SYNTHESES OF 4A ZEOLITE IN DETERGENTS WITH KAOLIN

The main technical conditions for synthesizing 4A zeolite with kaolin were determined. The whiteness and calcium ion exchange capacity (CIEC) of the product were increased by calcining and screening the colouring ions, and the high quality 4A zeolite was synthesized successfully. Moreover, the formation mechanism of zeolite also discussed.

Studies on the Synthesis, Properties and Preparation Methods of Zeolite ZK-4

A zeolite designated as ZK-4 was synthesized hydrothermally in the system (TMA)2ONa2O-Al2O3- SiO2- H2O at 80 - 100℃ with tetramethylammonium hydroxide as an organic templating agent. The pure zeolite ZK-4 could be prepared by using the mother liquor obtained after filtration as the source of templating agent. The effect of some synthetic conditions such as the amount of tetramethylammonium hydroxide used, n [ (TMA)2O + Na2O] /n (Al2O3) ratio, n (SiO2)/n(Al2O3) ratio and crystallization time, etc. on the crystalline phase of the product was investigated. When the following molar ratios of the reaction mixture, n (SiO2)/n (Al2O3) 4-10, n[(TMA)2O+Na2O]/ n (Al2O3 ) > 7, n (Na2O)/n (Al2O3)=0. 5-2. 0, n (H2O)/ n(A12O3)=80-450, were used, pure zeolite ZK-4 could be obtained. The synthetic products were characterized by X-ray powder diffraction, atomic absorption spectrophotometry (AAS), adsorption measurement, thermogravimetric analysis(TGA), and 29Si magic angle spinning nuclear magnetic resonance technique. Zeolite ZK-4 has a higher thermal stability than sodium zeolite A due to higher n(Si)/n(Al) ratio of zeolite ZK-4.

Organotemplate-free Hydrothermal Synthesis of SUZ-4 Zeolite: Influence of Synthesis Conditions

Various conditions were investigated in detail for the novel organic template-free static hydrothermal synthesis of SUZ-4 zeolite in the presence of seeds. The obtained samples were characterized by XRD （X-ray diffraction）, SEM （scanning electron microscope）, TG （thermal gravimetric analysis）, ICP （inductively coupling plasma） elemental analysis, nitrogen sorption isotherm and surface area. The results show that pure SUZ-4 zeolites with high crystallinity are obtained in a broad window of synthesis conditions： seed mass concentration 0.2%-2%, SIO2/A1203 molar ratio 21 25, KOH/SiO2 molar ratio 0.33 0.43, H20/SiO2 molar ratio 7.14-38.1, aging time 24 h, crystallization temperature 160℃, and crystallization time 6-10 d. Also, crystallinity and size of the rod-like SUZ-4 zeolite crystals are found to alter with the conditions.

PtSnNa/SUZ-4:An efficient catalyst for propane dehydrogenation

The structure and catalytic properties of PtSn catalysts supported on SUZ-4 and ZSM-5 zeolite have been studied by using various experimental techniques including XRD,nitrogen adsorption,NH3-TPD,TG,H2-TPR and TPO techniques combined with propane dehydrogenation tests.It has been shown that SUZ-4-supported PtSnNa（PtSnNa/SUZ-4） was determined to be a better catalyst for propane dehydrogenation than conventional catalysts supported on ZSM-5,owing to its higher catalytic activity and stability.Dibenzothiophene poisoning experiments were performed to investigate the detailed structures of the two supported catalysts.The characterization of the two catalysts indicates that the distribution of Pt on the porous support affects the activity.In contrast to ZSM-5-supported catalysts,Pt particles on the PtSnNa/SUZ-4 are primarily dispersed over the external surface and are not as readily deactivated by carbon deposition.This is because that the strong acid sites of the SUZ-4 zeolite evidently prevented the impregnation of the Pt precursor H_2PtCl_6 into the zeolite.In contrast,the weak acid sites of the ZSM-5 zeolite led to more of the precursor entering the zeolite tunnels,followed by transformation to highly dispersed Pt clusters during calcination.In the case of the PtSnNa/ZSM-5,the interactions between Sn oxides and the support were lessened,owing to the weaker acidity of the ZSM-5 zeolite.The dispersed Sn oxides were therefore easier to reduce to the metallic state,thus decreasing the catalytic activity for hydrocarbon dehydrogenation.

Utilization of Bauxite Tailing

The characteristics of bauxite tailing in China were reviewed,and the current utilization methods and the actuality were discussed.It is found that the bauxite tailing is mainly used for production of building materials and chemical products,and extraction of useful component,etc.Meanwhile,the shortages of these utilization methods were analyzed.In order to enlarge the bauxite tailing application,some new utilization paths were proposed,such as preparing zeolite 4A and corundum-mullite composite materials,which are high value added materials.The utilization ways of bauxite tailing were widened,the utilization ratio of resources and the economic benefit were improved.

Medium effect on dielectric relaxation behaviors of 4A zeolite bulk dispersion system

Dielectric spectra of 4A zeolite particles bulked in deionized water（4A/W） or cyclohexane（4A/C） were measured respectively under different temperatures, and two dielectric relaxations were found in both of 4A/W and 4A/C. Because of existence of water molecules in pores, both low and high frequency relaxation times（t LFR and t HFR） of 4A/W decreased more sharply than 4A/C with increasing temperature.According to the temperature dependence of t LFR and t HFR, the activation energies of Na＋interacting with framework under hydrated and dehydrated environments were calculated respectively, and the original properties of Na＋in dehydrated zeolite were obtained by analyzing the dielectric properties of 4A/C.Furthermore, a transient state of Na＋motion with temperature was found in 4A/C system.