WO2004072002A1

WO2004072002A1 - Method for producing lower olefin

Info

Publication number: WO2004072002A1
Application number: PCT/JP2004/000676
Authority: WO
Inventors: Phala Heng; Michiaki Umeno; Teruo Muraishi; Toshihiro Takai
Original assignee: Mitsui Chemicals, Inc.
Priority date: 2003-02-14
Filing date: 2004-01-27
Publication date: 2004-08-26
Also published as: KR20050097513A; JP4335144B2; JPWO2004072002A1; KR100714257B1; TWI243201B; TW200424162A

Abstract

A method for producing a lower olefin product containing ethylene and propylene as main components in which a hydrocarbon raw material containing olefins is subjected to a catalytic cracking by the use of a zeolite catalyst to produce an olefin lower that in the raw material, wherein a raw material comprising at least one olefin having 4 to 12 carbon atoms and 10 to 70 wt % of at least one saturated hydrocarbon having 1 to 12 carbon atoms is contacted with a catalyst comprising a MFI zeolite catalyst under a reaction pressure of 0.05 to 2 MPa, with a feed rate of the raw material per unit weight of the catalyst (WHSV) of 32 to 256 hr-1, at a reaction temperature of 400 to 580°C, to thereby produce ethylene and propylene. The method allows the suppression of the formation of by-products such as hydrogen, a saturated hydrocarbon, an aromatic hydrocarbon and coke, the reduction of the deterioration of the catalyst for a long period of time, and the selective production of ethylene and propylene with high productivity, even when use is made of a raw material containing a relatively large amount of a diene which frequently lowers the activity of a catalyst.

Description

Manufacturing method of low-grade off-line

TECHNICAL FIELD The present invention relates to a process for producing lower-order olefins, particularly ethylene and propylene, from a raw material by catalytically cracking a 4- to 12-carbon olefin using a catalyst. ,

Background Art Ethylene and propylene are important substances as basic raw materials for various chemicals and resins. Conventionally, these olefins are obtained by thermal or catalytic decomposition in naphtha crackers, but their production ratio is around 1: 0.6, which is the source of the difference between the supply and demand of ethylene or propylene. It has become. Therefore, in recent years, a method for selectively obtaining propylene from a hydrocarbon material containing C4 to C12 olefins, which are components of low utility such as butene and pentene, has become important. Many methods are known for catalytically converting these hydrocarbon raw materials containing 4 to 12 olefins using a zeolite catalyst. However, it is difficult to stably produce ethylene and propylene with high productivity over a long period of time by catalytically cracking a hydrocarbon raw material containing 4 to 12 carbon atoms using a catalyst. It was difficult for the following reasons. For example, European Patent No. 1 909 59 states that butene is catalytically cracked using Proton-type ZSM-5 zeolite (another name for MFI zeolite) to produce propylene. A method is disclosed. The process describes reaction conditions of low reaction temperatures at 400 and 500 and a high feed rate per unit weight of catalyst (WHSV) of 60 hr- ¹ or more. However, the raw material butene concentration used in this method 1 0 0% and high and, for low and _{_{S i O 2 / A 1 2}} 0 3 molar ratio of 2 8 Zeorai bets catalyst used, but the description is not However, under these conditions, the amount of coke generated is large, and therefore the activity of the catalyst decreases rapidly, so that it cannot be used for a long time.

European Patent No. 1,090,600 discloses a method for producing propylene by catalytic decomposition of butene using a protonated silica light. Subsequent studies revealed that the silicalite used in this method was a zeolite having an MFI type zeolite structure. However, the raw material butene concentration used in this method is as high as 100%, and the catalyst activity decreases rapidly under the conditions of high feed rate per unit weight of catalyst (WHSV), which provides high productivity. . Also described in Example, the reaction conditions of low temperature 5 0 0 catalyst for a long time can be used, per unit weight of the catalyst feeding rate of (WH SV) is 6 hr ¹ and low and therefore the propylene and Echiren Low productivity.

U.S. Pat.No. 5,981,181 discloses a process for producing propylene using pentasil-type zeolite under the following low-reaction temperature conditions at 500 in the presence of water in the raw material. Is disclosed. However, with this method, the feed rate of raw material per unit weight of catalyst (WH SV) is as low as ¹ to 3 hr1, and high propylene and ethylene productivity cannot be obtained.

Japanese Patent Application Laid-Open Publication No. Hei 6-73332 discloses an example of proton type ZSM-5. In order to obtain high productivity assuming a fluidized bed, the reaction temperature is as high as 600 X: a large amount of coke is deposited, equivalent to 6 OOP PM based on the total weight of the supplied raw materials. Is described in the Examples, and it is expected that the catalyst activity decreases rapidly when used in a fixed bed.

Japanese Unexamined Patent Publication No. Hei 11 — 2464445 (corresponding to WO9928905), Japanese Unexamined Patent Publication No. Hei11-24669 (Japanese Patent No. Japanese Patent Application Laid-Open No. H11-246680 (corresponding to WO9928980), Japanese Patent Application Laid-Open No. H11-246981 (W09929) No. 804), Japanese Patent Application Laid-Open No. H11 — 2464872 (WO 9292980)

No. 06), Japanese Unexamined Patent Application Publication No. 11-26639 (corresponding to WO992907), Japanese Unexamined Patent Application Publication No. 11-266710 (WO9) 9 2 9 4 2 1), Japanese Unexamined Patent Publication No.

1-266786 Publication (corresponding to W〇07071222), Japanese Patent Application Laid-Open No. H02-31-1997 (corresponding to WO077123) ), Japanese Patent Application Laid-Open No. 2000-31980

(Corresponding to WO0100749), Japanese Patent Application Laid-Open No. 2000-41069 (corresponding to WO078894) and European Patent 1 195 542 No. 4 discloses a method for producing a product containing ethylene and propylene by catalytically cracking a hydrocarbon feedstock containing olefins using proton-type MFI zeolite.

According to the described embodiments, these methods,. S i 〇 ₂ / A 1 ₂ 〇 ₃ molar ratio is used 3 6 0 or more MFI catalyst, reaction temperature 5 5 0 ° C and relatively mild Under such reaction conditions, it was disclosed that the catalytic cracking reaction of butene was performed without a decrease in the activity of the catalyst for a long period of time. However, in these methods, the feed rate of raw material per unit weight of catalyst (WH SV) is as low as 30 hr- ¹ or less, so that high ethylene and propylene productivity cannot be obtained.

Further, in this series of patents, there is a description that the gen compound in the raw material is reduced by hydrogenation treatment to suppress the decrease in the activity. Is preferably set to 0.1 wt% or less. It is listed. For example, according to the description in JP-A-11-246871 (corresponding to W992 9804), when the amount of the gen compound in the raw material is 0.5 wt%, the activity of propylene is not stable. Over time (Comparative Example 4, page 16 and FIG. 8, page 38).

International patent WO 010948 describes the use of silver-exchanged ZSM-5 catalysts. In the method using such a modified MFI catalyst, the catalytic activity is reduced, so that even when the reaction is performed at a slightly higher temperature of 600 ° C, the amount of coke deposited is reduced to some extent. However, the amount of co-precipitation with respect to the total weight of the supplied raw materials is still large, for example, 74 weight ppm. In addition, in this method, it is difficult to carry out the reaction under the condition of a high feed rate of raw material per unit weight of catalyst (WHSV), and high productivity of ethylene and propylene cannot be obtained.

In other words, under higher reaction temperature conditions, coke formation is accelerated, and the activity of the catalyst is rapidly reduced. Therefore, the feed rate (WHSV) of the raw material must be lowered, and the by-product hydrogen and saturated carbon In addition to increasing the yield of hydrogen and aromatic hydrocarbons, high ethylene and propylene productivity cannot be obtained. On the other hand, by modification, when a lower activity zeolite catalyst is used, or when the catalytic decomposition reaction is carried out at a lower reaction temperature, the unreacted raw material is not sufficiently converted because the orefin raw material is not sufficiently converted. And the yields of ethylene and propylene decrease, resulting in that high productivity cannot be obtained. Under these conditions, if carbon 生産 4 to 12-olefin feedstock is supplied at a high rate (high WHSV) in order to obtain high productivity, the production of coke is accelerated, and the activity of the catalyst decreases rapidly. become.

The present invention uses a zeolite catalyst to catalytically crack a hydrocarbon containing 4 to 12 carbon atoms to form a lower molecular weight material mainly composed of ethylene and propylene. In the production of benzene, by-products such as hydrogen, saturated hydrocarbons, aromatic hydrocarbons, and coke are suppressed, and coke precipitates on the catalyst even in raw materials containing relatively large amounts of gen compounds. An object of the present invention is to provide a method for producing ethylene and propylene selectively and with high productivity while suppressing the deterioration of the catalyst over a long period of time. Disclosure of the invention

The present inventors have intensively studied to solve the above problems. As a result, we have developed a production technology that exhibits high ethylene and propylene selectivity, low coke accumulation, which can be expected for long catalyst life, and high productivity.

This manufacturing technology was created as a result of studying the catalytic cracking reaction mechanism, which had not been systematically studied. That is, the mechanism of the reaction for producing ethylene and propylene from carbon atoms having 4 to 12 carbon atoms is significantly different from those of carbon atoms having 4 carbon atoms (butene). That is, in the case of an olefin having more than 4 carbon atoms, a carpocation is generated at an acidic active site of the catalyst, and a lower carbon olefin is generated by breaking a carbon-carbon bond. On the other hand, in the case of butene, it can be explained as follows with reference to the mechanism of isolemination of olefin reported in Applied Catalysis A: General 206 (2001) 57-66. That is, in the case of butene, octene is first formed by dimerization, and becomes propylene and pentene via a more stable secondary carpocation. This reaction proceeds rapidly because the reaction intermediate is stable. The resulting pentene then decomposes, yielding ethylene and propylene, but the reaction is slow because the primary primary force lipocation is used to produce ethylene. Further, the present inventors have studied using a computational chemistry technique, and have obtained results supporting this estimation. That is, There are multiple reactions to obtain propylene from butene, but there are differences in the ease with which the reaction can proceed.To obtain ethylene and propylene more selectively, catalytic activity, reaction temperature, and contact It is important to precisely control reaction conditions such as time and to selectively advance a preferable reaction.

In the present invention, the raw material contains at least one kind of carbon having 4 to 12 carbon atoms, and contains 10 to 70 wt% of at least one kind of carbon having 1 to 12 saturated hydrocarbons. Under the reaction pressure of 0.05 to 2 MPa, the feed rate (WH SV) per unit weight of catalyst (WH SV) is 32 to 25 under the reaction pressure of 0.05 to 2 MPa. By contacting at a reaction temperature of 400 to 580 for 6 hours, preferably, the weight ratio of pentene to propylene in the reaction product effluent is controlled to 0.20 to 0.80. As a result, by-products such as hydrogen, saturated hydrocarbons, aromatic hydrocarbons, and coke are suppressed, and precipitation of coke on the catalyst is suppressed even in a raw material containing a relatively large amount of a gen compound. High ethylene and propylene selectivity and productivity, and long catalyst life are obtained. Brief description of the drawings

FIG. 1 shows the changes over time in butene conversion, ethylene and propylene yield in Examples 9, 10 and 1. A graph connecting diamonds represents Example 9, a graph connecting squares represents Example 10, and a graph connecting a circle represents Example 1. The top graph shows the conversion of the putene, the middle graph shows the propylene yield, and the bottom graph shows the ethylene yield. BEST MODE FOR CARRYING OUT THE INVENTION According to the present invention, the raw material contains at least one or more carbon atoms of 4 to 12 olefins, and contains 10 to 70 wt% of at least one or more carbon atoms of 1 to 12 saturated hydrocarbons. Ethylene and propylene can be selectively obtained mainly from the olefin component by catalytic cracking of a contained raw material using a catalyst. The present inventors have surprisingly found that by using such a mixed raw material of olefin and saturated hydrocarbon, the generation of coke is suppressed, and the decrease in catalytic activity is suppressed. Furthermore, they have found that even with a raw material containing a relatively large amount of a gen compound, the deposition of coke on the catalyst is suppressed, and a decrease in catalyst activity is suppressed. Also, even if hydrogen is contained in the raw materials used, coke generation can be similarly suppressed. In this case, the value of the partial pressure of hydrogen is preferably in the range of 0.1 to 0.9.

According to the present invention, the starting material used has 4 to 12 carbon atoms, for example, 1-butene, cis-1-butene, trans-1-butene, isobutene, 1-pentene, cis-1-pentene , Trans-1-pentene, 2-methyl-1-butene, 2-methyl-2-butene, 3-methyl-11-butene, cyclopentene, 1-1hexene, 2-hexene, 3-hexene, methylbutenes, dimethyl Butenes, neohexene, cyclohexene, methylcyclopentene, linear heptene, branched heptene, cyclic heptene, methylcyclohexene, C9-C12 linear, branched, or cyclic Olefins.

According to the present invention, the content of the saturated hydrocarbon having 1 to 12 carbon atoms in the raw material used is 10 to 70 wt%, preferably 10 to 60 wt%, more preferably 20 to 20 wt%. Expressed as ~ 50wt%. Under the conditions of the present invention, substantially no such conversion of saturated hydrocarbons occurs, but surprisingly, if the content of these saturated hydrocarbons in the feedstock used is below this range, the activity of the catalyst is reduced. Be faster. 1 to 12 carbon atoms Examples of hydrocarbons include methane, ethane, propane, n-butane, isobutane, linear, branched and cyclic pentane, linear, branched and cyclic, hexane, linear, branched and cyclic heptane, linear and branched And cyclic octane. As other components, aromatic hydrocarbons such as benzene, toluene and xylene may be contained.

The gen compound contained in the raw material used in accordance with the present invention is a hydrocarbon gen having 3 to 12 carbon atoms, such as propagene, 1,2-butadiene, 1,3-butadiene, 1,2-pentadiene, 1,3-Penyugen, 1,4-Penyugen, 2,3-Penyugen, 1,2-Hexagen, 1,3-Hexagen, 1,4-Hexagen, 1,5-Hexagen , 2,3-hexadiene, 2,4-hexadiene, 1,2-heptadiene, 1,3-heptadiene, 1,4-heptadiene, 1,5-heptadiene, 1,6-heptadiene , 2,3-Heptadiene, 2,4-Heptogen, 2,5-Heptogen, 3,4-Heptogen, 1,2-Octadien, 1,3-Octogen, 1 , 4-Octadien, 1,5-Octadien, 1,6-Octadien, 1,7-Octadjen, 2,3-Octadjen, 2,4-Octoyjen, 2,5-Octadjen, 2,6-Octadjen , 3, 4-ok Linear gen compounds such as tajen, 3,5-octane, etc., 2-methyl-1,3-butane, 3-methyl-1,2-butadiene, 2,3-dimethyl-1,3- Butadiene, 2-ethyl-1,3-butadiene, 3-ethyl-1,2-butadiene, 2-methyl-1,3-pentane, 3-methyl-1,3-pentadiene, 4-methyl-1, 3-pentadiene, 2-methyl-1,4-pentane, 3-methyl-1,4-pentadiene, 2,3-dimethyl-1,3-pentane, 2,4-dimethyl-1,3 -Pentagen, 3,4-dimethyl-1,3-pentane, 2,3-dimethyl-1,4-pentane, 2,4-dimethyl-1,4-pentane, 2-methyl- 1,3-hexadiene, 3-methyl-1,3-hexadiene, 4-methyl-1,3-hexadiene, 5-methyl-1,3-hexadiene, 2-methyl-1,4- Hexadiene, 3-methyl-1,4-hexadiene, 4-methyl-1,4-hexadiene, 5-methyl-1,4-hexadiene Branched Jen compounds such E down, cyclopentadiene, 1- Mechirushiku Mouth pen- 1,3-Gen, 2-Methylcyclopen- 1,3-Gen, 5-Methylcyclopen- 1,3-Gen, 1,3-Cyclohexadiene, 1,4-Cyclo 'A cyclic gen compound such as xadiene may be contained, but since it may cause undesired reduction in catalytic activity, its content is preferably 2 wt% or less, more preferably lwt% or less.

Examples of the raw material having such a component include a naphtha pyrolysis furnace or a distillate obtained from the top of a debutane tower sent after separating a C1 to C3 fraction from a mixture obtained in a naphtha catalytic cracking furnace. Fraction (cruft C1 fraction) after extraction and removal of butadiene from crude C4 fraction (crude C4 fraction) or butadiene in the C4 fraction of crude C4 without selectively extracting the total amount of contact water Fraction obtained by adding isotope to 2 wt% or less, or a fraction obtained by separating isopten from rough rice (rough rice 2), or obtained from the bottom of a debutanizer. A fraction obtained by extracting and removing isoprene from a fraction (a C5 fraction of a cloud), or the entire amount thereof is selectively catalytically hydrogenated without extracting an isoprene from a C5 fraction of a crude to reduce the gen component. Off-line distillation with wt% or less Butadiene disolen is extracted from the fraction obtained from the top of the depentanizer sent after separating the C1 to C3 fraction from the mixture obtained in the naphtha pyrolysis furnace or the naphtha catalytic cracking furnace. In addition, there can be mentioned, for example, an orefin fraction in which the total amount is selectively catalytically hydrogenated to reduce the gen component to 2 wt% or less.

These raw materials may be used alone, or may be used as a mixture in an arbitrary amount. The raw materials are not limited to those described above, and may be those containing at least one kind of saturated hydrocarbons having 4 to 12 carbon atoms and 10 to 70 wt% of at least one carbon atom. Any material can be used. As the catalyst used in the present invention, an MFI type zeolite catalyst is used. _{_{S i 0 2 / A 1 2}} 0 3 molar ratio of Zeorai Bok until 5 0 0 0 beyond normal .1 2 0, preferably 2 0 0 5 0 0 0, more preferably 2 8 0 5 0 0 0 And particularly preferably 280 000. If the molar ratio S i 0 ₂ / A 1 ₂ 〇 ₃ is lower than this, the catalytic activity is too high, so that the coke deposition rate is high in the temperature range where the decomposition reaction is thermodynamically favorable, Is not preferred because of its stability when repeatedly used. On the other hand, when the molar ratio of SiO ₂ / A 12 O ₃ is higher than this range, the number of active points decreases, and it is not preferable because the active point can no longer function as an acid catalyst.

MF I type Zeorai DOO catalyst may be used as a commercial product having a S i 〇 _₂ ZA 1 ₂ O ₃ molar ratio of purpose, a known method by the Zeorai bets composition deviating these ranges as a starting material It is also possible to obtain by That is, a commercial product having a low SiO 2 SZAlz O ₃ molar ratio can be dealuminated and converted to a higher silica zeolite. Examples of the method for dealumination are described in Catalysis and Zeolites, Fundamentals and Applications J. Weitkamp, .Puppe Hi Collection, Springer, 1999, 1 271 155, steam treatment, treatment with silicon tetrachloride, Hexaful mouth silicate treatment and the like can be mentioned.

Many commercially available MFI zeolite products contain sodium or ammonium as a cation, but any of them can be used in the present invention if the following treatment is performed. That is, the zeolite exchanged with the ammonium cation is converted, for example, to a proton type by treating it at 500 with 5 hours, and then used as a catalytic cracking reaction catalyst. On the other hand, those having an alkali metal ion such as sodium are stirred by a known method, that is, in an aqueous solution of about 110% ammonium nitrate at 60 for 6 hours, filtered, washed, and then washed at 500X. 5 hours This can be converted to a proton type and used. Since the above-mentioned MFI-type zeolite catalyst is required to exhibit acidity, the zeolite may be a zeolite exhibiting acidity exchanged with a metal ion in addition to the protonic zeolite. Specific examples of the metal ion include monovalent metal ions such as Group IB metals such as Cu and Ag, and divalent or higher metal ions include Mg, Ca, and S Examples thereof include alkaline earth metals such as r and Ba, rare earth metals such as La and Ce, and transition metals such as Fe, Ni, Mn, Co, and V. These may be present at the same time as the protons in any proportion. At this time, all of the exchange capacity of the zeolite may be replaced with the above-mentioned proton or the above-mentioned metal. However, if the activity is too high, a part of the exchange capacity is reduced by L 1 at an arbitrary ratio. , Na, K or the like to reduce the acidity. However, if the ratio of the alkali metal to the exchange capacity exceeds 90%, the acidity becomes too low, so that it is preferable to set the ratio below this.

As the above-mentioned MFI zeolite, those containing an element such as P which shows acidity can be used. At this time, the content of P is preferably equal to or more than the content of protons and other metal thiones in terms of mole. -As a method for incorporating these elements into the catalyst, known methods are used. For example, a method of exchanging the cation of a metal atom with proton by ion exchange with a proton-type MFI zeolite, or a method of impregnating a salt-complex compound containing these elements into the MFI zeolite Is mentioned.

According to a known method, the above-mentioned MFI type zeolite catalyst is used as a third metal other than Si and A1 for the purpose of controlling activity, improving selectivity, suppressing coke formation and suppressing catalyst deterioration rate. B, S n, G a, M n, F e and T i are converted to MFI zeolite Those contained in the skeleton of the structure can also be used.

The above MFI zeolite catalyst can be used after being subjected to steam treatment by a known method. As the method of the above treatment, the temperature is preferably 5,000 to 750: the vapor pressure is preferably 0.1 to 1 MPa, and the processing time is preferably 10 to 48. Further, the above treatment can be performed after the catalyst is molded by the method described below. The aforementioned catalyst is charged to the reactor in the following form. That is, MFI zeolite obtained by hydrothermal synthesis is essentially in a fine powder state. The resulting finely powdered MFI zeolite catalyst may be directly charged into a fixed bed reactor, but in order to prevent pressure loss from increasing, a filler inert to the catalytic cracking, for example, silica pole However, it may be physically mixed with aluminum balls and filled. Further, the obtained fine powdered MFI zeolite catalyst may be kneaded with a sintering agent (binder) which does not change the catalytic performance, and then molded. The sintering agent is typically a silica type, but may be selected from alumina, titania, zirconia, and diatomaceous types. ,

Sintering is preferably performed in the range of 500-800. The shapes to be molded are: Tablets, Extrusion, Pellets, Spheres, Micro spheres, CDS Extrusion (CDS Extrusions)> Trilobes, Trilobes ), Quardlobes, Rings, Two-spoke rings (2 Sporkes rings;), HGS, EW, LDP and other special spokes, Ribs rings, Granules, etc. Can be exemplified.

According to the present invention, catalytic cracking can be used in any type of reactor, such as a fixed bed, a fluidized bed, and a moving bed, but a fixed bed reactor with simple equipment can be used. preferable. The catalytic cracking reaction is carried out by filling the above-mentioned catalyst into such a reactor and supplying the olefin-containing hydrocarbon raw material. When performing this catalytic cracking reaction, the reaction conditions are precisely controlled as follows.

The reaction temperature is 400 to 580, preferably 480 to 580 ° (:, more preferably 480 to 560. If the reaction temperature is lower than this range, supply On the other hand, if the reaction temperature is higher than this range, the rate of coke formation accelerates, and the catalyst conversion rate decreases. · The activity of the product decreases faster.

The reaction pressure is adjusted to 0.05 MPa to 2 MPa, preferably 0.05 to: L MPa, more preferably 0.05 to 0.5 MPa.

The feed rate (WHSV) of the entire raw material per unit weight of the MFI catalyst is 32 to 256 hr-1 or more, preferably 40 to 256 hr-1, more preferably 40 to: L28 hr-1. i. If the feed rate (WHSV) is lower than this range, the pentene content in the reaction distillate is reduced and the rate of catalyst activity reduction is suppressed to some extent, but hydrogen, saturated hydrocarbon and aromatic The yield of aromatic hydrocarbons increases and high selectivity and productivity of ethylene and propylene cannot be obtained. On the other hand, under the reaction conditions of the raw material supply rate (WHSV) larger than this range, the rate of coke formation is increased, which is not preferable.

In addition, the reactor may be a single reactor or a plurality of reactors. In the case of a plurality of reactors, the reaction conditions are more precisely controlled by installing the reactors in series. it can. When the reactors are installed in parallel, catalytic cracking operation is performed in one of the reactors, and regeneration and other operations are performed in the other reactor. It becomes. Under these reaction conditions, This maximizes the selectivity, yield and productivity of len, and suppresses the formation of coke, which causes a decrease in catalyst activity.

According to the process of the present invention, the weight ratio of pentene to propylene in the reaction product distillate at the reactor outlet is usually from 0.20 to 0.80, preferably from 0.25 to 0.8. It is preferably 80, more preferably 0.30 to 0.80. In the case of a plurality of reactors installed in series, the weight ratio of pentene to propylene in the reaction product distillate at the outlet of the first reactor is usually 0.20 to 0.80. It is preferably 0.25 to 0.80, more preferably 0.30 to 0.80. In other words, in the catalytic cracking reaction, as described above, a plurality of reactions having different reaction rates are proceeding simultaneously, and by suppressing the decomposition of pentene, which has a slow reaction rate, to a certain extent, accumulation of undesirable coke is achieved. Therefore, it is possible to maintain a constant catalytic activity for a sufficiently long time. When ethylene and propylene were removed from the products of the first reactor of multiple reactors, the reaction in the second reactor was carried out under more severe conditions to supply the whole. Most of the raw materials can be converted. '

On the other hand, when only one reactor is used, the olefins having 4 or more carbon atoms, including pentene, are separated from the distillate of the reaction product and then recycled to the catalytic cracking reactor to be combined with new raw materials. It is also possible to use these naphtha crackers together with new naphtha raw materials after separation of these carbons having 4 or more carbon atoms. '

In the present invention, the raw material contains at least one kind of carbon having 4 to 12 carbon atoms, and contains 10 to 70 wt% of at least one kind of carbon having 1 to 12 saturated hydrocarbons. The raw material containing 2 wt% or less of the gen compound in some cases At a reaction pressure of 0.05 to 2 MPa, the feed rate (WH SV) of all raw materials per unit weight of the MFI catalyst is 32 to 256 hri, 400 to 5 at a reaction pressure of 0.05 to 2 MPa. By contacting at a reaction temperature of 80 ° C, hydrogen and saturated hydrocarbons are controlled by controlling the weight ratio of pentene to propylene in the reaction product distillate to 0.20 to 0.80. In addition, it suppresses by-products such as aromatic hydrocarbons and coke, and also suppresses the deposition of coke on the catalyst, even in raw materials containing relatively large amounts of gen compounds, resulting in high propylene selectivity and long catalyst life. can get. Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples. Example 1

Commercially powdered Anmoniumu salt _{Z SM- 5 (S i 0 2} ZA l 2 0 3 molar ratio of 2 8 0) powder in 5 5 0 ° C, was calcined for 5 hours. After firing, a catalyst having a particle size of 250 to 500 m was obtained by compression molding, pulverization and classification.

The reaction was carried out in a fixed-bed flow reactor (10.7 mm ID, 250 mm length). A quartz tube was filled with 0.125 g of the above catalyst and quartz wool and quartz sand as a holding material so that the entire length became 250 mm. This quartz tube was charged into the reactor, the temperature of the catalyst layer was maintained at 550, and the C4 fraction raw material C (Table 1) obtained by cracking of naphtha was supplied at a flow rate of 8 g / hour. The catalytic cracking reaction was performed under a reaction pressure of 0.5 MPa. The effluent reaction product was kept in a gaseous state and analyzed using a gas chromatograph.

After reacting for a predetermined time, supply of the raw material is stopped, and the temperature of the catalyst layer is lowered to 450 ° C. I got it. One hour after the feed was stopped, the combustion of coke accumulated with air diluted with nitrogen was started. The air supply was continued until the combustion of the accumulated coke was completed. Hydrogen, carbon monoxide and carbon dioxide generated by the combustion reaction were quantified by gas chromatography, and the weight of coke produced was calculated from the weight of these gases produced.

The conversion of the raw material and the yield of the product were calculated by the following formula.

(1) Putene conversion (%) = (1 — (weight of unreacted butene Z weight of butene supplied)) X 100

(2) Product yield (%) = (weight of each component produced / supply butene weight) XI 00 (3) Coke yield (PPM) = (total coke production weight total supplied butene weight) X 1,0 0 0, 0 0 0

Table 2 shows the results of the reaction. This is a result that the productivity of ethylene and propylene can be stably obtained over 90 hours. In addition, the production yield of coke is low, and a method of burning and removing accumulated coke is used, so the amount of heat generated by coke combustion is small and the amount of steam generated that is not desirable for catalyst deterioration Less. Therefore, when the catalyst is used repeatedly, its life can be expected to be longer. Comparative Example 1

A catalytic cracking reaction was carried out under the same conditions as in Example 1 except that the raw material C in Example 1 was changed to an n-butene raw material. Table 3 shows the results. Under these conditions, which use a raw material that does not contain the saturated hydrocarbon butane, the reaction time for stable production of ethylene and propylene was only 20 hours. Table 1 (Raw material composition)

Table 2 (Example 1)

Catalyst _{H-ZS -5 (Si0 2 /} Al 2 O s 280), the raw material C (saturated hydrocarbon reaction conditions

40.0 wt%), temperature 550 ° C, WHSV 64 hr- ¹ , pressure 0.05 MPa reaction time (hr) 4 12 20 30 42 54 66 78 84 90 conversion ratio of ptene (%) 76.5 74.9 75.1 76.3 69.8 72.5 66.4 65.5 70.1 68.6 Yield ( _wt %)

Hydrogen 0.10 0.08 0.11 0.09 0.06 0.05 0.05 0.03 0.04 0.05 methane 0.43 0.33 0.48 0.41 0.28 0.24 0.23 0.18 0.26 0.28 ethane 0.54 0.40 0.61 0.53 0.32 0.26 0.24 0.17 0.27 0.28 propane 4.7 3.5 4.7 4.2 2.7 2.2 2.0 1.3 1.9 2.0 butane 2.3 0.1 4.2 1.0 2.5 3.0 3.1 0.9 3.2 4.1 Ethylene 10.1 8.3 10.4 9.2 7.3 6.5 6.0 4.8 6.0 6.2 Propylene 31.4 30.7 33.2 30.5 32.0 30.0 31.3 28.9 29.5 32.2 Pentene 9.5 10.0 9.8 9.4 11.5 10.6 12.5 12.4 10.7 12.6

C5 or higher Non-aromatic 17.2 17.1 17.7 16.3 18.6 16.7 19.0 18.1 16.4 19.1 Aromatic 5.1 4.0 5.4 4.6 3.0 2.7 2.6 1.7 2.4 2.6 Cork 35 PPM Table 3 (Comparative Example 1)

Examples 2 to 4

In Examples 2 to 4, the same conditions as in Example 1 were used except that the raw materials shown in Table 4 were used, respectively, to obtain saturated hydrocarbons mainly of butanes at 18.4 wt%, 30.6 wt% and This is an example of catalytic cracking of a raw material containing 61.2 wt%. The results are shown in Table 4. Compared to Comparative Example 1, the raw material contains only 18.4 wt% of saturated hydrocarbons, the coke production yield is reduced by half, and the reaction time for stable production of ethylene and propylene is 20 hours. It can be seen that the time has rapidly increased from 42 hours to 42 hours. Example 4 is an example of catalytic cracking of a raw material having a saturated hydrocarbon content as high as 61.2 wt%. The operation was stopped at 100 hours, at which point the catalyst activity was slightly reduced. Table 4 (Examples 1 to 4, Comparative Example 1)

Examples 5 to 6 and Comparative Example 2

In Examples 5 to 6 and Comparative Example 2, catalytic cracking was carried out under the same reaction conditions as in Example 1 except that the reaction temperature was 500 ° C, the WHSV shown in Table 5 was used, and raw material D was used. . Table 5 shows the results. As shown in Example 5, the value of 1 2 8 hr ¹ and higher conditions of feed rate of raw material (WHSV) of catalyst per weight unit, the weight ratio flop propylene pentenes to zero. 5 or more since it I have. Under these conditions, it can be seen that the formation of coke is extremely low. However, as shown in Comparative Example 2, under reaction conditions with reduced productivity, that is, when the value of WHSV is as low as 8 hr- ¹ , although the yield of pentene decreases, saturated hydrocarbons, aromatic hydrocarbons, On the contrary, the yield of undesired by-products such as coke is becoming very high. Table 5 (Examples 5 and 6, Comparative Example 2)

Zeolite preparative Example _{_{7 S i O 2 ZA 1 2}} O 3 molar ratio 5 0 0

In this embodiment, except that S I_〇 ₂ / A 1 ₂ 0 ₃ molar ratio was used 5 00 MF I Zeorai DOO catalyst in the same conditions as in Example 1 was subjected to catalytic cracking 1 3 7 hours Example Table 6 shows the results. By that you use the high _{S i O 2 / A 1 2} O 3 molar ratio Zeorai DOO, without substantially reducing the productivity of ethylene and propylene, S i 〇 ₂ / A 1 2 O ₃ molar ratio of 2 8 The reaction could be performed 1.5 times or more as compared with Example 1 using the MF zeolite catalyst of 0. Table 6 (Example 7)

Example 8

This example shows an example of repeated use of the catalyst. In Example 1, the catalytic cracking reaction was performed, and the produced coke was burned. The catalyst was held in the reactor, the raw materials were supplied under the same conditions as in Example 1, and the catalytic cracking reaction was restarted. After the reaction, coke combustion was performed under the same conditions. As a result of repeating this operation six times, no deterioration of the catalyst was observed. Example 9, 10

In Examples 9 and 10, the same reaction conditions as in Example 1 were used except that butadiene was added to raw material C, and raw materials having butadiene contents of 0.51 and 1.1 wt% were used, respectively. Catalytic cracking was carried out. The results are shown in Figure 1. Compared with the butadiene content of Example 1 of 0.05 wt%, the propylene yield could be stably obtained for 60 hours or more even with the butadiene content of 1 lwt%. In addition, the production yield of coke was 37 ppm and 40 ppm, which was a slight increase.

Claims

The scope of the claims

1. A method for producing lower-order olefins by catalytically cracking hydrocarbon raw materials containing orefins using a catalyst. A raw material containing 12 or more and at least 10 to 70 wt% of at least one kind of saturated hydrocarbon having 1 to 12 carbon atoms is produced in the presence of a catalyst including an MFI type zeolite catalyst. Under the reaction pressure of 0.05 to 2 MPa, the feed rate of raw material per unit weight of catalyst (WH SV) is 32 to 256 h r-i, and the reaction temperature is 400 to 580. A method for producing ethylene and propylene by contacting with t.

2. A process for producing lower-grade olefins by catalytically cracking hydrocarbon-containing raw materials using a catalyst, and distilling off the reaction products at the outlet of the reactor. 2. The method for producing ethylene and propylene according to claim 1, wherein the weight ratio of pentene to propylene contained in the product is from 0.20 to 0.80.

3. The MF I type Zeorai S i 0 ₂ / A 1 ₂ 0 ₃ molar ratio of bets catalyst, ethylene and propylene production how according to claim 1 or 2 is up to 5 00 0 exceed 1 20 .

4. The method for producing ethylene and propylene according to any one of claims 1 to 3, wherein the content of the saturated hydrocarbon having 1 to 12 carbon atoms in the raw material is 10 to 60 wt%.

5. The method for producing ethylene and propylene according to any one of claims 1 to 4, wherein the reaction temperature of the catalytic cracking is 480 to 580 :.

6. The production rate of ethylene and propylene according to any one of claims 1 to 5, wherein a feed rate (WHS V) of the raw material per unit weight of the catalyst is 40 to 256 hr-1. Construction method.

7. The method for producing ethylene and propylene according to any one of claims 1 to 6, wherein the at least one kind of olefin contained in the raw material is an olefin having 4 to 8 carbon atoms.

8. The method for producing ethylene and propylene according to any one of claims 1 to 7, wherein the saturated hydrocarbon contained in the raw material is a saturated hydrocarbon having 1 to 8 carbon atoms.

9. The method for producing ethylene and propylene according to any one of claims 1 to 8, wherein the raw material contains 2 wt% or less of gen.