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The chemical effects of carbon dioxide on the oxidation of biodiesel surrogate, methyl butanoate (MB) were investigated experimentally in the SJTU laminar flow reactor at equivalence ratios of 1.5, 1 and 0.5, at atmospheric pressure. Generally, there are three kinds of effects from carbon dioxide (CO 2 ): thermal, dilution and chemical effects. In this study, argon was replaced by CO 2 as the dilute gas as a way to isolate the chemical effects by keeping the factors of temperature profile and dilution ratio constant. Therefore, the differences in concentrations of species at the exit from the flow reactor could be attributed to the chemical effects of CO 2 . Good agreement was found between the experimental and the computational results. The chemical effects were classified into two types. First, there was the radical factor, by which the reaction CO 2 + H = OH + CO played a significant role in the oxidation of MB. In CO 2 atmosphere, radical factors led to the reduction in reactivity and suppressed the decomposition of MB. The second effect was the collision factor, which derived from the high frequency of third-body collisions of CO 2 . This collision factor contributed to the formation of carbon monoxide and ethane. Moreover, in the combustion of biodiesel engine with EGR, pure chemical effects of CO 2 addition decreased the concentration of acetylene as well as suppressed formation of larger PAHs. [ABSTRACT FROM AUTHOR]

Nickel diimine late transition metal (LTM) and CpTiCl metallocene catalysts were supported on the TIBA-modified MgCl·nEtOH adduct, separately and concurrently, at different ratios, to yield hybrid catalysts, where the catalytic precursors were activated in the ethylene polymerization with TEA as the cocatalyst. Polymerization activities revealed that supported LTM catalysts show very high levels of activity, in an adverse trend with polymerization temperature ranging from 30 to 70 °C, in opposition to the activity of metallocene component. Consequently, the proportion of corresponding polymer fractions were tuned by changing reaction temperature as well as catalyst composition. Study of thermal properties confirmed that LTM component is responsible for production of less crystallizable branched chains, while metallocene fraction makes highly crystallizable linear chains. All samples showed noticeable thermorheological complexity due to coexistence of linear and branched microstructures. Interestingly, it was found that increase in metallocene fraction of the hybrid catalyst stalls the terminal relaxation of the produced polymers and increases the entanglement density by decreasing the extent of branching. Study of dynamic mechanical properties revealed that the intensity of β transition could be correlated with the branching level and catalyst composition accordingly. [ABSTRACT FROM AUTHOR]

The present study is the first part of research into modeling flocculation processes in a tubular reactor with different width baffles. Computational fluid dynamics numerical simulation methods were used to identify intensive mixing zones and turbulent flow zones. The influence of geometry and baffle width on velocity components of the liquid flow and turbulence parameters was analyzed. The obtained results were represented as vector and contour distribution maps of the determined quantities. Flow visualization was performed to illustrate the structure and size of vortices formed behind baffles. The correctness of the numerical model was experimentally validated based on anemometric measurements using laser Doppler anemometry (LDA) method. [ABSTRACT FROM PUBLISHER]

Froth flotation is one of the most frequently used processes for separation of valuable from gangue minerals. Modeling and simulation of the flotation process is a difficult task because of nonlinear and dynamic nature of the process. In this contribution, the relationship between the process variables (i.e., gas flow rate, slurry solids%, frother/collector dosages, and pH) and the metallurgical parameters (i.e., copper/mass/water recoveries and concentrate grade) in the batch flotation of a copper sulfide ore is discussed and modeled. Statistical (i.e., nonlinear regression) and intelligent (i.e., neural network and adaptive neuro-fuzzy) techniques are applied to model the process behavior at different conditions. The results indicate that intelligent approaches are more efficient tools for modeling of the complicated process like flotation, which are of central importance for development of the model-based control systems. [ABSTRACT FROM PUBLISHER]

This paper deals with an analytical method to assess the maximum temperature value along a tubular chemical reactor at steady state. This reactor is provided with a jacket in which a counter current cooling liquid flows. The thermal behavior of the chemical reactor is calculated with the McCormack numerical method. Comparison of the exothermic reaction generated flux with the removed flux from the separating wall leads to a two-part reactor subdivision. In the first part, the reactor behaves as an adiabatic reactor followed by a zone in which the flux removed from the wall is not negligible and remains constant. In the second part, the reactor behaves like a simple heat exchanger without internal energy source. Analytical integration of mass and energy balance equations in each subsystem was used to determine the analytical expression of maximum temperature. [ABSTRACT FROM PUBLISHER]

Abstract: Problem of the coal mine shafts ventilation air methane (VAM) utilization is briefly presented. A research and demonstration plant experiments were carried out as the first step to a future industrial application. The plant contained a thermal flow reversal reactor (TFRR) as the main unit where lean methane–air mixture is combusted. The study consisted of the plant experiments and mathematical model simulations as well. The paper presents the mathematical model description and its experimental validation based on comparison of the model results with measured plant data. The aim of the paper is to assess whether dynamic, one dimensional (in space) model may be useful for a fairly large scale reactor simulations. The model was developed and tested in the 2 versions: without and with heat accumulation in the reactor wall. [Copyright &y& Elsevier]

Abstract: Ultraviolet irradiation constitutes an alternative to thermal treatment that is being studied and developed to obtain a better final product sensory quality, but without neglecting microbial safety. In order to quantify and predict chemical changes produced by ultraviolet radiation in a food system and to infer essential information for reactors design, a concrete modeling is required in each case, since the absorbed amount of radiation has a definitive effect on the reaction rate of the process in each point of the reaction medium depending on its location. Although the basic equations were set decades ago, there are still several concrete cases whose three-dimensional modeling cannot be found in literature. In this piece of work, the linear spherical emission model has been applied to a system composed by a plane photoreactor and a single lamp, obtaining different profiles that show how radiation is absorbed as a function of the position inside the reactor and the absorbance of the reaction medium. [Copyright &y& Elsevier]

Abstract: The NH3-SCR activity of the small-pore zeolites, Cu-SSZ-13, Cu-SSZ-16, and Cu-SAPO-34, is investigated using a high-throughput reactor system. These copper exchanged small-pore zeolites have high SCR activity between 150 and 500°C and are shown to be much more hydrothermally stable than the medium-pore zeolite, Cu-ZSM-5. The degree of copper exchange, the dimensionality of the framework, and heteroatom framework substitution all impact the SCR activity and hydrothermal stability of the materials. Of the small-pore zeolites tested, Cu-SSZ-13 and Cu-SAPO-34 display superior SCR performance, both before and after high-temperature hydrothermal treatment. [Copyright &y& Elsevier]

Abstract: The knowledge of thermal properties of technical components or internals in chemical reactors is often a key characteristic for planning and designing chemical engineering processes. As an alternative to packed beds or packings, sponges turned out to be used in new application fields in chemical and process engineering. Therefore an experimental study was performed to investigate the two-phase thermal conductivity of solid ceramic sponges made of alumina, mullite and oxidic-bonded silicon carbide (OBSiC) at moderate temperatures. A two-dimensional model is used for analysing the measured temperature profiles and for calculating the thermal conductivity. It can be observed, that the thermal conductivity increases with decreasing porosity and is nearly constant when the pore size (ppi number) is varied. The thermal conductivity data are modelled by an approach similar to the well known Krischer model. Compared to a packed bed of spherical particles, the values of the thermal conductivity of sponges turn out to be about five times higher. [Copyright &y& Elsevier]

Abstract: The oxidation of during oxy-fuel combustion of methane, i.e., at high , has been studied in a flow reactor. The experiments covered stoichiometries ranging from fuel rich to very fuel lean and temperatures from 973 to 1773K. The results have been interpreted in terms of an updated detailed chemical kinetic model. A high level enhanced formation of NO under reducing conditions while it inhibited NO under stoichiometric and lean conditions. The detailed chemical kinetic model captured fairly well all the experimental trends. According to the present study, the enhanced CO concentrations and alteration in the amount and partitioning of O/H radicals, rather than direct reactions between N-radicals and , are responsible for the effect of a high concentration on ammonia conversion. When is present as a bulk gas, formation of NO is facilitated by the increased OH/H ratio. Besides, the high CO levels enhance HNCO formation through . However, reactions to form HNO and to form NH are inhibited due to the reduced concentration of O and H radicals. Instead reactions of with species from the hydrocarbon/methylamine pool preserve reactive nitrogen as reduced species. These reactions reduce the availability to form NO by other pathways like via HNO or NH and increase the probability of forming instead of NO. [Copyright &y& Elsevier]

The present study consists of an experimental and theoretical study of the performance of Rh-coated honeycomb monoliths for methane partial oxidation. The thermal behavior of Rh-coated honeycomb monoliths was studied under representative operating conditions, at steady state and during light-off. Model analysis (based on a dynamic heterogeneous reactor model that incorporates a kinetic scheme of the process independently developed, and well-assessed correlations for heat and mass transfer) provided a key for interpreting the observed effects. The comprehension of how transport phenomena and surface kinetics affect the reactor behavior leads to the conclusion that the feasibility of small-scale production of syngas via CH4catalytic partial oxidation relies on thermal management of the short contact time reactor and not the obtainment of high syngas yields (which is not a challenging task). Severe operating conditions (and high surface temperatures) can deplete the catalyst activity and cause unstable reactor operation. Guidelines for optimal reactor design are proposed. [ABSTRACT FROM AUTHOR]

This work analyses the possible axial-and transversal thermal spatio-temporal patterns that may emerge in a two-dimensional thin annular catalytic bed model using a detailed micro-kinetic model for CO oxidation. This work is motivated by experimental IR-imaging observations made with a cylindrical catalytic surface impregnated with Pd. Stationary, oscillating-and travelling axial-pulses are shown to emerge, in agreement with the experimentally observed axial patterns, and simulations, backed by linear analysis, show that transversal patterns may emerge as well. The implications for fixed-bed reactor modelling are discussed. [Copyright &y& Elsevier]

This contribution contains an overview on process analysis and process development in the field of fixed-bed processes for gas–gas and gas–solid reactions. The examples are mainly taken from the work performed during the last 20 years at the Institut für Chemische Verfahrenstechnik in Stuttgart. Its main intention is to show how process analysis and process intensification can benefit from the simplified representation of typical thermal reaction front patterns which evolve in such reactors. Favourable patterns should be used as natural building blocks for the robust design of integrated processes. The processes considered include heat integrated processes for exothermic and endothermic gas–gas reactions as well as exothermic gas–solid reactions, with a special view on automotive Diesel exhaust purification. [Copyright &y& Elsevier]

Abstract: Low texture and isotropic pyrocarbon were prepared by hot wall reactor chemical vapor deposition between 950°C and 1050°C using natural gas as the carbon source. The morphology and texture of the pyrocarbon was characterized by transmission electron microscopy, and the coefficients of thermal expansion (CTE) were measured in the directions of parallel and perpendicular to the specimen thickness direction using a Netszch Dilatometer 402C. The results showed that as the deposition temperature increased from 950°C to 1050°C, the fracture surface of the pyrocarbon became rougher and the length of the graphene layers was gradually increased and the pyrocarbon changed from low texture to isotropic. The CTEs in both directions were almost the same and negative below 300°C. [Copyright &y& Elsevier]