Study On The Catalytic Ammination Of Glycerol And Derivation To Pyridine Bases

Glycerol was converted to pyridine bases through a continuous two-step process in a series-connected two-stage fixed-fed reactor.Firstly,dehydration of glycerol to acrolein was achieved in high selectivity over a catalyst FeP-P in the first reactor.The dehydration products were directly introduced into the second reactor charged with a bimetallic catalyst Cu_4.6Pr_0.3/HZSM-5,contacting ammonia over the catalyst to afford pyridine bases in high yield.Under optimized reaction conditions,the conversion of glycerol was 100%,and the total yield of pyridine base reached up to 60.2%.The catalyst characterization results revealed that the doping of copper and praseodymium did not destroy the framework of HZSM-5,but increased the Lewis acidity of the catalyst which enhanced the activity and selectivity of the catalyst in the conversion of acrolein to pyridine bases.The doping of minute amount of praseodymium led to the high dispersion of the CuO nanoparticles,thus enhanced the dehydrogenation activity of CuO species,and finally improved the performance of the bimetallic catalyst.In addition,the interaction of copper and praseodymium in the bimetallic catalyst might have positive effect on the performance of the catalyst in the conversion of acrolein to pyridine bases.A bimetallic catalyst Cu4.6Ru1.0/HZSM-5 was found efficient in the synthesis of3-picoline from acrolein and ammonia in the presence of hydrogen as carrier gas.The hydrogen as a carrier gas enhanced the selectivity of 3-picoline and the total yield of pyridine bases.Under the optimal reaction conditions the yield of 3-picoline was 37.0%,10point higher than that of pyridine,meanwhile,the total yield of pyridine bases reached up to 69.4%.The characterization results revealed that copper and ruthenium are present in the forms of CuO and RuO₂ species,respectively.The two metal species are exactly located in the same area and close to each other,allowing synergistic effect between the two metals in the hydrogenation and dehydrogenation elementary steps in the reaction.The good performance of Cu4.6Ru1.0/HZSM-5 compared to the other tested Cu-Ru bimetallic catalysts was derived from the comprehensive results of its surface area and hydrogenation or dehydrogenation activity.The characterization results of TEM,EDX,XPS,IR spectra of adsorbed pyridine,and N₂ adsorption–desorption analysis revealed that the deactivation of the catalyst was due to the carbonaceous deposition on the active sites of the catalyst during the catalytic run.The deposited carbonaceous substances could be removed by calcination in air at 550°C for 6 h,and the catalytic performance of the Cu4.6Ru1.0/HZSM-5 catalyst could be recovered completely.This catalyst also showed long lifetime compared to some of the reported catalysts.