Two-stage thermochemical valorisation of sugar-derived humins

The majority of commercial bulk chemicals is still derived from fossil resources. The development of green biobased chemicals is high on the global research and development agenda. Lignocellulosic biomass and particularly the cellulose and hemicellulose fraction are considered interesting feeds for the production of key bulk chemicals to serve as building blocks for the chemical industry. Efficient chemo-catalytic conversion technologies for C5 and C6 sugars are under development to generate selected existing bulk chemicals, such as Levulinic acid (LA), caprolactam (CAP), butadiene (BD), furfural and 5-hydroxymethylfurfural (HMF), a very promising platform chemical for the synthesis of a.o. novel monomers for polymer synthesis. To improve the economic viability of the proposed value chains, it is mandatory to valorize byproducts such as humins which are inevitably formed in chemo-catalytic routes to platform chemicals like HMF and levulinic acid (LA) from C6-sugars. Humins are carbonaceous, heterogeneous, polydisperse materials and their formation is a major problem in conversion of carbohydrates to value added platform chemicals. The molecular structure of humins is largely unknown and, depending on the specific conversion process, humins appear as near-solid to syrup-like subtances with a high viscosity at room temperature. It is likely that sugar-derived humins will have variations in phenylic and furanic aromatic character. Please click Additional Files below to see the full abstract

Pyrolysis Of Lignin-Rich Biomass For Renewable Aromatics

Currently, several national projects are conducted as an activity along the thermochemical horizon towards functionalized aromatics from lignin and lignin-rich biomass sources in the framework of the BIORIZON shared research center in the south of the Netherlands [1]. Regarding the pyrolytic valorization of lignin-rich biomass towards aromatic chemicals for various applications, it is thought that the collection of pyrolysis vapors in separate fractions [2] offers interesting opportunities for valorization, e.g. towards (additives for) bitumen, resins, rubber and specific marine biofuels. For these high market volume – medium market value products, earlier work has revealed that the application of lignin as such (so without derivatization / modification) was not successful because of various incompatibilities. Consequently, it was deduced that specific depolymerized fractions from lignin-rich residues would possibly be usable because of lower molecular weight and/or higher reactivity and/or better miscibility with their petrochemical counterparts. Please click Additional Files below to see the full abstract

HYBRID STAGED THERMOLYSIS TO VALORISE BIOMASS

The need for a renewable ‘green’ chemistry is adamant because of the adverse effects of the increasing use of fossil fuels on our society, like global warming and the depletion of fossil fuel resources. Therefore, the use of ligno-cellulosic (woody) types of biomass as a renewable source for chemicals and energy is increasingly becoming important. Unfortunately, the heterogeneity of biomass presents a major obstacle to chemical utilization. The main constituents hemicellulose, cellulose and lignin are strongly interconnected by a variety of physico-chemical bonds that makes it difficult to extract individual chemicals in high yields. So an efficient and cost-effective fractionation technology to cleanly split the biomass into its main constituents is a valuable asset. It opens up the possibility to treat each constituent separately, using dedicated conversion technologies to get specific target chemicals. Thermolysis is a heat-treatment option to convert the biomass into chemicals according to differences in thermochemical stability between the main biomass constituents. However, since these thermochemical stabilities –at least partially- overlap, a careful selection of thermolysis process conditions is necessary to ensure a selective degradation of the chosen biomass constituent. At the same time a premature degradation of the other fractions should be prevented. Main parameters are temperature, heating rate, residence times, reaction medium and the application of catalysts. At present there is a lack of integrated processes that valorise the whole of the biomass in a cost-effective manner. The synergistic combination of aqua-thermolysis (heat-treatment in water at elevated pressure) and pyrolysis (thermal degradation in the absence of oxygen) is a promising thermolysis option in which the fractionation of the lignocellulosic biomass is integrated with the production of valuable chemicals. Preliminary non-catalytic experiments with beech, poplar and spruce wood and wheat straw have indicated the potential of this combination of aqua-thermolysis and pyrolysis to valorise lignocellulosic biomass. The relatively low-temperature (150 – 250°C) aqua-thermolysis focusses on the production of e.g. furfural from exclusively the hemicellulose fraction of the biomass. In a subsequent (fast) pyrolysis of the hemicellulose-free residu at slightly higher temperatures (300 – 500°C), the cellulose fraction can be selectively depolymerised into e.g. levoglucosan, a promising chemical building block for a variety of products. Finally, the resulting refractory lignin-residu (char) may be used as fuel, soil-improver or converted into monomeric phenols by an oxidative pyrolysis. Up to 7 weight percent (dry base) of furfural, 10 weight percent (dry base) of levoglucosan and 20 weight percent (dry base) of char have been obained in a two-step process consisting of a batch-type aqua-thermolysis in an autoclave and a bubbling fluidised bed (fast) pyrolysis. The use of specific catalysts is considered to boost these yields. Another important issue that will be addressed, is the separation of the target chemicals from the crude product mixture. Finally, to better understand the relations between the chemical changes in the biomass during the course of the integrated process and type and amount of the resulting chemical products that are formed an extensive C13-solid state NMR study has been conducted

Creating awareness of kinaesthetic learning using the Experience API: current practices, emerging challenges, possible solutions

We describe our use of the Experience API in preparing blue-collar workers for three frequently arising work contexts, including, for example, the requirement to perform maintenance tasks exactly as specified, consistently, quickly, and without error. We provide some theoretical underpinning for modifying and updating the API to remain useful in near-future training scenarios, such as having a shorter time allowed for kinaesthetic learning experiences than in traditional apprenticeships or training. We propose ways to involve a wide range of stakeholders in appraising the API and ensuring that any enhancements to it, or add-ons, are useful, feasible and compatible with current TEL practices and tools, such as learning-design modelling languages

Experimental studies on a combined pyrolysis/staged condensation/hydrotreatment approach to obtain biofuels and biobased chemicals

Fast pyrolysis is an efficient technology to convert lignocellulosic biomass to a liquid product. However, the high contents of oxygenated compounds and water hinder the direct utilization of pyrolysis oils. Here, we report an upgrading concept to obtain liquid products with improved product properties and enriched in valuable low molecular weight chemicals and particularly alkylphenols. It entails two steps, viz. i) pyrolysis with in-situ staged condensation at multiple kg scale followed by ii) a catalytic hydrotreatment of selected fractions using a Ru/C catalyst. Of all pyrolysis oil fractions after staged condensation, the product collected in a condenser equipped with an electrostatic precipitator (ESP) at 120 °C was identified as the most attractive for hydrotreatment when considering product yields and composition. The best hydrotreatment results (Ru/C, 350 °C, 100 bar H2, 4 h) were achieved using beechwood and walnut shells as feedstock, resulting in a high oil yield (about 64 wt% based on pyrolysis oil fraction intake) with a higher heating value of about 37 MJ/kg and enriched in alkylphenols (about 16 wt%). Overall, it was shown that the type of biomass (beech sawdust, walnut granulates, and pine/spruce sawdust) has a limited impact on liquid and alkylphenols yields which implies feedstock flexibility of this integrated concept

Realizing non-Abelian statistics

We construct a series of 2+1-dimensional models whose quasiparticles obey non-Abelian statistics. The adiabatic transport of quasiparticles is described by using a correspondence between the braid matrix of the particles and the scattering matrix of 1+1-dimensional field theories. We discuss in depth lattice and continuum models whose braiding is that of SO(3) Chern-Simons gauge theory, including the simplest type of non-Abelian statistics, involving just one type of quasiparticle. The ground-state wave function of an SO(3) model is related to a loop description of the classical two-dimensional Potts model. We discuss the transition from a topological phase to a conventionally-ordered phase, showing in some cases there is a quantum critical point.Comment: 20 pages in two-column format. v2: fixed typos and added reference

Measurements of CaII absorption, metals, and dust in a sample of z~1 DLAs and subDLAs

We present observations of CaII, ZnII, and CrII absorption lines in 16 DLAs and 6 subDLAs at 0.6 < z < 1.3, obtained for the dual purposes of: (i) clarifying the relationship between DLAs and absorbers selected via strong CaII lines, and (ii) increasing the still limited sample of Zn and Cr abundances in this redshift range. We find only partial overlap between current samples of intermediate-z DLAs (which are drawn from magnitude limited surveys) and strong CaII absorbers: approximately 25% of known DLAs at these redshifts have an associated CaII 3935 line with REW>0.35A, the threshold of the SDSS sample assembled by Wild and her collaborators. The lack of the strongest systems (with REW>0.5A) is consistent with these authors' conclusion that such absorbers are often missed in current DLA surveys because they redden/dim the light of the background QSOs. We rule out the suggestion that strong CaII absorption is associated exclusively with the highest-N(HI) DLAs. Furthermore, we find no correlation between the strength of the CaII lines and either the metallicity or depletion, although the strongest CaII absorber in our sample is also the most metal-rich DLA yet discovered, with [Zn/H] ~ solar. We conclude that a complex mix of parameters determine the strengths of the CaII lines, including the density of particles and UV photons in the ISM of the galaxies hosting the DLAs. We find tentative evidence (given the small size of our sample) that strong CaII systems may preferentially sample regions of high gas density, perhaps akin to the DLAs exhibiting molecular hydrogen absorption at redshifts z>2. If this connection is confirmed, strong CaII absorbers would trace possibly metal-rich, H2-bearing columns of cool, dense gas at distances up to tens of kpc from normal galaxies. (abridged)Comment: Accepted for publication in MNRAS; 15 pages, 10 figure

Spontaneously broken abelian Chern-Simons theories

A detailed analysis of Chern-Simons (CS) theories in which a compact abelian direct product gauge group U(1)^k is spontaneously broken down to a direct product H of (finite) cyclic groups is presented. The spectrum features global H charges, vortices carrying flux labeled by the elements of H and dyonic combinations. Due to the Aharonov-Bohm effect these particles exhibit toplogical interactions. The remnant of the U(1)^k CS term in the discrete H gauge theory describing the effective long distance physics of such a model is shown to be a 3-cocycle for H summarizing the nontrivial topological interactions cast upon the magnetic vortices by the U(1)^k CS term. It is noted that there are in general three types of 3-cocycles for a finite abelian gauge group H: one type describes topological interactions among vortices carrying flux w.r.t. the same cyclic group in the direct product H, another type gives rise to topological interactions between vortices carrying flux w.r.t. two different cyclic factors of H and a third type leading to topological interactions between vortices carrying flux w.r.t. three different cyclic factors. Among other things, it is demonstrated that only the first two types can be obtained from a spontaneously broken U(1)^k CS theory. The 3-cocycles that can not be reached in this way turn out to be the most interesting. They render the theory nonabelian and in general lead to dualities with planar theories with a nonabelian finite gauge group. In particular, the CS theory with finite gauge group H = Z_2 x Z_2 x Z_2 defined by such a 3-cocycle is shown to be dual to the planar discrete D_4 gauge theory with D_4 the dihedral group of order 8.Comment: 72+2 pages, LaTeX, 10 eps figures uuencoded. Postscript version also available at http://parthe.lpthe.jussieu.fr/~mdwp