Catalytic Functionalized Structured Monolithic Micro-/Mesoreactors: Engineering, Properties, and Performance in Flow Synthesis: An Overview and Guidelines

Abstract

In this review article, we first discussed the development of silica monoliths with hierarchical macro-/mesopore structure and their potential figures of merit as continuous-flow micro-/mesoreactors of up to 30 ml working volume. Making use of the flow hindrance of different pore structures seen from the Darcy law perspective, we discriminated four structures of the monoliths (M1–M4). We then summarized the most important results, mainly from our studies of continuous-flow structured monolithic reactors and rotating bed reactors (RBRs) filled with structured pellets, activated with various catalytic entities and enzymes. The results show that an increase in the flow rate and thus velocity in reactors activated with more conventional catalytic sites has no or a minor positive effect on the apparent reaction rate. On the contrary, in those with the most open structure (M1) and functionalized with enzymes, it could increase by more than two orders of magnitude even at low overpressures. The production systems worked stably for at least 200 h. To conclude, the synthetic system made of the hierarchically structured monoliths, or RBRs filled with structured catalytic pellets, lay the foundation for a new platform for the high-yield production of a wide variety of specialty chemicals, even on a multikilogram scale, in a safe and sustained manner.

Controllable Enzyme Immobilization via Simple and Quantitative Adsorption of Dendronized Polymer–Enzyme Conjugates Inside a Silica Monolith for Enzymatic Flow-Through Reactor Applications

“…Concerning the monolith MH1, similar types of silica monoliths, possibly with different pore sizes, 67 might work equally well and might be applied as well if for some reason MH1 would not satisfy the requirements for a given enzymatic reaction. In the work presented here, we always used MH1.…”

Treatment of Wastewater Containing Pharmaceutical Micropollutants by Adsorption under Flow in Highly Porous Carbon Monoliths

“…Highly porous carbon monoliths (CM) with well-controlled hierarchical micro/meso/macropores were obtained by replicating silica monoliths by hydrothermal nanocasting. , CM proved to be very suitable for high flow, a low drop pressure, and a homogeneous contact time. ,, This family of monoliths, prepared by spinodal decomposition, can have different natures (silica, zeolites, titania, etc.) and has proven to be extremely efficient in flow chemistry in many applications such as high-performance liquid chromatography and electrochromatography, , heterogeneous catalysis, − photocatalysis, biocatalysis, ,, oil purification, decontamination of water containing radioactive elements, metal capture, , etc. In this study, CM were used to deplete some antibiotics from waters by adsorption under flow.…”

Hierarchical Macro-Mesoporous Silica Monolithic Tablets as a Novel Dose–Structure-Dependent Delivery System for the Release of Confined Dexketoprofen

“…For several years, materials with a hierarchical porous structure have attracted great interest in the scientific community due to their similarities to structures found in nature. − Such materials have large channel-like macropores (1–50 μm) and smaller mesopores (2–50 nm), guaranteeing high surface area. , These properties make the materials suitable for the application as enzyme carriers, precursors of chemical microreactors, − or monolithic columns for chromatography. , Little space is devoted to the use of these materials as pharmaceutical carriers, especially for the controlled release of poorly water-soluble drugs that account for nearly 50% of currently marketed drugs and an estimated 70% of pipeline active pharmaceutical ingredients (APIs) …”