| A lot of the occurrence and spread of fire are related to the wood.Because it is easy to burn.But, due to the gas phase flame retardant mechanism, the flame retardant interrupted combustion reaction, which ofen produce more smoke and carbon monoxide as the representative of the incomplete combustion of toxic and harmful gases. Therefore, the flame retardant treatment of wood in the same time, it is necessary to smoke suppression, reduce toxicity, reduce the smoke generated as the representative of the release of toxic gases by burning wood and carbon monoxide. MCM-41 mesoporous molecular sieve has a large specific surface area, regular pore structure, good hydrothermal stability and other characteristics, which widely used in various fields, such as catalyst loading, adsorption and separation, etc.. Some transition metals have strong catalytic oxidation characteristics for some incomplete oxidation products, which are usually used for the purification of automobile exhaust gas, such as CO, NO, and so on. In this thesis, the MCM-41 as a carrier, the study of transition metal Sn and Mn as catalyst modified molecular sieve catalytic oxidation of CO is on behalf of the timber produced by the combustion of harmful gases and explore the APP (poly ammonium phosphate) flame retardant treated wood flame retardant and smoke suppression and reduction characteristics and mechanism of toxicity. The following important conclusions are obtained.MCM-41 mesoporous molecular sieves with mesoporous structure were prepared by hydrothermal crystallization method. The effect of crystallization time on the structure of the synthesized zeolite was explored. The results showed that the crystallization temperature of sixteen alkyl three methyl ammonium bromide as the template, the ethyl silicate as the silicon source, the crystallization temperature of 105℃ and the crystallization time of 48h, can be obtained with good structure MCM-41 mesoporous molecular sieve. Metal Sn and Mn modified by impregnation and skeleton doping method. Nitrogen isothermal curve and pore size distribution shows that the pore size of the modified molecular sieve is about 6.2nm in two ways. The molecular sieve modified by impregnation method has a good pore structure, but because of the entry of metal ions, the area of hysteresis loop is decreased, and the specific surface area is reduced. The peak on the pore size distribution curve was slightly lower than that of the modified impregnation, which indicated that the metal ions enter the molecular sieve structure in the process of doping modification.By using the cone calorimeter method, the effect of MCM-41 mesoporous molecular sieve and its metal modified molecular sieve on the amount of flue gas emission from wood and the characteristics of combustion were studied. The addition of molecular sieve, the rate of carbon residue has been improved, which shows that the combustion of wood has a certain effect on the formation of carbon. The experiments showed that the total heat release of the wood powder was decreased by 8% and the total amount of wood powder modified by Mn was decreased by, and the total amount of wood powder was decreased by 55%. The results showed that the effect of Mn doped modified MCM-41 on the smoke suppression was the best.The combustion characteristics and gas release characteristics of APP flame retardant treated wood were studied by using the cone calorimeter method. Carbon residue rate showed that the APP, as well as the addition of metal modified-APP molecular sieve of wood powder samples, the residual carbon rate was significantly higher than that of wood powder. Description, APP to join, to promote the role of wood powder into carbon. Among them, the residual carbon ratio of -APP and Mn skeleton doped modified wood powder was higher than 162%. It is showed that the proportion of carbon in wood powder burning can be greatly improved by using the modified molecular sieve and APP composite.The total heat release rate and total smoke release rate of the wood were decreased by 25% and 31% respectively, but the average yield of CO (COY) was 1.6 times of that of wood. This indicates that poly ammonium phosphate has good flame retardancy and smoke suppression effect, but due to the gas phase flame retardant mechanism has blocking free radical chain combustion reaction and has the characteristics of oxygen isolating, the pyrolysis gas products can not be completely burned, and produced more with CO as a representative of the poisonous and harmful gases. Therefore, in the use of poly ammonium phosphate as a flame retardant, at the same time, it is necessary to add the material with the effect of reducing the toxicity of the substance.The total heat release (APP) increased by. while the total heat release (THR) increased by 13%, while the total heat release (CO) increased by 32% in the Sn treated wood (W-APP), but the total amount of smoke (TSP) decreased by 34%. So the metal modified after of mesoporous molecular sieve can effective catalysis to the toxic gas components on behalf of the CO transformation, and effectively reduce the combustion flue gas in the process of production, so as to achieve the smoke suppression role in reducing the toxic.The mechanism of APP, molecular sieve and metal modified MCM-41 molecular sieve to reduce the smoke toxicity of wood were studied by using pY-GC-MS. Studies have shown that molecular sieve and Sn elements added to catalytic oxidation to CO as the representative of products of incomplete combustion, and the carbonyl, carboxyl, hydroxyl, methyl etc. The elimination reaction and polycyclic aromatic reaction depth, into less toxic to CO2 as representative full oxygen products, among which the alcohol accounted for main product of 30.96%, acid accounted for 15.12%, ketones accounted for 10.32%. The content of oxygen containing compounds increased, indicating that the Sn impregnated modified molecular sieve had catalytic oxidation to APP flame retardant wood powder. Adding MCM-41 mesoporous molecular sieve modified by impregnation process can effectively reduce the toxicity of APP flame retardant wood fire. APP changed the direction of the wood pyrolysis, prompting the wood to crack to generate more carbon and water in the direction. The heterocyclic compounds accounted for 20.27% of main product, compared to the Chunmu powder pyrolysis was 5.79%, the production increased dramatically, so as to promote the formation of stable and compact carbon layer to protect the internal wood, and stable carbon layer is not easy to produce small particles of carbon, and reduce the release of dust.The characteristics and innovations of this study are the Sn, Mn metal modified molecular sieve used in the flame retardant process of wood flue gas conversion and smoke suppression and toxicity reduction. |
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