# Combination of Chemo- and Biocatalysis: Conversion of Biomethane to Methanol and Formic Acid
## 4 Conclusions  
We presented a successful cascadic combination of (i) chemocatalytic direct methane conversion to formaldehyde and (ii) its biocatalytic disproportionation to methanol and formic acid. Moreover, we illustrate possible pathways for the separation of the two final products.  
The cascade is characterized by the following facets:  
1. Productivity. It was possible to produce methanol with an initial FDM activity up to 17,900 nmol\(\cdot\)mg\({}^{-1}\cdot\)min\({}^{-1}\), which is significantly higher compared to those obtained over MMO, which use methane as substrate.
2. Production stages. Nowadays, formic acid is prepared in four production stages (methane \(\rightarrow\) syngas \(\rightarrow\) methanol \(\rightarrow\) methyl formate \(\rightarrow\) formic acid) whereas the herein presented route requires two steps, only. Moreover, methanol is being produced conventionally in a two-step process including the high endothermic syngas production. In this regard our method is clearly favored due to the exothermic nature of the chemocatalytic oxidation process.
3. Biomass utilization. It was demonstrated that the production of methanol and formic acid is possible using biogas as methane source. It could be one option for present and future fermentation plants to broaden their product portfolio beyond the generation of electrical energy and biomethane.  
With this approach, a novel synthesis route towards both methanol and formic acid starting from methane is now available.  
The following are available online at [[http://www.mdpi.com/2076-3417/9/14/2798/s1](http://www.mdpi.com/2076-3417/9/14/2798/s1)]([http://www.mdpi.com/2076-3417/9/14/2798/s1](http://www.mdpi.com/2076-3417/9/14/2798/s1)), Figure S1: X-ray diffraction patterns of V/SBA-15 and SBA-15, Figure S2: Small angle X-ray diffraction patterns of V/SBA-15 and SBA-15, Figure S3: BET isotherms of SBA-15, V/SBA-15 and spent V/SBA-15, Figure S4: Pore size distributions of SBA-15, V/SBA-15 and spent V/SBA-15, Figure S5: Raman spectra of V/SBA-15 and SBA-15 under ambient conditions, Figure S6: IR spectra of V/SBA-15 and SBA-15 at room temperature after drying at 600 \({}^{\circ}\)C for 2 h, Figure S7: UV-vis DRS spectra of V/SBA-15 after 2 h at 600 \({}^{\circ}\)C in air and after application in the chemocatalytic part of the cascade process, Figure S8: Specific FDM activity at different pH values, Figure S9: Loading rate at different loadings of ion exchange Fluoride A111.  
Conceptualization, M.S. and S.W.; methodology, D.S. and M.S.; validation, B.K. and M.S.; investigation, B.K., D.S., T.P. and M.S.; writing--original draft preparation, B.K.; writing--review and editing, S.W., T.P., M.S., D.S.; visualization, B.K.; supervision, M.S. and S.W.; project administration, M.S. and S.W.; funding acquisition, M.S. and S.W.  
This research was funded by Bundesministerium fur Bildung und Forschung (BMBF), grant number 031A168A and 031A168C, by Deutsche Forschungsgemeinschaft (DFG), grant number WO 1531/4-1 and by Deutsche Bundestiftung Umwelt (DBU) with a PhD Scholarship.  
The authors are grateful to the permanent support of [PERSON], [PERSON], [PERSON] and [PERSON].  
The authors declare no conflict of interest.