Comparative Study of the Physicochemical Properties of Petroleum Products Sold in the Republic of Congo: The Case of Lubricants

Petroleum products play a vital role in global economic development and are fundamental to numerous industries as well as daily life. They are commonly used in transportation (as fuels) and in the petrochemical industry for the production of first- and second-generation synthesis intermediates. The most common petroleum products include gasoline, diesel fuels, liquefied petroleum gases (LPG), and lubricants. These products must meet sales standards and specifications to ensure optimal performance and environmental compliance. This study focuses exclusively on lubricants. Among the key properties required for petroleum products are: the octane number for gasoline, the cetane index for diesel, flash point, freezing point, density, vapor pressure, viscosity, and volatility. However, this study concentrates solely on the physicochemical properties of lubricants. Specifically, it investigates their density, relative density, viscosity, and pH which constitute the main objective of this research. The quantities analyzed were measured using standard laboratory equipment such as a precision balance, test tubes, pH paper, and a Hoppler-type viscometer (ball viscometer). All lubricant samples were collected from fuel stations and various informal vendors in Brazzaville, Republic of Congo. The results of the analyses indicate that lubricants sold at fuel stations are denser than those sold by informal vendors. Furthermore, station-sold lubricants are typically yellow in color, while those from informal sources range from light yellow to pink, and tend to exhibit slightly less stable viscosity levels.