Inhibitory Effect Of CO2 Research Articles

Innovative strategy for corrosion protection and drag reduction in coiled tubing: Design, fabrication, and performance evaluation

To improve the anti-corrosive and drag-reducing properties of 70 carbon steel coiled tubing and extend its service life, we presented an innovative approach involving composite electroplating. This method allows for the deposition of high-performance, anti-corrosive, and drag-reducing coatings on the inner walls of coiled tubing. And a continuous, uniform, and dense Ni-Co-Al2O3 coating was successfully prepared on the inner wall of coiled tubing. This economically viable technique was systematically applicable in industrial settings for enhancing drag reduction and corrosion resistance in continuous petroleum pipelines, offering a practical solution for manufacturing functional coatings with desirable properties. Furthermore, considering the inhibitory effect of Co(OH)2 on Ni deposition, we developed a novel anomalous co-deposition model for Ni-Co binary alloys. The simulation results using the COMSOL® demonstrated a high correlation with the experimental data, underscoring the model as effective for controlling and predicting the composition and structure of Ni-Co coatings.

A bispecific antibody targeting the Ig domains of Siglec-E displays enhanced antitumor effects

Siglec-9 is a promising immune checkpoint molecule, and therapeutics targeting Siglec-9 have the potential to augment anti-tumor immunity. Here, we generated a bispecific antibody, named as aSE4-1-Fc, by fusing two distinct alpaca derived nanobodies, which can simultaneously target the extracellular Ig variable (V)-set domain and C2-set domains of murine Siglec-9 (also known as Siglec-E) with high affinity. In vivo studies showed that aSE4-1-Fc was better than its component antibodies in inhibiting tumor growth/metastasis, and Siglec-E blockade using aSE4-1-Fc generated protective anti-tumor T cell memory. Furthermore, the combination of aSE4-1-Fc with anti-PD-L1 therapy greatly improved the antitumor effects by augmenting both T and NK cells. Taken together, this study emphasizes the importance of Siglec-9 as a potential cancer therapeutic target, demonstrates the synergistic effect of co-inhibition of Siglec-9 and PD-L1, and may have implications for developing engineered antibodies targeting Siglec-9 with enhanced therapeutic efficacy.

Transcriptome analysis reveals the humic acids and chitosan suppressing Alternaria solani growth.

Understanding the inhibitory effects of natural organic substances on soil-borne pathogenic fungi and the relevant molecular mechanisms are highly important for future development of green prevention and control technology against soil-borne diseases. Our study elucidates the inhibitory effect of the combined application of humic acids (HAs) and chitosan on Alternariasolani and the light on the corresponding mechanism. The effect on A. solani growth by HAs incorporated with chitosan was investigated by plate culture and the corresponding mechanism was revealed using transcriptomics. The colony growth of A. solani was suppressed with the highest inhibition rate 33.33% when swine manure HAs was compounded with chitosan at a ratio of 1:4. Chitosan changed the colony morphology from round to irregularly. RNA-seq in the HAs and chitosan (HC) treatment revealed 239 differentially expressed genes compared with the control. The unigenes associated with enzymes activities related to growth and biological processes closely related to mycelial growth and metabolism were downregulated. RNA-seq also revealed that chitosan altered the expression of genes related to secondary metabolism, fungal cell wall formation and polysaccharide synthesis, and metabolism. Meanwhile, weighted gene co-expression network analysis showed that, genes expression in the module positively correlated with mycelial growth was significantly reduced in the HC treatment; and the results were verified by real-time quantitative polymerase chain reaction. The co-inhibition effect of HAs and chitosan on A. solani is associated with downregulated genes expression correlated with mycelial growth.

Experimental study on inhibition of coal spontaneous combustion by carbon dioxide and nitrogen

ABSTRACT Injecting CO2 and N2 to reduce the concentration of O2 in the air is a commonly used measure to prevent coal spontaneous combustion (CSC). To study the difference in inhibitory effects of CO2 and N2 on coal oxidation, experiments in this study were conducted using a setup of self-developed gas-bath coal oxidation for low temperatures. The oxidation process of the coal-oxygen system was then analyzed using reaction kinetics. Two different coal samples were tested in experiments under two inert gas environments, i.e. CO2 and N2 with various O2 concentrations, respectively. The changes in O2 and CO concentrations were measured during the oxidation process. By studying the standard oxygen consumption rate (SOCR) and the apparent activation energy of the coal-oxygen reaction system, inhibitory effects of CO2 and N2 on CSC were analyzed and compared. The results showed that the SOCR of the same coal sample remained consistent and independent of the O2 concentration within the same inert gas environment although under different O2 levels. In both CO2-O2 and N2-O2 environments, the SOCR of the coal sample exhibits exponential growth with temperature. The SOCR was found to have a functional connection with temperature, it can be represented as y = a ⋅ e bT , and the R 2 (determination coefficients) of the fitting formulas are all greater than 0.94. In the correlation, the inert gas environment has minimal impact on coefficient “b,” while in the CO2-O2 environment, reducing the value of coefficient “a” can effectively lower the coal sample’s SOCR. The GBMK sample and YMWK sample have an “a” value that is 20% of the value in the N2-O2 environment when oxidizing in the CO2-O2 environment. The SOCR in the CO2-O2 environment showed a decrement of between 26.0% and 52.1% when compared to that in the N2-O2 environment, whereas the activation energy showed an increment between 1.4% and 18.6%. The findings in this work provide an in-depth understanding of the prevention of CSC in the gob for risk mitigation.

Effects of CO2 on the low-temperature NH3-SCR performance of CeOx-biochar catalyst

Low-temperature NH3-SCR of NOx technology was recognized as a promising way to control NOx emissions from industrial kilns at low temperatures. Except for SO2 and H2O, lots of CO2 exist in the flue gas of industrial kilns. However, there are few researches on the effects of CO2 on the low-temperature NH3-SCR activity. To investigate the effects of CO2 on the low-temperature NH3-SCR performance and mechanism of CeOx-biochar catalyst, a series of experiments employed. The results showed that the presence of CO2 had an obvious inhibitory effect on the NH3-SCR performance of CeOx-biochar0.6 at 150 °C. There was competitive adsorption between CO2 and NO on the surface of CeOx-biochar0.6. CO2 was mainly adsorbed on CeO2, which hindered the oxidation of NO and the adsorption of NOx on the catalyst surface. Meanwhile, although the presence of CO2 could improve NH3 adsorption capacity of CeOx-biochar0.6 due to the formation of NH4HCO3 and (NH4)2CO3, the existence of carbonates and bicarbonates blocked the formation of active intermediates NH4NO2 and NH2NO for NH3-SCR reaction. As a result, the NOx conversion of CeOx-biochar0.6 was dropped from 96.9% to 40.8% at 200 °C. In view of the bicarbonate and carbonate species was unstable at high temperatures, the inhibitory effect of CO2 on NH3-SCR reaction was gradually weakened with the increase of reaction temperature. The NH3-SCR activity of CeOx-biochar0.6 was seldom affected by CO2 at 300 °C. Finally, a CO2 poisoning mechanism for NOx removal by NH3-SCR at low temperature was proposed.

Co-inhibition of adenosine 2b receptor and programmed death-ligand 1 promotes the recruitment and cytotoxicity of natural killer cells in oral squamous cell carcinoma.

Adenosine promotes anti-tumor immune responses by modulating the functions of T-cells and natural killer (NK) cells in the tumor microenvironment; however, the role of adenosine receptors in the progression of oral squamous cell carcinoma (OSCC) and its effects on immune checkpoint therapy remain unclear. In this study, we obtained the tumor tissues from 80 OSCC patients admitted at the Shandong University Qilu Hospital between February 2014 and December 2016. Thereafter, we detected the expression of adenosine 2b receptor (A2BR) and programmed death-ligand 1 (PD-L1) using immunohistochemical staining and analyzed the association between their expression in different regions of the tumor tissues, such as tumor nest, border, and paracancer stroma. To determine the role of A2BR in PD-L1 expression, CAL-27 (an OSCC cell line) was treated with BAY60-6583 (an A2BR agonist), and PD-L1 expression was determined using western blot and flow cytometry. Furthermore, CAL-27 was treated with a nuclear transcription factor-kappa B (NF-κ B) inhibitor, PDTC, to determine whether A2BR regulates PD-L1 expression via the NF-κ B signaling pathway. Additionally, a transwell assay was performed to verify the effect of A2BR and PD-L1 on NK cell recruitment. The results of our study demonstrated that A2BR and PD-L1 are co-expressed in OSCC. Moreover, treatment with BAY60-6583 induced PD-L1 expression in the CAL-27 cells, which was partially reduced in cells pretreated with PDTC, suggesting that A2BR agonists induce PD-L1 expression via the induction of the NF-κ B signaling pathway. Furthermore, high A2BR expression in OSCC was associated with lower infiltration of NK cells. Additionally, our results demonstrated that treatment with MRS-1706 (an A2BR inverse agonist) and/or CD274 (a PD-L1-neutralizing antibody) promoted NK cell recruitment and cytotoxicity against OSCC cells. Altogether, our findings highlight the synergistic effect of co-inhibition of A2BR and PD-L1 in the treatment of OSCC via the modulation of NK cell recruitment and cytotoxicity.

Metabolic responses and microbial community changes to long chain fatty acids: Ammonia synergetic co-inhibition effect during biomethanation

Anaerobic co-digestion is an established strategy for increasing methane production of substrates. However, substrates rich in proteins and lipids could cause a long chain fatty acids (LCFA)-ammonia synergetic co-inhibition effect. The microbial mechanisms of this co-inhibition are still unclear. The current study explored the effect of the synergetic co-inhibition on microbial community changes and prediction of metabolic enzymes to reveal the microbial mechanisms of the co-inhibition effect. The results indicated that during the synergetic co-inhibition, methanogens were mainly affected by ammonia. Decreased relative abundances of Petrimonas (82%) and Paraclostridium (67%) showed that ammonia inhibition contributed to the suppression of LCFA β-oxidation under the synergetic co-inhibition conditions. The accumulation of more LCFA could further suppress microorganisms’ activities involved in several steps of anaerobic digestion. Finally, decrease of critical enzymes’ abundances confirmed the synergetic co-inhibition effect. Overall, the current study provides novel insights for the alleviation of synergetic co-inhibition during anaerobic digestion.

Inhibitory effect of CO on NH3-SCR of NO over Mn/TiO2 catalyst at low temperature: Inhibitory mechanism investigated by in situ DRIFTS

The reaction of NO with NH3 over Mn/Ti catalyst in the presence of CO has been investigated at low temperature. CO can significantly decrease the NOx conversion between 100 and 300 °C and improve the N2 selectivity, especially above 200 °C. Besides, flue gas compositions reduce the CO oxidation due to the competitive adsorption among them. The XPS data suggested that surface chemical states of spent Mn/Ti catalyst in the presence and absence of CO did not vary obviously, pointing to that the surface chemical states of Mn/Ti catalyst don't account for the decrease in NOx conversion. The transient reactions and in situ DRIFTS experiments suggested that CO can compete with NO to adsorb on Mn/Ti catalyst and it can remarkably restrain NH3 to be adsorbed on weakly acid sites due to that these sites were occupied by carbonate species. This leads to the marked decrease in NOx conversion at low temperature and an increase in N2 selectivity because the amount of NH3 adsorbed on weakly acid sites decreases and it is mainly adsorbed on strong acid sites. In addition, the gaseous CO does not interfere with the reaction of gaseous NO with adsorbed NH3.

Inhibitory effects of typical inert gases on the flame propagation and structures in TiH2 dust clouds

The inhibitory effects of CO2, N2 and Ar on TiH2 dust explosion had been experimentally studied. The results showed that the inhibitory effects of the three inert gases on the flame morphology, propagation velocity and temperature of TiH2 dust explosion were in the order of CO2 > N2 > Ar under the same oxygen concentration. CO2 accelerated the cooling and extinguishing processes of the incomplete burning particles to inhibit the further dehydrogenation and combustion reactions of TiH2 particles. N2 reacted with TiH2 particles and form ternary Ti-O-N solutions on its surface to hinder the binding progress of TiH2 and O2. In the process of Ar dilution, OH radical was adsorbed on the surface of TiH2-x to enhance its surface reactivity. N2 and CO2 mainly inhibited the explosion of TiH2 dust cloud through dilution of O2, cooling and chemical reactions, whereas Ar mainly played the roles of diluting O2 and cooling.

Effects of CH4 and CO on hydrogen embrittlement susceptibility of X80 pipeline steel in hydrogen blended natural gas

The slow strain rate tensile experiments are carried out to investigate the tensile properties of X80 pipeline steel in hydrogen blended natural gas environments with different H2/CH4/CO contents. Mechanical properties and fracture morphologies are further analyzed. The results show that the hydrogen embrittlement susceptibility of X80 steel can be inhibited by the presence of CH4/CO, and the inhibition mechanisms are discussed. When the CH4 contents increase above 20 vol%, the inhibition on hydrogen embrittlement of X80 steel is stabilized. By comparison, the inhibitory effect of CO is more significant.

A Bifunctional Pt/CeO2-Cu1/CeO2 Catalyst System for Isooctane Oxidation under Fully Simulated Engine-Exhaust Condition: Eliminating the Inhibition by CO

Pt-based catalysts, because of their outstanding activity for hydrocarbon oxidation, are widely used in the engine-exhaust aftertreatment system to remove hydrocarbon emissions. However, the CO and NOx present in real engine exhausts compete with hydrocarbons for active Pt sites, and thus inhibit hydrocarbon oxidation. In this work, we evaluated the inhibition effects of CO and NO on isooctane oxidation over a Pt/CeO2 catalyst under the simulated condition of the US DRIVE test protocol (S-GDI, stoichiometric gasoline direct injection). We also leveraged a low-cost single-atom Cu1/CeO2 catalyst, which is highly active for low-temperature CO oxidation, to eliminate the inhibition effect of CO. Specifically, by physically mixing Cu1/CeO2 and Pt/CeO2, all the CO is completely converted below 200 °C under simulated exhaust condition, which helps lower the isooctane oxidation temperature. However, the unconverted NO still strongly suppresses HC oxidation. Possible strategies to address the NO inhibitor were proposed.

Effects of inhibiting astrocytes and BET/BRD4 chromatin reader on spatial memory and synaptic proteins in rats with Alzheimer's disease.

Communication between astrocytes and neurons has a profound effect on the pathophysiology of Alzheimer's disease (AD). Astrocytes regulate homeostasis and increase synaptic plasticity in physiological situations, however, they become activated during the progression of AD. Whether or not these reactions are supportive or detrimental for the central nervous system have not been understood yet. Considering epigenetic regulation of neuroinflammatory genes by chromatin readers, particularly bromodomain and extraterminal domain (BET) family, here we examined the effect of chronic co-inhibition of astrocytes metabolism (with fluorocitrate) and also BRD4 (with JQ1) on cognition deficit at early stages of AD. Forty adult male Wistar rats underwent stereotaxic cannulation for inducing AD by intrahippocampal injection of Aβ1-42 (4μg/8μl/rat). Then animals were divided into five groups of Saline+DMSO, Aβ + saline+DMSO, Aβ + JQ1, Aβ + FC (fluorocitrate), and Aβ + JQ1 + FC and received the related treatments. Two weeks later, spatial memory was recorded by Morris Water Maze (MWM), and the levels of phosphorylated cyclic-AMP response element binding protein (CREB), postsynaptic density 95 (PSD95), synaptophysin (SYP), and tumor necrosis factor-alpha (TNF-α) were measured in the hippocampus by western blotting and RT-qPCR. Administration of JQ1 significantly improved both acquisition and retrieval of spatial memory, which were evident by decreased escape latency and increased total time spent (TTS) in target quadrant, and significant rise in p-CREB, PSD95, and synaptophysin compared with Aβ + saline+DMSO group. In contrast, both groups receiving FC demonstrated memory decline, and reduction in p-CREB, PSD95 and synaptophysin in parallel with increase in TNF-α. Our data indicate that chronic inhibition of BRD4 significantly restores memory impaired by amyloid β partly via CREB signaling and upregulating synaptic proteins of PSD95 and synaptophysin. However, inhibition of astrocytes nullifies the memory-boosting effects of JQ1 and reduces CREB/PSD95/synaptophysin levels in hippocampus.

CO and C3H6 poisoning of hydrogen permeation across Pd77Ag23 alloy membranes: A comparative study with pure palladium

In this work, we compare the poisoning (inhibiting) effects of CO and C3H6 on H2 permeation across Pd77Ag23 and Pd foil membranes under identical conditions to investigate the influence of alloying Pd with Ag on its sensitivity to poisoning by these contaminants. H2 flux measurements show that H2 permeation across Pd77Ag23 is significantly more sensitive to CO poisoning, but less sensitive to C3H6 poisoning, than Pd. CO inhibits H2 permeation across both Pd and Pd77Ag23 primarily by adsorbing on the membrane surfaces—exclusively on Pd atoms—and by blocking H2 dissociative adsorption at these sites. Density functional theory calculations show that CO binds more strongly to the Pd3Ag(111) surface, both bulk-terminated and Pd-terminated, than to the Pd(111) surface. Thus, H2 permeation across Pd77Ag23 is more sensitive to CO poisoning than Pd because there is a higher coverage of CO and fewer available sites for H2 adsorption than on Pd. C3H6 poisoning of H2 permeation across Pd77Ag23 and Pd is much more complex than CO poisoning and involves decomposition of C3H6 and deposition of at least four different carbonaceous species. In contrast to the CO site blocking mechanism, C3H6 poisoning of Pd and Pd77Ag23 is primarily an electronic effect where the carbonaceous deposits modify the electronic structure of the Pd77Ag23 and Pd surfaces making them less active for H2 dissociation. Thus, even though Pd77Ag23 accumulates ∼ 10 × more carbon during C3H6 exposure than Pd, due to the higher carbon solubility of Pd77Ag23, the Pd77Ag23 surface is more resistant to deactivation from carbon deposits than Pd. This work highlights the importance of benchmarking, which is surprisingly rare in the Pd-alloy membrane literature, but is critical for understanding alloying effects.

Combined inhibition of AURKA and HSF1 suppresses proliferation and promotes apoptosis in hepatocellular carcinoma by activating endoplasmic reticulum stress.

In this study we aimed to assess the anti-tumor effect of co-inhibition of Aurora kinase A (AURKA) and heat shock transcription factor 1 (HSF1) on hepatocellular carcinoma (HCC), as well as to explore the mechanism involved. Expression of AURKA and HSF1 in primary HCC tissues and cell lines was detected by immunohistochemistry (IHC), qRT-PCR and Western blotting. AURKA was knocked down in HepG2 and BEL-7402 HCC cells using lentivirus-mediated RNA interference. Next, CCK-8, clone formation, transwell and flow cytometry assays were used to assess their viability, migration, invasion and apoptosis, respectively. The expression of proteins related to cell cycle progression, apoptosis and endoplasmic reticulum stress (ERS) was analyzed using Western blotting. In addition, in vivo tumor growth of HCC cells was assessed using a nude mouse xenograft model, and the resulting tumors were evaluated using HE staining and IHC. Both AURKA and HSF1 were highly expressed in HCC tissues and cells, while being negatively related to HCC prognosis. Knockdown of AURKA significantly inhibited the colony forming and migrating capacities of HCC cells. In addition, we found that treatment with an AURKA inhibitor (Danusertib) led to marked reductions in the proliferation and migration capacities of the HCC cells, and promoted their apoptosis. Notably, combined inhibition of AURKA and HSF1 induced HCC cell apoptosis, while increasing the expression of ERS-associated proteins, including p-eIF2α, ATF4 and CHOP. Finally, we found that co-inhibition of AURKA and HSF1 elicited an excellent in vivo antitumor effect in a HCC mouse model with a relatively low cytotoxicity. Combined inhibition of AURKA and HSF1 shows an excellent anti-tumor effect on HCC cells in vitro and in vivo, which may be mediated by ERS. These findings suggest that both AURKA and HSF1 may serve as targets for HCC treatment.

H2 production by methane steam reforming over Rh/Al2O3 catalyst packed in Cu foams: A strategy for the kinetic investigation in concentrated conditions

The concept of Rh/Al2O3 catalyst pellets packed in highly conductive copper foams has been successfully tested in methane steam reforming showing the beneficial effects of thermal conductivity on the obtainment of gradient-less radial temperature profiles. In this work, the same concept is proposed as a strategy for the lab-scale kinetic investigation under concentrated conditions at ambient pressure; thanks to the homogeneous heating of the catalyst mass across the reactor section and the measurement of axial temperature profiles, well-controlled temperature conditions are obtained, and the experimental investigation can be extended to usually unfeasible conditions of high reactant concentrations, overcoming the typical challenges for the kinetic study. Here, steam reforming experiments were performed with CH4 and H2O feed molar fractions in the ranges of 10−20 % and 40–90 %, respectively. The co-feed of CO and H2 was also investigated. A kinetic scheme was developed that substantially confirmed the main results of previous kinetic investigations in annular micro-reactor, performed under diluted conditions; in particular, the first order dependence of the rate of steam reforming on methane partial pressure, the independence from H2O partial pressure, and the important inhibiting effect of CO were confirmed. The independence of the reaction rate from the H2 co-feed was here demonstrated for the first time. The new experimental campaign allowed to identify more clearly the kinetic dependencies of the water gas shift reaction, positively influenced by H2O partial pressure but scarcely affected by CO partial pressure, which could be also explained based on the inhibiting effect of surface CO coverage. Parameter estimates were obtained by model fit over a wide temperature range (400−850 °C), conveying robustness to the proposed kinetic scheme for future reactor design applications.

Effect of coal particle size on gasification performance of two‐stage entrained‐flow coal gasifier

AbstractTo clarify the effect of coal particle sizes on gasification performance of an advanced two‐stage entrained‐flow coal gasifier for IGCC (integrated gasification combined cycle) application, a comprehensive three‐dimensional numerical model is established by incorporating the shrinking core model combined with the Langmuir‐Hinshelwood kinetic rate expression, which considers the inhibitory effect of CO on char‐CO2 reaction. The flow, temperature, and species distributions were obtained, and the results are consistent with the operating data. Results show that the helical flow and eight recirculation zones in the gasifier improve carbon conversion efficiency through extending the residence time of coal particles. Slow devolatilization of large particles caused by slow heating retards volatiles combustion, and thus char combustion and gasification. As a result, less char gasification and higher gas temperature appear in the injection region of the first stage. Higher inertia of larger particles produces higher slip velocity, which enhances heat transfer and mass diffusion to char particles and increases char consumption rate in diffusion‐limited regions. The regions of high inner wall temperature spread from locations around burners to the whole inner wall of the injection and bottom regions in the first stage with increase of coal particle sizes.

The effect of CO on CO2-char gasification

The effect of CO on the gasification of a Polish coal-derived char was investigated in a fluidised bed from 1123 to 1248 K. Rate expressions developed from Ergun's mechanism or a modified three-step reaction mechanism, coupled with Cylindrical Pore Interpolation Model (CPIM) to account for the intra-particle mass transfer, were developed to predict gasification and the effect of CO. Compared to the Ergun's rate expression, the three-step expression has an extra term for pco, making the inhibition effect of CO more pronounced. The agreement between experimental and numerical results was satisfactory for both models simulating gasification by CO2/N2. Then, when CO (1% or 3%) was intentionally introduced in the feed gas (CO2/N2), the gasification rates significantly decreased. It was found that the model based on Ergun's mechanism over-estimated the gasification rate, while the results from the model with the three-step mechanism agreed with the experimental data.

Inhibition Effect of CO on Hydrogen Permeation Through a Pd/Al2O3 Composite Membrane: A Comprehensive Study on Concentration Polarization and Competitive Adsorption Effect

Palladium membranes have been used for hydrogen purification for a long time due to their infinite selectivity and excellent permeation performance. However, a coexisting impurity gas, like CO, will inhibit the hydrogen permeation flux that results from the concentration polarization (CP) and competitive adsorption inhibition effects. This work aims to investigate the two inhibition effects separately and quantitatively under different temperatures and pressures. Therefore, permeation experiments of H2 (90%)/N2 (10% to 5%)/CO (0% to 5%) mixtures have been carried out at temperatures ranging from 623 to 698 K and H2 partial pressure drops from 30 to 100 kPa. The permeation of H2/N2 is used to study CP because the competitive adsorption of N2 can be ignored. Then, the further H2 flux reduction of xH2/(1-x-z)N2/zCO permeation relative to that of xH2/(1-x)N2 permeation can be attributed to the competitive adsorption of CO. The experimental results show that the CP effect would be enhanced by increasing temperature and pressure, while the CO competitive adsorption effect would be depressed. Meanwhile, the CO inhibition effect generally becomes smaller when the membrane thickness becomes thicker. Based on the results in this work, operation conditions are suggested to be at a higher temperature and higher pressure for a thicker Pd membrane in consideration of increasing the H2 permeation flux and reducing the CO adsorption effect. The experimental and calculation methods used in this work can provide a new way for investigating the inhibition effect on hydrogen permeation caused by other nonpermeable gases like CO2, Ar, or H2O.

PGM based catalysts for exhaust-gas after-treatment under typical diesel, gasoline and gas engine conditions with focus on methane and formaldehyde oxidation

The HC and CO oxidation activity of Pt/Al2O3, Pd/Al2O3 and Pd-Pt/Al2O3 catalysts was compared under three exhaust-gas model conditions typical for stoichiometric gasoline as well as lean burn diesel by means of temperature programed conversion tests on laboratory test benches. In order to understand the differences in emission reduction performance, the impact of gas mixture composition was systematically studied with a particular focus on methane and formaldehyde conversion.The catalysts used in this study were prepared by incipient wetness impregnation of Al2O3 followed by washcoating on ceramic honeycombs, and were pre-treated in an equal manner before each activity test.Distinct differences in pollutant conversion were observed over the three catalysts under the investigated conditions. Pd-based monometallic and bimetallic catalysts revealed the lowest temperature for CH4 oxidation (<450 °C) under lean conditions, being lower under lean Diesel than Compressed Natural Gas (CNG) conditions. The reason for this behavior seems to be the higher water concentration in the CNG gas mixture. Furthermore, it was found that the presence of HCs shifts the conversion of methane to higher temperatures, most probably due to produced water during combustion of the HCs. Pt/Al2O3 on the other hand only converts methane at temperatures above 500 °C but no sensitivity to water or the amount of additional HCs was observed. The lowest light-out temperature for formaldehyde oxidation in excess of oxygen was measured on Pt/Al2O3 with full conversion below 125 °C. While this was the case for a model gas mixture of HCHO, H2O and O2, under simulated lean burn gas engine conditions, formaldehyde is oxidized at lower temperature on Pd-Pt/Al2O3 than on Pt/Al2O3 due to the strong inhibiting effect of CO on Pt-particles.Under stoichiometric gasoline conditions, Pt had the highest activity for methane oxidation whereas Pd/Al2O3 and Pd-Pt/Al2O3 hardly convert methane below 500 °C. Unsaturated HCs and CO on the other hand were converted at lower temperature over Pd containing monometallic and bimetallic catalysts in comparison to Pt/Al2O3, showing once again the multiple and complex effects generated by variations in exhaust gas mixture and catalyst composition.

The correlation between coal char structure and reactivity at rapid heating condition in TGA and heating stage microscope

The coal pyrolysis and char gasification process have been widely studied in TGA at a low heating rate, which is far lower than the heating rate when coal particle enters into the boiler and gasifier. In this work, the isothermal CO2 gasification reactivity of in-situ coal chars was performed in rapid heating TGA and a heating stage microscope. The char structure parameters determined by XRD and Raman were combined to describe the char reactivity at the same temperature. Results showed that maximum weight loss rate (DTGmax) of raw coal evidently increased and the corresponding maximum rate temperature raised with the increasing of heating rate during pyrolysis. Nonetheless, the heating rate had slightly effect on gasification reactivity of in-situ char samples when it exceeded 50 K/min. Considering the physical meaning and universality of the coal char structure and gasification reactivity fitting, the XRD and Raman structural parameters were combined to describe the gasification reactivity. The new method for coal char reactivity under rapid heating rate is established, Rs=0.174+43.14d002,aLc,a+3.58ID3×ID4IG2. Furthermore, a visually heating stage microscope was also applied for determining the in-situ char reactivity through image analyzing. The gasification process of in-situ coal char particles fits the shrinking particle pattern at the original and midterm stages. However, the shrinking particle pattern changed into the shrinking core pattern at high carbon conversion. Moreover, the CO inhibition effect and inter-particle interaction account for the difference of gasification reactivity by rapid heating TGA and heating stage microscope.