浆态床费托合成技术研究进展

综述了近年来浆态床费托合成反应的研究进展。重点评述了浆态床F-T工艺特点,分析了铁基催化剂和钴基催化剂以及工艺条件对浆态床F-T合成反应的影响,介绍了浆态床上费托合成的一些数学模型,概述了浆态床中催化剂与液相产物分离的一些方法。     

钴基催化剂的制备及性能评价

以γ-Al_2O_3为载体,采用等体积浸渍法制备F-T合成钴基催化剂,在F-T合成小型固定床反应装置评价催化剂。考察并优化了钴源、焙烧温度、钴负载量、反应温度和原料气空速等工艺条件对催化荆活性和F-T合成产物收率的影响,测试了Co/γ-Al_2O_3催化剂的稳定性。结果表明,最佳制备条件:以硝酸钴为钴源,焙烧温度400℃,钴负载质量分数10%。在温度230℃、压力2 MPa、原料气组成n(H_2)∶n(CO)=2和反应空速1 800 h~(-1)的条件下,进行60 h运转实验,CO转化率可达69.1%,C_5~+烃收率高达89.6%。     

F- T合成液体燃料催化剂

介绍了F-T合成反应特征、合成烃碳数分布规律;讨论了催化剂载体、主金属、助剂和制备方法等因素对催化剂活性和选择性等方面的影响;介绍了Sasol公司铁催化剂、Shell公司钴催化剂生产液体燃料的产物分布。     

钴基费-托合成催化剂研究进展

钴基费-托合成催化剂具有优异的本征活性和碳链增长能力,是费-托合成催化剂领域的研究热点。对钴基费-托合成催化剂的活性钴物种的性能、其它钴物种的作用、钴基催化剂相关助剂以及钴颗粒的粒径效应等研究进行了综述,主要包括对HCP-Co(六方密堆积结构)和FCC-Co(面心立方结构)两种活性钴物种在体对称性和原子堆积顺序等拓扑结构方面的差异以及两者不同晶面的反应活性的分析,对碳化钴、氧化钴、钴载体混合化合物等其它钴物种对费-托合成反应活性和选择性的影响的探讨,对助剂和钴颗粒粒径对费-托合成反应产物选择性作用机制的总结。针对以上几点,对理性设计制备具有高目标产物选择性的钴基费-托合成催化剂提出了建议。     

费托合成催化剂表面碳-氧键活化的研究

本研究针对费托合成反应中催化剂的活性相,即金属碳化物的生成进行了表面碳-氧键活化的研究。在催化剂的预处理阶段,采用CO对铁基催化剂和钴基催化剂进行渗碳处理,形成碳化铁和碳化钴。XRD图和TEM图的分析结果证实了产物的形成。进一步的实验结果表明,钴基催化剂的目标产物选择性高于铁基催化剂。通过密度泛函理论模拟计算,发现铁基催化剂表面碳-氧键的活化能力低于钴基催化剂,差异为1.26eV。因此,钴基催化剂在费托合成反应中具有更高的活性和选择性。     

钴基费托合成催化剂载体表面改性及失活机理研究进展

综述了费托合成钴基催化剂载体材料表面改性及催化剂失活机理的研究进展。指出对载体表面进行预处理可以调节载体和钴物种之间的相互作用,进而影响费托合成催化剂的还原度、分散度和催化性能。同时利用氧掺杂和氮掺杂的方法改变碳材料表面的化学性质,可以提高锚定钴物种的能力。钴基催化剂的失活是费托合成反应的主要问题之一,针对失活机理的研究可以提高钴基催化剂的稳定性。由于钴基催化剂合成的成本较高,因此通过对载体的表面改性和催化剂失活机理的研究来改善钴基催化剂的活性、稳定性以及产物的选择性是值得深入研究的课题。     

F-T合成Co基催化剂研究进展

由于日趋严重的石油危机,寻找一种石油替代品显得尤其重要。F-T合成反应是将含碳资源转化成液体燃料的核心技术,关键是开发活性高、选择性高和稳定性好的催化剂。而Co基催化剂被认为是F-T合成最有前途的催化剂。综述了近年来Co基催化剂F-T合成反应的研究进展,重点介绍Co基催化剂的载体、助剂、制备方法和前驱体等方面对催化剂活性和选择性的影响,认为未来Co基催化剂的发展方向是增加催化剂活性和对重质烃的选择性,减少甲烷和 CO₂ 排放,研究趋势将是催化剂的复合化和多功能化。     

焙烧温度对Co-Ru-ZrO2/γ-Al2O3F-T合成催化剂性能的影响

采用浸渍法制备钴基催化剂,考察了催化剂焙烧温度对其F-T合成反应性能和产物分布的影响。制备催化剂时,不对催化剂进行焙烧,Co物种容易还原,并可较好分散,催化剂具有较高的催化活性和重质烃选择性。较高温度下焙烧,Co物种和载体间的相互作用增强,形成难还原的铝酸钴化合物,同时氧化钴晶粒聚集或烧结,Co物种的还原程度下降,催化剂CO加氢活性降低,重质烃选择性下降。在原料气n(H₂)∶n(CO)=2.0、483 K、1.5 MPa和800 h^-1条件下,未焙烧、673 K和923 K焙烧的催化剂上进行F-T合成反应,CO的转化率分别为80.27%、78.41%和61.14%,重质烃的选择性C₅⁺分别为88.54%、88.57%和77.95%。较低焙烧温度有利于反应速率的提高和重质烃的合成,较高焙烧温度使CO加氢活性下降,有利于低碳烃的生成。     

费托合成工艺发展现状

概述了当前应用于费托合成工业的铁基和钴基催化剂的特点,比较了铁基和钴基催化剂的成本,综述了费托合成工艺在工业应用和实验室规模方面的进展,评述了铁基和钴基催化剂在工业应用中存在的问题以及研究人员正寻求解决的办法,探讨了催化剂强度、载体种类、反应器结构以及超临界流体和油循环工艺对费托合成反应过程控制的影响,对费托合成的前景提出了一些展望和建议。     

稀土-钴簇合物为前体的催化剂制备及其费-托反应性能测试

费–托(F-T)合成是由煤炭、天然气或生物质等原料加工生成合成气(CO和H2),再经过催化剂的催化作用转化为高品质液态燃料的合成方法,这项技术不仅可以有效地减少大气污染,而且为替代石油资源提供了新的途径。因此,研制开发低甲烷、高液态烃选择性的钴基催化剂显得尤为重要。本文以γ-Al2O3为载体,(CO)6Co2HCCCOOH、Co3(CO)9CCOOH和Yb4O{(CO)9Co3CCOO}4为前体,按照Co5%(质量分数)的负载量制备了一系列钴基催化剂。用X-射线衍射、程序升温还原、比表面测试等技术考察了钴基催化剂的结构和还原性能,分析了不同前体对F-T反应性能的影响。结果表明,不同钴前体所制备的催化剂,钴物种的分散度和还原度有很大的差别。其中,含稀土的钴羰基簇合物为前体的催化剂,具有较小的晶粒度和比较好的分散度,较小的钴晶粒对液态烃的选择性有利。其相应的Co/Al2O3催化剂的费-托活性由大到小依次为:Yb4O{(CO)9Co3CCOO}4,(CO)6Co2HCCCOOH,Co3(CO)9CCOOH+Yb4O{(CO)9Co3CCOO}4,Co3(CO)9CCOOH。     

A highly active silica(silicon)-supported vanadia catalyst for C1 oxygenates and hydrocarbon production from partial oxidation of methane

A very low surface area silica-silicon substrate has been used as a support for vanadium oxide and has been tested in the partial oxidation of methane. Use of a reactor with variable dead volume ahead of the bed of the catalyst allows determining the relevance of gas phase reactions in initiating methane conversion. Experimental evidence supports that at atmospheric pressure C₁ oxygenates are essentially produced on the catalyst surface rather than in the gas phase. Comparison with a high surface area silica-supported vanadium oxide catalyst clearly highlights the double role of surface area in promoting catalytic activity, but also in promoting non-selective further oxidation of reaction products. It is shown that a reaction system combining dead volume upstream the bed of the catalyst and a very low surface area is very promising to activate methane conversion to C₁ oxygenates and C₂₊ hydrocarbons at remarkable TOF number preventing further non-selective oxidation. In addition, production of C₂₊ hydrocarbons is observed at temperatures as low as 750 K.     

Direct synthesis of middle iso-paraffins from synthesis gas on hybrid catalysts

This paper focuses on the synthesis of iso-paraffin-rich hydrocarbons by Fischer–Tropsch synthesis (FTS) over silica gel supported Co catalyst (Co/SiO₂). The basic concept is to isomerize and/or hydrocrack the primary FTS hydrocarbon products. A physical mixture consisting of a small amount of zeolite or Pd/zeolite mixed with Co/SiO₂ enhanced the formation of C₄–C₁₀ iso-paraffins while suppressing the formation of higher molecular hydrocarbons, probably because of the selective cracking of these hydrocarbons on them. In separate experiments, a two-reactor system was used. The first reactor contained a physical mixture of Co/SiO₂ and zeolite, and the second reactor contained zeolites or Pd-supported zeolites. The two-reactor system gave sharp C-number distribution within C₃–C₆ and iso-paraffins-rich products. The hydrocracking of n-octane and n-decane (model compound simulating products of the FTS reaction) over mixed catalysts composed of various compositions of Pd/SiO₂ and ZSM-5 in the presence of gaseous hydrogen showed high and stable activity, and produced primarily iso-paraffin-rich hydrocarbons. The isomerization was favored for mixtures rich in Pd/SiO₂. The role of Pd was thought to be the inlet of hydrogen spillover to the zeolite surface.     

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.     

Effect of type of polymerization catalyst system on the degradation and stabilization of polyethylenes in the melt state—Part 4: Comparative antioxidant effectiveness on organoleptic extractables

Several polyethylene resins using Ziegler, metallocene, and Phillips catalyst technologies were examined to obtain more detailed information about the effect of different polymerization catalyst systems on the production of extractable thermo-oxidative degradation products formed during melt processing cycles. This produces volatile organoleptic components (VOCs and extractable) such as hydrocarbons, alcohols, aldehydes, ketones, and carboxylic acids. Although some of the oxidation products are in-chain bound, many are produced as free, easily extractable entities or volatile components. The purpose of this study is to identify the nature of the products by gas chromatography–mass spectrometry (GC–MS) and FTIR analysis. The identity of the VOCs formed is necessary to modify the product's quality or establish which are toxic and/or leachable with food products. The results show that the evolution of carbonyl products, nature, and quantity is influenced significantly by the polymer type and catalyst used. Over 300 organoleptics low molar mass degradation products, such as alkane, alkene, carbonyl, and alcohol functionalities were detected by GC–MS analysis coupled with FTIR analysis on hexane extractables. Certain stabilizers can control the generation of certain functionalities and inhibit others. Of importance was the discovery of the relationship between additive activity and structure and inhibition of the formation of specific types of oxidation functionalities to a particular catalyst system.     

Effect of hydrocarbon compositions in the M85 fuel on catalytic conversion

To identify hydrocarbon components suitably blended in the M85 (Methanol: 85 vol%, Gasoline: 15 vol%) fuel while maintaining high emission control performance of the catalyst, the effects of various hydrocarbons on the methanol conversion efficiency were investigated. Saturated hydrocarbons having about 5–7 carbon atoms did not inhibit the methanol conversion efficiency. In contrast, unsaturated hydrocarbons and aromatic hydrocarbons inhibited the methanol conversion efficiency. It was concluded that low saturated hydrocarbons such as light-naphtha were suitable for hydrocarbons mixed with methanol fuel.     

Pyrolysis of used sunflower oil in the presence of sodium carbonate by using fractionating pyrolysis reactor

Pyrolysis of used sunflower oil was carried out in a reactor equipped with a fractionating packed column (in three different lengths of 180, 360 and 540 mm) at 400 and 420°C in the presence of sodium carbonate (1, 5, 10 and 20% based on oil weight) as a catalyst. The use of packed column increased the residence times of the primer pyrolysis products in the reactor and packed column by the fractionating of the products which caused the additional catalytic and thermal reactions in the reaction system and increased the content of liquid hydrocarbons in gasoline boiling range. The conversion of oil was high (42–83 wt.%) and the product distribution was depended strongly on the reaction temperature, packed column length and catalyst content. The pyrolysis products consisted of gas and liquid hydrocarbons, carboxylic acids, CO, CO₂, H₂ and water. Increase in the column length increased the amount of gas and coke–residual oil and decreased the amount of liquid hydrocarbon and acid phase. Also, increase of sodium carbonate content and the temperature increased the formation of liquid hydrocarbon and gas products and decreased the formation of aqueous phase, acid phase and coke–residual oil. The major hydrocarbons of the liquid hydrocarbon phase were C₅–C₁₁ hydrocarbons. The highest C₅–C₁₁ yields (36.4%) was obtained by using 10% Na₂CO₃ and a packed column of 180 mm at 420°C. The gas products included mostly C₁–C₃ hydrocarbons.     

Poisoning effect of nitrogen compounds on the transformation of model hydrocarbons and real feed under catalytic cracking conditions

The effect of the content and nature of nitrogen compounds on the distribution of target products in transforming model hydrocarbons under cracking conditions over equilibrium zeolite-containing catalyst was studied. Using cracking of n-undecane as an example, a nearly 50% drop in the conversion and in yields of propane-propene (PPF) and butane-butene fractions (BBF) was observed when the pyrrol content in the feed was raised to 3000 ppm of nitrogen. Increasing the nitrogen content in the feed led to a nonlinear reduction in the rate constants of n-undecane cracking. It was found that the dependence of the yields of PPF, BBF, and isobutane in BBF on the conversion remained constant upon the cracking of n-undecane with various of nitrogen compounds; poisoning was likely to proceeds only because the acidic sites of the catalyst were blocked. The high poisoning effect of pyrrol and indole upon the cracking of n-undecane and decalin (strong proton donors) was observed along with the formation of ammonia. Quinoline exhibited high poisoning ability in the catalytic cracking of cumene with low [H]-donor activity. Quinoline poisoned catalysts to a greater degree than indole, during the catalytic cracking of non-hydrofined vacuum gasoil with a high content of aromatic structures. Indole exhibited the highest poisoning ability in processing heavy hydrocracking residue which was rich of paraffin-naphthene hydrocarbons.     

Steady-state conversion of methane to C4+ aliphatic products in high yields using an integrated recycle reactor system

Conversion of methane in high yields to C₄₊ nonaromatic hydrocarbons was demonstrated in a recycle system. The principal components of the recycle system included an oxidative coupling reactor with a Mn/Na₂WO₄/SiO₂ catalyst at 800°C for conversion of methane to ethylene, and a reactor with an H-ZSM-5 zeolite at 275°C for subsequent conversion of ethylene to higher hydrocarbons. Total yields of C₄₊ products were in the range of 60–80%, and yields of C₄₊ nonaromatic hydrocarbons were in the range of 50–60%. This revised version was published online in July 2006 with corrections to the Cover Date.     

Synthesis of hydrocarbons from a model gas of the gasification of oil shale

Gases from the gasification of oil shale contain CO and H₂; this fact makes it possible to use them as a raw material in the synthesis of higher hydrocarbons. The possibility of obtaining a long distillate of hydrocarbons on a cobalt catalyst was demonstrated using a CO-CO₂-H₂-N₂ model mixture of the gasification products of Leningrad shale as an example. In this case, to 83.8% selectivity for C₅₊ hydrocarbons with a low yield of methane (7.3%) was reached. The resulting hydrocarbons were characterized by a chain growth probability to 0.84.     

催化汽油和C4烃类在LBO-A催化剂上芳构化反应的实验研究

在小型固定流化床实验装置上，单独利用催化裂化提高辛烷值助剂LBO-A为催化剂，分别对催化汽油和C₄烃类进行了催化转化反应的实验研究，考察了反应温度和空速对反应产物分布和组成的影响。实验结果表明，LBO-A单独作为催化剂对催化汽油和C₄烃类具有较强的芳构化性能，同时，所产裂化气体中，丙烯含量远高于普通裂化催化剂。因此，在适宜的反应条件下，可生产高辛烷值的汽油组分，同时，增产丙烯，并且这两种性能随反应温度的升高而增强。