In this research, synthetic ZEOLITES, their differences from natural ZEOLITES, synthesis methods, and their benefits compared to natural ZEOLITES have been discussed. Zeolite is a hydrated tectoaluminosilicate. Natural ZEOLITES are hydrothermal and of mainly volcanic origin. Due to its special crystal structure, this mineral has special features such as low density and the large volume of free spaces, high crystallization degree and the possibility of absorbing molecules and ions. Natural ZEOLITES are not suitable for industrial use due to the presence of very small channels. On the other hand, the production of synthetic ZEOLITES faces many challenges. Hydrothermal synthesis, molten salt method, fusion method, alkaline activation, microwave-assisted synthesis, and dialysis synthesis are among the most important production methods of synthetic ZEOLITES. One of the most significant benefits of zeolite mineral is the suitable absorber for radioactive waste and the larger pore size in its crystalline structure.

ZEOLITES are hydrated crystalline aluminosilicates of alkali and alkaline earth cations. Their three dimensional framework consist of [SiO4]- and [AlO4]- tetrahedra. Beside their low price and abundance, three main properties of ZEOLITES i.e: adsorption, ion exchange and catalytical properties promote their versatile industrial applications. In Iran, lack of a systematic and comprehensive research on the characterization of natural ZEOLITES causes these valuable minerals to be relatively unknown. The aim of this research is to characterize some of the Iranian natural ZEOLITES by means of thermal analysis methods including thermogravimetry (TG), and derivative thermogravimetry (DTG). In some cases, X-ray diffractometry and chemical analysis were used as complementary methods.  

In the present research synthesis of ZEOLITES, merlinoite minerals of natural clinoptiloite mineral in the presence of alkaline mediums, was investigated. The analyzed variants are a result of a concentration of Na+and K+ions, temperature and time. Phase transition of clinoptiloite was conducted in the presence of an 8 molar potash solution (KOH) and a 4 molar soda solution (NaOH). Results indicated that merlinoite phase occurs at a temperature of 200 degrees centigrade and the presence of highly concentrated ions of Na+. With the passage of reaction time, the concentration of the synthesized merlinoite is increased accordingly. XRD studies suggest orthorhombic synchrony with the dimensions of c=9.45 Ao, a=14.12 Ao, d=2.19 Ao, n=1.494 Ao for merlinoite.

The paper reports the production of liquid fuels from waste plastics' thermal and catalytic pyrolysis, including polypropylene (PP), high-density polyethylene (HDPE), low-density polyethylene (LDPE), and polystyrene (PS). For this purpose, three different types of ZEOLITES (4A, ZSM-5, and 13X) and Cu/4A, Cu/ZSM-5, and Cu/13X were used in catalytic pyrolysis. The acidity and textural properties of the catalysts are the main parameters in the decomposition of polymers. The order of acidity of the catalysts was as follows: Cu/13X> Cu/4A> Cu/ZSM-5. The main product of thermal pyrolysis was liquid, mostly linear heavy hydrocarbons, whereas catalytic pyrolysis by copper/zeolite catalysts produced liquid products containing more branched hydrocarbons at lower temperatures. The liquid products carried out analysis through the use of FTIR and GC/MS techniques. The results indicated the presence of paraffin, olefins, and aromatic hydrocarbons in the liquid products. It was also found that light liquid hydrocarbons and gaseous products were produced over Cu/13X (higher acidity, large pore size, and high surface area). For Cu/4A, Cu/13X, and Cu/ZSM-5 catalysts, the main liquid products of catalytic pyrolysis were in the range of diesel, gasoline, and kerosene, respectively.