Study On The Performance Of SBA-15 Supported Catalyst For CO₂ Hydrogenation To Methanol

CO₂ is the main carbon source of nature p articipating in carbon cycle,and also the main factor causing"greenhouse effect".There are two ways to solve a series of environmental problems caused by CO ₂:one is to increase energy conservation and emission reduction;the other is to realize CO ₂ resource.The hydrogenation of CO₂ to methanol can not only solve the problem of"greenhouse effect",but also produce additional economic benefits.At present,copper based catalyst is the mainstream catalyst in the process of methanol production from CO ₂ and H₂.However,the low conversion and selectivity are still the biggest bottleneck.From the point of view of additive and carrier modification,the effects of different additives and carrier modification on methanol selectivity were studied.Firstly,the catalysts of Cu/SBA-15,Cu-Zn/SBA-15,Cu-Zn-Mn/SBA-15 and Cu-Zn-Zr/SBA-15 were prepared by traditional over volume impregnation method with mesoporous SBA-15 as support.A series of characterization methods(XRD,BET,XPS and TEM etc.)were used to study t he physical and chemical properties of the catalyst.The results show that Zr species promote the dispersion of Cu and reduce its grain size,while the formation of Zr-O cluster provides an effective alkaline site for methanol synthesis,which makes the ca talytic performance of Cu-Zn-Zr/SBA-15significantly higher than the others.It has a higher oxygen vacancy concentration,which is more conducive to the formation of methanol.Two kinds of carriers,Zr/SBA-15 and Zr-SBA-15,were obtained by the modification of SBA-15 with the Zr in different ways Cu-Zn/SBA-15,Cu-Zn@Zr/SBA-15 and Cu-Zn/Zr-SBA-15 series catalysts were used to study the effect of different Zr modification methods on the performance of the catalysts.In situ CO₂ adsorption experiments show th at porous support SBA-15 can greatly promote the adsorption of CO₂ on the catalyst,and the catalyst modified by Zr can promote the dissociation of CO₂ into linear or bridged*CO,which can then be converted into monodentate and bidentate formates.However,the unmodified Cu-Zn/SBA-15 hydroxylates the activated*CO ₂ into bicarbonate,and then further transforms it into bidentate formate.The results of drifts show that the catalysts all pass through formate path during the hydrogenation of carbon dioxide.I n addition,the effect of Zr content on the performance of the catalyst was also discussed.The results show that only a small amount of Zr can replace Si to enter the SBA-15framework,and the best effect is when the Zr/Si molar ratio is 0.05.Finally,Cu-La_x/Zr-SBA-15 series catalysts with different La content were synthesized,and the interaction between La and support was discussed.The results showed that La species promoted the dispersion of Cu and La on the catalyst surface,enhanced the interaction between Cu and La,and further promoted the formation of methanol through Zr interaction in SBA-15 framework.