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A simple schlieren technique is used to visualize strong gradients of refractive index in liquids under atmospheric conditions and elevated pressure. The gradients are mainly caused by concentration differences within a thin liquid sheet. A simple system using Matlab and open source applications is designed and applied to demonstrate the challenges and limitations of a quantitative approach for strong gradients in liquids. Possibilities for the optimization regarding the detection of strong gradients are shown, but rather qualitative than quantitative results are obtained.

Abstract In the conventional leather production process, basic chromium sulphate (BCS) penetrates fully inside the collagen matrix during tanning and forms oligo-nuclear complexes that stabilize the skin structure during basification. Accelerated chromium sulphate complexation by basifying the BCS before full penetration leads to surface tanning and low leather qualities. Therefore, long processing times of 16 h for tanning and basification are common in modern tanneries. We used sodium hydrogen carbonate to basify BCS before penetration. However, instead of conventional tanning we performed CO2 tanning at 30 bar. The influence of accelerated chromium sulphate complexation on the leather quality was investigated. To estimate the structures of the formed chromium complexes, we considered the pH trend of the tanning solution during basification depending on the amount of basifying agent. The distribution of chromium oxide (Cr2O3) and the shrinkage temperature (Ts) in three different layers of the cross section were analysed. The analytics allowed the assessment whether the tanning agent penetrates through the whole cross section or adheres to the surface during CO2 tanning. We show that CO2-intensified tanning allows accelerated chromium sulphate complexation and a reduction in the tanning time from 16 to 4 h. The Cr2O3 is equally distributed, and Ts above 100 °C meets the standards of high-quality wet blue. However, the pH value of the tanning solution must not rise above 4.5 during basification. Otherwise, the Ts decrease dramatically. The feasibility of the process is demonstrated in a 1700-L drum, with a batch size of about 500 kg. The CO2-intensified tanning process has high potential to save time and chemicals and reduce emissions in industrial applications and is commercially competitive. Graphic abstract

Water jet cutting is of increasing interest in manufacturing technology. By using carbon dioxide (CO2) instead of water, a dry processing becomes possible. To realize cutting results comparable to water, liquid and coherent CO2-jets with high specific energy have to be formed. However, CO2 does not exist as a liquid in thermodynamic equilibrium at atmospheric pressure. During the expansion through a nozzle from a liquid state to atmospheric pressure the saturation curve is crossed and a spray consisting of a gaseous and solid phase is generated. We show that with sufficiently low injection temperatures the phase change is delayed and liquid jets emanate from the nozzle even at atmospheric pressure. These jets disintegrate closer to the nozzle than water jets at same pressure and nozzle conditions. The shorter jet length results in lower kerf depths. But the kerf width is smaller with CO2 and a more precise cutting is possible.

In this study compressed carbon dioxide and silver nitrate as antimicrobial agent were used to equip injection moulded polycarbonate parts with antibacterial properties. Experiments were performed in a high pressure view cell of 63 mL and scaled up in a high pressure vessel of 2 L. Temperatures of 20 °C and 80 °C and CO 2 pressures of ambient pressure and 120 bar were applied. The impregnated samples were analysed regarding the durability of their antibacterial activity. Abrasion tests, elution tests as well as UV irradiation were performed. The influence on the silver content, the transmission and the antibacterial activity were investigated. Depending on the used parameter the samples were able to reduce bacterial activity up to 99.9% after one hour of contact time in a dynamic shake flask tests according to ASTM E2149 classification.

Conventional leather dyeing consumes high amounts of dyes and increases pollution of tannery wastewater. We have focused on the reduction of dyestuff and the avoidance of water and additional chemicals for the colorization of leather. Waterless leather dyeing with supercritical CO2 as solvent for the dye 1-(methylamino)anthraquinone was performed in a technical scale autoclave. The intensity and uniformity of the dyed leathers was assessed using spectroscopic color measurements. The rub fastness was assessed according to DIN EN ISO 11640. In the result, waterless dyeing at 100 bar and 40 °C leads to uniform, intensive colorizations of the leather surface at a usage of 0.1 g of dye per square foot of leather. The dyed leathers achieve the highest rub fastness grades. The exhaustion of dyestuff is almost 100%. The waterless dyeing process offers potential to save significant amounts of dyestuff and reduce wastewater emissions by 100%.

The leather industry transforms raw hides and skins into high-performance leather products. This transformation requires a high usage of chemicals. About 90% of all leather products are tanned by basic chromium sulphate tanning agents. The use of large quantities of tanning agent causes elevated chromium and sulphate concentrations in the wastewater of conventional tanneries. This article focuses on the reduction of tanning agent consumed by the chromium tanning procedure. Compressed carbon dioxide is used to intensify the process. Carbon dioxide-intensified tanning at 60 bar allows the production of high-quality leather by using about 50 wt% less of tanning agent compared to the conventional tanning process. The chromium and sulphate concentrations in the wastewater generated by the tanning process are highly reduced. Results of full skin tanning (bull skin; up to 10 square metre per skin) in a high-pressure reactor with a volume of 1700-L are presented for the first time.

This work describes the possibility to hydrolyze rutin (quercetin-3- O -rutinoside) to quercetin using carbon dioxide (CO 2 ) and water without the addition of acids or enzymes. Eight hours of CO 2 -intensified hydrolysis of aqueous rutin-solutions were carried out to investigate temperature (373.15 K–433.15 K) and pressure dependence (4–150 bar). Both temperature and CO 2 -pressure dependence are studied. The parameter combination of 413.15 K and 150 bar gave a complete (100 %) conversion of rutin to quercetin. Temperature and pressure dependence were modelled. Models achieved correlation coefficients between R 2 = 0.85 and 0.99. Influence of H + ions was described by implementing the »H + -factor« to explain the hydrolysis effect of CO 2 -pressure in more detail. The results of this work demonstrate that CO 2 -intensified hydrolysis is possible at moderate temperatures and pressures.

The electrochemical reduction of carbon dioxide is usually studied in aqueous solutions under ambient conditions. However, the main disadvantages of this method are high hydrogen evolution and low faradaic efficiencies of carbon-based products. Supercritical CO2 (scCO(2)) can be used as a solvent itself to suppresses hydrogen evolution and tune the carbon-based product yield; however, it has received little attention for this purpose. Therefore, the focus of this study was on the electrochemical reduction of scCO(2). The conductivity of scCO(2) was increased through the addition of supporting electrolyte and a cosolvent (acetonitrile). Furthermore, the addition of protic solutions of different pH to scCO(2) was investigated. 1m H2SO4, trifluoroethanol, H2O, KOH, and CsHCO3 solutions were used to determine the effect on current density, faradaic efficiency, and selectivity of the scCO(2) reduction. The reduction of scCO(2) to methanol and ethanol are reported for the first time. However, methane and ethylene were not observed. Additionally, corrosion of the Cu electrode was noticed.

Supercritical fluid extraction (SFE) with and without entrainer combined with organic solvent extraction was used for fractionation of bioactive natural products as alkaloids and antioxidants from cat's claw ( Uncaria tomentosa (Willd.) DC.) bark. Extracts obtained from this plant have a number of beneficial effects, including anti-inflammatory or immune stimulator. The aim of this work was to obtain extracts of enriched and limited alkaloid concentrations, good antioxidants and tannin agents. The results demonstrated that a hybrid process involving SFE is a selective method to obtain an oxindole alkaloid rich fraction (186.0 ± 3.2 mg total pentacyclic oxindole alkaloids/g extract) and a product enriched in tannins (23.8 ± 1.9% tannin content in extract) and antioxidants (IC 50 = 5.88 ± 0.54 μg/ml extract).

This work addresses European medicinal herbs as possible resources for vegetable tannins and their usage in leather production but also for further applications such as in the food, pharmaceutical or chemical industry. A detailed review of literature was conducted to identify herbs with promising tannin contents. 47 European medicinal herbs were identified for further analysis. Two plants from Rosaceae ( Potentilla erecta and Geum urbanum ) and one from Ericaceae ( Arctostaphylus uva-ursi ) show the highest tannin contents between 15 w% and 30 w% in literature. To verify the data from literature the identified 47 herbs were extracted and analyzed on their tannin content per plant by the radial diffusion method. 16 plants interfered with the radial diffusion method. Maximum tannin content per plant of 11,6 w% and maximum tannin content per dried extract of 38,4°w% were analyzed for Rubi fruticosus . For six plants of the sixteen plants it was possible to confirm the tannin contents from literature ( Alchemilla vulgaris, Acrtostaphylus uva-ursi, Fragaria, Potentilla anserine, Potentilla erecta and Rubi fruticosus ). For the remaining seven plants, lower tannin contents were obtained than listed in literature ( Geum urbanum, Melissa officinalis, Mentha piperita, Origanum vulgare, Rubi idaei, Salicis folium and Vaccinium vitis-idaea ). In the end, those six plants were evaluated on their theoretical availability in Germany as resource for new tanning agents. Fragaria, Alchemilla vulgaris and Rubi fruticosus showed the highest potential for application in leather production and for further applications. Highest amount of vegetable tannin extracts – up to 1900 kg/ha was estimated for Alchemilla vulgaris .

Due to the brittle nature of poly(lactic acid) many attempts have been made to flexibilize this polyester for applications such as thin films and foils. However, due to complex phase behavior, many drawbacks for plasticizer and blend components are described. To overcome miscibility, post crystallization and migration issues a principle of click-chemistry was employed to change the molecular characteristics from external to internal plasticization by fixation of a plastisizing unit with help of a stereocomplex crystallization. Hydroxyl terminated polycaprolactone oligomers were used as a macroinitiator for the ring opening polymerization of d-lactide, resulting in blockcopolymers with plasticizing unit polycaprolactone and compatibilizing poly(d-lactic acid)-blocks. The generated block copolymers were blended with a poly(l-lactic acid)-matrix and formed so called stereocomplex crystals. In comparison to unbound polycaprolactone the polycaprolactone blocks show a lower migration tendency regarding a solution test in toluene. Besides that, trapping the plasticizing units via stereocomplex also improves the efficiency of the plasticizer. In comparison to polymer blends with the same amount of non-bonded polycaprolactone oligomers of the same molecular weight, block copolymers with poly(d-lactic acid) and polycaprolactone can shift the glass transition temperature to lower values. This effect can be explained by the modulated crystallization of the polycaprolactone-blocks trapped into the matrix, so that a higher effective amount can interact with the poly(l-lactic acid)-matrix.

The electrocatalytic reduction of carbon dioxide (CO2) by means of renewable energies is widely recognized as a promising approach to establish a sustainable closed carbon cycle economy. However, widespread application is hampered by the inherent difficulty in suppressing the hydrogen evolution reaction and controlling the overall process selectivity. Further critical parameters are the limited solubility of CO2 in many electrolytes and its hindered mass transport to the electrodes. Herein we report on a series of nanoparticle Cu electrocatalysts on different carbon supports and their potential to perform the electrochemical CO2 reduction under supercritical conditions (scCO2). Herein, CO2 serves as the reaction medium and reactant alike. By a detailed comparison to ambient conditions we show that scCO2 conditions largely suppress the undesirable hydrogen evolution and favor the production of formic acid by the Cu electrodes. Furthermore, we show that scCO2 conditions significantly prevent Cu nanoparticle agglomeration during electrocatalysis.

The wastewater pollution of tanneries is of high concern. The investigation of technologies to minimize the consumption of chemicals in the leather production process can reduce the environmental burden. We focus on the reduction of ammonium salts in the leather production process. Salt-free deliming of animal hides with compressed carbon dioxide as deliming agent is performed for the first time in a technical scale 20-L drum. As a result, CO2-deliming at 30 bar and 30 °C is two times faster than conventional deliming. In addition, the deliming efficiency is slightly improved. The initial calcium (Ca) content of the hides of 8 g/kg reaches the lowest value of 2 g/kg after a process time of 3 h. However, a process time of 60 min is sufficient to reach an elimination of 50 wt% of the initial lime. The resulting Ca-content of 4 g/kg after 60 min CO2-deliming at 30 bar is comparable with the Ca-content of conventional delimed hide. We clarify that the ampholytic character of the collagen itself enables a buffering of the pH-value at pH-7. The stable pH-value supports the selection of specific bating enzymes that decompose non-collagen proteins. No buffering salts contaminate the wastewater. The high-pressure CO2-deliming process has high potential to reduce wastewater emissions, save costs for chemicals, and process time in industrial beamhouse applications.

The high pressure phase equilibrium of the system tristearin and carbon dioxide was investigated at 70, 80, 90 and 100 °C and pressures up to 250 bar. Solubility measurements were also carried out for the system rapeseed oil and carbon dioxide at 40, 60 and 80 °C and pressures up to 310 bar. In both cases the solubility of CO 2 in the liquids increased with rising pressure and falling temperature. The maximum determined solubility of CO 2 in tristearin was 33 wt% and was measured at 70 °C and 250 bar, for rapeseed oil this was 34 wt% and it was measured at 40 °C and 309 bar. Both tristearin and rapeseed oil showed low solubility, under 1 wt% in the CO 2 in the investigated temperature and pressure range. The viscosity and density of the CO 2 saturated tristearin and rapeseed oil were determined at 70, 80, 90 and 100 °C, and 60 and 80 °C, respectively, for pressures up to 200 bar. The viscosity of rapeseed oil at 80 °C decreased by about 94% from 1 to 200 bar. The density of tristearin at 80 °C increased from 867 kg/m3 at 1 bar to 889,74 kg/m3 at 200 bar. The interfacial tension of CO 2 saturated tristearin and rapeseed oil in a CO 2 atmosphere at temperatures of 80, 90 and 100 °C for the tristearin and 60 and 80 °C for rapeseed oil and pressures up to 200 bar, were also carried out. The interfacial tension of the triglycerides decreased with falling temperature and rising pressure. For rapeseed oil at 60 °C it decreased from 31,3 mN m at 1 bar to 2,93 mN m at 200 bar.

Bioelectrochemical power-to-gas (BEP2G) is considered a potentially convenient way of storing renewable surplus electricity in the form of methane. In methane-producing bioelectrochemical systems (BESs), carbon dioxide and electrical energy are converted into methane, using electrodes that supply either electrons or hydrogen to methanogenic archaea. This review summarizes the performance of methane-producing BESs in relation to cathode potential, electrode materials, operational strategies, and inoculum. Analysis and estimation of energy input and production rates show that BEP2G may become an attractive alternative for thermochemical methanation, and biochemical methanogenesis. To determine if BEP2G can become a future power-to-gas technology, challenges relating to cathodic energy losses, choice of a suitable electron donor, efficient reactor design/operation, and experience with large reactors need to be overcome.

In this work, a simple optical measurement method for two-phase bubbly flow investigations was developed using backlight imaging and particle image velocimetry techniques. Besides information about bubble sizes, surface area and volumes, the mean dispersed phase mass flow rate and the mean dissolution of the dispersed phase in the continuous phase at the end of a static mixer were accurately estimated. The method was validated with air-in-glycerol and water-in-oil systems, and then proven with CO2-glycerol and CO2-PEG6000 dispersions under high pressure. A 30-element SMX4 plus static mixer with a nominal outer diameter of 4.8 mm was used for all mass transfer investigations. Measurements of the dispersed phase mass flow and the dissolution of the dispersed phase at the end of the mixer are reported with combined uncertainties of 8.1 % and 1.0 wt-%. The first experiments with CO2-glycerol and CO2-PEG6000 prove the applicability of this method for systems under high pressure.

Methane production at biocathodes is an innovative approach of storing renewable electrical energy in chemical energy via the biological conversion of carbon dioxide. Methane-producing microorganisms use electricity to catalyze the conversion of carbon dioxide into methane; a form of carbon-neutral natural gas. However, the rates of methane production remain too low for practical application. To improve performance, high area-to-volume ratio with good mass transfer is required. In this study, we used the design of redox flow-batteries with a high area-to-volume ratio of 2.0 cm2/cm3 and an external capillary manifold for flow distribution. Current densities up to 35 A/m2 were applied, resulting in volumetric methane production rates of up to 12.5 L CH4/L/d, three times higher than rates reported so far. The highest energy efficiency of 30% was obtained at 25 A/m2. Even with a low relative abundance of methanogens in the microbial community (20%), dense biofilm growth was observed on the outer surface of the biocathode. Flow-battery cell design shows promising performance for application of methane-producing biocathodes.

Verkapselte Systeme sind vor allem für die Lebensmittelindustrie und Pharmazie von großer Bedeutung. Die Herausforderung bei der Herstellung von Mikrokapseln liegt darin, eine möglichst große Menge an verkapseltem Material zu erreichen und das Freisetzungsverhalten des verkapselten Materials zu kontrollieren. In dieser Studie werden zwei lipophile Emulgatoren und deren Einfluss auf die Verkapselungseffizienz sowie das Freisetzungsverhalten der erhaltenen Mikrokapseln, bestehend aus einem Hartfett und einer Salzlösung, hinsichtlich der Freisetzung in wässriger Umgebung gegenübergestellt.

Impregnation of solid materials has drawbacks such as low diffusion, long contact times, and overdosing of impregnates causing pollution and high consumption of additives that can be overcome with CO2-intensified processes. Wood is already protected against biological deterioration in industrial scale by supercritical impregnation. Industrial plants for dyeing of fabrics are built in Asia at present. A number of processes are far advanced - giving hope for numerous applications in the coming years. In a process analysis addressing the unit operations mixing, sorption, expansion, and pretreatment advantageous design features for processes and products using pressurized CO2 are summarized. Four examples - impregnation of hip implants, of polycarbonate with silver nitrate, of nuts with antioxidants and reactive impregnation (tanning) of leather − illustrate that commercially competitive solutions can be derived and scaled up. Boundary conditions and empirical rules are suggested how CO2 can be used to generate impregnated materials.

We present an experimental investigation on liquid, superheated carbon dioxide jets. Our main goal is to identify the setting up requirements for generating coherent jets because these raise expectations on applications in the cleaning and cutting industry. The study leads us through a number of phenomena, which are described, categorized and explained. The experiments are based on compressed (350 MPa) and cooled carbon dioxide, which expands through a cylindrical nozzle into the atmosphere. The nozzle provokes hydraulic flip by a sharp-edge inlet leading to separation and constriction. Upstream-temperature and pressure are varied and the jet’s structure and phase state are monitored by a high-speed camera. We observe coherent, liquid jets far from equilibrium, which demands the solid or gaseous state. Therefore, these jets are superheated. Carbon dioxide jets, like water jets, below certain nozzle diameters are subject to fluid dynamic instabilities resulting in breakup. Above certain diameters flashing jet breakup appears, which is associated with nucleation.

The electrochemical reduction of carbon dioxide is usually studied in aqueous solutions under ambient conditions. However, the main disadvantages of this method are high hydrogen evolution and low faradaic efficiencies of carbon-based products. Supercritical CO

Im Leitprojekt „Strom als Rohstoff“ werden neue elektrochemische Verfahren entwickelt, technisch demonstriert und die Einkopplung in das deutsche Energiesystem vorbereitet. Das Leitprojekt konzentriert sich auf zwei Syntheserouten: Dezentrale elektrochemische Herstellung von Wasserstoffperoxid (H2O2) Elektrochemische und elektrokatalytischeKonversion von Kohlenstoffdioxid (CO2) zu Ethen, Alkoholen und Treibstoffen

Fruits of oil plants, like nuts, are widely used in food industry and regarded as healthy due to their content of unsaturated fatty acids. Handling, processing and storage of products containing nuts are challenging, because oxidation has to be avoided. The consumer is able to taste rancidity, the consequence of oxidation, in an early stage. Therefore suitable precautions have to be considered. A promising possibility to enhance the oxidation stability was investigated – high pressure impregnation with antioxidants. A two steps procedure and the use of a CO 2 -rosemary extract, containing carnosic acid, gave the best result in terms of homogeneous impregnation. The effect on prolonging the shelf life was successfully observed using three different analytical methods – peroxide value, rancidity test and DPPH method. The oxygen stability and hence the shelf life of nuts was increasing with an increasing concentration of carnosic acid.

This article introduces a new high-pressure process for the gentle drying, micronisation and formulation of high molecular mass gelatine. Spray drying of gelatine solutions is a well-established process for very low molecular weight gelatine, aqueous solutions containing low gelatine concentrations or gelatine solutions containing viscosity reducing additives. In the introduced process, supercritical CO 2 was applied to micronised aqueous gelatine solutions and was then expanded from high pressure into a spraying chamber to remove the water content by extraction and evaporation under moderate conditions. The resulting product was analysed using common powder analysis methods. Aqueous gelatine solutions with a dry mass content of up to 50 wt.% with a molecular mass of 156,000 g mol −1 were pulverised and dried with this process, with only limited degradation by hydrolysis during processing.

Die Hochdruckextraktion mit nah- und uberkritischen Fluiden ist ein seit Jahrzehnten bewahrtes und industriell grostechnisch genutztes Verfahren, etwa bei der Entkoffeinierung von Kaffee mit Kohlendioxid. Neben dieser sehr bekannten Anwendung gibt es jedoch weitere Prozesse, die die speziellen Eigenschaften nah- und uberkritischer Fluide nutzen. Diese Eigenschaften und einige dieser Prozesse werden im Artikel beschrieben. Es handelt sich dabei um das Strahlreinigen, die Hochdruck-Flashreinigung, die Textil- und Bauteilreinigung, einen gasunterstutzten Abpressprozess (Gas Assisted Pressing GAP/Gas Assisted Mechanical Expression GAME Prozess), die Emulsionsspaltung, die Hochdruck-Dekontamination und die Absorption mit ionischen Flussigkeiten. High pressure extraction with near and supercritical fluids has been in use on an industrial scale for decades. It is a well-established process and is, e.g., used for decaffeination of coffee with carbon dioxide. Apart from that well-known process, there are several others which make use of the unique and special properties of near and supercritical fluids. These properties and some of these processes are described in this article, i.e., dry ice-blasting, high pressure flash-cleaning, cleaning of textiles and parts, a gas supported pressing process (gas assisted pressing (GAP)/gas assisted mechanical expression (GAME) process), splitting of emulsions, high pressure decontamination and absorption with ionic liquids.

Micronization of polyethylene glycol from aqueous solutions has been successfully performed with a Particles from Gas Saturated Solutions (PGSS)-drying process, producing spherical PEG particles with average particle size of 10 μm and residual water content below 1 wt%. A detailed experimental analysis of the influence of different process and design parameters (temperature, pressure, flow rates, design of the static mixer used to put into contact aqueous solution and CO2) has been carried out. Smaller particles were obtained when carbon dioxide/solution ratio, pressure and temperature were increased. The residual humidity in the product decreased when carbon dioxide/solution ratio and temperature were increased and when pressure was decreased.

Micronization of polyethylene glycol from aqueous solutions has been successfully performed with particles from gas-saturated solutions (PGSS)–drying process, producing spherical PEG particles with average particle size of 10 μm and residual water content below 1 wt%. Based on experimental results, an analysis of the fundamentals of the process has been developed, discussing mass and energy balances, phase equilibrium conditions, mass transfer rates and atomization mechanisms. Some discrepancies between experimentally observed moisture concentration in powder and calculations based on the mass balance and the phase equilibrium have been observed, which have been attributed to the kinetic evolution of pressure and temperature along the expansion path. The static mixer used to saturate the solution with CO 2 has been analyzed with phase equilibrium and mass transfer calculations, concluding that a significant fraction of water is extracted to the gas phase already in the static mixer, and high CO 2 concentrations are achieved in the liquid due to the high solubility of CO 2 in PEG. All experimental trends of variation of particle size with process parameters can be explained considering a flash-boiling atomization mechanism dependant on the concentration of CO 2 in the solution after the static mixer.

Hochviskose Zuckerlosungen liegen nach einer Pulverisierung grostenteils amorph vor und sind damit stark hygroskopisch. Eine Pulverisierung wird dennoch angestrebt, da sich diese Flussigkeiten durch ihre hohe Viskositat nur schlecht dosieren oder mit anderen Pulvern mischen lassen. Es wird dargestellt, mit welchen Verfahren zum einen qualitativ hochwertige Pulver hergestellt werden konnen und zum anderen die Hygroskopizitat umgangen werden kann. Different processes for pulverizing malt extract are compared in view of quality and hygroscopicity. Three different processes with and without carriers are verified and it is demonstrated that processes without carriers (spray-drying) yield very hygroscopic powders. Processes with carriers, i.e., flour, using fluidised bed agglomeration are proved to be reasonable.

Phase equilibria of carbon dioxide + poly ethylene glycol (PEG) of average mol weight 6000 g/mol + water mixtures has been measured by the static method at conditions of interest for the development of Particles from Gas Saturated Solutions (PGSS)-drying processes (pressure from 10 MPa to 30 MPa, temperature from 353 K to 393 K). A thermodynamic model based on the Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT) equation of state has been developed for correlating experimental data. The model is able to predict the composition of the liquid phase with an average deviation of 8.0%. However, the model does not calculate correctly the concentration of PEG in the gas phase. The model is also capable of predicting VLE data reported in the literature of PEG + CO2 mixtures with PEGs of molecular weights ranging from 1500 g/mol to 18500 g/mol as well as solid–fluid equilibrium of carbon dioxide + PEG mixtures at pressures below 10 MPa.

The leather producing industry transforms untreated hides that may rot under wet conditions and are brittle under dry conditions into durable, imperishable leather by processes which incorporate tanning agents into the hides. Several steps of the tanning process can be intensified by high-pressure technology. Compressed carbon dioxide can be used to shorten tanning times, to reduce water effluents and pollution and to save leather-finishing-fats [ E. Weidner, H. Geihsler, 1995, Verfahren zur Zurichtung von tierischen Hauten, DE 195 07 572 A 1 ]. This article focuses on the reduction of time of the process for the tanning step. Typically, about 30 h are used to tan skins with chrome. It is shown that the same tanning result is obtained in only 5 h if the process is performed under CO 2 -pressure between 30 and 100 bar. Based on a newly developed analytical method for monitoring the tanning success via the ion content in the tanning liquid the process principle and the acceleration of the tanning process is proven and demonstrated.

In spite of high prices for fossil raw materials the production of biomass-based products is rarely economically successful today. Depending on the location feedstock prices are currently so high that products from renewable resources are not marketable when produced in existing process chains. Apart from the higher feedstock costs one reason is that at present no optimized production systems exist in contrast to the chemical and petrochemical industry where these systems have been established over the last decades. If we succeed in developing production systems modelled on those of petroleum refineries where we can provide a flexible coupled production of energy, fuels, materials and chemicals chances are good to enable a lastingly successful production on the basis of renewable resources. Based on examples of fat-based and sugar-based concepts ideas for platform oriented biorefineries are outlined.

Micronization processes using the unique properties of supercritical fluids (SCF) have reached a state, where they are entering industrial application. Results from almost 3 decades of basic research concerning thermodynamics and mass transfer during solidification in presence of SCF have been applied to develop a multitude of process ideas. Selected processes from the anti-solvent- and PGSS-type have been scaled up and are successfully operated. The key to success was not only to develop the technologies and to demonstrate their technical and economical feasibility but also to generate new concepts for applications in the food area. Selected examples will be presented and the achievements and challenges still to be met are summarized.

The concentrated powder form (CPF) process allows the production of liquid-loaded, free-flowing powders. In the process a powderous carrier material is loaded with a liquid by a gas assisted high-pressure spraying process. A powderous emulsion is obtained, if the powderous carrier material is loaded with an emulsion. In this article is shown, how emulsions can be efficiently produced by a new high-pressure homogeniser and how they can be subsequently converted to a powderous emulsion. On the basis of examples it is also presented that powderous emulsions can be released almost unchanged in an adequate fluid.

The interest in natural food colorants shows an increasing tendency due to the strictening rules and consumers’ concerns over synthetic additives. One of natural pigments with high potential are anthocyanins, which are providing colours from yellow to blue in berries, flowers and vegetables. However the use of anthocyanins as food colorants is still limited because of their relatively low stability during processing, formulation and storage. In this work extraction of anthocyanins from grape marc was investigated with different concentrations of acetone (50 wt%, 70 wt% and 100 wt%) at 20 °C and at 60 °C temperatures. Pilot-scale extraction of grape marc was performed upon the results obtained from laboratory scale experiments. High-pressure concentrated powder form (CPF) technique was applied in order to formulate the obtained extracts in powderous form. Carrier materials, such as starch and silica were tested. Colorimetric properties (lightness, chroma and hue angle) of powderous products were measured and compared with synthetic colorants. Colour stability was monitored during storage at different conditions (light/dark and ambient temperature/refrigerator). The results were compared with the non-formulated extracts, which were stored at same conditions. Product formulation with CPF improved the colour stability of anthocyanin extracts, while for the non-formulated extracts degradation of colour rapidly occurred. The results show that formulated anthocyanin extracts have potential use as natural colorants. However, the major difference compared to synthetic colorants is still in the saturation of the colour.

Producción Científica, The effect of viscosity reduction caused by the solubilization of CO2 is studied in order to improve the biomass processing in ionic liquids. To do so, densities and viscosities of the pure ionic liquid 1-allyl-3-methylimidazolium chloride and its mixtures with CO2 up molar fractions of 0.25 and temperatures between 333 and 372 K have been experimentally determined. Viscosities were correlated as a function of temperature and CO2 molar fractions with an average relative error of 2.5%. The viscosities of other mixtures CO2 + ionic liquids were also correlated for other ionic liquids with an average relative error between 4.4 and 13%. In general these ionic liquids present a linear decrease of viscosity with CO2 molar fractions up to around 0.5 that is more pronounced at lower temperatures and depends of each ionic liquid, and can reach between 60 and 100% viscosity reduction with respect the viscosity of the pure ionic liquid, making the CO2 a promising co-solvent for viscosity reduction in process with ionic liquids., 2018-01-29, Junta de Castilla y León VA295U14, Marie Curie Program. Project DoHip, Ministerio de Economía. Programa Ramon y Cajal, RyC RYC-2013-13976, Cluster of Excellence RESOLV (EXC 1069) funded by the Deutsche Forschungsgemeinschaft f

Green tea is a beverage widely consumed throughout the world and is produced from non-fermented leaves of Camellia Sinensis. Traditionally, green tea leaves are extracted with water. To form solid products, these aqueous products have to be dried. The main focus of the investigation is how to avoid antioxidant degradation during solvent removal. The work was separated in two major sections, firstly investigation of the extraction process secondly, optimizing of the drying process. In the first experiments extractions with different solvents (H2O, EtOH and MeOH), at different temperatures (20, 40, 60 and 80 ?C) and extraction times (15, 30, 60, 90 and 120 min) were preformed to obtain optimum conditions for further processing. For further work extracts obtained with water extraction at 80?C for 15 min were used. In the PGSS (Particles from Gas Saturated Solutions) drying process, extracts with up to 98 wt % water are mixed with preheated carbon dioxide in a static mixer in order to obtain a homogenous mixture. The mixture is led via a single path nozzle into a spray tower. Driven by the expansion of the gas, fine droplets are formed and the heated gas evaporates the solvent, which is exhausted together with CO^ by a blower. Fine powder is formed and collected in the spray tower. The amount of solvent which is to be removed and the residual humidity obtained in the product depend strongly on flow rate and temperature of the gas. From obtained results it can be seen, that high pre-expansion temperatures Tp (145 ?C) cause degradation of polyphenols (1.05 wt %). Maintaining Tp at approximately 130 ?C and lower gave satisfying results; total amount of polyphenols in the obtained powders was between 4.97 and 8.77 wt %. Temperature in spray tower ranging from 33 to 65 ?C has no significant effect on the amount of total polyphenols, but higher temperature results in lower water residue in the sample.

Micro composites are commonly characterized in bulk. Here we study the temperature triggered release of a bioactive compound from single isolated microcapsules. We monitor the release process in real-time using a novel thermal microscopy method combining laser-induced heating and fluorescence imaging.

New catalysts and environmentally benign processes allow generation of biodiesel with improved properties at competitive costs. Different amine-based liquid catalysts are screened with respect to conversion rates. Experimental investigations of the complex phase behavior between methanol, different oils, and catalysts as reactants and methyl ester and glycerol as products are the key to define suitable process conditions for reaction and product recovery. An optimized procedure results in a conversion higher than 98% in a one-stage operation. By using sodium- or potassium-free catalysts, soap formation is avoided and glycerol and methyl ester separate rapidly. Effluents of washing water are minimized or even avoided.