Papers by Keyword: Carbon Monoxide

Abstract: Herein, a one-pot solvothermal method was employed to synthesize Fe-doped carbon nanodots using waste expanded polystyrene as the carbon source and ferric chloride hexahydrate for iron doping. Three synthesis parameters-reaction time, temperature, and dopant weight-were optimized using Response Surface Methodology (RSM) based on Box-Behnken design, with relative fluorescence (FL) intensity as the response. Model validation showed a percentage error of 0.66% between replication experiments and predicted maximum intensity, confirming the model's reliability to maximize FL intensity in synthesis. FTIR spectroscopy identified the presence of a medium peak at 538 cm^-¹, associated with Fe-O stretching, indicating successful Fe doping, supported by EDX analysis. TEM analysis confirmed the nanosized properties of Fe-CDs, with an average particle size of 1.84 nm, and HR-TEM revealed an onion-like structure with a lattice spacing of 0.369 nm, and the presence of amorphous shells, suggesting structural heterogeneity. The synthesized doped and undoped CDs were employed in a drop-casting method to produce films that were used for carbon monoxide detection. Results displayed significant effects of operating temperature and gas concentration on the gas response of Fe-CDs and CDs films on resistance. The significant statistical difference in gas response between Fe-CDs and undoped CDs suggests that Fe doping enhances electron mobility, due to more pronounced changes in resistivity, yielding higher responses to carbon monoxide gas.

Abstract: Emissions are substances that enter the air, whether or not they have the potential as pollutants. Emission gases can have adverse effects on the health of living beings, especially humans, and can contribute to an increase in the Earth's temperature. Therefore, separation efforts are needed to minimize the negative impacts caused by them. Adsorption method was categorized as absorption, cryogenic distillation, and membrane. Although there were shortcomings in adsorbing emission gases through the method, it remained a promising approach. Adsorption was recognized for its economic viability, technological effectiveness, thermally stability, corrosion resistance, high load capacity, and tunable surface properties. However, adsorption materials were categorized as porous carbon, zeolites, metal-organic frameworks (MOFs), porous polymers, and porous silica. A significant limitation of the method was its susceptibility to decreased capacity in the presence of water vapor. The analysis results showed that porous silica became a superior adsorption material due to its high porosity, which facilitated rapid gas diffusion. To enhance selectivity and adjust pore size, material modifications, particularly silica, became necessary. This showed that surface modification for silicasupported the improvements in selectivity and pore size.

Abstract: Electrical appliances have been suspected to contribute harmful pollutants to the atmosphere hence reducing the quality of outdoor ambient air, this suspicion has given rise to environmentalists carrying out research to determine whether these appliances are pollutant free or not. In the course of this research, carbon monoxide and hydrogen sulfide emissions were assessed from the outdoor part of window air-conditioners. Eight window air-conditioners of four prominent brands labeled as A1, A2, A3 and A4 were identified. The air from the outdoor part of the window air-conditioner was monitored for one hour with readings taken at two minutes intervals using the MSA Altair Xcell 5X Gas Sensor. Raw data of results were obtained for the eight window air-conditioners and they were analysed to obtain the daily, weekly, monthly and yearly contributions of carbon monoxide and hydrogen sulfide to the atmosphere. The yearly contributions of carbon monoxide for each brand was 15360.00 ppm for A1, 15360.00 ppm for A2, 7680.00 ppm for A3 and 5760.00 ppm for A4 while the hydrogen sulfide contributions for each of the brands was 3840.00 ppm for A1, 1920.00 ppm for A2, 0.00 ppm for A3 and 0.00 ppm for A4. From the results obtained, A1window air conditioner had the highest contribution to both carbon monoxide and hydrogen sulfide concentrations in the atmosphere.

Abstract: Temperature-programmed reduction (TPR) was used to observe the chemical reduction behaviour of molybdenum trioxide (MoO₃) and zirconia (Zr)-doped MoO₃ catalyst by using carbon monoxide (CO) as the reductant. The characterisation of catalysts was performed by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) and transmission electron microscopy (TEM) analyses. The reduction performance were examined up to 700°C and reduction was continued for 60 min at 700°C in a stream of 20 vol. % CO in nitrogen. The TPR profile showed that the doped MoO­₃ catalyst was slightly moved to a higher temperature (580°C) as compared to the undoped MoO₃ catalyst, which began at around 550°C. The interaction between zirconia and molybdenum ions in doped MoO₃ catalyst led to an increase in the reduction temperature. According to characterisation of the reduction products by using XRD, it revealed that the reduction behaviour of pure MoO₃ to MoO₂ by CO reductant involved two reduction stages with the formation of Mo₄O₁₁ as the intermediate product. Meanwhile, MoO₃ catalyst doped with zirconia caused a delay in the reduction process and was proven by the presence of Mo₄O₁₁ species at the end of reactions. Physical analysis by using BET showed a slight increase in surface area of 3% Zr-MoO₃ from 6.85 m²/g to 7.24 m²/g. As for TEM analysis, black tiny spots located around MoO₃ particles revealed that the zirconia was successfully intercalated into MoO₃ particles. This confirmed that formation of intermetallic between Zr-MoO₃ catalyst will give new chemical and physical properties which has a remarkable chemical effect by disturbing the reduction progression of MoO₃ catalyst.

Abstract: The reduction behaviour of cobalt doped with nickel oxide and undoped nickel oxide (NiO) by hydrogen (H₂) in nitrogen (20%, v/v) and carbon monoxide (CO) in nitrogen (40%, v/v) atmospheres have been investigated by temperature programmed reduction (TPR). The phases formed of partially and completely reduced samples were characterized by X-ray diffraction spectroscopy (XRD). TPR results indicate that the reduction of Co doped and undoped nickel oxide in both reductants proceed in one step reduction (NiO → Ni) without intermediate. TPR results also suggested that by adding Co metal into NiO, the reduction to metallic Ni by both reductant gaseous give different intensity of the peak. The reduction process of Co and undoped NiO become faster when H₂ was used as a reductant. Furthermore, in H₂ atmosphere, Co-NiO give complete reduction to metallic Ni at 700 °C. Meanwhile, XRD analysis indicated that NiO without Co composed better crystallite phases of NiO with higher intensity.

Abstract: The chemical reduction behavior of NiO under various carbon monoxide (CO) concentration as a reduction agent was studied. The NiO and Ni⁰ transformations were identified using TPR and XRD techniques. It was shown that, the completed reduction occurred at temperature 700 °C for 40% CO and 900 °C for 10% and 20% CO. During the chemical reduction process, nickel carbide was formed at temperature 400 °C and another formation of carbon amorphous appeared at 500 °C and proved through diffraction of XRD pattern at 2θ: 22.86 under 20% CO/N₂ and and 2θ: 26.15 under 40% CO/N₂. The interpretation of physisorption data showed that the pore size after reduction with various CO concentration comprised as microporous size in the range of 6-40 nm. Therefore, CO as a mild reduction agent stated that as the concentration of CO high, the rate of reduction affected and formed a very crystalline of Ni⁰ particle.

Abstract: Smoking can cause various ongoing complications in the body. One of the dangerous components of cigarette smoke is carbon monoxide which is one of the most toxic pollutants produced from cigarette gas emissions. Reducing levels in the air can utilize the adsorbent in the form of activated carbon which has the capacity and selectivity to these pollutants. Activated carbon was prepared from corn stalks which were activated by KOH at 750 °C based on previous research. The activated carbon which produced have Iodine number equal to 602 mg/g and SBET reached 599 m²/g. To strengthen the adsorption power, the results of activated carbon will be modified by impregnation of NiO metal. Metal impregnation varied with loading percentage 0.5, 1 and 2%. Modified activated carbons were then characterized by the Iodine Number test, BET test, SEM test, and EDX test. Each of the modified activated carbon will be tested for the capacity and selectivity of adsorption of CO and cigarette smoke. The best modified activated carbon is Mod 0.5% with Iodine number equal to 844 mg/g and SBET reached 839 m²/g. The best adsorption ability is obtained by 0.5% NiO-modified activated carbon which able to reduce CO gas levels by 29.9% and for cigarette smoke reaching 82.16%.

Abstract: The possibility of reduction of chromium and iron from complex oxides by gaseous carbon monoxide and solid carbon was investigated. The chromium ore concentrates of Kempirsai and Aganozero deposits used in present study had different ratio of iron and chromium content. The Reduction in CO gas atmosphere did not result in reduction of chromium and iron from spinels; however, it resulted in reduction of fines from the drying apparatus, where the particles of coke presented along with the particles of the Kempersai chromite. At the same time, iron and nickel were reduced from the silicates of the gangue minerals. In the samples mixed with solid carbon a continuous layer of carbides formed on the surface of the spinel grains. The formation of a continuous shell retarded and practically stopped the reduction process. The further development of reduction was possible after destruction of the shell that occurred as a result of smelting of the carbides and silicides mixture that constitute the shell.

Abstract: This study was undertaken to investigate the effect of carburization of metallic Fe by (20%,v/v) carbon monoxide (CO). Carburization of Fe by carbon monoxide was examined by using temperature-programmed reduction (TPR), X-Ray powder diffractometry (XRD) and Carbon Hydrogen Nitrogen Sulfur (CHNS) technique. Based on a thermodynamic calculation, the free energy Gibb’s value to produce carbon is-8.08 kcal/mol which are favorable. However, production of iron carbide from the same reaction, the free energy Gibb’s value is +9.24 kcal/mol which is not feasible. From the XRD results, shows that after carburization of Fe, the peak appears only for Fe but there is a broad peak between 20 – 30°. The peak might be indicated as carbon in amorphous form. This finding is supported by the percent of carbon content in CHNS analysis which are increasing when the temperature is increased. This shows that after carburization the carbon content is increasing with increasing in temperature due to carbon deposited on metallic iron. In this research, three different temperatures were used which are 300°C, 500°C and 700°C.

Abstract: The reduction behavior of silver doped molybdenum trioxide (Ag/MoO₃) and undoped MoO₃ by using carbon monoxide, CO were investigated by using temperature programmed reduction (TPR). The reduced phases were characterized by X-ray diffraction (XRD). In the carbon monoxide atmosphere, the XRD results indicated that the reduction of Ag/MoO₃ and undoped MoO₃ to MoO₂ phase proceed in two steps (MoO₃ → Mo₄O₁₁ → MoO₂) with Mo₄O₁₁ present as an intermediate state. A complete reduction to metallic molybdenum for both samples cannot occurred since in an excess CO atmosphere, MoO₂ is promoted to form carbides rather than reduce to metallic molybdenum. Nevertheless, addition of silver to modified MoO₃ shows the better reducibility compared to MoO₃ alone by lower the reducing temperature of MoO₃. TPR results show that the reduction peak of Ag/MoO₃ is slightly shifts to lower temperature as compared with the undoped MoO₃. The interaction between silver and molybdenum ions leads to this slightly decrease of the reduction temperature of silver doped MoO₃. It can be seen that doping with silver has a remarkable influence in the reduction process of the MoO₃ catalyst.