We gratefully acknowledge the financial support provided by National Key Research &#38; Development Program of the Ministry of Science and Technology of China (2016YFB0600305), National Natural Science Foundation of China (Nos. 21573031 and 21373038), Program for Excellent Talents in Dalian City (2016RD09) and Technological and Higher Education Institute of Hong Kong (THEi SG1617105 and THEi SG1617127).

Caution: For the proper handling methods, properties and toxicities of the chemicals described in this paper, refer to the relevant material safety data sheets (MSDS). Some of the chemicals used are toxic and carcinogenic and special cares must be taken. Nanomaterials may potentially pose safety hazards and health effects. Inhalation and skin contact should be avoided. Safety precaution must be exercised, such as performing the catalyst synthesis in the fume hood and catalyst performance evaluation with ...

<ol>
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One of the common methods to prepare the nickel-doped bulk niobium oxide nanoparticles is rotary evaporation method.9 By employing various pressure and temperature conditions during the process of rotary evaporation, the precipitation of Ni-Nb-O particles commerce with the slow removal of the solvent. In contrast to the rotary evaporation method, the chemical precipitation method reported in this study has received increasing attention to prepare the nanoparticles as this do not require the remova...

The preparation of nanocomposites has received increasing attention due to their crucial application in various field. To prepare Ni-Nb-O mixed oxide nanoparticles,1,2,3,4,5,6 different methods have been developed such as dry mixing method,7,8 evaporation method,9,10,11,12,13 sol gel method,14 thermal decomposition method,15 and auto-combustion.16 In a typical evaporation method9, aqueous solutions containing the appropriate amount of metal precursors, nickel nitrate hexahydrate and ammonium niobium oxalate were heated at 70 &#176;C. After the removal of solvent and further drying and calcination, the mixed oxide was obtained. These oxide catalysts exhibit excellent catalytic activity and selectivity towards the oxidative dehydrogenation (ODH) of ethane, which is related to the electronic and structural rearrangement induced by the incorporation of niobium cations in the NiO lattice.11 The insertion of Nb drastically decreases the electrophilic oxygen species, which is responsible for the oxidation reactions of ethane12. As a result, extensions of this method have been done on the preparation of different types of mixed Ni-Me-O oxides, where Me = Li, Mg, Al, Ga, Ti and Ta.13 It is found that the variation of metal dopants could alter the unselective and electrophilic oxygen radicals of NiO, thus systematically tune the ODH activity and selectivity towards ethane. However, generally the surface area of these oxides is relatively small (&#60; 100 m2/g), due to the extended phase segregation and formation of large Nb2O5 crystallites, and thus hampered their uses in other catalytic applications.
Dry mixing method, also known as the solid-state grinding method, is another commonly used method to prepare the mixed-oxide catalysts. Since the catalytic materials are obtained in a solvent-free way, this method provides a promising green and sustainable alternative to the preparation of mixed-oxide. The highest surface area obtained by this method is 172 m2/g for Ni80Nb20 at calcination temperature of 250 &#176;C.8 However, this solid-state method is not reliable as reactants are not well mixed on the atomic scale. Therefore, for better control of chemical homogeneity and specific particle size distribution and morphology, other suitable methods to prepare Ni-Nb-O mixed oxide nanoparticles are still being sought.7
Among various strategies in the development of nanoparticles, chemical precipitation serves as one of the promising methods to develop the nanocatalysts, since it allows the complete precipitation of the metal ions. Also, nanoparticles of higher surface areas are commonly prepared by using this method. To improve the catalytic properties of Ni-Nb-O nanoparticles, we herein report the protocol for the synthesis of a series of Ni-Nb-O mixed oxide catalysts with high surface area by chemical precipitation method. We demonstrated that the Nb:Ni molar ratio is a crucial factor in determining the catalytic activity of the oxides towards the hydrodeoxygenation of lignin-derived organic compounds. With high Nb:Ni ratio above 0.087, inactive NiNb2O6 species were formed. Ni0.92Nb0.08O, which had the largest surface area (173 m2/g), exhibits fold-like nanosheets structures and showed the best activity and selectivity towards the hydrodeoxygenation of anisole to cyclohexane.

<table>
	<tbody>
		<tr>
			<td>Niobium(V) oxalate hydrate, 98%</td>
			<td>Alfa</td>
			<td>L04481902</td>
			<td></td>
		</tr>
		<tr>
			<td>Nickel nitrate hexahydrate, 99%</td>
			<td>Aladdin</td>
			<td>N108891</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium hydroxide, 98%</td>
			<td>Aladdin</td>
			<td>S111501</td>
			<td></td>
		</tr>
		<tr>
			<td>Ammonium hydroxide, 23-25%</td>
			<td>Aladdin</td>
			<td>A112077</td>
			<td></td>
		</tr>
		<tr>
			<td>Anisole, 99%</td>
			<td>Sinopharm</td>
			<td>81001728</td>
			<td></td>
		</tr>
		<tr>
			<td>Diphenyl ether, 98%</td>
			<td>Aladdin</td>
			<td>D110644</td>
			<td></td>
		</tr>
		<tr>
			<td>Phenol, 98%</td>
			<td>Sinopharm</td>
			<td>100153008</td>
			<td></td>
		</tr>
		<tr>
			<td>2-Methoxyphenol, 98%</td>
			<td>Sinopharm</td>
			<td>30114526</td>
			<td></td>
		</tr>
		<tr>
			<td>Vanillin, 99.5%</td>
			<td>Sinopharm</td>
			<td>69024316</td>
			<td></td>
		</tr>
		<tr>
			<td>Potassium hydroxide, AR</td>
			<td>Aladdin</td>
			<td>P112284</td>
			<td></td>
		</tr>
		<tr>
			<td>N,N-Dimethylformamide, 99.5%</td>
			<td>Sinopharm</td>
			<td>40016462</td>
			<td></td>
		</tr>
		<tr>
			<td>2-Bromoacetophenone,98%</td>
			<td>Aladdin</td>
			<td>B103328</td>
			<td></td>
		</tr>
		<tr>
			<td>Diethyl ether,99.5%</td>
			<td>Sinopharm</td>
			<td>10009318</td>
			<td></td>
		</tr>
		<tr>
			<td>Decane,98%</td>
			<td>Aladdin</td>
			<td>D105231</td>
			<td></td>
		</tr>
		<tr>
			<td>Dodecane,99%</td>
			<td>Aladdin</td>
			<td>D119697</td>
			<td></td>
		</tr>
		<tr>
			<td>Niobic acid</td>
			<td>CBMM</td>
			<td>1313968</td>
			<td></td>
		</tr>
		<tr>
			<td>Heating and Drying Oven</td>
			<td></td>
			<td></td>
			<td>DHG Series (shanghai jinghong laboratory instrument co. ltd)</td>
		</tr>
		<tr>
			<td>Autoclave Reactor</td>
			<td></td>
			<td></td>
			<td>CJF-0.05&#8212;0.1L (Dalian Tongda Equipment Technology Development Co., Ltd)</td>
		</tr>
		<tr>
			<td>Tube&#160;furnace</td>
			<td></td>
			<td></td>
			<td>SK2-1-10/12 (Luoyang Huaxulier Electric Stove Co., Ltd)</td>
		</tr>
		<tr>
			<td>Heating magnetic stirrer</td>
			<td></td>
			<td></td>
			<td>DF-101 (Yu Hua Instrument Co. Ltd.)</td>
		</tr>
		<tr>
			<td>Rotary evaporator</td>
			<td></td>
			<td></td>
			<td>RE-3000A (Shanghai Yarong Biochemical Instrument Factory)</td>
		</tr>
		<tr>
			<td>Synthetic air</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Hydrogen gas</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Argon gas</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

chemical precipitation method for the synthesis of nb2o5 modified bulk nickel catalysts with high specific surface area

We demonstrate a method for the synthesis of NixNb1-xO catalysts with sponge-like and fold-like nanostructures. By varying the Nb:Ni ratio, a series of NixNb1-xO nanoparticles with different atomic compositions (x = 0.03, 0.08, 0.15, and 0.20) have been prepared by chemical precipitation. These NixNb1-xO catalysts are characterized by X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopy. The study revealed the sponge-like and fold-like appearance of Ni0.97Nb0.03O and Ni0.92Nb0.08O on the NiO surface, and the larger surface area of these NixNb1-xO catalysts, compared with the bulk NiO. Maximum surface area of 173 m2/g can be obtained for Ni0.92Nb0.08O catalysts. In addition, the catalytic hydroconversion of lignin-derived compounds using the synthesized Ni0.92Nb0.08O catalysts have been investigated.

X-ray diffraction (XRD) patterns (Figure 1 and Figure 2), BET surface areas, temperature-programmed reduction of hydrogen with hydrogen (H2-TPR), scanning electron microscopy (SEM) equipped with an energy-dispersive X-ray (EDX) analyzer, X-ray photoelectron spectroscopy (XPS) were collected for the nanoparticles NiO, Ni-Nb-O and Nb2O5 oxides17 (Figure 3...

Watch this Scientific Journal Video about Chemical Precipitation Method for the Synthesis of Nb2O5 Modified Bulk Nickel Catalysts with High Specific Surface Area at JoVE.com

Chemical Precipitation Method for the Synthesis of Nb2O5 Modified Bulk Nickel Catalysts with High Specific Surface Area

A protocol for the synthesis of sponge-like and fold-like Ni1-xNbxO nanoparticles by chemical precipitation is presented.

Chemical Precipitation Method for the Synthesis of Nb2O5 Modified Bulk Nickel Catalysts with High Specific Surface Area

We demonstrate a method for the synthesis of NixNb1-xO catalysts with sponge-like and fold-like nanostructures. By varying the Nb:Ni ratio, a series of ...

The overall goal of this chemical precipitation technique is to prepare niobium oxide modified nickel catalysts with high specific surface area for hydro conversion of lignin derived compounds. This method can help answer key questions in the nano-material fields, such as how the modified pore size and surface areas of nano-materials for catalytic applications. The main advantage of this technique is that the chemical precipitation methods allow the uniform dispersion of metal components and can be readily used to prepare nano-particles with relatively larger surface areas.The implications of this technique extend toward the development of NiNbO catalysts because it can provide a simple strategy to effectively improve the structures and the catalytic properties of nano-materials. Generally, individuals new to this method will struggle because the preparation procedure is quite different from other conventional methods, such as dry mixing and the evaporation method. To begin preparing the nickel niobium oxide catalyst with a molar ratio of niobium to nickel plus niobium at 0.03, add 100 milliliters of deionized water to a 250 milliliter three neck, round-bottom flask equipped with a stir bar.Add 0.4 grams of niobium five oxalate hydrate and 0.7 grams of nickel nitrate. Use a heating magnetic stir to heat the solution to 70 degrees Celsius, while stirring at 50 RPM, until the precipitate disappears. After this, raise the temperature to 80 degrees Celsius, at a rate of two degrees Celsius per minute.Add a mixed basic solution containing aqueous ammonium hydroxide and sodium hydroxide to the reaction mixture drop wise until the Ph reaches 9.0. While stirring, raise the temperature to 120 degrees Celsius at a rate of two degrees Celsius per minute. This step is especially difficult to learn because constant control must be maintained over both the rate at which the basic solution is added and at the solution's page.Stir the solution overnight at 50 RPM and 120 degrees Celsius until the green color has completely disappeared from the solution. Then use inductively coupled plasma optical emissions spectroscopy to ensure that the remaining nickel nitrate has precipitated completely. Using a buchner flask, filter the solution to collect the solid.Wash the solid with deionized water repeatedly for 20 minutes. Collect the washed solid in a watch glass. Use a dry oven to dry the solid for 12 hours at 110 degrees Celsius.Then use a tube furnace to calcine the solids in synthetic air at 450 degrees Celsius for five hours. After this collect one gram of the prepared catalyst. To begin, transfer one gram of the nickel niobium oxide catalyst to the tube furnace and reduce them in a hydrogen atmosphere at 400 degrees Celsius for two hours.After this, passivate the reduced cyclist under argon overnight. The next day, dissolve 1.1712 grams of anesol and 0.2928 grams of n-dodecane in 20 milliliters of n-decane resulting in an internal standard to be used during quantitative gas chromatography analysis. Quickly transfer the reduced catalyst to the autoclave reactor, avoiding prolonged exposure with air.Seal the reactor and purge with hydrogen gas repeatedly at three MPA. Then set the reactor to atmospheric pressure and the stirring speed to 700 RPM. Begin heating to the desired temperature at a rate of two degrees Celsius per minute.After this, cool and analyze the deoxygenated products as outlined in the text protocol. In this study, nickel niobium oxide catalysts with various atomic compositions are synthesized. X-ray diffraction analysis for the mixed oxide formed by nickel nitrate and hydrated niobium five oxalate corresponds with that observed for hydrated nickel oxalate.Similarly, the peaks observed in the precipitate, after calcination for two hours at 700 degrees Celsius, correspond to those seen in nickel niobate's crystalline phase. X-ray diffraction analysis of the synthesized nanoparticles, after calcination for five hours at 450 degrees Celsius, reveals main diffraction peaks that correspond to those seen in the crystalline nickel two oxide. However, analysis after calcination at 700 degrees Celsius reveals peaks corresponding to the mixed phase, indicating the existence of an amorphous phase after calcination at 450 degrees Celsius which were not present in the nickel niobium composite phase.Next, scanning electron microscopy analysis is performed. While pure nickel two oxide is seen to have a well-defined nanosheet crystalline structure, the synthesized nanoparticles have a foam-like and sponge-like appearance. Once mastered, this technique for catalyst preparation can be done in 48 hours, if it is performed properly.While attempting this procedure, it's important to remember to monitor the Ph using a calibrated Ph meter and to carefully control the rate of addition of the base. Following this procedure, we can prepare catalyst with different metal standards in order to answer additional questions like how to optimize the hydro conversions of anesol. Though this method can provide insight into the development of catalysts for hydro deoxygenation of anesol, it can also be applied to prepare other mixed matter, nano-materials for different catalytic processes.This technique paves the way for researchers in the field of nano-technologies to use chemical precipitation methods to synthesize niobium five oxide modified nickel with different surface areas and the applications in the hydro conversion process. After watching this video, you should have a good understanding of how to carefully prepare the catalyst to obtain high specific surface area by a chemical precipitation method. Don't forget that working with hydronized niobium oxinades can be extremely toxic and in addition the sodium hydroxide autoclave reactor require careful handling.

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JoVE Journal

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11.7K vistas.  Dalian University of Technology. The overall goal of this chemical precipitation technique is to prepare niobium oxide modified nickel catalysts with high specific surface area for hydro conversion of lignin derived compounds. This method can help answer key questions in the nano-material fields, such as how the modified pore size and surface areas of nano-materials for catalytic applications. The main advantage of this technique is that the chemical precipitation methods allow the uniform dispersion of metal components and ...