A Fixed Bed Reactor is a type of chemical reactor where solid catalyst particles are packed in a stationary bed. Reactants flow through this bed, allowing chemical reactions to occur as they contact the catalyst. This design is commonly used in processes like catalytic cracking and hydrogenation. The main advantage of fixed bed reactors is their simplicity and ease of operation. They are often more efficient for reactions that require a solid catalyst, as the fixed bed allows for better control of temperature and pressure. However, they can face challenges like catalyst deactivation and uneven flow distribution over time.