MCM-49 Zeolite Supported Ru Catalysts And The Application In Levulinic Acid Hydrogenation

The rapid development of economy has posed a great challenge to the traditional energy industry structure.As the most abundant organic carbon source in nature,biomass,if utilized,will be an inexhaustible resource of energy.Levulinic acid,as one of the 12 most promising biomass platform molecules,can be obtained by lignocellulosic acid hydrolysis.The product γ-valerolactone is widely used and its toxicity is lower than ethanol,which can be used as food additives,green solvents,biofuels and fine chemicals.At present,the research of the hydrogenation of levulinic acid mainly focuses on the catalysts.The non-noble metal catalysts are cheap,but the load capacity of metal is very high.In addition,the catalysts are not stable and the reaction conditions are harsh.On the contrary,the noble metal catalyst with load capacity exhibits higher activity and selectivity.Moreover,the metal is more likely to achieve high dispersion which shows stronger interaction between metal and supports.Therefore,the catalyst could be more stable at reaction conditions.In this paper,molecular sieves,which have been less studied in this field,are selected as supports to study the influence of alkali metals as auxiliaries on catalytic performance and the load capacity of alkali metals,as well as the influence of different impregnation method on catalytic performance.The effects of Mg,Ca and Mn were studied.The catalytic data showed that the addition of Mn increased the reactivity of the catalyst.Compared with the single metal Ru catalyst,the LA conversion of Ru-Mn catalyst increased by 30%,and the intrinsic activity of the catalyst also increased by more than 50%.The characterization results show that the addition of Mn enhances the interactionbetween Ru and the supports.Moreover,the synergetic effect between Mn and Ru makes the electron cloud moving from Mn to Ru.Based on the above results,the loading capacity of Mn was explored.With Mn loading increase,the particle size of Ru gradually decreases with dispersion increases.At the same time,with the synergetic effect,more electron transfer from Mn to Ru.The binding energy of Ru3 d is decreased and the binding energy of the Ru3 p is not changed.The addition of Mn is festinates the formation of strong interaction between Ru and the supports,when the catalysts have a small Mn loading.The catalytic data show that the activity of the catalyst first increased and then decreased with the increase of Mn loading.The catalytic activity and intrinsic activity were the highest when the Mn loading capacity is 0.7wt%.This indicates that the interaction between Ru and supports has a stronger effect on the catalytic activity than the electron transfer and the particle size.Moreover,the stability of Ru-07Mn-DT catalyst needs to be strengthened.After five cycles,it will be deactivated due to metal agglomeration and carbon deposition.Finally,different impregnation method were explored.It is founded that the samples prepared by deposition precipitation had high dispersion,small particle size,and strong interaction between metal and carrier,which showed highest LA conversion and GVL selectivity.Ru-DP catalyst activity was retained even at high reduction temperature,which indicated that the Ru-DP catalyst had better sintering resistance.Catalytic results show that Ru-DT-150 has the highest TOF value,reached 3110.7 h^-1.In the cyclic stability test,Ru-DT-150 catalyst can achieve 10 cycles without loss of activity,with excellent stability.By exploring different reaction conditions,we found that 2.5 Mpa of H₂ pressure and 80 ℃ of reaction temperature is the optimal reaction conditions.