CN104857988A - Heteropolyacid-modified Zr-MOF catalyst as well as preparation method and application thereof - Google Patents

Abstract

The invention discloses a heteropolyacid modified Zr-MOF catalyst, which is formed by modifying a Zr-MOF carrier with a heteropolyacid. The invention also discloses the preparation method of the catalyst and its application in the reaction of catalyzing the dehydration of glycerin to prepare acrolein. Compared with the prior art, the present invention has long catalyst life, high glycerin conversion rate and acrolein selectivity; Zr-MOF carrier has good thermal stability and chemical stability, and the skeleton structure remains stable; heteropolyacid and Zr-MOF carrier Interaction force is strong, not easy to lose.

Description

A kind of heteropolyacid modified Zr-MOF catalyst and its preparation method and application

technical field

The invention belongs to the field of chemical synthesis, and in particular relates to a heteropolyacid modified Zr-MOF catalyst, a preparation method and application thereof.

Background technique

With the depletion of global petrochemical resources, biodiesel, as one of the alternative energy sources, is favored. However, as the production of biodiesel continues to rise, the production of its by-product glycerin also continues to increase. At present, since glycerin is mainly used in the pharmaceutical and cosmetic industries, the demand is very limited. Therefore, the research on the preparation of high value-added chemicals from glycerin has received great attention. Acrolein is an important fine chemical intermediate, mainly used in the production of pesticide imidacloprid, pharmaceutical antineoplastic drug dibromopropanal, feed additive methionine, fungicide glutaraldehyde; acrolein can be oxidized to produce acrylic acid, further Synthesis of acrylate; Synthesis of 1,3-propanediol through hydration reduction; Propanol can be produced through reduction. It is an important intermediate in the synthesis of perfumes, pharmaceuticals, allylthiourea, and allyl isothiocyanate. The traditional method for the industrial production of acrolein is the selective oxidation of propylene. In response to this situation, the preparation of acrolein from glycerol can not only effectively utilize excess glycerol, but also get rid of the dependence of acrolein production on the petrochemical product propylene.

There are many research reports on the use of heteropolyacids loaded on carriers as catalysts in the reaction of glycerol dehydration to acrolein. Heteropolyacids commonly used in glycerol dehydration are mainly phosphotungstic acid (HPW) and silicotungstic acid (HSiW) supported on oxide supports. For phosphotungstic acid, the HPW/α-Al ₂ O ₃ catalyst deactivates quickly due to its small specific surface area; when silica is used as a carrier, it is thermally stable due to its weak interaction with phosphotungstic acid Sex is poor. In order to overcome the above problems, Chai et al. prepared HPW/ZrO ₂ . Because phosphotungstic acid can be better dispersed on the ZrO ₂ carrier, the catalyst has good thermal stability, and then by improving the carrier preparation method, prepared nano-ZrO ₂ , so that the catalyst life can be extended to a certain extent, but the selectivity of acrolein is only 71%. Silicotungstic acid has better low-temperature activity than phosphotungstic acid, and has a higher selectivity to acrolein. When loaded on silica with a pore size of 10nm, the selectivity to acrolein can reach 86.2%, but the catalyst is prone to deactivation . Atia et al. prepared HSiW/Al ₂ O ₃ catalyst, which greatly improved the deactivation problem when used in glycerin dehydration reaction. The conversion rate of glycerol was higher than 80% within 200h, and the selectivity of acrolein was 75%. Influenced by the performance of the catalyst, it was found that the performance of the catalyst was not significantly improved, and the thermal stability of the catalyst was poor, which made its regeneration and reuse a great obstacle. In short, due to the problems of short lifetime or poor thermal stability of supported heteropolyacid catalysts, the requirements of industrial applications cannot be met.

Metal-organic frameworks (MOFs) are a promising class of hybrid crystalline materials composed of organic ligands and node metals. It has a relatively high specific surface area, large porosity, and adjustable pores and functionalization of ligands, which makes it attract more and more attention in catalysis, adsorption, and chemical separation. However, there are no reports on the use of MOF materials as carriers to load heteropolyacids for the dehydration of glycerol to acrolein.

Contents of the invention

The technical problem to be solved by the present invention is to provide a heteropolyacid modified Zr-MOF catalyst to solve the problems of poor catalytic effect of existing similar catalysts.

The technical problem to be solved by the present invention is to provide the preparation method of the above-mentioned catalyst.

The final technical problem to be solved by the present invention is to provide the application of the above-mentioned catalyst in the reaction of catalyzing the dehydration of glycerol to prepare acrolein.

In order to solve the problems of the technologies described above, the technical scheme adopted in the present invention is as follows:

A kind of preparation method of heteropolyacid modified Zr-MOF catalyst, it comprises the steps:

(1) Mix zirconium source, bridging ligand, templating agent and chelating agent and dissolve in an organic solvent. After the dissolution is complete, move it to a hydrothermal synthesis kettle, and then place it in a homogeneous reactor at 200-250°C for reaction 24～72h;

(2) Cool and filter the mixed system obtained after the treatment in step (1), take the solid part, wash it, dry it in vacuum for 12-24 hours, and then roast it for 3-5 hours to obtain the Zr-MOF carrier;

(3) Immerse the Zr-MOF carrier obtained in the step (2) in the heteropolyacid aqueous solution, and after equal volume impregnation, dry at 110-120°C for 12-24h to obtain the heteropolyacid-modified Zr-MOF catalyst.

In step (1), the preferred temperature is 220°C, and the preferred reaction time is 36h.

In step (1), the zirconium source is zirconium tetrachloride, zirconium oxychloride or zirconium n-propoxide; Triacid or 2-sulfonic terephthalic acid; the template agent is cetyltrimethylammonium bromide, sodium dodecylbenzenesulfonate or sodium petroleum sulfonate; the chelating agent is Citric acid, tartaric acid or malic acid; the organic solvent is N,N-dimethylformamide or absolute ethanol.

Wherein, the zirconium source is preferably zirconium oxychloride, the bridging ligand is preferably terephthalic acid, the templating agent is preferably cetyltrimethylammonium bromide, and the chelating agent is preferably citric acid.

In step (1), the molar ratio of zirconium source, bridging ligand, templating agent and chelating agent is 1:1～3:0.5～1:0.3～1, preferably 1:2:0.6:0.6 .

In step (2), the vacuum drying temperature is 50-80°C, preferably 70°C, and the calcination temperature is 300-400°C, preferably 350°C.

In step (3), the heteropolyacid is phosphotungstic acid, silicotungstic acid or phosphomolybdic acid; the mass ratio of heteropolyacid to Zr-MOF carrier is 1:9-49, preferably 1:19; the In the heteropolyacid aqueous solution, the mass percentage of the solute heteropolyacid is 0.5% to 2.0%, preferably 1.0%.

The heteropolyacid modified Zr-MOF catalyst prepared by the above preparation method is also within the protection scope of the present invention.

The application of the above-mentioned heteropolyacid-modified Zr-MOF catalyst in catalyzing the dehydration of glycerol to prepare acrolein is also within the protection scope of the present invention.

Wherein, in the reaction of preparing acrolein by dehydration of glycerin, the raw material is preferably 5-15 wt% aqueous glycerin solution, and the catalyst dosage is 1.0 g.

Wherein, the catalytic temperature is 280-320°C, and the raw material space velocity is 0.3-15h ^-1 ; among them, the preferred catalytic temperature is 300°C, and the preferred raw material space velocity is 10h ^-1 .

Beneficial effect:

Compared with the prior art, the present invention has the following advantages:

The catalyst obtained by the invention has long service life, high glycerin conversion rate and acrolein selectivity; the Zr-MOF carrier has good thermal stability and chemical stability, and the skeleton structure remains stable; drain.

Detailed ways

The present invention can be better understood from the following examples. However, those skilled in the art can easily understand that the content described in the embodiments is only for illustrating the present invention, and should not and will not limit the present invention described in the claims.

Example 1:

Synthesis of Zr-MOF support: 0.01mol zirconium tetrachloride, 0.01mol terephthalic acid, 0.005mol cetyltrimethylammonium bromide, 0.003mol citric acid were added to 50mL of N,N-dimethyl In formamide (DMF), stir; after stirring until the solids are completely dissolved, transfer the mixed solution to a polytetrafluoroethylene-lined hydrothermal synthesis kettle, and place it in a homogeneous reactor at a temperature of 220°C for 24h. Then cool to room temperature; filter the mixture in the reaction kettle, and wash the filtered solid with N,N-dimethylformamide (DMF) 5 times, each time using 10mL, and then place the solid in a vacuum at a temperature of 60°C Dried in a drying oven for 12 hours; the vacuum-dried solid was placed in a muffle furnace at a temperature of 300° C. and calcined for 3 hours to obtain a Zr-MOF carrier.

Synthesis of heteropolyacid/Zr-MOF: First, dissolve 0.1g of phosphotungstic acid in 15mL of deionized water, stir to make a solution, impregnate 4.9g of the Zr-MOF carrier prepared above in aqueous solution of phosphotungstic acid, put it in 110 ℃ oven drying for 12 hours to prepare phosphotungstic acid/Zr-MOF catalyst.

Catalyst performance evaluation uses a fixed-bed reactor, using 5wt% glycerol aqueous solution as raw material, catalyst dosage 1.0g, reaction temperature 290°C, raw material space velocity 0.3h ^-1 , the conversion rate of glycerol is 85.5%, and the selectivity of acrolein is 96.3 %.

Example 2:

Synthesis of Zr-MOF support: 0.01mol zirconium oxychloride, 0.02mol terephthalic acid, 0.006mol cetyltrimethylammonium bromide, 0.008mol citric acid were added to 50mL of N,N-dimethyl In formamide (DMF), stir; after stirring until the solids are completely dissolved, transfer the mixed solution to a polytetrafluoroethylene-lined hydrothermal synthesis kettle, and place it in a homogeneous reactor at a temperature of 220°C for 24h. Then cool to room temperature; filter the mixed solution in the reaction kettle, and wash the filtered solid with N,N-dimethylformamide (DMF) 5 times, each time using 10mL, and then place the solid in a vacuum at a temperature of 70°C Dried in a drying oven for 12 hours; the vacuum-dried solid was placed in a muffle furnace at a temperature of 350° C. and calcined for 3 hours to prepare the Zr-MOF carrier.

Synthesis of heteropolyacid/Zr-MOF: Dissolve 0.1g of phosphotungstic acid in 8mL of deionized water, stir to make a solution, impregnate 1.15g of the Zr-MOF carrier prepared above in aqueous solution of phosphotungstic acid, put it in 110 ℃ oven drying for 12 hours to prepare phosphotungstic acid/Zr-MOF catalyst.

Catalyst performance evaluation uses a fixed-bed reactor, using 10wt% glycerol aqueous solution as raw material, catalyst dosage 1.0g, reaction temperature 280°C, raw material space velocity 10h ^-1 , the conversion rate of glycerol is 96.4%, and the selectivity of acrolein is 98.9% .

Example 3:

Synthesis of Zr-MOF carrier: Add 0.01mol zirconium tetrachloride, 0.03mol trimesic acid, 0.001mol sodium dodecylbenzenesulfonate, and 0.007mol tartaric acid to 50mL of absolute ethanol, stir; stir until solid After all dissolved, the mixed solution was transferred to a polytetrafluoroethylene-lined hydrothermal synthesis kettle, and placed in a homogeneous reactor at a temperature of 250°C for 36 hours, and then cooled to room temperature; the mixed solution in the reactor was Filter and wash the filtered solid with absolute ethanol 5 times, using 10 mL each time, then place the solid in a vacuum oven at 70°C for 12 hours; place the vacuum-dried solid in a muffle furnace at 400°C for roasting After 3h, the Zr-MOF carrier was prepared.

Synthesis of heteropolyacid/Zr-MOF: Dissolve 0.1g of silicotungstic acid in 6mL of deionized water and stir to form a solution. Immerse 0.9g of the Zr-MOF carrier prepared above in the aqueous solution of silicotungstic acid and put it in 110 ℃ oven drying for 12 hours to prepare silicotungstic acid/Zr-MOF catalyst.

Catalyst performance evaluation uses a fixed bed reactor, using 10wt% glycerol aqueous solution as raw material, catalyst dosage 1.0g, reaction temperature 300°C, raw material space velocity 8.5h ^-1 , the conversion rate of glycerol is 92.1%, and the selectivity of acrolein is 97.9% %.

Example 4:

Synthesis of Zr-MOF carrier: Add 0.01mol zirconium n-propoxide, 0.02mol 2-sulfonic acid terephthalic acid, 0.008mol cetyltrimethylammonium bromide, 0.008mol citric acid to 50mL of N, Stir in N-dimethylformamide (DMF); stir until the solids are completely dissolved, transfer the mixed solution to a polytetrafluoroethylene-lined hydrothermal synthesis kettle, and place it in a homogeneous reaction at a temperature of 220°C Keep it in the container for 24h, then cool to room temperature; filter the mixed solution in the reaction kettle, and wash the filtered solid with N,N-dimethylformamide (DMF) 5 times, each time using 10mL, and then place the solid in Drying in a vacuum oven at a temperature of 60° C. for 12 hours; placing the vacuum-dried solid in a muffle furnace at a temperature of 350° C. for 3 hours and roasting to obtain a Zr-MOF carrier.

Synthesis of heteropolyacid/Zr-MOF: Dissolve 0.1g of phosphotungstic acid in 10mL of deionized water, stir to make a solution, impregnate 1.9g of the Zr-MOF carrier prepared above in aqueous solution of phosphotungstic acid, put it in 110 ℃ oven drying for 12 hours to prepare phosphotungstic acid/Zr-MOF catalyst.

Catalyst performance evaluation uses a fixed-bed reactor, using 10wt% glycerin aqueous solution as raw material, catalyst dosage 1.0g, reaction temperature 320°C, raw material space velocity 15h ^-1 , the conversion rate of glycerol is 88.7%, and the selectivity of acrolein is 98.2% .

Example 5:

Synthesis of Zr-MOF support: 0.01mol zirconium oxychloride, 0.02mol 2-aminoterephthalic acid, 0.007mol sodium petroleum sulfonate, 0.005mol malic acid were added to 50mL of N,N-dimethylformamide (DMF ), stirred; after stirring until all the solids were dissolved, the mixed solution was transferred to a polytetrafluoroethylene-lined hydrothermal synthesis kettle, and placed in a homogeneous reactor at a temperature of 220°C for 30h, and then cooled to room temperature ; Filter the mixed solution in the reaction kettle, and wash the filtered solid with N,N-dimethylformamide (DMF) 5 times, each time using 10mL, and then dry the solid in a vacuum oven at 50°C for 12h ; The vacuum-dried solid was placed in a muffle furnace at a temperature of 350° C. and calcined for 3 hours to obtain a Zr-MOF carrier.

Synthesis of heteropoly acid/Zr-MOF: Dissolve 0.1g of phosphotungstic acid in 12mL of deionized water, stir to form a solution, impregnate 2.9g of the Zr-MOF carrier prepared above in aqueous solution of phosphotungstic acid, put it in 110 ℃ oven drying for 12 hours to prepare phosphotungstic acid/Zr-MOF catalyst.

Catalyst performance evaluation uses a fixed-bed reactor, using 10wt% glycerin aqueous solution as raw material, catalyst dosage 1.0g, reaction temperature 220°C, raw material space velocity 5.3h ^-1 , the conversion rate of glycerin is 88.1%, and the selectivity of acrolein is 97.5% %.

Embodiment 6:

Synthesis of Zr-MOF support: 0.01mol zirconium tetrachloride, 0.02mol trimesic acid, 0.007mol cetyltrimethylammonium bromide, 0.007mol malic acid were added to 50mL of N,N-dimethyl In formamide (DMF), stir; after stirring until the solids are completely dissolved, transfer the mixed solution to a polytetrafluoroethylene-lined hydrothermal synthesis kettle, and place it in a homogeneous reactor at a temperature of 230°C for 24h. Then cool to room temperature; filter the mixed liquid in the reaction kettle, and wash the filtered solid with N,N-dimethylformamide (DMF) 5 times, each time using 10mL, and then place the solid in a vacuum at a temperature of 80°C Drying in a drying oven for 12 hours; the vacuum-dried solid was placed in a muffle furnace at a temperature of 400° C. for 3 hours and then calcined to obtain a Zr-MOF carrier.

Synthesis of heteropolyacid/Zr-MOF: Dissolve 0.1g of phosphomolybdic acid in 6mL of deionized water and stir to form a solution, then impregnate 0.9g of the Zr-MOF support prepared above into the aqueous solution of phosphomolybdic acid, put it in 110 ℃ oven drying for 12 hours to prepare phosphomolybdic acid/Zr-MOF catalyst.

Catalyst performance evaluation uses a fixed-bed reactor, using 8wt% glycerin aqueous solution as raw material, catalyst dosage 1.0g, reaction temperature 300°C, raw material space velocity 8h ^-1 , the conversion rate of glycerol is 93.7%, and the selectivity of acrolein is 96.2% .

Claims (9)

1. a preparation method for heteropoly acid modification Zr-MOF catalyst, it is characterized in that, it comprises the steps:

(1) by being dissolved in organic solvent after zirconium source, bridging ligand, template and chelating agent mixing, dissolving completely and moving in Hydrothermal Synthesis still, then react 24 ~ 72 at being placed in homogeneous reactor 200 ~ 250 DEG C;

(2) the mixed system cooled and filtered obtained after step (1) being processed, gets solid portion washing final vacuum drying 12 ~ 24h, then roasting 3 ~ 5h, obtains Zr-MOF carrier;

(3) be dipped in the heteropoly acid aqueous solution by the Zr-MOF carrier of step (2) gained, after incipient impregnation, at 110 ~ 120 DEG C, dry 12 ~ 24h, obtains heteropoly acid modification Zr-MOF catalyst.

2. preparation method according to claim 1, is characterized in that, in step (1), described zirconium source is zirconium chloride, zirconium oxychloride or zirconium-n-propylate; Described bridging ligand is terephthalic acid (TPA), 2-amino terephthalic acid (TPA), trimesic acid or 2-sulfonic group terephthalic acid (TPA); Described template is softex kw, neopelex or petroleum sodium sulfonate; Described chelating agent is citric acid, tartaric acid or malic acid; Described organic solvent is DMF or absolute ethyl alcohol.

3. preparation method according to claim 1, is characterized in that, in step (1), the mol ratio of zirconium source, bridging ligand, template and chelating agent is 1:1 ~ 3:0.5 ~ 10.3 ~ 1.

4. preparation method according to claim 1, is characterized in that, in step (2), vacuum drying temperature is 50 ~ 80 DEG C, and sintering temperature is 300 ~ 400 DEG C.

5. preparation method according to claim 1, is characterized in that, in step (3), described heteropoly acid is phosphotungstic acid, silico-tungstic acid or phosphomolybdic acid; The mass ratio of heteropoly acid and Zr-MOF carrier is 1:9 ~ 49; In the described heteropoly acid aqueous solution, the mass percent of solute heteropoly acid is 0.5% ~ 2.0%.

6. the heteropoly acid modification Zr-MOF catalyst that in Claims 1 to 5, any one preparation method prepares.

7. the application in acrolein reaction prepared by heteropoly acid modification Zr-MOF catalyst according to claim 7 at dehydrating glycerin with catalyst.

8. application according to claim 8, is characterized in that, using the glycerine water solution of 5-15wt% as raw material, catalyst amount is 1.0g.

9. application according to claim 9, is characterized in that, catalytic temperature is 280 ~ 320 DEG C.