Butane Isomer Membrane Separation & Purification
MFI molecular sieve membrane technology replacing energy-intensive distillation for n/i-C4 separation. Kinetic size-exclusion sieving delivers >=99% product purity at 58% lower energy consumption.
Industrial Background
Domestic low-carbon C4 separation and purification - covering n/i-butane and n/i-butene - exceeds 20 million tonnes per year, with the market growing at approximately 5% annually.
At Jingbo Petrochemical's existing 250,000 t/y mixed-alkane dehydrogenation unit, n/i-butane separation currently relies on conventional distillation.
2021 Post-ETBE C4 Distribution (China)
Core Separation Mechanism
Separation shifts from thermodynamic equilibrium (boiling-point distillation) to kinetic size-exclusion sieving. Oriented MFI zeolite micropores bypass phase change and reflux, enabling disruptive energy savings.
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Membrane Matrix
Silicalite-1 (pure-silica MFI)
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Pore Channel
0.51 x 0.55 nm / 0.56 x 0.54 nm
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Selectivity Basis
Sized between n-C4 and i-C4 kinetic diameters
Engineering Component Parameters
Industrial-scale 61-channel MFI molecular sieve membrane elements in modular, high-mass-transfer detachable housings - each module accommodates 7 x 50 cm elements in parallel.
Pilot Performance & Mass Balance
Process-simulation-optimized skid-mounted pilot unit with daily throughput >=120 Nm3/d. Aspen Plus simulation validated against experimental data.
- check_circleStable separation across n/i-C4 feed ratios of 12/88, 10/90, 8/92, and 4/96.
- check_circleThree-module cascade maintains enrichment at n/i-C4 >=97/3 ultra-lean n-butane feed.
- check_circlei-C4 peak enrichment concentration: 98.37% in pilot trials.
- check_circleTemperature-sensitive membrane performance - strict thermal control required.
Aspen Plus Simulation & Experimental Validation
| Stream | Temp (C) | Pressure (MPa) | Flow (kg/h) | n-C4 (wt%) | i-C4 (wt%) | C3/C4 (wt%) |
|---|---|---|---|---|---|---|
| Feed (pre-vaporization) | 26 | 0.22 | 12.95 | 27.67% | 72.03% | 0.30% |
| Feed (post-vaporization) | 120 | 0.20 | 12.95 | 27.67% | 72.03% | 0.30% |
| Stage-1 Permeate (Pass 1) | 45 | 0.01 | 1.50 | 87.30% | 12.64% | 0.06% |
| Stage-1 Permeate (Pass 2) | 110.3 | 0.01 | 5.30 | 42.56% | 57.34% | 0.10% |
| Stage-1 Retentate | 45 | 0.15 | 6.15 | 0.28% | 99.18% | 0.54% |
| Stage-2 Retentate | 120 | 0.18 | 2.13 | 0.53% | 99.33% | 0.14% |
| Stage-2 Permeate | 120 | 0.01 | 3.17 | 87.30% | 12.64% | 0.06% |
Economic Benefits
Integrated membrane separation coupled with a butane isomerization reactor - breaking the thermodynamic equilibrium ceiling on single-pass conversion.
Skid Equipment Power Breakdown
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