Adsorbents phenol-formaldehyde resin

Chemical stability of carbon over the entire pH range has led to considerable interest in the development of carbon-based stationary phases for RPC. Porous graphitised carbon with sufficient hardness, well-defined and stable pore structure without micropores, which ensures sufficient retention and fast mass transfer can be prepared by a complex approach consisting of impregnation of the silica gel with a mixture of phenol and formaldehyde followed by formation of phenol-formaldehyde resin in the pores of the silica gel, then thermal carbonisation and dissolution of the silica gel by hydrofluoric acid or a hot potassium hydroxide. solution [48. The retention and selectivity behaviour of carbon phases significantly differs from that of chemically bonded pha.ses for RPC. Carbon adsorbents have greater affinity for aromatic and polar substances so that compounds can be separated that are too hydrophilic for adequate retention on a Cix column. Fixed adsorption sites make these materials more selective for the separation of geometric isomers [49]. 

Highly active catalysts have been produced by adsorption of lipases onto macroporous acrylate beads, polypropylene particles and phenol-formaldehyde weak anion exchange resins. Protein is bound, presumably essentially as a monolayer, within the pores of the particles. The large surface area of the particles (10m2 g 1) means that substantial amounts of protein can be adsorbed, and the pores are of sufficient size to allow easy access of reactants to this adsorbed protein. 

Immobilization. We have worked with different carriers for immobilization. Active immobilized preparations have been obtained by adsorption on macroporous, weakly basic anion exchange resins, and on nonionic adsorbent resins. Resins of both acrylic and phenol-formaldehyde have been used (8). In the following examples we have used lipase immobilized on nonionic adsorbent acrylic resin. 

Resins such as phenol formaldehyde and highly sulphonated styrene/divinyl benzene macroporous ion exchange resins can be pyrolysed to produce carbonaceous adsorbents which have macro-, meso- and microporosity. Surface areas may range up to 1100 m /g. These adsorbents tend to be more hydrophobic than granular activated carbon and therefore one important application is the removal of organic compounds from water. 

The strength of articles based on phenolic compositions and solidified without additional pressure and heat supply is 2-4 times lower than the strength of thermally solidified resins this limits their applications as engineering materials. One of the primary causes of material strength decrease is pore formation due to volatilization of water and formaldehyde during polycondensation. Different water adsorbents (calcium carbonate, clay, silicates, methasilicates, zeolites, etc.) should be... 

It is important to note here that higher temperatures probably increase emissions from phenolic panels simply by accelerating the release of that small amount of residual formaldehyde that originates from the adhesive and subsequently becomes adsorbed to the wood substance and water in the wood. Because phenolic resins are very stable chemically, any temperature-related increase in emissions would not be expected to be associated with resin degradation. Consequently, temperature would be expected to exert much less influence on emissions from panels which have been aired out than from fresh panels. Indeed, this trend is shown by the data, as discussed below. 

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