(13f) Use of Molecular Sieves and Other Adsorbents for Contaminant Removal in Ethylene and Propylene Production

Ethylene and propylene producers have faced the challenge of contaminants for decades. Adsorbents, both molecular sieve and alumina based, have been successfully used to help olefin producers manage their operations as contaminated feeds and increasingly sensitive polymerization catalysts continue to offer them increasing challenges. The most widely used adsorbents are the 3A based molecular sieve products utilized to remove water from the cracked gas, liquids, ethylene-ethane and hydrogen. Elsewhere in the production of ethylene, adsorbents are used to remove not only water but also other contaminants from product ethylene and propylene.

As we move downstream to the polymer plant, contaminants are a problem for sensitive polymerization catalysts and polymer quality. Catalyst life can be greatly diminished by the presence of oxygen compounds, sulfur compounds, nitrogen compounds and even arsine and phosphine. In this part of the plant, adsorbent beds of various combinations can be utilized to remove a variety of compounds. Key to trace contaminant removal from olefinic streams is the use of adsorbents with low reactivity towards the process stream. Although adsorbents are a cost effective option for olefin stream dehydration and purification, it is critical to select the right product.

Selection criteria for matching adsorbent products with specific contaminants as well as tips for optimal operation will be covered.