查看更多>>摘要：Copper phyllosilicate (CuPS) was used as a bifunctional catalyst for hydrodeoxygenation of methyl palmitate (MP) to produce long-chain alpha-olefins without the loss of carbon backbone. The CuPS catalysts were prepared by ammonia evaporation-hydrothermal method. The crystal structure, surface area, reducibility, Cu dispersion, Cu particle size and acidity of the catalysts were examined by XRD, BET, H-2-TPR, TEM, NH3-TPD and Py-IR. The existence of Cu2+ species (octahedral (O-h)/square planar (Sq)), Cu+ and Cu-0 upon calcination/reduction was investigated by in situ TR-XANES. The Cu dispersion was related to the Cu+ fraction in CuPS, while Bronsted acid sites (BAS) depends on Cu-0 particles. The MP conversion to 1-hexadecene proceeds via hydrogenation-dehydration promoted by the synergy of Cu-0 surface and Bronsted acid sites at the interface. The alpha-olefin selectivity depends on a balance between Cu+ and Cu loading. The 20CuPS possessing 10% Cu+ fraction, provides a high conversion of 72% with 45% alpha-olefin selectivity.
查看更多>>摘要：Fe, Ni, Mn, and Ti were directly doped into CeO2 lattice by hydrothermal method to form solid solution catalysts. Various techniques including N2 adsorption/desorption, XRD, HRTEM, XPS, H2-TPR, CO2-TPD, O2-TPD, Raman, and thermogravimetric techniques were applied to study the structural evolution under the preparation/reaction conditions. The incorporation of metal elements distorted the lattice, the difference of interaction resulted in the differences of redox, oxygen activity, basicity and surface etc. properties. The catalytic conversion of ethane with CO2 exhibited dry reforming feature on Ni doped ceria because of the in situ formed metallic Ni0, and selective oxidation feature on Fe, Mn and Ti doped samples. The number and activity of lattice oxygen played the dominant role in affecting activity and selectivity. The solid solution catalysts revealed good coke resistance.
查看更多>>摘要：Controlling the stoichiometry of supported bimetallic nanoparticles is essential in many catalytic reactions, notably selective CO2 hydrogenation. Thus, a new strategy to ensure the preferred stoichiometry (1:1) of supported bimetallic PdZn nanoparticles is presented, involving the deposition of a heterobimetallic precursor, [PdZn(mu-OOCMe)4]2 on a CeZrOx support. After calcination and reduction, the material contained mainly a PdZn alloy, as revealed by powder XRD and XAFS, and further supported by XPS, TEM-EDX, elemental analysis and insitu IR at low temperature using CO as probe molecule. Moreover, a minor phase of oxidized Zn was determined by XAFS. This PdZn/CeZrOx reduced catalyst was combined with SAPO-34 to form a tandem catalytic system for CO2 conversion to hydrocarbons. This system could readily convert CO2 and H2 at high temperature (380 degrees C) into hydrocarbons with a conversion of 24% and high relative selectivity in light hydrocarbons (C2-C3: 82%) with virtually no deactivation of the catalyst after 16 h on stream. Controlled experiments were performed with Pd/ CeZrOx and Zn/CeZrOx in order to gain supplementary insights on this system: Pd/CeZrOx gave only methane and Zn/CeZrOx gave mainly CO under the same conditions. The latter clearly shows that the control of the formation of PdZn phase has great impact for the selective production of hydrocarbons.
查看更多>>摘要：A series of cobalt catalysts loaded on ZSM-5 and ZSM-11 zeolites with different aluminum spatial distribution were prepared by wet ion-exchanged method and characterized by XRD, N-2 adsorption, SEM, Al-27 MAS NMR, H-2-TPR, Py-IR, XPS and diffuse reflectance UV-vis. Their catalytic performance in CO2 assisted dehydrogenation of ethane to ethylene has been evaluated. These catalysts display both superior activity and selectivity, with maximum ethane conversion of 51.3% and ethylene yield of 46.3%. Characterization results show that the excellent catalytic performance results from the high dispersion of cobaltous species stabilized on the exchange sites of zeolitic framework, which is positive correlated with the amount of divalent Co ions located in the internal channels (i.e. alpha-type and gamma-type). The promotional effect of CO2 on stability can be attributed to the removal of coke deposition through Boudouard reaction. The activity is not enhanced by CO2 since the reverse water-gas shift reaction is not evident here.
查看更多>>摘要：Selective conversion of syngas to olefins has aroused extensive attention while some challenges still existed such as high CO2 selectivity. Herein, a series of hydrophobic FeMnOx@SiO2-y-(CH3)(3) (y represents SiO2 weight percent of the catalyst) catalysts with various SiO2 shell content were synthesized for Fischer-Tropsch to olefins (FTO). During the activation process, high hydrophobic SiO2-coating content catalysts suppressed the reduction/carburization of iron species to iron carbide. During FTO reaction, iron carbide of low hydrophobic SiO2-coating content catalysts was re-oxidized while it was stabilized for high hydrophobic SiO2-coating content catalysts. The trade-off among CO2, CH4 selectivity and SiO2-coating content was reflected as an increasing trend relationship, while olefins selectivity exhibited a decreasing trend. Additionally, a desirable hydrophobic SiO2-coating (8.2 wt %) catalyst apparently suppressed CO2 formation (4.7 C%) with high olefins selectivity (54.6 C%) at CO conversion of 50.7%. This study provides an efficient approach to inhibit CO2 formation of Fe-based FTO catalyst.
查看更多>>摘要：For the first time, it was demonstrated that the catalytic properties of semiconductors can be activated using an external electric field only. More particularly, the TiO2 and Fe2O3 were found to produce noticeable amounts of carbon monoxide from carbon dioxide - water vapor gas mixture under the electric field with the strength in the 10(4) V/cm range. The reported process, i.e. the activation of semiconductors using the electric field is more efficient than the utilization of UV-vis radiation in terms of energy efficiency and amount of products formed.& nbsp;
查看更多>>摘要：Monodisperse CoxPdy alloy nanoparticles supported on reduced graphene oxide (CoxPdy @rGO) were synthesized and served as an efficient and recyclable catalyst for the chelation-assisted ortho C-H bond the alkenylation and cyclization of benzamides. The effect of the metal composition in CoxPdy on the catalytic activity was studied, and it was found that there is a synergistic effect between the Co and Pd. The rGO has been proved to play a crucial role in preventing aggregation of alloy nanoparticles, maintaining good dispersion, high catalytic activity and stability. Controllable synthesis of alkenylation and cyclization products can be achieved by modifying the reaction conditions. In addition, the catalyst was stable and recyclable, and the activity decay in the recovery and scale-up experiments is negligible, providing a mild and highly efficient method for direct C(sp(2))-H functionalization.
查看更多>>摘要：The current study's major issue is the transition from trash to value-added products. Eggshell waste is one of the most typical byproducts of food manufacturing. Eggshell is a calcium-rich material that can be used as an economical supply of Ca2+ for the construction of Ca-BTC MOFs. The catalytic impact of an eggshell-based metal-organic framework was explored in the Knoevenagel condensation reaction. To find the best condensation reaction setup, we looked at the effects of different solvents, such as ethanol, ethyl acetate, and toluene, as well as the effects of different temperatures, such as 30-80 degrees C, and different dosages of Calcium-BTC. Ca-BTC's recoverability, reusability, and durability were also confirmed under optimal conditions. Ca-BTC's catalytic performance in the Knoevenagel reaction for condensing various aldehydes with malononitrile derivatives yielded benzylidenemalononitrile with yields up to 99% in a relatively short period under ecologically friendly settings.
查看更多>>摘要：Octahedral molecular sieve (OMS) materials classified by their different tunnel sizes are defined by edge-sharing MnO6 octahedra. Four different OMS materials (OMS-1, OMS-2, OMS-5, and OMS-6) are benchmarked for ethane (C2H6) and cyclohexane (C6H12) oxidative dehydrogenation (ODH) and compared with commercial MnO2, M1 phase MoVTeNb oxide, and vanadium oxide (V2O5). The accessibility of the quadrilateral tunnels of the OMS materials to C(2)H(6 )and C6H12 were further evaluated using density functional theory (DFT). C2H6 and C6H12 ODH rates for the four OMS materials were higher than those measured for commercial MnO2, MoVTeNbO, and V2O5. The C2H6/C(6)H(12 )rate ratios on the four OMS oxides are larger than V2O5. Rate relations for selective accessibility for C(2)H(6 )in small pores, accessibility to both molecules in large pores, and the presence of tunnel defects are discussed. Product selectivities show slightly higher ethylene selectivity in smaller pores suggesting possible connections between pore confinement and selectivity.
查看更多>>摘要：SBA-15 mesoporous silica materials with short mesochannels functionalized with various amino-groups, including NH2-, MeNH-, diamine-, triamine-and guanidine-groups were prepared through one-pot co-condensation of tetraethylorthosilicate (TEOS) and amino-containing trimethoxysilanes in the presence of P123 as pore directing agent and an appropriate amount of Zr(IV) ions. The resultant materials immobilized with CuCl were examined as reusable catalysts in the oxidative homocoupling of phenylacetylene at room temperature with air as the oxidant. Efforts were made to avoid the liquid base additives. The Cu-guanidine-SBA-15 catalyst with Cu/guanidine molar ratio of 0.6 was found to satisfy this objective and gave the highest yield (up to ca. 97%) and nearly 100% selectivity of 1,4-diphenyl-1,3-butadiyne in 24 h. Moreover, the catalyst could retain around 90% yield after reuses for three times.
NSTL
Elsevier