Support effects on hydrotreating activity of NiMo catalysts (original) (raw)
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Comparative study of spent and virgin NiMo/γ-Al2O3 hydrodesulphurization catalysts
2ND INTERNATIONAL CONFERENCE ON MATHEMATICAL TECHNIQUES AND APPLICATIONS: ICMTA2021
It is well known that supported (Co) or (Ni) molybdenum/alumina catalysts are extensively used in hydrotreating (HT) processes for the production of environmentally friendly fuels, and these catalysts have been in need of extensive studies in term of their use and deactivation. This work demonstrate a comparative physical and chemical study of virgin and spent NiMo-γ alumina catalysts and characterized them by thermo gravimetric analysis (TGA), field emission scanning electron microscopy (FESEM), atomic force microscope (AFM) and fourier , transform , infrared , spectroscopy (FTIR). It was noted that there is obvious changes in structural, textural, particle size, physical properties, such as densities, porosity of the virgin catalysts with use as a result of carbon deposition and change in its structural components.
Journal of Catalysis, 2007
The activity of NiMoS catalysts supported on niobia, alumina, and niobia/alumina was compared for the thiophene hydrodesulfurization (HDS) and 2,6-dimethylaniline (2,6-DMA) hydrodenitrogenation (HDN) reactions. To evaluate the acidity of the supports and identify the nature of the sulfide sites, adsorption of 2,6-dimethylpyridine, pyridine, and CO was performed and followed by IR spectroscopy. This study has shown that with niobia as a support, the activity of NiMoS catalysts in thiophene HDS and in HDN of 2,6-DMA was no longer promoted by the synergy between Ni and Mo. The absence of synergy between molybdenum and nickel on niobia can be explained by the strong interaction of each metal with niobia at the expense of interaction with each other. Moreover, it has been shown that on a niobia/alumina support, the formation of the NiMoS phase can be directly linked to the presence of alumina not covered by niobia. However, niobia is an interesting support for the HDN of 2,6-DMA, because it favors the formation of xylene through direct ammonia elimination involving low H 2 consumption. The activity for xylene formation on niobia is linked to the electron-deficient nature of the Mo sulfide site, as demonstrated by CO adsorption followed by IR.
Catalysis Letters, 2020
The effect of Zn/Al ratio and addition of silica to Al-Zn x oxides on the structure and catalytic properties of supported NiMo catalysts in hydrodesulfurization reaction of thiophene was studied. NiMo catalysts were synthesized by simultaneous impregnation of Ni acetate and 12-molybdophosphoric acid on Al-Zn x and Al-Zn 0.16-Si mixed oxide (with x = Zn/Al ratio of 0.05-0.57) prepared by hydrothermal synthesis at 180 °C. Colloidal SiO 2 was added to the Al-Zn x oxides (Si/Al = 0.3 ratio) to modify textural and structural properties of NiMo catalysts. These materials were characterized by N 2 physisorption, SEM, XRD, FTIR, UV-Vis DRS, TPR-H 2 , TPD-NH 3 , XPS, HRTEM and tested in thiophene conversion at 280-400 °C and 1.0 MPa. It was found out that the surface area of the supports calcined at 500 °C, decreases with the increasing Zn/Al ratio, which could be due to the interaction of the Zn with the alumina, leading to formation of Zn-spinel. After impregnation of the supports with NiMo active components, the presence of Zn increases the amount of surface Mo in octahedral sites at Zn/Al = 0.21 ratio. At this ratio maximum in HDS activity of NiMo/Al-Zn x samples was observed. Addition of silica to Al-Zn mixed oxide (Zn/Al = 0.16) leads to more active NiMo catalyst due to formation of more Ni(Zn)-Mo-S active species as revealed by XRD and HRTEM.
Catalytic hydrotreatment on alumina–titania supported NiMo sulphides
Catalysis Today, 2001
MoNi/Al 2 O 3 catalysts have been widely used for hydrodesulphurisation of oil fractions. In order to enhance the catalytic activities for HDS and HDN, catalysts supported on titania-modified alumina carriers have been studied. The MoNi/Al 2 O 3 -TiO 2 catalysts were characterised by benzene sorption, ammonia sorption, temperature programmed reduction, X-ray diffraction and scanning electron microscopy. The supports effect was examined by comparing thiophene conversion and sulphur or nitrogen contents in diesel oil fraction.
Bulletin des Sociétés Chimiques Belges, 2010
Two industrial hydrotreating catalysts, CoMo/AlnOs and NiMo/Ai203, were compared with respect to their activity and selectivity In thiophene hydrodesuiphurisation and cyclohexene hydrogenation at 280°C and 4 MPa. Their difference in catalytic properties for HDS and hydrogenation was found strongly dependent on the experimental conditions. Addition of small amounts of H2S to the feed inhibits the activity of both catalysts; but at high H2S levels, the catalysts remain active. A new type of site Is proposed to operate at high H2S levels. The NiMo catalyst was found far more active than the CoMo catalyst at low H2S pressure, while the two catalysts became equivalent at high H2S levels.
Catalytic hydrotreating of heavy gasoil FCC feed on alumina–titania-supported NiMo catalysts
Applied Catalysis A: General, 2005
An experimental study was conducted in a pilot plant fixed-bed reactor in order to evaluate the effect of hydrogen sulfide on hydrotreating activity of an industrial heavy gasoil Fluid Catalytic Cracking (FCC) feed recovered from a Mexican refinery. Hydrotreating reactions were carried out at three temperatures (603, 638 and 673 K), 11.76 MPa of pressure and LHSVof 6 h À1. Studies were done varying hydrogen sulfide concentration 0, 100, 450 and 750 vol ppm (0, 3100, 12,960 and 23,210 Pa, respectively) at the same operating conditions over a commercial NiMo/g-Al 2 O 3-TiO 2 catalyst. Experimental results showed different behavior for these reactions. An inhibiting effect on hydrodesulfurization (HDS), hydrodearomatization (HDA) and hydrodenitrogenation (HDN) was observed, whereas the hydrodemetallization (HDM) reaction showed an increase in the activity. Apparent activation energies were also determined for each reaction.
Influences of Various Supports, γ-Al2O3, CeO2, and SBA-15 on HDO Performance of NiMo Catalyst
Catalysis Letters, 2014
Hydrodeoxygenation (HDO) of guaiacol (GUA), has been carried out over c-Al 2 O 3 , CeO 2 , SBA-15 supported NiMo catalysts in an autoclave at 250°C and a hydrogen pressure of 5 MPa. In comparison with NiMo/c-Al 2 O 3 , both NiMo/CeO 2 and NiMo/SBA-15 catalysts showed their higher activities. NiMo/SBA-15 has been found to be the most potential one for HDO of GUA with GUA conversion and HDO degree of 90 and 67.5 %, respectively. The main product was cyclohexane with its yield of 56 mol%. The outstanding activity of this catalyst results from a high dispersion of its active sites on SBA-15 as catalyst support. For CeO 2 supported catalyst, some interactions of Ce-Mo can be occurred, leading to an enhancement of its HDO performance.
Applied Catalysis A: General, 2007
The effect of the support g-Al 2 O 3 modified with CaO by deposition-precipitation method on the structure, catalytic activity and selectivity of Mo and Ni-Mo catalysts for HDS was investigated. The resistance of the catalysts to deactivation by coke formation was also investigated. The samples have been characterized by means of XRD, DRS, XPS, Al 27 NMR, TPR, and specific surface area and pore size distribution. The reaction of thiophene hydrodesulphurization, carried out at atmospheric pressure, was used as a model reaction for estimating the activity of the catalyst samples. The obtained results show that the applied method of modification with CaO leads to the formation of support with mesoporous structure and a considerable higher mechanical strength than that of the pure g-Al 2 O 3. Mo and Ni-Mo catalysts deposited on the modified support have higher HDS activity and resistance to coke formation. The presence of Ca 2+ ions in the lattice of the support hinders the formation of crystallites of MoO 3 and Al 2 (MoO 4) 3 phase. The higher catalytic activity of the samples with modified support is due to the higher degree of their sulfidation.