Catalyst hazards

Derivation By reaction of ethylene and trichlorosi-lane in the presence of a peroxide catalyst. Hazard Flammable, dangerous fire risk, may form explosive mixture with air. A strong irritant. Use Intermediate for silicones. 

Removal of oxygenated volatile organic compounds by catalytic oxidation over Zr-Ce-Mn catalysts. /. Hazard. Mater., 188 (1-3), 422-427. 

This hydrolysis reaction is accelerated by acids or heat and, in some instances, by catalysts. Because the flammable gas hydrogen is formed, a potential fire hazard may result unless adequate ventilation is provided. Ingestion of hydrides must be avoided because hydrolysis to form hydrogen could result in gas embolism. 

Novel palladium catalysts show marked improvements in both yields and selectivities, compared to nickel carbonyl catalysts utilized in eadier commercial carbonylation processes (83,84). The palladium catalysts are also expected to be less hazardous. 

LLDPE by itself does not present any health-related hazard on account of its chemical inertness and low toxicity. Consequently, film, containers, and container Hds made from LLDPE are used on a large scale in food and dmg packaging. Some LLDPE grades produced with unsupported metallocene catalysts have an especially high purity due to high catalyst productivity and a low contamination level of resins with catalyst residue. FDA approved the use of film manufactured from these resins for food contact and for various medical appHcations (80). However, if LLDPE articles contain fillers, processing aids, or colorants, thek health factors must then be judged separately. 

Polymers and higher a-olefins are not toxic their main potential health hazards are associated with residual monomer, antioxidants, and catalyst residues. 

Chemical Hazards. Chemical manufacturers and employees contend with various ha2ards inherent ia productioa of evea commonplace materials. For example, some catalysts used ia the manufacture of polyethylene (see Olefin polymers) ignite when exposed to air or explode if allowed to become too warm the basic ingredient ia fluorocarboa polymers, eg, Tefloa (see Fluorine compounds, organic), can become violently self-reactive if overheated or contaminated with caustic substances (45,46) one of the raw materials for the manufacture of acryflc fibers (see Fibers, acrylic) is the highly toxic hydrogen cyanide (see Cyanides). 

Great care must be exercised ia the preparation and use of Ziegler-Natta catalysts. They are easily poisoned by moisture, among other things. They are pyrophoric and are used ia conjunction with large amounts of flammable monomer and solvent, and so can present a significant safety hazard. 

One important consideration in any catalyst oxidation process for a complex mixture in the exhaust stream is the possible formation of hazardous incomplete oxidation products. Whereas the concentration in the effluent may be reduced to acceptable levels by mild basic aqueous scmbbing or additional vent gas treatment, studying the kinetics of the mixture and optimizing the destmction cycle can drastically reduce the potential for such emissions. 

Spent catalyst maybe considered hazardous waste... 

There is persisting interest in nylon-RIM materials as alternatives to polyurethane-RIM. Advantages of the nylon materials are the better shelf life and lower viscosity of the reaction components, ability to mould thick-walled articles, absence of a need for mould lubrication and the ability to avoid using isocyanates with their associated hazards. The main disadvantages of nylon-RIM are the need to have heated storage tanks and elevated temperature reactions, difficulties in catalyst handling and the high water absorption of the product. Possible markets include exterior car body components and appliance and business machine components. 

Skin proteetion may neeessitate use of full proteetive suits. When eatalysts are dumped from reaetors at the end of a proeess they may prove to be extremely dusty as a result of reduetion in partiele size during the reaetion proeess. Again, depending upon the nature of the hazard, ventilation, personal proteetion, and use of temporary enelosures to prevent contamination of the general work area should be considered. Some catalysts are pyrophoric and some catalyst beds are inerted with the added possibility of fire, or release of inerting gas into the workplace which may cause asphyxiation. 

Hydroprocesses Hydrogen is chemically stable and relatively unreactive at ordinary temperatures most processes utilizing it require a catalyst. Above 500°C it reacts readily with oxygen and confined flammable mixtures explode violently if ignited Main hazards fire, explosion, metallurgical problems arising from hydrogen attack... 

Impurities or the delayed addition of a catalyst causes inhibition or delayed initiation resulting in accumulation in the reactors. The major hazard from accumulation of the reactants is due to a potentially rapid reaction and consequent high heat output that occurs when the reaction finally starts. If the heat output is greater than the cooling capacity of the plant, the reaction will run away. The reaction might commence if an agitator is restarted after it has stopped, a catalyst is added suddenly, or because the desired reaction is slow to start. 

Basic process chemistry using less hazardous materials and chemical reactions offers the greatest potential for improving inherent safety in the chemical industry. Alternate chemistry may use less hazardous raw material or intermediates, reduced inventories of hazardous materials, or less severe processing conditions. Identification of catalysts to enhance reaction selectivity or to allow desired reactions to be carried out at a lower temperature or pressure is often a key to development of inherently safer chemical synthesis routes. Some specific examples of innovations in process chemistry which result in inherently safer processes include ... 

Immobilization of hazardous reagents and catalysts by attaching active groups to polymeric or immobile backbones. 

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