Pyrophorics transport

The volatiles contents of product chars decreased from ca 25—16% with temperature. Char (lower) heating values, on the other hand, increased from ca 26.75 MJ /kg (11,500 Btu/lb) to 29.5 MJ /kg (12,700 Btu/lb) with temperature. Chars in this range of heating values are suitable for boiler fuel apphcation and the low sulfur content (about equal to that of the starting coal) permits direct combustion. These char products, however, are pyrophoric and require special handling in storage and transportation systems. 

Pyrophoric and other spontaneously combustible substances will generally be identified as such on their product literature, material safety data sheets (MSDSs), or International Chemical Safety Cards (ICSCs). If transported, these substances should be identified as DOT/UN Hazard Class 4.2 materials for shipping purposes and labeled as spontaneously combustible. For pyrophoric substances, the NFPA 704 diamond for container or vessel labeling has a red (top) quadrant with a rating of 4, indicating the highest severity of flammability hazard (NFPA 704, 2001). Note that pyrophoric materials often exhibit one or more other reactivity hazards as well, such as water reactivity. 

Lists of pyrophoric materials that include less common chemicals, including metals, can be found in volume 2 of Brethericks Handbook of Reactive Chemical Hazards (Urben, 1999). Other spontaneously combustible substances are tabulated by their proper shipping names and UN/NA numbers in the U.S. Dept, of Transportation regulation 49 CFR 172.101. 

In a literature review with 115 references, factors influencing the pyrophoricity of metals are identified as particle size, presence of moisture, nature of the surface of the particle, heat of formation of the oxide or nitride, mass, hydrogen content, stress, purity and presence of oxide, among others. Static charge hazards, fire and explosion incidents, handling procedures and transport considerations are also discussed. References are given to reviews of incidents involving barium, beryllium,... 

Oxycarbides have also been described (176). They are of interest for catalysis because oxophilic metals may not form carbides easily in preparations from metal oxides by treatment with methane, oxycarbides rather than carbides may form. Furthermore, carbides and nitrides are usually passivated after preparation they are slowly exposed to oxygen or air to form a thin protective oxide layer on the metal carbide surface. In this passivated form, these materials are not pyrophoric and can be transported through the air. After insertion into a catalytic reactor, they must be reactivated either by methane or ammonia treatment, as used in their preparation, or by reduction with hydrogen. In these cases, pure carbide or nitride is not always reformed at the surface an oxycarbide or oxynitride is often formed instead. 

While the decomposition of these compounds under the right conditions produces exquisitely tailored materials, it is important to recall that most of these compounds are highly toxic, pyrophoric, and air and moisture sensitive. Therefore, special equipment is necessary to produce thin films by chemical vapor transport. The method itself appears quite simple. The appropriate vapors are brought into contact with a substrate maintained at a particular temperature. The vapors decompose, leaving behind the desired material. In Figure 3.20, the three vapors introduced into the reaction chamber decompose and produce the desired... 

This conversion of actinide oxides of lower oxidation states into fully oxidized forms has a great advantage. The actinides of lower oxidation states are pyrophoric. Once converted into their fuUy oxidized form and encapsulated in the phosphate matrix, they are not spontaneously combustible and, hence, are safe for transportation and storage. Thus, because of this oxidation, the phosphate matrix removes the pyrophoricity during the stabihzation process. 

Caution. Transition metal carbonyl derivatives of magnesium are pyrophoric and must be handled with extreme care (see Properties). The toxicity of the magnesium derivatives is not known but is probably of the same magnitude as the parent carbonyls. The magnesium-transition metal-carbonyl complexes exhibit low vapor pressures and therefore do not present a vapor-transport toxicity problem when an inert-atmosphere enclosure is employed. 

A pyrophoric liquid is classified in a single category for this class using test N.3 in Part III, sub-section 33.3.1.5 of the UN Recommendations on the Transport of Dangerous Goods, Manual of Tests and Criteria, according to the following table ... 

As isolated from toluene solution, neat MAO is an amorphous, friable white solid containing 43-44% Al (theory 46.5%). Like most commercially available aluminum alkyls, it is pyrophoric and explosively reactive with water. Freshly prepared MAO solutions form gels within a few days when stored at ambient temperatures (>20 °C). However, lower storage temperatures (0-5 °C) delay gel formation. Consequently, manufacturers store and transport MAO solutions in refrigerated containers. Commercially available MAO contains residual TMAL (15-30%), called "free TMAL" or "active aluminum." The literature is contradictory on the influence of free TMAL on activity of single site catalysts both reductions and increases have been reported (18-20). Perhaps the most important drawback of methylaluminoxane is its cost, which is substantially higher than conventional aluminum alkyls. Despite these untoward aspects, methylaluminoxane remains the most widely used cocatalyst for industrial single site catalysts. 

Once reduced, the metals may be pyrophoric or selfheating upon exposure to air. This is problematic if the reduction is done at the catalyst manufacturing plant and must be shipped to the end-user s plants. In this case, a stabilization procedure is employed at the catalyst manufacturing plant so the material is safe for transport as per U.S. Department of Transportation standards. 

The pyrophoricity of the various hydrocarbon formulations of omegar-(/-butyldimethylsilyloxy)-l-alkyllithiums were tested, according to the official Department of Transportation (DOT) protocol. In this test, samples of the solution were placed on indented filter paper. After five minutes, the filter paper was examined for signs of charring. All the formulations tested by this official protocol were classified as NON-Pyrophoric. 

Division 4.2 Substances liable to spontaneous combustion. Substances which are liable to spontaneous heating under normal conditions encountered in transport, or to heating up in contact with air, and being then liable to catch fire. The following types of substances are classified in Division 4.2 pyrophoric substances and self-heating substances. lATA 3.4.2.1... 

Any liquid pyrophoric material poses a special hazard to an aircraft in flight, and severe limitations apply to such materials. Where a radioactive substance which has the subsidiary hazard of pyrophoricity is also a liquid, there is a greater probability of a spiU occurring, and it is therefore absolutely forbidden to transport such a substance by air. 

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