Degree Of Deactivation Research Articles

Development of the Mathematical Model of Diesel Fuel Catalytic Dewaxing Process Taking into Account Factors of Nonstationarity

The paper describes the results of mathematical modelling of diesel fuel catalytic dewaxing process, performed taking into account the factors of process nonstationarity driven by changes in process technological parameters, feedstock composition and catalyst deactivation. The error of hydrocarbon contents calculation via the use of the developed model does not exceed 1.6 wt.%. This makes it possible to apply the model for solution to optimization and forecasting problems occurred in catalytic systems under industrial conditions. It was shown through the model calculation that temperature in the dewaxing reactor without catalyst deactivation is lower by 19 °C than actual and catalyst deactivation degree accounts for 32 %.

Rietveld analysis of computed tomography and its application to methanol to olefin reactor beds

This article reports the creation of tomographic reconstructions giving three-dimensional data on the distribution of various structural features for SAPO-34 zeolite catalyst beds used in the commercially important methanol to olefin conversion process. The data were processed using parametric Rietveld refinement to treat entire slices of the tomograph as single refined data sets, allowing extraction of real structural parameters from all voxels of the reconstruction. This has the advantage over more traditional methods of X-ray diffraction computed tomography using peak intensities, that the structural parameters are independent of the intensity, meaning that information can still be extracted from poor data sets: an example is shown where part of the sample was no longer in the beam during data collection. Reconstructions using several structural parameters are presented and the results compared. Analysis of the variation of the catalystcaxis (linked to the degree of deactivation in earlier work) shows small but significant three-dimensional variations in the degree of deactivation with patterns which depend on the silicon content of the catalyst. Average data for the tomographic slices compare well with the results of earlieroperandotwo-dimensional reactor scanning experiments.

Effect of Cu additives on the performance of a cobalt substituted ceria (Ce0.90Co0.10O2–δ) catalyst in total and preferential CO oxidation

The study reports the modification of the developed Ce0.90Co0.10O2–δ catalyst by incorporating copper ions in order to improve the catalytic activity for total and preferential CO oxidation (TOX and PROX). A series of metal ion substituted ceria catalysts, Ce0.90Co0.10O2–δ and Ce0.90-xCuxCo0.10O2–δ (x=0.01, 0.03 and 0.05) were synthesized in a single step by the urea-assisted solution combustion method. The compositions, textural and structural properties of the catalysts were characterized by XRD, XPS, Raman, H2-TPR and ICP-OES. The insertion of Cu ions in Ce0.90Co0.10O2–δ greatly enhanced the reducibility and improved the activity, with especially the Ce0.85Cu0.05Co0.10O2–δ catalyst showing superior catalytic performance compared to other bimetallic catalysts. Analysis of the reaction profiles and rate calculations suggest that H2 and CO oxidation over Ce0.90Co0.10O2–δ may be occurring on the same active sites, while the two reactions appear to be taking place on independent sites over the Cu-containing catalysts. In addition, the effect of H2O/CO2 in PROX has been studied. The degree of deactivation by H2O and CO2 decreased with increasing the Cu content in the catalysts. The presented catalysts are highly active, selective and stable in TOX and PROX.

Default Mode Network Activity Predicts Early Memory Decline in Healthy Young Adults Aged 18-31.

Functional magnetic resonance imaging (fMRI) research conducted in healthy young adults is typically done with the assumption that this sample is largely homogeneous. However, studies from cognitive psychology suggest that long-term memory and attentional control begin to diminish in the third decade of life. Here, 100 participants between the ages of 18 and 31 learned Lithuanian translations of English words in an individual differences study using fMRI. Long-term memory ability was operationalized for each participant by deriving a memory score from 3 convergent measures. Age of participant predicted memory score in this cohort. In addition, degree of deactivation during initial encoding in a set of regions occurring largely in the default mode network (DMN) predicted both age and memory score. The current study demonstrates that early memory decline may partially be accounted for by failure to modulate activity in the DMN.

CO2 reforming of methane over Mn promoted Ni/Al2O3 catalyst treated by N2 glow discharge plasma

The N2 plasma treated Ni/Al2O3 catalyst was enhanced by manganese (Mn) promoter with doping content ranging from 5wt% to 15wt%. Compared to the plasma treated nickel catalyst without Mn additive, the introduction of Mn promoter further increased the CH4 conversion of studied catalysts about 10% at 700°C for CO2 reforming of methane. After 360min reaction of time-on-stream, the deactivation degree value was decreased to 1.46%. Relatively lower value of 5–10wt% doping amount of Mn was appropriate. Mn promoter further intensified the reducibility of plasma treated catalyst according to the shift to lower temperature of the reduction peak shown in H2-TPR profiles. CO2-TPD results suggested that the modification effect of Mn promoter on the basicity of plasma treated catalyst was speculated to account for the concentration increase of absorbed CO2. It was beneficial to the carbon deposition elimination and it increased the coking-resistant ability of catalyst surface, while this result was in good agreement with the CO2-TPSR and TG results. The lower temperature and smaller area of CO peak was observed over plasma treated Ni-Mn/Al2O3 catalyst in CO2-TPSR test, i.e., less coke formation on the Mn promoted sample.

Redox Transformation of Poly(o-aminophenol) (POAP) Film Electrodes under Continuous Potential Cycling

The aim of this work was to study the effect of prolonged potentiodynamic cycling (PPC) on the conducting properties of poly(o-aminophenol) (POAP) film electrodes. PPC reduces strongly the electron and ion transport rates at POAP films. Cyclic Voltammetry (CV), Rotating Disc Electrode Voltammetry (RDEV) and Electrochemical Impedance Spectroscopy (EIS) were employed in this study. The attenuation of the voltammetric response of the polymer with the increase in the number of oxidation-reduction cycles allowed one to define a degree of deactivation. RDEV and EIS were employed to obtain dependences of charge-transport and charge-transfer parameters on the degree of deactivation of the polymer. RDEV data were interpreted on the basis of the electron hopping model. Impedance spectra of POAP films in the presence of an electroactive solution containing p-benzoquinone (Q) and hydroquinone (HQ) species were analyzed on the basis of an impedance model which considers a uniform and nonporous polymer film and no penetration of redox species into the film from the solution While diffusion coefficients for electron (De) and ion (Di) transport decrease, interfacial resistances related to ion (Rifǀs) and electron (Rmǀf, Refǀs) transfer across the different interfaces involved in the metal/polymer film/solution system increase as the degree of deactivation increases. The slower electron transport with the increase in the degree of deactivation was attributed to the increase of the electron hopping distance between redox sites. Transport parameters, such as, Rifǀs and Di, were associated with proton movements. POAP films maintain their conducting properties almost unaltered for about 500 potential cycles at a scan rate of 0.010V s-1. However, a loss of conductivity was observed as the number of potential cycles was extended beyond 500.

Deactivation of poly(o-aminophenol) film electrodes by storage without use in the supporting electrolyte solution and its comparison with other deactivation processes

The effect of storage time without use (STWU) in the supporting electrolyte solution on the conducting properties of poly(o-aminophenol) (POAP) film electrodes was studied. Cyclic voltammetry (CV), rotating disc electrode voltammetry (RDEV), and surface resistance (SR) were employed. The storage of a POAP film without use for time periods longer than 32h strongly reduces its electroactivity. Here, this effect is called deactivation. The attenuation of the voltammetric response of the polymer film with the increase of the storage time allows one to define a degree of deactivation (θd). A decrease of the electron transport rate (De) with the increase of the degree of deactivation of POAP films was obtained from RDEV measurements. This effect was attributed to the increase of the mean distance between active redox sites in the bulk of the POAP film. The relative surface resistance change (ΔR/R) of a gold film coated with POAP is also attenuated by the increase of the STWU. The attenuation was attributed to interfacial (gold/POAP) redox site distributions where the nearest neighbor distance between redox sites gradually increases as the degree of deactivation increases. The deactivation of POAP films by the STWU studied in this work was compared with deactivations caused by other electrochemical and chemical treatments, such as prolonged potential cycling (PPC), high positive potential limits (HPPL) and soaking in a ferric ion solution (SFeIS), described in previous work.

Promoted RhPt bimetallic catalyst supported on δ-Al2O3 and CeO2–ZrO2 during full-scale autothermal reforming for automotive applications: Post-mortem characterization

The influence of sulfur and coke formation on the steam reforming of diesel was evaluated for two promoted RhPt bimetallic catalysts, composed of 1:1 Rh:Pt/10:10 La2O3: CeO2/ δ-Al2O3 (CAT 1) and 1:1 Rh:Pt/4:5 MgO: Y2O3/CeO2−ZrO2 (CAT 2). The intrinsic activity is related to the total Rh and Pt area observed after the exposure to sulfur. Therefore, the degree of deactivation is related to the amount of sulfur deposited on the active metal sites. Sulfur analysis on the aged catalyst washcoat showed a decreasing sulfur concentration in the axial direction of the reformer. The estimated sulfur coverage related to metal surface area after 40h on stream reached values of 0.145 in CAT 2, below the equilibrated sulfur coverage of 0.19 after tests with DIN 590. Thus, showing a partial deactivation due to sulfur poisoning. Further catalyst characterization on carbon deposits and thermal aging was performed by TPO, TGA, BET, CO chemisorption, and TEM analysis.

Effect of the composition and acidity of supported sulfide catalysts on their activity and deactivation in guaiacol hydrodeoxygenation

The following catalysts have been prepared: XMo6HPC/Al2O3, based on Anderson-type heteropoly compounds (HPCs), with the general formula XMo6HPC in which the central heteroatom is a fourth-row p- or d-element (X = Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Al); Co6(CA)-PMo12/support, based on 12-phosphomolybdic acid and cobalt citrate, in which the support is Sibunit, Al2O3, carbonized alumina, or alumina modified with zeolite ZSM-5 or Beta. The supports and catalysts have been characterized by low-temperature nitrogen adsorption, X-ray powder diffraction, and temperature-programmed ammonia desorption. The properties of the catalysts in guaiacol hydrodeoxygenation (HDO) have been investigated in a flow reactor at 260°C, 3.0 MPa, a feed hourly space velocity of 80 h−1, and H2: feed = 500 L/L. The activity of the XMo6HPC/Al2O3 catalysts depends on the kind of heteroatom X: the most active catalysts are those with X = Co or Ni, and the least active ones are those with X = Cu. There is a linear antibatic correlation between the HDO activity of the catalysts and the acidity of the support. The lower activity of the zeolite-containing catalysts is due to their high degree of deactivation. Catalysts supported on carbonized alumina, which proved to be most active and most resistant to deactivation, are recommended for the HDO of vegetable raw materials.

Plasma flux-dependent lipid A deactivation

This paper reports the influence of gas plasma flux on endotoxin lipid A film deactivation. To study the effect of the flux magnitude of reactive species, a modified low-pressure inductively coupled plasma (ICP) with O radical flux ∼1016 cm−2 s−1 was used. After ICP exposures, it was observed that while the Fourier transform infrared absorbance of fatty chains responsible for the toxicity drops by 80% through the film, no obvious film endotoxin deactivation is seen. This is in contrast to that previously observed under low flux exposure conducted in a vacuum beam system: near-surface only loss of fatty chains led to significant film deactivation. Secondary ion mass spectrometry characterization of changes at the film surface did not appear to correlate with the degree of deactivation. Lipid A films need to be nearly completely removed in order to detect significant deactivation under high flux conditions. Additional high reactive species flux experiments were conducted using an atmospheric pressure helium plasma jet and a UV/ozone device. Exposure of lipid A films to reactive species with these devices showed similar deactivation behaviour. The causes for the difference between low and high flux exposures may be due to the nature of near-surface structural modifications as a function of the rate of film removal.

Effect of prolonged electrode potential cycling on the conduction properties of poly(o-aminophenol) film electrodes

The aim of this work was to study the effect of prolonged potentiodynamic cycling (PPC) on the conducting properties of poly(oaminophenol) (POAP) film electrodes. PPC reduces strongly the electron transport rate at POAP films. This effect is called herein deactivation. Cyclic Voltammetry (CV), Rotating Disc Electrode Voltammetry (RDEV) and Electrochemical Impedance Spectroscopy (EIS) were employed in this study. The attenuation of the voltammetric response of the polymer with the increase in the number of oxidation-reduction cycles allowed one to define a degree of deactivation. RDEV and EIS were employed to obtain the dependence of some charge-transport parameters on the degree of deactivation of the polymer. RDEV data were interpreted in terms of the electron hopping model. Impedance spectra were analysed on the basis of a model which considers a protonation reaction coupled with a self-exchange process between oxidized and reduced sites. POAP films maintain their conducting properties almost unaltered for about 500 potential cycles at a scan rate of 0.010 Vs−1. However, a loss of conductivity was observed as the number of potential cycles was extended beyond 500.

Characterization of Pt-TiO2 film used in three formaldehyde photocatalytic degradation systems: UV254 nm, O3+UV254 nm and UV254+185 nm via X-ray photoelectron spectroscopy

Photocatalytic degradation of gaseous formaldehyde for 35 h was performed using Pt-TiO 2 film in the following irradiation systems: UV 254 nm , O 3 +UV 254 nm , and UV 254+185 nm . Concurrent improvements in formaldehyde degradation and O 3 removal were achieved by modifying TiO 2 with Pt nanoparticles, resulting in a 3.13.4-fold O 3 elimination increase. X-ray photoelectron spectroscopy (XPS) of the Pt-TiO 2 film was carried out to assess the electronic states of the Pt nanoparticles and accumulated organic species. The deconvoluted C 1 s and O 1 s XPS spectra revealed that the content of carbonyl and carboxyl groups on Pt-TiO 2 and degree of catalyst deactivation in the systems studied decreased in the following order: UV 254 nm > O 3 +UV 254 nm > UV 254+185 nm . Metallic Pt 0 was oxidized to a mixture of PtO ads and Pt 4+ species under O 3 +UV 254 nm and UV 254+185 nm irradiation owing to the presence of O 3 and hydroxyl radicals, but remained stable under UV 254 nm irradiation. Pt species at higher oxidation states can act as electron trapping centers, and improve the photocatalytic activity of Pt-TiO 2 and provide reactive sites for O 3 decomposition under UV irradiation, resulting in a faster O 3 removal rate than that displayed by TiO 2 . The XPS studies provided valuable information to elucidate the beneficial role of Pt species and the reduction of catalyst deactivation under UV 254+185 nm irradiation. O 3 byproduct can be photocatalytically decomposed on both TiO 2 substrate and Pt nanoparticles under UV 254+185 nm irradiation. The oxidized Pt species can trap the photogenerated electrons to increase the photocatalytic activity of Pt-TiO 2 .

Effect of prolonged electrode potential cycling on the charge transport parameters of poly(o-aminophenol) films. A study employing rotating disc electrode voltammetry and surface resistance

The aim of this work was to study the effect of prolonged potentiodynamic cycling (PPC) on the conducting properties of poly(o-aminophenol) (POAP) film electrodes. Cyclic Voltammetry (CV), Rotating Disc Electrode Voltammetry (RDEV) and Surface Resistance (SR) were employed in this study. The attenuation of the voltammetric response of the polymer with the increase in the number of oxidation–reduction cycles allowed one to define a degree of deactivation. RDEV was employed to obtain the dependence of the electron diffusion coefficient on the degree of deactivation of the polymer. The slower electron transport with the increase in the degree of deactivation was attributed to the increase of the electron hopping distance between redox sites. The attenuation of the relative resistance changes (ΔR/R) of a gold film coated with a POAP film as the degree of deactivation increases was also associated to changes in the redox site configuration at the gold/POAP interface after PPC. POAP films maintain their conducting properties almost unaltered for about 500 potential cycles at a scan rate of 0.010Vs−1. However, a loss of conductivity was observed as the number of potential cycles was extended beyond 500.

The Effect of Acupuncture Needle Combination on Central Pain Processing-An fMRI Study

BackgroundEmpirical acupuncture treatment paradigm for acute pain utilizing Tendinomuscular Meridians (TMM) calls for the stimulation of Ting Points (TPs) and Gathering point(GP). This study aims to compare the supraspinal neuronal mechanisms associated with both TPs and GP needling (EA3), and TPs needling alone (EA2) with fMRI.ResultsA significant (P < 0.01) difference between pre-scan (heat Pain) HP, and post-EA HP VAS scores in both paradigms was noted (n = 11). The post-EA HP VAS score was significantly (P < 0.05) lower with EA3 comparing to EA2 Within-group random effect analysis indicated that EA3+HP>EA3 (condition EA3+HP subtracted by condition EA3) appeared to exert a significant degree of activity suppression in the affective supraspinal regions including the IPL, anterior cingulate cortex (ACC) and the insular cortex (IN). This level of suppression was not observed in the EA2+HP>EA2 (condition EA2+HP subtracted by condition EA2) within-group random effect analysis Between-group random effect analysis indicated that EA3 induced a significantly (P < 0.01, cluster size threshold 150) higher degree of deactivation than EA2 in several pain related supraspinal regions including the right prefrontal cortex, rostral anterior cingulate (rACC), medial cingulate cortex, left inferior frontal lobe and posterior cerebellum. The 2-factor ANOVA in those regions indicated both rACC and posterior cerebellum had a significant (P < 0.01) needle effect, and the right prefrontal area showed a significant (P < 0.01) HP effect. However, a significant interaction between the two factors was only found in the right prefrontal lobe. Granger causality analysis showed EA3 induced a much higher degree of inference among HP related supraspinal somatosensory, affective and modulatory components than EA2. Deactivation pattern at the medullary-pontine area casted a direct inference on the deactivation pattern of secondary somatosensory cortices which also affected the deactivation of the IN.ConclusionsWhile both EA2 and EA3 induced a significant degree of deactivation in the human brain regions related to pain processing, the addition of GP stimulation further exerts an inhibitory effect on the ascending spinoreticular pain pathway. Therefore, different needling position as mandated in different empirical acupuncture treatment paradigms may play a different role in modulating pain related neuronal functions.

Oxidative degradation of silica-supported polyethylenimine for CO2adsorption: insights into the nature of deactivated species

The oxidative degradation of polyethylenimine-impregnated mesoporous SBA-15 silica for CO2 capture was investigated at the molecular level. The adsorbents were exposed to flowing air at different temperatures, and their degree of deactivation was evaluated through the measurement of CO2 adsorption capacity prior and subsequent to air exposure. A solvent-extraction method was employed to isolate the deactivated species from the silica support. The extracted species were investigated by a variety of 1D and 2D NMR techniques such as (13)C, (1)H, (1)H-(15)N HMBC, (1)H-(13)C HMQC, and (1)H-(13)C HMBC. This in-depth investigation showed that they contain predominantly fragments involving imine and carbonyl groups. Several structural units were conclusively established.

Temperature and pH Dependent Deactivation of Cutinases from &lt;i&gt;Thermobifida fusca&lt;/i&gt; : A Comparative Study of Homologous Enzymes

Thermostability of two homologous cutinases, Cut1 and Cut2 from Thermobifida fusca NRRL B-8184 was inves-tigated at combination of different pH and temperature in the range of pH 6 - 9 and temperature 45℃ - 80℃, re-spectively. The deactivation rate constants, the half-life and thermodynamic parameters, viz., △H*, △S*, △G* and activation energy kinetics of inactivation of the cutinases were assessed at different combinations of pH and temperature and compared. The optimal pH and temperature for the least degree of deactivation for Cut1 and Cut2 were found to be 8℃ and 45℃, respectively. The deactivation process was found to be faster at pH 6 and 9, with minimum deactivation at pH 8 for both the cutinases. It was found that △S* values are negative for both the enzymes and △H* value of Cut2 was 1.5 fold higher than that of Cut1 in the range of pH studied. Cut2 was found to be thermodynamically more stable with 1.7 fold higher deactivation energy at pH 6 and 7 and 1.4 fold higher deactivation energy at pH 8 and 9 in comparison to Cut1.

Supraspinal Characterization of the Thermal Grill Illusion with fMRI

BackgroundSimultaneous presentation of non-noxious warm (40°C) and cold (20°C) stimuli in an interlacing fashion results in a transient hot burning noxious sensation (matched at 46°C) known as the thermal grill (TG) illusion. Functional magnetic resonance imaging and psychophysical assessments were utilized to compare the supraspinal events related to the spatial summation effect of three TG presentations: 20°C/20°C (G2020), 20°C/40°C (G2040) and 40°C/40°C (G4040) with corresponding matched thermode stimuli: 20°C (P20), 46°C (P46) and 40°C (P40) and hot pain (HP) stimuli.ResultsFor G2040, the hot burning sensation was only noted during the initial off-line assessment. In comparison to P40, G4040 resulted in an equally enhanced response from all supraspinal regions associated with both pain sensory/discriminatory and noxious modulatory response. In comparison to P20, G2020 presentation resulted in a much earlier diminished/sedative response leading to a statistically significantly (P < 0.01) higher degree of deactivation in modulatory supraspinal areas activated by G4040. Granger Causality Analysis showed that while thalamic activation in HP may cast activation inference in all hot pain related somatosensory, affective and modulatory areas, similar activation in G2040 and G2020 resulted in deactivation inference in the corresponding areas.ConclusionsIn short, the transient TG sensation is caused by a dissociated state derived from non-noxious warm and cold spatial summation interaction. The observed central dissociated state may share some parallels in certain chronic neuropathic pain states.

Chemical deactivation of Fe-BEA as NH3-SCR catalyst—Effect of phosphorous

Fe-BEA as catalyst for selective catalytic reduction (SCR) of NOX with NH3 was experimentally studied with focus on chemical deactivation caused by phosphorous exposure. Cordierite supported Fe-BEA samples were exposed to 10 or 50ppm H3PO4 for 14, 24 and 48h in a continuous gas flow reactor at 350°C. The catalytic activity of the samples was studied by NH3- and NO-oxidation, NH3 inhibition and NH3-SCR experiments. The phosphorous exposed samples were further characterized by NH3- and NO-TPD, XPS and XRD. The results from the activity studies show that the degree of deactivation due to phosphorous exposure is strongly dependent on the exposure time, while the rate of deactivation is the same for exposure with 10 and 50ppm H3PO4. The XPS results show that primarily phosphorous pentoxides (P2O5) are formed after short time of phosphorous exposure while longer time of exposure results in formation of metaphosphates (PO3−). The relative amount of metaphosphates after 48h of H3PO4 exposure was about 45% compared to phosphorous pentoxides. The storage capacity of NO was shown to decrease with increasing relative amount of metaphosphates.The activity studies show that longer time of phosphorous exposure results in significantly decreased activity indicating that the active iron species are very sensitive to phosphorous forming metaphosphates. We suggest that metaphosphates replace the hydroxyl groups on the active iron species in Fe-BEA as the main mechanism for the decreased activity for NH3-SCR in connection with phosphorous exposure. Furthermore, the NH3 inhibition experiments show that the increased amount of strongly bound ammonia due to phosphorous exposure does not contribute to buffer the active iron sites with ammonia during transient SCR conditions.

Molecular‐Level Insights into the Oxidative Degradation of Grafted Amines

The oxidative degradation of CO2 adsorbents consisting of amine-grafted pore-expanded mesoporous MCM-41 silica was investigated. The adsorbents were treated under flowing air at various temperatures, and the degree of deactivation was evaluated through the measurement of their CO2 adsorption capacity prior and subsequent to exposure to air. To decipher the chemical structure of surface species upon air-deactivation of grafted amines, a solvent extraction procedure was developed using a deuterated basic solution. The obtained solutions were analyzed by a variety of 1D and 2D NMR spectroscopy techniques, such as (29)Si, (13)C, (1)H, [(1)H,(15)N] HMBC, [(1)H,(13)C] HMQC, COSY and DOSY. The surface species generated by oxidative degradation of amine-grafted silica were found to contain functional groups such as imine, amide and carboxylic groups. Several structural units were conclusively demonstrated.

Dependence of the thermodynamic characteristics of forms of hydrogen adsorbed on a porous nickel surface on the degree of deactivation

Thermodynamic characteristics of the adsorption equilibria of individual forms of adsorbed hydrogen are calculated using data from adsorption-calorimetric studies of liquid-phase hydrogenation in a model of a surface with discrete nonuniformity in the ideal adsorption layer approximation under conditions of liquid-phase hydrogenation. It is shown that partial deactivation raises the fraction of the molecular α form via the atomic β form of adsorbed hydrogen and increases the adsorbate-adsorbent binding energy.