Post-synthetic treatment of high-silica as-made ZSM-5 with organic template in the micropores was explored to reduce/remove the external surface acid density of ZSM-5. It is found that Na_2H_2 EDTA treatment can selec...Post-synthetic treatment of high-silica as-made ZSM-5 with organic template in the micropores was explored to reduce/remove the external surface acid density of ZSM-5. It is found that Na_2H_2 EDTA treatment can selectively remove the surface Al atoms, but generates new acid sites（likely silanol nests） on the external surface. H_3PO_4 treatment is unable to remove surface Al atoms, while small amount of P is left on the external surface, which effectively decreases the acid density. The catalytic performance of the resultant materials is evaluated in the methanol conversion reaction. H_3PO_4 treatment can effectively improve both the catalytic lifetime and the stability of propene selectivity.This occurs due to a combination of the increased tolerance to the external coke deposition and the depressed coking rate（reduced side reactions）. Na_2H_2 EDTA treatment only prolongs the catalytic lifetime, resulting from the improved tolerance to the external coke deposition. Under the optimized H_3PO_4 treatment condition, the resultant ZSM-5 gives a catalytic lifetime of about 1.5 times longer than the precursor. Moreover, the propene selectivity is improved, showing a slight increasing trend until the deactivation.展开更多
Routine solution reaction of Gd3＋ and p-phenylenediamine-N,N,N′,N′-tetraacetic acid （p-PhDTA） yields a dinuclear complex [Gd2（ox）（p-PhDTA）2（H2O）10]·6H2O （ox = oxalate）, which was characterized by sin...Routine solution reaction of Gd3＋ and p-phenylenediamine-N,N,N′,N′-tetraacetic acid （p-PhDTA） yields a dinuclear complex [Gd2（ox）（p-PhDTA）2（H2O）10]·6H2O （ox = oxalate）, which was characterized by single-crystal X-ray diffraction （MoKα radiation, = 0.71073）, elemental analysis and IR. This complex crystallizes in the monoclinic system, space group P21/n with a = 10.2522（8）, b = 10.0053（8）, c = 23.8834（18）, = 99.1080（10）°, V = 2419.0（3）3, Z = 2, Mr = 1367.32, Dc = 1.877 g/cm3, F（000） = 1368, = 2.830 mm-1, the final R = 0.0337 and wR = 0.0794 for 4747 observed reflections （I 〉 2 （I））. The exo-tetradentate oxalate ligand, generated in situ from the oxidative coupling of methanol, is incorporated to construct a dinuclear Gd2（ox）2 unit decorated with p-PhDTA ligands on the two sides with a monodentate coordination mode. The dinuclear molecules are further connected by the lattice water molecules to form a three-dimen- sional hydrogen network.展开更多
文摘Post-synthetic treatment of high-silica as-made ZSM-5 with organic template in the micropores was explored to reduce/remove the external surface acid density of ZSM-5. It is found that Na_2H_2 EDTA treatment can selectively remove the surface Al atoms, but generates new acid sites（likely silanol nests） on the external surface. H_3PO_4 treatment is unable to remove surface Al atoms, while small amount of P is left on the external surface, which effectively decreases the acid density. The catalytic performance of the resultant materials is evaluated in the methanol conversion reaction. H_3PO_4 treatment can effectively improve both the catalytic lifetime and the stability of propene selectivity.This occurs due to a combination of the increased tolerance to the external coke deposition and the depressed coking rate（reduced side reactions）. Na_2H_2 EDTA treatment only prolongs the catalytic lifetime, resulting from the improved tolerance to the external coke deposition. Under the optimized H_3PO_4 treatment condition, the resultant ZSM-5 gives a catalytic lifetime of about 1.5 times longer than the precursor. Moreover, the propene selectivity is improved, showing a slight increasing trend until the deactivation.
基金the National Natural Science Foundation of China (No. 21001030 and 21101032)the Foundation for the Authors of Excellent Doctoral Dissertation of Guangdong Province (No. sybzzxm201048)the "211" Creative Project of Guangdong Province
文摘Routine solution reaction of Gd3＋ and p-phenylenediamine-N,N,N′,N′-tetraacetic acid （p-PhDTA） yields a dinuclear complex [Gd2（ox）（p-PhDTA）2（H2O）10]·6H2O （ox = oxalate）, which was characterized by single-crystal X-ray diffraction （MoKα radiation, = 0.71073）, elemental analysis and IR. This complex crystallizes in the monoclinic system, space group P21/n with a = 10.2522（8）, b = 10.0053（8）, c = 23.8834（18）, = 99.1080（10）°, V = 2419.0（3）3, Z = 2, Mr = 1367.32, Dc = 1.877 g/cm3, F（000） = 1368, = 2.830 mm-1, the final R = 0.0337 and wR = 0.0794 for 4747 observed reflections （I 〉 2 （I））. The exo-tetradentate oxalate ligand, generated in situ from the oxidative coupling of methanol, is incorporated to construct a dinuclear Gd2（ox）2 unit decorated with p-PhDTA ligands on the two sides with a monodentate coordination mode. The dinuclear molecules are further connected by the lattice water molecules to form a three-dimen- sional hydrogen network.
