Preparation And Performance Of Catalytic-combustion Catalyst For Storage Tank VOCs

The emission control of volatile organic compounds(VOCs)is one of the important contents of current pollution prevention and control battle in China,and it is also an important content of the national air pollution prevention and control plan.And the emission of VOCs can not only aggravate PM 2.5 air pollution,but also cause direct harm to the human health.With the continuous development of the economy,the processing volume of petroleum refining industry is increasing rapidly in China.In2019,the total crude oil processing of China for the whole year is about 652 million tons,which makes the VOCs emissions of petroleum refining industry continue to increase.At present,the annual VOCs emissions of petroleum refining industry in China account for approximately 15.5%of the total annual VOCs emissions in China.Therefore,reducing VOCs emissions in the petroleum refining industry has become an important task in the daily production of the petroleum refining industry.The emission of storage tank VOCs is the main source of unorganized VOCs emissions from refineries.It is imminent to eliminate storage tank VOCs to reduce VOCs emissions from oil storage tanks.Catalytic combustion method is widely used in the field of eliminating VOCs because of its economic and effective characteristics.The technical core of the catalytic combustion method is the catalytic combustion catalyst.The catalytic activity and stability of the catalytic combustion catalyst not only directly affect the elimination effect of VOCs,but also directly affect the application cost of the method.Therefore,the preparation of high-activity,high-stability and low-cost catalytic combustion catalysts has become a hot spot for researchers.This article is devoted to the research and development of high activity,high stability and low cost catalytic combustion catalysts.Benzene series are the most difficult organic component to eliminate in storage tank VOCs.The benzene series in storage tank VOCs are mainly toluene.First,using toluene as a model reactant,the best noble metal active component Pd-Pt was selected,and its catalytic activity stability and catalytic combustion storage tank VOCs simulated gas were tested.The study found that doping a small amount of Pt can increase the dispersion of Pd substances and the active oxygen species supply performance of Pd.Pt doping can also properly adjust the acidity of the catalyst surface,which is conducive to improving the performance of catalytic combustion storage tank VOCs and the carbon deposition resistance.Next,the research on improving the anti-carbon deposition performance of Pd-Pt-based catalytic combustion catalyst was carried out.The study found that the carbon deposition of the prepared Pd-Pt-based catalytic combustion catalyst was not caused by the reaction of toluene on the acidic center of the catalyst to form polycyclic aromatic hydrocarbons during the catalytic combustion of low-concentration toluene.The carbon deposition of the catalyst is mainly generated by the disproportionation reaction of CO produced in the catalytic combustion process of toluene on the noble metal Pd⁰phase.The study also found that the addition of alkaline oxide K₂O will reduce the active oxygen species supply performance of the noble metal Pd active component,and the addition of K₂O will also promote the formation of noble metal Pd⁰phase.The addition of Ce O₂,an oxygen storage material,will increase the active oxygen species supply performance of the noble metal Pd active component and the content of the Pd O phase in the catalyst,thereby improving the anti-carbon deposition performance of the Pd-Pt-based catalytic combustion catalyst.In the study of the anti-SO₂poisoning performance of Pd-Pt-based catalytic combustion catalyst,it was found that a small amount of Pt doping can reduce the adsorption capacity of the noble metal Pd-Pt active component for SO_X,and at the same time,it can prevent the noble metal Pd active component from reacting with SO_X.The study also found that the use of mesoporous supports loaded with MgO to compete with noble metal active components for SO_Xadsorption can further improve the anti-SO₂poisoning performance of Pd-Pt-based catalytic combustion catalyst.At the same time,the highly dispersed MgO makes the generated sulfates also highly dispersed on the surface of the catalyst,which reduces the thermal decomposition temperature of the sulfates,which is beneficial to the regenerative desulfurization by roasting of the catalyst,and the catalytic combustion catalyst after regenerative desulfurization has good catalytic performance.Finally,the method of combining noble metal active components with non-precious metal oxide components reduces the loading of noble metal active components.Through research,it is found that the catalytic combustion catalyst prepared by using the noble metal Pd-Pt active component in combination with the copper-manganese composite oxide component has good catalytic performance.And the addition of Ce O₂,an oxygen storage material,can further enhance the catalytic performance of the catalyst.Finally,the molded catalytic combustion catalyst was compared with the existing commercial catalytic combustion catalyst.The results of the comparative study shows that the Pd-Pt/MgO/4.4Cu₁Mn₁O_X/1Ce O₂/?-Al₂O₃catalytic combustion catalyst prepared in this paper has better catalytic combustion performance for storage tank VOCs,and the preparation method of this catalyst is simple and easy,and has good industrialization prospects.