Preparation Of SAPO - 34 Molecular Sieve By Field Energy Assisted Liquid Phase Crystallization

SAPO-34 molecular sieve is the most suitable catalyst of Methanol to Olefins (MTO) process so far for its very high methanol conversion and excellent selectivity of ethylene and propylene. Liquid crystallization method is a new way to synthesize SAPO-34 molecular sieve, which was developed by our own laboratory. However, it also has some disadvantages, such as more time in materials mixing, easily materials agglomeration and longer crystallization time. In this paper, ultrasonic field and microwave field were separately introduced to materials mixing and crystallization process of the preparation of SAPO-34 molecular sieve. Besides, the effected factors in the molecular sieve preparation process were researched.Fisrt, the factors of ultrasonic field used in materials mixing stage of SAPO-34 molecular sieve preparation were researched. The result shows that the optimal preparation condition in mixing stage was ultrasonic power 280 W in 60 ℃-70 ℃ for 80 minutes. In this situation, methanol conversion can reach 96.52%, and the selectivity of ethylene and propylene can be 80.60% in MTO process.Then, the influences on microwave field in crystallization process were studied in SAPO-34 molecular sieve preparation process by liquid crystallization method. The best preparation condition was that microwave power 500 W, in temperature 180 ℃ for 120 minutes, the initial temperature increasing rate 40 ℃/min, and 10 ℃/min after 80 ℃. When the catalyst was used in MTO catalytic reaction, methanol conversion can reach 96.16%and the selectivity of ethylene and propylene can be 79.83%. Optimum ultrasonic conditions and the best condition of microwave preparation of SAPO molecular sieve-34, used for MTO catalytic reaction, the methanol conversion was 96.21%, the selectivity of ethylene and propylene is 79.92%.Finally, the paper also studied microwave crystallization dynamics of microwave assisted in the preparation of SAPO-34 molecular sieve. With the changing of microwave time and temperature, a series of experiments were researched for the changes of crystallization degree of SAPO-34 molecular sieve. And based on the Arrhenius equation, we calculated that after SAPO-34 molecular sieve is treated with microwave crystallization, the crystal nucleation apparent activation energy (En) of is 7.82 kJ · mol-1, and apparent growth activation energy (Eg) is 11.97 kJ·mol-1...