Gasoline, steam reforming

For higher hydrocarbons, such as gasoline, steam reforming has to be performed at high temperature. Using conventional Ni catalysts, the temperature must exceed 900°C, but addition of Co, Mo and Re or use of zeolites allows a reduction of the temperature by some 10% (Wang et al., 2004 Pacheco et al., 2003). 

It should be noted that these space velocities are similar to those typically found in autothermal reforming (ATR) so that catalyst volumes will not be excessive compared to autothermal reforming processes. Catalyst activity was found to be reasonably stable for the short duration tests in this work. However, the extremely endothermic nature of the reaction and the integral operation of the test reactor made it difficult to extract reaction kinetics. A new test reactor design was developed and fabricated, and work is in progress to obtain simplified kinetics for the gasoline steam reforming reaction adequate to model the catalytic process in the plate reactor simulation. 

Figure 23.1 Prototype ofa 5 kW reformer with integrated flue gas heating for gasoline steam reforming developed at the Forschungszentrum Karlsruhe, Germany (by courtesy of Forschungszentrum Karlsruhe).

Conventional Transportation Fuels. Synthesis gas produced from coal gasification or from natural gas by partial oxidation or steam reforming can be converted into a variety of transportation fuels, such as gasoline, aviation turbine fuel (see Aviation and other gas turbine fuels), and diesel fuel. A widely known process used for this appHcation is the Eischer-Tropsch process which converts synthesis gas into largely aHphatic hydrocarbons over an iron or cobalt catalyst. The process was operated successfully in Germany during World War II and is being used commercially at the Sasol plants in South Africa. 

The primary sources of toluene and xylenes are reformates from catalytic reforming units, gasoline from catcracking, and pyrolysis gasoline from steam reforming of naphtha and gas oils. As mentioned earlier, solvent extraction is used to separate these aromatics from the reformate mixture. 

Several other important commercial processes need to be mentioned. They are (not necessarily in the order of importance) the low pressure methanol process, using a copper-containing catalyst which was introduced in 1972 the production of acetic add from methanol over RhI catalysts, which has cornered the market the methanol-to-gasoline processes (MTG) over ZSM-5 zeolite, which opened a new route to gasoline from syngas and ammoxidation of propene over mixed-oxide catalysts. In 1962, catalytic steam reforming for the production of synthesis gas and/or hydrogen over nickel potassium alumina catalysts was commercialized. 

The plasma reformer efficiency reached 12.3% and 26% in gasoline auto thermal and steam reforming regimes, respectively. The typical composition of the effluent gas from the reformer operating in steam reforming mode was (vol%) H2—28.7, CO—15, C02—3, and CH4—40. 

Cold Hydrogenation A process for selectively hydrogenating petroleum fractions made by steam-reforming, in order to produce gasoline. Developed by Bayer and now in use in 70 refineries and chemical complexes worldwide. 

In the case of synthesis gasoline or diesel fuel from natural gas (GTL), synthesis gas is produced by a combination of steam reforming and partial oxidation processes (combined reforming) to achieve a H2 CO ratio of generally 2.1 1. This means that the overall process energy demand can be reduced to its minimum. The individual reactions are ... 

Methanol is unquestionably the easiest of the potential fuels to convert to hydrogen for vehicle use. Methanol disassociates to carbon monoxide and hydrogen at temperatures below 400°C and can be catalytically steam reformed at 250°C or less. This provides a quick start advantage. Methanol can be converted to hydrogen with efficiencies of >90 %. But methanol is produced primarily from natural gas requiring energy and it is less attractive than gasoline on a well-to-wheels efficiency (2). 

Due to methanol s corrosivity and its affinity for water, it cannot be readily distributed in today s fuel infrastructure. Methanol burns with a nearly invisible flame. Available luminosity additives won t reform in the low-temperature methanol steam reformers. Methanol is more acutely toxic than gasoline. Additives that are likely to be needed for safety and health reasons will impact the fuel processor s performance and cost. 

As we learned in Chapters 3 and 4, many inorganic compounds, not just ammonia, are derived from synthesis gas, made from methane by steam-reforming. In the top 50 this would include carbon dioxide, ammonia, nitric acid, ammonium nitrate, and urea. No further mention need be made of these important processes. We discussed MTBE in Chapter 7, Section 4, and Chapter 10, Section 9, since it is an important gasoline additive and C4 derivative. In Chapter 10, Section 6, we presented -butyraldehyde, made by the 0x0 process with propylene and synthesis gas, which is made from methane. In Chapter 11, Section 8, we discussed dimethyl terephthalate. Review these pertinent sections. That leaves only two chemicals, methanol and formaldehyde, as derivatives of methane that have not been discussed. We will take up the carbonylation of methanol to acetic acid, now the most important process for making this acid. Vinyl acetate is made from acetic... 

Small reformers R D areas include compact and low cost reformers (1-5 kW) to convert fossil fuels (natural gas, gasoline) or biomass fuels (ethanol) to hydrogen via different processes (steam reforming, partial oxidation, auto-thermal, non catalytic hybrid steam reforming). Improvements in reformer efficiency, capacities and response times, and integration of purification unit are also being studied. Examples of projects include ... 

Table 6) indicate that the fuel-processing efficiencies decrease in the order of steam reforming > autothermal reforming > partial oxidation for both gasoline and diesel fuels. 

TeGrotenhuis et al. [58] performed a 1 000 h stability test in a micro structured reactor for the steam reforming reaction with a catalyst not specified. A mixture of 74% isooctane, 20% xylene and 5% methylcyclohexane as simulated gasoline was fed to the reactor at a S/C ratio of three and a 650 °C reaction temperature. A regeneration step was performed after 500 h and finally the catalyst converted 97% of the feed. 

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