Scaled-up microwave-assisted batch and flow synthesis and life cycle assessment of a silica mesoporous material: UVM-7

Abstract

The development of scaled-up processes for the synthesis and functionalization of silica materials is a key issue for its adoption in various applications. This report introduces innovative batch and flow methodologies for the synthesis and functionalization of substantial quantities of UVM-7, a silica mesoporous material exhibiting a bimodal pore system. The synthesis benefits from the combination of the atrane route with a reduction in reaction time induced by microwaves generated with a solid-state source. To our knowledge, this is the first example of a flow microwave-assisted synthesis of silica mesoporous materials. The materials were characterized by thermogravimetric analysis, X-ray diffraction, transmission electron microscopy and N₂ absorption/desorption isotherms. The scaled-up procedures, encompassing both batch and flow, are capable of synthesizing as-made materials in less than 15 minutes, yielding materials with a topology characteristic of UVM-7 akin to those synthesized via conventional methodologies. The functionalization process can be executed in less than five minutes with loadings of organic moieties of 3.2 mmol of APTES (g of silica)⁻¹. Within an hour, the as-made material for more than 150 g of calcined UVM-7 could be synthesized, and up to 60 g could be functionalized. Life Cycle Assessment (LCA) using the ReCiPe method indicates that the most significant impacts are in the categories of freshwater ecotoxicity, marine ecotoxicity, and human carcinogenic toxicity. The scaled-up synthesis offers a substantial reduction in environmental impacts in these categories, a 5-fold reduction in CO₂ equivalent emissions compared to the non-scaled synthesis and up to half compared to conventional synthesis. The main contributors are solvents in the functionalization and energy consumption during the calcination.