Reaction Integration Of N-Butyraldehyed Self-condensation With Successive Hydrogenation And Its Kinetics Over NiO-MnO₂/Nb₂O₅-TiO₂ Catalyst

2-Ethylhexanol is an important organic chemical which is mainly used for production of plasticizers.At present,2-ethylhexanol is usually produced commercially through three consecutive reaction steps including propylene hydroformylation,n-butyraldehyde self-condensation and 2-ethyl-2-hexenal hydrogenation.The integration of the last two reaction steps can shorten process flow,reduce energy consumption and lower production costs.In view of a side-reaction of direct hydrogenation of n-butyraldehyde in this reaction system,improvement of 2-ethylhexanol selectivity is crucial for this integration.This thesis focuses on this issue and possesses important values in academia and application.First of all,a series of NiO-MO_x/Nb₂O₅-TiO₂ catalysts were prepared by a co-impregnation method and their catalytic performances in the reaction integration of n-butyraldehyde self-condensation with hydrogenation were evaluated.The results indicated that reduction-in-reaction mode can delay the appearance of metal sites and effectively inhibit the direct hydrogenation of n-butyraldehyde and thus improve the selectivity of 2-ethylhexanol.NiO-MnO₂/Nb₂O₅-TiO₂ shows the best catalytic performance and the selectivity of 2-ethylhexanol is 88.5%while that of n-butanol is 11.4%.The analysis results of H₂-TPR,XRD and BET showed that introduction of second-metal component is beneficial to decreasing the reduction temperature of NiO and achieving the complete reduction of NiO during the reaction process.The suitable Ni/Mn mass ratio and NiO-MnO₂ loading are separately 10 and 14.3 wt.%in NiO-MnO₂/Nb₂O₅-TiO₂ catalyst.The XPS analysis of the catalyst before and after reaction was carried out.The results showed variations of the electronic binding energies of metal Ni and Mn from the standard data,suggesting that there is an interaction between Ni and Mn.The correlation between number of holes in d-orbital and catalytic performance explains the effect of different Ni/Mn mass ratio.Secondly,effect of reaction conditions on NiO-MnO₂/Nb₂O₅-TiO₂ catalyzed reaction integration was studied and the suitable reaction conditions were determined as follows:a weight percentage of NiO-MnO₂/Nb₂O₅-TiO₂=15.0 wt.%,a reaction temperature of 200℃,a reaction pressure of 4 MPa and a reaction time of 5 h.Under the above reaction conditions,the selectivity of 2-ethylhexanol reached 90.0%at a 100.0%of n-butyraldehyde conversion.The catalyst could be used for four times without a substantial change in its catalytic performance,indicating that this catalyst has a good stability.Finally,the reaction integration catalyzed by NiO-MnO₂/Nb₂O₅-TiO₂ was kinetically studied and a possible kinetic model was established,laying foundation for reactor design and analysis.