Modification Of Diatomite And Its Applicationin Sulfuric Acid As Support Of Vanadium Catalyst

Vanadium catalyst plays an important role in oxidizing sulfur dioxide to sulfur trioxide.The quality of its support diatomite,the method used to synthesis it,the mode of its active element are the key to its catalytic activity.The conversion of SO₂ has a great significance to sulfuric acid production and the control of environmental pollution.Apart from the activity of vanadium oxide of the vanadium catalyst,alkali metal sulfates also exist in the form of as auxiliary,they were loaded on the activity of silica support diatomite.Whereas they are very important factors affecting the catalytic activity of vanadium catalyst by the quality of diatomite,the way of active components combination with support,the presence of active ingredients.In this thesis,the selection of high quality and high prospects of diatomite,the modification method of diatomite,the improvement of active component to the support distribution,reduce the active component of the particle size are investigated.Different five types of diatomite are studied in this thesis as the support of vanadium catalyst,they are Ep（Mex.）,Celite（from U.S.A.）,DB（from Jilin,P.R.C.）,YN（from Yunnan,P.R.C）,NM（from Inner Mongolia,P.R.C）.The differences between them in chemical component,micro morphology,pore structure,degree of crystallization were investigated.At last,DB was chosen as the support of vanadium catalyst,for its high porosity,high content of Si,stable thermal quality,last but most important,it’s a domestic diatomite of China.In this paper,four kinds of method（acid leaching method,electric field method,microwave method,flotation method）are used to modify the quality of the support DB.The result showed that after four modifying methods by the optimization of experimental conditions,the content of Silica in the four methods increased by 14.12%,15.07%,14.48%and 15.52%,respectively.Using the optimized DB^Mas support,the synthesized vanadium catalyst showed excellent performance,which proved that microwave modification is the most effective method.Vanadium catalyst remained stable even under the low temperature 440 ^oC,catalytic activity of VC-DB^Mis 12.03%higher than the vanadium catalystwhich made by the original DB.Organic reagent X was introduced into the active component solutionto make it more homogeneous,according to the nature of vanadium as transition element.Traditional mixed grinding method（MG）,mixed grinding method in lab（LMG）,impregnation method in lab（LI）and ultrasonic impregnation method（LUI）were in comparison with in this thesis,the result showed that the addition of dispersed agent X has improved on the activity component on support,the usage of ultrasonic impregnation methodin lab（LUI）has enhanced the quality of vanadium catalyst most in micro morphology,crystal structure,catalytic activity and so on.The catalytic quality of LUI is 17.35%higher than the conversion of MG under the analytic temperature 520 ^oC,at the same time keeping the original figure of diatomite.By using H₂O₂as strong oxidant,micro-dimension active colloidal vanadium was synthesized by ultrasonic impregnation method in lab（LUI）and supported on modified diatomite,the catalytic activity of VC-P is 81.23%under analytic temperature 520 ^oC,is closer to 85.07%of international high-top vanadium catalyst.