Pyrophoric chemicals

Airborne particulate matter may comprise liquid (aerosols, mists or fogs) or solids (dust, fumes). Refer to Figure 5.2. Some causes of dust and aerosol formation are listed in Table 4.3. In either case dispersion, by spraying or fragmentation, will result in a considerable increase in the surface area of the chemical. This increases the reactivity, e.g. to render some chemicals pyrophoric, explosive or prone to spontaneous combustion it also increases the ease of entry into the body. The behaviour of an airborne particle depends upon its size (e.g. equivalent diameter), shape and density. The effect of particle diameter on terminal settling velocity is shown in Table 4.4. As a result ... 

Listings of chemicals such as incompatible chemicals potentially explosive chemicals and reagent combinations water-reactive chemicals pyrophoric chemicals and peroxide-forming chemicals, including time limits on retention after opening the original container. 

Physical hazards include noise, vibration, extremes of temperature, compressed gases, combustible and flammable chemicals, pyrophorics, explosives, oxidizers, and reactive materials. Process employees are exposed to physical hazards on a daily basis because they woric outside on the unit among pipes containing compressed gases, fluids under high temperatures, and flammable and explosive chemicals. Examples of some these hazards on a process unit might include ... 

What kinds of chemicals are used in this lab, and in what quantities Are flammable liquids stored properly in fire-resistant cabinets Are there reactive chemicals being used in this laboratory such as air- or water-sensitive chemicals, pyrophorics or explosives Are there any particularly hazardous chemicals in this laboratory What air-sensitive compounds are used or generated What toxic gases are used or generated What water-sensitive compounds are used ... 

Disposal of spent hydrogenation catalyst requires a special chemical waste landfill because of its nickel content and the fact that oil-soaked catalysts tend to be pyrophoric. Compared to disposal costs, reprocessing to recover the nickel may become economically viable. 

Stabilized lithium acetyhde is not pyrophoric or shock-sensitive as are the transition-metal acetyhdes. Among its uses are ethynylation of halogenated hydrocarbons to give long-chain acetylenes (132) and ethynylation of ketosteroids and other ketones in the pharmaceutical field to yield the respective ethynyl alcohols (133) (see Acetylene-derived chemicals). 

The alkyls and aryls, R3AI (in monomer form), are colorless Hquids or low melting soHds easily oxidized and hydrolyzed when exposed to the atmosphere. Triethylalurninum (TEA), one of the most commercially important members of this family of chemicals, is so reactive it bursts into flame on contact with air, ie, it is pyrophoric, and it reacts violently with water. This behavior is typical and special techniques are necessary for the safe handling and use of organoalurninum compounds. 

Pyrophoric chemicals are so reactive that on contact with air they undergo vigorous reaction with atmospheric oxygen (under ambient conditions or at elevated temperatures), or with water (Table 6.9). Examples include ... 

A hazard may arise with a chemical because of its tendency to decompose spontaneously or to react violently on contact with other common chemicals, as illustrated in Figure 7.1. The case of pyrophoric chemicals is summarized in Chapter 6 some dangerous reactions of compressed gases are mentioned in Chapter 9 other cases are summarized here. 

For reactions with air or water, refer to pyrophoric chemicals (Chapter 6). 

Chemical reaction sources catalysis, reaction with powerful oxidants, reaction of metals with halocarhons, thermite reaction, thermally unstahle materials, accumulation of unstahle materials, pyrophoric materials, polymerization, decomposition, heat of adsorption, water reactive solids, incompatihle materials. 

An appraisal is needed of all chemicals which may be present, even if unintentionally (e.g. as intermediates, byproducts or wastes) and how they can react under the most extreme conditions (e.g. concentration, agitation, temperature, pressure) likely to arise. For reactions with air or water, refer to pyrophoric chemicals (Chapter 5). 

Safety. The MR is much safer than the MASR. (1) The reaction zone contains a much smaller amount of the reaction mixture (hazardous material), which always enhances process safety. (2) In case of pump failure, the reaction automatically stops since the liquid falls down from the reaction zone. (3) There is no need to filter the monolithic catalyst after the reaction has been completed. Filtration of the fine catalysts particles used in slurry reactors is a troublesome and time-consuming operation. Moreover, metallic catalysts used in fine chemicals manufacture are pyrophoric, which makes this operation risky. In a slurry reactor there is a risk of thermal runaways. (4) If the cooling capacity is insufficient (e.g. by a mechanical failure) a temperature increase can lead to an increase in reaction, and thus heat generation rate. 

Product Information Sheet No. 212 , Sandwich, Pfizer Chemicals, 1969 Calcium is pyrophoric when finely divided. 

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