A novel structured nanosized CaO on nanosilica surface as an alternative solid reducing agent for hydrogen fluoride removal from industrial waste water.

In the semiconductor industry, perfluorinated compound removal is a major concern owing to the formation of highly toxic and hazardous hydrogen fluoride (HF) as a by-product. Calcium oxide (CaO) can be considered a promising material for HF sorption reaction process. However, the easier reaction between CaO and H2O results in the formation of Ca(OH)2, which ultimately limits the usefulness of CaO. The objective of the research work is preparation of CaO nanoparticles on hydrophobic silica (SiO2) to use as a alternative solid reducing catalyst for efficient HF removal process. High-resolution transmission electron microscopy micrographs confirmed that the as-prepared CaO particles are <5 nm in size and the smaller sized CaO nanoparticles are homogeneously anchored on the entire surface of ∼100 nm spherical SiO2 nanoparticles. The reaction-enhanced regenerative catalytic system (RE-RCS) was used to measure the HF removal efficiency. HF is removed more efficiently using CaO on SiO2 than using CaO alone. At the outlet of the RE-RCS, the obtained HF concentrations are 2811.4 and 2166.1 ppm after a 3 h reaction using CaO and CaO on SiO2 as the sorbent, respectively. The lower concentration of HF at the outlet of the system using CaO on SiO2 indicates that HF sorption is remarkably enhanced using CaO on SiO2 inside the RE-RCS. In addition, the presence of a hydrophobic region in the catalyst sorbent prevents the reaction between CaO and water, which leads to avoiding the formation of Ca(OH)2. These phenomena significantly enhance the HF removal efficiency and CaF2 formation process.

Poly(styrene)-supported N-heterocyclic carbene coordinated iron chloride as a catalyst for delayed polyurethane polymerization.

An advanced organometallic catalyst based on N-heterocyclic carbene (NHC) coordinated FeCl3 has been synthesized and used to control the reaction rate in polyurethane (PUR) polymerization. The imidazolium (Im)-based NHC was functionalized on the surface of the supporting material of bead-type chloromethyl polystyrene (PS) resin. The PS-Im-FeCl3 catalyst was synthesized through the coordination reaction between Im and FeCl3. The successful formation, functional groups, structure, and geometry of the PS-Im-FeCl3 catalysts were confirmed by Fourier transform infrared and X-ray photoelectron spectroscopy techniques. A thin layer of Im was observed to be coated uniformly on the PS bead surface and FeCl3 nanoparticles were observed to cover the coating layer homogeneously, as determined by field-emission scanning electron microscopy, transmission electron microscopy, and energy dispersive X-ray spectroscopy measurements. The PUR polymerization reaction was investigated through viscosity measurements and non-isothermal activation energy calculations by differential scanning calorimetry analysis. Based on the viscosity measurements, delayed PUR polymerization was achieved using the PS-Im-FeCl3 catalyst system. The highest viscosity (6000 cP) was achieved without any catalyst, with triphenylene bismuth, and with the PS-Im-FeCl3 catalyst after 23, 5, and 25 h of reaction time, respectively. Furthermore, the calculated activation energies (E a) were 27.92 and 36.35 kJ mol-1 for the no-catalyst and the PS-Im-FeCl3 systems, respectively. Thus, the viscosity measurements and DSC analyses confirm that the PS-Im-FeCl3 catalyst considerably increases the PUR reaction time. The Im-FeCl3 catalyst supported by CMPS can control the reaction rate in PUR synthesis because of its high activity. Thus, the PS-Im-FeCl3 catalyst can be used as a curing retardant in the PUR industry.