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.

Pilot study on production of aviation fuel from catalytic conversion of corn stover

Aviation fuel is high energy density and is usually produced from refinery in petroleum industry. Production of renewable aviation fuel from biomass eases pressure of carbon emission regulation. The operational processes in this study include steam stripping, hydrolysis of residues, condensation reaction unit, autoclave hydrogenation, fixed-bed hydrodeoxygenation, and oil-upgrading unit. The biomass-derived aviation fuel has a low oxygen content of 0.4 %, while its high heat value is 45.5 MJ/kg. The aviation fuel ranges from C8 ∼ C15, and rich in isoparaffins (50.4 %) while the n-paraffins have a selectivity of 12.2 % and other components are cycloparaffins (19.0 %), aromatic hydrocarbons (11.3 %), and alkenes (5.6 %). The mass yield for aviation fuel from corn stover reaches 10.6 %. This pilot study achieved production of aviation fuel from raw biomass corn stover.

Catalytic Production of Oxygenated and Hydrocarbon Chemicals From Cellulose Hydrogenolysis in Aqueous Phase

As the most abundant polysaccharide in lignocellulosic biomass, a clean and renewable carbon resource, cellulose shows huge capacity and roused much attention on the methodologies of its conversion to downstream products, mainly including platform chemicals and fuel additives. Without appropriate treatments in the processes of cellulose decompose, there are some by-products that may not be chemically valuable or even truly harmful. Therefore, higher selectivity and more economical and greener processes would be favored and serve as criteria in a correlational study. Aqueous phase, an economically accessible and immensely potential reaction system, has been widely studied in the preparation of downstream products of cellulose. Accordingly, this mini-review aims at making a related summary about several conversion pathways of cellulose to target products in aqueous phase. Mainly, there are four categories about the conversion of cellulose to downstream products in the following: (i) cellulose hydrolysis hydrogenation to saccharides and sugar alcohols, like glucose, sorbitol, mannose, etc.; (ii) selective hydrogenolysis leads to the cleavage of the corresponding glucose C-C and C-O bond, like ethylene glycol (EG), 1,2-propylene glycol (PG), etc.; (iii) dehydration of fructose and further oxidation, like 5-hydroxymethylfurfural (HMF), 2,5-furandicarboxylic acid (FDCA), etc.; and (iv) production of liquid alkanes via hydrogenolysis and hydrodeoxygenation, like pentane, hexane, etc. The representative products were enumerated, and the mechanism and pathway of mentioned reaction are also summarized in a brief description. Ultimately, the remaining challenges and possible further research objects are proposed in perspective to provide researchers with a lucid research direction.

Selective Cellulose Hydrogenolysis to Ethanol Using Ni@C Combined with Phosphoric Acid Catalysts

Ethanol is an important bulk chemical with diverse applications. Biomass-derived ethanol is traditionally produced by fermentation. Direct cellulose conversion to ethanol by chemocatalysis is particularly promising but remains a great challenge. Herein, a one-pot hydrogenolysis of cellulose into ethanol was developed by using graphene-layers-encapsulated nickel (Ni@C) catalysts with the aid of H₃ PO₄ in water. The cellulose was hydrolyzed into glucose, which was activated by forming cyclic di-ester bonds between the OH groups of H₃ PO₄ and glucose, promoting ethanol formation under the synergistic hydrogenation of Ni@C. A 69.1 % yield of ethanol (carbon mole basis) was obtained, which is comparable to the theoretical value achieved by glucose fermentation. An ethanol concentration of up to 8.9 wt % was obtained at an increased cellulose concentration. This work demonstrates a chemocatalytic approach for the high-yield production of ethanol from renewable cellulosic biomass at high concentration.

Hydrothermal synthesis of bimodal mesoporous MoS2 nanosheets and their hydrodeoxygenation properties

Bimodal mesopore MoS₂ nanosheets were successfully synthesized by adjusting the pH value and exhibited high HDO activity.

Catalytic conversion of glucose and cellobiose to ethylene glycol over Ni–WO3/SBA-15 catalysts

The ratio of W to Ni is a crucial factor in controlling the production distribution for glucose and cellobiose conversion; the change of W/Ni ratio with Ni loading results from the change of W and Ni species distribution on the catalyst surface.