Fatima Maria Zanon Zotin

Thermal stability of Y zeolites containing different rare earth cations

In this paper, the influence of both nature and content of rare earth (RE) cations on the thermal stability and textural properties of NaY type zeolite was studied by differential thermal analysis (DTA) and specific surface area measurements. It was observed that, like RE elements from the light group, the introduction of the elements from the heavy group causes an increase in the thermal stability of the zeolite, increasing its structure collapse temperature, which is independent of the RE nature introduced for high exchange level. Moreover, micropore surface area decreases as a function of the rare earth exchange level, as an indication that the presence of bulky hydrated rare earth cations reduces the accessibility to micropores.

Rietveld refinement and solid state NMR study of Nd-, Sm-, Gd-, and Dy-containing Y zeolites

Abstract Na-Y zeolites ion exchanged with rare earth cations (Nd3+, Sm3+, Gd3+, Dy3+) were studied by X-ray diffraction in order to locate the rare earth cations in the zeolite framework and the resulting changes in its structural properties. The results indicate that the rare earth cations dealuminate the framework differently. This is observed as a decrease in the values of the unit cell parameters, a0. This systematic decrease in a0 is related to the rare earth ionic radius and its coordination to the oxygen framework. The correlation between the Si/Al ratio obtained from the Fichtner-Schmittler equation and the ionic radius of the rare earth cations reveals that smaller ionic radii gives higher dealumination and smaller a0. This is related to hydrolysis constant cation. Samples treated with Dy3+ cations show a higher level of dealumination than those treated with the other cations (Sm3+, Gd3+, Nd3+). In order to characterize the dealumination process 29 Si and 27 Al magic angle spinning NMR measurements were attempted. Except for the Sm3+ treated sample, the Nd3+, Gd3+, Dy3+ samples could not have their tetrahedral and octahedral aluminum signal detected due to the high concentration of the paramagnetic ions with large effective number of Bohr magnetons.

Conversion of natural gas to higher valued products : light olefins production from methanol over ZSM-5 zeolites

Abstract The conversion of methanol to light olefins catalyzed by ZSM-5 zeolites with different SAR or impregnated with phosphorus was investigated. The increase in SAR reduced the density and the strength of the acid sites, favoring both the catalytic stability and the production of light olefins, particularly propene. The incorporation of phosphorous also reduced the density and the strength of the acid sites of HZSM-5 zeolite; besides, BET specific area and microporous volume linearly decreased. The increase of P content decreased the activity and improved the stability. The highest propene/ethene molar ratio was observed for the sample with 4 wt. of P.

SnSO4as catalyst for simultaneous transesterification and esterification of acid soybean oil.

Biodiesel is an alternative biodegradable and non-toxic biofuel produced from renewable resources. Industrially, it is produced by catalytic transesterification of refined vegetable oil with methanol or ethanol. Biodiesel production costs can be reduced by using non-refined feedstocks whose market prices are lower than those of refined vegetable oils. This work studied the use of tin(II) sulfate (SnSO4), as catalyst for the simultaneous transesterification and esterification of model acid oil containing high levels of free fatty acids. The influence of experimental parameters, catalyst leaching as well as its reusability was investigated. For a model feedstock containing 70 wt. % of free fatty acids (oleic acid), the highest biodiesel yield (92%) was obtained at 100 oC, under autogenous pressure, using 5 wt. % of SnSO4 in excess of ethanol after 3 h of reaction. The catalyst was reused ten times without significant decrease in biodiesel yield.

Emissions of Criteria and Non-Criteria Pollutants by a Flex-Fuel Motorcycle

While criteria pollutants have established emission limits for motorcycles in Brazil, aldehydes limits have not been established and conclusive studies have not been found in the existing literature, despite the growing number of motorcycles using flex fuel in Brazil. This work presents results for the emissions of criteria pollutants, such as carbon monoxide, hydrocarbons and nitrogen oxides, acetaldehyde and formaldehyde. The motorcycle was tested with 22, 61, and 100% of ethanol in gasoline blends. Fourier transform infrared (FTIR) and high performance liquid chromatography (HPLC) were used to determine the pre- and post-catalytic converter emissions. Aldehyde emissions directly increased with the ethanol content in the fuel blend. The tailpipe aldehyde emissions for 22, 61, and 100% of ethanol in gasoline were 3.9, 8.5, and 38.8 mg km-1, respectively. These results demonstrated that aldehyde emissions in motorcycles are not negligible, and higher emissions are observed during the cold phase of the engine.

Influence of Metal Oxides Impregnated on Silica-Alumina in the Removal of Sulphur and Nitrogen Compounds from a Hydrotreated Diesel Fuel Stream

The environmental legislation of many countries imposes severe restrictions on the emissions of gaseous pollutants, including NOx and SOx. Efficient alternatives for the removal of nitrogen and sulphur contaminants are required to obtain increasingly cleaner fuels. In this regard, adsorption is economically promising, because it requires less energy than the traditional hydrotreating processes due to mild conditions of temperature and pressure required. The objective of this study was to evaluate the influence of nickel, cerium, molybdenum and cobalt oxides impregnated on silica–alumina in removing nitrogen and sulphur compounds from a hydrotreated diesel. The incorporation of metal oxides increased the density of acid sites and promoted the removal of nitrogen and sulphur compounds, especially the one impregnated with molybdenum oxide. The influence of molybdenum oxide loading was also studied. It was observed that this synthesis parameter affected acid sites density and contaminant removal.

O efeito da desativação térmica nas propriedades oxirredutoras e na atividade catalítica de catalisadores CZ e Pd-CZ

Automotive catalyst, using in Brazil since 1992, is a essential technology for vehicular emissions control. Noble metals are the active phase of these catalysts, and cerium zirconium mixed oxides (CZ), responsibles for the oxygen storage capacity (OSC), one of the most important aspect for the operational performance of the catalyst. In this context, the oxireduction properties analysis of CZ and Pd/CZ (palladium supported in CZ) system are the objective of this study, as well as, the impact of the thermal aging in the OSC. Aging consisted of treatments at 900 or 1200 °C, for 12 or 36 h, in oxidizing condition.

Esterification of high acidity vegetable oil catalyzed by tin-based catalysts with different sulfate contents: contribution of homogeneous catalysis

Abstract Biodiesel production costs can be significantly reduced by using nonrefined feedstock. Sulfated solid catalysts have been proposed for producing biodiesel from acid oils by esterification reactions. Nevertheless, leaching of sulfate species to the reaction medium may occur, but often it is not considered. In this article, a commercial tin sulfate (SnSO4) was used as a catalyst for the esterification of a feedstock with high content of free fatty acid in order to assess the contribution of the homogeneous catalysis in different situations. SnSO4 was calcined at different temperatures (300, 400, 500 and 700 °C) and converted into SnO2 after calcination at temperatures higher than 300 °C. Homogeneous catalysis seems possible to occur with all of the catalysts, but it was clearly observed for the uncalcined catalyst (SnSO4) and for that calcined at 300 °C (SnSO4(300)). For these catalysts, an important leaching of the sulfate species was confirmed. Higher conversions were obtained with the uncalcined SnSO4. Reactions at the same conditions using sulfuric acid as catalyst at concentrations of 0.1% were performed and confirmed conversions higher than 80%. Heterogeneous catalysis plays a significant role only with the catalyst that present the highest specific surface areas and acidity (SnSO4(400)). As some small amount of sulfate species is retained in the structure or surface of the calcined catalysts (even after calcination at 700 °C), we cannot exclude the possibility that these species are also leached during reaction. Thus, a possible contamination of biodiesel through the use of sulfated catalysts cannot be ruled out.

A Study on Regulated and Unregulated Emissions from a Set of Five Gasoline and Ethanol Fueled Motorcycles

The objective of this study was to investigate regulated and unregulated emissions from four motorcycles fueled with gasoline and one flex fuel motorcycle fueled with three different gasoline/ethanol blends. Regulated emissions (CO, HC, and NOx) have been measured with 7000 series Horiba benches. Unregulated emissions (formaldehyde, acetaldehyde and ammonia) were measured with a SESAM series AVL Fourier Transform Infrared Analyzer (FTIR). Tests were conducted over a chassis dynamometer according to the 97/24/EC drive cycle. Pre and post catalytic (pre-cat and post-cat) converter data were collected. The results showed that catalytic converters designed to reduce regulated emissions from gasoline-powered motorcycles produce ammonia emissions as a by-product of catalytic conversion. The results regarding pre-cat and post-cat conversion aldehydes were analyzed and discussed. The main conclusion was that catalytic conversion reduces aldehydes and regulated emissions on the tailpipe but increases ammonia emission levels significantly.