查看更多>>摘要：Nano-solid-base catalyst K sub(2)O/ gamma -Al sub(2)O sub(3) was prepared and adopted for the synthesis of biodiesel by transesterification of rapeseed oil with methanol. The particle diameter of the catalyst was about 50 nm, which was measured by transmission electron microscopy (TEM). The variables affecting the yield of biodiesel during transesterification, such as mass ratio of KNO sub(3) to gamma -Al sub(2)O sub(3), calcination temperature, calcination time, catalyst content, molar ratio of methanol to oil, reaction temperature and reaction time were investigated. The catalyst obtained by calcining a mixture of KNO sub(3) and gamma -Al sub(2)O sub(3)(m sub(KNO3)/m sub( gamma -Al2O3)=70%) at 600 degree C for 3 h, was found to be the optimum one, which gave the highest catalytic activity in the reaction. With 3% (m sub(catalyst)/m sub(oil)) catalyst, when the transesterification was carried out at a molar ratio of methanol to oil of 12::1, a reaction temperature of 70 degree C, and a reaction time of 3 h, yield of 94% was achieved.
查看更多>>摘要：The decomposition rate and the water-holding capacity of 6 kinds of grass litters were studied in the Jinshajiang river dry-hot valley. The results showed that the dry weight remains reduced with time but did not have a direct correlation with time. The decomposition litters were affected by climate, character of litter, animalcule and soil animal. The climate factors of temperature and humidity were important especially. The water-holding capacity was in the sequence of N. wightii (336%), P. notatum Flugge (248%), H. contortus (L.) Beauv (209%), B. pertusa (L.) A. Camus(206%), I. endecaphylla Jacq (174%), D. anmlatum (Forsk.) Stapf (168%). After 24 months decomposition the remaining dry weight of the litter was in the sequence as follows: 15.12% for N. wightii, 26.38% for I. endecaphylla Jacq, 27.23% for B. pertusa (L.) A. Camus, 30.78% for P. notatum Flugge, 39.72% for H. contortus (L.) Beauv and 39.76% for D. annulatum (Forsk.) Stapf. The decomposition rate and water-holding capacity of N. wightii are at the highest level. It is important for the development, improvement and conservation of the grassland soil.
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