Fe/activated carbon was found to be catalytically effective for the one-step hydroxylation of several typical substituted aromatic compounds under milder reaction conditions(303 K,atmospheric pressure). It was found t...Fe/activated carbon was found to be catalytically effective for the one-step hydroxylation of several typical substituted aromatic compounds under milder reaction conditions(303 K,atmospheric pressure). It was found that the ring oxidation is predominant for all the substrates studied and the selectivity to ring oxidation was much greater than those reported previously.A comparison of the conversions with that of benzene revealed that electron-donating substituents increase the conversions of the substrates,while electron-withdrawing substituents decrease the conversions.The formation of o-and p-hydroxylated products for electron-donating substituted aromatic compounds and o-,m-,p-hydroxylated products for electron-withdrawing substituted aromatic compounds revealed an electrophilc mechanism.The predominant selectivity to o-hydroxylated products for the aromatic compounds with substituents which could coordianated with Fe also shows a new mechanism.This coordianation was affected by the steric hindrance of the substituents.The latter mechanism was also confirmed by DFT method.展开更多
在活性炭掺量为10%~15%,煅烧温度为1100~1250℃条件下,从动力学和热力学角度对磷石膏分解煅烧制胶凝材的可行性进行了研究。在该温度范围内,通过等温热分析法确定了磷石膏分解体系的表观活化能为299.88~382.85 k J·mol^(-1),指前因...在活性炭掺量为10%~15%,煅烧温度为1100~1250℃条件下,从动力学和热力学角度对磷石膏分解煅烧制胶凝材的可行性进行了研究。在该温度范围内,通过等温热分析法确定了磷石膏分解体系的表观活化能为299.88~382.85 k J·mol^(-1),指前因子ln A为18.64~25.61 s^(-1),分解动力学方程为受三维扩散控制的Z-L-T方程。经Factsage软件计算和SEM、EDS、XRD等微观检测发现,煅烧过程中,不仅发生了硫酸钙的分解,还伴随着分解产物CaO和杂质SiO_2的合成反应。根据CaO-SiO_2-CaSO_4相图的理论计算结果表明,适量补充硅铝质改性组分,调节生料的配比范围,有使磷石膏基水硬性复合胶凝材料强度提升的潜能。展开更多
文摘Fe/activated carbon was found to be catalytically effective for the one-step hydroxylation of several typical substituted aromatic compounds under milder reaction conditions(303 K,atmospheric pressure). It was found that the ring oxidation is predominant for all the substrates studied and the selectivity to ring oxidation was much greater than those reported previously.A comparison of the conversions with that of benzene revealed that electron-donating substituents increase the conversions of the substrates,while electron-withdrawing substituents decrease the conversions.The formation of o-and p-hydroxylated products for electron-donating substituted aromatic compounds and o-,m-,p-hydroxylated products for electron-withdrawing substituted aromatic compounds revealed an electrophilc mechanism.The predominant selectivity to o-hydroxylated products for the aromatic compounds with substituents which could coordianated with Fe also shows a new mechanism.This coordianation was affected by the steric hindrance of the substituents.The latter mechanism was also confirmed by DFT method.
文摘在活性炭掺量为10%~15%,煅烧温度为1100~1250℃条件下,从动力学和热力学角度对磷石膏分解煅烧制胶凝材的可行性进行了研究。在该温度范围内,通过等温热分析法确定了磷石膏分解体系的表观活化能为299.88~382.85 k J·mol^(-1),指前因子ln A为18.64~25.61 s^(-1),分解动力学方程为受三维扩散控制的Z-L-T方程。经Factsage软件计算和SEM、EDS、XRD等微观检测发现,煅烧过程中,不仅发生了硫酸钙的分解,还伴随着分解产物CaO和杂质SiO_2的合成反应。根据CaO-SiO_2-CaSO_4相图的理论计算结果表明,适量补充硅铝质改性组分,调节生料的配比范围,有使磷石膏基水硬性复合胶凝材料强度提升的潜能。
