Process for increasing the yield of light olefins in heavy oil catalytic cracking

Abstract

The application discloses a method for improving low-carbon olefin yield of heavy oil catalytic cracking, and a catalyst used in the method comprises 5-25wt% aluminum binder, 25-70wt% molecular sieve, 0-60wt% clay and 0.01-10% inorganic oxide; the molecular sieve is ZSM-5 molecular sieve and acid-modified Y-type molecular sieve containing phosphorus and rare earth, and the mass ratio of the ZSM-5 molecular sieve to the acid-modified Y-type molecular sieve is 1:1-1:10; in the preparation process of the acid-modified Y-type molecular sieve containing phosphorus and rare earth, a NaY molecular sieve filter cake layer is first formed, then the molecular sieve after phosphorus and rare earth exchange is loaded on the NaY molecular sieve filter cake layer, and the NaY molecular sieve filter cake layer is used to adsorb and recover the excessive phosphorus and rare earth ions in the filtrate. The preparation method of the Y-type molecular sieve containing phosphorus and rare earth provided by the application can exchange Na+ in the molecular sieve, and can make the utilization of phosphorus and rare earth reach 100%, and the preparation method is simple; in the molecular sieve exchange process, the recovery and utilization of the phosphorus and rare earth ions are realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of catalytic conversion of heavy oil hydrocarbons, and in particular to a method for improving the yield of low-carbon olefins in catalytic cracking of heavy oil. BACKGROUND

[0002] As the growth of oil demand slows, many refineries worldwide are focusing on adjusting operations to co-produce basic chemicals. Gasoline consumption is expected to peak at around 1.7 million tons per year in 2025, and the global demand for chemicals will grow at an average annual rate of 3.6% from 2018 to 2025. Driven by the continued increase in demand for ethylene terminals, the global demand for ethylene is expected to grow at an average annual rate of about 3.8% by 2035. The consumption of chemical basic raw materials such as ethylene and propylene in China is increasing year by year, and the supply of ethylene and propylene is insufficient. Ethylene and propylene are very important chemical raw materials, among which propylene can produce polypropylene, acrylonitrile, acrylic acid, etc., and is widely used in food, clothing, art, etc. fields, and has high value. The current methods for producing ethylene and propylene mainly include steam cracking, methanol-to-olefins, and refinery catalytic cracking. Maximizing the production of low-carbon olefins while producing gasoline in catalytic cracking units is one of the strategies for reducing oil and increasing chemicals implemented by various refineries.

[0003] Chinese patent CN201210074500.0 provides a petroleum hydrocarbon catalytic cracking catalyst, the catalyst is composed of molecular sieve, filler and modified component, wherein the molecular sieve is ZSM type nanoscale molecular sieve, the molar ratio of SiO2 to A12O3 is 155:1-1000:1, the particle size is 50-900 nm; the filler is one or both of A12O3 and SiO2; the modified component is lanthanide series element and phosphorus. The nanoscale molecular sieve makes the catalytic ability of the catalyst stronger. This is because the small particle size molecular sieve makes the diffusion path shorter, so that the ethylene and propylene generated by the reaction can easily diffuse out of the pore of the molecular sieve, thereby improving the yield of low carbon olefin. At the same time, the aromatization tendency of the product is reduced, and the content of condensed ring aromatic hydrocarbon in the product is also very low. At the same time, due to the reduction of aromatization tendency, the amount of carbon deposited on the catalyst is also reduced, the catalytic efficiency of the catalyst remains high, and the utilization rate of petroleum hydrocarbon is improved. Chinese patent CN201410535604.6 discloses a catalyst for reducing coke formation and producing more low carbon olefins, which comprises 10-85 wt% aluminum binder, 15-60 wt% molecular sieve and 0-75 wt% clay, and the preparation method of the catalyst comprises the following steps: forming a slurry of aluminum binder, clay, molecular sieve, water and carboxymethyl cellulose, spray drying, and optionally calcining. The catalyst provided by the present invention has high sphericity, high yield of low carbon olefins and low yield of coke. Chinese patent CN201010296050.0 produces a low carbon olefin catalytic cracking catalyst and its application, which is composed of 0.5-15 parts by weight of particle A and 1 part by weight of particle B: based on the total mass of particle A, particle A includes 10-85 wt% aluminum binder, 15-60 wt% molecular sieve and 0-75 wt% clay, and based on the total weight of particle B, the particle B is composed of 20-80 wt% of rectorite and 20-80 wt% of silica binder calculated as silicon oxide. The catalyst provided by the present invention has high ethylene yield and good wear resistance. Chinese patent CN201110375175.7 proposes a method for catalytic conversion of hydrocarbons to produce more propylene, which is to contact hydrocarbon raw materials with a catalyst in a catalytic cracking reaction zone, and the obtained carbon four fraction rich in butene and / or olefin-rich gasoline fraction is contacted with a catalyst with modified pores in an oligomerization / cracking reaction zone for reaction, and the products including propylene-rich products are separated. The carbonized catalyst is divided into two parts after stripping and regeneration, one part is recycled to the catalytic cracking reaction zone, and the other part is first sent to the catalyst pore modification zone, contacted with a modifier and reacted, and then sent to the oligomerization / cracking reaction zone for recycling. The present invention adopts the method of modifying the pores of the catalyst, so that the dual-active-component catalytic cracking catalyst containing large-pore zeolite and medium-pore zeolite not only has high heavy oil conversion capacity and high propylene selectivity for catalytic cracking of heavy hydrocarbon raw materials, but also has high propylene selectivity for catalytic conversion of butene and high olefin gasoline, thereby achieving the purpose of producing more propylene.Chinese patent 201910327853.9 proposes a catalyst for catalytic cracking of hydrocarbon oil rich in naphthenic ring hydrocarbons, its preparation method and application method. The catalyst is composed of natural mineral, boron-aluminum-silicon composite oxide, inorganic oxide binder, Y-type molecular sieve and shape-selective molecular sieve. Its preparation method includes the steps of preparing boron-aluminum-silicon composite oxide, forming a slurry including the boron-aluminum-silicon composite oxide, molecular sieve, natural mineral, inorganic oxide binder and water, spray drying, etc. The catalyst is used in the catalytic cracking reaction process of hydro-upgraded heavy oil, the reaction temperature is 565℃, the mass ratio of catalyst to oil is 15, and the reaction results show that the conversion rate of hydro-upgraded heavy oil is 87.52%, and the mass yield of low-carbon olefins in the cracking product is 37.95%, among which the mass yield of ethylene is 6.62% and the mass yield of propylene is 25.14%. It can be seen that the catalytic cracking catalyst has high conversion activity of naphthenic ring hydrocarbons, and has high ethylene yield and propylene yield when used for conversion of hydrocarbon oil rich in naphthenic ring hydrocarbons. Chinese patent 202110342883.4 proposes a catalytic cracking catalyst, which includes modified ZSM-5 molecular sieve and binder and clay; the content of modified ZSM-5 molecular sieve on a dry basis is 20-60% by weight based on the dry weight of the catalyst, the content of clay on a dry basis is 0-50% by weight, and the content of binder on an oxide basis is 10-40% by weight; the modified ZSM-5 molecular sieve includes ZSM-5 molecular sieve and alkaline earth metal elements; the content of alkaline earth metal elements on an oxide basis is 10-30% by weight based on the dry weight of the modified ZSM-5 molecular sieve; the SiO2 / Al2O3 molar ratio of the modified ZSM-5 molecular sieve is 15-50. The catalyst is applied to the catalytic cracking reaction of Shanghai hydro-upgraded tail oil as raw material, and the mass yield of low-carbon olefins is increased to 39.07%. Among them, the mass yield of propylene is 30.01%, and at the same time, the coking rate of the catalyst is small, which is mainly due to the reduction of strong acid content in the modified molecular sieve, which effectively inhibits the hydrogen transfer reaction in the reaction process. On the other hand, the addition of mesoporous structure makes the intermediate products of isomerization and aromatization reaction more easily diffuse in the molecular sieve channel, thereby further inhibiting the coking effect in the reaction process.Chinese patent CN201810229971.1 proposes a method for producing more low-carbon olefins and light aromatics, which includes: feeding the catalytic cracking raw material into the first catalytic cracking reactor to contact with the first catalytic cracking catalyst and carry out the first catalytic cracking reaction to obtain the first oil agent mixture; feeding the hydrogenated cycle oil into the second catalytic cracking reactor to contact with the second catalytic cracking catalyst and carry out the second catalytic cracking reaction to obtain the second oil agent mixture; wherein the distillation range of the hydrogenated cycle oil is in the range of 190-230℃; feeding the obtained first oil agent mixture and second oil agent mixture into the third catalytic cracking reactor to carry out the third catalytic cracking reaction to obtain the spent catalyst and reaction oil gas; separating the obtained reaction oil gas to obtain low-carbon olefins, cracking gasoline, cracking cycle oil and cracking oil slurry. The method provided by the invention can produce more ethylene, propylene and light aromatics. Chinese patent CN200610080831.X proposes a method for producing propylene and high-quality gasoline and diesel by two-stage catalytic cracking, which mainly uses two-stage riser catalytic process, adopts catalyst rich in shape-selective molecular sieve, uses heavy petroleum hydrocarbons or various animal and plant oils rich in hydrocarbons as raw materials, optimizes the combination of feeding modes for different reaction materials, controls the appropriate reaction conditions of different materials, and can achieve the purposes of improving propylene yield, considering light oil yield and quality, and inhibiting dry gas and coke formation. Chinese patent CN201410411981.9 proposes a catalytic cracking method for naphtha raw material, which includes: (1) contacting the naphtha raw material with the first catalytic cracking catalyst in the first reaction zone and reacting; (2) introducing at least part of the C5+ components and the second catalytic cracking catalyst into the second reaction zone for reaction, and separating the obtained second oil agent mixture to obtain the second spent catalyst and the second reaction oil gas; wherein the reaction temperature of the second reaction zone is higher than that of the first reaction zone, and the temperature of the second catalytic cracking catalyst is higher than that of the first catalytic cracking catalyst. It can improve the yield of ethylene and propylene while significantly reducing the yield of non-ideal products such as hydrogen, methane and coke. Chinese patent CN201510671858.5 discloses a catalytic conversion method for producing more low-carbon olefins and light aromatics, which includes: continuously feeding raw oil and active components into different positions of the catalytic cracking reactor to contact with the catalytic cracking catalyst and carry out catalytic cracking reaction to obtain dry gas, liquefied gas rich in low-carbon olefins, gasoline rich in light aromatics, diesel and heavy oil. The method of the invention can increase the production of propylene, butylene and light aromatics. In recent years, researchers have conducted extensive research on the performance of feedstocks such as Fischer-Tropsch synthesis oil, waste plastic oil and biological fat oil for producing low-carbon olefins. Chinese patent CN202011169506.7 proposes a method and system for preparing low-carbon olefins from waste plastics.The waste plastic is treated by a waste plastic pretreatment unit to obtain a decontaminated plastic-containing solution; the obtained decontaminated plastic-containing solution is subjected to hydrofining in a hydrofining unit, and the liquid phase material of the reaction effluent is subjected to cracking to obtain a cracking product including ethylene and propylene. Chinese patent CN201410594746.X discloses a method for converting Fischer-Tropsch synthesis oil feedstock, which comprises: contacting Fischer-Tropsch synthesis oil feedstock with regenerated catalyst in a reactor of a catalytic cracking device to obtain a coked catalyst; introducing the coked catalyst into a regenerator through a spent catalyst delivery pipe after stripping to regenerate the coked catalyst and obtain the regenerated catalyst; the reactor comprises a riser reactor and a fluidized bed reactor connected in series, wherein the Fischer-Tropsch synthesis oil feedstock is introduced into the riser reactor, and fuel oil is introduced into the fluidized bed reactor, so that the Fischer-Tropsch synthesis oil feedstock is contacted with the regenerated catalyst in the presence of fuel oil. The above-mentioned method of the invention can adjust the process heat balance in the process of producing low-carbon olefins by catalytic conversion of Fischer-Tropsch synthesis oil under the premise of improving the yield of propylene produced from Fischer-Tropsch synthesis oil feedstock. Chinese patent 201910828885.7 discloses a method for improving oil quality and increasing the yield of low-carbon olefins by catalytic cracking of bio-oil. The method uses bio-oil or a mixture of bio-oil and hydrocarbon oil as raw oil for catalytic cracking reaction. After using this method, the octane number of gasoline in the product is significantly improved, and the content of propylene and other low-carbon olefins in the product is also increased.

[0004] Chinese patent 201710899614.1 proposes a processing method for biological oil, which comprises: feeding a raw material containing biological oil into a catalytic cracking reactor to contact with a catalytic cracking catalyst and perform a catalytic cracking reaction; wherein the catalytic cracking catalyst contains a molecular sieve and a metal oxide with adsorption function; the metal in the metal oxide with adsorption function includes at least one selected from alkali metal, alkaline earth metal and transition metal; the catalytic cracking catalyst contains 0.5-20 wt% of the metal oxide with adsorption function based on the total weight of the catalytic cracking catalyst. The processing method provided by the invention can improve product distribution, reduce coke yield, and increase the yield of low-carbon olefins and light aromatic hydrocarbons. Chinese patent 201610913437.3 proposes a processing technology for biological oil, which comprises: contacting biological oil with a catalytic cracking catalyst in a catalytic cracking reactor to perform a catalytic cracking reaction and obtain a catalytic cracking product; wherein the temperature of the catalytic cracking reaction is 50-500°C; contacting the obtained catalytic cracking product with a catalytic cracking catalyst in a catalytic cracking reactor to perform a catalytic cracking reaction and obtain a catalytic cracking product; the processing technology for biological oil provided by the invention can produce more low-carbon olefins and improve the utilization rate of carbon and hydrogen elements.

[0005] It is well known that Y-type molecular sieve is a key raw material for synthesizing catalytic cracking catalyst, which is widely used in catalytic cracking reaction due to its suitable acidity, extremely high specific surface area and good thermal stability.

[0006] In the prior art, after the rare earth ions and phosphorus of the molecular sieve are exchanged, the filter cake is generally subjected to calcination treatment, which causes that the rare earth and phosphorus cannot be completely exchanged onto the molecular sieve, a part of the rare earth and phosphorus enters the filtrate and is lost, and the utilization rate of the rare earth is not high and the phosphorus is lost. Therefore, how to improve the utilization rate of the rare earth in the ion exchange process of the Y-type molecular sieve and reduce the discharge of phosphorus-containing sewage has become the focus of research.

[0007] There are two methods for ion exchange of NaY molecular sieve in industry: the first method is to mix the Y-type molecular sieve with an aqueous solution containing rare earth ions to form a slurry, and then to perform ion exchange, filtration, washing, drying and calcination or without calcination. In this method, a plate and frame filter is used. The disadvantage of this method is low efficiency and large water consumption; the second method is to mix the Y-type molecular sieve with water to form a slurry, and then to directly load the slurry on the filter cloth of a belt filter to form a filter cake with a certain thickness, and then to add an aqueous solution containing ammonium ions and / or rare earth ions from above the filter cake, and under the action of vacuum in the liquid receiver below the filter cloth, the solution containing ammonium ions and / or rare earth ions continuously passes through the filter cake while ion exchange occurs. The belt filter has the characteristics of energy saving and high efficiency, and is widely used in large-scale industrial production.

[0008] US3943233 discloses a method for continuously ion exchanging fluidizable zeolite particles, which comprises slurring the zeolite particles with a first liquid, loading the slurry at a substantially constant rate into the feed end of a continuous horizontal belt vacuum filter, continuously moving the filter belt loaded with the slurry sequentially through a filter cake formation zone, at least one ion exchange zone and a washing zone, and simultaneously applying a vacuum to the liquid receivers below the respective filter belts, and discharging the filter cake from the filter belt. The method is characterized in that the filter cake leaving the filter cake formation zone is substantially free of surface cracks, but contains liquid in the interstices of the fluidizable zeolite particles, and during the ion exchange treatment, the filter cake is contacted with an ion exchange liquid in the ion exchange zone under filtration conditions, and the filter cake leaves the ion exchange zone in a form which is smooth, substantially free of surface cracks, and contains liquid in the interstices of the fluidizable zeolite particles, and the ion exchanged filter cake is rapidly washed under vacuum.

[0009] Chinese patent 01134276.5 discloses a rare earth ion exchange method of molecular sieve, which comprises beating a molecular sieve with water, continuously transferring the obtained slurry to the filter belt of a horizontal belt vacuum filter, sequentially passing through a filter cake forming area and an ion exchange area, applying vacuum to the liquid receiver under the filter belt in the filter cake forming area and the ion exchange area, washing and suction-drying the filter cake, and unloading the filter cake from the filter belt. The molecular sieve refers to Y-type molecular sieve, the slurry further comprises acid and / or salt, the amount of acid or salt is 0.1-5% by weight of the amount of molecular sieve, the vacuum degree in the liquid receiver of the filter cake forming area ensures that the surface of the filter cake is basically free of cracks, and the upper part of the filter cake in the ion exchange area is added with a solution containing rare earth ions, and the concentration of the solution containing rare earth ions is such that the weight ratio of rare earth oxide to molecular sieve is 0.01-0.5%.

[0010] Chinese patent 02130782.2 continuously loads a molecular sieve slurry with a pH value of 2-7 to the filter cloth of a horizontal belt filter, sequentially passes the filter cloth loaded with the molecular sieve slurry through a filter cake forming area, an ion exchange area and a water washing area, then suction-dries, unloads and dries, and finally obtains the exchanged molecular sieve filter cake. In the ion exchange area, an aqueous solution of rare earth compound with a temperature of 10-100°C is added to the upper part of the filter cake, and the amount of the aqueous solution of rare earth compound is such that the weight ratio of rare earth oxide to molecular sieve is 0.01-0.2.

[0011] Chinese patent 201711336762.9 provides a method for preparing rare earth Y-type molecular sieve, which comprises first mixing NaY molecular sieve, a rare earth chloride solution and deionized water, then performing ion exchange, adding an oxalic acid solution to the exchange liquid to completely precipitate the unexchanged rare earth, adding the rare earth chloride and deionized water to the filter cake after filtration to perform ion exchange, filtering to obtain a filter cake and a reused filtrate, calcining the filter cake in a muffle furnace to obtain a product REY, and completely or partially replacing the above-mentioned rare earth chloride solution with the reused filtrate to enter the ion exchange process of the next batch of NaY molecular sieve. This method can recycle and utilize rare earth, the utilization rate of rare earth is almost 100% without increasing equipment, the production cost is reduced, and the non-renewable rare earth resource is efficiently utilized.

[0012] The prior art mainly focuses on the efficient utilization of rare earth ions and the phosphorus removal method of phosphorus-containing wastewater, and there is no relevant report on improving the utilization rate of phosphorus in the molecular sieve exchange process. The existing technology is to use adsorbent to adsorb phosphorus to meet the emission standard. This operation requires the adsorbent to contact with wastewater for a long time, and the adsorbent needs to be regenerated regularly, which cannot meet the continuous production demand of the molecular sieve preparation process, and seriously affects the production capacity of the molecular sieve. While improving the conversion of heavy oil and other raw materials and increasing the yield of gasoline and low-carbon olefins, how to effectively improve the utilization rate of phosphorus and rare earth in the ion exchange process of Y-type molecular sieve belt filter is an important measure for molecular sieve production enterprises to reduce costs and increase efficiency, and is also one of the key research topics of molecular sieve production enterprises. The catalyst or processing technology used in the existing technology of petroleum hydrocarbon or Fischer-Tropsch synthetic oil, biomass oil improves the cracking degree of raw materials per pass, but cannot balance the effective utilization rate of raw materials, and the product structure is single or the product quality is low. SUMMARY

[0013] Based on the above technical problems, the purpose of the present application is to provide a method for improving the low-carbon olefin yield of heavy oil catalytic cracking.

[0014] To achieve the above-mentioned purpose, the present application provides a method for improving the low-carbon olefin yield of heavy oil catalytic cracking, which uses a catalyst including 5-25wt% aluminum binder, 25-70wt% molecular sieve, 0-60wt% clay, and 0.01-10% inorganic oxide. The molecular sieve is ZSM-5 molecular sieve and acid-modified Y-type molecular sieve containing phosphorus and rare earth with a mass ratio of 1:1-1:10. The preparation of the acid-modified Y-type molecular sieve containing phosphorus and rare earth includes the following steps: step 1: forming a NaY molecular sieve slurry into a NaY molecular sieve filter cake layer; step 2: mixing the NaY molecular sieve with a solution containing phosphorus filtrate and rare earth salt to form a RE-NaY molecular sieve filter cake layer on the NaY molecular sieve filter cake layer, and obtaining a composite filter cake; step 3: ion exchanging the phosphate solution with the composite filter cake obtained in step 2, and washing with water to obtain Y-type molecular sieve containing phosphorus and rare earth; step 4: mixing the Y-type molecular sieve containing phosphorus and rare earth with an organic acid to obtain acid-modified Y-type molecular sieve containing phosphorus and rare earth; wherein the ion exchange and water washing are at least once; and the organic acid addition amount is 0.1-3% of the dry basis mass of the Y-type molecular sieve containing phosphorus and rare earth.

[0015] The method for improving the low-carbon olefin yield of heavy oil catalytic cracking according to the present application, wherein the inorganic oxide is selected from one or more of aluminum phosphate, white carbon black, lanthanum oxide, and cerium oxide.

[0016] The method for improving the low-carbon olefin yield of heavy oil catalytic cracking according to the present application, wherein the NaY molecular sieve slurry includes NaY molecular sieve, alkali metal hydroxide, carbonate, humic acid, and water.

[0017] The NaY molecular sieve and the preparation method thereof in the present application are not particularly limited, and the NaY molecular sieve can be prepared by the existing method or can be commercially available. The preparation method of the NaY molecular sieve is, for example, the NaY molecular sieve synthesis method provided in patent CN103449468B: mixing water glass, sodium metaaluminate and deionized water, aging at 15-70℃ for 0.5-48 hours to obtain a crystallization directing agent; uniformly mixing the crystallization directing agent, water glass, an acidic aluminum salt and a sodium aluminate solution to prepare a silicon-aluminum gel; crystallizing the silicon-aluminum gel at 80-140℃; crystallizing for 0.1-80 hours; adding a peroxide to the crystallized silicon-aluminum gel, so that the molar ratio of O22- in the peroxide to Al2O3 in the gel is 0.05-20, and then continuing to crystallize for 5-20 hours to obtain the NaY molecular sieve. The content of sodium oxide in the NaY molecular sieve is, for example but not limited to, 9-15 wt%.

[0018] The preparation process of the slurry of the NaY molecular sieve is not particularly limited, which can be, for example, mixing the NaY molecular sieve, the hydroxide of the alkali metal, the carbonate of the alkali metal, humic acid and water to beat the slurry, to obtain the slurry of the NaY molecular sieve; the content of the NaY molecular sieve in the slurry is, for example but not limited to, 100-300 g / L. The temperature of the slurry can be 10-100℃, preferably 50-90℃, and the temperature and time of beating the slurry are not particularly limited in the present application, which can be, for example, stirring at 50-100℃ for 0.5-2 hours.

[0019] The method for improving the yield of low-carbon olefins in heavy oil catalytic cracking according to the present application is characterized in that the hydroxide of the alkali metal is potassium hydroxide, and the carbonate of the alkali metal is potassium carbonate; the weight ratio of potassium hydroxide: potassium carbonate: humic acid: NaY molecular sieve is 0.005-0.012: 0.005-0.012: 0.001-0.05: 1.

[0020] The method for improving the yield of low-carbon olefins in heavy oil catalytic cracking according to the present application is characterized in that the humic acid is one or more of yellow humic acid, brown humic acid and black humic acid.

[0021] The method for improving the yield of low-carbon olefins in heavy oil catalytic cracking according to the present application is characterized in that the mass ratio of the phosphorus-containing filtrate to the NaY molecular sieve is 2-10, preferably 3-6.

[0022] The method for improving the yield of low-carbon olefins in heavy oil catalytic cracking according to the present application is characterized in that, in step 2, the rare earth salt is added in an amount such that the mass ratio of the rare earth oxide to the NaY molecular sieve is 0.01-0.10, preferably 0.05-0.10.

[0023] The method for improving the low carbon olefin yield of heavy oil catalytic cracking in the application, in step 3, the phosphate solution is added from the upper part of the composite filter cake, flows through the composite filter cake, and ion exchange is carried out; the phosphate solution is calculated according to the phosphorus element, and the weight ratio of the phosphate solution in step 3 to the NaY molecular sieve in step 2 is 0.005-0.20.

[0024] The method for improving the low carbon olefin yield of heavy oil catalytic cracking in the application, step 3 is: the phosphate solution is ion exchanged with the composite filter cake obtained in step 2 once, is calcined once, and a calcined molecular sieve is obtained; the calcined molecular sieve is slurried with water, the slurry forms a filter cake, the phosphate solution is ion exchanged with the filter cake twice, and is calcined twice, and a Y-type molecular sieve containing phosphorus and rare earth is obtained; the total amount of the phosphate solution used in the ion exchange twice in step 3 is calculated according to the phosphorus element, and the weight ratio of the total amount of the phosphate solution to the calcined molecular sieve is 0.02-0.15.

[0025] The method for improving the low carbon olefin yield of heavy oil catalytic cracking in the application, the filtrate formed in the process of forming the composite filter cake in step 2 and / or the filtrate formed in the ion exchange process in step 3 is recycled as the phosphorus-containing filtrate in step 2, and the phosphorus-containing filtrate can also be a phosphorus-containing filtrate collected or prepared by other processes, and preferably the filtrate formed in the ion exchange process in step 3.

[0026] The method for improving the low carbon olefin yield of heavy oil catalytic cracking in the application, step 3 further comprises a drying and calcining step after the water washing step.

[0027] The water washing conditions in the application are not particularly limited, for example, the temperature can be 20-100 DEG C, preferably 60-80 DEG C, the mass ratio of water to molecular sieve is 1-15, preferably 3-5. The drying and calcining conditions are not particularly limited, for example, the drying temperature is room temperature to 200 DEG C, preferably 100-150 DEG C, the calcining temperature is 500-800 DEG C, preferably 600-700 DEG C, and the calcining time is 1-3 hours, preferably 2-3 hours.

[0028] The method for improving the low carbon olefin yield of heavy oil catalytic cracking in the application, the rare earth salt is one or more of water-soluble rare earth salts, preferably rare earth chloride and rare earth nitrate; the rare earth is selected from at least one of lanthanum, cerium, praseodymium, neodymium and yttrium.

[0029] The method for improving the low carbon olefin yield of heavy oil catalytic cracking in the application, the phosphate salt is one or more of water-soluble phosphate salts, preferably one or more of ammonium phosphate, dihydrogen ammonium phosphate and dihydrogen ammonium phosphate.

[0030] The method for improving the low carbon olefin yield of heavy oil catalytic cracking in the application, the organic acid is one or more of oxalic acid, citric acid, tartaric acid and acetic acid.

[0031] The preparation of the acid-modified Y-type molecular sieve containing phosphorus and rare earth is carried out on a belt filter; the belt filter comprises at least one filter cake forming area, at least one ion exchange area and at least one water washing area. Step 1 and step 2 use the same horizontal belt filter, which is provided with a NaY filter cake forming area and a RE-NaY ion exchange molecular sieve filter cake forming area in series, and the RE-NaY ion exchange molecular sieve slurry is loaded on the NaY filter cake layer in the RE-NaY ion exchange molecular sieve filter cake forming area to form a RE-NaY ion exchange molecular sieve composite filter cake layer.

[0032] The method for improving the yield of low-carbon olefins in heavy oil catalytic cracking of the application adds one or more of Fischer-Tropsch synthetic oil, waste plastic oil and bio-oil to the heavy oil, and the mass ratio of the one or more of Fischer-Tropsch synthetic oil, waste plastic oil and bio-oil to the heavy oil is 1:20-1:5.

[0033] The application has the following beneficial effects:

[0034] The application provides a method for improving the yield of heavy oil catalytic cracking gasoline and low-carbon olefins, in which one or a mixture of Fischer-Tropsch synthetic oil, waste plastic oil or bio-oil is added to heavy oil feedstock; the molecular weight of the Fischer-Tropsch synthetic oil, waste plastic oil and the like is smaller than that of the heavy oil feedstock, so the high-temperature catalyst in the reactor first reacts with the Fischer-Tropsch synthetic oil, waste plastic oil and the like to rapidly crack a large amount of small-molecule olefins, and a large amount of carbenium ions are generated at the same time, which promotes the rapid cracking of heavy oil macromolecules to generate more carbenium ions, thereby accelerating the cracking of heavy hydrocarbons and achieving the purpose of increasing the yield of low-carbon olefins.

[0035] In the preparation process of the acid-modified Y-type molecular sieve containing phosphorus and rare earth, a NaY molecular sieve filter cake layer is first formed, and then the molecular sieve exchanged with phosphorus and rare earth is loaded on the NaY molecular sieve filter cake layer to adsorb and recover the excess phosphorus and rare earth ions in the filtrate through the NaY molecular sieve filter cake layer. The preparation method of the Y-type molecular sieve containing phosphorus and rare earth provided by the application can not only exchange Na+ in the molecular sieve, but also achieve 100% utilization of phosphorus and rare earth. Moreover, the preparation method of the Y-type molecular sieve containing phosphorus and rare earth provided by the application is simple, and realizes the recycling of phosphorus and rare earth ions in the molecular sieve exchange process, which can provide technical support for continuous production of molecular sieves and energy saving and consumption reduction of enterprises.

[0036] Further, the present application can remove the amorphous silicon aluminum on the surface of NaY molecular sieve by adding the hydroxide and carbonate of alkali metal in the slurry of NaY molecular sieve, and can avoid destroying the structure of the molecular sieve, and improve the exchange efficiency of rare earth and Na ion. The humic acid added in the present application is a multi-element organic complex, which forms sodium humate and potassium humate in the alkaline system formed by the NaY molecular sieve and the hydroxide and carbonate of alkali metal, and the sodium humate and potassium humate can synthesize organic rare earth complex with rare earth ions by adsorption, exchange and complexation, so as to limit the migration of rare earth ions in the filtrate and reduce the loss of rare earth ions with the filtrate; and the humic acid also has the function of fixing phosphorus elements, so that the phosphorus elements are not easy to lose with the filtrate. The preparation method of Y-type molecular sieve containing phosphorus and rare earth provided by the present application recovers the rare earth and phosphorus lost in the filtrate through the NaY filter cake layer and humic acid adsorption, realizes the dual function of recovering phosphorus and rare earth in the exchange process of NaY molecular sieve. At the same time, the recovered phosphorus and rare earth mainly exist on the surface of Y-type molecular sieve, and the phosphorus hydroxyl and rare earth ions generate more acid centers through polarized water, which improves the number of acid centers on the surface of Y-type molecular sieve and is beneficial to improve the pre-cracking performance of heavy oil molecules.

[0037] The present application uses organic acid to modify Y-type molecular sieve containing phosphorus and rare earth, further cleans the pore channel of Y-type molecular sieve after the exchange of phosphorus and rare earth, improves the accessibility of heavy oil molecules in the pore channel of Y-type molecular sieve, and further improves the heavy oil conversion performance of Y-type molecular sieve; at the same time, the addition of organic acid modification further strengthens the number of acid centers on the surface of Y-type molecular sieve, and further improves the pre-cracking performance of heavy oil molecules on the outer surface of Y-type molecular sieve. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 The flow chart of the first exchange process of an embodiment of the preparation method of the present application.

[0039] Figure 2 The flow chart of the second exchange process of an embodiment of the preparation method of the present application.

[0040] Among them, the reference signs are:

[0041] 1, 5, 15, pulp tank

[0042] 2, 6, 10, 13, 16, 20, 24, 26, pipeline

[0043] 3, 17, filter cloth

[0044] 4, NaY molecular sieve filter cake formation area

[0045] 7, first exchange molecular sieve filter cake formation area

[0046] 8, 22, liquid receiver

[0047] 9, 12, 19, 23, container

[0048] 11,21 ion exchange zone

[0049] 14,25 water washing zone

[0050] 18, two-stage molecular sieve filter cake formation zone DETAILED DESCRIPTION

[0051] The present application will be described in detail below by way of examples. It is necessary to point out here that the following examples are only used to further illustrate the present application and cannot be understood as limiting the scope of protection of the present application, and those skilled in the art can make some non-essential improvements and adjustments to the present application according to the above content of the present application.

[0052] Figure 1 Process flow diagram of a primary ion exchange process for an embodiment of the preparation method of the present application, Figure 2 Process flow diagram of a secondary ion exchange for an embodiment of the preparation method of the present application. In this embodiment, the preparation method of the acid-modified Y-type molecular sieve containing phosphorus and rare earth of the present application can specifically include the following steps:

[0053] I. Formation of NaY molecular sieve filter cake

[0054] A slurry of NaY molecular sieve, alkali metal hydroxide, carbonate, humic acid and water at 10-100°C, preferably 50-90°C is continuously loaded from the beater tank 1 through the pipeline 2 to the filter cloth 3 of the horizontal vacuum belt filter, the filter cloth continuously moves into the NaY molecular sieve filter cake formation zone 4. The liquid receiver 8 is located below the filter cloth 3, and the liquid receiver 8 is vacuumed, under the action of vacuum, the liquid in the slurry on the filter cloth 3 enters the liquid receiver 8 through the filter cloth 3. At the same time, the NaY slurry on the filter cloth 3 forms a filter cake, and the loading speed of the NaY slurry should ensure that the thickness of the NaY filter cake is 0.5-1.5 centimeters, preferably 0.8-1.5 centimeters. The vacuum degree in the liquid receiver 8 makes the surface of the filter cake free of cracks. The vacuum degree in the liquid receiver 8 is, for example but not limited to, 0.02-0.08 MPa, preferably 0.05-0.08 MPa.

[0055] II. Formation of the first-stage filter cake

[0056] The 1st exchange molecular sieve slurry at 50-100°C is continuously loaded from the slurry tank 5 through line 6 onto the horizontal vacuum belt filter's NaY filter cake layer, and moves with the filter cloth into the 1st exchange molecular sieve filter cake formation zone 7. The filtrate containing phosphorus can be provided by the liquid receiver 22 of the 2nd exchange process described later, or can be provided by the filtrate collected in the liquid collector 8, on the one hand to reduce the amount of water used, and on the other hand to recover phosphorus in the 2nd exchange process filtrate, reduce sewage discharge, and improve the utilization rate of phosphorus elements. At the same time, the 1st exchange molecular sieve slurry forms a filter cake on the filter cloth 3, and the loading speed of the 1st exchange molecular sieve slurry should ensure that the thickness of the 1st exchange molecular sieve filter cake is 0.5-1.5 cm, and preferably 0.8-1.5 cm.

[0057] Three, 1st exchange phosphorus exchange

[0058] As the filter cloth 3 moves, the filter cakes formed in the NaY molecular sieve filter cake formation zone 4 and the 1st exchange filter cake formation zone 7 enter the ion exchange zone 11, and a phosphate solution at a temperature of 20-100°C, preferably 30-90°C, is added from the container 9 through line 10. Under the action of vacuum, the phosphate solution is ion exchanged while passing through the filter cake.

[0059] Four, 1st exchange washing

[0060] The washing method can use methods known to those skilled in the art, and the filter cake obtained in the ion exchange zone 11 enters the water washing zone 14, and deionized water is added from the container 12 through line 13. The weight ratio of deionized water to molecular sieve is generally 1-15, and preferably 2-10. The temperature of the deionized water is 20-100°C, and preferably 30-90°C. Under the action of vacuum, the liquid permeates the filter cake, and the residual ions, especially anions, in the filter cake are washed away.

[0061] Five, formation of 2nd exchange filter cake

[0062] The 1st exchange filter cake after washing is dried and calcined to obtain a calcined molecular sieve slurry, and the calcined molecular sieve slurry at 10-100°C, preferably 50-90°C, is continuously loaded from the slurry tank 15 through line 16 onto the filter cloth 17 of the horizontal vacuum belt filter, and the filter cloth continuously moves into the 2nd exchange molecular sieve filter cake formation zone 18. The liquid receiver 22 is located below the filter cloth 17, and the liquid receiver 22 is vacuumed. Under the action of vacuum, the liquid in the slurry on the filter cloth 17 enters the liquid receiver 22 through the filter cloth 17. At the same time, the calcined molecular sieve slurry forms a filter cake on the filter cloth 17, and the loading speed of the calcined molecular sieve slurry should ensure that the thickness of the calcined molecular sieve filter cake is 0.5-2.0 cm, and preferably 0.8-1.5 cm. The vacuum degree in the liquid receiver 22 prevents cracks on the surface of the filter cake. The vacuum degree in the liquid receiver 22 is, for example but not limited to, 0.02-0.08 MPa, and preferably 0.03-0.08 MPa.

[0063] Six, di-interchange exchange

[0064] With the movement of the filter cloth 17, the filter cake formed in the di-interchange filter cake forming zone 18 enters the ion exchange zone 21, and a phosphate solution with a temperature of 20-100°C, preferably 30-90°C, is added from the container 19 through the pipeline 20. Under the action of vacuum, the phosphate solution is ion-exchanged while passing through the filter cake.

[0065] Seven, di-interchange washing

[0066] The washing method can adopt a method known to those skilled in the art. The filter cake obtained in the ion exchange zone 21 enters the water washing zone 25 with the movement of the filter cloth 17, and deionized water is added from the container 23 through the pipeline 24. The weight ratio of deionized water to molecular sieve is generally 1-15, preferably 2-10, and the temperature of the deionized water is 20-100°C, preferably 30-90°C. Under the action of vacuum, the liquid passes through the filter cake to wash away the residual ions in the filter cake, and the filtrate received by the liquid receiver 22 is discharged through the pipeline 26 for use as a phosphorus-containing filtrate or for external discharge.

[0067] The technical solutions of the present application are further described below through specific examples. Unless otherwise specified, the following percentage contents % all refer to mass percentage contents. Unless otherwise specified, the rare earth content in the filtrate in the following examples and comparative examples refers to the content of rare earth in the form of oxide in the filtrate; the amount of added rare earth refers to the amount in the form of rare earth oxide; the rare earth oxide and the rare earth oxide in the following examples both refer to RE2O3 form oxide; the mass of the rare earth-containing filtrate refers to the mass of the rare earth-containing filtrate itself.

[0068] Source of raw materials:

[0069] 1) NaY molecular sieve: industrial product, produced by Lanzhou Petrochemical Company, crystallinity 94%, silicon-aluminum ratio 5, Na2O content 14.3%;

[0070] Chlorinated rare earth solution: industrial product, produced by Lanzhou Petrochemical Company, containing rare earth oxide 288.7 g / L, among which the content of lanthanum oxide is 46%, the content of cerium dioxide is 53%, and the content of other rare earths is 1%;

[0071] 2) Lanthanum-rich chlorinated rare earth: industrial product, produced by Lanzhou Petrochemical Company, containing rare earth oxide 290 g / L, among which the content of lanthanum oxide is 83%, the content of cerium dioxide is 15%, and the content of other rare earths is 2%;

[0072] 3) Lanthanum chloride, cerium chloride, yttrium chloride, potassium carbonate, potassium hydroxide, fulvic acid, brown humic acid, black humic acid, ammonium phosphate, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, oxalic acid, citric acid, tartaric acid, acetic acid, lanthanum oxide, cerium oxide, aluminum phosphate, white carbon black: analytical pure, all are chemical reagents;

[0073] Evaluation method used in the examples

[0074] Evaluation of the selectivity of the catalytic cracking reaction: The selectivity of the cracking reaction of the catalyst was evaluated in a small fixed fluidized bed (FFB) test device (XGL-2, origin Luoyang). The catalyst was previously treated at 800°C under 100% steam for 10h. The specific properties of the raw material oil are shown in Table 1, the reaction temperature was 500-535°C, the space velocity was 12-15h -1 , and the catalyst / oil ratio was 5.

[0075] Table 1 Properties of the raw material oil

[0076]

[0077]

[0078] Specific analysis method:

[0079] 1) Sodium, phosphorus and rare earth oxide content of the molecular sieve: X-ray fluorescence spectroscopy was used for analysis.

[0080] 2) Phosphorus and rare earth content of the filtrate: ICP (Inductive Coupled Plasma Emission Spectrometer) was used for detection.

[0081] 3) Calculation method of the rare earth utilization rate:

[0082]

[0083] C i - Rare earth concentration (calculated as rare earth oxide) of the solution containing rare earth added, g / mL;

[0084] V- Volume of the solution containing rare earth added, mL;

[0085] R i - Mass of the solid rare earth added (calculated as rare earth oxide), g;

[0086] C O - Rare earth concentration (calculated as rare earth oxide) of the filtrate collected after the filtration of the filter cake, g / mL;

[0087] V O - Volume of the filtrate collected after the filtration of the filter cake, mL.

[0088] The following examples use a cloth funnel filter device to perform experiments to illustrate the method provided by the present application. Since the cloth funnel filter device also undergoes filter cake formation, ion exchange and washing stages, only these steps are performed separately, and thus are equivalent to the continuous process on the belt filter.

[0089] Comparative Example 1

[0090] Preparation of molecular sieve sample: The molecular sieve in the catalyst was prepared into a calcined molecular sieve sample according to the method provided in patent CN1485136A.

[0091] I. Filter cake formation

[0092] NaY molecular sieve was mixed with deionized water to prepare a slurry with pH value of 9 and solid content of 100 g / L. The obtained slurry was heated to 70°C under stirring and poured into a Buchner funnel. At the same time, the filter cake in the Buchner funnel was vacuumed to 0.05 MPa. Under the action of vacuum, a filter cake with a thickness of about 1.2 cm was formed on the filter cloth of the Buchner funnel, and the waste liquid in the filter bottle was emptied.

[0093] II. Ion exchange

[0094] The vacuum in the filter bottle was maintained, and when the liquid on the surface of the filter cake was about to be exhausted, a 50 g / L lanthanum chloride aqueous solution containing lanthanum oxide with a temperature of 65°C was slowly added. The adding speed was such that there was always liquid on the surface of the filter cake, until the weight ratio of lanthanum oxide to molecular sieve in the added aqueous solution was 0.05.

[0095] III. Washing

[0096] The vacuum in the filter bottle was maintained, and when the liquid on the surface of the filter cake was about to be exhausted, deionized water with a temperature of 65°C was slowly added. The adding speed was such that there was always liquid on the surface of the filter cake, until the amount of deionized water added was 3 times the weight of the molecular sieve in the filter cake.

[0097] IV. Suction drying

[0098] Vacuum was continued until no liquid flowed out of the funnel, and a suction-dried filter cake and a filtrate A were obtained.

[0099] V. Removal of filter cake and drying

[0100] The filter cloth was removed from the funnel, and the filter cake was removed from the filter cloth and dried at 140°C to obtain a calcined molecular sieve. The sodium oxide content of the calcined molecular sieve was 4.6%, the rare earth content was 4.53%, and the rare earth content of the filtrate A was 3208 ppm.

[0101] Then the sample was prepared according to the method provided in patent CN1416951A.

[0102] The prepared molecular sieve, deionized water and the above filtrate A were mixed and beaten to prepare a molecular sieve-containing slurry with a molecular sieve content of 120 g / L, wherein the amount of salt (i.e. the rare earth chloride and sodium chloride contained in the filtrate used) was 1.1 wt% of the molecular sieve. The obtained molecular sieve slurry was heated to 90°C and poured into a Buchner funnel, while the filter bottle was vacuumed to 0.07 MPa, and a filter cake with a thickness of 10 mm was formed on the filter cloth. When there was no liquid on the surface of the filter cake, an ammonium phosphate solution with a phosphorus content of 50 g / L and a temperature of 90°C was immediately added, and the addition speed ensured that no cracks were formed on the surface of the filter cake, and the amount of the ammonium phosphate solution was such that the weight ratio of phosphorus to molecular sieve was 0.1. When there was no liquid on the surface of the filter cake, deionized water with a temperature of 90°C was immediately added to wash the filter cake, and the weight ratio of deionized water to molecular sieve was 3. Then the filter cake was removed and the filtrate B was collected, and the filter cake was dried at 120°C to obtain a rare earth Y-type molecular sieve D1. The sodium oxide content of the D1 molecular sieve sample was 1.0%, the phosphorus content of the filtrate B was 125 ppm, and the rare earth content was 796 ppm.

[0103] Preparation of the catalyst: 30 g of D1 molecular sieve, 10 g of ZSM-5 molecular sieve, 20 g of pseudoboehmite, 35 g of kaolin, 5 g of lanthanum oxide and 300 g of water were mixed and beaten uniformly, 4 g of hydrochloric acid was added and stirred for 60 minutes, and then spray drying and calcination were performed to prepare a catalyst X1.

[0104] Comparative Example 2

[0105] The sample was prepared according to the patent CN108097288A.

[0106] Take NaY molecular sieve dry base 150 grams, add 70℃ deionized water 750 grams, stirring while adding lanthanum chloride 3.2 grams, stirring exchange 60 minutes at 70℃, then add 15% concentration oxalic acid solution, continue stirring 20 minutes, then washed with 225 grams of 70℃ deionized water, filtration, the waste filtrate is discarded, the reuse filter cake is obtained; in the reuse filter cake, add 50℃ deionized water 525 grams, stirring while adding lanthanum chloride 18.75 grams, stirring 60 minutes at 50℃, then washed with 225 grams of 70℃ deionized water, filtration, the product filter cake A and reuse filtrate C are obtained; take NaY molecular sieve dry base 150 grams, add to 750g of reuse filtrate C, stirring 60 minutes at 70℃, then add 15% concentration oxalic acid solution, continue stirring 20 minutes, then washed with 225 grams of 70℃ deionized water, filtration, the waste filtrate is discarded, the reuse filter cake is obtained; in the reuse filter cake, add 50℃ deionized water 525 grams, stirring while adding lanthanum chloride 17.13 grams, stirring 60 minutes at 70℃, then washed with 225 grams of 50℃ deionized water, filtration, the product filter cake B and reuse filtrate D are obtained; product filter cake A and B, calcined in a muffle furnace at 580℃ for 3h, the product rare earth Y molecular sieve D2 is obtained, the sodium oxide content is 3.5%, the rare earth content is 23.5%, and the rare earth utilization rate is 97.9%.

[0107] Preparation of catalyst: 30g D2 molecular sieve, 10g ZSM-5 molecular sieve, 20g pseudo-boehmite, 35g kaolin, 5g lanthanum oxide and 300g water are mixed and beaten to be uniform, 4g hydrochloric acid is added and stirred for 60 minutes, then spray dried and calcined to prepare catalyst X2.

[0108] Comparative example 3

[0109] The sample is prepared according to patent CN200810223770.7.

[0110] Take 30 grams of potassium hydroxide and dissolve in 1200 grams of distilled water, stir uniformly to prepare an alkali solution, and then heat to 60℃. Take 200 grams of NaY molecular sieve (dry base) and add to the above alkali solution, stir at 60℃ for 10 hours, filter, wash with deionized water until the pH of the filtrate is less than 10, collect the sample and dry.

[0111] Take 90 grams of the above-mentioned alkali-treated product, mix with 15.8 mL of mixed rare earth solution (RE2O3 content 285 g / L) into 450 grams of distilled water, stir to uniformity, then exchange at 80°C for 1 hour. The exchange process uses 1 mol / L hydrochloric acid solution to adjust the pH of the exchange slurry to 3.5 and maintain. After the exchange is complete, filter, add ammonium phosphate solution at a temperature of 90°C, the amount of ammonium phosphate solution is such that the weight ratio of phosphorus to molecular sieve is 0.20, and wash thoroughly with water, then take the filter cake and dry at 120°C, calcine at 600°C for 2 hours, to obtain a calcined molecular sieve sample, with a sodium oxide content of 4.8%, a RE2O3 content of 4.1%, a first exchange process rare earth utilization rate of 82%, and a filtrate phosphorus content of 17893 ppm.

[0112] Take 50 grams of the above-mentioned calcined molecular sieve sample, mix with ammonium phosphate solution into 180 grams of distilled water, stir to uniformity, the amount of ammonium phosphate solution is such that the weight ratio of phosphorus to molecular sieve is 0.1, then exchange at 80°C for 3 hours. The exchange process uses 1 mol / L hydrochloric acid solution to adjust the pH of the exchange slurry to 4.2 and maintain. After the exchange is complete, filter and wash thoroughly with water, to obtain a molecular sieve sample D3, with a sodium oxide content of 2.1%, a RE2O3 content of 3.8%, and a second exchange filtrate phosphorus content of 5124 ppm.

[0113] Preparation of the catalyst: mix 30g of D3 molecular sieve, 10g of ZSM-5 molecular sieve, 20g of pseudoboehmite, 35g of kaolin, 5g of lanthanum oxide, and 300g of water to form a slurry, add 4g of hydrochloric acid and stir for 60 minutes, then spray dry and calcine to obtain the catalyst X3.

[0114] Example 1

[0115] Preparation of the acid-modified Y-type molecular sieve containing phosphorus and rare earth:

[0116] 1) Mix NaY molecular sieve, potassium hydroxide, potassium carbonate, fulvic acid, and water to form a slurry, with a dry basis weight ratio of potassium hydroxide:potassium carbonate:fulvic acid:NaY molecular sieve of 0.012:0.005:0.05:1, to form a molecular sieve slurry with a molecular sieve content of 180 grams per liter, heat the obtained molecular sieve slurry to 80°C, pour into a Buchner funnel, and simultaneously vacuum the filter bottle to 0.07 megapascals, to form a filter cake with a thickness of 10 millimeters on the filter cloth.

[0117] 2) The NaY molecular sieve was mixed with the phosphorus-containing filtrate B (obtained in Comparative Example 1) and lanthanum chloride to form a slurry having a molecular sieve content of 120 g / L. The slurry was heated to 70°C and stirred for 1 h. The slurry was poured into the Buchner funnel, and the filter bottle was evacuated to 0.07 MPa. A filter cake having a thickness of 10 mm was formed on the filter cloth.

[0118] 3) When the filter cake surface was free of liquid, an ammonium phosphate solution having a temperature of 90°C was immediately added at a rate that ensured that the filter cake surface did not crack. The amount of ammonium phosphate solution added was such that the weight ratio of phosphorus to NaY molecular sieve in step 2) was 0.20. When the filter cake surface was free of liquid, deionized water having a temperature of 80°C was immediately added to wash the filter cake. The weight ratio of deionized water to molecular sieve was 5. The product filter cake and filtrate E were obtained, and the filter cake was removed and dried at 120°C and calcined at 600°C for 2 h to obtain a calcined molecular sieve.

[0119] 4) The calcined molecular sieve was mixed with water to form a slurry having a molecular sieve content of 110 g / L. The slurry was heated to 80°C and poured into the Buchner funnel. The filter bottle was evacuated to 0.06 MPa, and a filter cake having a thickness of 10 mm was formed on the filter cloth.

[0120] 5) When the filter cake surface in step 4) was free of liquid, an ammonium phosphate solution having a phosphorus content of 50 g / L and a temperature of 90°C was immediately added at a rate that ensured that the filter cake surface did not crack. The amount of ammonium phosphate solution added was such that the weight ratio of phosphorus to NaY molecular sieve in step 2) was 0.1. When the filter cake surface was free of liquid, deionized water having a temperature of 90°C was immediately added to wash the filter cake. The weight ratio of deionized water to molecular sieve was 5. The filter cake was removed, and a sample of the molecular sieve and filtrate F were obtained. The sodium oxide content of the sample was 0.9%, the phosphorus content of the filtrate E was 1.5 ppm, and the rare earth content was 6 ppm.

[0121] 6) The filter cake molecular sieve in step 5) was added to 0.1% oxalic acid based on the dry weight of the filter cake and stirred for 1 h to obtain the acid-modified phosphorus- and rare earth-containing Y-type molecular sieve product S1.

[0122] Preparation of the catalyst: 30 g of S1 molecular sieve, 10 g of ZSM-5 molecular sieve, 20 g of pseudoboehmite, 35 g of kaolin, 5 g of lanthanum oxide, and 300 g of water were mixed to form a slurry. 4 g of hydrochloric acid was added, and the mixture was stirred for 60 min. The slurry was spray-dried and calcined to obtain the catalyst Y1.

[0123] Example 2

[0124] Preparation of the acid-modified phosphorus- and rare earth-containing Y-type molecular sieve:

[0125] The operating steps are the same as in Example 1, except that:

[0126] Step 1) The weight ratio of potassium hydroxide: potassium carbonate: brown acid: NaY molecular sieve is 0.005:0.012:0.001:1, the slurry content of NaY molecular sieve is 300 g / L, the slurry temperature is 15°C, the vacuum degree of the filter bottle is 0.08 MPa, and the filter cake thickness is 5 mm.

[0127] Step 2) The mass of the filtrate F containing phosphorus and rare earth is 2 times that of the molecular sieve, and the mass of cerium chloride is such that the mass ratio of cerium oxide to molecular sieve is 0.10, the slurry temperature is 50°C, stirring is performed for 2 h, the vacuum degree of the filter bottle is 0.08 MPa, and the filter cake thickness is 15 mm.

[0128] Step 3) The temperature of the ammonium phosphate solution is 100°C, the amount of ammonium phosphate solution used is such that the weight ratio of phosphorus to molecular sieve is 0.05, and the temperature of the deionized water is 100°C, and the weight ratio of deionized water to molecular sieve is 1. The filter cake and filtrate G are obtained, the filter cake is dried at a temperature of 200°C, and calcined at a temperature of 500°C for 3 h.

[0129] Step 4) The slurry content of the calcined molecular sieve is 300 g / L, the slurry temperature is 100°C, the vacuum degree of the filter bottle is 0.02 MPa, and the filter cake thickness is 5 mm.

[0130] Step 5) The temperature of the diammonium hydrogen phosphate solution is 100°C, the phosphorus content is 100 g / L, the weight ratio of phosphorus to molecular sieve is 0.06, the temperature of the deionized water is 20°C, and the weight ratio of deionized water to molecular sieve is 15. The molecular sieve sample and the collected filtrate H are obtained, which has a sodium oxide content of 1.1%, a phosphorus content of 1 ppm in filtrate G, and a rare earth content of 3 ppm.

[0131] 6) The filter cake molecular sieve in step 5) above is added to 3% acetic acid based on the filter cake, and stirred for 1.5 h to obtain the acid-modified phosphorus and rare earth-containing Y-type molecular sieve product S2.

[0132] Preparation of the catalyst: 35 g of S2 molecular sieve, 35 g of ZSM-5, 25 g of aluminum sol, 0.01 g of white carbon black, 4.99 g of kaolin, and 120 g of water are mixed and uniformly slurried, and then spray-dried and calcined to obtain the catalyst Y2.

[0133] Example 3

[0134] Preparation of the acid-modified phosphorus and rare earth-containing Y-type molecular sieve:

[0135] The operating steps are the same as in Example 1, except that:

[0136] Step 1) Potassium hydroxide: potassium carbonate: black acid: NaY molecular sieve dry base weight ratio of 0.008:0.01:0.02:1, NaY molecular sieve slurry content of 100 g / L, slurry temperature 100°C, filter bottle vacuum degree 0.02 MPa, filter cake thickness of 15 mm.

[0137] Step 2) Add phosphorus and rare earth containing filtrate H with a mass of 10 times the molecular sieve, add yttrium chloride with a mass ratio of yttrium oxide to molecular sieve of 0.01, slurry temperature 100°C, stirring for 0.5 h, filter bottle vacuum degree 0.02 MPa, filter cake thickness of 5 mm.

[0138] Step 3) Ammonium phosphate solution at a temperature of 20°C, the amount of ammonium phosphate solution is such that the weight ratio of phosphorus to molecular sieve is 0.005. Deionized water temperature is 20°C, the weight ratio of deionized water to molecular sieve is 15. Get filter cake and filtrate I, filter cake drying temperature 20°C, calcination temperature 800°C, calcination time 1 h.

[0139] Step 4) One calcined molecular sieve slurry with a molecular sieve content of 100 g / L, slurry temperature 20°C, filter bottle vacuum degree 0.08 MPa, filter cake thickness of 20 mm.

[0140] Step 5) Ammonium dihydrogen phosphate solution with a phosphorus content of 15 g / L, temperature of 20°C, weight ratio of phosphorus to molecular sieve of 0.15. Deionized water temperature is 100°C, the weight ratio of deionized water to molecular sieve is 15. Get molecular sieve sample and collect filtrate J, which has a sodium oxide content of 1.0%, a phosphorus content of 0.8 ppm in filtrate I, and a rare earth content of 4 ppm.

[0141] 6) Add 1% citric acid to the filter cake molecular sieve in step 5) above, stir for 0.5 h, to obtain the acid modified phosphorus and rare earth containing Y type molecular sieve product S3.

[0142] Preparation of catalyst: mix 22.73 g of S3 molecular sieve, 2.27 g of ZSM-5, 5 g of aluminum sol, 60 g of kaolin, 10 g of aluminum phosphate, and 80 g of water, stir for 80 minutes, then spray dry and calcine to obtain catalyst Y3.

[0143] Example 4

[0144] Preparation of acid modified phosphorus and rare earth containing Y type molecular sieve:

[0145] The operation steps are the same as in Example 1, except that:

[0146] Step 1) Potassium hydroxide: potassium carbonate: mixture of black and yellow humic acid: NaY molecular sieve dry base weight ratio of 0.011:0.007:0.006:1, NaY molecular sieve slurry content of 180 g / L, slurry temperature of 75°C, filter bottle vacuum of 0.04 MPa, filter cake thickness of 8 mm.

[0147] Step 2) Add the filtrate J containing phosphorus and rare earths in an amount of 5 times the mass of the molecular sieve, and add lanthanum chloride in an amount such that the mass ratio of lanthanum oxide to the molecular sieve is 0.06, slurry temperature of 70°C, stirring for 1.5 h, filter bottle vacuum of 0.04 MPa, filter cake thickness of 13 mm.

[0148] Step 3) Ammonium phosphate solution at a temperature of 50°C, the amount of ammonium phosphate solution used being such that the weight ratio of phosphorus to the molecular sieve is 0.17. Deionized water at a temperature of 40°C, the weight ratio of deionized water to the molecular sieve being 8. Obtain the filter cake and filtrate K, filter cake drying temperature of 60°C, calcination temperature of 600°C, calcination time of 1.5 h.

[0149] Step 4) Slurry of the calcined molecular sieve, molecular sieve content of 170 g / L, slurry temperature of 60°C, filter bottle vacuum of 0.04 MPa, filter cake thickness of 18 mm.

[0150] Step 5) Ammonium dihydrogen phosphate solution, phosphorus content of 75 g / L, temperature of 45°C, weight ratio of phosphorus to the molecular sieve being 0.07. Deionized water at a temperature of 60°C, weight ratio of deionized water to the molecular sieve being 9. The filter cake is dried at 200°C and then calcined at 500°C for 1 h to obtain the molecular sieve sample and collect the filtrate L, which has a sodium oxide content of 1.2%, a phosphorus content of 3 ppm in the filtrate K, and a rare earth content of 1 ppm.

[0151] 6) Add the filter cake molecular sieve from step 5) above to tartaric acid at a filter cake dry base of 0.7%, citric acid at 0.2%, and stir for 1 h to obtain the acid-modified phosphorus- and rare earth-containing Y-type molecular sieve finished product S4.

[0152] Preparation of the catalyst: Mix 3 g of silica sol, 45.8 g of kaolin, 0.2 g of white carbon black, 3 g of cerium oxide, and 230 g of water and beat the slurry for 120 minutes, then add 28 g of S4 molecular sieve and 20 g of ZSM-5 molecular sieve and stir until uniform, then spray dry and calcine to obtain the catalyst Y4.

[0153] From the results of the molecular sieve samples S1 to S4 obtained from Examples 1-4, it can be seen that the acid-modified phosphorus and rare earth-containing Y-type molecular sieve obtained by the method of the present application has a higher rare earth introduction amount than the conventional phosphorus and rare earth Y-type molecular sieve, and the rare earth introduction amount is controllable. Compared with the molecular sieve D1 prepared by the comparative example of the prior art, the molecular sieve prepared by the example of the present application has a sodium oxide content comparable to that of the comparative molecular sieve, but in the process of preparing the molecular sieve, there is no loss of phosphorus and rare earth, and the utilization rate of phosphorus and rare earth is more than 99%. However, the molecular sieve D1 prepared by the comparative example has a rare earth content significantly lower than the feeding amount, and a large amount of phosphorus and rare earth is not exchanged onto the molecular sieve in the exchange process, but is lost with the filtrate in the filtration process, resulting in a low utilization rate of phosphorus and rare earth, and the phosphorus and rare earth in the filtrate will cause environmental pollution if not treated. From the molecular sieve sample S1 obtained from the example and the rare earth Y-type molecular sieve D2 obtained from the comparative example, it can be seen that under the condition of the same rare earth amount, the acid-modified phosphorus and rare earth-containing Y-type molecular sieve prepared by the method provided by the present application can take into account the utilization rate of phosphorus and rare earth and the sodium oxide content of the molecular sieve, without affecting the subsequent use of the molecular sieve, and has a good industrial application prospect.

[0154] X1-X3 and Y1-Y4 were evaluated on a fixed fluidized bed device, and in addition, when the Y2 sample was evaluated, 20% Fischer-Tropsch synthetic oil was added to the raw oil, and the obtained evaluation results were Y2-1, and when the Y3 sample was evaluated, 5% waste plastic oil was added to the raw oil, and the obtained evaluation results were Y3-1, and the results are listed in Table 2.

[0155] Table 2 Catalyst evaluation data

[0156]

[0157] It can be further known from the data in Table 2 that the heavy oil conversion capacity can be significantly improved by using the method, and the yield of high value-added product low-carbon olefin is increased.

[0158] Of course, the present application can have other various embodiments, and those skilled in the art can make various corresponding changes and modifications according to the present application without departing from the spirit and essence of the present application, but these corresponding changes and modifications should all belong to the protection scope of the claims of the present application.

Claims

1. A method for improving the yield of low-carbon olefins in heavy oil catalytic cracking, characterized in that, The catalyst used in this method comprises 5-25 wt% aluminum binder, 25-70 wt% molecular sieve, 0-60 wt% clay, and 0.01-10% inorganic oxides. The molecular sieve is ZSM-5 molecular sieve with a mass ratio of 1:1-1:10 and acid-modified phosphorus- and rare-earth-containing Y-type molecular sieve. The preparation of the acid-modified phosphorus- and rare-earth-containing Y-type molecular sieve includes the following steps: Step Step 1: Form a NaY molecular sieve filter cake layer from the slurry of the first NaY molecular sieve; Step 2: Mix the second NaY molecular sieve with a phosphorus-containing filtrate and a rare earth salt solution to form an RE-NaY molecular sieve filter cake layer on the NaY molecular sieve filter cake layer, obtaining a composite filter cake; Step 3: Perform a single ion exchange with the composite filter cake obtained in Step 2 using a phosphate solution, followed by a single calcination to obtain a calcined molecular sieve; the calcined molecular sieve is then mixed with water to form a filter cake, and a secondary ion exchange is performed between the phosphate solution and the filter cake. The process involves ion exchange and secondary calcination to obtain a phosphorus- and rare-earth-containing Y-type molecular sieve. The phosphate solution, calculated as elemental phosphorus, has a weight ratio of 0.02-0.15 between the total amount of phosphate solution used in the two ion exchanges in step 3 and the weight of the calcined molecular sieve. Step 4 involves mixing the phosphorus- and rare-earth-containing Y-type molecular sieve with an organic acid and slurrying to obtain an acid-modified phosphorus- and rare-earth-containing Y-type molecular sieve. The ion exchange and water washing processes are performed at least once. The amount of organic acid added is 0.1-3% of the dry basis mass of the phosphorus- and rare-earth-containing Y-type molecular sieve. The slurry of the first NaY molecular sieve includes the first NaY molecular sieve, alkali metal hydroxide, carbonate, humic acid and water.

2. The method for improving the yield of low-carbon olefins in heavy oil catalytic cracking according to claim 1, characterized in that, The inorganic oxide is selected from one or more of aluminum phosphate, silica, lanthanum oxide, and cerium oxide.

3. The method for improving the yield of low-carbon olefins in heavy oil catalytic cracking according to claim 1, characterized in that, The alkali metal hydroxide is potassium hydroxide, and the carbonate is potassium carbonate; the dry weight ratio of potassium hydroxide:potassium carbonate:humic acid:first NaY molecular sieve is 0.005-0.012:0.005-0.012:0.001-0.05:

1.

4. The method for improving the yield of low-carbon olefins in heavy oil catalytic cracking according to claim 1, characterized in that, The humic acid is one or more of fulvic acid, brown humic acid, and black humic acid.

5. The method for improving the yield of low-carbon olefins in heavy oil catalytic cracking according to claim 1, characterized in that, The mass ratio of the phosphorus-containing filtrate to the second NaY molecular sieve is 2-10.

6. The method for improving the yield of low-carbon olefins in heavy oil catalytic cracking according to claim 1, characterized in that, The mass ratio of the phosphorus-containing filtrate to the second NaY molecular sieve is 3-6.

7. The method for improving the yield of low-carbon olefins in heavy oil catalytic cracking according to claim 1, characterized in that, In step 2, the rare earth salt, calculated as rare earth oxide, is added in a mass ratio of 0.01-0.10 to the second NaY molecular sieve.

8. The method for improving the yield of low-carbon olefins in heavy oil catalytic cracking according to claim 1, characterized in that, In step 2, the rare earth salt, calculated as rare earth oxide, is added in a mass ratio of 0.05-0.10 to the second NaY molecular sieve.

9. The method for improving the yield of low-carbon olefins in heavy oil catalytic cracking according to claim 1, characterized in that, The filtrate from the process of forming the composite filter cake in step 2 and / or the filtrate from the ion exchange process in step 3 are recycled as the phosphorus-containing filtrate described in step 2.

10. The method for improving the yield of low-carbon olefins in heavy oil catalytic cracking according to claim 1, characterized in that, The rare earth salt is one or more water-soluble rare earth salts; the rare earth is selected from at least one of lanthanum, cerium, praseodymium, neodymium, and yttrium.

11. The method for improving the yield of low-carbon olefins in heavy oil catalytic cracking according to claim 1, characterized in that, The rare earth salts are rare earth chloride and rare earth nitrate.

12. The method for improving the yield of low-carbon olefins in heavy oil catalytic cracking according to claim 1, characterized in that, The phosphate is one or more of the water-soluble phosphates.

13. The method for improving the yield of low-carbon olefins in heavy oil catalytic cracking according to claim 1, characterized in that, The phosphate is one or more of ammonium phosphate, diammonium hydrogen phosphate, and ammonium dihydrogen phosphate.

14. The method for improving the yield of low-carbon olefins in heavy oil catalytic cracking according to claim 1, characterized in that, The organic acid is one or more of oxalic acid, citric acid, tartaric acid, and acetic acid.

15. The method for improving the yield of low-carbon olefins in heavy oil catalytic cracking according to claim 1, characterized in that, The heavy oil contains one or more of Fischer-Tropsch synthetic oil, waste plastic oil, and bio-oil, and the mass ratio of one or more of the Fischer-Tropsch synthetic oil, waste plastic oil, and bio-oil to the heavy oil is 1:20-1:5.

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