Production Of Nitriles From Glycerol Via Two Steps

Glycerol was successively converted to nitriles via a two-step process.In the first step,glycerol was efficiently converted to allyl alcohol in a yield of 96.7%with formic acid as deoxydehydration agent under 235°C as described in literature.In the second step,the obtained allyl alcohol reacted with ammonia over a catalyst in a fixed-bed reactor to afford nitriles thorough a series of reactions including condensation,hydrogenation and dehydrogenation.In the second step,being the key step in the trsansformation,a series of supported mono-metallic catalysts were prepared by kneading-extruding method intially.It was found from catalytic experimental results that the mono-metallic catalyst Zn₃₀/?-Al₂O₃exihibited good performance in the reaction.Based on this catalyst a serieous of bimetallic catalysts were then prepared by wet impregnation method.Experimetal results revealed that the doping of ruthenium increased the activity of the catalyst obviously,and Zn₃₀Ru_1.0/?-Al₂O₃ showed best among all the bimetallic catalysts prepared.The effects of reacton parameters including reaction temperature,molar ratio of ammonia to allyl alcohol and GHSV were investigated,and the optimized reaction conditions were obtanined,which are reaction temperature of 450°C,molar ratio of ammonia to allyl alcohol of 3:1,and GHSV of 600 h^-1.Under the optimized reaction conditions,the total carbon yield of propionitrile and acetonitrile reached 79.3%from allyl alcohol,and the carbon balance was 92.1%.Integration of the two steps,a total yield of76.6%of propionitrile and acetonitrile was obtained from glycerol.Characterization results revealed that zinc is present in the form of ZnAl₂O₄nano-crystallites in the bimetallic catalyst,and the ruthenium species are present exactly in the same area of zinc species.The close distance allowed effective interaction of the two metals leading to synergistic effect between ZnAl₂O₄ crystallites and ruthenium species,facilitating the conversion of allyl alcohol to nitriles.The characterization in combination with catalytic results disclosed that the deactivation of the catalyst is mainly due to the carbon deposition during the catalytic run and the activity can be recovered by calcination in air.