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A hybrid montmorillonite (Mt)-rich/chitosan composite (MCC) with high adsorption performance was synthesized for the decolorization of water used in the joss paper process. The performance was reported in terms of the dye removal. The composite expressed higher performance than chitosan or Mt-rich clay, respectively. The optimum condition for complete dye removal was achieved when using at least 0.6 g of the composite over a wide pH range (3–10) and initial dye concentration (10–100 mg L−1). The composite showed good reusability without the requirement of regeneration, adsorbing the dye completely for up to eight successive cycles of adsorption (>1.33 gdye gMCC−1). Thermodynamic analyses revealed the degree of spontaneity and the endothermic adsorption process. From the isotherm studies, the Koble–Corrigan isotherm model fitted very well to the experimental data, revealing that the composite had a heterogeneous surface with various active sites to adsorb the dye molecules. This also evidenced the synergistic electrostatic attraction and hydrophobic interaction between the dye and the composite. The pseudo-second-order model best explained the kinetic rate of adsorption. From evaluation of the adsorption process using the Webber and Morris equation and Boyd model, the rate-limiting step consisted of film diffusion and intra-particle diffusion. [ABSTRACT FROM AUTHOR]

CO 2 capture performance of bifunctional activated bleaching earth (ABE) was investigated at atmospheric pressure. The sorbents were characterized by means of X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), Caron-Hydrogen-Nitrogen analysis (CHN), Fourier transform infrared (FT-IR) and thermal gravimetric analysis (TGA). The CO 2 capacity was enhanced via basic-modification and monoethanolamine (MEA) loading of the ABE sorbent to obtain a bifunctional surface property. Here, basic-modified calcined ABE with a 30 wt.% MEA loading (SAB-30) showed the highest CO 2 capture capacity, but this was decreased with excess MEA loading (> 30 wt.%). At a 10% ( V / V ) initial CO 2 concentration feed, the maximum capacity of SAB-30 increased from 2.71 mmol/g at 30°C (without adding moisture to the feed) to 3.3 mmol/g at 50°C when adding 10% ( V / V ) moisture to the feed. Increasing the moisture concentration further reduced the maximum CO 2 capacity due to the blocking effect of the excess moisture on the sorbent surface. However, SAB-30 could completely capture CO 2 even in a 100% ( V / V ) initial CO 2 concentration feed. A maximum CO 2 capacity of 5.7 mmol/g for SAB-30 was achieved at 30°C. Varying the ratio of sorbent weight to total flow rate of the gas stream had no discernible effect on the equilibrium CO 2 capture capacity. Avrami's equation and Toth's isotherm model provided a good fitting for the data and suggested the presence of more than one reaction pathway in the CO 2 capture process and the heterogeneous adsorption surface of SAB-30. Thermodynamics studies revealed that CO 2 capture on the bifunctional SAB-30 is feasible, spontaneous and exothermic in nature. [ABSTRACT FROM AUTHOR]

Abstract: The catalytic performance for the preferential oxidation of CO over a 1% (w/w) PtAu/CeO2–ZnO catalyst prepared by co-precipitation was investigated using a full 2k factorial design with three central points and a 95% confidence interval, in order to screen for the importance of the operating temperature (°C) and the H2O and CO2 contents (%) in the simulated reformate gas on the CO conversion and selectivity. The catalyst was characterized by TEM, BET, XRD and FTIR. The temperature and CO2 content had a significant influence on the conversion, whilst the selectivity depended on the temperature only. A face-centered central composite design was then used to evaluate the optimal conditions by simultaneously considering the maximal conversion, selectivity and constraints of the composition of realistic reformate gas. The difference in the estimated response and the experimental one was within ±2% and ±3% for routing simulated and realistic reformate gases, respectively. [Copyright &y& Elsevier]

Abstract: The catalytic performance of Cu–Zn–Fe composite-oxide catalysts prepared by the urea–nitrate combustion (UNC) method for the WGS reaction was investigated in this study. The catalysts were characterized by means of X-ray diffraction (XRD), X-ray fluorescence (XRF), and the Brunauer–Emmet–Teller (BET) method. In order to reduce the total number of experiments to achieve the optimal condition of CO conversion in the reaction and to reveal the interactions among the factors, two sets of statistical designs of experiments were carried-out. Initially, a full 25 factorial design with three central points was done. Increased CO conversion is obtained when increasing the H2O concentration and the O2 concentration in the influent, the W/F ratio, and the reaction temperature. On the other hand, the CO conversion is decreased with increasing Cu/(Cu+Zn+Fe) molar ratio, increasing interaction between O2 concentration in the influent and reaction temperature, and increasing interaction between Cu/(Cu+Zn+Fe) molar ratio and reaction temperature. In order to continue the optimization, the application of the face-centered central composite design (FCCCD) falling under response surface methods was done. Two independent factors were selected from the five main factors. Based on the important variabilities in the conversion, the O2 concentration in the feedstream and the reaction temperature were then selected to achieve the optimal conditions for CO conversion. The maximum CO conversion of 0.87 was obtained when adding 0.10% O2 and 30% H2O in the feedstream at a reaction temperature of 333°C, a W/F ratio of 0.24gscm−3, and a Cu/(Cu+Zn+Fe) molar ratio of 0.30. After optimizing CO conversion by statistical design of the experiments, validation of the model was performed. The estimated values of the statistical response surface analysis were well fitted with the observed ones. This elucidated that the response surface methodology with appropriate experimental design can be effectively applied to the optimization of CO conversion in the WGS reaction. [Copyright &y& Elsevier]

Abstract: Single- and double-stage catalytic preferential CO oxidation (CO-PrOx) over-Fe2O3-promoted CuO–CeO2 in a H2-rich stream has been investigated in this work. The catalyst was prepared by the urea-nitrate combustion method and was characterized by X-ray diffractometer (XRD), X-ray fluorescence (XRF), Brunauer–Emmet–Teller (BET), transmission electron microscope (TEM), and scanning electron microscope (SEM). The catalytic activity tests were carried out in the temperature range of 50–225°C under atmospheric pressure. The results of the single-stage reaction indicated that complete CO oxidation was obtained when operating at a O2/CO ratio of 1.5, W/F ratio of 0.36gs/cm3, and at a reaction temperature of 175°C. At these conditions, H2 consumption in the oxidation was estimated at 58.4%. Applying the same conditions to the double-stage reaction, complete CO oxidation was found and H2 consumption in the oxidation was reduced about 4.9%. When decreasing the double-stage reaction temperature to 150°C, the results elucidated that CO could be converted to CO2 completely while H2 consumption in the oxidation was further reduced to 33.5%. A temperature blocking 22 factorial design has been used to describe the importance of the factors influencing the catalytic activity. The factorial design was according to the experimental results. When adding CO2 and H2O in feed, reduction of CO conversion for single- and double-stage reaction is obtained due to a blocking of CO2 and H2O at a catalytic active site. Comparing CO conversion obtained when operating with/without CO2 and H2O in feed for single- and double-stage reaction, less reduction is achieved when operating in double-stage reaction. [Copyright &y& Elsevier]

Abstract: The objective of this paper was to study a preferential oxidation (PROX) of carbon monoxide over monometallic catalysts including Pt, Au and Pt–Au bimetallic catalyst supported on ceria in hydrogen-rich reformate. Single step sol–gel method (SSG) and impregnation on sol–gel method (ISG) were chosen for the preparation of the catalysts. The characteristics of these catalysts were investigated by X-ray diffractometer (XRD), Brunauer–Emmet–Teller (BET) method, transmission electron microscope (TEM), scanning electron microscope (SEM) and temperature-programmed reduction (TPR). The XRD patterns of the catalysts showed only the peaks of ceria crystallite and no metal peak appeared. From TEM images, the active components were seen to be dispersed throughout the ceria support. The TPR patterns of PtAu/CeO2 catalyst prepared by SSG showed the reduction peaks were within a low temperature range and therefore, the catalysts prepared by SSG exhibited excellent catalytic activity for preferential oxidation of CO. Bimetallic Pt–Au catalyst improved the activity (90% conversion and 50% selectivity at 90°C) because of the formation of a new phase. When the metal content of (1:1) PtAu/CeO2 catalyst prepared by SSG was increased, the CO conversion did not change much while the selectivity decreased in the low temperature range (50–90°C). The CO conversion increased with increasing W/F ratio. The presence of CO2 and H2O had a negative effect on CO conversion and selectivity due to blocking of carbonate and water on active sites. [Copyright &y& Elsevier]

Abstract: Platinum–Palladium supported on ceria catalysts has been studied for preferential oxidation of CO in the presence of hydrogen. The catalysts were prepared by impregnation method using different supports. The catalytic activity tests were performed using a fixed bed reactor in the temperature range of atmospheric pressure. Effects of support, ratio of Pt–Pd, O2 concentration water vapor concentration, CO2 concentration, and the combination of H2O and CO2 in the feed stream on the catalytic performance of Pt–Pd/CeO2 catalysts were also investigated. The experimental results showed that 1% (1:7) Pt–Pd/CeO2 (sol–gel) exhibited higher activity than other catalysts examined. Water vapor in the feed substantially increased the activity of the catalysts, whereas CO2 in the feed stream drastically decreased the activity of the catalysts. When both H2O and CO2 were added in the feed stream, the positive effect of H2O is more pronounced than the negative effect of CO2. [Copyright &y& Elsevier]

The synthesis of carbon nanoparticles (Cn) and oxygen-doped nanocarbon (OCn) was successfully done through a one-step synthesis by the solution plasma process (SPP). The Cn and OCn were nitrogen-doped by nitridation under an ammonia atmosphere at 800 °C for 2 h to yield NCn and NOCn, respectively, for carbon dioxide (CO2) adsorption. The NOCn exhibited the highest specific surface area (~570 m2 g−1) and highest CO2 adsorption capacity (1.63 mmol g−1 at 25 °C) among the synthesized samples. The primary nitrogen species on the surface of NOCn were pyridinic-N and pyrrolic-N. The synergistic effect of microporosity and nitrogen functionality on the NOCn surface played an essential role in CO2 adsorption enhancement. From the thermodynamic viewpoint, the CO2 adsorption on NOCn was physisorption, exothermic, and spontaneous. The NOCn showed a more negative enthalpy of adsorption, indicating its stronger interaction for CO2 on the surface, and hence, the higher adsorption capacity. The CO2 adsorption on NOCn over the whole pressure range at 25–55 °C best fitted the Toth model, suggesting monolayer adsorption on the heterogeneous surface. In addition, NOCn expressed a higher selective CO2 adsorption than Cn and so was a good candidate for multicycle adsorption. [ABSTRACT FROM AUTHOR]

Catalytic activities of Ce–Mg promoted Cu/Al 2 O 3 catalysts via methanol steam reforming was investigated in terms of the methanol conversion level, carbon monoxide selectivity and hydrogen yield. The factors chosen were the reaction temperature, copper content, Mg/(Ce + Mg) weight-percentage and steam to carbon ratios. The catalysts were prepared by co-precipitation and characterized by means of XRD, BET, H 2 -TPR, and FESEM. The Ce–Mg bi-promoter catalysts gave higher performance due to magnesium penetration into the cerium structure causing oxygen vacancy defects on the ceria. A response-surface-model was then designed to optimize the condition at a 95% confidence interval for complete methanol conversion to a high H 2 yield with a low CO content, and revealed an optimal copper level of 46–50 wt%, Mg/(Ce + Mg) of 16.2–18.0%, temperature of 245–250 °C and S/C ratio of 1.74–1.80. No deactivation of the Cu 0.5 Ce 0.25 Mg 0.05 /Al catalyst was observed during a 72-h stability test. [ABSTRACT FROM AUTHOR]

In this work, three preparation methods (an incipient wetness impregnation on Mg–Al hydrotalcite, co-precipitation (CP) and double-step-co-precipitation) were employed to prepare Cu-based Mg–Al layered double oxides for the water–gas shift reaction. The Cu 0.15 Mg 3 Al-CP300 catalyst formed by CP had a higher reducing the CO level with a lower H 2 consumption. Varying Mg/Al molar ratios from 1 to 4, the Cu 0.15 Mg 3 Al-CP300 showed the lowest reduction temperature and highest catalytic activity. Increasing the calcination temperature from 300 °C to 500 °C resulted in a higher CO conversion level. Increasing the Cu/(Cu + Mg + Al) molar ratio from 0.15 to 0.30 reduced the crystallite sizes of the periclase phase with a markedly enhanced catalytic activity at temperatures below 350 °C. No marked deactivation of the Cu 0.30 Mg 3 Al-CP500 catalyst was found over a period test even though adding CO 2 in the feed. After regeneration, the catalytic activity of the spent catalyst was the same as the fresh catalyst. [ABSTRACT FROM AUTHOR]

Abstract: The catalytic performance for steam reforming of methanol over 5wt.% Au/CuO–CeO2 catalysts prepared by deposition–precipitation was investigated using a statistical set of experiments in order to optimize the methanol conversion with minimal carbon monoxide (CO) selectivity. The operating temperature, steam to methanol (S/M) ratio, liquid feed rate and the catalyst weight to He flow rate (W/F) ratio, were evaluated with a full 24 factorial design experimental matrix with four central points. The liquid feed rate displayed a much greater influence on the response, masking the importance of the other factors. At a fixed low liquid feed rate, only the operating temperature had a significant influence on the methanol conversion, whilst this plus the S/M ratio and their interaction influenced the CO selectivity. A central composite rotatable design was then used to approximate the optimal conditions by simultaneously considering the methanol conversion and CO selectivity. The optimum theoretical conditions were found to lie within an operating temperature of ~295°C to ~307°C and an S/M ratio of ~1.82 to 2.00 (at a liquid feed rate of 1cm3 h−1 and a W/F ratio of 0.17gscm−3), in close agreement with the experimental results. [Copyright &y& Elsevier]

Abstract: A series of Pt–Au catalysts prepared by co-precipitation (CP) and single step sol-gel (SSG) methods was investigated for selective CO oxidation. The characteristics of the prepared catalysts were determined by XRD, BET surface area, SEM, H2-TPR, chemisorption analysis, and FTIR. The simulated reformatted gas consisted of 1% CO, 1% O2, 0% to 10% H2O, 0–20% CO2, and 40% H2 in He balance. The operating temperature range was varied from 50°C to 190°C at atmospheric pressure. The experimental results elucidated that the catalytic preparation method had a significant effect on the catalyst characteristics and its activity. The catalytic performance over PtAu/Ce1Zn1O2 prepared by co-precipitation was higher than that of PtAu/CeO2 and PtAu/ZnO because of the incorporation of Ce4+ ions and the Zn2+ ions in the lattice. To encourage better catalytic performance, the catalysts should be calcined at 500°C for 5h and pretreated in a H2 atmosphere. The CO conversion for the single- and double-stage reaction was reduced when adding water vapor and CO2 to the feedstream; the water vapor and CO2 molecules compete for the adsorption with CO on the active sites of the catalysts. During the deactivation test for 60h, the CO conversion and selectivity are maintained. [Copyright &y& Elsevier]

In the present paper,- promoted CuO– catalysts prepared by urea–nitrate combustion (UNC) and single-step citrate (SSC) method have been studied for the low-temperature selective CO oxidation in the presence of excess hydrogen. The characteristic of Cu–Ce–Fe–O composite-oxide catalysts have been determined by X-ray diffraction (XRD), X-ray fluorescence (XRF), Brunauer–Emmett–Teller (BET) surface area measurements, transmission electron microscope (TEM) and temperature-programmed reduction (TPR). The characteristic results reveal that the combination of Ce and Fe oxide in the catalysts can lead to the improvement of surface area and pore volume. Urea/nitrate ratio has a significant influence in the BET specific area and crystallite size. TEM micrograph of these nano-catalysts shows that CuO, , and- disperse well all over the catalyst. The catalytic performances for selective CO oxidation are strongly influenced by pretreatment. Cu active species react with and virtually form CuO active species on the catalyst which promote the selective CO oxidation activities. Adding more amount of CuO content into the lattice, it promotes the interaction between CuO and . Further adding Cu content to the catalyst, the active site for selective CO oxidation is lost due to aggregation of the dispersed CuO active species. Promoting of- in Cu–Ce–O catalyst exhibits catalytic activities. Therefore,- promotes the active species of Cu–Ce–Fe–O catalysts to obtain catalytic activities. The catalytic activity tests also reveal that the performances of catalyst prepared by the UNC are higher than those prepared by SSC due to the smaller crystallite size of-. catalyst prepared by the UNC gives the highest activity. The decrease of the catalytic activity obtained in the presence of in feed stream is lower than that obtained in the presence of in the feed stream. [Copyright &y& Elsevier]