Is Steam Explosion a Promising Pretreatment for Acid Hydrolysis of Lignocellulosic Biomass?

For the production of sugars and biobased platform chemicals from lignocellulosic biomass, the hydrolysis of cellulose and hemicelluloses to water-soluble sugars is a crucial step. As the complex structure of lignocellulosic biomass hinders an efficient hydrolysis via acid hydrolysis, a suitable pretreatment strategy is of special importance. The pretreatment steam explosion was intended to increase the accessibility of the cellulose fibers so that the subsequent acid hydrolysis of the cellulose to glucose would take place in a shorter time. Steam explosion pretreatment was performed with beech wood chips at varying severities with different reaction times (25–34 min) and maximum temperatures (186–223 °C). However, the subsequent acid hydrolysis step of steam-exploded residue was performed at constant settings at 180 °C with diluted sulfuric acid. The concentration profiles of the main water-soluble hydrolysis products were recorded. We showed in this study that the defibration of the macrofibrils in the lignocellulose structure during steam explosion does not lead to an increased rate of cellulose hydrolysis. So, steam explosion is not a suitable pretreatment for acid hydrolysis of hardwood lignocellulosic biomass

A Distributed Public Key Infrastructure Based on Threshold Cryptography for the HiiMap Next Generation Internet Architecture

In this article, a security extension for the HiiMap Next Generation Internet Architecture is presented. We regard a public key infrastructure which is integrated into the mapping infrastructure of the locator/identifier-split addressing scheme. The security approach is based on Threshold Cryptography which enables a sharing of keys among the mapping servers. Hence, a more trustworthy and fair approach for a Next Generation Internet Architecture as compared to the state of the art approach is fostered. Additionally, we give an evaluation based on IETF AAA recommendations for security-related systems

Optimized design and techno-economic analysis of novel DME production processes

The shift from gas to liquid phase DME synthesis enables an intensified process concept towards efficient large scale DME production. In this work, four process concepts based on liquid phase DME synthesis were proposed and optimized. A comprehensive economic model was applied with the objective of minimizing the total production cost. All concepts were evaluated applying our previously validated reaction kinetics for commercial ion exchange resin selected catalysts. Furthermore, every process concept was studied with a pure MeOH feed and water-rich (crude) MeOH feedstock. The conventional gas-phase DME production process was simulated and evaluated using the same technical and economic parameters to serve as a benchmark. Using a chlorinated high temperature stable IER catalyst led to significant cost reduction in all the considered concepts. This was due to the higher reaction rate enabled by the higher operating temperature of this catalyst. In the integrated process concept with H2 and CO2 as sustainable feedstocks, it was shown that the reactive distillation process shows a 27% lower production cost, when the crude methanol is directly fed to the DME process instead of being purified in a dedicated crude methanol distillation column. A further techno-economic optimization can be achieved when complementing the reactive distillation column with an additional reactor. Overall, the process concept of a reactive distillation column with a side reactor presents the most promising process concept, enabling a 39% lower production cost than the conventional gas-phase process. By heat integration with a CO2-based MeOH plant, a DME production technology with no external heat demand and a net conversion cost of 54.4 € per tDME is possible

Modeling martensitic transformation in shape memory alloys using multi-phase-field elasticity models based on partial rank-one energy relaxation on pairwise interfaces

To model the mechanically-driven phase transformations, e.g. martensitic transformation, using the phase-field theory, suitable models are needed for describing the mechanical fields of the individual non-vanishing phase-fields in the interface regions in order to obtain the mechanical driving forces of phase-field motion. Quantitative modeling requires satisfying the interfacial static equilibrium and kinematic compatibility conditions which have already been achieved in the literature for dual-phase-field materials by using the rank-one relaxation (or convexification) of the energy density. A direct generalization to the multi-phase-field case is not applicable without breaking these conditions partially. To the best of our knowledge, no existing multi-phase-field elasticity model has been able to satisfy the jump conditions between all the locally-active phase-fields on their pairwise normals in triple and higher-order junctions. In this work, we introduce a novel multi-phase-field elasticity model based on the partial rank-one relaxation of the elastic energy density defined on the pairwise interfaces...... (see PDF for the rest of the abstract

Proton irradiation of gold targets for 197(m)Hg production

Introduction Irradiation of gold with protons provides access to no-carrier-added 197mHg and 197Hg. Interests in these radionuclides were awakened by the unique chemical and physical properties of mercury and its compounds combined with convenient nuclear properties like suitable half life (197mHg: T1/2 = 23.8 h, 197Hg: T1/2 = 64.14 h), low energy gamma radiations for imaging, Auger – and conversion electrons for therapy. The high thermal conductivity of gold enables high current irradiations and the monoisotopic natural abundance of 197Au supersedes expensive enrichment of the target material. The 197Au(p,n)197(m)Hg reaction was applied until now only for beam monitoring1, stacked foil meas-urements2 or very small scale tracer production. Material and Methods The irradiations were performed at a Cyclone 18/9 (IBA, Louvain la Neuve, Belgium). Its beam-line was sealed with a 1.0 mm vacuum foil (high purity aluminum, 99.999 %) from Goodfellow (Huntingdon, England). High purity gold disks (23 mm diameter, 2 mm thickness, 99.999% pure, 1 ppm Cu) as target material were purchased from ESPI (Ashland, USA). Gold foils as alternative gold targets (12.5×12.5 mm, 0.25 mm thickness, 99.99+ %, 1 ppm Cu) between an aluminum disk (22 mm diameter, 1 mm thickness, 99.0 %, hard) and an aluminum lid (23 mm diameter, 99.0 %, hard) were purchased from Goodfellow (Huntingdon, England). Hydrochloric acid (30%) and nitric acid (65%) were purchased from Roth (Karlsruhe, Germany) in Rotipuran® Ultra quality. Deionized water with > 18 MΩcm resistivity was prepared by a Milli-Q® system (Millipore, Molsheim, France). For separation of target material and side products a liquid-liquid extraction method (Gold was extracted with methyl isobutyl ketone (MIBK) from 2 M HCl target solution) and an ion exchange method (cation exchange resin (Dowex50W-x8, 100–200 mesh, H+ form) were applied. Results and Conclusion No-carrier-added 197(m)Hg was produced from gold via the 197Au(p,n)197(m)Hg reaction at proton energies of 10 MeV in sufficient quantity and quality for imaging studies. Two different methods were studied for the separation of Hg radionuclides generated from Au targets. The results demonstrate the possibility to produce 197(m)Hg from gold at low proton energies. Combined with the presented radiochemical separation methods, the 197Au(p,n) reaction could be the basis for repeatable production of 197(m)Hg for imaging and therapy research on sufficient activity level

Isomerization of Glucose to Fructose in Hydrolysates from Lignocellulosic Biomass Using Hydrotalcite

The isomerization of glucose-containing hydrolysates to fructose is a key step in the process from lignocellulosic biomass to the platform chemical hydroxymethylfurfural. We investigated the isomerization reaction of glucose to fructose in water catalyzed by hydrotalcite. Catalyst characterization wasperformedvia IR, XRD, and SEM. Firstly, glucose solutions at pH-neutral conditions were converted under variation of the temperature, residence time, and catalyst loading, whereby a maximum of 25 wt.% fructose yield was obtained at a 38 wt.% glucose conversion. Secondly, isomerization was performed at pH = 2 using glucose solutions as well as glucose-containing hydrolysates from lignocellulosic biomass. Under acidic conditions, the hydrotalcite loses its activity for isomerization. Consequently, it is unavoidable to neutralize the acidic hydrolysate before the isomerization step with an inexpensive base. As a neutralizing agent NaOH is preferred over Ba(OH)2, since higher fructose yields are achieved with NaOH. Lastly, a pH-neutral hydrolysate from lignocellulose was subjected to isomerization, yielding 16 wt.% fructose at a 32 wt.% glucose conversion. This work targets the application of catalytic systems on real biomass-derived samples

Acid hydrolysis of lignocellulosic biomass: Sugars and furfurals formation

Hydrolysis of lignocellulosic biomass is a crucial step for the production of sugars and biobased platform chemicals. Pretreatment experiments in a semi-continuous plant with diluted sulphuric acid as catalyst were carried out to measure the time-dependent formation of sugars (glucose, xylose, mannose), furfurals, and organic acids (acetic, formic, and levulinic acid) at different hydrolysis temperatures (180, 200, 220° C) of one representative of each basic type of lignocellulose: hardwood, softwood, and grass. The addition of the acid catalyst is followed by a sharp increase in the sugar concentration. Xylose and mannose were mainly formed in the initial stages of the process, while glucose was released slowly. Increasing the reaction temperature had a positive effect on the formation of furfurals and organic acids, especially on hydroxymehtylfurfural (HMF) and levulinic acid, regardless of biomass type. In addition, large amounts of formic acid were released during the hydrolysis of miscanthus grass. Structural changes in the solid residue show a complete hydrolysis of hemicellulose at 180° C and of cellulose at 200° C after around 120 min reaction time. The results obtained in this study can be used for the optimisation of the hydrolysis conditions and reactor design to maximise the yields of desired products, which might be sugars or furfurals

Herd mobility leads the way for sustainable pastoral development: the case of Borana rangelands, southern Ethiopia 1

Abstract Insights gained from experiences in pastoral developmen