Thin Palladiun/SiO 2 composite membrane supported on porous stainless steel has been fabricated by a novel preparation procedure. SiO 2 colloid suspensions with different particle sizes were applied to modify the pore size of the substrate and also form an intermediate SiO 2 layer to support the palladium layer. Palladium nuclei were seeded by a chemical vapor deposition process using Pd(F 6 acac) 2 as metal precursor, and then a palladium layer thinner than 10 μm was prepared by electroless plating. The membrane had a hydrogen permeance of 2.7×10 −6 mol/m 2 .s.Pa and a permselectivity of P H2 / P N2 in the range of 300–400 at 773K. The preparation process showed that SiO 2 layer had a unique property for palladium adhesion compared with other studied metal oxides. The seeding process by chemical vapor deposition showed this step is significant for the preparation of a defect-free membrane. A novel electroless plating process was also applied using a weak acidic both, which is different from the usually used basic ones containing N 2 H 4 . The surface morphology and component of the membrane have been studied by scanning electron micrograph (SEM) and energy-dispersive X-ray analysis (EDX). The permeance and permselectivity of the membrane to hydrogen have bean measured at different temperatures.

TiO2 is known as a low-temperature selective catalyst for the reduction (LT-SCR) of NO with NH3. Furthermore, it is well-known that the oxidation of NO over the catalyst plays an important role in the LT-SCR. Adsorption of SO2 and NO over two kinds of TiO2 catalysts was investigated using a conventional flow type fixed-bed reactor at 100 degrees C under atmospheric pressure. The effect of the presence of SO2 on the adsorption of NO over the catalysts and the formation NO2 from NO was studied. The relationship between the NO2 formation, the NO adsorption, and the SO2 adsorption was also studied. The presence of SO2 was essential for the oxidative adsorption of NO over the catalysts. SO2 was adsorbed and converted to SO42-, then NO adsorbed on the SO2 pre-adsorbed catalyst and converted to NO3-. The presence of both SO2 and NO contributed to the formation NO2 from NO over the TiO2 samples. It was found that NO2 was evolved from an equimolar reaction of NO and SO2.

Inorganic-organic hybrid membranes containing silica as the structure matrix, poly(N-vinylpyrrolidone) (PVP) as the organic mediating agent and silver ions as olefinic carriers were prepared using sol–gel method and dip-coating process. The structure and permeances of the membranes for N 2 , He, C 2 H 4 , C 2 H 6 at different temperatures indicated that defect-free membranes were obtained and the transportation of the C 2 H 4 through the membranes followed the dissolution and diffusion mechanism. Ideal separation factors of C 2 H 4 /C 2 H 6 through the membranes were evaluated at the temperature of 298, 373 and 423 K respectively using mixture gas of 50% C 2 H 4 -50% C 2 H 6 . The results showed that the ideal separation factors of C 2 H 4 /C 2 H 6 through the membranes were obviously greater than the ratio of PC 2 H 4 /PC 2 H 6 obtained from the single gas measurement due to the hindering effect by the adsorbed C 2 H 4 . The ideal separation factors of C 2 H 4 /C 2 H 6 increased with temperature and reached 10 at 423 K, which suggested that C 2 H 4 and C 2 H 6 could be separated at lower humidity compared to the reported organic polymer/silver salt membranes in which humidified gases and higher silver loading were usually used. The transport of C 2 H 4 in the inorganic-organic hybrid membrane was proposed to follow the hopping mechanism, that is, olefins moved across the fixed silver sites.

A thin palladium film supported on SiO2-modified porous stainless steel has been fabricated by a novel preparation procedure. SiO2 colloid suspensions with different particle sizes were applied to modify the pore size of the substrate and form an intermediate SiO2 layer to support the palladium layer as well. Palladium nuclei were seeded inside the pores of the modified substrate besides some particles deposited over the surface by a chemical vapor deposition process using Pd(F6acac)2 as the metal precursor, and then a palladium layer of 2−6 μm was prepared by an electroless plating process. The membrane had a H2 permeance of 2.7 × 10-6 mol/m2·s·Pa and a permselectivity of PH2/PN2 in the range of 300−450 measured using single pure gases at a pressure difference of 0.5 × 105 Pa and at 773 K. The surface morphology and the components of the different layers of the membrane have been studied by scanning electron microscopy and energy-dispersive X-ray analysis. The permeance and permselectivity of the membran...

A thin Pd membrane with a thickness of 6μm has been prepared on a commercially available macro porous stainless steel (MPSS) tube using an electroless plating technique followed by the surface modification with cerium hydroxide particles. The hydrogen flux through the membrane is as high as 0.235mol/(m2s) at 773K with a pressure gradient of 100kPa, but the separation factor (H2/Ar) is only 14 due to the surface defects. The other membrane with a Pd thickness of 10μm prepared by the same method produces a high separation factor of 108, but the hydrogen flux decreases to 0.178mol/(m2s). The defects of the 6μm membrane can be removed by the chemical vapor deposition (CVD) of a Pd complex on the surface. After the CVD treatment for three times, the separation factor increases greatly to 565 without decreasing the original hydrogen flux. Hence, the combined method of electroless plating and CVD provides a good route for preparing thin Pd/CeO2/MPSS composite membranes with high hydrogen permeability and selectivity.

The effects of halogen ions on the activities of Al2O3, TiO2, and ZrO2 for the low-temperature SCR of NO with NH3 have been studied. The results showed that Cl- and Br- ions increased the life of the catalysts from 1 to 2 h to several tens of hours (NO removal greater than or equal to90%), F- had no clear influence on the performances of the studied metal oxides, but I- was a fatal poison to the catalysts due to the formation of 12, which would cover the active sites needed for the reaction. The doping effect of Cl- and Br- ions on the catalysts was due to the increase of both the strength of acidity and the amount of acidic sites on the surface of the catalysts, which was confirmed by the temperature-programmed desorption of NH3 from the Al2O3-based samples. On the other hand, the accumulation of nitrate salts during the reaction decreased obviously over the Cl- and Br- ions-doped samples; as a result, the average selectivity to N-2 during the reaction time increased correspondingly.

The activity of slaked lime for the simultaneous absorption of SOx and NOx from flue gases of coal combustion has been studied using a fixed bed reactor at 90 degreesC. The slaked lime samples were prepared by swelling the natural lime using water vapor. It was found that NO and SO2 enhanced the adsorption of each other. The results of IR showed that SO2 was absorbed as SO42- salt by Ca(OH)(2) in the presence of NO; however, it was mainly absorbed as SO32- salt in the absence of NO. It is interesting that NO could not be absorbed by the slaked lime without SO2 at the low temperature, while it was converted to NO3- salts with the presence of SO2. This implied that some species formed from SO2 played a role as catalysts for the adsorption of NO by the slaked lime, which indicated a possible way to remove SOx and NOx simultaneously from the flue gases of coal combustion.

A highly active macroporous sorbent for high-temperature desulfurization was prepared by swelling raw lime in a water-acetic acid mixture. The desulfurization capacity of the macroporous lime was compared with the raw lime, lime treated with liquid water, and lime treated with acetic acid vapor. It was found that the reactivity of the lime treated with water-acetic acid mixture depended on the content of calcium acetate in the precursor, a mixture of calcium acetate and calcium hydroxide. The desulfurization capacity of this sample reached the same level as the acetic acid vapor treated lime when the calcium acetate content of the precursor was 46.7%, but was much higher than the water-treated sample or the raw lime. The acetic acid-water swelling process is much more economical than the acetic acid vapor swelling method. Furthermore a mixture of water-acetic acid has a less offensive odor than pure acetic acid vapor. The higher reactivity of the lime prepared by acetic acid-water swelling method was due to the macropores (larger than 200 nm) produced during the swelling process. These macropores provide a diffusion route for SO2 in the sorbent during the sulfation and did not become plugged. It was concluded that a highly reactive and practical lime should possesses an adequate number of pores, adequate pore distribution, and good connection of the different size pores for good permeability of reactant gases and to prevent the plugging of the pores by sulfation.

To develop a SO2 sorbent that is highly reactive in the presence of high concentrations of CO2 at high temperature, the effect of the pore-size distribution on the reactivity was investigated at 800 degreesC using a natural limestone, natural lime, modified macroporous lime, and limestone. The modified lime samples were prepared from a kind of natural lime by water-acetic acid swelling and water swelling methods. The modified limestone was prepared from the modified lime by carbonation. Pores smaller than ca. 200 nm in the modified lime and natural lime virtually disappeared, and pores larger than ca. 200 nm also considerably decreased in pore size after carbonization. The reactivity of the modified limestone depended on the degree of development of pores larger than 200 nm, because the macropores provided a diffusion route for SO2 in the sorbent during sulfation.

To develop an easily regenerable high-temperature desulfurization sorbent, the oxidation of spent Fe2O3 and CuO sorbents in the presence of O-2 and H2O was studied. The effect of H2O on the oxidation of the spent Fe2O3 and CuO was examined using a temperature-programmed reduction technique and isotopic (H2O)-O-18. In this study, it was found that H2O directly contributed to the oxidation of the spent metal oxides in the presence of O-2. The oxidation of the spent metal oxides (containing metal sulfide MexSy) in the presence of 10% H2O and 10% O-2 could be explained by the following two reactions: MexSy + (z + 2y)H2O double left right arrow MexOz + SO2 + (z + y)H-2 and (z + 2y)H-2 + {(z + 2y)/2}O-2 double right arrow (z + 2y)H2O.

The selective catalytic reduction (SCR) of NO to N-2 by NH3 over TiO2, ZrO2, and Al2O3 was studied at 90 degreesC using a feed stream that was simulated to represent the effluent from a coal combustion boiler. The effects of SO2 on the reduction of NO were studied. It is interesting that the SCR reaction was interrupted when SO2 was absent from the feed gas. This indicated that SO2 participated in the reduction process of NO at low temperature. A mechanism for this low-temperature SCR process was proposed, which was based on the reaction results and studies of NO, NH3, and SO2 temperature-programmed desorption (TPD) profiles under different experimental conditions. Among the three catalysts, ZrO2 and TiO2 had higher activities than Al2O3 The selectity to N-2 over the different catalysts changed in the sequence of ZrO2 > TiO2 > Al2O3 The activities of these three catalysts decayed with reaction time as a result of the accumulation of ammonium sulfate and nitrate salts plugged in the pores of the catalysts. However, the deactivated catalysts could be easily regenerated by washing with water.

Novel inorganic–organic membranes that contained Ag+ ions as olefin carriers were prepared using sol–gel and dip‐coating processes. The permeance of the membranes for nitrogen, helium, ethane (C2H6), and ethene (C2H4) were evaluated using the single‐gas permeation method at temperatures of 298, 373, and 423 K. The results showed that the selectivity of the membranes to C2H4 against C2H6 increased as the measurement temperature increased, because the decomplexation rate of C2H4 molecules from Ag+ sites is enhanced by increases in the temperature. Fourier transform infrared spectrophotometry of the hybrid membranes and the performance of the membranes at 373 and 423 K indicated that poly(N‐vinylpyrrolidone) (PVP) had a role in increasing the flexibility of the inorganic network and also served as a mediation agent to fix Ag+ ions in the polymer segments, because of the coordination interaction between the Ag+ ions and the PVP.

The promoting effects of various calcium salts on the activity and selectivity of ZrO2 in isosynthesis were studied in this work. Calcium salts were added into zirconia by mechanical mixing methods. Catalytic tests were performed under relatively mild operation conditions (673K, 650h−1, 5.0MPa). CaF2 and CaSO4 were found to be effective additives, which could remarkably enhance the i-C4 selectivity in total hydrocarbons while maintaining the activity of pure ZrO2 when being added into zirconia. However, Ca(NO3)2, Ca(BO2)2 and CaCl2 wholly changed the distribution of hydrocarbons to favor the methanation. The results of temperature-programmed desorption (TPD) of NH3 and CO2 indicated that the performance of the catalysts depended on the acid–base properties of the catalysts. The appropriate amount of acid and base and the ratio of the basic to acidic sites on the catalysts are significant for the synthesis of i-C4 hydrocarbons from CO hydrogenation.

The influences of precipitation pH, zirconium salt precursors and the calcination temperatures on the crystal structure and catalytic performance of zirconia in isosynthesis have been studied. The results indicated that the catalytic performance of zirconia in isosynthesis was strongly influenced by the pH of precipitating solution, zirconium salt precursors and the calcination temperatures, However, the crystal phase of zirconia was not so sensitively dependent on the pH. Monoclinic was always the main crystal phase when the value of pH was changed in the range of 6–14. Zirconia prepared from Zr(NO3)4, ZrCl4, ZrOCl2 were monoclinic/tetragonal, but monoclinic was the dominant phase. Zirconia prepared from Zr(SO4)2 was a mixture of tetragonal/amorphous. Even trace of SO42− involved in the gel, the crystallization of zirconia was delayed, the phase transformation from tetragonal to monoclinic being inhibited.

CH 3 OCH 3 , CH 3 OH, and i-C 4 H 8 were the main products in different temperature ranges (523–600 K, 623 K and 698 K) in the CO hydrogenation over zirconia-based catalysts. The relationships between CH 3 OH, CH 3 OCH 3 and i-C 4 H 8 were investigated by two methods: (1) the space velocity of the feed was changed at different temperatures over ZrO 2 -based catalyst. (2) CH 3 OH and CH 3 OCH 3 were added into the reaction system, and the distributions of products were compared. The results of changing space velocity showed that CH 3 OCH 3 is a primary product of the reaction, but not the product of CH 3 OH dehydration. The product distribution of the reaction indicated that both CH 3 OH and DME participated in the process of hydrocarbon formation, especially for the formation of CH 4 , C 2 H 4 and C 2 H 6 , but they are not the intermediates for i-C 4 H 8 formation.

Performances of nanosize zirconium oxides prepared by precipitation, supercritical fluid drying (SCFD) and freeze-drying (FD) methods were evaluated for the selective synthesis of isobutene from synthesis gas (syn-gas). The crystal structure, particle size and specific surface area were measured by XRD, TEM and BET. The acidic and basic properties of the catalysts were studied by NH3- and CO2-TPD, respectively. The results showed that the crystal phases, acidic and basic properties of nanosize zirconia depend remarkably on the drying conditions. The catalysts over which the formation of isobutene is favored show a higher ratio of basic to acidic sites on their surfaces. The results of adding acidic and basic components into zirconia suggested that both the acidic and basic sites on the catalysts are required for the isosynthesis. The conversion of CO was increased by adding acidic component into zirconia, and the selectivity for i-C4H8 was increased greatly by adding basic component into zirconia. It is suggested that the acidic sites are responsible for the activation of reactant molecules and the basic sites of the catalysts are significant for the formation of i-C4H8 from CO hydrogenation.

Different mesoporous molecular sieves, MCM -41, Al - MCM - 41, HMS etc. are prepared under different conditions. The specific surface areas are measured by using BET method. The structures are characterized with XRD, SEM, etc.. The influences of synthesis conditions on the structures of mesoporous molecular sieves are described. The mesoporous molecular sieves are used as supports for catalysts in the hydrogenation of CO. The activity and selectivity to C 1∼C 4 hydrocarbons of these catalysts are studied and compared with that of ZrO 2/ZSM -5, ZrO 2/β and ZrO 2/HY. Because of the higher surface area and special pore structure of MCM -41, Zirconia supported on MCM -41 prepared under different conditions has higher selectivity to C 2 =∼C 4 = for CO hydrogenation than that of ZrO 2/ ZSM-5, ZrO 2/β and ZrO 2/HY.

Different kinds of zeolites, such as ZSM-5, β, HY, NaY, Al-MCM-41, MCM and HMS, were used as catalyst supports for CO hydrogenation. The product distribution over these catalysts was compared. The results show that the performance of different catalysts depends on the characteristics of the supports. The selectivity for i-C 0 4 on ZrO 2/ZSM-5, ZrO 2/β and ZrO 2/HY is much higher than that on ZrO 2/MCM, ZrO 2/Al-MCM-41 and ZrO 2/HMS, but C = 2 ∼ C = 4 produced on the latter catalysts are much higher than those on the formers. The selectivity for i-C 0 4 and i-C = 4 is sensitive to the acidity of the catalysts. Potassium and sodium influence the reaction selectivity for isobutane and isobutene through changing the acidity of the catalysts. The electronic effect of alkali metals enhances the reaction activity, and their basicity promotes the reaction selectivity for C = 2 ∼ C = 4.