Biodiesel is one of the most attractive sources of clean energy. It is produced by the transformation of vegetable oils with up to 10% formation of glycerol as a by-product. Therefore, development of new approaches for processing bio-glycerol into such value-added chemical compounds as solketals is necessary. Thus, various six- and five-membered cyclic compounds can be prepared by acetalization of glycerol with aldehyde or ketone. The resulting glycerol oxygenates are excellent fuel additives that increase viscosity, octane or cetane number, and stability to oxidation. In addition, these products significantly reduce carbon monoxide emissions from standard diesel fuel. In this review, we highlight recent advances in the glycerol valorization for the sustainable production of bio-additives. The review includes a discussion of the innovative and potential catalysts to produce solketals.

This paper describes the chemical engineering aspects for the preparation of highly active and stable nanocomposite photocatalysts based on N-doped TiO₂. The synthesis is performed using titanium oxysulfate as a low-cost inorganic precursor and ammonia as a precipitating agent, as well as a source of nitrogen. Mixing the reagents under a control of pH leads to an amorphous titanium oxide hydrate, which can be further successfully converted to nanocrystalline anatase TiO₂ through calcination in air at an increased temperature. The as-prepared N-doped TiO₂ provides the complete oxidation of volatile organic compounds both under UV and visible light, and the action spectrum of N-doped TiO₂ correlates to its absorption spectrum. The key role of paramagnetic nitrogen species in the absorption of visible light and in the visible-light-activity of N-doped TiO₂ is shown using the EPR technique. Surface modification of N-doped TiO₂ with copper species prevents its intense deactivation under highly powerful radiation and results in a nanocomposite photocatalyst with enhanced activity and stability. The photocatalysts prepared under different conditions are discussed regarding the effects of their characteristics on photocatalytic activity under UV and visible light.

The heightened interest in liquid organic hydrogen carriers encourages the development of catalysts suitable for multicycle use. To ensure high catalytic activity and selectivity, the structure–reactivity relationship must be extensively investigated. In this study, high-loaded Ni–Cu catalysts were considered for the dehydrogenation of methylcyclohexane. The highest conversion of 85% and toluene selectivity of 70% were achieved at 325 °C in a fixed-bed reactor using a catalyst with a Cu/Ni atomic ratio of 0.23. To shed light on the relationship between the structural features and catalytic performance, the catalysts were thoroughly studied using a wide range of advanced physicochemical tools. The activity and selectivity of the proposed catalysts are related to the uniformity of Cu distribution and its interaction with Ni via the formation of metallic solid solutions. The method of introduction of copper in the catalyst plays a crucial role in the effectiveness of the interaction between the two metals.

At present, one of the most promising methods of processing renewable raw materials is pyrolysis, which allows liquid organic products (bio-oil) to be derived from biomass. For obtaining fuel products from bio-oil, the latter needs to be preliminarily upgraded. It is appropriate to carry out this process in two stages. The first stage—decarboxylation—is intended to reduce the corrosiveness (acidity) of the feedstock and hydrogen consumption at the second stage. Decarboxylation is usually conducted over noble metal-based catalysts. There are examples of employing cheaper catalysts based on alkaline-earth metals; however, these catalysts suffer from insufficient stability. Here, we report the activity of MgO-based catalysts in the decarboxylation of pentanoic acid, a model compound imitating bio-oil, and the effect of dopants on the stability of the magnesium-containing catalysts. The process has been carried out in an inert atmosphere at a temperature of 350°C and a pressure of 0.50 MPa. Raising the MgO calcination temperature to 1200°C and introducing stabilizing admixtures (Al₂O₃, SiO₂, and ZrO₂) affords catalysts that are mainly deactivated via carbonate formation rather than the formation of soluble magnesium salts and are, therefore, more promising from the standpoint of regenerability.

CuFe-containing catalysts with different copper oxide content were prepared by fusion of metal salts. The obtained catalyst showed high activity in the hydrogenation of furfural to furfuryl alcohol (FA) in the batch reactor in the presence of isopropanol as a solvent at a temperature of 100 °C and a hydrogen pressure of 6.0 MPa. The yield of FA and furfural conversion are 97% and 98%, respectively. In the solvent-free reaction in the flow-type reactor; the most active catalyst Cu₂₀Fe₆₆Al₁₄ leads to the 96% formation of FA with 100% conversion of furfural at liquid hourly space velocity (LHSV) = 1 h⁻¹; 160 °C and a hydrogen pressure of 5.0 MPa during 30 h. According to the X-ray diffraction (XRD) method, the active component of the spent and fresh Cu₂₀Fe₆₆Al₁₄ catalyst is the same and is represented by metallic copper and Fe₃O₄-type spinel. Using different methods, the formation of active sites was investigated.

The modification effect of NiCu–SiO2catalysts by molybdenum on their activity and selectivity in the hydrogenation of furfural—a product of the acid hydrolysis of hemicellulose biomass—was...