The combustion of renewable fuels such as methanol or ethanol produces comparatively large concentrations of formaldehyde (CH2O) as a combustion intermediate. This intermediate needs to be quantitatively measured using non-intrusive laser diagnostics to provide a better understanding of the chemical processes in the reaction zone. Spontaneous Raman scattering is used in reactive flow diagnostics to measure spatially resolved species concentrations. For diagnostics of CH2O using Raman scattering, the temperature-dependent Raman spectra of gaseous CH2O are required, but not yet available. One reason for this is that gaseous CH2O polymerizes very rapidly, especially at higher temperatures, and can only be made available in pure form for spectroscopic investigations by specific preparation. For this purpose, a continuous flow reactor was developed in which trioxane is pyrolyzed to monomeric CH2O by means of thermal decomposition in a tube reactor. Using a CW-Raman spectrometer, the products of a thermal decomposition at isothermal conditions are analyzed downstream of the tube reactor and CH2O is detected as the only product of the pyrolysis process. Raman spectra of gaseous CH2O are characterized for the first time using the continuous flow system. The Raman scattering in the CH-bend and CH-stretch regions show characteristic bands, which are, for instance, different in the spectral position to the ones from ethanol, allowing for a spectral discrimination. Raman cross sections reveal that the harmonic-oscillator assumption substantially deviates for the tetratomic CH2O, which underlines the relevance of an experimental characterization at elevated temperatures. Finally, the flow systems developed for the generation of monomeric gaseous CH2O can potentially be employed to improve diagnostics, such as laser induced fluorescence for a quantitative measurement of CH2O.