Preparation of heterogeneous catalysts supported on mesoporous molecular sieves modified with various N-groups and their use in the Heck reaction

Synthesis of a Graphene-Encapsulated Fe3C/Fe Catalyst Supported on Sporopollenin Exine Capsules and Its Use for the Reverse Water-Gas Shift Reaction

Bioderived materials have emerged as sustainable catalyst supports for several heterogeneous reactions owing to their naturally occurring hierarchal pore size distribution, high surface area, and thermal and chemical stability. We utilize sporopollenin exine capsules (SpECs), a carbon-rich byproduct of pollen grains, composed primarily of polymerized and cross-linked lipids, to synthesize carbon-encapsulated iron nanoparticles via evaporative precipitation and pyrolytic treatments. The composition and morphology of the macroparticles were influenced by the precursor iron acetate concentration. Most significantly, the formation of crystalline phases (Fe3C, α-Fe, and graphite) detected via X-ray diffraction spectroscopy showed a critical dependence on iron loading. Significantly, the characteristic morphology and structure of the SpECs were largely preserved after high-temperature pyrolysis. Analysis of Brunauer-Emmett-Teller surface area, the D and G bands from Raman spectroscopy, and the relative ratio of the C=C to C-C bonding from high-resolution X-ray photoelectron spectroscopy suggests that porosity, surface area, and degree of graphitization were easily tuned by varying the Fe loading. A mechanism for the formation of crystalline phases and meso-porosity during the pyrolysis process is also proposed. SpEC-Fe10% proved to be highly active and selective for the reverse water-gas shift reaction at high temperatures (>600 °C).

Anchoring of Pd(ii) complex in functionalized MCM-41 as an efficient and recoverable novel nano catalyst in C–C, C–O and C–N coupling reactions using Ph3SnCl

Pd(ii) complex on functionalized mesoporous MCM-41 as an efficient and recoverable novel nano catalyst in C–C, C–O and C–N coupling reactions using Ph₃SnCl.

Pd-grafted functionalized mesoporous MCM-41: a novel, green and heterogeneous nanocatalyst for the selective synthesis of phenols and anilines from aryl halides in water

The preparation of phenols and anilines from aryl halides in the presence of MCM-41-dtz-Pd as a heterogeneous nanocatalyst has been introduced.

Heterogeneous Pd catalysts supported on silica matrices

Features, advantages and limitations associated with palladium catalysts deposited over various siliceous supports in different types of practically useful organic transformations are reviewed.

The solid phase extraction of some metal ions using palladium nanoparticles attached to silica gel chemically bonded by silica-bonded N-propylmorpholine as new sorbent prior to their determination by flame atomic absorption spectroscopy

In this research at first palladium nanoparticle attached to a new chemically bonded silica gel has been synthesized and has been characterized with different techniques such as X-ray diffraction (XRD), fourier transform infrared (FT-IR), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). Then, this new sorbent (chemically modified silica gel with N-propylmorpholine (PNP-SBNPM)) was efficiently used for preconcentration of some metal ions in various food samples. The influence of effective variables including mass of sorbent, flow rate, pH of sample solutions and condition of eluent such as volume, type and concentration on the recoveries of understudy metal ions were investigated. Following the optimization of variables, the interfering effects of some foreign ions on the preconcentration and determination of the investigated metal ions described. At optimum values of variables, all investigated metal ions were efficiently recovered with efficiency more than 95%, relative standard deviation (RSD) between 2.4 and 2.8, and detection limit in the range of 1.4–2.7 ng mL⁻¹. The present method is simple and rapidly applicable for the determination of the understudied metal ions (ng mL⁻¹) in different natural food samples.

Hybrid materials based on Pd nanoparticles on carbon nanostructures for environmentally benign C-C coupling chemistry

The combination of different nanomaterials such as metallic nanoparticles and carbon nanostructures in a new hybrid material should give rise to interesting properties that combine the advantages of each of the nanocomponents. This review highlights the latest advances in the synthetic design of these hybrid materials where carbon nanostructures act as supports as well as stabilizing agents for very reactive metallic nanoparticles. The striking applications of Pd nanoparticles anchored on the surface of carbon nanostructures in C-C coupling chemistry are analyzed. Special emphasis is placed on the stability of these materials, which is linked to their recyclability. Numerous examples are given that involve the use of these catalysts in Heck, Suzuki and Sonogashira coupling reactions.

Palladium catalysts supported on mesoporous molecular sieves bearing nitrogen donor groups: preparation and use in Heck and Suzuki C-C bond-forming reactions

A series of supported catalysts is prepared by treatment of SBA-15-type mesoporous molecular sieve bearing [triple chemical bond]SiCH(2)CH(2)CH(2)NHCH(2)CH(2)NEt(2) groups with palladium(II) acetate. These catalysts are studied in Suzuki biaryl couplings and in Heck reactions to establish the influence of metal loading and innocent surface modifications (trimethylsilylation). The Suzuki reaction proceeded efficiently with model and practically relevant substrates; the catalyst performance increasing with an increasing degree of metalation (decreasing N/Pd ratio). Catalyst poisoning tests revealed that the reaction takes place in the liquid phase with the catalyst serving as a reservoir of active metal species and also as a stabilizing support once the reaction is performed. In the Heck reactions, on the other hand, the catalyst performance strongly changed with the reaction temperature and with the N/Pd ratio. The material with the lowest metal loading (0.01 mmol palladium per gram of material, N/Pd ratio ca. 100:1) proved particularly attractive in the Heck coupling, being highly active at elevated temperatures, recyclable, and capable of acting as a bifunctional catalyst (i.e., functioning without any external base.