磷改性ZSM-5分子筛及其在催化增产丙烯中的应用研究进展

ZSM-5分子筛具有良好的催化活性和择型性,常被作为催化剂或助剂活性组分广泛应用于丙烯生产过程,但其在高温水热反应过程中存在易失活的问题.使用磷元素对ZSM-5分子筛进行改性能够有效改善其酸性并提高其水热稳定性,进而减少催化剂的失活.综述了磷改性ZSM-5分子筛机理的研究进展,分析了改性方法、改性磷质量分数和分子筛硅铝...     

液相硅沉积对乙醇制乙烯催化剂结构和稳定性的影响

利用XRD、NH3-TPD和TGA等方法考察了硅沉积处理对改性ZSM-5分子筛催化剂晶体结构、酸性和积碳的影响,并评价了处理前后催化剂在乙醇脱水制乙烯反应中的活性和稳定性.结果表明,硅沉积对改性ZSM-5分子筛预处理后,其晶体结构未发生明显变化;催化剂的总酸量有所下降,主要是强酸下降比例为原分子筛的53.7%;催化剂的乙醇转化率和乙烯产率分别维持在98%和90%;其催化活性和稳定性增强,并进一步表明过多的强酸位存留在催化剂上会引起积碳的生成,降低催化剂的稳定性,而硅沉积能除去了分子筛外表面的部分酸位.     

ZSM-5分子筛合成及其改性研究进展

ZSM-5分子筛在化学化工中应用广泛.详细阐述了ZSM-5沸石分子筛的各种合成方法,并介绍了常用的高温水热处理、金属改性和磷改性等改性技术现状及其应用,以及近年来的研究和开发应用最新进展,为ZSM-5分子筛的开发利用提供新的思路.     

用于MTP反应ZSM-5分子筛的磷改性研究

将P改性用于甲醇制丙烯(MTP)反应ZSM-5分子筛的改性研究,以提高丙烯选择性和分子筛活性稳定性。采用XRD、SEM和NH_3-TPD表征催化剂物化性能。对不同硅铝比ZSM-5分子筛P改性研究发现,3种不同硅铝物质的量比(50、150和300)ZSM-5分子筛进行P改性时,在n(P)∶n(Al)=0.5~0.7时,ZSM-5分子筛改性后丙烯选择性和寿命得到提升。研究分子筛晶粒尺寸与P负载量关系时发现,随着分子筛晶粒尺寸的增大,位于分子筛表面的P含量逐渐增加,并且分子筛晶粒越小,最佳的P负载量越小。     

ZSM-5分子筛碱处理的研究进展

ZSM-5分子筛由于其具有稳定的水热性、规整的孔结构、适宜的酸性分布,已经被广泛应用在石油化工领域。最近新兴的碱改性后处理办法是选择性的从分子筛骨架上脱去硅原子,从而在分子筛孔道体系中引入介孔和大孔,通过控制碱改性的条件,保护ZSM-5分子筛原先特有的微孔体系不被完全破坏,从而形成一个具有介微孔孔道梯级分布的ZSM-5分子筛。     

硅钛改性ZSM-5分子筛抑制“反相效应”的探讨

采用SiCl4和TiCl4对ZSM-5分子筛进行改性，考察硅和钛的氯化物改性对分子筛的调变作用，关联甲苯乙醇乙基化反应与表面酸性及孔结构的变化。阐明了能够兼顾调整酸强度和保持孔结构畅通性的改性方法，有助于克服ZSM-5分子筛改性过程中“反相效应”的现象。从试验结果看，ZSM-5分子筛经水蒸气老化处理后，以TiCl4进行改性，能制出对甲苯乙基化具有较高初活性和对位选择性的催化剂。     

碳四烯烃制丙烯催化剂的稳定性

以超细氧化硅为载体,高硅铝比的ZSM-5分子筛为活性组分,挤条制成催化剂,用氧化钙和氧化镧的前驱体化合物改性,分别在800℃焙烧和600℃水蒸汽的条件下进行处理,在500℃、0.1MPa、水与碳四质量比0.2和碳四空速3 h-1的条件下,对催化剂性能进行评价.对成型、改性、水热处理和再生后的催化剂采用BET、NH3-T...     

白炭黑在ZSM-5分子筛工业合成中的应用

将不同比例的白炭黑替代B型硅胶作为固体硅源在水热体系中进行ZSM-5分子筛工业生产,合成质量合格的ZSM-5分子筛晶化料,且加入白炭黑后合成的分子筛晶化料相对结晶度较完全采用B型硅胶合成的分子筛晶化料明显提高。对白炭黑与B型硅胶物质的量比1:1作为固体硅源合成的ZSM-5分子筛晶化料进行改性,结果表明,改性后的成品ZSM-5分子筛质量稳定,理化性能优于100%B型硅胶合成的成品ZSM-5分子筛。     

高温水蒸汽处理对HZSM-5分子筛催化甲醇制丙烯的影响

考察不同硅铝比的HZSM-5分子筛催化剂和经过高温水蒸汽处理后的HZSM-5分子筛催化剂在甲醇制丙烯反应中的催化性能,考察温度和空速对催化反应的影响。结果表明,随着HZSM-5分子筛硅铝比的增加,产物中丙烯选择性增大,可能是分子筛的酸性降低所致;经过高温水蒸汽处理后的HZSM-5分子筛表面酸性降低,提高了催化剂的催化性能。在反应温度450 ℃和空速1.0 h^-1条件下,600 ℃高温水蒸汽处理后的催化剂HT-600的丙烯选择性从改性前的26.8%提高到33.5%。     

乙醇制乙烯催化剂P改性ZSM-5的研究进展

介绍了P改性ZSM-5分子筛中P的来源和ZSM-5分子筛上生物乙醇制乙烯的反应机理(包括未改性ZSM-5分子筛和P改性的ZSM-5分子筛),分别从催化效果和催化剂结构2方面阐述了P改性ZSM-5分子筛的研究进展,介绍了P改性ZSM-5分子筛的微观结构的研究现状.P改性后的ZSM-5催化剂可有效地降低反应温度、提高催化剂...     

Effect of Si/Al ratio on performance of Pt–Sn-based catalyst supported on ZSM-5 zeolite for n-butane conversion to light olefins

The performance of Pt–Sn-based catalyst, supported on ZSM-5 of different Si/Al ratios were investigated for simultaneous dehydrogenation and cracking of n-butane to produce light olefins. The catalysts were characterized by number of physio-chemical techniques including XRF, TEM, IR spectra, NH₃-TPD and O₂-pulse analysis. Increase in Si/Al ratio of zeolite support ZSM-5 significantly increased light olefin's selectivity, while feed conversion decreases due to lower acidity of support. The results indicated that both the n-butane cracking and dehydrogenation activity to light olefin's over Pt–Sn/ZSM-5 samples with increasing Si/Al ratios greatly enhanced catalytic performance. The catalysts were deactivated with time-on-stream due to the formation of carbon-containing deposits. A coke deposition was significantly related to catalyst activity, while at higher Si/Al ratio catalyst the coke precursors were depressed. These results suggested that the Pt–Sn/ZSM-5 catalyst of Si/Al ratio 300 is superior in achieving high total olefins selectivity (above 90 wt.%). The Pt–Sn/ZSM-5 also demonstrates resistance towards hydrothermal treatment, as analyzed through the three successive reaction-regeneration cycles.     

Enhancing the Production of Light Olefins by Catalytic Cracking of FCC Naphtha over Mesoporous ZSM-5 Catalyst

The enhanced production of light olefins from the catalytic cracking of FCC naphtha was investigated over a mesoporous ZSM-5 (Meso-Z) catalyst. The effects of acidity and pore structure on conversion, yields and selectivity to light olefins were studied in microactivity test (MAT) unit at 600 °C and different catalyst-to-naphtha (C/N) ratios. The catalytic performance of Meso-Z catalyst was compared with three conventional ZSM-5 catalysts having different SiO₂/Al₂O₃ (Si/Al) ratios of 22 (Z-22), 27 (Z-27) and 150 (Z-150). The yields of propylene (16 wt%) and ethylene (10 wt%) were significantly higher for Meso-Z compared with the conventional ZSM-5 catalysts. Almost 90% of the olefins in the FCC naphtha feed were converted to lighter olefins, mostly propylene. The aromatics fraction in cracked naphtha almost doubled in all catalysts indicating some level of aromatization activity. The enhanced production of light olefins for Meso-Z is attributed to its small crystals that suppressed secondary and hydrogen transfer reactions and to its mesopores that offered easier transport and access to active sites.     

不同硅铝比ZSM-5分子筛催化剂一步法甲醇制汽油

分别使用硅铝比为26、38、60和90的ZSM-5分子筛原粉制备4种催化剂ZSM-5-26、ZSM-5-38、ZSM-5-60和ZSM-5-90,用于一步法甲醇制汽油实验,并对催化剂进行XRD、IR、BET和NH3-TPD表征。利用100 m L微反固定床实验装置,在反应温度380℃、系统压力2.0 MPa和空速1.0 h-1条件下,考察4种催化剂一步法合成汽油过程的甲醇转化率、产物分布和产品组成等性质。结果表明,ZSM-5-60分子筛催化剂性能相对较好,拥有32.2%较为理想的汽油收率和产物组成。     

Promoting Xylene Production in Benzene Methylation using Hierarchically Porous ZSM-5 Derived from a Modified Dry-gel Route

Methylation of benzene is an alternative low-cost route to produce xylenes, but selectivity to xylene remains low over conventional zeolitic catalysts. In this work, a combined dry-gel-conversion and s...     

正丁烷及丁烯-1在不同硅铝比ZSM-5分子筛上吸附的实验与模型

Four ZSM-5 zeolite catalysts with different Si/Al ratios for the catalytic cracking of C4 fractions to produce ethylene and propylene were prepared in this study.First,the adsorption isotherms of pure n-butane and butene-1 and their mixtures on these catalysts at 300K and p=0—100kPa were measured using the intelligent gravimetric analyzer.The experimental results indicate that the presence of Al can significantly affect the adsorption of butene-1 than that of n-butane on ZSM-5 zeolites.Then,the double Langmuir（DL）model was applied to study the pure gas adsorption on ZSM-5 zeolites for pure n-butane and butene-1.By combining the DL model with the ideal adsorbed solution theory（IAST）,the IAST-DL model was applied to model the butene-1（1）/n-butane（2）binary mixture adsorption on ZSM-5 zeolites with different Si/Al ratios.The calculated results are in good agreement with the experimental data,indicating that the IAST-DL model is effective for the present systems.Finally,the adsorption over a wide range of variables was predicted at low pressure and 300K by the model proposed.It is found that the selectivity of butene-1 over n-butane increases linearly with the decrease of Si/Al ratio.A correlation between the selectivity and Si/Al ratio of the sample was proposed at 300K and p=0.08MPa.     

Ethanol steam reforming study over ZSM-5 supported cobalt versus nickel catalyst for renewable hydrogen generation

The renewable hydrogen generation through ethanol steam reforming is one of the anticipated areas for sustainable hydrogen generation. To elucidate the role of Ni and Co with ZSM-5 support, catalysts were prepared by wet impregnation method and ethanol steam reforming(ESR) was performed. The catalysts were characterized by HR-XRD, ATR–FTIR, HR-SEM, TEM with SAED, EDAX, surface area analyzer and TPR. It had shown complete ethanol conversion at 773 K, but the selectivity in hydrogen generation was found higher for 10% Ni/ZSM-5 catalyst as compared to 10% Co/ZSM-5. The 10% Ni/ZSM-5 catalyst has about 72% hydrogen selectivity at temperature 873 K. It indicates that Ni is a more sustainable catalyst as compared to Co with ZSM-5 support for ESR. The C_2H_4 was found major undesirable products up to 823 K temperature. Nevertheless, the 10% Ni/ZSM-5 catalyst had shown its stability for high temperature(873 K) ESR performance.     

不同硅铝比ZSM-5负载铁基催化剂二氧化碳加氢性能

CO₂加氢在铁基催化剂上直接制取高附加值化学品是实现其资源化利用的重要途径。通过等体积浸渍法制备了不同硅铝比（25,70,150）的ZSM-5负载的铁基催化剂,考察硅铝比对铁基催化剂上CO₂加氢性能的影响。结果表明,随着硅铝比的升高,催化剂活性先升高后降低,最优化硅铝比为70。CO₂-DRIFTS和CO₂-TPD结果显示,硅铝比为70的ZSM-5载体制备的催化剂具有较多且较强的表面碱性位,促进CO₂分子的活化解离。通过H₂-TPR、XRD、Raman等表征揭示了催化剂结构的演变过程。还原后催化剂的活性金属以单质Fe形式存在,反应过程中单质Fe向Fe₃O₄和FeC_x物种转化。不同硅铝比配位环境影响Fe与C的相互作用,影响FeC_x的生成,从而影响CO₂加氢的活性和选择性。     

ZSM-5分子筛在MTP反应中的催化性能

合成了3种不同晶粒尺寸的ZSM-5分子筛,并制得MTP催化剂,对ZSM-5分子筛催化剂在MTP反应中的性能进行系统研究。采用XRD、SEM、N2物理吸附和TGA等对ZSM-5分子筛催化剂进行表征,发现小晶粒的ZSM-5分子筛具有良好的抗积炭性能,在MTP反应中具有较高的稳定性。采用小晶粒分子筛制成的催化剂,考察反应工艺条件对催化剂催化性能的影响,结果表明,丙烯选择性随反应温度和空速提高而增加,降低反应压力和提高水醇质量比也有利于提高丙烯选择性,为调整MTP工艺的产物分布和优化反应工艺条件提供了技术依据。     

N-烷基-N-甲基咪唑系列离子液体中ZSM-5分子筛催化环已烷氧化反应

Heterogeneous oxidation of cyclohexane by tert-butyl hydroperoxide (TBHP) was carried out over ZSM-5 catalysts with different Si/Al ratios in ionic liquids and organic molecular solvents. Higher yield and selectivity of the desired products were found in ionic liquids than in molecular solvents. The conversion of cyclohexane exhibits a decrease from 15.8% to 10.8% with the increase of Si/Al ratio of the HZSM-5 catalyst, and all the catalysts exhibit good selectivity of monofunctional oxidation products at around 97%. The activity of catalyst is found strongly de-pendent on the alkyl chain length of ionic liquid.     

CeO2复合改性ZSM-5分子筛用于催化甲醇制丙烯研究

在甲醇制丙烯(MTP)反应中,ZSM-5分子筛较强的酸性易使甲醇与ZSM-5接触发生氢转移、芳构化等二次反应,堵塞孔道,使得其微孔结构更加不利于分子的扩散,加速催化剂积碳失活,导致丙烯选择性和丙烯/乙烯(P/E)比值下降。因此,本文利用催化活性较高的CeO₂对ZSM-5分子筛进行复合改性以达到有效降低其酸性并增大介孔的目的来提高丙烯选择性和P/E比。通过XRD、NH₃-TPD和N₂吸脱附技术表征,研究了不同ZSM-5硅铝比(摩尔比)、两相质量比(m(CeO₂)/m(ZSM-5))对CeO₂/ZSM-5复合催化剂物化性质的影响。在反应温度480 ℃、重时空速2.6 h^-1、N₂流量100 mL·min^-1、常压纯甲醇进料的条件下,考察了所制备的复合催化剂催化MTP的性能。结果表明,硅铝比为250、m(CeO₂)/m(ZSM-5)为1∶4的复合催化剂比以往研究结果具有更优异的MTP催化性能,甲醇转化率为99.9%,丙烯选择性为42.78%,P/E比为6.3。