Pure and Al-doped ZnO obtained by the modified Pechini method applied in ethanolic transesterification of cottonseed oil

Abstract

Pure zinc oxide (ZnO) and 5% Al-doped ZnO (ZNAL) were synthesized using the modified Pechini method and characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF), Raman spectroscopy, infrared spectroscopy and UV-visible spectroscopy. XRF confirmed the theoretical stoichiometry, while XRD and Raman spectroscopy indicated that Al 3+ was incorporated into the ZnO wurtzite lattice with no secondary phases, leading to a decrease in the band gap value and to a meaningful increase of the Lewis basic sites. Pure and doped ZnO were used as catalysts in the ethylic transesterification of cottonseed oil using a factorial design to determine the best synthesis conditions. Oil conversion into biodiesel was evaluated by viscosity measurements and 1 H NMR spectroscopy. The results analyzed by factorial design indicated that the catalyst type and temperature were the determinant factors in the conversion indices. The highest basicity of the ZNAL lead to a significant increase of the catalytic potential, reaching a reduction of the oil viscosity next to 71% at 130 °C and greater than 85% at 200 °C.

Doubly Coated, Organic–Inorganic Paraffin Phase Change Materials: Zinc Oxide Coating of Hermetically Encapsulated Paraffins

“…However, homogeneous nucleation and growth of zinc hydroxide was predominant, and nonspecific deposition outside the microcapsules took place (Figure c). For similar thermal stability reasons, the Pechini route was not attempted, though zinc oxide formation by the Pechini route has been reported . Therefore, we reverted to the hydrogen peroxide sol–gel process involving the deposition of zinc peroxide as a first stage.…”

“…Coating of capsules of paraffins by metal and metalloid oxides is not an easy task. Whereas the low temperature, thin film coating of large flat surfaces by spray‐, dip‐, spin‐, and spread‐coating and related thin film processing is relatively straightforward nowadays, the coating of particulates is, by and large, dominated by (hydro‐ and solvo‐) thermal treatments and variants of the Pechini process which are both incompatible with thin film formation on microencapsulated paraffinic cores . We stipulated that hydrogen peroxide sol–gel processing is an alternative coating pathway that should be explored, though, as outlined below, its application to coating of microencapsulated materials was less straightforward than anticipated.…”

Insights into the effect of halide enriched ZnO synthesized using tetrabutylammonium halides toward photocatalytic degradation of Rhodamine 6G

“…The peak at 338 cm À1 could be assigned to the second-order Raman spectrum originating from the zone boundary phonons 3E2H-E2L. [45][46][47] The peak observed at 444 cm À1 labeled as E2 (high) represents the characteristic Raman active optical phonon mode. This peak is intense in ZnO-X samples which could be due to stronger interactions between Zn and halide ions.…”

Avaliação do tratamento térmico no catalisador magnético Ni0,5Zn0,5Fe2O4 e sua atividade catalítica na produção de biodiesel por transesterificação e esterificação simultânea do óleo de fritura

“…Recentes pesquisas relataram que as nanopartículas têm grande área de superfície e área de transferência de massa elevada, critérios ideais para um suporte de catálise [18,19]. O uso de catalisadores sólidos nas reações de transesterificação e esterificação para a obtenção de biodiesel tem se tornado cada vez mais usual, pois, além de apresentarem características físicas e químicas, como sítios ácidos e básicos e área superficial que são favoráveis para a execução destas reações, existe ainda a possibilidade de recuperação e reuso destes materiais [20][21][22]. Nesse contexto, a catálise heterogênea à base de óxidos ternários com características magnéticas, como as ferritas do tipo espinélio, é uma proposta promissora, visto que vários estudos vêm sendo desenvolvidos com o uso de ferritas como catalisadores para biodiesel, pois a separação magnética reduz a perda do material e aumenta o tempo de reuso [6,18,23,24].…”