Technology

Overview

SINOPEC’s ST-PP is a modular loop-reactor polypropylene platform developed by Sinopec Research Institute of Petroleum Processing (RIPP) and commercialized by Sinopec Tech Development. Across three generations (ST‑I, ST‑II, ST‑III), the platform has evolved from basic homopolymer/random copolymer capability to a high-capacity, multi-reactor system producing advanced impact copolymers and specialty grades, leveraging proprietary catalysts and modern automation.

Process configuration

Reactor system

• ST‑I: single liquid‑phase loop reactor with hydrogen regulation for molecular weight control; primarily homopolymer and random copolymer; legacy capacities ≤200 kt/y.
• ST‑II: two cascade loop reactors with optional downstream gas‑phase reactor for rubber phase formation, enabling impact copolymer and broader grade flexibility; ypical capacities ~300–400 kt/y.
• ST‑III: advanced multi‑loop configuration with upgraded heat/mass transfer features, digital APC, and fast grade change; compared with earlier generation, ST-III emphasizes high throughput, reduced off‑spec, improved specific energy consumption and reduced flaring/vent losses; ST-III also 
  supports high ethylene incorporation, improved rubber dispersion, and specialty product windows; capacities up to 450 kt/y.

 Loop Reactors

Loop reactor characteristics are: 

• High (time and volume) production rate (>400 kg PP/h m³)
• High speed of materials circulation, high polymer concentration in slurry, and high efficiency heat transfer between liquid monomer and polymer powder
• Uniformed distribution of catalyst system, condensed monomer easily recovered
• Rapid product grade transition, off-spec product minimized
• Full liquid reactors
• Small diameter of reactors , and thin wall even with high design pressure

Degassing and finishing

• Multi‑stage monomer degassing, pelletizing with additive dosing for stabilization, antistatic, nucleation, and processing aids suited to application grades.

References

1. SINOPEC > Chemical Process Solutions > Polyolefin Technologies > Loop Reactor Polypropylene Process (ST-PP). (accessed Oct 12, 2024)