NiAI催化剂催化5-羟甲基糠醛加氢制备2,5-二羟甲基四氢呋喃OACSTPCD

[Objective]5-Hydroxymethylfurfural(HMF)is one of the most important biomass-based platform chemicals that serve as the raw material for the production of various high-value added chemicals through catalytic hydrogenation.This study investigates the effect of NiAl catalyst on the performance of HMF reduction to 2,5-bis(hydroxymethyl)tetrahydrofuran(BHMTHF).[Methods]In this study,NiAl catalysts were prepared using the urea coprecipitation method.The effects of different Ni/Al ratios,calcination temperature,and reduction temperature on the physicochemical properties of the catalysts were systematically studied using X-ray diffraction(XRD),H2 temperature-programmed reduction(H2-TPR),scanning electron microscope(SEM),NH3 temperature-programmed desorption(NH3-TPD),X-ray photoelectron spectroscopy(XPS),transmission electron microscopy(TEM),and other characterization methods.The active hydrogenation reaction of the catalyst was carried out in a 25 mL reactor:0.25 g HMF,5 mL methanol and 0.125 g catalyst were placed into the reactor,followed by the addition of 2.5 MPa hydrogen.The reactor was then heated in a 100 ℃ oil bath.[Results]The phase structure of catalysts,prepared with different Ni/Al ratios and temperatures,and its impact on the hydrogenation activity of catalysts prepared from HMF to BHMTHF were thoroughly investigated.The results show that,with an increase in the Ni/Al ratio,the peaks corresponding to Al2O3 become nearly undetectable,likely due to the weak intensity of the diffraction peaks.However,with the increase of the Ni/Al ratio,the specific surface area of the catalyst and the proportion of Al elements gradually decreases.This is accompanied by a reduction in intermediate acid sites and the total acid content,leading to speculation that the acidic sites are mainly provided by Al metal.In addition,with the increase of Ni/Al ratio,the proportion of Ni0 initially increases and then decreases,among which Ni3 Al had the best catalytic activity,and the peak area of Ni0 is relatively large,suggesting that Ni0 is the active component.The obvious NiO phase diffraction peaks and NiAl2O4 phase diffraction peaks in the XRD pattern of Ni3 Al-650-650 indicate enhanced interaction between Ni species and Al2O3 at higher calcination temperature of the catalyst.This interaction makes it more challenging to reduce NiO,thus increasing the difficulty of subsequent catalyst reduction and activation.With the increase in calcination temperature,the required reduction temperature of the sample gradually shifts to a high temperature,as observed in the comparison of the H2-TPR spectra for oxides prepared at different calcination temperatures.This shift indicates that complete reduction to elemental Ni occurs at a higher temperature,consistent with the XRD characterization results.It is speculated that the reduced catalyst has the ability to activate hydrogen.During the second reduction,the active center activates part of hydrogen to form part of active hydrogen species,leading to a hydrogen consumption peak below 300 ℃.As the calcination temperature and reduction temperature increase,the crystal size of the catalyst continuously increases,the pore volume decreases,and the specific surface area decreases.The catalytic effect initially increases and then decreases.Among them,it is found that Ni3Al-350-650,which has the highest BHMTHF yield,has the maximum medium-strength acid sites.[Conclusion]The catalytic performance of NiAl catalysts in the reduction of HMF to BHMTHF was investigated.A Ni/Al ratio that is too high will result in a small specific surface area,reducing the number of exposed active site,and thus,decreasing catalytic activity.The reducibility of NiAl catalyst precursors can be adjusted by the calcination temperature,which would in turn affect the catalytic activity of NiAl catalysts.This study achieves a 99.5％HMF conversion with a BHMTHF yield of 87.5％.This work holds significant guidance for the design of non-noble metal catalysts for HMF hydrogenation.