Deactivating agent

The silica gel surface is extremely polar and, as a result, must often be deactivated with a polar solvent such as ethyl acetate, propanol or even methanol. The bulk solvent is usually an n-alkane such as n-heptane and the moderators (the name given to the deactivating agents) are usually added at concentrations ranging from 0.5 to 5% v/v. Silica gel is very effective for separating polarizable materials such as the aromatic hydrocarbons, nitro hydrocarbons (aliphatic and aromatic), aliphatic ethers, aromatic esters, etc. When separating polarizable substances as opposed to substances with permanent dipoles, mixtures of an aliphatic hydrocarbon with a chlorinated hydrocarbon such as chlorobutane or methylene dichloride are often used as the mobile... 

The reactions between (methyl)chlorosilanes and the surface of silica have been investigated by many researchers, primarily because of the utility of these reagents as coupling agents in polymer chemistry and as surface deactivating agents in chromatography. 

Accelerated aging tests have been commonly used in facilities ranging from academic bench scale to industrial pilot-plant scale. In such tests, the addition of an accelerant increases the deactivating agent or its precursor, so that a certain Level of deactivation (however measured) is reached at lower run times. In this manner, the performance of a catalyst at a high deactivation level can, in principle, be measured without expending the time and effort required under normal conditions to bring the catalyst to this level of deactivation,... 

Since the mordenite type zeolite has two dimensional pore structure with nonintersecting parallel channels, the internal surface area of the catalyst may be easily blocked by the adsorption of reactants as well as by the deposition of deactivating agents. To confirm the speculation that the adsorbed reactants can block the pores, the change in surface... 

The dependence of SCR activity of CuHM31 on its sulfur content with respect to reaction temperatures also shows the similar behavior to HM catalyst as shown in Fig. 4B. The catalytic activity reveals an exponential decrease with the sulfur content of the catalyst at 250 °C, while no deactivation is observed at 400 °C, despite the deposition of sulfur up to 1.78 wt.% on the catalyst surface. As discussed in the previous study, it is probably due to the deposition location of the deactivating agents on the pores of catalyst structure (ref 1). 

For the formation of ammonium salts such as ammonium sulfate and ammonium bisulfate on the catalyst surface, the S02 should be first oxidized to S03, and then S03 should react with NH3 and HjO. Since the formation of these ammonium salts depends on the oxidizing ability of the catalyst converting S02 into S03 the deactivating agent deposited on HM-250 catalyst could be formed less than CuHM catalysts as shown in Table 1. 

Chemical solutions In the event of an emergency you may be directed to perform decontamination with other chemical deactivation agents. These vary depending on the chemical warfare agent and may include alkaline solutions of hypochlorite. 

Polymerization without termination living polymers. If care is taken, all termination reactions can be avoided. Polymerization then proceeds until all monomer is used up or the reaction is quenched by addition of a deactivating agent. Under such conditions, the rate of monomer consumption is the sum of the rates of initiation and propagation ... 

In copolymerization, several different combinations of initiation and termination mechanisms are possible, giving rise to a variety of different polymerization rate equations. Only two cases will be singled out here free-radical copolymerization with termination by coupling, and ionic polymerization with termination by chain transfer to a deactivating agent or impurity. For other combinations, the derivation of rate equations follows along the same lines. 

With ROH or HCl as deactivating agent MWD is narroved or broadened respectively ... 

Sulfhydryl compounds cause significant reductions in the activity of bronopol, and cysteine hydrochloride may be used as the deactivating agent in preservative efficacy tests lecithin/ polysorbate combinations are unsuitable for this purpose. Bronopol is incompatible with sodium thiosulfate, with sodium metabisulfite, and with amine oxide or protein hydrolysate surfactants. Owing to an incompatibility with aluminum, the use of aluminum in the packaging of products that contain bronopol should be avoided. 

A deactivating agent for copper-activated sphalerite is any species that has sufficient affinity for copper(I) or (II) to compete for it with sulfide ions in the surface lattice of the mineral, thus removing it from the surface. Ligands such as cyanide or ethylenediamine, which coordinate strongly to copper, have therefore been found to be the most effective. A knowledge of the stability of the species present in a system composed of and CN ions has enabled ... 

At 250"C catalyst activity decreases exponentially with temperature. This is probably due to formation of ammonium sulfate at the exterior surface of the catalyst at this tow temp> erature. causing severe pore blockage. However, at 400<>C, a temperature above that required for decomposition of ammonium sulfate, deposition of the deactivating agent, ammonium sulfat probably occurs deep inside pores leading to selective pore filling rather than pore blockage. 

In the catalyst removal section, the active catalyst in the reactor effluent is deactivated by adding a catalyst deactivating agent. The catalyst is then separated fi om the reactor effluent by means of vaporization where the liquid withdrawn from the reactor is vaporized and the residue contains the spent catalyst and a small amount of hydrocarbons. 

With catalyst control, the ratio ko/ky may be increased to optimize the desirable product D. Benefits are obvious and include greater yields of D and less extensive separation operations. An especially important case occurs when U is a deactivating agent such as coke" or carbonaceous deposits. 

Addition of promoters to remove deactivating agents. One example is steam reforming, in which carbon is removed, as it forms, by reaction with steam, catalyzed by alkali additives. 

U.S. 5441661 08/1995 Beaujean et al.l Henkel KgaA surfactant-rich phase can be incorporated into the liquid phase without segregation or separation Nonaqueous liquid detergent containing a hydrated zeolite stabilized by a polar deactivating agent... 

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