Pyrolysis of polyacrylonitrile

Valorizing plastic toy wastes to flammable gases through CO2-mediated pyrolysis with a Co-based catalyst

Toys are discarded due to their short life cycle. Unfortunately, development of sustainable disposal platform for toy has not gained particular concern. To establish a reliable disposal platform, this study employed a pyrolysis platform to valorize plastics into value-added fuels. To confer more environmentally resilient process, CO₂ was used as a feedstock to enhance the process efficiency from a perspective of the yield of flammable gases. To this end, waste toy brick (WTB) was used as a model compound. The exact types of plastics (polyacrylonitrile, polybutadiene, polystyrene, and polymethyl methacrylate) in WTB were experimentally determined. In pyrolysis of WTB, the complicated mixture of benzene derivatives was inevitably generated. To detoxify them by means of syngas (H₂/CO) production, catalytic pyrolysis was performed. Co catalyst effectively induced chemical bond scissions, leading to substantially enhanced H₂ formation. Also, the gas phase reactions (GPRs) between CO₂ and volatile compounds over Co catalyst expedited the production rate of CO, and such CO enhancement effectively offered a chance to mitigate toxic chemical generations. The synergistic contribution of CO₂ and Co catalyst enhanced syngas formation more than 25 times in reference to pyrolysis of WTB without Co catalyst. The GPRs also greatly prevented catalyst deactivation.

Noble-Metal-Free Hybrid Membranes for Highly Efficient Hydrogen Evolution

Free-standing and flexible WS₂ /WO_2.9 /C hybrid membranes are synthesized and used as catalytic electrodes for electrochemical hydrogen evolution, exhibiting a high and stable catalytic activity. By virtue of the synergetic effect, a low onset overpotential of 20 mV and a Tafel slope of 36 mV dec^-1 are achieved.

Rapid Fabrication of Periodic Patterns on Poly(styrene-co-acrylonitrile) Surfaces Using Direct Laser Interference Patterning

Periodic microstructures in styrene-acrylonitrile (SAN) copolymers are fabricated by two-beam direct laser interference patterning using a nanosecond pulsed laser operating at a wavelength of 266 nm. The SAN copolymers are synthesized using different molar ratios (styrene to acrylonitrile) by a free radical polymerization process. The chemical composition of the copolymers and their properties are determined using Fourier transformed infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). Depending on the composition of the irradiated copolymer films, with weight ratios ranging from 58 to 96.5% of styrene to acrylonitrile, different ablation behaviors are observed. The laser fluence necessary to locally ablate the copolymer is found to be dependent on the copolymer composition. Unlike other dielectric polymers, the laser irradiation produced both direct ablation of the irradiated material and collapse of the surface. It is shown that, by varying the laser fluence and the copolymer composition, the surface structure can be changed from a periodic pattern with a swelled topography to an ablated-like structure. The number of holes does not depend monotonically on the amount of PS or PAN units but shows a more complex behavior which depends on the copolymer composition and the laser fluence.