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Macroporous ion exchange resin supported palladium nanoparticle (Pd-NP) catalysts are prepared by an intermatrix synthesis. For the first time, the effect of resin functionality (weak acid, strong acid, strong base) on the NP size, their catalytic activity, and leaching is investigated in the Suzuki cross-coupling of iodobenzene and phenylboronic acid. Whereas the smallest NPs (1.34 nm) are found in the thiol Ambersep GT74 resin, the sulfonic acid Lewatit K2629 and quaternary amine Lewatit MP500 OH resins resulted in NPs of a similar size (2.42 and 2.59 nm, respectively). Despite their smaller size, the NPs on Ambersep GT74 exhibited the lowest conversion (21.6 %), which is attributed to a too strong coordination of the NPs by the thiol groups. The conversions obtained by using Lewatit K2629 (76.8 %) and Lewatit MP500 OH (94.2 %) were considerably higher, the excellent performance of the latter catalyst being ascribed to the promoting effect of the hydroxyl groups on the transmetallation and reductive elimination steps in Suzuki cross-coupling. No Pd leaching was observed when using Ambersep GT74 as the support, compared with Pd leaching amounting to 1.1 % and 4.8 % when using Lewatit MP500 OH and Lewatit K2629, respectively. Such low values indicate that ion exchange resins are ideal supports to stabilize the NPs. Particularly, the combination of high conversion and limited leaching on Lewatit MP500 OH opens up new perspectives for catalyzing Suzuki cross-coupling with a heterogeneous catalyst. [ABSTRACT FROM AUTHOR]

Natural organic matter (NOM) negatively affects water quality and can cause serious issues during water treatment processes. Anion exchange resins (AER) have already proven their effectiveness to remove a major part of this NOM. However, due to its complexity, understanding and improving NOM removal remains challenging. This study aimed to provide in-depth insights in NOM removal with macroporous styrenic weak (WBA), strong (SBA) and combined weak/strong basic AER. Batch experiments were performed with resins in two industrially relevant counter ion forms: OH- and free base form for SBA and WBA resins respectively, using NaOH conditioning, and Cl- form resins using NaCl and HCl conditioning for SBA and WBA resins respectively. Synthetic water containing model compounds for different NOM fractions was used, focussing on the biopolymer fraction which is typically poorly removed by classical ion exchange processes and is a known disinfection by-product precursor in drinking water. The applied resin conditioning procedure influenced the equilibrium pH and consequently NOM removal efficiency and mechanisms. When ion exchange is the dominant driving force for NOM removal, the Cl- form proved to be most efficient. For uncharged NOM containing hydroxyl groups, SBA resins in the OH- form are preferable due to H-bonding. Adsorption of aromatic NOM through π-π interactions with the polystyrene backbone was not affected by the resin conditioning. This work clearly demonstrates that not only the AER type, but also the conditioning procedure and the corresponding counter ion form play a key role in the design of successful NOM removal processes. [Display omitted] • Resin, conditioning procedure and resulting counter ion influence NOM removal. • π-π interactions are involved in the removal of aromatic NOM under all tested conditions. • H-bridges and ion exchange are main interactions based on NOM functionality and pH. [ABSTRACT FROM AUTHOR]

Highlights: [•] Resin swelling determines active site accessibility and, hence, catalytic activity. [•] Gel resins outperform macroporous ones in ethyl acetate transesterification with methanol. [•] The kinetic model implicitly accounts for swelling by assuming full active site coverage. [•] Protonated ethyl acetate reaction with bulk methanol is rate determining. [•] The selected Eley–Rideal mechanism is independent of the resin used. [ABSTRACT FROM AUTHOR]

• The leaching behaviour and mechanisms are elucidated via combined data analysis. • A homogeneous-heterogeneous catalytic system prevails for both NP catalysts. • The leaching pathway critically depends on the resin functionality. • Phenylpalladium(II)hydroxide complexes are proposed as the leached Pd2+ species. The Pd leaching behaviour of a strongly acid (Lewatit K2629) versus strongly basic (Lewatit MP500 OH) ion exchange resin supported Pd nanoparticle (Pd-NP) catalyst is elucidated in the Suzuki reaction between iodobenzene and phenylboronic acid with K 2 CO 3 as base in 1:1 (v/v) DMF/H 2 O at 40 °C. Reaction and leaching kinetic analyses combined with hot filtration tests indicated heterogeneous-homogeneous catalysis for both Pd-NP catalysts. More particularly, leaching experiments showed that for Pd-NP Lewatit K2629, Pd-NP as well as molecular Pd2+ leaching (as phenylpalladium(II)hydroxide complexes) occurred due to, respectively, the disturbance of the electrostatic NP stabilization by dissociated K 2 CO 3 and reaction with iodobenzene and hydroxide. For Pd-NP Lewatit MP500 OH, however, molecular Pd2+ leaching induced by iodobenzene, dominates. Hence, the resin functionality determines the contribution of each leaching pathway. Furthermore, at high conversions, Pd re-deposition occurred due to the decreased amount of leaching inducing reagents causing enlarged NPs in the resin which leached less in subsequent runs. [ABSTRACT FROM AUTHOR]