Hydrierung von Diethylsuccinat zu γ‐Butyrolacton, 1,4‐Butandiol und Tetrahydrofuran

The shortage of fossil resources necessitates the search for alternative sources for the production of important bulk chemicals. Diethyl succinate derived from biobased succinic acid can be used as a renewable alternative to fossil resources for the production of γ‐butyrolactone, 1,4‐butanediol and tetrahydrofuran. Commercially available ZnO‐free copper catalysts in a fixed‐bed reactor show promising selectivity to C4 products, but 1,4‐butanediol dehydration to tetrahydrofuran occurs over acidic sites, like alumina and zirconia.     

Hydrierung von p‐Nitrophenol zu p‐Aminophenol als Testreaktion für die katalytische Aktivität von Pt‐Trägerkatalysatoren

The hydrogenation of p‐nitrophenol (PNP) to p‐aminophenol (PAP) using NaBH₄ as a reducing agent was studied as a test reaction for determining the catalytic activity of supported Pt catalysts. The initial reaction rate, which is accessible within less than 10 minutes via online UV‐vis spectroscopy at room temperature, ambient pressure and in water as a solvent, was used as measure for the catalytic activity. For three Pt catalysts supported on porous SiO₂, porous glass and Al₂O₃, respectively, significant differences in the catalytic activity were observed. However, especially in case of very active catalysts, limitations of the reaction by internal or external mass transfer have to be considered.     

Caged CO2 for the Direct Observation of CO2‐Consuming Reactions

CO₂‐consuming reactions, in particular carboxylations, play important roles in technical processes and in nature. Their kinetic behavior and the reaction mechanisms of carboxylating enzymes are difficult to study because CO₂ is inconvenient to handle as a gas, exists in equilibrium with bicarbonate in aqueous solution, and typically yields products that show no significant spectroscopic differences from the reactants in the UV/Vis range. Here we demonstrate the utility of 3‐nitrophenylacetic acid and related compounds (caged CO₂) in conjunction with infrared spectroscopy as widely applicable tools for the investigation of such reactions, permitting convenient measurement of the kinetics of CO₂ consumption. The use of isotopically labeled caged CO₂ provides a tool for the assignment of infrared absorption bands, thus aiding insight into reaction intermediates and mechanisms.     

Inline‐Bestimmung der CO2‐Beladung von wässrigem Diglykolamin in Abhängigkeit von Viskosität und Temperatur

The solvents CO₂ loading is an important factor when evaluating the efficiency of an absorption/desorption process. There is almost no possibility to measure the CO₂ loading inline. Therefore experiments were made to determine a correlation between the CO₂ loading and the solvents viscosity as well as the solvents temperature. The correlation was verified using control tests and values from the literature. An overall maximum relative error under 10 % could be observed. Simultaneously investigations were made to understand if the solvents electrical conductivity and pH value are suitable for a similar correlation.     

Degradations‐ und Energieverhalten reaktiver Amin‐Lösungen bei der CO2‐Absorption/Desorption

Reactive absorption using aqueous amine solutions is the technically most feasible retrofit option for the separation of CO₂ from flue gases. Frequently discussed issues are the realization of a cost‐effective increase in efficiency in the sophisticated overall absorption process and the minimization of the energy demand for solvent regeneration under operating conditions. However, the influence of degradation phenomena on capacity and energy efficiency during the absorption‐regeneration cycles using blended monoethanolamine solutions has been less considered so far. The decrease in capacity depends in particular on time, temperature, O₂‐ and SO₂ concentration in the flue gas and has to be considered in plant design. Addition of degradation inhibitors decreases the energy requirements.     

Adsorptionshysterese von Phosphorsäure in Polybenzimidazol‐Hochtemperatur‐Polymerelektrolytmembran‐Brennstoffzellen

During thermal cycling investigations on polybenzimidazole high temperature polymer electrolyte membrane fuel cells a stationary hysteresis behavior of the cell current was observed. With the Tafel equation a correlation to the surface oxygen concentration on the platinum is given. Because no such hysteresis of oxygen adsorption on platinum is known a new theory is proposed. This theory is based on the thermal dependence of the surface coverage of phosphoric acid on platinum. The resulting adsorption hysteresis is confirmed as being the reason for the observed cell current hysteresis by the results of a Monte Carlo simulation. This is validated through a qualitative comparison with measured data from aged test cells.     

Standortplanung für die Herstellung CO2‐basierter Chemikalien am Beispiel der Olefinproduktion

The use of CO₂ as raw material is increasingly gaining in importance as an option for climate protection and as an alternative raw material feedstock. Both direct electrochemical syntheses and thermochemical processes are associated with a high demand for electrical energy. A contribution to climate protection is only possible in the case of low‐carbon power generation, as can be realized, e.g., by wind power or solar energy. This article presents a methodology for identifying suitable sites for the CO₂‐based production of olefins in Germany.     

Absorption von CO2 mittels wässriger Natronlauge – Experimente und Simulationen mit dem Ansatz der Hydrodynamischen Analogien

An approach for the simulation of separation processes in packed columns is based on hydrodynamic analogy between complex flow pattern in real equipment units and geometrically simplified model flow and is known as the Hydrodynamic Analogy (HA) approach. In this work, the HA approach was applied to reactive absorption of CO₂ in aqueous sodium hydroxide solution under turbulent gas flow conditions. An extensive experimental study was carried out to measure the CO₂ concentration profiles along the column height. These data provided a basis for a successful validation of the HA approach.     

Untersuchung der CO2‐Absorptionskinetik in wässrigen Lösungen von N,N‐Diethylethanolanmin und N‐Ethylethanolamin

N‐Ethylethanolamine (EEA) and N,N‐diethylethanolamine (DEEA) represent promising alkanolamines for CO₂ removal from gaseous streams, as they can be prepared from renewable resources. In this work, the reaction rate constant for the reaction between CO₂ and EEA and the liquid‐side mass transfer coefficient were determined from the absorption rate measurements in a blend comprising DEEA, EEA and H₂O. A stirred‐cell reactor was applied for the absorption studies, whereas a zwitterion mechanism for EEA and a base‐catalyzed hydration mechanism for DEEA were used to describe the reaction kinetics.     

Schnelle lokale Raman‐Messung zur Untersuchung von Konzentrationsprofilen bei Mischvorgängen in Mikrokanälen

For the evaluation of mixing processes in microreactors, it is necessary to be able to investigate them in detail. For this purpose, a novel optical measuring system is presented, which allows the visualization of mixing and diffusion‐limited processes as well as concentration differences in fluid films. It consists of focusing optics with a microscope objective. In combination with a Raman spectrometer, various processes such as diffusion in the microreactor can be measured and investigated non‐invasively.     

Synthesis,characterization of the luminescent lanthanide complexes with copolymer of (Z)‐4‐oxo‐4‐phenyloxyl‐2‐butenoic acid and styrene

The copolymers of (Z)‐4‐oxo‐4‐phenoxyl‐2‐butenoic acid with styrene (PSt/OPBA) and their macromolecular luminous lanthanide complexes (Ln‐PSt/OPBA) have been synthesized and characterized by means of GPC, elemental analysis, FTIR, X‐ray powder diffraction, spectral analysis, and thermal analysis. The IR studies showed that the carboxylic groups on the side chain of the polymer were coordinated to lanthanide ions by bidentate manner. However, the ethereal oxygen, instead of carbonyl, also bonded to the central lanthanide ions, which was an intriguing phenomenon for ester‐coordinated complexes. X‐ray diffraction experiments revealed that these PSt/OPBA copolymers were amorphous, but Ln‐PSt/OPBA were crystalline, in which the complex Eu‐L^c belonged to a high symmetric structure of orthorhombic quadratic system, with a = 10.59 ± 0.02 Å, c = 8.02 ± 0.01 Å; c/a = 0.763. In addition, the value δ (the number of free carboxylic groups) in Ln‐PSt/OPBA complexes increased with the decreasing mole ratio of styrene in the copolymers, while it decreased with increasing pH values of the solution. Eu³⁺ and Tb³⁺ complexes exhibited characteristic fluorescence with comparatively high brightness and good monochromaticity, and the fluorescence intensity was enhanced with increasing the content of lanthanide up to around 18 wt % without typical fluorescence concentration quenching behavior in the solid state. So using polymers as a matrix, Ln‐PSt/OPBA are likely to provide new materials that possess specific properties and desired features. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Degradation of 1‐amino‐4‐bromoanthraquinone‐2‐sulfonic acid using combined airlift bioreactor and TiO2‐photocatalytic ozonation

BACKGROUND: Traditional treatment systems failed to achieve efficient degradation of anthraquinone dye intermediates at high loading. Thus, an airlift internal loop reactor (AILR) in combination with the TiO₂‐photocatalytic ozonation (TiO₂/UV/O₃) process was investigated for the degradaton of 1‐amino‐ 4‐bromoanthraquinone‐2‐ sulfonic acid (ABAS). RESULTS: The AILR using Sphingomonas xenophaga as inoculum and granular activated carbon (GAC) as biocarrier, could run steadily for 4 months at 1000 mg L^?1 of the influent ABAS. The efficiencies of ABAS decolorization and chemical oxygen demand (COD) removal in AILR reached about 90% and 50% in 12 h, respectively. However, when the influent ABAS concentration was further increased, a yellow intermediate with maximum absorbance at 447 nm appeared in AILR, resulting in the decrease of the decolorization and COD removal efficiencies. Advanced treatment of AILR effluent indicated that TiO₂/UV/O₃ process more significantly improved the mineralization rate of ABAS bio‐decolorization products with over 90% TOC removal efficiency, compared with O₃, TiO₂/UV and UV/O₃ processes. Furthermore, the release efficiencies of Br^? and SO₄^2? could reach 84.5% and 80.2% during TiO₂/UV/O₃ treatment, respectively, when 91.5% TOC removal was achieved in 2 h. CONCLUSION: The combination of AILR and TiO₂/UV/O₃ was an economic and efficient system for the treatment of ABAS wastewater. © 2012 Society of Chemical Industry     

Design of active NiCo2O4‐δ spinel catalyst for abatement of CO‐CH4 emissions from CNG fueled vehicles

Increasing number of CNG vehicles on road emits considerable amount of CO, a poisonous gas and CH₄, a greenhouse‐gas. Highly active and oxygen‐deficient NiCo₂O_4‐δ spinel and its individual metal‐oxides were synthesized by calcination of precipitated/co‐precipitated basic‐carbonates followed by calcination under different strategies of stagnant air(s), flowing air(f) and reactive calcination(RC) for total oxidation of CO‐CH₄ mixture. The catalysts were characterized by XRD, XPS, BET surface‐area, SEM‐EDX and TEM. The performance order of the catalysts for the oxidation of CO‐CH₄ mixture was as follows: NiCo_RC>NiCo_f>NiCo_s>Co_RC>Co_f>Co_s>Ni_RC> Ni_f>Ni_s. The pairing of Ni and Co in spinel‐structure together with RC produced catalyst was oxygen‐deficient highly active for total oxidation of the mixture at the lowest temperature of 350°C. The NiCo_RC was found stable under reaction‐conditions for 50h at 350°C and after four successive heating (350°C)‐cooling (35°C) cycles besides accelerated‐aging tests up to 600°C. © 2018 American Institute of Chemical Engineers AIChE J, 64: 2632–2646, 2018     

SO42−/ZrO2 supported on γ‐Al2O3 as a catalyst for CO2 desorption from CO2‐loaded monoethanolamine solutions

In this work, the composite catalysts, SO₄²/ZrO₂/γ‐Al₂O₃ (SZA), with different ZrO₂ and γ‐Al₂O₃ mass ratios were prepared and used for the first time for the carbon dioxide (CO₂)‐loaded monoethanolamine (MEA) solvent regeneration process to reduce the heat duty. The regeneration characteristics with five catalysts (three SZA catalysts and two parent catalysts) of a 5 M MEA solution with an initial CO₂ loading of 0.5 mol CO₂/mol amine at 98°C were investigated in terms of CO₂ desorption performance and compared with those of a blank test. All the catalysts were characterized using X‐ray diffraction, Fourier transform infrared spectroscopy, N₂ adsorption–desorption experiment, ammonia temperature programmed desorption, and pyridine‐adsorption infrared spectroscopy. The results indicate that the SZA catalysts exhibited superior catalytic activity to the parent catalysts. A possible catalytic mechanism for the CO₂ desorption process over SZA catalyst was proposed. The results reveal that SZA1/1, which possesses the highest joint value of Brφnsted acid sites (BASs) and mesopore surface area (MSA), presented the highest catalytic performance, decreasing the heat duty by 36.9% as compared to the catalyst‐free run. The SZA1/1 catalyst shows the best catalytic performance as compared with the reported catalyst for this purpose. Moreover, the SZA catalyst has advantages of low cost, good cyclic stability, easy regeneration and has no effect on the CO₂ absorption performance of MEA. © 2018 American Institute of Chemical Engineers AIChE J, 64: 3988–4001, 2018     

Modularisierung von Gaswäschern für die CO2‐Entfernung aus Biogas

Modularization has been identified as one of the research fields of the ?50 % idea”?. A development methodology for modules must consider both the economies of scale for investment costs and costs of operation and maintenance. In this paper, the impact of an absorber module, which is offered as discretized diameter scaling, on the total process is investigated at the example of the CO₂ separation from biogas. The simulation shows the effect of this approach to the stripper diameter and the energy demand of the process. The calculations form the basis for applying cost models.