The Synthesis Of N,N-diethyl-2,6-diemethyl-piperidinium And Its Application In The Preparation Of SSZ-39 Molecular Sieve

N,N-diethyl-2,6-dimethyl-piperidinium quaternary ammonium salt(DEDMPI)and quaternary ammonium base(DEDMPOH)are widely used in the fields of industry,agriculture and medicine.SSZ-39 molecular sieve synthesized with DEDMPI and DEDMPOH as template agent has good catalytic performance in MTO and SCR processes.The main work of this paper is to select suitable process routes to synthesize and separate DEDMPI,and further prepare DEDMPOH by DEDMPI.The applications of DEDMPI and DEDMPOH in the preparation of SSZ-39 molecular sieve were also studied.DEDMPI was synthesized in one step using 2,6-dimethyl-piperidine and iodoethane in the ethanol solvent,and potassium bicarbonate as acid binding agent.The single factor experiments and response surface analysis method were used to optimize the synthesis process.The optimized process conditions were as follows:the reaction time 64 h,reaction temperature56?and reactant molar ratio 3.7:1.Under the optimized reaction conditions,the maximum yield of product was 68.31%.The product was characterized by FI-IR,1H-NMR,ESI-MS and SEM-EDS.And the results showed that the product was the target product.In the separation of products,DEDMPI was obtained by the separation method of filtration,vacuum distillation and concentration,and diethyl ether recrystallization.The reaction mechanism was analyzed as S_N2.And the main role of acid-binding agent potassium hydrogen carbonate is "eliminating hydrogen and precipitating iodine".DEDMPOH was prepared using DEDMPI by column-type ion-exchange method.The better process conditions were:Amberlite IR-78 resin as ion exchange resin,DEDMPI solution mass fraction 30%,and 6%NaOH solution as regenerant.Under this condition,the exchange degree was 92.3%and the DEDMPOH solution mass fraction was 21.7%.In the preparation of molecular sieves,AEI molecular sieves were synthesized by precrystallizing and recrystallization by two stages crystallization.The preferred silicon source and aluminum source are silica sol and Y type molecular sieves,and DEDMPOH template can be used to prepare SSZ-39 molecular sieves.The alkalinity of the gel affects the molecular sieve type.The prolongation of crystallization time will transform the molecular sieve from the MOR crystal to the AEI crystal.