Research On Preparation Of Magnetic Nanocatalysts And Catalyzed Hydrogenation Reaction

Hydrogenation of ?-pinene?to prepare cis-pinane?,hydrogenation of rosin?to prepare hydrogenated rosin?and hydrogenolysis of cellulose?to prepare hydrogenated 1,2-propanediol?are very important hydrogenation reactions in the deep processing of biomass.The production of cis-pinane,hydrogenated rosin and 1,2-propanediol are widely used in the industrial fields.Till now,cis-pinane and hydrogenated rosin were prepared mainly using Pd/C as catalyst in industry production.While such catalysts have drawbacks including separation difficulty,easy deactivation and hard to reuse,and above disadvantages can lead to the increase the cost of such reactions.Transforming cellulose into oxygenated chemicals,such as polyols,was a high atom-economic reaction.Proton acids combine with metal particles were used as the catalyst in the hydrogenolysis of cellulose,but they can pollute the environment and corrode equipment.As a result,to find a newly green catalyst that can be separated easily and had a good reusability is a crucial aspect to be resolved.Magnetic nanocatalyst is one of new type nanocatalysts that can be recovered by applying an appropriate magnetic field and has high catalytic activity.Magnetic catalyst showed incomparable catalytic performance than many traditional catalysts in a variety of liquid phase catalytic reaction.Magnetic nanocatalyst which own excellent superparamagnetic propertieswere easily separated from the reaction system with an external magnet and can redisperse quickly with a slight shake once the magnetic field was removed.Magnetic nanocatalyst is also a kind of multi-function loading catalyst that owned excellent reusable ability.Based on the characteristics of of magnetic nanocatalyst that have high catalytic activity and convenient recycling,twenty-one kinds of magnetic nanocatalysts such as Fe₃O₄@SiO₂/APTS/Ru,Fe₃O₄@SiO₂/MPTS/Ru,Fe₃O₄@C/Ru,Fe₃O₄/1,6-hexanediamine/Ru et al.that loaded different metals were designed and synthesized.The magnetic catalyst was characterized using XRD,VSM,TEM,FT-IR,BET and XPS.Results showed that Fe₃O₄ exhibited morphological regularity and size uniformity.The active metal particles showed small size distribution and good monodisperse performance.By using TEOS and glucose as a source of silicon and carbon source,respectively,the materials which own the obvious core-shell structure were synthesized.By adjusting the amount of silicon source and carbon source to synthesize the core-shell materials that the thicknesses of shell were well controlled.Magnetic nanocatalysts were used in the hydrogenation of ?-pinene.The catalytic activity,selectivity and life of magnetic catalysts were studied and the remarkable magnetic catalysts were selected to the hydrogenation of ?-pinene.Compared with the traditional catalyst,the reaction results showed that Fe₃O₄@Si O₂/APTS/Ru,Fe₃O₄@C/Ru and Fe₃O₄/1,6-hexanediamine/Ru had better catalytic effect for the hydrogenation of ?-pinene,the conversion of ?-pinene exceed 98%,the selectivity for cis-pinane exceed 97%,respectively.After reaction,three kinds of catalysts could be easily separated from the reaction mixture when applying an external magnetic field and had good reusability.Magnetic nanocatalysts were used in the hydrogenation of rosin.The results showed that Fe₃O₄@C/Ru and Fe₃O₄@SiO₂/APTS/Ru had better catalytic effect for the hydrogenation of rosin,the conversion rate of rosin was 99.1% and 98.6%,at the same time tetrahydroabietic acid content were 58.3% and 56.4%,respectively.The Fe₃O₄@C/Ru catalyst can be easily separated from the reaction mixture when applying an external magnetic field,the catalytic efficiency showed no obvious loss after ten repeated cycles.However,the catalytic efficiency of Fe₃O₄@SiO₂/APTS/Ru showed obvious loss after three repeated cycles.Thermogravimetric analysis showed that when the reaction temperature is too high,it is easy to cause the shedding of APTS,which in turn affected the stable effects of active material and reduce the catalytic efficiency.Nine kinds of bifunctional magnetic nanocatalysts such as Fe₃O₄/SiO₂/Ru-WO₃ et al.that load different metals and different quantity of WO₃ were designed and synthesized.The magnetic nanocatalysts were characterized using XRD,VSM,Raman,Py-FTIR,H2-TPR and NH₃-TPD.Results showed that active metal particles and tungsten oxide can better disperse on the surface of Fe₃O₄/SiO₂.There are abundant of Lewis acid on the surface of catalyst.Bifunctional magnetic nanocatalysts were used in the hydrogenolysis of glucose,cellobiose and cellulose to form 1,2-propanediol.The reaction results showed that Fe₃O₄/SiO₂/Ru-WO₃ had better catalytic effect for the hydrogenolysis reaction.The conversion of substrate was 100%,the selectivity for 1,2-propanediol was 70.1%,65.6% and 51.6%,respectively.Fe₃O₄/SiO₂/Ru-WO₃ was easily recovered by an external magnet when the reaction was finished and the reusability was good.Different means of analysis was used to analyze the intermediate and reaction products of the hydrogenolysis reaction,reaction mechanism that the hydrogenolysis of cellulose to form 1,2-propanediol was put forward combined with literature research progress.The results showed that cellulose was first hydrolysis to form the monosaccharide glucose under the acid environment.The process that glucose hydrogenolysis prepared low carbon alcohol mainly occurred isomerization reaction,dehydration reaction,dehydration reaction and reverse aldol condensation reaction.There is a competing relationship between the reaction,and decided product distribution eventually.The hydrogenolysis of glucose to 1,2-propanediol contains two steps: the isomerization of glucose to fructose on Lewis acid/base sites,the retro-aldol condensation reaction of fructose to glyceraldehyde and dihydroxyacetone,followed by dehydration and hydrogenation to form 1,2-propanediol.