JPH11246869A - Production of olefin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing an olefin in high yield and purity by converting olefins as feedstocks not so valuable which are found in oil refinery or petrochemical plants to a lighter olefin, esp. propylene through catalytic cracking. SOLUTION: This method for producing an olefin is a catalytic cracking process for olefin feedstock selective toward light olefin-rich effluents, comprising the following process: a hydrocarbon feedstock containing one or more kinds of olefins is brought into contact with a MFI-type crystalline silicate catalyst with an atom ratio Si/Al of at least about 300 at an inlet temperature of 500-600 deg.C and olefin partial pressure of 0.1-2 bar and passed through the catalyst at a LHSV of 1 per 10-30 h, thereby producing an effluent containing an olefin-contg. product with a molecular weight lower than that of the feedstock.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for cracking an olefin-rich hydrocarbon feedstock having selectivity in the direction of light olefins in an effluent. In particular, it is possible to selectively convert olefinic feeds from refineries or petrochemical plants and redistribute the olefin content of the feeds in the resulting effluent.

[0002]

BACKGROUND OF THE INVENTION The use of zeolites to convert long chain paraffins to lighter products, for example, in the catalytic dewaxing of petroleum feedstocks, is known in the art. Although it is not the purpose of dewaxing, at least some of the paraffinic hydrocarbons are converted to olefins. It is known to use crystalline silicates of the MFI type in such a method, for example, and the three-letter designation "MFI" stands for Structu
re Commission of the Inte
rational Zeolite Associate
2 shows the type of structure of a particular crystalline silicate as determined by Tion. Examples of crystalline silicates of the MFI type are the synthetic zeolite ZSM-5 and silicalite, other MFIs
Type crystalline silicates are known in the art.

GB-A-1323710 discloses a dewaxing process for removing normal and slightly branched paraffins from hydrocarbon feedstocks using crystalline silicate catalysts, in particular ZSM-5. . US-A-424738
8 also discloses a method for catalytic hydrodewaxing of petroleum and synthetic hydrocarbon feedstocks using crystalline silicates of the ZSM-5 type. Similar dewaxing methods are disclosed in US-A-4284529 and US
-A-5614079. The catalyst is a crystalline alumino-silicate, and the above prior art references disclose the use of a wide range of Si / Al ratios and various reaction conditions for the disclosed dewaxing process.

[0004] GB-A-21855753 discloses the dewaxing of hydrocarbon feedstocks using a silicalite catalyst. US
-A-4394251 discloses hydrocarbon conversion using crystalline silicate particles having an aluminum-containing shell.

It is also possible to selectively convert hydrocarbon feedstocks containing linear and / or slightly branched hydrocarbons, especially paraffins, to a mixture of lower molecular weight products containing significant amounts of olefins. It is known in the art. GB-A-2075045, US-A-4
As disclosed in US Pat. No. 401,555 and US Pat. No. 4,309,276, the conversion is carried out by contacting the feed with a crystalline silicate known as silicalite. Silicalite is disclosed in U.S. Pat. No. 4,061,724.

[0006] Silicalite catalysts exist with various silicon / aluminum atomic ratios and various crystal forms. Co
sden Technology, Inc. E in the name of
PA-0146524 and 0146525 disclose silicalite-type crystalline silica having monoclinic symmetry and a method for producing the same. These silicates have a silicon to aluminum atomic ratio of greater than 80.

WO-A-97 / 04871 discloses treating medium pore zeolites with steam, followed by an acidic solution to improve the butene selectivity of the zeolites in catalytic cracking. .

[0008] Elsevier Science B.
V. Title "De-Aluminati" published by
on of HZSM-5 zeolite: Effe
ctof steaming on acidity
and aromatization activit
y ", de Lucas et al. Applied
Catalyst A: General 154
The 1997 221-240 article discloses the conversion of an acetone / n-butanol mixture to a hydrocarbon on such a dealuminated zeolite.

Further, for example, from US Pat. No. 4,171,257, a petroleum distillate is dewaxed using a crystalline silicate catalyst such as ZSM-5 to produce a light olefin fraction such as a C ₃ -C ₄ olefin fraction. It is known to manufacture. Typically, the reactor temperature reaches about 500 ° C. and the reactor uses a low hydrocarbon partial pressure which favors the conversion of petroleum distillate to propylene. Dewaxing decomposes the paraffinic chains and reduces the viscosity of the feed distillate, but also produces small amounts of olefins from the decomposed paraffins.

[0010] EP-A-0305720 discloses the production of gaseous olefins by catalytic conversion of hydrocarbons.
EP-B-0347003 discloses a process for converting hydrocarbonaceous feedstocks into light olefins. WO-A-90 /
11338 discloses a method for converting C ₂ -C ₁₂ paraffinic hydrocarbons into petrochemical feedstocks, especially C ₂ -C ₄ olefins. US-A-5043522 and EP-A-03
95345 discloses the production of olefins from paraffins having 4 or more carbon atoms. EP-
A-0511013 discloses the production of olefins from hydrocarbons using a steam activated catalyst containing phosphorus and H-ZSM-5. U.S. Pat. No. 4,810,356 discloses a method for treating gas oil by dewaxing over a silicalite catalyst. GB-A-2156845 discloses the production of isobutylene from propylene or a mixture of hydrocarbons containing propylene. GB-A-2159833 discloses the production of isobutylene by catalytic cracking of light distillates.

For the crystalline silicates exemplified above, it is known in the art that long chain olefins tend to degrade much faster than the corresponding long chain paraffins.

It is further known that when crystalline silicates are used as catalysts for the conversion of paraffins to olefins, such conversions are not time-stable. The conversion rate decreases with increasing uptime, due to the formation of coke (carbon) that deposits on the catalyst.

[0013] These known methods are used to break down heavy paraffinic molecules into lighter molecules. However, if the production of propylene is desired, not only is the yield low, but also the stability of the crystalline silicate catalyst is low. For example FC
Typical propylene production in the C unit is 3.5% by weight
It is. By introducing the known ZSM-5 catalyst into the FCC unit and "squeezing" more propylene from the cracked incoming hydrocarbon feedstock, the propylene production from the FCC unit can be reduced to about 7-8 wt% propylene. Can be increased. Not only is this increase in yield very small, but the ZSM-5 catalyst is less stable in FCC units.

There is an increasing demand for propylene, especially for the production of polypropylene. At present, the petrochemical industry is facing major difficulties in the availability of propylene as a result of the growth of propylene derivatives, especially polypropylene. Conventional methods of increasing propylene production are not entirely satisfactory. For example, an additional naphtha steam cracker (ad) that produces about twice as much ethylene as propylene
divisionalnaphtha steam cra
Quing units are an expensive method for obtaining propylene because the raw materials are expensive and the investment is very high. Since naphtha is the basis for the production of gasoline in refineries, it competes as a feedstock for steam crackers. Although the dehydrogenation of propane gives a high yield of propylene, the feedstock (propane) is cost-effective only for a limited period of one year, which makes the process expensive and limits the production of propylene. I have.
Propylene can be obtained from FCC units but in relatively low yields, and the improvement in yield has proven to be expensive and limited. Yet another route, known as metathesis or disproportionation, allows for the production of propylene from ethylene and butene. Often combined with a steam cracker, this method is expensive because it uses at least as expensive ethylene as propylene as a feedstock. EP-A-0 109 059 discloses a process for converting olefins having 4 to 12 carbon atoms to propylene. The olefin is crystalline and has a zeolite structure (for example, ZSM-5 or ZSM-1).
Is contacted with silicate - 1), 300 alumino having the following SiO ₂ / Al ₂ O ₃ molar ratio. The description states that 1 kg of pure zeolite is used to achieve a high propylene yield.
It requires a high space velocity of more than 50 kg / hour. The description generally states that the higher the space velocity, the higher the SiO 2
It also states that the ₂ / Al ₂ O ₃ molar ratio (called the Z ratio) is low. This specification exemplifies only the olefin conversion process over a short period of time (e.g., several hours), and the catalyst is stable for the long period of time required for commercial production (e.g., at least 160 hours or several days). Does not deal with the problem. Further, the need for high space velocities is undesirable in the commercial practice of olefin conversion processes.

[0015] Thus, there is a need for a high yield propylene process that can be easily incorporated into refineries or petrochemical plants using feedstocks that are not very valuable to the market (there are few alternative uses in the market). .

On the other hand, crystalline silicates of the MFI type are also well-known catalysts for the oligomerization of olefins. For example, EP-A-0031675 discloses the conversion of an olefin-containing mixture to gasoline over a catalyst such as ZSM-5. As will be apparent to those skilled in the art, the operating conditions for the oligomerization reaction are significantly different from those used for cracking. Typically, in the oligomerization reactor, the temperature does not exceed about 400 ° C., and high pressure favors the oligomerization reaction.

GB-A-2156844 discloses a process for the isomerization of olefins over silicalite as a catalyst. U.S. Pat. No. 4,579,899 discloses the conversion of olefins to higher molecular weight hydrocarbons on silicalite catalysts. US-A-474676
No. 2 discloses the upgrading of light olefins over crystalline silicate catalysts to produce hydrocarbons rich in C ₅ + liquids. US-A-5004852 discloses a two-stage process for the conversion of olefins to high-octane gasoline, the method comprising the olefin in the first stage C ₅ +
Oligomerized to olefin. US-A-5171
331, discloses C ₂ -C ₆ olefin containing feedstock silicalite, a method for the production of gasoline comprising to oligomerize pore size siliceous crystalline molecular sieve on the catalyst in such as a halogen stabilized silicalite or zeolite doing. U.S. Pat. No. 4,414,423 discloses a multi-step process for producing high boiling hydrocarbons from normally gaseous hydrocarbons, the first step being to convert a normally gaseous olefin into a medium pore size siliceous crystalline molecular. Feeding over a sieve catalyst. US-A-44170088
Discloses dimerization and trimerization of high carbon olefins on silicalite. U.S. Pat. No. 4,417,086 discloses an oligomerization process for olefins on silicalite. GB-A-2106131 and G
B-A-2106132 discloses the oligomerization of olefins over a catalyst such as zeolite or silicalite to produce high boiling hydrocarbons. GB-A-21
06533 discloses oligomerization of gaseous olefins on zeolites or silicalites.

[0018]

SUMMARY OF THE INVENTION In contrast to the above prior art processes, the object of the present invention is to provide a refinery and a feedstock for a process for catalytically converting olefins to lighter olefins, especially propylene. It is to provide a method for using low value olefins present in petrochemical plants.

Another object of the present invention is to provide a method for producing propylene having a high propylene yield and purity.

It is a further object of the present invention to provide such a process capable of producing an olefin effluent that is at least within chemical grade quality.

Yet another object of the present invention is to provide a process for producing olefins having a stable olefin conversion and a stable product distribution over time. Yet another object of the present invention is to provide a method for converting an olefinic feed having a high olefin base yield toward propylene, regardless of the origin and composition of the olefinic feed.

[0022]

SUMMARY OF THE INVENTION The present invention is a process for the catalytic cracking of olefin-rich feedstocks that is selective in the direction of light olefins in the effluent and contains one or more olefins. 500 to 6 hydrocarbon raw materials
Contacting with an MFI-type crystalline silicate catalyst having a silicon / aluminum atomic ratio of at least about 300 at an inlet temperature of 00 ° C. and an olefin partial pressure of 0.1 to 2 bar;
A process comprising passing a feed over a catalyst at 1 LHSV per 10 to 30 hours to produce an effluent having a lower molecular weight olefin content than that of the feed.

Thus, the present invention is directed to an olefin-rich hydrocarbon stream (product) from refineries and petrochemical plants.
Can be provided not only to light olefins but also to propylene in particular. Olefin-rich raw materials with at least about 300 specific Si /
It can be passed over an MFI-type crystalline silicate catalyst having an Al atomic ratio. The catalyst is preferably a commercially available catalyst that has been prepared by crystallization using an organic template and has not been subjected to a subsequent steaming or de-aluminum process. The raw material is heated at a temperature in the range of
Olefin partial pressure of bar and 1 LH per 10-30 hours
It can be passed over a catalyst with an SV to produce at least 30-50% propylene based on the olefin content in the feed.

In this specification, the term "silicon / aluminum atomic ratio" is intended to mean the Si / Al atomic ratio of the whole material, which can be determined by chemical analysis. Especially in the case of crystalline silicate materials, the stated Si / Al ratio applies to all materials, not just the Si / Al skeleton of the crystalline silicate.

The raw material can be supplied undiluted or diluted with an inert gas such as nitrogen. In the latter case, the absolute pressure of the feed constitutes the partial pressure of the hydrocarbon feed in the inert gas.

Various aspects of the invention will now be described in more detail with reference to the accompanying drawings, which are by way of example only.

According to the invention, the cracking of the olefins is carried out in the sense that the olefins in the hydrocarbon stream are cracked to lighter olefins and selectively to propylene.
The feed and the effluent preferably have substantially the same olefin weight content. Typically, the olefin content in the effluent is within ± 15% by weight, more preferably within ± 10% by weight of the olefin content of the feed. The feed may include any type of olefin-containing hydrocarbon stream. The feedstock may typically contain from 10 to 100% by weight of olefin, and may be supplied undiluted or diluted with a diluent, the diluent optionally including non-olefinic hydrocarbons be able to. In particular olefin - containing feedstock, optionally carbon number range to C ₁₀ in the mixture from C ₄ with a straight chain or branched chain paraffins and / or aromatics in the carbon number range to C ₁₀ C _4, more Preferably, it can be a hydrocarbon mixture containing a linear or branched olefin having a carbon number in the range of C ₄ to C ₆ . Typically, the olefin-containing stream is from about -15 to about 180
It has a boiling point of ° C.

In a particularly preferred embodiment of the invention, the hydrocarbon feed comprises a C ₄ mixture from a refinery and a steam cracker. Such steam crackers crack various feedstocks including ethane, propane, butane, naphtha, light oil, fuel oil and the like. Most specifically the hydrocarbon feed, heavy oil can include C ₄ fraction from a fluidized bed catalytic cracking (FCC) unit in a crude oil refinery which is employed to convert the product of the gasoline and lighter. Typically such C ₄ fraction from FCC unit contains about 50 wt.% Olefins. For another, the hydrocarbon feedstock may comprise a C ₄ cut from the device of crude oil refinery for producing methyl tert- butyl ether (MTBE) which is prepared from methanol and isobutene. Also in this case, MTB
Such C ₄ cut from the E unit contains typically about 50 wt.% Olefins. Each of these C ₄ fraction is fractionated at the outlet of the FCC or MTBE unit. Naphtha steam hydrocarbon feedstock further petrochemical plants - can include C ₄ fraction from cracker, where about 1
Naphtha containing C ₅ -C ₉ species having a boiling range of 5 to 180 ° C. is decomposed water vapor, among others give C ₄ fraction. Such C ₄ fraction is typically wt by 40-50% of 1,3-butadiene, about 25% of isobutylene, from about 15
% Butene (in the form of 1-butene and / or 2-butene) and about 10% n-butane and / or isobutane. Olefin - containing hydrocarbon feedstock may also comprise a C ₄ cut from a steam cracking unit after the butadiene extraction (raffinate 1) or butadiene hydrogenation.

The raw material still other cases, typically may include rich C ₄ fraction of hydrogenated butadiene contains more C ₄ than 50% by weight olefins.
In another case, the hydrocarbon feed may comprise a pure olefin feed produced in a petrochemical plant.

[0030] The olefin-containing feedstock may furthermore be
Light cracked naphtha (LCN) (otherwise the light catalytically cracked spirit (LCCS) as known) may include a C ₅ fraction from or steam cracker or light cracked naphtha,
Light cracked naphtha is rectified at the crude oil refinery from the effluent of the FCC unit as discussed above. Both such feedstocks contain olefins. The olefin-containing feed may, in yet another case, be a medium cracked naphtha from such an FCC unit.
tha) or visbroken naphtha obtained from a visbreaking unit for the treatment of vacuum distillation unit residues in a crude oil refinery.

The olefin-containing feedstock may comprise a mixture of one or more of the above-mentioned feedstocks.

Olefins according to the preferred process of the present invention
Use of C ₅ fraction as containing hydrocarbon feedstock, it is necessary anyway remove C ₅ species from the gasoline produced by refineries is particularly advantageous. This is because the presence of C ₅ in gasoline increases the possibility of ozone, thus improving the photochemical activity of the resulting gasoline. When light cracked naphtha is used as the olefin-containing feedstock, the olefin content of the remaining gasoline fraction is reduced, thereby reducing the gasoline vapor pressure and also the photochemical activity.

For the conversion of light cracked naphtha, C ₂ -C ₄ olefins can be produced according to the process of the present invention. The C ₄ cut is very rich in olefins, especially isobutene,
It is an interesting feed for MTBE equipment.
When converting the C ₄ fraction, whereas C ₂ -C ₃ olefins are produced by mainly iso on the other - C ₅ containing olefin
-C ₆ olefin is produced. The remaining C ₄ fraction is butane,
In particular are isobutane concentration, it is an interesting feedstock for alkylate C ₃ and C ₅ feed alkylation unit refinery produced from a mixture of for use in gasoline. C ₅ containing mainly iso-olefins
-C ₆ fraction is tertiary amyl methyl ether (TAME)
Is an interesting feedstock for the manufacture of.

Surprisingly, the inventors have found that, according to the process of the present invention, the olefinic feed can be selectively decomposed and the olefin content of the feed redistributed in the resulting effluent. The catalyst and process conditions are chosen so that the process has a specific olefin-based yield for the specific olefin in the feed. Typically the catalyst and process conditions are thus C ₄ fraction from process FCC unit, C ₄ fraction from MTBE unit, the examples and C ₅ fractions from light cracked naphtha or light cracked naphtha olefins Regardless of the origin of the raw materials, they are selected to have the same high olefin base yield on propylene. This cannot be expected at all based on the prior art. The olefin yield based on propylene is typically from 30 to 30, based on the olefin content of the feedstock.
50%. The olefin-based yield of a particular olefin is defined as the weight of that olefin in the effluent divided by its content by weight of the original total olefin. For example, in the case of a raw material containing 50% by weight of olefin,
If the effluent contains 20% by weight of propylene, the olefin yield of propylene is 40%. This can be compared to the actual yield for the product, defined as the weight of the product produced divided by the weight of the feed. According to a preferred aspect of the present invention, the paraffins and aromatics contained in the feed are only slightly converted.

According to a preferred aspect of the present invention, the catalyst for the decomposition of olefins comprises a crystalline silicate of the MFI group, which is zeolite, silicalite or any other silicate in the group. be able to.

Preferred crystalline silicates have pores or grooves defined by 10 oxygen rings and a high silicon / aluminum atomic ratio.

Crystalline silicates are microporous crystalline inorganic polymers based on a skeleton of XO ₄ tetrahedra linked together by sharing oxygen ions, where X is trivalent (eg, Al, B , ...) or tetravalent (eg, Ge, S
i,. . . ). The crystal structure of a crystalline silicate is defined by the particular order in which the network of tetrahedral units is connected. The size of the pore openings of the crystalline silicate is determined by the number of tetrahedral units or, in other words, oxygen atoms required for pore formation and the nature of the cations present in the pores. It has a unique combination of the following properties: high internal surface area; uniform pores with one or more discontinuous dimensions; ion exchangeability; excellent thermal stability; and the ability to adsorb organic compounds. . Because the pores of these crystalline silicates are similar in size to many organic molecules of practical interest, they control the entry and exit of reactants and products, resulting in specific selectivity in catalysis. MF
Crystalline silicates having the I structure have a two-way cross-pored system with the following pore size: straight grooves along [010]:
0.53-0.56 nm and sinusoidal groove along [100]: 0.51-0.55.

Crystalline silicate catalysts have structural and chemical properties that facilitate catalytic cracking and are used under such special reaction conditions. Various reaction paths can take place on the catalyst. About 500-600 ° C, preferably 5
Under process conditions having an inlet temperature of 20-600 ° C, more preferably 540-580 ° C and an olefin partial pressure of 0.1-2 bar, most preferably about atmospheric pressure,
Transfer of the double bond of the olefin in the feed is easily achieved, leading to double bond isomerization. Further, such isomerization tends to reach thermodynamic equilibrium. For example, propylene can be produced directly by catalytic cracking of hexane or heavier olefinic feedstock. Olefinic catalytic cracking can be understood to include processes that give shorter molecules via bond cleavage.

The catalyst preferably has a high silicon / aluminum atomic ratio of greater than about 300, whereby the catalyst has a relatively low acidity. The hydrogen transfer reaction is directly related to the strength and density of the acid sites on the catalyst, and it is preferred that such reactions be suppressed and avoid coke formation during the olefin conversion process, otherwise coke may save time. Would reduce the stability of the catalyst over time. Such hydrogen transfer reactions tend to give saturated compounds such as paraffins, intermediate labile dienes and cyclo-olefins and aromatics, none of which is advantageous for cracking to light olefins. Cyclo-olefins are precursors of aromatics and coke-like molecules, especially in the presence of solid acids, i.e. acidic solid catalysts. The acidity of the catalyst can be determined by the amount of residual ammonia on the catalyst after contacting the catalyst with ammonia, as measured by differential thermogravimetry, which adsorbs to the acid sites on the catalyst and increases it. Ammonium desorption at the given temperature follows. Preferably the silicon / aluminum ratio is between 300 and 10
00, most preferably in the range of 300-500. One of the features of the present invention is to use such a high silicon / aluminum ratio in the crystalline silicate catalyst and to obtain 30-50% irrespective of the origin and composition of the olefinic feedstock.
That is, stable olefin conversion can be performed with a high olefin-based yield of propylene. Such a high ratio reduces the acidity of the catalyst, thereby improving the stability of the catalyst.

In accordance with the present invention, it is not only necessary to achieve a high olefin-based yield of propylene, but also the percentage of olefins that are decomposed into olefins instead of being decomposed into paraffins or aromatic compounds, It is also necessary to achieve high purity of propylene in the C ₃ species in the effluent, coupled with the high purity in effluent. Preferably propylene has a purity of at least 96%. Preferably at least 85% by weight of the olefins in the feed are cracked to olefins or are present as the first olefins. Further according to the invention, the catalyst has a high stability in the cracking process in the sense that the activity of the catalyst is not reduced as a result of the coke being progressively deposited on or formed on the catalyst. Is also preferred. It has been found by the inventors that such coke formation, over time, significantly reduces the ability of the catalyst to crack olefins with high propylene yields. All of these desired results in the cracking process, together with the required process parameters of temperature and pressure, provide the present invention with a silicon / aluminum atomic ratio of at least about 300 in a crystalline silicate catalyst of the MFI-type. Can be achieved according to:

It has been found that the various preferred catalysts of the present invention exhibit high stability, and in particular can provide stable propylene yields for several days, for example up to 10 days. This allows the olefin cracking process to be carried out continuously in two parallel "swing" reactors where one reactor is running while the other is undergoing catalyst regeneration. The catalyst of the present invention can be regenerated several times.
The catalyst is pure or comes from various sources in refineries or petrochemical plants and is flexible in that it can be used to crack a variety of feedstocks as a mixture having various compositions. But also.

In the catalytic cracking process, the process conditions are selected to give a high selectivity towards propylene, a stable olefin conversion over time and a stable distribution of olefinic products in the effluent. For such purposes it is advantageous to use a low acid density (ie high Si / Al atomic ratio) in the catalyst together with low pressure, high inlet temperature and short contact time, all of which process parameters Interrelated and provide an overall cumulative effect (eg, relatively high pressures can be offset or compensated for by even higher inlet temperatures). The process conditions are chosen to favor the hydrogen transfer reaction leading to the formation of paraffins, aromatics and coke precursors. Thus, the process operating conditions use high space velocities, low pressures and high reaction temperatures. Preferably the LHSV is in the range of 1 per 10 to 30 hours. The partial pressure of the olefin is 0.1 to 2 bar, more preferably 0.5 to 2 bar.
１．５1.5 bar. A particularly preferred olefin partial pressure is atmospheric pressure (ie, 1 bar). The hydrocarbon feed is suitably provided at an overall inlet pressure sufficient to transport the feed through the reactor. The hydrocarbon feed can be supplied neat or diluted in an inert gas, such as nitrogen. Preferably the total absolute pressure in the reactor ranges from 0.5 to 10 bar. We have found that the use of olefin partial pressures, for example, as low as atmospheric pressure, tends to reduce the probability of hydrogen transfer reactions in cracking processes,
It has now been found that it reduces the likelihood of coke formation, which tends to reduce the stability of the catalyst. Decomposition of the olefin is performed at 500 to 600 ° C, more preferably at 520 to 600 ° C.
It is carried out at a feed inlet temperature of the raw material of 00C, even more preferably 540-580C, typically about 560-570C.

The catalytic cracking process can be carried out in a fixed-bed, moving-bed or fluidized-bed reactor. A typical fluidized bed reactor is a F.sub.2 used for fluidized bed catalytic cracking in a refinery.
It is one of the CC types. Typical moving bed reactors are of the continuous catalytic reforming type. As noted above, the process can be run continuously using a pair of parallel "swing" reactors.

The catalyst may be used for a long period, typically at least about 10
The frequency of catalyst regeneration is low due to the high stability to olefin conversion for one day. Thus, more particularly, the catalyst may have a lifetime of more than one year.

After the catalytic cracking process, the reactor effluent is sent to a rectifier where the desired olefin is separated from the effluent. If catalytic cracking process is employed for the production of propylene, C ₃ fraction containing at least 93% propylene are rectified, then sulfur species is purified to remove all contaminants such as arsine. Olefin C ₃ larger more heavy can be recycled.

According to various aspects of the present invention, not only can a wide variety of different olefinic feedstocks be used in the cracking process, but also the effluent obtained by appropriate choice of process conditions and the particular catalyst used. The olefin conversion process can be controlled so as to selectively provide a particular olefin distribution in.

For example, according to a first aspect of the present invention, an olefin-rich stream from a refinery or petrochemical plant is cracked into light olefins, especially propylene. Light fraction of the effluent, namely C ₂ and C ₃ cuts, can contain more than 95% olefins. Such a cut is pure enough to constitute a chemical grade olefin feed. The present inventors have such propylene olefin basis yield in the process is in the range of 30-50% based on the olefin content of the feed containing C ₄ or greater of one or more olefins I found what was possible. In that process, the effluent has a different olefin distribution as compared to the feed olefin distribution, but has substantially the same total olefin content.

In yet another embodiment, the process of the present invention produces C ₂ -C ₃ olefins from C ₅ olefinic feedstocks. The catalyst is of a crystalline silicate having a silicon / aluminum ratio of at least 300 and the process conditions are 500-600 ° C. inlet temperature, 0.1-2 bar olefin partial pressure and 1 LHSV per 10-30 hours. There, at least 40 present as C ₂ -C ₃ olefins
This gives an olefinic effluent having a% olefin content.

Another preferred embodiment of the present invention provides a process for the production of C ₂ -C ₃ olefins from light cracked naphtha. The light cracked naphtha is contacted with a crystalline silicate catalyst having a silicon / aluminum ratio of at least 300 and at least 40% of the olefin content is C _2-
Obtained by decomposing olefinic effluent present as C ₃ olefins. In this method, the process conditions are between 500 and
Includes an inlet temperature of 600 ° C., an olefin partial pressure of 0.1 to 2 bar and 1 LHSV per 10 to 30 hours.

[0050] Various aspects of the invention are illustrated below with reference to the following non-limiting examples.

[0051]

EXAMPLE 1 In this example, a feed containing 1-hexene was charged via a reactor at an inlet temperature of about 580 DEG C., an outlet hydrocarbon pressure of atmospheric pressure and 1 LHSV per 25 hours via a CUChem reactor.
ie Ueticon AG of Switcher
and supplied on a commercially available ZSM-5 type catalyst under the trade name of ZEOCAT P2-2 from the company and. Commercially available catalysts are produced by crystallization using an organic template and have not been subjected to a subsequent steaming or de-aluminum process. The catalysts are 50, 200, 300 and 49
It had various silicon / aluminum atomic ratios of zero.
The crystal size of each catalyst was 2-5 microns and the pellet size was 35-45 mesh. Perform several experiments,
The effluent composition was examined for each experiment and various Si / Al
With respect to the value of the atomic ratio, the total of olefin, saturated compound and aromatic compound in the effluent is shown. The results of these experiments, obtained after 5 hours of operation, are shown in FIG. FIG. 1 shows the yield of propylene in the effluent, the percent conversion of the 1-hexene olefinic feed after the olefin catalytic cracking process of the present invention, and the sum of saturated compounds, olefins and aromatics in the effluent. . The purity of propylene in terms of the amount of propylene in the C ₃ species in the effluent was 70%, 91%, 93% and 97% for four experiments with increasing Si / Al atomic ratio.

For silicon / aluminum atomic ratios of about 200-300 in commercial catalysts, both the olefin yield in the effluent and the olefin base yield of propylene were below the desired values of 85% and 30%, respectively. . Propylene purity was also below the commercially typically desired value of 93%. This indicates that the steaming and de-alumination as well as the de-alumination require the Si / Al atomic ratio of the commercially available catalyst to be typically higher than 300. In contrast, when such steaming and de-aluminization processes are used, the resulting Si / Al ratio is determined by the desired olefin content in the effluent, the olefin base yield of propylene and the purity of propylene. Preferably, it is only higher than 180. At a Si / Al atomic ratio higher than about 300 in a commercially available catalyst that has not been pretreated by steaming and de-alumination, at least about 85% of the olefins in the feed are decomposed to olefins or Present as an olefin. Thus, at Si / Al atomic ratios higher than 300, the feed and the effluent have an olefin weight content substantially up to a range where the olefin weight content of the feed and the effluent is within ± 15% by weight of each other. Have inside. Further, with an Si / Al atomic ratio of at least about 300 in such commercially available untreated catalysts, the yield of propylene is at least about 30% by weight based on olefins.
It is. At an Si / Al atomic ratio of about 490 in such a commercially available untreated catalyst, the olefin content of the effluent is higher than about 90% by weight of the feedstock olefin content and the olefin yield of propylene is based on olefin. 40%
Reach

Example 2 In this example, a variety of different crystalline MFI-type silicates having different silicon / aluminum atomic ratios were used in the catalytic cracking of olefinic feedstocks. MFI silicates are zeolites of the ZSM-5 type, in particular PQ Corpora
Tion of Southpoint, P.M. O. Box
840, Valley Forge, PA 1948
2-0840, commercially available H from the USA company
-Includes zeolite sold commercially under the trade name ZSM-5. The crystalline silicate has a particle size of 35-45 mesh and has not been modified by pretreatment.

The crystalline silicate is charged into a reaction tube, and about 5
Heated to a temperature of 30 ° C. Thereafter, 1 gram of 1-hexene was injected into the reaction tube within 60 seconds. Injection rate is 2
It had a WHSV of 0 hour 1 and a catalyst to oil weight ratio of 3. The cracking process was carried out at an outlet hydrocarbon pressure of 1 bar (atmospheric pressure).

Table 1 shows the yields by weight of the various components in the resulting effluent and also the amount of coke formed on the catalyst in the reactor.

It can be seen that for crystalline silicates having a low Si / Al atomic ratio, a significant degree of coke is formed on the catalyst. This, when used in catalytic cracking for olefins, in turn leads to poor stability of the catalyst over time. In contrast, for example silicon as high as about 350 /
It can be seen that in the case of a crystalline silicate catalyst having an aluminum atomic ratio, no coke is formed on the catalyst, resulting in a high stability of the catalyst.

For a catalyst with a high Si / Al atomic ratio (350), the olefin based yield of propylene is about 28.8% in the effluent, and the propylene in two experiments using a low Si / Al atomic ratio It turns out that it is significantly higher than the yield.
Thus, it can be seen that the use of a catalyst having a high silicon / aluminum atomic ratio improves the olefin-based yield of propylene in the catalytic cracking of olefins to produce other olefins.

It has also been found that increasing the Si / Al atomic ratio reduces propane production.

COMPARATIVE EXAMPLES 1 AND 2 In these comparative examples, a commercially available silicalite catalyst which has not been subjected to a dealumination process by steaming and extraction is used in the catalytic cracking of a raw material containing butene. Was.

In the catalytic cracking process, the butene-containing feed had the composition specified in Tables 2a and 2b.

The catalytic cracking method uses an inlet temperature of 545 ° C., an outlet hydrocarbon pressure of atmospheric pressure, and 1 LSHV per 30 hours.
I went in.

Tables 2a and 2b show the reduction in the amount of propylene, iso-butene and n-butene present in the effluent.

For Comparative Example 1, the catalyst contained a silicalite having a silicon / aluminum ratio of about 120, a crystallite size of 4-6 microns and a surface area (BET) of 399 m ² / g. Compress silicalite, wash and 3
The 5-45 mesh fraction was retained. The catalyst has not been subjected to steaming and aluminization extraction. In the case of Comparative Example 2, the catalyst comprises the same starting silicalite as in Comparative Example 1, at a temperature of 550 ° C. and at atmospheric pressure.
It was subjected to a steaming method in an atmosphere of 72% by volume of steam and 28% by volume of nitrogen for 48 hours, but not to the aluminum extraction method. The results are shown in Tables 2a and 2b, respectively.

In the case of Comparative Examples 1 and 2, it can be seen that the catalyst did not show stability. In other words, over time, the catalyst has diminished in its ability to catalyze the cracking process. This appears to be due to the formation of coke on the catalyst, which itself results from using a low silicon / aluminum atomic ratio in the catalyst, resulting in relatively high acidity for the catalyst.

In the case of Comparative Example 1, there is also a significant production of paraffin, for example propane.

Example 3 In this example, a feed containing a 1-butene feed having the composition specified in Table 3 was obtained at an inlet temperature of about 560 ° C., an outlet hydrocarbon pressure of atmospheric pressure, and 1 LHS per 23 hours.
At V, it was fed via a reactor onto the same catalyst used in Example 1. The catalyst had a silicon / aluminum atomic ratio of 300 as in one of the catalysts used in Example 1. The catalyst is commercially available as in Example 1 and has been prepared by crystallization using an organic template and has not been subjected to the subsequent steaming or dealumination process. The crystal size and pellet size of each catalyst were as specified in Example 1. The composition of the effluent was checked after 40 hours of operation and after 112 hours of operation, and the results of the effluent analysis are shown in Table 3. Table 3 shows that catalysts having a silicon / aluminum atomic ratio of 300 have high stability with respect to selective catalytic cracking in the direction of propylene in the effluent. Thus, after 40 hours of operation, propylene constitutes 18.32% by weight in the effluent, and after 112 hours of operation, propylene comprises 1% of the effluent.
8.19% by weight. After 162 hours of operation, propylene constitutes 17.89% by weight of the effluent. This indicates that the propylene content in the effluent is not significantly reduced over a very long period of more than 3 days, up to about 5 days. The three day period is a recycle or regeneration period typically used in the case of two parallel fixed bed "swing" reactors. The results of Example 3 after the 112 and 162 hour periods can be compared to the results of Comparative Example 1 after the 97 and 169 hour periods, respectively. In the case of Comparative Example 1, the catalyst is reasonably stable over 97 hours and the decrease in propylene content in the effluent is about 1.1% compared to the original volume, but the stability is It dropped significantly between 97 hours and 169 hours, and not for the corresponding periods of 112 hours and 162 hours in Example 3.

Comparative Example 3 In this comparative example, a commercially available ZSM-5 catalyst having a silicon / aluminum atomic ratio of 25 was used in the catalytic cracking of a butene-containing feedstock. In the catalytic cracking process, the butene-containing feed had the composition specified in Table 4.

The catalytic cracking method employs an inlet temperature of 560 ° C., an outlet hydrocarbon pressure of atmospheric pressure, and 1 LHSV per 50 hours.
I went in.

The catalyst and process conditions, especially the high space velocities, were chosen to mimic the corresponding catalyst and conditions disclosed in EP-A-0 090 059 cited above.

The catalytic cracking process was carried out for almost 40 hours and the composition of the effluent was determined periodically after a continuous operating time (TOS). The effluent composition after the specified run-time is specified in Table 4 with the corresponding instructions for the degree of butene conversion.

From Table 4, low silicon / about 25 with high space velocities indicates that EP-A-0 090 059 is important for achieving high propylene yields.
When a ZSM-5 catalyst having an aluminum atomic ratio is used, the propylene yield is sufficiently high that about 16
% Propylene, which occurs after about 15-20 hours of operation, after which time the propylene yield is found to deteriorate rapidly. This is EP-A-01
It shows low catalyst stability when using a low silicon / aluminum atomic ratio together with a high space velocity as used in the method disclosed in 09059.

[0072]

[Table 1]

[0073]

[Table 2]

[0074]

[Table 3]

[0075]

[Table 4]

[0076]

[Table 5]

[0077]

[Table 6]

[0078]

[Table 7]

The main features and aspects of the present invention are as follows.

1. A process for the catalytic cracking of olefin-rich feedstocks with selectivity in the direction of light olefins in the effluent, comprising the step of reducing a hydrocarbon feedstock containing one or more olefins at an inlet temperature of 500-600 ° C. .1
Contact with an MFI-type crystalline silicate catalyst having a silicon / aluminum atomic ratio of at least about 300 at an olefin partial pressure of ２2 bar and an LHS of 1
V. Passing the feed over the catalyst at V to produce an effluent having a lower molecular weight olefin content than that of the feed.

2. The process of claim 1 wherein the catalyst is produced by crystallization using an organic template and has not been subjected to a subsequent steaming or dealumination process.

3. The above 2 wherein the catalyst comprises a ZSM-5 type catalyst
The method described in the section.

4. Silicon / aluminum atomic ratio of 300
Item 4. The method according to any one of Items 1 to 3, above.

5. The method according to any one of the above 1 to 4, wherein the raw material contains a C ₄ -C ₁₀ hydrocarbons.

6. 6. The method according to any of the preceding claims, wherein the effluent is rich in propylene.

7. Propylene is present in the effluent C ₃
7. The method of claim 6, wherein the method comprises at least 93% of the compound.

8. 8. The process according to claim 6 or 7, wherein the catalytic cracking has a propylene-based yield of propylene of 30 to 50% based on the olefin content of the raw material.

9. 9. The method according to any one of the above items 1 to 8, wherein the olefin content by weight of the raw material and the effluent is within ± 15% of each other.

10. Item 10. The method according to any one of Items 1 to 9, wherein the inlet temperature is 540 to 580 ° C.

[Brief description of the drawings]

FIG. 1 shows the amount of olefin feed conversion, propylene yield and the sum of other components and silicon /
2 shows the relationship between aluminum atomic ratios.

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Jacques-François Grootzyan Belgium B-3061 Leafdar Ney Lillesteinbeek 39 (72) Inventor Xavier Van Aeran Belgium B-1332 Jianbal View Choumandlerup 63 ( 72) Inventor Walter Vermeilen Belgium B-3530 Outalen Winningstraat 4

Claims (1)

[Claims] 1. A process for catalytically cracking an olefin-rich feedstock having selectivity in the direction of light olefins in an effluent, comprising the steps of: At the inlet temperature, 0.1 ~
Contacting with an MFI-type crystalline silicate catalyst having a silicon / aluminum atomic ratio of at least about 300 at an olefin partial pressure of 2 bar and 1 LHSV per 10-30 hours
Passing the feed over the catalyst in to produce an effluent having a lower molecular weight olefin content than that of the feed.