Anti-metallic contaminant catalytic cracking aid and its preparation method and application

Abstract

The application provides an anti-metal contamination catalytic cracking aid and a preparation method and application thereof. Components of the catalytic cracking aid include: 4-40% of a phosphorus compound calculated by P2O5, 0.5-30% of a phosphorus aluminum material calculated by dry basis, 5-60% of an aluminum compound calculated by oxide, 0-20% of an alkaline earth metal compound calculated by oxide, 0-30% of a phosphorus aluminum molecular sieve calculated by dry basis, 0-70% of clay calculated by dry basis, and a residual amount of inorganic carrier material; wherein a molar ratio of phosphorus element to aluminum element of the phosphorus aluminum material is 1-5:1. The catalytic cracking aid of the application uses a phosphorus compound, a phosphorus aluminum material, an aluminum compound and an alkaline earth metal compound to capture, passivate and reduce deposition of contaminating metals such as iron, nickel and vanadium on a catalyst, so that the catalyst maintains excellent cracking reaction selectivity and use performance.

Description

Technical Field

[0001] This invention belongs to the field of refining catalysts and additives, specifically relating to a catalytic cracking additive resistant to metal contamination, its preparation method, and its application. Background Technology

[0002] Catalytic cracking feedstock contains metallic contaminants such as iron, nickel, and vanadium. These metallic contaminants deposit on the catalyst during catalytic cracking, causing catalyst poisoning and deactivation. This leads to poor selectivity in the catalytic cracking reaction, increased yields of coke and dry gas, and reduced yields of target products such as gasoline and diesel. Consequently, the stable operation of the catalytic cracking unit and the economic benefits of the refinery are affected.

[0003] As fluid catalytic cracking (FCC) feedstocks become increasingly heavier and of lower quality, the effects of metal poisoning on FCC catalysts are becoming more severe. Specifically, iron deposits on the catalyst surface, forming low-melting-point eutectics with sodium and silicon in the catalyst, clogging the catalyst pores, affecting the diffusion and mass transfer of oil and gas molecules within the pores, reducing the accessibility of active sites, and thus decreasing the catalyst's heavy oil conversion capacity and the selectivity of the catalytic cracking reaction. Vanadium in the feedstock forms vanadate under FCC conditions, causing dealuminization and structural collapse of the molecular sieve framework, ultimately leading to the deactivation of the molecular sieve and catalyst, which also reduces the catalyst's heavy oil conversion capacity and the selectivity of the catalytic cracking reaction. Nickel in crude oil deposits on the catalyst; during the catalytic cracking reaction, nickel has strong dehydrogenation activity, increasing hydrogen yield and promoting the coking reaction of unsaturated hydrocarbons, clogging the catalyst pores, reducing the catalyst's specific surface area, and thus decreasing the selectivity of the catalytic cracking reaction.

[0004] To address the adverse effects of metal contaminants such as iron, nickel, and vanadium on catalysts, current technologies mainly focus on three aspects: improving the resistance of catalytic cracking catalysts to metal contamination, using catalytic cracking promoters, and using metal passivators. Among these, the use of catalytic cracking promoters and metal passivators is convenient to use, eliminates the need to replace all catalysts in the catalytic cracking unit to achieve a specific reaction target, and is characterized by low dosage and rapid effectiveness.

[0005] Regarding catalysts for resisting metal contamination, CN1057022C discloses a zeolite catalyst with a chemically modified matrix and its preparation method. The catalyst matrix is ​​a novel composition of alkaline earth metal titanate and phosphorus-containing γ-Al₂O₃. Specifically, the catalyst consists of 10-60 wt% of one of HY, REY, or USY zeolites, 5-40 wt% of natural or synthetic kaolinite, 5-40 wt% of 0.1-4.0 wt% high-temperature resistant phosphorus-containing γ-Al₂O₃, and 1-30 wt% of alkaline earth metal titanate selected from Ba, Sr, or Mg. This catalyst exhibits high activity, high resistance to carbon, and strong resistance to heavy metal contamination by nickel and vanadium.

[0006] CN104014361B discloses a catalytic cracking catalyst and its preparation method. The catalyst comprises 1-60 wt% modified biporous alumina, 10-70 wt% molecular sieve with a FAU structure, 1-60 wt% binder, and 5-70 wt% clay. Based on the weight of the modified biporous alumina, it contains 0.05-1 wt% rare earth elements (based on RE₂O₃) and 0.5-10 wt% silicon (based on SiO₂). The modified biporous alumina has a γ-alumina crystal structure, with accessible pore sizes of 4-9.5 nm for smaller pores and 12-25 nm for larger pores, and a specific surface area of ​​250-500 m². 2 / g, pore volume 0.6-1.8cm³ 3 / g. This catalyst can improve gasoline quality and increase liquid product yield, and has strong heavy oil cracking capability under metal contamination conditions.

[0007] CN103769192B discloses a catalytic cracking catalyst and its preparation method. The catalyst contains a biporous silica-alumina material and a molecular sieve. The smaller pore of the biporous silica-alumina material has a visible pore size of 2-10 nm, and the larger pore has a visible pore size of 10-25 nm. Based on the total catalyst volume, the content of the biporous silica-alumina material is 1-52% by weight, the clay content is 9-60%, the phosphorus content (based on P2O5) is 0-8%, the rare earth metal content (based on RE2O3) is 0-3%, the binder content is 19-70%, and the Y-type molecular sieve content is 20-70%. This catalyst exhibits strong resistance to metal contamination, strong heavy oil cracking ability, high liquid yield, and can improve the quality of gasoline in the cracking products.

[0008] Regarding anti-metal contamination additives, CN100478420C discloses a catalytic cracking additive and its preparation method. This additive contains alumina and molecular sieves, with or without clay. The alumina is n-alumina and / or X-alumina, or a mixture of n-alumina and / or X-alumina with γ-alumina. The additive also contains phosphorus and alkaline earth metals. Based on the additive weight, the content of n-alumina and / or X-alumina is 0.5-50 wt%, the content of γ-alumina is 0-50 wt%, the content of molecular sieve is 0.5-20 wt%, the content of clay is 0-75 wt%, the phosphorus content (based on P2O5) is 0.1-4 wt%, and the alkaline earth metal content (based on oxides) is 0.1-4 wt%. The molecular sieve is Y-type zeolite. This additive has strong resistance to heavy metal contamination and can improve the quality of gasoline in cracking products.

[0009] CN200810238705.1 discloses a heavy hydrocarbon oil catalytic cracking additive and its preparation method, comprising the following components (wt%): Al2O3 10-65%, P (based on elemental P) 2-13%, SiO2 1-15%, and clay 10-65%. The preparation method includes: a. Preparation of aluminum phosphate colloid: dissolving a phosphorus source compound and hydrated alumina separately in deionized water according to a molar ratio of P:Al2O3 = 0.5-5:1, and preparing an aluminum phosphate colloid with a solid content of 20-40 wt%; stirring and dissolving at 20℃-60℃ for 1-5 hours; obtaining the aluminum phosphate colloid for later use; b. Preparation of aluminum phosphate colloid: adding water glass to the dissolved aluminum phosphate colloid, wherein the amount of water glass added is by weight percentage. The ratio of SiO2:Al2O3 is 0.01-1.5:1. Under stirring, the mixture is aged at 20℃-80℃ for 1-3 hours to obtain a silica-alumina phosphate gel for later use. c. Mixing and pulping: Clay is added to the silica-alumina phosphate gel, with the amount of clay added ensuring that the clay content in the final additive is 10-65 wt%. The mixture is then mixed and pulped for 1-3 hours. d. Spray molding; e. Washing and drying: The filtrate is washed with deionized water until the pH value is between 6-7, and then dried at 80-120℃. This additive has a strong resistance to heavy metal contamination and improves the selectivity of heavy hydrocarbon oil cracking reactions. However, this technology does not provide information on the additive's resistance to heavy metal contamination, nor does it specify which heavy metal contamination the additive resists. The presence of silica is detrimental to the resistance to iron contamination. The additive contains SiO2 provided by water glass, while iron oxide forms a low melting point eutectic with sodium and silica with a melting point below 500℃. Under reaction-regeneration temperature conditions, it has strong fluidity, blocks the catalyst pores, prevents the diffusion of macromolecules, affects the accessibility of the catalyst active center, and reduces the heavy oil conversion capacity. Reference [1] Shi Lei, Bi Lintian, Yao Yuan. The effect of iron on catalytic cracking catalyst [J]. Qilu Petrochemical, 2012, 40(1): 50-53; Reference [2] Bai Rui. Study on the iron migration law of catalytic cracking reactor bed and industrial application of new iron-resistant catalyst [J]. Petroleum Refining and Chemical Industry, 2022, 53(4): 38-42).

[0010] Regarding anti-metal contamination passivating agents, CN88102585A discloses a method for suppressing the poisoning effect of contaminating metals on cracking catalysts during fluidized catalytic cracking. This method involves depositing a small amount of bismuth-containing passivating agent onto the catalyst to suppress the poisoning effect of contaminating metals such as nickel, vanadium, and iron on the cracking catalyst during fluidized catalytic cracking with hydrocarbon feed containing contaminating metals. Ideally, the weight ratio of bismuth to nickel equivalent (nickel + 0.2 vanadium and 0.1 iron) is approximately 0.01:1 to 1:1. The passivating agent may also contain mixtures of bismuth and antimony, as well as compounds of bismuth and tin.

[0011] CN100540141C discloses a catalytic cracking metal passivator and its preparation method, which provides boron-containing compounds and compounds containing both boron and phosphorus as catalytic cracking metal passivators. This passivator exhibits a significant passivation effect on nickel on the catalytic cracking catalyst, resulting in a marked improvement in the distribution of reaction products. The yield of the ideal product, gasoline, increases by 2.5-4 percentage points, while the yields of the non-ideal products, coke and hydrogen, decrease, with the hydrogen yield decreasing by 20-40%. However, if boron migrates onto the catalyst, even a small amount can disrupt the structure of the active component molecular sieve in the catalyst, leading to a decrease in the catalyst's cracking activity and conversion rate.

[0012] CN1133717C discloses a water-soluble catalytic cracking (FCC) metal passivator and its preparation method. This passivator is effective against heavy metal contamination on catalytic cracking catalysts, especially nickel, iron, vanadium, and sodium. The agent uses antimony, aluminum, and rare earth metal elements lanthanum (or cerium) as the main active components. After the compounds of these metal elements react with organic carboxylic acids, they are mixed to form highly stable compounds. It has the characteristics of high efficiency, low toxicity, stable properties (does not decompose below 300℃), convenient use, and water miscibility. It can passivate the contamination of catalysts by nickel, iron, vanadium, and sodium, improve the yield of gasoline and light oil, reduce hydrogen yield and hydrogen / methane ratio, improve product selectivity, and enhance catalyst activity.

[0013] In existing technologies, anti-metal contamination catalytic cracking catalysts generally contain metal trapping components, such as rare earth oxides and alkaline earth metals, in their formulation design. They also employ porous active support materials or modify catalyst preparation techniques to increase the pore volume and the proportion of mesopores and macropores, thereby passivating heavy metals, reducing the adverse effects of metal contamination on the catalyst, and improving the catalyst's resistance to metal contamination. However, the rare earth oxides and alkaline earth metals used for metal trapping in the catalyst can transfer to the molecular sieve during use. Rare earths can increase the acid density and coke yield of the molecular sieve catalyst, while excessive alkaline earth metals can neutralize the acid active sites of the molecular sieve, reducing catalyst activity. Therefore, the content of rare earth and alkaline earth metals used for metal contamination resistance in catalytic cracking catalysts is usually low, affecting their anti-metal contamination effect. Regarding anti-metal contamination additives, their anti-wear properties and anti-metal contamination capabilities also need to be improved.

[0014] In existing technologies, passivating agents for resisting metal contamination are liquid-phase and generally contain organic solvents and metal trapping components, such as Sb, rare earth oxides, and alkaline earth metals. During catalytic cracking, the passivating agent is added to the reactor along with the feedstock. The passivating agent droplets deposit on the surface of catalyst microspheres and interact with harmful contaminating metal components, thereby passivating heavy metals, reducing the adverse effects of metal contamination on the catalyst, and improving the catalyst's resistance to metal contamination. However, the metal passivating agents with industrial application value are mainly organometallic passivating agents such as antimony-based, bismuth-based, and tin-based agents. These organometallic passivating agents are highly toxic and harmful to human health and the environment, limiting their use. Furthermore, the stability of the passivating agent also affects its performance.

[0015] Therefore, in order to reduce the adverse effects of metal contaminants such as iron, nickel, and vanadium contained in catalytic cracking feedstock on catalysts, despite recent advancements in catalyst, additive, and metal passivator technologies, there is still a need for new additive preparation technologies that are environmentally friendly, simple, and feasible, while also possessing excellent resistance to metal contamination such as iron, nickel, and vanadium. Summary of the Invention

[0016] To overcome the shortcomings of existing technologies, the present invention aims to provide a catalytic cracking aid resistant to metal contamination, its preparation method and application, which is resistant to metal contamination such as iron, nickel, and vanadium, especially iron contamination.

[0017] To achieve the above objectives, the present invention provides a catalytic cracking additive resistant to metal contamination. The catalytic cracking additive comprises, by mass percentage: 4-40% phosphorus compound (based on P2O5), 0.5-30% phosphorus-aluminum material (on a dry basis), 5-60% aluminum compound (based on oxides), 0-20% alkaline earth metal compound (based on oxides), 0-30% phosphorus-aluminum molecular sieve (on a dry basis), 0-70% clay (on a dry basis), and the balance being an inorganic support material; wherein the molar ratio (P / Al) of phosphorus to aluminum in the phosphorus-aluminum material is 1-5:1.

[0018] In fluidized catalytic cracking, the feedstock and catalyst surface contain contaminating metals such as iron, nickel, and vanadium. The catalytic cracking aid of this invention uses phosphorus compounds, phosphorus aluminum materials, aluminum compounds, and alkaline earth metal compounds to capture and passivate contaminating metals such as iron, nickel, and vanadium, and combine with the contaminating metals to form stable compounds, reducing the deposition of contaminating metals on the catalyst, thereby enabling the catalyst to maintain excellent cracking reaction selectivity and performance.

[0019] In the catalytic cracking additive of the present invention, phosphorus compounds can capture and passivate iron, aluminum compounds have the effect of passivating nickel, and alkaline earth metals can passivate heavy metal vanadium; the phosphorus-aluminum molecular sieve contains phosphorus and also has the effect of passivating iron. In addition, the phosphorus-aluminum material added in the present invention, besides passivating iron, can also improve the pore structure of the additive, increase the proportion of mesopores and macropores in the additive, and improve the diffusion and mass transfer effect of the catalytic cracking additive.

[0020] To better enable the aforementioned effective components in the catalytic cracking additive that passivate contaminating metals to function, while avoiding the adverse effects of these effective components on the activity and selectivity of the Y-type molecular sieve, the catalytic cracking additive of this invention does not contain Y-type molecular sieves or rare earth elements. Furthermore, the catalytic cracking additive of this invention also does not contain elements such as antimony, bismuth, and tin, which are harmful to human health and are commonly used in metal passivating agents.

[0021] In the aforementioned anti-metal contamination catalytic cracking additive, preferably, by mass percentage, the components of the catalytic cracking additive include: 10-30% phosphorus compound (based on P2O5), 1-20% phosphorus-aluminum material (based on a dry basis), 8-30% aluminum compound (based on oxides), 1-10% alkaline earth metal compound (based on oxides), 1-20% phosphorus-aluminum molecular sieve (based on a dry basis), 5-62% clay (based on a dry basis), and the balance being inorganic oxide carrier material; wherein, the molar ratio of phosphorus to aluminum in the phosphorus-aluminum material is 1.5-4:1.

[0022] In the aforementioned catalytic cracking aid for resisting metal contamination, preferably, the phosphorus source providing the phosphorus compound includes one or more combinations of phosphoric acid, phosphate, phosphorous acid, phosphite, pyrophosphate, pyrophosphate, polyphosphate, polyphosphate, metaphosphate, and metaphosphate. More preferably, the phosphorus source includes one or more combinations of phosphoric acid, ammonium phosphate, ammonium hydrogen phosphate, diammonium hydrogen phosphate, magnesium phosphate, aluminum phosphate, phosphorous acid, ammonium phosphite, sodium pyrophosphate, sodium tripolyphosphate, and sodium hexametaphosphate. The phosphorus compound of this invention does not contain phosphorus contained in aluminum phosphate materials or aluminum phosphate molecular sieves.

[0023] In the above-mentioned catalytic cracking additives for resisting metal contamination, preferably, the aluminum phosphate material is prepared by the following method: acid-soluble aluminum precursor is slurried with deionized water to form an aluminum-containing slurry with a solid content of 15-45 wt%; phosphoric acid with a mass concentration of 10-85% is added to the aluminum-containing slurry under stirring, preferably with the addition of an acid regulator; after reaction, an aluminum phosphate sol with a pH value of 0.1-4.5 is obtained; the aluminum phosphate sol is dried and then calcined at 400-800℃ for 0.5-4 h to obtain the aluminum phosphate material.

[0024] For the reaction of boehmite with phosphoric acid, if the phosphorus-aluminum molar ratio is <1, acid can be added; if the phosphorus-aluminum ratio is >3, the reaction can form a transparent phosphorus-aluminum gel, in which case acid does not need to be added.

[0025] In the above-mentioned catalytic cracking aid for resisting metal contamination, preferably, in the method for preparing the phosphorus-aluminum material, the acid-soluble aluminum precursor is selected from one or more combinations of alumina, aluminum hydroxide, aluminum nitrate, aluminum chloride, aluminum sol, phosphorus-aluminum colloid, boehmite, and pseudoboehmite; the acid regulator is selected from one or more combinations of hydrochloric acid, nitric acid, formic acid, oxalic acid, and citric acid.

[0026] In the aforementioned catalytic cracking aids for resisting metal contamination, preferably, the aluminum source providing the aluminum compound includes one or more combinations of boehmite, gibbsite, amorphous alumina, and aluminum sol.

[0027] In the above-mentioned catalytic cracking additives for resisting metal contamination, preferably, the phosphorus aluminum molecular sieve is selected from one or more of APO-5 molecular sieve, APO-11 molecular sieve, APO-31 molecular sieve, APO-34 molecular sieve, APO-41 molecular sieve, VPI-5 molecular sieve, HMA molecular sieve, DNL-1 molecular sieve, SAPO-5 molecular sieve, SAPO-11 molecular sieve, and SAPO-34 molecular sieve.

[0028] In the above-mentioned catalytic cracking additives for resisting metal pollution, preferably, the alkaline earth metal element is selected from one or more combinations of magnesium, calcium, and barium; the alkaline earth metal source providing the alkaline earth metal compound includes one or more combinations of oxides, chlorides, nitrates, carbonates, oxalates, and acetates of alkaline earth metals.

[0029] In the above-mentioned catalytic cracking additives for resisting metal contamination, preferably, the clay is selected from one or more combinations of kaolin, hydrous kaolin, montmorillonite, diatomite, halloysite, sepiolite, and bentonite, and more preferably, the clay is selected from one or more combinations of kaolin, hydrous kaolin, halloysite, and sepiolite.

[0030] In the aforementioned catalytic cracking aids for resisting metal contamination, preferably, the inorganic carrier material includes titanium dioxide and / or zirconium oxide.

[0031] In the aforementioned catalytic cracking additive for resisting metal contamination, preferably, the raw materials of the catalytic cracking additive further include quaternary ammonium salt surfactants, wherein the mass of the quaternary ammonium salt surfactants is 0.1-10% of the total mass of the catalytic cracking additives. In this invention, the addition of quaternary ammonium salt surfactants improves the pore structure of the catalytic cracking additives and increases their specific surface area.

[0032] In the above-mentioned anti-metal contamination catalytic cracking additives, preferably, the mass of the quaternary ammonium salt surfactant is 0.3-6% of the total mass of the catalytic cracking additives.

[0033] In the aforementioned catalytic cracking additives for resisting metal contamination, preferably, the quaternary ammonium salt surfactant includes one or a combination of two or more of dodecyltrimethylammonium chloride, dodecyltrimethylammonium bromide, hexadecyltrimethylammonium chloride, and hexadecyltrimethylammonium bromide.

[0034] The present invention also provides a method for preparing the above-mentioned anti-metal contamination catalytic cracking additive, the method comprising the following steps:

[0035] The phosphorus source, phosphorus-aluminum material, aluminum source, alkaline earth metal source, phosphorus-aluminum molecular sieve, clay, inorganic carrier material and preferred added quaternary ammonium salt surfactant are mixed and pulped, and then sent into a high-pressure jet reactor for processing to obtain a mixed slurry.

[0036] The mixed slurry is spray-dried and then calcined to solidify, thereby obtaining the metal-resistant catalytic cracking aid.

[0037] In the above-mentioned method for preparing the anti-metal contamination catalytic cracking additive, preferably, the cavity diameter of the high-pressure jet reactor is ≤300um and the pressure is ≥10000psi; the average particle size of each component in the mixed slurry is less than 1μm.

[0038] The average particle size of each component in the slurry treated by the high-pressure jet reactor can reach 500 nm, which can achieve efficient dispersion of each component of the additive and improve the anti-wear and reaction performance of the catalytic cracking additive. This invention controls the sieving distribution of the spray-formed additive microspheres by controlling the spray forming conditions such as spray pressure and nozzle size.

[0039] In the above-mentioned method for preparing the anti-metal contamination catalytic cracking aid, preferably, when the aluminum source is boehmite, the preparation method further includes: during the slurry preparation process, adding an inorganic acid to the slurry containing boehmite to adjust its pH value to the range of 0.2-4.5, and then aging it. The inorganic acid can be one or more of hydrochloric acid, sulfuric acid, and nitric acid. This step can make the boehmite in the slurry colloidal (acid-soluble), and the colloidal boehmite has a smaller particle size and certain binding properties, which can improve the anti-wear performance of the catalytic cracking aid of the present invention.

[0040] In the above-mentioned method for preparing catalytic cracking additives resistant to metal contamination, preferably, the aging temperature in the sol of pseudoboehmite is 40-90℃ and the aging time is 0.5-3h.

[0041] In some specific embodiments of the present invention, the aluminum source is selected from boehmite with different specific surface areas and pore volumes. More preferably, boehmite with smaller surface areas and pore volumes is soluble (acid-soluble), while boehmite with larger surface areas and pore volumes is not soluble. By utilizing its own physical structure, the proportion of macropores in the catalytic cracking promoter is increased, thereby improving the diffusion and mass transfer effect of the catalytic cracking promoter.

[0042] In the above-mentioned method for preparing catalytic cracking additives resistant to metal contamination, preferably, the furnace temperature of the spray tower used for spray drying is 450-550℃, and the spray exhaust gas temperature is 200-300℃.

[0043] In the above-mentioned method for preparing the anti-metal contamination catalytic cracking additive, preferably, the preparation method further includes: washing the calcined and solidified particles with water. When the sodium oxide content in the calcined particles exceeds 0.40 wt%, water washing is required; otherwise, water washing is unnecessary.

[0044] The present invention also provides the application of the above-mentioned anti-metal contamination catalytic cracking additive in petroleum fluidized catalytic cracking reaction, wherein the metal contamination includes at least one of iron, nickel, and vanadium, preferably iron.

[0045] In some specific embodiments of the present invention, when the catalytic cracking additive prepared by the present invention is mixed with LDO-70 industrial catalyst (base agent) at a weight ratio of 9:1, the conversion rate of the catalytic cracking reaction is increased by 4.35 percentage points compared with that without the additive, and the total liquid yield (liquefied gas + gasoline + diesel) of the catalytic cracking reaction is increased by 1.55 percentage points, showing excellent iron resistance.

[0046] In other specific embodiments, when the catalytic cracking additive prepared according to this invention is mixed with the base agent LDO-70 industrial catalyst at a weight ratio of 9:1, it still exhibits high conversion rate and total liquid yield even with V contamination of 5000 μg / g and Ni contamination of 3000 μg / g. The conversion rate is increased by more than 3 percentage points, and the total liquid yield is increased by more than 1 percentage point. The hydrogen / methane and coke factors are reduced, demonstrating excellent resistance to nickel and vanadium. Furthermore, the catalytic cracking additive of this invention has strong heavy oil conversion capacity, low coking rate, is easy to use, requires small dosage, and is fast-acting.

[0047] The technical solution provided by this invention has the following beneficial effects:

[0048] (1) The catalytic cracking additive of the present invention uses phosphorus compounds, phosphorus aluminum materials, aluminum compounds and alkaline earth metal compounds to capture and passivate contaminating metals such as iron, nickel and vanadium in the feedstock oil, so that the contaminating metals form stable compounds with the phosphorus compounds, phosphorus aluminum materials, aluminum compounds and alkaline earth metal compounds in the additive, reducing their deposition on the catalyst, thereby maintaining the excellent cracking reaction performance and performance of the catalyst.

[0049] (2) The catalytic cracking additive of the present invention does not contain Y-type molecular sieve, which can avoid the adverse effects of a large amount of phosphorus and alkaline earth metals on the molecular sieve structure and cracking reaction selectivity, and fully ensure the capture and passivation effect of phosphorus and alkaline earth metals on polluting metals.

[0050] (3) The catalytic cracking additive of the present invention does not contain rare earth, thus avoiding the formation of stable rare earth phosphate with phosphorus, thereby reducing the capture and passivation effect of phosphorus on polluting metals such as iron, nickel, and vanadium.

[0051] (4) The catalytic cracking additive provided by the present invention has a simple and environmentally friendly preparation process; the content of phosphorus compounds, phosphorus aluminum materials, aluminum compounds and alkaline earth metal compounds in the additive can be adjusted within a wider range, so that the additive can give full play to its anti-metal pollution performance without affecting the activity and reaction performance of the main catalyst. Detailed Implementation

[0052] In order to provide a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

[0053] In an embodiment of the present invention, the elemental content in the sample catalyst was determined by X-ray fluorescence analysis.

[0054] The origin and specifications of the raw materials used in the embodiments of this invention are as follows:

[0055] (1) Kaolin (loss on ignition 29%), halloysite (loss on ignition 16.2%), pseudoboehmite 1 (loss on ignition 38%, specific surface area 356 m²) 2 / g, pore volume 0.56mL / g), pseudoboehmite 2 (30% loss on ignition, specific surface area 420m²) 2 / g, pore volume 1.10mL / g), alumina sol (containing 21.2wt% alumina), boehmite (loss on ignition 17.0%), REY zeolite (RE2O3 content 18.0wt%, reduced by 7%), USY zeolite (Na2O content 1.2wt%, excluding rare earth elements, reduced by 4%): all are industrial products, sourced from Lanzhou Petrochemical Company Catalyst Plant; LDO-70 industrial catalyst: industrial product, produced by Lanzhou Petrochemical Company Catalyst Plant;

[0056] (2) SAPO-11 molecular sieve (P content 5.50%): industrial product, produced by Fushun Petrochemical Company;

[0057] (3) β-alumina trihydrate (loss on ignition 36%): Produced by Shandong Aluminum Industry Research Institute;

[0058] (4) Magnesium chloride, magnesium oxide, calcium carbonate, phosphoric acid (concentration 85%), ammonium dihydrogen phosphate, diammonium hydrogen phosphate, titanium dioxide, zirconium oxide, dodecyltrimethylammonium chloride, hexadecyltrimethylammonium chloride, ferric naphthenate, and petroleum ether: all are chemical reagents;

[0059] (5) Hydrochloric acid: 36% concentration, chemical reagent;

[0060] Example 1

[0061] This embodiment provides a phosphorus aluminum material, the preparation method of which is as follows:

[0062] 1.33 kg of aluminum sol and 7.47 kg of deionized water were added to a pulping tank and pulped for 15 minutes. While stirring, 3.198 kg of 85% concentrated phosphoric acid was added to the slurry, and the reaction was continued for 30 minutes to obtain a colorless and transparent aluminum phosphide sol with a pH of 0.2. The sol was dried at 120°C and then calcined at 650°C for 2 hours to obtain the aluminum phosphide material PA1-1.

[0063] The composition of the phosphorus aluminum material PAl-1 is as follows: 14.8 wt% alumina from aluminum sol, 85.2 wt% phosphorus pentoxide from phosphoric acid, and P / Al (molar ratio) of 5.

[0064] Example 2

[0065] This embodiment provides a phosphorus aluminum material, the preparation method of which is as follows:

[0066] 0.934 kg of pseudoboehmite 1 and 2.112 kg of deionized water were added to a pulping tank and pulped for 10 minutes. While stirring, 3.931 kg of 85% concentrated phosphoric acid was added to the slurry, and the reaction was continued for 1 hour to obtain a colorless and transparent aluminum phosphate sol with a pH of 0.53. The sol was dried at 150°C and then calcined at 600°C for 3 hours to obtain aluminum phosphate material PA1-2.

[0067] The composition of the phosphorus aluminum material PAl-2 is as follows: 19.3 wt% alumina from boehmite 1, 80.7 wt% phosphorus pentoxide from phosphoric acid, and P / Al (molar ratio) of 3.

[0068] Example 3

[0069] This embodiment provides a catalytic cracking aid resistant to metal contamination, and its preparation method is as follows:

[0070] 1.035 kg of kaolin (dry basis), 0.36 kg of boehmite 1 (dry basis), 0.75 kg of SAPO-11 molecular sieve, and 3.88 kg of deionized water were added to a pulping tank and pulped for 1 hour. Then, 39 mL of hydrochloric acid was added and stirred for 1 hour. After that, the mixture was aged at 50 °C for 2 hours. Then, 0.877 kg of phosphoric acid, 15 g of phosphorus aluminum material PA1-1 (dry basis) from Example 1, 0.30 kg of boehmite 2 (dry basis), and 30 g of dodecyltrimethylammonium chloride were added and mixed and pulped for 1 hour. The mixture was then fed into a high-pressure jet reactor for processing to make the average particle size of each component in the resulting slurry 600 nm. The slurry was then spray-dried and calcined at 550 °C for 2 hours to obtain catalytic cracking aid CAT-1.

[0071] The composition of catalytic cracking additive CAT-1 is as follows: 34.5 wt% kaolin (dry basis), 0.5 wt% aluminum phosphate material PA1-1 (dry basis), 12 wt% alumina from boehmite 1, 10 wt% alumina from boehmite 2, 18 wt% phosphorus pentoxide from phosphoric acid, and 25 wt% SAPO-11 molecular sieve.

[0072] Example 4

[0073] This embodiment provides a catalytic cracking aid resistant to metal contamination, and its preparation method is as follows:

[0074] 1.020 kg of kaolin (dry basis), 0.75 kg of halloysite (dry basis), 150 g of the phosphorus aluminum material PA1-1 from Example 1 (dry basis), 0.6 kg of boehmite 1 (dry basis), 0.566 kg of aluminum sol, and 5.8 kg of deionized water were added to a slurry tank and slurried. The mixture was stirred for 0.5 hours, then 40 mL of hydrochloric acid was added and stirred for 1 hour. The mixture was then aged at 40 °C for 1 hour. Next, 0.486 kg of ammonium dihydrogen phosphate, 60 g of dodecyltrimethylammonium chloride, and 60 g of magnesium oxide were added and mixed and slurried for 1.5 hours. The mixture was then fed into a high-pressure jet reactor for processing to make the average particle size of each component in the resulting slurry less than 1 μm. The slurry was then spray-dried and calcined at 450 °C for 1.5 hours to obtain catalytic cracking aid CAT-2.

[0075] The composition of catalytic cracking additive CAT-2 is as follows: 34 wt% kaolin (dry basis), 25 wt% halloysite (dry basis), 5 wt% aluminum phosphate material PA1-1 (dry basis), 20 wt% alumina from boehmite 1, 4 wt% alumina from alumina sol, 10 wt% phosphorus pentoxide from ammonium dihydrogen phosphate, and 2 wt% magnesium oxide.

[0076] Example 5

[0077] This embodiment provides a catalytic cracking aid resistant to metal contamination, and its preparation method is as follows:

[0078] 0.720 kg of kaolin (dry basis), 0.24 kg of titanium dioxide, 0.3 kg of phosphorus aluminum material PA1-2 (dry basis) from Example 2, 0.54 kg of boehmite 1 (dry basis), 1.525 kg of magnesium chloride, and 3.7 kg of deionized water were added to a pulping tank and pulped for 2 hours. Then, 1.461 kg of phosphoric acid and 60 g of hexadecyltrimethylammonium chloride were added and mixed and pulped for 0.5 hours. The mixture was then fed into a high-pressure jet reactor for processing. The average particle size of each component in the resulting slurry was 520 nm. The slurry was spray-dried and calcined at 600 °C for 1 hour to obtain catalytic cracking aid CAT-3.

[0079] The composition of catalytic cracking additive CAT-3 is as follows: 24 wt% kaolin (dry basis), 8 wt% titanium dioxide (dry basis), 10 wt% aluminum phosphate material PA1-2 (dry basis), 18 wt% alumina from boehmite 1, 30 wt% phosphorus pentoxide from phosphoric acid, and 10 wt% magnesium oxide from magnesium chloride.

[0080] Example 6

[0081] This embodiment provides a catalytic cracking aid resistant to metal contamination, and its preparation method is as follows:

[0082] 1.26 kg of kaolin (dry basis), 0.12 kg of zirconium oxide, 0.45 kg of PA1-2 (dry basis) from Example 2 of phosphorus aluminum material, 0.54 kg of pseudoboehmite 1 (dry basis), 0.15 kg of boehmite (dry basis), and 5.1 kg of deionized water were added to a pulping tank and pulped for 1 hour. Then, 23 mL of hydrochloric acid was added and stirred for 1 hour. Then, 54 g of calcium carbonate, 0.731 kg of phosphoric acid, and 120 g of dodecyltrimethylammonium chloride were added and mixed and pulped for 2 hours. The mixture was then fed into a high-pressure jet reactor for processing. The average particle size of each component in the resulting slurry was 650 nm. The slurry was spray-dried and calcined at 500 °C for 1 hour to obtain catalytic cracking aid CAT-4.

[0083] The composition of catalytic cracking additive CAT-4 is as follows: 42 wt% kaolin (dry basis), 4 wt% zirconium oxide (dry basis), 15 wt% aluminum phosphate material PA1-2 (dry basis), 18 wt% alumina from boehmite 1, 5 wt% alumina from boehmite, 15 wt% phosphorus pentoxide from phosphoric acid, and 1 wt% calcium oxide from calcium carbonate.

[0084] The water droplet pore volume of the catalytic cracking aid CAT-4 is 0.40 mL / g.

[0085] Comparative Example 1

[0086] This comparative example provides a catalytic cracking aid, which is prepared according to the method of Example 1 in the specification CN100478420C, and uses a Y-type molecular sieve, as detailed below:

[0087] 1.05 kg of β-alumina trihydrate (dry basis), 120 g of USY zeolite (dry basis), 60 g of REY zeolite (dry basis), 1.713 kg of kaolin (dry basis), 183 g of magnesium chloride, 39 g of diammonium hydrogen phosphate, and 4.6 kg of deionized water were added to a pulping tank and pulped for 1 hour to obtain a slurry with a solid content of 33 wt%. The slurry was homogenized, spray-dried into particles of 40-150 micrometers, and calcined at 500℃ for 1 hour to obtain the comparative additive DCAT-1.

[0088] The composition of additive DCAT-1 is as follows: 57.1 wt% kaolin (dry basis), 35 wt% β-alumina trihydrate (dry basis), 4 wt% USY zeolite (dry basis), 2 wt% REY zeolite (dry basis), 0.7 wt% phosphorus pentoxide from diammonium hydrogen phosphate, and 1.2 wt% magnesium oxide from magnesium chloride.

[0089] Comparative Example 2

[0090] This comparative example is identical to Example 6, except that 0.45 kg of phosphorus aluminum material PA1-2 (dry basis) is omitted and the amount of kaolin (dry basis) added is changed from 1.26 kg to 1.71 kg. Comparative additive DCAT-2 was obtained.

[0091] The composition of additive DCAT-2 is as follows: 57 wt% kaolin (dry basis), 4 wt% zirconium oxide (dry basis), 18 wt% alumina from boehmite 1, 5 wt% alumina from boehmite, 15 wt% phosphorus pentoxide from phosphoric acid, and 1 wt% calcium oxide from calcium carbonate.

[0092] The water droplet volume of the additive DCAT-2 is 0.32 mL / g.

[0093] Experimental Example 1

[0094] This experimental example is used to evaluate the performance of CAT-1, the catalytic cracking aid of Example 1.

[0095] Industrial catalyst LDO-70 was mixed with catalytic cracking aid CAT-1 from Example 3 and comparative aid DCAT-1 from Comparative Example 1 at a weight ratio of 9:1 to obtain two catalyst mixtures (LDO-70 catalyst + CAT-1 and LDO-70 catalyst + CAT-2). These two catalyst mixtures and the LDO-70 industrial catalyst alone were subjected to iron contamination, followed by aging at 800°C and 100% steam for 10 hours. The catalytic cracking performance was then evaluated on a heavy oil microreactor (ACE) device. The iron contamination method involved impregnating the three catalyst mixtures with a petroleum ether solution of ferric naphthenate for 1 hour, drying at 120°C, and calcining at 600°C for 2 hours, contaminating the catalysts with 8000 μg / g (based on catalyst weight) of iron.

[0096] The evaluation results are shown in Table 1.

[0097] In Table 1, total liquid yield = LPG yield + gasoline yield + diesel yield; coke factor = (100 - conversion rate) × coke yield / conversion rate.

[0098] Table 1. Results of Selectivity Evaluation of CAT-1 and DCAT-1 Catalytic Cracking Reactions

[0099]

[0100] Table 1 shows that, compared with the LDO-70 industrial catalyst, the addition of the catalytic cracking aid CAT-1 of this invention resulted in a higher conversion rate and total liquid yield in the catalyst mixture, despite the presence of up to 8000 μg / g of iron contamination. The conversion rate and total liquid yield increased by 4.35 percentage points and 1.55 percentage points, respectively. The decrease in hydrogen / methane and coke factors indicates that the addition of the catalytic cracking aid CAT-1 of this invention reduced the dehydrogenation reaction in the catalytic cracking process, decreased coke formation, and improved the selectivity of the catalytic cracking reaction. The aid of this invention has a good effect against heavy metal iron.

[0101] Compared with the LDO-70 industrial catalyst, the addition of the comparative additive DCAT-1 improved the conversion rate and total liquid yield, but the improvement was less than that of the catalytic cracking additive CAT-1 of the present invention. In addition, the hydrogen / methane and coke factors were higher than those of the catalytic cracking additive CAT-1 of the present invention, indicating that the iron resistance of the catalytic cracking additive CAT-1 of the present invention is better than that of the comparative additive DCAT-1.

[0102] Experimental Example 2

[0103] This experimental example is used to evaluate the performance of the catalytic cracking aids in Examples 3-6.

[0104] The industrial catalyst with the industrial grade LDO-70 was mixed with the catalytic cracking promoters CAT-1, CAT-2, CAT-3, and CAT-4 prepared in Examples 3, 4, 5, and 6, and the promoter DCAT-2 prepared in Comparative Example 2, at a weight ratio of 9:1 to obtain 5 catalyst mixtures. These 5 catalyst mixtures and the LDO-70 industrial catalyst alone were impregnated with 3000 μg / g Ni and 5000 μg / g V (based on catalyst weight). After the nickel and vanadium contaminated catalysts were aged at 800°C and 100% water vapor for 4 hours, the catalytic cracking reaction performance was evaluated on a heavy oil microreactor (ACE) device.

[0105] The evaluation results are shown in Table 2. In the table, total liquid yield = LPG yield + gasoline yield + diesel yield; coke factor = (100 - conversion rate) × coke yield / conversion rate.

[0106] Table 2 Evaluation results of catalytic cracking reaction of the catalytic cracking aids in Examples 3-6

[0107]

[0108] Table 2 shows that, compared with the LDO-70 industrial catalyst, the addition of the catalytic cracking aids CAT-1, CAT-2, CAT-3, and CAT-4 of this invention resulted in a catalyst mixture exhibiting high conversion and total liquid yield despite contamination levels as high as 3000 μg / g Ni and 5000 μg / g V. The conversion rate increased by more than 3.00 percentage points, and the total liquid yield increased by more than 1 percentage point. The hydrogen / methane and coke factors decreased, indicating that the use of the catalytic cracking aids CAT-1, CAT-2, CAT-3, and CAT-4 of this invention reduced the dehydrogenation reaction in the catalytic cracking process, decreased coke formation, and improved the selectivity of the catalytic cracking reaction. The catalytic cracking aids of this invention have good resistance to heavy metal Ni and V contamination.

[0109] The results in Table 2 also show that, compared with the comparative additive DCAT-2 prepared by adding Comparative Example 2, the catalyst mixture has a higher conversion rate and total liquid yield after adding the catalytic cracking additive CAT-4 of the present invention, and the hydrogen / methane and coke factors are reduced. This indicates that the use of the phosphorus-aluminum material described in the present invention in the additive not only increases the pore volume of the additive, but also improves the selectivity of the catalytic cracking reaction, giving the catalytic cracking additive of the present invention a better effect against heavy metal Ni and V pollution.

Claims

1. A catalytic cracking additive resistant to metal contamination, comprising, by weight percentage: The composition comprises 10-40% phosphorus compounds (based on P2O5), 0.5-30% phosphorus-aluminum materials (based on a dry basis), 5-60% aluminum compounds (based on oxides), 1-20% alkaline earth metal compounds (based on oxides), 1-30% phosphorus-aluminum molecular sieves (based on a dry basis), 5-70% clay (based on a dry basis), and the balance being inorganic carrier materials; wherein the molar ratio of phosphorus to aluminum in the phosphorus-aluminum materials is 1-5:

1. The aluminum phosphorus material is prepared by the following method: an acid-soluble aluminum precursor is slurried with deionized water to form an aluminum-containing slurry with a solid content of 15-45 wt%. Phosphoric acid with a mass concentration of 10-85% is added to the aluminum-containing slurry under stirring. After reaction, an aluminum phosphate sol with a pH value of 0.1-4.5 is obtained. The aluminum phosphate sol is dried and then calcined at 400-800℃ for 0.5-4 hours to obtain the aluminum phosphorus material. This anti-metal contamination catalytic cracking additive is free of Y-type molecular sieves and rare earth elements; The phosphorus aluminum molecular sieve is selected from one or more of the following molecular sieves: APO-5 molecular sieve, APO-11 molecular sieve, APO-31 molecular sieve, APO-34 molecular sieve, APO-41 molecular sieve, VPI-5 molecular sieve, HMA molecular sieve, DNL-1 molecular sieve, SAPO-5 molecular sieve, SAPO-11 molecular sieve, and SAPO-34 molecular sieve. The inorganic carrier material includes titanium dioxide and / or zirconium oxide.

2. The anti-metal contamination catalytic cracking additive according to claim 1, wherein, The composition, by mass percentage, includes: 10-30% phosphorus compound (based on P2O5), 1-20% phosphorus-aluminum material (based on a dry basis), 8-30% aluminum compound (based on oxides), 1-10% alkaline earth metal compound (based on oxides), 1-20% phosphorus-aluminum molecular sieve (based on a dry basis), 5-62% clay (based on a dry basis), and the balance inorganic oxide carrier material; wherein the molar ratio of phosphorus to aluminum in the phosphorus-aluminum material is 1.5-4:

1.

3. The anti-metal contamination catalytic cracking additive according to claim 1 or 2, wherein, The phosphorus source for the phosphorus compound is selected from one or more combinations of phosphoric acid, phosphate, phosphorous acid, phosphite, pyrophosphate, pyrophosphate, polyphosphate, polyphosphate, metaphosphate, and metaphosphate.

4. The anti-metal contamination catalytic cracking additive according to claim 3, wherein, The phosphorus source is selected from one or more combinations of phosphoric acid, ammonium phosphate, ammonium hydrogen phosphate, diammonium hydrogen phosphate, magnesium phosphate, aluminum phosphate, phosphorous acid, ammonium phosphite, sodium pyrophosphate, sodium tripolyphosphate, and sodium hexametaphosphate.

5. The anti-metal contamination catalytic cracking additive according to claim 1 or 2, wherein, The aluminum phosphate material is prepared by the following method: an acid-soluble aluminum precursor is slurried with deionized water to form an aluminum-containing slurry with a solid content of 15-45 wt%. Phosphoric acid with a mass concentration of 10-85% is added to the aluminum-containing slurry under stirring, and an acid regulator is added. After the reaction, an aluminum phosphate sol with a pH value of 0.1-4.5 is obtained. The aluminum phosphate sol is dried and then calcined at 400-800℃ for 0.5-4 hours to obtain the aluminum phosphate material.

6. The anti-metal contamination catalytic cracking additive according to claim 5, wherein, The acid-soluble aluminum precursor is selected from one or more combinations of alumina, aluminum hydroxide, aluminum nitrate, aluminum chloride, aluminum sol, aluminum phosphate, boehmite, and pseudoboehmite.

7. The anti-metal contamination catalytic cracking additive according to claim 5, wherein, The acid regulator is selected from one or more of hydrochloric acid, nitric acid, formic acid, oxalic acid, and citric acid.

8. The anti-metal contamination catalytic cracking additive according to claim 1 or 2, wherein, The aluminum source for the aluminum compound is selected from one or more combinations of boehmite, boehmite, amorphous alumina, and aluminum sol.

9. The anti-metal contamination catalytic cracking additive according to claim 1 or 2, wherein, The alkaline earth metal element in the alkaline earth metal compound is selected from one or more combinations of magnesium, calcium, and barium; the alkaline earth metal source providing the alkaline earth metal compound is selected from one or more combinations of oxides, chlorides, nitrates, carbonates, oxalates, and acetates of alkaline earth metals.

10. The anti-metal contamination catalytic cracking additive according to claim 1 or 2, wherein, The clay is selected from one or more combinations of kaolin, diatomite, halloysite, sepiolite, and bentonite.

11. The anti-metal contamination catalytic cracking additive according to claim 10, wherein, The clay is selected from one or more of kaolin, halloysite, and sepiolite.

12. The anti-metal contamination catalytic cracking additive according to claim 10, wherein, The kaolin includes water-rich kaolin.

13. The anti-metal contamination catalytic cracking additive according to claim 11, wherein, The kaolin includes water-rich kaolin.

14. The anti-metal contamination catalytic cracking additive according to claim 1 or 2, wherein, The raw materials for the catalytic cracking additive also include quaternary ammonium salt surfactants, and the mass of the quaternary ammonium salt surfactants is 0.1-10% of the total mass of the catalytic cracking additive.

15. The anti-metal contamination catalytic cracking additive according to claim 14, wherein, The mass of the quaternary ammonium salt surfactant is 0.3-6% of the total mass of the catalytic cracking additive.

16. The anti-metal contamination catalytic cracking additive according to claim 14, wherein, The quaternary ammonium salt surfactants include one or more of dodecyltrimethylammonium chloride, dodecyltrimethylammonium bromide, hexadecyltrimethylammonium chloride, and hexadecyltrimethylammonium bromide.

17. A method for preparing a catalytic cracking additive resistant to metal contamination as described in any one of claims 1-16, comprising the following steps: Phosphorus compounds, phosphorus aluminum materials, aluminum compounds, alkaline earth metal compounds, phosphorus aluminum molecular sieves, clay, and inorganic carrier materials are mixed and pulped, and then fed into a high-pressure jet reactor for processing to obtain a mixed slurry. The mixed slurry is spray-dried and then calcined to obtain the metal-resistant catalytic cracking aid.

18. The method for preparing the anti-metal contamination catalytic cracking additive according to claim 17, wherein, The preparation method includes the following steps: Phosphorus compounds, phosphorus aluminum materials, aluminum compounds, alkaline earth metal compounds, phosphorus aluminum molecular sieves, clay, inorganic carrier materials and quaternary ammonium salt surfactants are mixed and pulped, and then fed into a high-pressure jet reactor for processing to obtain a mixed slurry. The mixed slurry is spray-dried and then calcined to solidify, thereby obtaining the metal-resistant catalytic cracking aid.

19. The method for preparing the anti-metal contamination catalytic cracking additive according to claim 17 or 18, wherein, The high-pressure jet reactor has a chamber diameter ≤300µm and a pressure ≥10000psi; the average particle size of each component in the mixed slurry is below 1µm.

20. The method for preparing the anti-metal contamination catalytic cracking additive according to claim 17 or 18, wherein, When the aluminum source of the aluminum compound is boehmite, the preparation method further includes: during the pulping process, adding an inorganic acid to the pulp containing boehmite to make its pH value within the range of 0.2-4.5, and then aging it.

21. The method for preparing the anti-metal contamination catalytic cracking additive according to claim 20, wherein, The aging temperature is 40-90℃, and the aging time is 0.5-3h.

22. The method for preparing the anti-metal contamination catalytic cracking additive according to claim 17 or 18, wherein, The furnace temperature of the spray tower used for spray drying is 450-550℃, and the temperature of the spray exhaust gas is 200-300℃.

23. The method for preparing the anti-metal contamination catalytic cracking additive according to claim 17 or 18, wherein, The preparation method further includes washing the calcined and solidified particles with water.

24. The application of the anti-metal contamination catalytic cracking additive according to any one of claims 1-16 in petroleum fluidized catalytic cracking reactions, wherein, Metal contamination includes at least one of iron, nickel, and vanadium.

25. The application according to claim 24, wherein, The metal contamination is iron.

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