Upscaled Al-Fumarate Synthesis and Shaping by Spray Drying

This study presents a spray-drying Al-fumarate synthesis that allows simultaneous synthesis and workup. This all-in-one step synthesis produces calibrated Al-fumarate grains of high quality without the need for further processing. Obtained materials are characterized by PXRD, TGA, N₂ and H₂O adsorption, PSD, and microscopy imaging. The synthesis has been upscaled to the 60 kg scale. Whereas all reported synthesis routes in the aqueous phase proceed in base conditions by addition of NaOH, the synthesis reported herein is obtained at a pH below 3, with aluminum isopropoxide acting as a base that can steadily react with fumaric acid without the need for pH adjustment. Major differences in the large meso- to macroporous structure are observed depending on the drying process, with an absence of intergranular porosity for the spray-dried pilot batch, reflecting the high-density nature of the obtained MOF powder. Large productivity can be achieved at spray-driers due to their important evaporation capacity (up to several hundreds of tons of/h), opening the perspectives of mass production of Al-fumarate. Air dehumidification in a fluidized bed is carried out as a proof-of-concept application. The fluidized bed’s breakthrough curve profile, with a longer t_50%, is in line with a better column isothermicity, connected to the fluidization conditions. Ultimately, we developed a comprehensive 3-in-1 process that integrates synthesis, drying, and shaping while also exploring its potential for production intensification. We believe that this synthesis approach could pave the way for the scalable production of other Al-MOFs, a topic currently under investigation.