Actually I have prepared Al-VPO. But I did not get any peak of Al in the XRD pattern of Al-VPO. So it might be well dispersed or amorphous? If so then which is the active sites if I'll use it for any oxidation reaction?
Maybe Al exists in other form. what is the calcination temperature of the sample? You also can scan the sample slowly when you do the XRD experiment. Sometimes the XRD intensity of sample is weak, the slower of the scan rate, the higher of the intensity of XRD. If all these detail have been considered, you can confirm Al exist atmorphous or dispersed in your sample.
Al, or Al2O3 can be reacted into other compounds contained Al. Plz describe obviously reaction conditions or environment in your case.?
Hi Gobinda: 5wt % of Al should be enough to be detectable on XRD. I have seen on alumina samples with K impregnated that concentration lower than 5 wt % was not enough t be detectable. The commnets of Zhun Hu are pertinent before make final conclusion. you may check on XPS the Al concentration to confirm that you have it in your matrix.
5-20 wt% Al is well enough to be detectable in XRD but in the same time instrument sensitivity matters. You may check slow scan of your sample as mentioned by Zhun Hu. Another thing is the calcination temperature, Al should remain in your catalyst after calcination. So check the boiling point of aluminum oxide. You may check Al content in your sample by ICP analysis or by XPS and then only you can conclude whether Al is perfectly dispersed in the VPO matrix or it leached out from material.
Dear Gobinda, first you check whether your sample contain any Al species by the techniques available (ICP, EDX, NMR). the reason behind your XRD analysis maybe as follows:
May be your Al content is low enough that the response is not shown;
May be Al is incorporated in crystal system, that case you may find little peak shifting,
In this situation you can do elemental mapping analysis in TEM instrument to know how your Al is present in the matrices that is well dispersed or ice land.
Thanks to all for your valuable suggestions. Actually I just wana to conclude from the XRD pattern. I have done ICP-OES and XPS analysis . All the results are in good agreement with the Al content. But the matter is what could be drawn from XRD pattern.
Mr. Behera i feel that your optimization of rection condition was not enough for synthesis of Al- VPO catalyst. if the XRD pattern dosnt show any crystalline nature it May problem persist in reaction temperature and time factors was not sufficient. some times the fluctuvation during the synthesis might be cause this effects. From basic XRD pattern it self we can conlcusion whether Al enter in the lattice or not. if it is ion exchange check the additional peaks in refference pattern of VPO catalyst 20 theta at 23 and near 30. As your synthesized gel condition suppose to be an alkaline ph condition aluminum content may form free alumina which we can see additional peaks at 43, 57, and 29 of 2 theta values. in case it suppose to be isomorphic subsitution the structural collapse may be happend by high percent loading of alumina content. some times optimum of aging, nucleation times and stirring optimization may help you. By your synthesized material contains vanadium can be cappable for oxidation reaction. in presence of aluminum to creates weak acid sites with adjusant phosphates facilitates high conversion rather than isomers. it also possible in competion aluminium phosphte complex incapable to maintain VPO structure, which as resulting amorphous. try to use in acidic conditions. Additional suggession for you, after the stirring try to keep the solution in sonification may the crystals will develope without amorphous form in material synthesis by solgel or hydor thermal process. Once there is crystalline material you got check do further as such preceeding suggessions XPS, NMR, EDS results. suppose the material is not formed, i feel personally such a characterizations is wasting of time. check the reference is there is amorphous material is active for your studies.
In my opinion, for your case have 2 possibility. 1) Al leached out from the VPO structure, hence in the no crystalline peak was observed in XRD diffratogram. In order to test the presence of the Al in the sample, I suggest you to run AAS/ICP/XRF analysis to confirm the presence of Al in the sample. If Al is presence in your sample, then your sample can be said is amorphous and the Al is well distributed.
Hi,
I also would try to do a TEM - EDX which would give you a rapid and cheap answer to your question about the composition of your final material
- Badges
- Science method
- Similar topics
- Methodology
- Crystallography
- X-ray Diffraction