Effects of Calcination Temperature on the Acidity and Catalytic Performances of HZSM-5 Zeolite Catalysts for the Catalytic Cracking of n-Butane

The acidic modulations of a series of HZSM-5 catalysts were successfully made by calcination at different treatment temperatures, i.e. 500, 600, 650, 700 and 800 ℃, respectively. The results indicated that the total acid amounts, their density and the amount of B-type acid of HZSM-5 catalysts rapidly decreased, while the amounts of L-type acid had almost no change and thus the ratio of L/B was obviously enhanced with the increase of calcination temperature （excluding 800 ℃）. The catalytic performances of modified HZSM-5 catalysts for the cracking of n-butane were also investigated. The main properties of these catalysts were characterized by means of XRD, N2 adsorption at low temperature, NH3-TPD, FTIR of pyridine adsorption and BET surface area measurements. The results showed that HZSM-5 zeolite pretreated at 800 ℃ had very low catalytic activity for n-butane cracking. In the calcination temperature range of 500-700 ℃, the total selectivity to olefins, propylene and butene were increased with the increase of calcination temperature, while, the selectivity for arene decreased with the calcination temperature. The HZSM-5 zeolite calcined at 700 ℃ produced light olefins with high yield, at the reaction temperature of 650 ℃ the yields of total olefins and ethylene were 52.8% and 29.4%, respectively. Besides, the more important role is that high calcination temperature treatment improved the duration stability of HZSM-5 zeolites. The effect of calcination temperature on the physico-chemical properties and catalytic performance of HZSM-5 for cracking of n-butane was explored. It was found that the calcination temperature had large effects on the surface area, crystallinity and acid properties of HZSM-5 catalyst, which further affected the catalytic performance for n-butane cracking.

Surface Modification of Natural Fibrous Brucite with Stearic Acid

Fibrous brucite,a kind of brucite with unique structure and physical properties,was modified with stearic acid as a surface modifier.In order to investigate the mechanism of surface modification,the fixation of stearic acid on fibrous brucite and the induced changes in surface properties were studied by using X-ray diffraction（XRD）,scanning electron microscopy（SEM）,infrared spectroscopy（IR）,Raman spectroscopy and thermo-gravimetric analysis（TGA）.XRD analysis indicates that the modification of fibrous brucite with stearic acid does not cause any changes in the structure of fibrous brucite mineral.Spectroscopy and thermal analysis show that the surfactant molecules are not only directly adsorbed on the surface of the mineral,but also chemisorbed on mineral surface by forming chemical bonds between the modifier and magnesium hydroxide.

Catalytic activity of phosphorus and steam modified HZSM-5 and the theoretical selection of phosphorus grafting model

The modification of HZSM-5 zeolite with phosphorus and steam has been studied. Results show that 1% phosphorus and steam modified HZSM-5 has the highest catalytic activity for n-heptane. Physicochemical and catalytic properties of 1% phosphorus and steam modified HZSM-5 zeolites have been investigated. The X-ray diffraction （XRD） results exhibit that there is considerable variation in the relative intensity of the individual diffraction peaks. The acidity of the samples decreases with an increase in the steaming temperature, which is determined by the IR of adsorbed pyridine and temperature programmed desorption （TPD） of ammonia. The oxidation state of phosphorus shown by XPS is ＋5, and a model for surface structure modification is proposed. The nitrogen adsorption isotherm for all samples is a combination of type I and type IV, all hysteresis loops resemble the H4-type. The density functional and cluster model methods have been invoked to select the phosphorus grafting model, and it was found that the phosphorus grafting model were more probable in the form of the terminal oxygen coordinating with aluminum.

Modification of Cu/ZSM-5 catalyst with CeO_2 for selective catalytic reduction of NO_x with ammonia

Cu/ZSM-5 and CeO_2-modified Cu/ZSM-5 catalysts were prepared by a wetness impregnation method. The addition of CeO_2 was found to enhance the NO_x selective catalytic reduction（SCR） activity of the catalyst at low temperatures, but the high-temperature activity was weakened. The catalysts were characterized by X-ray diffraction（XRD）, nitrogen physisorption, inductively coupled plasma optical emission spectrometry（ICP-OES）, X-ray photoelectron spectroscopy（XPS）, electron paramagnetic resonance（EPR）, H_2 temperature-programmed reduction（TPR） and NH_3 temperature-programmed desorption（TPD）. The results showed that more CuO clusters instead of isolated Cu^（2＋） species were obtained on the modified catalyst. These active CuO clusters, as well as the Cu-Ce synergistic effect, improved the redox property of the catalyst and low-temperatures SCR activity via promoting the oxidation of NO to NO_2 and fast SCR reaction. The loss in high-temperatures activity was attributed to the enhanced competitive oxidation of NH_3 by O_2 and decreased surface acidity of the catalyst.

A novel approach for Apocynum venetum/cotton blended fabrics modification by cationic polymer nanoparticles

Apocynum venetum/cotton blended fabrics have been subjected to treat with cationic polymer nanoparticles followed by dyeing with Acid Red B,and then studied for their dyeing performance and morphology.The investigation on the effect of modification factors on the blended fabrics indicated that the 0.5 g/L nanoparticles concentration,60 min treating time,60 ℃ treating temperature and pH 6-8 are the optimum modification process to improve the dyeability of acid dye.In addition,the SEM images show that nanoparticles can be adsorbed on the surface of modified A.venetum or cotton fibers,and the two different fibers could have the same adsorption ability to Acid Red B.

Effect of Phosphoric Acid on HZSM-5 Catalysts for Prins Condensation to Isoprene from Isobutylene and Formaldehyde

A series of HZSM-5 zeolites modified with different amounts of phosphoric acid（P/HZSM-5） was prepared. The physicochemical features of the P/HZSM-5 catalysts were characterized via X-ray diffraction（XRD）, N2 adsorption-desorption, NH3-temperatttre programmed desorption（NH3-TPD） and Fourier tranform infrared（FTIR） spectra of the adsorbed pyridine, and the performances of the catalysts for Prins condensation to isoprene from isobutylene and formaldehyde were investigated. The maximum isobutene conversion and isoprene selectivity were 10.3% and 94.6% on the HZSM-5 catalyst with a Si/A1 molar ratio of 600 using 5%（mass fraction） phosphoric acid. The phosphoric acid modification not only modulated the amount of acidic sites but also regulated the acid type. An appropriate amount of weak Lewis and Bronsted acid sites served as the active sites for the condensation of isobutene with formaldehyde, and the strong acid sites could cause side reactions and coke deposition.

DNA alkylation promoted by an electron-rich quinone methide intermediate

Biological application of conjugates derived from oligonucleotides and quinone methides have pre- viously been limited by the slow exchange of their covalent self-adducts and subsequent alkylation of target nucleic acids. To enhance the rates of these processes, a new quinone methide precursor with an electron donating substituent has been prepared. Additionally, this substi- tuent has been placed para to the nascent exo-methylene group of the quinone methide for maximum effect. A conjugate made from this precursor and a 5＇-aminohex- yloligonucleotide accelerates formation of its reversible self-adduct and alkylation of its complementary DNA as predicted from prior model studies.

Electrosynthesis and catalytic properties of silver nano/microparticles with different morphologies

Electrosynthesis of powdery silver particles can be effectively carried out with an H20-oleic acid or an H20-glycerol mix solvent （volume ratio 1：1） as the electrolytic medium and AgN03 as the supporting electrolyte. Experimental results indicate that the presence or absence of the surfactant sodium dodecyl sulfate （SDS） and the choice of electrolytic medium have a significant impact on the shape and size of the prepared Ag particles. With H20-glycerol as the electrolytic medium, spherical Ag nanoparticles can be obtained in the presence of SDS （0.6g/L）, while an Ag sample electrodeposited without SDS has a dendritic microcrystalline structure. For the reduction of methyl orange （MO） and methylene blue （MB） with NaBH4 as the reducing agent, the spherical Ag nanoparticles exhibit much better catalytic activity than the dendritic Ag microparticles. Further investigations show that surface modification by an oleic acid medium could greatly improve the catalytic activity of the electrodeposited Ag particles for the reduction of MO and MB.

Hydrothermal fabrication of selectively doped organic assisted advanced ZnO nanomaterial for solar driven photocatalysis

Hydrothermal fabrication of selectively doped（Ag＋＋ Pd3＋） advanced ZnO nanomaterial has been carried out under mild pressure temperature conditions（autogeneous; 150°C）.Gluconic acid has been used as a surface modifier to effectively control the particle size and morphology of these ZnO nanoparticles. The experimental parameters were tuned to achieve optimum conditions for the synthesis of selectively doped ZnO nanomaterials with an experimental duration of 4 hr. These selectively doped ZnO nanoparticles were characterized using powder X-ray diffraction（XRD）, Fourier transform infrared spectroscopy（FT-IR）, UV–Vis spectroscopy and scanning electron microscopy（SEM）. The solar driven photocatalytic studies have been carried out for organic dyes, i.e., Procion MX-5B dye,Cibacron Brilliant Yellow dye, Indigo Carmine dye, separately and all three mixed, by using gluconic acid modified selectively doped advanced ZnO nanomaterial. The influence of catalyst, its concentration and initial dye concentration resulted in the photocatalytic efficiency of 89% under daylight.