Alinda Samsuri

Studies of Fe Metal Carburization by Carbon Monoxide Using XRD and TPR Techniques

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.

Influence of cerium additive on the reduction behaviour of tungsten oxide under carbon monoxide atmosphere

The reduction of pure WO3 and Ce/WO3 has been studied by using temperature programmed reduction (TPR), X-ray diffraction (XRD), and FESEM analysis. The reduction behavior were examined by non-isothermal reduction up to 900 oC then continued with isothermal reduction at 900 oC for 45 min under (40% v/v) carbon monoxide in nitrogen (CO in N2) atmosphere. The TPR results shows that reduction peak of Ce/WO3 were shifts to lower temperature as compared with to the pure WO3. In addition, TPR results indicate that addition with ceria give better reducibility compared to pure WO3. Based on the characterization of the reduction products after hold 45 min using XRD, pure WO3 were completely converted to WO2 and W metal phases. While, after addition of Ce to the WO3, the reduction was enhanced to W phases and some suboxide W5O14 and W3O5 with no WO2 phase remained and carbide observed. This is associated to the formation of alloy complex Ce2WO6 which gave remarkable effect to the reduction.

Effect of Noble Metal Silver on the Reduction Behaviour of Molybdenum Oxide Using Carbon Monoxide

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.

Reduction of Molybdenum Trioxide by Using Hydrogen

Metallic molybdenum was synthesized through reduction of molybdenum trioxide (MoO3) by using hydrogen as a reducing agent. The reduction behavior of MoO3 were investigated by using temperature programmed reduction (TPR). The reduced phases were characterized by X-ray diffraction spectroscopy (XRD). The XRD results indicate that the reduction of MoO3 proceed in two steps reduction (MoO3 → MoO2 → Mo) with formation of intermediate phases of Mo4O11 during first step of reduction. However, the TPR results showed only one broad peak that correspond to all reduction step that was merge into one peak. It seem that, increasing the temperature cause the rapid reduction that correlated with thermodynamic consideration data that show the formation of metallic molybdenum is become feasible by increasing the temperature.

Study on the Reduction Behaviour of Nickel Doped Molybdenum Trioxide by Using Carbon Monoxide as Reductant

The reduction behaviour of molybdenum trioxide, (MoO3) and nickel (Ni) doped MoO3 using carbon monoxide (CO) as reductant was investigated by temperature programmed reduction (TPR) and characterized by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) and transmission electron microscope analysis (TEM). The reduction characteristics of MoO3 to MoO2 were examined up to temperature 700 oC and continued with isothermal reduction by 20 vol. % CO in nitrogen. The studies show that, TPR spectra of doped MoO3 slightly shift to a lower temperature as compared to the undoped MoO3 which begins at 630 oC. The interaction between nickel and molybdenum ions leads to this slightly decrease of the reduction temperature of Ni doped MoO3. Analysis using XRD confirmed, the addition of Ni enhances the reducibility of MoO3. By addition of Ni, complete reduction to MoO2 were take place at only 30 minutes starting of the isothermal reduction at 700 °C. Whereas, for undoped MoO3 it takes about 60 minutes to completely reduce to MoO2. However, excess of CO brings to the formation of molybdenum carbide (Mo2C). Based on the results, it is confirmed addition of Ni to MoO3 has a remarkable influence by reducing temperature in the reduction process. The ability to enhance the reducibility involved in MoO3 may be associated to the presence of nickel molybdate, NiMoO4 compound.