The overall goal of this procedure is to synthesize novel catalytic materials with nano gold interated in the walls of meso porous silica. This is accomplished by first forming my cells with the addition of surfactant, which act as a template for the formation of meso porous silica. A silicon source and a surface modification agent are then added to the solution before adding a gold precursor dropwise to result in nano gold particles.
After stirring for 24 hours, the solution is transferred to an oven for hydrothermal processing. During the hydrothermal processing treatment, silica is polymerized to form its meso porous structure, and gold precursor starts to grow at the nanoscale. The final step is to calcine the material to remove any remaining surfactant and obtain a well-defined meso porous structure.
Ultimately, fiz absorption, x-ray diffraction and transmission electron microscopy are used to show that gold nanoparticles are interated into the well-defined walls of the meso porous silica. The main advantage of this method over others, such as direct precipitation, is that the materials synthesized here are very thermally robust. Generally, individuals new to this method will struggle because a successful synthesis requires process control over temperature and solution conditions.
Nanotechnology is defined as a size regime, the nanoscale regime in which the properties of a material change as a function of changing the size of the particles. In this case, we're talking about gold nanoparticles, and gold also suffers from being a soft metal that's easily melted. So the proof of principle here that we can demonstrate for adding thermal stability to gold should be applicable to all metal systems.
To begin preparation of gold in intercalated into the wall of meso porous silica or GMS, add 2.0 grams of P 1 23 to 75 milliliters of two molar hydrochloric acid solution. At room temperature, apply magnetic stirring to the solution. At a speed of 350 rotations per minute until P 1 23 is completely dissolved, the solution will be clear.
Add four grams of TEOS to a small vial, followed by 180 microliters of T-E-S-P-T-S. Slowly shake the vial to mix the two chemicals in another vial dissolve 38 milligrams of chloro oric acid in one milliliter of deionized water. Increase the P 1 23 solution temperature to 35 degrees Celsius in an oil bath with temperature controlled by thermocouple.
Then add all of the TEOS and T-E-S-P-T-S mixture to the P 1 23 solution and keep the solution at vigorous magnetic stirring of 700 rotations per minute. After the solution stirs for two minutes, add all of the prepared chloro ORIC acid solution dropwise within 30 seconds. Stir the solution at 700 rotations per minute for 24 hours at 35 degrees Celsius.
After 24 hours, transfer the solution into a sealed bottle and store in an oven set at 100 degrees Celsius for 72 hours. This is called hydrothermal processing. After the hydrothermal processing, filter the solution with a number one filtration paper and negative pressure under a funnel.
Then wash the sample two times with water and three times with ethanol to remove the remaining hydrochloric acid. During each wash process, add water or ethanol one centimeter above the solid and wait for the material to dry. Transfer the precipitation from filtration to a ceramic crucible to calcine in a furnace.
Set the ramp program to increase from 25 to 550 degrees Celsius for two hours, and to maintain 550 degrees Celsius for four hours. Then allow the sample to remain in the furnace with the door closed until the temperature falls below 40 degrees Celsius. After calcination transfer the product to a glass vial with a plastic spatula, the synthesized material has a red color through the oxidation of benzo alcohol.
As a benchmark reaction, the GMS materials are tested and show high selectivity and recyclability. Since the oxidation of benzo alcohol is a liquid phase reaction without a separate solvent transfer five milliliters of benzo alcohol to a 25 milliliter three neck flask. Then add 10 milligrams of the GMS catalyst to the benzo alcohol.
Set up a temperature controlled oil bath with magnetic stirring at 100 degrees Celsius. To ensure accurate and uniform control of the reaction temperature. Put the flask with benzoyl alcohol and catalyst into the oil bath and stir at 150 rotations per minute.
Flow oxygen gas with 99.9%purity into the flask at two milliliters per minute controlled by a mass flow controller. When the temperature of the oil bath reaches 100 degrees Celsius and stabilizes, introduce oxygen gas into the three neck flask. Keep the oxygen flow rate and temperature constant and allow the reaction to proceed for six hours.
After the reaction, filter the product with a number one filtration paper. Collect the liquid phase and transfer an to a gas chromatography vial in the vial mix four parts HPLC grade acetic acid. For every one part sample, put the vial on a gas chromatograph autos sampler for analysis.
Wash off the solid precipitate on the filter paper with deionized water and then ethanol before allowing the precipitate to air dry with a spatula. Collect the dried solid, which is the recycled catalyst. Repeat this procedure with recycled catalyst three times in each repeat, adjust the amount of benzo alcohol for the amount of recycled catalyst to remain the same ratio.
Weigh three separate 300 milligram portions of synthesized GMS store. The portions of synthesized GMS in glass vials marked as batch one, batch two, and batch three. Batch one will serve as the control group while batch two and batch three will be subjected to thermal processing.
Program the furnace to ramp from 25 degrees Celsius to 400 degrees Celsius in 0.5 hours, and then maintain 400 degree Celsius for four hours. Put batch two in a crucible and start the program allowing the sample to remain in the furnace with the door closed until the temperature falls below 40 degrees Celsius. For batch three, program the furnace to ramp up from 25 degrees Celsius to 650 degrees Celsius in 0.75 hours and maintain its 650 degrees Celsius for four hours.
Put batch three in a crucible and start the program as before. Allow the sample to remain in the furnace with the door closed until the temperature falls below 40 degrees Celsius on the fiz absorption instrument. DGAs the GMS materials at 90 degrees Celsius for 60 minutes, and then 350 degrees Celsius for 480 minutes.
Run full isotherm analysis on the DGAs materials to obtain fizzy absorption data. Disperse the GMS sample on a 200 mesh wholly carbon transmission electron microscope or TEM grid, and observe the sample under a transmission electron microscope. Also run x-ray diffraction with copper K alpha radiation as described in the text protocol.
A TEM image of the GMS reveals that the silica matrix formed well-defined long channels with a stable wall. The pore diameter was identified to be around five nanometers and hexagonal in the shape, as is typical for meso porous silica. Comparison of the BET fiz absorption, isotherm for silica matrix without gold interation to the isotherm for GMS with gold and interated in the walls reveals that there is no significant difference between the two materials.
Both of them show the typical shape for meso porous materials with a hysteresis loop indicating that the golden interation did not impose any alteration on the pore structure. BET pore structure and BJH Poor distribution for GMS material calcine at different temperatures are also shown. High temperature calcination did not alter the meso porous silicon matrix.
Further, both pore structure and pore distribution remained the same after temperature treatment as high as 650 degrees Celsius, indicating that the gold did not aggregate and block the pores. The thermal stability of the gold in GMS is further verified by x-ray diffraction through the diffraction pattern of GMS material, calcine at different temperatures. Peak location, peak intensity, and peak width do not show any change due to the calcination process indicating that gold particles did not change in size or morphology.
One master, this technique can be done in 120 hours if performed properly. When attempting this synthesis, it's important to control the reaction conditions precisely as the templating agent is sensitive to small changes in pH temperature and concentration Realization of this technology has provided researchers a paradigm by which we can impart thermal stability to catalyst systems. This is being implemented presently in systems for biomass upgrading and antico technologies for a broad portfolio of renewable energy technologies.
