How do primary chemical products differ from secondary and tertiary chemical products?

In the chemical industry, the distinction between primary, secondary, and tertiary products is based on their proximity to the ultimate consumer.1

• Primary products: These are the most remote from the consumer. They are typically derived directly from raw materials—such as fossil fuels, air, water, salt, and sulfur—and serve as the foundational building blocks for further manufacturing.1
• Secondary and tertiary products: These represent successive stages of processing. A defining characteristic of the chemical industry is that its products rarely reach the end user in their initial form; instead, they are often passed between factories multiple times, undergoing further chemical transformation at each stage.1

Because of this structure, the chemical industry is frequently described as its own best customer, as the output of one process becomes the essential input for the next.1