CN101233213B - Process for producing light olefins from a hydrocarbon feedstock - Google Patents

Abstract

A process for producing light olefins from a hydrocarbon feedstock is disclosed. The method is characterized by producing light olefins, particularly ethylene and propylene, from a hydrocarbon feedstock with high selectivity using a porous molecular sieve catalyst composed of a product obtained by evaporating water from a raw material mixture of a molecular sieve containing a framework of-Si-OH-Al-groups, a water-insoluble metal salt and a phosphate compound. According to the process of the present invention, light olefins can be selectively produced from a hydrocarbon feedstock, particularly a full boiling range naphtha, in high yield and high selectivity by using a specific catalyst having hydrothermal stability. In particular, the process of the present invention can maintain higher cracking activity at a lower reaction temperature than required in the conventional thermal cracking process for producing light olefins, thereby producing light olefins from hydrocarbon feedstocks with high selectivity and high conversion.

Description

Process for producing light olefins from hydrocarbon feedstocks

technical field

The present invention relates to a method for producing light olefins from hydrocarbon raw materials, and in particular, to a method for producing light olefins from hydrocarbon raw materials with high yield and high selectivity using a catalyst that can be used even in an atmosphere of high temperature and high humidity still has a relatively stable structure, so it maintains its catalytic activity for a long time and shows thermal stability.

Background technique

Olefins, especially light olefins such as ethylene and propylene, are widely used in the petrochemical industry.

These light olefins are usually produced by thermally cracking naphtha (steam cracking) in the presence of steam. In many areas, steam cracking technology is being improved to cope with high processing temperatures and reduced residence time, and to optimize energy efficiency. However, it is not easy to improve energy efficiency only by simple operation techniques, and currently, in the petrochemical industry, the energy required for the steam cracking process accounts for about 40% of the total energy demand. Therefore, in order to reduce environmental pollution and increase economic benefits, improved operating techniques that optimize energy, reduce raw material usage, minimize carbon dioxide emissions, and the like are required. Also, light naphtha is generally used as a raw material, but it is expensive compared with full-range naphtha described below, and thus, there is a limit to an increase in economic efficiency. In particular, in the currently used steam cracking technology, not only is it difficult to control the composition of olefins, but also the reaction temperature is 800-900°C, indicating that a large amount of heat energy is required. Therefore, it is necessary to improve the steam cracking technology.

In addition, light olefins can also be produced by fluid catalytic cracking (FCC) processes. The FCC process is a catalytic cracking technique known in the art using a catalyst in the form of fine particles that behave like a fluid when treated with steam. In particular, deep catalytic cracking (DCC) is known as a method developed by modifying the FCC process to increase the yield of olefins (mainly propylene) other than gasoline. In the FCC process, the present invention uses heavy fractions rather than full-range naphthas, such as vacuum residues, atmospheric residues or gaseous oils, as feedstock.

Regarding the production of olefins, in addition to the aforementioned steam cracking and FCC methods, an olefin conversion method using catalytic cracking has also been proposed. Among these methods, HZSM-5 catalyst is widely used as solid acid catalyst in most of them. However, in a conventional catalytic cracking process using a solid acid catalyst, the reaction temperature is usually at least 650°C, and at least 30% of the reaction feedstock is steam. A problem with porous solid acid catalysts such as zeolites used in these catalytic cracking methods is that, when the catalyst is placed in a steam atmosphere exceeding 500°C, dealumination of its tetrahedral framework occurs, causing its structure to collapse, And at the same time, the acid sites of the solid acid catalyst will be reduced, so that the activity and reactivity of the catalyst will decrease rapidly.

Therefore, in the above-mentioned conventional light olefin production methods including the catalytic cracking method, researches on reducing catalyst instability are being actively conducted, and thereby reducing reduction in process performance.

Regarding these studies, US Patent No. 6,867,341 discloses a naphtha cracking catalyst obtained by controlling the distribution of aluminum atoms and the crystal size of zeolite, and a method of cracking naphtha using the catalyst. According to the disclosure of the patent, the catalyst is designed to chemically neutralize the aluminum existing outside the pores, thereby minimizing the generation of aromatic compounds on the surface of the pores, while the quantity and size of ethylene and propylene are small, which can By increasing the concentration of aluminum ions inside the pores to increase the number of acid sites, ethylene and propylene are more selectively produced. Meanwhile, as disclosed in said patent, when a ferrierite zeolite catalyst obtained by this technique is used for catalytic cracking, even under a rather severe operating environment, such as keeping the catalyst at 690°C, The catalyst still has excellent reactivity after 2 hours in a 50% steam atmosphere. However, with regard to the hydrothermal stability of the catalyst, it can be expected that the catalyst cannot maintain its structural stability and reactivity when the catalyst is treated in 100% steam at 750° C. for 24 hours.

U.S. Patent No. 6,835,863 discloses a method for preparing light olefins by catalytically cracking naphtha (boiling point: 27-221° C.) using a granular catalyst, wherein the catalyst contains 5-75% by weight of ZSM- 5 and/or ZSM-11, 25-95% by weight of silica or kaolin, and 0.5-10% by weight of phosphorus. However, the patent does not mention hydrothermal stability in harsh environments of high temperature and high humidity.

Japanese Patent Application Hei 6-192135 discloses a catalytic cracking method for preparing ethylene and propylene, which uses HZSM-5 and HZSM-11 catalysts (molar ratio of SiO ₂ /Al ₂ O ₃ : 150-300) at 620-750 Under the temperature of ℃ and the weight hourly space velocity (WHSV) of 1-200h ^-1 , light naphtha (density: 0.683g/cc; component: normal chain of 42.7% by weight) is composed of C _2-12 containing paraffin Alkanes, 36.1% by weight of isoparaffins, 0.1% by weight of olefins, 14.0% by weight of naphthenes, and 7.1% by weight of aromatics; the distribution of paraffin components is: 0.1% by weight of C ₃ , 5.2% by weight of C ₄ , 18.7 wt% _C5 , 19.0 wt% _{C6 ,} 15.2 wt% C7, 13.5 wt% _C8 , 6.1 wt% _C9 , 0.1 wt% _C10 and 0.1 wt% _C11 ) to produce ethylene and propylene. According to the disclosure of this patent, under the reaction conditions of 680° C. and a WHSV of 25 h ^-1 , a conversion rate of 93.6% by weight can be achieved, and the total yield of ethylene and propylene is 44.9% by weight. However, the HZSM-5 or HZSM-11 catalysts were used in the FCC reaction in a non-particulate state, and no steam or inert gas was provided during the reaction. Therefore, the catalyst has excellent initial activity but may be easily deactivated. Therefore, it can be expected that the reactivity of this catalyst will decrease significantly in the harsh environment of high temperature and high humidity.

Meanwhile, according to the report of Japanese Patent Application Laid-Open No. 6-199707, in a catalytic cracking process for producing ethylene and propylene as main products from light naphtha containing _C2-12 paraffins, a proton loaded with 100 ppm iron (Fe) is used The zeolite (SiO ₂ /Al ₂ O ₃ =20-500) catalyst enables the preparation of light olefins with good selectivity. Since no steam or inert gas is supplied during the reaction, the catalyst has excellent initial activity, but there is a possibility that the catalyst is easily deactivated in a high-temperature reaction in the presence of steam. Therefore, it can be expected that the reactivity of this catalyst will decrease significantly in the harsh environment of high temperature and high humidity.

Therefore, there is an urgent need to develop a method that maintains reactivity even in the harsh environment of high temperature and high humidity, so that the reaction raw materials, especially full-range naphtha, can be synthesized at high conversion and high selectivity. Selectively produces light olefins such as ethylene and propylene.

Contents of the invention

Therefore, in order to solve the above-mentioned problems in the prior art, the inventors of the present invention conducted extensive research and found that when a specific catalyst having excellent hydrothermal stability is used, even in a severe operating environment, the Light olefins can be produced from hydrocarbon feedstocks in high selectivity and high yield without loss of catalyst reactivity. Based on this fact, the present invention has been accomplished.

Accordingly, it is an object of the present invention to provide a process for selectively producing light olefins such as ethylene and propylene, by which, even in a harsh environment of high temperature and high humidity, it is possible to produce Using naphtha as raw material, light olefins such as ethylene and propylene can be selectively prepared under high selectivity and high yield.

Another object of the present invention is to provide a process in which high cracking activity is maintained even at lower reaction temperatures than those required by existing thermal cracking processes for producing light olefins, so that hydrocarbons can be produced from Raw materials are produced with high selectivity and high conversion to light olefins.

In order to achieve the above object, the present invention provides a method for preparing light olefins from hydrocarbon feedstock, the method comprising the following steps: (a) providing a hydrocarbon fraction as a feedstock; (b) feeding the feedstock to at least one fixed-bed or fluidized-bed reaction a reactor in which the reaction is carried out in the presence of a catalyst; and (c) separating and recovering light olefins from the effluent of the reaction zone; wherein the catalyst consists of a product obtained by evaporating water from a raw material mixture Composition, the raw material mixture contains 100 parts by weight of molecular sieve with -Si-OH-Al-group skeleton, 0.01-5.0 parts by weight of water-insoluble metal salt and 0.05-17.0 parts by weight of phosphate compound.

In the method of the present invention, the feedstock is preferably full range naphtha or kerosene, more preferably naphtha containing _C2-15 hydrocarbons.

Preferably, the total content of paraffin components (normal paraffins and isoparaffins) in the full-range naphtha is 60-90% by weight, and the content of olefins in the naphtha is less than 20% by weight.

Moreover, the method of the present invention may further comprise the step of mixing the remaining C _4-5 hydrocarbons after separating and recovering light olefins in step (c) with naphtha, and providing the C _4-5 hydrocarbons/naphtha mixture as raw material.

Meanwhile, if the reactor is a fixed bed reactor, the reaction is preferably carried out at a temperature of 500-750° C., a hydrocarbon/steam weight ratio of 0.01-10, and a space velocity of 0.1-20 h ⁻¹ .

If the reactor is a fluidized bed reactor, the reaction is preferably at a temperature of 500-750°C, a hydrocarbon/steam weight ratio of 0.01-10, a catalyst/hydrocarbon weight ratio of 1-50 and a hydrocarbon residence time of 0.1-600 seconds under the conditions.

At the same time, if the catalyst is used after steaming at 750°C for 24 hours in a 100% steam atmosphere, the total content of ethylene and propylene in the discharge from the reaction zone will be higher than 30% by weight, and the ethylene/propylene weight ratio will be 0.25 -1.5.

According to the present invention, the use of a specific catalyst with hydrothermal stability shows excellent reaction performance, even in the harsh preparation environment of high temperature and high humidity, it can be produced from hydrocarbons, especially It is the selective preparation of light olefins from full-range naphtha. In particular, since high cracking activity can be maintained even at a temperature lower than the reaction temperature required for the thermal cracking of existing light olefins, it is possible to produce light olefins from hydrocarbon raw materials with high selectivity and high conversion rate. Olefins, the method of the present invention is very useful.

Description of drawings

FIG. 1 shows a system for measuring the reaction activity of a catalyst in the preparation of light olefins according to Examples and Comparative Examples of the present invention.

Detailed ways

The present invention will be described in further detail below.

As mentioned above, according to the present invention, due to the use of the porous molecular sieve catalyst with hydrothermal stability, it is possible to selectively prepare light oil from hydrocarbon raw materials, especially full-range naphtha, with high selectivity and high yield. olefins.

In the method for the present invention, the porous molecular sieve catalyst for preparing light olefins consists of molecular sieves containing 100 parts by weight of a -Si-OH-Al-group skeleton, 0.01-5.0 parts by weight of water-insoluble metal salts and 0.05- Product composition obtained by water-evaporating 17.0 parts by weight of a raw material mixture of a phosphate compound. When the product is used as a catalyst for preparing light olefins, it exhibits excellent hydrothermal stability, reactivity and selectivity, and simultaneously improves economic benefits. Porous molecular sieve catalysts with ideal physical and chemical properties can be prepared by properly selecting and adjusting the types of starting materials used for modifiers, the combination ratio of each component, the loading amount, pH value, and the temperature of the solution when loading, etc. . During the preparation process of the catalyst, the following technical points need to be considered:

(1) A technique for selectively modifying only pores on the surface of a molecular sieve by a phosphate compound, wherein the phosphate compound exists as an ion selected from monohydrogen phosphate ions, dihydrogen phosphate ions, and phosphate ions ;

and

(3) A technique of stabilizing molecular sieves modified with phosphate compounds and metals by water evaporation.

In this technical context, any catalyst support can be used as long as the catalyst support is a molecular sieve containing a skeleton of -Si-OH-Al-groups.

，Si/Al摩尔比为1-300、优选约为25-80的中孔分子筛催化剂，包括孔径为4-10

的沸石。Preferably, any one selected from a pore size of 10-100

, a mesoporous molecular sieve catalyst with a Si/Al molar ratio of 1-300, preferably about 25-80, including a pore size of 4-10

of zeolites.

Among them, ZSM-5, Ferrierite, ZSM-11, mordenite, β-zeolite, MCM-22, L-zeolite, MCM-41, SBA-15 and/or Y-zeolite are more preferred, and General properties are well known in the art.

In this context, the term water-insoluble metal salt refers to a metal salt with a solubility (Ksp) of less than 10 ⁻⁴ , ie a pKsp greater than 4. Examples of the metal salt may be oxides, hydroxides, carbonates or oxalates of metals whose oxidation state is higher than positive 2. Preferably, the metal salt is at least one metal oxide, hydroxide, carbonate or oxalate selected from the group consisting of alkaline earth metals, transition metals and heavy metals whose oxidation state is positive 3 to positive 5. salt.

Preferably, the alkaline earth metals may include Mg, Ca, Sr and Ba, the transition metals may include Ti, V, Cr, Mn, Fe, Co, Ni and Cu, and the heavy metals may include B, Al, Ga , In, Ti, Sn, Pb, Sb and Bi.

Meanwhile, the phosphate compound is not particularly limited as long as it is known to those skilled in the art. However, since the use of phosphoric acid as the phosphate compound has certain disadvantages, that is, the crystallinity of porous materials is lowered, alkylphosphine derivatives can be used instead of phosphoric acid, but there are also certain problems, that is, due to uneconomical and not easy to handle , so it is not suitable for large-scale production. For this reason, phosphoric acid, ammonium phosphate ((NH ₄ ) ₃ PO ₄ ; (NH ₄ ) ₂ HPO ₄ ; (NH ₄ ) ₃ H ₂ PO ₄ ) or alkyl phosphates are preferably used as phosphate compounds.

It is known that the acid dissociation constants pKa(1), pKa(2) and pKa(3) of phosphoric acid (H ₃ PO ₄ ) are 2.2, 7.2 and 12.3 respectively, and phosphoric acid is monohydrogen with pH values of 2.2, 7.2 and 12.3 respectively. Phosphate ion ([HPO ₄ ] ^2- ), dihydrogen phosphate ion ([HPO ₄ ] ^- ) and phosphate ion ([PO ₄ ] ^3- ) exist. It is therefore evident that the desired chemical species of phosphate ions can be selectively produced by properly adjusting the pH of aqueous solutions containing phosphate compounds.

The porous molecular sieve catalyst prepared from the above composition is modified with one compound selected from the compounds represented by Formulas 1 to 3 below.

Formula 1

M _x (H ₂ PO ₄ ) _y , wherein M is a metal, x is 1, and y is an integer from 2 to 6;

Formula 2

M _x (HPO ₄ ) _y , where M is a metal, x is 2, and y is an integer from 2 to 6; and

Formula 3

M _x (PO ₄ ) _y , wherein M is a metal, x is 3, and y is an integer from 2 to 6.

Accordingly, modifying the acid sites exposed outside the pores of the porous molecular sieve with a modifying agent having physical and chemical stability in a high-temperature and high-humidity environment can prevent dealumination of the surface of the zeolite.

Although the description of the preparation of molecular sieve catalysts is not to be bound by a particular theory, it is believed that, as shown in Reaction Schemes 1 and 2 below, modification of -Si-OH-Al-groups forming molecular sieves using phosphate compound/metal composite structures Therefore, it is concentrated by the protons of zeolite. In this way, the ≡P=O group stabilizes the unstable Al, and at the same time, the two -OH groups are also stabilized by the metal. Therefore, even in high temperature and high humidity environments In this case, the skeleton structure can also be relatively stably maintained.

Reaction Scheme 1

Reaction scheme 2

The methods for preparing porous molecular sieve catalysts can be broadly classified into two methods involving a step of removing water contained in the above raw material mixture by selective evaporation to recover a solid product.

A method of preparing a catalyst according to a preferred embodiment of the present invention will be described below.

(1) A phosphate compound is added and mixed with an aqueous slurry containing a water-insoluble metal salt. Adjust the mixture to a suitable pH with conventional alkaline or acidic aqueous solution, such as NaOH, KOH, _NH4OH , HCl or _HNO3 , and stir at about 20-60°C, preferably at about 40-50°C, for about 30 minutes to 3 hours, preferably about 1-3 hours, so that the phosphate compound exists in the form of ions selected from monohydrogen phosphate ions, dihydrogen phosphate ions and phosphate ions in the aqueous solution.

In particular, it is preferred that the mixture is adjusted to a desired pH range such that only one chemical species of phosphate ions is formed in the aqueous solution within this pH range. That is, if the specific pH range is not reached, one or more phosphate ion species will coexist in the aqueous solution, so that the chemical species on the pore surface of the modified molecular sieve will not be uniform, so it is difficult to maintain the stability of the modified catalyst. Persistence.

(2) Molecular sieves having a skeleton of -Si-OH-Al-groups are added to the mixture in part (1). Within a specific pH range determined according to the purpose, preferably at a temperature of about 10-90°C, more preferably at a temperature of about 50-70°C, the resulting mixture is stirred until the water in the aqueous slurry is completely evaporated. Thus, while removing water from the slurry, the phosphate ion species of the modified molecular sieve are stabilized by the metal ions. Then, vacuum filtration was performed to recover the solid product. In this way, molecular sieve catalysts having a framework of Si-OH-Al-groups modified with phosphate-metal salts are produced.

Meanwhile, the composition of the raw material mixture used to prepare the catalyst is as follows: 100 parts by weight of molecular sieves with a -Si-OH-Al-group skeleton, 0.01-5.0 parts by weight of water-insoluble metal salts and 0.05-17.0 parts by weight Phosphate compounds in parts by weight.

A method of preparing a catalyst according to another embodiment of the present invention will be described below.

(1) A phosphate compound is added and mixed with an aqueous slurry containing a water-insoluble metal salt. Adjust the mixture to a suitable pH with conventional alkaline or acidic aqueous solutions, such as NaOH, KOH, _NH4OH , HCl or _HNO3 , and at a temperature of about 20-60°C, preferably at a temperature of about 40-50°C Next, stir for about 30 minutes to 3 hours, preferably about 1-3 hours, so that the phosphate compound exists in the form of ions selected from monohydrogen phosphate ions, dihydrogen phosphate ions and phosphate ions in the aqueous slurry. Then, the resulting mixture is stirred at a temperature of about 10-90° C., more preferably at a temperature of about 50-70° C., within a specific pH range determined according to the purpose until the water in the aqueous slurry is completely evaporated . The solid product is then vacuum filtered and washed to isolate the first solid product. Water-insoluble phosphate-metal salts are thus produced.

(2) Add an aqueous solution containing a molecular sieve having a -Si-OH-Al-group skeleton to the first solid product in part (1). The resulting mixture is preferably stirred at a temperature of about 20-60°C, more preferably at about 40-50°C, for about 30 minutes to 7 hours, preferably about 1-5 hours, until the water in the mixture is completely evaporated. The remaining solid product was then vacuum filtered to isolate a second solid product. In this way, molecular sieve catalysts having a framework of Si-OH-Al-groups modified with phosphate-metal salts are produced.

However, the raw material mixture used to prepare the catalyst is used in a controlled manner, and the composition of the raw material mixture is as follows: 100 parts by weight of molecular sieves with -Si-OH-Al-; 0.01-5.0 parts by weight of water-insoluble a metal salt; and 0.05-17.0 parts by weight of a phosphate compound. In particular, in order to achieve the desired effect, based on 100 parts by weight of the molecular sieve, the preferred amount of the first solid product is 0.01-20.0 parts by weight.

In the above method for preparing the catalyst, certain conditions must be found so that the metal ions formed after the metal salt in the aqueous solution is decomposed will only stabilize the modified phosphate ions, and will not ion-exchange with the protons in the molecular sieve. Otherwise, the dissolved metal ions would ion-exchange with the protons in the molecular sieve, reducing the number of acid sites and resulting in a lower reactivity of the modified catalyst.

Therefore, as described above, by using a water-insoluble metal salt having a solubility in aqueous solution of less than 10 ⁻⁴ , it is possible to significantly prevent the phenomenon of ion exchange with protons in molecular sieves in the presence of a large amount of metal ions, so The above-mentioned water-insoluble metal salt is preferably at least one metal oxide, hydroxide, carbonate selected from the group consisting of alkaline earth metals, transition metals and heavy metals whose oxidation state is positive 3 to positive 5 valence or oxalates. The phenomenon of ion exchange with the protons in molecular sieves is problematic when using water-soluble metal salts, and when using water-soluble metal salts, the desired metal ion is likely to maximize the stabilization of the modified phosphate ion.

Meanwhile, the raw material mixture in the aqueous slurry used to prepare the catalyst should have the following composition: 100 parts by weight of molecular sieves; 0.01-5.0 parts by weight of water-insoluble metal salts; and 0.05-17.0 parts by weight of phosphate compounds . If the composition of the raw material mixture is outside the specified composition range, the pores on the surface of the molecular sieve will not be selectively modified by the modifier, and the number of acidic sites will be significantly reduced, resulting in a decrease in catalytic activity. In particular, the molar ratio of the water-insoluble metal salt to the phosphate compound is 1.0:0.3-10.0, preferably 1.0:0.7-5.0. If the molar ratio of the phosphate compound to the water-insoluble metal salt is lower than 0.3, it will lead to the problem of reducing the number of acidic sites in the molecular sieve due to the presence of too many unnecessary metal ions, thereby reducing the reactivity of the modified catalyst . On the other hand, if the molar ratio of the phosphate compound to the water-insoluble metal salt is higher than 10.0, there will be a problem that the structural modification of the molecular sieve is insufficient and the hydrothermal stability of the modified molecular sieve becomes poor.

Hereinafter, the method of the present invention for producing light olefins from hydrocarbon feedstock using the above-mentioned porous molecular sieve catalyst, which requires the catalyst to have hydrothermal stability under harsh conditions of high temperature and high humidity, will be described.

Full range naphtha or kerosene can be used as the hydrocarbon feedstock. More preferably, a full range naphtha containing _C2-15 hydrocarbons is used. The most suitable reaction for hydrocarbon feedstock is catalytic cracking reaction, but not limited thereto.

Examples of feedstocks that can be used in the present invention include, in addition to full-range naphtha, expensive light naphtha used in steam cracking processes for the production of light olefins, olefin-containing olefins commonly used in many catalytic cracking processes Feedstock and C _20-30 heavy fractions used in existing FCC processes.

Among the hydrocarbon feedstocks, full-range naphtha is a fraction containing _C2-12 hydrocarbons prepared in the crude oil refining process, and contains paraffins (normal paraffins and isoparaffins), naphthenes And aromatic compounds, etc., may contain olefinic compounds. Generally, the higher the paraffin content in the naphtha, the lighter the naphtha; the lower the paraffin content in the naphtha, the heavier the naphtha.

According to the present invention, yield and economic effect etc. should be considered when selecting raw materials. In this consideration, in the full-range naphtha that can be used, the total content of paraffin components (normal paraffins and isoparaffins) is 60-90% by weight, more preferably 60-80% by weight, and most preferably 60-70% by weight. Furthermore, the selected naphtha may contain olefins in an amount of less than 20 wt%, preferably less than 10 wt%, most preferably less than 5 wt%. Table 1 below exemplifies raw material compositions (unit: weight %) that can be used in the present invention.

Furthermore, in the present invention, the naphtha feedstock can also be mixed with _C4-5 hydrocarbons remaining after separation and recovery of light olefins and heavy products from the effluent in the reaction zone containing the catalyst, and used in the form of a mixture .

Table 1

n-paraffins Isoparaffins Naphthenic Aromatic compounds Olefins naphtha 31.7% 53.0% 9.3% 2.7% 3.3%

In the present invention, the reaction zone may comprise at least one reactor, and preferably a fixed bed reactor or a fluidized bed reactor. In the reactor, the feedstock is converted by a conversion reaction (eg, a catalytic cracking reaction) to large quantities of light olefins using the catalyst of the present invention.

Generally, the catalytic activity depends largely on the reaction temperature, space velocity, and the weight ratio of naphtha to steam, etc. In the present invention, the following factors must be considered in determining the reaction conditions: the lowest possible temperature to minimize energy consumption, the best conversion, the best olefin yield, and the reduction of catalyst deactivation due to the formation of coke as much as possible. According to a preferred embodiment of the present invention, the reaction temperature is about 500-750°C, preferably about 600-700°C, more preferably about 610-680°C. In addition, the weight ratio of hydrocarbon to steam is about 0.01-10, preferably about 0.1-2.0, most preferably about 0.3-1.0.

If a fixed bed reactor is used, the space velocity is about 0.1-20h- ¹ , preferably about 0.3-10h ^-1 , most preferably 0.5-4h ^-1 . If a fluidized bed is used, the weight ratio of catalyst to hydrocarbon is about 1-50, preferably about 5-30, more preferably about 10-20; the residence time of hydrocarbon is about 0.1-600 seconds, preferably about 0.5- 120 seconds, more preferably about 1-20 seconds.

In order to determine whether the molecular sieve catalyst of the present invention can maintain a certain degree of catalytic activity in a harsh environment or be deactivated in this environment, the catalyst of the present invention is steamed in a 100% steam atmosphere at a temperature of 750 ° C. 24 hours. That is, if the catalyst of the present invention is used after steaming in the above-mentioned atmosphere, the content of light olefins (i.e., ethylene and propylene) in the effluent of the reaction zone is preferably higher than about 30% by weight, more preferably Above about 35% by weight, most preferably above about 40% by weight. In this case, the weight ratio of ethylene to propylene is preferably about 0.25-1.5, more preferably 0.5-1.4 and most preferably 0.7-1.3, indicating a relatively high yield of propylene.

Hereinafter, the present invention will be described in more detail by way of examples. However, it should be understood that these examples do not limit the scope of the present invention.

Example 1

A) Preparation of catalyst

10 g of HZSM-5 (Zeolyst) with a Si/Al molar ratio of 25 and 0.55 g of concentrated phosphoric acid (85% H ₃ PO ₄ ) were added to 100 ml of distilled water and stirred for 20 minutes. 0.36 g of Mg(OH) ₂ was added to the stirred solution, and the pH of the mixture was adjusted to 7-8 with aqueous ammonia, followed by stirring at about 45° C. for about 20 minutes. The mixture was then stirred at about 50°C until the water was completely evaporated, then the solid product was isolated by vacuum filtration. The separated solid product was calcined in air at 500°C for 5 hours to prepare a Mg-HPO ₄ -HZSM-5 catalyst.

B) Procedure for steam treatment to evaluate hydrothermal stability

In order to evaluate the hydrothermal stability of the catalyst, the catalyst was placed in a 100% steam atmosphere at 750°C for 24 hours.

C) Preparation of light olefins

As shown in Figure 1, a kind of system that detects catalyst activity in the process of preparing light olefins, comprises naphtha feeding device 4, water inlet device 3, fixed bed reactor 5 and 5 ', and activity evaluation device, these The devices are interconnected to form a whole. In this case, the naphtha in Table 1 above was used as a raw material. Naphtha and water are added with a fluid injection pump, and mixed with each other and with helium and nitrogen in a preheater (not shown) at 300°C, wherein, through the helium feeding devices 2 and 2' He was fed at a rate of 6 ml/min, _N2 was fed at a rate of 3 ml/min through nitrogen feeders 1 and 1', and the mixture was then fed into fixed bed reactors 5 and 5'. At this time, the amounts and speeds of the various gases were controlled by flow controllers (not shown). The fixed bed reactor is divided into an internal reactor and an external reactor, wherein the external reactor is a reactor made of Inconel with a length of 38 cm and an outer diameter of 4.6 cm; the internal reactor is made of stainless steel made to a length of 20 cm and an outer diameter of 0.5 inches. The temperature in the reactor was displayed by temperature output devices 7 and 7', and the reaction conditions were controlled by a PID controller (8 and 8'NP200; Han Young Electronics Co., Ltd, Korea).

The gas entering the reactor first passed through the inner reactor and then through the outer reactor, and the rate of He passing through the reactor was 40 ml/min. The bottom of the internal reactor contains the catalyst. The mixed gas is catalytically cracked at the catalyst layers 6 and 6', and after the reaction, the vapor phase product 12 is quantitatively analyzed online by a gas chromatograph 11 (model: HP6890N). The retained liquid phase product 13 is recovered to storage tanks 10 and 10' through condensers 9 and 9' and quantitatively analyzed by gas chromatography (model: DS 6200; not shown). The amount of catalyst used in the catalytic cracking reaction was 0.5 g, the addition amount of naphtha and water were both 0.5 g/hour, and the reaction was carried out at 675°C.

The results obtained for conversion, selectivity of light olefins (ethylene and propylene) in the reaction product and ethylene/propylene weight ratio are shown in Table 3 below.

Example 2

A) Preparation of catalyst

10 g of HZSM-5 (Zeolyst) with a Si/Al molar ratio of 25 and 0.26 g of concentrated phosphoric acid (85% H ₃ PO ₄ ) were added to 100 ml of distilled water and stirred for about 20 minutes. To the stirred solution was added 0.08 g of Mg(OH) ₂ , and the pH of the mixture was adjusted to 2-3 with aqueous nitric acid, followed by stirring at about 45° C. for about 20 minutes. The mixture was stirred at about 50°C until the water was completely evaporated, then the solid product was isolated by vacuum filtration. The separated solid product was calcined in air at 500°C for 5 hours to prepare a Mg-H ₂ PO ₄ -HZSM-5 catalyst.

B) Procedure for steam treatment to evaluate hydrothermal stability

The steam treatment step was performed in the same manner as in Example 1.

C) Preparation of light olefins

Light olefins were prepared in the same manner as in Example 1.

The results obtained for conversion, selectivity of light olefins (ethylene and propylene) in the reaction product and ethylene/propylene weight ratio are shown in Table 3 below.

Example 3

A) Preparation of catalyst

A slurry containing 6.6 kg of Mg-H ₂ PO ₄ -HZSM-5 prepared in part (A) of Example 2, 0.7 kg of Y zeolite and 3 kg of alumina binder was stirred and then spray-dried to obtain an average Granular catalyst with a particle diameter of 80 microns.

B) Procedure for steam treatment to evaluate hydrothermal stability

The steam treatment step was performed in the same manner as in Example 1.

C) Preparation of light olefins

In this example, a fluidized bed reaction system was used to detect the activity of the catalyst in the production process of light olefins. A fluidized bed reaction system includes a riser reactor, a regenerator, a stripper, and a stabilizer. The riser reactor is 2.5 meters high and 1 cm in diameter; the regenerator is 1.5 meters high and 12 cm in diameter; the stripper is 2 meters high and 10 cm in diameter; the stabilizer is 1.7 meters high and 15 cm in diameter centimeter.

The naphtha in Table 1 above was used as a raw material.

Raw material, steam and catalyst are added through the feed port of the riser reactor and mixed with each other, wherein the raw material is added at a feed rate of 133 g/h at 400°C; into the steam; the catalyst was added at a feed rate of 5320 g/h at 725°C. When the mixture passes through the riser, the fluidized catalytic cracking reaction occurs, and the temperature at the outlet of the riser is 675°C. The mixture passing through the riser is separated into a catalyst and a fraction in a stripper at 500°C. The separated catalyst is returned to the regenerator, while the distillate goes to the stabilizer. The catalyst fed to the regenerator was regenerated by contacting with air at 725°C, and the regenerated catalyst was re-fed into the riser. The fraction fed to the stabilizer was separated at -10°C into gaseous and liquid components.

The prepared gas components and liquid components were analyzed in the same manner as in Example 1.

The results obtained for conversion, selectivity of light olefins (ethylene and propylene) in the reaction product and ethylene/propylene weight ratio are shown in Table 3 below.

Example 4

A) Preparation of catalyst

10 g of HZSM-5 (Zeolyst) with a Si/Al molar ratio of 25 and 0.18 g of concentrated phosphoric acid (85% H ₃ PO ₄ ) were added to 100 ml of distilled water and stirred for 20 minutes. 0.146 g of Mg(OH) ₂ was added to the stirred solution, and the pH of the mixture was adjusted to 12-13 with aqueous ammonia, and then stirred at about 45° C. for about 20 minutes. The mixture was stirred at about 50°C until the water was completely evaporated, then the solid product was isolated by vacuum filtration. The separated solid product was calcined in air at about 500°C for 5 hours to prepare a Mg-PO ₄ -HZSM-5 catalyst.

B) Procedure for steam treatment to evaluate hydrothermal stability

The steam treatment step was performed in the same manner as in Example 1.

C) Preparation of light olefins

Light olefins were prepared in the same manner as in Example 1.

The results obtained for conversion, selectivity of light olefins (ethylene and propylene) in the reaction product and ethylene/propylene weight ratio are shown in Table 3 below.

Example 5-10

A) Preparation of catalyst

A catalyst was prepared in the same manner as in Example 1, except that the composition of the raw material mixture was changed to that shown in Table 2 below.

B) Procedure for steam treatment to evaluate hydrothermal stability

The steam treatment step was performed in the same manner as in Example 1.

C) Preparation of light olefins

Light olefins were prepared in the same manner as in Example 1.

The results obtained for conversion, selectivity of light olefins (ethylene and propylene) in the reaction product and ethylene/propylene weight ratio are shown in Table 3 below.

Comparative example 1

A) Preparation of catalyst

10 g of HZSM-5 (Si/Al=25; Zeolyst) were calcined in air at about 500° C. for 5 hours to prepare the HZSM-5 catalyst.

B) Procedure for steam treatment to evaluate hydrothermal stability

No steaming step was performed.

C) Preparation of light olefins

Light olefins were prepared in the same manner as in Example 1.

The results obtained for conversion, selectivity of light olefins (ethylene and propylene) in the reaction product and ethylene/propylene weight ratio are shown in Table 3 below.

Comparative example 2

A) Preparation of catalyst

10 g of HZSM-5 (Si/Al=25; Zeolyst) were calcined in air at about 500° C. for 5 hours to prepare the HZSM-5 catalyst.

B) Procedure for steam treatment to evaluate hydrothermal stability

The steam treatment step was performed in the same manner as in Example 1.

C) Preparation of light olefins

Light olefins were prepared in the same manner as in Example 1.

The results obtained for conversion, selectivity of light olefins (ethylene and propylene) in the reaction product and ethylene/propylene weight ratio are shown in Table 3 below.

Comparative example 3

A) Preparation of catalyst

10 g of HZSM-5 (Si/Al=25; Zeolyst) and 0.15 g of concentrated phosphoric acid (85% H ₃ PO ₄ ) were added to 100 ml of distilled water. The pH of the mixture was adjusted to 7-8 with aqueous ammonia, and then the mixture was stirred at about 50°C until the water was completely evaporated. The solid product was isolated by vacuum filtration. The separated solid product was calcined in air at about 500°C for 5 hours to prepare the HPO ₄ -HZSM-5 catalyst.

B) Procedure for steam treatment to evaluate hydrothermal stability

The steam treatment step was performed in the same manner as in Example 1.

C) Preparation of light olefins

Light olefins were prepared in the same manner as in Example 1.

The results obtained for conversion, selectivity of light olefins (ethylene and propylene) in the reaction product and ethylene/propylene weight ratio are shown in Table 3 below.

Comparative example 4

A) Preparation of catalyst

10 g of HZSM-5 (Si/Al=25; Zeolyst) and 1.4 g of La(NO ₃ ) ₃ ·xH ₂ O were added to 100 ml of distilled water. The mixture was stirred at about 50°C until the water was completely evaporated. The remaining material was then isolated by vacuum filtration to give a solid product. The separated solid product was calcined at 500° C. for 5 hours in air to prepare a La-HZSM-5 catalyst.

B) Procedure for steam treatment to evaluate hydrothermal stability

The steam treatment step was performed in the same manner as in Example 1.

C) Preparation of light olefins

Light olefins were prepared in the same manner as in Example 1.

The results obtained for conversion, selectivity of light olefins (ethylene and propylene) in the reaction product and ethylene/propylene weight ratio are shown in Table 3 below.

Comparative example 5

A) Preparation of catalyst

10 g of HZSM-5 (Si/Al=25; Zeolyst) and 0.74 g of concentrated phosphoric acid (85% H ₃ PO ₄ ) were added to 100 ml of distilled water, and stirred for about 20 minutes. 1.40 g of La(NO ₃ ) ₃ ·xH ₂ O was added to the solution, and the pH of the mixture was adjusted to 7-8, followed by stirring at about 45° C. for 20 minutes. The mixture was then stirred at about 50°C until the water was completely evaporated. The remaining material was then isolated by vacuum filtration to give a solid product. The separated solid product was calcined in air at 500°C for 5 hours to prepare La-H ₃ PO ₄ -HZSM-5 catalyst.

B) Procedure for steam treatment to evaluate hydrothermal stability

The steam treatment step was performed in the same manner as in Example 1.

C) Preparation of light olefins

Light olefins were prepared in the same manner as in Example 1.

The results obtained for conversion, selectivity of light olefins (ethylene and propylene) in the reaction product and ethylene/propylene weight ratio are shown in Table 3 below.

Comparative example 6

A) Preparation of catalyst

10 g of HZSM-5 (Si/Al=25; Zeolyst) and 0.55 g of concentrated phosphoric acid (85% H ₃ PO ₄ ) were added to 100 ml of distilled water, and stirred for about 20 minutes. 1.58 g of Mg(NO ₃ ) ₂ ·6H ₂ O was added to the solution, and the pH of the mixture was adjusted to 7-8 with aqueous ammonia, and then stirred at about 45° C. for about 20 minutes. The mixture was stirred at about 50°C until the water was completely evaporated and the solid product was isolated by vacuum filtration. The separated solid product was calcined in air at about 500°C for 5 hours to prepare Mg-H ₃ PO ₄ -HZSM-5 catalyst.

B) Procedure for steam treatment to evaluate hydrothermal stability

The steam treatment step was performed in the same manner as in Example 1.

C) Preparation of light olefins

Light olefins were prepared in the same manner as in Example 1.

The results obtained for conversion, selectivity of light olefins (ethylene and propylene) in the reaction product and ethylene/propylene weight ratio are shown in Table 3 below.

Comparative example 7

A) Preparation of catalyst

The catalyst was prepared according to the method disclosed in US Patent 6211104B1. Catalysts were prepared in the specific manner described below. 20 g of NH ₄ -ZSM-5 was added to 40 g of aqueous solution of 85% phosphoric acid and MgCl ₂ ·6H ₂ O, loaded with the metal ion, and then stirred. The supported molecular sieves were dried in an oven at 120°C, and finally calcined at 550°C for 2 hours.

B) Steam treatment step for evaluation of hydrothermal stability

The steam treatment step was performed in the same manner as in Example 1.

C) Preparation of light olefins

Light olefins were prepared in the same manner as in Example 1.

The results obtained for conversion, selectivity of light olefins (ethylene and propylene) in the reaction product and ethylene/propylene weight ratio are shown in Table 3 below.

Table 2

Composition (weight%) Zeolite Alkaline earth metal salt Transition metal/heavy metal salt   Types of Phosphates Example 1 HZSM-5 Mg(OH) ₂ (1.5) - HPO ₄ (1.5) Example 2 HZSM-5 Mg(OH) ₂ (1.5) - H ₂ PO ₄ (1.5) Example 3 HZSM-5 Mg(OH) ₂ (1.5) - H ₂ PO ₄ (1.5) Example 4 HZSM-5 Mg(OH) ₂ (1.5) - PO ₄ (1.5) Example 5 HZSM-5 MgCO ₃ (1.5) - HPO ₄ (1.5) Example 6 HZSM-5 Ca(C ₂ O ₄ )(1.5) - HPO ₄ (1.5) Example 7 HZSM-5 - Ce ₂ O ₃ (2.0) HPO ₄ (2.0) Example 8 HZSM-5 BaCO ₃ (1.5) - H ₂ PO ₄ (1.5) Example 9 HZSM-5 - La ₂ O ₃ (1.7) HPO ₄ (1.7) Example 10 HZSM-11 - Fe(C ₂ O ₄ )(2.0) HPO ₄ (2.0) Comparative example 1 HZSM-5 - - - Comparative example 2 HZSM-5 - - - Comparative example 3 HZSM-5 - - HPO ₄ (1.5) Comparative example 4 HZSM-5 - La(NO ₃ ) ₃ xH ₂ O(6.0) - Comparative example 5 HZSM-5 - La(NO ₃ ) ₃ xH ₂ O(6.0) HPO ₄ (2.0) Comparative example 6 HZSM-5 Mg(NO ₃ ) ₂ 6H ₂ O(1.5) - HPO ₄ (1.5) Comparative example 7 HZSM-5 MgCl ₂ 6H ₂ O (3.0) - P(3.0)

table 3

Result of catalytic cracking reaction (unit: weight %) Conversion rate(%) C2 ⁼ C3 ⁼ C2 ⁼ +C3 ⁼ C2 ^＝ /C3 ^＝ Example 1 76.8 18.1 19.4 37.5 0.93. Example 2 77.0 16.3 18.0 34.3 0.90 Example 3 86.1 22.8 20.1 42.9 1.13 Example 4 76.2 16.2 17.8 34.0 0.91 Example 5 76.8 14.8 18.6 33.4 0.80 Example 6 80.1 18.0 17.7 35.7 1.01 Example 7 76.0 16.6 18.5 35.1 0.90 Example 8 79.2 16.7 19.6 36.3 0.85 Example 9 80.4 17.4 18.5 35.9 0.94 Example 10 79.7 17.4 19.7 37.1 0.89 Comparative example 1 77.7 21.8 18.7 40.5 1.17 Comparative example 2 67.7 10.8 13.7 24.5 0.79 Comparative example 3 66.5 8.9 11.9 20.8 0.75 Comparative example 4 58.4 10.4 12.8 23.2 0.82 Comparative example 5 75.4 13.1 17.4 30.5 0.75 Comparative example 6 72.1 12.5 15.7 28.2 0.80 Comparative example 7 13.6 16.3 29.9 0.83

It can be seen from FIG. 3 that according to the examples and comparative examples, the reactivity of different catalysts in the process of preparing light olefins is different. That is to say, in the case of Examples 1-10 of the present invention, even using a steam-treated catalyst in a high-temperature and high-humidity environment (750°C, 100% humidity for 24 hours), it can show about 76-80 The high conversion in weight %, at the same time, shows a high selectivity to a total amount of ethylene and propylene of about 33-37 weight % (ethylene/propylene weight ratio = about 0.8-1.0).

On the other hand, it can be seen that the unsteamed HZSM-5 used in Comparative Example 1 exhibited a conversion of 77.7% by weight and a total amount of ethylene plus propylene of 40.5% by weight, but that used in Comparative Example 2 at For steam-treated HZSM-5 in a harsh hydrothermal environment, the conversion decreased rapidly to 67.7% by weight, and the total amount of ethylene plus propylene decreased to 24.5% by weight. In Comparative Examples 2, 3, 4 and 6, the conversion rate is about 58-75% by weight, while the total amount of ethylene plus propylene is 20-30% by weight, which shows that these Comparative Examples except Comparative Example 5 are comparable to the present invention. Compared with the inventive preparation method, the conversion rate and the yield of light olefins are all very low.

Meanwhile, Comparative Example 5 exhibited a conversion of 75.4% by weight and a total amount of ethylene plus propylene of 30.5%. This result is inferior to the results of Examples 1-9, which is considered to be due to the use of water-soluble nitrates instead of water-insoluble salts, resulting in lower hydrothermal stability.

Moreover, the reactivity of the catalyst prepared according to the method disclosed in US Patent 6211104B1 is inferior to that of the catalyst prepared by the method of the present invention.

As mentioned above, in the method of the present invention, even after hydrothermal treatment at 750°C and 100% humidity for 24 hours, the catalyst can exhibit C2 ⁼ +C3 ⁼ = 33-37% by weight, wherein, using HZSM- 5. P-HZSM-5 and La-HZSM-5 catalysts exhibit C2 ⁼ +C3 ⁼ = 23-24 wt%, while La-P-HZSM-5 exhibits C2 ⁼ +C3 ⁼ = about 30 wt%. Moreover, adjusting the types and composition ratios of the chemical substances used for modifying the catalyst used in the method for producing light olefins of the present invention exhibits the characteristics of ensuring that the hydrothermal stability of the catalyst is changed, and at the same time, the production of olefins can be controlled. Process conversion and ratio of C2 ⁼ /C3 ⁼ . In addition, the catalyst of the present invention has excellent reactivity required in the process of producing light olefins from naphtha containing _C2-12 hydrocarbons.

As described above, according to the present invention, even under high temperature and high temperature hydrothermal environment, the use of a specific catalyst having hydrothermal stability exhibits excellent conversion of hydrocarbon feedstocks (especially full-range naphthas) with high yield and high selectivity. oil) to prepare hydrocarbonaceous olefins. In particular, the method of the present invention is highly practical because it maintains high cracking activity at lower temperatures than the reaction temperatures required in existing thermal cracking processes for producing light olefins, making light olefins Olefins can be produced from hydrocarbon feedstocks with high selectivity and high conversion.

Through the preferred embodiments of the present invention disclosed above for the purpose of illustration, those skilled in the art can make various possible modifications, additions and substitutions without departing from the scope disclosed in the appended claims of the present invention and spirit.

Claims (8)

1. one kind prepares the method for light olefin by hydrocarbon feed, and this method comprises:

(a) supply raw materials, said raw material is selected from by the raw material that contains alkene of the petroleum naphtha of full range, kerosene, light naphtha, catalyst cracking method use and the C that the FCC method is used _20-30The group that last running is formed;

(b) with this raw material supplying at least one fixed bed or fluidized-bed reactor, in this reactor drum, in the presence of catalyzer, react; And

(c) separation and recovery light olefin from the elute of reaction zone;

Wherein, Said catalyzer is by forming through mixture of raw material being evaporated the product that moisture content obtains, and said mixture of raw material contains the phosphate compounds of the having of the 100 weight parts-molecular sieve of Si-OH-Al-group skeleton, the water-fast metal-salt of 0.01-5.0 weight part and 0.05-17.0 weight part;

Wherein, said water-fast metal-salt is oxide compound, oxyhydroxide, carbonate or the oxalate that oxidation state is higher than the metal of positive divalent; Said phosphate compounds is phosphoric acid, (NH ₄) ₃PO ₄, (NH ₄) ₂HPO ₄, (NH ₄) H ₂PO ₄Or alkylphosphonic.

2. method according to claim 1, wherein, said raw material is full boiling range naphtha or kerosene.

3. method according to claim 1, wherein, said raw material is for containing C _2-15The petroleum naphtha of hydrocarbon.

4. method according to claim 2, wherein, in the said raw material, the total content that comprises the paraffinic hydrocarbons composition of normal paraffin and isomerization alkanes is 60-90 weight %, and the content of alkene is lower than 20 weight % in the said raw material.

5. method according to claim 3, wherein, this method also comprises the steps: separation in the step (c) and residual C after reclaiming hydrocarbon matter alkene _4-5Hydrocarbon mixes with petroleum naphtha, and this C is provided _4-5Hydrocarbon/petroleum naphtha mixture is as raw material.

6. method according to claim 1; Wherein, When said reactor drum was fluidized-bed reactor, the said temperature that is reflected at was that 500-750 ℃, hydrocarbon/steam weight ratio are that 0.01-10, catalyzer/hydrocarbon weight ratio are that 1-50 and hydrocarbon residence time are to carry out under the 0.1-600 condition of second.

7. method according to claim 1, wherein, when said reactor drum was fixed-bed reactor, the said temperature that is reflected at was that 500-750 ℃, hydrocarbon/steam weight ratio are that 0.01-10 and air speed are 0.1-20h ^-1Condition under carry out.

8. method according to claim 1; Wherein, When said catalyzer when VT was used after 24 hours under 100% steam, 750 ℃ of environment, the total content of ethene and propylene is for being higher than 30 weight % in the said reaction zone elute, and the weight ratio of ethylene/propene is 0.25-1.5.