hydrodewaxing

Hydrodewaxing is a catalytic refining process that removes waxy paraffins from petroleum fractions under hydrogen to lower the product pour point. It is a type of hydroprocessing used to upgrade lubricating oil base stocks and certain distillates by converting long-chain paraffins into shorter or branched molecules that stay liquid at lower temperatures.

The process uses bifunctional catalysts that provide both hydrogenation and acidic cracking or isomerization. Feedstocks commonly include waxy distillates such as vacuum gas oil, gas oil, or lubricating oil basestock fractions. Under elevated temperature and hydrogen pressure, long-chain n-alkanes and paraffins are cracked and/or isomerized to shorter and more branched compounds, reducing crystallization and lowering pour point while preserving or improving viscosity index and sulfur/nitrogen levels.

There are two main configurations. Catalytic dewaxing (CDW) employs fixed-bed or slurry reactors with acidic catalysts such as zeolites or alumina supports, often in combination with metal hydrogenation components (for example nickel, platinum, or other noble metals). Hydrodewaxing can also be integrated within a broader hydrocracking sequence, enabling simultaneous dewaxing, saturation, and some cracking.

Typical catalysts are designed to balance wax cracking with isomerization to branched structures, using metals (Pt, Ni, or others) paired with zeolitic or acidic supports. Operating conditions emphasize high hydrogen availability and careful control of temperature to maximize wax removal while preserving desirable base-oil properties.

Hydrodewaxing is commonly followed by finishing steps to meet final base-stock specifications. See also hydrocracking, hydrotreating, and catalytic dewaxing.