Alexander K. L. Yuen

Biocrude yield and productivity from the hydrothermal liquefaction of marine and freshwater green macroalgae

Six species of marine and freshwater green macroalgae were cultivated in outdoor tanks and subsequently converted to biocrude through hydrothermal liquefaction (HTL) in a batch reactor. The influence of the biochemical composition of biomass on biocrude yield and composition was assessed. The freshwater macroalgae Oedogonium afforded the highest biocrude yield of all six species at 26.2%, dry weight (dw). Derbesia (19.7%dw) produced the highest biocrude yield for the marine species followed by Ulva (18.7%dw). In contrast to significantly different yields across species, the biocrudes elemental profiles were remarkably similar with higher heating values of 33-34MJkg(-1). Biocrude productivity was highest for marine Derbesia (2.4gm(-2)d(-1)) and Ulva (2.1gm(-2)d(-1)), and for freshwater Oedogonium (1.3gm(-2)d(-1)). These species were therefore identified as suitable feedstocks for scale-up and further HTL studies based on biocrude productivity, as a function of biomass productivity and the yield of biomass conversion to biocrude.

From macroalgae to liquid fuel via waste-water remediation, hydrothermal upgrading, carbon dioxide hydrogenation and hydrotreating

This article showcases a proof-of-concept in the production of high quality renewable biofuel from algae. Here, we introduce a path combining a number of approaches that, when integrated as a whole, create a process that takes algae grown in waste-water through to a liquid fuel containing fractions ready for blending with regular gasoline, jet fuel and diesel. With the overarching goal of reducing the nitrogen content invariably associated with whole algal biomass, we apply a number of approaches including (i) nutrient starvation to reduce the internal nitrogen of the freshwater alga Oedogonium (ii) continuous co-solvent (10 wt% n-heptane) hydrothermal liquefaction (HTL) to produce a non-polar biocrude containing <1 wt% N; (iii) blending the biocrude with green feed produced from the hydrogenation of CO2 to obtain <0.5 wt% N; (iv) hydrogenation and hydro-isomerization of the blend in two stages over nanodisperse silica-supported Ni2P (achieving 630 ppm N) and acidic zeolite-supported Pt catalysts respectively to produce a synthetic paraffinic mixture (SPM) containing 277 ppm N and 0.12% O. With the incorporation of renewable H2 (which can be from gasification of polar organics produced in the solvent HTL, or other renewable sources) and captured CO2 the process demonstrates a new and technically cohesive approach to the production of renewable, high-quality biofuels for demanding transport applications.

Preparation of the central tryptophan moiety of the celogentin/ moroidin family of anti-mitotic cyclic peptides

The central functionalized tryptophan core of the celogentin/moroidin family of cyclic peptides has been prepared. The strategy incorporates a novel preparation of 4-iodobenzaldehyde and employs a Larock annulation as the key step.

Ionic liquids are compatible with on-water catalysis.

A major limitation of on-water catalysis has been the need for liquid reactants to enable emulsification. We demonstrate that ionic liquids are compatible with on-water catalysis, enabling on-water catalysed reactions for otherwise unreactive solid-solid systems. The unique solvation properties of ionic liquids dramatically expands the scope of on-water catalysis.

A Palladium‐Catalyzed Multicascade Reaction: Facile Low‐Temperature Hydrogenolysis of Activated Nitriles and Related Functional Groups

The facile hydrogenolysis of various nitriles, imines, and amines over Pd/C has been achieved by using straightforward and relatively mild conditions. Substrates that contain an aryl group adjacent to the nitrogen‐containing functionality were hydrogenolyzed most effectively. The stabilization of the proposed η2‐coordinated palladium intermediate by this group was partly responsible for this observation and is borne out by ab initio calculations.

Measurement of Long-Range Interatomic Distances by Solid-State Tritium-NMR Spectroscopy

For the structural determination of a ligand bound to an amorphous macromolecular system, solid-state NMR can be used to provide interatomic distances. It is shown here that selective labeling in discrete locations with tritium enables accurate measurement of long-range distances owing to the high gyromagnetic ratio of this nucleus, without structural modification of the molecule. This approach gives access to the largest NMR distance ever measured between two nuclei (14.4 A). (3)H MAS NMR appears to be a promising tool for structural applications in the biological and material sciences.

Molecular capsules and coordination polymers from a backbone-modified cyclic peptide bearing pyridyl arms

A tris-pyridyl-substituted Lissoclinum-type cyclic peptide forms a trinuclear molecular capsule on addition of Ag(I) ions and an infinite one-dimensional coordination polymer on addition of Pd(II) ions.

Controlling viscosity in methyl oleate derivatives through functional group design

Fatty acid methyl ester (FAME) derivatives have received considerable attention as potential biofuel additives and as sustainable lubricants. One common strategy for the modification of FAMEs, such as methyl oleate, involves epoxidation of the C9–C10 alkene followed by oxirane ring-opening to introduce branches into the FAME backbone. This strategy has been shown to improve cold-flow properties and oxidative stability relative to the parent oleates, and some derivatives have shown promise as lubricants. However, the effect of this strategy on viscosity has not been well established, if at all. Here we present the viscosity properties of methyl oleate derivatives as controlled by rational functional group manipulation with important implications for the preparation of bio-derived lubricants, where viscosity properties must be tightly controlled. The effect of selected derivatives as cold-flow additives in biodiesel is also reported.

Unravelling Some of the Key Transformations in the Hydrothermal Liquefaction of Lignin

Using both experimental and computational methods, focusing on intermediates and model compounds, some of the main features of the reaction mechanisms that operate during the hydrothermal processing of lignin were elucidated. Key reaction pathways and their connection to different structural features of lignin were proposed. Under neutral conditions, subcritical water was demonstrated to act as a bifunctional acid/base catalyst for the dissection of lignin structures. In a complex web of mutually dependent interactions, guaiacyl units within lignin were shown to significantly affect overall lignin reactivity.

Renewable Aromatics from Kraft Lignin with Molybdenum-Based Catalysts

The catalytic depolymerization of Kraft lignin in supercritical ethanol was explored in the presence of Mo2C‐ and MoS2‐based catalysts. At 280 °C, Mo2C and Mo2C/Al2O3 afforded aromatic yields of 425 and 419 mg g−1 lignin, respectively: amongst the highest yields reported to date. Ionic–liquid–assisted delamination of MoS2 resulted in highly active catalysts, capable of quantitative conversion of lignin at the expense of aromatic yield (approximately 186 mg g−1 lignin). Across all the catalysts studied, between 0.04 wt % and 0.38 wt % of molybdenum leached into the solution under supercritical conditions, according to inductively coupled plasma (ICP) analyses (corresponding to 27–570 μg of molybdenum in the reaction supernatant). A small contribution to the molybdenum in solution comes from the reactor itself (Hastelloy C contains 16 wt % Mo). Analysis of a depolymerization performed with fresh Kraft lignin and the soluble portion of the reaction mixture from a previous reactor run indicated that the leached species were neither active enough to afford the high conversions observed, nor selective enough to give high yields of aromatic products. In conjunction with the ICP data and differential chemoselectivities of the Mo2C‐ and MoS2‐based catalysts, these results suggest that the bulk of the catalysis is heterogeneous.