*5.2. Catalyst Performance*

The comparison of both catalytic processes' performance is given in Table 6. It can be observed that the size of the Molybdenum Oxide plant is larger due to the greater amount of air requirement, whereas the size of silver oxide plant is lesser.

#### *5.3. Comparsion of Molybdenum- and Silver-Based Processes*

It can be observed from the results that the amount of methanol used was slightly different, but the amount of air varied significantly in the two processes. In the molybdenum oxide plant, the methanol was utilized at a rate of 46.25 kmol/h whereas it was utilized at a rate of 49.9 kmol/h in the silver-based plant. The amount of oxygen consumed in the silver-based plant was 27.56 kmol/h whereas the amount of oxygen required was at a rate of 15.12 kmol/h. Therefore, the lesser requirement oxygen in the silver-based plant lowers the utilities cost as well as decreasing the size of the equipment used. The capital cost in the case of silver is greater due to presence of an additional distillation column, however the size of overall plant is smaller though. The payback period of the silver-based plant is 2.8 years while it is 3.5 years for the molybdenum-based plant. The lesser payback period in the silver-based plant is due to a lower utility cost in the case of the silver-based process. The regeneration of silver catalyst is also possible. Therefore, from our results we can see that the silver plant has lower utility cost, shorter payback period, lower amount of oxygen required, and compact size as compared to molybdenum. Figures 3 and 4 show the comparison of the outcomes of the two processes for the formaldehyde formation i.e., Molybdenum-based and silver-based processes.

**Figure 3.** Molybdenum-based process.



**Table 6.** Catalyst performance parameters.

**Figure 4.** Silver oxide-based process.
