Studies Of The Catalysts On Selective Hydrogenation Of Furfural And Maleic Anhydride

Selective hydrogenation of organic substrates containing conjugated C=C, C=Obond is an important type of reaction in the industrial production, lots of chemical canbe obtained though this type of reaction. Catalytic hydrogenation over heterogeneouscatalyst was thought to be the most economical and efficient way among all thetechnics. However, a lot of problems still existed in this technic, for example, copperchromite catalyst which cause sever environmental pollution has been used in thehydrogenation of furfural for decades. For the hydrogenation of maleic anhydride, thecatalysts were mainly noble metal catalysts and the reaction always operated in baltchsystem. So, environmental and economical catalysts still need to develop for thesereactions. Otherwise, the clear relationship between the physicochemical properties ofthe catalysts and their catalytic performance need to be built.In this work, different types of catalysts were prepared and their catalyticperformance was investigated in the hydrogenation of furfural and maleic anhydride.For the furfural hydrogenation, Cu-MgO catalysts were prepared by combustionmethod and their catalytic performance was improved by modification; An efficientand convenient way was used to prepare ultrafine amorphous alloy and their catalyticperformance were investigated in the hydrogenation of furfural. For hydrogenation ofmaleic anhydride, a series of non-noble catalysts were prepared and catalyticperformance were examined in the fixed bed system. Characterizations were used toclear the relationship between the catalytic performance and physicochemicalproperties of the catalysts. The main research contents and results are as followed:1. Selective hydrogenation of furfural to furfuryl alcohol on Cu-based catalystsA series of Cu-MgO catalysts were prepared by combustion method, andcharacterized by XRD, BET, H2-TPR and N₂O chemisorption techniques. The effectof Cu-loading and fuel ratio （actual fuel/stoichiometric fuel） on the catalyticperformance were investigated in the hydrogenation of furfural. It is obtained thatwhen the urea ratio was4, the catalyst with12.1%wt. Cu-loading get best catalytic performance. In the range of urea ratio changing, the Cu dispersion of12.1%Cu-MgO first increase and then decrease with the urea ratio increasing, and highestCu dispersion was obtained when urea ratio was4. High furfuryl alcohol selectivityover Cu-MgO catalyst as prepared was attributed to suitable Cu particle size andrepulsion between C=C bond and base support.In order to improve the catalytic performance, Zr was introduced to the Cu-MgOcatalysts. The effect of fuel ratio and the Mg/Zr on the catalytic performance wereinvestigated in the hydrogenation of furfural. It can be obtained that, when fuel ratiowas2and Mg/Zr ratio was2/8, the obtained Cu-Mg-Zr-O showed the best catalyticperformance. Compared with Cu-MgO and Cu–ZrO2prepared by the same method,Cu-Mg-Zr-O showed much higher activity and better stability, these might due tohigher Cu dispersion and stronger interaction between Cu and support.2. Preparation of ultrafine NiB amorphous alloy catalysts and their applicationin hydrogenation reactionsA series of NiB amorphous alloy catalysts were prepared through introducingAlCl₃into the preparation process, and their catalytic performance was investigated inthe hydrogenation of furfural and methyl isobutyl ketone. XRD, SAED and XPScharacterizations were used to verify the amorphous alloy structure of the materials asprepared. The catalytic performance demonstrated that the NiB catalysts showedmuch higher activity than the one prepared by conventional method. In the range ofAl/Ni ratio changing （Al/Ni=0.5/2-2/2）, catalytic activity increased with theincreasing of Al/Ni ratio. The characterizations showed that particle size and surfacearea of the as-prepared NiB catalysts can be controlled by changing the amount ofAlCl₃in the preparation process. When Al/Ni ratio was1/1, the NiB particle size wasabout3-5nm, it is about tenth of the NiB particle size prepared by conventionalmethod. Combined the characterizations and catalytic results, it was speculated thatthe increase of surface area should be not the only factor in improving the catalyticactivity of NiB alloy catalysts, some other reason, like relatively small particle sizemay also be have some effect in influencing the catalytic performance.The influence of AlCl₃added in the preparation process on the formation ofNiB amorphous alloy was investigated. It was believed that when AlCl₃added in thepreparation process, the formation of Al（OH）₃might be the key factor of theformation of nanoparticles size of NiB particle size. The formation of Al（OH）₃sol could play a role in isolating the reduced NiB nanoparticles, and inhibiting the rapidagglomeration during the reduction course by NaBH₄.3. Selective hydrogenation of maleic anhydride to succinic anhydride overNi-based catalystsA series of Ni-based catalysts were prepared by impregnation method, and theircatalytic performance was investigated in the hydrogenation of maleic anhydride. Itwas found that in the non-noble catalysts, MA conversion and SA selectivity wasaffected by the calcination temperature over Ni/TiO₂catalysts. Relatively highcalcination temperatures were benefit for the improvement of SA selectivity, however,too higher temperature may result in the formation of NiTiO₃phase, which is inactivefor the hydrogenation reaction. When the calcination temperature was1023K,Ni/TiO₂showed the best catalytic performance with95%maleic anhydride and96%succinic anhydride in the test condition （493K and0.2MPa）.Combined the results and the literatures, the factors which might have effect onthe selectvity of hydrogenation of maleic anhydride was discussed. H2-TPR showedthat the interaction between Ni species and support become stronger with the increaseof calcination temperature, thus may result in the production of electron-deficient Niactive centers, which are more favorable for the activation of C=C bond rather thanC=O bond. Otherwise, the decrease the Lewis acid sites with the increasing oftemperature might inhibit the activation of C=O bond, which also result in thereducing the side-product of GBL.