdenum. Desirably, the aromatization catalyst comprises a catalyst metal on an inorganic support. The inorganic support may be an inorganic oxide such as a zeolite, preferably a hydrogen form zeolite. The zeolite can be at least one of Y-type zeolite, X-type zeolite, mordenite, ZSM-5 (e.g., HZSM-5), ALPO-5, VPI-5, FSM-16, MCM-22, or MCM-41. In certain aspects, the zeolite can be MCM-22. Desirably, the zeolite comprises HZSM-5. The zeolite may have a silicon to aluminum molar ratio in the range of 10 to 50, or 13 to 30, preferably 25 to 30. The zeolite catalyst may be, for example, molybdenum/ZSM-5, molybdenum/ZSM-11, and molybdenum/MCM 22. For example, a ZSM-5 catalyst may be used in the methane dehydroaromatization reaction, such as a molybdenum oxide ZSM-5 (Mo-oxide/ZSM-5) catalyst. The Mo-oxide/ZSM-5 catalyst provides good catalytic performance, high aromatics selectivity and productivity (e.g., greater than 85%, and even up to 90% selectivity).

The invention is further illustrated by the following examples, which are exemplary and not limiting.