Atomic layer deposition (ALD) was applied to deposit Pt into KL zeolite channels. The location of Pt deposition and the interaction between Pt and the KL zeolite have been investigated by various characterization methods as well as DFT simulations. It has been demonstrated that Pt nanoparticles (NPs) with precisely controlled size (∼0.8 nm) and high dispersion have been successfully deposited into the micropores of the KL zeolite. The produced Pt/KL catalysts exhibited highly efficient performance for n-heptane reforming to aromatics with a high toluene selectivity up to 67.3% (toluene/total aromatics = 97.8%) and a low methane selectivity (0.9%), in spite of an ultralow Pt loading (0.21 wt%). It was revealed that the strong interaction between Pt and the KL zeolite resulting in the electron-enriched state of Pt and the confinement of Pt in the micropores of the KL zeolite facilitated the aromatization of n-heptane. The small size and high dispersion of Pt NPs contributed to inhibition of the hydrogenolysis reaction. Prevention of agglomeration of Pt NPs due to confinement inside the micropores of the KL zeolite and the strong interaction led to the high stability of the Pt/KL catalysts.

•A novel process was proposed for upgrading heavy oil using a non-thermal plasma.•The noticeably high reactivity of plasma was demonstrated by experiments results.•Loss of the side chain and breakage of the bridged bond were mainly involved.•Intra-molecular condensation was significant than inter-molecular condensation.A process was proposed for upgrading heavy oil using non-thermal plasma technology in a conventional thermal cracking system under atmospheric pressure. Results from a comparison of the reactivity of a N2, H2 and CH4 plasma showed that the plasma can increase the trap oil yield significantly. The trap oil yield increased by ∼9% when the N2 plasma was applied and showed a further increase of ∼19% when the H2 or CH4 plasma was applied. A detailed study on the H2 plasma-enhanced upgrading process was carried out and the results showed that the trap oil yields of the plasma-on runs can be 8–33% higher than those of the plasma-off runs, depending on experimental conditions. Compared with the plasma-off runs, trap oil from the plasma-on runs had a higher (H/C)atomic but less heteroatoms (S and N). Over-balanced hydrogen in the products from plasma-on runs revealed the H2 plasma reactivity, which was further demonstrated by an increase in the substitution and condensation indices of trap oil from the plasma-on runs. Although thermal cracking was mainly involved whether the plasma was applied or not, the electrical field for generating the plasma and the generated plasma may assist with hydrocarbon bond cleavage. This was shown by the increased trap oil yield with the N2 plasma and the hydrogen and carbon residue distribution. Compared with the feedstock, more aromatic and γ-hydrogen (HA and Hγ, respectively) and less α- and β-hydrogen (Hα and Hβ, respectively) were present in the residues, which agrees with the bond dissociation energy data. Similarly, the amounts of saturated (Cs) and alkyl (Cp) carbons in the residues were significantly lower than those in the feedstock while the amount of aromatic carbons (Ca) in the residues was higher than the feedstock. The changes in hydrogen and carbon distribution were more significant for the plasma-on runs. This implies that mainly side chain losses and bridged bond breakage are involved in the processes. This was demonstrated further by the molecular weight distribution. In general, the molecular weight of the residues was lower than that of the feedstock, especially for residues from the plasma-on runs. However, compared with the feedstock, the residues contained less saturated, aromatic and resin fractions but more asphaltene and toluene insoluble fractions. This implies that intra-molecular condensation was more significant than inter-molecular condensation, especially in the plasma-on runs. This should be attributed to the higher stabilization ability of the H2 plasma for fragments or radicals and gas (plasma) flow by which the fragments or radicals are separated rapidly.

Precipitated Fe/Cu/K Fischer–Tropsch Synthesis (FTS) catalysts incorporated with precipitated and binder Al2O3 were characterized by N2 physical adsorption, Temperature-Programmed Reduction/Desorption (TPR/TPD), and Mössbauer Effect Spectroscopy (MES). It was found that the Al2O3 incorporation manner plays an important role on metal dispersion and metal–support interaction, which dramatically influence the H2/CO adsorption, reduction, and carburization, as well as FTS performances of iron catalysts. Specifically, the incorporation of Al2O3 during precipitation (i.e., precipitated Al2O3) leads to high Fe2O3 dispersion and strengthens the Fe–Cu and Fe–K contacts, which in turn promote the reduction and increase the surface basic sites as well as H2 and CO adsorptions. In sharp contrast, Al2O3 added either after precipitation or after heat treatment of the iron precursor (i.e., binder Al2O3) is likely to form a strong metal–support interaction (i.e., Fe–Al2O3 interaction) and decrease the surface basicity, thereby inhibiting CO adsorption. Correspondingly, in slurry-phase FTS reaction, it was observed that the addition of precipitated Al2O3 facilitates catalyst carburization and improves the FTS activity. As expected with the presence of binder Al2O3, the reduced catalysts contain small amounts of iron carbides and show low FTS activity as well as water gas shift (WGS) reactivity. Further, presumably because of more basic sites than binder Al2O3 supported catalysts, the catalyst incorporated with precipitated Al2O3 shows lower selectivity to light hydrocarbons (methane, C2–C4, C5–C11, and C12–C18) but remarkably higher selectivity to heavy hydrocarbons (C19+). These observations were explained in terms of the influence of the Al2O3 incorporation manner on the promotional effects of Cu and K.Keywords: binder Al2O3; Fischer−Tropsch synthesis; iron catalyst; metal dispersion; metal-support interaction; precipitated Al2O3;

Effect of Pt impregnation on the textural properties, surface element distributions and catalytic behavior of a precipitated iron-based catalyst for Fischer–Tropsch synthesis (FTS) was investigated by N2 physical adsorption, temperature-programmed reduction (TPR), Mössbauer effect spectrometer (MES), X-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscopy (HRTEM). Low levels of Pt addition lead to an increase in BET surface area. The result of XPS indicates that Pt enriches on the catalyst surface after being calcined. HRTEM shows that Pt crystallites with diameter about 2 nm are well dispersed on the surface of the catalyst (100Fe/1Pt/4 K/16SiO2). The results of TPR and MES clearly indicate that Pt facilitates the reduction and carburization of Fe2O3 to some extend. The reaction tests in a slurry reactor give the result that the Pt impregnation remarkably increases the FTS activity, and suppresses the selectivities of the light hydrocarbons and the olefins.

An Fe/Cu/K/Al2O3 catalyst for Fischer-Tropsch synthesis (FTS) was prepared by using a combination of co-precipitation and spray-drying method. Thermal gravity (TG), N2 physisorption, X-ray diffraction (XRD), H2 temperature programmed reduction (H2-TPR), CO temperature programmed reduction (CO-TPR), and Mössbauer effect spectroscopy (MES), were used to investigate the effects of different calcination temperatures on the structural properties, reduction, and carburization behaviors of the iron-based catalyst. The results indicated that an increase in calcination temperature facilitated the carbonate decomposition and H2O removal and promoted the reduction of the catalyst. With further increasing the calcination temperature, the BET surface area of the catalyst decreased, and the size of the catalyst crystallite and the average pore diameter increased. Furthermore, high calcination temperature enhanced the metal-support interaction, which weakened the promotional effect of CuO and K2O, and therefore, severely suppressed the reduction and carburization behaviors of the catalyst.

Two spherical iron-based catalysts (Fe/Cu/K/SiO2 and Fe/Cu/K/Al2O3) were prepared by the combination of coprecipitation and spray drying method for the application of slurry Fischer–Tropsch synthesis (FTS). The effects of SiO2 and Al2O3 on the reduction and the carburization behaviors of iron-based catalysts were studied using temperature-programmed desorption (TPD) in H2 and CO, isothermal reduction in syngas, and Mössbauer-effect spectroscopy (MES). The results indicate that SiO2 suppresses the H2 adsorption, facilitates the CO adsorption, and the carburization as compared with Al2O3. The FTS performances of the catalysts were evaluated in a slurry reactor under the industrial relevant reaction conditions of 260°C, 1.5 MPa, H2/CO = 0.67, and a space velocity of 2000 h−1. This indicates that SiO2-supported catalyst has higher FTS activity, higher water-gas shift reaction (WGS) reactivity, and higher selectivities to heavy hydrocarbons. Furthermore, the run stability of Al2O3 supported, iron-based catalyst is better than SiO2 supported catalyst.

Atomic layer deposition (ALD) was applied to deposit Pt into KL zeolite channels. The location of Pt deposition and the interaction between Pt and the KL zeolite have been investigated by various characterization methods as well as DFT simulations. It has been demonstrated that Pt nanoparticles (NPs) with precisely controlled size (∼0.8 nm) and high dispersion have been successfully deposited into the micropores of the KL zeolite. The produced Pt/KL catalysts exhibited highly efficient performance for n-heptane reforming to aromatics with a high toluene selectivity up to 67.3% (toluene/total aromatics = 97.8%) and a low methane selectivity (0.9%), in spite of an ultralow Pt loading (0.21 wt%). It was revealed that the strong interaction between Pt and the KL zeolite resulting in the electron-enriched state of Pt and the confinement of Pt in the micropores of the KL zeolite facilitated the aromatization of n-heptane. The small size and high dispersion of Pt NPs contributed to inhibition of the hydrogenolysis reaction. Prevention of agglomeration of Pt NPs due to confinement inside the micropores of the KL zeolite and the strong interaction led to the high stability of the Pt/KL catalysts.