Effect of addition of Zn on the catalytic activity of a Co/HZSM-5 catalyst for the SCR of NOx with CH4

The selective catalytic reduction (SCR) of NO_x by methane in the presence of excess oxygen was studied on a Zn-Co/HZSM-5 catalyst. It was found that the addition of Zn could improve effectively the selectivity of methane towards NO_x reduction. When prepared by a coimpregnation method, the Zn-Co/HZSM-5 catalyst showed much higher catalytic activity than the two catalysts of a Zn/Co/HZSM-5 and Co/Zn/HZSM-5 prepared by the successive impregnation method. It is considered that there exists a cooperative effect among the Zn, Co and zeolite, which enhances the reduction of NO to NO₂ reaction and the activation of methane.     

Catalytic cracking of tricyclo [5.2.1.0] decane over HZSM-5 molecular sieves

The catalytic cracking of a high density hydrocarbon fuel, tricyclo [5.2.1.0^2.6] decane (JP-10) over HZSM-5 molecular sieves with different Si/Al mole ratios of 25, 38, and 50 was investigated at the temperature range from 773 to 873 K. Compared with the thermal cracking and the catalytic cracking over ZSM-5, conversions of JP-10 from the catalytic cracking over HZSM-5 molecular sieves at the same temperature were evidently heightened. The predominant hydrocarbon products from the catalytic cracking, checked at room temperature and atmospheric pressure, were methane, ethane, ethene, propane and propylene in the gaseous phase and benzene, indene, naphthalene and their homologues in the liquid phase. The contents of ethane, propane and propene decrease with increasing Si/Al mole ratio of a catalyst while those of methane and ethene increase simultaneously with the increase of Si/Al mole ratio of HZSM-5. The contents of the main components in the liquid products produced on the catalyst surface at a given temperature also decreased with the increase of Si/Al mole ratio. To keep high yields of alkenes, the HZSM-5 catalyst with high Si/Al mole ratio could be chosen.     

Methane aromatization using Mo-based catalysts prepared by microwave heating

Mo/HZSM-5 and Cu–Mo/HZSM-5 catalysts for the non-oxidative aromatization of methane have been prepared by microwave heating method. The effects of Mo loading, the molar ratio of Cu/Mo and preparation method on the catalytic performance of catalysts were studied. The results were compared with those for the methane aromatization over catalysts prepared by conventional heating. Both two kinds of catalysts have the maximum methane conversion when the Mo loading is 6%. The catalysts prepared by microwave heating exhibited higher selectivity to benzene than that prepared by conventional heating. The addition of metal Cu to Mo/HZSM-5 catalyst prepared by microwave heating enhanced the lifetime of catalyst, and gave rise to a little increase in methane conversion. The molar ratio of Cu/Mo influenced the methane conversion, and the maximum value was attained when Cu/Mo = 0.05, whereas no significant influence on the benzene selectivity was observed with the increase molar ratio of Cu/Mo. N₂ adsorption results showed that the catalysts prepared by microwave heating have the larger surface area and the similar pore volume compared with the catalysts prepared by conventional heating. This fact revealed that the more Mo species located on the outer surface of catalysts prepared by microwave heating is the main reason why they have better catalytic performance. XRD analysis indicated that the Mo species are highly dispersed on HZSM-5 zeolite. The addition of Cu influenced the dispersion. The actual active phase Mo₂C can be identified on the catalyst surface after reaction. TEM analysis revealed the carbonaceous deposition to have the form of carbon nanotube after reaction, with a uniform size range of 10–20 nm. TG analysis indicated that carbonaceous deposition on the catalysts prepared by microwave heating is lower than that by conventional heating, and the metal Cu further prompts the stability of catalyst. Most of the carbonaceous deposition on catalysts prepared by microwave heating is formed at low temperature and it is easy to burn-off. Coke accumulation at high temperature is the main reason of catalyst deactivation. The carbonaceous deposition formed on the catalysts for non-oxidative aromatization of methane is different from those formed on the catalysts for partial oxidation of methane.     

Hydrothermal Post-synthesis of HZSM-5 Zeolite to Enhance the Coke-resistance of Mo/HZSM-5 Catalyst for Methane Dehydroaromatization

Hydrothermal post-synthesis was used to modify the micropores and acidity of commercially available HZSM-5 zeolites. The recrystallization and the dynamic incorporation and extraction of the framework Al not only stabilized the framework with high crystallinity, but also inhibited the creation of extra-pores during the post-synthesis in NaOH aqueous solution. The resulted Mo/HZSM-5 catalyst showed rather high catalytic stability and greatly enhanced selectivity towards aromatics for methane dehydroaromatization reaction by effectively inhibiting the coke formation.     

An excellent support of Pd catalyst for methane combustion: Thermal-stable Si-doped alumina

Thermal-stable Si-doped alumina was prepared by the reverse microemulsion method and was used as the support of Pd catalyst for the methane combustion. The physicochemical properties of Si-alumina and catalytic performance of Pd/Si-Al₂O₃ were characterized by XRD, N₂ adsorption, FT-IR, XPS and methane catalytic combustion. The results indicate that the presence of Si can increase the thermal stability of alumina and promote the coordination state of aluminum from tetrahedral to octahedral, but its content added should be controlled appropriately to 5–6 wt%. Si-doped alumina prepared by the reverse microemulsion method is an excellent support of Pd catalyst for the methane combustion, which can increase both the catalytic activity and thermal stability of the Pd catalyst. The studies also show that the calcination temperature of support affects remarkably the performance of catalyst, and the high thermal stability of support is very important to increase the performance of Pd catalyst for the methane combustion.     

Catalytic reduction of nitrogen oxides with methane in the presence of excess oxygen

We discovered a family of catalysts that can effectively reduce NO_x with methane in the presence of excess oxygen. This new catalytic chemistry offers an alternative means for controlling NO_x emissions. Complete reduction of nitric oxide was obtained at 400°C over a Co-ZSM-5 catalyst. The presence of oxygen in the feed greatly enhances the nitric oxide reduction activity on Co-ZSM-5, and the nitric oxide conversion is strongly related to the inlet methane level. On the other hand, Cu-ZSM-5, which is a unique catalyst for the direct nitric oxide decomposition, is a poor catalyst for nitric oxide reduction by methane in the presence of excess of oxygen.     

晶化条件对Mo-ZSM-5分子筛粒径的影响

采用静态水热法在n(SiO_2)∶n[(NH4)2Mo O4]∶n(四丙基氢氧化铵)∶n(H2O)=40∶1∶6∶y体系中,合成Mo-ZSM-5杂原子分子筛,并考察水用量、晶化温度和晶化时间对其粒径的影响。结果表明,在晶化温度170℃和晶化时间24 h下,当投料n(SiO_2)∶n(Mo)=40和n(H2O)∶n(Mo)=200得到晶粒大小为(10~30)nm的Mo-ZSM-5分子筛。降低晶化温度和延长晶化时间,有利于杂原子Mo进入ZSM-5分子筛骨架。     

甲烷芳构化反应催化剂Ｍｏ-Ｍ／ＨＺＳＭ-５表面性质的研究

对甲烷芳构化催化剂Ｍｏ-Ｍ／ＨＺＳＭ-５进行了异丙醇分解、ＮＨ３-ＴＰＤ-ＭＳ、积炭量测定表征,其结果均与芳构化性能有关。芳烃收率高,稳定性好,积炭量较少,而且具有相当量的酸量和一定量强酸量及较强的脱氢中心。     

Production of gasoline range hydrocarbons from catalytic reaction of methane in the presence of ethylene over W/HZSM-5

The catalytic conversion of a methane and ethylene mixture to gasoline range hydrocarbons has been studied over W/HZSM-5 catalyst. The effect of process variables, such as temperature, percentage of volume of ethylene in the methane stream and catalyst loading on the distribution of hydrocarbons was studied. The reaction was conducted in a fixed-bed quartz-micro reactor in the temperature range of 300–500 °C using percentage of volume of ethylene in methane stream between 25 and 75% and catalyst loading of 0.2–0.4 g. The catalyst showed good catalytic performance yielding hydrocarbons consisting of gaseous products along with gasoline range liquid products. The mixed feed stream can be converted to higher hydrocarbons containing a high-liquid gasoline product selectivity (>42%). Non-aromatics C₅–C₁₀ hydrocarbons selectivity in the range of 12–53% was observed at the operating conditions studied. Design of experiment was employed to determine the optimum conditions for maximum liquid hydrocarbon products. The distribution of the gasoline range hydrocarbons (C₅–C₁₀ non-aromatics and aromatics hydrocarbons) was also determined for the optimum conditions.     

Oxidative coupling of methane with microwave and RF plasma catalytic reaction over transitional metals loaded on ZSM-5

In the microwave and radio frequency (RF) plasma catalytic reaction at room temperature, the oxidative coupling of methane (OCM) over transitional metals loaded on ZSM-5 has been carried out. The transitional metals, Fe, Ni, Co and Cu (1B family element), loaded on ZSM-5 have been tested for the OCM using the plasma catalytic reaction. In this work, the conversion of methane to C2 products has been improved without the carbon deposition when the oxygen as a co-reactant gas was supplied. The order of the catalysts of higher conversion to C2 products in the microwave plasma reaction with plasma power of 120 W is Co–ZSM-5>Fe–ZSM-5Cu–ZSM-5>Ni–ZSM-5. Selectivity to ethylene is as high as 29.8%, to ethane 10% and to acetylene 49.9% and conversion of methane was as high as about 54.9% with pressure of 5–10 Torr, total flow rate of 125 ml/min and a methane/oxygen ratio of 4:1 over Co–ZSM-5. It is suggested that the catalyst may provide an active site for combination of radicals. It was found that yield of C2 products has been enhanced in the microwave plasma catalytic reaction, as microwave plasma system of high frequency has better energy efficiency than RF plasma system of low frequency.     

Modification of acidity of Mo-Fe/HZSM-5 zeolite via argon plasma treatment

The NH₃-TPD characterization was conducted to confirm that the acidity of Mo-Fe/HZSM-5 zeolite could be selectively modified via the glow discharge plasma treatment. The plasma catalyst treatment could totally change the distribution of aromatic products with higher methane conversion compared to the untreated catalyst. Some polycyclic aromatics such as anthracene, pyrene and phenanthrene were also produced over the plasma treated catalyst, in addition to benzene, toluene and naphthalene, which were normally obtained over the untreated catalyst.     

负载型铜铈催化剂选择性氧化富氢气体中CO的催化性能

CO选择性氧化法是去除重整气中少量CO的有效方法。对采用共沉淀法和浸渍法制备含铜和铈的催化剂进行了比较。结果表明,负载型铜铈催化剂的最佳催化温度明显低于非负载型铜铈催化剂。用浸渍法制得的Cu-Ce/ZSM-5催化剂在180℃能将CO含量降到5×10~(-6)。考察了CO_2和H_2O对催化剂催化性能的影响,Cu-Ce/ZSM-5在最佳催化温度下具有一定的耐CO_2和H_2O能力。对Cu-Ce/ZSM-5的稳定性进行了初步考察。     

焙烧条件对Fe-Mo/ZSM-5催化剂上NO选择性催化还原性能的影响

采用共浸渍法制备了m(Fe):m(Mo)=1的Fe-Mo/ZSM-5催化剂,并对其在不同焙烧条件所得样品上NO选择性催化还原反应活性进行了测试。结果表明,焙烧条件对Fe-Mo/ZSM-5催化性能影响明显,600℃焙烧6 h的样品在低温范围具有较好的催化性能,随着焙烧时间或焙烧温度的增加,其NOx转化率依次向高温方向移动,在800℃焙烧后的样品催化活性明显下降。采用XRD和BET对Fe-Mo/ZSM-5样品的体相结构和表面性能进行了研究。结果表明,不同焙烧条件下Fe-Mo/ZSM-5催化剂的晶胞参数和比表面积产生了差别,特别是焙烧温度达到800℃时,其比表面积显著减小,这可能是导致Fe-Mo/ZSM-5催化性能突然下降的主要原因。焙烧过程中残留在的表面含氮物种对Fe-Mo/ZSM-5催化剂上NO选择性催化还原反应活性影响较大。     

Thermo-catalytic decomposition of waste lubricating oil over carbon catalyst

The thermo-catalytic decomposition of waste lubricating oil over a carbon catalyst was investigated in an I.D. of 14.5mm and length of 640mm quartz tube reactor. The carbon catalysts were activated carbon and rubber grade carbon blacks. The decomposition products of waste lubricating oil were hydrogen, methane, and ethylene in a gas phase, carbon in a solid phase and naphthalene in a liquid phase occurring within the temperature ranges of 700 °C-850 °C. The thermo-catalytic decomposition showed higher hydrogen yield and lower methane yield than that of a non-catalytic decomposition. The carbon black catalyst showed higher hydrogen yield than the activated carbon catalyst and maintained constant catalytic activity for hydrogen production, while activated carbon catalyst showed a deactivation in catalytic activity for hydrogen production. As the operating temperature increased from 700 °C to 800 °C, the hydrogen yield increased and was particularly higher with carbon black catalyst than activated carbon. As a result, carbon black catalyst was found to be an effective catalyst for the decomposition of waste lubricating oil into valuable chemicals such as hydrogen and methane.     

负载型纳米Au/HZSM-5催化剂的制备及其在甲烷吸附中的应用

采用离子交换法制备负载型纳米HZSM-5分子筛,采用负压-沉积沉淀法制备负载型纳米Au/HZSM-5催化剂,对载体及催化剂进行XRD、UV-Vis、TEM、XPS、NH₃-TPD和FT-IR等表征,并评价催化剂的甲烷吸附性能。XRD与TEM表征结果表明,N₂气氛焙烧的2.0%Au/HZSM-5催化剂金粒子尺寸较小,为（5~10） nm;UV-Vis表征结果表明,焙烧导致负载金的价态由离子态转为零价态,且N₂气氛焙烧的2.0%Au/HZSM-5催化剂上零价金的吸收峰较弱,即相应的颗粒度较小;XPS表征结果表明,金负载量越高,催化剂上零价金占总金的比例越高;NH₃-TPD表征结果表明,金负载量较小时,催化剂强酸中心峰面积较载体下降,负载量较大时,强酸和弱酸中心峰面积均下降;FT-IR表征结果表明,低温下金催化剂能将甲烷转化为含有烯烃双键的吸附物种,显示出载金催化剂对甲烷较强的C-H键活化能力。     

全结晶ZSM-5分子筛催化剂研究及工业应用

制备了全结晶ZSM-5分子筛催化剂,采用XRD、SEM、N2物理吸附-脱附及NH3-TPD等对催化剂进行表征,并考察其用于碳四烯烃催化裂解制丙烯(OCC)反应的催化性能。结果表明,制备的全结晶ZSM-5分子筛催化剂比常规成型的催化剂具有更高的结晶度、更大的比表面积、更丰富的孔结构以及更多的活性中心。高空速有利于反应的进行,提高压力对反应不利,升高温度有利于提高产物丙烯收率。在实验室研究的基础上,将全结晶ZSM-5分子筛催化剂用于OCC工业装置,取得良好的应用效果。     

甲醇制汽油工艺及催化剂制备的研究进展

甲醇制汽油既能缓解国内油品短缺又能解决甲醇产能过剩。本文综述了甲醇制汽油工艺技术,包括固定床和流化床技术,简要说明了这些工艺的技术特点。同时介绍了甲醇制汽油催化剂的研究现状,着重说明了碱处理和金属改性处理对ZSM-5结构和催化性能的影响,指出了高比表面积催化剂的研制和高稳定性催化剂的开发是甲醇制汽油催化剂的研究方向,并对甲醇制汽油催化剂失活的原因及催化机理进行了初步的探讨。     

含分子筛重整催化剂反应性能研究

对含有ZSM-5沸石的重整催化剂的催化性能进行了研究。结果表明,ZSM-5催化剂具有比常规重整催化剂更高的芳构化活性,并且产物中苯和二甲苯的含量较高,对二甲苯的含量高于其热力学平衡含量。当锌的质量分数为3.0%时,表现出更好的催化性能,铂的增加对重芳烃的产生具有明显的抑制作用。     

间戊二烯C5石油树脂的生产应用研究

∶针对间戊二烯石油树脂合成反应,采用了一种DPE/AlCl3均相复合催化体系,实验结果表明,与传统的AlCl3催化剂相比,采用了这种均相复合催化体系可提高间戊二烯石油树脂的收率和软化点,同时可提高树脂的相对分子质量和降低相对分子质量分布,配比为1∶1.5的DPE/AlCl3复合催化体系为较佳的选择。此时制备的间戊二烯树脂平均收率比AlCl3催化剂时的平均收率高出2.8%;DPE/AlCl3复合催化体系得到的间戊二烯树脂软化点明显高于AlCl3引发制备的树脂软化点,平均高出9.8℃。而且此时DPE/AlCl3复合催化体系合成的间戊二烯树脂的相对分子质量高于AlCl3引发制备的树脂,相对分子质量分布低于AlCl3引发制备的树脂。     

Study on attrition of spherical-shaped Mo/HZSM-5 catalyst for methane dehydro-aromatization in a gas-solid fluidized bed

As a potential methane efficient conversion process,non-oxidative aromatization of methane in fluidized bed requires a catalyst with good attrition resistance,especially in the states of high temperature,long-time rapid movement and chemical reaction.Existing evaluation methods for attrition resistance,such as ASTM D5757 and Jet Cup test,are targeted for fresh catalysts at ambient temperature,which cannot well reflect the real process.In this study,spherical-shaped Mo/HZSM-5 catalyst prepared by dipping and spray drying was placed in a self-made apparatus for attrition testing,in which the catalyst attrition under differ-ent system temperatures,running time and process factors was investigated with percent mass loss (PML),particle size-mass distribution (PSMD) and scanning electron microscope (SEM).Carbon deposition on the catalyst before and after activation,aromatization and regeneration was analyzed by thermogravimetry(TG),and the attrited catalysts were evaluated for methane dehydro-aromatization (MDA).The results show that the surface abrasion and body breakage of catalyst particles occur continuously,with the increase of system temperature and running time,and make the PML rise gradually.The process factors of activation,aromatization and regeneration can cause the catalyst attrition and carbon deposits,which broaden the PSMD in varying degrees,and the carbon-substances on catalysts greatly improve their attrition resistance at high temperature.Catalyst attrition has a certain influence on its catalytic performance,and the main reasons point to particle breakage and fine powder escape.