New Mechanism Insight for the Hydrogenation of CO/CO\u3csub\u3e2\u3c/sub\u3e Gas Mixtures to Hydrocarbons over Iron-Based Catalyst

Iron-based catalysts are the most suitable candidates for converting CO2 or CO2-rich syngas to hydrocarbons. However, several issues about the mechanism of CO2 hydrogenation are still unclear. In this work, we investigated the performance of an iron-based catalyst with H2/CO2, H2/CO/N2 and H2/CO/13CO2/N2 gas mixtures at the same process conditions (T = 270°C, P = 175 psi and SV = 3 NL/h/gcat). The CO2 hydrogenation rate was much lower than that observed for CO hydrogenation. 13CO2 tracer experiments indicated that CO2 is hydrogenated to hydrocarbons via the reverse water-gas shift even when present in small concentration (1.8 vol%). 13C enrichment was observed in both CO and C1-C4 hydrocarbons

Badoga, Sandeep_PhD_thesis_April_2015

Bitumen-derived heavy gas oil contains large amounts of sulfur (~4.0 wt.%) and nitrogen (~0.4 wt.%), which need to be lowered before it becomes suitable as a feedstock for refineries. The most widely used upgrading process is hydrotreating, and the conventional catalyst used for hydrotreating is Ni or Co and Mo or W supported on γ-Al2O3. Additionally, environmentally driven regulations impose strict limits on sulfur and nitrogen levels in transportation fuels. Therefore, the main focus of this work was to enhance the activity of a NiMo supported catalyst through its modification and to improve its selectivity to removal of bulky sulfur- and nitrogen-containing compounds from heavy gas oil under industrial hydrotreating conditions. This work was divided into four phases, and this thesis summarizes the research outcomes of each phase. The first phase examined the effects of chelating ligands, specifically, ethylenediaminetetraacetic acid (EDTA), on hydrotreating activity and the sulfidation mechanism. EDTA was seen to have a beneficial effect on hydrotreating activity. Detailed mechanistic aspects of interactions between support and EDTA, EDTA and metallic species, support and metal, support and active phase, and metallic species and metallic species at different reaction conditions, were also studied. Characterization by XANES revealed that the presence of a chelating agent delayed nickel sulfidation, which was the main cause of improvement in hydrodesulfurization (HDS) and hydrodenitrogenation (HDN) activities. It also showed that EDTA plays a role in redistribution of active phases during sulfidation and favors the formation of octahedral molybdenum oxides. The second phase studied the effects of support modification and combinations of different supports and EDTA. In this phase, several mesoporous materials, including M-SBA-15 (M= Al, Ti and Zr), mesoporous mixed metal oxides (TiO2-Al2O3, ZrO2-Al2O3 andSnO2-Al2O3) and mesoporous metal oxides (ZrO2, Al2O3), were synthesized and used as support materials for a NiMo catalyst. NiMo/M-SBA-15 catalysts showed higher HDS and HDN activities and, the increase in activity is attributed to incorporation of heteroatoms in an SBA-15 matrix, which resulted in increase in metal support interaction, acidic strength and dispersion of active metals. The addition of EDTA to these catalysts helps in the formation of octahedral molybdenum oxide, which are easily reducible during sulfidation. This is evident from the XANES Mo LIII-edge study of the oxide catalysts. The increase in hydrodenitrogenation (HDN), hydrodesulfurization (HDS) and hydrodearomatization (HDA) activities as compared to that shown by the NiMo/γ-Al2O3 catalyst were also observed on addition of EDTA in large-pore, high-surface-area mesoporous zirconia supported NiMo catalysts. The incorporation of different metal oxides in alumina, as in the case of mixed metal oxides, resulted in a change in acidic strength and metal support interactions. It was observed with acridine-FTIR analysis that the catalysts with higher acidic strength tightly held acridine at high temperatures. This implies that catalysts with higher acidity are prone to inhibition by nitrogen-containing compounds present in feed, which will affect catalytic activity. The HDS and HDN activities for hydrotreating of heavy gas oil suggest that mesoporous alumina and titania-alumina supported catalysts perform better as compared to the conventional NiMo/γ-Al2O3 catalyst. Therefore, the effects of EDTA to Ni molar ratio (EDTA/Ni = 0 to 2) on the activities of the NiMo/MesoAl2O3 and NiMo/MesoTiO2-Al2O3 catalysts were studied, and EDTA was observed to have a negative impact on catalytic activity for these catalysts. This is attributed to a decrease in the active metal dispersion in these catalysts caused by the addition of EDTA. The catalysts NiMo/MesoAl2O3 and NiMo/MesoTiO2-Al2O3 without EDTA showed high active metal dispersion due to their high surface area and ordered structure. The third phase studied the combined effects of phosphorus and EDTA on the hydrotreating activity of NiMo supported catalysts. The effects of method of phosphorus addition (sequential and co-impregnation method) were also studied. When phosphorus was added using a co-impregnation method, as in the catalyst NiMoP/MesoAl2O3(CI), an increase in HDN, HDA and HDS activities was observed. However, the catalysts containing both EDTA and phosphorus showed a decrease in HDS and HDN activities. The fourth phase included a kinetic study using the Power Law and L-H models. The catalyst, NiMoP/mesoAl2O3(CI), was found to have higher HDN and HDS activities as compared to a conventional γ-Al2O3 supported catalyst containing phosphorus

Degradation of Phenol With A Microwave-Uv Irradiation Treatment System Using NANO-TiO2

 The degradation of phenol from various industrial effluents becomes essential and studied in this work. The microwave (MW), ultra-violet (UV) and combination treatment systems were designed and TiO2 nanoparticles were used as photocatalyst for the degradation of 1500ppm phenol in a solution. It was observed that the degradation efficiency was less than 10% in both MW and MW-UV systems without a catalyst. However, the addition of TiO2 particles in MW-UV system has increased the phenol degradation efficiency significantly. The extent of increase in degradation efficiency is dependent on the structural and optical characteristics of TiO2, which is affected by the TiO2 preparation method. In this work, the TiO2 nanoparticles with anatase structure were synthesized by hydrothermal (HT) and sol-gel (SG) methods. The synthesized materials were characterized using X-ray diffraction, FT-IR, thermogravimetric analysis, SEM, high resolution TEM and BET method. The higher degradation efficiency of 24% shown by MW-UV-TiO2 (HT) system in 120 minutes as compared to 20% shown by MW-UV-TiO2 (SG) system could be due to higher surface area and better textural properties of TiO2 prepared by hydrothermal treatment. The effect of various initial concentration of phenol (500-1500ppm) on degradation efficiency of MW-UV-TiO2 (HT) system revealed that the increase in the initial phenol concentration decreased the phenol degradation efficiency

Degradation of Phenol With A Microwave-Uv Irradiation Treatment System Using NANO-TiO2

 The degradation of phenol from various industrial effluents becomes essential and studied in this work. The microwave (MW), ultra-violet (UV) and combination treatment systems were designed and TiO2 nanoparticles were used as photocatalyst for the degradation of 1500ppm phenol in a solution. It was observed that the degradation efficiency was less than 10% in both MW and MW-UV systems without a catalyst. However, the addition of TiO2 particles in MW-UV system has increased the phenol degradation efficiency significantly. The extent of increase in degradation efficiency is dependent on the structural and optical characteristics of TiO2, which is affected by the TiO2 preparation method. In this work, the TiO2 nanoparticles with anatase structure were synthesized by hydrothermal (HT) and sol-gel (SG) methods. The synthesized materials were characterized using X-ray diffraction, FT-IR, thermogravimetric analysis, SEM, high resolution TEM and BET method. The higher degradation efficiency of 24% shown by MW-UV-TiO2 (HT) system in 120 minutes as compared to 20% shown by MW-UV-TiO2 (SG) system could be due to higher surface area and better textural properties of TiO2 prepared by hydrothermal treatment. The effect of various initial concentration of phenol (500-1500ppm) on degradation efficiency of MW-UV-TiO2 (HT) system revealed that the increase in the initial phenol concentration decreased the phenol degradation efficiency

Hydrotreatment Followed by Oxidative Desulfurization and Denitrogenation to Attain Low Sulphur and Nitrogen Bitumen Derived Gas Oils

To lower the sulphur content below 500 ppm and to increase the quality of bitumen derived heavy oil, a combination of hydrotreating followed by oxidative desulfurization (ODS) and oxidative denitrogenation (ODN) is proposed in this work. NiMo/γ-Al2O3 catalyst was synthesized and used to hydrotreat heavy gas oil (HGO) and light gas oil (LGO) at typical operating conditions of 370⁻390 °C, 9 MPa, 1⁻1.5 h−1 space velocity and 600:1 H2 to oil ratio. γ-Alumina and alumina-titania supported Mo, P, Mn and W catalysts were synthesized and characterized using X-ray diffractions, N2 adsorption-desorption using Brunauer⁻Emmett⁻Teller (BET) method, X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR). All catalysts were tested for the oxidation of sulphur and nitrogen aromatic compounds present in LGO and HGO using tert-butyl hydroperoxide (TBHP) as oxidant. The oxidized sulphur and nitrogen compounds were extracted using adsorption on activated carbon and liquid-liquid extraction using methanol. The determination of oxidation states of each metal using XPS confirmed the structure of metal oxides in the catalyst. Thus, the catalytic activity determined in terms of sulphur and nitrogen removal is related to their physico-chemical properties. In agreement with literature, a simplistic mechanism for the oxidative desulfurization is also presented. Mo was found to be more active in comparison to W. Presence of Ti in the support has shown 8⁻12% increase in ODS and ODN. The MnPMo/γ-Al2O3-TiO2 catalyst showed the best activity for sulphur and nitrogen removal. The role of Mn and P as promoters to molybdenum was also discussed. Further three-stage ODS and ODN was performed to achieve less than 500 ppm in HGO and LGO. The combination of hydrotreatment, ODS and ODN has resulted in removal of 98.8 wt.% sulphur and 94.7 wt.% nitrogen from HGO and removal of 98.5 wt.% sulphur and 97.8 wt.% nitrogen from LGO

Effect of Pretreatment on Physicochemical Properties and Performance of Multiwalled Carbon Nanotube Supported Cobalt Catalyst for Fischer–Tropsch Synthesis

The influence of different nitric acid concentrations (35, 50, 70 wt %) on the physicochemical properties of multiwalled carbon nanotube was investigated. 15 wt % cobalt was impregnated on acid treated nanotubes. The corresponding catalysts were characterized by BET, XRD, Raman, SEM, TEM, TPR, CO chemisorption techniques to further study the impact of acid functionalization on textual properties, metal dispersion, crystallite size, defect generation, and reducibility of 15Co/CNT catalysts. The performance of prepared catalysts was tested for 30% CO and 60% H₂ with balanced Ar in a fixed bed microreactor for Fischer–Tropsch synthesis at 220 °C, 2 MPa, and GHSV of 3000 cm³·g^–1·h^–1. Pretreatment of CNTs with 70 wt % nitric acid exhibited improved physicochemical properties of 15Co/CNT catalyst and hydrocarbon yield by 35% as compared to untreated CNT supported catalyst