**5. Results and Discussion**

The results in this section include the materials and energy balance of both plants, costing, payback period, and comparison on the basis of size for the two catalytic processes. Section 5.3 presents the discussions on the results.

## *5.1. Material and Energy Balance*

The materials and energy balance sheets that were obtained from Aspen Plus ® are given in Sections 5.1 and 5.2.

#### 5.1.1. Material Balance of Molybdenum Oxide

The material balance of Molybdenum Oxide catalyzed process is shown in Table 2. The table shows the flow rates and densities of all of the components of the process. The methanol in inlet stream is 46.25 kmol/h. The flow rate of oxygen in the inlet air stream is 27.56 kmol/h. The formaldehyde in the product stream is 45.7875 kmol/h.

#### 5.1.2. Energy Balance of Molybdenum Oxide

The energy balance of Molybdenum oxide process is shown in Table 3. The table shows the temperatures, pressures, and enthalpies of all the components of the process. The pressure varies from 1 bar to 1.8 bar during the process and temperature varies from 25 to 246.69 ◦C during the process. The input air has a temperature of 25 ◦C and the temperature of DTH going out of condenser is 246.69 ◦C. The enthalpy in reactor is −18,685.22 cal/mol. The highest pressure during the process is inside the absorption column, which is 1.8 bar.

#### 5.1.3. Material Balance of Silver Oxide

The materials and energy balance of the silver oxide catalyzed process obtained from aspen plus is shown in Table 4. The table shows the material balance for silver oxide plant. The molar flow rate of oxygen in the air stream is 14.28 kmol/h. The molar flow rate of methanol in the inlet stream is 49.5 kmol/h. The formaldehyde in the product stream is 46.728 kmol/h.



**Table 3.** Energy balance of Molybdenum-based process.




Liq Vol 60F (L/min) 60.698 106.782 65.294 69.733 33.276 61.717 69.733 98.414 4.439 106.782 24.668 19.554 19.554

#### 5.1.4. Energy Balance of Silver Oxide

The energy balance of the Molybdenum oxide process is shown in Table 5. The table shows the temperatures, pressures, and enthalpies of all the components of the process. The pressure varies from 0.5 bar to 1.8 bar during the process and temperature varies from 25 ◦C to 600 ◦C during the process. The inlet gas is at 25 ◦C, whereas the reactor has a temperature of 600 ◦C. The enthalpy in the reactor is −19,619.55 cal/mol. The highest pressure during the process is in the absorption column, which is 1.8 bar.
