ABOUT CATALYSTS

Catalyst is a substance which accelerates the rate of reaction between two reactants without itself getting altered at the end of the reaction. A catalyst can, therefore, be used and reused again and again till it gets deactivated as a result of impurities present in the reactants which block the active sites of the Catalyst or react with the catalyst and change its chemical composition.

When one of the two reactants happen to be Hydrogen gas, the catalyst used is termed as Hydrogenation Catalyst.

The word "accelerates" used in the terminology implies that the hydrogenation reaction is taking place even without the catalyst, maybe at a slow pace. The fact, however, is, that the reaction practically does not take place in the absence of the catalyst. Presence of Catalyst is essential for reaction to proceed at a noticeable rate.

A promoter is a substance which enhances the activity of a catalyst. Promoters are specific for a specific type of hydrogenation. Molybdenum, Chromium, Copper, Iron are known promoters for certain specific reactions involving Raney Nickel. Promoters are not added separately to the reactants but are to be incorporated in the Catalyst metal during their preparation.

Inhibitors are substances which retard the activity of a catalyst. Sulfur and Lead are inhibitors for precious metal Catalysts.

Presence of oxidizing agents or small amounts of deactivators causes deactivation or poisoning of a hydrogenation catalyst. Amines and Chlorides are also known to deactivate the catalyst.

Sometimes the product of the reaction, reaction intermediates or by-products act as catalytic deactivators and do not allow completion of the reaction. Under such situations, user should opt for a different type of catalyst.

The user should make a careful study of deactivators and poisons before conducting large scale hydrogenation. Care should be taken to minimize the presence of catalytic deactivators and poisons in the reaction mixture so as to prolong the life of the catalyst.

Catalyst manufactured by Vineeth Chemicals are normally resistant to catalytic poisons if present in small quantities. For more details please mail us at vineethchemicals@gmail.com or call us at +91-8149095779

For Base Metal Catalyst

• Raney nickel catalyst (active) is highly pyrophoric when it gets dried up on exposure to air/ atmosphere/ oxygen. it should therefore always be kept under demineralized/ distilled water.
• The containers of the catalyst should be stored in a cool and ventilated place protected from direct exposure to sunlight.
• Protective gloves, shoes, and goggles must be used while transferring catalyst from containers to the reaction vessel.
• Hydrogen gas continuously evolves from the catalyst slurry. smoking cigarette/ bidi and lighting matchstick/ lighter should be strictly prohibited while opening the containers of the catalyst.
• The catalyst slurry should be manually stirred using a steel rod / spoon to restore it in suspension for an easy and smooth transfer.
• Care should be taken while transferring catalyst so as to avoid/minimize spillage of the catalyst. skilled personnel should be employed for handling the catalyst.
• In the event of spillage of small quantity, the spilled material may be deactivated by using a 0.5 % solution of potassium permanganate followed by flushing the area with sufficient water.
• In the event of spillage of significant quantity, the spilled catalyst slurry should be collected back manually and put in a polythene bag thereafter be packed in a plastic or m.s.container and retrieval of the spilled catalyst should be flushed with water. a 0.5 % solution of potassium permaganate [KMnO₄] may also be used as an additional measure.
• In the event of contact with skin, the skin should be washed immediately with running water. dry with a clean towel and apply a soothing ointment (viz soframycin)
• Empty polythene bags and containers after the transfer of catalyst should be washed profusely with water before scrapping them.
• Great care should be taken in deciding temperature and pressure condition and selection of solvent for the hydrogenation reaction.

DISPOSAL PRECAUTIONS : Nickel is a costly metal. Do not, therefore, discard even such of the spent Raney Nickel Catalysts which can not be reactivated any more.

For Precious Metal Catalyst

• As far as possible use wet form of the catalyst.
• Can cause a fire when dry mixed with Methanol. For reactions using Methanol as a solvent, first, mix the catalyst with water to form a paste before charging the catalyst into the reactor.
• During transfer of dry catalyst powder (from its plastic) bag into the reactor, it can catch fire due to static charge generated due to abrasion of dry catalyst powder with a plastic bag (container). Therefore do not empty out the bag into the reaction vessel at once with force. Add slowly.
• During filtration and thereafter do not allow spent catalyst to dry due to vaporization of the solvent. Give D.M. Water washing after solvent removal. Pack and transport in wet cake form for recovery and regeneration.
• In the event of a fire, contain it by pouring water. After fire has been put off, collect all the wet residues manually and pack the same in a plastic bag and send it to Vineeth Chemicals, Vasai, for recovery of Palladium/ Platinum metal and consequent conversion into the fresh catalyst.
• Inhalation of catalyst powder can cause irritation of the respiratory tract. Therefore use a mask while handling this product.
• In case of powder particles coming into contact with skin or falling into eyes, wash the affected part of the body or eyes profusely with water.

DISPOSAL PRECAUTIONS : Palladium/ Platinum on Carbon Catalyst is a costly product. The precious Palladium/ Platinum metal from the used catalyst can be recovered. Do not therefore discard the used product as waste material. Arrangements should be made to send back the material to the manufacturer for recovery of the precious Palladium/ Platinum Metal which can be reused for making a fresh batch of the catalyst.