發(fā)布時(shí)間：2019-03-18 11:35

【摘要】：納米ZSM-5分子篩的制備通常采用常規(guī)水熱合成法,傳統(tǒng)的加熱方式容易使反應(yīng)物料產(chǎn)生外高內(nèi)低的溫度梯度,造成加熱不均勻、合成時(shí)間較長(zhǎng)、晶化溫度較高、成本較高等問(wèn)題,并且合成產(chǎn)物易團(tuán)聚、平均粒徑較大(≥100 nm)、粒徑分布較寬。鑒于此,本課題根據(jù)微波輻射加熱具有能耗低、速度快、加熱均勻等特點(diǎn),采用微波輔助水熱合成法制備納米ZSM-5分子篩,考察不同合成因素對(duì)納米HZSM-5分子篩和納米NaZSM-5分子篩結(jié)構(gòu)性質(zhì)的影響,并對(duì)納米ZSM-5分子篩的MTO催化性能和工藝條件進(jìn)行研究。采用微波輔助水熱合成在較溫和的條件下直接制備了納米HZSM-5分子篩,借助XRD、FT-IR、SEM、BET和NH_3-TPD等表征手段,考察了鋁源種類、模板劑用量、水量、晶化時(shí)間、晶化溫度和老化溫度對(duì)HZSM-5分子篩的結(jié)構(gòu)性質(zhì)的影響。結(jié)果表明:以異丙醇鋁(AIP)為鋁源,按原料摩爾配比n(SiO_2):n(Al_2O_3):n[(TPA)_2O]:n(H_2O)=300:1:37.5:1500,設(shè)定老化溫度80℃,在短時(shí)間(晶化時(shí)間1.5 h)內(nèi)于較溫和的條件下(晶化溫度160℃)合成了納米HZSM-5分子篩,其微觀形貌為球形,分散程度較好、粒徑較均一且較小(約60nm);同時(shí)具有微孔、介孔結(jié)構(gòu)和較大的比表面積(398.45 m~2·g~(-1))、孔容(0.63 cm~3·g~(-1))和平均孔徑(6.27nm);晶體表面具有弱酸特征。采用微波輔助水熱合成法在較溫和的條件下制備了納米NaZSM-5分子篩,借助XRD、SEM、BET和NH_3-TPD等表征手段,考察了模板劑種類和用量、鈉源種類和用量對(duì)NaZSM-5分子篩的結(jié)構(gòu)性質(zhì)的影響。結(jié)果表明:以四丙基氫氧化銨(TPAOH)和氫氧化鈉(NaOH)為模板劑和鈉源,按原料摩爾配比n(SiO_2):n(Al_2O_3):n[(TPA)_2O]:n(H_2O):n(Na_2O)=300:1:37.5:1500:15,合成了納米NaZSM-5分子篩,其微觀形貌為球形,分散程度較好、粒徑較均一、平均粒徑較小(約30nm);同時(shí)具有微孔、介孔結(jié)構(gòu)和較大的比表面積(419.64m~2·g~(-1))、孔容(0.68cm~3·g~(-1))和最小平均孔徑(3.83nm),晶體表面具有弱酸特征。采用管式固定床評(píng)價(jià)裝置,借助氣相色譜等分析手段,對(duì)納米ZSM-5分子篩的MTO催化性能及工藝條件進(jìn)行研究,結(jié)果表明,30 nm的NaZSM-5分子篩(Na-30)在MTO反應(yīng)中具有最優(yōu)的催化性能,其甲醇轉(zhuǎn)化率、低碳烯烴選擇性和收率可分別達(dá)到97.56%、73.18%、71.39%,其適宜的MTO催化反應(yīng)條件為反應(yīng)溫度360℃,進(jìn)料空速為1.5 h~(-1),N_2流量為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，

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