CN115007196B - Catalyst for synthesizing N, N-dimethylaniline by gas phase method, preparation and use method thereof - Google Patents
Catalyst for synthesizing N, N-dimethylaniline by gas phase method, preparation and use method thereof Download PDFInfo
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Abstract
The invention provides a catalyst for synthesizing N, N-dimethylaniline by a gas phase method and a preparation method and a use method thereof. By adopting a surfactant-induced step-by-step controllable deposition technology, a pore-shell structure composite material with a high specific surface area and ordered mesoporous channels is constructed, the limited-domain synthesis of double active components can be realized through subsequent steps of dipping, roasting and the like, the catalyst can provide more L acid active sites, and better catalytic activity is shown in the reaction of synthesizing N, N-dimethylaniline by a gas phase method.
Description
Technical Field
The invention belongs to the field of materials and chemical engineering, and particularly relates to a catalyst for synthesizing N, N-dimethylaniline by a gas phase method, and a preparation method and a use method thereof.
Background
N, N-dimethylaniline (DMA for short) is an important chemical raw material. The method is mainly used for producing trityl methane dyes, can be used as raw materials of solvents, explosives, medicines, plastics and the like, and can also be used for producing alkaline brilliant blue RB, alkaline violet 5BN, alkaline tenderine O, cationic red 2BL, alkaline dye intermediate tetramethyl micheli ketone and the like. In the perfumery industry, DMA is used in the production of vanillin, which is the main raw material for fixatives, off-flavours and blenders, but also for organic synthesis and for certain pharmaceutical intermediates.
The synthesis method of DMA is divided into a liquid phase method and a gas phase method, wherein the former mainly takes inorganic acid as a catalyst to be carried out in an intermittent reaction kettle, and has the disadvantages of frequent operation, long production period, low production efficiency, serious corrosion of the inorganic acid to equipment, difficult post-treatment and environmental pollution. The gas phase method mainly uses aniline and methanol as raw materials to synthesize N, N-dimethylaniline in a gas phase reaction in a normal pressure fixed bed reactor, uses solid acid as a catalyst, not only avoids a plurality of adverse factors of the liquid phase method, but also can realize the continuous production of DMA under normal pressure; and the process has the advantages of low equipment investment, simple operation, no corrosion and environmental protection.
The patent (CN 1137082C) reports gamma-Al 2 O 3 ZrO supported on carrier 2 Can be used as a catalyst for the reaction; the catalyst can be prepared by an isometric impregnation method or a sol deposition method, wherein ZrO 2 The mass content of (A) is 1-40%. Patent CN102233266A reports a method for gas phase synthesis of N, N-dimethylanilineThe solid catalyst is mainly prepared from Al 2 O 3 The content is more than 98 percent, the bulk density is 0.6-0.7g/mL, the pore volume is more than 0.56mL/g, and the specific surface area is 200-300m 2 Per g, average pore diameter 8-10 nm) and pseudo-thin aluminum hydroxide as adhesive on a bar extruder. The patent (CN 102728367B) reports a method for synthesizing N, N-dimethylaniline and a catalyst used in the method; the catalyst is prepared from metal salt and a carrier, wherein the metal salt is composed of nickel salt, cobalt salt and zinc salt, the sum of the metals accounts for 15-40% of the total weight of the supported catalyst, each metal accounts for more than or equal to 1% of the total weight of the supported catalyst, and the weight of zinc accounts for less than or equal to 5% of the total weight of the supported catalyst.
As is well known, commonly used gamma-Al 2 O 3 The specific surface area of the support is relatively low, which is a major factor affecting its catalytic performance. In addition, low specific surface area also makes it difficult to achieve high dispersion of the supported active species.
Disclosure of Invention
In order to solve the technical problems, the invention provides a catalyst for synthesizing N, N-dimethylaniline by a gas phase method and a preparation and use method thereof.
The technical scheme adopted by the invention is as follows: a preparation method of a catalyst for synthesizing N, N-dimethylaniline by a gas phase method comprises the steps of adding sodium metaaluminate into a deionized water solution of cetyl trimethyl ammonium bromide, and stirring under the condition of a pH value of 7-9; adding water glass and hydrochloric acid in a parallel flow manner, stirring under the condition of pH value of 7-9, and reacting at 130-150 ℃ after sealing to obtain a sample A; with SiO 2 Water glass is calculated as Al 2 O 3 The molar ratio of sodium metaaluminate, water glass, sodium metaaluminate and hexadecyl trimethyl ammonium bromide is 1;
alternatively, the first and second liquid crystal display panels may be,
adding zirconium oxychloride into a deionized water solution of cetyl trimethyl ammonium bromide, and stirring under the condition that the pH value is 8-9; adding water glass and hydrochloric acid in parallel flow, stirring under the condition of pH value of 8-9, sealing, reacting at 130-150 deg.C to obtain sample A, adding SiO 2 The molar ratio of the water glass, the zirconium oxychloride and the hexadecyl trimethyl ammonium bromide is 1;
placing the sample A in the air and roasting at 300-350 ℃ to obtain a sample B, loading a second active component on the sample B, wherein the second active component is zirconium oxide, zinc oxide or aluminum oxide, roasting at 400-450 ℃ after dipping and drying, and then heating to 600-650 ℃ for roasting to obtain the catalyst for synthesizing the N, N-dimethylaniline by the gas phase method.
Preferably, the specific steps are as follows:
the method comprises the following steps: dissolving hexadecyl trimethyl ammonium bromide in deionized water, adding sodium metaaluminate, regulating the pH value to 7-9 by hydrochloric acid, and then stirring for reaction;
adding water glass and hydrochloric acid in parallel flow, and stirring for reaction under the condition of pH 7-9; sealing the reaction kettle, and reacting at 130-150 ℃ to obtain a sample A;
wherein, siO is used 2 Water glass is calculated as Al 2 O 3 The molar ratio of sodium metaaluminate, water glass, sodium metaaluminate, hexadecyl trimethyl ammonium bromide and deionized water is 1;
or dissolving cetyl trimethyl ammonium bromide in deionized water, adding zirconium oxychloride, adjusting the pH value to 8-9 with ammonia water, and stirring for reaction;
adding water glass and hydrochloric acid in a concurrent flow manner, and stirring and reacting under the condition of pH 8-9; sealing the reaction kettle, and reacting at 130-150 ℃ to obtain a sample A;
wherein, siO is used 2 The molar ratio of the water glass, the zirconium oxychloride, the hexadecyl trimethyl ammonium bromide and the deionized water is 1;
step two: placing the sample A in a muffle furnace, and roasting for 2-4 h at 300-350 ℃ in the air to obtain a sample B;
step three: dipping nitrate of a second active component into the sample B by adopting an isometric dipping method, drying at 60-80 ℃, roasting for 2-3 h at 400-450 ℃ in flowing air, then heating to 600-650 ℃ and roasting for at least 3h, and cooling to room temperature to obtain the catalyst for synthesizing N, N-dimethylaniline by using a gas phase method; wherein the amount of nitrate of the second active component accounts for 0.3-5% of the total mass of the sample B.
Preferably, the silicon content of the water glass is in the range of 2.3-2.5 mol/kg, the molar ratio of Si to Na is 3.2-3.4:1.
preferably, after the impregnated sample B is calcined at 400-450 ℃ in flowing air, the temperature is raised to 600-650 ℃ under flowing nitrogen environment, and the calcination is continued.
The catalyst is prepared by the preparation method of the catalyst for synthesizing N, N-dimethylaniline by a gas phase method.
The method for preparing the N, N-dimethylaniline by using the catalyst comprises the following specific steps:
filling a catalyst into a constant temperature interval of a continuous flow normal pressure fixed bed reactor, filling a ceramic ring of at least 20 cm as a preheating layer on the upper layer of the catalyst, and heating to 270-300 ℃ under flowing nitrogen for pretreatment for at least 1 h;
closing nitrogen, pumping the mixed solution of methanol and aniline with the molar ratio of 2.5-3 into the reactor through a pressure pump, wherein the liquid hourly space velocity of the mixed solution is 0.1-1.0 h –1 。
The invention has the advantages and positive effects that: the prepared catalyst with the pore-shell structure has larger specific surface area and higher catalytic activity; by adopting a surfactant-induced step-by-step controllable deposition technology, a pore-shell structure composite material with a high specific surface area and ordered mesoporous channels is constructed, the limited-domain synthesis of double active components can be realized through subsequent steps of dipping, roasting and the like, the catalyst can provide more L acid active sites, and better catalytic activity is shown in the reaction of synthesizing N, N-dimethylaniline by a gas phase method.
Drawings
FIG. 1 is a high resolution TEM image of the catalyst prepared in example 1;
FIG. 2 preparation of catalyst from example 1 27 Nuclear magnetic spectrum of Al solid.
Detailed Description
Embodiments of the present invention will be described below with reference to the accompanying drawings.
The invention discloses a catalyst for synthesizing N, N-dimethylaniline by a gas phase method, and preparation and application thereofThe catalyst has a pore-shell structure, and the inner layer of the catalyst has hexa-coordinated gamma-Al 2 O 3 Or zirconium oxychloride, and the outer side of the zirconium oxychloride is provided with a mesoporous channel structure formed by silicon oxide; the catalyst has larger specific surface area and higher catalytic activity, and can overcome the problems of lower specific surface area, poor dispersion of active components and lower reaction activity of the traditional catalyst.
Specifically, a pore-shell structure composite material with a high specific surface area and ordered mesoporous channels is constructed by adopting a surfactant-induced step-by-step controllable deposition technology, the limited-domain synthesis of double active components can be realized by subsequent steps of dipping, roasting and the like, the catalyst can provide more L acid active sites, and better catalytic activity is shown in the reaction of synthesizing N, N-dimethylaniline by a gas phase method.
The specific preparation process can be carried out according to the following steps:
the method comprises the following steps: fully dissolving Cetyl Trimethyl Ammonium Bromide (CTAB) in deionized water in a reaction kettle at the temperature of 60-70 ℃ under the stirring state, adding sodium metaaluminate, continuing stirring for at least 0.5 hour, slowly adding hydrochloric acid to adjust the pH value to 7-9, and then stirring for 1-3 hours;
adding water glass and hydrochloric acid in a parallel flow manner, and stirring for 1-3 h for reaction under the condition of pH 7-9; sealing the reaction kettle, heating to 130-150 ℃, keeping for 5-10 h, washing the obtained product to be neutral by using deionized water, and drying the filter cake obtained after suction filtration to obtain a sample A;
wherein the water glass is SiO 2 Calculated as Al), sodium metaaluminate (calculated as Al) 2 O 3 Meter), CTAB, deionized water (H) 2 O) is 1 (SiO) 2 ）:0.01–0.2（Al 2 O 3 ）:0.08–0.15（CTAB）:40–60（H 2 O）；
Step two: placing the sample A obtained by the reaction in a muffle furnace, and roasting for 2-4 h at 300-350 ℃ in the air to obtain a sample B;
step three: dipping nitrate of a second active component on the sample B by adopting an isometric dipping method, drying at 60-80 ℃, roasting at 400-450 ℃ in air, and then heating to 600-650 ℃ for roasting to obtain a catalyst for synthesizing N, N-dimethylaniline by a gas phase method; the dosage of the second active component nitrate is 0.3-5% of the mass of the sample B.
The prepared catalyst takes silicon oxide as a framework, a mesoporous structure of an alumina or zirconia inner shell is formed in the framework, a second active component is loaded on the inner wall through an impregnation method, and a pore-shell structure formed by the silicon oxide and the alumina/zirconia can be used as an active center of the catalyst to generate a difunctional synergistic effect with the loaded second active component.
CTAB is used as a surfactant, and a step-by-step controllable deposition technology is adopted to prepare the pore-shell structure catalyst with ordered mesopores. Different from the common molecular sieve synthesis technology, the invention adopts a step-by-step controllable deposition strategy of firstly depositing an aluminum oxide layer and then depositing a silicon oxide layer to obtain Al with a hole-shell structure 2 O 3 The @ MCM-41 vector. The ordered mesoporous carrier Al with high specific surface can be prepared by adjusting the content of alumina 2 O 3 @ MCM-41, the carrier being capable of realizing gamma-Al 2 O 3 The mesoporous structure can also be solidified through a silicon framework of MCM-41 to construct a carrier with a novel hole-shell structure which has L acid and large specific surface. Wherein, the silicon oxide is used for forming a stable mesoporous pore canal structure, and the hexa-coordinated aluminum oxide is embedded in the silicon oxide pore canal as a shell layer. In the traditional molecular sieve synthesis method, an aluminum source and a silicon source are deposited together, and the obtained aluminum atoms are all embedded in a silicon framework and exist in a four-coordinate framework aluminum structure. The four-coordinate framework aluminum is in proportion to six-coordinate gamma-Al 2 O 3 Has stronger acidity, but has lower selectivity and more byproducts in the reaction of synthesizing N, N-dimethylaniline by a gas phase method.
During the preparation process, sodium metaaluminate is added and stirred in a cetyl trimethyl ammonium bromide solution for 0.5 hour, and during the period, the sodium metaaluminate can be dissolved to generate metaaluminate ions to be combined with ammonium ions on the surface of the cetyl trimethyl ammonium bromide, and then aluminum hydroxide precipitate can be generated to wrap the CTAB micelle after the pH value is adjusted to be 7-9. Then stirring for a period of timeAnd finally, depositing a silicon dioxide layer on the outer layer of the aluminum hydroxide by adopting a mode of adding water glass and hydrochloric acid in a concurrent flow manner. If the water glass and the hydrochloric acid are not added in a parallel flow mode, only the water glass is added, and the generated aluminum hydroxide precipitate is dissolved due to the strong alkalinity of the water glass, so that the dissolved metaaluminate ions enter a silicon framework to form a four-coordinate aluminum structure. Therefore, the invention adopts a parallel flow mode to add the water glass and the hydrochloric acid, and controls the pH value of the solution within the range of 7-9 all the time, thereby ensuring that the deposited aluminum hydroxide can not be redissolved, and obtaining the Al with a six-coordination structure required by people 2 O 3 @ MCM-41 pore-shell structure material. In the preparation method, the aluminum source is required to adopt sodium metaaluminate to realize the controllable deposition of the alumina layer, and the required catalyst structure cannot be obtained if aluminum nitrate and the like are used as the aluminum source.
In the synthesis process, the lower sodium metaaluminate dosage is limited, and due to the instability of an alumina framework and the overhigh sodium metaaluminate dosage, an ordered mesoporous structure cannot be obtained; in addition, a very thin aluminum hydroxide precipitate layer can be obtained with a low aluminum content, and in the subsequent baking process, the surface of the thin aluminum hydroxide layer is cracked due to unstable skeleton, so that more effective active sites are exposed.
In addition, the silicon source used in the preparation process is high-modulus water glass, the silicon content of the water glass is within the range of 2.3-2.5 mol/kg, and the molar ratio of Si to Na is 3.2-3.4; if the content of sodium ions in the water glass is too high, competitive adsorption can be generated with ammonium ions on the surface of hexadecyl trimethyl ammonium bromide, so that silicate ions can not be deposited on micelles of the surfactant, and a hexagonal ordered arrangement structure can not be formed. In addition, compared with silicon sources such as tetraethoxysilane and the like, water glass can be rapidly hydrolyzed by adjusting the pH value, which is a key point for shortening the hydrothermal crystallization time.
And step two, aiming at the roasting of the sample A, the sample A is not roasted at high temperature to completely remove the template agent in the pore channel, but the sample A is roasted for 2-4 h in the air at 300-350 ℃, the template agent is decomposed and carbonized by roasting treatment at the temperature, and residual carbon species after carbonization are remained in the pore channel. The part of residual carbon species can play the role of a soft template in the subsequent steps of dipping, drying, roasting and the like, and can prevent the agglomeration and sintering of active components.
The second active component in step three is zirconia, zinc oxide or alumina, and the sample B can be impregnated with zirconium nitrate, zinc nitrate or aluminum nitrate, respectively. In this step, the calcination temperature is 600-650 deg.C, the purpose is to make the alumina shell layer convert crystal to form gamma-Al 2 O 3 Shell layer of the structure.
The calcination of the second active component loaded catalyst is carried out in a tube furnace in flowing air at 400-450 deg.C for 2-3 h, in some embodiments of the invention, it may be switched to flowing nitrogen and then calcined in a nitrogen environment at 600-650 deg.C for at least 3 h. The step can further decompose the residual carbon species in the third step of the preparation process of the carrier, so as to keep less carbon species to play the role of a soft template in the pore channels and prevent the active component from sintering in the roasting process at 600-650 ℃, and the result proves that the part of carbon species does not influence the catalytic activity and improves the selectivity of the N, N-dimethylaniline. Meanwhile, the flowing gas can take away small molecular gas generated in the roasting process, and carbon deposition in the pore canal is prevented.
In some embodiments of the present invention, zirconium oxychloride may be used instead of alumina, and the method may specifically comprise the following steps:
the method comprises the following steps: fully dissolving a template agent cetyl trimethyl ammonium bromide into deionized water in a reaction kettle at the temperature of 60-70 ℃ under the stirring state, continuing stirring for at least 0.5 hour after adding zirconium oxychloride, then slowly adding ammonia water to adjust the pH value to 8-9, and then stirring for 1-3 hours;
adding water glass and hydrochloric acid in a parallel flow manner, controlling the pH value of the solution within the range of 8-9 all the time, continuously stirring for 1-3 h, sealing the reaction kettle, then heating to 130-150 ℃ and keeping for 5-10 h, washing the obtained product to be neutral by using deionized water, and drying the filter cake obtained after suction filtration to obtain a sample A;
wherein the water glass (SiO) 2 Meter), zirconium oxychloride (ZrOCl) 2 ) CTAB, deionized water (H) 2 O) is 1 (SiO) 2 ）:0.01–0.2（ZrOCl 2 ）:0.08–0.15（CTAB）:40–60（H 2 O）；
Step two: placing the initial product sample A obtained by the reaction in a muffle furnace, and roasting for 2-4 h at 300-350 ℃ in the air to obtain a sample B;
step three: dipping nitrate of a second active component on the sample B by adopting an isometric dipping method, drying at 60-80 ℃, roasting at 400-450 ℃ in the air, and then heating to 600-650 ℃ for roasting to obtain the catalyst for synthesizing the N, N-dimethylaniline by adopting a gas phase method; the dosage of the second active component nitrate is 0.3-5% of the mass of the sample B.
The prepared catalyst with zirconium oxychloride as an inner shell also has excellent catalytic activity.
The method for preparing the N, N-dimethylaniline by using the prepared catalyst for synthesizing the N, N-dimethylaniline by the gas phase method comprises the following specific steps:
(1) Filling a catalyst into a constant temperature interval of a continuous flow normal pressure fixed bed reactor, filling a ceramic ring of at least 20 cm as a preheating layer on the upper layer of the catalyst, and heating to 270-300 ℃ under flowing nitrogen for pretreatment for at least 1 h;
(2) The nitrogen is closed, and the mixed solution of methanol and aniline with the molar ratio of 2.5-3 is pumped into the reactor through a pressure pump, wherein the liquid hourly space velocity of the mixed solution is 0.1-1.0 h –1 ；
(3) Collecting products by condensation, and then carrying out qualitative and quantitative analysis on the products after reaction by using gas chromatography;
(4) After the reaction is finished, stopping feeding, continuously purging with nitrogen for 0.5-1 hour, cooling, and closing the nitrogen after the temperature is reduced to below 150 ℃.
The following describes the scheme of the present invention with reference to the accompanying drawings, wherein experimental methods without specific description of operation steps are all performed according to corresponding commercial specifications, and instruments, reagents and consumables used in the examples can be purchased from commercial companies if no special description is provided. The following examples are intended to provide those skilled in the art with a more detailed understanding of the present invention, or to provide further insubstantial modifications and adaptations of the invention in light of the above teachings. However, the scope of the present invention is not limited by these examples.
Example 1
(1) Fully dissolving Cetyl Trimethyl Ammonium Bromide (CTAB) into deionized water in a reaction kettle at the temperature of 60 ℃ under the stirring state, then adding sodium metaaluminate and continuing stirring for 0.5h, then slowly adding hydrochloric acid to adjust the pH value of the solution to 9, and continuing stirring for 1 h; then adding water glass and hydrochloric acid in a parallel flow manner, controlling the pH value of the solution to be 9 all the time, continuously stirring for 3 hours, sealing the reaction kettle, then heating to 130 ℃ and keeping for 5 hours, then washing the obtained product to be neutral by using deionized water, and drying the filter cake obtained after suction filtration to obtain a sample A; wherein the water glass is made of SiO 2 Calculated as Al), sodium metaaluminate (calculated as Al) 2 O 3 Meter), CTAB, deionized water (H) 2 O) is 1 (SiO) 2 ）:0.01（Al 2 O 3 ）:0.08（CTAB）:40（H 2 O）；
(2) Placing the sample A in a muffle furnace, and roasting for 4 hours at 350 ℃ in the air to obtain a sample B;
(3) Soaking zirconium nitrate into the sample B by adopting an isometric soaking method, drying the obtained sample at 60 ℃, then placing the obtained sample into a muffle furnace, roasting at 400 ℃ in air for 3h, then heating to 650 ℃ for roasting for 3h, and then cooling to room temperature to obtain the required catalyst, wherein the using amount of the zirconium nitrate accounts for 0.3% of the total mass of the sample B; the resulting catalyst was numbered CAT-1.
The obtained catalyst CAT-1 is prepared by transmission electron microscopy and nuclear magnetic verification respectively, and as shown in figure 1, the high-resolution transmission electron microscopy picture of the prepared catalyst CAT-1 is shown; FIG. 2 shows the preparation of CAT-1 27 Nuclear magnetic spectrum of Al solid.
Example 2
The procedure of example 2 was the same as in example 1 except that the amount of zirconium nitrate used in step (3) was changed to 5% based on the total mass of sample B, and the catalyst obtained was named CAT-2.
Example 3
Example 3 the procedure was the same as in example 1 except that the molar ratio in step (1) was changed to 1 (SiO) 2 ）:0.2（Al 2 O 3 ）:0.08（CTAB）:40（H 2 O), the obtained catalyst is numbered CAT-3.
Example 4
Example 4 was prepared by the same procedure as in example 1 except that the molar ratio in step (1) was changed to 1 (SiO) 2 ）:0.2（Al 2 O 3 ）:0.15（CTAB）:40（H 2 O), the catalyst obtained is numbered CAT-4.
Example 5
Example 5 was prepared by the same procedure as in example 1 except that the zirconium nitrate in step (3) was changed to zinc nitrate, and the catalyst obtained was named CAT-5.
Example 6
(1) Fully dissolving Cetyl Trimethyl Ammonium Bromide (CTAB) into deionized water in a reaction kettle at the temperature of 60 ℃ under the stirring state, then adding sodium metaaluminate and continuing stirring for 0.5h, then slowly adding hydrochloric acid to adjust the pH value of the solution to 9, and continuing stirring for 1 h; then adding water glass and hydrochloric acid in a parallel flow manner, controlling the pH value of the solution to be 9 all the time, continuously stirring for 3 hours, sealing the reaction kettle, then heating to 130 ℃ and keeping for 5 hours, then washing the obtained product to be neutral by using deionized water, and drying the filter cake obtained after suction filtration to obtain a sample A; wherein the water glass is made of SiO 2 Calculated), sodium metaaluminate (calculated as Al) 2 O 3 Meter), CTAB, deionized water (H) 2 O) is 1 (SiO) 2 ）:0.02（Al 2 O 3 ）:0.08（CTAB）:40（H 2 O）；
(2) Placing the sample A in a muffle furnace, and roasting for 4 hours at 350 ℃ in the air to obtain a sample B;
(3) Soaking zirconium nitrate into the sample B by adopting an isometric soaking method, drying the obtained sample at 60 ℃, then placing the obtained sample into a tubular furnace, roasting for 3h at 450 ℃ in flowing air, switching to flowing nitrogen, then heating to 600 ℃, roasting for 3h, and then cooling to room temperature to obtain the required catalyst, wherein the using amount of the zirconium nitrate accounts for 0.3% of the total mass of the sample B; the catalyst obtained was numbered CAT-6.
Example 7
Example 7 was prepared by the same procedure as in example 6 except that the zirconium nitrate in step (3) was changed to zinc nitrate, and the catalyst obtained was named CAT-7.
Example 8
(1) Fully dissolving Cetyl Trimethyl Ammonium Bromide (CTAB) into deionized water in a reaction kettle at the temperature of 70 ℃ under the stirring state, then adding zirconium oxychloride, continuously stirring for 0.5h, then slowly adding ammonia water to adjust the pH value of the solution to 8, and then continuously stirring for 3 h; then adding water glass and hydrochloric acid in a parallel flow manner, controlling the pH value of the solution to be 8 all the time, continuously stirring for 3 hours, sealing the reaction kettle, then heating to 150 ℃ and keeping for 5 hours, then washing the obtained product to be neutral by using deionized water, and drying the filter cake obtained after suction filtration to obtain a sample A; wherein the water glass is made of SiO 2 Meter), zirconium oxychloride (ZrOCl) 2 ) CTAB, deionized water (H) 2 O) is 1 (SiO) 2 ）:0.02（ZrOCl 2 ）:0.15（CTAB）:40（H 2 O）；
(2) Placing the sample A in a muffle furnace, and roasting for 2 h at 350 ℃ in the air to obtain a sample B;
(3) Dipping aluminum nitrate into the sample B by an isometric dipping method, drying the obtained sample at 60 ℃, then placing the obtained sample into a muffle furnace, roasting at 450 ℃ for 2 h in the air, then heating to 650 ℃ for roasting for 3h, and then cooling to room temperature to obtain the required catalyst; wherein the dosage of the aluminum nitrate accounts for 0.3 percent of the total mass of the sample B; the resulting catalyst was numbered CAT-8.
Comparative example 1
The simultaneous addition of the aluminium source and the silicon source is intended to illustrate the effect of the stepwise addition of aluminium source on the catalyst in comparison with example 1.
(1) Stirring in a reaction kettle at 60 DEG CFully dissolving Cetyl Trimethyl Ammonium Bromide (CTAB) into deionized water, then adding sodium metaaluminate and water glass together, continuously stirring for 0.5h, then slowly adding hydrochloric acid to adjust the pH value of the solution to 9, continuously stirring for 3h, sealing the reaction kettle, then heating to 130 ℃ and keeping for 5h, then washing the obtained product to be neutral by using the deionized water, and drying the filter cake obtained after suction filtration to obtain a sample A; wherein the water glass (with SiO) 2 Calculated as Al), sodium metaaluminate (calculated as Al) 2 O 3 Meter), CTAB, deionized water (H) 2 O) is 1 (SiO) 2 ）:0.01（Al 2 O 3 ）:0.08（CTAB）:40（H 2 O）；
(2) Placing the sample A in a muffle furnace, and roasting for 4 hours at 350 ℃ in the air to obtain a sample B;
(3) Soaking zirconium nitrate into a sample B by adopting an isometric soaking method, drying the obtained sample at 60 ℃, then placing the obtained sample into a muffle furnace, roasting for 3 hours at 400 ℃ in the air, heating to 650 ℃, roasting for 3 hours, and then cooling to room temperature to obtain the required catalyst, wherein the dosage of the zirconium nitrate accounts for 0.3 percent of the total mass of the sample B; the resulting catalyst was numbered CAT-9.
Comparative example 2
The water glass is added firstly, and hydrochloric acid is added to adjust the pH value, so as to compare with the example 1 and illustrate the influence of the concurrent addition of the water glass and the hydrochloric acid on the catalyst in the invention.
(1) Fully dissolving Cetyl Trimethyl Ammonium Bromide (CTAB) into deionized water in a reaction kettle at the temperature of 60 ℃ under the stirring state, then adding sodium metaaluminate and continuing stirring for 0.5h, then slowly adding hydrochloric acid to adjust the pH value of the solution to 9, and continuing stirring for 1 h; then adding water glass, adding hydrochloric acid to adjust the pH value of the solution to 9, continuously stirring for 3 hours, sealing the reaction kettle, heating to 130 ℃ and keeping for 5 hours, washing the obtained product to be neutral by using deionized water, and drying the filter cake obtained after suction filtration to obtain a sample A; wherein the water glass is made of SiO 2 Calculated as Al), sodium metaaluminate (calculated as Al) 2 O 3 Meter), CTAB, deionized water (H) 2 O) is 1 (SiO) 2 ）:0.01（Al 2 O 3 ）:0.08（CTAB）:40（H 2 O）；
(2) Placing the sample A in a muffle furnace, and roasting for 4 hours at 350 ℃ in the air to obtain a sample B;
(3) Soaking zirconium nitrate into the sample B by adopting an isometric soaking method, drying the obtained sample at 60 ℃, then placing the obtained sample into a muffle furnace, roasting at 400 ℃ in air for 3h, then heating to 650 ℃ for roasting for 3h, and then cooling to room temperature to obtain the required catalyst, wherein the using amount of the zirconium nitrate accounts for 0.3% of the total mass of the sample B; the catalyst obtained is numbered CAT-10.
Comparative example 3
Na is selected + The purpose of using water glass with higher content as silicon source is to illustrate Na in water glass compared with example 1 + Influence of the content on the catalyst.
The procedure of comparative example 3 was the same as in example 1 except that water glass having a molar ratio of Si/Na =3.2 in step (1) was replaced with water glass having a molar ratio of Si/Na =2.1 as a silicon source, and the resulting catalyst was numbered CAT-11.
Comparative example 4
The purpose is to illustrate the effect of incomplete removal of cetyltrimethylammonium bromide by carbonation in air in example 1, step (2), on the catalyst in accordance with the present invention, in comparison with example 1.
Comparative example 4 was prepared in the same manner as in example 1 except that the calcination at 350 ℃ in the air in step (2) was changed to the calcination at 600 ℃ to obtain a catalyst, which was named CAT-12.
Comparative example 5
The purpose is to illustrate the effect of calcining step (3) of example 1 in air at 400 ℃ for 3h on the catalyst in the present invention, compared with example 1.
(1) Fully dissolving Cetyl Trimethyl Ammonium Bromide (CTAB) into deionized water in a reaction kettle at the temperature of 60 ℃ under the stirring state, then adding sodium metaaluminate and continuing stirring for 0.5h, then slowly adding hydrochloric acid to adjust the pH value of the solution to 9, and continuing stirring for 1 h; then adding water glass andcontrolling the pH value of the solution to be 9 all the time, continuously stirring for 3h, sealing the reaction kettle, then heating to 130 ℃ and keeping for 5h, washing the obtained product to be neutral by using deionized water, and drying the filter cake obtained after suction filtration to obtain a sample A; wherein the water glass is made of SiO 2 Calculated as Al), sodium metaaluminate (calculated as Al) 2 O 3 Meter), CTAB, deionized water (H) 2 O) is 1 (SiO) 2 ）:0.01（Al 2 O 3 ）:0.08（CTAB）:40（H 2 O）；
(2) Placing the sample A in a muffle furnace, and roasting for 4 hours at 350 ℃ in the air to obtain a sample B;
(3) Soaking zirconium nitrate into the sample B by adopting an isometric soaking method, drying the obtained sample at 60 ℃, then placing the obtained sample into a muffle furnace, heating to 650 ℃ in air, roasting for 3h, and then cooling to room temperature to obtain the required catalyst, wherein the using amount of the zirconium nitrate accounts for 0.3% of the total mass of the sample B; the resulting catalyst was numbered CAT-13.
Comparative example 6
The purpose is to illustrate the effect of introducing zirconium nitrate in step (3) of example 1 on the catalyst in the present invention, compared with example 1.
(1) Fully dissolving Cetyl Trimethyl Ammonium Bromide (CTAB) into deionized water in a reaction kettle at the temperature of 60 ℃ under the stirring state, then adding sodium metaaluminate and continuing stirring for 0.5h, then slowly adding hydrochloric acid to adjust the pH value of the solution to 9, and continuing stirring for 1 h; then adding water glass and hydrochloric acid in a parallel flow manner, controlling the pH value of the solution to be 9 all the time, continuously stirring for 3 hours, sealing the reaction kettle, then heating to 130 ℃ and keeping for 5 hours, then washing the obtained product to be neutral by using deionized water, and drying the filter cake obtained after suction filtration to obtain a sample A; wherein the water glass is made of SiO 2 Calculated), sodium metaaluminate (calculated as Al) 2 O 3 Meter), CTAB, deionized water (H) 2 O) is 1 (SiO) 2 ）:0.01（Al 2 O 3 ）:0.08（CTAB）:40（H 2 O）；
(2) And (3) placing the sample A in a muffle furnace, roasting for 4 h at 350 ℃ in the air, heating to 650 ℃, roasting for 3h, and cooling to room temperature to obtain the required catalyst, wherein the obtained catalyst is CAT-14.
Example 9: catalyst activity test methods and conditions:
(1) Filling 10 mL of catalyst into a constant-temperature interval of a continuous-flow normal-pressure fixed bed reactor, filling a ceramic ring of at least 20 cm as a preheating layer on the upper layer of the catalyst, and heating to 280 ℃ under flowing nitrogen for pretreatment for 1 h;
(2) The nitrogen was turned off, and a mixed solution of methanol and aniline in a molar ratio of 3 –1 ；
(3) Collecting the product by condensation, and carrying out qualitative and quantitative analysis on the product after 5 hours of reaction by using gas chromatography;
(4) After the reaction is finished, stopping feeding, then continuously purging for 1 hour by using nitrogen, then cooling, and closing the nitrogen after the temperature is reduced to below 150 ℃.
CAT-1 to CAT-14 catalysts and technical alumina supports (Al) 2 O 3 ) And an alumina-supported 5% by mass zirconia catalyst (5 wt% ZrO) 2 /Al 2 O 3 ) The results of the activity evaluation of (a) are shown in table 1:
TABLE 1
The embodiments of the present invention have been described in detail, but the description is only for the preferred embodiments of the present invention and should not be construed as limiting the scope of the present invention. All equivalent changes and modifications made within the scope of the present invention shall fall within the scope of the present invention.
Claims (4)
1. The preparation method of the catalyst for synthesizing the N, N-dimethylaniline by the gas phase method is characterized by comprising the following steps of: adding sodium metaaluminate into deionized water solution of cetyl trimethyl ammonium bromide,stirring under the condition of pH value of 7-9; adding water glass and hydrochloric acid in a parallel flow manner, stirring under the condition of pH value of 7-9, and reacting at 130-150 ℃ after sealing to obtain a sample A; with SiO 2 Water glass as Al 2 O 3 The molar ratio of sodium metaaluminate, water glass, sodium metaaluminate, hexadecyl trimethyl ammonium bromide and deionized water is 1;
alternatively, the first and second electrodes may be,
adding zirconium oxychloride into a deionized water solution of cetyl trimethyl ammonium bromide, and stirring under the condition that the pH value is 8-9; adding water glass and hydrochloric acid in parallel, stirring under the condition of pH value of 8-9, sealing, reacting at 130-150 deg.C to obtain sample A, and mixing with SiO 2 The molar ratio of the water glass, the zirconium oxychloride, the hexadecyl trimethyl ammonium bromide and the deionized water is 1;
placing the sample A in the air and roasting at 300-350 ℃ to obtain a sample B, loading a second active component on the sample B, wherein the second active component is zirconium oxide, zinc oxide or aluminum oxide, roasting at 400-450 ℃ after dipping and drying, heating to 600-650 ℃ and roasting, and cooling to room temperature after roasting to obtain the catalyst for synthesizing the N, N-dimethylaniline by a gas phase method;
wherein, the silicon content of the water glass is within the range of 2.3-2.5 mol/kg, the mol ratio of Si to Na is 3.2-3.4:1.
2. the method for preparing the catalyst for synthesizing N, N-dimethylaniline by the gas phase method according to claim 1, which is characterized in that: after the impregnated sample B is roasted at 400-450 ℃ in flowing air, the temperature is raised to 600-650 ℃ to continue roasting under the flowing nitrogen environment.
3. The catalyst obtained by the method for preparing the catalyst for synthesizing N, N-dimethylaniline according to claim 1 or 2.
4. A method for producing N, N-dimethylaniline using the catalyst of claim 3, characterized in that: the method comprises the following specific steps:
filling a catalyst into a constant-temperature interval of a continuous-flow normal-pressure fixed bed reactor, filling a ceramic ring of at least 20 cm as a preheating layer on the upper layer of the catalyst, and heating to 270-300 ℃ under flowing nitrogen for pretreatment for at least 1 h;
closing the nitrogen, pumping the mixed solution of methanol and aniline with the molar ratio of 2.5-3 to 1 into the reactor by a pressure pump, wherein the liquid hourly space velocity of the mixed solution is 0.1-1.0 h –1 。
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| CN105032476A (en) * | 2015-05-22 | 2015-11-11 | 浙江工业大学 | Biological alkane hydroisomerization catalyst and preparation method and application thereof |
| CN110038582A (en) * | 2018-01-16 | 2019-07-23 | 中国石油化工股份有限公司 | A kind of preparation method of hydrocracking catalyst |
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| US20070037693A1 (en) * | 2005-08-15 | 2007-02-15 | China Petroleum & Chemical Corporation | Process for the manufacture of catalysts used for producing para-xylene by toluene shape selective alkylation |
| CN105032476A (en) * | 2015-05-22 | 2015-11-11 | 浙江工业大学 | Biological alkane hydroisomerization catalyst and preparation method and application thereof |
| CN110038582A (en) * | 2018-01-16 | 2019-07-23 | 中国石油化工股份有限公司 | A kind of preparation method of hydrocracking catalyst |
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