What is hydro-treating?

Hydro-treating is primarily defined as a method that utilizes hydrogen in a chemical process to remove impurities from petroleum products. This process often focuses on contaminants such as sulfur, nitrogen, and other undesirable substances present in crude oil and its derivatives. During hydro-treating, the hydrogen reacts with these impurities under high temperature and pressure, resulting in their conversion to more benign compounds that can be easily separated from the oil. This is essential for producing cleaner fuels and ensuring that products meet regulatory standards for emissions and quality.

The other options mention processes that do not align with the definition of hydro-treating. For instance, carbonizing petroleum products refers to a process of transforming hydrocarbons into carbon-rich substances, which is not related to the removal of impurities. Cooling crude oil implies a temperature manipulation that does not address the quality of the oil in terms of impurities. Lastly, adding sulfur to petroleum products is contrary to the goal of hydro-treating, as it aims to decrease sulfur content rather than increase it. Hence, option B accurately captures the essence of hydro-treating as a vital refining process.