Wet Reaction Conditions Research Articles

Impact of gas treatment of CuAl-LDH on NO reduction by CO under oxidative conditions

Removal of NO from cement-type industrial flue gases can be achieved by its catalytic reduction with CO (NO-Selective Catalytic Reduction) over a suitable noble metal free catalyst. Cu-Al mixed metal oxides derived from parent Layer-Double Hydroxide (LDH) after thermal decomposition under different pre-treatment gas conditions: inert (He), oxidising (air), reducing gas (1 %CO in He) at 500 °C have been used to achieve it. Additionally, a mixed oxide was prepared by the treatment of the LDH under 100 % CO2 at 500 °C, a novel method for synthesis of mixed oxides is reported in this study. Different characterization techniques (N2-Physisorption, XRD, H2-TPR, TGA and FTIR) were used to investigate physico-chemical properties of CuAl mixed oxide materials to determine their role on the catalytic performances. It was observed that gas treatments did not affect the crystal size (∼20 nm) of the corresponding Cu-Al mixed oxide except for CO/He treatment, where highly crystalline phases of Cu(0) were formed predominantly instead of CuO as in other Cu-Al mixed oxide samples. Further, the catalytic tests were performed using a simulated industrial gas composition from a cement industry consisting of CO (0.13 vol%), CO2 (20 vol%), NO (475 ppm), O2 (8.8 vol%) and without or with H2O (8.2 vol%), the rest being balanced by He. Both NO reduction and oxidation reactions occurred in the presence of water over CuAl-CO/He, CuAl-He, CuAl-CO2 and CuAl-air samples. However, only CuAl-CO2 was the only sample active for the NO reduction (N2 selectivity was 83 %) in the absence of water in the reaction feed. Moreover, under wet reaction conditions, CuAl-CO2 sample showed similar catalytic activity like its CuAl-air and CuAl-He counterparts (NO reduction yield of 13–16 % at peak temperatures of 420–400 °C). The plausible formation of monodentate and/or bidentate carbonates onto the material during the CO2-treatment at 500 °C (inferred from TGA and FTIR measurements) was proposed to promote NO reduction activity in the absence of water while under wet conditions, these carbonate species supposedly reacted with the water species and formed in active formiate species. This resulted in a mixed oxide with material properties similar to that of the CuAl-air and CuAl-He samples and therefore, led to similar catalytic performance. Finally, our study showcased the effect of novel CO2 treatment for CuAl-LDH precursor in improving the performances for NO reduction.

Improving the solubility of myofibrillar proteins in water by destroying and suppressing myosin molecular assembly via glycation

Filamentous myosin is a self-assembling polymer that prevents myofibrillar proteins (MPs) from functioning in low ionic strength media. This study was aimed at investigating if glycation has the potential to improve the solubility of MPs in water. MPs were conjugated with monosaccharides, oligosaccharides, and polysaccharides under wet reaction conditions at 37 °C. The conjugation was verified by SDS-PAGE, FT-IR and amino acid analyses. MPs conjugated with dextran (DX) exhibited a higher solubility and dispersion stability in water, which corresponded to smaller particle size and more uniform distribution (P < 0.05). According to secondary and tertiary structure analyses, the loss of α-helix structures and unfolding of the MPs appear to be the main reasons for MP solubilization. Additionally, according to the zeta-potential, confocal laser scanning microscopy, and atomic force microscopy observation results, glycation can provide electrostatic repulsion or steric hindrance to disintegrate existing filamentous myosin aggregates and inhibit further self-assembly behavior.

Deep oxidation of propane over WO3 - promoted Pt/BN catalysts: The critical role of Pt - WO3 interface

The addition of WO3 in the Pt/BN catalyst significantly promotes the performance for deep oxidation of propane. A catalyst with a W content of 7 wt.% (1 Pt-7 W/BN) has the highest activity (a reaction rate of 367.1 μmol gPt-1 s-1 at 220 °C), which is 7-fold as high as that on the 1 Pt/BN (a reaction rate of 52.4 μmol gPt-1 s-1). The W-promoted catalysts are stable under dry and wet reaction conditions, showing promising potential in practical applications. Based on detailed kinetics and in-situ diffuse reflectance infrared spectroscopy results, the Pt-WO3 interfacial sites serve as new active sites which are responsible for the improved activity. The facile reaction between propane adsorbed on Pt atom and surface hydroxyl groups on adjacent WOx accelerates the cleavage of the C-H bond, which is the kinetically essential step in this reaction system.

Phase transformation and oxygen vacancies in Pd/ZrO2 for complete methane oxidation under lean conditions

A series of ZrO2 materials were prepared by calcining ZrO2·xH2O at temperatures from 600 to 900 °C. The oxide materials were used to prepare Pd/ZrO2 catalysts coated on the monolith. Under lean conditions, the monolithic catalysts were tested for complete oxidation of CH4 in the presence and absence of water. In process of the preparation of supports, the ratio of monoclinic ZrO2 (m-ZrO2) to tetragonal ZrO2 (t-ZrO2) increased with calcination temperature. Strong interaction between palladium and ZrO2 further induced the transformation of t-ZrO2 to m-ZrO2 when supporting Pd on ZrO2. Phase transformation in samples including ZrO2 supports and Pd/ZrO2 catalysts was accompanied by an increase in the concentration of surface oxygen vacancies, improving the mobility of oxygen species over the samples. It was found that the Pd catalyst using ZrO2 calcined at 900 °C as the support had the highest oxygen vacancy concentration among the four catalysts as synthesized. Under dry reaction conditions, this catalyst showed considerably higher activity in methane oxidation promoted by oxygen vacancies. However, under wet reaction conditions (10 vol% H2O), water poisoned the surface-active sites for all the catalysts. The promoting effect of increasing oxygen vacancies on the activity of CH4 oxidation was thus weakened significantly by the water poisoning, resulting in slight differences in activity among the catalysts.

Relationship between surface functional properties and flexibility of soy protein isolate-glucose conjugates

Flexibility had been determined to be an important indicator governing the surface properties of proteins and it was identified using the protease digestion method. In this study, the Maillard reaction between glucose and soy protein isolate was reacted under wet reaction conditions to obtain different flexible protein molecules. The effects of different reaction times (0, 2, 3, 4, 5, 6 h) on the flexibility, emulsifying and foaming properties of conjugates compared with soy protein isolate were studied and the correlation between them was analyzed by SPSS 20 Statistical Software. At the same time, the other structural indexes were also measured. These indexes changes responsible for the variation of flexibility were given detailed analysis. The results showed that emulsifying activity and emulsion stability were positively correlated with flexibility, the correlation coefficients were 0.976 (P < 0.01) and 0.968 (P < 0.01), respectively. Meanwhile, good correlations were obtained between foaming capability, foam stability and flexibility with correlation coefficients of 0.954 (P < 0.01), 0.754 (P < 0.05), respectively. In this study, the concept of flexibility was introduced into the effect of the Maillard reaction on the functional properties of soy protein isolate, which was of great significance.

Functional properties of Maillard reaction products of rice protein hydrolysates with mono-, oligo- and polysaccharides

The Maillard reaction was carried out under wet reaction conditions using rice protein product from limited hydrolysis to conjugate with various mono-, oligo- and polysaccharides. The Maillard reaction products (MRPs) prepared with rice protein hydrolysates at 5% degree (hydrolysed by Protease N) and dextran T20 (20 min at 100 °C) showed the greatest improvement in functionality. The solubility, emulsification activity (EA), and emulsification stability (ES) of the MRPs increased by factors of 3.5, 5.3 and 7.3 times, respectively as compared to MRPs formed with native rice proteins and dextran T20. Amino acid analysis indicated that lysine and arginine decreased significantly in the MRPs. Formation of MRPs reduced the surface hydrophobicity, which was in agreement with the change of solubility. However, further decreasing of the surface hydrophobicity resulted in lower EA and ES during the late stage of the reaction. Fluorescence analysis suggested that formation of late stage MRPs occurred after 20 min of the Maillard reaction. The molecular weight distributions showed that the functional properties of MRPs and the mechanisms of formation were affected by the peptide chain length.

Characteristics and functional properties of wheat germ protein glycated with saccharides through Maillard reaction

SummaryThe Maillard reaction (MR) under wet reaction conditions with several common saccharides, such as xylose, glucose, lactose, dextran and maltodextrin, were applied to improve the functional properties of wheat germ protein (WGP). The MR products (MRPs) prepared with dextran at pH 11.0 heated at 90 °C in 2% aqueous dispersions heating for 20 min showed better solubility and emulsifying properties. The fluorescence intensity analysis proved the MR occurred, and thinner sheet MRPs were observed by scanning electron microscope (SEM). The relative contents of Cys, Lys and Arg were decreased, which could reduce the chance of protein aggregation through ‐S‐S bonds. Circular dichroism (CD) spectrum expressed the difference in the secondary structures between WGP and MRPs, which may make MRPs show better functional properties than WGP. These results suggested that MR with dextran under wet reaction conditions can be a promising way to improve functional properties of WGP.

Pt/K–βAl 2O 3 solid electrolyte cell as a “smart electrochemical catalyst” for the effective removal of NO x under wet reaction conditions

This study has shown that the phenomenon of electrochemical promotion can be used to activate a metal catalyst for the selective catalytic reduction of nitrogen oxides (NO x ) in the presence of water in the feed. The application of different potentials optimized the catalytic performance of the Pt catalyst-working electrode at each reaction temperature range. In addition, the measurement of the open circuit voltage in the cell gave useful information on the competitive adsorption between the reactants. Thus, very interestingly, the combined use of the Pt/K–βAl 2O 3 cell as a sensor and as an electrochemical catalyst allows anticipating and optimizing the catalytic behaviour of the system under changing reaction conditions, such as those found in the exhaust of an engine. Finally, characterization of the cell by Cyclic Voltammetry along with NO x analysis and XRD provided useful information about the nature of the promoter species under wet reaction conditions.

Two forms of apatite deposited during mineralization of the hen tendon

Old hen tendon provides a model suitable for the study of calcification in an extracellular matrix. In the present study, we observed the mineralizing substances of hen tendon by scanning electron microscopy of plasma-osmium-coated specimens and by transmission electron microscopy of those processed by a plasma-polymerization film replica method. The mineralizing front area revealed a number of elliptical particles fused to each other and forming rod-like structures oriented parallel to collagen fibrils. The area of advanced mineralization possessed non-mineralizing cavities, in which tendon cells were likely to exist. At this site, we recognized a second form of mineral structure, one in which the crystals had a scale-like morphology and were deposited onto the major first-form mineral component. This crystal form was similar to hydroxyapatite synthesized under wet reaction conditions. These findings strongly suggest that the second form of mineral formed independent of collagen fibrils existed together with the predominant, collagen-dependent form of mineral. We speculate that cell membranes and an extremely slow mineralization process may contribute to the formation of this form of mineral during the mineralization process in the hen tendon.

Promotional Effect of Reduction Treatments of PtIn(ferrierite) on Its Activity in the SCR of NO with Methane. Kinetics and Novel Characterization Studies

K−ferrierite co-exchanged with Pt and In (PtIn(ferrierite)), with different pretreatments, is characterized by EXAFS (extended X-ray absorption fine structure), TDPAC (time differential perturbed angular correlation), TPR (temperature-programmed reduction), and hydrogen chemisorption. The presence of different In and Pt species is correlated with activity and selectivity during the NO selective reduction (SCR) with CH4 in the presence of excess oxygen. The reduction of PtIn(ferrierite) catalyst under controlled conditions (hydrogen at 350 or 500 °C) strongly promotes the activity of the said catalyst. The reduction at 350 °C results in the formation of small Pt° crystals, stable under wet reaction conditions, which probably favor both the oxidation of NO to NO2 and the adsorption of the said species, thus increasing the overall reaction rate. The reduction at 500 °C further increases the reaction rate because it promotes the formation of new (InO)+ active species from the reduction of In2O3 at the catalys...

EXAFS, TDPAC and TPR characterization of PtInFerrierite: The role of surface species in the SCR of NOx with CH4

Ferrierite exchanged with In and with Pt, In (InFerrierite and PtInFerrierite) is characterized by extended X-ray absorption fine structure (EXAFS), time differential perturbed angular correlation (TDPAC) and temperature-programmed reduction (TPR). The presence of different In and Pt species is correlated with activity and selectivity during the NO selective reduction (SCR) with CH4 in the presence of excess oxygen. Both catalysts are active and selective for the said reaction. When a dry feed is used, both monometallic and bimetallic catalysts behave similarly. However, when water is present in the feed, while InFerrierite loses activity in the whole temperature range, PtInFerrierite increases its activity at temperatures above 450°C. EXAFS characterization indicates that in PtInFerrierite only a fraction of Pt is at exchange positions, the remaining fractions adopting the form of PtO2 crystals located in the outer-surface of the zeolitic structure. When this bimetallic catalyst is treated under wet reaction conditions, the formation of small metal clusters due to the reduction of PtO2 crystals occurs. Thus, the increase in activity could be due to a catalytic effect of Pt metal clusters on the NO oxidation reaction (NO+1/2O2→NO2).TDPAC characterization indicates the presence of two In species both in the monometallic and in the bimetallic catalysts: In2O3 and (InO)+Z− (In at exchange positions), the latter being the active In species for the reaction under study. TPR results also suggest the presence of highly dispersed non-crystalline In oxide species not bonded to the zeolite matrix. Neither EXAFS results nor TDPAC characterization show the presence of intermetallic Pt–In species. The results of this work prove that EXAFS and TDPAC techniques, combined with TPR and activity measurements, are powerful tools for the characterization of bimetallic catalysts.

Promoting Effect of Pt on CoZeolites upon the SCR of NOx

The promoting effect of Pt incorporated to Cozeolites (viz., mordenite, ferrierite, ZSM-5, and Y-zeolites) on the selective catalytic reduction (SCR) of NOxwith CH4was studied. The PtCo bimetallic zeolites showed higher NO to N2conversion and selectivity than the monometallic ones under all reaction conditions tested. The Y-zeolite based samples which were inactive both in the mono and bimetallic samples constituted an exception. The promoting effect was a function of the zeolite type and, for a given zeolite, of the pretreatment of the catalysts and Pt loading. The best results were obtained for a 0.5% Pt loading after reduction of the samples in H2flow for 1 h at 350°C. Under dry conditions Pt0.5Co2.0mordenite converted 60% of NO to N2at GHSV of 100,000 h−1with a CH4/NO ratio of 3 at 500°C and 2% oxygen in the feed stream. The specific activities given as molecules of NO converted per total metal atoms per second at 500°C were 16.5 10−4s−1for Pt0.5Co2.0Fer, 13 10−4s−1for Pt0.5Co2.0Mor, and 4.33 10−4s−1for Pt0.5Co2.0ZSM-5. The incorporation of Pt also shows a positive effect in the stability of the samples under wet reaction conditions. The XPS results revealed that in the calcined samples most of the Co2+and Pt2+was located at exchange positions. After reduction no changes in the binding energies (B.E.) were observed in samples with low Pt loading. For higher contents (viz., 1 to 5 wt%) the B.E. characteristics of Co° and Pt°, as well as Co2+and Pt2+, were detected. No evidence of alloy or intermetallic compounds at the surface level was observed. The incorporation of Pt also promoted the Co reducibility in the zeolitic matrix. The greater reducibility and a shift of the maxima in the temperature-programmed reduction profiles suggest a Pt-Co interaction inside of the zeolitic channels. The solid that the reacting mixture initially “sees” has Co° and Pt° metallic particles highly dispersed in the zeolitic matrix, together with Co2+. Some Pt2+and protons generated during reduction also appeared. Such species remained after reaction but some reorganization occurred. In order to get an efficient catalysts for nitric oxide abatement it is necessary for such species to be in intimate contact. A synergetic effect among the different sites could be responsible for the high activity of the bimetallic zeolites.

Preparation and X‐ray crystal structure analysis of cis‐2, 4‐bis(2, 4, 6‐tri‐t‐butylphenyl)‐1, 2, 4‐oxadiphosphetane 2, 4‐disulfide and cis/trans isomerization of the corresponding 1, 2, 4‐thiadiphosphetane derivative

Abstract1,3‐Bis(2,4,6‐tri‐t‐butylphenyl)‐1,3‐diphosphaallene (1) reacted with elemental sulfur under wet reaction conditions to give cis‐ and trans‐2,4‐bis(2,4,6‐tri‐t‐butylphenyl)‐1,2,4‐thiadiphosphetane 2,4‐disulfide (cis‐2 and trans‐2) and cis‐2,4‐bis(2,4,6‐tri‐t‐butylphenyl)‐1,2,4‐oxadiphosphetane 2,4‐disulfide (cis‐3). The structure of cis‐3 was determined by X‐ray crystallography, and the cis/trans isomerization of 2 was studied.

Reduction at 300 K of NO by CO over supported platinum catalysts

Removal of NO from cement-type industrial flue gases can be achieved by its catalytic reduction with CO (NO-Selective Catalytic Reduction) over a suitable noble metal free catalyst. Cu-Al mixed metal oxides derived from parent Layer-Double Hydroxide (LDH) after thermal decomposition under different pre-treatment gas conditions: inert (He), oxidising (air), reducing gas (1 %CO in He) at 500 °C have been used to achieve it. Additionally, a mixed oxide was prepared by the treatment of the LDH under 100 % CO2 at 500 °C, a novel method for synthesis of mixed oxides is reported in this study. Different characterization techniques (N2-Physisorption, XRD, H2-TPR, TGA and FTIR) were used to investigate physico-chemical properties of CuAl mixed oxide materials to determine their role on the catalytic performances. It was observed that gas treatments did not affect the crystal size (∼20 nm) of the corresponding Cu-Al mixed oxide except for CO/He treatment, where highly crystalline phases of Cu(0) were formed predominantly instead of CuO as in other Cu-Al mixed oxide samples. Further, the catalytic tests were performed using a simulated industrial gas composition from a cement industry consisting of CO (0.13 vol%), CO2 (20 vol%), NO (475 ppm), O2 (8.8 vol%) and without or with H2O (8.2 vol%), the rest being balanced by He. Both NO reduction and oxidation reactions occurred in the presence of water over CuAl-CO/He, CuAl-He, CuAl-CO2 and CuAl-air samples. However, only CuAl-CO2 was the only sample active for the NO reduction (N2 selectivity was 83 %) in the absence of water in the reaction feed. Moreover, under wet reaction conditions, CuAl-CO2 sample showed similar catalytic activity like its CuAl-air and CuAl-He counterparts (NO reduction yield of 13–16 % at peak temperatures of 420–400 °C). The plausible formation of monodentate and/or bidentate carbonates onto the material during the CO2-treatment at 500 °C (inferred from TGA and FTIR measurements) was proposed to promote NO reduction activity in the absence of water while under wet conditions, these carbonate species supposedly reacted with the water species and formed in active formiate species. This resulted in a mixed oxide with material properties similar to that of the CuAl-air and CuAl-He samples and therefore, led to similar catalytic performance. Finally, our study showcased the effect of novel CO2 treatment for CuAl-LDH precursor in improving the performances for NO reduction.