The main objective of this paper was to characterize the voltammetric profiles of the Pt/C,Pt/C-ATO,Pd/C and Pd/CATO electrocatalysts and study their catalytic activities for methane oxidation in an acidic electrolyte...The main objective of this paper was to characterize the voltammetric profiles of the Pt/C,Pt/C-ATO,Pd/C and Pd/CATO electrocatalysts and study their catalytic activities for methane oxidation in an acidic electrolyte at 25 ℃ and in a direct methane proton exchange membrane fuel cell at 80 ℃. The electrocatalysts prepared also were characterized by X-ray diffraction( XRD) and transmission electron microscopy( TEM). The diffractograms of the Pt/C and Pt/C-ATO electrocatalysts show four peaks associated with Pt face-centered cubic( fcc) structure,and the diffractograms of Pd/C and Pd/C-ATO show four peaks associated with Pd face-centered cubic( fcc) structure. For Pt/C-ATO and Pd/C-ATO,characteristic peaks of cassiterite( SnO_2) phase are observed,which are associated with Sb-doped SnO_2( ATO) used as supports for electrocatalysts. Cyclic voltammograms( CV) of all electrocatalysts after adsorption of methane show that there is a current increase during the anodic scan. However,this effect is more pronounced for Pt/C-ATO and Pd/C-ATO. This process is related to the oxidation of the adsorbed species through the bifunctional mechanism,where ATO provides oxygenated species for the oxidation of CO or HCO intermediates adsorbed in Pt or Pd sites. From in situ ATR-FTIR( Attenuated Total Reflectance-Fourier Transform Infrared) experiments for all electrocatalysts prepared the formation of HCO or CO intermediates are observed,which indicates the production of carbon dioxide. Polarization curves at 80 ℃in a direct methane fuel cell( DMEFC) show that Pd/C and Pt/C electroacatalysts have superior performance to Pd/C-ATO and Pt/C-ATO in methane oxidation.展开更多
In pyrometallurgical process, Al-and Si-bearing minerals in iron and aluminum ores are easily transformed into sodium aluminosilicates in the presence of Na_2O constituents, which alters the leaching behaviors of Al_2...In pyrometallurgical process, Al-and Si-bearing minerals in iron and aluminum ores are easily transformed into sodium aluminosilicates in the presence of Na_2O constituents, which alters the leaching behaviors of Al_2O_3 and SiO_2. It was confirmed that sodium aluminosilicates with different phase compositions synthesized at various roasting conditions were effectively digested in the alkaline digestion process. Under the optimum conditions at temperature of 100–120°C, liquid-to-solid ratio(L/S) of 10:2 mL/g, caustic ratio of 4, and Na_2O concentration of 240 g/L, the actual and relative digestion ratio of Al_2O_3 from the synthesized sodium aluminosilicates reached maximums of about 65% and 95%, respectively, while SiO_2 was barely leached out. To validate the superior digestion property of sodium aluminosilicate generated via an actual process, the Bayer digestion of an Al_2O_3-rich material derived from reductive roasting of bauxite and comprising Na_(1.75) Al_(1.75) Si_(0.25)O_4 was conducted; the relative digestion ratio of Al_2O_3 attained 90% at 200°C.展开更多
目的:探索鲜切生菜工业化加工过程中细菌群落的动态变化规律。方法:通过高通量测序结合传统培养技术对鲜切生菜不同加工环节(原料M、预清洗PW、第一道清洗W1、第二道清洗W2、第三道清洗W3、成品P)的细菌组成进行研究。结果:生菜经过四...目的:探索鲜切生菜工业化加工过程中细菌群落的动态变化规律。方法:通过高通量测序结合传统培养技术对鲜切生菜不同加工环节(原料M、预清洗PW、第一道清洗W1、第二道清洗W2、第三道清洗W3、成品P)的细菌组成进行研究。结果:生菜经过四道清洗,菌落总数、大肠菌群和霉菌计数分别下降为2.85±0.06 lg CFU/g、1.01±0.03 lg CFU/g和1.47±0.04 lg CFU/g,低于企业现行标准Q/WWK0002S-2020;高通量测序结果显示,在门水平上,变形菌门(Proteobacteria)是鲜切生菜加工过程中的绝对优势菌,相对丰度在整个加工过程中均在70%以上;在属水平上,生菜原料和预清洗环节优势菌为不动杆菌属(Acinetobacter)、假单胞菌属(Pseudomonas)和Alkanindiges;经过第一道NaClO清洗后,食酸菌属(Acidovorax)成为主要优势菌,均在40%以上,其次为假单胞菌属和不动杆菌属。通过相对丰度热图及PCoA分析可以看出6个样品的菌群差异:样品M和PW菌群组成较相似,聚为一类;样品W1、W2、W3、P四个样品菌群结构更接近。通过传统培养结果发现,解鸟氨酸拉乌尔菌(Raoultella ornithinolytica)是鲜切蔬菜整个加工过程中的优势菌,其次还有不动杆菌属和Enterobacter bugandensis。结论:鲜切生菜加工过程中大量微生物来自于生菜生长的土壤环境,实施标准化规范种植,在源头上减少微生物污染,是控制鲜切生菜品质的首要环节,同时,严格控制加工过程中的交叉污染也是保障品质的关键。明确加工过程中不动杆菌属、假单胞菌属、食酸菌属等优势腐败菌,对于制定针对性的精准杀菌策略,进一步提升鲜切生菜的安全具有重要意义。展开更多
基金The project was supported by the FAPESP(2014/09087-4,2014/50279-4).
文摘The main objective of this paper was to characterize the voltammetric profiles of the Pt/C,Pt/C-ATO,Pd/C and Pd/CATO electrocatalysts and study their catalytic activities for methane oxidation in an acidic electrolyte at 25 ℃ and in a direct methane proton exchange membrane fuel cell at 80 ℃. The electrocatalysts prepared also were characterized by X-ray diffraction( XRD) and transmission electron microscopy( TEM). The diffractograms of the Pt/C and Pt/C-ATO electrocatalysts show four peaks associated with Pt face-centered cubic( fcc) structure,and the diffractograms of Pd/C and Pd/C-ATO show four peaks associated with Pd face-centered cubic( fcc) structure. For Pt/C-ATO and Pd/C-ATO,characteristic peaks of cassiterite( SnO_2) phase are observed,which are associated with Sb-doped SnO_2( ATO) used as supports for electrocatalysts. Cyclic voltammograms( CV) of all electrocatalysts after adsorption of methane show that there is a current increase during the anodic scan. However,this effect is more pronounced for Pt/C-ATO and Pd/C-ATO. This process is related to the oxidation of the adsorbed species through the bifunctional mechanism,where ATO provides oxygenated species for the oxidation of CO or HCO intermediates adsorbed in Pt or Pd sites. From in situ ATR-FTIR( Attenuated Total Reflectance-Fourier Transform Infrared) experiments for all electrocatalysts prepared the formation of HCO or CO intermediates are observed,which indicates the production of carbon dioxide. Polarization curves at 80 ℃in a direct methane fuel cell( DMEFC) show that Pd/C and Pt/C electroacatalysts have superior performance to Pd/C-ATO and Pt/C-ATO in methane oxidation.
基金financially supported by the National Natural Science foundation of China (Nos. 51234008 and 51174230)the Program for New Century Excellent Talents in University of Ministry of Education of China (No. NCET-11-0515)
文摘In pyrometallurgical process, Al-and Si-bearing minerals in iron and aluminum ores are easily transformed into sodium aluminosilicates in the presence of Na_2O constituents, which alters the leaching behaviors of Al_2O_3 and SiO_2. It was confirmed that sodium aluminosilicates with different phase compositions synthesized at various roasting conditions were effectively digested in the alkaline digestion process. Under the optimum conditions at temperature of 100–120°C, liquid-to-solid ratio(L/S) of 10:2 mL/g, caustic ratio of 4, and Na_2O concentration of 240 g/L, the actual and relative digestion ratio of Al_2O_3 from the synthesized sodium aluminosilicates reached maximums of about 65% and 95%, respectively, while SiO_2 was barely leached out. To validate the superior digestion property of sodium aluminosilicate generated via an actual process, the Bayer digestion of an Al_2O_3-rich material derived from reductive roasting of bauxite and comprising Na_(1.75) Al_(1.75) Si_(0.25)O_4 was conducted; the relative digestion ratio of Al_2O_3 attained 90% at 200°C.
文摘目的:探索鲜切生菜工业化加工过程中细菌群落的动态变化规律。方法:通过高通量测序结合传统培养技术对鲜切生菜不同加工环节(原料M、预清洗PW、第一道清洗W1、第二道清洗W2、第三道清洗W3、成品P)的细菌组成进行研究。结果:生菜经过四道清洗,菌落总数、大肠菌群和霉菌计数分别下降为2.85±0.06 lg CFU/g、1.01±0.03 lg CFU/g和1.47±0.04 lg CFU/g,低于企业现行标准Q/WWK0002S-2020;高通量测序结果显示,在门水平上,变形菌门(Proteobacteria)是鲜切生菜加工过程中的绝对优势菌,相对丰度在整个加工过程中均在70%以上;在属水平上,生菜原料和预清洗环节优势菌为不动杆菌属(Acinetobacter)、假单胞菌属(Pseudomonas)和Alkanindiges;经过第一道NaClO清洗后,食酸菌属(Acidovorax)成为主要优势菌,均在40%以上,其次为假单胞菌属和不动杆菌属。通过相对丰度热图及PCoA分析可以看出6个样品的菌群差异:样品M和PW菌群组成较相似,聚为一类;样品W1、W2、W3、P四个样品菌群结构更接近。通过传统培养结果发现,解鸟氨酸拉乌尔菌(Raoultella ornithinolytica)是鲜切蔬菜整个加工过程中的优势菌,其次还有不动杆菌属和Enterobacter bugandensis。结论:鲜切生菜加工过程中大量微生物来自于生菜生长的土壤环境,实施标准化规范种植,在源头上减少微生物污染,是控制鲜切生菜品质的首要环节,同时,严格控制加工过程中的交叉污染也是保障品质的关键。明确加工过程中不动杆菌属、假单胞菌属、食酸菌属等优势腐败菌,对于制定针对性的精准杀菌策略,进一步提升鲜切生菜的安全具有重要意义。
