(1) Study of the selective catalytic reduction (SCR) of nitrogen oxides (NOx) and applied research on the cleaning of automobile exhausts

The diffuse reflectance infrared Fourier transform spectroscopy equipment is developed to realize the in situ research on the mechanism of the SCR of NOx. A novel enolic reaction intermediate is first found on the surface of Ag/Al2O3 catalyst, and it is found that this surface species plays a crucial role during the NOx reduction. Based on this, a mechanism of the NOx reduction was proposed which can successfully explain many experimental phenomena confused us for a long time as follows: ethanol and acetaldehyde show the similar excellent efficiency of the NOx reduction, while the selectivity of methanol is very low; the low temperature activity of propylene is much lower than that of ethanol in the SCR of NOx; the presence of water vapor inhibits the NOx reduction by propylene while enhances the NOx reduction by ethanol over Ag/Al2O3; and ect. In the case of methanol, the enolic structure which requires two carbon atoms at least cannot be produced from methanol. As for the SCR of NOx by propylene, the formation of surface enolic species also becomes very difficult resulting in the reaction must go through the approach of adsorbed acetate, while the reactivity of surface enolic species with NOx is much higher than that of acetate. These results radically established the superiority of Ag/Al2O3-ethanol system during the NOx reduction. These results were respectively published in journals including J. Phys. Chem. B, Appl. Catal. B and etc.

According to the theory of “selective catalytic reduction of NOx in oxygen-rich exhausts, the de-NOx catalyst is developed with high activity and resistance to water vapor poisoning, and the catalyst and catalytic reduction method are used to remove NOx from diesel engine exhausts. The high-efficient catalytic converter is also built up for the removal of NOx in emissions of diesel engines. National “863” expert team has highly appraised the research result: (1) Determining the technical route for the SCR of NOx, and combinational system of catalyst (Ag/Al2O3) and reductant (ethanol) is originally developed. The breakthrough progress on the theory of the SCR of NOx successfully explains the high efficiency of Ag/Al2O3-ethanol system. (2) The developed catalyst shows high average conversion of NOx (above 80%) within the typical diesel engine exhaust temperature range. The catalytic converter is extremely effective for the NOx reduction on an actual engine bench, which meets the requests for the Euro Ⅲ level. (3) Optimizing the process and design of catalyst coating, and setting up a set of automatically vacuumizing coating equipment with proprietary intellectual property rights, which laid a foundation for the industrialization of the technology. Seven invention patents have been declared for the research, and the practical preparation is conducted for the large-scale application.

(2) Non-photocatalytic disinfection theory and high-efficient technology on the solid-gas interface for indoor air

Research is developed on the adsorption and deactivation of microorganisms on the surface of metal catalyst, which shows that in the air the catalyst indicates strong biological deactivated effect for SARS virus adsorbed on the surface at room temperature, and within five minutes, the SARS coronavirus is completely inactivated. Simultaneously, it has excellent disinfected and decomposed functions for E. coli. and feast, with important scientific research and practical application values. Due to the predominant innovation of the achievement, the paper was rapidly accepted after the contribution, and now it has published in Catal. Commun. and the editor considers the work as a new cross-field.

The developed catalyst has good purification roles on volatile organic compounds, which can decompose formaldehyde and other organic compounds at room temperature. Due to the technical innovation and important application values for the achievement, it has been paid high attention by related domestic and foreign enterprises.

(3) Environmental catalytic material of nano gold and its applied research in environment and industrials

The supported gold catalysts are new industrial and environmental catalytic materials developed in recent years, and have been applied not only gas purification, but also as sensor materials, show a continuously increasing and more extensive application prospects. Generally speaking, gold is an inert metal with no catalytic activity, but in a nano special state it becomes a good catalytic material, which is a challenge for chemists to the current catalysis theory and catalyst preparation science.

Systems research was conducted in the aspects including the preparation science for environmental catalytic materials of nano gold (J. Mol. Catal. A, 2003, 200(1-2), 229), assembly of nano gold in mesoporous materials (Appl. Catal. A, 2003, 242(2), 275), reactant adsorption (Science in China. B., 2001, 44(6), 596), surface oxygen species (Appl. Catal. A, 2001, 213(2): 173), active sites of gold catalytic materials (React. Kinet. & Catal. Lett., 2000, 70(1): 153), active mechanism of gold (J. Envirn. Sci., 2004, 16(2), 381), oxidation of CO and VOCs (Chin. J. Catal., 2002, 23(6), 489), decomposition reaction mechanism of ozone (Appl. Catal. B, 2001, 33: 217), and their environmental protection applications. The rules on the preparation and activation of environmental catalytic material of nano gold, and surface oxygen species（O2-） of oxidation reaction and its reaction activity at room temperature, the adsorption and reaction mechanism of typical pollutants, the active sites (Auδ+) and mechanism of nano gold, the oxidation of CO and selective oxidation mechanism at hydrogen-mixed atmosphere, and the main results were reported on the international academic journals (Appl. Catal.B, Appl. Catal., Reat. Kinet. Catal. Lett, Indus. Eng. Chem. Res), which received good appraisals from the international authoritative experts (Bond, G. C. and Thompson, D. T,). These developed CO low temperature oxidation catalytic materials and ozone- decomposed catalytic materials can be respectively applied to air purification, closed CO2 laser, fire extinguishers, aviation and etc. Idea for designing new catalysts for hydrogen elimination from CO2 feed gas in urea synthesis were suggested. An excellent catalyst with high activity for H2/O2 and CO/O2 reactions, good resistance to sulfur and good performances for energy saving was developed (Ind. Eng. Chem. Res., 2001, 40(7): 1591, Chem. Rese. in Chin. Univ., 2000, 16(5), 342).

(4) Mechanism of heterogeneous photocatalysis and application for the purification of environment

Heterogeneous photocatalysis using semiconductors is a very promising technology for the purification of water and closed environmental indoor air. In this field, we have achieved some science innovation results shown in the following. (a)Surface bond-conjugated TiO2/SiO2 was prepared by means of the impregnation. Compared with TiO2 powder, th catalyst showed three times higher photoactivity for the degradation of azodyes, formaldehyde, bacteria. The fixed catalyst is much easier to decant from purification system than powder. It is very promising for the practical cleaning water and indoor air. The results was published on Appl. Catal. B 2001，35:95 and was cited for 21 times by other authorsin SCI. (b) The photocatalyst power was coated on the nickel meshwork by hydroxyl of silical and aluminum sol. It could mineralize formaldehyde, acetaldehyde more than 90% , photocatalytic remove E.coli 100% under weak indoor light. The high efficient photocatalysts supported nickel meshwork is very promising to be used for eliminating bacteria in drinking water and indoor air. (c) C, N-modified TiO2/silical gel was prepared by impregnation method with ethanediamine, which have an absorbance band from 400 nm to 600 nm. Under indoor light (fluorescence light), the catalyst shows the same photoactivity as P25 TiO2 for the destruction of E.coli, Bacillus Pumilus and formaldehyde. However, under visible light（0.098 mW/cm2）irradiating C, N-modified TiO2/silical gel, the above two bacteria are completely removed, and 98% formaldehyde is transformed into CO2. P25 TiO2 is ineffective at the same condition. (d) Weak light multifunctional antibacterial material was prepared by combining inorganic antibacterial material with photocatalyst. E.coli, Bacillus Pumilus could be completely removed and transformed into CO2 under indoor weak light with the material. The material not only avoids mocrooganism resistance to inorganic antibacterial material but also decreases the light intensity required activating photocatalysts, leading the weakk light effective for removing most of bacteria. The material has potential capacity for destruction of bacteria in drinking water and indoor. (e) (5) Nanoparticles supported on TiO2/Silical gel were prepared by photocatalytic deposition. Ethylene, acetaldehyde and carbon monoxide were mineralized to 90% by photothermal synergism. The introduction of noble metals leads to photothermal synergism to enhance the selectivity of CO2 production to decrease the accumulation of intermediates and prevent deactivation of the catalyst.