二维M-Co3O4负载Ir对香草醛加氢脱氧性能研究

以二维金属-有机框架M-Co₃O₄为载体制备了具有高活性的Ir/M-Co₃O₄催化剂.采用X射线粉末衍射(XRD)、X射线光电子能谱(XPS)、透射电子显微镜(TEM)、电感耦合等离子体发射光谱仪(ICP-OES)、 N₂物理吸/脱附等方法对催化剂进行了表征,并研究了催化剂、温度、时间、溶剂等因素对香草醛加氢脱氧反应的影响.结果表明, Ir/M-Co₃O₄催化剂具有较好的普适性和稳定性,在香草醛加氢脱氧制备4-甲基愈创木酚(MMP)反应中表现出较高的活性和选择性,香草醛的转化率达100%, MMP的选择性不低于99%.     

Nitrogen‐Doped Ordered Mesoporous Carbon Supported Bimetallic PtCo Nanoparticles for Upgrading of Biophenolics

Hydrodeoxygenation (HDO) is an attractive route for the upgrading of bio‐oils produced from lignocellulose. Current catalysts require harsh conditions to effect HDO, decreasing the process efficiency in terms of energy and carbon balance. Herein we report a novel and facile method for synthesizing bimetallic PtCo nanoparticle catalysts (ca. 1.5 nm) highly dispersed in the framework of nitrogen‐doped ordered mesoporous carbon (NOMC) for this reaction. We demonstrate that NOMC with either 2D hexagonal (p6m) or 3D cubic (Im m) structure can be easily synthesized by simply adjusting the polymerization temperature. We also demonstrate that PtCo/NOMC (metal loading: Pt 9.90 wt %; Co 3.31 wt %) is a highly effective catalyst for HDO of phenolic compounds and “real‐world” biomass‐derived phenolic streams. In the presence of PtCo/NOMC, full deoxygenation of phenolic compounds and a biomass‐derived phenolic stream is achieved under conditions of low severity.     

Highly Selective Catalytic Conversion of Phenolic Bio‐Oil to Alkanes

Oil and water : A new energy‐efficient and atom‐economical catalytic route for the production of alkanes and methanol by upgrading the phenolic fraction of bio‐oil has been developed. The one‐pot aqueous‐phase hydrodeoxygenation process is based on two catalysts facilitating consecutive hydrogenation, hydrolysis, and dehydration reactions.

     

负载的Ni催化剂上植物油脂加氢脱氧制备第二代生物柴油

在半连续反应器中,以棕榈酸甲酯为植物油脂模型化合物,进行了加氢脱氧制取高品质生物柴油燃料的研究。采用浸渍法制备了HY、SiO₂、γ-Al₂O₃及SAPO-11四种载体负载的Ni催化剂,采用XRD、NH₃-TPD、H₂-TPR、BET、SEM等技术进行催化剂表征。结果表明,Ni/SAPO-11催化剂由于SAPO-11表面呈现的弱酸和中强酸性质,在保持较高的加氢脱氧反应性的同时,抑制了裂解反应的发生,具有较好的催化性能。进一步对SAPO-11上不同的Ni负载量、反应温度、反应压力等进行了研究,发现当Ni负载量为7%,反应温度为220℃,压力为2MPa时,催化剂具有较高的催化性能,棕榈酸甲酯的转化率达到了99.8%,C_9~16烷烃的总选择性为92.71%。     

Selective Production of Renewable para‐Xylene by Tungsten Carbide Catalyzed Atom‐Economic Cascade Reactions

Tungsten carbide was employed as the catalyst in an atom‐economic and renewable synthesis of para‐xylene with excellent selectivity and yield from 4‐methyl‐3‐cyclohexene‐1‐carbonylaldehyde (4‐MCHCA). This intermediate is the product of the Diels–Alder reaction between the two readily available bio‐based building blocks acrolein and isoprene. Our results suggest that 4‐MCHCA undergoes a novel dehydroaromatization–hydrodeoxygenation cascade process by intramolecular hydrogen transfer that does not involve an external hydrogen source, and that the hydrodeoxygenation occurs through the direct dissociation of the C=O bond on the W₂C surface. Notably, this process is readily applicable to the synthesis of various (multi)methylated arenes from bio‐based building blocks, thus potentially providing a petroleum‐independent solution to valuable aromatic compounds.     

Hydrodeoxygenation of benzofuran over sulfided and reduced Ni–Mo/γ-Al2O3 catalysts: Effect of H2S

Effect of H₂S on the catalytic performance of the reduced and sulfided Ni–Mo/Al₂O₃ catalysts in hydrodeoxygenation of benzofuran is studied. The steady-state reaction experiments showed a decrease in activity for both reduced and sulfided catalysts when H₂S was introduced into the feed. The reaction conversion of benzofuran over the reduced catalyst still remained superior to that of the sulfided catalyst in the presence of H₂S, however, at high reaction temperatures, the product distribution over the pre-reduced catalyst is similar to the sulfided catalyst. The studies with temperature-programmed desorption (TPD), temperature-programmed reaction (TPRxn) and X-ray photoelectron spectroscopy (XPS) techniques showed a partial sulfidation of the reduced catalysts when exposed to H₂S under reaction conditions, however, the catalyst does not go through a complete conversion to a molybdenum sulfide phase. Instead oxygen–sulfur exchange on the surface leaves behind oxisulfide species, with catalytic activity closely resembling that of the reduced catalysts. The effect of H₂S on the reaction performance is mainly coming from the competitive adsorption between H₂S and benzofuran and the formation of SH groups with decomposition of H₂S at high temperatures.     

The Effect of Pristine and Hydroxylated Oxide Surfaces on the Guaiacol HDO Process: A DFT Study

The acid-base character of oxide supports is crucial for catalytic reactions. In this work, the acid-base properties of five oxide surfaces common in heterogeneous catalysis were investigated and related to their interaction with monolignol compounds derived from lignin. We have used density functional theory simulations also to understand the role of the surfaces’ hydroxylation state. The results show that moderate hydroxyl coverage on the amphoteric γ-Al₂O₃ (110) slightly strengthens the oxy-compounds’ adsorption due to an increase in Lewis acidity. Similarly, low hydroxyl coverage on the reducible TiO₂ (101) enlarges its adsorption capacity by up to 42 % compared with its clean surface. The higher affinity is attributed to the more favourable interaction between the surface-OH groups and the aromatic rings. Overall, the results indicate that hydroxyl coverage enhances the amphoteric and reducible adsorption capacity towards aromatic species.     

Ni晶粒粒径对Ni/SiO_2催化月桂酸甲酯脱氧制烃性能的影响

采用等体积浸渍-干燥-还原法及等体积浸渍-干燥-焙烧-还原法制备了3种具有不同Ni晶粒粒径的Ni/SiO2催化剂,利用H2-TPR、XRD、TEM、H2-TPR、NH3-TPD及TGA技术对其及前驱体进行了表征,并在固定床反应器上评价了其催化月桂酸甲酯脱氧制十一烷(C11)和十二烷(C12)的性能,分析了Ni晶粒粒径对其脱氧性能的影响。结果表明,采用等体积浸渍-干燥-还原法制备的催化剂中Ni晶粒粒径较小,提高还原温度可以促进Ni晶粒长大。随Ni晶粒粒径增大,月桂酸甲酯的转换频率提高,而C11和C12总选择性、C11/C12物质的量比及裂解产物选择性降低,Ni/SiO2催化剂上月桂酸甲酯脱氧为结构敏感反应。此外,还考察了重时空速对Ni/SiO2催化剂脱氧性能的影响,随重时空速提高,月桂酸甲酯转化率、C11和C12总选择性、C11/C12物质的量比及裂化产物选择性降低。月桂酸甲酯通过脱羰/脱羧反应路径生成的CO/CO2几乎全部加氢转化为CH4,表明Ni/SiO2催化剂具有很高的甲烷化活性。研究还发现,较小Ni晶粒烧结、有机物种吸附及积炭会导致催化剂失活。     

负载型磷化镍催化剂的空气表面改性法制备及其加氢脱氧性能

以MCM-41为载体,采用先前驱体氢气低温(673 K)还原、空气表面改性的方法制备了高活性的Ni2P/M CM-41催化剂,并采用XRD、BET、SEM、TEM、XPS和CO吸附等手段对催化剂进行了表征。以苯并呋喃(BF)加氢脱氧(HDO)为探针反应,考察了空气表面改性对Ni2P/M CM-41催化剂结构和HDO性能的影响。结果表明,空气表面改性得到的催化剂,活性相为单一的Ni2P;空气表面改性能够降低催化剂表面P物种的集聚,有助于小尺寸、高分散的Ni2P活性相的生成。在573 K、3.0 M Pa、质量空速为4.0 h-1、H2/油体积比为500的条件下,Ni2P/M CM-41催化剂上BF转脱氧产物收率高达88%,较程序升温还原法制备的催化剂高50%。