Deactivation and regeneration on the ZSM-5-based catalyst for the synthesis of pyridine and 3-picoline

The deactivation and regeneration of the ZSM-5-based catalyst was investigated in the reaction of acrolein diethyl acetal and ammonia toward pyridine and 3-picoline. The coke was the main reason leading to deactivation for all the tested catalysts, and it was basically combusted at high temperature under the air and water streams in order to recover the initial catalytic performance. The best catalyst through the reaction-regeneration treatment could effectively promote the formation of pyridine and 3-picoline. The results showed that the total yield of pyridine and 3-picoline was raised above 20% while the reaction was operated the 10th reaction-regeneration cycle relative to the 1st reaction at TOS (time on stream) = 1-3 h. The catalysts were characterized by means of XRD, N-2-physisorption, FT-IR and NH3-TPD techniques. By relating the performance and structure of the catalyst, it was found that the dealumination and the residual coke were responsible for boosting the catalytic activity after several reaction-regeneration cycles. The dealumination generated more mesopores and less acidity while the residual coke resulted in lowering the acidity. The relationship between the catalyst and the regeneration was well established. (C) 2016 Elsevier Inc. All rights reserved.