Supported Aqueous-Phase Catalysis Research Articles

Synthesis and dilute solution properties of branched poly(benzyl methacrylate) using na‐clay supported aqueous‐phase catalysis

ABSTRACTThe supported aqueous‐phase catalysis (SAPC) using hydrated interface has been used to synthesize branched polymers (star and graft) of benzyl methacrylate (BnMA) via atom‐transfer radical polymerization (ATRP) in the presence of Na‐clay supported catalyst in anisole at ambient temperature. The propagation of star poly(BnMA)s using diPENDTA‐Br6, as hexa‐functional initiator is confined at the hydrated interface between the support and the liquid medium as evident from the obtained polymers that are catalyst contamination‐free, and exhibited moderately narrow molecular weight distributions (Mw/Mn ≤ 1.33). The hexa‐functionality of synthesized stars is verified by 1H NMR, the measurement of their intrinsic viscosity ([η]), and radius of gyration (Rg). The polymerization was also recycled up to 5 times to produce star PBnMAs with high initiator efficiency. The star polymers prepared using hydrated Na‐clay supported is compared with star prepared using covalent silica supported catalyst system. The star polymer obtained from covalently supported catalyst gave broad Mw/Mn and poor initiator efficiency. The polystyrene‐graft‐PBnMA (PS‐g‐PBnMA) copolymer is also prepared using hydrated Na‐clay supported catalyst system in anisole at ambient temperature. The graft‐copolymer had narrow Mw/Mn and was confirmed using 1H NMR and atomic force microscopy. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 2225–2237

Hydrocarboxylation of olefins by supported aqueous-phase catalysis

Pd-TPPTS complexes supported on acidic macro-porous resins (Pd-TPPTS/resin) have been employed for the hydrocarboxylation of 1-hexene and styrene derivatives by supported aqueous phase catalysis (SAPC). Acidic macroporous resins acted as substitutes for both heterogeneous acids and supports of Pd-TPPTS complexes afforded many advantages, such as easy separation from organic products and good reusability. The prepared Pd-TPPTS/resin catalysts were characterized by FT-IR, TG, SEM and N2 physisorption, which demonstrated that the Pd-TPPTS complexes were loaded on the resin. Compared with homogeneous analogue, the present SAP catalyst offered higher total acid yield and selectivity towards linear acid in the hydrocarboxylation of 1-hexene. Moreover, it was found that water had a significant influence on the catalytic activity and selectivity toward linear acid over the SAP catalyst. Optimum water/resin ratio at about 66.7% in the SAP catalyst afforded maximum activity under the given reaction temperature. The present SAP catalyst was highly Pd-leaching resistant and can be reused at least four times without obvious loss in activity.

Hydration Mediation in Supported Aqueous-Phase Catalysis for Atom Transfer Radical Polymerization

Hydrated sodium montmorillonite (Na-clay) and silica gel are used as solid supports for atom transfer radical polymerization (ATRP) of benzyl methacrylate and methyl methacrylate. The catalyst complexes of CuBr2 and CuBr with N,N,N′,N′,N″-pentamethyldiethylenetriamine, which are physically adsorbed on Na-clay and silica gel, are efficiently retained by the solid supports via small amounts of hydration. The supported aqueous-phase catalysis (SAPC) over Na-clay and silica produces catalyst-free polymers for activator generated electron transfer ATRP and conventional ATRP processes. The kinetics for the catalyst supported Na-clay and silica systems show that the polymerization proceeded only in the presence of hydrated catalyst support and ceased when the polymerization solution was separated from the hydrated catalyst support. In the case of Na-clay SAPC, the polymerization follows a linear first-order time–conversion plot and produces polymers with moderately narrow molecular weight distribution (MWD, Mw/Mn ≤ 1.30). However, for silica SAPC the first-order time–conversion plot is curved, indicating that the polymerization proceeds with termination and polymers exhibited broad MWD (Mw/Mn > 1.50). The poor performance of silica SAPC is attributed to the inefficient mobility of the catalyst and the nature of hydrogen bonding of the water molecules on its surface. The bilogarithmic plot of apparent rate constant kapp vs [I]0 in SAPC for ATRP indicates a zero order, suggesting that the polymerization is independent of the bulk initiator concentration, and the propagation is confined to the hydrated interface between the solid support and the organic phase.

Selective hydrogenation of cinnamaldehyde in biphasic system catalysed by chlorotris ( M-trisulphonato triphenylphosphine) rhodium (I) complex, [formula omitted

The selective hydrogenation of cinnamaldehyde by a RhCl ( TPPTS ) 3 aqueous solution, ex situ synthesised from RhCl 3 · nH 2 O and TPPTS (tris( M-sulphonatophenyl)phosphine) with pH control by NaOH solution, was investigated under a biphasic (water/toluene) system in a batch reactor. The hydrogenation more usually occurred at C C bonds, giving hydrocinnamaldehyde as the main product. Important parameters were varied carefully in order to maximise the selectivity toward hydrocinnamaldehyde for which the highest selectivity of 99.9% was achieved. Both the kinetic and mass transfer aspects were also evaluated and the results implied that the biphasic system was under mass transfer control. In addition, supported aqueous phase (SAP) catalysts of the RhCl ( TPPTS ) 3 solution supported on fine silica were prepared and tested for the selective hydrogenation of cinnamaldehyde under similar conditions for comparison and they gave a very high selectivity to hydrocinnamaldehyde which was an advantage, although their activity was lower than the biphasic catalysts. The mass transfer characteristic in SAP catalysis was also evaluated using a first-order film model.

Hydroformylation of linalool in a supported aqueous phase catalyst by immobilized rhodium complex: kinetic study

In this paper, we report on the kinetics of linalool hydroformylation using supported aqueous phase catalysis (SAPC). Hydroformylation of linalool by SAPC has been carried out in the presence of toluene as the solvent and using [Rh 2(μ-S t Bu) 2(CO) 2(TPPTS) 2]=[D2] as the catalyst supported on the silica DS50. The effects of temperature, pressure and concentrations of catalyst, water and linalool on the monoterpene conversion have been investigated. The rate was found to be first order with respect to catalyst and olefin concentrations and hydrogen and carbon monoxide pressure. A kinetic model was fitted to the observed data, and it was found to predict the rates with a good agreement. The activation energy was found to be as low as 14.5 kcal mol −1.

Apatitic Tricalcium Phosphate as Novel Smart Solids for Supported Aqueous Phase Catalysis (SAPC)

Apatitic tricalcium phosphate was used as support for supported aqueous phase catalysis (SAPC) in the hydroformylation reaction of oct-1-ene, at 80 °C in toluene using a dinuclear rhodium complex bearing TPPTS as hydrophilic ligands. The reaction yield is maximum and constant when the hydration rate of the support is ranging from 20 to 35%, before starting to decrease dramatically. The support was examined initially and after catalytic runs by XRD, FTIR, 1H and 31P NMR, SEM and EDS. No change was observed when the hydration rate is less than 35%. Beyond 35%, some decomposition of the support into monetite and stoichiometric apatite occurred; the drop in the yield is essentially due to a loss of droplets of water from the support. The outstanding yield observed with the apatitic tricalcium phosphate, when compared to silica usually used in SAPC, was attributed to the orientation of the catalytic molecule arising from the adsorption of some of the TPPTS ligands onto the hydrophilic surface of apatite.

Multifactorial analysis in the study of hydroformylation of oct-1-ene using supported aqueous phase catalysis

The influence of the hydration and the surface characteristics of five supports in the hydroformylation of oct-1-ene by supported aqueous phase catalysis (SAPC) using [Rh 2(μ-S tBu) 2(CO) 2(TPPTS) 2] as catalyst was studied. The results confirm that the size of the pores and the amounts of water were found to be the determining factors contributing to the SAPC. According to the size of pores there is a critical value for which the SAPC takes place either in the classical model or in conditions where the pores are filled. When the pores are fully filled the SAPC can operate efficiently onto the external surface, stabilising the conversion in a relatively wide range of support hydration.

Asymmetric Synthesis of Naproxen by Supported Aqueous-Phase Catalysis

A supported aqueous-phase, asymmetric, hydrogenation catalyst, SAP-Ru-BINAP-4SO3Na, is synthesized. Impregnation of water from an organic phase, ethyl acetate, is used to hydrate the SAP catalyst. Both the activity and enantioselectivity for the asymmetric hydrogenation of 2-(6′-methoxy-2′-naphthyl)acrylic acid to naproxen are found to be dependent on the water content. Maximum activity and e.e. are observed when water-saturated ethyl acetate is used to hydrate the SAP catalyst, an initial turnover frequency of 18.2 hr−1 and a 70.0% e.e. at room temperature under ≅ 1350 psig of hydrogen pressure. At similar conditions, initial turnover frequencies of 131 and 0.34 hr−1 are observed from Ru-BINAP-4SO3Na in homogeneous (methanol as solvent) and two-phase (water-ethyl acetate) reaction systems, respectively. Although an excellent 96.1 % e. e. (at 4°C and 1230 psig of H2) is found in neat methanol (homogeneous), the enantioselectivity of the SAP catalyst (up to 70% e.e.) is bounded by the intrinsic enantioselectivity limit of the ruthenium complex in water. Recycling of the SAP catalyst is easily achieved without any leaching of ruthenium into the organic phase.