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Ni-based bi- and trimetallic Mn, Mg and aluminum containing catalysts prepared by the solution combustion synthesis (SCS) method were tested in dry reforming of methane (DRM). As a comparison 12 wt.% Ni/α-Al2O3 catalyst prepared by wet impregnation was also investigated. The catalysts were characterized by means of XRD, N2 physisorption, H2-TPR, CO2-TPD, NH3-TPD, TPO, CHNS, TGA, SEM and TEM. Formation of crystalline MnAl2O4 was observed at high temperatures during SCS. The average nickel particle size varied in the range of 12–36 nm. Addition of Mn promoted reduction of Ni and elevated the amount and strength of the basic sites. [ABSTRACT FROM AUTHOR]

Hydrodeoxygenation (HDO) of isoeugenol was carried out at 200 °C and 30 bar of H2 in a batch reactor using a series of bifunctional catalysts consisting of platinum supported on zeolite H-Beta-25 or H-Beta-300 and Bindzil as a binder. The purpose of the matrix was to understand the effect of the binder on the reaction, emulating the components of industrial catalysts and therefore facilitating catalyst scale-up. The effect of the supports acid strength, the location of metal nanoparticles, and their proximity to acid sites was also studied. The catalysts were characterized by N2 physisorption, inductively coupled plasma atomic emission spectrometry, Fourier transform infrared spectroscopy of adsorbed pyridine and scanning and transmission electron microscopy. It was found that platinum supported only on the zeolite was more active compared to platinum located on the binder. High levels of isoeugenol conversion (ca. 100%), propylcyclohexane yield (56%) and the liquid-phase mass balance (68%) were obtained for the catalyst consisting of Pt supported on both zeolite H-Beta-25 and Bindzil. [ABSTRACT FROM AUTHOR]

Citronellal was converted to menthol in a one-pot approach using H-Beta zeolite-based Ni catalyst in a batch reactor at 80 °C, under 20 bar of total pressure. The effects of H-Beta acidity (H-Beta-25 with the molar ratio SiO2/Al2O3 = 25 and H-Beta-300 with SiO2/Al2O3 = 300) and Ni loading (5, 10 and 15 wt %) on the catalytic performance were investigated. Ni was impregnated on H-Beta support using the evaporation-impregnation method. The physico-chemical properties of the catalysts were characterized by XRD, SEM, TEM, ICP-OES, N2 physisorption, TPR, and pyridine adsorption–desorption FTIR techniques. Activity and selectivity of catalysts were strongly affected by the Brønsted and Lewis acid sites concentration and strength, Ni loading, its particle size and dispersion. A synergetic effect of appropriate acidity and suitable Ni loading in 15 wt.% Ni/H-Beta-25 catalyst led to the best performance giving 36% yield of menthols and 77% stereoselectivity to (±)-menthol isomer at 93% citronellal conversion. Moreover, the catalyst was successfully regenerated and reused giving similar activity, selectivity and stereoselectivity to the desired (±)-menthol isomer as the fresh one. [ABSTRACT FROM AUTHOR]

A set of low-cost monometallic Fe, Ni, and bimetallic Fe–Ni bifunctional H–Y-5.1 catalysts with different metal ratios were synthesized by sequential incipient wetness impregnation. The catalysts were characterized in detail by N2 physisorption, Fourier transform infrared spectroscopy with pyridine, inductively coupled plasma optical emission spectroscopy, X-ray diffraction (XRD), transmission and scanning electron microscopy (TEM–SEM), magic angle spinning nuclear magnetic resonance, X-ray photoelectron spectroscopy (XPS), Mössbauer spectroscopy, magnetic measurements, temperature-programmed reduction (TPR), and X-ray absorption spectroscopy (XAS). The results revealed that introduction of Fe led to a decrease of strong acid sites and an increase of medium Brønsted acid sites, while introduction of Ni increased the number of Lewis acid sites. The particle size of iron was approx. 5 nm, being ca. fourfold higher for nickel. XPS demonstrated higher iron content on the catalyst surface compared to nickel. Both Mössbauer spectroscopy and magnetic measurement confirmed the ferromagnetic behavior of all catalysts. In addition, the results from XRD, TEM, XPS, XAS, and magnetization suggested strong Fe–Ni nanoparticle interactions, which were supported by modeling of TPR profiles. Catalytic results of the co-processing of fossil feedstock with lignin-derived isoeugenol clearly showed that both product distribution and activity of Fe–Ni catalysts strongly depend on the metals' ratio and their interactions. Key properties affected by the Fe–Ni metal ratio, which played a positive role in co-processing, were a smaller medial metal nanoparticle size (<6 nm), a lower metal–acid site ratio, as well as presence in the catalyst of fcc FeNi alloy structure and fcc Ni doped with Fe. [ABSTRACT FROM AUTHOR]

One-pot synthesis of menthol from citronellal or citral was summarized. Both batch and continuous reactors have been recently applied. This reaction is very complex and a bifunctional catalyst exhibiting especially Lewis acid sites for cyclisation of citronellal to isopulegol are needed, while metal particles are required for its hydrogenation to menthols. Typically, too mild acidity of the catalyst and small particles do not catalyze menthol formation. Furthermore, too high acidity causes catalyst deactivation and dehydration of menthol. Very high menthol yields have been obtained in batch reactor over nobel and transition metal supported bifunctional catalysts. Shape selectivity was demonstrated for Ni-supported on Zr-modified beta zeolite, which gave high diastereoselectivity to the desired L-menthol. Recently one-pot synthesis of menthol in a trickle bed reactor has been investigated. Catalyst suffers only minor deactivation in transformation of citronellal to menthol, while more severe catalyst deactivation occurred in transforming citral to menthols. Noteworthy from the industrial point of view is that the product distribution obtained with the same catalyst under kinetic regime or under diffusional limitations differs from each other. The metal location and synthesis method of extrudates can have a major effect on the catalyst performance. Kinetic modelling of the data obtained from the trickle bed reactor considering the effectiveness factor is discussed. The results from one-pot synthesis of menthol finding applications in pharmaceuticals and fragrances from citral and its hydrogenated product, citronellal over bifunctional catalysts metal–acid are summarized. The relationship between the catalyst properties and the performance is discussed. In the continuous mode catalyst deactivation becomes apparent and in such mode of operation the product distribution might differ from those obtained in a batch reactor. [ABSTRACT FROM AUTHOR]

Mesoporous materials are promising catalysts for production of biofuels. Herein, H-MCM-41 catalysts with different concentrations of the silica Bindzil binder (10–50 wt%) were prepared and characterized using pulsed-field gradient (PFG) NMR in the powder form and as extrudates. Effective diffusion coefficients (De) are measured in all cases. Diffusivities of n-hexadecane were found smaller for extrudates as compared to the powder catalysts. The estimates of diffusive tortuosity were also determined. PFG NMR data showed one major component that reveals diffusion in interconnected meso- and micropores and one other minor component (1–2%) that may correspond to more isolated pores or may represent complex effects of restricted diffusion. Therefore, several approaches including initial slope analysis of spin-echo attenuation curves, two-component fitting and Laplace inversion were used to discuss different aspects of diffusional transport in the studied H-MCM-41 materials. Correlations between De and the amount of Bindzil, the specific surface area, the micropore volume, the particle size, the total acid sites and the Lewis acid sites are discussed. [ABSTRACT FROM AUTHOR]

BACKGROUND: The metal–acid bifunctional catalysts are widely used in many industrially significant chemical processes, including hydroisomerization of n‐hexane. Deactivation and regeneration of metal–acid bifunctional extrudates was investigated in continuous n‐hexane hydroisomerization in a fixed‐bed reactor. Four Pt/H‐Beta‐25 catalysts containing 30% Bindzil binder were prepared with the same composition and controlled metal deposition. RESULTS: Different preparation steps led to differences in the mechanical strength, Pt particle size, acidity and strength, metal‐to‐acid site (cPt/cAS) ratio and proximity between two types of active sites. A very slow deactivation and high selectivity to C6 isomers was obtained when Pt was deposited on H‐Beta‐25 zeolite. CONCLUSION: Initial selectivity to the desired products was correlated with the physicochemical properties of the catalysts. Location of the metal has a larger influence on catalyst deactivation of the bifunctional catalysts rather than the metal‐to‐acid site ratio or site proximity. Decline of n‐hexane conversion and selectivity to C6 isomers were correlated with changes in the textural properties and acidity of the deactivated catalyst, respectively. © 2021 The Authors. Journal of Chemical Technology & Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Abstract: All input experimental errors for membrane flux determination were analyzed. The overall error in pressure did not largely influence the determination of membrane flux. The main contribution to errors was ascribed to flow meters and membrane thickness. The choice of an optimal operational range for input parameters led to elimination of at least 2/3 of the theoretical relative error for subsequent evaluation of the permeability of individual species. This is especially valuable for low‐permeable membranes, whereas a very low relative theoretical error can be obtained in the case of highly permeable materials. [ABSTRACT FROM AUTHOR]