Simple filtration

Incipient hazes may not be removed at all by simple filtration. An array of fining procedures have been developed to achieve stable clarity in such cases. Fining agents ate substances that ate or become insoluble in wines, and, as they precipitate, adsorb or coptecipitation incipient sources of cloudiness. Ptopedy used, the fining agents themselves ate not retained in the wines and thein effect is subtractive rather than additive. 

Acidic Cation-Exchange Resins. Brmnsted acid catalytic activity is responsible for the successful use of acidic cation-exchange resins, which are also soHd acids. Cation-exchange catalysts are used in esterification, acetal synthesis, ester alcoholysis, acetal alcoholysis, alcohol dehydration, ester hydrolysis, and sucrose inversion. The soHd acid type permits simplified procedures when high boiling and viscous compounds are involved because the catalyst can be separated from the products by simple filtration. Unsaturated acids and alcohols that can polymerise in the presence of proton acids can thus be esterified directiy and without polymerisation. 

By a simple filtration step, catalyst-free products can be obtained. 

The catalyst can be recovered frequently by means of a simple filtration step. 

In practice, treatment (1) usually involves a contractor collecting a segregated batch of oil, reconditioning and returning it for re-use. A contractor can carry out the simple filtration process, but it is more usually done on-site. Re-refining is the removal of contaminants and oxidation products and previously incorporated additives to recover the lube base stock for new lubricant or other applications. 

When the reaction product is soluble in water, enzyme regeneration is difficult to achieve, since the enzyme is often lost during isolation of the product. One way to overcome this problem is application of immobilised enzyme systems. The enzyme is either covalently or ionically attached to an insoluble carrier material or is entrapped in a gel. Depending on the size of the particles used, a simple filtration and washing procedure can be used to separate the immobilised enzyme from the dissolved product A well-known example of this technique is the industrial production of 6-APA. 

A remarkable effect of the reaction temperature on the enantioselectivity of the addition of butyllithium to benzaldehyde was found with polystyrene-bound cvs-enofo-S-dimethylamino -(benzyloxy)bornane (8)12. When the soluble monomeric ligand 9 was tested, the enantioselectivity increased with decreasing temperature (53% ee at — 78 C). In contrast, the polymer-bound chiral additive 8 showed an optimum at — 20 C (32% ee). Although the enantioselectivity of this addition reaction is low, an advantage of a polymer-bound chiral auxiliary is that it can be removed by a simple filtration. 

In most cases homogeneous chiral catalysts afford higher enantioselectivities than heterogenous catalysts. Nevertheless, the development of heterogeneous chiral catalysts has attracted increasing interest because workup of the reaction, and recovery of often valuable chiral auxiliaries by simple filtration, is more convenient than in the case of homogeneous catalysts. 

In many instances, the dichloromethane solution can be dried adequately by a simple filtration through coarse filter paper. 

Two-phased samples, where the components of interest are present in high concentration in the liquid, can often be dealt with by simple filtration as the amount of material adsorbed on the surface of the solid phase, relative to that in the liquid phase is likely to be insignificant. Alternatively if the material is dispersed as a solid throughout the solid phase, then the sample can be filtered and the solid extracted exclusively. 

In the case of products prepared from hydrolysis/condensation reactions, the time of reaction varies from a few hours to more than 3 months. Generally, the crude products precipitate from the reaction mixture and pure compound can be obtained by simple filtration followed by washing or recrystallization. However, the yields are often low and rarely exceed 50%. 

The usual aromatic bromination are performed by free bromine in the presence of a catalyst, most often iron. However, liquid bromine is not easy to handle because of its volatile and toxic character. On the other hand, alumina-supported copper(II) bromide can be treated easily and safely as a solid brominating reagent for aromatic compounds. The advantages of this procedure using the solid reagent are simple workups, mild conditions, and higher selectivities. Products can be isolated in good yield by simple filtration and solvent evaporation, and no extraction steps are required. 

A most important issue in the present method was the ability to reuse the catalyst, without losing its activity. This proved to be one of the most salient advantages offered by 4. Catalyst recovery was straightforward, since it involved a simple filtration step. In our hands, it was possible to perform several cycles of catalyst reuse by simple filtration and washing steps (see Table 7). 

The use of palladium as a catalyst is common in the development and synthesis of active pharmaceutical ingredients (APIs). Palladium is an expensive metal and has no known biological function. Therefore, there is a need to recover spent palladium, which is driven both by cost and by government regulations requiring residual palladium in APIs to be <5 ppm (1). Thus, much research has been conducted with the aim of heterogenizing active palladium that can then be removed via simple filtration and hopefully reused without significant loss of activity. 

Reaction mixtures, separated by simple filtration, were analyzed by GC (HP-6890) using a non-bonded, bis-cyanopropylpolysiloxane (100 m) capillary... 

Preparation of ligand 31 Originally, chiral ligand 31 was prepared from (1R,2R)-1,2-diaminocydohexane 33 based on the racemic synthesis reported by Barnes et al. in 1978 [15], where picolinic acid 34 was activated with P(OPh)3 and then coupled with trans-l,2-diaminocyclohexane. The reported isolated yield in the case of racemate was only 47%. We optimized the preparation as shown in Scheme 2.8 [16]. Picolinic acid 34 was activated with CDI in THF. After confirmation of activation, chiral diamine 33 was added to the solution. When complete, the reaction was quenched via the addition of a small amount of water (to quench excess CDI). The reaction solvent was then switched from THF to EtOH, when the desired ligand 31 directly crystallized out. Ligand 31 was isolated in 87% yield by simple filtration of the reaction mixture in high purity. With a 22 litter flask, 1.25 kg of 31 was prepared in a single batch. 

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