Heterogeneous Reaction Mechanism Of Carbonyl Compounds On The Surface Of Atmospheric Mineral Particles And Inorganic Salts

Carbonyl compounds are a kind of important oxygen-containing volatile organic compounds in the atmosphere,which play a key role in atmospheric chemistry and have an important impact on the ecological environment and human health.The heterogeneous reaction of carbonyl compounds on particulate matter has some problems such as gas particle distribution.As the main medium of atmospheric reaction,mineral particles and inorganic salts are the main contributors of atmospheric particles,especially PM2.5.Different specific surface area and structure of mineral particles make them have different physical and chemical reaction activities.The sedimentation process of mineral particles is closely related to respiratory and cardiovascular diseases and air pollution.Inorganic salts are affected by secondary conversion,biomass combustion,dust and sea salt,and react with various substances in the environment,which will affect the acidity of precipitation and so on.They also play an important role in the process of geochemical cycle.Current studies mainly focus on the heterogeneous reactions of inorganic gases such as NOX and SOy on single particulate matter.Therefore,it is of great significance to study the heterogeneous reaction mechanism among mineral particles,inorganic salts and carbonyl compounds in the atmosphere.In this thesis,the physicochemical properties of particulate matter and inorganic salt before and after inhomogeneous reaction and compound reaction were studied by various characterization methods.Proton transfer mass spectrometry combined with flow tube reaction system was used to qualitatively and quantitatively analyze the products at the heterogeneous phase interface.The solid-phase interface of heterogeneous reaction was analyzed qualitatively and quantitatively by in situ INFRARED spectroscopy and gas chromatography mass spectrometer.The main conclusions are as follows:1.The physical and chemical adsorption of single carbonyl compound acetone on the three mineral particlesα-alumina,α-ferro oxide and silicon dioxide is certain,but there is no physical and chemical adsorption on the surface of the two inorganic salts,and its adsorption efficiency has the following magnitude relationship:Si O₂>Fe₂O₃>Al₂O₃.Meanwhile,inorganic salts inhibited the adsorption of acetone on particles,and ammonium sulfate inhibited the adsorption of acetone more than sodium chloride.2.Under the single carbonyl compound acetone reaction system,for the change of environmental factors,under the condition of dark reaction,the mineral particles on the surface of material adsorption dominated remains ketones,inorganic salt its surface will have adsorption of acetone,acetone does not react in the surface of inorganic salt,in the presence of mineral particles together with inorganic salt,Inorganic salts do not change the reaction products on the surface,but the specific surface area decreases with the addition of inorganic salts.It is speculated that on the one hand,it inhibits the uptake and adsorption reaction of mineral particles to acetone on the physical level,and on the other hand,it may change the binding site of the adsorption between acetone and mineral particles.At 40%humidity,the adsorption of water inhibits the heterogeneous adsorption process of acetone on the surface of each particle phase,but promotes the formation of free hydroxyl groups on the surface.Light can promote the conversion process of acetone to acetaldehyde on the surface of mineral particles,and the light on the surface of inorganic salts still does not react with acetone,but the addition of inorganic salts will affect the conversion process of acetone to acetaldehyde on the surface of mineral particles.At the thermodynamic temperature of 303K to 323K,the uptake of acetone on the surface of mineral particles decreases with the increase of temperature.However,at the same temperature,the amount of acetone absorbed by the same mineral particles in the whole one-hour reaction time still shows an overall increase trend with the increase of time.3.For the mixed system of acetone and propionic acid,when single mineral particles,the alumina surface is dominated by the absorption of propionic acid,iron oxide surface acetone and propionic acid have obvious absorption,propionic acid is slightly stronger than acetone;The surface of silica is mainly adsorbed by acetone.The monoinorganic salt system has no adsorption on acetone and ammonium propionate sulfate,and some dimers are formed on the surface of sodium chloride.After ammonium sulfate was added,the surface of alumina changed little,and the adsorption of propionic acid was still dominant.The uptake of propionic acid on the surface of iron oxide is decreased and acetone is dominant.The surface of silica is dominated by acetone adsorption,and the content of hydroxyl group and adsorbed water increases.After the addition of sodium chloride,the surface of alumina is still dominated by propionic acid,iron oxide by acetone,and silicon dioxide by acetone.The addition of inorganic salts has little effect on the competition mechanism of alumina and silicon dioxide,but has great effect on the competition mechanism of iron oxide surface.4.The physical and chemical properties of granular phase change before and after heterogeneous reaction.Macroscopically,the contact Angle is almost unchanged.Microscopically,the internal structure of the compound was greatly changed by scanning electron microscopy.