Fischer–Tropsch synthesis on monolithic catalysts of different materials

Activation of Cobalt Foil Catalysts for CO Hydrogenation

CO hydrogenation has been studied on cobalt foils as model catalysts for Fischer–Tropsch (FT) synthesis. The effect of pretreatment (number of calcinations and different reduction times) for cobalt foil catalysts at 220 °C, 1 bar, and H2/CO = 3 has been studied in a microreactor. The foils were examined by scanning electron microscopy (SEM). It was found that the catalytic activity of the cobalt foil increases with the number of pretreatments. The mechanism is likely an increase in the available cobalt surface area from progressively deeper oxidation of the foil, supported by surface roughness detected by SEM. The highest FT activity was obtained using a reduction time of only 5 min (compared to 1 and 30 min). Prolonged reduction caused the sintering of cobalt crystallites, while too short of a reduction time led to incomplete reduction and small crystallites susceptible to low turn-over frequency from structure sensitivity. Larger crystals from longer reduction times gave increased selectivity to heavier components. The paraffin/olefin ratio increased with the increasing number of pretreatments due to olefin hydrogenation favored by enhanced cobalt site density. From the results, it is suggested that olefin hydrogenation is not structure sensitive, and that mass transfer limitations may occur depending on the pretreatment procedure. Produced water did not influence the results for the low conversions experienced in the present study (<6%).

The Effect of Cobalt Catalyst Loading at Very High Pressure Plasma-Catalysis in Fischer-Tropsch Synthesis

The influence of different catalyst cobalt loadings on the C1–C3 hydrocarbon product yields and energy consumption in plasma-catalytic Fischer-Tropsch synthesis (FTS) was investigated from the standpoint of various reactor operating conditions: pressure (0.5 to 10 MPa), current (250 to 450 mA) and inter-electrode gap (0.5 to 2 mm). This was accomplished by introducing a mullite substrate, coated with 2 wt%-Co/5 wt%-Al2O3, 6 wt%-Co/5 wt%-Al2O3 or 0 wt%-Co/5 wt%-Al2O3 (blank catalyst), into a recently developed high pressure arc discharge reactor. The blank catalyst was ineffective in synthesizing hydrocarbons. Between the blank catalyst, 2 wt%, and the 6 wt% Co catalyst, the 6 wt% improved C1–C3 hydrocarbon production at all conditions, with higher yields and relatively lower energy consumption at (i) 10 MPa at 10 s, and 2 MPa at 60 s, for the pressure variation study; (ii) 250 mA for the current variation study; and (iii) 2 mm for the inter-electrode gap variation study. The inter-electrode gap of 2 mm, using the 6 wt% Co catalyst, led to the overall highest methane, ethane, ethylene, propane and propylene yields of 22 424, 517, 101, 79 and 19 ppm, respectively, compared to 40 ppm of methane and <1 ppm of C1–C3 hydrocarbons for the blank catalyst, while consuming 660 times less energy for the production of a mole of methane. Furthermore, the 6 wt% Co catalyst produced carbon nanotubes (CNTs), detected via transmission electron microscopy (TEM). In addition, scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDX) and x-ray diffraction (XRD) showed that the cobalt catalyst was modified by plasma treatment.

Chemical and Structural Characterization of Amorphous and Crystalline Alumina Obtained by Alternative Sol-Gel Preparation Routes

Aluminum oxide is one of the most commonly used materials in the industry. It is used in the field of catalysis, refractories, and optics. Despite the fact that there are many techniques available, there is still a great challenge in obtaining a material with desired and designed properties. Nevertheless, there is a great flexibility in making customized alumina materials with desired physicochemical properties synthesized by sol–gel methods. This work consists in characterizing the physicochemical properties of sol–gel synthesized aluminum oxide using different sol–gel preparation routes. Three different sols were obtained by using organic precursors and underwent thermal treatment. The structure (Middle Infrared Spectroscopy, Diffused Reflectance Infrared Spectroscopy, X-ray Diffraction, Magic Angle Spinning Nuclear Magnetic Resonance) and microstructure (Scanning Electron Microscopy with Electron Dispersive Spectroscopy) tests of the materials were carried out. The specific surface area was determined by using the Brunauer–Emmett–Teller (BET) method. Thermal analysis was performed for all the powders, in order to analyze the specific temperature of materials transformation.

Plasma-Catalytic Fischer–Tropsch Synthesis at Very High Pressure

This study explored Fischer–Tropsch synthesis (FTS) by combining a non-thermal plasma (NTP), generated by an arc discharge reactor at pressures >> 1 MPa, coupled with a mullite-coated 2 wt%-Co/5 wt%-Al2O3 catalyst. The FTS product yields and electrical energy consumption for the pure plasma (no catalyst) and plasma-catalytic FTS processes were compared under the scope of various reactor operating parameters, namely, pressure (0.5 to 10 MPa), current (250 to 450 mA) and inter-electrode gap (0.5 to 2 mm). The major products, obtained in low concentrations for both processes, were gaseous C1–C3 hydrocarbons, synthesised in the order: methane >> ethane > ethylene > propane. The hydrocarbon product yields were observed to increase, while the specific required energy generally decreased with increasing pressure, decreasing current and increasing inter-electrode gap. Plasma-catalysis improved the FTS performance, with the optimum conditions as: (i) 10 MPa at 10 s and 2 MPa at 60 s for the pressure variation study with the longer treatment time producing higher yields; (ii) 250 mA for the current variation study; (iii) 2 mm for the inter-electrode gap variation study. Plasma-catalysis at a gap of 2 mm yielded the highest concentrations of methane (15,202 ppm), ethane (352 ppm), ethylene (121 ppm) and propane (20 ppm), thereby indicating the inter-electrode gap as the most influential parameter.

Monolith catalyst design via 3D printing: a reusable support for modern palladium-catalyzed cross-coupling reactions

The use of an additive manufacturing procedure for the modification of catalytic structures is currently gaining popularity in the field of catalysis.

Enhancing internal mass transport in Fischer–Tropsch catalyst layers utilizing transport pores

A one-dimensional model of Fischer–Tropsch catalyst layers is used for optimization of layer thickness and transport pore fraction to avoid diffusive restrictions and improve productivity.

Opportunities for intensification of Fischer–Tropsch synthesis through reduced formation of methane over cobalt catalysts in microreactors

In this review we discuss the reasons responsible for higher than expected methane selectivity during Fischer–Tropsch synthesis (FTS) over cobalt-based catalysts and describe novel microreactors for use in FTS.

Methods for the catalytic activation of metallic structured substrates

The review addresses the methods for depositing catalytic layers onto metallic structured substrates, specifically focusing on honeycomb monoliths and open-cell foams.