Diesel Pour Point Depressant, often translated into Chinese as Diesel Pour Point Depressant or diesel flow improver, is a chemical additive added to diesel to improve the flow performance of diesel at low temperatures and prevent it from solidifying.

1. Core question: Why does diesel solidify at low temperatures?
Diesel is a complex mixture of hydrocarbons, which contains normal alkanes (paraffin). These paraffins dissolve in diesel at room temperature, but when the temperature drops, they will start to form flaky or needle-like wax crystals. As the temperature drops further:

Wax crystals precipitate in large quantities, grow and connect with each other, forming a three-dimensional network structure.

This reticular structure will enclose the remaining liquid oil content within it.

Ultimately, the entire diesel system lost its fluidity, became like jelly, and even solidified completely.

There are two key temperature points in this process:

Cloud point: The temperature at which diesel begins to show visible wax crystals to the naked eye and becomes cloudy.

Pour point: The highest temperature at which diesel loses its fluidity.

The core function of pour point depressants is to intervene in this process.

2. The Functions and benefits of diesel pour point depressants
By altering the formation mode of wax crystals, pour point depressants can bring the following main benefits:

Lowering the freezing point/pour point: This is the most direct effect, enabling diesel to remain flowing at a lower temperature and thus ensuring the normal operation of the fuel supply system.

Improve low-temperature filtration performance: Prevent wax crystals from clogging the fuel filter, which is one of the most common problems during winter driving.

Expand the applicable temperature range of diesel: Enable diesel of the same grade to be used in colder environments or allow for the use of more low-cost heavy components during blending in refineries.

Ensure the normal operation of the engine: Avoid problems such as engine stalling and difficult starting caused by poor fuel supply.

Improving economic efficiency: Compared with the high-cost processes required for producing low pour point diesel (such as deep dewaxing), adding pour point depressants is a more economical and effective solution.

3. Main mechanism of action
Pour point depressants do not prevent the precipitation of paraffin but rather alter the morphology and nature of its crystals.

Eutectic and adsorption: At the moment when the wax crystal begins to form, the molecules of the pour point depressant will co-crystallize or adsorb onto the surface of the wax crystal.

Altering crystal morphology: It inhibits the growth of wax crystals in unfavorable directions (such as forming large plate-like or long needle-like shapes), promoting the formation of more, smaller, smooth-surface spherical or granular crystals.

Disruption of the network structure: These tiny and dispersed crystals cannot effectively connect with each other to form a three-dimensional network structure, thus being unable to encapsulate the liquid oil component.

Maintain fluidity: Therefore, even if the wax has precipitated, diesel can still flow under the effect of gravity and pass smoothly through the filter screen and pipes.

A simple metaphor: Just like snowfall, without pour point depressants, what falls are just "snowflakes" (large wax crystals), which are prone to stick together into solid snow blocks. After the application of the pour point depressant, what comes down is fine and round "snow sand" (small wax crystals), which are loose and not easy to stick together, and are easier to be "swept away" (pumped).

4. Main chemical components
Common diesel pour point depressants are high-molecular polymers, mainly including:

Ethylene-vinyl acetate copolymer

Polymethacrylate

Polyα -olefins

Maleic anhydride - olefin copolymer

5. Application scenarios
Refineries and blending companies: Add diesel before it leaves the factory to ensure it meets the low-temperature performance standards of specific seasons or regions (for example, in China, diesel is classified into different grades such as 0 #, -10 #, -20 #, and -35 #).

Gas station: Add fuel to the gas station's storage tank during seasonal changes.

End users: Car owners or fleets purchase and add fuel tanks on their own before winter arrives or when traveling to cold regions as a preventive measure. The best practice is to add it before the temperature drops and wax crystals precipitate.