Syngas properties

It would be highly desirable for reasons of thermodynamic consistency and to avoid energy discontinuities to use just one thermodynamic model representing the properties of all parts of a process but no consistent thermodynamic model can with a sufficient accuracy calculate the thermodynamic properties of all relevant syngas mixtures. This is not only due to the absence of adequate mixing rules for mixtures of steam/water and other compounds, but also that water has 

A practical solution is therefore to calculate thermodynamic properties by combining the steam/water model from the Steam Tables with the properties of the other components as calculated from the SRK equation of state. 

For a gas phase, this can in practice be carried out by first calculating the properties using the SRK equation of state for the complete mixture and then interpolate with the pure steam properties, so that for a mixture without water, the SRK equation state is used, whereas for pure steam, the steam formulas are used. 

The advantage of using such a method is that the impact on the reaction properties is small and that heat duties connected with condensation and steam generation are in agreement with the Steam 

Example 1.3 resulted in an overall tubular reformer duty equal to 108 MW when using ideal gas thermodynamie properties. If the non-ideal gas is considered by use of the method described above, the duty inereases to 109 MW. 

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Two conqiletely different behaviors of oxidative transformation of methane, namely the Oxidative Coupling of Methane to C2 Hydrocarbons(OCM) and the Partial Oxidation of Methane to Syngas(POM), were performed and related over the nickel-based catalysts due to different modification and different supports. It is concluded that the acidic property favors keeping the reduced nickel and the reduced nickel is necessary for POM reaction, and the bade property frvors keeping the oxidized nickel and the oxidized mckel is necessary for OCM reaction. POM and OCM reactions proceed at different active sites caused by different... 

Beneficial Micro Reactor Properties for Syngas Formation... 

Foreseen syngas market in 2040 compared with the current one, differentiated toward utilization. (Reproduced from Boerrigter, H., and van der Drift, A., Bio Key Intermediate in Production of Renewable Transportation Fuel, Chemicals and Electricity, Optimum and Economic Properties of Fischer-Tropsch Plants, ETA, 2005. Copyright by ECN. With permission.)... 

Diesel exhaust, 10 60-61 health effects of, 12 421 Diesel fuel, 12 420-13 13 668 from coal gasifier syngas, 6 7780 cold temperature properties of, 12 423 manufacture of, 12 426-429 requirements for, 12 421—426 specifications for, 12 426t... 

Within such a plant, depending on the pressure of the syngas, the separation can be performed by chemical absorption (usually with amine solvents) under lower pressure conditions or by physical absorption (e.g., with methanol) under higher pressure conditions (see also Chapter 6). Likewise, pressure-swing absorption can be employed. With the special properties of hydrogen, membrane separation processes could also be a very promising solution for the separation task. 

The inner cavity of carbon nanotubes stimulated some research on utilization of the so-called confinement effect [33]. It was observed that catalyst particles selectively deposited inside or outside of the CNT host (Fig. 15.7) in some cases provide different catalytic properties. Explanations range from an electronic origin due to the partial sp3 character of basal plane carbon atoms, which results in a higher n-electron density on the outer than on the inner CNT surface (Fig. 15.4(b)) [34], to an increased pressure of the reactants in nanosized pores [35]. Exemplarily for inside CNT deposited catalyst particles, Bao et al. observed a superior performance of Rh/Mn/Li/Fe nanoparticles in the ethanol production from syngas [36], whereas the opposite trend was found for an Ru catalyst in ammonia decomposition [37]. Considering the substantial volume shrinkage and expansion, respectively, in these two reactions, such results may indeed indicate an increased pressure as the key factor for catalytic performance. However, the activity of a Ru catalyst deposited on the outside wall of CNTs is also more active in the synthesis of ammonia, which in this case is explained by electronic properties [34]. 

Dynamic smdies of the alloy system in CO and H2 demonstrate that the morphology and chemical surfaces differ in the different gases and they influence chemisorption properties. Subnanometre layers of Pd observed in CO and in the synthesis gas have been confirmed by EDX analyses. The surfaces are primarily Pd-rich (100) surfaces generated during the syngas reaction and may be active structures in the methanol synthesis. Diffuse scattering is observed in perfect B2 catalyst particles. This is attributed to directional lattice vibrations, with the diffuse streaks resulting primarily from the intersections of 111 reciprocal lattice (rel) walls and (110) rel rods with the Ewald sphere. 

Syngas composition, most importantly the H2/CO ratio, varies as a function of production technology and feedstock. Steam methane reforming yields H2/CO ratios of three to one whereas coal and biomass gasification yields ratios closer to unity or lower. Conversely, the required properties of the syngas are a function of the synthesis process. Fewer moles of product almost always occur when H2 and CO are converted to fuels and chemicals. Consequently, syngas conversion processes are more thermodynamically favorable at higher H2 and CO partial pressures. The optimum pressures depend on the specific synthesis process. 

Rare earth oxides are useful for partial oxidation of natural gas to ethane and ethylene. Samarium oxide doped with alkali metal halides is the most effective catalyst for producing predominantly ethylene. In syngas chemistry, addition of rare earths has proven to be useful to catalyst activity and selectivity. Formerly thorium oxide was used in the Fisher-Tropsch process. Recently ruthenium supported on rare earth oxides was found selective for lower olefin production. Also praseodymium-iron/alumina catalysts produce hydrocarbons in the middle distillate range. Further unusual catalytic properties have been found for lanthanide intermetallics like CeCo2, CeNi2, ThNis- Rare earth compounds (Ce, La) are effective promoters in alcohol synthesis, steam reforming of hydrocarbons, alcohol carbonylation and selective oxidation of olefins. 

Methanol is currently the largest volume carbonylation product and is made by passing syngas (CO -f H2 Section 4.1.2) over a solid Cu-Zn oxide catalyst. Most of the other carbonylation reactions are catalyzed by the later c -block transition metals, often under homogeneous conditions in solution. This is despite a public perception that the use of heavy metals (such as the complexes of the 4d and 5d transition metals) is generally undesirable. However their extremely effective catalytic properties now make their use mandatory in many... 

A consideration opposing the methanol route is that it does not lead to a product for direct application as fuel (additive), because it must first be converted to methyl tertiar-butyl ether (MTBE). In Europe there is no infrastructure for the large-scale use of MTBE, while in the USA (California) 8 ban on MTBE is expected. Furthermore, methanol from syngas has the same properties as nonnal methanol. On the long-term methanol is a fuel to be used in fuel cells. 

Many catalytic formulation are proposed for the hydroconversion of CO2, most of them are based on promoted copper-zinc oxides given by the long industrial experience on methanol synthesis from syngas (CO+CO2+H2) [3-6]. Specific methanol catalysts working for CO2 are proposed including promoted Cu-Zn catalysts [3,6], zirconia supported systems [7] as well as copper associated with stabilized rare earth oxides [8,9]. In the last case Cu-LaZr and CuZn-Lcfer catalysts were proposed and showed interesting catalytic properties in the methanol formation. 

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