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
Solvent extraction equilibria of four main alkaline earth metals(magnesium, calcium, strontium and barium) with di (2-ethylhexyl)phosphoric acid (DEHPA), 2-ethylhexyl phosphonic acidmono-(2-ethylhexyl) esters, di (2, ...Solvent extraction equilibria of four main alkaline earth metals(magnesium, calcium, strontium and barium) with di (2-ethylhexyl)phosphoric acid (DEHPA), 2-ethylhexyl phosphonic acidmono-(2-ethylhexyl) esters, di (2, 4, 4-tri-methylpentyl) phosphinicacid and IR spectra of the extracts have been studied. Theselectivity order is dependent on the e/r value and hydration energyof the metal ions. The minor shift of the P→O in IR absorption ofthe alkaline earth metal extracts indicates that the interactionbetween the metal ions and P→O is much weaker for alkaline earthmetals than for transitional metals.展开更多
Dibenzo[b,fi[1,5]diazocines are a class of eight-membered heterocycles,which exhibit unique rigid saddle-shaped structure and possess inherent chirality.In this study,we report a convenient and straightforward method ...Dibenzo[b,fi[1,5]diazocines are a class of eight-membered heterocycles,which exhibit unique rigid saddle-shaped structure and possess inherent chirality.In this study,we report a convenient and straightforward method for the catalytic enantioselective synthesis of these unique chiral molecules through chiral phosphoric acid-catalyzed dimerization of 2-acylbenzoisocyanates.Notably,the addition of corresponding 2-acylaniline as the co-catalyst significantly improved the efficiency of these reactions,and a simple phase separation operation resulted in products with excellent enantiopurity.Experimental studies were performed to elucidate the mechanism behind these reactions,leading to the proposal of a plausible reaction mechanism based on the study findings.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. 50074028).
文摘Solvent extraction equilibria of four main alkaline earth metals(magnesium, calcium, strontium and barium) with di (2-ethylhexyl)phosphoric acid (DEHPA), 2-ethylhexyl phosphonic acidmono-(2-ethylhexyl) esters, di (2, 4, 4-tri-methylpentyl) phosphinicacid and IR spectra of the extracts have been studied. Theselectivity order is dependent on the e/r value and hydration energyof the metal ions. The minor shift of the P→O in IR absorption ofthe alkaline earth metal extracts indicates that the interactionbetween the metal ions and P→O is much weaker for alkaline earthmetals than for transitional metals.
基金The authors gratefully acknowledge NSFC(grant nos.22222107,22171186)China Postdoctoral Science Foundation(2023M742365)+2 种基金Postdoctoral Fellowship Program of CPSF(GZC20231671)ShanghaiTech University start-up funding for financial support.Prof.Guangxin Liang was acknowledged for sharing the optical rotation polarimeter,and Mr.Huanchao Gu was acknowledged for the assistance with X-ray crystallographic analysissupport from Analytical Instrumentation Center(#SPST-AIC10112914),SPST,ShanghaiTech University.
文摘Dibenzo[b,fi[1,5]diazocines are a class of eight-membered heterocycles,which exhibit unique rigid saddle-shaped structure and possess inherent chirality.In this study,we report a convenient and straightforward method for the catalytic enantioselective synthesis of these unique chiral molecules through chiral phosphoric acid-catalyzed dimerization of 2-acylbenzoisocyanates.Notably,the addition of corresponding 2-acylaniline as the co-catalyst significantly improved the efficiency of these reactions,and a simple phase separation operation resulted in products with excellent enantiopurity.Experimental studies were performed to elucidate the mechanism behind these reactions,leading to the proposal of a plausible reaction mechanism based on the study findings.
