Direct process residue

Disilanes, direct-process residue, 22 552 Disilicide pest, 25 386 Disinfectant/Disinfection Byproducts Rule (D/DBPR), 17 807 Disinfectants, 8 605, 606... 

Methylchloroisothiazolinone, antimicrobial used in cosmetics, 7 831t Methylchlorosilane(s) (MCS) direct-process residue, 22 552 as silylating agents, 22 697 in TD resin preparation, 22 588 Methylchlorosilane process, 22 548, 549 a-Methylcinnamaldehyde, 3 595... 

Methylchlorodisilanes are by-products of the direct-process residue, commonly called high boiling point residue or simply residue, and are formed in about 4% of the total (CH3)2SiQ2 produced, which in 1994 was about 30,000 tons per year. Disilanes are key constituents of the residue, and novel reactions forming Si—Cl bonds have been described (44,45). Some chemical reactions of direct-process disilanes are shown in Figure 2. Qeavage chemistry of Si—Si compounds with HQ practiced industrially has also been described (47). 

The polymers described in this chapter are derived from the residue of the manufacture of methylchlorosilanes by the direct process. Approximately 10% of the reaction product of methylchlorosilane manufacture is a residue (called the direct-process residue) (2). The fraction of direct-process residue boiling between 150 and 160 °C consists primarily of 1,2-dimethyltetra-chlorodisilane and 1,1,2-trimethyltrichlorodisilane (3). 

Keywords trichlorosilane, tetrachlorosilane, direct process, direct process residue, characterization, shock-sensitive, hydrolysis, pyrophoric... 

Fig. 2. Chemistry of direct-process residue methylchlorodisilanes. The reactions are discussed in detail in the following References (i), 46 (ii), 44,45 (iii), 47 ...

The ratio of cycHc to linear oligomers, as well as the chain length of the linear sdoxanes, is controlled by the conditions of hydrolysis, such as the ratio of chlorosilane to water, temperature, contact time, and solvents (60,61). Commercially, hydrolysis of dim ethyl dichi oro sil a n e is performed by either batch or a continuous process (62). In the typical industrial operation, the dimethyl dichi orosilane is mixed with 22% a2eotropic aqueous hydrochloric acid in a continuous reactor. The mixture of hydrolysate and 32% concentrated acid is separated in a decanter. After separation, the anhydrous hydrogen chloride is converted to methyl chloride, which is then reused in the direct process. The hydrolysate is washed for removal of residual acid, neutralized, dried, and filtered (63). The typical yield of cycHc oligomers is between 35 and 50%. The mixture of cycHc oligomers consists mainly of tetramer and pentamer. Only a small amount of cycHc trimer is formed. 

Boilers may be direct fired or indirect fired. Energy supply designs account for various combustion methods using fossil fuels, municipal waste, process residues, waste heat, and by-products. Special boiler combustion systems to reduce pollution or improve efficiency include fluidized-bed and combined cycle. 

Raw Materials. In the early days, the raw materials were mainly zinc ores or concentrates for the direct process, or metal from zinc producers for the indirect process. Nowadays, zinc oxide manufacturers mainly use residues and secondary zinc. This fact, combined with the demand for chemical purity imposed by the users, means that processes have had to be modified and a number of purification techniques are used. 

Under suitable conditions the Penniman process can also be used to produce reds directly. The residual scrap iron and coarse particles are removed from the pigment, which is then dried [3.35] and ground using disintegrators or jet mills. These pigments have unsurpassed softness. They usually have purer color than the harder red pigments produced by calcination. 

A. High Boiling Residues from the Direct Process. 1592... 

Primary coal liquids must be upgraded in order to serve these markets. A logical route is to use current black oil conversion technology as practiced in the petroleum industry (2). An applicable UOP process is RCD Unibon (3). This comprises the direct processing of petroleum residues to reduce the sulfur and nitrogen content of heavy fuel oil or to combine desulfurization with conversion of residue to lighter, more valuable products. 

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