| Energy is an essential part of human daily activities,and has been associated with human civilization for a long time.It is expected that the demand for energy will continuously increase along with increasing human population.The conventional energy source such as petroleum and natural gas will not be able to cope up with the increasing global demand for energy in the future.Search for alternative and renewable energies such as solar,wind,hydro or geotherma has been a major issue.Biodiesel is a promising alternative energy that has been studied and explored in recent years.This is not only an environmentally friendly fuel,but is also considered sustainable and renewable form of energy.At present,biodiesel is prepared by transesterification by solid base catalyst.The base catalysis can have even more tremendous potential in biodiesel production.Conventionally,the transesterification was carried out with these because of their high activity and conversion and low cost.In this paper,hydrotalcite and auxiliaries were loaded on alumina by in-situ synthesis and used for the catalytic preparation of biodiesel.The mesoporous?-Al2O3 was prepared by precipitation and hydrothermal method using cetyltrimethylammonium bromide?CTAB?and sodium dodecyl sulfate?SDS?as the dual template and aluminum nitrate as the raw.The effects of template selection,reaction crystallization time and calcination temperature on?-Al2O3 were investigated.The catalysts were characterized by TG-DTG,XRD,SEM,TEM,BET,FT-IR and TPD.The results show that the crystallinity of?-Al2O3 was high with Al?NO3?3:SDS:CTAB molar ratio of 1:0.25:0.1,crystallization time 24 h,and calcination at 800°C for 4 h.The pore size of the synthesized?-Al2O3 is 19.72 nm,the surface is alkaline,and the thermal stability is high.NiMgAl-LDHs/?-Al2O3 was prepared by in-situ coprecipitation method by using?-Al2O3as support and aluminum source,which was further transformed to the NiMg?Al?O/?-Al2O3catalyst through calcination.The Ni Mg?Al?O/?-Al2O3 catalyst was characterized by TG-DTG,XRD,SEM,EDS,BET,FT-IR and CO2-TPD and its performance in the transesterification of biodiesel with microalgae oil and methanol as raw materials was investigated.The results show that when the Ni2+doping content is 14%,the mass ratio of NiMg?Al?O/?-Al2O3 and microalgae oil is 0.03,and the molar ratio of methanol to microalgae oil is 12,biodiesel yields can reach 95%at 65°C for 3 hours under optimal conditions of reaction.After 7 times of catalyst recycling,the biodiesel yield can still reach 82.3%.The K-modified K/NiMg?Al?O/?-Al2O3 catalyst was prepared by an equal volume impregnation method.The K/Ni Mg?Al?O/?-Al2O3 catalyst was characterized by TG-DTG,XRD,SEM,EDS,BET,FT-IR,CO2-TPD.The results of catalyst performance show that when the K+doping content is 20%,the mass ratio of(K/NiMg?Al?O/?-Al2O3 and microalgae oil is 0.025,and the molar ratio of methanol to microalgae oil is 11,biodiesel yields can reach97.8%at 65°C for 2.5 hours under optimal conditions of reaction.After 7 times of catalyst recycling,the biodiesel yield can still reach 84.2%. |
PDF Full Text Request