Efficient low-cost recovery and purification processes for the production of linear alkylbenzene (LAB)-grade and/or high-purity normal-paraffin (n-paraffin) products from kerosine.
The ExxonMobil Chemical (EMC) process offers commercially proven technologies for efficient recovery and purification of high-purity n-paraffin from kerosine feedstock. Kerosine feedstocks are introduced to the proprietary ENSORB recovery process developed by ExxonMobil Chemical, wherein the long-chain aliphatic normal paraffins are selectively removed from the kerosine stream in vapor phase by adsorption onto a molecular sieve. Isoparaffins, cycloparaffins, aromatics and other components not adsorbed are typically returned to the refinery kerosine pool. The cyclical process uses a low pressure ammonia desorbate to recover the n-paraffins from the sieve for use as LAB-quality product or for further purification.
Significant savings in capital cost are achieved by minimizing the need for feed pretreatment before the kerosine enters the recovery system. The ENSORB process exhibits a high tolerance to feed impurities, up to 400 ppmwt sulfur and 80 ppmwt nitrogen. For feedstocks with higher sulfur and nitrogen content, only mild hydrotreating is needed to reduce the impurity levels in the kerosine feed to an acceptable range. The robust adsorbent is able to last long cycle lengths with a total life up to 20 years, as commercially demonstrated by ExxonMobil. The LAB-grade product from the recovery process is further processed in an optional purification section, where residual aromatics and other impurities are further reduced to below 100 ppmwt. Purification is accomplished in a liquid-phase, fixed-bed adsorption system. The impurities are selectively adsorbed on a molecular sieve, and subsequently removed with a hydrocarbon desorbent.
The ENSORB adsorbent offers a high recovery of n-paraffins and a tolerance for sulfur and nitrogen that is unparalleled in the industry. Process conditions can be optimized for a targeted range of molecular weights, and an optimized post-recovery fractionation section allows for fine-tuning of product compositions. The need for a sharp cut in a front-end fractionation section is eliminated, thereby reducing the energy consumption of the process.
Licensor: Kellogg Brown & Root LLC