CN108339558B

CN108339558B - Vanadium-phosphorus-oxygen catalyst for preparing maleic anhydride by oxidizing n-butane and preparation method thereof

Info

Publication number: CN108339558B
Application number: CN201710053664.8A
Authority: CN
Inventors: 师慧敏; 张明森; 张东顺; 贾雪飞; 冯晔; 张作峰; 苗小培
Original assignee: Sinopec Beijing Research Institute of Chemical Industry; China Petroleum and Chemical Corp
Current assignee: Sinopec Beijing Research Institute of Chemical Industry; China Petroleum and Chemical Corp
Priority date: 2017-01-24
Filing date: 2017-01-24
Publication date: 2020-12-18
Anticipated expiration: 2037-01-24
Also published as: CN108339558A

Abstract

The invention provides a vanadium-phosphorus-oxygen catalyst for preparing maleic anhydride by n-butane oxidation, which is prepared by treating a vanadium-phosphorus-oxygen catalyst substrate by adopting a pore-enlarging agent. The mass content of vanadium in the catalyst is 28-35%, and the mass content of phosphorus in the catalyst is 15-25%. The pore-expanding agent comprises one or more of 1,1, 1-trimethylolethane, trimethylolpropane, phthalic anhydride, maleic anhydride, tartaric acid, citric acid and citric acid, and the mass ratio of the pore-expanding agent to the vanadium-phosphorus-oxygen catalyst substrate is (5-20) to (80-95). The invention controls the addition of the pore-expanding agent and the removal process of the pore-expanding agent in the post-treatment process of the catalyst, thereby controlling and improving the specific surface area and the pore structure of the treated catalyst, and further improving the activity of the catalyst in the selective oxidation reaction of catalyzing butane and the selectivity of generating maleic anhydride.

Description

Vanadium-phosphorus-oxygen catalyst for preparing maleic anhydride by oxidizing n-butane and preparation method thereof

Technical Field

The invention belongs to the technical field of catalyst synthesis, and relates to a vanadium-phosphorus-oxygen catalyst for preparing maleic anhydride by oxidizing n-butane and a preparation method thereof.

Background

Maleic anhydride (maleic anhydride) is an important organic chemical raw material and a fine chemical product, is the third largest anhydride which is only second to phthalic anhydride and acetic anhydride in the world at present, is mainly used for producing thermosetting resin and unsaturated polyester resin, and is used in the fields of pesticides, medicines, coatings, printing ink, lubricating oil additives, papermaking chemicals, textile finishing agents, food additives, surfactants and the like. In addition, a series of widely used fine chemical products such as 1, 4-butanediol (GBL), Tetrahydrofuran (THF), maleic acid, fumaric acid, tetrahydrochysene anhydride and the like can be produced by using maleic anhydride as a raw material, the development and utilization prospects are very wide, and the application range of the maleic anhydride is continuously expanded at present.

The maleic anhydride production process mainly comprises a benzene catalytic oxidation method, an n-butane catalytic oxidation method, a C4 olefin catalytic oxidation method and a phthalic anhydride byproduct method according to raw materials. Early maleic anhydride production used benzene as a raw material, but benzene was expensive and toxic, and was neither economical nor meeting increasingly stringent environmental requirements. In recent years, a process for producing maleic anhydride from low-cost carbon four-fraction (n-butane) has become an absolute mainstream of maleic anhydride production worldwide. In 1960, Petroleum-Texas Chemical company (Petrotex Chemical corp.) in the United states established an industrial plant for the oxidation of butene to maleic anhydride. In 1974 Monsanto corp, USA, the company Monsanto corp realized the industrial production of maleic anhydride by oxidation of n-butane in a fixed bed process. In addition, the production of maleic anhydride by the n-butane method is similar to the device used by the benzene method, and the trend of converting the benzene oxidation method into the butane oxidation method to prepare the maleic anhydride is increasingly obvious in recent years. These factors have greatly stimulated the need for vanadium phosphorus oxide catalysts for the butane process to produce maleic anhydride.

The catalyst for preparing maleic anhydride by oxidizing n-butane comprises V-P-O series, V-Mo-O series, Ti-P-O series and Mo-P-O series, and the most effective industrial catalyst for the reaction is Vanadium Phosphorus Oxide (VPO) series catalyst. The surface property of the catalyst, the addition of the auxiliary agent, the activation method of the catalyst and the like all have obvious influence on the performance of the catalyst. Although the current production route using n-butane as a raw material has a dominant position in the production of maleic anhydride, the catalyst needs to further improve the activity and selectivity of the catalyst and increase the yield of the maleic anhydride.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention provides the vanadium-phosphorus-oxygen catalyst for preparing the maleic anhydride by n-butane oxidation and the preparation method thereof. The method has the advantages of simple process, low cost and easy realization.

According to one aspect of the invention, the vanadium-phosphorus-oxygen catalyst for preparing maleic anhydride by n-butane oxidation is prepared by carrying out pore-enlarging treatment on a vanadium-phosphorus-oxygen catalyst substrate by using a pore-enlarging agent.

According to some embodiments of the invention, the vanadium content of the catalyst is between 28% and 35%, preferably between 30% and 34%; and/or the mass content of the phosphorus element in the catalyst is 15-25%, preferably 18-22%.

The vanadium and phosphorus in the catalyst of the invention are mainly (VO)₂P₂O₇Exists in the form of (1); further, the (VO)₂P₂O₇Is prepared from VO (HPO) as precursor in organic solvent by liquid-phase method₄)₂·0.5H₂O is obtained after activation in a specific atmosphere.

According to some embodiments of the present invention, the ratio of the mass of the pore-expanding agent to the mass of the vanadium phosphorus oxygen catalyst substrate is (5-20): 80-95), preferably (8-15): 85-92), more preferably (10-13): 87-90.

In some specific embodiments, the pore-enlarging agent comprises one or more of 1,1, 1-trimethylolethane, trimethylolpropane, phthalic anhydride, maleic anhydride, tartaric acid, citric acid, and citric acid, preferably one or more of 1,1, 1-trimethylolethane, tartaric acid, and maleic anhydride.

The invention controls the addition of the pore-expanding agent and the removal process of the pore-expanding agent in the post-treatment process of the catalyst, thereby controlling and improving the specific surface area and the pore structure of the treated catalyst, and further improving the activity of the catalyst in the selective oxidation reaction of catalyzing butane and the selectivity of generating maleic anhydride.

During the course of the study, the inventors found the ratioThe change of the surface area has important influence on the activity of the catalyst, the butane conversion rate, the maleic anhydride selectivity and the like, so that in one embodiment of the invention, the specific surface area of the catalyst is 5-80m²(ii)/g; preferably 10-70m²Per g, particularly preferably from 10 to 50m²(ii) in terms of/g. Within the range, the surface of the catalyst is beneficial to the effective contact of reactant molecules and active sites of the catalyst, and simultaneously, the further peroxidation of a target product maleic anhydride can be inhibited, so that the effects of improving the activity of the catalyst and generating the selectivity of the maleic anhydride can be achieved. In the invention, through improving the addition and removal of pore-expanding agent of the formed catalyst and simultaneously under the further promotion of metal auxiliary agent, the obtained catalyst is evaluated by a fixed bed pilot scale reactor, under the same operation condition, the conversion rate of butane can be improved by 0-10 percent and can be up to 9.7 percent, the selectivity of generated maleic anhydride can be improved by 0-20 percent and can be up to 19.3 percent, and the molar yield of the maleic anhydride can be improved by 0.2-16 percent and can be up to 15.0 percent.

The mole ratio of the vanadium element and the phosphorus element on the surface of the vanadium phosphorus oxygen catalyst substrate before treatment has important influence on the aspects of improving the activity of the catalyst, generating the selectivity of the maleic anhydride and the like. Therefore, according to a preferred embodiment of the present invention, the molar ratio of the vanadium element to the phosphorus element on the surface of the vanadium phosphorus oxide catalyst substrate is 1 (0.8-4), preferably 1 (1.5-3), and more preferably 1 (2-3).

In the course of research, the inventors found that the bulk density of the catalyst is also an important factor in the performance of the catalyst, and the bulk density of the catalyst directly reflects the mass of the actual catalyst that can be loaded in a fixed length of reaction tube, which is related to the catalyst sample itself and the sample pores and their sample interstitial volumes, as well as the catalyst shape, size and mechanical strength. The proper bulk density can be matched with corresponding catalytic reaction and reactor, and the catalyst can fully exert its catalytic performance. The bulk density is too low, and although the pressure drop in the reaction tube is small, the actual mechanical strength and the number of active centers of the catalyst are possibly correspondingly reduced, so that the surface utilization rate of the catalyst is small; the bulk density is too high, and the number of active centers in unit volume is increasedHowever, it is possible that the surface utilization of the catalyst is reduced due to the large internal mass transfer resistance, which is disadvantageous for the improvement of the selectivity of the catalyst, and therefore, in a preferred embodiment of the present invention, the bulk density of the catalyst is 0.6 to 0.85g/cm³Preferably 0.7 to 0.8g/cm³. Within the range, the pressure drop of the bed layer is proper, the pressure drop range is 3.5-30kPa (the height of the bed layer is 0.5-4 m), and the catalyst can keep the structural integrity and exert good performance.

According to some embodiments of the invention, the catalyst further comprises a promoter metal element comprising one or more of indium, niobium, bismuth, cobalt, zinc, and tungsten.

According to a preferred embodiment of the present invention, the molar ratio of the promoter metal element to the vanadium element is (1-5): 100-.

In the research process, the inventor finds that the performance of the catalyst can be obviously improved by adding the auxiliary metal element, and particularly, the activity and the selectivity of generating the maleic anhydride can be obviously improved, so that the yield of the maleic anhydride is improved. When the niobium element is added as an auxiliary metal element, the effect is particularly obvious. In a specific example, under the same operating conditions, the catalyst, evaluated in a fixed bed pilot reactor, had an increase in butane conversion of 7.6 to 8.2%, an increase in the selectivity to maleic anhydride of 0.9 to 1.2%, and an increase in the yield of maleic anhydride of 5.7 to 6.2%, compared to the catalyst without niobium addition.

According to another aspect of the present invention, there is provided a method for preparing a vanadium phosphorus oxide catalyst for n-butane oxidation to produce maleic anhydride, comprising:

step A, adding a vanadium source and a phosphorus source into a liquid medium for reaction to prepare a vanadium-phosphorus-oxygen catalyst precursor;

b, activating the vanadium-phosphorus-oxygen catalyst precursor to prepare a vanadium-phosphorus-oxygen catalyst substrate;

and step C, treating the vanadium-phosphorus-oxygen catalyst substrate by using a pore-expanding agent to prepare the vanadium-phosphorus-oxygen catalyst for preparing maleic anhydride by oxidizing n-butane.

The feeding ratio of the vanadium element and the phosphorus element has a more important influence on the aspects of improving the activity of the catalyst, the selectivity of the generated maleic anhydride and the like, so according to some embodiments of the invention, the feeding molar ratio of the vanadium source to the phosphorus source in the step A is 1 (0.8-2), preferably 1 (1-1.4), and more preferably 1 (1.1-1.2), wherein the vanadium source is calculated by the vanadium element, and the phosphorus source is calculated by the phosphorus element.

According to a preferred embodiment of the invention, the vanadium source comprises one or more of an oxide of vanadium and a vanadate, preferably vanadium pentoxide and/or ammonium metavanadate; the phosphorus source comprises phosphoric acid or phosphorus pentoxide, preferably 85-105 wt% of at least one of phosphoric acid, pyrophosphoric acid and polyphosphoric acid.

The addition of the metal element as an auxiliary agent can obviously improve the performance of the catalyst, and particularly can obviously improve the activity and the selectivity of generating maleic anhydride, thereby improving the yield of the maleic anhydride. Thus, in step a, an auxiliary metal element species may optionally be added. In some embodiments, the molar ratio of the promoter metal element to the vanadium element is (1-5): 100-.

According to a preferred embodiment of the invention, the promoter metal element comprises one or more of indium, niobium, bismuth, cobalt, zinc and tungsten. According to some embodiments of the present invention, the auxiliary metal element substance is not particularly limited, and a compound containing the auxiliary metal element may be selected, and for example, a metal salt or a metal oxide of the auxiliary metal element may be selected. In some specific embodiments, the promoter metal element species may be a carboxylate, nitrate, phosphate, oxide or chloride of a promoter metal element, preferably a nitrate or oxide of a promoter metal element.

According to some embodiments of the invention, step a comprises:

step A1, adding a vanadium source into a liquid medium, and heating and refluxing;

step A2, adding a phosphorus source and a polyenol into the reaction system of the step A1, and continuously heating and refluxing to obtain a reaction solution containing a precipitate;

step A3, optionally, adding an auxiliary metal element substance into the reaction system of the step A2;

and A4, carrying out solid-liquid separation treatment on the reaction liquid containing the precipitate, and washing and drying the obtained precipitate to obtain the vanadium-phosphorus-oxygen catalyst precursor.

According to an embodiment of the present invention, the liquid medium in step a1 is not particularly limited, and an organic solvent commonly used in the art may be selected, and is preferably an organic alcohol or polyol solvent, and particularly preferably a mixed solvent of isobutanol and benzyl alcohol in any volume ratio. In some embodiments, it is preferred that the volume ratio of isobutanol to benzyl alcohol is (100-85) to (0-15).

According to a preferred embodiment of the present invention, the reaction time of step A1 is 0 to 5 hours, preferably 3 to 5 hours.

According to some embodiments of the present invention, the method and conditions in step a2 are not particularly limited, and may be operated, for example, as follows: cooling the reaction system obtained in the step A1 to 25-80 ℃, adding a phosphorus source and polyenol into the reaction system, and continuously heating and refluxing the mixture for reaction; preferably, the reaction system of the step A1 is cooled to 25-60 ℃, a phosphorus source and the polyenol are added, and the reaction is carried out by continuously heating and refluxing.

According to a preferred embodiment of the present invention, the reaction time of step A2 is 5-24h, preferably 16-20 h.

According to the preparation method of the present invention, the order of addition of the phosphorus source and the polyenol is not particularly limited, and the phosphorus source may be added first and then the polyenol may be added first, or the polyenol may be added first and then the phosphorus source may be added, or the phosphorus source may be added simultaneously.

According to some embodiments of the present invention, the poly (enol) is not particularly limited, and the poly (enol) suitable for use in the present invention is preferably polyethylene glycol. In some specific embodiments, the polyethylene glycol has a molecular weight of 1500-10000, preferably 1500-6000, and more preferably 1500-2000.

According to a preferred embodiment of the present invention, an additive metal element substance may or may not be optionally added to the reaction system of step a 2. In some specific embodiments, the temperature of the reaction system in step a2 may be optionally reduced to 25-80 ℃, and the promoter metal element substance is added thereto, and the reaction is continued to be heated and refluxed to obtain a reaction solution containing the precipitate.

The treatment in step A4 according to the production method of the present invention is not particularly limited, and for example, the reaction solution containing the precipitate is filtered or centrifuged to obtain a precipitate, the precipitate is washed with absolute ethanol at a volume ratio of absolute ethanol to precipitate (310):1, which can be carried out three to five times, and finally dried at 60 to 150 ℃ for 6 to 24 hours, preferably at 120 ℃ for 12 to 24 hours.

According to some embodiments of the invention, step B comprises:

step B1, mixing the vanadium phosphorus oxide catalyst precursor with a lubricant, and then carrying out heating treatment to obtain a mixed material;

step B2, performing pressing treatment on the mixed material to obtain a compact;

and step B3, putting the compact in air and/or water vapor and/or nitrogen atmosphere for activation treatment to obtain the activated vanadium phosphorus oxygen catalyst substrate.

According to a preferred embodiment of the present invention, the mass ratio of the lubricant to the vanadium phosphorus oxide catalyst precursor is (0-10): 90-100), preferably (0-5): 95-100, more preferably (3-5): 95-97. In some specific embodiments, the lubricant comprises one or more of graphite, starch, and stearate, and in a preferred embodiment, the lubricant is graphite.

According to some embodiments of the invention, the vanadium phosphorus oxide catalyst precursor is mixed with a lubricant, then heat treated at a temperature of 120-275 ℃ for 5-24h, and finally pressed into a shaped compact. In some preferred embodiments, the vanadium phosphorus oxide catalyst precursor powder is mixed with a lubricant, then heat treated at a temperature of 150 ℃ and 250 ℃ for 5-7h, and finally pressed into a cylindrical compact.

According to a preferred embodiment of the invention, the density of the compact is between 1.0 and 1.5g/cm³Preferably 1.1 to 1.3g/cm³。

According to some embodiments of the invention, the activation treatment comprises: placing the compact in an air and/or steam and/or nitrogen atmosphere, raising the temperature to 380-480 ℃ at a certain temperature raising rate, and then keeping the compact for a period of time under the condition of changing or not changing the atmosphere, wherein the preferable time range is 3-8 h; and then cooling the activated compact to room temperature under the protection of inert gas to obtain the finished product. In a preferred embodiment, the compact is first placed in an air atmosphere, the temperature is raised to 375 ℃ at a heating rate of 2.5 ℃/min, and then the atmosphere is replaced by a mixed atmosphere of 50% water vapor and 50% air at a space velocity of 1500h^-1The temperature is raised to 425 ℃ at the heating rate of 4 ℃/min, the temperature is maintained for 1h under the condition, the atmosphere is replaced by 100 percent nitrogen, the roasting is continued for 5 to 6h in the atmosphere, and then the temperature is reduced to room temperature under the protection of nitrogen, so that the activated vanadium-phosphorus-oxygen catalyst is obtained.

According to some embodiments of the invention, step C comprises:

step C1, mixing the vanadium phosphorus oxygen catalyst substrate with a pore-expanding agent, and then performing compression molding to obtain a catalyst rough blank;

and step C2, performing pore-expanding agent removal treatment on the rough blank to obtain the vanadium-phosphorus-oxygen catalyst for preparing maleic anhydride by oxidizing n-butane.

According to a preferred embodiment of the invention, the vanadium phosphorus oxide catalyst substrate is crushed into powder of 40-100 meshes, then mixed with pore-expanding agent and pressed into a catalyst rough blank with a certain shape. The forming method is not particularly limited, and the mixture can be formed by a method known to those skilled in the art, preferably by using a forming device such as a punch, and the formed catalyst and its blank can be in any shape, and in some specific embodiments, can be a cylinder, a hollow annular cylinder, a sphere, a sheet, a body column with a Y-shaped cross section, or an irregular shape, preferably a cylinder, a hollow annular cylinder, or a body column with a Y-shaped cross section. The size of the catalyst blank is not particularly limited, and in some specific embodiments, the diameter of the blank is preferably 4-13mm, and the height of the blank is preferably 2-8 mm; further preferably, the diameter of the rough blank is 5-8mm, and the height is 3-6 mm.

According to a preferred embodiment of the present invention, the pore-enlarging agent is removed from the green compact by a solvent impregnation method. The solvent is selected such that the pore-expanding agent is slightly soluble therein, which facilitates slow removal of the pore-expanding agent from the catalyst structure, thereby preventing rapid collapse of the catalyst structure due to rapid removal of the pore-expanding agent and protecting the overall mechanical hardness and abrasion resistance of the catalyst. Therefore, the solvent suitable for the present invention is selected from one or more of acetone, ethanol, dehydrated ether, n-butanol, methyl ethyl ketone, dichloromethane and ethyl acetate, preferably from one or more of acetone, n-butanol and ethyl acetate.

The amount of the pore-expanding agent used in the preparation method according to the present invention is also an important factor in the removal of the pore-expanding agent, and the solvent should immerse the green body to be treated, and in some specific embodiments, the volume ratio of the solvent to the green body is (1-5):1, preferably (1-3): 1.

According to the preparation method, in the process of dipping and removing the pore-expanding agent, the control of dipping time is very important for the structure and the performance of the catalyst, if the time is too short, the removal of the pore-expanding agent is not good, and the specific surface area and the pore structure of the catalyst are not good; if the time is too long, part of the lubricant will be separated from the blank by elution of the pore-expanding agent, causing further changes in the pore structure of the catalyst, which in turn affects the overall mechanical hardness and abrasion resistance of the catalyst, and therefore the time of the impregnation treatment must be controlled. In some specific embodiments, the solvent immersion process has a treatment time of 1 to 24 hours, preferably 10 to 24 hours, and more preferably 16 to 24 hours.

According to a preferred embodiment of the invention, the pore-expanding agent in the rough blank is removed through a heat treatment method, wherein the treatment temperature of the heat treatment is 120-300 ℃, and preferably 150-250 ℃; the treatment time is 12-24h, preferably 20-24 h.

The method for preparing the vanadium-phosphorus-oxygen catalyst for preparing maleic anhydride by oxidizing n-butane expands the pore structure of the catalyst, increases the specific surface area of the catalyst and improves the performance of the catalyst by adding the pore-expanding agent and removing the pore-expanding agent in the catalyst forming process.

According to another aspect of the present invention, there is provided a process for producing maleic anhydride by oxidation of n-butane, which comprises subjecting n-butane to an oxidation reaction in the presence of the above vanadium phosphorus oxide catalyst for the oxidation of n-butane to produce maleic anhydride.

The vanadium phosphorus oxide catalyst for preparing maleic anhydride by oxidizing butane is used for catalyzing the reaction for preparing the maleic anhydride by oxidizing the butane to obtain the maleic anhydride, and the reaction effect is good, and the yield of the maleic anhydride is high. At the reaction temperature of 400 ℃ and the space velocity of 1500h^-1Under the condition that the butane concentration is 1.7%, the butane conversion rate can reach 81.9%, the yield of the maleic anhydride is 63.8%, and the selectivity is 77.9%; under the same condition, the vanadium-phosphorus-oxygen catalyst without being improved by the pore-expanding agent has the catalytic performance that the conversion rate of butane is 83.3 percent, the selectivity of maleic anhydride is 58.6 percent, and the yield of the maleic anhydride is 48.8 percent, thereby obtaining better technical effect.

Drawings

FIG. 1 is an XRD spectrum of a vanadium phosphorus oxide catalyst precursor (A) and a vanadium phosphorus oxide catalyst matrix (B);

FIG. 2 is an SEM image of a vanadium phosphorus oxide catalyst precursor (A) and a vanadium phosphorus oxide catalyst substrate (B);

FIG. 3 is a diagram showing the distribution of pore diameters of a vanadium phosphorus oxide catalyst substrate (A) and a vanadium phosphorus oxide catalyst (B) for n-butane oxidation to produce maleic anhydride.

Detailed Description

The present invention will be further described in detail with reference to specific examples below:

in the examples, the crystal phase was measured by an X-ray diffractometer from Pasacaceae, Netherlands, and the specific surface area was measured by an ASAP-2020 full-automatic specific surface area and pore size analyzer from Quantachrome, USA.

Example 1

127.2g V was added to a 3L round bottom flask₂O₅1350mL of a mixed solution of isobutanol and 150mL of benzyl alcohol, and heating and stirring the mixed solution to reflux for 3 hours, adding 10.0g of polyethylene glycol with the molecular weight of 1500 thereto, dropwise adding 150g of 105 wt% phosphoric acid, heating and stirring the mixed solution to reflux for 16 hours, wherein the V/P feeding molar ratio is 1/1.15, and drying the obtained precipitate at 120 ℃ for 12 hours after centrifuging and washing the precipitate with absolute ethanol. Adding graphite with the mass ratio of 3/97 to the dried catalyst precursor powder, uniformly mixing, heating in air at 250 deg.C for 5 hr, pressing into cylindrical structure with height of 3mm and diameter of 6mm, and density of the structure being 1.2g/cm³The temperature of the obtained catalyst precursor structure is raised to 375 ℃ at the heating rate of 2.5 ℃/min in the air atmosphere, then the atmosphere is replaced by the mixed atmosphere of 50 percent of water vapor and 50 percent of air, and the airspeed is 1500h^-1The temperature is raised to 425 ℃ at the temperature raising rate of 4 ℃/min, the temperature is kept for 1 hour under the condition, the atmosphere is replaced by 100 percent nitrogen, the roasting is continued for 6 hours in the atmosphere, and then the temperature is reduced to the room temperature under the protection of the nitrogen, so that the activated vanadium-phosphorus-oxygen catalyst is obtained. Crushing the catalyst for many times, adding 1,1, 1-trihydroxyethane with the mass ratio of the catalyst substrate powder being 11/89, sieving and mixing uniformly, and continuously pressing to form a formed catalyst with a Y-shaped cross section, wherein the diameter of the formed catalyst structure is 6mmAnd the height is 5 mm. Soaking in acetone for 21 hr to obtain catalyst structure, drying at 60 deg.C under vacuum for 24 hr to obtain vanadium-phosphorus-oxygen catalyst with bulk density of 0.75g/cm for preparing maleic anhydride³Having a specific surface area of 33.5m²(ii)/g, the catalyst external surface P/V (atomic ratio) was 3.1/1, the mass content of vanadium in the catalyst was 33%, and the mass content of phosphorus was 21%. The catalyst obtained was evaluated in a 120mL fixed bed pilot scale reactor with 1.7% butane feed for 1500h^-1At the airspeed of (2), at 400 ℃, the conversion rate of butane reaches 81.9 percent, the selectivity of maleic anhydride reaches 77.9 percent, and the yield of the maleic anhydride is 63.8 percent; at 410 ℃, the conversion rate of butane reaches 87.3 percent, the selectivity of maleic anhydride reaches 70.8 percent, and the yield of the maleic anhydride reaches 61.8 percent.

Comparative example 1

The procedure was as in example 1 except that 1,1, 1-trihydroxyethane was not added as a pore-expanding agent and no corresponding pore-expanding agent treatment was performed. The bulk density of the obtained catalyst was 0.79g/cm³With a specific surface area of 22.5m²The catalyst surface P/V (atomic ratio) was 2.2/1. The catalyst obtained was evaluated in a 120mL fixed bed pilot scale reactor with 1.7% butane feed for 1500h^-1At the airspeed of (2), at 400 ℃, the conversion rate of butane reaches 83.3 percent, the selectivity of maleic anhydride reaches 58.6 percent, and the yield of the maleic anhydride is 48.8 percent; at 410 ℃, the conversion rate of butane reaches 89.2%, the selectivity of maleic anhydride reaches 56.8%, and the yield of maleic anhydride is 50.7%.

Example 2

127.2g V was added to a 3L round bottom flask₂O₅1250mL of isobutanol and 250mL of benzyl alcohol, heating and stirring to reflux for 3 hours, adding 20.0g of polyethylene glycol with the molecular weight of 2000, dropwise adding 156g of 105 wt% phosphoric acid, heating and stirring to reflux for 20 hours, keeping the feeding molar ratio of V/P at 1/1.20, centrifuging the obtained precipitate, washing with absolute ethyl alcohol, and drying at 120 ℃ for 12 hours. Adding the dried catalyst precursor powder into graphite with the mass ratio of 3/97 to the catalyst precursor powder, uniformly mixing, heating in air at 250 ℃ for 5 hours, and pressing the powder into a cylindrical structure with the height of 3mm and the diameter of 13mmThe density of the structure is 1.22g/cm³The temperature of the obtained catalyst precursor structure is raised to 375 ℃ at the heating rate of 2.5 ℃/min in the air atmosphere, then the atmosphere is replaced by the mixed atmosphere of 50 percent of water vapor and 50 percent of air, and the airspeed is 1500h^-1The temperature is raised to 425 ℃ at the temperature raising rate of 4 ℃/min, the temperature is kept for 1 hour under the condition, the atmosphere is replaced by 100 percent nitrogen, the roasting is continued for 5 hours in the atmosphere, and then the temperature is reduced to the room temperature under the protection of the nitrogen, so that the activated vanadium-phosphorus-oxygen catalyst is obtained. The catalyst is crushed for a plurality of times, tartaric acid with the mass ratio of 5/95 to the catalyst matrix powder is added, sieved and mixed evenly, and pressed continuously into a hollow cylindrical formed catalyst, the diameter of the formed catalyst structure is 6mm, the height is 4mm, and the hollow diameter is 3 mm. Soaking the catalyst structure in n-butanol for 3 hours (catalyst bulk volume/solvent volume: 1/1), drying the obtained catalyst structure at 60 deg.C under vacuum for 24 hours to obtain vanadium-phosphorus-oxygen catalyst for preparing maleic anhydride by n-butane oxidation, wherein the catalyst bulk density is 0.74g/cm³Having a specific surface area of 29.0m²The catalyst surface P/V (atomic ratio) was 2.6/1, the mass content of vanadium in the catalyst was 34%, and the mass content of phosphorus was 22%. The resulting catalyst was evaluated in a 120mL fixed bed pilot reactor with 1.8% butane feed for 1750h^-1At 410 ℃, the butane conversion rate reaches 84.7%, the maleic anhydride selectivity is 65.4%, and the maleic anhydride yield is 55.4%; at 415 ℃, the conversion rate of butane reaches 86.6 percent, the selectivity of maleic anhydride reaches 63.9 percent, and the yield of the maleic anhydride is 55.3 percent.

Comparative example 2

The procedure was as in example 2 except that tartaric acid was not added as a pore-enlarging agent and no corresponding pore-enlarging agent treatment was performed. The bulk density of the obtained catalyst was 0.76g/cm³Having a specific surface area of 27.2m²The catalyst surface P/V (atomic ratio) was 2.6/1. The resulting catalyst was evaluated in a 120mL fixed bed pilot reactor with 1.8% butane feed for 1750h^-1At 410 ℃, the butane conversion rate reaches 86.1%, the maleic anhydride selectivity is 62.8%, and the maleic anhydride yield is 54.1%; at 415 ℃, the conversion rate of butane reaches 87.6 percent, and the selectivity of maleic anhydride reaches 62 percent4% and the yield of maleic anhydride is 54.7%.

Example 3

127.2g V was added to a 3L round bottom flask₂O₅1250mL of isobutanol and 250mL of benzyl alcohol, heating and stirring to reflux for 3 hours, adding 10.0g of polyethylene glycol with the molecular weight of 6000, dropwise adding 130g of 105 wt% phosphoric acid, heating and stirring to reflux for 10 hours, keeping the feeding molar ratio of V/P at 1/1, centrifuging the obtained precipitate, washing with absolute ethyl alcohol, and drying at 120 ℃ for 12 hours. Adding graphite with the mass ratio of 5/95 to the catalyst precursor powder into the dried catalyst precursor powder, uniformly mixing, heating in air at 250 ℃ for 5 hours, pressing the powder into a cylindrical structure with the height of 3mm and the diameter of 6mm, wherein the density of the structure is 1.12g/cm³The temperature of the obtained catalyst precursor structure is raised to 375 ℃ at the heating rate of 2.5 ℃/min in the air atmosphere, then the atmosphere is replaced by the mixed atmosphere of 50 percent of water vapor and 50 percent of air, and the airspeed is 1500h^-1The temperature is raised to 425 ℃ at the temperature raising rate of 4 ℃/min, the temperature is kept for 1 hour under the condition, the atmosphere is replaced by 100 percent nitrogen, the roasting is continued for 5 hours in the atmosphere, and then the temperature is reduced to the room temperature under the protection of the nitrogen, so that the activated vanadium-phosphorus-oxygen catalyst is obtained. The catalyst is crushed for a plurality of times, maleic anhydride with the mass ratio of 15/85 to the catalyst matrix powder is added, the mixture is sieved and mixed evenly, and the mixture is pressed continuously into a formed catalyst with a Y-shaped cross section of a body column, wherein the diameter of the formed catalyst structure is 6mm, and the height of the formed catalyst structure is 4 mm. Soaking the catalyst structure in acetone for 1 hour (catalyst bulk volume/solvent volume: 1/1), drying the obtained catalyst structure at 60 deg.C under vacuum for 24 hours to obtain vanadium-phosphorus-oxygen catalyst for preparing maleic anhydride by n-butane oxidation, wherein the catalyst bulk density is 0.72g/cm³With a specific surface area of 41.7m²(g), the P/V (atomic ratio) of the outer surface of the catalyst is 1.8/1, the mass content of vanadium in the catalyst is 33%, and the mass content of phosphorus is 18%. The catalyst obtained was evaluated in a 120mL fixed bed pilot scale reactor with 1.8% butane feed for 1500h^-1At 410 ℃, the butane conversion rate reaches 89.2 percent, the maleic anhydride selectivity is 60.4 percent, and the yield of the maleic anhydride is 53.9 percentPercent; at 415 ℃, the conversion rate of butane reaches 91.3%, the selectivity of maleic anhydride reaches 58.2%, and the yield of maleic anhydride reaches 53.1%.

Comparative example 3

The procedure is as in example 3 except that maleic anhydride is not added as a pore-enlarging agent and no corresponding pore-enlarging agent treatment is performed. The bulk density of the obtained catalyst was 0.73g/cm³Having a specific surface area of 14.5m²The catalyst surface P/V (atomic ratio) was 1.8/1. The catalyst obtained was evaluated in a 120mL fixed bed pilot scale reactor with 1.8% butane feed for 1500h^-1At 410 ℃, the butane conversion rate reaches 88.2 percent, the selectivity of maleic anhydride reaches 59.7 percent, and the yield of the maleic anhydride reaches 52.7 percent; at 415 ℃, the conversion rate of butane reaches 89.9 percent, the selectivity of maleic anhydride reaches 56.8 percent, and the yield of the maleic anhydride is 51.1 percent.

As can be seen from comparison of the data of examples 1 to 3 with those of comparative examples 1 to 3, the conversion of butane and the selectivity of maleic anhydride to maleic anhydride were improved and the yield of maleic anhydride was also improved after the pore-expanding treatment with the pore-expanding agent. This is because the pore-enlarging treatment improves the porosity of the catalyst, so that the specific surface area of the catalyst is increased, thereby making a large contribution to the active surface area where the catalytic reaction takes place. Meanwhile, feed gas (hydrocarbon and oxygen) enters the inner surface of the catalyst main body (sheet or particle) which is effectively utilized through the pore channel, reaction products are diffused through the surface, and the effective diffusion of the catalyst promotes the adsorption of reactants on the surface of the catalyst and the desorption of products on the surface of the catalyst, so that the improvement of the conversion rate of the reactants and the selectivity of generated maleic anhydride is facilitated, and the improvement of the yield of the maleic anhydride is finally promoted.

Example 4

The procedure of example 1 was repeated except that 104.3g of 105 wt% phosphoric acid was charged into the reaction system at a molar ratio of V/P charged of 1/0.8. The bulk density of the resulting shaped catalyst was 0.75g/cm³Having a specific surface area of 26.9m²The catalyst has an outer surface P/V (atomic ratio) of 1.5/1, a vanadium content of 35% by mass and a phosphorus content of 15% by mass. The catalyst obtained was evaluated in a 120mL fixed bed pilot scale reactor with 1.7% butane feed for 1500h^-1At 400 ℃, the butane conversion rate reaches 76.3 percent, and the selectivity of maleic anhydride is high59.8 percent and the yield of the maleic anhydride is 45.6 percent.

Example 5

The procedure of example 1 was repeated except that 260.9g of 105 wt% phosphoric acid was added to the reaction system at a molar ratio of V/P feed of 1/2. The bulk density of the resulting shaped catalyst was 0.76g/cm³Having a specific surface area of 29.1m²(ii)/g, the catalyst external surface P/V (atomic ratio) was 3.8/1, the mass content of vanadium in the catalyst was 29%, and the mass content of phosphorus was 20%. The catalyst obtained was evaluated in a 120mL fixed bed pilot scale reactor with 1.7% butane feed for 1500h^-1At 400 ℃, the butane conversion rate reaches 64.7%, the selectivity of maleic anhydride reaches 79.0%, and the yield of the maleic anhydride reaches 51.1%.

Comparative example 4

The procedure of example 1 was repeated except that 65.2g of 105 wt% phosphoric acid was added to the reaction system at a molar ratio of V/P fed of 1/0.5. The bulk density of the resulting shaped catalyst was 0.72g/cm³With a specific surface area of 22.3m²The catalyst surface P/V (atomic ratio) was 0.8/1, the mass content of vanadium in the catalyst was 48%, and the mass content of phosphorus was 12%. The catalyst obtained was evaluated in a 120mL fixed bed pilot scale reactor with 1.7% butane feed for 1500h^-1At 400 ℃, the butane conversion rate reaches 63.2%, the selectivity of maleic anhydride reaches 51.6%, and the yield of the maleic anhydride is 32.6%.

Comparative example 5

The procedure of example 1 was repeated except that 391.3g of 105 wt% phosphoric acid was charged into the reaction system, and the molar ratio of V/P charged was 1/3. The bulk density of the resulting shaped catalyst was 0.74g/cm³Having a specific surface area of 28.4m²(g), the P/V (atomic ratio) of the outer surface of the catalyst is 4.2/1, the mass content of vanadium in the catalyst is 30%, and the mass content of phosphorus is 26%. The catalyst obtained was evaluated in a 120mL fixed bed pilot scale reactor with 1.7% butane feed for 1500h^-1At 400 ℃, the butane conversion rate reaches 60.1%, the selectivity of maleic anhydride reaches 73.7%, and the yield of the maleic anhydride is 44.3%.

As can be seen from the comparison of the data of examples 1,4 and 5 with those of comparative examples 4 to 5, the molar ratio of V/P fed is within the range of 1:0.8 to 2.0 according to the invention, and the catalysts obtained have a molar ratio of V/P fed at 400 ℃,the conversion rate of butane is 64.7-81.9%, and the yield of maleic anhydride is 45.6-63.8%; beyond the V/P molar ratio range of the present invention, the butane conversion is 60.1-63.2% and the yield of maleic anhydride is 32.6-44.3%. The molar ratio of V/P is selected to be within the range of the invention, which is favorable for forming a certain amount of P enrichment on the surface of the catalyst while forming the active phase of the catalyst. The enriched P is generally derived from pyrophosphate and phosphate particles formed in the catalyst activation process, and the excessive phosphorus on the surface can not only prevent the beta-VOPO with more stable body phase₄While effectively limiting the excessive oxidation of surface species, and is beneficial to V in the active phase of the catalyst^IVThe stability of the center has obvious effect on promoting the selectivity of the catalyst, so that the maleic anhydride selectivity and the final maleic anhydride yield of the catalyst can be obviously improved.

Example 6

The procedure of example 1 was repeated except that 20/80 was used as the mass ratio of 1,1, 1-trihydroxyethane to the catalyst substrate powder, and the bulk density of the dried catalyst was 0.60g/cm³With a specific surface area of 18.3m²(ii)/g, the catalyst external surface P/V (atomic ratio) was 2.3/1, the mass content of vanadium in the catalyst was 35%, and the mass content of phosphorus was 25%. The catalyst obtained was evaluated in a 120mL fixed bed pilot scale reactor with 1.7% butane feed for 1500h^-1At 400 ℃, the butane conversion rate reaches 78.8%, the selectivity of maleic anhydride reaches 68.2%, and the yield of the maleic anhydride is 53.7%.

Example 7

The procedure of example 1 was repeated except that the mass ratio of the added 1,1, 1-trihydroxyethane to the catalyst base powder was 15/85, and the dried catalyst had a bulk density of 0.69g/cm3 and a specific surface area of 22.0m²(g), the P/V (atomic ratio) of the outer surface of the catalyst is 2.2/1, the mass content of vanadium in the catalyst is 33%, and the mass content of phosphorus is 21%. The catalyst obtained was evaluated in a 120mL fixed bed pilot scale reactor with 1.7% butane feed for 1500h^-1At 400 ℃, the butane conversion rate reaches 79.9 percent, the selectivity of maleic anhydride reaches 68.7 percent, and the yield of the maleic anhydride is 54.9 percent.

Example 8

Except for the addition of 1,1, 1-trihydroxyethaneThe procedure of example 1 was repeated except that the mass ratio of the dried catalyst to the catalyst base powder was 8/92, and the bulk density of the dried catalyst was 0.79g/cm³With a specific surface area of 22.4m²The catalyst surface P/V (atomic ratio) was 2.6/1, the mass content of vanadium in the catalyst was 32%, and the mass content of phosphorus was 20%. The catalyst obtained was evaluated in a 120mL fixed bed pilot scale reactor with 1.7% butane feed for 1500h^-1At 400 ℃, the butane conversion rate reaches 81.4%, the maleic anhydride selectivity is 69.2%, and the maleic anhydride yield is 56.3%.

Example 9

The procedure of example 1 was repeated except that 5/95 was used as the mass ratio of the added 1,1, 1-trihydroxyethane to the catalyst substrate powder, and the bulk density of the dried catalyst was 0.84g/cm³Having a specific surface area of 15.7m²The catalyst has an outer surface P/V (atomic ratio) of 2.2/1, a vanadium content of 31% by mass and a phosphorus content of 20% by mass. The catalyst obtained was evaluated in a 120mL fixed bed pilot scale reactor with 1.7% butane feed for 1500h^-1At 400 ℃, the butane conversion rate reaches 84.1%, the selectivity of maleic anhydride reaches 63.3%, and the yield of the maleic anhydride reaches 53.2%.

Comparative example 6

The procedure of example 1 was repeated except that 25/75 was used as the mass ratio of the added 1,1, 1-trihydroxyethane to the catalyst substrate powder, and the bulk density of the dried catalyst was 0.56g/cm³Having a specific surface area of 11.5m²(ii)/g, the catalyst external surface P/V (atomic ratio) is 2.2/1, the mass content of vanadium in the catalyst is 35%, and the mass content of phosphorus is 24%. The catalyst obtained was evaluated in a 120mL fixed bed pilot scale reactor with 1.7% butane feed for 1500h^-1At 400 ℃, the butane conversion rate reaches 75.7%, the selectivity of maleic anhydride is 63.3%, and the yield of the maleic anhydride is 47.9%.

Comparative example 7

The procedure of example 1 was repeated except that the mass ratio of the added 1,1, 1-trihydroxyethane to the catalyst base powder was 3/97, and the bulk density of the dried catalyst was 0.86g/cm³With a specific surface area of 18.1m²(g), the P/V (atomic ratio) on the outer surface of the catalyst is 2.4/1, and the mass content of vanadium in the catalyst is 33 percent and the mass content of phosphorus is 21 percent. The catalyst obtained was evaluated in a 120mL fixed bed pilot scale reactor with 1.7% butane feed for 1500h^-1At 400 ℃, the butane conversion rate reaches 86.7%, the selectivity of maleic anhydride reaches 59.8%, and the yield of the maleic anhydride is 51.8%.

Examples 1 and 6 to 9 are experimental examples in which 1,1, 1-trihydroxyethane is added as a pore-enlarging agent to perform pore-enlarging treatment and the addition amount thereof is within the range of the present invention, comparative examples 6 to 7 are experimental examples in which 1,1, 1-trihydroxyethane is added within the range of the present invention, and comparative example 1 is an experimental example in which no pore-enlarging agent is added, and it is known from the common knowledge in the art and comparison of experimental data that the resistance to internal diffusion in the main body of the catalyst can become a rate limiting factor of the reaction, and it is common knowledge that, compared with a catalyst in which pore-enlarging treatment is not performed or the pore-enlarging agent is not within the range of the present invention, pore-enlarging treatment is performed using a pore-enlarging agent within the range of the present invention, porous pore channels are formed inside catalyst particles, and reaction gas is favorably diffused to contact with the inner surface of the catalyst, so that not only the surface utilization rate of, thereby improving the diffusion path of reactants and products and obviously improving the maleic anhydride selectivity and the maleic anhydride yield of the catalyst.

Example 10

127.2g V was added to a 3L round bottom flask₂O₅1350mL of a mixed solution of isobutanol and 150mL of benzyl alcohol, heated under stirring to reflux for 4 hours, 15.0g of polyethylene glycol having a molecular weight of 6000 and 1.85g of niobium pentoxide were added thereto, and the molar ratio of the auxiliary metal element to V in this example was 1: 100, 150g of 105 wt% phosphoric acid was added dropwise thereto and heated under stirring to reflux for 20 hours at a V/P feed molar ratio of 1/1.15, and the resulting precipitate was dried at 120 ℃ for 12 hours after centrifugation and washing with anhydrous ethanol. Adding graphite with the mass ratio of 4/96 to the catalyst precursor powder into the dried catalyst precursor powder, uniformly mixing, heating in air at 250 ℃ for 5 hours, pressing the powder into a cylindrical structure with the height of 3mm and the diameter of 3mm, wherein the density of the structure is 1.16g/cm³The obtained catalyst precursor structure is heated up at a rate of 2.5 ℃/min in the air atmosphereThe temperature is increased to 375 ℃, then the atmosphere is replaced by a mixed atmosphere of 50 percent of water vapor and 50 percent of air, and the space velocity is 1500h^-1The temperature is raised to 425 ℃ at the temperature raising rate of 4 ℃/min, the temperature is kept for 1 hour under the condition, the atmosphere is replaced by 100 percent nitrogen, the roasting is continued for 5 hours in the atmosphere, and then the temperature is reduced to the room temperature under the protection of the nitrogen, so that the activated vanadium-phosphorus-oxygen catalyst is obtained. The catalyst is crushed for a plurality of times, tartaric acid with the mass ratio of 5/95 to the matrix powder of the catalyst is added, sieved and mixed evenly, and pressed into a cylindrical formed catalyst continuously, and the diameter of the formed catalyst structure is 5mm, and the height of the formed catalyst structure is 4 mm. After soaking in ethyl acetate for 16 hours (catalyst bulk/solvent volume: 1/1), the resulting catalyst structure was dried under vacuum at 60 ℃ for 24 hours, the dried catalyst having a bulk density of 0.74g/cm³Having a specific surface area of 25.1m²(g), the P/V (atomic ratio) of the outer surface of the catalyst is 2.0/1, the mass content of vanadium in the catalyst is 33%, and the mass content of phosphorus is 21%. The resulting catalyst was evaluated in a 120mL fixed bed pilot reactor with 1.9% butane feed for 1750h^-1At 410 ℃, the butane conversion rate reaches 82.6 percent, the selectivity of maleic anhydride reaches 64.4 percent, and the yield of the maleic anhydride is 53.2 percent; at 415 ℃, the conversion rate of butane reaches 85.3 percent, the selectivity of maleic anhydride reaches 62.7 percent, and the yield of the maleic anhydride is 53.5 percent.

Comparative example 8

The procedure is as in example 4 except that 1.85g of niobium oxide is not added and the corresponding hole enlargement is not performed. The bulk density of the catalyst was 0.75g/cm³With a specific surface area of 17.2m²The catalyst surface P/V (atomic ratio) was 2.0/1. The resulting catalyst was evaluated in a 120mL fixed bed pilot reactor with 1.9% butane feed for 1750h^-1At 410 ℃, the butane conversion rate reaches 72.9 percent, the selectivity of maleic anhydride reaches 66.3 percent, and the yield of the maleic anhydride is 48.3 percent; at 415 ℃, the conversion rate of butane reaches 75.6 percent, the selectivity of maleic anhydride reaches 64.8 percent, and the yield of the maleic anhydride reaches 49.0 percent.

Example 10 and comparative example 8 a set of control experiments with 1.9% butane feed, example 10 with tartaric acid added as a pore-expanding agent treatment and niobium pentoxide added as a metal element as a co-agentCompared with the comparative example 8, the specific surface area of the catalyst is improved by 45.9%, the butane conversion rate is improved by 12.8-13.3%, and the yield of the maleic anhydride is improved by 9.2-10.1%. Niobium is added as a metal additive, Nb⁵⁺Can replace VO²⁺V in⁴⁺Thereby possibly forming V_1-xNb_xO₂P₂O_7+x。Coordinately unsaturated cations may be present as L-acid sites of lower acid strength, favoring activation of the C-H bond during initial alkane oxidation, as evidenced by an increase in the conversion of butane by the catalyst catalyzing the butane oxidation reaction.

Example 11

The procedure was as in example 10 except that 4.08g of indium acetate was added instead of 1.85g of niobium pentoxide, and maleic anhydride was used as a pore-expanding agent in a mass ratio of 5/95 with respect to the catalyst base powder, and the catalyst structure was immersed in ethyl acetate for 10 hours (catalyst bulk volume/solvent volume: 1/1), in which the molar ratio of the promoter metal element to V was 1: 100. the bulk density of the obtained catalyst was 0.73g/cm³The specific surface area thereof was 11.0m²(mg/g), the catalyst external surface P/V (atomic ratio) was 2.0/1, the mass content of vanadium in the catalyst was 32%, and the mass content of phosphorus was 21%. The resulting catalyst was evaluated in a 120mL fixed bed pilot reactor with 1.9% butane feed for 1750h^-1At 410 ℃, the butane conversion rate reaches 82.6 percent, the selectivity of maleic anhydride reaches 64.4 percent, and the yield of the maleic anhydride is 53.2 percent; at 415 ℃, the conversion rate of butane reaches 85.3 percent, the selectivity of maleic anhydride reaches 62.7 percent, and the yield of the maleic anhydride is 53.5 percent.

Example 12

The procedure is as in example 11 except that 0.51g of indium acetate is added instead of 4.08g of indium acetate, the molar ratio of the promoter metal element to V being 1: 800. the bulk density of the resulting shaped catalyst was 0.76g/cm³With a specific surface area of 21.7m²The catalyst surface P/V (atomic ratio) was 2.2/1, the mass content of vanadium in the catalyst was 34%, and the mass content of phosphorus was 20%. The resulting catalyst was evaluated in a 120mL fixed bed pilot reactor with 1.9% butane feed for 1750h^-1At 410 ℃, the butane conversion rate reaches 82.4 percent, cisThe anhydride selectivity was 65.3% and the yield of maleic anhydride was 53.8%.

Example 13

The procedure is as in example 11 except that 5.44g of indium acetate is added instead of 4.08g of indium acetate, the molar ratio of promoter metal element to V being 2: 150. the bulk density of the resulting shaped catalyst was 0.75g/cm³Having a specific surface area of 10.7m²(g), the P/V (atomic ratio) of the outer surface of the catalyst is 2.1/1, the mass content of vanadium in the catalyst is 33%, and the mass content of phosphorus is 21%. The resulting catalyst was evaluated in a 120mL fixed bed pilot reactor with 1.9% butane feed for 1750h^-1At 410 ℃, the butane conversion rate reaches 81.8%, the maleic anhydride selectivity is 66.3%, and the maleic anhydride yield is 54.2%.

Example 14

The procedure is as in example 11 except that 24.5g of indium acetate is added instead of 4.08g of indium acetate, the molar ratio of promoter metal element to V being 6: 100. the bulk density of the resulting shaped catalyst was 0.75g/cm³With a specific surface area of 10.5m²The catalyst surface P/V (atomic ratio) was 2.2/1, the mass content of vanadium in the catalyst was 31%, and the mass content of phosphorus was 22%. The resulting catalyst was evaluated in a 120mL fixed bed pilot reactor with 1.9% butane feed for 1750h^-1At 410 ℃, the butane conversion rate reaches 79.4%, the selectivity of maleic anhydride reaches 61.2%, and the yield of the maleic anhydride is 48.6%.

Example 15

The procedure is as in example 11 except that 0.08g of indium acetate is added instead of 4.08g of indium acetate, the molar ratio of promoter metal element to V being 1: 5140. the bulk density of the resulting shaped catalyst was 0.74g/cm³With a specific surface area of 19.8m²The catalyst surface P/V (atomic ratio) was 2.2/1, the mass content of vanadium in the catalyst was 34%, and the mass content of phosphorus was 20%. The resulting catalyst was evaluated in a 120mL fixed bed pilot reactor with 1.9% butane feed for 1750h^-1At 410 ℃, the butane conversion rate reaches 76.5%, the maleic anhydride selectivity is 62.5%, and the maleic anhydride yield is 47.8%.

Example 16

The procedure of example 11 was repeated, except that 4.08g of indium acetate was not added. The bulk density of the catalyst was 0.73g/cm³With a specific surface area of 22.4m²(g), the catalyst surface P/V (atomic ratio) was 1.9/1, the mass content of vanadium in the catalyst was 33%, and the mass content of phosphorus was 22%. The resulting catalyst was evaluated in a 120mL fixed bed pilot reactor with 1.9% butane feed for 1750h^-1At 410 ℃, the butane conversion rate reaches 82.8 percent, the selectivity of maleic anhydride reaches 63.2 percent, and the yield of the maleic anhydride is 52.3 percent; at 415 ℃, the conversion rate of butane reaches 84.7 percent, the selectivity of maleic anhydride reaches 62.6 percent, and the yield of the maleic anhydride is 53.0 percent.

Examples 11-16 are a set of 1.9% butane feed, and a comparison of the data shows that, due to the large butane feed, the addition of promoter metal elements, the metal promoter and vanadium center form a suitable ratio, which acts as a structural function in the catalyst and contributes to the improvement of butane conversion, maleic anhydride selectivity and maleic anhydride yield; however, if the amount of the metal element as an auxiliary is too large or too small, the conversion of butane, the selectivity of maleic anhydride and the yield of maleic anhydride are lowered. Due to different electronic and atomic properties of the auxiliary agents, the proper proportion required by the auxiliary agents is different after the auxiliary agents are cooperated with the vanadium center. Some metal auxiliary agents and the catalyst active phase form like [ (VO)_1-x]M_x]₂P₂O₇The solid solution of (3) controls the diffusion of oxygen atoms, and reduces the non-selective oxidation of butane to the maximum extent; some metal additives inhibit the formation of inactive phases and promote V^IVThe center is stabilized while the activity and surface acidity of the catalyst are adjusted to increase the initial dehydrogenation rate. The addition of the metal promoter therefore has its preferred range defined.

Example 17

The catalyst substrate powder preparation and catalyst activation stages were the same as in example 1. The activated vanadium phosphorus oxygen catalyst is crushed for a plurality of times, stearic acid with the mass ratio of 10/90 to the catalyst matrix powder is added, sieved and mixed evenly, and pressed continuously into a formed catalyst with a Y-shaped cross section, and the diameter of the formed catalyst structure is 6mm, and the height is 5 mm. The temperature of the catalyst is raised to 180 ℃ in the air at a rate of 2 ℃/minKeeping the temperature for 6 hours, continuously increasing the temperature to 190 ℃ at the heating rate of 4 ℃/min, keeping the temperature for 6 hours, then continuously increasing the temperature to 200 ℃ at the heating rate of 2 ℃/min, continuously keeping the temperature for 6 hours, continuously increasing the temperature to 250 ℃ at the heating rate of 2 ℃/min, and keeping the temperature for 2 hours. The bulk density of the obtained catalyst was 0.74g/cm³Having a specific surface area of 24.0m²The catalyst surface P/V (atomic ratio) was 2.6/1. The catalyst obtained was evaluated in a 120mL fixed bed pilot scale reactor with 1.7% butane feed for 1500h^-1At the airspeed of (2), at the temperature of 400 ℃, the conversion rate of butane reaches 81.8 percent, the selectivity of maleic anhydride reaches 75.7 percent, and the yield of the maleic anhydride reaches 61.9 percent; at 410 ℃, the conversion rate of butane reaches 85.3 percent, the selectivity of maleic anhydride reaches 66.8 percent, and the yield of the maleic anhydride reaches 57.0 percent.

Any numerical value mentioned in this specification, if there is only a two unit interval between any lowest value and any highest value, includes all values from the lowest value to the highest value incremented by one unit at a time. For example, if it is stated that the amount of a component, or a value of a process variable such as temperature, pressure, time, etc., is 50 to 90, it is meant in this specification that values of 51 to 89, 52 to 88 … …, and 69 to 71, and 70 to 71, etc., are specifically enumerated. For non-integer values, units of 0.1, 0.01, 0.001, or 0.0001 may be considered as appropriate. These are only some specifically named examples. In a similar manner, all possible combinations of numerical values between the lowest value and the highest value enumerated are to be considered to be disclosed in this application.

It should be noted that the above-mentioned embodiments are only for explaining the present invention, and do not constitute any limitation to the present invention. The present invention has been described with reference to exemplary embodiments, but the words which have been used herein are words of description and illustration, rather than words of limitation. The invention can be modified, as prescribed, within the scope of the claims and without departing from the scope and spirit of the invention. Although the invention has been described herein with reference to particular means, materials and embodiments, the invention is not intended to be limited to the particulars disclosed herein, but rather extends to all other methods and applications having the same functionality.

Claims

1. A vanadium phosphorus oxygen catalyst for preparing maleic anhydride by oxidizing n-butane is prepared by carrying out pore-enlarging treatment on a vanadium phosphorus oxygen catalyst substrate by adopting a pore-enlarging agent;

wherein the mass content of vanadium in the catalyst is 28-35%, the mass content of phosphorus in the catalyst is 15-25%,

the catalyst also comprises an auxiliary agent metal element, wherein the auxiliary agent metal element comprises one or more of indium, niobium, bismuth, cobalt, zinc and tungsten,

the preparation method of the catalyst comprises the following steps:

2. The catalyst of claim 1 wherein the ratio of the pore-expanding agent to the mass of the vanadium phosphorus oxygen catalyst substrate is (5-20) to (80-95); and/or the pore-expanding agent comprises one or more of 1,1, 1-trimethylolethane, trimethylolpropane, phthalic anhydride, maleic anhydride, tartaric acid, citric acid and citric acid.

3. The catalyst of claim 2 wherein the ratio of the pore-expanding agent to the mass of the vanadium phosphorus oxide catalyst substrate is (8-15) to (85-92).

4. The catalyst of claim 3 wherein the ratio of the pore-expanding agent to the mass of the vanadium phosphorus oxide catalyst substrate is (10-13) to (87-90).

5. The catalyst of claim 2 wherein the pore-expanding agent comprises one or more of 1,1, 1-trimethylolethane, tartaric acid and maleic anhydride.

6. The catalyst according to claim 1, wherein the mass content of vanadium in the catalyst is 30-34%; and/or the mass content of the phosphorus element in the catalyst is 18-22%.

7. The catalyst as claimed in claim 1, wherein the molar ratio of the promoter metal element to the vanadium element is (1-5): (100- > 1000).

8. The catalyst as recited in claim 7, wherein the molar ratio of said promoter metal element to said vanadium element is (2-3) (150- > 200).

9. The catalyst according to claim 1, wherein the specific surface area of the catalyst is 5 to 80m²(ii)/g; the molar ratio of the vanadium element to the phosphorus element on the surface of the catalyst is 1 (0.8-4); and/or the bulk density of the catalyst is 0.6-0.85g/cm³。

10. The catalyst according to claim 9, wherein the specific surface area of the catalyst is 10 to 70m²/g。

11. The catalyst according to claim 10, wherein the specific surface area of the catalyst is 10 to 50m²/g。

12. The catalyst of claim 9, wherein the molar ratio of the vanadium element to the phosphorus element on the surface of the catalyst is 1 (1.5-3).

13. The catalyst of claim 12, wherein the molar ratio of the vanadium element to the phosphorus element on the surface of the catalyst is 1 (2-3).

14. The catalyst of claim 9, wherein the bulk density of the catalyst is from 0.7 to 0.8g/cm³。

15. A method of preparing a catalyst as claimed in any one of claims 1 to 14, comprising:

16. The preparation method of claim 15, wherein the molar ratio of the vanadium source to the phosphorus source in step A is 1 (0.8-2), wherein the vanadium source is calculated by vanadium element and the phosphorus source is calculated by phosphorus element;

and/or the vanadium source comprises one or more of an oxide of vanadium and a vanadate;

and/or the phosphorus source comprises phosphoric acid or phosphorus pentoxide.

17. The preparation method according to claim 16, wherein the molar ratio of the vanadium source to the phosphorus source in step A is 1 (1-1.4), wherein the vanadium source is calculated by vanadium element and the phosphorus source is calculated by phosphorus element.

18. The preparation method according to claim 17, wherein the molar ratio of the vanadium source to the phosphorus source in step A is 1 (1.1-1.2), wherein the vanadium source is calculated by vanadium element and the phosphorus source is calculated by phosphorus element.

19. The method according to claim 16, wherein the vanadium source is vanadium pentoxide and/or ammonium metavanadate.

20. The method of claim 16, wherein the phosphorus source is 85 to 105 wt% of at least one of phosphoric acid, pyrophosphoric acid, and polyphosphoric acid.

21. The method as claimed in claim 15, wherein in step A, an auxiliary metal element is optionally added, and the molar ratio of the auxiliary metal element to the vanadium element is (1-5): (100-); and/or the promoter metal element comprises one or more of indium, niobium, bismuth, cobalt, zinc and tungsten.

22. The method as claimed in claim 21, wherein the molar ratio of the promoter metal element to the vanadium element is (2-3): (150-.

23. The method of claim 15, wherein the step a comprises:

24. The method of claim 15, wherein the step B comprises:

25. The method of claim 24, wherein the mass ratio of the lubricant to the vanadium phosphorus oxide catalyst precursor is (0-10) to (90-100); and/or the lubricant comprises one or more of graphite, starch, and stearate.

26. The method of claim 25, wherein the mass ratio of the lubricant to the vanadium phosphorus oxide catalyst precursor is (0-5) to (95-100).

27. The method of claim 26, wherein the mass ratio of the lubricant to the vanadium phosphorus oxide catalyst precursor is (3-5) to (95-97).

28. The method of claim 15, wherein the step C comprises:

29. The method of claim 15, wherein the ratio of the pore-expanding agent to the vanadium phosphorus oxide catalyst by mass is (5-20) to (80-95);

and/or the pore-expanding agent comprises one or more of 1,1, 1-trimethylolethane, trimethylolpropane, phthalic anhydride, maleic anhydride, tartaric acid, citric acid and citric acid.

30. The method of claim 29, wherein the ratio of the pore-expanding agent to the vanadium phosphorus oxide catalyst by mass is (8-15) to (85-92).

31. The method of claim 30, wherein the ratio of the pore-expanding agent to the vanadium phosphorus oxide catalyst by mass is (10-13) to (87-90).

32. The method of claim 29, wherein the pore-enlarging agent is one or more of 1,1, 1-trimethylolethane, tartaric acid and maleic anhydride.

33. The method for preparing a porous material according to claim 28, wherein the pore-expanding agent in the green compact is removed by a solvent impregnation method in step C2;

and/or the volume ratio of the solvent to the blank is (1-5): 1;

and/or the treatment time of the solvent dipping method is 1-24 h;

and/or, the solvent is selected from one or more of acetone, ethanol, anhydrous ether, n-butanol, methyl ethyl ketone, dichloromethane and ethyl acetate;

and/or removing the pore-expanding agent in the rough blank by a heat treatment method;

and/or the treatment temperature of the heat treatment is 120-300 ℃; the treatment time is 12-24 h.

34. The method of claim 33, wherein the ratio of the solvent to the volume of the blank is (1-3): 1.

35. The method of claim 33, wherein the solvent dipping method is performed for a treatment time of 10 to 24 hours.

36. The method of claim 35, wherein the solvent dipping method is performed for a treatment time of 16 to 24 hours.

37. The method of claim 33, wherein the solvent is selected from one or more of acetone, n-butanol, and ethyl acetate.

38. The method as claimed in claim 33, wherein the heat treatment is carried out at a temperature of 150 ℃ to 250 ℃.

39. The method of claim 38, wherein the heat treatment is performed for a treatment time of 20 to 24 hours.

40. A process for producing maleic anhydride by oxidation of n-butane, which comprises subjecting n-butane to oxidation reaction in the presence of the vanadium phosphorus oxide catalyst for producing maleic anhydride by oxidation of n-butane according to any one of claims 1 to 14 or the vanadium phosphorus oxide catalyst for producing maleic anhydride by oxidation of n-butane prepared by the process according to any one of claims 15 to 39.