CN1072032C - Pentabasic cyclic molecular sieve composite for high output of ethylene and propylene - Google Patents

Abstract

A molecular sieve composition that can be used for catalytic cracking to produce more ethylene and propylene, which is made of a five-membered ring molecular sieve with a SiO ₂ /Al ₂ O ₃ molar ratio of 15-60, which is activated and modified by P, alkaline earth metals and transition metals have to. The P ₂ O ₅ content of the modified molecular sieve is 2-10% by weight, the content of alkaline earth metal oxide is 0.3-5% by weight, and the content of transition metal oxide is 0.3-5% by weight. The structure and active center of the molecular sieve have high thermal and hydrothermal stability. Its most notable feature is that the catalyst made of it can have an ethylene yield of more than 18% under catalytic thermal cracking conditions, and ethylene~ The yield of butene can reach more than 50%.

Description

Five-membered ring molecular sieve compositions prolific in ethylene and propylene

The invention relates to a Pentasil type zeolite molecular sieve composition for catalytic thermal cracking to produce ethylene and propylene.

ZSM-5 (USP3,702,886,1976), ZSM-8 (GB1334243A) and ZSM-11 (USP3,709,979,1973) or ZSM-5/ZSM-11 (USP4,289,607,1981) invented by Mobil Corporation of the United States Year) and other five-membered ring molecular sieves have been widely used in the conversion of hydrocarbons such as aromatic hydrocarbon alkylation, disproportionation, isomerization, catalytic cracking, catalytic dewaxing, and methanol synthesis of gasoline after modification. Among them, ZSM-5 molecular sieve application is the most successful.

The early synthesis of ZSM-5 molecular sieves required the use of organic amine templates, including tetra-n-propylammonium, tetraethylammonium, hexamethylenediamine, ethylenediamine, n-butylamine, ethylamine, etc. Due to the high price of organic amines and the pollution of the environment, while using organic amines to synthesize ZSM-5 molecular sieves, a large number of synthetic methods without using organic amines have also been explored. For example, EP111748A (1984) reported the use of water glass, aluminum phosphate and phosphoric acid to synthesize ZSM-5 zeolite. CN85100463A reported that water glass, inorganic aluminum salt and inorganic acid were used as raw materials to synthesize ZSM-5 zeolite. CN1058382A reported that water glass , aluminum phosphate and inorganic acid as raw materials and REY or REHY as seed crystals to synthesize ZSM-5 zeolite containing rare earths. JP8571519 and JP8577123 reported the synthesis of ZSM-5 molecular sieves by adding ZSM-5 seeds under amine-free conditions.

In order to meet the needs of different types of reactions, many methods and effects of modifying ZSM-5 molecular sieves have been reported in the literature. For example, USP3,972,382 and USP3,965,208 reported the method of modifying ZSM-5 molecular sieve with phosphorus-containing compounds, that is, reacting HZSM-5 with SiO ₂ /Al ₂ O ₃ of 70 and trimethyl phosphite to prepare Phosphorus-containing molecular sieves are obtained. The preparation conditions of this method are relatively complicated, and the cost is high, and the activity of the prepared sample is lower than that of the phosphorus-free sample, but the selectivity of the reaction is improved.

U.S. Patents USP4,365,104,4,137,195,4,128,592 and 4,086,287 report the method of modifying ZSM-5 molecular sieves with P and Mg, the purpose of which is to use the modified molecular sieves for xylene isomerization, toluene and methanol alkylation, Reactions such as toluene disproportionation to improve the selectivity of p-xylene. The introduction of P and Mg is mainly to enhance the shape-selective properties of molecular sieves. But on the other hand, the acidity and reactivity of hydrocarbon conversion of the modified molecular sieve are reduced. In these patents, P and Mg are supported by a step-by-step impregnation method, that is, molecular sieves or catalysts containing molecular sieves are impregnated with NH ₄ H ₂ PO ₄ or (NH ₄ ) ₂ HPO ₄ aqueous solutions, filtered and dried , roasting; then impregnated with Mg(NO ₃ ) ₂ or an aqueous solution of magnesium acetate, filtered, dried, and roasted to obtain a molecular sieve modified with P and Mg or a catalyst sample containing molecular sieve. In this method, the content of P and Mg has uncertainty, which is related to the reaction temperature, time, roasting and other conditions. At the same time, the state of Mg is not easy to be uniform.

US Patent No. 4,260,843 reports a method for modifying ZSM-5 molecular sieves with P and Be to improve the performance of shape-selective reactions. USP4,288,647 reported the method of modifying ZSM-5 molecular sieve with Ca, Sr, Ba and P to improve the performance of shape-selective reaction. In these patents, the method of modifying the molecular sieve used is basically the same as that of P-Mg modification, but the activity of the modified molecular sieve is lower.

In the above patents, the description of the molecular sieve precursor is that SiO ₂ /Al ₂ O ₃ is greater than 12, and generally SiO ₂ /Al ₂ O ₃ is required to be greater than 30 (USP3,972,832). The content of the modifying element P is generally greater than 0.25% by weight, and the content of alkaline earth metal elements is required to be greater than 0.25% by weight, and the content range is between 0.25 and 25% by weight. In the embodiment, the content of generally used alkaline earth metal elements (Mg, Ca, etc.) is greater than that of P. The application purpose of the above-mentioned patents is mainly to improve the shape-selective performance of molecular sieves, and they are all used in reactions such as isomerization and disproportionation to increase the selectivity of p-xylene. It is generally believed that the acidity of molecular sieves is reduced after being modified by alkaline earth metals. At the same time, the activity of the hydrocarbon conversion reaction is also reduced.

Catalytic cracking to ethylene is a new way to increase ethylene production. Traditional steam cracking to ethylene has the disadvantages of high cracking temperature and strict requirements on raw materials. It is generally believed that steam cracking to ethylene is carried out through a free radical reaction mechanism, so the reaction temperature is very high. The applicant proposes a series of catalytic cracking processes and catalysts for prolific low-carbon olefins in patents such as CN1031834A, CN1072201A, CN1085825A, CN1085885A, CN1093101A, CN1099788A, CN1102431A, CN1114916A and CN1117518A. Phosphorus and rare earth are generally used in these patents The five-membered ring silicalite cracking catalysts are all aimed at increasing the production of C ₃ ⁼ ~ C ₅ ⁼ olefins, and the ethylene yield is not very high. Under catalytic cracking reaction conditions, when the catalyst containing ZSM-5 molecular sieve is used, the C ₃ ⁼ ~C ₅ ⁼ olefins in the reaction product increase significantly, which is due to the ZSM-5 molecular sieve has medium pores and strong shape-selective cracking ability. , but the reaction mechanism is carried out according to the positive carbon ion mechanism. CN1083092A reports a method for producing ethylene and propylene by catalytic thermal cracking. The method uses a catalyst containing layered clay molecular sieves or rare earth-containing five-membered ring molecular sieves, and can increase the output of ethylene at a reaction temperature of 680°C to 780°C.

Considering that high reaction temperature and regeneration temperature are required to produce more ethylene, it is required that the molecular sieve active components have good thermal and hydrothermal stability in terms of structure and active center, that is, under harsh steam treatment conditions, molecular sieves can To maintain high activity, in addition, it is necessary to increase the generation and direct cracking of carbocations, especially to increase the generation and direct cracking of primary carbocations, and to inhibit the isomerization of primary carbocations to secondary and tertiary carbocations, so it is necessary to increase Molecular sieves have shape-selective cracking ability, and at the same time, it is better to have certain dehydrogenation ability to increase the yield of olefins.

The purpose of the present invention is to provide a five-membered ring molecular sieve composition capable of producing more ethylene and propylene, which has good hydrothermal activity stability, and can be compared with the prior art when used for catalytic thermal cracking reaction Further increase the yield of ethylene.

The five-membered ring molecular sieve composition capable of producing more ethylene and propylene provided by the present invention _consists of 85-95% by weight, preferably 88-98% by weight of _the five- _membered ring ( Pentasil type) molecular sieve, 2-10 wt%, preferably 2-8 wt% (calculated as oxides) of phosphorus, 0.3-5 wt%, preferably 0.5-3 wt% (calculated as oxides) of an alkaline earth metal, And 0.3-5% by weight, preferably 0.5-3% by weight (calculated as oxides) of a transition metal.

Said five-membered ring molecular sieve in the molecular sieve composition of the present invention is the molecular sieve of ZSM-5, ZSM-8, or ZSM-11 structure type, wherein preferably is the molecular sieve of ZSM-5 structure type, and its silicon aluminum ratio is 15～ 60, more preferably 15-40, and the lower the silicon-aluminum ratio is, the more favorable it is for more ethylene production.

The alkaline earth metal in the molecular sieve composition of the present invention is preferably magnesium or calcium.

Said transition metal in the molecular sieve composition of the present invention is a metal with dehydrogenation function selected from Groups IB, IIB, VIB, VIIB or VIII of the Periodic Table of Elements, preferably selected from Cr, Mn, Fe, A metal selected from Co, Ni, Cu and Zn, more preferably a metal selected from Ni, Cu or Zn.

The phosphorus, alkaline earth metals and transition metals in the molecular sieve composition of the present invention are introduced into the molecular sieve from their compounds through impregnation, mixing and other methods, and then dried and calcined to make them interact with the molecular sieve and firmly combine Together; wherein the compound of phosphorus may be phosphoric acid, hydrogen phosphate or phosphate, and the compound of alkaline earth metal and transition metal may be nitrate, sulfate or chloride.

In previous patent reports, the introduction of activating elements can enhance the performance of the shape-selective reaction, but the activity of the reaction is reduced, which is due to the limitation of the amount of activating elements introduced by molecular sieves. In the research of the present invention, it is found that the amount of activating elements introduced is restricted by the silicon-aluminum ratio of the molecular sieve itself. That is, the lower the silicon-aluminum ratio, the greater the capacity for the introduction of activating elements, and the molecular sieve with a low silicon-aluminum ratio can still maintain high reactivity when the amount of activating elements introduced is large. In view of the fact that the greater the amount of activated elements introduced, the stronger the shape-selective reaction performance of the molecular sieve, so the selection of a molecular sieve matrix with a low silicon-aluminum ratio is beneficial to the catalytic thermal cracking of ethylene, while the prior art generally emphasizes a high silicon-aluminum ratio Molecular sieves are beneficial to the reaction. This is a feature of the present invention.

In the present invention, it is found that the introduction of activating elements such as alkaline earth metals can reduce the B acid centers of molecular sieves, while the L acid centers are relatively increased, and the increase of L acid centers is beneficial to increase the production of ethylene.

Introducing transition metals such as Ni, Co, Zn, Cu, Cr, Mn into five-membered ring molecular sieves is generally used as active components for reactions such as dehydrogenation or aromatization, because these elements have strong hydrogen transfer Reaction performance In the reaction of catalytic cracking to ethylene, the introduction of these elements will increase the hydrogen transfer ability of molecular sieves, which is not conducive to increasing the selectivity of olefin products. However, according to the research results of the present invention, it is found that in the presence of P element, the hydrogen transfer reaction ability of transition metal elements is significantly inhibited, and at the same time, due to the certain dehydrogenation activity, the selectivity of olefins, especially ethylene and propylene, is increased instead. Therefore, in the present invention, on the basis of introducing P and alkaline earth metals into the five-membered ring molecular sieve, transition metal elements such as Ni, Zn, and Cu are introduced to increase the ethylene yield; simultaneously, the presence of phosphorus is important for improving the hydrothermal activity of the molecular sieve. Stability is good. This is another feature of the present invention.

In a word, when the molecular sieve composition provided by the present invention is used for catalytic pyrolysis reaction, compared with the prior art, the yield of low-carbon olefins, especially ethylene and propylene, can be significantly improved, and it also has good hydrothermal activity stability .

The synthesized ZSM-5 molecular sieve belongs to the orthorhombic crystal system, and is prepared into NH4ZSM-5 through inorganic NH ₄ ⁺ salt exchange, and then prepared into HZSM-5 through roasting (500-600° C.). During these preparations, the structural symmetry of the molecular sieves remained largely unchanged. However, after high-temperature steam treatment, the structural symmetry of ZSM-5 molecular sieves will change, and its typical feature is that the peak at 2θ=24.4° in the X-ray diffraction (XRD) spectrum is broadened or even split. The change in symmetry is in a consistent relationship with a significant decrease in the cracking reactivity of the molecular sieve. Therefore, in each example and comparative example of the present invention, the hydrothermal stability of the active center is judged according to the XRD pattern. Meanwhile, n-tetradecane (nC ₁₄ ) pulse microreaction activity was used to evaluate and judge.

In the present invention, the molecular sieve raw material and properties used in each embodiment and comparative examples are as follows:

1. ZSM-5A, produced by Zhoucun Catalyst Factory of Qilu Petrochemical Company, synthesized with ethylamine as a template, has been calcined to remove the template, the silicon-aluminum ratio is 52.0, and its Na ₂ O≤0.10% by weight after ammonium exchange.

2. ZSM-5B, produced by Catalyst Factory of Changling Refinery and Chemical Plant, with a silicon-aluminum ratio of 25.0, and Na ₂ O≤0.15% by weight after NH ₄ ⁺ exchange.

3. ZSM-5C, synthesized in the laboratory (Example 1), has a silicon-aluminum ratio of 19.0, and its Na ₂ O=0.05% by weight after NH ₄ ⁺ exchange.

Other chemicals used in each example and comparative example are commercially available chemically pure reagents.

The analytical method used in each embodiment of the present invention and comparative example is as follows:

1. The X-ray diffraction (XRD) spectrum of the molecular sieve was measured by a Japanese Rigaku D/Max-ⅢA X-ray diffractometer.

2. The chemical composition of the molecular sieve composition was determined by X-ray fluorescence spectrometry (XRF), and the instrument used was a Japanese Rigaku 3271E X-ray fluorescence spectrometer.

The following examples will further illustrate the present invention.

Example 1

This example illustrates the synthesis of the low silicon to aluminum ratio ZSM-5 zeolite used in the present invention.

24.6g of sodium metaaluminate (produced by Beijing Chemical Plant) was dissolved in 667g of deionized water, and 71.7g of concentration was added under stirring to be 85% by weight H ₃ PO ₄ , the mixture was stirred uniformly and added to 643g of water glass (SiO ₂ 28% by weight, Na ₂ O 9.0% by weight), placed under stirring for 4 hours, then added 19.5g of ZSM-5 molecular sieve (produced by Zhoucun Catalyst Factory, SiO ₂ /Al ₂ O ₃ =52.0) as a seed crystal, and continued to stir After 2 hours, put it into a stainless steel autoclave, stir and crystallize at 175°C for 15 hours, take out the crystallized product after cooling down to room temperature, filter, wash with water, and dry at 120°C to obtain a ZSM-5C sample. Analyzed by XRD, the relative crystallinity (relative to ZSM-5A) of the sample was 92%.

The sample was exchanged at 90°C for 2 hours under the condition of molecular sieve: ammonium nitrate: deionized water (weight ratio)=1:1:20, filtered and washed, repeated exchange once under the same conditions, and dried at 120°C , to obtain an ammonium ZSM-5C sample with a Na ₂ O content of 0.05% by weight.

Comparative example 1

This comparative example illustrates the effect of a conventional hydrogen form ZSM-5 molecular sieve.

Take an appropriate amount of ZSM-5A molecular sieve after NH ₄ ⁺ exchange, put it into a baking dish, bake it in a muffle furnace at 550°C for 2 hours, press it into a tablet, and sieve out 20-40 mesh particles. Take an appropriate amount of the granular molecular sieve and put it into a stainless steel tube. Under the conditions of 800 ° C and deionized water space velocity of 8 hours ^-1 , carry out aging treatment in a 100% water vapor atmosphere for 4 hours. The ZSM-5B and ZSM-5C samples were subjected to roasting and high-temperature steam aging treatment respectively, and the obtained samples were respectively marked as DZSM-5A, DZSM-5B, and DZSM-5C. XRD analysis and n-tetradecane (nC ₁₄ ) pulsed microreflective evaluation were carried out on the samples after the above three treatments, and the evaluation results are listed in Table 1. The pulse microreactor evaluation conditions are as follows: molecular sieve loading is 0.g, reaction temperature is 480°C, carrier gas _N2 flow rate is 30 milliliters/minute (ml/min), _nC14 injection volume is 0.5 microliters (μl).

Table 1 Molecular sieve XRD 24.4° peak shape nC ₁₄ conversion, % DZSM-5A twin peaks 26.6 DZSM-5B twin peaks 33.1 DZSM-5C twin peaks 30.5

It can be seen that after the conventional hydrogen-type ZSM-5 molecular sieve is treated with high-temperature water vapor, the structure of the molecular sieve changes, the diffraction peak at 24.4° in the XRD spectrum splits into two peaks, and the conversion rate of nC ₁₄ also decreases significantly.

Comparative example 2

This comparative example illustrates the effect of prior art ZSM-5 molecular sieves modified with P and Mg.

Take 19g of ZSM-5B molecular sieve sample (dry basis weight), put it into a solution prepared by 1.9g (NH ₄ ) ₂ HPO ₄ and 40g deionized water, stir at room temperature for 12 hours, dry at 120°C, and then Baking at 550°C for 2 hours. The obtained sample was mixed with a solution prepared by 1.51g Mg(CH ₃ COO) ₂ 4H ₂ O and 40g deionized water, stirred at room temperature for 12 hours, dried at 120°C, and then calcined at 550°C for 2 Hours, the obtained molecular sieve is recorded as D-2. Analysis by XRF showed that the P ₂ O ₅ content of the sample was 5.0% by weight, and the MgO content was 1.4% by weight. According to the method described in Comparative Example 1, the above-mentioned sample D-2 was pressed into tablets and subjected to aging treatment at 800°C/4h in a 100% water vapor atmosphere, then evaluated by XRD and nC ₁₄ pulse microreflection. The results are shown in Table 2.

Comparative example 3

Take 19g (dry basis weight) of ZSM-5A molecular sieve sample, put it into a solution prepared by 1.9g (NH ₄ ) ₂ HPO ₄ and 40g deionized water, stir at room temperature for 12 hours, dry at 120°C, and then Baking at 550°C for 2 hours.

The obtained sample was mixed with a solution prepared by 0.43g ZnCl ₂ and 40g deionized water, stirred at room temperature for 12 hours, dried at 120°C, and then calcined at 550°C for 2 hours, and the obtained molecular sieve was marked as D-3 . Analysis by XRF showed that the P ₂ O ₅ content of the sample was 5.0% by weight, and the ZnO content was 1.3% by weight.

According to the method described in Comparative Example 1, the above-mentioned sample D-3 was pressed into tablets, and after aging treatment at 800°C/4 hours and 100% water vapor atmosphere, XRD and nC ₁₄ pulse micro-reflective evaluation were carried out, and the results are shown in Table 2 .

Example 2

Take 19g (dry basis) ZSM-5B molecular sieve sample, and 1.62g 85% by weight H ₃ PO ₄ , 40g deionized water, 1.48g MgCl ₂ 6H ₂ O and 0.70g Ni(NO ₃ ) ₂ 6H ₂ O After the prepared solutions were mixed, they were stirred at room temperature for 2 hours, dried at 120°C, and then calcined at 550°C for 2 hours. The resulting molecular sieve was designated as ZEP-11. According to XRF analysis, the sample contained 4.9% by weight of P ₂ O ₅ , 1.4% by weight of MgO, and 0.86% by weight of NiO.

According to the method of Comparative Example 1, the obtained ZEP-11 sample was subjected to high-temperature water vapor aging treatment, and then evaluated by XRD and nC ₁₄ pulse microreflection. The results are shown in Table 2.

Example 3

Take 19g (dry basis) ZSM-5B molecular sieve sample, and 1.62g 85% by weight H ₃ PO ₄ , 40g deionized water, 0.98g MgCl ₂ 6H ₂ O and 2.09g Ni(NO ₃ ) ₂ 6H ₂ O After the prepared solutions were mixed, they were stirred at room temperature for 2 hours, dried at 120°C, and then calcined at 550°C for 2 hours. The obtained molecular sieves were designated as ZEP-12. According to XRF analysis, the sample contained 4.9% by weight of P ₂ O ₅ , 0.91% by weight of MgO, and 2.6% by weight of NiO.

According to the method of Comparative Example 1, the obtained ZEP-12 sample was subjected to high-temperature water vapor aging treatment, and then evaluated by XRD and nC ₁₄ pulse microreflection. The results are shown in Table 2.

Example 4

Take 19g (dry basis) ZSM-5B molecular sieve sample, mix it with a solution made of 1.62g 85% by weight H ₃ PO ₄ , 40g deionized water, 1.48g MgCl ₂ 6H ₂ O and _0.33g ZnCl Stir at room temperature for 1 hour, then dry at 120°C, and then bake at 550°C for 2 hours, and the obtained molecular sieve is designated as ZEP-13. According to XRF analysis, the sample contained 4.9% by weight of P ₂ O ₅ , 1.4% by weight of MgO, and 0.94% by weight of ZnO.

According to the method of Comparative Example 1, the obtained ZEP-13 sample was subjected to high-temperature water vapor aging treatment, and then evaluated by XRD and nC ₁₄ pulse microreflection. The results are shown in Table 2.

Example 5

Take 19g (dry basis) ZSM-5C molecular sieve sample, mix it with a solution made of 1.62g 85% by weight H ₃ PO ₄ , 40g deionized water, 1.00g MgCl ₂ 6H ₂ O and _0.65g ZnCl Stir at room temperature for 2 hours, then dry at 120°C, and then bake at 650°C for 1 hour, and the obtained molecular sieve is designated as ZEP-14. According to XRF analysis, the sample contained 4.9% by weight of P ₂ O ₅ , 0.94% by weight of MgO, and 1.9% by weight of ZnO.

According to the method of Comparative Example 1, the obtained ZEP-14 sample was subjected to high-temperature steam aging treatment, and then evaluated by XRD and nC ₁₄ pulse microreflector. The results are shown in Table 2.

Example 6

Take 19g (dry basis) ZSM-5B molecular sieve sample, and 1.62g 85% by weight H ₃ PO ₄ , 40g deionized water, 1.48g MgCl ₂ 6H ₂ O and 0.57g Cu(NO ₃ ) ₂ 3H ₂ O After the prepared solutions were mixed, they were stirred at room temperature for 2 hours, dried at 120°C, and then calcined at 550°C for 2 hours. The obtained molecular sieves were designated as ZEP-15. According to XRF analysis, the sample contained 4.9% by weight of P ₂ O ₅ , 1.4% by weight of MgO, and 0.91% by weight of CuO.

According to the method of Comparative Example 1, the obtained 7EP-15 sample was subjected to high-temperature steam aging treatment, and then evaluated by XRD and nC ₁₄ pulse microreflection. The results are shown in Table 2.

Example 7

Take 19g (dry basis) ZSM-5C molecular sieve sample, and 1.62g 85% by weight H ₃ PO ₄ , 40g deionized water, 0.53g CaCl ₂ 2H ₂ O and 1.15g Cu(NO ₃ ) ₂ 3H ₂ O After the prepared solutions were mixed, they were stirred at room temperature for 2 hours, dried at 120°C, and then calcined at 550°C for 2 hours. The obtained molecular sieves were designated as ZEP-16. According to XRF analysis, the sample contained 4.9% by weight of P ₂ O ₅ , 1.0% by weight of CaO, and 1.9% by weight of CuO.

According to the method of Comparative Example 1, the obtained ZEP-16 sample was subjected to high-temperature water vapor aging treatment, and then evaluated by XRD and nC ₁₄ pulse microreflection. The results are shown in Table 2.

Table 2 Molecular sieve XRD 24.4° peak shape nC ₁₄ conversion, % D-2 Unimodal 98.0 D-3 Unimodal 95.5 ZEP-11 Unimodal 99.6 ZEP-12 Unimodal 98.9 ZEP-13 Unimodal 99.3 ZEP-14 Unimodal 97.5 ZEP-15 Unimodal 92.2 ZEP-16 Unimodal 90.5

It can be seen from Table 2 that after introducing transition metals Ni and Zn, the 24.4° peak in the XRD pattern of the molecular sieve remains a single peak, and the conversion rate of nC ₁₄ is also very high.

Example 8

According to the weight ratio of molecular sieve: aluminum sol (as Al ₂ O ₃ ): kaolin=15:15:70 on a dry basis, the obtained unaged D-2, D-3, ZEP-11, 7EP-13 and ZEP were respectively The -15 molecular sieve sample is prepared into five catalysts according to the conventional spray drying method, and the catalyst (containing HZSM-5 molecular sieve containing HZSM-5 molecular sieve 20% by weight) as a comparative catalyst. After the six catalysts were aged at 800°C/4 hours in a 100% steam atmosphere, they were evaluated for light oil micro-reaction and fixed fluidized bed reaction.

Table 3 shows the light oil micro-reaction evaluation results. Evaluation conditions are as follows: reaction temperature 520°C, solvent-to-oil ratio 3.2, weight space velocity 16 hours ^-1 , catalyst loading 5.0 g. The distillation range of raw oil is 229-340°C.

The evaluation results of fixed fluidized bed catalytic pyrolysis are listed in Table 4. Evaluation conditions are: reaction temperature 700°C, agent-to-oil ratio 10, feed space velocity 10 hours ^-1 , water injection 80% by weight. The raw material oil used is Daqing wax oil with a distillation range of 346-546°C.

It can be seen from the results in Table 3 and Table 4 that the introduction of transition metals such as Ni, Zn, and Cu into molecular sieves can significantly increase the yield of ethylene.

table 3 Molecular sieve HZSM-5 D-2 D-3 ZEP-11 ZEP-13 ZEP-15 Conversion rate, weight % 44.0 62.38 61.01 63.92 64.05 63.21 Cracked gas yield, weight % of which ethylene propylene butene 16.760.826.505.63 27.232.887.574.95 26.463.027.324.20 27.633.517.344.71 27.653.467.614.82 26.983.327.925.22

Table 4 Molecular sieve HZSM-5 D-2 D-3 ZEP-11 ZEP-13 ZEP-15 Conversion rate, weight % 89.93 91.02 90.51 92.72 93.63 90.75 Product distribution, weight % cracked gas yield in which ethylene propylene butene C ₂ ⁼ +C ₃ ⁼ +C ₄ ⁼ gasoline (C ₅ ~221°C)diesel (221~330°C)heavy oil (>330°C)coke 62.7517.2518.9112.1148.2724.816.513.566.37 69.7020.7722.4710.6953.1315.225.333.656.10 70.5020.3219.5711.3951.2813.165.773.726.85 70.1823.2021.668.3753.2314.334.183.108.21 71.3023.9522.087.6853.7114.963.792.587.37 69.8020.9821.339.3551.6614.215.383.876.74

Claims (9)

1. A five-membered ring molecular sieve composition, characterized in that the composition is composed of 85-95% by weight of five-membered ring molecular sieves with a SiO ₂ /Al ₂ O ₃ molar ratio of 15-60, 2-10% by weight of oxides phosphorus, 0.3 to 5% by weight of an alkaline earth metal as an oxide, and 0.3 to 5% by weight of an alkaline earth metal selected from Group IB, IIB, VIB, VIIB or VIII of the Periodic Table of Elements It is composed of a transition metal with dehydrogenation function. 2. According to the molecular sieve composition of claim 1, it is characterized in that the composition is composed of 88-98% by weight of five-membered ring molecular sieves with a SiO ₂ /Al ₂ O ₃ molar ratio of 15-60, 2-8% by weight of oxides Phosphorus, 0.5-3% by weight of an alkaline earth metal as an oxide, and 0.5-3% by weight of a transition metal as an oxide. 3. The molecular sieve composition according to claim 1, wherein said five-membered ring molecular sieve is a ZSM-5, ZSM-8, or ZSM-11 structure type molecular sieve. 4. The molecular sieve composition according to claim 3, wherein said five-membered ring molecular sieve is a molecular sieve of the ZSM-5 structure type. 5. The molecular sieve composition according to claim 1, wherein said five-membered ring molecular sieve has a silicon-aluminum ratio of 15-60. 6. The molecular sieve composition according to claim 5, wherein said five-membered ring molecular sieve has a silicon-aluminum ratio of 15-40. 7. The molecular sieve composition according to claim 1, wherein said alkaline earth metal is magnesium or calcium. 8. The molecular sieve composition according to claim 1, wherein said transition metal is a metal selected from the group consisting of Cr, Mn, Fe, Co, Ni, Cu, Zn. 9. The molecular sieve composition according to claim 8, wherein said transition metal is a metal selected from Ni, Cu or Zn.