Technology

The Appryl PP process is a proprietary bulk-phase liquid polymerisation technology developed jointly by Elf Atochem (later TotalFinaElf / ATOFINA, now TotalEnergies/Arkema) and BP Chemicals (later BP Amoco). It is classified as a second-generation bulk polypropylene process, belonging to the same family as other liquid-phase CSTR-based technologies.

The technology was developed and operated exclusively by the Appryl joint venture. Following its dissolution into INEOS (via the 2024 TotalEnergies acquisition), the process know-how and intellectual property now reside within INEOS O&P.

Core Process — Bulk Liquid-Phase CSTR Polymerisation

The Appryl process polymerises propylene in liquid bulk phase — liquid propylene acts simultaneously as the monomer and the reaction medium, with no solvent or diluent required. Polymerisation is conducted at approximately 60–80°C and 30–40 atm pressure, sufficient to maintain propylene in the liquid state.

The central reactor is a large Continuous Stirred Tank Reactor (CSTR), described in published literature as the world's largest polypropylene reactor at the time of its commissioning around 1998, producing 250,000 t/yr from a single reactor. This is a distinguishing feature of the Appryl process — its scale-up of a single CSTR to extremely large volume, rather than using multiple loop reactors in series as in competing technologies.

The process is described as operating with a single residence time (ττ) maintained constant, producing a near-monodisperse residence time distribution characteristic of a well-mixed CSTR.

Catalyst System

The process uses a Ziegler-Natta catalyst system. The catalyst undergoes an activation pre-processing step before entering the reactor, which introduces a characteristic and measurable time delay (δδ) between catalyst injection and its activity in the reactor. This delay is a defining operational characteristic of the Appryl CSTR process and was the primary driver for the development of its advanced flatness-based controller.

Hydrogen is used as a chain transfer agent to control molecular weight (and therefore melt index) of the polymer, fed directly to the reactor without delay.

Deployments

Three plants have historically been built. 

Product Range

The original Appryl process is capable of producing homopolymers (HPP) and random copolymers (RCP). A proprietary block copolymerisation process was developed as the latest Appryl technology generation.

Distinguishing Characteristics vs. Competing Technologies

Deployments

Three plants have historically been built. 

References

1. LôôkChem  — Appryl Polypropylene- Home (archive) 
2. Petit N. et al.. Semantic Scholar — Control of an industrial polymerization reactor using flatness (Aug 1, 2002). Journal of Process Control 2002 (12), 559-565. DOI: 10.1016/S0959-1524(01)00049-X
3. Naphthachimie — Subsidiary: APPRYL (accessed Jun 3, 2026)