Controllers are crucial in catalysis for several reasons: 1. Efficiency: They help in maintaining the reaction conditions at optimal levels, ensuring high efficiency and productivity. 2. Selectivity: Controllers aid in fine-tuning the process to favor the formation of desired products over unwanted by-products. 3. Safety: Proper control systems are essential for maintaining safe operating conditions, especially in exothermic or high-pressure reactions. 4. Consistency: They ensure that the reaction conditions remain consistent over time, which is vital for industrial-scale production.