Erol Seker

Transesterification of Nannochloropsis oculata microalga’s lipid to biodiesel on Al2O3 supported CaO and MgO catalysts

In this study, we present the activities of Al(2)O(3) supported CaO and MgO catalysts in the transesterification of lipid of yellow green microalgae, Nannochloropsis oculata, as a function of methanol amount and the CaO and MgO loadings at 50 degrees C. We found that pure CaO and MgO were not active and CaO/Al(2)O(3) catalyst among all the mixed oxide catalysts showed the highest activity. Not only the basic site density but also the basic strength is important to achieve the high biodiesel yield. Biodiesel yield over 80 wt.% CaO/Al(2)O(3) catalyst increased to 97.5% from 23% when methanol/lipid molar ratio was 30.

Nitric oxide reduction by propene over silver/alumina and silver–gold/alumina catalysts: effect of preparation methods

Abstract The activities of alumina supported silver catalysts prepared by co-precipitation, impregnation and single step sol–gel methods were studied for selective NO x reduction by propene in the presence of oxygen. Catalysts prepared by the sol–gel method were found to be the most active catalysts for selective reduction of NO x with almost 100% selectivity to N 2 . Catalysts prepared by the co-precipitation technique had poor activity. While the maximum activities of the sol–gel and impregnation catalysts were comparable under certain conditions, the silver loading of the sol–gel catalysts could be increased to 5% without adversely affecting activity. Increased silver loading resulted in a catalyst that was more active at higher space velocities and had a broader activity window. The sol–gel catalysts also had better performance in the presence of water vapor.

High-throughput screening of nanoparticle catalysts made by flame spray pyrolysis as hydrocarbon/NO oxidation catalysts.

We describe here the use of liquid-feed flame spray pyrolysis (LF-FSP) to produce high surface area, nonporous, mixed-metal oxide nanopowders that were subsequently subjected to high-throughput screening to assess a set of materials for deNO(x) catalysis and hydrocarbon combustion. We were able to easily screen some 40 LF-FSP produced materials. LF-FSP produces nanopowders that very often consist of kinetic rather than thermodynamic phases. Such materials are difficult to access or are completely inaccessible via traditional catalyst preparation methods. Indeed, our studies identified a set of Ce(1-x)Zr(x)O(2) and Al(2)O(3)-Ce(1-x)Zr(x)O(2) nanopowders that offer surprisingly good activities for both NO(x) reduction and propane/propene oxidation both in high-throughput screening and in continuous flow catalytic studies. All of these catalysts offer activities comparable to traditional Pt/Al(2)O(3) catalysts but without Pt. Thus, although Pt-free, they are quite active for several extremely important emission control reactions, especially considering that these are only first generation materials. Indeed, efforts to dope the active catalysts with Pt actually led to lower catalytic activities. Thus the potential exists to completely change the materials used in emission control devices, especially for high-temperature reactions as these materials have already been exposed to 1500 degrees C; however, much research must be done before this potential is verified.

NO reduction by urea under lean conditions over alumina supported catalysts

We prepared Pt on alumina and Au on alumina catalysts using a single step sol–gel process and traditional techniques, such as impregnation and deposition–precipitation. The activity of these catalysts was tested for NO x reduction with aqueous urea solutions under oxidizing conditions. Our results show that when a bubbler was used to feed urea and water, catalysts prepared by the sol–gel process had better performance than the catalysts prepared with impregnation and deposition–precipitation methods. The NOx conversion changed almost linearly over Au on alumina catalysts regardless of preparation techniques but over the single step sol–gel synthesized Pt on alumina catalyst (Pt-SG) a typical dome shape of the conversion versus temperature curve was observed. Oxygen in the feed increased the conversion activity and the presence of SO2 did not have an adverse effect on the activity of Pt-SG and the single step sol–gel Au on alumina (Au-SG) and the impregnation Au on sol–gel alumina (Au-IMP-SG) catalysts.

Transesterification of sunflower oil on single step sol–gel made Al2O3 supported CaO catalysts: Effect of basic strength and basicity on turnover frequency

The activities of single step sol-gel made calcium oxide on alumina catalysts were studied as a function of CaO loading, methanol/oil molar ratio and the amount of the catalyst in the transesterification of sunflower oil at 50°C. Also, the turnover frequency (TOF) of the catalysts was calculated to better understand the relationship between the basicity/basic strength and the catalytic activity. From volcano curve (TOF vs. basic strength), it was found that under 50°C and methanol/oil molar ratio of 9, 60% CaO/Al(2)O(3) had the highest turnover frequency, 0.028s(-1), whereas 85% CaO/Al(2)O(3) showed the highest biodiesel yield, ∼96.6%, but TOF obtained on it was 0.012s(-1). It seemed that 60% CaO catalyst had the proper basic strength to obtain the highest TOF.