Catalyst avoidance

There are several other examples of ZSM-5 being used commercially to reduce waste and give high product selectivity. One of these is the alkylation of benzene with ethene to produce ethylbenzene selectively. The pore size of ZSM-5 successfully minimizes dialkylation reactions whilst the ability to regenerate the catalyst avoids waste issues associated with older catalysts such as aluminium chloride. 

The original conditions, called the Gattermann Reaction / Formylation, were to add HCN, HC1 and ZnCh (known as Adam s Catalyst) directly. Use of Adam s catalyst avoids using gaseous HCN. 

Silica gel G (30), and Uni si 1 (31,32). All of these LC procedures are hampered by the absence of an adequate detection system. Although the lack of on-line detection has impeded the adaptation of the LC procedures to HPLC, preparative HPLC of glycolipids has been performed on silica SI 60 with post-column, off-line TLC detection (30) and with a moving wire detector (31). The procedure described below for per-O-benzoylation of glycolipids with benzoic anhydride in pyridine and DMAP as catalyst avoids N-benzoylation problem and provides a convenient method for the detection and preparative isolation of glycolipids. The application of this procedure for the isolation of 15 mg of glycolipids in a single HPLC run is described. 

Mitigation approach Mitigation via. potential control air bleed, CO tolerant catalysts,, avoid potential contaminants in conduits and m new alloy catalysts new alloy catalysts, avoid OCV p 0 ten tial-cycling Surface modifica- tion Alternative material, increase compression avoid high T, dry RH- cycling... 

For safety reasons, solidified ammoitium nitrate should not be broken up by blasting. Products containing ammonium nitrate must be stored separately from oxidizable and inflammable materials and, if ammonium nitrate must be heated (during production, evaporation, etc ), the quantity must be kept small and catalysts avoided. In several countries, inert materials snch as limestone powder, dolomite, or precipitated calcium carbonate, are added to ammonium... 

Highly Increased Number of Effective Collisions Active Site Preorganization of Solvation and General Acid/Base Catalysts Avoiding High-Energy Intermediates Electrostatic Catalysis by Metal Ions Covalent Catalysis by Enzyme-Bound Electrophiles and Nucleophiles Coupling ATP Hydrolysis to Drive Equilibria... 

A reaction under neat conditions, with or without catalyst, avoiding the use of organic solvents in the entire operation, including isolation and purification, is of great significance in the design of a green process for industrial application. 

The rate of formation of by-product 2 is independant of palladium concentration. But on the other hand, the rate of formation of 2 is directly proportional to palladium concentration. This is very important in controlling the selectivity and you have to maintain the activity of the palladium catalyst (avoid poisoning...) in order to obtain good yields... 

An application of this principle is in the telomerization of butadiene with ethylene glycol. One-phase reactions yield both mono- and ditelomers, while the two-phase system using a water/glycol phase containing a polar palladium catalyst avoids the... 

Mono-O-allyl derivatives of o-fructose have been prepared in order to test the specificity of the fructose transporter GLUT5. Tris(triphenylphosphine)ruthe-nium(II) dichloride is an excellent catalyst for the isomerization of allyl to prop-l-enyl ethers in a de-O-allylation procedure. The catalyst avoids the problem of reduction of the alkene as a side reaction. " Another method uses Pd(0)-catalysed allyl transfer to p-toluenesulfinic acid for the cleavage of allyl ethers on a solid support."... 

Fire non combustible. but enhances combustion of other substances catalystically. avoid contact with combustible substances. In case of fire in immediate vicinity use any extinguishing agent. 

The organometallic compounds, such as Re2(CO)io and Re(OC2Hs), are added to alumina after the impregnation and reduction of platinum. In this way, the rhenium compound is preferentially adsorbed on the platinum surface, thus favoring the formation of the alloy. However, industrially it is complicated to work with prereduced platinum catalyst avoiding its reoxidation. 

Pure hydrogen and oxygen mixtures are highly explosive. Reactions that involve such mixtures are carried out safely in microchannel reactors. For example, the direct preparation of hydrogen peroxide is obtained with a special catalyst, avoiding the circuitous anthraquinone process, used at the industrial scale. Calculations of explosion limits clearly demonstrate that there is a considerable shift when explosive reactions are carried out in microchannels. The safety of the process is not only due to the avoidance of thermal runaway (because of large surface-area-to-volume ratio), but also due to the fact that radical chains are broken down due to the increased wall collision in the small channels of the reactor. 

The catalyst could be recovered ten times without losing its activity. This catalyst avoids the use of any type of expensive and difficult to handle organic ligand, showing excellent yields, under mild reaction conditions. The catalyst is very easy to remove from the reaction medium, just by using a simple magnet. However, a relatively high reaction temperature was required. 

The sensitivity to pH is another aspect not always considered. Homogeneous Fenton processes need to operate in a narrow pH range (2.5. 0) and this is a main process issue, as it requires the addition of large amounts of salts to the wastewater for pH control. The use of solid Fenton-type catalysts allows, in principle, operation at natural pH, without the need to adjust the pH, with better process economics. In addition, solid Fenton-type catalysts avoid the need for precipitation of iron and remove the iron sludges after treatment. This is a relevant process issue, especially when the operation is a pre-treatment before further stages such as biological treatments. 

Structure, and MAA desorption from the catalyst, avoiding its further oxidation by consecutive reactions. 

Nanoparticles are attracting increasing attention as catalysts from both the homogeneous- and heterogeneous catalysis communities, because they are ligandless catalysts avoiding toxic phosphines, and they show remarkable activities and selectivities [60]. 

The solvent is also a critical parameter as it must be compatible with both catalysts avoiding their deactivation and must be inert with the acyl donor. The requirement of an initial activation of metal catalyst for the racemization step has led to the common selection of THF and toluene as ideal solvents, the latter having the advantage of its higher boiling point where a high temperature is required in the system although temperatures over 100 °C are not recommendable due to enzyme denaturation. 

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