Hydrocarbon periodic effluent

Carbon is deposited on a catalytic reactor bed as a result of the cracking of hydrocarbons. Periodically, hydrogen gas is passed through the reactor in an ef-fon to remove the carbon and to preserve the reduced state of the catalyst. It has been found, by experiment, that the effluent gas contains about 10 mol % methane and 90 mol % hydrogen when the temperature is 1000 K and the pressure is 1 bar. Is this conversion thermodynamically limited Can a higher concentration of methane be produced by re-... 

The most significant issue during the tests was the occurrence of periodic spikes in the concentrations of hydrocarbons and CO in the gaseous effluent from low steady-state values. These spikes lasted about 1 minute each. Foster Wheeler has offered some possible explanations, but further testing will be needed to identify the cause and provide a remedy for the problem. 

The catalysts evaluated are active for synthesis gas conversion the percent conversion of H2 and CO is shown for each catalyst in Figure 1 as a function of time under evaluation conditions and temperature. At 280°C the percent conversion of synthesis gas increases with time for the acidic zeolite-supported catalysts, Fe/ZSM-5 and Fe/Mordenite, but decreases for the larger pore, non-acidic zeolite-supported catalyst Fe/13X. The percent conversion increases for all catalysts at 300°C for Fe/ZSM-5 and Fe/Mordenite the conversions remain constant at this temperature for several days, although for Fe/13X the conversion increases with time. The trends in % synthesis gas conversion, particularly % CO, are reflected in the weight % hydrocarbons, carbon dioxide and water obtained in the reactor effluent over the period of evaluation, see Figure 2. It is apparent that the catalysts are effective for the production of hydrocarbons from synthesis gas, but also catalyze the water gas shift reaction the % hydrocarbons and%C02 obtained are greater at the higher temperature (300°C) whereas the % H2O is less at this temperature than at 280°C. 

Figure 2. Steady-state (solid line) and periodic (broken lines—see legend) effluent hydrocarbon distributions for various time-average hydrogen/ acetylene feed ratios for Catalyst I...

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