Butene-1

A brief account of the process and production diagram

Jam Petrochemical's butene-1 unit, built under licence from AXENS with basic engineering by Nargan and with a capacity of 100,000 tons a year, is the largest butene production unit in the country. Besides meeting the needs of the complex's downstream units, it can supply other polyolefin companies in the country, and the bulk of its output is intended for export to consumer markets.

Butene-1 is produced by dimerising two ethylene molecules in the liquid phase. The reaction takes place in the presence of an LC catalyst and a TEA co-catalyst in two parallel reactor trains. The reaction is exothermic, and its heat is removed through circulation loops by chilled water supplied by the propylene refrigeration system.

The stream containing butene-1 and C6+ is drawn from the bottom of the reactor and, after injection of amine as the reaction-stopping agent, sent to the evaporation section. Once the lighter compounds have been separated in the flash drum and the catalysts and spent amine removed in the thin film evaporator (TFE), the vapour stream — containing butene-1, C6+ and unreacted ethylene — passes to the distillation section. This section comprises two columns: the overhead stream of the first column is unreacted ethylene, which is returned to the reactors, while its bottom stream goes to the second column, where butene-1 is separated as the overhead product and C6+ as the bottom product.