Kinetic model of Fischer-Tropsch synthesis in a slurry reactor on Co-Re/Al<inf>2</inf>O<inf>3</inf> catalyst

A kinetic model for Fischer-Tropsch synthesis is derived using a Langmuir-Hinshelwood-Hougen-Watson approach. Experiments were conducted over 25% Co/0.48% Re/Al 2 O 3 catalyst in a 1 L slurry reactor over a range of operating conditions (T = 478, 493, 503 K; P = 1.5, 2.5 MPa; H 2 /CO = 1.4, 2.1; WHSV = 1.0-22.5 NL/(g cat ·h)). Rate equations were based on the elementary reactions corresponding to a form of well-known carbide mechanism. The 1-olefin desorption rate constant was assumed to be a function of carbon number due to the effect of weak interaction of the hydrocarbon chain with the catalyst surface. Values of estimated activation energies are in good agreement with those reported previously in the literature. The kinetic model was able to correctly predict all of the major product distribution characteristics, including the increase in chain growth probability and decrease in olefin-to-paraffin ratio with carbon number, as well as formation rates of methane and ethylene. © 2012 American Chemical Society

INFLUENCE OF VANADIUM CONTENT ON THE TRIBOLOGICAL BEHAVIOUR OF X140CrMol2-l AIR-HARDENING STEEL

The paper presents experimental testing of wear resistance of steel samples from the same groups of steel. Test results were recorded and presented in the form of diagrams showing the wear resistance of the tested materials in different sliding conditions. The tested steels have high carbon content; the addition of chromium and molybdenum results in the high hardness and low impact toughness of the steels. The addition of vanadium changes the microstructure when the metal grain becomes smaller and the whole structure is martensitic, with chromium and vanadium carbides in the metal matrix. A change in the microstructure causes a change in mechanical properties. The obtained results showed that the addition of vanadium increases impact toughness. However, it is not known how it affects wear resistance and hardness. This type of steel belongs to a new group of steels resistant to wear. A change in the vanadium content causes a decrease in the hardness and wear resistance of the steel and an increase in its impact toughness

Optimization of forced periodic operations in milli-scale fixed bed reactor for Fischer-Tropsch synthesis

One-dimensional pseudo-homogenous dynamic reactor model, incorporating detailed Fischer-Tropsch kinetics, was applied in a theoretical analysis of forced periodic operations. A milli-scale fixed-bed reactor was analyzed, using design and operation parameters, obtained previously in a steady-state optimization. Dynamic optimization and NLP methods were utilized to obtain optimal values of amplitude(s), frequency and phase shift(s) of sine-wave variation of inputs, around the corresponding optimal steady-state values, which maximize the productivity of C5+ hydrocarbons. Inlet variables that were modulated are: coolant temperature, reactants molar ratio, mass flow rate and pressure. In addition to the single input forcing, simultaneous modulations of multiple inputs were also considered, with combinations of the listed inlet variables. Among the single input cases, periodic variation of the coolant temperature resulted in the highest relative improvement of C5+, productivity by 30%. Multiple inputs forcing showed additional potential for improvement, resulting in relative c(5+) productivity increase of 52% for synchronized modulation of the coolant temperature, reactants molar ratio and mass flow rate. However, the increase in C5+ productivity is accompanied with relative increase in methane selectivity of 22-33% (relative to the steady-state value). The results suggest that, in the case of multiple input variations with high amplitudes, modulation of the inlet reactants molar ratio mainly contributes to the increase of CO conversion (e.g. reaction rate), the coolant temperature forcing slightly increases selectivity towards the desirable higher hydrocarbons (C5+), while the variation of the inlet mass flow rate enables better reaction temperature control and prevents a thermal runway

Kinetic Model of Fischer–Tropsch Synthesis in a Slurry Reactor on Co–Re/Al₂O₃ Catalyst

A kinetic model for Fischer–Tropsch synthesis is derived using a Langmuir–Hinshelwood–Hougen–Watson approach. Experiments were conducted over 25% Co/0.48% Re/Al₂O₃ catalyst in a 1 L slurry reactor over a range of operating conditions (<i>T</i> = 478, 493, 503 K; <i>P</i> = 1.5, 2.5 MPa; H₂/CO = 1.4, 2.1; WHSV = 1.0–22.5 NL/(g_cat·h)). Rate equations were based on the elementary reactions corresponding to a form of well-known carbide mechanism. The 1-olefin desorption rate constant was assumed to be a function of carbon number due to the effect of weak interaction of the hydrocarbon chain with the catalyst surface. Values of estimated activation energies are in good agreement with those reported previously in the literature. The kinetic model was able to correctly predict all of the major product distribution characteristics, including the increase in chain growth probability and decrease in olefin-to-paraffin ratio with carbon number, as well as formation rates of methane and ethylene