In this work the effects of nutrients starvations on Chlorella vulgaris were investigated in different trophic regimens. For all the tested conditions, the cellular response to nutrient starvation and trophic regimen ...In this work the effects of nutrients starvations on Chlorella vulgaris were investigated in different trophic regimens. For all the tested conditions, the cellular response to nutrient starvation and trophic regimen was evaluated on specific growth rate, biomass and lipids productivity, lipids content and quality. These parameters are all crucial for microalgae biodiesel production, but in literature the lipids quality, in terms of polar and nonpolar lipids, is often neglected. Thus the typical high content of polar lipids, a class of molecules that negatively affects the biodiesel production process, of microalgae crude oil is generally not analyzed. In the tested conditions the triggering effect of nitrogen starvation on total lipids productivity is confirmed only in autotrophic regimen, while in mixotrophic and heterotrophic conditions the total lipids productivity is reduced, as a consequence of the lowered biomass productivity, but with an evident compositional shift towards nonpolar lipids production (from 0.5 mg/Ld to 41.6 mg/Ld in mixotrophic regimen). Nitrogen and phosphorus co-starvation induced the highest nonpolar lipids productivity in all trophic regimens. Maximum nonpolar lipids productivity was obtained in nitrogen limited and phosphorus deprived condition during mixotrophic growth, equal to 118.2 mg/Ld, representing the 80% of produced lipids. On the basis of the obtained results, the possibility of a short pre-harvesting cultural step to maximize the nonpolar lipids yield of the crop could be envisaged.展开更多
Methane cracking is considered a bridge technology between gray and green hydrogen production processes.In this work an experimental study of methane cracking in molten tin is performed.The tests were conducted in a q...Methane cracking is considered a bridge technology between gray and green hydrogen production processes.In this work an experimental study of methane cracking in molten tin is performed.The tests were conducted in a quartz reactor(i.d.=1.5 cm,L=20 cm)with capillary injection,varying temperature(950–1070℃),inlet methane flow rate(30–60 mL·min^(-1))and tin height(0–20 cm).The influence of the residence time in the tin and in the headspace on methane conversion and on carbon morphology was investigated.The conversions obtained in tin and in the empty reactor were measured and compared with results of detailed kinetic simulations(CRECK).Furthermore,an expression of a global kinetic constant for methane conversion in tin was also derived.The highest conversion(65%at Q_(0)=30 mL·min^(-1) and t=1070℃)is obtained for homogeneous gas phase reaction due to the long residence time(70 s),the presence of tin leads to a sharp decrease of residence time(1 s),obtaining a conversion of 35%at 1070℃,thus meaning that tin owns a role in the reaction.Carbon characterization(scanning electron microscopy,Raman)reported a change in carbon toward sheet-like structures and an increase of the carbon structural order in the presence of molten tin media.展开更多
文摘In this work the effects of nutrients starvations on Chlorella vulgaris were investigated in different trophic regimens. For all the tested conditions, the cellular response to nutrient starvation and trophic regimen was evaluated on specific growth rate, biomass and lipids productivity, lipids content and quality. These parameters are all crucial for microalgae biodiesel production, but in literature the lipids quality, in terms of polar and nonpolar lipids, is often neglected. Thus the typical high content of polar lipids, a class of molecules that negatively affects the biodiesel production process, of microalgae crude oil is generally not analyzed. In the tested conditions the triggering effect of nitrogen starvation on total lipids productivity is confirmed only in autotrophic regimen, while in mixotrophic and heterotrophic conditions the total lipids productivity is reduced, as a consequence of the lowered biomass productivity, but with an evident compositional shift towards nonpolar lipids production (from 0.5 mg/Ld to 41.6 mg/Ld in mixotrophic regimen). Nitrogen and phosphorus co-starvation induced the highest nonpolar lipids productivity in all trophic regimens. Maximum nonpolar lipids productivity was obtained in nitrogen limited and phosphorus deprived condition during mixotrophic growth, equal to 118.2 mg/Ld, representing the 80% of produced lipids. On the basis of the obtained results, the possibility of a short pre-harvesting cultural step to maximize the nonpolar lipids yield of the crop could be envisaged.
文摘Methane cracking is considered a bridge technology between gray and green hydrogen production processes.In this work an experimental study of methane cracking in molten tin is performed.The tests were conducted in a quartz reactor(i.d.=1.5 cm,L=20 cm)with capillary injection,varying temperature(950–1070℃),inlet methane flow rate(30–60 mL·min^(-1))and tin height(0–20 cm).The influence of the residence time in the tin and in the headspace on methane conversion and on carbon morphology was investigated.The conversions obtained in tin and in the empty reactor were measured and compared with results of detailed kinetic simulations(CRECK).Furthermore,an expression of a global kinetic constant for methane conversion in tin was also derived.The highest conversion(65%at Q_(0)=30 mL·min^(-1) and t=1070℃)is obtained for homogeneous gas phase reaction due to the long residence time(70 s),the presence of tin leads to a sharp decrease of residence time(1 s),obtaining a conversion of 35%at 1070℃,thus meaning that tin owns a role in the reaction.Carbon characterization(scanning electron microscopy,Raman)reported a change in carbon toward sheet-like structures and an increase of the carbon structural order in the presence of molten tin media.
