| Reducing tar and other harmful components is the key work of the future development of cigarette industry in China. Reducing CO concentration as well as flavor-enhancing using adsorption method have wide application future in tobacco industry. It is an urgent need to develop novel porous materials with high adsorption capacity of CO or excellent release properties of some flavor compounds. This work is mainly concerned with study on synthesis and modification of kinds of porous adsorbents(e.g., modified activated carbon, modified zeolites and metal-organic frameworks) and their adsorption performance for CO as well as slow release property for flavor compounds in cigarettes. This research is an interdisciplinary subject of chemical engineering, material engineering and surface science, which has the value of scientific research and practical significance.The dynamic adsorption properties of CO from smoke gas on the modified activated carbon, molecular sieve and MOFs were studied in this work. Adsorption breakthrough curves of CO through fixed beds were measured to investigate the effects of pore structure and surface groups of adsorbents on the CO adsorption property. The results showed that some commercial adsorbents(e.g., activated carbon and zeolites) had very low adsorption capacity for CO, which were less than 3.0 mL/g at ambient temperatures. Three MOFs materials possessed much high CO capacity compared to activated carbon and zeolites due to their abundant unsaturated transition metal sites. For example, the adsorbed amount of CO on the MOF-74(Ni) was up to 45.6 m L/g. The high unsaturated metal sites Ni can form strong π-π interaction, and thus improved the adsorption capacity of CO greatly.Cu(I) and Ag(I) salts were used to modify the β-zeolite and their adsorption property of CO were investigated systematically. The adsorption selectivities of CuCl@β zeolite for CO/N2 and CO/CO2 mixtures were estimated on the basis of ideal adsorbed solution theory(IAST). The results showed that the dynamic CO adsorption capacity of Ag(I)@β-zeolite reached 9.5 m L/g, when Ag(I) loading was about 0.1 g/g. The dynamic CO adsorption capacity of 0.4 g/g Cu(I) loaded β-zeolite was up to 27.1 mL/g, which was 14 times of that on the original β-zeolite. The 0.4CuCl@β adsorbent achieved a superior adsorption selectivity up to 1600-5200 and 120-370 for CO/N2 and CO/CO2 mixtures at low pressure range of 0~10 kPa, much higher than parent β-zeolite. It still remained the adsorption selectivity of 500-1200 and 8-31 for CO/N2 and CO/CO2 mixtures at pressure range of 20~100 kPa.A series of adsorbents CuCl@ACs were synthesized by using spontaneous monolayer dispersion technology. Their pore structures were characterized and their adsorbent property of CO was tested. The results showed that the dynamic CO adsorption capacity of 1.2CuCl@AC was up to 14.35 m L/g, which was was 6.7 times of that of the original AC. The isosteric heats of CO adsorption on the 1.2 CuCl@AC and original AC were 43.4-56.7 and 22.0 kJ/mol, respectively. The high isosteric heat revealed a very high adsorption affinity of the modified ACs toward CO. In addition, the 1.2CuCl@AC present high CO adsorption selectivity for CO/CO2/N2 gases. In practice, the application of CuCl@ACs cut down 7 key harmful components of the cigarettes sharply, especially the HCN reduction up to 79.72 % and 85.64 %. The cigarette hazard index was reduced by 57.42-61.72 %. Therefore, CuCl@AC can be a promising candidate for reducing cigarettes harmful compound materials.The interactions of aroma substances including γ-nonaalactone, damascenone, ethyl vanillin, ethyl maltol and ethyl acetate with the surfaces of activated carbons and MCM-41 zeolite were investigated by using temperature programmed desorption method. Meanwhile, the effects of the electronegativity, molecule diameter as well as electric dipole moment of the selected five molecules on the interaction of activated carbon and MCM-41 zeolite were investigated. Results showed that desorption activation energies of five flavor chemicals on the activated carbon were decreased with their molecule diameters, implying that the force field from pore surfaces played an important role in the activated carbon adsorption toward flavor chemicals. The desorption activation energy of five flavor chemicals on MCM-41 followed the order of damascenone > ethyl vanillin> ethyl maltol > ethyl maltol > γ- nonaalactone. The desorption activation energy of the β-benzyl alcohol on five adsorbents was in the order of XF-AC>MCM-41 > A-silicon > SBA-15 > B-silicon. The desorption activation energy of β-benzyl alcohol on four kinds of non carbon porous materials increased with the concentration of the surface acid groups. Because of the activated carbon surface conjugate curled keys can and beta phenethyl alcohol benzene ring occurred curled- curled a strong adsorption effect, so beta phenylethanol in XF activated carbon desorption activation energy maximum.The highest interaction of β-benzyl alcohols with XF-AC was attributed to the ?-? interaction of β-benzyl alcohols with the XF-AC activated carbon.A novel carbonization method was proposed to modify activated carbon at different temperature for controlling interaction of flavor compounds with the ACs. Results showed that modification by carbonization can effectively change the content and composition of activated carbon surface acidic groups, More importantly, it can not only keep the adsorption capacity of the resulting activated carbon toward two kinds of flavor compounds, but also weaken the interaction of the two kinds of flavor compounds with the modified activated carbons. For example, the desorption activation energies of two kinds of flavor compounds on YK-300 were separately decreased by 38.16 % and 30.75 %, which will be very helpful to improve the release property of ACs toward some organic flavor compounds. |
PDF Full Text Request