Bimetallic iron-ruthenium nanoparticles on supported ionic liquid phases as selective hydrodeoxygenation and decarboxylation catalysts for the synthesis of phenol and aniline derivatives

• Bimetallische Eisen-Ruthenium Nanoparticle auf Supported Ionic Liquid Phases als selektive Hydrodeoxygenierungs- und decarboxylierungscatalysatoren for die Synthese von Phenol- und Anilinderivaten

Goclik, Lisa; Leitner, Walter (Thesis advisor); Bolm, Carsten (Thesis advisor)

Aachen : RWTH Aachen University (2022, 2023)
Dissertation / PhD Thesis

Dissertation, RWTH Aachen University, 2022

Abstract

This thesis deals with the development of metal nanoparticles immobilized on supported ionic liquid phases (SILPs) as catalysts for the synthesis of phenol and aniline derivatives. To overcome limitations of the classical synthesis pathways, two transformations are focused: The selective hydrodeoxygenation of hydroxy-, amino- and nitroacetophenone derivatives and the selective decarboxylation of hydroxy-, amino- and nitrobenzoic acids. Bimetallic iron ruthenium nanoparticles are considered as the starting point for the screening and development of suitable catalyst systems, since FeRu@SILP is known to catalyze selective hydrogenation and hydrodeoxygenation reactions. Fe25Ru75@SILP was synthesized using an organometallic approach and further functionalized by physisorption of an acidic ionic liquid to prepare Fe25Ru75@SILP+IL-SO3H. Small and well-dispersed nanoparticles were determined on both materials. Compared to various reference materials, the Fe25Ru75@SILP showed high activity and excellent selectivity in the hydrodeoxygenation of 4´-hydroxyacetophenone as model substrate, while the acidic Fe25Ru75@SILP+IL-SO3H caused deacylation and dimerization reactions. The excellent performance of the Fe25Ru75@SILP catalyst motivated its application on other acetophenone derivatives. Functionalities in ortho- or para- position ( OH, Me, OPh, NH2, NHCOCH3, OCOCH3) provide a mesomeric stabilization of the intermediates and, thus, enable the acid free hydrodeoxygenation using Fe25Ru75@SILP. Recording a time profile for the hydrodeoxygenation of 4´-hydroxyacetophenone allowed to follow the reaction progress and the build-up of the intermediate and the product. The addition of small amounts of water to the reaction mixture accelerated the reaction by increasing the local concentration of the substrate at the active sites of the catalyst through solubility effects. Monitoring the development of intermediates and the product in the hydrodeoxygenation of 4´ nitroacetophenone showed a consecutive nitro group reduction and hydrodeoxygenation sequence. A broad scope of hydroxy-, amino- and nitroacetophenone derivatives was successfully hydrodeoxygenated using Fe25Ru75@SILP. Recycling experiments under batch conditions confirmed the stability and reusability of the catalyst. The application of the Fe25Ru75@SILP material in a small-scale continuous flow system evidenced its good productivity and stability over six hours on stream. An alternating use of two substrates was carried out successfully, highlighting the high flexibility of the catalyst. A systematic comparison of the proposed synthesis pathway (Friedel-Crafts acylation and hydrodeoxygenation) to commonly employed synthesis routes towards phenol and aniline derivatives revealed promising potential improvements in terms of green chemistry metrics. A hydrodeoxygenation of lignin-derived aromatic diketones might provide excess to fine chemicals based on a renewable resource. Fe25Ru75@SILP was modified by physisorption of an amine-functionalized ionic liquid producing Fe25Ru75@SILP+IL-NEt2, to enable a selective decarboxylation of hydroxy-, amino- and nitrobenzoic acids. The characterization of the material by electron microscopy and N2 adsorption measurements confirmed the conservation of the nanoparticle size and distribution as well as the reduced surface area and pore volume upon immobilization of IL-NEt2. Comparison experiments with reference materials on the model substrate 4´-hydroxybenzoic acid showed that the activity and selectivity provided by Fe25Ru75@SILP+IL-NEt2 exceeds those of the single components or other investigated catalytic materials. The role of hydrogen was investigated in the decarboxylation of 4´ hydroxybenzoic acid to phenol by performing labeling experiments using D2. The scope of the reaction was explored for a broad range of hydroxy- and aminobenzoic acids. These experiments showed the necessity for the decarboxylation of an activating functional group in ortho- or para-position to the carboxyl group. The reaction progress for the one-pot decarboxylation and reduction of 3´-nitro-4´-hydroxybenzoic acid was monitored, showing a sequence of first reduction of the nitro group and then decarboxylation. Several substrates possessing reducible functional groups were successfully transformed in the one-pot decarboxylation and reduction using Fe25Ru75@SILP+IL-NEt2. Recycling experiments under batch conditions confirmed the stability and reusability of the catalytic system under conservation of the physico-chemical properties of the material. The evaluation of the decarboxylation approach compared to classical synthesis pathways for aniline and phenol derivatives highlighted its advantageous application to lignin derived benzoic acid derivatives.

Institutions

• Department of Chemistry [150000]
• Chair of Technical Chemistry and Petrochemistry [154110]