Process Modeling of Catalyst Free Direct Methane Conversion into Formaldehyde Using Micro Reactors

Conventional technology for the conversion of methane to formaldehyde involves three expensive and complex stages; reforming of methane to syngas, conversion of syngas to methanol and the oxidation of methanol to formaldehyde. This process suffer from a severe need for a catalyst and costly and energy-intensive intermediate step of syngas production as well as implementation of its operational units which are only economically feasible for a large scale of natural gas. Although there are several small scale natural gas resources available in the remote and abandoned areas which can be used for syngas-based technologies. The catalyst free direct conversion of methane to formaldehyde is a possible option for using the natural gas resources, specifically small-scale ones, economically and integrally. In this study, the catalyst free direct conversion of methane to formaldehyde in an annual micro reactor by finite element method was modeled and the impacts of several operating parameters including temperature, residence time, oxygen / methane ratio and NO2 concentration were comprehensively analyzed. To simulate the process, the extended mechanism of GRI-Mech 3.0 as reaction kinetic, was selected and a relatively good agreement between the simulation results with experimental data in various terms of conversion of methane and formaldehyde concentration were obtained. One of the results of this study was attainment and development of a valid and flexible mathematical model to predict the behavior of complex reaction kinetics. Reaching the single-pass yield of 10% of formaldehyde is also one of the most promising results of this study.