Hydrothermal Liquefaction of Kraft Lignin - The influence of capping agents and residence time

In the context of exploring alternatives to replace fossil resources, lignin has been acknowledged as a renewable source of various aromatic compounds that have the potential of being precursors to chemicals as well as fuel additives. Originating from lignocellulosic biomass such as wood, lignin is an amorphous polymer with a high content of aromatic units and, in order to harness these units, it must be depolymerised. A major problem with current depolymerisation techniques, however, is that lignin repolymerises after being depolymerised, and forms an undesirable char fraction. The addition of capping agents and fine-tuning the reaction conditions can be used to mitigate such formation of char.This work has investigated the depolymerisation of kraft lignin in hydrothermal conditions under varying temperatures (290-335 \ub0C), residence times (1-12 min) and charges of isopropanol (IPA/dry lignin, 0-4.9) which, aside from being a co-solvent, was hypothesised as acting as a capping agent. The influence of these reaction parameters on the molecular weights, yields and elemental compositions of the products was studied, along with changes in the molecular structure compared to the starting lignin. The product is a suspension of solid material, i.e. char, in an aqueous phase and thus any desired organic liquid phase requires extraction from the aqueous product. While the yield of char increased with temperature and residence time, it decreased with increasing isopropanol loading, suggesting that the isopropanol does in fact act as a capping agent.Most of the lignin forms a water-soluble fraction that precipitates when the aqueous product phase is acidified, thereby forming the precipitated solids fraction (PS). The components remaining dissolved after acidification of the product phase are known as acid soluble organics (ASO). A portion of the ASO fraction was aromatic monomers, with guaiacol dominating: this result was expected since the lignin was sourced from softwood. The amount of such monomers increased with residence time in the reactor.Molecular weight analyses showed a rapid depolymerisation of the lignin within 1 min of hydrothermal liquefaction (HTL) treatment via a significant decrease in the molecular weight of all product fractions: char, PS and ASO. Moreover, the carbon-oxygen inter-unit linkages were found to break in this timeframe as well. The repolymerisation reactions started to exceed depolymerisation between residence times of 4 and 12 min, causing the weight average molecular weight (Mw) to increase again. Although minimising the residence time allows the char yield and Mw to be kept low, more monomers were formed at longer residence times. This calls for careful tuning of the residence time in the HTL of kraft lignin

On the rationality of Manx crabs

This paper accepts the challenge posed by Godfrey Baldacchino in “Islands and despots”, published in Commonwealth & Comparative Politics in February 2012, to acknowledge and investigate the implications of the “expressions of harmony and solidarity” often observed in small island societies. To do so, aspects of the Isle of Man’s political and social life are discussed from the perspectives of popular rule and rationality. This paper argues that a homogeneity in preferences and the political practices of small island states might be a rational way of protecting a vulnerable economy and thus ensuring economic growth and a sufficient allocation to each island resident of the scarce resources required to survive. Such small island homogeneity and consensualism is therefore not necessarily indicating a deficient democratic practice, but might just connote another way of conducting democratic governance, spawned from a particular way of living and a particular range of need

An autobiographical history of Ethno Sweden: a testimonial about its origins, underlying ideology and initial goals

Ethno is a multicultural summer camp for young musicians interested in traditional, folk and world music which began in Sweden in 1990 and continues today, having spread over 15 countries in the last decade. It is characterized by its peer-to-peer learning approach whereby young people teach each other the music from their countries and cultures. This article reconstructs part of the history of Ethno Sweden through an autobiographical report written by its founder, Magnus Bäckström, about the origin, ideology, strategies, and organization of the event. Interviews with the current organizer, Peter Ahlbom, complement this report detailing the organization of the event after Magnus’ departure, the process of its affiliation to the non-governmental organization Jeunesses Musicales International, and its expansion to other countries. Information is given about how the organization of Ethno Sweden went from the Falun Folkmusic Festival to Rikskonserter (Concerts Sweden) and then to Folkmusikens Hus in Rätvik

High-frequency effects in the FitzHugh-Nagumo neuron model

The effect of a high-frequency signal on the FitzHugh-Nagumo excitable model is analyzed. We show that the firing rate is diminished as the ratio of the high-frequency amplitude to its frequency is increased. Moreover, it is demonstrated that the excitable character of the system, and consequently the firing activity, is suppressed for ratios above a given threshold value. In addition, we show that the vibrational resonance phenomenon turns up for sufficiently large noise strength values.Comment: 4 pages, 4 figures (to appear in Physical Review E

On the hydrothermal depolymerisation of kraft lignin using glycerol as a capping agent

Depolymerisation of kraft lignin under hydrothermal conditions was investigated at short residence times (1–12\ua0min) with glycerol being used as a capping agent. The weight average molecular weight (M w) of the products decreased within the first minute of residence time, with the inter-unit ether linkages breaking accordingly. Furthermore, the M w of the product fractions decreased at increasing residence times, while the char yield increased. Short residence times thus appear to be beneficial for mitigating the formation of char. Also, addition of NaOH reduced the yield of char. Although the addition of glycerol caused a decrease in the M w of the products, it seemed to increase the yield of char and therefore might not be a suitable capping agent for kraft lignin depolymerisation

Using guaiacol as a capping agent in the hydrothermal depolymerisation of kraft lignin

The depolymerisation of softwood kraft lignin was investigated, under hydrothermal conditions at 290 \ub0C and 250 bar, with guaiacol in the reactor feed to evaluate its impact on the formation of char and on the molecular weights of the products. The effect of residence time was investigated in the time span 1-12 min. Lignin is depolymerised during the process and guaiacol is both formed and consumed during the reaction, with clearly noticeable changes as early as in the first minute of reaction. Although the addition of guaiacol in the reactor feed causes a reduction in the weight average molecular weight of the products, the yield of char increases. Longer residence times result in repolymerisation of the reaction products as well as a further increase in the yield of monoaromatic components and char