Liquid flow texture analysis in trickle bed reactors using high-resolution gamma ray tomography

Trickle bed reactor performance and safety may suffer from radial and axial liquid maldistribution and thus from non-uniform utilization of the catalyst packing. Therefore, experimental analysis and fluid dynamic simulation of liquid–gas flow in trickle bed reactors is an important topic in chemical engineering. In the present study for the first time a truly high-resolution gamma ray tomography technique was applied to the quantitative analysis of the liquid flow texture in a laboratory cold flow trickle bed reactor of 90 mm diameter. The objective of this study was to present the comparative analysis of the liquid flow dynamics for two different initial liquid distributions and two different types of reactor configurations. Thus, the hydrodynamic behavior of a glass bead packing was compared to a porous Al₂O₃ catalyst particle packing using inlet flow from a commercial spray nozzle (uniform initial liquid distribution) and inlet flow from a central point source (strongly non-uniform initial liquid distribution), respectively. The column was operated in downflow mode at a gas flow rate of 180 L h⁻¹ and at liquid flow rates of 15 and 25 L h⁻¹.     

Analysis and specification of the crash behaviour of plastics/metal-hybrid composites by experimental and numerical methods

Plastics materials are nowadays used in many structural applications for the substitution of metals with respect to weight reduction. In order to utilize the high freedom of design and the light-weight potential of plastics materials in crash-relevant structural parts, so-called hybrid composites which combine the high rigidity and strength of steel with the advantages of plastics materials are investigated in the outlined research. Thereby, the joining of both materials as well as the design by means of numerical methods such as the finite element analysis (FEA) are challenges which have to be met. A new approach in joining is based on the modified arc welding process where metal pin structures are formed in one working step and subsequently welded onto the surface. The pins are formed with ball-shaped, cylindrical or spiky ends and produced directly from the welding wire without requiring additional pre-fabricated components such as studs or similar. This allows the small-scale surface structuring of metal components that can be adapted optimally for a form fit on the respective plastics structure. Subsequently, injection molding is used for the application of the plastics material onto the pin-structured metal part in order to generate a positive fit between metal and plastics in an intrinsic joining process. An additional joining process, which is carried out after injection molding, is not required. Within the framework of the research presented, comprehensive mechanical tests are presented to illustrate the suitability of pin-structured metal-hybrid composites in crash applications. In comparison to structures which are in particular exposed to static loads and therefore designed to exhibit maximum component strength, crash applications are designed to fail in a continuous process to achieve maximum energy consumption. The outlined research illustrates the enhanced failure behavior of pin-structured plastics/metal-hybrid composites and the increased energy consumption under impact loading. Moreover, a comparison between pin structuring and laser structuring with regard to the obtainable mechanical properties under impact loading is given. Concluding, the current potential and weak points in the simulation of plastics/metal-hybrid structures using FEA is presented and discussed.     

Selective Oxidation of Propene with Air to Propylene Oxide,a Case Study of Autoxidation Versus Catalytic Oxidation with AMM-Catalysts

The formation of propylene oxide from propene by direct oxidation with air has been studied with a series of new microporous amorphous catalysts containing isolated active sites. Although the materials showed good activities as heterogeneous oxidation catalysts, the formation of acroleine dominated in the gas phase. Oxidation selectivities of the various catalysts are reported. Significant PO-formation was only observed under reaction conditions involving pressures larger 5 bar. Promoting effects of solvents or additives like acetaldehyde could be excluded. Best results were observed in continuous gas phase flow experiments. All catalysts studied proved detrimental to the PO-yield and control experiments pointed to catalyst free autoxidation conditions. A factorial design followed by an optimization of the reaction conditions provided PO-selectivities of 60 % at propene conversion of 11.4 % (T = 290 °C; pressure = 25 bar; propene content = 75 %; total feed = 39.5 ml/min) at continuous reaction conditions. By passivating the inner reactor surfaces with gold, a PO-selectivity of 62.8 % at a propene conversion of 15.1 % could be obtained, indicating, that autoxidation of propene may become a serious contender in the search for improved production processes. This work is a case study of attempted catalyzed selective oxidation with air illustrating potential pitfalls and misleading interpretations.     

Suppression of Water as a Nucleophile in Candida antarctica Lipase B Catalysis

A water tunnel in Candida antarctica lipase B that provides the active site with substrate water is hypothesized. A small, focused library created in order to prevent water from entering the active site through the tunnel was screened for increased transacylation over hydrolysis activity. A single mutant, S47L, in which the inner part of the tunnel was blocked, catalysed the transacylation of vinyl butyrate to 20 mM butanol 14 times faster than hydrolysis. The single mutant Q46A, which has a more open outer end of the tunnel, showed an increased hydrolysis rate and a decreased hydrolysis to transacylation ratio compared to the wild‐type lipase. Mutants with a blocked tunnel could be very useful in applications in which hydrolysis is unwanted, such as the acylation of highly hydrophilic compounds in the presence of water.     

A New Research Infrastructure for Investigating Flow Hydraulics and Process Equipment at Critical Fluid Properties

An optimized equipment design for natural gas processing and liquefaction plants becomes increasingly difficult with changing process conditions: Particularly low values of surface tension create rising challenges on the design of phase separators and column internals. The TERESA test rig at HZDR was designed to allow the investigation of multiphase thermohydraulics and phase separator performance under critical fluid properties in industrial dimensions. A versatile pipe test section is available in DN200 and equipment internals may be tested in a sectional DN300/DN500 test separator. The applied test fluid shows a high vapor-liquid density difference between 1470 and 940 kg m⁻³, viscosity as low as 0.12 mm²s⁻¹, and surface tension down to 1.3 mN m⁻¹. Volumetric liquid and vapor flow rates may be varied up to 9 and 530 m³h⁻¹ in the test rig, respectively.     

Morphology of Flashing Feeds at Critical Fluid Properties in Larger Pipes

Tailored conditioning and control of flashing feeds in industrial applications requires knowledge of the evolving flow morphology and phase fractions along the feed pipe. Design methods obtained from reference systems (e.g. water-air) are hardly applicable for commercial scales and critical fluid properties (e.g. high vapor densities, low surface tension). In this study, the flow morphology of flashing feeds in a novel refrigerant test rig at critical fluid properties was analyzed using wire-mesh sensors at two locations along the feed pipe and experimental data from the water-air system.     

Energy Metabolites as Biomarkers in Ischemic and Dilated Cardiomyopathy

With more than 25 million people affected, heart failure (HF) is a global threat. As energy production pathways are known to play a pivotal role in HF, we sought here to identify key metabolic changes in ischemic- and non-ischemic HF by using a multi-OMICS approach. Serum metabolites and mRNAseq and epigenetic DNA methylation profiles were analyzed from blood and left ventricular heart biopsy specimens of the same individuals. In total we collected serum from n = 82 patients with Dilated Cardiomyopathy (DCM) and n = 51 controls in the screening stage. We identified several metabolites involved in glycolysis and citric acid cycle to be elevated up to 5.7-fold in DCM (p = 1.7 × 10⁻⁶). Interestingly, cardiac mRNA and epigenetic changes of genes encoding rate-limiting enzymes of these pathways could also be found and validated in our second stage of metabolite assessment in n = 52 DCM, n = 39 ischemic HF and n = 57 controls. In conclusion, we identified a new set of metabolomic biomarkers for HF. We were able to identify underlying biological cascades that potentially represent suitable intervention targets.     

Hydraulic reactivity and cement formation of baghdadite

In this study, the hydraulic reactivity and cement formation of baghdadite (Ca₃ZrSi₂O₉) was investigated. The material was synthesized by sintering a mixture of CaCO₃, SiO₂, and ZrO₂ and then mechanically activated using a planetary mill. This leads to a decrease in particle and crystallite size and a partial amorphization of baghdadite as shown by X-ray powder diffraction (XRD) and laser diffraction measurements. Baghdadite cements were formed by the addition of water at a powder to liquid ratio of 2.0 g/ml. Maximum compressive strengths were found to be ~2 MPa after 3-day setting for a 24-h ground material. Inductively coupled plasma mass spectrometry (ICP-MS) measurements showed an incongruent dissolution profile of set cements with a preferred dissolution of calcium and only marginal release of zirconium ions. Cement formation occurs under alkaline conditions, whereas the unground raw powder leads to a pH of 11.9 during setting, while prolonged grinding increased pH values to approximately 12.3.     

Facile Fabrication of Ultrafine Copper Nanoparticles in Organic Solvent

A facile chemical reduction method has been developed to fabricate ultrafine copper nanoparticles whose sizes can be controlled down to ca. 1 nm by using poly(N-vinylpyrrolidone) (PVP) as the stabilizer and sodium borohyrdride as the reducing agent in an alkaline ethylene glycol (EG) solvent. Transmission electron microscopy (TEM) results and UV–vis absorption spectra demonstrated that the as-prepared particles were well monodispersed, mostly composed of pure metallic Cu nanocrystals and extremely stable over extended period of simply sealed storage.