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首页> 外文期刊>Dalton transactions: An international journal of inorganic chemistry >Dimeric 1,3-propanediaminetetraacetato lanthanides as the precursors of catalysts for the oxidative coupling of methane
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Dimeric 1,3-propanediaminetetraacetato lanthanides as the precursors of catalysts for the oxidative coupling of methane

机译：1,3-丙二胺四乙酸镧系二聚体镧系元素作为甲烷氧化偶联催化剂的前体

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From neutral solutions, dimeric 1,3-propanediaminetetraacetato lanthanides (NH_4)_2[Ln_2(1,3-pdta)_2-(H_2O)_4]·8H_2O [Ln = La, 1; Ce, 2] and K_2[Ln_2(1,3-pdta)2(H_2O)_4]·11H_2O [Ln = La, 3; Ce, 4] (1,3-H_4pdta = 1,3-propanediaminetetraacetic acid, C_(11)H_(18)N_2O_8) were isolated in high yields. The reaction of excess strontium nitrate with 1 resulted in the formation of a two dimensional coordination polymer [La2(1,3-pdta)_2(H_2O)_4]_n·[Sr_2(H_2O)_6]_n·[La_2(1,3-pdta)_2(H_2O)_2]_n·18nH_2O (5) at 70 °C. Complexes 1-4 show a similar central molecular structure. The lanthanide ions are coordinated by two nitrogen atoms, four carboxy oxygen atoms from one 1,3-pdta ligand, two from the neighboring 1,3-pdta ligand forming a fourmembered ring and two water molecules. Complex 5 has two kinds of dimeric lanthanum unit and extends into a 2D coordination polymer through strontium ions and bridged oxygen atoms, and forms a fourteen membered ring linked by oxygen atoms from carboxy groups of pdta. Complexes 1-4 are soluble in water. The ~(13)C{~1H} NMR experiments for complex 1 were tested in solution. Thermal products from 1 and 5 show good catalytic activities towards the oxidative coupling reaction of methane (OCM). The conversion of methane and selectivity to C_2 reached 29.7% and 51.7% at 750 °C for the product of 5. From TGA, XRD and SEM analyses, the thermal products from 1 and 5 are rod- and poly-shaped, which are assigned as lanthanum oxocarbonate and a mixture of La_2O_3, SrCO_3 and La_2O_2CO_3 for 1 and 5, respectively. The precursor method is favorable for the formation of regular shaped mixed oxides.
机译：从中性溶液中，得到二聚的1,3-丙二胺四乙酸镧系元素（NH_4）_2 [Ln_2（1,3-钯）_2-（H_2O）_4]·8H_2O [Ln = La，1; Ce，2]和K_2 [Ln_2（1,3-pdta）2（H_2O）_4]·11H_2O [Ln = La，3; Ce，4]（1,3-H_4pdta = 1,3-丙二胺四乙酸，C_（11）H_（18）N_2O_8）的分离产率很高。过量硝酸锶与1的反应导致形成二维配位聚合物[La2（1,3-pdta）_2（H_2O）_4] _n·[Sr_2（H_2O）_6] _n·[La_2（1,3 -pdta）_2（H_2O）_2] _n·18nH_2O（5）在70°C下。配合物1-4显示相似的中心分子结构。镧系元素离子由两个氮原子，一个1，3-pdta配体的四个羧基氧原子，相邻的1，3-pdta配体的两个羧基形成一个四元环和两个水分子配位。配合物5具有两种二聚镧单元，并且通过锶离子和桥连的氧原子延伸成2D配位聚合物，并形成由来自钯的羧基的氧原子连接的十四元环。配合物1-4可溶于水。在溶液中测试了配合物1的〜（13）C {〜1H} NMR实验。来自1和5的热产物对甲烷（OCM）的氧化偶联反应显示出良好的催化活性。对于5的产物，在750°C下甲烷的转化率和对C_2的选择性分别达到29.7％和51.7％。根据TGA，XRD和SEM分析，来自1和5的热产物为棒状和多形，分别为分别为碳酸氧镧和La_2O_3，SrCO_3和La_2O_2CO_3的混合物分别为1和5。前体法有利于形成规则形状的混合氧化物。

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