📋 Case Study

Supercritical CO₂ Extraction of Caffeine

Low caffeine yield and inconsistent selectivity due to inaccurate P–T–x phase diagrams

🏗️ Project Overview

Starbucks sustainable decaffeination pilot in Colombia

🎯 Challenge

Low caffeine yield and inconsistent selectivity due to inaccurate P–T–x phase diagrams

🔧 Design Approach

Used PC-SAFT EOS (validated against ternary CO₂–caffeine–water data) to map solute solubility surfaces and optimize extraction window (100–150 bar, 40–60°C)

📐 Design Diagram

AI-generated project design illustration

📐 Key Calculations

Solubility (g caffeine/kg CO₂)

ln(x_i) = ln(ϕ_i^sat/P_i^sat) + (v_i/RT)(P − P_i^sat)

Result: 12.4 g/kg

Determines column sizing and recycle ratio

Density of scCO₂

ρ = P / (ZRT)

Result: 682 kg/m³

Controls mass transfer driving force

📊 Results

Yield increased from 71% to 96.3%, energy use reduced by 37%, eliminated chlorinated solvents

💡 Lessons Learned

• •PC-SAFT outperforms cubic EOS for polar + supercritical systems
• •Density-driven diffusivity modeling improved mass transfer predictions

✅ Key Takeaways

• 1PC-SAFT outperforms cubic EOS for polar + supercritical systems
• 2Density-driven diffusivity modeling improved mass transfer predictions