Chemistry
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Chemical Precipitation Method for the Synthesis of Nb2O5 Modified Bulk Nickel Catalysts with High Specific Surface Area
Chapters
Summary February 19th, 2018
A protocol for the synthesis of sponge-like and fold-like Ni1-xNbxO nanoparticles by chemical precipitation is presented.
Transcript
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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