1. Definition and Basic Characteristics of Catalysts
A catalyst is a substance that alters the rate of a chemical reaction by interacting with reactants, without shifting chemical equilibrium or changing final reaction products. Upon completion of the reaction, the catalyst retains its total mass, chemical composition and chemical properties, while its physical properties may alter.
2. Core Performance Indicators of Industrial Catalysts
Industrial catalysts must meet comprehensive performance requirements:
①High catalytic activity and excellent target selectivity to achieve efficient feedstock conversion and suppress side reactions
②Superior activity stability with minimal performance degradation during long-term operation
③Favorable physical structures including specific surface area, pore size and pore volume
④Robust mechanical strength with qualified compression resistance and abrasion resistance
⑤Uniform particle size, particle size distribution and morphology to match reactor loading and fluid operating conditions
3. Selectivity and Stability of Catalysts
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Selectivity
Essentially, a catalyst drastically reduces the activation energy of the main reaction while exerting a weaker reduction effect on the activation energy of side reactions. It is governed by three key factors: intrinsic selectivity determined by reaction mechanism, diffusion selectivity derived from catalyst pore structure, and process selectivity affected by operating parameters such as temperature, pressure and space velocity.
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Stability
Stability is critical for long-cycle catalyst operation, covering thermal stability, chemical stability, coking resistance, mechanical stability and poison resistance. These properties respectively enable the catalyst to withstand high temperatures, chemical deterioration, coke deposition, mechanical abrasion and erosion by toxic impurities in feedstock.
4. Common Industrial Catalytic Reactors
Three major types of catalytic reactors are widely applied in industry:
· Fixed-bed Reactor: Simple structure with stationary catalyst packing, widely adopted for gas-solid reactions such as ammonia synthesis, flue gas desulfurization and hydrocarbon conversion.
· Fluidized-bed Reactor: Catalyst particles are suspended and fluidized by process fluid, delivering uniform mass and heat transfer, ideal for fast reaction systems.
· Moving-bed Reactor: Enables continuous movement and regeneration of catalysts, suitable for industrial processes requiring uninterrupted catalyst renewal and long-term continuous production.