贵金属和载体对催化剂催化脱氧裂化性能的影响

采用浸渍法制备了一系列分别负载活性组分Pt,Pd,Ru的γ-Al2O3载体催化剂和分别以固体酸γ-Al2O3,Si O2-Al2O3,USY-Al2O3为载体的Pd催化剂。通过XRD、HRTEM、H2-TPR、NH3-TPD、BET等分析表征技术和以油酸甲酯为模型化合物的反应体系,考察了贵金属及载体性质对催化剂催化加氢脱氧性能和催化裂化性能的影响。结果表明:贵金属及其粒子大小是影响催化剂催化加氢脱氧活性的主要因素;载体的酸强度、酸量是影响催化剂催化裂化性能的主要因素。同时,该性能也受比表面积和孔结构特征的影响;Pd/USY-Al2O3在系列催化剂中表现出了良好的催化加氢脱氧活性和最佳的催化裂化活性。     

Hydrotreating of Gas Oil,Jatropha Oil,and Their Blends Using a Carbon Supported Cobalt-Molybdenum Catalyst

Hydrotreating of Jatropha oil and Jatropha oil blended gas oil feeds were studied under diesel hydrotreating conditions using Cobalt-Molybdenum catalyst on activated carbon. The experiments were carried out in pilot plant for more than 90 days first with gas oil, followed by 5%, 10%, and 20% Jatropha oil in gas oil and finally with Jatropha oil alone. Deactivation of the catalyst was not observed up to hydrotreating of 20 wt% Jatropha oil in gas oil, but, the reactor pressure shoots up after seven days of running neat Jatropha oil. The liquid products were characterized by GC-MS analysis, distillation, density, sulfur, nitrogen, and Cetane Index.     

生物燃料加氢脱氧催化剂的研究进展

简要阐述了生物燃料中不同含氧物的加氢脱氧机理,重点介绍了近几年国内外在生物燃料加氢脱氧催化剂方面的研究现状及进展,研究主要集中在负载过渡金属氧化物催化剂上,也包括负载贵金属、负载金属碳化物、负载金属氮化物和非负载金属氧化物催化剂。该领域未来研发趋势是低温高活性、高选择性、耐水、抗积碳、稳定的复合载体负载多元金属催化剂的研究。     

Application of new 13C n.m.r. techniques to the study of products from catalytic hydrodeoxygenation of SRC-II liquids

A middle-heavy SRC-II distillate (b.p. 230–455 °C), containing 3.0 wt% of oxygen, has been studied by means of ¹³C n.m.r. at 75, 100 and 125 MHz. The magnetization refocussing techniques INEPT and J-resolved two-dimensional Fourier transform have been utilized to demonstrate methods by which resonance line multiplicities may be determined in complex liquid mixtures. Products derived from the above coal liquid by hydrodeoxygenation at temperatures from 200 to 370 °C, using sulphided Co—Mo and Ni-W catalysts, were also examined. The fraction of aromatic carbon in the hydrotreated liquids was found to correlate directly with their C/H atomic ratio and inversely with the hydrogen content. Comparison of O/C atomic ratios with f_a values for these liquids indicates that hydrogen uptake < 260 °C is associated primarily with hydrogenolytic oxygen removal without attendant ring hydrogenation, while at temperatures between 260 and 350 °C hydrodeoxygenation is accompanied by ring hydrogenation and dealkylation reactions.     

Highly Dispersed Copper Nanoparticles Supported on Activated Carbon as an Efficient Catalyst for Selective Reduction of Vanillin

Highly dispersed copper nanoparticles (Cu NPs) supported on activated carbon (AC) are effectively synthesized by one‐pot carbothermal method at temperature range of 400–700 °C. The X‐ray diffraction, transmission electron microscopy, X‐ray photoelectron spectroscopy, and Brunauer–Emmett–Teller analysis reveal that Cu NPs with diameters of 20–30 nm are evenly anchored in carbon matrix. The 15 wt%‐Cu/AC‐600 catalyst (derived at 600 °C) exhibits best bifunctional catalysis of aqueous‐phase hydrodeoxygenation (HDO) and organic‐phase transfer‐hydrogenation reaction (THR) to selectively transform vanillin to 2‐methoxy‐4‐methylphenol (MMP). In HDO of vanillin, the as‐prepared catalyst achieves a 99.9% vanillin conversion and 93.2% MMP selectivity under 120 °C, 2.0 MPa H₂ within 5 h. Meanwhile, near‐quantitative vanillin conversion and 99.1% MMP selectivity are also obtained under 180 °C within 5 h in THR of vanillin by using 2‐propanol as hydrogen donor. The transforming pathways of vanillin are also proposed: vanillin is transformed into MMP via intermediate of 4‐hydroxymethyl‐2‐methoxyphenol in HDO case and by direct hydrogenolysis of vanillin in THR course. More importantly, the activity and the selectivity do not change after 5 cycles, indicating the catalyst has excellent stability. The Cu‐based catalyst is relatively cheap and preparation method is facile, green, and easy scale‐up, thus achieving a low‐cost transformation of biomass to bio‐oils and chemicals.     

Slowing the Kinetics of Alumina Sol–Gel Chemistry for Controlled Catalyst Overcoating and Improved Catalyst Stability and Selectivity

Catalyst overcoating is an emerging approach to engineer surface functionalities on supported metal catalyst and improve catalyst selectivity and durability. Alumina deposition on high surface area material by sol–gel chemistry is traditionally difficult to control due to the fast hydrolysis kinetics of aluminum‐alkoxide precursors. Here, sol–gel chemistry methods are adapted to slow down these kinetics and deposit nanometer‐scale alumina overcoats. The alumina overcoats are comparable in conformality and thickness control to overcoats prepared by atomic layer deposition even on high surface area substrates. The strategy relies on regulating the hydrolysis/condensation kinetics of Al(^sBuO)₃ by either adding a chelating agent or using nonhydrolytic sol–gel chemistry. These two approaches produce overcoats with similar chemical properties but distinct physical textures. With chelation chemistry, a mild method compatible with supported base metal catalysts, a conformal yet porous overcoat leads to a highly sintering‐resistant Cu catalyst for liquid‐phase furfural hydrogenation. With the nonhydrolytic sol–gel route, a denser Al₂O₃ overcoat can be deposited to create a high density of Lewis acid–metal interface sites over Pt on mesoporous silica. The resulting material has a substantially increased hydrodeoxygenation activity for the conversion of lignin‐derived 4‐propylguaiacol into propylcyclohexane with up to 87% selectivity.     

超临界甲醇中2,3-二氢苯并呋喃加氢脱氧的理论研究

以2,3-二氢苯并呋喃(DHBF)作为木质素单体模型物,采用密度泛函理论B3LYP/6-31G++(d,p)方法对其在超临界甲醇中加氢脱氧的机理进行了研究。研究中,利用SMD溶剂化模型,考虑了甲醇的溶剂效应。研究结果表明:在活性氢的作用下2,3-二氢苯并呋喃的杂环断裂相对容易,主要加氢产物为2-乙基苯酚。而2-乙基苯酚又可能会进一步发生醇解和加氢脱氧两条反应路径,通过能量对比发现苯环上剩余位置均有醇解的可能性,但以生成2-乙基-6-甲基苯酚最为容易;而加氢脱氧反应中加氢过程优于氢解过程,且脂肪环上的C-O键比苯环上的C-O键更易断裂。     

Adsorption characteristics of reduced Mo and Ni–Mo catalysts in the hydrodeoxygenation of benzofuran

The promotional effect of Ni on the hydrodeoxygenation (HDO) of benzofuran (BF) over reduced Ni–Mo/γ-Al₂O₃ catalysts was studied. The adsorption characteristics of Al₂O₃ support, mono-metallic Mo, and bi-metallic Ni–Mo catalysts that were pre-reduced were investigated using the feed molecule (BF) and a probe molecule (NO) as adsorbates. NO was used to probe the coordinatively unsaturated sites (CUS). Three adsorption modes for benzofuran over reduced Al₂O₃ support, Mo, and Ni–Mo catalysts were proposed that involved OH groups, Brønsted acid sites, and CUS, respectively. Benzofuran molecule adsorbed more strongly on B acid sites and CUS than on OH groups and was activated with weakening of the C–O bond. With increasing catalytic hydrogenation activity (increasing CUS) and/or decreasing hydrogenolysis activity (decreasing acidity), the reaction pathway for benzofuran HDO changes from a hydrogenolysis route to a route that involves saturation of the benzene ring before any heteroatom removal takes place.     

油酯加氢脱氧反应机理研究进展

采用可再生资源（如植物油、动物油和废弃油脂等）制备生物柴油是有效解决能源供给问题和化石燃料引发的环境问题的有效途径之一。综述了油脂加氢脱氧（HDO）制得的生物柴油具有的优点及涉及的反应,并详细叙述了催化反应机理。重点介绍了贵金属催化剂（如Rh、Pt、Pd和Ru）和过渡金属Mo和Ni催化剂用于油脂HDO的反应机理,阐述了催化剂中金属种类、载体性质和助剂等对油脂催化HDO反应机理的影响,并对其未来的发展进行了展望。通过对催化剂HDO反应机理的深刻理解,以及对活性组分的优化与组合,能有效调控相应催化剂的HDO反应性能,为生物柴油工业化生产奠定了良好的理论基础。