A series of metal ion (M = Sn2+, Fe3+, Ni2+, Co2+, Ag+, Cu2+) exchanged tungstophosphoric acid (H3PW12O40; TPA) catalysts with tunable Brønsted/Lewis acidity were synthesized and exploited for the oxidation of benzyl alcohol (BzOH) to benzaldehyde (BzH) using hydrogen peroxide (H2O2) as oxidant. The structure of these M-TPA composite salts was also characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analyses (TGA) and solid-state 31P nuclear magnetic resonance (NMR) probe molecule method. Among these M-TPAs, the Sn1/2H2PW12O40 catalyst, which presented strong Brønsted acidity, the synergistic effect of Brønsted/Lewis and pseudo-liquid characteristic property, exhibited excellent catalytic activity and durability with 98.2% of BzH selectivity and 95.1% of BzH yield. The optimal conditions for the oxidation of BzOH optimized by response surface methodology (RSM) were as follows: n(BzOH)/n(H2O2) = 1:1.25, catalyst amount of 5.5 wt.% to BzOH, water amount of 17 mL, 3.3 h of reaction time, and temperature 393 K. Moreover, further kinetic study confirmed that the reaction order was 2.64 and the activation energy was 21.75 kJ mol-1.

Based on single factor experiments, a three level, four variable central composite designs were carried out to establish a quadratic regression model for the catalytic synthesis of isoamyl isovalerate over sulfonated organic heteropolyacid salts as a function of molar ratio of alcohol to acid, reaction time, the amount of water-carrying agent and the amount of catalyst. The optimum conditions were obtained as follows: n (isoamyl alcohol): n (isovaleric acid) = 1.1:1, amount of catalyst was 6.4% of acid, reaction time 2 h and water-carrying agent 10 mL. Under these conditions, the yield of isoamyl isovalerate reached 97.5%. The ionic liquid could be reused six times without noticeable drop in activity. Under optimum conditions, catalysts showed a superior catalytic efficiency and reusability due to better superacidity, lower molecular transport resistance and self-separation characteristics.

A síntese de biodiesel foi realizada entre o ácido palmítico e o metanol em microemulsão reversa (w/o) preparada a partir da mistura de ácido dodecilbenzenossulfônico (DBSA)/isooctano/água. O planejamento Box-Behnken foi adotado para avaliar o efeito de importantes fatores que afetam o rendimento de palmitato de metila e a metodologia de superfície de resposta (RSM) foi empregada para descrever os parâmetros do processo de esterificação. Os resultados mostraram que as condições ideais para preparação do palmitato de metila foram: 3,33 w0 ([H2O]/[surfactante]), tempo de reação (4,2 h), razão molar 5:1 de metanol/ácido e concentração de lipase de 130 mg g-1 ([lipase]/[ácido]) obtendo-se nestas condições 98% de rendimento de biodiesel. As constantes cinéticas do modelo foram determinadas a partir de experimentos à temperatura de 40 ºC com concentrações iniciais de 0,025-0,25 mol L-1 de ácido palmítico e 0,025-0,3 mol L-1 de metanol no sistema de microemulsão. Os estudos cinéticos mostraram que a reação obedece ao mecanismo Ping-Pong bi-bi com inibição por metanol.

The synthesis between palmitic acid and methanol was carried out in a w/o reverse microemulsion prepared from the mixture of dodecylbenzenesulfonic acid (DBSA)/isooctane/water. Box-Behnken design was adopted to evaluate the effect of significant factors on the methyl palmitate yield and response surface methodology (RSM), which was employed to optimize the process parameters in the esterification. The conditions that showed optimal results for methyl palmitate preparation were: 3.33 w0 ([H2O]/[surfactant]), 4.2 h reaction time, 5:1 methanol/acid molar ratio, and 130 mg g-1 lipase ([lipase]/[acid]) concentration. The following verification experiment obtained a result of 97% in almost total agreement with the expected value (98%). The kinetic constants of the model were determined by experiments at 40 °C with initial concentrations of 0.025-0.25 mol L-1 palmitic acid and 0.025-0.3 mol L-1 methanol in the microemulsion system. The kinetic studies showed that the reaction obeyed the Ping-Pong bi-bi mechanism with inhibition by methanol.