
External users: registration to be carried out only through I-STEM portal
Additional information about sample and analysis details should be filled in the pdf form provided in the I-STEM portal under “DOWNLOAD CSRF”
Internal users (IITB): registration to be carried out only through DRONA portal
Additional information about sample and analysis details should be filled in the pdf form provided here.
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Category
- Material Characterization » Chemical Characterisation
Booking Details
• Temperature Programmed Desorption (TPD).
• Temperature Programmed Oxidation (TPO).
• Pulse Titration.
Facility Management Team and Location
Prof. Sanjog S. Nagarkar.
Prof. Chidambar Kulkarni.
Prof. Narendra Shiradkar (Electrical Eng).
Prof. Ateeque Malani (Chemical Eng).
Facility Features, Working Principle and Specifications
Facility Description
The ChemBET Pulsar is a fully automated chemisorption analyzer designed for high-precision titration and surface characterization. The system is equipped with TPRWin software, allowing for programmed analysis sequences, including metal area and dispersion determination. An automatic loop injector and gas switching enhance accuracy and efficiency. The Pulsar uses a highly sensitive Thermal Conductivity Detector (TCD), resistant to oxidation and ammonia, ensuring baseline stability and reproducible signals. The system is optimized for a wide range of gases, with high-temperature quartz sample cells and in-cell thermocouples for accurate sample temperature measurement.
Chemisorption is a chemical adsorption process that involves the formation of a chemical bond between an adsorbent and an adsorbate
Sample Preparation, User Instructions and Precautionary Measures
Sample should be dry, and only solid samples in the form of powder are accepted.
Explosive and poisonous sample is not allowed
Charges for Analytical Services in Different Categories
Internal User | Rs. 100/- Per sample |
External User (Academic) | Rs. 200/- Per sample |
External User (National labs) | Rs. 400/- Per sample |
External Users (Industry & Non-Govt. Agency) | Rs. 500/- Per sample |
Charges for TA as per institute norm. |
Applications
CO₂-TPD:-
To measure the basic sites on a catalyst or adsorbent by quantifying the desorption of chemisorbed CO₂ as the temperature increases.
Step-by-Step Procedure for CO₂-TPD
1. Sample Preparation
- Weigh an appropriate amount of the sample (typically 50–200 mg) and load it into a quartz tube.
- Secure the sample in the instrument .
2. Pre-treatment (Activation)
- Purpose: To remove any physically adsorbed species or contaminants.
- Conditions:
- Flow: Inert gas (e.g., Helium or Argon).
- Temperature: Usually 350–500 °C (depending on sample stability).
- Time: ~30–60 minutes.
- Cool down to adsorption temperature (commonly ~50 °C or RT).
3. CO₂ Adsorption
- Introduce CO₂ gas into the system.
- Flow: Typically 5–10% CO₂ in inert gas (e.g., He or Ar).
- Time: 30–60 minutes or until saturation is achieved.
- Temperature: Keep constant at adsorption temperature (~50 °C).
4. Purging (Physisorbed Gas Removal)
- Switch to inert gas flow (He or Ar) to remove loosely bound or physisorbed CO₂.
- Time: 30–60 minutes.
- Keep the temperature constant during purge.
5. Temperature Programmed Desorption (TPD)
- Start ramping the temperature at a controlled rate (typically 10 °C/min).
- Final temperature: ~600–800 °C, depending on the sample.
- Detector: TCD (Thermal Conductivity Detector) or MS (Mass Spectrometer) monitors desorbed CO₂.
6. Data Collection and Analysis
- Obtain TPD profile: Desorption peaks correspond to different types of basic sites (weak, moderate, strong).
- Quantify the desorbed CO₂ (area under peaks) to estimate the total basic site concentration.
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NH₃-TPD
To determine the amount, type (strength), and distribution of acid sites on the surface of catalysts or adsorbents by measuring ammonia desorption as a function of temperature.
Step-by-Step Procedure for NH₃-TPD
1. Sample Loading
- Weigh ~50–200 mg of the powdered sample.
- Load it into a quartz tube and fix inside the chemisorption analyzer.
2. Pre-treatment (Activation)
- Purpose: To remove surface impurities, water, and pre-adsorbed gases.
- Gas: Flow of inert gas (Helium or Nitrogen).
- Temperature: 400–550 °C depending on the sample.
- Duration: 1–2 hours.
- After pretreatment, cool the sample to the NH₃ adsorption temperature (usually 50–100 °C).
3. NH₃ Adsorption
- Introduce NH₃ gas or diluted NH₃ in inert carrier (e.g., 5–10% NH₃ in He).
- Flow time: ~30–60 minutes to ensure saturation.
- Maintain constant adsorption temperature (typically 50–100 °C).
- NH₃ adsorbs onto both Brønsted and Lewis acid sites.
4. Purging (Desorption of Physisorbed NH₃)
- Switch to inert gas (e.g., He or N₂) to purge weakly adsorbed or physisorbed ammonia.
- Temperature: Keep the same as adsorption (no ramp yet).
- Time: 30–60 minutes or until the baseline stabilizes.
- This step ensures only chemisorbed ammonia remains on the surface.
5. TPD Run (Desorption)
- Ramp the temperature gradually (e.g., 10 °C/min) up to 600–800 °C.
- Carrier gas: Continue with inert gas (He or N₂).
- Detection: Use a TCD (Thermal Conductivity Detector) or MS (Mass Spectrometer) to monitor desorbed NH₃.
6. Data Collection & Analysis
- TPD Profile: The desorption curve typically shows multiple peaks:
- Low-temp peaks = weak acid sites.
- Mid-temp peaks = moderate acid sites.
- High-temp peaks = strong acid sites.
Integration of peaks gives total acid site concentration (in µmol/g or mmol/g).
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H₂-TPR
To study the reducibility of metal oxides or supported catalysts by measuring H₂ consumption as temperature increases.
You can:
- Identify reduction peaks for different metal oxides.
- Determine reduction temperatures.
Quantify H₂ uptake (→ calculate oxygen content or reducible species).
Step-by-Step H₂-TPR Procedure
- 1. Sample Loading
- Weigh ~50–100 mg of the sample.
- Load into a U-shaped tube.
Place in the instrument sample holder.
2. Pre-treatment (Optional)
If needed, remove moisture or contaminants:
- Gas: Inert (He or N₂)
- Temperature: 150–200 °C
- Time: 30–60 min
- Then cool to starting TPR temperature (~50 °C)
3. TPR Gas Introduction
- Begin flow of H₂ gas (usually 5–10% H₂ in He or N₂).
- Set flow rate to 30–50 mL/min.
Allow system to stabilize at starting temperature (~50 °C).
4. Temperature Programmed Reduction(TPR)
- Begin temperature ramp:
- Heating rate: typically 5–10 °C/min
- Final temperature: 600–900 °C depending on material
- The TCD (Thermal Conductivity Detector) monitors H₂ consumption as the sample is heated.
As reduction occurs, the sample consumes H₂ → decrease in TCD signal.
5. Data Collection
- The TPR profile shows reduction peaks.
- Each peak corresponds to a specific reducible species or metal oxide state.
Quantify H₂ consumed:
- Use calibration or integrate area under curve.
- Gives amount of oxygen removed → degree of reduction.
- Post-Analysis
- Peak positions → indicate reduction temperature for metal oxides.
- Area under peaks → H₂ consumed → used to calculate:
- Oxygen stoichiometry
- Metal reducibility
- Degree of reduction in % or µmol H₂/g
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H₂ Pulse Chemisorption
To measure the amount of chemisorbed hydrogen on a reduced metal catalyst surface, which helps calculate:
- Metal dispersion (%)
- Active metal surface area (m²/g)
Average particle size (nm)
Step-by-Step Procedure for H₂ Pulse Titration Chemisorption
1. Sample Loading
- Weigh ~50–200 mg of catalyst.
Load into the quartz sample tube in the chemisorption instrument.
2. Sample Pretreatment (Reduction)
- Purpose: To reduce the metal oxide (e.g., PtO, NiO) to metallic form.
- Gas: Pure H₂ or 10% H₂ in Ar/N₂.
- Temperature: 300–500 °C depending on metal type.
- Flow rate: 30–50 mL/min.
- Duration: ~1–2 hours.
- ✅ After reduction:
- Switch to inert gas (He or N₂).
- Purge at the same temperature for ~30–60 minutes to remove excess H₂.
Cool the sample to adsorption temperature (typically 35–50 °C).
3. Titration by H₂ Gas (Pulse Chemisorption)
- Start injecting pulses of a known volume of H₂ gas (commonly 0.1–0.5 mL per pulse).
- Use inert carrier gas (He or N₂) to carry the pulses over the sample.
- Monitor the amount of H₂ not adsorbed using a TCD (Thermal Conductivity Detector).
Repeat pulses until the TCD signal for H₂ stabilizes (i.e., the sample surface is saturated and no more H₂ is chemisorbed).
4. Data Collection
- Record H₂ uptake per pulse.
- Sum of all chemisorbed H₂ = total H₂ uptake (µmol or mL STP).
- Convert this to:
- Dispersion (%)
- Metal surface area (m²/g)
- Average metal particle size (nm)
(using known stoichiometry and assumptions, e.g., 1 H₂ molecule per 1 surface metal atom)
Key Calculations
- Total uptake (µmol/g) = Total chemisorbed H₂.
- Dispersion (%) = (Surface metal atoms / Total metal atoms) × 100
- Metal surface area = Based on atomic cross-sectional area of the metal.
- Average particle size (nm) = Calculated using known shape factors and atomic dimensions.
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Sample Details
Sample should be well dried and in pure form