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LPG Purification with zeolite 13X and 3A molecular sieve
Table of Contents
Customer Background
An LPG refinery faced issues with H₂S, mercaptans, moisture, and heavy hydrocarbons in its product stream—leading to equipment corrosion, odor, and catalyst poisoning. Traditional adsorbents couldn’t effectively remove all impurities. A three-stage adsorption process using activated carbon, 13X, and 3A molecular sieves was adopted for deep desulfurization, dehydration, and heavy hydrocarbon removal.
Process Overview
1.LPG Feed Composition & Targets
Impurity Before (ppm) Target (ppm)
H₂S 200 < 0.5
CH₃SH 50 < 1 H₂O 100 < 5
C5+ 300 < 10
2.Three-Stage Adsorption Design
- Stage 1 – Activated Carbon:
Removes C5+ hydrocarbons and partial sulfur compounds.
Prevents clogging and protects downstream adsorbents. - Stage 2 – 13X Molecular Sieve:
Removes H₂S, mercaptans, and moisture.
High sulfur capacity (4–6 wt%), reduces water to <10 ppm. - Stage 3 – 3A Molecular Sieve:
Final dehydration to <5 ppm H₂O.
Selective to water, prevents LPG loss and freezing.
3.Regeneration Methods
- Activated Carbon: Hot N₂ or steam (150–200°C)
- Zeolite 13X: High-temp N₂ (250–300°C)
- Zeolite 3A: Low-temp purge (180–220°C)
Results
Impurity Before (ppm) After (ppm)
H₂S 200 < 0.5
CH₃SH 50 < 1
H₂O 100 < 3
C5+ 300 < 10
Benefits
- 30% lower operating cost than traditional processes.
- Longer adsorbent life (Carbon: 1 yr, 13X: 3 yrs, 3A: 5 yrs).
- Reduced waste—saves ~¥800,000/year in alkali treatment.
- Meets GB 11174-2011 and reduces SO₂ emissions.
Application Scope & Value
Ideal for
- LPG/natural gas purification (refineries, depots)
- Raw gas (propylene, butene) purification
- Autogas treatment
Optimization Tips:
- Adjust desiccants 13X loading based on sulfur content.
- Use TSA (Temperature Swing Adsorption) for efficiency.
- Monitor pressure drop to prevent bed clogging.
Conclusion
The 13X + 3A + activated carbon process offers a cost-effective, environmentally friendly solution for ultra-deep LPG purification, making it suitable for high-standard energy and chemical applications.