1Fully automatic chemical adsorption instrumentPre-experiment preparation
Gas path inspection and carrier gas setting
Confirm that the gases required for the experiment (such as Ar, H ₂, N ₂, O ₂, etc.) have been correctly connected to the instrument gas circuit, and check the cylinder pressure (usually 0.6 MPa for N ₂ and 0.3 MPa for other gases).
Turn on the exhaust ventilation switch to ensure a safe experimental environment.
Turn on the instrument power and software (such as ChemStar), preheat for 30 minutes to bring the TCD detector to a stable temperature (such as 100 ℃).
sample preparation
Weighing and sample loading:
Insert quartz wool into the thick end of the U-shaped tube and compact it to ensure that the sample height does not exceed 2cm and does not come into contact with the thermocouple.
Use a paper slot or a long necked funnel to add the powder sample (mass 0.05-0.1g) into a U-shaped tube, record the empty tube mass (m ₁) and the mass after loading (m ₂).
Sample requirements:
Powder or granular samples (particle size 40-80 mesh), fully dried and free of corrosive components such as S and halogens.
Block or film samples need to ensure that gas molecules can diffuse into the interior.
Install sample tube
Install fixed jackets, sealing sleeves, and O-rings at both ends of the sample tube in sequence to ensure no risk of air leakage.
Insert the sample tube vertically into the slot, tighten the sleeve and close the furnace door, and check the position of the thermocouple (1cm above the heating furnace).
2、 Equipment operation process
Software unlocking and port checking
Enter the password (such as "demo" or "altamira") to unlock the main program (AMI), and check whether the gas connections of each port are consistent with the actual ones.
Gas path leak detection
Turn on Ar gas (flow rate 25cc) and pass the gas through the U-shaped tube through the three-way valve and the six way valve.
Apply soapy water or use a leak detector at the top of the U-shaped tube and the thermocouple fastening point, and turn off the leak detection gas after confirming that there is no leakage.
Experimental program editing
New method:
Click on 'Experiment Define' to establish a process by adding procedures (such as Treatment, TPR, TPD).
Example: TPR program
Pre treatment: Blow at 400 ℃ for 1 hour under Ar atmosphere, then cool down to 100 ℃.
Reduction stage: Switch to a 10% H ₂ - Ar mixture and raise the temperature to 800 ℃ at a rate of 10 ℃/min.
Call template: Directly load existing methods (such as TPD_Program) and modify parameters (such as heating rate and gas flow rate) according to experimental requirements.
Parameter Setting and Startup
Select the testing method in the "Experiment Schedule" and set the data save path (file name must start with "@").
Enter the sample quality, click "Immediate Start" to run the program, and the instrument will automatically complete the heating, gas switching, and data acquisition.
3、 Key experimental steps and precautions
Pre treatment and adsorption
Oxidation treatment (if required): Heat up the oxidation at a flow rate of 40-60mL/min in an O ₂ atmosphere (temperature and time depend on the sample).
Cooling and blowing: Switch to inert gas (such as Ar) and blow to room temperature to remove physically adsorbed impurities.
Program heating experiment
TPR (temperature programmed reduction):
After the baseline stabilizes, raise the heating furnace and record the relationship curve between H ₂ consumption and temperature.
Peak temperature represents the temperature of the reduction center, and peak area reflects the consumption of H ₂.
TPD (temperature programmed desorption):
After adsorbing gases (such as NH3, CO ₂) to saturation, inert gas is blown to remove the physically adsorbed portion.
Programmed temperature desorption, determining the strength of acid/base centers through peak temperature, and quantifying the number of active sites through peak area.
Safety operation standards
TCD protection: First turn on the carrier gas and then turn on the TCD. After completion, turn off the TCD before handling other operations.
Cold trap usage: Low temperature experiments (such as H ₂ - TPR) require the addition of a cold trap to prevent water vapor contamination of TCD.
Gas switching: When continuously introducing H ₂ and O ₂, inert gas must be blown in between to avoid the risk of explosion.
4、 Data collection and processing
data saving
After the experiment is completed, save the original data file (such as. dfn format), ensuring that the file name includes sample information and the experiment date.
data analysis
Open data analysis software (such as AMI Analysis), import data files, and select the TPD/TPO option.
Set the X-axis to Bed Temperature and adjust the zoom mode to display the complete curve.
Mark peak positions and baselines using the Peak Editor tool, and calculate parameters such as peak area and desorption energy.
Interpretation of results
TPR case: In the H ₂ - TPR curve of cerium oxide supported rare earth doped nickel oxide catalyst, the low-temperature peak represents NiO reduction, the high-temperature peak reflects CeO ₂ reduction, and the peak temperature shift indicates enhanced metal support interaction.
TPD case: In the NH ∝ - TPD curve, the low-temperature peak (<200 ℃) corresponds to weak acidic sites, and the high-temperature peak (>400 ℃) corresponds to strong acidic sites. The peak area ratio reflects the distribution of acidic sites.
5Fully automatic chemical adsorption instrumentPost experiment maintenance
Equipment cleaning
Remove the U-shaped tube, clean it with detergent, alcohol, or acetone, and dry it for later use.
Clean the experimental bench, turn off the gas cylinder, instrument power, and software.
Record filling
Record sample information, experimental conditions, and abnormal situations in the experimental logbook for easy traceability and reproduction.