Characterization of Al2O3–ZrO2 Mixed Oxide Supported Mo Hydrotreating Catalyst

Abstract

A series of molybdenum catalysts supported on Al₂O₃–ZrO₂ mixed oxide containing 50% ZrO₂ and 50% Al₂O₃ were prepared by incipient wetness technique and characterized by BET surface area, X-ray diffraction, temperature programmed reduction and oxygen chemisorption. The catalytic activities for hydrodesulphurization (HDS), hydrogenation (HYD), and hydrocracking (HYC) were determined using thiophene, cyclohexene, and cumene as model compounds, respectively. Results indicate that up to 8 wt% Mo loading, the catalyst is well dispersed and crystallite growth occurred beyond this loading. Also both oxygen uptake and catalytic activities increase with Mo loading up to 8 wt% and then decreases at higher loading. A linear correlation was obtained between oxygen uptake and all catalytic activities and the correlation coefficients obtained suggest that the order of catalytic activities for HDS, HYD, and HYC is: HDS > HYD > HYC. Furthermore, the catalytic activities of the mixed oxide supported catalyst for HDS, HYD, and HYC were higher than those supported on pure alumina and pure zirconia. The incorporation of 3% Co on 8% Mo catalyst was determined to result in enhanced activity for HDS, HYD, and HYC.     

Study of the productivity of MWCNT over Fe and Fe–Co catalysts supported on SiO2, Al2O3 and MgO

In the present study, multi-walled carbon nanotubes (MWCNT) were prepared in good quality and quantity, MWCNT were produced using the catalytic chemical vapor deposition (CCVD) technique and the carbon source was acetylene. Different catalysts were synthesized based on iron and a mixture of iron and cobalt metal supported on SiO₂, Al₂O₃ or MgO. The effect of parameters such as iron concentration, support type, bimetallic catalyst and the method of catalyst preparation has been investigated in the production of MWCNT. The quality of as-made nanotubes was investigated by the high-resolution transmission electron microscopy (HRTEM) and thermogravimetric analysis (TGA). The best yield of MWCNT was 30 times of the amount of the used catalyst. The high yield of MWCNT was gained by 40 wt.% Fe on alumina support which was prepared by the sol–gel method. TEM analysis was done for the carbon deposit, which revealed that the walls of the MWCNT were graphitized, with regular inner channel and uniform diameter. It reflected a reasonable degree of purity. The TGA showed that MWCNT was decomposed at 635 °C by a small rate indicating a high thermal stability and well crystalline formation of the produced MWCNT.     

The ignition and combustion characteristics of Al/Ni(IO3)2·4H2O nanothermites

ABSTRACT

Nickel iodate tetrahydrate (Ni(IO₃)₂·4H₂O) particles with different morphology and size were synthesized by precipitation method (PM) and electrospray precipitation method (EPM). The electrospray was used in chemical precipitation to synthesize nanoscale metal iodate particles with a narrow size distribution. The thermal decomposition mechanism of Ni(IO₃)₂·4H₂O at different heating rates, ignition, and combustion of Al/Ni(IO₃)₂·4H₂O nanothermites was studied by thermogravimetry–differential scanning calorimetry–mass spectrometry, T-jump and time-of-flight mass spectrometry, T-jump equipped with high-speed camera, and combustion cell test. The Al/Ni(IO₃)₂·4H₂O prepared by EPM had a lower ignition temperature (587 ± 14°C) and a shorter burn time (159 µs). The ignition processes of Al/Ni(IO₃)₂·4H₂O nanothermites prepared by EPM and PM were solid–solid and gas–liquid reactions, respectively. The rate-determining step of their combustion processes was the burning of aluminum powder and the decomposition of Ni(IO₃)₂· 4H₂O, respectively.     

Optimization of reaction condition on the product selectivity of Fischer–Tropsch synthesis over a Co–SiO2/SiC catalyst using a fixed bed reactor

The Fischer–Tropsch (FT) synthesis is an important method for producing valuable key raw materials such as heavy and light hydrocarbons in various industries. The effects of process conditions (temperature of 503–543 K, pressure of 10–25 bar, and gas hourly space velocity (GHSV) of 1,800–3,600 Nml g _cat^?1 h^?1) on the FT product distribution using Co–SiO₂/SiC catalyst in a fixed bed reactor were studied by the design of experimental procedure and the Taguchi method. The optimization of the reaction conditions for the production selectivity of C₂–C₄ and heavy hydrocarbon (C₅₊) that has not been completely indicated elsewhere was investigated. The effect of operating conditions on the average carbon number distribution, dispersion, and skewness was also studied. Data analysis indicated the highest selectivity for the light hydrocarbons at a pressure of 20 atm, GHSV of 2,400 Nml g _cat^?1 h^?1, and temperature of 543 K resulting in a highest selectivity for heavier hydrocarbons (C₅₊) and the minimum amount of methane in the reaction products that is optimal at the pressure of 10 atm, GHSV of 1,800 Nml g _cat^?1 h^?1, and a temperature of 503 K. Furthermore, based on the surface plot, temperature has more significant effects than the other parameters. In addition, the obtained results indicated that the maximum average number of carbon was obtained in a pressure of 10 atm and a temperature of 503 K.     

Various characteristics of Ni and Pt–Al2O3 nanocatalysts prepared by microwave method to be applied in some petrochemical processes

Alumina-supported metal nanocatalysts were prepared via the microwave method, by loading nano Ni particles (at 1, 3 and 5 wt%) or nano Pt particles (at 0.3, 0.6 and 0.9 wt%). Structural and adsorption features of the nano catalysts were revealed through XRD, DSC-DTA, TEM, H₂-chemisorption and N₂-physisorption. N₂-adsorption–desorption isotherms of type IV were related typically to mesoporous materials with H₂ class of hysteresis loops characterizing ink bottle type of pores. The well dispersed nano-sized metal particles were evidenced in the studied catalytic systems, exhibiting marked thermal stability up to 800 °C. The catalytic performances of different catalyst samples were assessed during cyclohexane, normal hexane and ethanol conversions, using the micro-catalytic pulse technique at different operating conditions. The 5% Ni–γ–Al₂O₃ sample was found to be the most active in dehydration of ethanol to produce ethylene, as well as in n-hexane cracking. However, the 1% Ni–Al₂O₃ sample showed the highest dehydrogenation activity for selective production of benzene from cyclohexane. On the other hand, the 0.9% Pt–γ–Al₂O₃ sample exhibited the highest activity in the dehydration of ethanol and in the dehydrogenation of cyclohexane. The 0.3% Pt–γ–Al₂O₃ sample was the most active in the dehydrocyclization of normal hexane, as compared to the other catalyst samples under study.     

Hydrotreating of vacuum gas oil on modified Ni–Mo/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalysts

The effect of the introduction of P₂O₅ into Ni–Mo/Al₂O₃ catalysts on their activity in the hydrotreating of vacuum gas oil has been studied. As the support, γ-Al₂O₃ prepared from aluminum hydroxide AlOOH powder of the TH-100 brand (Sasol) has been used. The catalytic properties of the catalysts obtained have been examined in the hydrotreating of vacuum gas oil in a continuous-flow unit under hydrogen pressure. The amounts of sulfur and polycyclic aromatic hydrocarbons, the hydrocarbon group composition, and the carbon residue of the feedstock and the hydrotreating product have been determined. The catalysts after testing have been studied using differential thermal analysis in combination with thermogravimetry (DTA–TGA); the influence of the amount of the modifier on the catalytic activity and coking of the catalysts has been shown.     

Olefin Synthesis from Dimethyl Ether in the Presence of a Hydrothermally Treated Mg–HZSM-5/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> Catalyst: Effect of Reaction Conditions on the Product Composition and Ratio

Systematic studies of olefin synthesis from dimethyl ether (DME) in the presence of a hydrothermally treated HZSM-5 zeolite catalyst modified with magnesium have been conducted. Dependences of DME conversion, product yield and selectivity, and lower olefin ratio on space time in the temperature range of 320–360°C have been analyzed. The type of the resulting products has been determined, and assumptions about the reaction chemistry have been made to reveal the role of methylation and hydrogen-transfer reactions in the products formation.     

Acid Properties of the Surface of Zn–B–P/γ-Al<Subscript>2</Subscript>O<Subscript>3</Subscript>/Al Catalysts and Their Activity in Microwave-Stimulated Reaction of Diethylamine Acylation with <Emphasis Type="Italic">m</Emphasis>-Toluic Acid

The acid–base properties of Zn–B–P/γ-Al₂O₃/Al catalysts for the direct acylation of diethylamine with m-toluic acid have been studied using ammonia temperature-programmed desorption, probe adsorption, and IR spectroscopy techniques, the catalysts having been synthesized and tested under conditions of microwave-assisted thermal treatment. A correlation between the activity of the microwave-absorbing catalysts in the target N,N-diethyl-m-toluamide formation reaction and the concentration of acid sites of medium strength on the surface of the samples has been revealed. It has been shown that the main reason behind the higher activity of Zn–B–P/γ-Al₂O₃/Al catalysts prepared under conditions of the thermal action of microwave field is the formation of a more developed active surface characterized by a prevalence of medium acid sites.