Liquid-phase catalytic processing of biomass-derived oxygenated hydrocarbons to fuels and chemicals

Biomass has the potential to serve as a sustainable source of energy and organic carbon for our industrialized society. The focus of this Review is to present an overview of chemical catalytic transformations of biomass-derived oxygenated feedstocks (primarily sugars and sugar-alcohols) in the liquid phase to value-added chemicals and fuels, with specific examples emphasizing the development of catalytic processes based on an understanding of the fundamental reaction chemistry. The key reactions involved in the processing of biomass are hydrolysis, dehydration, isomerization, aldol condensation, reforming, hydrogenation, and oxidation. Further, it is discussed how ideas based on fundamental chemical and catalytic concepts lead to strategies for the control of reaction pathways and process conditions to produce H(2)/CO(2) or H(2)/CO gas mixtures by aqueous-phase reforming, to produce furan compounds by selective dehydration of carbohydrates, and to produce liquid alkanes by the combination of aldol condensation and dehydration/hydrogenation processes.     

Biofuels and biomass-to-liquid fuels in the biorefinery: catalytic conversion of lignocellulosic biomass using porous materials

At a time when the focus is on global warming, CO(2) emission, secure energy supply, and less consumption of fossil-based fuels, the use of renewable energy resources is essential. Various biomass resources are discussed that can deliver fuels, chemicals, and energy products. The focus is on the catalytic conversion of biomass from wood. The challenges involved in the processing of lignocellulose-rich materials will be highlighted, along with the application of porous materials as catalysts for the biomass-to-liquids (BTL) fuels in biorefineries. The mechanistic understanding of the complex reactions that take place, the development of catalysts and processes, and the product spectrum that is envisaged will be discussed, along with a sustainable concept for biorefineries based on lignocellulose. Finally, the current situation with respect to upgrading of the process technology (pilot and commercial units) will be addressed.     

Catalysis for Oleochemical Platforms

The present review articles the most recent efforts, made in the Department of Chemical Sciences of the University of Naples Federico II, in the catalytic treatment of biomasses derived from vegetable oils. The review is focused on several technologies aimed at the production of either biofuels or valuable chemicals: (i) biodiesel production; (ii) esterification to obtain high-added value products; (iii) epoxidation of vegetable oils; (iv) glycerol ketalization; (v) oxidative cleavage of unsaturated fatty acids. The results are critically summarized to highlight the scientific activities and the main results in the field of biorefinery concept.     

Catalytic Production of Alanine from Waste Glycerol

Chemical synthesis of amino acids directly from biomass feedstock is rare. Reported here is a one‐step protocol to convert crude glycerol, from the biodiesel industry, into 43 % alanine over a Ru₁Ni₇/MgO catalyst. The multifunctional catalytic system promotes glycerol conversion into lactic acid, and then into alanine. X‐ray absorption spectroscopy and scanning transmission electron microscopy revealed the existence of bimetallic RuNi species, whereas density‐functional theory calculations suggested Ni‐doped Ru substantially decreased the E_a of C?H bond dissociation of lactate alkoxide to form pyruvate, which is the rate‐determining step. The catalytic route established in this work creates new opportunities for glycerol utilization and enriches the substrate scope of renewable feedstock to access value‐added amino acids.     

Hydrodeoxygenation of the Angelica Lactone Dimer,a Cellulose‐Based Feedstock: Simple,High‐Yield Synthesis of Branched C7–C10 Gasoline‐like Hydrocarbons

Dehydration of biomass‐derived levulinic acid under solid acid catalysis and treatment of the resulting angelica lactone with catalytic K₂CO₃ produces the angelica lactone dimer in excellent yield. This dimer serves as a novel feedstock for hydrodeoxygenation, which proceeds under relatively mild conditions with a combination of oxophilic metal and noble metal catalysts to yield branched C₇–C₁₀ hydrocarbons in the gasoline volatility range. Considering that levulinic acid is available in >80 % conversion from raw biomass, a field‐to‐tank yield of drop‐in, cellulosic gasoline of >60 % is possible.     

Recent Advances in the Deoxydehydration of Vicinal Diols and Polyols

Deoxydehydration (DODH) is one of the most promising tools to reduce the oxygen content of biomass (sugars and polyols) and provide analogues of platform chemicals that are derived from fossil resources. This reaction converts a vicinal diol into an alkene and is typically catalyzed by high‐oxidation‐state metal‐oxo compounds in the presence of a stoichiometric reductant, with examples of both homogeneous and heterogeneous systems. This minireview will highlight the developments in this field over the past 5 years and focus on efforts to solve the problems that currently prevent DODH being performed on a commercial scale, including the nature of the reductant, substrate scope and selectivity, and catalyst recovery and expense.     

Utility of Core–Shell Nanomaterials in the Catalytic Transformations of Renewable Substrates

In recent years, core–shell nano-catalysts have received increasing attention due to their tunable properties and broad applications in catalysis. Control of the two components of these materials allows their catalytic properties to be tuned to various sustainable processes in synthetic and energy-related applications. This Concept article describes recent state-of-the-art core–shell materials and their application as heterogeneous catalysts for a range of sustainable catalytic transformations, focusing on two important classes of renewable substrates, CO₂ and biomass. In the discussion, emphasis is directed to the role of the constituent parts of the core–shell structure and how they can be manipulated to enhance activity.     

An Inexpensive and Recyclable Silver‐Foil Catalyst for the Cyclopropanation of Alkenes with Diazoacetates under Mechanochemical Conditions

The diastereoselective cyclopropanation of various alkenes with diazoacetate derivatives can be achieved under mechanochemical conditions using metallic silver foil and a stainless‐steel vial and ball system. This solvent‐free method displays analogous reactivity and selectivity to solution‐phase reactions without the need for slow diazoacetate addition or an inert atmosphere. The heterogeneous silver‐foil catalyst system is easily recyclable without any appreciable loss of activity or selectivity being observed. The cyclopropanation products were obtained with excellent diastereoselectivities (up to 98:2 d.r.) and in high yields (up to 96 %).