Pt-w catalysts on defective titania and methods for making the same

Abstract

The application belongs to the technical field of low carbon alcohol selective hydrogenolysis catalysts, and particularly relates to a Pt-W catalyst with a defective state titanium dioxide BTNSs as a carrier and a preparation method thereof. In an ice water bath, under gentle stirring, a titanium source is dropped into H2O, and urea and DL-sodium lactate are sequentially added. The mixture is stirred, poured into a Teflon-lined autoclave, and subjected to hydrothermal treatment, purification, and drying to obtain a defective state titanium dioxide BTNSs carrier with unsaturated Ti 3+ ions; and then, the defective state titanium dioxide BTNSs carrier is used as a carrier, a tungsten-containing precursor solution and a platinum-containing precursor solution are sequentially loaded, and the Pt-W catalyst is prepared through impregnation, drying, and calcination. The catalyst prepared by the application is stable in performance and can be applied to selective hydrogenolysis reactions of glycerol and the like, and provides a train of thought for developing new high-efficiency selective hydrogenolysis catalysts.

Description

Technical Field

[0001] The present invention belongs to the technical field of low-carbon alcohol selective hydrogenolysis catalysts, and particularly relates to a Pt-W catalyst using defective titanium dioxide BTNSs as a carrier and a preparation method thereof. Background Art

[0002] Biodiesel is a typical renewable energy source. It is a green and high-quality alternative to fossil fuels, formed by converting animal and vegetable oils, waste oils, or microbial oils into fatty acid methyl or ethyl esters through esterification with methanol or ethanol. Glycerol is a byproduct of biodiesel production, vegetable oil hydrolysis, and triglyceride saponification (soap) production. Currently, supply far exceeds demand, and converting it into high-value-added chemicals has significant economic benefits. Glycerol contains both primary and secondary hydroxyl groups. Common conversion methods include selective oxidation, esterification, etherification, dehydration, hydrogenolysis, fermentation, reforming, reduction, ammoxidation, carboxylation, and oligomerization. Among the many glycerol derivatives, 1,3-propylene glycol has a wide range of uses and is in short supply.

[0003] A large amount of literature has shown that the hydrogenolysis of CO bonds usually requires a bifunctional catalyst consisting of a transition metal (for hydrogenation) and an acidic promoter or support. However, most of these metal-acid bifunctional catalysts have a promoting effect on the selective formation of 1,2-propylene glycol. To date, glycerol hydrogenolysis to 1,3-propylene glycol catalysts mainly include two typical catalytic systems: Ir-Re based oxidation catalysts and Pt-W based metal catalysts. For the glycerol hydrogenolysis process, Pt based catalysts show good catalytic performance in the glycerol hydrogenolysis reaction. At the same time, by adding tungsten oxide (WO x) are introduced into supported noble metal catalysts. In order to control the dispersion and morphology of oxide-supported metal catalysts, the support surface is modified. This can be achieved through strong metal-support strong interaction (SMSI) and metal-oxide interaction (SMOI). In fact, by constructing defect sites on the support surface, using the defects of the support as "traps" to capture metal precursors, and then enhancing the metal-support strong interaction with the charge transfer effect between the metal and the defect sites, the defect engineering strategy can effectively disperse and stabilize metal particles, determine the morphology of metal clusters, and thus determine the catalytic activity of the metal clusters. For example, Lopez et al. (LOPEZ N. The adhesion and shape of nanosized Au particles in a Au / TiO2 catalyst [J]. Journal of Catalysis, 2004, 225 (1): 86-94.) used density functional theory (DFT) to prove the correlation between the number of oxygen defects on the TiO2 support and the dispersion and morphology of nanoscale Au particles. Chen et al. (CHEN MS, GOODMAN D W. The structure of catalytically active gold ontitania [J]. Science, 2004, 306 (5694): 252-5.) experimentally described the formation of stable two-dimensional (2D) Au clusters on defect-rich TiO2 films.

[0004] Recent studies have found that the defect concentration of the support can also be regulated to target the strong metal-support interaction. is the anchor point of Pt (JHKwak, J.Hu, D.Mei, C.-W.Yi, DHKim, CHFPeden, LFAllard, J.Szanyi, Coordinatively unsaturatedAl 3+ centers as binding sites for active catalyst phases of platinumonγ-Al2O3,Science,2009,325(5948):1670-1673.). Contains 27% The γ-Al2O3 nanosheets can well disperse and stabilize Pt-Sn clusters due to the strong interaction between metal and support, and the electronic interaction between Pt-Sn increases the electron density of Pt particles. Defective TiO2 is widely used in photocatalysis, lithium-ion batteries and supercapacitors. In photocatalysis, surface defects can directly act on the absorption and dissociation of reactants, thereby affecting the conversion of reactants to products. For example, Lan et al. (LANK, WANG R, WEIQ, et al. Stable Ti(3+) Defects in Oriented Mesoporous Titania Frameworks for EfficientPhotocatalysis[J]. Angew Chem Int Ed Engl, 2020, 59(40): 17676-83.) Stable Ti on mesoporous TiO2 microspheres 3+ Defects can improve electron-hole separation and increase the generation rate of H2. 3+ defect-riched TiO2 nanosheets for benzene semi-hydrogenation[J].Journal ofCatalysis,2021,398:148-60.) prepared Ti 3+ Defect concentration of TiO2 nanosheets, found in the benzene hydrogenation reaction Ti 3+ Defects affect the particle size of active metals Ru, Ti 3+ The higher the defect content, the greater the net formation rate of cyclohexene. At present, there is a lack of reports on the regulation of defect sites in the use of Ti-containing carriers in Pt-W systems for glycerol hydrogenolysis reactions. As a widely used TiO2 carrier, controlling appropriate reduction conditions (NaBH4, H2 or hydrazine reduction) can induce the generation of oxygen vacancy defects and coordinated unsaturated metal ions. Metal / metal oxide doping can also regulate defects in oxides. Loading metals with hydrogenation activity can regulate the defects on the oxide surface. The in situ generation method is used to prepare Ti with oxygen vacancy defects and coordinated unsaturated metal ions. 3+ The glycerol hydrogenolysis performance of Pt-W particles can be well controlled, and a simple and efficient method is used to design and prepare Pt-W particles with rich oxygen vacancies and Ti 3+ The TiO2 support material is used to regulate the interaction between Pt-W clusters and the support by defects, thereby improving the performance of glycerol hydrogenolysis of Pt-W based catalysts. Summary of the Invention

[0005] The purpose of the present invention is to provide a Pt-W catalyst with defective titanium dioxide BTNSs as a carrier and a preparation method thereof, wherein defective titanium dioxide BTNSs is used as a carrier, oxygen vacancies or coordination unsaturated Ti are introduced into titanium dioxide by an in situ generation method. 3+ ions to obtain defective titanium dioxide BTNSs, which are then used to load platinum and tungsten. The resulting catalyst has good selective hydrogenolysis activity and good stability.

[0006] To achieve the above objectives, the present invention adopts the following technical solutions:

[0007] A method for preparing a Pt-W catalyst using defective titanium dioxide BTNSs as a support comprises the following steps:

[0008] 1) Under gentle stirring in an ice-water bath, a titanium source is added dropwise to H2O, followed by the addition of urea and sodium DL-lactate. The mixture is stirred and poured into a Teflon-lined autoclave, where it is hydrothermally purified and dried to obtain Ti 3+ Doped defective titanium dioxide BTNSs support;

[0009] 2) The obtained defective titanium dioxide BTNSs is used as a carrier, and a tungsten-containing precursor solution is used to stir, dry, and calcine it, and then a platinum-containing precursor solution is used to stir, dry, and calcine it to prepare the Pt-W catalyst.

[0010] Furthermore, the mass ratio of the titanium source, H2O, urea and DL-sodium lactate used in step 1) is 0.9:32.4:2.7:3.6.

[0011] Furthermore, the titanium source in step 1) is titanium tetrachloride.

[0012] Furthermore, in step 1), the titanium source is added at a rate of 1 d / s. After all the addition is complete, stirring is continued in an ice-water bath for 30 minutes to mix.

[0013] Furthermore, the hydrothermal treatment in step 1) is carried out in a blast drying oven for 1 to 48 hours at a temperature of 180 to 230°C.

[0014] Furthermore, the purification in step 1) is performed by washing with water 3 to 6 times.

[0015] Furthermore, the drying in step 1) is carried out in a forced air drying oven at 50-100° C. for 12-20 hours.

[0016] Furthermore, the platinum precursor in step 2) includes any one of platinum nitrate, chloroplatinic acid, potassium chloroplatinate, tetraamminedichloroplatinum, and platinum acetylacetonate; and the tungsten precursor includes any one of silicotungstic acid, ammonium metatungstate, sodium tungstate, and phosphotungstic acid.

[0017] Furthermore, the stirring time in step 2) is 12 to 20 hours.

[0018] Furthermore, in step 2), the mixture is first dried on a rotary evaporator at 60-90° C. until no obvious liquid is left on the surface, and then dried in a forced air drying oven at 50-100° C. for 12-20 hours.

[0019] Furthermore, the calcination in step 2) is carried out at 500° C. for 3 hours in an air atmosphere.

[0020] Furthermore, the loading amount of platinum in the obtained catalyst is 0-3wt%, and is not 0; the loading amount of tungsten is 0-15wt%, and is not 0.

[0021] The Pt-W catalyst supported on defective titanium dioxide BTNSs can be used for the selective hydrogenolysis of lower alcohols at a reaction temperature of 140-180° C., a pressure of 1-6 MPa, and a reaction time of 0-12 h.

[0022] The remarkable effects of the present invention are:

[0023] The present invention successfully introduces coordination unsaturated Ti into titanium dioxide through in-situ generation and other methods. 3+ ions, and loaded the active components platinum and tungsten on the carrier, so that the platinum and tungsten metal particles are effectively dispersed and stabilized on the defective titanium dioxide BTNSs carrier. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The XPS Ti 2p spectrum of the catalyst obtained in Example 1 is shown in the figure. As can be seen from the figure, the Ti 2p spectrum consists of two types of Ti ions, Ti 2p 2 / 3 The peak with a binding energy of 485.95 eV represents the Ti in TiO2 4+ , the peak at 485.78eV represents the Ti in TiO2 3+ .

[0025] Figure 2 This is the EPR graph of the catalyst obtained in Example 1. It shows a strong response when the g value is 2.003. This signal is usually attributed to the reaction between O2 and O v- Related Ti 3+ Surface O generated by defect interactions - Anion radicals, which confirms the presence of Ti on BTNSs 3+ and oxygen vacancies. Specific implementation methods

[0026] A method for preparing a Pt-W catalyst using defective titanium dioxide BTNSs as a support comprises the following steps:

[0027] 1) Under gentle stirring in an ice-water bath, a titanium source is added dropwise to H2O, followed by the addition of urea and sodium lactate. The mixture is stirred and poured into a Teflon-lined autoclave, where it is hydrothermally purified and dried to obtain Ti 3+ Doped defective titanium dioxide BTNSs support;

[0028] 2) The obtained defective titanium dioxide BTNSs is used as a carrier, and a tungsten-containing precursor solution is used to stir, dry, and calcine it, and then a platinum-containing precursor solution is used to stir, dry, and calcine it to prepare the Pt-W catalyst.

[0029] Wherein, the mass ratio of tetrabutyl titanate, H2O, urea and DL-sodium lactate used in step 1) is 0.9:32.4:2.7:3.6.

[0030] Wherein, the platinum precursor in step 2) includes any one of platinum nitrate, chloroplatinic acid, potassium chloroplatinate, tetraamminedichloroplatinum, and platinum acetylacetonate; and the tungsten precursor includes any one of silicotungstic acid, ammonium metatungstate, sodium tungstate, and phosphotungstic acid.

[0031] The loading amount of platinum in the obtained catalyst is 0-3wt% and is not 0; the loading amount of tungsten is 0-15wt% and is not 0.

[0032] In order to make the contents of the present invention easier to understand, the technical solutions of the present invention are further described below in conjunction with specific implementation methods, but the present invention is not limited thereto.

[0033] Example 1:

[0034] (1) In a 500 ml flask, 4.5 ml of TiCl₄ was added dropwise to 162 ml of H₂O, followed by the addition of 13.5 g of urea and 13.5 ml of sodium lactate. The mixture was stirred in an ice-water bath for 0.5 h, transferred to a Teflon-lined autoclave (200 ml), and stored in a forced air drying oven at 200°C for 12 h. The resulting solid was then thoroughly purified three times with H₂O and subsequently transferred to a forced air drying oven at 80°C for 12 h to obtain the final product, labeled as BTNSs.

[0035] (2) Weigh 0.2076g of ammonium metatungstate hydrate, the precursor of tungsten, and place it in 15mL of deionized water. Stir it at room temperature for 30min. Weigh 1.5g of carrier, add it to the ammonium metatungstate hydrate solution, and stir it at room temperature for 16h. Rotate it in an evaporator at 80℃ until dry. Place it in a blast drying oven at 120℃ and dry it for 12h. The dried sample is placed in a muffle furnace and calcined at 500℃ for 3h to obtain WO x / BTNSs. Weigh 1gWO x / BTNSs were added to 4 mL of an aqueous solution of hydrated chloroplatinate (HPtCl) at ambient temperature for 16 hours. The mixture was then dried in a 120°C air drying oven for 12 hours. The resulting sample was calcined at 500°C for 3 hours to obtain a Pt-W / BTNSs catalyst with a platinum loading of 2 wt% and a tungsten loading of 10 wt%.

[0036] Example 2:

[0037] (1) In a 500 ml flask, 2.8 ml of TiCl₄ was added dropwise to 100 ml of H₂O, followed by the addition of 8.3 g of urea and 11.1 ml of sodium lactate. The mixture was stirred in an ice-water bath for 0.5 h, transferred to a Teflon-lined autoclave (200 ml), and stored in a forced air drying oven at 230°C for 6 h. The resulting solid was then thoroughly purified three times with H₂O and subsequently transferred to a forced air drying oven at 50°C for 12 h to obtain the final product, which was labeled as BTNSs.

[0038] (2) Weigh 0.2076g of ammonium metatungstate hydrate, the precursor of tungsten, and place it in 15mL of deionized water. Stir it at room temperature for 30min. Weigh 1.5g of carrier, add it to the ammonium metatungstate hydrate solution, and stir it at room temperature for 16h. Rotate it in an evaporator at 80℃ until dry. Place it in a blast drying oven at 120℃ and dry it for 12h. The dried sample is placed in a muffle furnace and calcined at 500℃ for 3h to obtain WO x / BTNSs. Weigh 1gWO x / BTNSs were added to 4 mL of an aqueous solution of hydrated chloroplatinate (HPtCl) at ambient temperature for 16 hours. The mixture was then dried in a 120°C air drying oven for 12 hours. The resulting sample was calcined at 500°C for 3 hours to obtain a Pt-W / BTNSs catalyst with a platinum loading of 2 wt% and a tungsten loading of 10 wt%.

[0039] Example 3:

[0040] (1) In a 200 ml flask, 1.6 ml of TiCl₄ was added dropwise to 50 ml of H₂O, followed by the addition of 4.3 g of urea and 5.6 ml of sodium lactate. The mixture was stirred in an ice-water bath for 0.5 h, transferred to a Teflon-lined autoclave (100 ml), and stored in a forced-air drying oven at 180°C for 24 h. The resulting solid was then thoroughly purified three times with H₂O and subsequently transferred to a forced-air drying oven at 90°C for 12 h to obtain the final product, labeled as BTNSs.

[0041] (2) Weigh 0.2076g of ammonium metatungstate hydrate, the precursor of tungsten, and place it in 15mL of deionized water. Stir it at room temperature for 30min. Weigh 1.5g of carrier, add it to the ammonium metatungstate hydrate solution, and stir it at room temperature for 16h. Rotate it in an evaporator at 80℃ until dry. Place it in a blast drying oven at 120℃ and dry it for 12h. The dried sample is placed in a muffle furnace and calcined at 500℃ for 3h to obtain WO x / BTNSs. Weigh 1gWO x / BTNSs were added to 4 mL of an aqueous solution of hydrated chloroplatinate (HPtCl) at ambient temperature for 16 hours. The mixture was then dried in a 120°C air drying oven for 12 hours. The resulting sample was calcined at 500°C for 3 hours to obtain a Pt-W / BTNSs catalyst with a platinum loading of 2 wt% and a tungsten loading of 10 wt%.

[0042] Evaluation of catalyst performance

[0043] 10 mL of glycerol solution (10 wt%) and 0.5 g of catalyst were added to a 100 mL autoclave, and the reactor was replaced with H2 six times to remove the air. 3 MPa of H2 was injected into the reactor as the initial pressure, and the reaction was rapidly heated to 160°C and maintained at this temperature for 12 hours with stirring at 600 rpm. After each reaction, the reactor was immediately cooled to room temperature using an ice-water bath. After removing the solid catalyst, the liquid phase synthesis product was collected. The reaction products were analyzed using a liquid chromatograph.

[0044] Table 1 Catalytic data of hydrogenolysis reaction catalyzed by Pt-W / BTNSs for 12 h

[0045]

[0046] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the patent application of the present invention should fall within the scope of the present invention.

Claims

1. A method for preparing a Pt-W catalyst with defective titanium dioxide BTNSs as a support, characterized in that: The following steps are involved: (1) Under gentle stirring in an ice-water bath, a titanium source is added dropwise to H2O, and urea and sodium DL-lactate are added in sequence; the mixture is stirred and poured into a Teflon-lined autoclave, and subjected to hydrothermal treatment, purification, and drying to obtain Ti 3+ Doped defective titanium dioxide BTNSs support; (2) using the obtained defective titanium dioxide BTNSs as a carrier, stirring, drying, and calcining the tungsten-containing precursor solution, and then stirring, drying, and calcining the tungsten-containing precursor solution to obtain the Pt-W catalyst; The mass ratio of the titanium source, H2O, urea, and DL-sodium lactate used in step (1) is 0.9:32.4:2.7:3.6; the titanium source is titanium tetrachloride; The titanium source was added at a rate of 1 d / s in step (2); the mixture after all additions were completed was stirred in an ice-water bath for 30 min for mixing; The hydrothermal treatment in step (1) is performed by placing the product in a blast drying oven for 1 to 48 hours at a temperature of 180 to 230° C.; the purification is performed by washing the product with water 3 to 6 times; and the drying is performed in a blast drying oven at 50 to 100° C. for 12 to 20 hours. The platinum precursor in step (2) includes any one of platinum nitrate, chloroplatinic acid, potassium chloroplatinate, tetraamminedichloroplatinum, and platinum acetylacetonate; the tungsten precursor includes any one of silicotungstic acid, ammonium metatungstate, sodium tungstate, and phosphotungstic acid.

2. The method for preparing a Pt-W catalyst with defective titanium dioxide BTNSs as a support according to claim 1, characterized in that: The stirring time in step (2) is 12 to 20 hours; the drying is first carried out on a rotary evaporator at 60 to 90° C. until there is no obvious liquid on the surface, and then in a blast drying oven at 50 to 100° C. for 12 to 20 hours.

3. The method for preparing a Pt-W catalyst with defective titanium dioxide BTNSs as a support according to claim 1, characterized in that: The calcination in step (2) is carried out at 500° C. for 3 h in an air atmosphere.

4. The method for preparing a Pt-W catalyst with defective titanium dioxide BTNSs as a support according to claim 1, characterized in that: The loading amount of platinum in the obtained catalyst is 0-3wt% and is not 0; the loading amount of tungsten is 0-15wt% and is not 0.

5. A Pt-W catalyst prepared by the method according to any one of claims 1 to 4 and supported by defective titanium dioxide BTNSs.

6. Use of the Pt-W catalyst supported by defective titanium dioxide BTNSs as claimed in claim 5 in catalytic selective hydrogenolysis reaction.

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