Advancing catalysis by colloidal metal nanoparticles

Abstract

The significant improvement of cost, energy, and material efficiency in chemical processes is the goal of process intensification, with catalysis playing a crucial role. To achieve this, new catalysts are continuously developed and initially tested. A highly active research subtopic focuses on the synthesis of nanoparticles and their catalytic application on a laboratory scale. However, transfer to continuous processes often remains unrealized. Despite extensive development efforts, specific challenges persist for certain catalytic transformations like selective partial hydrogenations of polyenes and alkynes. Newly developed catalysts and preparation methods enable unprecedented innovation in the design and intensification of novel chemical production processes. The present work combines the use of partly newly synthesized colloidal, solvent-stabilized nanocatalysts with elements of all levels of process intensification. In a holistic, hierarchical development approach, operation in a continuous reactor shall be enabled. At the molecular level, various colloidal nanocatalysts are tested for their applicability in the selective partial hydrogenation of different substrates. Investigations into structural changes of the catalyst material are included. At the phase level, an alternative microwave-based heating method for Suzuki couplings using a similar catalytic system is examined. The most promising catalyst system is then applied to establish a reaction sequence at the process-unit level. In a tandem catalytic system, the selective hydrogenation of fatty acid methyl esters followed by isomerizing methoxycarbonylation is analyzed regarding compatibility of both reaction steps in terms of solvent choice, gas-phase change, and subsequent catalyst activation. At the plant level, the combination of a reactor with a mass-transfer unit is realized: Selective partial hydrogenation of fatty acid methyl esters in a capillary reactor with gas-liquid slug flow is coupled with continuous gas replenishment via permeation. This should maintain favorable slug-flow characteristics along the entire reactor length, offering transferability to similar reactions involving homogeneous liquid phases with reactive gases.