155 resultados para Potassium chloride
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To elucidate the physicochemical properties of silk protein, we studied the effects of calcium chloride and ethanol on the gelation of fibroin. Fibroin was treated with 5.0 M calcium chloride in water (Ca/W) or 5.0 M calcium chloride in 20% (v/v) ethanol (Ca/Et) and the rheological properties of colloidal fibroin were investigated. The Ca/W-treatment promoted an increased rate of gelation and gave higher gel strength than the Ca/Et-treatment. The maximum gel strengths of Ca/W- and Ca/Et-treated fibroins were obtained at pH 7.0 and pH 5.5, respectively. Scanning electron micrographs showed that the Ca/W-treated fibroin gel had a more developed three-dimensional molecular network than the Ca/Et-treated gel. Further, FT-IR spectra suggested that Ca/W-treated fibroin has more of a beta-structure than Ca/Et-treated one in colloidal conditions. This study indicated that the use of calcium chloride alone was more beneficial to the gelation of fibroin than combined use with ethanol.
Resumo:
Catalytic cracking of butene over potassium modified ZSM-5 catalysts was carried out in a fixed-bed microreactor. By increasing the K loading on the ZSM-5, butene conversion and ethene selectivity decreased almost linearly, while propene selectivity increased first, then passed through a maximum (about 50% selectivity) with the addition of ca. 0.7-1.0% K, and then decreased slowly with further increasing of the K loading. The reaction conditions were 620 degrees C, WHSV 3.5 h(-1), 0.1 MPa 1-butene partial pressure and 1 h of time on stream. Both by potassium modification of the ZSM-5 zeolite and by N(2) addition in the butene feed could enhance the selectivity towards propene effectively, but the catalyst stability did not show any improvement. On the other hand, addition of water to the butene feed could not only increase the butene conversion, but also improve the stability of the 0.7%K/ZSM-5 catalyst due to the effective removal of the coke formed, as demonstrated by the TPO spectra. XRD results indicated that the ZSM-5 structure of the 0.07% K/ZSM-5 catalyst was not destroyed even under this serious condition of adding water at 620 degrees C.