Editorial: Special Issue on “Catalytic Processes in Biofuel Production and Biomass Valorization”

The valorization of waste materials is a viable alternative to traditional disposal systems, including in the field of renewable energy, biofuels and biomass.

Public attention to energy consumption and the related emissions of pollutants is increasing. The constant increase in the costs of raw materials derived from petroleum and the growing concerns surrounding the environmental impact have given considerable impetus to research into new products from renewable raw materials and to the proposal of technological solutions that reduce energy consumption, the use of hazardous substances and waste production, while promoting a model of sustainable development.

The Special Issue on “Catalytic Processes in Biofuel Production and Biomass Valorization” aimed to focus on sustainable chemistry, biomass valorization, biofuels, biodiesel production, waste production, raw materials and recovery of glycerol. The topics of this Special Issue included both experimental and theoretical contributions and eight original research papers and review articles were published.

Yang et al. studied the enzymatic production of sugars from rice straw biomass assisting by ion-liquid or surfactant. This study was focused to increase the biodelignification pretreatment of rice straw using laccase in a single system. The enzymatic saccharification process was carried out by using different strategies [1].

Perosa et al. described a study on the conversion of unsaturated fatty acids into the corresponding cyclic organic carbonates. The authors described an assisted-tandem protocol for the direct oxidative carboxylation of methyl oleate to its corresponding carbonate. The product was obtained in 99% yield with high retention of cis-configuration using hydrogen peroxide and CO₂ as green reagents, in a biphasic system and in the presence of an ammonium tungstate ionic liquid catalyst and KBr as co-catalyst. However the intermediate epoxide was not isolated [2].

Maree et al. reported the development of a mesoporous silica-supported layered double hydroxide catalyst for the reduction of oxygenated compounds in E. Grandis fast pyrolysis oils, using CaAl- and MgAl-layered double hydroxides (LDHs), synthesised at different pH to obtain different pore sizes and surface areas [3].

Wisniewski and Raffelt presented the assessment of sugarcane bagasse pyrolysis over the influence of different gas atmospheres inside the reactor and the influence on the chemical profile of produced organic compounds using a tandem catalytic process for vapor phase upgrade. Non-catalytic thermochemical conversion process, as well as the catalytic upgrading of the vapor phase were studied in a microscale pyrolysis reactor evaluating two Ni-based catalysts over an inert and reactive atmospheres. The molecular behavior of the chemicals produced during the different processes was discussed [4].

Nichio et al. prepared activated bentonite nanocomposite and used for the synthesis of solketal from glycerol in liquid phase. The authors obtained a catalyst based on a composite containing natural bentonite and also analyzed its structural and acidic properties as well as their catalytic yield in the synthesis of (2,2-dimethyl-1,3-dioxolan-4-yl)methanol from glycerol and acetone [5].

Fattah et al. summarized the results of the last two decades in a review-article concerning the production of biodiesel from triglycerides via homogeneous or heterogeneous transesterification. The authors included discussions regarding the transesterification mechanism, types of catalysis reaction, as well as the yield of the resultant reactions [6].

Carlucci described a review-article dealing with various aspects related with the valorization of glycerol, through chemical and/or biotechnological processes. Glycerol is a “waste” material mostly deriving from biodiesel production units. Its valorization through chemical or biotechnological ways constituted a major challenge concerning the production chain of biodiesel [7].

In another review Carlucci reported the current state of biodiesel synthesis by transesterification for the continuous process at the laboratory level, in homogeneous, heterogeneous catalysis, using enzymes, without catalyst, and in supercritical conditions. The mechanism of the transesterification reaction in homogeneous catalysis using basic catalysts, respectively acid catalysts together with the advantages and disadvantages of using these catalysts, were shown. Heterogeneous catalyzed transesterification presented advantages compared to homogeneous catalyzed synthesis and the influence of parameters in biodiesel production—molar ratio (alcohol/triglycerides), temperature, water content, FFA content, and the co-solvent was investigated. The continuous flow chemistry had the advantage of better control of reaction parameters: types of flow, temperature, residence time, and reactor type. The reactors used in the production of biodiesel as micro-channel reactors, packed bed reactors, reactors with immobilized and co-immobilized lipases, fixed bed reactors, reactive distillation, closed-loop static mixer reactors and microwave- and ultrasonic-assisted processes have been studied compared to conventional methods, mainly observing the shortening of the reaction time and the reduction of energy consumption [8].

I would like to thank all the authors for their interesting contributions, the reviewers for their precious remarks and also the Editorial Office for the constant support to this Special Issue.