Catalyst breakdown products

The activities of the often used hydroxides and siloxanolates decreases in the order Cs > Rb > K > Li (33). At equal molar concentrations, the rates using the hydroxide or siloxanolate of the same metal have been found to be similar (30). Tetramethy1ammonium siloxanolates exhibit activities close to the cesium siloxanolates (33). Tetramethy1ammonium hydroxide, silanolate, and siloxanolate rapidly decompose above 130 C yielding methanol, methoxy trimethylsilane, or methoxysiloxane respectively and trimethyl amine ( 35). In the cases of the first two compounds listed above, the catalyst breakdown products are fugitive at the decomposition temperature. Thus, the usual need for catalyst neutralization and removal following polymerization is eliminated. They are often termed "transient" catalysts (34). 

Source. Breakdown product of azobisisobu-tyronitrile used as a blowing agent for the production of vinyl foam by-product of a polymerization catalyst in photocopier toner... 

When dispersion systems are used some residual dispersants can remain in the plastic and then migrate out. In the case of homogeneous catalysts migration can also occur. In particular this applies to the residual organic parts of the organo-metal compounds which remain as breakdown products in the plastic after completion of polymer synthesis and destruction of the catalyst. This also applies to residual solvents that are not fully evaporated. 

Marci et al. [233] concluded that the presence of O2, a catalyst and irradiation was required for toluene degradation. They found that the intermediate breakdown products were benzyl alcohol, benzoic acid and benzaldehyde. However, the benzaldehyde was only generated in small quantities and large amounts of benzoic acid were found adsorbed onto the catalyst surface. With the two forms of Ti(>2 used in this study, Degussa P25 and Merck, it was observed that the P25 material deactivated even in the presence of water vapour. 

Platinum—soluble salts (sodium chloroplatinate ammonium chloroplatinate, platinum tetrachloride) Sensitizers causing asthma and dermatitis. Metallic platinum does not share these effects. Soluble platinum compounds are also highly irritating to eyes, mucous membranes, and respiratory tract. 0.002 mg/m (as Pt) 4mg/m (as Pt) Appearance varies with the compound. Thermal-breakdown products of some chloride salts Include chlorine gas. Used as Industrial catalysts and In specialized photographic applications. 

Intellectual property assigned to Hoechst covers hydrolysis [190-192], methanolysis [193,194] and a method of purifying recovered EG fractions via solvent extraction in xylene [195]. The hydrolysis process is carried out in large volumes of water at high pressure and temperature, typically 4.2 MPa and 250 °C, with residence times of 2-3 hours. The methanolysis process differs from other known versions of this approach in that the polyester is first reacted (preferably in the melt) with a transesterification catalyst and that methanolysis is carried out on the resulting breakdown products. This is said to allow the second stage to be carried out under milder conditions. 

The composition of such breakdown products is highly dependent on the precursor, the heating conditions and whether a catalyst is used or not. The term catalyst in this sense is a substance which has an influence on the actual cellulose pyrolysis process. Tamaru [66] investigated the effect of inorganic salts on the pyrolysis and combustion of cellulose. Garn and Denison [67] investigated flame retardants for cotton, which had a direct spin-off for carbon fiber manufacture. Typical treatment products/catalysts that have been investigated... 

This technique, discussed in Chapter 1, can be applied to the separation of mixtures of organic substances and as such may have applications in the analysis of additives, additive breakdown products, or catalyst residues in polymer extracts. Phenols and carboxylic acids are possibilities in this respect. 

A novel way of studying a partially reacted polydiene is to deconnpose it in a metathesis reaction with a small olefin then to separate and identify the low molecular weight products by standard methods such as gas chromatography-mass spectrometry. This method has been applied to polybuta-1,4-diene partially aralkylated or hydrobrominated, to confirm the structure and position of the substituents. " The small olefin was oct-4-ene and the metathesis was promoted by a WCU/Sn(CH3)4 catalyst. The products of such a metathesis breakdown are, of course, dependent also on the nature and distribution of double bonds within the parent polymer. ... 

Feedstocks. A separate breakdown between fuels and feedstocks (qv) for the chemical industry (2) shows that the quantity of hydrocarbons (qv) used direcdy for feedstock is about as great as that used for fuel (see Fuels, synthetic Gasoline and other motor fuels). Much of this feedstock is oxidized accompanied by the release of heat, and in many processes, by-product energy from feedstock oxidation dominates purchased fuel and electricity. A classic example is the manufacture of nitric acid (qv) [7697-37-2] HNO. Ammonia (qv) [7664-41-7] burned in air on a catalyst at a pressure... 

There are no fall-out products resulting from DEHA breakdown consequently, it can generally be safely used at pressures in excess of 2,500 psig, similar to hydrazine. A complication, however, is that HQ (the primary catalyst for DEHA), breaks down above 1,250 psig, so the DEHA reaction rate tends to slow down. 

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