Carbon monoxide/methanol molar ratio

The carbon monoxide/methanol molar ratio had a positive influence only on the rate of acetic acid, while the rate of the methyl acetate is decreasing smoothly, being almost constant in the range of ncc/nMeOH == 2 2.5 (see Figure 12). 

Methanol is the fuel which may be converted at the lowest reaction temperatures, normally not exceeding 300 °C. Hence relatively small amounts of carbon monoxide are generated. Figure 2.2 shows the CO concentration theoretically expected in the product flow according to a DuPont patent [17]. Thus, assuming a water/methanol molar ratio of > 2 and a reaction temperature of 300 °C, not more than 1.2% of CO will be present in the feed. This reduces the workload of the subsequent gas purification steps. Water-gas shift is therefore obsolete for fuel processors applying methanol steam reforming. 

The processor was operated at atmospheric pressure and at 117—130 °C or 200 °C. A methanol-water mixture (1 1.5 molar ratio) was fed at 0.1 cm /h using a syringe pump. The reactors loaded with powder and pellets had comparable results, but the researchers preferred the powder packed bed form for its smaller volume and mass. The best hydrogen production was obtained at low temperatures, providing, on a dry gas basis, 70% hydrogen, 0.5% carbon monoxide, and residual carbon dioxide. Methanol conversion or thermal efficiency was not reported. 

An autoclave was charged with palladium acetate (0.0140 g), l,3-bis[bis(2-methoxy-5-methylphenyl)phosphino]propane (0.0398 g), trifluoroacetic acid (0.0499 g), benzothiazole (0.4225 g), and 100 ml of acetone. The solution was then treated with 2497.5 ml of methanol and water (1000 ppm) and then sealed and stirred at 800 rpm. The mixture was heated to 70°C and carbon monoxide and ethylene having a molar ratio of 1 1.8, respectively, added until the internal pressure of the autoclave was 100 bar. The mixture was then stirred for 2 hours while the internal temperature and the internal pressure were maintained at 100 bar and 70°C. After cooling the contents were removed, degassed, filtered, washed with methanol several times, and 51.5 g of product isolated. 

Figure 2.2 Theoretical carbon monoxide concentration obtained by methanol steam reforming as a function of the molar water/methanol feed ratio and reaction temperature [17].

The actual process is a combination of the gas-phase and heterogeneous reactions mentioned earlier, with the additional formation of water. The typical product composition observed in the experiments with pulsed microwave discharge in methanol is (molar fractions in gas phase) 55% hydrogen, 12% carbon monoxide (CO), 10% methane, 20% water, 1% carbon dioxide, 1% ethane, and 1% etlylene. The solid-to-gas ratio (C(s) C(g)) is close to 1 in this case, in good agreement with formula (10-17). 

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