Hydrogen peroxide(H2O2)precipitation from sodium aluminate(SA)solution at close-ambient temperature is an efficient method to synthesize boehmite and its derived alumina with high surface area,but the precipitation yi...Hydrogen peroxide(H2O2)precipitation from sodium aluminate(SA)solution at close-ambient temperature is an efficient method to synthesize boehmite and its derived alumina with high surface area,but the precipitation yield of Al2O3 is usually below 50%in highly alkaline SA solutions.Here the synthesis of boehmite is enhanced through a precarbonization-assisted H2O2 route in highly alkaline SA solutions.It is found that the crystal structure of the precipitation product is evidently influenced by the precipitation conditions.As the precipitation temperature increases from 273 to 325 K,a small amount of gibbsite by-product is formed.As the aging temperature increases from 301 to 333 K,the crystallinity of boehmite decreases and part of the boehmite dissolves due to an increase in the pH value.Based on the above results,a precarbonization-assisted H2O2 route is proposed to obtain pure boehmite with more complete recovery of Al2O3 from highly alkaline SA solutions.The route includes a controllable precarbonization step of SA solutions with a molar ratio of Na2O to Al2O3 higher than 2:1,followed by the H2O2-precipitated step with a molar ratio of H2O2 to Al2O3 less than 7:1.Because of its facile operation conditions,no extraneous impurity,time saving and a possible recycle of the filtrate,the route has great potential to be an alternative method for preparation of boehmite and its derived alumina.展开更多
With the depletion of fossil resources, there is a need to find alternative resources of fuels and chemicals. The use of renewable feedstock such as those from seed oil processing is one of the best available resource...With the depletion of fossil resources, there is a need to find alternative resources of fuels and chemicals. The use of renewable feedstock such as those from seed oil processing is one of the best available resources that have come to the fore-front recently. This paper critically analyzes and highlights major factors in the biodiesel industry, such as seeds oil composition, production methods, properties of biodiesel, problems and potential solutions of using vegetable seed oil, the composition, quality and effective utilization of crude glycerol, the catalytic conversion of glycerol into possible fuels and chemicals.展开更多
To meet the rising demand of graphene in electronics and optoelectronics, developing an efficient synthesis strategy for effective control of the layer thickness is highly necessary. Herein, we report the synthesis of...To meet the rising demand of graphene in electronics and optoelectronics, developing an efficient synthesis strategy for effective control of the layer thickness is highly necessary. Herein, we report the synthesis of strictly single- layer graphene on the foil of an early transition metal, tungsten （W）, via a simple chemical vapor deposition route. The cracking of hydrocarbons is facilitated by the catalytically active metal surface of W, while the subsequent two-dimensional growth is mediated by the carbide-forming ability within the underlying bulk, leading to the formation of uniform monolayer graphene. The as-grown graphene layers can be transferred onto target substrates rapidly through the recently developed electrochemical method, which also allows for reuse of the substrates at least five times without introducing quality deteriora- tion. Moreover, considering the refractory nature of W foils, a complementary component of nickel is added, by means of which the growth temperature of graphene can be significantly reduced. In brief, a highly-efficient and low-cost synthesis route has been developed for the growth of graphene towards large-area uniformity, single-layer thickness and high crystalline quality.展开更多
基金Supported by the China Postdoctoral Science Foundation （20080440142）. ACKNOWLEDGEMENTS We thank Dr. Stacy M. Morris, Kent State University, for her reviews and improvement of the manuscript.
文摘Hydrogen peroxide(H2O2)precipitation from sodium aluminate(SA)solution at close-ambient temperature is an efficient method to synthesize boehmite and its derived alumina with high surface area,but the precipitation yield of Al2O3 is usually below 50%in highly alkaline SA solutions.Here the synthesis of boehmite is enhanced through a precarbonization-assisted H2O2 route in highly alkaline SA solutions.It is found that the crystal structure of the precipitation product is evidently influenced by the precipitation conditions.As the precipitation temperature increases from 273 to 325 K,a small amount of gibbsite by-product is formed.As the aging temperature increases from 301 to 333 K,the crystallinity of boehmite decreases and part of the boehmite dissolves due to an increase in the pH value.Based on the above results,a precarbonization-assisted H2O2 route is proposed to obtain pure boehmite with more complete recovery of Al2O3 from highly alkaline SA solutions.The route includes a controllable precarbonization step of SA solutions with a molar ratio of Na2O to Al2O3 higher than 2:1,followed by the H2O2-precipitated step with a molar ratio of H2O2 to Al2O3 less than 7:1.Because of its facile operation conditions,no extraneous impurity,time saving and a possible recycle of the filtrate,the route has great potential to be an alternative method for preparation of boehmite and its derived alumina.
基金supported by the National Natural Science Foundation of China(21325208,21172209,21272050)the Chinese Academy of Sciences(KJCX2-EW-J02)FRFCU(WK2060190025,WK2060190033)
文摘With the depletion of fossil resources, there is a need to find alternative resources of fuels and chemicals. The use of renewable feedstock such as those from seed oil processing is one of the best available resources that have come to the fore-front recently. This paper critically analyzes and highlights major factors in the biodiesel industry, such as seeds oil composition, production methods, properties of biodiesel, problems and potential solutions of using vegetable seed oil, the composition, quality and effective utilization of crude glycerol, the catalytic conversion of glycerol into possible fuels and chemicals.
文摘To meet the rising demand of graphene in electronics and optoelectronics, developing an efficient synthesis strategy for effective control of the layer thickness is highly necessary. Herein, we report the synthesis of strictly single- layer graphene on the foil of an early transition metal, tungsten （W）, via a simple chemical vapor deposition route. The cracking of hydrocarbons is facilitated by the catalytically active metal surface of W, while the subsequent two-dimensional growth is mediated by the carbide-forming ability within the underlying bulk, leading to the formation of uniform monolayer graphene. The as-grown graphene layers can be transferred onto target substrates rapidly through the recently developed electrochemical method, which also allows for reuse of the substrates at least five times without introducing quality deteriora- tion. Moreover, considering the refractory nature of W foils, a complementary component of nickel is added, by means of which the growth temperature of graphene can be significantly reduced. In brief, a highly-efficient and low-cost synthesis route has been developed for the growth of graphene towards large-area uniformity, single-layer thickness and high crystalline quality.
