abbas taeb

In the present study, the applicability of a bimetallic Pt-Sn/Al2O3 in propane dehydrogenation with different promoters, namely, Ca, Mg, and incorporation of Mg-K and Ca-K was studied. The catalysts were prepared by the sequential impregnation of γ-alumina support and characterized by TPD, SEM, XRD, and UV analysis. The propane conversion and propylene selectivity were evaluated under representative industrial conditions. The results showed that the Pt-Sn-Mg-K/γ-Al2O3 catalyst had a better performance in terms of propane conversion and propylene selectivity and yield, due to the partially neutralized and synergistic effect of Mg and K (probably by increasing the platinum dispersion and preventing side reaction and coke formation). TPD results also showed the effects of all these promoters (Ca, Mg, Ca-K and Mg-K) on the reduction of acidic sites of the catalyst, which are favorable sites for cracking reaction and coke formation. In the meantime, Ca is more effective in reducing strong acidic sites, but also Mg is more effective in reducing weak and medium-strength acid sites. Therefore, alkaline-earth metals and also using them with potassium could reduce side reaction products and lead to a more selective reaction to propylene, and improve catalyst performance compared to industrial catalysts.

In this research study, methanol synthesis catalysts were manufactured with various mole ratios of metal carbonates (zinc, copper and aluminum carbonate) and ammonium hydrogen carbonate via a green solid-state method that employed a ball mill apparatus. Some parameters for the catalyst preparation, such as Al mole percent, Cu/Zn mole ratio, rotations milling speeds and aging time, were optimized to obtain the maximum catalyst activity. The prepared catalysts were compared with the best quality industrial catalyst under the same temperature and pressure condition in a titanium tabular fixed bed reactor. This novel method has many advantages in comparison to the conventional method. The main advantage of the solid-state method is that the methanol synthesis catalyst can be produced without using solvent. Furthermore, this new method reduces operating costs due to the elimination of the filtration and washing steps. Methanol synthesis catalytic activity was maximized at an optimized mole ratio of Cu/Zn of 1.9234 and an Al mole percent of 8 at the maximum grinding speed (450 rpm) during an aging time of 30 min, which showed higher activity (240 gCH3OH/kg cat.h) in comparison with an industrial catalyst sample (218 gCH3OH/kg cat.h). The production of a green catalyst, which requires less water and results in higher catalyst activity, can be widely used for methanol synthesis catalytic applications.

In this paper, the deactivation of Pd-Ag/Al2O3 catalyst was investigated in acetylene selective hydrogenation. Therefore, the commercial catalyst performance was used in Godinez kinetic model. The deactivation kinetic constant of catalyst was calculated by appropriate deactivation order. The activity of main and side reaction was evaluated during time on stream.
If first or second deactivation kinetic order was assumed, the activity lost was 90% and 1%, respectively. Since lower order was increased deactivation, so the second order deactivation model was proposed. As well the effect of temperature on the activity lost by using this model in acetylene selective hydrogenation was investigated.