Abstract
Over the last decade, due to the increase of energy demand and lower cost of bio-ethanol production, the conversion of bio-ethanol to valuable products such as light olefins, paraffins and aromatics have been received considerable attention. From the previous result, it was found that tin oxide doped on SAPO-34 was discovered to have properties that enhance the formation of cooking gas and larger hydrocarbons. However, during the preparation, tin oxide doped on SAPO-34 cannot be made pure as a single oxide of tin; therefore, the outcomes from bio-ethanol were influenced by the oxidation states of tin. The aim of this work was therefore to examine the oxidation states of tin oxide doped on previously-tested SAPO-34support, and study their effects on products. Metallic Sn- and SnO2- doped on SAPO-34 were employed as model catalysts in order to investigate the influences of Sn0 and Sn+4 oxidation states on the products from bio-ethanol dehydration. The results were compared with those obtained from the tin-oxide-doped SAPO-34 catalyst previously tested. The loading percentage of tin oxides was fixed at 7 wt%, and the catalysts were characterized by using SAA, XRD, XRF and, mainly, XPS. The reaction was carried out in an isothermal fixed bed reactor at atmospheric pressure 400 °C and at WHSV of 0.5 h-1. The product sampling was taken at 1 hour of time-on-stream. The gaseous products were analyzed by using an online- GC while the liquid products needed a SIMDIST-GC and a GC-TOFMS to identify petroleum fractions and hydrocarbon species, respectively. It was found that from XPS spectra, tin oxides on the previously-testedcatalyst were found to be in the form of Sn–OH and SnO2. After the catalytic test, tin oxide doped on SAPO-34 contained mixed valences of Sn0 and Sn+4, which affect the product distribution of both gas and liquid. The liquid product was distributed in gasoline range, and comprised, mainly, of benzene andoxygenate compounds. From the result, it was also observed that Sn+4 seems to contribute in the production of oxygenate compounds; whereas, metallic tin contributes on benzene formation.
