Zeolite as a catalyst in petrochemical refining processes

Zeolite Membranes

Catalyst

Catalyst is a substance that can cause a change in the rate of a chemical reaction itself being consumed in the reaction; the changing of the reaction rate by use of a catalyst is called catalysis. Substances that increase the rate of reaction are called positive catalysts or, simply, catalysts, while substances that decrease the rate of reaction are called negative catalysts or inhibitors.

Zeolites

Compositionally, zeolites are similar to clay minerals. More specifically, both are alumino-silicates. They differ, however, in their crystalline structure. Many types of clay have a layered crystalline structure (similar to a deck of cards) and are subject to shrinking and swelling as water is absorbed and removed between the layers. In contrast, zeolites have a rigid, 3-dimensional crystalline structure (similar to a honeycomb) consisting of a network of interconnected tunnels and cages. Water moves freely in and out of these pores but the zeolite framework remains rigid. Another special aspect of this structure is that the pore and channel sizes are nearly uniform, allowing the crystal to act as a molecular sieve.

When zeolite was discovered and who discovered it?

The first zeolite, stilbite, was discovered in 1756 by a Swedish chap called Cronstedt, who found that the mineral lost water rapidly on heating and seemed to boil. The name zeolite comes from the Greek words zeo (to boil) and lithos (stone), literally meaning "the rock that boils."

Why this is an important catalyst?

Zeolites are important catalysts used in petrochemistry industry where zeolites are used in oil refining as cracking catalysts and in the Methanol to Gasoline (MTG) catalytic conversion process.

Use of Zeolites

Health

Toothpaste

Nutrition

Fertilizer

Animal Nutrition

Construction

Latent Hydraulic Additive

Energy

Solar Energy Use

Environment

Waste Water Treatment

Ammonia removal in municipal sludge / waste water

Heavy metal removal

Septic leach fields

Waste Gas Treatment

Industry

Oxygen Production

Transportation

Petroleum Production

Hygiene

Water Softening

What are its advantages?

The high cation exchange capacity (CEC) make zeolite particularly valuable in holding and slow releasing valuable nutrients to plants, mainly ammonium nitrogen (NH4+), potassium (K+) and magnesium (Mg+), calcium (Ca+) and trace elements.

Promotes better plant growth by improving the value of fertilizer. Helps prevent plant burning from over use of fertilizers by trapping and slowly releasing valuable nutrients when and as the plants need them.

Improves the cation exchange capacity of soil resulting in less fertilizer requirements.

Natural zeolites make an excellent soil amendment, and are environmentally friendly for landfill dump sites (with the exception of zeolite that has been used as a molecular sieve or filter medium for the removal of radioactive waste or the removal of heavy chemical toxins deemed hazardous by government regulations.)

Reduces nutrient and fertilizer loss through heavy rains, leaching and irrigation, resulting in less environmental damage through water runoff.

The water retention capability of zeolites allows less irrigation applications.

Zeolite is used to reduce offensive odors, especially ammonia from sewage, animal manure and waste water situations.

This retained valuable nitrogen improves the quality of the resulting manures and sludges making them worthwhile in fertilizers.

Improves water quality and filtration in aquaculture.

Increases the biological activity of sewage treatment and improves the value of resultant sludges.

Zeolite can be used in the removal of heavy metals from mining and metallurgical wastewaters.

Under the Clean Air Act of 1990, producers are required to phase out designated substances that have Ozone Depleting potential. The manufacturing process of "W-Way Zeolite" products does not contain, nor are they packaged with any Ozone Depleting Compounds (ODC); this includes both Class 1 and Class 2 Compounds.

Natural Zeolites are regulated as non-hazardous material by the Dept. Of Transport.

Properties of Zeolites

Natural conductor (surface and bulk)

High sorption, ion-exchange and binding energies

Inherently electrically charged (-)

Durable and regenerative

Selective ion-exchanged capacity pH, chemical and temperature stable

High porosity and very large reactive surface area

Environmentally beneficial

Mineralogy

Modifications or improvement for this type of catalyst (Zeolite)

One of the modifications of zeolites is modification by iron oxides, which increases capacity of adsorption. In this work, we prepared a modified zeolite by the precipitation of magnetite on the surface of zeolite. This new adsorbent was used to remove of Pb (II) from waste water. The maximum adsorption capacity was 73, 25 mg/g from the solution of PB with the concentration of 400 mg/l.