Excerpt:
Molecular sieve dewaxing (MSDW) is a process that uses zeolite catalysts to selectively convert long-chain n-paraffins into isoparaffins, thereby reducing the pour point and cloud point of diesel and lubricating oil. MSDW is an alternative to conventional solvent dewaxing, which has high energy consumption and environmental pollution.
One of the key factors affecting the performance of MSDW is the choice of desorbent, which is used to regenerate the catalyst after the reaction. Desorbent should have a low boiling point, a high selectivity for n-paraffins, and a low solubility in the product oil. Among various candidates, n-pentane has been widely used as a desorbent in MSDW due to its advantages of low cost, easy availability, and high efficiency.
n-Pentane can effectively desorb the n-paraffins from the catalyst pores and restore the catalyst activity. n-Pentane can also improve the product quality by reducing the aromatics and sulfur content in the product oil. Moreover, n-pentane can be easily separated from the product oil by distillation, and recycled for reuse in the process.
In this article, we will introduce the principle and mechanism of MSDW, the properties and advantages of n-pentane as a desorbent, and the optimization and control of the process parameters. We will also review the recent developments and challenges of MSDW, and provide some suggestions for future research.