Deactivation Conditions Research Articles

Dynamics of Dilute Nanoalloy Catalysts.

Capturing the dynamic character of metal nanoparticles under the reaction conditions is one of the major challenges within heterogeneous catalysis. The role of nanoparticle dynamics is particularly important for metal alloys as the surface composition responds sensitively to the gas environment. Here, a first-principles-based kinetic Monte Carlo method is developed to compare the dynamics of dilute PdAu alloy nanoparticles in inert and CO-rich atmospheres, corresponding to reaction conditions for catalyst deactivation and activation. CO influences the dynamics of the activation by facilitating the formation of vacancies and mobile Au-CO complexes, which are needed to obtain CO-stabilized Pd monomers on the surface. The structure of the catalyst and the location of the Pd monomers determine the rate of deactivation. The rate of catalyst deactivation is slow at low temperatures, which suggests that metastable structures determine the catalyst activity at typical operating conditions. The developed method is general and can be applied to a range of metal catalysts and reactions.

Signed expressions spotting and recognition in an assistive technology system

An algorithm for processing the continuous stream of incoming video data to detect and recognize signed expressions is proposed. The aim is to improve an assistive technology system. The method is based on the dynamic flow of expression models between a repository of inactive models and pools of active and completed models. When modeling signed expressions, so-called visemes are used. These are units smaller than words - the equivalent of phonemes known from speech recognition. Visemes are extracted by clustering descriptors of the holistic skeletons. The sequential-simultaneous nature of gestures is considered, and the modeling is carried out in four parallel channels related to the position and shape of both hands. The conditions for activation, deactivation, and recognition of the model as completed are formulated, assuming asynchronous changes in individual channels. The method is successfully tested on a demanding dataset recorded by potential users.

In Situ X-ray Diffraction as a Basic Tool to Study Oxide and Metal Oxide Catalysts

X-ray diffraction (XRD) is a standard technique that is widely applied in heterogeneous catalysis to determine phase composition, atomic structure, and size of crystallites. This review is focused on the application of in situ XRD for studying the catalysts during their “lifetime” (under synthesis, activation, operation, and deactivation conditions), limiting the objects of research to oxide and metal oxide catalysts. Also included is a brief overview of modern techniques and instruments and the latest works illustrating different aspects of this technique in catalyst research. The main conclusion is that the field of heterogeneous catalysis research would benefit substantially from the application of in situ XRD for the structural, phase, and morphological characterization of solid catalysts. Even more useful information can be obtained if XRD is combined with other techniques that are more sensitive at length scales different from that of XRD.

Effects of enzyme deactivation conditions on the structure, bound phenol content and antioxidant property of phenol modified Tartary buckwheat protein hydrolysate

In this study, the effects of different enzyme deactivation methods (80, 100, 4 °C and pH 6.0) on the structural characteristics, bound polyphenol content and antioxidant activity of buckwheat protein hydrolyzate-phenol complex (BHP) were investigated. Alcalase was selected for enzymolysis. Amino acid analysis showed that glutamic acid was the most important amino acid in hydrolysate. Molecular weight distribution analysis showed that the hydrolysis can be completed at 3 h. After enzyme deactivation treatment, all hydrolysates were dialyzed to remove aggregates/enzymes (15 kDa). Fourier transform infrared spectroscopy (FTIR) analysis revealed that the characteristic peaks of BHP shifted after treatment. The fluorescence spectra and surface hydrophobicity (Ho) showed that the corresponding values of BHP increased significantly when deactivated at 80 °C and pH 6.0, decreased at 100 °C and remained no change at 4 °C. The content of total bound polyphenol increased when treated at 80 and 4 °C, and decreased at 100 °C and pH 6.0. Meanwhile, the results showed that all BHP have high antioxidant capacity. This work can provide more support for the systematic evaluation of enzyme deactivation methods containing phenolic hydrolysates.

Organic matter deactivation can increase the amount of hydroxyl radical transfer leading to the oriented oxidation of long-chains alkanes

In order to investigate the effect of deactivated organic matter in soils on the removal of long-chain alkanes (C20-C30), eight sets of deactivation experiments were carried out on two soil samples (S1 and S2) with the four deactivation conditions (soil: NaOH = 50:1, 100:1, 150:1, 200:1). Subsequently, a series of crude oil oxidation experiments were conducted on the oil-spiked S1 and S2 using the modified Fenton process (Fe2+ = 5.8 mM and H2O2 = 100 mM). The results showed that the amount of oriented oxidation of long chains (C20-C30) was 3201–4712 mg/kg in the completely deactivated group with deactivated degree K ＞ 47.5%, which was 3.5–7.5 times than that of the incompletely deactivated group (K ＜ 47.5%). In addition, the oriented oxidation of long-chains (C20-C30) increased from 3201 to 4712 mg/kg with the increase of •OH transfer from 0.20 to 0.85 a.u. For the completely deactivated group, the deactivation of the C-O and COO- on the organic matter led to the deactivation of the protein-like substances. The deactivation of the protein-like substances resulted in a K value greater than 47.5%, which ultimately increased the amount of •OH transfer. The results showed that the maximum amounts of oriented oxidation in both S1 (4712 mg/kg) and S2 (3201 mg/kg) were achieved when the ratio of soil to NaOH was 100:1.

Performance of BS-VI catalyst and influence of deactivation conditions on emission durability for commercial vehicle applications

On one hand, to bring down the vehicular pollution levels, the Indian government implemented BS-VI emission standards from April 2020. On the other hand, future regulatory requirements for in-use compliance of large sources like heavy-duty vehicles (HDV) are monitored using Portable Emissions Measurement Systems (PEMS). Henceforth, to meet these regulatory emissions requirements, the advancement in catalyst technologies is progressing rapidly to meet the ever-tightening control on tailpipe emissions. It is also imperative to ensure no significant catalyst performance deterioration throughout the useful emission life of the vehicle. However, for such catalyst technology, performance durability validation is important based on vehicle market and duty cycle applications. Moreover, the durability of the selected catalyst is validated for emission performance after accelerated regeneration conditions to understand the thermal stability and the sintering effect of catalyst behaviour in an engine rig. Based on this, the significance of catalyst technology selection for commercial vehicle applications as well as catalyst validations for the Indian market are discussed in this paper. Related to in-use performance, the catalyst performance behaviour after a vehicle mileage accumulation of 160,0000 km and the exhaust emissions under real-world conditions using PEMS are also conversed.

Design of carbon supports for metal-catalyzed acetylene hydrochlorination

For decades, carbons have been the support of choice in acetylene hydrochlorination, a key industrial process for polyvinyl chloride manufacture. However, no unequivocal design criteria could be established to date, due to the complex interplay between the carbon host and the metal nanostructure. Herein, we disentangle the roles of carbon in determining activity and stability of platinum-, ruthenium-, and gold-based hydrochlorination catalysts and derive descriptors for optimal host design, by systematically varying the porous properties and surface functionalization of carbon, while preserving the active metal sites. The acetylene adsorption capacity is identified as central activity descriptor, while the density of acidic oxygen sites determines the coking tendency and thus catalyst stability. With this understanding, a platinum single-atom catalyst is developed with stable catalytic performance under two-fold accelerated deactivation conditions compared to the state-of-the-art system, marking a step ahead towards sustainable PVC production.

Improving frictional performance of ring-liner system under cylinder deactivation conditions by surface texturing

In this study, a method of surface texture is considered to improve the frictional performance of the ring-liner system (i.e. RLS) under the conditions of cylinder deactivation (i.e. CDA). To assess the effectiveness of the method, a lubrication model is developed with considerations of the liner deformation, the actual rheological properties of lubricant, and the lubricant transport. By solving the model numerically, the friction reduction effect of surface texture for the RLS under the CDA is investigated. The results show that the surface texture can improve the friction properties significantly. For a six-cylinder gasoline engine, 7.57% and 7.28% decreases in the total average friction loss and power loss are observed when the RLS under the CDA is surface textured.

Catalytic pyrolysis of pine bark over Ni/SiO2 in a CO2 atmosphere

Syngas was produced by catalytic pyrolysis of pine bark (PB) using CO2 as a raw feedstock as part of an effort to realize the sustainable utilization of biomass carbon. An examination of both liquid and gaseous pyrolysates from pyrolysis revealed that CO2 expedited gas-phase reactions (GPRs) with volatile pyrolysates (VPs) evolved from thermolysis of PB. The GPRs between CO2 and VPs led to the generation of CO at ≥ 600 °C regardless of Boudouard reactions. Two-step pyrolysis was conducted with an additional heating source, and the synergetic use of Ni/SiO2 and CO2 stimulated syngas formation at ≤ 600 °C. Evolution of H2 and CO from catalytic pyrolysis at 700 °C in CO2 atmosphere was greater by factors of 10 and 5, respectively, compared with those from two-step pyrolysis. The conditions for catalytic deactivation between virgin and used catalysts were compared using temperature-programmed oxidation. An apparent reduction of organic species on the surface of used catalysts by CO2 indicates that the addition of CO2 suppressed the formation of coke for deposition. Accordingly, combinational use of CO2 and Ni/SiO2 in catalytic pyrolysis can be recommended as an advanced technical option for production of syngas under favorably retarded conditions for catalyst deactivation.

Determination of hydrogen isotopes and isomers by different deactivated alumina PLOT columns

To determine residual H2 and D2 concentrations in high purity HD, gas chromatography was used to separate the hydrogen isotopes in a 5 A molecular sieve porous layer open tubular (PLOT) column cooled in a slowly warmed dewar. It took more than 15 min to produce one chromatogram in which a platform existed between o-H2 and p-H2, and resolution between o-D2 and p-D2 was hardly investigated. In this study, to improve thermal stability of the column oven, the column is designed to be immersed in pure liquid nitrogen instead of a mixture of liquid nitrogen and isopentane. Several alumina PLOT columns under different deactivation conditions are used to separate the hydrogen isotopes at 78 K. Results show that the sulfate deactivated column performs higher elution resolution than the chloride deactivated column. The platform was decreased in a 15 m sodium sulfate deactivated column; o-H2 and p-H2 was baseline separated within 1 min; o-H2: p-H2 = 72:28 according to peak areas. o-D2 and p-D2 was separated in less than 2 min in the same column, the ratio o-D2:p-D2 = 67:33. Relative short analysis time would help reduce the platform. Residual concentrations of high purity HD (HD = 96%) were determined within 3 min in a 15 m sulfate deactivated column modified by magnesium sulfate.

Signals from the Gut Influence Mouse Behavior: Examination of Mechanisms

The intestinal microflora can have significant influences on brain activity. Gut microbiota release neurotransmitters that are hypothesized to send signals via the vagal nerve back to the brain. However, such afferent interactions have never been proven. The current experiments utilized optogenetic vectors (AAV‐CaMKIIa‐eNpHR3.0‐EYFP) placed within the jejunum to label vagal nerves. These vectors induce the insertion of light sensitive chloride channels into neuronal membranes that when stimulated with light deactivate the neuron. By placing these vectors in the jejunum, the experiment selectively deactivated only the select fibers that run from the jejunum to the brain. Control animals were injected with saline.In all animals, normal animal behavior was recorded for anxiety measures (elevated plus maze), open field behaviors, and forced swim tests. Each test was performed with both light deactivation of the vagus, and no‐light conditions. Results indicated that mouse behavior was not affected for the control animals nor for animals in the no‐light vector conditions. However, the animal behavior was dramatically altered for each animal in the optogenetic light deactivation condition. In each behavioral test, animals showed a freezing behavior for the extent of time that the vagus was deactivated. Within the forced swim experiments, frozen animals did not keep their head above water and tended to sink to the bottom of the tank (requiring multiple rescues during each session).The results support the hypothesis that the jejunum can influence brain activity via vagal nerve efferents. I conclude that optogenetic deactivation of the vagal afferents of the jejunum has a direct influence on animal behavior and thus brain circuits. Therefore, this pathway provides an optimal mechanism by which future nutritional therapies can be devised for a variety of brain pathologies.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Process of Development of a County-wide Crisis Care Plan - Riverside County, California, 2016-7.

Introduction: Disasters with substantial impacts to the health care and public health systems can have multiple reverberating effects, including the need to alter the medical standard of care as well as centrally control scarce medical resources. A current crisis care plan can help to establish an ethical and operational framework for stakeholders before such a disaster takes place. However, there are few examples of such a plan that cover large areas and health jurisdictions. This article describes the process of developing such a “Crisis Care Plan.”Methods: Plan developers from the Riverside County Department of Public Health and Riverside County Emergency Management Department first developed an ethical framework for decision making, followed by the development of a full operational crisis care plan with conditions for activation, life cycle and deactivation. The plan was then reviewed by major county stakeholders, including local emergency medical services, the county medical association and the hospital association, and additional comments incorporated. Before the final plan is implemented it will be submitted for public review and provider training materials will be developed.Results: The development of a prerequisite ethical framework helped to reduce the risk that the operational plan would cause or exacerbate care disparities by informing a blinded, objective process for evaluating resource requests centrally prior to distribution. The ethical framework served to establish the grounding principle of all lives having an equal claim on value. Stakeholders recognized the need for such a Crisis Care Plan and agreed with the underlying ethical principles. Stakeholders also contributed useful recommendations to enable the plan to operate in as successful a manner as possible under the difficult conditions within which it would exist.Discussion: The development of a clear ethical framework and the early identification and involvement of stakeholders can enable even very large health jurisdictions to construct crisis care plans that enable the best care under difficult circumstances, while protecting individual rights and incorporating the concerns of the public and the health care community.

Assessing the optimal conditions for surface-mediated disinfection of Influenza A virus solutions

Environmental contextTransmission of viruses is related to their survival while being outside the host body. By means of experimental and computational simulations we assess the optimal conditions for virus deactivation upon contact with particularly functionalised substrates. These results constitute the basis for the design of new surfaces with high antiviral activity that can be important in public or sensitive environments such as in hospitals where the contamination and spreading of viruses are a critical issue. AbstractThe abundance of pathogenic microorganisms in the environment and the ease of their transmission through several paths is a critical issue in many daily human activities. Within the different transmission paths, contact with contaminated surfaces provides a chance for the development of surfaces with special characteristics that are able to reduce the spread of microorganisms through their deactivation by contact. The development of ‘active’ surfaces with antiviral properties requires the understanding of the molecular interaction mechanisms between functionalised surfaces and lipid-enveloped entities. By means of a study based on experimental and computational methods we have assessed that surfaces that are simultaneously hydrophobic and oleophilic are more efficient for disinfecting aqueous virus solutions. The combination of these features causes the disruption of the viral lipid envelope upon contacting the surface, and as a consequence the virus’ destruction and deactivation. Our results suggest new and more effective design strategies for functionalised surfaces that may be of interest for applications in sensitive environments.

Effect of Ionic Radius of Rare Earth on USY Zeolite in Fluid Catalytic Cracking: Fundamentals and Commercial Application

The ultrastable Y zeolite (USY) in fluid cracking catalyst is commonly stabilized by ion-exchange with rare earth (RE) cations. The RE-exchange provides hydrothermal stability to the zeolite by improving surface area retention, as well as inhibiting dealumination, resulting in greater preservation of acid sites. Though La and Ce are commonly used in fluid catalytic cracking (FCC) catalysts, we have observed that the stability of REUSY catalysts improves as the ionic radius of the RE cation decreases. In this paper, we compare the activity and selectivity of REUSY catalysts, stabilized with La and heavy (Ho, Er, and Yb) rare earth cations, the latter having a smaller ionic radius, due to the well-known phenomenon of lanthanide contraction. The experimental data show that a significant improvement in catalytic activity is achieved when RE elements having a smaller ionic radius are used to make the REUSY catalyst. Yttrium is even more effective than the heavier lanthanides in stabilizing Y-zeolite, leading to higher cracking activity and gasoline selectivity under a variety of deactivation conditions. These benefits of yttrium exchange does not only result from a larger resistance to dealumination, but also to an increase of the catalyst intrinsic cracking activity, which may be explained by changes in the adsorption of hydrocarbons at the active sites. Examples of commercial applications of yttrium-based FCC catalysts are given.

Application of Parallel Factor Analysis (PARAFAC) to electrophysiological data.

The identification of important features in multi-electrode recordings requires the decomposition of data in order to disclose relevant features and to offer a clear graphical representation. This can be a demanding task. Parallel Factor Analysis (PARAFAC; Hitchcock, 1927; Carrol and Chang, 1970; Harshman, 1970) is a method to decompose multi-dimensional arrays in order to focus on the features of interest, and provides a distinct illustration of the results. We applied PARAFAC to analyse spatio-temporal patterns in the functional connectivity between neurons, as revealed in their spike trains recorded in cat primary visual cortex (area 18). During these recordings we reversibly deactivated feedback connections from higher visual areas in the pMS (posterior middle suprasylvian) cortex in order to study the impact of these top-down signals. Cross correlation was computed for every possible pair of the 16 electrodes in the electrode array. PARAFAC was then used to reveal the effects of time, stimulus, and deactivation condition on the correlation patterns. Our results show that PARAFAC is able to reliably extract changes in correlation strength for different experimental conditions and display the relevant features. Thus, PARAFAC proves to be well-suited for the use in the context of electrophysiological (action potential) recordings.

Genesis of HDT catalysts prepared with the use of Co2Mo10HPA and cobalt citrate: Study of their gas and liquid phase sulfidation

Genesis of alumina supported hydrotreating (HDT) catalysts prepared with the use of decamolybdodicobaltate heteropolyanion (Co2Mo10HPA) and cobalt citrate during their sulfidation processes and deactivation in diesel HDT has been investigated. The sulfidation stage was studied for two procedures: gas phase sulfidation by H2S/H2 and liquid phase treatment by a mixture of dimethyldisulfide in diesel at various temperatures and durations. The catalysts have been studied by N2 adsorption, thermogravimetric analysis, X-ray photoelectron spectroscopy and high-resolution transmission electron microscopy methods. The catalysts were tested in HDT of mixture of 70wt.% straight run gas oil with 16wt.% light cycle oil and 14wt.% light coker gas oil. Mechanisms of the active phase formation in the course of gas and liquid phase sulfidation processes have been established. It was found that gas phase sulfidation led to formation of the CoMoS active phase with higher cobalt content comparing to liquid sulfidation of the catalyst and initial activity of the gas phase treated catalysts in diesel HDT was also higher than catalysts subjected to liquid sulfidation. Catalytic examination after accelerated deactivation conditions showed that the liquid phase sulfided sample was more resistant to the deactivation. Probably it is due to stabilization of active phase particles by coke formed intensively during liquid phase sulfidation. The results were discussed using the recently developed concept of interlayer dynamics of the active sites of the CoMoS phase.

Deactivation Analysis of a Cu/ZnO-Based Catalyst for Low-Temperature Water-Gas Shift Reaction

The deactivation rate equation for a commercial Cu/ZnO water–gas shift catalyst was derived on the basis of a high-order power-law equation for sintering rate. The parameters for the equation were then calculated from experimental data obtained over a short period during which the deactivation conditions were severe (250–350°C). The values calculated from an 11th-order deactivation rate equation were in good agreement with the experimental values over a long period (1000 h) under practical conditions (200°C).

Accelerated Deactivation of Hydrotreating Catalysts by Coke Deposition

Pilot plant experiments are designed to allow for evaluation of the impact caused by increasing the severity of key operation variables on deactivation of hydrotreating (HDT) catalysts, through accelerated runs performed in short periods of time. One of the main aspects of this work is the use of a kinetic approach in order to observe the impact of accelerated deactivation conditions upon catalyst performances during hydrodesulfurization (HDS), hydrodenitrogenation (HDN), and aromatic hydrogenation (HDA) reactions. This approach allows for evaluation of catalyst deactivation for each of the analyzed reactions. Results obtained with a reference catalyst indicate that the proposed methodology is able to deactivate the catalyst effectively, leading to proper representation of actual industrial deactivation at the end of a catalyst life cycle.

Deactivation of ZSM-5 additives in laboratory for realistic testing

ZSM-5 deactivates differently from Y zeolite. Dealumination of Y zeolite during deactivation causes UCS shrinkage and thereby decline in activity and changes in selectivity. For ZSM-5 instead deactivation removes alumina from the zeolite structure, but in spite of that the zeolite structure does not collapse. Therefore, deactivation causes activity decline due to loss of active alumina sites, but no significant changes in the strength and separation between acid sites. Unlike with FCC catalyst, physical properties of ZSM-5 additive do not change significantly with deactivation and surface area and pore volume measurements cannot be used as indications of additive performance. Yet, since both Y and ZSM-5 are used simultaneously in practice, the information on the relative rates of deactivation between the two zeolites is very important. Therefore, the question remains, what is the best way to deactivate and test ZSM-5 additives in the laboratory to obtain realistic performance, e.g. propylene yield and to obtain proper ranking of various additives. This paper discusses the effect of deactivation conditions as well as performance testing aspects of ZSM-5 additives. It is shown that choice of deactivation conditions has an effect on additive ranking and performance. By choosing the deactivation conditions properly ranking can be made clearer and more realistic additive performance is obtained.

Experimental Study on Intelligent Monitoring of Diamond Grinding Wheel Wear

In order to research the relationship between grinding wheel wear and the signal of grinding strength and grinding vibration, the grinding strength signal and grinding vibration signal under different wear condition were carried on digital processing by time-domain, frequency-domain, and wavelet-pocket analysis, and characteristic signal reflecting grinding wheel wear condition was obtained. Grinding wheel wear was monitored by time-domain statistics average value of grinding strength and energy value of three layers wavelet-pocket decomposition frequency band. The method how to set design parameters of neural network is introduced, and their value in condition monitoring network is determined. Mapping model of grinding wheel wear and characteristic signal is established. Recognition effect is satisfied in the experiment of grinding wheel wear condition monitoring. It confirmed the model is reliable and effective. The result shows that the new intelligent monitoring method is effective on monitoring grinding wheel deactivation condition. One new method of diamond grinding wheel wear condition monitoring under precision and ultra-precision grinding is introduced.