Catalyst initiator

Methyl violet [8004-87-3] Cl Basic Violet 1 (17), is made by the air oxidation of dimethyl aniline in the presence of salt, phenol, and a copper sulfate catalyst. Initially, some of the dimethyl aniline is oxidized to formaldehyde and /V-methyl aniline under those conditions. The formaldehyde then reacts with dimethyl aniline to produce N,N,]S7,1S7-tetramethyldiaminodiphenylmethane, which is oxidized to Michler s hydrol [119-58-4]. The hydrol condenses with... 

Styrene—Butadiene Rubber (SBR). This is the most important synthetic mbber and represents more than half of all synthetic mbber production (Table 3) (see Styrene-butadiene rubber). It is a copolymer of 1,3-butadiene, CH2=CH—CH=CH2, and styrene, CgH5CH=CH2, and is a descendant of the original Buna S first produced in Germany during the 1930s. The polymerization is carried out in an emulsion system where a mixture of the two monomers is mixed with a soap solution containing the necessary catalysts (initiators). The final product is an emulsion of the copolymer, ie, a fluid latex (see Latex technology). 

This is an exothermic reaction, and both homogeneous (radical or cationic) and heterogeneous (soHd catalyst) initiators are used. The products range in molecular weight from below 1000 to a few million (see Olefin polymers). Reaction mechanisms and reactor designs have been extensively discussed (10-12). 

If a vinyl monomer is polymerized in the presence of cellulose by a free radical process, a hydrogen atom may be abstracted from the cellulose by a growing chain radical (chain transfer) or by a radical formed by the polymerization catalyst (initiator). This leaves an unshared electron on the cellulose chain that is capable of initiating grafting. As cellulose is a very poor transfer agent [10], very little copolymer results from the abstraction of hydrogen atoms by a growing chain radical. The... 

Ideally, the metal complex is a catalyst and, in principle, is only required in very small quantities. However, the kinetics of initiation for the systems described to date dictate that relatively large amounts are used and catalyst initiator ratios are typically in the range 1 1 to 1 10. The most commonly used catalysts are metal... 

The effect of reactant concentrations on reaction rate was studied using unpromoted skeletal copper catalysts initially leached at 278 K and then... 

Standard conditions acetone (or -cf), water (5 equiv) and 2 mol % catalyst, initial alkyne concentration 0.50 M, reaction temperature 70 2 °C, reaction monitored by ll NMR or GC using appropriate internal standards. b In situ generation of catalyst see text for further details. 

M/g-catalyst initial concentrations. The first sample for each experiment was taken for time equal to zero minutes and filtered through a 0.45 pm hydrophilic Millipore filter to remove catalyst powder into a capped vial for subsequent analysis. 

Monomers, such as ethylene, propylene, isobutylene, and isoprene, containing the carbon-carbon double bond undergo chain polymerization. Polymerization is initiated by radical, anionic or cationic catalysts (initiators) depending on the monomer. Polymerization involves addition of the initiating species R, whether a radical, cation, or anion, to the double bond followed by its propagation by subsequent additions of monomer... 

An alcohol could initiate the ring-opening polymerization of lactones by lipase catalyst ( initiator method ). In the lipase CA-catalyzed polymerization of DDL using 2-hydroxyethyl methacrylate as initiator, the methacryloyl group was quantitatively introduced at the polymer terminal, yielding the methacryl-type polyester macromonomer [98]. This methodology was expanded to synthesis of co-alkenyl- and alkynyl-type macromonomers by using 5-hexen-l-ol and 5-hexyn-l-ol as initiator. 

The active species generated when bis(arylimino)pyridine iron (5) and cobalt (6) halides are activated with MAO was, by analogy with metallocene catalysts, initially considered to be a highly reactive mono-methylated cobalt(II) or iron(II) cation of the form LM-Me+ bearing a weakly coordinating counter-anion such as [X-MAO]-(X = halide, Me). To examine this theory a number of spectroscopic investigations have been directed towards identifying the active species (vide infra). 

Since the rate of chain oxidation of hydrocarbon is v v,1/2 and does not depend on [02] (see Chapter 2), the catalyst initiates the chains via two parallel reactions by the reaction with ROOH and by the reaction with dioxygen. The following mechanism was proposed ... 

In the very recent past, metal complex catalysis has been used with advantage for the stereo- and enantio selective syntheses based on the Henry and Michael reactions with SENAs (454-458). The characteristic features of these transformations can be exemplified by catalysis of the reactions of SENAs (327) with functionalized imides (328) by ligated trivalent scandium complexes or mono-and divalent copper complexes (454) (Scheme 3.192). Apparently, the catalyst initially forms a complex with imide (328), which reacts with nitronate (327) to give the key intermediate A. Evidently, diastereo- and enantioselectivity of the process are associated with preferable transformations of this intermediate. 

Figure 20. Hydrogenation of surface carbon over catalyst initially reduced for 15 h at 500°C and then cooled to 250°C. At t — 0 flow is switched to Ht/CO = 9, 250°C. At 20 h feed is switched to pure Hu, 250°C at 24 h temperature is...

The rate of CO removal from the Pt surface is also affected by the presence of O2 in the gas phase, as demonstrated in Figure 12. In this experiment the catalyst, initially in equilibrium with 1 vol % CO (in N ), was suddenly exposed to a feedstream of 0.7 vol % O2 (in 1 7 It can be seen from Figure 12 that the Pt-CO band decays much faster in O2 (Curve B) than in (Curve A for reference). This indicates that the surface reaction between CO and oxygen is faster than the rate of CO desorption. 

Figure 8. Transient responses (top) and reaction trajectories (bottom) with the catalyst initially at low oxidation level (1). Key ISS, initial steady state and ESS,...

Accidently, using hexafluoro-p-xylene with the contaminated copper wire obtained from the precursor method experiments, a polymer film was deposited on the silicon substrates. Obviously, some dibromotetrafluoro-p-xylene from the precursor method that adhered to, or reacted with, the metal could somehow initiate this VDP process. However, a complete explanation of these results is not yet available. As an extension of this discovery, commercially available 1,4-bis(trifluoromethyl)benzene in conjunction with a catalyst/initiator has proved to be a potential alternative by which to deposit poly(tetrafluoro-p-xylylene) film successfully.23... 

A typical condensation procedure involves a one-step reaction where the monomer and suitable catalyst/initiator are mixed and heated to the required reaction temperature. To accomplish a satisfactory conversion, the low molar mass condensation products formed throughout the reaction have to be removed. This is most often accomplished by using a flow of inert gas and/or by reducing the pressure in the reaction vessel. The resulting polymer is generally used without any purification or, in some cases, after precipitation of the dissolved reaction product from a nonsolvent. 

Fig. 3.46. High-performance ion chromatographic analysis of C.I. Reactive yellow 84 after 120 min of the catalytic oxidation over Fe-Y80 catalyst. Initial conditions were 100 mg/1 azo-dye, pH 5, t = 50°C, catalyst concentration 1 g/1 and 20 mmol H202. Peak identities are as follows 1, acetate 2, formate 3, chloride (used for pH adjusting) 4, nitrate 5, malonate 6, sulphate 7, oxalate. Reprinted with permission from M. Neamtu et al. [121].

The next study of wood modification was that reported by Baird (1969), who performed vapour-phase reactions of spruce with ethyl, n-butyl, /-butyl, allyl and phenyl isocyanate (PhNCO). Unfortunately, DMF was used as a catalyst for the reactions, which resulted in polymerization of PhNCO in the cell wall of the wood, leading to unpredictable results. No evidence was presented in support of the contention that polymerization had occurred, and since this requires an anionic catalyst initiator, this is considered unlikely. However, the presence of side reactions when DMF is used in conjunction with isocyanates has already been mentioned. Greater success was reported when butyl isocyanate was reacted with wood (presumably a consequence of the lower reactivity of this isocyanate... 

Weight fraction of coke on catalyst, lbs coke/Ib catalyst Initial weight fiaction of coke on catalyst, lbs coke/lb catalyst Distance along kiln, ft Distance along kiln at which 99% of coke is burned off Fraction of the original coke left on catalyst, Cc/C ... 

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