RU2698912C1 - Catalyst for liquid-phase conversion of bio-renewable raw material and method of its production - Google Patents

Abstract

FIELD: manufacturing technology.

SUBSTANCE: invention relates to production of novel catalytically active materials, particularly, materials containing catalytically active centers of various nature. Invention relates to a catalyst for liquid-phase conversion of bio-renewable raw material containing porous unsubstituted terephthalate of zirconium with structure UiO-66 as a carrier and silver-palladium nanoparticles with size less than 3 nm as an active component. Invention also relates to a method of producing a catalyst.

EFFECT: immobilization of bimetallic nanoparticles with size less than 3 nm in porous space of zirconium terephthalate with UiO-66 structure, prevention of formation of slightly soluble silver chloride at the stage of preparation by using metal nitrates as precursors; reduction of material and energy costs and as a result, material cost reduction.

2 cl, 2 tbl, 3 ex

Description

The invention relates to the field of creating new catalytically active materials, in particular materials containing catalytically active centers of various nature - redox centers (metal nanoparticles) and acid-base centers (oxide clusters), which differ in regular size and controlled composition.

A known method of obtaining a material of the composition Ag, Pd / α-Al ₂ O ₃ [1]. This material is obtained by introducing a predetermined amount of α-Al ₂ O ₃ support into a solution of palladium chloride acidified with hydrochloric acid. The resulting material with a mass fraction of palladium equal to 0.017% of the mass was then introduced into a solution of silver nitrate and stirred for several minutes. The resulting material was separated by decantation, followed by drying and calcination at a temperature of 370 ° C. The mass fraction of silver in the material was 0.055% of the mass. This material can be used as a catalyst for selective hydrogenation. The disadvantages of this material are: low content of the active component, lack of control at the stage of formation of bimetallic nanoparticles on the surface of aluminum oxide, which provides a high probability of formation of active particles with sizes greater than 10 nm, the use of the method of sequential introduction of salts of precursors on the surface of the carrier, which leads to the formation of a large number of individual metal nanoparticles, along with bimetallic Ag / Pd particles, a small specific surface area of the carrier and weak the interaction of the active component with the carrier makes it impossible to significantly increase the mass fraction of the active component.

A known method of obtaining a material of the composition Ag, Pd / α-Al ₂ O ₃ [2]. This material is obtained by reacting a “base catalyst”, which is a freshly prepared silver-palladium catalyst deposited on an oxide support (aluminum, titanium, zirconium oxides or mixtures thereof) or a regenerated freshly prepared silver-palladium catalyst deposited on an inorganic carrier with a liquid reducing composition , which is a solution containing one of the following components: sodium and potassium borohydrides, hydrazine, aldehydes (formaldehyde), carboxylic acids (a sorbic and formic), dextrose, aluminum, zinc powders and mixtures thereof. The resulting material was separated by decantation and dried. Optionally, calcination is carried out at temperatures of 300-700 ° C. The material obtained by this method can be used as a catalyst for the selective hydrogenation of hydrocarbon feedstocks. The disadvantages of this method of obtaining the material are: the use of an already prepared selective hydrogenation catalyst containing all active components in its composition, low content of the active component, lack of control at the stage of formation of bimetallic nanoparticles on the surface of aluminum oxide, which ensures a high probability of formation of active particles with sizes greater than 10 nm, using the method of sequential introduction of salts of precursors on the surface of the carrier, which leads to the formation of large The number of individual metal nanoparticles, along with bimetallic Ag / Pd particles, the small specific surface area of the carrier and the weak interaction of the active component with the carrier make it impossible to significantly increase the mass fraction of the active component.

A known method of obtaining a material of the composition Pd (Ag, Au, Pt) / [M (LIG) ₂ A (SOL) ₂ ] -x (SOL), where M is Zn ₃ or Zn ₄ O, A = 0 at M = Zn ₄ O, LIG is a ligand containing at least one arylamine unit, SOL is one of the solvents (methanol, ethanol, water or pyridine), x is an integer from 0 to 4 [3]. This material is obtained by introducing a carrier of the composition [M (LIG) ₂ A (SOL) ₂ ] -x (SOL) in an acetonitrile solution of metal nitrate (Pd, Ag, Au, Pt), then metal ions are reduced, followed by diffusion of the neutral particle onto the outer surface of the carrier with the formation of a metal nanoparticle with a size of 3-5 nm. This material can be used in the storage and separation of gas mixtures. The disadvantages of this material include the low thermal stability of the carrier, the use of ligands included in the carrier for the reduction of metal ions, which leads to a decrease in the stability of the carrier structure, the lack of control over the growth of metal nanoparticles on the outer surface of the carrier, which leads to a wide distribution of particle sizes and does not provide high selectivity during the catalytic process.

A known method of obtaining a material of the composition Ag, Pd / C, where carbon is presented in the form of graphene, and silver and palladium is a bimetallic nanosized alloy deposited on the surface of graphene [4]. The material was prepared by irradiating a coherent beam of waves of a given frequency with a mixture of graphene in an oxidized form with metallic silver and palladium, followed by separation of the finished material. The disadvantages of this method are: the use of an energetically unfavorable method of preparing the material, the impossibility of producing small bimetallic particles (less than 5 nm), the uneven distribution of metal or alloy particles on the surface of graphene, and the use of a chemically inactive carrier (graphene).

A known method of obtaining a material of the composition Au-Pd0.03@UiO-66-NH ₂ , where UiO-66-NH ₂ is a porous zirconium aminoterephthalate [5]. This material was obtained by the following method: 0.2 g of a powdered carrier UiO-66-NH _{2 was} dispersed in 20 ml of a water-ethanol mixture by ultrasonic treatment for 30 minutes. To the resulting mixture was added dropwise 15 ml of a solution of tertachlorooaurate and tertachloropalladate hydrogen with a given ratio of metal precursors. The resulting mixture was stirred for 4 hours in an ice bath. Next, 5 ml of a freshly prepared sodium borohydride solution was added to the obtained suspension. The resulting mixture was stirred for 30 minutes in an ice bath. The resulting material was separated by centrifugation, washed with water 3 times and dried at a temperature of 80 ° C. This material can be used as a catalyst for the reductive amination of nitro compounds. The disadvantages of this method are: the use of expensive reagents (aminoterephthalic acid, tetrachloroaurate and hydrogen tetrachloropalladate), the irrational use of expensive reagents (using the method of impregnation with an excess of impregnating solution implies the loss of metal precursors remaining in the solution after impregnation, or their regeneration) and the lack of size control and the distribution of metal nanoparticles on the surface of the carrier.

The closest (prototype) in composition and structure to the claimed material is a catalyst for the dehydrogenation of formic acid at room temperature of the composition Ag _x Pd _y @ UiO-66-NH ₂ , where x and y represent the mass fraction of the corresponding metal, UiO-66-NH ₂ - porous zirconium aminoterephthalate, wt. %: Ag 3.80-13.1, Pd 3.4-12.59, UiO-66-NH ₂ - the rest, the specific surface area of the material is 406.4 m ² / g [6]. The preparation of the catalyst is carried out in the following way: 0.2332 g of zirconium chloride and 0.1812 g of 2-aminoterephthalic acid were dissolved in 50 ml of N, N-dimethylformamide (DMF), the resulting solution was heated in a steel autoclave with a Teflon insert to 120 ° C and kept in within 48 hours. The crystals formed after cooling were filtered and washed several times with anhydrous ethanol until complete removal of DMF. The obtained yellow crystals of UiO-66-NH _{2 were} dried at a temperature of 80 ° C under vacuum. 100 mg of the obtained powdered UiO-66-NH _{2 was} dispersed in 6.8 ml of a silver nitrate solution of a given concentration with stirring for 1 h at room temperature. To the resulting suspension was poured 28 ml of a solution of hydrogen tetrachloropalladate of a given concentration with stirring for 4 hours at room temperature. The recovery of metal precursors in the resulting suspension was carried out using 2 ml of a 1M sodium borohydride solution with vigorous stirring. The resulting Ag _x Pd _y @ UiO-66-NH ₂ material was separated by centrifugation. This material was used as a catalyst for the dehydrogenation of formic acid and the catalytic hydrolysis of ammonium borane. The disadvantages of this material are: low specific surface area of the material obtained by blocking the porous space of the polymer with metal nanoparticles, the formation of large (more than 3 nm) metal nanoparticles, the possibility of the formation of poorly soluble silver chloride on the surface of the carrier in contact with palladium hydrochloric acid, which leads to uneven the distribution of metals in the material, the formation of individual Ag particles on the outer surface of the carrier.

The objective of the present invention is to develop a bifunctional catalyst containing catalytically active centers of various nature (Lewis type acid centers in the form of zirconium-containing clusters, redox centers in the form of bimetallic Ag-Pd nanoparticles with sizes less than 3 nm) and a method for its preparation .

The technical result of the invention is:

- development of a material of the composition Ag, Pd / UiO-66;

- development of a method for producing material Ag, Pd / UiO-66;

- increasing the specific surface area of the catalyst (compared with the prototype);

- immobilization of bimetallic nanoparticles with a size of less than 3 nm in the porous space of zirconium terephthalate with a UiO-66 structure;

- preventing the formation of sparingly soluble silver chloride at the preparation stage by using metal nitrates as precursors;

- reducing material and energy costs and, as a result, reducing the cost of the material (compared with the prototype).

The technical result from the creation of material Ag, Pd / UiO-66, containing bimetallic Ag, Pd particles of small size (<3 nm) and porous zirconium terephthalate obtained from zirconyl nitrate, terephthalic acid by solvothermal synthesis, followed by single or multiple impregnation with a solution containing a mixture of metal precursors and liquid-phase reduction of bimetallic nanoparticles is achieved by using silver and palladium nitrates as metal precursors, zirconyl nitrate as a zirconium precursor, m Toda liquid-phase reduction of precursors of nanoparticles using hydrazine as the reducing agent solution, which reduces the resource and energy in the production process.

The composition of the final material, mass. %:

Silver - 0.1-10

Palladium - 0.1-10

Porous zirconium terephthalate (UiO-66) - the rest is up to 100

The composition of the material of the prototype, wt.%:

Silver - 3.80-13.10

Palladium - 3.4-12.59

Zirconium aminoterephthalate (UiO-66-NH ₂ ) - the rest is up to 100%.

A comparative analysis of the prototype and the present invention shows that the common features are the presence of silver-palladium nanoparticles, the use of an organometallic coordination polymer as a carrier.

A distinctive feature of the patented material is that the carrier was used porous unmodified zirconium terephthalate (the prototype used porous zirconium aminoterephthalate), the method of impregnation by moisture capacity with a solution containing a mixture of metal salts with anion of the same nature was used, the method of liquid-phase reduction of metal was used nanoparticles, the size of the formed bimetal nanoparticles was less than 3 nm, the specific surface area of the patented material after recovery has a large value (at least 20%) compared with the analogue.

A method of obtaining the claimed catalyst is as follows:

A portion of zirconyl nitrate and terephthalic acid is dissolved in 60 ml of DMF, 3-10 ml of modifier is added (formic, acetic, hydrofluoric, hydrochloric, sulfuric and other acids can be used as a modifier). The resulting mixture is heated in a steel autoclave to a temperature of 80-250 ° C, then kept at a given temperature for 12-48 hours, depending on the modifier. The resulting white precipitate of porous zirconium terephthalate (UiO-66) is filtered off and washed in DMF and ethanol. The resulting white precipitate was dried by step heating under vacuum. The impregnating solution is prepared according to the following method: the calculated amount of distilled water is poured into the container, then the calculated amount of silver and palladium nitrates is added with vigorous stirring until a clear solution is formed. The calculated amount of UiO-66 is placed in a container for impregnation (heat-resistant ceramic crucibles, dishes made of heat-resistant glass, and other heat-resistant laboratory glassware with a volume of more than 20 ml can be used as a container for impregnation). With intensive mechanical stirring of the resulting suspension, the calculated amount of the impregnating solution is introduced into the container with UiO-66. After the impregnation is completed, 15 or more ml of a non-polar solvent is added to the container (any liquid n-alkanes can be used as a non-polar solvent) with vigorous stirring. Then, the calculated amount of an aqueous solution of the reducing agent is introduced into the container (hydrazine, sodium or potassium borohydrides, sodium formate, ethanol, methanol, DMF, etc. can be used as reducing agent, and the reducing agent is used with a 3-10-fold excess) and incubated for 30 minutes at room temperature. The resulting material is dried in air with stepwise heating for 3-10 hours, heating is carried out to 50 ° C with an exposure of 30 minutes, then the temperature is raised to 75 ° C with an exposure of 30 minutes, then the temperature is raised to 100 ° C and maintained for 30 min, then increase the temperature to the desired value and incubate for 1.5-8.5 hours.

Examples:

Example 1. P. 1. 3.204 g of zirconyl nitrate and 1.968 g of terephthalic acid were dissolved in 60 ml of DMF, 8 ml of modifier (hydrochloric acid, chemically pure) was added. The resulting mixture was heated in a steel autoclave to a temperature of 120 ° C, then kept at a given temperature for 24 hours. The resulting white precipitate of porous zirconium terephthalate (UiO-66) was filtered and washed in DMF and ethanol. The resulting white precipitate was dried by step heating under vacuum. P. 2. An impregnating solution was prepared according to the following procedure: 2 ml of distilled water was poured into the container, then 0.0115 g of silver nitrate and 0.034 ml of palladium nitrate (3 mol / liter) were added with vigorous stirring until a clear solution was formed. P. 3. 1 g of UiO-66 was placed in a container for impregnation. With vigorous mechanical stirring, 1.45 ml of the impregnation solution were added to the UiO-66 container. After the end of the impregnation, 15 ml of n-heptane were introduced into the container with vigorous stirring. Then, 0.03 ml of a 62% aqueous solution of hydrazine was introduced into the container with constant stirring and kept for 30 minutes at room temperature. P. 4. The resulting material was dried in air with stepwise heating for 5.5 hours, heating was carried out to 50 ° C with an exposure of 30 minutes, then the temperature was raised to 75 ° C with an exposure of 30 minutes, then the temperature was raised to 100 ° C and held for 30 minutes, then raised the temperature to 150 ° C and held for 4 hours.

Example 2. A carrier (UiO-66) was prepared according to the procedure described in paragraph 1. Example No. 1. P. 2. An impregnating solution was prepared according to the following procedure: 2 ml of distilled water was poured into a container, then 0.0733 g of silver nitrate and 0.073 ml of palladium nitrate (3 mol / liter) were added with vigorous stirring until a clear solution was formed. P. 3. 0.7 g of UiO-66 was placed in a container for impregnation. With vigorous mechanical stirring, 0.9 ml of the impregnating solution was added to the UiO-66 container. After the end of the impregnation, 15 ml of n-heptane were introduced into the container with vigorous stirring. Then, 0.03 ml of a 62% aqueous solution of hydrazine was introduced into the container with constant stirring and kept for 30 minutes at room temperature. The material was dried by the method described in paragraph 4. Example No. 1

Example 3. (UiO-66) was prepared according to the procedure described in paragraph 1. Example No. 1. p. 2. An impregnating solution was prepared according to the following procedure: 1 ml of distilled water was poured into the tank, then 0.0673 g of silver nitrate and 0.134 ml of palladium nitrate (3 mol / liter) were added with vigorous stirring until a clear solution was formed. P. 3. 0.7 g of UiO-66 was placed in a container for impregnation. With vigorous mechanical stirring, 0.9 ml of the impregnating solution was added to the UiO-66 container. After the end of the impregnation, 15 ml of n-heptane were introduced into the container with vigorous stirring. Then, 0.03 ml of a 62% aqueous solution of hydrazine was introduced into the container with constant stirring and kept for 30 minutes at room temperature. Drying of the material was carried out by the method described in paragraph 4. Example No. 1. Examples of the preparation of materials are presented in table 1. Characteristics of the finished catalysts and the prototype material are presented in table 2.

Table 1

table 2

Literature

1. US patent No. 4404124, B01J 23/44, B01J 23/48, B01J 23/50, C07C 5/00, C07C 5/08, C07C 7/00, C07C 7/167, publ. 09/13/1983

2. Patent EP No. 0689872, B01J23 / 50, B01J23 / 58, B01J23 / 66, B01J37 / 16, C07B35 / 02, C07B61 / 00, C07C5 / 09, C07C5 / 11, C07C7 / 167, publ. 01/03/1996

3. Patent WO No. 2009093817, C07F3 / 06, publ. 07/30/2009

4. Patent WO No. 2011072213, B01J23 / 00, C01B31 / 02, C02F1 / 04, H01L31 / 042, H01L33 / 00, publ. June 16, 2011

5. CN patent No. 107497488, B01J23 / 52, B01J31 / 22, B01J37 / 16, C07C209 / 26, C07C211 / 45, publ. 12/22/2017

6. Shu-Tao Gao et al. Ag-Pd alloy supported on amine-functionalized UiO-66 as an efficient synergetic catalyst for dehydrogenation of formic acid at room temperature // Catalysis Science & Technology. - 2015. - V. 6. - P. 869–874.

Claims (2)

1. A catalyst for the liquid-phase conversion of bio-renewable raw materials, comprising porous zirconium terephthalate with a UiO-66 structure, characterized in that unsubstituted zirconium terephthalate with a UiO-66 structure is used as a carrier and unsubstituted zirconium terephthalate as a carrier and silver-palladium nanoparticles of less than 3 nm in size as an active ingredient. 2. A method of producing a catalyst according to claim 1, which is Ag-Pd nanoparticles immobilized inside the porous space of porous zirconium terephthalate with a UiO-66 structure, prepared by the method of solvothermal synthesis in a steel autoclave with a Teflon insert, followed by filtration, washing the precipitate with ethanol and N, N-dimethylformamide, followed by drying under vacuum, with further impregnation of the obtained powder of zirconium-containing porous coordination polymer with a UiO-66 structure with an aqueous solution of salts Ag and Pd in one step from one impregnating solution and reduction using an aqueous solution of a reducing agent, characterized in that the unsubstituted porous zirconium terephthalate with a UiO-66 structure is used as a porous polymer of the carrier, the introduction of salt solutions - Ag-Pd precursors of nanoparticles into the porous space The carrier polymer is carried out in a single step from a single impregnation solution.