Synthesis And Characterization Of Nano-zeolite NaY

Nano-zeolite NaY have larger outer surface, more acidic sites, morecatalytic active center, short regular pore structure and high intragranulardiffusion rate, in terms of enhancing the transforming capability ofmacromolecule, improving the utilization rate of catalysts, reducing the amountof secondary cracking products, reducing the depth of the reaction, andimproving selectivity and reducing the coked catalyst deactivation andanti-sulfur, nitrogen and heavy metals pollution and other aspects show moresuperior performance than conventional grain size of NaY, having a broadapplication prospect in the field of the FCC catalyst. Therefore, to synthesisnano-zeolite NaY with good performance has an important industrial applicationvalue.Nanosized NaY zeolite molecular sieves with high crystallinity weresuccessfully synthesized using industrial grade sodium silicate as silica sourcewithout the presence of template or directing agent under conditions of dynamichydrothermal method. The influence of Na2O/Al2O3、SiO2/Al2O3、H2O/Al2O3、Aluminum sulfate acidity, initial gel staying temperature and time, gelationcrystallization temperature and time in the synthesis system on the grain size ofzeolite NaY were investigated by XRD, FTIR, SEM, Particle size analyzer, N2adsorption-desorption, ICP,29Si and27Al NMR. The results showed that with theincrease of Na2O/Al2O3not only decrease the grain size of zeolite NaY,but also reduce its crystallinity and skeleton silica alumina ratio, and it will lead tozeolite NaY transform to P-type zeolite if Na2O/Al2O3≥17; With theSiO2/A12O3ratio was increased, the grain size of the molecular sieve productwas gradually increased, while framework silica to alumina ratio andcrystallinity were higher. Reducing the H2O/Al2O3promoted the formation ofsmall NaY crystals, but once H2O/Al2O3≤240, there will be generate P-typeimpurity crystals. Molecular sieve grainsize,crystallinity and skeleton silicaalumina ratio decreased with the loss of the aluminium sulfate acidity, but toolower acidity would lead to form P type zeolite. The average particle of zeoliteNaY decreased with the increase of temperature of initial gel,when thetemperature increased to70℃, zeolite NaY had been transformed into P-typezeolite. With the extension of the initial gel aging time, the particle size of NaYwere gradually reduced,and if the aging time was extended to5h, there will beform P-type zeolite. Extend the crystallization time is not conducive to theformation of small grains molecular sieve; improving the crystallizationtemperature could accelerate the crystallization rate, but meanwhile the zeoliteparticle size became larger, so choose the crystallization temperature at90℃.The nanosized zeolite NaY with high crystallinity of a narrow particle sizedistribution with the average diameter about80nm were synthesized byoptimizing the synthesis condition: the initial gel molar ratio was16Na2O:Al2O3:15SiO2:360H2O, aluminum sulfate acidity was1.150mol/L, gel stayingtemperature was65℃, staying time was4h, crystallization temperature was90℃, crystallization time was24h,and were compared with conventionalindustrial zeolite NaY.Studied the different additives on the influence of dispersed state ofsynthesized nano-zeolite NaY. Experimental results showed that a small amount of ethanol was added did play a role in the dispersion, NaCl was added to reducethe particle size and silica alumina ratio of the synthesized NaY zeolite, but didnot have the effect of dispersant.It indicated that join in the surfactants OACcould synthesize molecular sieve with uniform particle size distribution,aggregation of small degree, high crystallinity. The addition of JEM did notreduce the degree of aggregation of synthesized molecular sieve. Adding MESreduced the degree of agglomeration of molecular sieve, but the size was aslightly larger. Join in SDS or AOS had no influence on the particle size ofmolecular sieve and agglomeration nor slowing; Adding the surfactant and NaClsimultaneously reduced the grain size of the molecular sieve, but the particlesize distributionwas wider and more uneven.