Formox process

Abstract: Alkali earth metal molybdates (MMoO4, M = Mg, Ca, Sr, and Ba) were investigated as catalysts for the selective oxidation of methanol to formaldehyde in the search for more stable alternatives to the current industrial iron molybdate catalyst. The catalysts were prepared by either sol-gel synthesis or co-precipitation with both stoichiometric ratio (Mo:M = 1.0) and 10 mol% to 20 mol% excess Mo (Mo:M = 1.1 to 1.2). The catalysts were characterized by X-ray diffraction (XRD), nitrogen physisorption, Raman spectroscopy, temperature programmed desorption of CO2 (CO2-TPD), and inductively coupled plasma (ICP). The catalytic performance of the catalysts was measured in a lab-scale, packed bed reactor setup by continuous operation for up to 100 h on stream at 400 °C. Initial selectivities towards formaldehyde of above 97% were achieved for all samples with excess molybdenum oxide at MeOH conversions between 5% and 75%. Dimethyl ether (DME) and dimethoxymethane (DMM) were the main byproducts, but CO (0.1%–2.1%) and CO2 (0.1%–0.4%) were also detected. It was found that excess molybdenum oxide evaporated from all the catalysts under operating conditions within 10 to 100 h on stream. No molybdenum evaporation past the point of stoichiometry was detected.

Abstract: Molybdenum oxide (5 to 20 wt.%) supported on calcium or strontium hydroxyapatite were investigated as catalysts for selective oxidation of methanol to formaldehyde. These catalysts were both active and selective, with a maximum yield achieved at 95 % conversion and 96 % selectivity. The main byproducts were CO (3.2 %) and dimethyl ether (DME, 0.7 %). The catalytic performance of the catalysts was measured for up to 600 h at 350 °C. Compared to an industrial iron molybdate catalyst, the hydroxyapatite based catalysts deactivated slower. The active species were found to be a surface layer of MoOx on the hydroxyapatite support, while excess molybdenum formed crystalline (Ca/Sr)MoO4, acting as a reservoir replenishing surface MoOx lost by volatilization with methanol. The excess molybdenum in the form of (Ca/Sr)MoO4 was found to volatilize significantly slower than the excess MoO3 in iron molybdate catalysts. The combination of high activity and selectivity with low rate of Mo volatilization makes this class of catalysts interesting for industrial production of formaldehyde.

Abstract: Formaldehyde is one of the most important intermediate chemicals and has been produced industri- ally since 1889. Formaldehyde is a key feedstock in several industries like resins, polymers, adhesives, and paints, making it one of the most valuable chemicals in the world. However, not many studies have been dedicated to review- ing the production of this economically important prod- uct. In this review paper, we study the leading commercial processes for formaldehyde production and compare them with recent advancements in catalysis and novel processes. This paper compares, in extensive detail, the reaction mechanisms and kinetics of water ballast process (or BASF process), methanol ballast process, and Formox process. The thermodynamics of the reactions involved in the formaldehyde production process was investigated using HSC Chemistry ™ software (Outotec Oyj, Espoo, Finland). Exergy analysis was carried out for the natural gas to methanol process and the methanol ballast process for formaldehyde production. The former process was sim- ulated using Aspen HYSYS ™ and the latter using Aspen Plus ™ software (Aspen technology, Burlington, MA, USA). The yield and product specifications from the simulation results closely matched with published experimental data. The exergy efficiencies of the natural gas to synthesis gas via steam reforming, methanol synthesis, and formalde- hyde synthesis processes were calculated as 60.8%, 61.6%, and 66%, respectively. The overall exergy efficiency of natural gas conversion into formaldehyde was found to be only 43.2%. The main sources of exergy losses were the steam reformer and methanol loss in formaldehyde syn- thesis process. Despite high conversions and selectivities of these processes, the low exergy efficiency suggests that innovations in formaldehyde production processes could give a more sustainable product. Novel methods of direct conversion of natural gas or synthesis gas into formalde- hyde will improve the exergy efficiency, but the conver- sion rate must also be increased with advancements in catalysis.