CN108246320B - Catalyst, and preparation method and application thereof - Google Patents
Catalyst, and preparation method and application thereof Download PDFInfo
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- CN108246320B CN108246320B CN201810014932.XA CN201810014932A CN108246320B CN 108246320 B CN108246320 B CN 108246320B CN 201810014932 A CN201810014932 A CN 201810014932A CN 108246320 B CN108246320 B CN 108246320B
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- B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
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- B01J27/00—Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
- B01J27/14—Phosphorus; Compounds thereof
- B01J27/16—Phosphorus; Compounds thereof containing oxygen, i.e. acids, anhydrides and their derivates with N, S, B or halogens without carriers or on carriers based on C, Si, Al or Zr; also salts of Si, Al and Zr
- B01J27/18—Phosphorus; Compounds thereof containing oxygen, i.e. acids, anhydrides and their derivates with N, S, B or halogens without carriers or on carriers based on C, Si, Al or Zr; also salts of Si, Al and Zr with metals other than Al or Zr
- B01J27/1802—Salts or mixtures of anhydrides with compounds of other metals than V, Nb, Ta, Cr, Mo, W, Mn, Tc, Re, e.g. phosphates, thiophosphates
- B01J27/1806—Salts or mixtures of anhydrides with compounds of other metals than V, Nb, Ta, Cr, Mo, W, Mn, Tc, Re, e.g. phosphates, thiophosphates with alkaline or alkaline earth metals
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- C07C45/45—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by condensation
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Abstract
The invention provides a preparation method of a catalyst, which comprises the following steps: calcining strontium phosphate to obtain a strontium pyrophosphate carrier; soaking the strontium pyrophosphate carrier in phosphoric acid for 4h, then carrying out suction filtration, washing and drying to obtain a phosphoric acid modified strontium pyrophosphate carrier; mixing the phosphate-modified strontium pyrophosphate carrier with Cs+Mixing and roasting to obtain the catalyst of the invention. The phosphoric acid impregnated strontium pyrophosphate supported cesium catalyst is simple to prepare, green and environment-friendly, low in cost and high in catalytic activity, improves the catalytic performance of preparing 2, 3-pentanedione by lactic acid condensation reaction, and has high commercial development value.
Description
Technical Field
The invention relates to the technical field of materials, in particular to a catalyst and a preparation method and application thereof.
Background
2, 3-pentanedione is a valuable fine chemical with a very wide range of uses. The classical methods for preparing 2, 3-pentanedione are mainly 2: firstly, the extract is extracted from essential oil such as fenugreek, but the raw material source is limited, the production cost is high and the yield is low. And secondly, in the presence of hydroxylamine hydrochloride and under the protection of nitrogen, excessive sodium nitrite and dilute hydrochloric acid are used for oxidizing methyl propyl ketone to prepare the catalyst. With the continuous shortage of petroleum resources and the stricter environmental policy, development of chemicals produced by replacing fossil raw materials with renewable bio-based raw materials is receiving wide attention. The derivative of biomass, which is typical of lactic acid series, is used as a raw material to produce 2, 3-pentanedione, and is a clean production process route.
Through summarizing and collating the existing lactic acid synthesis literature, the lactic acid synthesis is mainly found to have two methods, namely microbial enzyme catalysis and chemical catalysis. The raw materials for preparing the lactic acid comprise corn starch, cellulose and hemicellulose in leaves, plant straws and the like, and glycerin which is a byproduct of biodiesel. The raw materials for preparing the lactic acid are cheap and have wide sources, and the fermentation method in the lactic acid synthesis method is mature in technology, so that the lactic acid is cheaper. How to improve the value of the lactic acid, the fine and further processing of the lactic acid is a better choice at present, namely the development and the process of the catalyst for preparing the 2, 3-pentanedione by the condensation reaction of the lactic acid.
Although a small amount of literature reports on the preparation of 2, 3-pentanedione by lactic acid condensation reaction, the activity of the catalyst used is not high, and most of the catalysts lack the investigation of catalytic stability. The designed catalyst is more prominent in the alkalinity of the catalyst (decarboxylation reaction matched with the condensation process) and ignores the acidity of the catalyst (dehydration reaction matched with the condensation process). Therefore, the acid-base properties of the designed catalyst do not match the acid-base sites required to catalyze the lactic acid condensation process, which results in poor performance of the catalyst.
Disclosure of Invention
The invention aims to solve the defects of the prior art and provide a strontium pyrophosphate supported cesium catalyst for the characteristics of lactic acid condensation reaction, namely acid-base concerted catalysis, wherein phosphoric acid is used for impregnating the strontium pyrophosphate supported cesium catalyst, the weak acid site on the surface of the strontium pyrophosphate is used for facilitating dehydration reaction, the alkalinity of the introduced cesium species is used for facilitating decarboxylation reaction, and in order to match the acid-base property of the prepared catalyst with the acid-base site required for catalyzing the lactic acid condensation process, phosphoric acid with a certain mass concentration is used for impregnating strontium pyrophosphate to increase the acid site on the surface of the strontium pyrophosphate, so that the constructed strontium pyrophosphate supported cesium catalyst impregnated with phosphoric acid has good catalytic performance in the reaction of preparing 2, 3-pentanedione by lactic acid condensation.
A method of preparing a catalyst comprising the steps of:
step 1: calcining strontium phosphate to obtain a strontium pyrophosphate carrier;
step 2: soaking the strontium pyrophosphate carrier in phosphoric acid for 4h, then carrying out suction filtration, washing and drying to obtain a phosphoric acid modified strontium pyrophosphate carrier;
and step 3: mixing the phosphate-modified strontium pyrophosphate carrier with Cs+Mixing and roasting to obtain the catalyst of the invention.
Further, in the preparation method of the catalyst, the mass concentration of the phosphoric acid in the step 2 is 0.05-2%.
Further, the preparation method of the catalyst, Sr in the strontium pyrophosphate in step 32+And said Cs+The molar mass ratio of (A) to (B) is: 2.5:(0.5-2).
Further, the preparation method of the catalyst as described above, step 3, comprises: mixing the phosphate-modified strontium pyrophosphate carrier with Cs+Performing ultrasonic treatment in distilled water, evaporating to remove water, and calcining.
Further, in the preparation method of the catalyst, the calcination condition in the step 3 is 450-800 ℃ calcination for 3 h.
Further, the preparation method of the catalyst as described above, the preparation of the strontium phosphate comprises: stirring strontium nitrate and diammonium hydrogen phosphate to react for 2h, and then performing suction filtration, washing and drying to obtain the product.
A catalyst prepared by the method as described in any one of the preceding.
The application of the catalyst in catalyzing lactic acid to carry out condensation reaction to prepare 2, 3-pentanedione.
Has the advantages that:
the strontium pyrophosphate-loaded cesium catalyst prepared by the method has the advantages that the surface of the strontium pyrophosphate-loaded cesium catalyst has a proper acidic site and a proper alkaline site, so that the catalytic performance of the strontium pyrophosphate-loaded cesium catalyst is improved in the process of preparing 2, 3-pentanedione by catalyzing the condensation of lactic acid. Such as strontium ion (Sr) when strontium pyrophosphate is not impregnated with phosphoric acid2+) With cesium ions (Cs)+) The catalyst with the mass ratio of 2.5:1 has the conversion rate of lactic acid of more than 80 percent and the selectivity of 2, 3-pentanedione of about 50 percent at 300 ℃. When strontium phosphate is soaked in 0.15 mass percent phosphoric acid for 4 hours, Sr2+And Cs+The catalyst prepared when the mass ratio of the materials is still 2.5:1 has the conversion rate of lactic acid of more than 90 percent and the selectivity of 2, 3-pentanedione of more than 60 percent at 300 ℃. When the strontium phosphate is still soaked for 4 hours by using phosphoric acid with the mass concentration of 0.15 percent, Sr2+And Cs+Catalyst (Cs) with mass ratio of 2.5:1.5+The loading is increased), the conversion rate of the lactic acid is more than 90 percent at 300 ℃, and the selectivity of the 2, 3-pentanedione is about 65 percent. The catalyst is continuously operated for 23h, and the selectivity of the catalyst is almost unchanged. The phosphoric acid impregnated strontium pyrophosphate supported cesium catalyst is simple to prepare, green and environment-friendly, low in cost and high in catalytic activity, improves the catalytic performance of preparing 2, 3-pentanedione by lactic acid condensation reaction, and has high commercial development value.
Drawings
FIG. 1 shows the infrared ray of acid and alkali modified strontium pyrophosphate supported cesium catalysts with different mass concentrations
A spectrogram; FIG. 2 shows acid-and base-modified strontium pyrophosphate supported cesium catalysts at different mass concentrations
A dose XRD pattern;
FIG. 3 is a Scanning Electron Microscope (SEM) image of strontium pyrophosphate modified with phosphate according to the example;
FIG. 4 is a Scanning Electron Microscope (SEM) image of strontium pyrophosphate of comparative example 1;
FIG. 5 is a Scanning Electron Microscope (SEM) image of strontium pyrophosphate soaked in distilled water of comparative example 2;
FIG. 6 is a Scanning Electron Microscope (SEM) photograph of strontium pyrophosphate modified with phosphoric acid at a mass concentration of 0.15% in comparative example 3;
FIG. 7 is a Scanning Electron Microscope (SEM) photograph of strontium pyrophosphate modified with phosphoric acid at a mass concentration of 0.25% in comparative example 4;
FIG. 8 is a Scanning Electron Microscope (SEM) photograph of strontium pyrophosphate modified with phosphoric acid at a mass concentration of 2% in comparative example 5;
FIG. 9 is a Scanning Electron Microscope (SEM) image of strontium pyrophosphate soaked with n-butylamine having a mass concentration of 2% in comparative example 6;
FIG. 10 is a bar graph of the stability experiment of strontium pyrophosphate supported cesium catalyst after 0.15 wt% phosphoric acid impregnation.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention are described below clearly and completely, and it is obvious that the described embodiments are some, not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example one
Dissolving 12.7g of strontium nitrate in 200mL of distilled water, fully stirring for 30min, adding 6.34g of diammonium phosphate into the solution, stirring for reaction for 2h, filtering, washing the precipitate with distilled water for 3 times, and transferring the precipitate into an oven at 120 ℃ for drying for 10 h. Thereafter, the resulting mixture was calcined at 500 ℃ for 3 hours in a muffle furnace to obtain strontium pyrophosphate. 2.00g of strontium pyrophosphate was immersed in 15.00g of phosphoric acid having a mass concentration of 0.05% for 4 hours, followed by suction filtration, washing, and drying in an oven at 120 ℃ for 5 hours. Then, the prepared strontium pyrophosphate modified by phosphoric acid is used as a carrier, and Sr is added2+And Cs+Respectively taking a corresponding amount of carrier and cesium nitrate to dissolve in 20mL of distilled water according to the molar mass ratio of 2.5:1, carrying out ultrasonic treatment for 10min, slowly evaporating to dryness in an oil bath kettle at 80 ℃, and roasting in a muffle furnace at 600 ℃ for 3h to obtain the corresponding catalyst. A quartz tube 400mm long and 4mm in inner diameter was selected, and 0.23g of the above-mentioned catalyst was filled in the quartz tube, the length of the catalyst in the tube was 30mm, and both ends of the catalyst were capped with quartz wool. After the filling of the catalyst is finished and the fixed bed reactor is completely installed, the carrier gas is opened, the fixed bed is heated to 300 ℃ at the speed of 5 ℃/min, and after the temperature is stabilized for 1h, the material is introduced into the reactor. The nitrogen carries the lactic acid aqueous solution to pass through the quartz tube filled with the catalyst, the lactic acid aqueous solution is firstly vaporized on the surface of quartz cotton and then undergoes a gas-solid catalytic reaction on the surface of the catalyst. The process conditions are as follows: the concentration of the lactic acid is 20 wt%, and the feeding speed of the lactic acid aqueous solution is 1.63 g/h; the flow rate of nitrogen was 0.8 mL/min.
Comparative example 1
Dissolving 12.7g of strontium nitrate in 200mL of distilled water, fully stirring for 30min, adding 6.34g of diammonium phosphate into the solution, stirring for reaction for 2h, filtering, washing the precipitate with distilled water for 3 times, and transferring the precipitate into an oven at 120 ℃ for drying for 10 h. Thereafter, the resulting mixture was calcined at 500 ℃ for 3 hours in a muffle furnace to obtain strontium pyrophosphate. 0.13g of the above-mentioned catalyst for future use was packed in a quartz tube, the length of the catalyst in the tube was 30mm, and both ends of the catalyst were capped with quartz wool. And (3) allowing the nitrogen carrying lactic acid aqueous solution to pass through the quartz tube filled with the catalyst, raising the temperature to 300 ℃ at a program of 5 ℃/min, wherein the lactic acid concentration is 20wt, the feeding speed of the lactic acid aqueous solution is 1.63g/h, and the flow rate of the nitrogen is 0.8 mL/min.
Comparative example 2
Dissolving 12.7g of strontium nitrate in 200mL of distilled water, fully stirring for 30min, adding 6.34g of diammonium phosphate into the solution, stirring for reaction for 2h, filtering, washing the precipitate with distilled water for 3 times, and transferring the precipitate into an oven at 120 ℃ for drying for 10 h. Thereafter, the resulting mixture was calcined at 500 ℃ for 3 hours in a muffle furnace to obtain strontium pyrophosphate. 2.00g of strontium pyrophosphate is taken and soaked in 15.00g of distilled water for 4 hours, and then is filtered, washed and dried in an oven at 120 ℃ for 5 hours. Subsequently, the prepared strontium pyrophosphate was used as a carrier. And (3) according to the mass ratio of strontium ions to cesium ions of 2.5:1, dissolving barium pyrophosphate and cesium nitrate with corresponding mass in 20mL of distilled water, performing ultrasonic treatment for 10min, evaporating to dryness in an oil bath kettle at 80 ℃, and roasting in a muffle furnace at 600 ℃ for 3h to obtain the corresponding catalyst. A quartz tube 400mm long and 4mm in inner diameter was selected, and 0.22g of the above-mentioned catalyst was filled in the quartz tube, the length of the catalyst in the tube was 30mm, and both ends of the catalyst were capped with quartz wool. And (3) allowing the nitrogen carrying lactic acid aqueous solution to pass through the quartz tube filled with the catalyst, raising the temperature to 300 ℃ by a program of 5 ℃/min, wherein the lactic acid concentration is 20 wt%, the flow rate of the nitrogen is 0.8mL/min, and the feeding speed of the lactic acid aqueous solution is 1.63 g/h.
Comparative example 3
Dissolving 12.7g of strontium nitrate in 200mL of distilled water, fully stirring for 30min, adding 6.34g of diammonium phosphate into the solution, stirring for reaction for 2h, filtering, washing the precipitate with distilled water for 3 times, and transferring the precipitate into an oven at 120 ℃ for drying for 10 h. Then placing the mixture in a muffle furnace to be roasted for 3 hours at 500 ℃ to obtainTo strontium pyrophosphate. 2.00g of strontium pyrophosphate is soaked in 15.00g of phosphoric acid with the mass concentration of 0.15 percent for 4 hours, filtered, washed and dried in an oven at 120 ℃ for 5 hours. Subsequently, the prepared strontium pyrophosphate was used as a carrier. According to Sr2+And Cs+Respectively taking a corresponding amount of carrier and cesium nitrate to dissolve in 20mL of distilled water according to the molar mass ratio of 2.5:1, performing ultrasonic treatment for 10min, evaporating to dryness in an oil bath kettle at 80 ℃, and roasting in a muffle furnace at 600 ℃ for 3h to obtain the corresponding catalyst. A quartz tube 400mm in length and 4mm in inner diameter was selected, and 0.24g of the above-mentioned catalyst was filled in the quartz tube, the length of the catalyst in the tube was 30mm, and both ends of the catalyst were capped with quartz wool. And (3) allowing the nitrogen carrying lactic acid aqueous solution to pass through the quartz tube filled with the catalyst, raising the temperature to 300 ℃ by a program of 5 ℃/min, wherein the lactic acid concentration is 20 wt%, the feeding speed of the lactic acid aqueous solution is 1.63g/h, and the flow rate of the nitrogen is 0.8 mL/min.
Comparative example 4
Dissolving 12.7g of strontium nitrate in 200mL of distilled water, fully stirring for 30min, adding 6.34g of diammonium phosphate into the solution, stirring for reaction for 2h, filtering, washing the precipitate with distilled water for 3 times, and transferring the precipitate into an oven at 120 ℃ for drying for 10 h. Thereafter, the resulting mixture was calcined at 500 ℃ for 3 hours in a muffle furnace to obtain strontium pyrophosphate. 2.00g of strontium pyrophosphate is soaked in 15.00g of phosphoric acid with the mass concentration of 0.25 percent for 4 hours, filtered, washed and dried in an oven at 120 ℃ for 5 hours. The strontium pyrophosphate thus obtained was used as a carrier. According to Sr2+And Cs+Respectively taking a corresponding amount of carrier and cesium nitrate to dissolve in 20mL of distilled water according to the molar mass ratio of 2.5:1, performing ultrasonic treatment for 10min, evaporating to dryness in an oil bath kettle at 80 ℃, and roasting in a muffle furnace at 600 ℃ for 3h to obtain the corresponding catalyst. A quartz tube 400mm long and 4mm in inner diameter was selected, and 0.28g of the above-mentioned catalyst was filled in the quartz tube, the length of the catalyst in the tube was 30mm, and both ends of the catalyst were capped with quartz wool. And (3) allowing the nitrogen carrying lactic acid aqueous solution to pass through the quartz tube filled with the catalyst, raising the temperature to 300 ℃ by a program of 5 ℃/min, wherein the lactic acid concentration is 20 wt%, the feeding speed of the lactic acid aqueous solution is 1.63g/h, and the flow rate of the nitrogen is 0.8 mL/min.
Comparative example 5
Dissolving 12.7g of strontium nitrate in 200mL of distilled water, fully stirring for 30min, adding 6.34g of diammonium phosphate into the solution, stirring for reaction for 2h, filtering, washing the precipitate with distilled water for 3 times, and transferring the precipitate into an oven at 120 ℃ for drying for 10 h. Thereafter, the resulting mixture was calcined at 500 ℃ for 3 hours in a muffle furnace to obtain strontium pyrophosphate. 2.00g of strontium pyrophosphate is soaked in 15.00g of phosphoric acid with the mass concentration of 2% for 4 hours, filtered, washed and dried in an oven at 120 ℃ for 5 hours. The strontium pyrophosphate thus obtained was used as a carrier. According to Sr2+And Cs+Respectively taking a corresponding amount of carrier and cesium nitrate to dissolve in 20mL of distilled water according to the molar mass ratio of 2.5:1, performing ultrasonic treatment for 10min, evaporating to dryness in an oil bath kettle at 80 ℃, and roasting in a muffle furnace at 600 ℃ for 3h to obtain the corresponding catalyst. A quartz tube 400mm long and 4mm in inner diameter was selected, and 0.37g of the above-mentioned catalyst was filled in the quartz tube, the length of the catalyst in the tube was 30mm, and both ends of the catalyst were capped with quartz wool. And (3) allowing the nitrogen carrying lactic acid aqueous solution to pass through the quartz tube filled with the catalyst, raising the temperature to 300 ℃ by a program of 5 ℃/min, wherein the lactic acid concentration is 20 wt%, the feeding speed of the lactic acid aqueous solution is 1.63g/h, and the flow rate of the nitrogen is 0.8 mL/min. Comparative example 6
Dissolving 12.7g of strontium nitrate in 200mL of distilled water, fully stirring for 30min, adding 6.34g of diammonium phosphate into the solution, stirring for reaction for 2h, filtering, washing the precipitate with distilled water for 3 times, and transferring the precipitate into an oven at 120 ℃ for drying for 10 h. Thereafter, the resulting mixture was calcined at 500 ℃ for 3 hours in a muffle furnace to obtain strontium pyrophosphate. 2.00g of strontium pyrophosphate is soaked in 15.00g of n-butylamine with the mass concentration of 2% for 4 hours, filtered, washed and dried in an oven at 120 ℃ for 5 hours. The strontium pyrophosphate thus obtained was used as a carrier. According to Sr2+And Cs+Respectively taking a corresponding amount of carrier and cesium nitrate to dissolve in 20mL of distilled water according to the molar mass ratio of 2.5:1, performing ultrasonic treatment for 10min, evaporating to dryness in an oil bath kettle at 80 ℃, and roasting in a muffle furnace at 600 ℃ for 3h to obtain the corresponding catalyst. A quartz tube 400mm in length and 4mm in inner diameter was selected, and 0.24g of the above-mentioned catalyst was filled in the quartz tube, the length of the catalyst in the tube was 30mm, and both ends of the catalyst were capped with quartz wool. Passing the aqueous solution of lactic acid carried by nitrogen through the quartz tube filled with the catalyst at 5 ℃min temperature programming is carried out to 300 ℃, the concentration of lactic acid is 20 wt%, the speed of feeding the lactic acid aqueous solution is 1.63g/h, and the flow rate of nitrogen is 0.8 mL/min.
Comparative example 7
Dissolving 12.7g of strontium nitrate in 200mL of distilled water, fully stirring for 30min, adding 6.34g of diammonium phosphate into the solution, stirring for reaction for 2h, filtering, washing the precipitate with distilled water for 3 times, and transferring the precipitate into an oven at 120 ℃ for drying for 10 h. Thereafter, the resulting mixture was calcined at 500 ℃ for 3 hours in a muffle furnace to obtain strontium pyrophosphate. 2.00g of strontium pyrophosphate is soaked in 15.00g of phosphoric acid with the mass concentration of 0.15 percent for 4 hours, filtered, washed and dried in an oven at 120 ℃ for 5 hours. The strontium pyrophosphate thus obtained was used as a carrier. According to Sr2+And Cs+Respectively taking a corresponding amount of carrier and cesium nitrate to dissolve in 20mL of distilled water according to the molar mass ratio of 2.5:0.5, performing ultrasonic treatment for 10min, evaporating to dryness in an oil bath kettle at 80 ℃, and roasting in a muffle furnace at 600 ℃ for 3h to obtain the corresponding catalyst. A quartz tube 400mm long and 4mm in inner diameter was selected, and 0.22g of the above-mentioned catalyst was filled in the quartz tube, the length of the catalyst in the tube was 30mm, and both ends of the catalyst were capped with quartz wool. And (3) allowing the nitrogen carrying lactic acid aqueous solution to pass through the quartz tube filled with the catalyst, raising the temperature to 300 ℃ by a program of 5 ℃/min, wherein the lactic acid concentration is 20 wt%, the feeding speed of the lactic acid aqueous solution is 1.63g/h, and the flow rate of the nitrogen is 0.8 mL/min.
Comparative example 8
Dissolving 12.7g of strontium nitrate in 200mL of distilled water, fully stirring for 30min, adding 6.34g of diammonium phosphate into the solution, stirring for reaction for 2h, filtering, washing the precipitate with distilled water for 3 times, and transferring the precipitate into an oven at 120 ℃ for drying for 10 h. Thereafter, the resulting mixture was calcined at 500 ℃ for 3 hours in a muffle furnace to obtain strontium pyrophosphate. 2.00g of strontium pyrophosphate is soaked in 15.00g of phosphoric acid with the mass concentration of 0.15 percent for 4 hours, filtered, washed and dried in an oven at 120 ℃ for 5 hours. The strontium pyrophosphate thus obtained was used as a carrier. According to Sr2+And Cs+Respectively taking a corresponding amount of carrier and cesium nitrate to dissolve in 20mL of distilled water according to the molar mass ratio of 2.5:1.5, performing ultrasonic treatment for 10min, evaporating to dryness in an oil bath kettle at 80 ℃, and roasting in a muffle furnace at 600 ℃ for 3h to obtain the corresponding catalyst. Choose oneA quartz tube having a root length of 400mm and an inner diameter of 4mm was filled with 0.28g of the above-mentioned catalyst for future use, the length of the catalyst in the tube was 30mm, and both ends of the catalyst were capped with quartz wool. And (3) allowing the nitrogen carrying lactic acid aqueous solution to pass through the quartz tube filled with the catalyst, raising the temperature to 300 ℃ by a program of 5 ℃/min, wherein the lactic acid concentration is 20 wt%, the feeding speed of the lactic acid aqueous solution is 1.63g/h, and the flow rate of the nitrogen is 0.8 mL/min.
Comparative example 9
Dissolving 12.7g of strontium nitrate in 200mL of distilled water, fully stirring for 30min, adding 6.34g of diammonium phosphate into the solution, stirring for reaction for 2h, filtering, washing the precipitate with distilled water for 3 times, and transferring the precipitate into an oven at 120 ℃ for drying for 10 h. Thereafter, the resulting mixture was calcined at 500 ℃ for 3 hours in a muffle furnace to obtain strontium pyrophosphate. 2.00g of strontium pyrophosphate is soaked in 15.00g of phosphoric acid with the mass concentration of 0.15 percent for 4 hours, filtered, washed and dried in an oven at 120 ℃ for 5 hours. The strontium pyrophosphate thus obtained was used as a carrier. According to Sr2+And Cs+Respectively taking a corresponding amount of carrier and cesium nitrate to dissolve in 20mL of distilled water according to the molar mass ratio of 2.5:2, performing ultrasonic treatment for 10min, evaporating to dryness in an oil bath kettle at 80 ℃, and roasting in a muffle furnace at 600 ℃ for 3h to obtain the corresponding catalyst. A quartz tube 400mm in length and 4mm in inner diameter was selected, and 0.30g of the above-mentioned catalyst was filled in the quartz tube, the length of the catalyst in the tube was 30mm, and both ends of the catalyst were capped with quartz wool. And (3) allowing the nitrogen carrying lactic acid aqueous solution to pass through the quartz tube filled with the catalyst, raising the temperature to 300 ℃ by a program of 5 ℃/min, wherein the lactic acid concentration is 20 wt%, the feeding speed of the lactic acid aqueous solution is 1.63g/h, and the flow rate of the nitrogen is 0.8 mL/min.
And comparing the activity of the strontium pyrophosphate-loaded cesium catalysts impregnated with the acid and alkalinity agents with different mass concentrations and the activity of the catalysts with different loads.
Firstly, the performance of the strontium pyrophosphate supported cesium catalyst impregnated with acid and alkalinity agents with different mass concentrations is tested, and the results are shown in table 1. From the conversion of lactic acid and the selectivity of 2, 3-pentanedione, inconsistent results were obtained after impregnation with varying mass concentrations of acid and alkalinity agents, and the catalytic performance in comparative example 3 was superior to that of examples one and twoOther comparative examples, which illustrate the significant effect of different mass concentrations of phosphoric acid and n-butylamine impregnated on catalyst performance. Table 2 shows the different Sr2+/Cs+The ratio affects the results on catalyst performance. From the conversion of lactic acid and the selectivity of 2, 3-pentanedione, different Sr were found2+/Cs+The catalysts of the ratios gave inconsistent results, with the 2, 3-pentanedione selectivity in comparative example 8 being superior to that of the other comparative examples, which illustrates the different Sr of the catalysts2+/Cs+The ratio has obvious influence on the performance of the catalyst.
TABLE 1 influence of acid and alkali with different mass concentrations on the catalyst performance after treatment of strontium pyrophosphate carrier
TABLE 2 different Sr2+/Cs+Comparison of Effect on catalyst Performance
The following example is the application of 0.15 wt% phosphoric acid impregnated strontium pyrophosphate supported cesium catalyst in the preparation of 2, 3-pentanedione by lactic acid condensation.
Example two
0.27g of the strontium pyrophosphate-supported cesium catalyst prepared in the first example, which is impregnated with 0.15 wt% of phosphoric acid and has a particle size of 20-40 meshes, is placed in a quartz tube with an inner diameter of 4mm, the catalyst is fixed by quartz wool, then the quartz tube filled with the catalyst is placed in a heating furnace, nitrogen is opened, 0.8mL/min is introduced, a heating device is opened, the temperature is raised to 280 ℃ in a manner of 5 ℃/min temperature programming, the temperature is constant, 20 wt% of lactic acid water solution is introduced at 1.63g/h, a product is collected in an ice water bath manner, the product is yellow liquid, the product is analyzed, the conversion rate of lactic acid is 78.5%, and the selectivity of 2, 3-pentanedione is 83.3%.
EXAMPLE III
0.29g of the strontium pyrophosphate-supported cesium catalyst prepared in comparative example 3, which was impregnated with 0.15 wt% phosphoric acid having a particle size of 20 to 40 mesh, was placed in a quartz tube having an inner diameter of 4mm, the catalyst was fixed with quartz wool, the quartz tube filled with the catalyst was placed in a heating furnace, nitrogen was turned on and introduced at 0.8mL/min, a heating apparatus was turned on, the temperature was raised to 320 ℃ by a temperature program of 5 ℃/min, a 20 wt% aqueous solution of lactic acid was introduced at 1.63g/h, and the product was collected in an ice-water bath, and was a yellow liquid, and the product was analyzed to have a conversion of lactic acid of 92.4% and a selectivity of 2, 3-pentanedione of 56.1%.
Example four
0.26g of the strontium pyrophosphate-supported cesium catalyst prepared in comparative example 4, which was impregnated with 0.15 wt% phosphoric acid having a particle size of 20 to 40 mesh, was placed in a quartz tube having an inner diameter of 4mm, the catalyst was fixed with quartz wool, the quartz tube filled with the catalyst was placed in a heating furnace, nitrogen was turned on and introduced at 0.8mL/min, a heating apparatus was turned on, the temperature was raised to 300 ℃ by a temperature programming of 5 ℃/min, a constant temperature was maintained, a 10 wt% aqueous solution of lactic acid was introduced at 1.63g/h, and the product was collected in an ice-water bath as a yellow liquid, analyzed, and had a conversion of lactic acid of 91.5% and a selectivity of 2, 3-pentanedione of 58.0%.
EXAMPLE five
0.28g of the strontium pyrophosphate-supported cesium catalyst prepared in comparative example 5, which was impregnated with 0.15 wt% phosphoric acid having a particle size of 20 to 40 mesh, was placed in a quartz tube having an inner diameter of 4mm, the catalyst was fixed with quartz wool, the quartz tube filled with the catalyst was placed in a heating furnace, nitrogen was turned on and introduced at 0.8mL/min, a heating apparatus was turned on, the temperature was raised to 300 ℃ by a temperature programming of 5 ℃/min, a 30 wt% aqueous solution of lactic acid was introduced at 1.63g/h, and the product was collected in an ice-water bath, and was a yellow liquid, and the product was analyzed to have a conversion of lactic acid of 87.0% and a selectivity of 2, 3-pentanedione of 73.7%.
EXAMPLE six
0.298g of the strontium pyrophosphate supported cesium catalyst prepared in the control example 5, which is impregnated with 0.15 Wt% of phosphoric acid having a particle size of 20-40 meshes, is placed in a quartz tube having an inner diameter of 4mm, the catalyst is fixed with quartz wool, then the quartz tube filled with the catalyst is placed in a heating furnace, nitrogen is opened and 0.8mL/min is introduced, a heating device is opened, the temperature is raised to 300 ℃ in a manner of 5 ℃/min temperature programming, the temperature is constant, 20 Wt% of lactic acid water solution is introduced at 1.13g/h, a product is collected in an ice water bath manner, the product is yellow liquid, the product is analyzed, the conversion rate of lactic acid is 91.9%, and the selectivity of 2, 3-pentanedione is 71.3%.
EXAMPLE seven
0.29g of the strontium pyrophosphate-supported cesium catalyst prepared in comparative example 7, which was impregnated with 0.15 Wt% phosphoric acid having a particle size of 20 to 40 mesh, was placed in a quartz tube having an inner diameter of 4mm, the catalyst was fixed with quartz wool, the quartz tube filled with the catalyst was placed in a heating furnace, nitrogen was turned on and introduced at 0.8mL/min, a heating apparatus was turned on, the temperature was raised to 300 ℃ by a temperature programming of 5 ℃/min, a 20 Wt% aqueous solution of lactic acid was introduced at 2.26g/h, and the product was collected in an ice-water bath, and was a yellow liquid, and the product was analyzed to have a conversion of lactic acid of 79.4% and a selectivity of 2, 3-pentanedione of 73.6%.
Example eight
0.27g of the strontium pyrophosphate supported cesium catalyst prepared in comparative example 8, which was impregnated with 0.15 wt% phosphoric acid having a particle size of 20-40 mesh, was placed in a quartz tube having an inner diameter of 4mm, the catalyst was fixed with quartz wool, then the quartz tube filled with the catalyst was placed in a heating furnace, nitrogen was turned on and introduced at 0.8mL/min, a heating apparatus was turned on, the temperature was increased to 300 ℃ in a manner of a programmed temperature rise of 5 ℃/min, a constant temperature was maintained, a 20 wt% aqueous solution of lactic acid was introduced at 1.63g/h, and after the catalyst was continuously operated for 23h, the conversion of lactic acid was reduced to 64.4%, and the selectivity of 2, 3-pentanedione was 69.4%.
FIG. 1 is an infrared spectrum of acid-base modified strontium pyrophosphate supported cesium catalyst with different mass concentrations; FIG. 2 is XRD patterns of acid-base modified strontium pyrophosphate supported cesium catalysts with different mass concentrations; through the discovery of fig. 1 and fig. 2, the structure of the catalyst is not changed fundamentally, and the acid-base modification only slightly modulates the acid-base property of the catalyst; this modification regulates the performance of the catalyst. FIG. 3 is a Scanning Electron Microscope (SEM) image of strontium pyrophosphate modified with phosphate according to the example; FIG. 4 is a Scanning Electron Microscope (SEM) image of strontium pyrophosphate of comparative example 1; FIG. 5 is a Scanning Electron Microscope (SEM) image of strontium pyrophosphate soaked in distilled water of comparative example 2; FIG. 6 is a Scanning Electron Microscope (SEM) photograph of strontium pyrophosphate modified with phosphoric acid at a mass concentration of 0.15% in comparative example 3; FIG. 7 is a Scanning Electron Microscope (SEM) photograph of strontium pyrophosphate modified with phosphoric acid at a mass concentration of 0.25% in comparative example 4; FIG. 8 is a Scanning Electron Microscope (SEM) photograph of strontium pyrophosphate modified with phosphoric acid at a mass concentration of 2% in comparative example 5; FIG. 9 is a Scanning Electron Microscope (SEM) image of strontium pyrophosphate soaked with n-butylamine having a mass concentration of 2% in comparative example 6; also, it is found from fig. 3 to fig. 9 that the acid modification does not cause the change of the morphology, but only acts to modulate the acidity and basicity of the catalyst; FIG. 10 is a bar graph of stability experiments for strontium pyrophosphate supported cesium catalysts after phosphoric acid impregnation. It is found from fig. 10 that the catalyst after acid impregnation has better stability and effectively improved catalytic performance.
In conclusion, the performance of the phosphoric acid impregnated strontium pyrophosphate supported cesium catalyst for preparing 2, 3-pentanedione by the condensation reaction of lactic acid is greatly improved, the catalyst has strong adaptability to the change of reaction environment, and can bear the severe change of reaction conditions, and the conversion of lactic acid is only slightly fluctuated when the flow rate and the feeding rate of carrier gas are changed.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (4)
1. A preparation method of a catalyst is characterized by comprising the following steps:
step 1: calcining strontium phosphate to obtain a strontium pyrophosphate carrier;
step 2: soaking the strontium pyrophosphate carrier in phosphoric acid for 4h, then carrying out suction filtration, washing and drying to obtain a phosphoric acid modified strontium pyrophosphate carrier;
and step 3: mixing the phosphate-modified strontium pyrophosphate carrier with Cs+Mixing and roasting to obtain a catalyst;
in the step 2, the mass concentration of the phosphoric acid is 0.05-2%;
sr in the strontium pyrophosphate in step 32+And said Cs+The molar mass ratio of (A) to (B) is: 2.5 (0.5-2);
the step 3 comprises the following steps: mixing the phosphate-modified strontium pyrophosphate carrier with Cs+Performing ultrasonic treatment in distilled water, evaporating to remove water, and calcining.
2. The method as claimed in claim 1, wherein the calcination in step 3 is carried out at 800 ℃ for 3h and 450 ℃.
3. The method of preparing the catalyst according to claim 1, wherein the preparation of the strontium phosphate comprises: stirring strontium nitrate and diammonium hydrogen phosphate to react for 2h, and then performing suction filtration, washing and drying to obtain the product.
4. A catalyst prepared by the process of any one of claims 1 to 3.
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN101537362A (en) * | 2009-04-22 | 2009-09-23 | 中国科学院上海有机化学研究所 | Active carbon catalyst, preparation method and application thereof in preparing acrylic acid by dehydrating lactic acid |
| CN102775294A (en) * | 2012-08-06 | 2012-11-14 | 西华师范大学 | Method for preparing acrylic acid through lactic acid dehydration by use of phosphate-pyrophosphate composite catalyst of alkaline-earth metal |
| CN105749939A (en) * | 2016-03-09 | 2016-07-13 | 浙江工业大学之江学院 | Phosphoric acid modified montmorillonite loaded tungsten oxide catalyst, preparation method and application |
| CN107051557A (en) * | 2017-06-05 | 2017-08-18 | 西华师范大学 | A kind of barium pyrophosphate load cesium-promoted catalyst and preparation method thereof, application |
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Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN101537362A (en) * | 2009-04-22 | 2009-09-23 | 中国科学院上海有机化学研究所 | Active carbon catalyst, preparation method and application thereof in preparing acrylic acid by dehydrating lactic acid |
| CN102775294A (en) * | 2012-08-06 | 2012-11-14 | 西华师范大学 | Method for preparing acrylic acid through lactic acid dehydration by use of phosphate-pyrophosphate composite catalyst of alkaline-earth metal |
| CN105749939A (en) * | 2016-03-09 | 2016-07-13 | 浙江工业大学之江学院 | Phosphoric acid modified montmorillonite loaded tungsten oxide catalyst, preparation method and application |
| CN107051557A (en) * | 2017-06-05 | 2017-08-18 | 西华师范大学 | A kind of barium pyrophosphate load cesium-promoted catalyst and preparation method thereof, application |
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