Nonthermal Plasma Induced Fabrication of Solid Acid Catalysts for Glycerol Dehydration to Acrolein

Non-catalytic glycerol dehydrogenation to dihydroxyacetone using needle-in-tube dielectric barrier discharge plasma

Glycerol, a by-product of biodiesel production, could be converted into various value-added products. This work focuses on its dehydrogenation to dihydroxyacetone (DHA), which is mainly used in the cosmetics industry. While several methods have been employed for DHA production, some necessitate catalysts and involve harsh reaction conditions as well as long reaction times. A needle-in-tube type dielectric barrier discharge (DBD) plasma technique for catalyst-free and environmentally-friendly glycerol conversion into DHA via dehydrogenation process was investigated using 0.1 M glycerol dissolved in deionized (DI) water at ambient temperature and pressure. The optimal condition was 60 W input power, 5 mm gap distance between the end of the needle and the liquid surface, and 0.5 L/min He flow rate. The highest DHA yield of 29.3% was obtained at 3 h with a DHA selectivity of 51.6% and glycerol conversion of 56.9%. Although the system allowed over 80% of glycerol to transform after 5 h, the DHA yield decreased after 3 h because the DHA product could further react with the reactive species in the plasma. The catalyst-free DBD plasma technique offers a simple and environmentally conscious method for DHA production via the dehydrogenation of glycerol.

Plasma-Enabled Ligand Removal for Improved Catalysis: Furfural Conversion on Pd/SiO2

A nonthermal, atmospheric He/O2 plasma (NTAP) successfully removed polyvinylpyrrolidone (PVP) from Pd cubic nanoparticles supported on SiO2 quickly and controllably. Transmission electron microscopy (TEM) revealed that the shape and size of Pd nanoparticles remain intact during plasma treatment, unlike mild calcination, which causes sintering and polycrystallinity. Using Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS), we demonstrate the quantitative estimation of the PVP plasma removal rate and control of the nanoparticle synthesis. First-principles calculations of the XPS and CO FTIR spectra elucidate electron transfer from the ligand to the metal and allow for estimates of ligand coverages. Reactivity testing indicated that PVP surface crowding inhibits furfural conversion but does not alter furfural selectivity. Overall, the data demonstrate NTAP as a more efficient method than traditional calcination for organic ligand removal in nanoparticle synthesis.

Enhanced Catalytic Hydrodeoxygenation of Activated Carbon-Supported Metal Catalysts via Rapid Plasma Surface Functionalization

We employ a nonthermal, He/O₂ atmospheric plasma as an efficient surface functionalization method of activated carbons. We show that plasma treatment rapidly increases the surface oxygen content from 4.1 to 23.4% on a polymer-based spherical activated carbon in 10 min. Plasma treatment is 3 orders of magnitude faster than acidic oxidation and introduces a diverse range of carbonyl (C═O) and carboxyl (O-C═O) functionalities that were not found with acidic oxidation. The increased oxygen functionalities reduce the particle size of a high 20 wt % loading Cu catalyst by >44% and suppress the formation of large agglomerates. Increased metal dispersion exposes additional active sites and improves the yield of hydrodeoxygenation of 5-hydroxymethyl furfural to 2,5-dimethyl furan, an essential compound for biofuel replacement, by 47%. Surface functionalization via plasma can advance catalysis synthesis while being rapid and sustainable.

Towards Catalysts Prepared by Cold Plasma

Cold (non-equilibrium) plasma techniques have long been used as plasma deposition methods to create new materials, often with unique properties, which cannot be produced any other way, as well as plasma treatment methods for the sophisticated modification of conventional materials [...]

Glycerol waste to value added products and its potential applications

The rapid industrial and economic development runs on fossil fuel and other energy sources. Limited oil reserves, environmental issues, and high transportation costs lead towards carbon unbiased renewable and sustainable fuel. Compared to other carbon-based fuels, biodiesel is attracted worldwide as a biofuel for the reduction of global dependence on fossil fuels and the greenhouse effect. During biodiesel production, approximately 10% of glycerol is formed in the transesterification process in a biodiesel plant. The ditching of crude glycerol is important as it contains salt, free fatty acids, and methanol that cause contamination of soil and creates environmental challenges for researchers. However, the excessive cost of crude glycerol refining and market capacity encourage the biodiesel industries for developing a new idea for utilising and produced extra sources of income and treat biodiesel waste. This review focuses on the significance of crude glycerol in the value-added utilisation and conversion to bioethanol by a fermentation process and describes the opportunities of glycerol in various applications.

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