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Titanium silicalite (TS-1) zeolites with different distribution of Ti species were synthesized through altering different amounts of (NH4)2SO4 as crystallization-mediating agent. The distribution of titanium species of TS-1-X samples (X represents the molar ratio of (NH4)2SO4 to SiO2) was systematically investigated via ICP-AES, FT-IR, UV-vis, UV-Raman and other techniques. The TS-1-X zeolite samples were applied in the epoxidation of 1-hexene reaction. It was found that the appropriate amount of ammonium salt not only facilitated the enrichment of titanium species from liquid phase to solid phase and promoted the incorporation of Ti into the MFI skeleton, but also resulted in the formation of uniformly small TS-1 crystals due to the inhibition of rapid growth of crystals. However, much more amounts of (NH4)2SO4 led to the formation of extra-framework Ti, including anatase TiO2 and amorphous Ti species. Meanwhile it promoted the rapid growth of grain resulting in larger TS-1 crystals. Ti-rich TS-1 sample synthesized with molar ratio of (NH4)2SO4 to SiO2 of 0.2 exhibited higher conversion of 1-hexene (42%) and effective utilization of H2O2 (81.8%). In addition, the effect of ammonium salt's composition on the properties of TS-1 was investigated by experiments and characterizations. It was found that ammonium salt could regulate the process of crystallization through its own anion and changing pH of the synthesis gel.

Metal-modified SiO2 supports were prepared by sol-gel method with Mn, Zn, Zr, and Sr cations doping, and then iron-based catalysts supported on modified SiO2 were prepared by the impregnation method. The iron-based catalysts were characterized by XRD, N2 adsorption, and XPS. The reduction adsorption property of H2 and hydrogenation property of CO were studied by temperature programmed methods. The interaction between catalyst and H was studied by kinetic analysis. The results indicate that metal modification has no influence on phase composition of Fe and surface electronic state of Fe species. However, the modification reduces surface area of catalyst and dispersion of active phase, weakens adsorption ability of H2 and lowers H2 desorption activation energy of the catalyst. Zn and Zr doping restrain reduction of catalysts, while Mn and Sr doping promotes reduction of catalysts. The doping of Mn, Zn and Zr inhibits adsorption of CO on the catalyst surface, while Sr promotes dissociation and adsorption of CO. Mn, Zn, Zr and Sr promote C°C coupling and hydrogenation reaction. Among them, Mn and Zr are more prominent.

With terephthalic acid (H2BDC) as ligand and cobalt acetate as Co source, metal-organic frameworks (Co-BDC MOFs) were synthesized in water by co-precipitation; after that, core-shell Co@C catalysts were prepared by chemical vapor deposition (CVD) of Co-BDC MOFs in acetylene and Ar atmosphere. The structure, composition and properties of Co@C catalysts were characterized by XRD, nitrogen physisorption, SEM, TEM, XPS, TGA and Raman spectroscopy and their catalytic performance in Fischer-Tropsch synthesis (FTS) were investigated in a fixed-bed tubular reactor. The results demonstrated that the carbonization atmosphere has an important influence on the graphitization degree of carbon shell, whereas has little effect on the phase and size of Co core. The pore of graphite shell is significantly improved by CVD in acetylene, which can enhance the selectivity to heavier hydrocarbons (C5+) for CO hydrogenation; in particular, the Co@C-C2H2 catalyst shows a high selectivity of 82.66% to the C5+ hydrocarbons. As the carbon shell can effectively inhibit the cobalt nanoparticles from migration and agglomeration during the FTS reaction, the Co species were well distributed in both the fresh and spent catalysts and no significant sintering and deactivation are observed for the Co@C catalysts upon the FTS tests. During the FTS reaction, the active phase changes from metallic Co to a mixture of metallic Co and Co2C, whilst the catalytic activity of Co@C-C2H2 keeps almost unchanged, suggesting that Co2C may also be an active phase for the Fischer-Tropsch synthesis.

The monodisperse SiO2 microspheres with average diameter of 230 nm made by optimized Stober method were used as core to prepare core-shell structure SiO2@Fe2O3 catalysts with different shell thickness through hydrolysis precipitation. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2 physical adsorption and X-ray diffraction (XRD) were used to characterize the size, structure and morphology of catalysts and the effects of different preparation conditions on morphology were discussed. The characterization results indicate that SiO2@Fe2O3 catalysts possess obvious core-shell structure and the spherical morphology of catalyst is kept. Iron oxide nanoparticles are attached to the silica surface through hydroxyl-bond and a 2–10 nm thick dense shell is formed.

Three hydrocracking catalysts were prepared by impregnation method with different incorporation manners of Ni/W metals on HY/Al 2 O 3 support. The effect of combination methods on acidity, hydrogenation capability of the catalysts and its hydrocracking performance on FT wax was studied. The balance between hydrogenation performance and cracking performance could be modulated by adjusting the metal-support combination methods. Ni/W pre-impregnated on HY can increase the hydrogenation capability of the catalyst and simultaneously lower the acidity of the support. The results show that the coordination of high hydrogenation capability and low acidity of catalyst can inhibit the formation of secondary cracking on some extent, and increase the selectivity of diesel. While Ni/W metals supported on HY/Al 2 O 3 can achieve a relative balance of hydrogenation and cracking, thus the catalysts have a higher activity and the more flexible ability to modulate reaction.

A theoretical study of the carbon atoms adsorption and diffusion on the surface and into the subsurface of Fe (111) is performed using DFT calculations. Before the carbon coverages up to 1 ML, the adsorbed carbons tend to exist in an isolated atomic state and cause a reconstruction of Fe (111) surface. The configurations of “mC2+nC” are energetically favorable on the Fe (111) surface at 1 ML ≤ θC ≤ 2 ML. At a higher coverage, complicated adsorbed patterns such as chains and islands are found, and we predict that these carbon islands can function as the nucleation center of the precipitation of graphite or carbon nanotubes on the Fe(111) surface. In the subsurface region, the carbon atom prefers the octahedral site. The barriers for diffusion on and into the Fe (111) surface and subsurface are 0.45 eV and 0.73 eV, respectively. Actually, C2 formation is thermodynamically favored, whereas C migration into the subsurface region is kinetically feasible.

CO adsorption, CO dissociation and C-H and C-C bond-making reactions on Cu-covered Fe(100) have been computed within the framework of periodic density functional theory. Compared to the clean Fe(100) surface with strong CO activation, Cu monolayer-covered Fe(100) surface has weaker CO adsorption energy, lower CO activation degree; and ultra higher CO dissociation barrier (2.4 eV). Under H co-adsorption, CO dissociation is favored kinetically on Fe(100). On the Cu-monolayer covered Fe(100), co-adsorbed H largely facilitates CO dissociation via the formation of CHO. The energy barrier decreases to as low as 0.92 eV. It is also found that C-H and C-C bond-making reactions of Cu monolayer-covered Fe(100) surface have lower activation barriers and are more exothermic than on the clean Fe(100) surface.

The surface structures of Fe 3 O 4 (111), (110), and (001) have been studied at the level of density functional theory. It is found that there are two most stable Fe 3 O 4 (111) surfaces in close energy and terminated with the exposed tetrahedral and octahedral iron layers. Both Fe 3 O 4 (110) and Fe 3 O 4 (001) surfaces have two surface terminations in close energy. The computed results agree well with the experiments and explain reasonably the observed diversity and complexity of the experiments. The computed surface free energies indicate that (111) is less favorable thermodynamically than (110) and (001), and the formation of (111) should be kinetic controlled.

Water adsorption on the Fe(subscript tet1)-terminated and Fe(subscript oct2)-terminated surfaces of Fe3O4 (111) has been calculated at the level of density functional theory (GGA/PBE). On the Fe(subscript tet1)-terminated surface at 1/5 monolayer (ML), the molecular adsorption mode with a hydrogen bond and the heterolytically dissociative mode show the highest stability, whereas the hydronium-ion-like structure OH3(superscript +)-OH becomes possible at 2/5 ML, followed by the hydrogen-bonded water aggregate. These results agree well with the available experimental observations. For Fe(subscript oct2)-terminated surface, the molecular water prefers to adsorb on the surface Fe(subscript oct2) atom at 1/6 ML, whereas other adsorption modes become possible and may coexist at 1/3 ML. The Fe(subscript tet1)-terminated surface is more favorable than the Fe(subscript oct2)-terminated surface for water adsorption. The adsorption mechanism has been analyzed on the basis of the calculated local density of state.

Spin-polarized density functional theory (DFT) calculations have been performed on the structure and stability of Fe 2 C. It is found that orthorhombic Fe 2 C is more stable than hexagonal Fe 2 C by 0.16 eV on the basis of the computed cohesive energies. The structures and stability of the orthorhombic-Fe 2 C low index surfaces have also been investigated at the same level and the low index surfaces have the decreased stability order of (011) > (110) > (100) > (101) > (001). Comparison of the most stable Fe 3 C, Fe 4 C, and Fe 2 C surfaces shows that there is no linear correlation of surface energy and carbon content. And comparison of their most stable surface with the body-centered cubic Fe shows that these carbide surfaces have lower surface energies than the most stable (110) surface of body-centered cubic Fe, indicating that the surface thermodynamics favor carburization at Fe surfaces.

A systematic study of the structure, bonding and relative thermodynamic stability of known crystalline nickel phosphides, such as Ni3P, Ni12P5, Ni2P, Ni5P4, NiP, NiP2, and NiP3, were carried out by density functional theory. The elastic behaviors for structurally less-complex compounds (Ni2P and NiP3) were then predicted. These data may be helpful in understanding the catalytic behavior of nickel phosphides.

Ni promoter was introduced into the co-precipitated FeMnK/SiO 2 Fischer-Tropsch synthesis catalysts. The effects of Ni on catalyst structural properties, reduction and carburization behaviors were studied by N 2 physical adsorption, XRD, Mossbauer spectroscopy, temperature programmed reduction (TPR) in H 2 and CO, and isothermal reduction in syngas. The results indicate that Ni promoter increases the BET surface areas of catalysts and is favorable to the formation of smaller crystallite particles. H 2 -TPR results show that Ni decreases the reduction temperature of catalysts, and CO-TPR results show that Ni facilitates the oxygen removal and increases the carbon introduction content. These effects contribute to a significant improvement of the reduction and carburization behaviors of catalysts in syngas, and the promotion effect increases with the Ni loading content.