4. (L.Roint each &prints; . Explain each of the following observations for a Pt

Question

4. (L.Roint each &prints; . Explain each of the following observations for a Pt catalyzed washcoated monolith used in a pollution abatement application. a. The inlet temperature to the catalyst is doubled (200 to 400°C) but the conversion does not change significantly. Ans. (BMT Control) b. The concentration of catalytic component on the carrier is doubled and the washcoat loading (the amount of washcoat) on the monolith is decreased to one half its original value. Why does the conversion increase? c. The space velocity (SV) and flow rate are maintained the same but the diameter of the entire monolith is increased. How will the pressure drop change? d. The concentration of catalytic component (ie. P) in the catalyst is doubled but there is no change in conversion The diameter of the entire monolith is decreased but the SV and flow rate are maintained the same. The catalytic component (i.e. Pt) concentration in the carrier and washcoat loading on the monolith are the same. What process parameters cause an increase in the conversion and will there be a penalty? e. f. A catalyst consisting ofP, dAl2O monolith is returned from a customer's reactor. They complain that it no longer achieves the same maximum conversion of the hydrocarbon as the fresh catalyst. What are the two possible causes of deactivation? What characterization methods would you use to obtain possible reasons for deactivation? A 15 mm A120, particle containing 25% Ni is replaced with another 15 mm particle containing the same amount of Ni (concentrated) but with a hole in its center 6 mm in diameter. What will be the consequences for conversion and other process parameters if the reaction is limited by A. by chemical reaction B. g. pore diffusion bulk mass transfer h. The concentration of Ru on Al,03 is increased from 3 to 4.0% and the conversion increases from 15% to 25%

Explanation / Answer

a) The conversion is not changing significantly this can be attributed to the fact that reaction is either in diffusion control regime or mass transfer control regime and not in kinetically controlled regime where the temperature effects the conversion significantly.

b) The conversion increases as the active component is responsible for the conversion and the washcoat provides support for carrying the active components. So on increasing catalytic component conversion increases due to increased activity and by reducing washcoat thickness resistance offered by the washcoat for the reaction to take place also reduces. So both the factors contributes to increased conversion.

c) Since the space velocity and flow rate is same but the diameter has been increased so now same flow is experienced by larger area therefore the pressure drop will be decreased.

d) Conversion remains unaffected by increasing catalytic component this can be because the reaction is in mass transfer control regime.

e) Decreasing diameter will increase conversion as it will reduce the mass transfer limitations but there will be penalty of higher pressure drop.

f) To possible cause of deactivation are

i) Sintering

ii) Catalyst decativation by sulphur, lead and lube oil additives.

Characterization for determining cause of deactivation : we can operate in kinetic regime look at temperature and conversion profile, if the catalyst is sintered there will be very poor conversion achieved.

SEM-EDS can also be used to evaluate concentrations of deposited substance penetrating into the catalyst matrix. The method is very useful for obtaining a distribution profile of an element through a sample of catalyst.

g) A. by chemical reaction - there will be increased rate hence the conversion as more surface area is now available

B. by pore bulk diffusion mass transfer - more conversion will be there as there will be less diffusional limitations.

h) Ru is a promoter here it aids to the catalytic activity hence conversion is increased.

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