**6. Conclusions**

The performance of two catalysts was studied simultaneously and the results were compared. The molybdenum-based plant has a larger plant size, high utility cost, but low cost of installation. Moreover, it has higher conversion of methanol to product i.e., 99%. The silver-based plant requires half the amount of air as compared to the molybdenum-based process, so it has compact plant size, the installation cost is high, but utility cost is low. However, the conversion is less in this process i.e., 75–85% as compared to the molybdenum-based process. Based on the comparative study and calculations, the silver-based process for formaldehyde production is better on an industrial scale.

**Author Contributions:** Conceptualization, S.R.N.; Data curation, K.S.; Formal analysis, S.A.A.T.; Funding acquisition, M.B.K.N.; Investigation, M.J.; Methodology, Y.M.; Project administration, S.R.N.; Software, S.A.A.T.; Supervision, S.R.N.; Validation, M.T.M.; Writing—Original draft, S.A.A.T., S.R.N.; Writing—review & editing, F.U., U.S. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Acknowledgments:** The authors would like to acknowledge the National University of Sciences and Technology (NUST), Pakistan.

**Conflicts of Interest:** The authors declare no conflicts of interest.
