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生物质合成气一步法合成LPG的实验研究
由生物质气化合成液体燃料(甲醇、二甲醇和低碳烃类),是理想的碳中性绿色燃料,将其用作城市交通和民用燃料,已经引起全世界的广泛关注.[1,2]...
2020-09-30 09:14:00浏览：46
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Effects of ammonium exchange and Si/Al ratio on the conversion of methanol to propylene over a novel
One type of ZSM-5 zeolite with large partical size was prepared and characterized by XRD, SEM, N2 adsorption-desorption, XRF, Py-IR and NH3-TPD techniques. Effects of ammonium exchange and SiO2/Al2O3 molar ratios on the reaction of methanol to propylene (MTP) over Na-ZSM-5 and H-ZSM-5 zeolites have been studied in a fixed-bed flow reactor under the operating conditions of T = 500 ℃, P = 1 atm,and WHSV = 6 h-1. Ammonium exchange led to a rapid decrease in Na content for Na-ZSM-5 zeolite. The reaction results indicated that Na-ZSM-5 and H-ZSM-5 with different SiO2/Al2O3 molar ratios all exhibited high activity for methanol conversion. Ammonium exchange and the decreased SiO2/Al2O3 molar ratio of ZSM-5 zeolite led to an increase both in strong acid sites and weak acid sites. Na-ZSM-5 with high SiO2/Al2O3 molar ratio was favorable for the formation of propylene. The highest propylene selectivity (45.9%) was obtained over Na-ZSM-5 zeolite catalyst with SiO2/Al2O3 molar ratio of 220....
2020-07-08 21:52:19浏览：103
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Para-Xylene Maximization Part VIII: Promotion of H-ZSM-5 Zeolite by Pt and HF Doping for Use as Cata
Toluene was alkylated with methanol in a flow type reactor at temperatures between 300 and 500℃ using H-ZSM-5 zeolite, 0.2%Pt/H-ZSM-5 and hydrofluorinated 0.2%Pt/H-ZSM-5 with HF concentrations of 1.0%, 2.0%, 3.0%, or 4.0%. Pt primarily enhances toluene conversion, total xylenes production, and p-xylene relative to its thermodynamic equilibrium. As the concentration of HF increases from 1.0% to 3.0%, the catalyst activity increases because of the increase in the number of acid sites and their strength. Additionally, the surface area and Pt dispersion also increases. An advantage of increased HF doping is that the formation of voluminous trimethylbenzene (TMB) byproducts is inhibited. However, at a HF concentration of 4.0%, AI and Si are partially leached and then deposited mostly in the wider catalytic pores. This was determined by evaluating the pore volume distribution and we determined that reactivity inhibition was ob-viously present and was due to diffusion restriction....
2020-07-08 21:52:19浏览：88
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In-situ Synthesis of ZSM-5 Zeolite from Metakaolin/Spinel and Its Catalytic Performance on Methanol
ZSM-5 zeolite was in-situ synthesized from metakaolin or spinel by incorporating additional silica and alumina sources, respectively. The ZSM-5 zeolite was characterized by X-ray diffractometry (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy and N2 adsorption measurement. This supported zeolite was tested on the methanol to propylene (MTP) processes. Experimental results showed that the ZSM-5 zeolite exhibited high selectivity for propylene. The yield of propylene on ZSM-5 zeolite made from metakaolin was increased by 17.73%, while that on ZSM-5 zeolite made from spinel was raised by 9.90%, compared to that achieved with the commercial ZSM-5 zeolite. The significant increase in propylene production is probably due to the distinctive morphology of the ZSM-5 zeolite, which possessed a rough external surface covered with sphere-like particles and distribution of small crystals sized at around 400-500 nm. This morphology could help to generate more crystal defects so that more active centers could be exposed to the reaction mixture. In addition, the zeolite product had a gradient pore distribution and many medium Bronsted acid sites, both of which might also contribute to the increased propylene production....
2020-07-08 21:52:19浏览：72
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Study on the deactivation and regeneration of the ZSM-5 catalyst used in methanol to olefins
ZSM-5 zeolite catalyst modified by a trace of metal cations shows high activity and high selectivity for the reaction of methanol to olefins (MTO), but it inclines to deactivate during the reaction. In this paper, the mechanism of the catalyst deactivation and the regeneration method were studied by X-ray diffraction (XRD), N2 adsorption-desorption, infrared spectra (IR), and infrared spectra coupled with NH3 molecular probes (IR-NH3). These characterizations indicated that coke formation was the main reason for the catalyst deactivation. To regenerate the deactivated catalyst, two methods, i.e., calcination and methanol leaching, were used. N2 adsorption-desorption, IR and IR-NH3 characterizations showed that both methods can eliminate coke deposited on the catalyst and make the catalyst reactivated. XRD showed that the structure of the catalyst did not change after regeneration. Interestingly, the regenerated catalyst even showed better catalytic performance of the MTO reaction than the fresh one. Besides, the calcination regeneration can eliminate coke more completely, however, the methanol leaching method can be more easily carried out in situ in the reactor....
2020-07-08 21:52:19浏览：76
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Effect of water on the performance of Pd-ZSM-5 catalysts for the combustion of methane
Palladium-based catalysts were prepared using impregnation (I) and ion-exchange method (E) with ZSM-5 as support. Pd-ZSM-5(I) and Pd-ZSM-5(E) catalysts presented the high activity for the combustion of methane. The order of activity was consistent with Br0nsted acidity of the catalysts: Pd-ZSM-5(I)＞Pd-ZSM-5(E). It was shown by FT-IR that methane was adsorbed on the acidic bridging hydroxyl groups of ZSM-5-supported Pd catalysts. The effect of water on the activity of Pd-ZSM-5 was investigated. The inhibition effect of water on the conversion of methane was observed. However, water promoted the stability of Pd-ZSM-5 obviously during extended time periods. XPS measurement showed that Pd/Si ratio near the surface of Pd-ZSM-5(E) decreased more pronouncedly with time in dry stream than that of Pd-ZSM-5(I), this is attributed to the dispersion of Pd into the micropores. The addition of water, however, retarded Pd dispersion. And high partial pressure of methane reduced this effect of water vapor. The decrease in activity during the stability test can be explained on the basis of the reduction of Pd/Si ratio....
2020-07-08 21:52:19浏览：59
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低温合成HZSM-5分子筛上甲醇制丙烯反应性能
分别在不同温度下(180℃和120℃)水热合成了HZSM-5分子筛,并采用x射线衍射、扫描电子显微镜、N2低温物理吸附方法对分子筛进行了表征.表征结果显示,低温合成的分子筛晶粒较小,表面粗糙且有微晶晶粒；其比表面积、孔容和孔直径均较高温合成样品大.在常压、440℃以及甲醇质量空速为4.0h-1反应条件下,在固定床反应器上考察了HZSM-5分子筛的甲醇制丙烯(MTP)反应性能.评价结果表明,低温合成的HZSM-5分子筛用于MTP反应具有高的丙烯选择性(45.85％)和丙烯/乙烯质量比(4.08)....
2020-06-12 15:50:55浏览：1422
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甲醇制芳烃反应的研究进展
简单介绍了甲醇制芳烃（MTA）目前所面临的困难，以及 MTA 反应所适用的催化剂 ZSM-5及其优势。指出以 HZSM-5做催化剂时,MTA 反应的最优化反应条件，并综述了国内外目前对于 ZSM-5催化剂的几种改性方法。并提出适用 MTA 的催化剂的开发方向。...
2020-06-12 14:49:36浏览：1454
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低温合成HZSM-5分子筛上甲醇制丙烯反应性能
分别在不同温度下(180℃和120℃)水热合成了HZSM-5分子筛,并采用x射线衍射、扫描电子显微镜、N2低温物理吸附方法对分子筛进行了表征.表征结果显示,低温合成的分子筛晶粒较小,表面粗糙且有微晶晶粒；其比表面积、孔容和孔直径均较高温合成样品大.在常压、440℃以及甲醇质量空速为4.0h-1反应条件下,在固定床反应器上考察了HZSM-5分子筛的甲醇制丙烯(MTP)反应性能.评价结果表明,低温合成的HZSM-5分子筛用于MTP反应具有高的丙烯选择性(45.85％)和丙烯/乙烯质量比(4.08)....
2020-03-24 07:51:11浏览：1416
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ZSM-5/磷酸铝复合分子筛在甲醇制烯烃反应中的应用
水热体系中将ZSM-5添加到磷酸铝分子筛的合成液中,制得了ZSM-5/磷酸铝复合分子筛催化剂,采用XRD、SEM、FT-IR和NH3-TPD方法表征其物化性能,同时考察了该复合分子筛对甲醇制烯烃反应的催化活性.结果表明,制备的分子筛为ZSM-5/磷酸铝复合分子筛,磷酸铝分子筛中含有AlPO4-5与AlPO4-18 2种晶相；与纯ZSM-5分子筛相比,复合分子筛的酸性明显减弱且酸量减少.与ZSM-5和ZSM-5+磷酸铝分子筛机械混合样品相比,ZSM-5/磷酸铝复合分子筛表现出了良好的协同作用和优良的催化性能,在甲醇转化率为100％情况下,总低碳烯烃、乙烯和丙烯选择性分别为83.5％、36.5％和36.0％,产物中C2～C4烷烃以及C5+选择性较低....
2020-03-23 17:46:44浏览：1443
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甲醇制烯烃用ZSM-5分子筛的研究进展
综述了甲醇制烯烃用ZSM-5分子筛催化剂的研究进展，包括甲醇制低碳烯烃的合成机理、ZSM-5分子筛的结构与酸性对合成低碳烯烃性能的影响以及分子筛的改性。重点探讨了ZSM-5分子筛的改性（如水热处理改性、磷改性、氟改性、硼改性、金属离子改性及其他化学改性）对催化剂表面酸性和孔径、低碳烯烃选择性和催化剂稳定性的影响，指出分子筛孔径/表面酸性的调控和 MTO/MTP反应机理的研究是甲醇制低碳烯烃催化剂研究的发展方向。...
2020-03-23 17:42:27浏览：1434
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甲醇制烯烃催化剂研究进展
综述了甲醇制烯烃催化剂的研究进展，从晶体结构、改性方法、催化性能等方面分析了两种重要的甲醇制烯烃催化剂ZSM-5和SAPO-34；并介绍了由上述分子筛开发出的ZSM-5／磷酸铝复合分子筛。...
2020-03-23 17:42:03浏览：1422
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汽油降烯烃催化剂表征及反应性能评价
采用改性超细ZSM-5沸石基分子筛催化剂处理高烯DCC汽油可使烯烃体积分数降低46%,苯体积分数降低66%,同时保持辛烷值不降低;处理后油品各项指标完全满足国家标准的要求. 该催化剂具有良好的运转稳定性和再生反应性能,有良好的工业应用前景....
2020-03-23 17:41:35浏览：1417
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甲醇制芳烃反应的研究进展
简单介绍了甲醇制芳烃（MTA）目前所面临的困难，以及 MTA 反应所适用的催化剂 ZSM-5及其优势。指出以 HZSM-5做催化剂时,MTA 反应的最优化反应条件，并综述了国内外目前对于 ZSM-5催化剂的几种改性方法。并提出适用 MTA 的催化剂的开发方向。...
2020-03-17 17:39:39浏览：1453
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