Production of Low-Freezing-Point Highly Branched Alkanes through Michael Addition

Production of Renewable Hydrocarbon Biofuels with Lignocellulose and Its Derivatives over Heterogeneous Catalysts

In recent years, the issues of global warming and CO2 emission reduction have garnered increasing global attention. In the 21st Conference of the Parties (convened in Paris in 2015), 179 nations and the European Union signed a pivotal agreement to limit the global temperature increase of this century to well below 2 K above preindustrial levels. To fulfill this objective, extensive research has been conducted to use renewable energy sources as potential replacements for traditional fossil fuels. Among them, the production of hydrocarbon transportation fuels from CO2-neutral and renewable biomass has proven to be a particularly promising solution due to its compatibility with existing infrastructure. This review systematically summarizes research progress in the synthesis of liquid hydrocarbon biofuels from lignocellulose during the past two decades. Based on the chemical structure (including n-paraffins, iso-paraffins, aromatics, and cycloalkanes) of hydrocarbon transportation fuels, the synthesis pathways of these biofuels are discussed in four separate sections. Furthermore, this review proposes three guiding principles for the design of practical hydrocarbon biofuels, providing insights into future directions for the development of viable biomass-derived liquid fuels.

Synthesis of biofuel precursors from benzaldehyde and cyclopentanone via aldehyde-ketone condensation in a deep eutectic solvent system

Production of biofuel precursors from biomass-derived platform compounds (BDPC) has a profound influence on biofuel industries. Herein, an efficient catalytic system composed of the deep eutectic solvent (DES, i.e., ChCl/Fa) and SnCl4 (ChCl/Fa-SnCl4) was developed to produce biofuel precursors (C12 and C19) through aldehyde-ketone (A-K) condensation of benzaldehyde (BD) and cyclopentanone (CPO). ChCl/Fa-SnCl4 exhibited the prospective catalytic performance and given the high selectivity (SC12 = 49.20%, SC19 = 15.20%) and total yield (YC12+C19 = 64.37%) of C12 and C19, as well as 99.96% BD conversion under the optimized conditions (BD : CPO molar ratio of 1 : 6, ChCl : Fa molar ratio of 1 : 12, 4 mmol SnCl4, 80 °C for 120 min). Subsequently, the C12 and C19 precursors were successfully applied to generate cyclic alkanes (C12H14 and C19H18) by hydrodeoxygenation with selectivity of 37.61% and 24.10%, respectively. Finally, the potential catalytic mechanism was explored by density functional theory (DFT) calculations. The results unveiled that the formation of a stable structure for the ChCl/Fa-SnCl4 system was ascribed to the viable interactions among ChCl, Fa and SnCl4 by coordination bonds, electrostatic interactions and H-bonds, which decreased reaction energy barriers and drove the condensation of BD and CPO. In this case, the catalytic reactions between BD and CPO were enhanced to promote the synthesis of C12 and C19. This work provides a novel strategy for the applicability of different BDPC to synthesize fuel precursors for the development of liquid biofuels.

Rational integration of defense and repair synergy on PEEK osteoimplants via biomimetic peptide clicking strategy

Polyetheretherketone (PEEK) has been widely used as orthopedic and dental materials due to excellent mechanical and physicochemical tolerance. However, its biological inertness, poor osteoinduction, and weak antibacterial activity make the clinical applications in a dilemma. Inspired by the mussel adhesion mechanism, here we reported a biomimetic surface strategy for rational integration and optimization of anti-infectivity and osteo-inductivity onto PEEK surfaces using a mussel foot proteins (Mfps)-mimic peptide with clickable azido terminal. The peptide enables mussel-like adhesion on PEEK biomaterial surfaces, leaving azido groups for the further steps of biofunctionalizations. In this study, antimicrobial peptide (AMP) and osteogenic growth peptide (OGP) were bioorthogonally clicked on the azido-modified PEEK biomaterials to obtain a dual-effect of host defense and tissue repair. Since bioorthogonal clicking allows precise collocation between AMP and OGP through changing their feeding molar ratios, an optimal PEEK surface was finally obtained in this research, which could long-term inhibit bacterial growth, stabilize bone homeostasis and facilitate interfacial bone regeneration. In a word, this upgraded mussel surface strategy proposed in this study is promising for the surface bioengineering of inert medical implants, in particular, achieving rational integration of multiple biofunctions to match clinical requirements.

Chemicals from Lignin: A Review of Catalytic Conversion Involving Hydrogen

Lignin is the most abundant biopolymer with aromatic building blocks and its valorization to sustainable chemicals and fuels has extremely great potential to reduce the excessive dependence on fossil resources, although such conversions remain challenging. The purpose of this Review is to present an insight into the catalytic conversion of lignin involving hydrogen, including reductive depolymerization and the hydrodeoxygenation of lignin-derived monomers to arenes, cycloalkanes and phenols, with a main focus on the catalyst systems and reaction mechanisms. The roles of hydrogenation sites (Ru, Pt, Pd, Rh) and acid sites (Nb, Ti, Mo), as well as their interaction in selective hydrodeoxygenation reactions are emphasized. Furthermore, some inspirational strategies for the production of other value-added chemicals are mentioned. Finally, some personal perspectives are provided to highlight the opportunities within this attractive field.

Hydro(deoxygenation) Reaction Network of Lignocellulosic Oxygenates

Hydrodeoxygenation (HDO) is a key transformation step to convert lignocellulosic oxygenates into drop-in and functional high-value hydrocarbons through controlled oxygen removal. Nevertheless, the mechanistic insights of HDO chemistry have been scarcely investigated as opposed to a significant extent of hydrodesulfurization chemistry. Current requirements emphasize certain underexplored events of HDO of oxygenates, which include 1) interactions of oxygenates of varied molecular size with active sites of the catalysts, 2) determining the conformation of oxygenates on the active site at the point of interaction, and 3) effects of oxygen contents of oxygenates on the reaction rate of HDO. It is realized that the molecular interactions of oxygenates with the surface of the catalyst dominates the degree and nature of deoxygenation to derive products with desired selectivity by overcoming complex separation processes in a biorefinery. Those oxygenates with high carbon numbers (>C10), multiple furan rings, and branched architectures are even more complex to understand. This article aims to focus on concise mechanistic analysis of biorefinery oxygenates (C_10-35 ) for their deoxygenation processes, with a special emphasis on their interactions with active sites in a complex chemical environment. This article also addresses differentiation of the mode of interactions based on the molecular size of oxygenates. Deoxygenation processes coupled with or without ring opening of furan-based oxygenates and site-substrate cooperativity dictate the formation of diverse value-added products. Oxygen removal has been the key step for microbial deoxygenation by the use of oxygen-removing decarbonylase enzymes. However, challenges to obtain branched and long-chain hydrocarbons remain, which require special attention, including the invention of newer techniques to upgrade the process for combined depolymerization-HDO from real biomass.

Highly efficient alloyed NiCu/Nb2O5 catalyst for the hydrodeoxygenation of biofuel precursors into liquid alkanes

Hydrodeoxygenation (HDO) is a crucial process for the synthesis of biofuels from renewable biomass.

Selectively creating oxygen vacancies on PrCe/SiO2 catalysts for the transformation of a furfural–acetone adduct into a functionalized 1,3-diene

Oxygen vacancies were selectively created on PrCe/SiO₂ for efficient transformation of a furfural–acetone adduct into a functionalized 1,3-diene.