CN100443180C - A kind of catalyst with regular structure and preparation method thereof - Google Patents

Abstract

The catalyst in regular structure includes carrier in regular structure and active component coating distributed in the inner surface and/or outer surface of the carrier, with the thickness of the active component coating being in gradient distribution along pore canal axis of the carrier. Using the catalyst in regular structure can reduce the olefin content in FCC gasoline effectively from 43.6 wt% to 17.2 wt%, and convert 50.2 % of the converted olefin into propylene and ethylene. When the catalyst is used as the automobile tail gas catalyst, it can lower the ignition temperature of the tail gas by 30deg.c and raise the tail gas purifying rate up to 95 %.

Description

A kind of catalyst with regular structure and preparation method thereof

technical field

The invention relates to a catalyst with a regular structure and a preparation method thereof.

Background technique

The traditional reactors currently used in petrochemical and refining fields include fixed-bed reactors filled with catalysts, fluidized-bed reactors, and empty tube reactors without catalysts. They are the most commonly used reactors in industry at present. The fixed bed reactor has a large catalyst bed stack ratio, small space for reactants or products to pass through and large resistance, large reaction pressure drop, low space velocity, and is not suitable for chemical reactions with high or variable space velocity. Slow mass heat transfer can easily lead to uneven temperature distribution of the catalyst bed and further side reactions of the product, which is not conducive to improving the selectivity of the reaction. Empty tube reactors are also widely used in petrochemical and refining. Compared with fixed bed reactors, the reaction space velocity can be increased, but the increase in space velocity is also likely to cause temperature fluctuations in the reaction zone, which affects the reaction effect. Empty tube reactors The thermal efficiency and energy consumption of the reactor are obviously higher than those of the fixed bed reactor. Fluidized bed can overcome some shortcomings of fixed bed, and is most successfully applied in heavy crude oil processing. For example, the production of propylene as the main organic chemical raw material is currently mainly prepared by catalytic cracking of heavy crude oil in a fluidized bed. Catalytic thermal cracking is at 650-750 ℃, in the fluidized bed, heavy petroleum hydrocarbons are contacted with Ag or Cu-modified ZSM-5 molecular sieve catalysts, and large molecular heavy petroleum hydrocarbons are converted into small molecular hydrocarbons. While obtaining gasoline and diesel oil, it can achieve the purpose of producing more ethylene and propylene. Since catalytic cracking gasoline contains a large amount of olefins, it is a good raw material for cracking to produce propylene. Therefore, catalytic cracking gasoline (FCC gasoline) is used as raw material, and the high space velocity, high activity and selectivity, and good mass and heat transfer effect of the structured catalyst are used. , The characteristics of convenient catalyst regeneration are of great significance for the production of propylene.

However, since catalytic cracking is a parallel series reaction in which various hydrocarbons participate, the products produced may undergo further reactions and be converted into non-target products. In particular, if the contact time between the catalyst and gasoline is too long, it is easy to further react the cracked products into non-target products and reduce the selectivity of the reaction.

And the same problem has also been encountered in the purification of automobile exhaust. The most effective catalysts currently used for automobile exhaust purification are catalysts with a regular structure called "three-way catalysts". The structured structure catalyst is a new type of catalyst, which has good activity and selectivity under the conditions of high temperature 700-900 ℃, volume space velocity 60000-80000 h ^-1 , bed pressure drop is very small, mass transfer and heat transfer effect is good. However, due to the high light-off temperature, this catalyst cannot effectively purify the pollutants in the tens of seconds after the cold start of the car, and the hydrocarbon emissions during the cold start of the car account for more than 70% of the total emissions, so it cannot meet the requirements Euro III standard emission requirements. For the exhaust emission problem of cold start, the current methods include using an electrically heated converter, using a close-coupled converter, an improved three-way catalyst with a ceramic substrate, or reducing the light-off temperature of the three-way catalyst by increasing the content of catalyst precious metals . The improvement technique mentioned above is complex and costly.

Contents of the invention

The object of the present invention is to provide a regular structure catalyst with higher catalytic activity selectivity in order to overcome the disadvantage of low catalytic activity selectivity of the catalyst in the prior art.

The inventors unexpectedly found that by changing the structure of the catalyst, the active components in the catalyst are distributed on the carrier in a gradient manner, so that the space velocity of the catalyst in the reaction process can also be distributed in a gradient, and the reaction rate can be changed in a gradient, thereby achieving The purpose of improving the selectivity of catalytic activity.

The present invention provides a catalyst with a regular structure, which comprises a carrier with a regular structure and an active component coating distributed on the inner surface and/or outer surface of the carrier, wherein the thickness of the active component coating is along the Axial gradient distribution of the pores of a support with a regular structure.

The present invention also provides a method for preparing a catalyst with a regular structure, the method comprising distributing the slurry containing the active component onto the inner surface and/or the outer surface of the carrier, wherein the method further comprises distributing the slurry containing the active component After the slurry is distributed to the inner surface and/or outer surface of the carrier, the active component is purged with high-pressure gas in one direction along the axial direction of the carrier.

The regular structure catalyst provided by the present invention is a gradient regular structure catalyst, which has the characteristics of a regular structure catalyst. At the same time, since the thickness of the active component coating is a gradient structure, by adjusting the distribution of the active component of the catalyst at different positions on the carrier, without changing In the case of the total content of active components, the active components of the catalyst form a certain gradient distribution in the axial direction of the carrier, so that the catalytic activity of the catalyst is also a gradient distribution. This gradient distribution of catalytic performance is conducive to the realization of short-term Contact reactions, avoiding secondary reactions and improving the selectivity of catalytic reactions. Specifically, the catalyst of the present invention can achieve higher reactivity by reacting at a lower space velocity at the beginning of the reaction by starting the raw material (such as catalytic cracking gasoline, automobile exhaust) , to promote the transformation of raw materials, and then along the axial direction of the reaction zone, the content of active substances gradually decreases, and the reaction space velocity gradually increases, thereby reducing the occurrence of side reactions and achieving the purpose of improving selectivity. However, the current structured catalysts are difficult to achieve the purpose of changing the space velocity during the reaction process.

Experiments have proved that by using the gradient regular structure catalyst provided by the present invention, the olefin content in FCC gasoline can be effectively reduced, and the olefin content in FCC gasoline is reduced from 43.6% by weight to 17.2% by weight, and the converted olefin can be reduced to 17.2% by weight. The conversion to propylene and ethylene with a selectivity of 50.2% makes propylene and ethylene by-product while reducing the olefin content in FCC gasoline. However, when the catalyst is used as an automobile exhaust gas purification catalyst, it can reduce the light-off temperature (T ₅₀ ) of the automobile exhaust gas by about 30° C., and the exhaust gas purification rate is as high as 95%. In addition, the catalyst with gradient regular structure obtained in the present invention also has excellent catalytic stability.

Description of drawings

Fig. 1 is the SEM picture of the thickest end face of the catalyst with gradient structured structure prepared in Example 1 of the present invention;

Fig. 2 is the SEM picture of the thinnest end face of the catalyst with gradient structured structure prepared in Example 1 of the present invention;

Fig. 3 is the SEM picture of the axial section along the channel of the carrier at the thicker end of the catalyst with gradient structured structure prepared in Example 1 of the present invention;

Fig. 4 is the SEM picture of the thickest end face of the catalyst with gradient structured structure prepared in Example 4 of the present invention;

Fig. 5 is the SEM picture of the thinnest end face of the catalyst with gradient structured structure prepared in Example 4 of the present invention;

Fig. 6 is the SEM picture of the axial section along the channel of the carrier at the thicker end of the catalyst with gradient structured structure prepared in Example 4 of the present invention;

Fig. 7 is the SEM picture of the axial cross-section along the channel of the carrier at the smaller end of the gradient regular structure catalyst prepared in Example 4 of the present invention;

Figure 8 is a SEM image of an end face of a structured catalyst in the prior art;

Fig. 9 is the SEM figure of another end face of the regular structure catalyst in the prior art;

Fig. 10 is an SEM image of a cross-section along the axial direction of a carrier channel of a catalyst with a structured structure in the prior art.

Detailed ways

The present invention provides a catalyst with a regular structure, which comprises a carrier with a regular structure and an active component coating distributed on the inner surface and/or outer surface of the carrier, wherein the thickness of the active component coating is along the Axial gradient distribution of the pores of a support with a regular structure.

The present invention has no special restriction on the gradient distribution of the thickness of the active component coating, as long as the thickness of the active component coating changes in a gradient from one end to the other, preferably, the gradient of the thickness of the active component coating is 5-50 microns/cm. The thickness of the thickest end of the active component coating at the end is preferably 60-400 microns, and the thickness of the thinnest active component coating is preferably 1-60 microns. More preferably, the thickness of the active component coating at the thickest end is 70-350 microns, and the thickness of the active component coating at the thinnest end is 5-50 microns. However, the active component coating thickness of the regular structure catalyst in the prior art is uniform 50-200 microns. Various methods can be used to measure the thickness of the coating, for example, SEM and high-power microscope methods can be used for measurement, and the specific operation of the measurement is well known in the art, and will not be repeated here.

The carrier with a regular structure in the present invention refers to a catalyst carrier with macroscale hollow regular parallel channels and a regular surface. Examples of the structured support include, but are not limited to, cordierite honeycomb supports, mullite honeycomb supports, alumina honeycomb supports, and metal alloy honeycomb supports. Examples of the metal alloy honeycomb supports include Fe-Cr-Al alloy honeycomb supports. The cross-sectional hole density of the carrier is preferably 6-160 holes/square centimeter, the cross-sectional area of the holes is preferably 0.4-10 square millimeters, more preferably the cross-sectional hole density is 15-150 holes/square centimeter, and the cross-sectional area of the holes is preferably 0.4 -6 square millimeters. The present invention has no particular limitation on the structural shape of the hole, which may be square, triangular, hexagonal, square with thorn walls inside or other irregular shapes.

The active components can be various compounds, compositions, etc. that can be used as catalyst active components, and those skilled in the art can easily determine the components and proportions of the active components according to the desired application. For example, according to one aspect of the invention, the active ingredient may be a composition comprising a matrix and a molecular sieve. The content of the matrix and the molecular sieve is not particularly limited in the present invention, and the conventional content in the catalyst field can be used. Based on the total amount of the composition, the content of the preferred matrix in the present invention is 10-80% by weight, the content of molecular sieve is 20-90% by weight, more preferably the content of matrix is 20-70% by weight, and the content of molecular sieve is 30-90% by weight. 80% by weight.

The substrate may be various heat-resistant oxides, for example, one or more selected from alumina, silica, amorphous silica-alumina, zirconia, titania, boria, and alkaline earth metal oxides.

The molecular sieve of the present invention can be one or more of various zeolites and non-zeolite molecular sieves that can be used to reduce the content of olefins, for example, it can be selected from zeolites with MFI structure, faujasite, β-zeolite, omega One or more of zeolite, mordenite, and non-zeolite molecular sieves. The zeolite with the MFI structure may be ZSM-5 molecular sieve, and the faujasite may be Y-type zeolite and/or ultrastable Y zeolite. In the specific embodiment of the present invention, it is preferably one or more of ZSM-5 molecular sieve, phosphorus and/or rare earth-containing Y-type zeolite and/or ultrastable Y zeolite.

Preferably, the composition of the present invention also contains 0-10% by weight, preferably 0-5% by weight of adjuvants. Those skilled in the art can easily select suitable additives according to the catalytic performance required to be achieved, for example, the additives can be selected from phosphorus, germanium, tin, antimony, bismuth, lead, copper, silver, zinc, cadmium, vanadium , molybdenum, tungsten, manganese, iron, cobalt, nickel, lanthanum, cerium, cerium-rich misch metal, and lanthanum-rich misch metal compounds. The amount of the auxiliary agent may be the amount of the above-mentioned auxiliary agent in a conventional catalyst. Based on the total amount of the composition, the content of the auxiliary agent is preferably 3-5% by weight. The amount of the auxiliary agent is calculated by element content. Said compounds may be in the form of oxides, chlorides, sulfates, phosphates, nitrates, preferably in the form of water-soluble salts.

The auxiliary agent can exist in the matrix, also can exist in the molecular sieve, and can also exist in both the matrix and the molecular sieve. The present invention is preferably present in molecular sieves.

According to another aspect of the present invention, the active component is a composition, the composition contains a matrix and a noble metal, and the noble metal is supported on the matrix. In the present invention, there is no special limitation on the content of the substrate and the noble metal, which can be conventional content in the field of catalysts. Based on the total amount of the composition, the content of the preferred matrix of the present invention is 95-99.99% by weight, and the content of the noble metal is 0.01-5% by weight; more preferably, the content of the matrix is 96-98% by weight, and the content of the noble metal is 2- 4% by weight.

The substrate may be various heat-resistant oxides, for example, one or more selected from alumina, silica, amorphous silica-alumina, zirconia, titania, boria, and alkaline earth metal oxides. The noble metal can be various noble metals with different catalytic activities, for example, it can be one or more of platinum, palladium and rhodium. Preferably, the noble metal is supported on the substrate.

Preferably, the composition of the present invention also contains 0-10% by weight, preferably 0-5% by weight of adjuvants. Those skilled in the art can easily select suitable additives according to the catalytic performance required to be achieved, for example, the additives can be selected from phosphorus, germanium, tin, antimony, bismuth, lead, copper, silver, zinc, cadmium, vanadium , molybdenum, tungsten, manganese, iron, cobalt, nickel, lanthanum, cerium, cerium-rich misch metal, and lanthanum-rich misch metal compounds. The amount of the auxiliary agent may be the amount of the above-mentioned auxiliary agent in a conventional catalyst. Based on the total amount of the composition, the content of the auxiliary agent is preferably 3-5% by weight. The amount of the auxiliary agent is calculated by element content. Said compounds may be in the form of oxides, chlorides, sulfates, phosphates, nitrates, preferably in the form of water-soluble salts. The auxiliaries are preferably present in the matrix.

The method for preparing a catalyst with a regular structure provided by the present invention includes distributing the slurry containing the active component to the inner surface and/or the outer surface of the carrier, wherein the method also includes distributing the slurry containing the active component to the carrier The inner and/or outer surfaces of the carrier are then purged with high-pressure gas in one direction along the axial direction of the carrier.

Since the present invention only involves improving the distribution of active components, there is no particular limitation on the preparation method of the active component slurry. For example, the active ingredient is commercially available or prepared by various methods. Different catalysts have slightly different preparation methods for the active component slurry due to the different composition of the active component. According to the catalyst of the first aspect of the present invention, the active component slurry can be prepared by, for example, the following method: the slurry containing phosphorus, germanium, tin, antimony, bismuth, lead, copper, silver, zinc, cadmium, vanadium , molybdenum, tungsten, manganese, iron, cobalt, nickel, lanthanum, cerium, cerium-rich mixed rare earth metals, salts of lanthanum-rich mixed rare earth metals, or other soluble compounds are mixed with solvents to obtain concentrations It is a 10-20% by weight additive solution, and the solution is heated to 40-90°C and adjusted to pH=7.5-12.5 with alkali, then stirred at 60-85°C for 20-120 minutes, filtered and washed to a moisture content It is 40-80% by weight of wet filter cake; mix molecular sieves with solvent, stir evenly at 40-90°C to make a uniform slurry with a solid content of 15-25% by weight, and take out 10-90% by weight of the slurry , adjust the pH of the remaining slurry to 0.5-6 with acid, mix it with the slurry taken out and the above wet filter cake after stirring for 20-80 minutes, stir at 40-90°C for 20-80 minutes, dry and roast to obtain Contains phosphorus, germanium, tin, antimony, bismuth, lead, copper, silver, zinc, cadmium, vanadium, molybdenum, tungsten, manganese, iron, cobalt, nickel, lanthanum, cerium, cerium-rich misch metal, lanthanum-rich misch metal Molecular sieve active components of one or more elements. The solvent is preferably deionized water, and the alkali used to adjust pH=7.5-12.5 can be one or more of magnesium carbonate, ammonia water, urea, sodium bicarbonate or sodium carbonate solution, and the alkali used to adjust The acid with pH=0.5-6 can be one or more of citric acid, dilute hydrochloric acid, dilute sulfuric acid, fruit acid and carbonic acid. The drying temperature can be from room temperature to 300°C, preferably 100-200°C, and the drying time can be more than 0.5 hours, preferably 1-10 hours. The calcination temperature may be 400-800°C, preferably 500-700°C, and the calcination time may be more than 0.5 hours, preferably 1-10 hours.

According to the catalyst of the second aspect of the present invention, the active component slurry can be prepared, for example, by the following method: a mixture containing phosphorus, germanium, tin, antimony, bismuth, lead, copper, silver, zinc, cadmium, vanadium, One or more of molybdenum, tungsten, manganese, iron, cobalt, nickel, lanthanum, cerium, cerium-rich mixed rare earth metals, salts of lanthanum-rich mixed rare earth metals or other soluble compounds are mixed with a solvent to obtain a concentration of 10-20% by weight of additive solution, the solution is heated to 40-90°C and adjusted to pH = 7.5-12.5 with alkali, then stirred at 60-85°C for 20-120 minutes, filtered and washed until the water content is 40-80% by weight of the wet filter cake for use; mix the substrate with the solvent, stir and homogenize to obtain a slurry with a substrate content of 10-60% by weight, take out 10-90% by weight of the slurry, and leave the remaining slurry Adjust the pH of the material to 0.5-6, stir evenly, mix with the slurry taken out and wet filter cake and stir evenly, then dry and roast to obtain phosphorus, germanium, tin, antimony, bismuth, lead, copper, silver, The matrix active component of one or several elements in zinc, cadmium, vanadium, molybdenum, tungsten, manganese, iron, cobalt, nickel, lanthanum, cerium, cerium-rich mixed rare earth metal, and lanthanum-rich mixed rare earth metal, and then platinum, Noble metals such as rhodium and palladium are supported on the above active components to obtain the catalyst active components of the present invention. The solvent is preferably deionized water, and the alkali used to adjust pH=7.5-12.5 can be one or more of magnesium carbonate, ammonia water, urea, sodium bicarbonate or sodium carbonate solution, and the alkali used to adjust The acid with pH=0.5-6 can be one or more of citric acid, dilute hydrochloric acid, dilute sulfuric acid, fruit acid and carbonic acid. The drying temperature can be from room temperature to 300°C, preferably 100-200°C, and the drying time can be more than 0.5 hours, preferably 1-10 hours. The calcination temperature may be 400-800°C, preferably 500-700°C, and the calcination time may be more than 0.5 hours, preferably 1-10 hours. The loading of the noble metal on the active component can be achieved by impregnation. The specific operating conditions and methods of the dipping method are well known to those skilled in the art, and will not be repeated here.

The regular structure catalyst of the present invention can be prepared by distributing the active component slurry on the inner surface and/or outer surface of the carrier with a regular structure by various methods, for example, the active component can be coated on the carrier with a regular structure by a coating method. The regular structure catalyst is prepared on the regular structure support. The coating preferably includes dissolving the active component in a solvent to obtain an active component slurry containing the active component and a solvent, and adjusting the active component slurry to pH=1-7 with an acid or alkali, and then applying the above slurry The material is coated on the inner surface and/or outer surface of the carrier, and then the high-pressure gas is used to purge in one direction along the channel direction of the carrier to obtain a gradient distribution of the active component layer. Wherein, the pressure of the high-pressure gas is preferably 3.5-20 MPa, the flow rate is 5-50 liters/minute, and the purging time is preferably 1-10 minutes. The gas can be various gases that do not react with the carrier and/or active components, such as one or more of air, nitrogen, oxygen, carbon dioxide, and zero-group gases in the periodic table. Preferably, the gas is air since air is cheap and readily available. The solvent is preferably deionized water. The feed ratio of the active component and deionized water makes the solid content of the slurry 15-45% by weight, and the acid or base used to adjust the slurry to pH=1-7 can be hydrochloric acid, nitric acid, formic acid , acetic acid, oxalic acid, acrylic acid, citric acid, ammonia, ethanolamine, ethylenediamine, and urea. The slurry is preferably ball milled to control the particle diameter of the active component to be between 1 and 20 microns before coating. The coating amount of the slurry on the inner surface and/or outer surface of the carrier makes the thickness of the thickest end active component coating of the catalyst be 100-300 microns, and the thickness of the thinnest end active component coating be 10-50 microns. Microns. The coating temperature is preferably 10-70°C, more preferably 15-35°C, the coating pressure is preferably -0.04 MPa to 0.4 MPa, and the coating time is preferably 0.1-100 seconds. The coating method can be water coating method, dipping method or spraying method. The specific operation of coating can be carried out with reference to the method described in CN1199733C. Mainly preferably, the catalyst is placed for 5-30 minutes after purging, in such a way that the direction of the carrier channel of the catalyst is parallel to the direction of gravity.

The preparation method of the catalyst of the present invention may also include drying and calcining the prepared active component layer catalyst having a gradient distribution. The drying temperature is preferably 90-130°C, and the drying time is preferably 3-10 hours, more preferably the drying temperature is 110-120°C, and the drying time is 5-7 hours.

According to the present invention, surfactants may also be loaded onto the aforementioned active components and/or carriers prior to coating. The surfactant is preferably a nonionic surfactant, which refers to a surfactant that does not generate ions in water and has active groups such as polyhydroxyl or polyoxyethylene groups in the molecule. The active agent is relatively stable to acid and alkali, and mainly includes polyol type and polyoxyethylene type. Preferred nonionic surfactants are selected from one or more of polyethylene glycol, glycerol, carboxymethylcellulose, polyvinyl alcohol or polyacrylic acid.

The method for loading the surfactant onto the above-mentioned active components and/or carriers may be to dissolve the surfactant in deionized water to obtain a surfactant solution, and adjust the pH value of the solution to 0.5-6.0 or 7.5- 9.5, and then mix and contact the above-mentioned active components and/or carriers with the obtained surfactant solution with a pH value of 0.5-6.0 or 7.5-9.5, wherein the concentration of the surfactant solution is 1-10% by weight. If the surfactant is to be loaded into the active component, then 0.1-10% by weight of the surfactant solution relative to the dry weight of the active component is mixed with the active component. If the surfactant is to be loaded into the active component, the carrier is soaked in the surfactant solution for 1-300 seconds. One or more of formic acid, acetic acid, hydrochloric acid, citric acid or nitric acid can be used to adjust the pH value of the surfactant solution to 0.5-6.0; one or more of ammonia, sodium carbonate or sodium hydroxide can be used to adjust The pH value of the surfactant solution was adjusted to 7.5-9.5. The concentration of the surfactant solution is preferably 1 to 10% by weight.

The catalysts according to the invention may also be treated in various ways in order to achieve other modification purposes, for example cleaning the support prior to coating. Various treatments can be used simultaneously or independently, and those skilled in the art can easily choose according to the purpose to be achieved.

The following examples will further describe the present invention.

Example 1

This example is used to illustrate the gradient structured catalyst provided by the present invention.

Stir pseudoboehmite, ferric chloride, cerous chloride, and lanthanum chloride in deionized water evenly, adjust the pH to 10.5 with sodium bicarbonate, stir at a constant temperature of 80°C for 110 minutes, and filter and wash until the water content is 70% by weight of the wet cake was used.

HZSM-5 molecular sieve (SiO ₂ /Al ₂ O ₃ is 100, sodium oxide content is 0% by weight) is mixed with deionized water, stirred and homogenized at 80°C for 30 minutes to obtain a uniform slurry, and 70% of the slurry % by weight is taken out. The remaining slurry was adjusted to pH=4 with citric acid, then mixed with the taken out slurry and wet filter cake, stirred at 80°C for 70 minutes, baked at 130°C for 4 hours, and calcined at 850°C for 6 hours to obtain the active group point. The addition amount of HZSM-5 molecular sieve, pseudo-boehmite, ferric chloride, cerous chloride, lanthanum chloride is to make the content of molecular sieve in the active component be 75% by weight, the content of aluminum oxide matrix is 20% by weight, The content of iron oxide, lanthanum oxide and cerium oxide additives is 5% by weight.

Mix the above-mentioned active components containing molecular sieves and matrix additives with deionized water, adjust pH=4, make a slurry with a solid content of 35% by weight, and then wet ball mill until the particle diameter is 5 microns, and then the equivalent A polyvinyl alcohol solution (adjusting pH=4 with formic acid in advance) of active component dry basis weight 1.0% by weight is added in the above-mentioned slurry, after stirring evenly, at 15 ℃ in 60 seconds, the above-mentioned slurry is coated on On the cordierite honeycomb carrier (Corning, 100/0.5, the cross-sectional hole density is 15.5 holes/square centimeter, the cross-sectional area of the hole is 4.0 square millimeters), and the pressure is 5 MPa, the flow rate is 30 L/min. The axial direction of the carrier was purged in one direction for 6 minutes, then the catalyst was left for 30 minutes, dried at 120°C for 6 hours and calcined at 600°C for 1 hour to obtain the catalyst with gradient structured structure of the present invention. The SEM images of the obtained gradient structured catalysts are shown in Figures 1-3. It can be seen from the figure that the present invention has produced a catalyst with a gradient regular structure. The thickness of the active component coating at the thickest end is 210 microns, and the thickness of the active component coating at the thinnest end is 50 microns. According to the calculation, it is known that the axial gradient formed by the active component layer on the honeycomb carrier is 6.4 μm/cm.

Example 2

This example is used to illustrate the gradient structured catalyst provided by the present invention.

The regular structure catalyst is prepared according to the method of Example 1, the difference is that the carrier with the regular structure is the foamed alumina (200/0.33) provided by Shanghai Taishan Refractory Material Factory, the cross-sectional hole density is 31 holes/square centimeter, the The cross-sectional area is 2.0 square millimeters), the high-pressure air for purging is air with a pressure of 7 MPa and a flow rate of 20 liters/min, and the purging time is 5 minutes. In the obtained gradient regular structure catalyst, the axial gradient formed by the active component layer on the carrier is 10 microns/cm, the thickness of the active component coating at the thickest end is 190 microns, and the thickness of the active component coating at the thinnest end is 30 microns .

Example 3

This example is used to illustrate the gradient structured catalyst provided by the present invention.

Prepare regular structure catalyst according to the method of embodiment 1, difference is, described filter cake is mixed in deionized water by pseudo-boehmite, cupric chloride, zinc chloride, manganese chloride, titanium chloride, vanadium chloride Obtained, the carrier with a regular structure is the iron-chromium-aluminum alloy honeycomb carrier (400/0.05, the cross-sectional hole density is 120 holes/square centimeter, and the cross-sectional area of the holes is 0.8 square millimeters) provided by Yimitec Company. The molecular sieve is phosphorus-containing Y-type zeolite (SiO ₂ /Al ₂ O ₃ is 150, and the content of phosphorus pentoxide is 1.5% by weight), and the high-pressure air for purging is that the pressure is 17 MPa and the flow rate is 10 liters/minute. Air, the time of purging is 2 minutes. In the obtained gradient regular structure catalyst, the axial gradient formed by the active component layer on the carrier is 8.5 microns/cm, the thickness of the active component coating at the thickest end is 150 microns, and the thickness of the active component coating at the thinnest end is 20 microns .

Example 4

This example is used to illustrate the preparation of the gradient structured catalyst provided by the present invention.

Lanthanum-rich mixed rare earth (containing rare earth oxide RE ₂ O ₃ 52% by weight, RE ₂ O ₃ containing 53% by weight La ₂ O ₃ , 2.8% by weight CeO ₂ , 19% by weight Pr ₆ O ₁₁ , 0.3% by weight MgO , 0.2 wt% Al ₂ O ₃ , 1.2 wt% SO ₃ , 19 wt% Cl, 0.7 wt% K ₂ O, 3.8 wt% CaO), cerous chloride, zirconium oxychloride mixed with deionized water to obtain a concentration After the solution is 11% by weight, adjust the pH=9 with ammonia water, stir at a constant temperature of 65° C. for 40 minutes, filter and wash with suction until the wet filter cake with a moisture content of 40% by weight is set aside; add pseudo-boehmite to deionized water, Stir and homogenize at 80°C for 30 minutes to obtain a slurry with an alumina content of 16% by weight, take out 20% by weight of the slurry, adjust the pH of the remaining slurry to 1 with 20% by weight of dilute hydrochloric acid, and stir for 20 minutes Then mix with the taken out slurry and wet filter cake, stir at 40°C for 25 minutes, bake at 120°C for 3 hours, and bake at 600°C for 6 hours to obtain composite alumina. The amounts of pseudo-boehmite, lanthanum-rich mixed rare earth, cerous chloride and zirconium oxychloride are such that the weight ratio of matrix and additive in the composite alumina is 10:1. The above-mentioned composite alumina is impregnated in chloroplatinic acid solution, then dried at 120°C for 2 hours, calcined at 600°C for 2 hours, impregnated with rhodium chloride solution, dried at 120°C for 2 hours, and calcined at 600°C After 2 hours, an alumina active component containing platinum and rhodium was obtained. The content of the matrix in the active component is 90% by weight, the content of the auxiliary agent is 9% by weight, and the content of the noble metal is 1% by weight.

Add the above-mentioned active components containing the matrix and precious metals to deionized water, adjust pH=4, make a slurry with a solid content of 35% by weight, and then wet ball mill until the particle diameter is 3 microns, and then the equivalent active components Add polyvinyl alcohol solution of 1.0% by weight on a dry basis (adjust pH = 4 with formic acid in advance) into the above slurry, stir evenly and coat within 40 seconds at a temperature of 25°C and a pressure of 0.1 MPa In the iron-chromium-aluminum alloy honeycomb carrier provided by Yimitek (the cross-sectional hole density is 140 holes/square centimeter, the cross-sectional area of the hole is 0.44 square millimeters), and the pressure is 6 MPa, and the flow rate is 10 liters/minute. The high-pressure air is purged in one direction along the axial direction of the carrier for 8 minutes, and then the catalyst is left for 10 minutes, dried at 120°C for 6 hours and calcined at 600°C for 1 hour to obtain the gradient structured catalyst of the present invention. The SEM images of the obtained gradient structured catalysts are shown in Figures 4-7. It can be seen from the figure that the present invention has produced a catalyst with a gradient regular structure. The thickness of the active component coating at the thickest end is 150 microns, the thickness of the thinnest active component coating is 30 microns, and the axial gradient formed by the active component layer on the cordierite carrier is 10 microns/cm.

Example 5

This example is used to illustrate the preparation of the gradient structured catalyst provided by the present invention.

Prepare a gradient structured catalyst according to the steps of Example 4, except that the filter cake is obtained by mixing cerium chloride, zirconium oxychloride, lanthanum chloride and deionized water, and the content of the substrate in the active component is 95% by weight , the content of auxiliary agent is 1% by weight, and the content of precious metal is 4% by weight; The carrier is on a cordierite honeycomb carrier (Shanghai Corning Company, the cross-sectional hole density is 62 holes/square centimeter, and the cross-sectional area of the hole is 1 square millimeter ), the high-pressure air for purging is the air with a pressure of 17 MPa and a flow rate of 5 liters/minute, and the time of purging is 6 minutes. In the obtained gradient structured catalyst, the axial gradient formed by the active component layer on the carrier is 5 microns/cm, the thickness of the thickest end active component coating is 2000 microns, and the thickness of the thinnest end active component coating is 2000 microns. The thickness is 40 microns.

Example 6

This example is used to illustrate the preparation of the gradient structured catalyst provided by the present invention.

The regular structure catalyst was prepared according to the steps of Example 4, except that the filter cake was made of cerium-rich mixed rare earth (containing rare earth oxide RE ₂ O ₃ 45% by weight, containing 45% by weight CeO ₂ , 26% by weight in RE ₂ O ₃ %La ₂ O ₃ , 17% by weight Nd ₂ O ₅ , 5.5% by weight Pr ₆ O ₁₁ , 4% by weight Cl, 2.5% by weight CaO), zirconium oxychloride, lanthanum chloride and deionized water, the active group The content of the middle matrix is 97% by weight, the content of the auxiliary agent is 1% by weight, and the content of the noble metal is 2% by weight; the carrier is the mullite honeycomb carrier provided by Shanghai Corning Corporation (the cross-sectional hole density is 31 holes/square cm, the cross-sectional area of the hole is 2 square millimeters), the high-pressure air for purging is the air with a pressure of 15 MPa and a flow rate of 30 liters/minute, and the time of purging is 3 minutes. In the prepared gradient structured catalyst. The axial gradient formed by the active component layer on the honeycomb carrier is 20 microns/cm, the thickness of the active component coating at the thickest end is 350 microns, and the thickness of the active component coating at the thinnest end is 50 microns.

Comparative example 1

The structured catalyst was prepared according to the steps of Example 4, except that after the active component slurry was coated on the cordierite honeycomb carrier, the active component coating was not purged with high-pressure air to obtain a structured catalyst. The SEM images of the two end surfaces of the active component coating of the catalyst and the axial section along the channel of the carrier are shown in Figures 8-10. It can be seen from the figure that the active component coating does not form a gradient distribution on the structured carrier. The thickness of the active ingredient coating was uniform at 100 microns.

Catalytic Performance Test for Reducing Olefin Content in FCC Gasoline

35规格反应器中，然后将烯烃含量为31.2-43.6重量％的催化裂化汽油，经250℃预热注入上述反应器中，使汽油从催化剂活性组分厚度较大的一端进入，从厚度较小的一端排出，同时注入250℃预热的水蒸汽，保持原料油注入的重时空速为26.7小时^-1，水/油进料比为0.41，在反应温度为550℃、压力为常压，连续进料1小时，将所得产物取样进行分析。反应结果见表1。The regular structure catalyst that above-mentioned embodiment 1-3 is made is packed respectively in

35 specification reactor, then inject catalytically cracked gasoline with an olefin content of 31.2-43.6% by weight, preheated at 250°C, into the above-mentioned reactor, so that the gasoline enters from the end with a larger thickness of the catalyst active component, and from the end with a smaller thickness At the same time, the water vapor preheated at 250°C is injected to keep the weight hourly space velocity of the raw material oil injection at 26.7 hours ^-1 , the water/oil feed ratio is 0.41, and the reaction temperature is 550°C, the pressure is normal pressure, continuous Feed for 1 hour and the resulting product was sampled for analysis. The reaction results are shown in Table 1.

Table 1

As can be seen from the results in Table 1 above, when the catalyst provided by the present invention is used to reduce the olefin content in catalytic cracking gasoline, it can greatly reduce the olefin content in gasoline, and the olefin conversion rate is as high as 60%, far higher than the 15% of the prior art , and most of the olefins were transformed into easily separated propylene and ethylene, and unexpected results were obtained.

Catalytic Performance Test for Purifying Automobile Exhaust Gas

35规格反应器中，然后将浓度为一氧化碳9000ppm、碳氢化合物600ppm、氮氧化物900ppm的混合气体通入上述反应器中，使混合气体以26.7小时^-1的体积空速从催化剂活性组分厚度较大的一端进入，从厚度较小的一端排出，反应器以10℃/分钟的速度从室温程序升温至500℃，每升温10℃测定反应器出口处生成气中的一氧化碳、碳氢化合物和氮氧化物的浓度值，然后根据下列公式计算有害气体的净化率：The regular structure catalyst that above-mentioned embodiment 4-6 and comparative example 1 make are packed respectively in

35 specification reactor, then pass the mixed gas with the concentration of 9000ppm carbon monoxide, 600ppm hydrocarbon and 900ppm nitrogen oxide into the above reactor, so that the mixed gas flows from the thickness of the active component of the catalyst at a volume space velocity of ^26.7 hours The larger end enters and the smaller end exits. The reactor is programmed to heat up from room temperature to 500°C at a rate of 10°C/min. The carbon monoxide, hydrocarbons and The concentration value of nitrogen oxides, and then calculate the purification rate of harmful gases according to the following formula:

Plot the purification rate as a function of the purification temperature to obtain the purification temperature T ₅₀ value when the purification rate is 50%. This value is also called the tail gas light-off temperature and can be used as a standard for evaluating the performance of the catalyst on exhaust gas purification. Table 2 shows the T ₅₀ values of the structured catalysts measured by this method and the purification rates of CO, CH, and _NOx when the temperature is programmed to 350°C.

Catalyst Stability Test

The structured catalysts prepared in the above-mentioned Examples 4-6 and Comparative Example 1 were aged in the air at a temperature of 920° C. for 2 hours, and then the catalytic performance of the above-mentioned aged catalysts for purifying automobile exhaust was measured. The results of the measurements are shown in the following table 2.

Table 2

It can be seen from the results in Table 2 that the catalyst with gradient structured structure provided by the present invention can greatly reduce the light-off temperature of automobile exhaust, and effectively realize the purification of exhaust gas when the automobile is started. Moreover, the catalyst with gradient regular structure prepared by the invention also has very good catalytic stability.

Claims (24)

1, a kind of catalyst with ordered structure, this catalyst comprises the carrier with ordered structure and is distributed in the active component coating of carrier inner surface and/or outer surface, it is characterized in that the thickness of described active component coating distributes along the axial gradient in the duct of the carrier with ordered structure.

2, catalyst according to claim 1, wherein, described active component coating thickness along the axial gradient in carrier duct be changed to the 0.1-20 micron/centimetre.

3, catalyst according to claim 1, wherein, the thickness of the thickest end active component coating of described catalyst is the 60-400 micron, the thickness of the thinnest end active component coating is the 1-60 micron.

4, catalyst according to claim 1, wherein, the carrier of described ordered structure is the catalyst carrier with the regular parallel duct of hollow and structured surface.

5, catalyst according to claim 4, wherein, the carrier of described ordered structure is selected from cordierite honeycomb carrier, mullite honeycomb substrate, cellular alumina carrier or metal alloy honeycomb substrate.

6, catalyst according to claim 5, wherein, hole, the cross section density of described carrier is that the sectional area in 15-150 hole/square centimeter, hole is the 0.4-6 square millimeter.

7, catalyst according to claim 1, wherein, described active component is a kind of composition, said composition contains matrix and molecular sieve.

8, catalyst according to claim 7 wherein, is a benchmark with the total amount of composition, and the content of matrix is 20-70 weight %, and the content of molecular sieve is 30-80 weight %.

9, catalyst according to claim 7, wherein, described molecular screening one or more in zeolite, faujasite, beta-zeolite, omega zeolite, modenite, non-zeolite molecular sieve with MFI structure.

10, catalyst according to claim 9, wherein, the zeolite of the described MFI of having structure is the ZSM-5 molecular sieve, described faujasite is y-type zeolite and/or overstable gamma zeolite.

11, catalyst according to claim 7, wherein, described composition also contains the auxiliary agent of 0-10 weight %, and described auxiliary agent is present in molecular sieve and/or the matrix.

12, according to any described catalyst among the claim 1-3, wherein, described active component is a kind of composition, and said composition contains matrix and noble metal, and noble metal loads on the matrix.

13, catalyst according to claim 12 wherein, is a benchmark with the total amount of composition, and the content of matrix is 95-99.99 weight %, and the content of noble metal is 0.01-5 weight %.

14, catalyst according to claim 12, wherein, described noble metal is selected from one or more in ruthenium, rhodium, palladium, osmium, iridium, the platinum.

15, catalyst according to claim 12, wherein, described catalyst also contains the auxiliary agent of 0-10 weight %, and described auxiliary agent loads in the matrix.

16, according to claim 11 or 15 described catalyst, wherein, described auxiliary agent is selected from one or more in the compound of phosphorus, germanium, tin, antimony, bismuth, lead, copper, silver, zinc, cadmium, vanadium, molybdenum, tungsten, manganese, iron, cobalt, nickel, lanthanum, cerium, cerium-rich mischmetal metal, lanthanum rich norium.

17, according to claim 7,8 or 13 described catalyst, wherein, described matrix is selected from one or more in aluminium oxide, silica, amorphous silicon aluminium, zirconia, titanium oxide, boron oxide, the alkaline earth oxide.

18, the described Preparation of catalysts method of claim 1 with ordered structure, this method comprises that the slurry that will contain active component is distributed to the inner surface and/or the outer surface of carrier, it is characterized in that, this method comprises that also the slurry that will contain active component is distributed to after the inner surface and/or outer surface of carrier, is distributed to slurry carrier on to folk prescription to purging along carrier shaft with gases at high pressure.

19, method according to claim 18, wherein, described slurry contains molecular sieve and matrix, and described solid content of slurry is 15-45 weight %.

20, method according to claim 18, wherein, described slurry contains matrix and the noble metal that loads on the matrix, and described solid content of slurry is 15-45 weight %.

21, according to claim 19 or 20 described methods, wherein, described slurry also contains surfactant.

22, method according to claim 18, wherein, the pressure of described gases at high pressure is the 3.5-20 MPa, flow be the 5-50 liter/minute, purge time is 1-10 minute.

23, according to claim 18 or 22 described methods, wherein, described gas is selected from one or more in the zero group gas in air, nitrogen, oxygen, carbon dioxide, the periodic table of elements.

24, method according to claim 18, wherein, this method is placed catalyst 5-30 minute after also comprising purging, and the mode of placement is the direction that the carrier duct direction of catalyst is parallel to gravity.

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