CN1281722C - Catalytic conversion method for preparing light olefins by using C4-C6 distillates - Google Patents

Abstract

The present invention relates to a catalytic conversion method for producing alkene with light weight by fractions of C4 to C6. Gaseous hydrocarbon with rich C4 fractions injected in a first cracking reactor separately or with light gasoline fractions to contact and react with catalysts in the first cracking reactor, reaction products and catalysts after reaction are separated, C4 fractions or C4 fractions in products and light gasoline fractions are injected in an oligomerization reactor to contact and react with oligomerization catalysts in the oligomerization reactor, C4 fraction and fractions above C4 with rich paraffin hydrocarbon are separated in oligomerization products, C4 fractions return back to the first cracking reactor, fractions above C4 are injected in a second cracking reactor to contact and react with catalysts in the second cracking reactor, and obtained reaction products and catalysts to be generated are separated. The reaction products are further divided into products for various purposes, catalysts to be generated is recycled after stripped and regenerated. The method provides a feasible technical scheme for increasing low-carbon alkene in yield by effectively utilizing C4 fractions.

Description

Catalytic conversion method for producing light olefins from C4-C6 fractions

technical field

The invention belongs to a method for catalytic conversion of petroleum hydrocarbons in the absence of hydrogen, more specifically, a catalytic conversion method for producing light olefins by using C4-C6 fractions.

Background technique

Small molecule olefins such as ethylene, propylene and butene are the most basic raw materials for organic synthesis. At present, the production of small molecular olefins in the world mainly adopts steam cracking method, but because the high-temperature cracking furnace is easy to coke, the steam cracking device is only suitable for processing light raw material oil, such as natural gas, naphtha and light diesel oil, and also produces by-products A certain amount of aromatic hydrocarbons. The development of technologies to produce light olefins such as ethylene and propylene by using low value-added olefins, such as C4-C7 olefins, can greatly increase the production of light olefins while further broadening the source of raw materials for the production of light olefins.

At present, the technologies for producing propylene with C4 and above C4 olefin fractions as raw materials mainly include olefin disproportionation and catalytic cracking. Olefin disproportionation, also known as olefin metathesis or metathesis reaction. It is a catalytic reaction through the cleavage of olefinic carbon-carbon double bonds and regeneration of new olefinic products. Phillips Petroleum Company first developed the olefin disproportionation technology (Oiefins Conversion Technology, referred to as OCT), the French Petroleum Research Institute (IFP) and Taiwan CNPC also jointly developed a new olefin disproportionation process called "Meta-4", and completed the China Test certificate. After the 1990s, BASF has developed a new disproportionation process for the production of propylene that hardly requires additional ethylene. In addition, Sasol Company of South Africa has also developed a process for producing propylene by disproportionation of butene.

The technologies for producing propylene by catalytic cracking of C4 and above olefins can be roughly divided into two categories, one is fixed bed process and the other is fluidized bed process. In the fluidized bed process represented by KBR's Superflex process and Mobil's MOI technology, the catalyst used is ZSM-5. The Superflex process is aimed at increasing the production of propylene, processing the thermally cracked C4 fraction after selective hydrotreating, and can obtain a propylene yield of more than 40%. Mobil Corporation is developing an MOI process for increasing propylene production in steam cracking and FCC units, that is, using ZSM-5 catalyst to convert the by-product C4 fraction and light pyrolysis gasoline of steam cracking into propylene and ethylene, and at the same time Can convert refinery undesirable gasoline components, for example, light cracked naphtha, to propylene.

There are also many domestic units are carrying out research work in this area. However, all of the above-mentioned process technologies have not been industrialized.

EP109059 discloses a catalytic conversion method for producing propylene from C4-C12 olefins. The method is to contact and react olefin raw material with aluminosilicate catalyst to produce propylene under the conditions of reaction temperature 400-600 DEG C and reaction weight hourly space velocity (for molecular sieve weight in catalyst) greater than 50h ^-1 . The aluminosilicate catalysts are preferably ZSM-5 and ZSM-11, the molar ratio of SiO ₂ /Al ₂ O ₃ is equal to or less than 300. The catalyst can be modified by Mg, Ca, Sr, Ba, P, Cr, Cu and other metals. At the same time, it is proposed that the C4 fraction containing alkane components can be easily separated from the olefin oligomerization products through the oligomerization reaction between olefins, and then the olefin oligomerization products are cracked to produce light olefins such as propylene. The oligomerization catalysts are HZSM-5 and HZSM-11 or their modified products. The oligomerization conditions are reaction temperature 250-400°C, reaction weight hourly space velocity (relative to the molecular sieve weight in the catalyst, excluding adhesive) 2-10h ^-1 .

EP0109060 discloses a catalytic conversion method for producing propylene from C4-C12 olefins. Among them, the olefin raw material is mixed with ^{aluminosilicate} , aluminosilicate, Borate, chromium silicate catalyst contact reaction to produce propylene. The aluminosilicate catalysts are preferably ZSM-5 and ZSM-11 with a SiO ₂ /Al ₂ O ₃ molar ratio of at least 350. The catalyst can also be modified by Mg, Ca, Sr, Ba, P, Cr and other metals. At the same time, it is proposed that the C4 fraction containing alkane components can be easily separated from the olefin oligomerization products through the oligomerization reaction between olefins, and then the olefin oligomerization products are cracked to produce light olefins such as propylene. The oligomerization catalysts are HZSM-5 and HZSM-11 or their modified products. The oligomerization conditions are reaction temperature 250-400°C, reaction weight hourly space velocity (relative to the molecular sieve weight in the catalyst, excluding adhesive) 2-10h ^-1 .

CN1360623A discloses a catalytic production method for producing light olefins rich in propylene. This method is by making the raw material containing C4-C7 olefin and/or alkane and containing the catalyst of ZSM-5 and/or ZSM-11 and phosphorus that initial silica/alumina ratio is greater than about 300:1 at a reaction temperature of 510 Light olefins are produced by contact reaction under the conditions of -704.4°C, reaction pressure of 0.1-8 bar, agent-oil ratio of 0.1-10 and weight hourly space velocity of 1-20h ^-1 .

CN1370216A discloses a catalytic conversion method for producing light olefins from naphtha raw materials. The invention is achieved by reacting C4 ⁺ naphtha hydrocarbon feedstock with catalysts containing ZSM-5 and/or ZSM-11, substantially inert matrix materials such as silica and/or clay and phosphorus at a reaction temperature of 510-704.4 °C, the reaction hydrocarbon partial pressure is 0.1-8 bar, the agent-oil ratio is 0.01-30 and the weight hourly space velocity is 1-20h ^-1 , and the contact reaction generates light olefins and aromatics. The substantially inert matrix material comprises less than about 20 weight percent active matrix material, based on the total catalyst composition.

USP6339181 discloses a multi-feed process for producing propylene. The invention uses a hydrocarbon feedstock stream containing C5 and C6 components, preferably naphtha, as a raw material to remove light components (mainly C5/C6 components) and feedstock streams with a boiling point range of 120 ° C or lower. The heavy components left after the components are injected into the multi-stage bed reactor at different positions for reaction. The catalysts used include mesoporous aluminosilicate and silicoaluminophosphate catalysts. Aluminosilicate catalysts mainly include ZSM-5, ZSM-11, ZSM-23, ZSM-48 and/or ZSM-22, while silicoaluminophosphate catalysts mainly include SAPO-11, RESAPO-11, SAPO-41 and/or or RE-SAPO-41.

In summary, although many methods for producing ethylene and propylene with light petroleum hydrocarbons as raw materials are disclosed in the prior art, they do not relate to how to effectively utilize C4 fractions while cracking C4-C6 olefins to produce light olefins The problem of catalytic conversion of alkanes in and alkane components in light gasoline fractions to produce light olefins.

Contents of the invention

The purpose of the present invention is to provide a method to effectively utilize the alkane in the C4 fraction and the alkane component in the light gasoline fraction to produce light olefins through catalytic conversion while cracking C4-C6 olefins to produce light olefins on the basis of the prior art. Alkenes method.

The method provided by the invention is: inject gaseous hydrocarbons and/or light gasoline fractions rich in C4 fractions into the first cracking reactor, contact and react with the catalyst therein, the reaction temperature is 650-720°C, and the catalyst and raw hydrocarbon The weight ratio is 1-200:1, the bed weight hourly space velocity is 0.1-30 hours ^-1 , the reaction product and the catalyst after the reaction are separated, and the C4 fraction or C4 residue in the reaction product is injected into the oligomerization with the light gasoline fraction In the reactor, contact with the oligomerization catalyst in it, and react under oligomerization reaction conditions; separate the C4 fraction rich in alkanes and the fraction above C4 from the obtained oligomerization product, and the C4 fraction rich in alkanes Return to the above-mentioned first cracking reactor for reaction, and inject the fraction above C4 into the second cracking reactor, contact and react with the catalyst therein, the reaction temperature is 500-680°C, and the weight ratio of catalyst to raw hydrocarbon is 1 -100:1, the bed weight hourly space velocity is 0.1-50 hours ^-1 , the reaction product obtained and the spent agent are separated, and the reaction product is further separated into various target products, and the spent agent is stripped and regenerated Recycle later.

Compared with the prior art, the beneficial effects of the present invention are mainly reflected in the following aspects:

1. Based on the relatively mature catalytic cracking technology, the present invention organically combines the catalytic conversion process with the oligomerization process, and uses low value-added C4-C6 olefin fractions as raw materials to produce light olefins, mainly ethylene and propylene.

2. The present invention introduces an oligomerization reactor between the two-stage cracking reactors for combination, so that the difficult-to-convert C4 alkane fraction in the second-stage cracking reactor can be easily separated, and the feed characteristics of the second cracking reactor are improved. , can effectively improve the cracking conversion efficiency of the second cracking reactor. The separated C4 alkane fraction can be returned to the first-stage cracking reactor for catalytic conversion under high-severity conditions, thereby increasing the overall effective conversion rate of raw materials.

3. The present invention can process gasoline fractions with an olefin content of 20-90% by weight, especially light gasoline fractions rich in C5-C6 olefin fractions, and is suitable for different types of catalysts with five-membered ring structure molecular sieves.

4. The present invention can process olefin-rich C4 hydrocarbon fractions produced by different processes.

5. The present invention has no special requirements on the impurity content in the raw material, so no pretreatment of the raw oil is required.

Detailed ways

About the cracking reaction part:

The gaseous hydrocarbons rich in C4 fractions in the present invention refer to low-molecular hydrocarbons that exist in the form of gases at normal temperature and pressure with C4 fractions as the main component, including alkanes, alkenes or alkynes below C4. It can be gaseous hydrocarbon products rich in C4 fractions from catalytic cracking units or catalytic cracking units, or gaseous hydrocarbons rich in C4 fractions produced by other refining or chemical processes. In the gaseous hydrocarbons rich in C4 fractions, the content of C4 olefins is greater than 40 wt%, preferably greater than 50 wt%, most preferably above 60 wt%.

The light gasoline fraction described in the present invention is selected from: gasoline fractions produced by catalytic cracking naphtha, catalytic cracking stable gasoline, catalytic cracking naphtha, catalytic cracking stable gasoline, coker gasoline, visbreaking gasoline and other refining or chemical processes One or more mixtures of: catalytic cracking naphtha, catalytic cracking stable gasoline, catalytic cracking naphtha, catalytic cracking stable gasoline, coker gasoline; more preferably: catalytic cracking Naphtha, catalytic cracking stabilized gasoline, catalytic cracking naphtha, catalytic cracking stabilized gasoline. The final boiling point of the light gasoline fraction is preferably lower than 120°C, preferably lower than 85°C. The C5-C6 olefin content in the light gasoline fraction is 20-95% by weight, preferably 25-90% by weight, and most preferably above 50% by weight.

The cracking catalyst used in the first and second cracking reactors of the present invention may be a conventional FCC catalyst, preferably a catalyst containing zeolite with a five-membered ring structure. The active component of the cracking catalyst is composed of ZSM-5 series zeolite or zeolite with five-membered ring structure and Y or HY type zeolite containing or not containing rare earth, super stable Y type zeolite containing or not containing rare earth, β zeolite, Composed of one or more mixtures of ferrierite and SAPO. The carrier of the cracking catalyst is a conventional FCC catalyst carrier, for example, alumina, silica, aluminum silicate, natural clay plus alumina, and the like.

In the method provided by the present invention, the cracking catalyst that is in contact with the gaseous hydrocarbons and light gasoline fractions rich in C4 cuts is selected from: one or more mixtures of regenerated catalysts, semi-regenerated catalysts, and spent catalysts, preferably regenerated catalyst.

In the method provided by the present invention, there is no special requirement for the structural type of the first cracking reactor and the second cracking reactor, they can adopt the conventional FCC reactor type, for example, moving bed reactor, fixed fluidized Bed reactors, riser reactors, etc. are all available; the preferred reactor type is: the first cracking reactor is a fixed fluidized bed reactor, and the second cracking reactor is a riser reactor. In addition, the first cracking reactor and the second cracking reactor of the present invention can also be different reaction sections of the riser reactor, for example, the first cracking reactor is the upstream section of the riser reactor, and the second cracking reactor The riser is the downstream section of the riser reactor.

The first cracking reactor and the second cracking reactor described in the present invention can be respectively connected with respective regenerators, or can share the same regenerator.

In the method provided by the present invention, the reaction conditions of the gaseous hydrocarbons rich in C4 fractions and/or light gasoline fractions in the first cracking reactor are as follows: the reaction temperature is 650-720°C, preferably 680-700°C; The weight ratio of the catalyst to the raw material hydrocarbon is 1-200:1, preferably 20-100:1, most preferably 20-60:1; the bed weight hourly space velocity is 0.1-30 hr ^-1 , preferably 0.5-5 hr ^-1 .

In the method provided by the present invention, the reaction conditions of the fraction above C4 in the second cracking reactor are as follows: the reaction temperature is 500-680°C, preferably 550-650°C; the weight ratio of catalyst to raw hydrocarbon is 1 -100:1, preferably 5-15:1; bed weight hourly space velocity of 0.1-50 hours ^-1 , preferably 1-30 hours ^-1 .

In the method provided by the present invention, the reaction pressure of the first cracking reactor and the second cracking reactor is normal pressure-450 kPa, preferably normal pressure-300 kPa. During the cracking reaction, the weight ratio of water vapor to feedstock hydrocarbon is 0-0.50:1, preferably 0.01-0.25:1.

About the oligomerization section:

In the method provided by the present invention, the C4 fraction or the C4 fraction and the light gasoline fraction from the first cracking reactor are injected into the oligomerization reactor, contacted with the oligomerization catalyst therein, and react under oligomerization conditions. When the C4 fraction from the first cracking reactor is injected into the oligomerization reactor together with the light gasoline fraction for reaction, the molar ratio of the light gasoline fraction to the C4 fraction is 1-5:1, preferably 1-2:1.

In the method provided by the present invention, the oligomerization reactor is selected from any one of fixed bed, moving bed or fluidized bed, preferably: fixed bed reactor or fluidized bed reactor. The oligomerization reactor preferably adopts a structure of two or more stages, and the temperature of the bed is adjusted with steam.

In the method provided by the present invention, the oligomerization reaction conditions are as follows: the reaction operating pressure is 0.5-5.0Mpa, preferably 1.0-4.0Mpa; the reaction temperature is 150-400°C, preferably 190-360°C; the reaction weight hourly space velocity is 0.5-5.0h ^-1 , preferably 1-4h ^-1 .

In the method provided by the present invention, the oligomerization catalyst may be a molecular sieve catalyst containing a five-membered ring structure (MFI). The molecular sieve of the five-membered ring structure includes ZRP, ZSP, ZSM-11, ZSM-12, ZSM-22, ZSM-23, ZSM-35 and ZSM-48, etc., and its silicon-aluminum molar ratio is ≥25:1, preferably ≥ 70:1, the pore size is about 5-7 Ȧ, and the catalyst can be modified by one or more of metals such as Mg, Ca, Sr, Ba, P, Cr, and Cu.

In the method provided by the present invention, the formulation and properties of the oligomerization catalyst may be different from the cracking catalyst, or the same cracking catalyst used in the first and second cracking reactors. When using the same cracking catalyst as the first and second cracking reactors, the oligomerization can share the regenerator of the cracking reaction section. When a catalyst different from that of the first and second cracking reactors is used, the regeneration of the reacted oligomerization catalyst is preferably in a separate regenerator.

The method provided by the present invention will be further described by enumerating two specific implementations below in conjunction with the accompanying drawings, but the present invention is not limited thereto.

The first implementation is as follows: as shown in Figure 1, the C4 fraction enters the bottom of the first-stage cracking reactor A through the pipeline 1, mixes with the regenerated catalyst from the regenerated inclined pipe 12, and reacts. After the reacted oil agent mixture is separated from oil and agent, the spent agent can be stripped and returned to the regenerator D for charring regeneration (the corresponding pipeline is not marked in the figure), and the regenerated agent can be returned to the first cracking reactor for recycling . The spent agent can also directly enter the second cracking reactor to participate in the reaction. And the first cracked product enters the cracked product separation equipment E through pipeline 7 for separation, reclaims high-value low-carbon olefins such as ethylene and propylene, and the C4 fraction and/or light gasoline fraction therein are drawn through pipeline 10 as all or part of the The oligomerization reaction raw material is injected into the oligomerization reactor C after being mixed with another stream of light gasoline fraction or C4 fraction from outside the reaction system of the present invention through the pipeline 3. The oligomerization product enters the oligomerization product separation device F through the pipeline 4, and the C4 fraction rich in alkanes and the fraction above C4 rich in olefins can be obtained through conventional separation. The reacted catalyst can be recycled after regeneration (the regeneration system is not shown in the figure). The C4 fraction rich in alkanes is drawn out through the pipeline 6 and mixed with the gaseous hydrocarbons of the C4 fraction rich in the pipeline 1, and enters the first cracking reactor A to continue the reaction. The fraction above C4 is led out through the pipeline 5 into the second cracking reactor B, and contacts and reacts with the catalyst in it. In the second cracking reactor B, the fraction above C4 can be contacted with the reacted spent agent from the first cracking reactor, or can be contacted and reacted with the regeneration agent drawn through the regeneration inclined pipe 13, or can be contacted with the regeneration agent from the second cracking reactor B. The reacted spent agent in a cracking reactor contacts and reacts with the mixture of the regenerated agent drawn through the regeneration inclined pipe 13 . After the reacted oil agent mixture is separated from the oil agent, the spent agent is stripped and then returned to the regenerator D through the inclined pipe 14 of the spent agent to be burnt for regeneration, and the regenerated catalyst is recycled. The cracked product of the second cracking reactor enters the cracked product separation equipment E through pipeline 8, and is separated with the cracked product of the first cracking reactor to recover high-value low-carbon olefins such as ethylene and propylene, and its products such as dry gas, gasoline, The recovery of diesel oil, etc. is the same as the conventional FCC process. The C4 cut and/or the light gasoline cut in the product are drawn by pipeline 10, as all or part of the oligomerization raw material, and are mixed with another stream of light gasoline cut or C4 cut from outside the reaction system of the present invention by pipeline 3 Post-inject into oligomerization reactor C.

The second embodiment is as follows: as shown in Figure 2, the C4 fraction is firstly injected into the upstream of the first cracking reactor through the pipeline 2, and contacts and reacts with the regenerated catalyst from the regenerator. The light gasoline fraction rich in C5-C6 olefins is injected into the first cracking reactor downstream of the injection point of the above-mentioned C4 fraction, and contacts and reacts with the mixture formed by the C4 fraction and the regeneration agent. The feeding order of the C4 fraction and the light gasoline fraction rich in C5-C6 olefins is vice versa, that is, the light gasoline fraction rich in C5-C6 olefins is first injected into the upstream of the first cracking reactor through pipeline 2, and the The regenerated catalyst of the reactor contacts and reacts, and the C4 fraction is injected into the first cracking reactor downstream of the injection point of the light gasoline fraction rich in C5-C6 olefins, and contacts and reacts with the mixture formed by the light gasoline fraction and the regeneration agent. The two different feeding methods can make the second feed to deposit an appropriate amount of coke on the regenerant before contacting the catalyst to change the properties of the catalyst, which is beneficial to improve product distribution. After the oil agent mixture reacted in the above-mentioned first cracking reactor is separated from the oil agent, the spent agent can be stripped and returned to the regenerator D for burning and regenerated (the corresponding pipeline is not marked in the figure), and the regenerated agent is returned to the first cracking reactor. The first-stage cracking reactor is recycled; the spent agent can also directly enter the second-stage cracking reactor to participate in the reaction. And the first cracked product enters the cracked product separation equipment E through pipeline 7 for separation, reclaims high-value low-carbon olefins such as ethylene and propylene, and the C4 fraction and/or light gasoline fraction therein are drawn through pipeline 10 as all or part of the The oligomerization reaction raw material is injected into the oligomerization reactor C after being mixed with another stream of light gasoline fraction or C4 fraction from outside the reaction system of the present invention through the pipeline 3. The oligomerization reaction product enters the oligomerization product separation device F through the pipeline 4, and a C4 fraction rich in alkanes and a fraction above C4 rich in olefins can be obtained by using a conventional separation method, for example, using a fractionation tower. The reacted catalyst can be recycled after regeneration (the regeneration system is not marked in the figure). The C4 fraction rich in alkanes is drawn out through the pipeline 6, mixed with the C4 fraction in the pipeline 1, and enters the first cracking reactor A to continue the reaction. The fraction above C4 is drawn into the second cracking reactor B through the pipeline 5. In the second cracking reactor B, the fraction above C4 rich in olefins can contact and react with the reacted spent agent from the first cracking reactor, and can also contact and react with the regenerated agent introduced through the regeneration inclined pipe 13 , can also contact and react with the mixture of the reacted spent agent from the first cracking reactor and the regenerated agent introduced through the regeneration inclined pipe 13. After the reacted oil agent mixture is separated from oil and agent, the spent agent is stripped and returned to the regenerator D through the inclined pipe 14 of the spent agent to burn and regenerated, and the regenerated agent is recycled. The cracked product enters the cracked product separation equipment E through the pipeline 8 for separation, recovers high-value low-carbon olefins such as ethylene and propylene, and draws the C4 fraction and/or light gasoline fraction in it through the pipeline 10 as a whole or partial oligomerization reaction raw material, and inject oligomerization reactor C after being mixed with another stream of light gasoline cut or C4 cut from outside the reaction system of the present invention through pipeline 3. The recovery of other products, including dry gas, gasoline, diesel oil, etc., is the same as the conventional catalytic cracking process.

The following examples will further illustrate the present invention, but do not limit the present invention thereby. The properties of catalysts and raw materials used in the examples are listed in Table 1 and Table 2 respectively. The catalysts in Table 1 are industrially produced by the Catalyst Factory of Qilu Petrochemical Company, China Petrochemical Corporation, and the brand name is CIP.

Example 1

This example illustrates the case of using gaseous hydrocarbons rich in C4 fractions as raw materials and using a CIP catalyst to conduct a single-pass catalytic conversion test under relatively high severity conditions in a small fluidized bed reactor.

As shown in Table 3, the gaseous hydrocarbons rich in C4 cuts enter the fluidized bed reactor, and the reaction temperature is 650-680 ° C, the pressure at the top of the reactor is 200 kPa, and the water-hydrocarbon mass ratio is 0.08:1. Contact and react with catalyst. The reaction product, steam and spent agent are separated in the settler, and the reaction product is separated to obtain gaseous product and liquid product, while the spent agent is stripped by water vapor to remove the hydrocarbon products adsorbed on the spent agent. The stripped spent catalyst is contacted with heated hot air for regeneration, and the regenerated catalyst is then subjected to a new catalytic conversion reaction. The test conditions and main test results are shown in Table 3.

It can be seen from the test results in Table 3 that the C4 gaseous hydrocarbons can convert the alkane components in the C4 fraction under relatively high severity conditions (reaction temperature is 680° C.). Taking the C4 distillate raw material in the comparative example as a benchmark, the maximum single-pass apparent conversion rate of C4 alkane within the experimental research range is 11.86% by weight, wherein n-butane is easier to convert than isobutane, and the maximum single-pass apparent conversion rate of isobutane is 12.99% by weight. The olefin components in C4 are easier to convert than the alkane components. Within the scope of experimental research, the maximum single-pass apparent conversion rate is 55.84% by weight. Among the four main C4 olefin components, the order of apparent conversion strength is: butene -1 > isobutene > cis-butene-2 > trans-butene-2. When the reaction severity decreases (for example, the reaction temperature is 650°C), the apparent one-pass conversion rate of the alkane components in the C4 fraction is negative, indicating that the amount of alkane in the cracked product is higher than that of the raw material, indicating that the reaction conditions of low severity It is not conducive to the conversion of alkane components.

From the point of view of product distribution, when the reaction severity was higher (experiment A: 680° C. of reaction temperature, agent-oil ratio 40), the single-pass apparent conversion rate of total alkane components was 11.86% by weight, which was more moderate than the reaction severity (experiment D: The reaction temperature is 650°C, the solvent-oil ratio is higher than -5.00% by weight of 20), the yields of ethylene and propylene in experiment A are 5.37% by weight and 14.30% by weight respectively, and the yields of propylene higher than experiment D are 2.28 and 1.15% At the same time, the concentration of hydrogen in the cracked gas is also higher than that in Experiment D, indicating that under relatively suitable high-severity reaction conditions, the alkane components in the C4 fraction can be effectively converted into the target product light olefins through catalytic dehydrogenation and other reactions. : Ethylene and Propylene.

Example 2

This example illustrates the case of carrying out a catalytic conversion test in a small fluidized bed reactor using a CIP catalyst with combined feed of gaseous hydrocarbons rich in C4 fractions and light gasoline fractions.

As shown in Table 3, the gaseous hydrocarbons rich in C4 fractions first enter the fluidized bed reactor, and contact and react with the CIP catalyst at a reaction temperature of 680 ° C, so that an appropriate amount of coke is formed on the catalyst, and the catalyst is not decomposed. Charred regeneration, and continue to feed the light gasoline fraction shown in Table 2 and continue to contact with the catalyst for reaction. The reaction product, steam and spent agent are separated in the settler, and the reaction product is separated to obtain gaseous product and liquid product, while the spent agent is stripped by water vapor to remove the hydrocarbon products adsorbed on the spent agent. The stripped spent catalyst is regenerated by contacting with heated hot air, and the regenerated catalyst undergoes a new catalytic conversion reaction. The test conditions and main test results are shown in Table 4.

When the gaseous hydrocarbons and light gasoline fractions rich in C4 cuts are combined and fed according to the above method, under the substantially same operating conditions as in Comparative Example 2, the product propylene is 4.54g, an increase of 21.39% compared with Comparative Example 1, and the product Compared with the pure gasoline reaction, the distribution is significantly improved, and the dry gas and coke yields are both reduced.

Comparative example 1

This comparative example illustrates: when the feed is not combined with gaseous hydrocarbons rich in C4 fractions, only the same light gasoline raw material, catalyst, and operating conditions as in Example 2 are used to carry out the catalytic conversion test results.

Gasoline, as shown in Table 2, was injected into the fluidized bed reactor and contacted and reacted with the CIP catalyst at a reaction temperature of 680°C. The reaction product, steam and spent agent are separated in the settler, and the reaction product is separated to obtain gas product and liquid product, while the spent agent catalyst is stripped of the hydrocarbon product adsorbed on the spent agent by water vapor. The stripped spent catalyst is regenerated by contacting with heated hot air, and the regenerated catalyst undergoes a new catalytic conversion reaction. The test conditions and main test results are shown in Table 4.

It can be seen from the test results in Table 4 that the product propylene is 3.74g when the reaction temperature of gasoline is 680°C, which is 0.8g less than that in Example 2. Simultaneously, the yields of dry gas and coke in the product are as high as 25.80% by weight and 6.69% by weight respectively, far less than ideal product distribution in Example 2.

Example 3

This example illustrates the oligomerization of gaseous hydrocarbons rich in C4 fractions in a down-flow fixed-bed reactor.

The test device is a descending fixed bed, the maximum bed height can reach 50cm, the bed diameter is 2.2cm, and the catalyst storage capacity can be 50-100g. The catalyst is a high-silicon-aluminum-ratio molecular sieve with a five-membered ring (MFI) structure, and its specific preparation method is as described in Example 1 of CN1072032C. According to the dry basis weight ratio of molecular sieve: aluminum sol (calculated as _Al2O3 ): kaolin (produced in Suzhou, China) = _35:15:50 , extrude into trefoil-shaped strips on the extruder, crush after drying, Sieve, get 100g and pack into a fixed-bed reactor for experimentation. In the experiment, when the gauge pressure of the system was 4.0MPa and the temperature was operated in the range of 190-260°C, the oligomerized _C4 raw material was oligomerized at a weight hourly space velocity of 0.256h ^-1 , and the components above _C5 in the reaction product could reach 62.9% by weight, of which the diesel fraction Accounting for 4.1% by weight, the total liquid yield is about 38.8% by weight, and the conversion rate of olefins reaches 46.6% by weight.

Typical liquid product PONA values are shown in Table 5. The results show that the reaction products are mainly C ₇ and C ₈ , and mainly olefins, while C ₉ ~ C ₁₃ products are few, indicating that the reaction process is dominated by dimerization. A small amount of diesel fraction may be produced by dimerization of C ₇ and C ₈ .

Table 6 lists the composition analysis results of C ₄ oligomerization tail gas. The oligomerization temperatures corresponding to tail gas 01 and tail gas 02 are 190°C and 220°C respectively, and other operating conditions are the same. It can be seen that the content of propane and butane does not change much, and the content of cis and trans-butene-2 does not change much, indicating that the reactivity of alkanes and these two alkenes is not large. The content of butene-1 and isobutene in the tail gas is significantly lower than that in the raw material, which proves that these two olefins can undergo significant oligomerization and be converted into hydrocarbons with high carbon number, while C4 alkanes are less involved in the conversion, which can be The low-carbon C4 alkane fraction can be removed by simple cooling and separation of the alignment polymerization product.

Comparative example 2

This comparative example illustrates: when using petroleum hydrocarbons rich in C4 fractions as a raw material, only using the same catalyst as in Example 4, and performing single-pass catalytic conversion to produce light olefins under milder operating conditions.

As shown in Table 3, the C4 fraction was injected into the fluidized bed reactor and contacted and reacted with the CIP catalyst under the conditions of a reaction temperature of 650° C., a reactor top pressure of 200 kPa, and a water-to-hydrocarbon mass ratio of 0.10:1. The reaction product, steam and spent agent are separated in the settler, and the reaction product is separated to obtain gaseous product and liquid product, while the spent agent is stripped by water vapor to remove the hydrocarbon products adsorbed on the spent agent. The stripped spent catalyst is regenerated by contacting with heated hot air, and the regenerated catalyst undergoes a new catalytic conversion reaction. The test conditions and main test results are shown in Table 7.

As can be seen from the test results in Table 7, the C4 cuts have ethylene and propylene yields of 3.09% by weight and 13.15% by weight under milder operating conditions, and the volume ratio of propylene/total C3 cuts is 0.51, indicating that the C4 cuts Catalytic conversion to light olefins is less than ideal under milder operating conditions.

Example 4

This example illustrates: use light gasoline instead of oligomerization products of C4 fractionator (hydrocarbons rich in high carbon number olefins) as raw material, and use CIP catalyst to carry out single-pass catalysis under relatively mild operating conditions in a small fluidized bed reactor Experimental conversion to produce light olefins.

Gasoline enters the fluidized bed reactor as shown in Table 2, and the reaction temperature is 650 ° C and 550 ° C, the pressure at the top of the reactor is 200 kPa, and the water-hydrocarbon mass ratio is 0.10:1. . The reaction product, steam and spent agent are separated in the settler, and the reaction product is separated to obtain gaseous product and liquid product, while the spent agent is stripped by water vapor to remove the hydrocarbon products adsorbed on the spent agent. The stripped spent catalyst is regenerated by contacting with heated hot air, and the regenerated catalyst undergoes a new catalytic conversion reaction. The test conditions and main test results are shown in Table 7.

When light gasoline fractions with high carbon number (the number of carbon atoms in the molecule is greater than 4) and rich in olefins are used as raw materials, under the same operating conditions as in Comparative Example 4 (reaction temperature 650° C.), the yields of ethylene and propylene are 10.75% by weight and 26.38% by weight, which are respectively 2 times of the yields of ethylene and propylene in Comparative Example 4, and the volume ratio of its propylene/total C3 fraction is 0.89, much higher than that of Comparative Example 4. It shows that the production of light olefins from hydrocarbons rich in olefins with high carbon number is obviously better than the process of producing light olefins with C4 fraction as feedstock under milder operating conditions.

Changing the operation, such as lowering the reaction temperature to 550°C, and using light gasoline rich in olefins as the feedstock, the yields of ethylene and propylene can still reach 5.46% by weight and 18.16% by weight, while the yields of dry gas and coke are relatively high. Maximum reduction improves product distribution.

Table 1 catalyst brand CIP _{Chemical composition , % Fe2O3Al2O3Na2O} 0.6356.30.14 Physical properties Specific surface area, m ² /g pore volume, ml/g apparent bulk density, g/cm ³ 820.1370.86 Sieve, V%0～40μm40～80μm＞80μm 27.255.717.1 Microreactivity after aging treatment 62

Table 2 project gasoline Density (20℃), g/ ^cm3 0.6696 Mercaptan sulfur, μg/g 29 Diene value, gI ₂ /100g 1.0 Elemental composition, %CHS, mg/LN, mg/L 85.1814.4415211 PIONA*, weight % n-paraffins isoparaffins olefins of which C5+C6 olefins C5 olefins C6 olefins naphthenes aromatics 8.6912.2673.9167.80 (accounting for 91.73m% of total olefins) 45.2722.533.391.76 Distillation range, °C initial boiling point 10% 50% 90% final boiling point 3240486577

* Chromatography

table 3 raw material Gaseous hydrocarbons rich in C4 fractions catalyst CIP plan Raw material composition Example 1 Reaction temperature, ℃ Experiment number Agent oil specific space velocity, l/h 680 650 A B C D. 400.70 300.94 201.53 201.30 Material balance, m% dry gas liquefied gas C5 + gasoline coke total 13.4977.253.965.30100.00 12.6975.016.765.55100.00 11.2476.398.503.87100.00 6.7480.3610.142.76100.00 Total gas yield, weight % 90.74 87.70 87.63 87.10 Gas Composition, wt% Hydrogen Methane Ethylene Propane Propylene Isobutane n-Butane Butene-1 Isobutene Cis-Butene-2 Trans-Butene-2 Total C4 raw materials - 13.111.4014.357.6411.9126.8714.829.90100.00 1.296.591.075.9111.7215.7613.857.516.2315.248.606.23100.00 1.096.601.165.6212.1016.3314.767.586.0114.558.225.99100.00 0.945.691.155.0512.6017.7516.778.055.6413.057.695.62100.00 0.463.090.643.5514.6115.0918.148.376.3514.538.786.38100.00 Component Apparent Conversion Rate, wt% Isobutane n-Butane C4 Total Alkanes Butene-1 Isobutene Cis-Butene-2 Trans-Butene-2 C4 Total Olefins -12.42-10.80-11.86-48.53-47.34-42.90-9.26-48.13 -9.79-12.99-10.90-52.51-51.36-46.94-12.30-51.98 2.41-7.67-1.09-57.44-54.53-50.25-12.37-55.84 10.10-4.585.00-52.90-48.40-43.87-12.90-50.57 Propylene/total C3, v/v 0.57 0.57 0.58 0.51 Gas Yield, wt% Ethylene Yield Propylene Yield 5.3714.30 4.9314.32 4.4215.56 3.0913.15

Table 4 plan Example 2 Comparative example 1 Feed C4 raw material + gasoline gasoline Feed amount, g 7+15 15 catalyst CIP Reaction temperature, °C 680 680 Material balance, weight % (accounting for total feed amount) dry gas liquefied gas C5 + gasoline coke 21.7456.1516.905.21 25.8044.0723.446.69 total 100.00 100.00 Gas Composition, wt% Hydrogen Methane Ethylene Propane Propylene Isobutane n-Butane Butene-1 Isobutene Cis-Butene-2 Trans-Butene-2 Total 1.7710.253.0212.867.3426.508.094.204.4610.806.154.56100.00 1.6312.504.4718.333.8635.682.921.663.267.894.453.35100.00 Gas Yield, wt% Ethylene Yield Propylene Yield 10.0120.64 12.8124.93 Propylene production, g 4.54 3.74

table 5 plan Example 3 carbon number n-alkane Isoparaffin Olefin Naphthenic Aromatics total 3 0.00 0.00 0.44 0.00 0.00 0.44 4 4.69 5.03 31.05 0.00 0.00 40.77 5 0.14 0.47 1.70 0.00 0.00 2.31 6 0.26 0.17 0.95 0.06 0.00 1.44 7 0.10 0.28 16.63 0.74 0.01 17.76 8 1.87 5.54 24.74 2.57 0.03 34.75 9 0.04 0.27 0.10 0.03 0.60 1.04 10 0.03 0.06 0.66 0.09 0.38 1.22 11 0.01 0.15 0.10 0.01 0.02 0.29 12 0.00 0.00 0.00 0.00 0.00 0.00 13 0.00 0.00 0.00 0.00 0.00 0.00 total 7.14 11.97 76.37 3.50 1.04 100.02

Table 6 components raw material Exhaust 01 Exhaust 02 carbon dioxide 9.11 8.07 14.54 propane 13.2 13.33 18.23 Propylene 1.5 1.34 2.06 Isobutane 17.05 20.2 18.19 n-butane 6.47 6.82 5.76 Butene-1 10.78 8.52 6.72 Isobutylene 19.81 18.41 14.49 trans-butene-2 13.15 13.6 12 Butene-2 8.34 8.38 7.15 Isopentane 0.1 0.13 0 n-pentane 0.16 0.13 0.05 Total pentene 0.12 0.21 0.14 More than six carbons 0.21 0.8 0.67

Table 7 plan Comparative example 2 Example 4 raw material C4 fraction gasoline fraction catalyst CIP Reaction temperature, °C 650 650 550 Agent to oil ratio 20 20 20 air speed, l/h 1.3 1.3 0.9 Material balance, weight % dry gas liquefied gas C5 gasoline diesel coke total 6.7480.3610.140.002.76100.00 18.9949.4027.190.254.17100.00 7.1237.1452.100.682.96100.00 Gas Composition, wt% Hydrogen Methane Ethylene Propane Propylene Isobutane n-Butane Butene-1 Isobutene Cis-Butene-2 Trans-Butene-2 Total 0.463.090.643.5514.6115.0918.148.376.3514.538.786.38100.00 1.107.773.18l5.724.8738.575.232.653.688.395.043.80100.00 0.422.081.2612.335.5441.0410.582.523.8210.355.824.26100.00 Propylene/total C3, v/v 0.51 0.89 0.88 Gas Yield, wt% Ethylene Yield Propylene Yield 3.0913.15 10.7526.38 5.4618.16

Claims (23)

1. A catalytic conversion method utilizing C4-C6 cuts to produce light olefins is to inject gaseous hydrocarbons rich in C4 cuts and/or light gasoline cuts into the first cracking reactor, contact with the catalyst therein, react, react The temperature is 650-720°C, the weight ratio of the catalyst to the raw material hydrocarbon is 1-200:1, the bed layer weight hourly space velocity is 0.1-30 hours ^-1 , and the reaction product and the reacted catalyst are separated, and the C4 in the reaction product Distillate or C4 fraction and light gasoline fraction are injected into the oligomerization reactor, contact with the oligomerization catalyst in it, and react under oligomerization reaction conditions; from the obtained oligomerization products, the C4 fraction rich in alkanes and the C4 above The C4 fraction rich in alkanes is returned to the above-mentioned first cracking reactor for reaction, while the above-mentioned C4 fraction is injected into the second cracking reactor to contact and react with the catalyst therein, and the reaction temperature is 500-680 ℃, the weight ratio of the catalyst to the raw hydrocarbon is 1-100:1, and the bed weight hourly space velocity is 0.1-50 hours ^-1 , and the reaction product and the spent agent obtained are separated, and the reaction product is further separated for various purposes products, while the standby agent is recycled after being stripped and regenerated. 2. The method according to claim 1, characterized in that the gaseous hydrocarbons rich in C4 fractions include C4 and below C4 alkanes, alkenes or alkynes, wherein the content of C4 alkenes is at least greater than 40% by weight. 3. The method according to claim 1, wherein the light gasoline fraction is selected from the group consisting of: catalytic cracking naphtha, catalytic cracking stable gasoline, catalytic cracking naphtha, catalytic cracking stable gasoline, coking gasoline, visbreaking gasoline and One or more mixtures of gasoline fractions produced by other refining or chemical processes. 4. The method according to claim 3, wherein the light gasoline fraction is selected from one or more of: catalytic cracking naphtha, catalytic cracking stable gasoline, catalytic cracking naphtha, catalytic cracking stable gasoline mixture. 5. The method according to any one of claims 1, 3 or 4, characterized in that the end boiling point of the light gasoline fraction is less than 120°C, and the content of C5-C6 olefins therein is 20-95% by weight. 6. The method according to claim 5, characterized in that said light gasoline fraction has an end boiling point of less than 85°C and the content of C5-C6 olefins therein is 25-90% by weight. 7. A process according to claim 1, characterized in that the catalyst employed in said first and second cracking reactors contains a zeolite having a five-membered ring structure. 8. The method according to claim 1, characterized in that the catalyst in the first cracking reactor is a regenerated catalyst, and the catalyst in the second cracking reactor is selected from the group consisting of regenerated catalysts, semi-regenerated catalysts, spent catalysts One or more than one mixture. 9. The method according to claim 8, characterized in that the catalyst in the second cracking reactor is selected from the group consisting of regenerated catalyst, semi-regenerated catalyst, spent catalyst or a mixture of regenerated catalyst and spent catalyst. 10. The process according to claim 1, characterized in that said first cracking reactor is a fixed fluidized bed reactor and said second cracking reactor is a riser reactor. 11. The method according to claim 1, characterized in that the first cracking reactor and the second cracking reactor are different reaction sections of the same riser reactor, that is, the first cracking reactor is a part of the riser reactor The upstream section, the second cracking reactor is the downstream section of the riser reactor. 12. The method according to claim 1, characterized in that the reaction conditions of the gaseous hydrocarbons and/or light gasoline fractions rich in C4 fractions in the first cracking reactor are as follows: the reaction temperature is 680-700°C; the catalyst and the raw material The weight ratio of hydrocarbons is 20-100:1; the bed weight hourly space velocity is 0.5-5 hours ^-1 . 13. The method according to claim 1, characterized in that the reaction conditions of the fraction above C4 in the second cracking reactor are as follows: the reaction temperature is 550-650° C.; the weight ratio of catalyst to raw hydrocarbon is 5-15: 1; Bed weight hourly space velocity is 1-30 hours ^-1 . 14. The method according to any one of claims 1, 12 or 13, characterized in that the reaction pressure of the first cracking reactor and the second cracking reactor is normal pressure-450 kPa, and during the cracking reaction, water vapor The weight ratio to the feedstock hydrocarbon is 0-0.50:1. 15. The method according to claim 1, characterized in that when the C4 fraction from the first cracking reactor and the light gasoline fraction are injected into the oligomerization reactor for reaction, the molar ratio of the light gasoline fraction to the C4 fraction is 1-5:1. 16. The method according to claim 15, characterized in that the molar ratio of the light gasoline fraction to the C4 fraction is 1-2:1. 17. The method according to claim 1, characterized in that said oligomerization reactor is selected from any one of fixed bed, moving bed and fluidized bed. 18. Process according to claim 17, characterized in that said oligomerization reactor is selected from the group consisting of fixed bed reactors and fluidized bed reactors. 19. The method according to claim 17 or 18, characterized in that the oligomerization reactor adopts a structure of two or more stages, and the bed temperature is adjusted with steam. 20. The method according to claim 1, characterized in that the oligomerization reaction conditions are as follows: the reaction operating pressure is 0.5-5.0Mpa, the reaction temperature is 150-400°C, and the reaction weight hourly space velocity is 0.5-5.0h ^-1 . 21. The method according to claim 20, characterized in that the oligomerization reaction conditions are as follows: the reaction operating pressure is 1.0-4.0 Mpa, the reaction temperature is 190-360°C, and the reaction weight hourly space velocity is 1-4h ^-1 . 22. The process according to claim 1, characterized in that said oligomerization catalyst is a catalyst containing a molecular sieve with a five-membered ring structure. 23. The method according to claim 1, characterized in that the formulation and properties of the oligomerization catalyst are different from the cracking catalysts in the first and second cracking reactors, or different from the cracking catalysts in the first and second cracking reactors Same; when adopting the same cracking catalyst as the first and the second cracking reactor, the oligomerization catalyst share the regenerator of the cracking reaction part; The regeneration of the polymerization catalyst adopts a separate regenerator.

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