Preparation Of Bimetallic Based SAPO-34 DeNO_x Catalysts And Their Performance In Low-temperature SCR Process

Nitrogen Oxides has already became one of most dangerous air pollutants,with the rapidly development of economic,nitrogen Oxides emissions are increasing which has caused extremely bad effect on the ecological and environmental.Therefore,it is imperative to develop NO_x control technology.Currently,selective catalytic reduction?SCR?is the most widely used technology in flue gas denitrification technology.However,there are many problems for the commercial catalysts?V-W-Ti system?,such as narrow and high temperature window of 300?400 ?,easy to sinter,and are prone to be deactivated by high concentration of H2O or SO₂.If the SCR catalyst can still maintain a high denitration activity at temperature below 200?,and has better resistance to sulfur and water,and the working temperature of the SCR system can be further widened to realize the full load denitrification in the thermal power industry,furthermore,the SCR denitrification technology can be widely used in iron and stell cement and other low-temperature coal combustion industry,effectively control the iron and steel metallurgical and other industries of gas pollutant emissions.Therefore,it is of great significance to develop cheap and efficient low temperature SCR denitration catalyst.In this paper,the active components of the catalysts were screened by means of quantum chemistry calculations with Materials Studio2016.A series of single metal and bimetallic modified SAPO-34 zeolite catalysts were prepared by impregnation method,and then detect the activity of the catalysts under the temperature from 90 ? to 330 ?,during which the essay has a microscopic analysis on the selected catalysts together with the methods of BET,XRD,NH₃-TPD,TEM,XPS and so on.The experimental result shows that the optimal is Cu?2?-Mn?6?/SAPO-34,which the NO_x conversation rate can reach nearly 73.2%with the sapce velocity of 15000h-1,O2 concentration of 3%,ammonia ration of 1.1 temperature of 120 ?.When the temperature between 180? and 330?,catalyst activity can be maintained at 90%or more,and the highest up to 98.8%.Then,the anti-H2O and anti-SO₂ properties of Cu-Mn/SAPO-34 bimetallic composite molecular sieve catalysts were investigated.It is found that the effect of H2O on the catalyst is mainly due to the competitive adsorption of NH₃ and NO,and anti-SO₂ poisoning performance in general,the lower temperature the more prone to SO₂ poisoning and it is irreversible poisoning.In order to further improve the anti-SO₂ performance of the catalyst,combined with quantum chemistry to calculate the adsorption energy of NH₃,NO,H2O,SO₂ on the surface of the active component oxide,added additives such as Ce,Co,Fe,Mo on the basis of Cu?2?-Mn?6?/SAPO-34.Then,the catalysts were analyzed by BET,NH₃-TPD,TG-DTG,SEM,EDS,which was SO₂ poisoning before or after.lt was found that the catalyst modified by Ce was not only the activity of denitrification,but also the anti-SO₂ poisoning performance was improved obviously.After 8h of SO₂ poisoning,the activity of the catalyst was reduced from 96.6%to 85%,which was lower than that of the unmodified catalyst after 8h,and its anti-SO₂ performance was improved obviously.TG-DTG and SEM,EDS analysis showed that the addition of Ce was beneficial to inhibit the formation of ammonium sulfate on the catalyst surface.