The Snamprogetti Etherification Technology allows producing high-octane oxygenates compounds such as methyl tert-butyl ether (MTBE), ethyl tert-butyl ether (ETBE), tert-amyl methyl ether (TAME), tertamyl ethyl ether (TAEE) and etherified light cracked naphtha (ELCN). Feed: C4 streams from steam cracker, fluid catalytic cracking unit (FCCU) and isobutane dehydrogenation units, with isobutene contents ranging from 15 wt% to 50 wt%, C5 and light cracked naphtha (LCN – FCC light gasoline 35°C–100°C) from FCC units.
A typical MTBE/ETBE unit using FCC cut is based on a single-stage scheme, with a tubular (1) and an adiabatic (2) reactor. The front-end reactor uses the proprietary water-cooled tubular reactor (WCTR). The WCTR is a very flexible reactor and can treat all C4 cuts on a once-through basis.
It is the optimal solution for the etherification reaction since it enables an optimal temperature profile with the best compromise between kinetics and thermodynamics.
The reactor effluent is sent to the first column (3) where the product is recovered as a bottom stream while the residual C4s are sent to the washing column (4) to separate the alcohol. The water/alcohol leaving the column is sent to the alcohol-recovery column (5), to recycle both alcohol and water.
This scheme will provide a total isobutene conversion up to 95%. With the double stage scheme, it is possible to reach more than 99%. The industrial experience has proven that this plant with WCTR can be easily switched from ETBE to MTBE production, and vice versa, without stopping the plant and any reduction of feed rates. Process schemes are similar for production of heavier ethers starting from C5 or LCN streams.