CN112675913A

CN112675913A - Palladium-loaded titanium-based metal organic framework catalyst, preparation method and application

Info

Publication number: CN112675913A
Application number: CN201910993004.7A
Authority: CN
Inventors: 尹子萍; 鲍金日; 徐家贤; 陆国平
Original assignee: Nanjing University of Science and Technology
Current assignee: Nanjing University of Science and Technology
Priority date: 2019-10-18
Filing date: 2019-10-18
Publication date: 2021-04-20

Abstract

The invention discloses a palladium-loaded titanium-based metal organic framework catalyst, a preparation method and application. The catalyst is obtained by loading metal palladium on a titanium-based metal organic framework, and the loading is not more than 0.5wt%, and the loading is preferably 0.5 wt%. Under the action of the catalyst, water is used as solvent, normal pressure hydrogen is used as reducing agent, and the reduction of nitro and olefin is realized at room temperature.

Description

Palladium-loaded titanium-based metal organic framework catalyst, preparation method and application

Technical Field

The invention belongs to the field of metal catalysis, and particularly relates to a palladium-loaded titanium-based metal organic framework catalyst, a preparation method and application thereof in reduction of nitro and olefin.

Background

Aromatic amines are indispensable intermediates in the preparation of fine chemicals, biochemicals and pharmaceuticals, and although there are many synthetic routes to produce such species, the most common and most efficient method among them is by hydrogenation of nitroarenes; the catalytic hydrogenation of double bonds is a type of hydrogenation reaction which has the longest application time and the most extensive application, and has wide application value in petrochemical industry, fine chemical industry, agriculture and the like. Catalytic hydrogenation generally relies on the reduction of some precious metals, such as palladium, gold, ruthenium or some alloys, and in addition, transition metals such as iron, cobalt, nickel, etc. may be used to mediate the reduction. Palladium-based catalytic hydrogenation is one of the most widely used methods. The development of highly active and reusable palladium catalysts remains the main research direction in the research of this reaction, however, the palladium contents involved may cause product contamination and the various reaction conditions associated with their use may cause environmental problems.

One of the main methods for reducing nitro group at present is to reduce nitro group under high pressure hydrogen gas by metal catalyst catalysis, such as Pd/C catalyst or Fe catalyst (Angew. chem. int. Ed.2016,55, 8979-; although the method can efficiently reduce the nitro group, high-pressure hydrogen is needed, the requirement on equipment is high in industrial production, and certain potential danger exists; the other method can reduce the nitro group through Fe powder at normal temperature and normal pressure, but needs acidic conditions, organic solvents and the like (chem.Sci.2016,7,3031-3035) and is not beneficial to subsequent treatment and environmental protection.

With the recent emergence of hydrogen storage issues, hydrogenation of double bonds has received renewed attention. In the field of petrochemical industry, olefin in crude petroleum is removed by catalytic hydrogenation of olefin, oil products are improved, porous nickel is mostly used as a catalyst, and reduction is carried out at high temperature and high pressure; in laboratories or the field of fine chemistry, transition metals such as iron, cobalt, nickel and the like are mostly adopted for catalysis, and although pollution caused by noble metals is avoided, the wide use of the catalysts is limited due to the reasons such as complex manufacturing processes, limited reaction conditions and the like (J.Am.chem.Soc.2017,139, 13499-13506; int.J.hydrogen energy.2016,41, 5652-.

Disclosure of Invention

The invention aims to provide a palladium-loaded titanium-based metal organic framework catalyst which is simple in process and has high-efficiency and high-selectivity catalytic reduction activity.

The technical solution for realizing the purpose of the invention is as follows:

a palladium-supported titanium-based metal organic framework (Ti-MOF) catalyst for catalyzing the reduction of nitro, olefins, said catalyst being obtained by supporting metallic palladium (Pd) on a titanium-based metal organic framework (Ti-MOF) in a loading of not more than 0.5wt%, preferably in a loading of 0.5 wt%.

The preparation method of the catalyst comprises the following steps:

step 1, putting a Ti-MOF precursor into water, adding a sodium chloropalladate solution, and uniformly stirring;

and 2, adding a reducing agent sodium borohydride, stirring for a period of time under an ice bath condition, performing centrifugal separation, washing with alcohol, and drying to obtain the Pd/Ti-MOF.

Further, in step 1, the Ti-MOF precursor is prepared by the following steps: and (2) placing tetrabutyl titanate, a terephthalic acid ligand and a methanol regulator in a DMF solvent, uniformly stirring, carrying out hydrothermal reaction, carrying out centrifugal separation, washing with alcohol, and drying to obtain a Ti-MOF precursor.

Further, in step 2, stirring was carried out for 6 hours or more under ice-bath conditions.

The invention also provides application of the Pd/Ti-MOF catalyst prepared by the method in nitro and olefin bond compounds.

Further, the application process is as follows: adding a nitro compound, a Pd/Ti-MOF catalyst and solvent water into a reaction container, reacting for 9 hours at 30 ℃ under the condition of normal pressure and hydrogen, separating the catalyst and a reaction liquid after the reaction is finished, removing the solvent from an organic phase through rotary evaporation, and recrystallizing to obtain a reaction product, wherein the dosage of Pd in the catalyst is 0.12 mol% of the nitro compound.

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

(1) the dosage of the noble metal palladium is low (0.12 mol%), and the environmental pollution is greatly reduced while the catalytic activity is kept.

(2) The reaction condition is mild, water is used as a solvent, and normal pressure hydrogen is used as a reducing agent.

(3) The catalyst has high selectivity and only selectively reduces nitro and olefin.

Drawings

FIG. 1 is a TEM image of a Pd/Ti-MOF catalyst in the present invention.

Detailed description of the invention

Example 1: preparation of the catalyst

Adding 1.8mL of tetrabutyl titanate and 1.65g of terephthalic acid into a mixed solution of 27mL of DMF and 3mL of methanol, stirring uniformly at room temperature to obtain a milky suspension, transferring the suspension into a hydrothermal kettle with a polytetrafluoroethylene lining, reacting for 48 hours at 150 ℃, cooling to room temperature after the reaction is finished, centrifuging, and drying to obtain a Ti-MOF precursor, namely MIL-125 (Ti); dispersing 500mg of MIL-125(Ti) in 20mL of water, adding 0.5mL of sodium chloropalladate solution with the palladium content of 5mg/mL, and stirring at room temperature for 12 hours; dissolving 30mg of sodium borohydride in water, adding the reaction solution at 0 ℃ under the condition of stirring, stirring for 6 hours at 0 ℃, centrifuging, and drying to obtain Pd/Ti-MOF, wherein the microstructure of the Pd/Ti-MOF is shown in figure 1.

Example 2: reduction of nitro, alkene

0.2mmol of nitro/olefin compound, 5mg of Pd/Ti-MOF and 1.5mL of water are added into a reaction vessel and reacted for 9 hours at 30 ℃ under the condition of normal pressure and hydrogen. After the reaction is finished, separating the catalyst from the reaction liquid, removing the solvent from the organic phase through rotary evaporation, and recrystallizing to obtain a reaction product, wherein the test result is as follows:

Claims

1. a palladium-supported titanium-based metal organic framework catalyst, wherein the catalyst is obtained by supporting metallic palladium on a titanium-based metal organic framework at a loading of not more than 0.5wt%, preferably at a loading of 0.5 wt%.

2. The method of preparing the catalyst of claim 1, comprising the steps of:

step 1, putting a titanium-based metal organic framework precursor into water, adding a sodium chloropalladate solution, and uniformly stirring;

3. The method of claim 2, wherein in step 1, the titanium-based metal organic framework precursor is prepared by: and (2) placing tetrabutyl titanate, a terephthalic acid ligand and a methanol regulator in a DMF solvent, uniformly stirring, carrying out hydrothermal reaction, carrying out centrifugal separation, washing with alcohol, and drying to obtain the titanium-based metal organic framework precursor.

4. The method of claim 2, wherein in step 2, stirring is carried out for 6 hours or more under ice bath conditions.

5. Use of the catalyst of claim 1 for catalyzing nitro, alkene-bonded compounds.

6. The use according to claim 5, characterized in that the procedure is as follows: adding nitro, olefin bond compounds, the catalyst and solvent water into a reaction container, reacting for 9h at 30 ℃ under the condition of normal pressure and hydrogen, separating the catalyst and reaction liquid after the reaction is finished, removing the solvent from an organic phase through rotary evaporation, and recrystallizing to obtain a reaction product, wherein the dosage of Pd in the catalyst is 0.12 mol% of the nitro compounds.