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低硅/铝比X型(LSX)分子筛通常采用钠钾体系合成,该体系中钠钾比例及总碱度是合成纯相LSX型分子筛的2个关键条件。采用两步水热法在钠钾体系中,引入碱性较弱的Na_2CO_3作为第2钠源,辅助NaOH合成LSX型分子筛进行考察,旨在对体系钠钾含量及碱度进行精细调变。采用XRD、FT-IR、SEM、Raman光谱和化学分析等手段对LSX型分子筛样品的晶体结构和物化性能进行了表征。结果表明,以Na_2CO_3和NaOH为双钠源,当n(Na_2CO_3)/n(Na_2O)=0.5时,在n(H_2O)/n(NaK)=11~16比值范围内均可以合成出纯相LSX型分子筛。与NaOH单钠源相比,使用Na_2CO_3辅助合成LSX型分子筛可以有效拓宽其合成配比中n(H_2O)/n(NaK)的比值范围,降低LSX型分子筛的合成难度。
Low silicon / aluminum ratio X-type (LSX) molecular sieves are usually synthesized by the sodium-potassium system. The sodium-potassium ratio and the total alkalinity in the system are two key conditions for synthesizing the pure phase LSX molecular sieve. A two-step hydrothermal method was adopted to introduce Na_2CO_3 with weaker alkalinity into the sodium-potassium system as the second sodium source to aid the synthesis of LSX-type molecular sieve by NaOH. The aim was to finely tune the sodium and potassium content and alkalinity of the system. The crystal structure and physicochemical properties of LSX zeolite samples were characterized by XRD, FT-IR, SEM, Raman spectroscopy and chemical analysis. The results showed that the pure phase LSX could be synthesized in the range of n (H_2O) / n (NaK) = 11 ~ 16 with n (Na_2CO_3) / n Molecular sieve. Compared with NaOH monosodium source, the use of Na_2CO_3 aided synthesis of LSX zeolite can effectively broaden the ratio of n (H_2O) / n (NaK) in the synthesis ratio and reduce the difficulty of synthesizing LSX zeolite.