Cobalt Catalysts Preparation and Characterization over Alumina Support for Fischer Tropsch Synthesis

An investigation was done to develop and characterize the alumina supported cobalt catalyst for Fischer-Tropsch Synthesis to produce biodiesel from biomass with the aim to produce alumina-supported cobalt catalysts containing 7 to 19 wt.% cobalt content. By using incipient wetness impregnation of γ-Al2O3 supports with cobalt nitrate hexahydrate with ethanol and distilled water solutions; the 14 wt.% cobalt content in catalyst was achieved. Nitrogen adsorption-desorption, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray fluorescence (XRF), H2temperature programmed reduction (H2-TPR), temperature programmed desorption (TPD), temperature programmed oxidation (TPO) and carbon monoxide chemisorption were used for the characterization of the catalysts to attain an appropriate cobalt catalyst. In order to investigate the effect of the impregnation on the crystalline size, surface area and cobalt content, three different impregnation methods with various durations were investigated. In addition, increasing the impregnation duration increased the cobalt content and its dispersion. Based on results, positive effect of the alumina support and impregnation duration on the crystallite size, surface area, and pore diameter, reducibility of the catalyst and cobalt dispersion were investigated. Thus, cobalt catalyst for using in fixed bed reactor to produce biodiesel from biomass through Fischer-Tropsch Synthesis was prepared and characterized.

A review of Fischer Tropsch synthesis process, mechanism, surface chemistry and catalyst formulation

For more than half a century, Fischer-Tropsch synthesis (FTS) of liquid hydrocarbons was a technology of great potential for the indirect liquefaction of solid or gaseous carbon-based energy sources (Coal-To-Liquid (CTL) and Gas-To-Liquid (GTL)) into liquid transportable fuels. In contrast with the past, nowadays transport fuels are mainly produced from crude oil and there is not considerable diversity in their variety. Due to some limitations in the first generation bio-fuels, the Second-Generation Biofuels (SGB)’ technology was developed to perform the Biomass-To-Liquid (BTL) process. The BTL is awell-known multi-step process to convert the carbonaceous feedstock (biomass) into liquid fuels via FTS technology. This paper presents a brief history of FTS technology used to convert coal into liquid hydrocarbons; the significance of bioenergy and SGB are discussed aswell. The paper covers the characteristics of biomass, which is used as feedstock in the BTL process. Different mechanisms in the FTS process to describe carbon monoxide hydrogenation aswell as surface polymerization reaction are discussed widely in this paper. The discussed mechanisms consist of carbide, CO-insertion and the hydroxycarbene mechanism. The surface chemistry of silica support is discussed. Silanol functional groups in silicon chemistry are explained extensively. The catalyst formulation in the Fischer Tropsch (F-T) process as well as F-T reaction engineering is discussed. In addition, the most common catalysts are introduced and the current reactor technologies in the F-T indirect liquefaction process are considered.

Combustion Characteristics and Laminar Flame Speed of Premixed Ethanol-Air Mixtures with Laser-Induced Spark Ignition

Laser-induced spark-ignition (LISI) has an advanced ignition technique with a few benefits over spark ignition. In this study, flame morphology, laminar flame characteristics and combustion characteristics of premixed anhydrous ethanol and air mixtures were investigated using LISI generated by a Q-switched Nd: YAG laser (wavelength: 1064 nm). Experiments were conducted in a constant volume combustion chamber (CVCC) at the initial condition of T0=358 K and P0=0.1 MPa, respectively, and with equivalence ratios (ɸ) of 0.6-1.6. Flame images were recorded by using the high-speed Schlieren photography technique, and the in-vessel pressure was recorded using a piezoelectric pressure transducer. Tests were also carried out with spark ignition, and the results were used as a reference. It has been found that the laminar flame speed of ethanol-air mixtures with LISI was comparable with those of spark ignition, proving that ignition methods have no influence on laminar flame speed which is an inherent characteristic of a fuel-air mixture. The peak laminar burning velocities for LISI and spark ignition with nonlinear extrapolation methods were approximately 50 cm/s at ɸ=1.1. However, LISI was able to ignite leaner mixtures than spark ignition. The maximum pressure rise rate of LISI was consistently higher than that of spark ignition at all tested ɸ, although the maximum pressure was similar for LISI and spark ignition. The initial combustion duration and main combustion duration reached the minimum at ɸ=1.1.

Numerical investigation of a cold bubbling bed throughout a dense discrete phase model with KTGF collisional closure

A hybrid Euleran-Lagrangian Dense Discrete Particle Model (DDPM) was used to numerically simulate the bubbling behavior of a fluidized bed reactor. The model exploits the parcels concept to reduce the number of particles to simulate while exploiting the Kinetic Theory of Granular Flow (KTGF) to account for their repulsive interactions. The DDPM-KTGF was explored throughout a model sensitivity analysis to identify the most influent parameters impacting on the numerical accuracy and performances to ultimately assess its potential use for industrial purposes. Because of the measurement simplicity as well as its strong connection with the bed fluid-dynamic, pressure-drop data was used and processed to obtain the power spectral density (PSD) distribution to empirically and numerically characterize the behavior of this system under a bubbling fluidization regime. The DDPM-KTGF model was found to be sensitive to mesh size, restitution coefficients but mostly to the drag law. However, poor sensitivity to the kinetic viscosity, solid pressure, radial distribution function as well as to the number of parcels was revealed. Besides having an effect on the physical outputs, the mesh refinement was also required to numerically verify the model which also had a significant impact on the simulation time-performance. Moreover, a major barrier was found when using this model to simulate fixed bed regime, showing the limitation of the KTGF approach to high particle density regions as a result of a poor estimation of particles force interactions.

Optimization of melon oil methyl ester production using response surface methodology

In this research work, melon oil was used as feedstock for methyl ester production. The research was aimed at optimizing the reaction conditions for methyl ester yield from the oil. Response surface methodology (RSM), based on a five level, four variable central composite designs (CCD)was used to optimize and statistically analyze the interaction effect of the process parameter during the biodiesel production processes. A total of 30 experiments were conducted to study the effect of methanol to oil molar ratio, catalyst weight, temperature and reaction time. The optimal yield of biodiesel from melon oil was found to be 94.9% under the following reaction conditions: catalyst weight - 0.8%, methanol to oil molar ratio - 6:1, temperature - 55°C and reaction time of 60mins. The quality of methyl ester produced at these conditions was within the American Society for Testing and Materials (ASTM D6751) specification.

Effect of storage conditions on industrial sugar retention in energy beets

Energy beets could compete with corn grain as important industrial-sugar feedstocks for biofuels. However, long-term energy beet storage is necessary to maximize processing equipment use, and storage conditions may entirely differ from those established in the sugar industry. This work evaluated combined effects of surface treatment, temperature, and storage atmosphere on beet sugar retention. Initially, beets were dipped in solutions of either a senescence inhibitor (N6-benzylaminopurine) or one of two antimicrobial agents (acetic acid and pHresh 10.0r) at weight fractions of 0.05 and 0.1%, and 0.1 and 1%, respectively. Beets were then stored for up to 36 wk either under aerobic conditions or in sealed containers, at 6ºC or 25ºC. Surface treatment did not show a statistically significant effect on sugar retention. Aerobic storage at 25ºC enabled initial beet sugar retention due to dehydration caused by low relative humidity (37%) in air. In contrast, aerobic storage at 6ºC enabled sugar retention for 24 wk; however, sugar retention decreased sharply thereafter to 56%. This decrease coincided with mold appearance on beet surfaces. Beets stored in sealed containers at both temperatures retained 38% of initial sugars. Increasing surface area to better incorporate preservatives into beet tissue could improve long-term sugar retention.