纳米ZSM-5微波辅助水热合成及结构性质研究
发布时间：2019-03-18 11:35
【摘要】：纳米ZSM-5分子筛的制备通常采用常规水热合成法,传统的加热方式容易使反应物料产生外高内低的温度梯度,造成加热不均匀、合成时间较长、晶化温度较高、成本较高等问题,并且合成产物易团聚、平均粒径较大(≥100 nm)、粒径分布较宽。鉴于此,本课题根据微波辐射加热具有能耗低、速度快、加热均匀等特点,采用微波辅助水热合成法制备纳米ZSM-5分子筛,考察不同合成因素对纳米HZSM-5分子筛和纳米NaZSM-5分子筛结构性质的影响,并对纳米ZSM-5分子筛的MTO催化性能和工艺条件进行研究。采用微波辅助水热合成在较温和的条件下直接制备了纳米HZSM-5分子筛,借助XRD、FT-IR、SEM、BET和NH_3-TPD等表征手段,考察了铝源种类、模板剂用量、水量、晶化时间、晶化温度和老化温度对HZSM-5分子筛的结构性质的影响。结果表明:以异丙醇铝(AIP)为铝源,按原料摩尔配比n(SiO_2):n(Al_2O_3):n[(TPA)_2O]:n(H_2O)=300:1:37.5:1500,设定老化温度80℃,在短时间(晶化时间1.5 h)内于较温和的条件下(晶化温度160℃)合成了纳米HZSM-5分子筛,其微观形貌为球形,分散程度较好、粒径较均一且较小(约60nm);同时具有微孔、介孔结构和较大的比表面积(398.45 m~2·g~(-1))、孔容(0.63 cm~3·g~(-1))和平均孔径(6.27nm);晶体表面具有弱酸特征。采用微波辅助水热合成法在较温和的条件下制备了纳米NaZSM-5分子筛,借助XRD、SEM、BET和NH_3-TPD等表征手段,考察了模板剂种类和用量、钠源种类和用量对NaZSM-5分子筛的结构性质的影响。结果表明:以四丙基氢氧化铵(TPAOH)和氢氧化钠(NaOH)为模板剂和钠源,按原料摩尔配比n(SiO_2):n(Al_2O_3):n[(TPA)_2O]:n(H_2O):n(Na_2O)=300:1:37.5:1500:15,合成了纳米NaZSM-5分子筛,其微观形貌为球形,分散程度较好、粒径较均一、平均粒径较小(约30nm);同时具有微孔、介孔结构和较大的比表面积(419.64m~2·g~(-1))、孔容(0.68cm~3·g~(-1))和最小平均孔径(3.83nm),晶体表面具有弱酸特征。采用管式固定床评价装置,借助气相色谱等分析手段,对纳米ZSM-5分子筛的MTO催化性能及工艺条件进行研究,结果表明,30 nm的NaZSM-5分子筛(Na-30)在MTO反应中具有最优的催化性能,其甲醇转化率、低碳烯烃选择性和收率可分别达到97.56%、73.18%、71.39%,其适宜的MTO催化反应条件为反应温度360℃,进料空速为1.5 h~(-1),N_2流量为15 ml·min~(-1)。
[Abstract]:The preparation of the nanometer ZSM-5 molecular sieve generally adopts a conventional hydrothermal synthesis method, the traditional heating mode is easy to lead the reaction material to generate a temperature gradient with low internal temperature, the heating is not uniform, the synthesis time is long, the crystallization temperature is high, the cost is higher, and the synthetic product is easy to be agglomerated, The average particle size is larger (about 100 nm), and the particle size distribution is wider. In view of this, the nano-ZSM-5 molecular sieve was prepared by microwave-assisted hydrothermal synthesis, and the effect of different synthesis factors on the structure properties of the nano-HZSM-5 molecular sieve and the nano-NaZSM-5 molecular sieve was investigated by microwave-assisted hydrothermal synthesis. The MTO catalytic performance and process conditions of the nano-ZSM-5 molecular sieve were studied. The nano-HZSM-5 molecular sieve was prepared by microwave-assisted hydrothermal synthesis under mild conditions, and by means of XRD, FT-IR, SEM, BET and NH _ 3-TPD, the type of aluminum source, the amount of template agent, the amount of water and the crystallization time were investigated. The effect of crystallization temperature and aging temperature on the structural properties of HZSM-5 molecular sieve. The results showed that Al _ 2O _ 3: n[(TPA) _ 2O]: n (Al _ 2O _ 3): n[(TPA) _ 2O]: n (Al _ 2O _ 3): n[(TPA) _ 2O]: n (H _ 2O) = 300:1: 37.5:1500, the aging temperature was 80 鈩，
本文编号：2442826
[Abstract]:The preparation of the nanometer ZSM-5 molecular sieve generally adopts a conventional hydrothermal synthesis method, the traditional heating mode is easy to lead the reaction material to generate a temperature gradient with low internal temperature, the heating is not uniform, the synthesis time is long, the crystallization temperature is high, the cost is higher, and the synthetic product is easy to be agglomerated, The average particle size is larger (about 100 nm), and the particle size distribution is wider. In view of this, the nano-ZSM-5 molecular sieve was prepared by microwave-assisted hydrothermal synthesis, and the effect of different synthesis factors on the structure properties of the nano-HZSM-5 molecular sieve and the nano-NaZSM-5 molecular sieve was investigated by microwave-assisted hydrothermal synthesis. The MTO catalytic performance and process conditions of the nano-ZSM-5 molecular sieve were studied. The nano-HZSM-5 molecular sieve was prepared by microwave-assisted hydrothermal synthesis under mild conditions, and by means of XRD, FT-IR, SEM, BET and NH _ 3-TPD, the type of aluminum source, the amount of template agent, the amount of water and the crystallization time were investigated. The effect of crystallization temperature and aging temperature on the structural properties of HZSM-5 molecular sieve. The results showed that Al _ 2O _ 3: n[(TPA) _ 2O]: n (Al _ 2O _ 3): n[(TPA) _ 2O]: n (Al _ 2O _ 3): n[(TPA) _ 2O]: n (H _ 2O) = 300:1: 37.5:1500, the aging temperature was 80 鈩，
本文编号：2442826
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