Effects of pseudoboehmite on catalytic behaviors of hydroisomerization catalyst
Zhang Fang, Wang Yongli, Lü Hongan, He Guanwei*
Xi’an Origin Chemical Technologies Co.,Ltd.,Xi’an 710061,China
Abstract
The effects of three types of pseudoboehmite with different pore structure on the physicochemical properties and wax catalytic hydroisomerization behaviors of the isomerization catalyst were investigated in this paper.The physicochemical properties of the pseudoboehmite and corresponding catalysts were characterized by XRD,BET,FT-IR and NH3-TPD.The behaviors of the catalysts were tested in a fixed bed reactor.The results showed that the three types of pseudoboehmite had the same phase.The catalyst prepared from the pseudoboehmite with stronger hydroxyl peak strength and solubility possessed the largest specific surface area and pore volume,the weakest acidity,and the best performance for wax hydroisomerization,producing lubricant base oil with pour point of lower than -30 ℃ and viscosity index of over 180,which met the requirement of high quality lubricant base oil.
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ZSM-22 and ZSM-23 zeolites were synthesized via conventional hydrothermal methods. Then，two kinds of catalysts contained aforementioned molecular sieves were prepared respectively. The typical structure and acidity of molecular sieves and catalysts were characterized by using XRD，SEM，NH3-TPD and Py-IR. Then the hydroisomerization performance of these catalysts was studied in a continuous down-flow fixed bed，a stainless steel tubular reactor，where n-dodecane was chosen as the probe molecule. The reaction results indicated that the activity of the catalysts mainly depended on their acid quantity，acid intensity and acid distribution. ZSM-22 zeolite based catalyst with the relative higher amount of weak and mild acid sites exhibited better hydroisomerization selectivity than ZSM-23 zeolite based catalyst.
采用机械混合法在H-ZSM-5分子筛中添加不同氧化物粘结剂,考察其对甲醇制烯烃(MTO)催化反应性能的影响,并采用x射线衍射(XRD)、氨气-程序升温脱附(NH3-TPD)实验、傅立叶红外光谱(FT-IR)和热重(TG)分析表征催化剂结构.结果表明:在H-ZSM-5中分别添加不同的氧化物粘结剂SiO2,γ-Al2O3和Kaolin(H-ZSM-5和氧化物质量比2∶1),在催化剂1 g,CH3OH与N2物质的量之比1∶4,催化剂质量与原料流速之比(W/F)为10(g·h)/mol,反应压力0.1 MPa和反应温度723 K的条件下,反应3 h,甲醇转化率为100%;与H-ZSM-5相比,烯烃产物分布发生了变化,添加SiO2使C3=选择性下降,添加γ-Al2O3使C1选择性增加,添加Kaolin使C3=选择性增加,同时添加Kaolin与SiO2(Kaolin和siO2质量比2∶1)的H-ZsM-5具有最高的C2=～C4=选择性,其中C3=选择性为38%.添加氧化物降低了催化剂的总酸量,反应11 h前后催化剂的物相没有发生明显变化,积炭不明显. Abstract： Some catalysts were prepared from H-ZSM-5 molecular sieve and different oxide binders by mechanical mixture method. The effects of binders on the catalytic activity for methanol to olefins (MTO) were investigated and the structural of catalysts were characterized by means of X-ray diffraction spectrum (XRD), temperature-programmed desorption (NH3-TPD), Fourier transformed infrared spectroscopy (FT-IR) and thermogravimetric analysis (TG). The results showed that the conversion of methoal reached 100% after reaction 3 h over the catalysts with different binders SiO2,γ-Al2O3 or Kaolin (mass fraction of H-ZSM-5 molecular sieve to binder 2∶1) under the conditions of calatlyst 1 g, molar ratio of CH3OH to N21∶4, ratio of catalyst mass and feed flow (W/F) 10(g·h)/mol,reaction pressure 0.1 MPa and reaction temperature 723 K. Compared with H-ZSM-5 molecular sieve,the distribution of products was different over H-ZSM-5 molecular sieve with different binders, and the selectivity of C3= decreased over H-ZSM-5 molecular sieve with SiO2, the selectivity of C1 increased over H-ZSM-5 molecular sieve with γ-Al2O3, the selectivity of C3= increased over H-ZSM-5 molecular sieve with Kaolin and the selectivity of C2= -C4= reached the highest and the selectivity of C3= reached 38% over H-ZSM-5 molecular sieve with Kaolin and SiO2 (2∶1 of mass fraction of Kaolin to SiO2).The total acid amount of the catalyst decreased due to the addition of oxide binders.H-ZSM-5 molecular sieve catalyst and the phase did not change obviously and the carbon deposit was not remarkable.
严加松, 龙军, 苏毅, 等. 黏结剂对FCC催化剂孔结构的影响[J]. 工业催化, 2012, 20(9): 51-55. YanJiasong, LongJun, SuYi, et al. Effect of the binders on the pore structure of FCC catalysts[J]. Industrial Catalysis, 2012, 20(9): 51-55.
