| The feasibility of using a membrane reactor to shift the equilibrium of formaldehyde production from methanol is investigated. Formaldehyde production from methanol over a silver catalyst is an endothermic, reversible, and conversion-limited dehydrogenation reaction. The industrial practice to overcome these limitations is to oxidize the hydrogen with air to drive the equilibrium to completion and generate heat to sustain the reaction. In the membrane reactor, the equilibrium is further shifted by removing the hydrogen through the membrane. This enables the membrane reactor to be operated economically at a lower temperature.; The permeabilities of gases (hydrogen, oxygen, nitrogen, and carbon dioxide) and vapors (methanol, water, and formaldehyde) are measured using a porous Vycor glass membrane. The reaction kinetics are investigated over a temperature range of 300-400{dollar}spcirc{dollar}C at atmospheric pressure in a fixed-bed differential reactor over 99.998% silver needle catalyst. The membrane reactor performance is experimentally analyzed at atmospheric pressure to study the effect of changing operating variables such as temperature, space velocity, air/methanol feed ratio, and membrane surface area.; Higher conversions are obtained using longer space time and larger membrane area. At 70:30 air/methanol feed ratio 33.7%, 25.9%, and 16.0% of a maximum equilibrium is achieved at 300{dollar}spcirc{dollar}C, 350{dollar}spcirc{dollar}C, and 400{dollar}spcirc{dollar}C, respectively by the combination of the longest space time (6.0 sec) and the largest permeation area (58.4 cm{dollar}sp2{dollar}). At higher temperatures, the membrane reactor plays an important role because of higher hydrogen partial pressure.; A theoretical model is derived and a computer simulation is carried out based on the Runge-Kutta method to verify the above experimental data. Using an isothermal cocurrent model, a parametric study is conducted to provide basic information regarding scale-up and optimum operating conditions.; In conclusion, the current study has not only demonstrated the enhanced equilibrium shift by the membrane, but also introduced a new process using a membrane reactor as an economical alternative to the conventional processes. The experimental study and parametric analysis of the present study point to the necessity of developing an improved permselective inorganic membrane material, which should also be heat-resistant, inexpensive, and easy to handle. Such a new membrane will make the membrane reactor method an attractive alternative in many industrial applications. |
