What is the structure of zeolite?

What is the structure of zeolite?

A zeolite is a hydrated aluminosilicate mineral with a structure characterized by a framework of linked tetrahedra, each consisting of four oxygen atoms surrounding a silicon or aluminum cation.

What is zeolite A PPT?

ZEOLITES • Some aluminosilicates lose water when heated to forms a porous structure with a large surface area. • These aluminosilicates are called ZEOLITES. • Zeolites are also known as Permutits.

How many zeolite structures are there?

There are 232 known framework zeolite structures that exist [10]. Of this number, only a few have found commercial applications.

What is zeolite and its uses?

Zeolites are widely used as ion-exchange beds in domestic and commercial water purification, softening, and other applications. In chemistry, zeolites are used to separate molecules (only molecules of certain sizes and shapes can pass through), and as traps for molecules so they can be analyzed.

Are zeolites acidic or basic?

The alkali-exchanged zeolites are designated as basic zeolites. Indeed, the acid–base pairs in cation exchanged zeolites are Lewis acids (cations) and Lewis bases (framework oxygens) pairs. Many factors are known to affect the Lewis acidity and Lewis basicity in cation exchanged zeolites.

What is the properties of zeolites?

Zeolites have two main properties: adsorption and ion exchange. These two properties are due to reactive surfaces, due to the presence of Al3+ on adsorption sites with a Si4+ ion resides, and the micropores crystalline system. These properties allow the zeolite for several applications.

What are zeolites and types?

There are nearly 50 different types of zeolites (clinoptilolite, chabazite, phillipsite, mordenite, etc.) with varying physical and chemical properties. Crystal structure and chemical composition account for the primary differences. Some of the commercial materials are: A, beta, mordenite, Y, ZSM-5.

How do zeolites Work?

How does Zeolite work? Zeolite is an alkaline mineral that is very porous and has a negative charge. Since most toxins, such as heavy metals, radiation, and pesticides are positively charged, Zeolite is pulled towards toxins like a magnet and sucks them up into its structure.

Why are zeolites used?

Based on the pore size and absorption properties, zeolites are among the most important inorganic cation exchangers and are used in industrial applications for water and waste water treatment, catalysis, nuclear waste, agriculture, animal feed additives, and in biochemical applications (Bogdanov et al., 2009).

How does zeolite work as a catalyst?

Zeolites can be shape-selective catalysts either by transition state selectivity or by exclusion of competing reactants on the basis of molecular diameter. They have also been used as oxidation catalysts. The reactions can take place within the pores of the zeolite, which allows a greater degree of product control.

What is a Lewis basic site?

A Lewis base is a substance that donates a pair of electrons to form a covalent bond. So, a Lewis acid-base reaction is represented by the transfer of a pair of electrons from a base to an acid. A hydrogen ion, which lacks any electrons, accepts a pair of electrons.

Where does the structure of zeolites come from?

Like most silicates – the zeolites are based on TO4tetrahedra, where T is an aluminium or silicon atom (phosphorus in aluminophosphates). The vast 3-dimensional networks are a result of all four corners for the tetrahedra being shared, producing low density microporous materials.

How are zeolites a result of the tetrahedra?

The vast 3-dimensional networks are a result of all four corners for the tetrahedra being shared, producing low density microporous materials. Zeolite structures can be thought to exist of finite or infinite (chains, layers etc..) component units.

What happens when aluminium is added to a zeolite?

The inclusion of aluminium into the zeolite structure has two major effects: an increase in the net negative charge – which are netralised from protons hydrogen bonded to the lone pairs of the bridging oxygens. These acidic sites play a significant role in the zeolite catalytic activity. the materials become hydrophilic.

Why is the X / Y ratio important in zeolites?

The X/Y refers to the silicon/aluminum ratio. This structure has very large microporous spaces, allowing organic molecules to diffuse in and out. This zeolite is one of the most important catalytic systems, and is used in the cracking of long chain hydrocarbons into shorter chain length fuels.