Preparation and Characterization of Pd Modified TiO₂ Nanofiber Catalyst for Carbon–Carbon Coupling Heck Reaction

Abstract

TiO 2 fibers were prepared through electrospinning of poly methyl methacrylate (PMMA) and titanium isopropoxide (TIP) solution followed by calcination of fibers in air at 500 ∘ C. Cetyltrimethylammonium bromide (CTAB) protected palladium nanoparticles (Pd NPs) prepared through reduction method were successfully adsorbed on the TiO 2 nanofibers (NF). Combined studies of X-ray diffraction (XRD), scanning electron microscope (SEM), and transmission electron microscope (TEM) indicated that the synthesized Pd/TiO 2 had anatase. BET indicated that the synthesized TiO 2 and Pd/TiO 2 had a surface area of 53.4 and 43.4 m 2 /g, respectively. The activity and selectivity of 1 mol% Pd/TiO 2 in the Heck reaction have been investigated towards the Mizoroki-Heck carbon-carbon cross-coupling of bromobenzene (ArBr) and styrene. Temperature, time, solvent, and base were optimized and catalyst was recycled thrice.1 H NMR and 13 C NMR indicated that stilbene, a known compound from literature, was obtained in various Heck reactions at temperatures between 100 ∘ C and 140 ∘ C but the recyclability was limited due to some palladium leaching and catalyst poisoning which probably arose from some residual carbon from the polymer. The catalyst was found to be highly active under air atmosphere with reaction temperatures up to 140 ∘ C. Optimized reaction condition resulted in 89.7% conversions with a TON of 1993.4 and TOF value of 332.2 hr −1 .

Ultrafine PdCu Nanoclusters by Ultrasonic-Assisted Reduction on the LDHs/rGO Hybrid with Significantly Enhanced Heck Reactivity

“…Additionally, it can catalyze efficiently the reaction of iodobenzene with methyl acrylate or ethyl acrylate with a TOF of 9500 or 9900 h –1 (Table , entries 6 and 7), respectively. Meanwhile, for the Heck reaction of bromobenzene with styrene or methyl acrylate, it exhibits excellent activity with a TOF of 1758 or 2087 h –1 (Table , entries 8 and 9), respectively, much higher than previous catalysts [Pd 2 (C 5 H 5 N) 2 (L)]­[BF 4 ] 2 (1194 h –1 , Table , entry 11), Pd 0 /SiO 2 (485 h –1 ) and Pd/TiO 2 (332.2 h –1 ) . As for the Heck reaction of inactive chlorobenzene with styrene, it also shows certain activity with a TOF of 528 h –1 (Table , entry 10).…”

“…Meanwhile, for the Heck reaction of bromobenzene with styrene or methyl acrylate, it exhibits excellent activity with a TOF of 1758 or 2087 h −1 (Table 2, entries 8 and 9), respectively, much higher than previous catalysts 2, entry 11), 41 Pd 0 /SiO 2 (485 h −1 ) 42 and Pd/TiO 2 (332.2 h −1 ). 43 As for the Heck reaction of inactive chlorobenzene with styrene, it also shows certain activity with a TOF of 528 h −1 (Table 2, entry 10). These results indicate that present hierarchically structured ultrafine PdCu alloy NC catalysts m-PdCu x / LDHs/rGO possess excellent adaptability for the substrates.…”

Facile Synthesis of Fiber‐Reinforced Catalyst for High Performance Ethanol and 2‐Propanol Oxidation

“…SEM images of Pd@TiO 2 , as seen in Figure 3a,b, show the presence of Pd nanoparticles on the fibers upon the addition of Pd nanoparticles to TiO 2 fibers. [ 36 ] In addition, the SEM EDAX analysis shown in Figure 3c revealed the presence of Pd, Ti, and O elements in the structure. TEM images of the Pd@TiO 2 structure are shown in Figure 3d,e.…”

TiO2–Based Nanofibrous Membranes for Environmental Protection

“…Typically, the preparation of TiO 2 nanofibers via electrospinning is accomplished by mixing a TiO 2 precursor with a polymer, and to modify the TiO 2 amorphous phase into a crystalline phase, the material is often calcined [71]. For instance, Nyangasi et al produced nanofibers, which were calcined at 500 • C to generate TiO 2 in anatase phase by mixing titanium isopropoxide with polymethylmethacrylate (PMMA) [72].…”