What are Pour Point Depressants?
Pour point depressants (PPDs) are polymeric additives blended into distillate fuels such as diesel, heating oil, kerosene and jet fuel in order to lower the pour point and prevent wax crystallization at low temperatures. They work by attaching to the wax crystals as they begin to form and inhibiting further crystallization. This allows the wax to remain uniformly dispersed within the liquid phase and prevents solidification even at temperatures below the pour point.

Types of Pour Point Depressants
There are two main types of PPD chemistries used in distillate fuels:
Polymethacrylate Esters: These are random vinyl copolymers of methacrylates and esters which have excellent effectiveness at lowering pour points. They are easier to disperse and tend to be more cost-effective.
Polyalphaolefins: These are synthetic hydrocarbons made via oligomerization which have wax-like solubilizing properties. They provide very good low-temperature performance but are more expensive than polymethacrylates. Blends of the two types are also used to optimize effectiveness and cost.

Mechanism of Action
Upon addition to a fuel below its normal pour point, Pour Point Depressants  molecules surround the wax crystals as they begin nucleating and growing. They adhere to the crystalline surface and physically hinder further association of wax molecules. This disrupts the ordering of wax crystals into larger three-dimensional structures. As a result, the wax remains as small dispersed crystalline domains maintained in a meta-stable state within the liquid fuel. This collloidal dispersion allows for flow even at temperatures below the typical pour point.

Dose Requirements
The amount of PPD needed varies depending on factors like the fuel composition, season, geographical location and targeted lowest operable temperature. Generally, doses range between 50-150 ppm (parts per million) by volume though higher doses up to 400 ppm may be used for extreme low temperature applications. Higher wax content fuels require more PPD to be effectively treated. The additive should be blended uniformly into the fuel bulk storage or day tanks.

Get more insights on This Topic- Pour Point Depressant