An Improved Method for the Purification of Polyether−Polyols Using Phosphoric Acid as Neutralization Agent (original) (raw)
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Organic Process Research & Development, 2010
The aim of this study was the development of a crystallization process for the removal of the alkaline catalyst (cesium hydroxide) from crude polyether polyols and its recycling process. Hydrochloric, phosphoric, carbonic, and sulphuric acids were tested to choose the best neutralization agent. Sulphuric acid was chosen because its recycling process seems to be easier than with the other acids assayed. The process involves a first step of neutralization with an aqueous solution of sulphuric acid. After that, the removal of water must be done following an adequate profile of pressure and temperature with time to reach a large particle size that makes possible the filtration of the polyol. The influence of the water/ polyol ratio and the P-T profiles were studied in order to decrease the process time and enlarge the size of the crystals. Once polyol is filtrated, the cake of Cs 2 SO 4 was dissolved again to precipitate the sulphate ion with barium hydroxide, thus obtaining a solution of CsOH that can be recycled in the process. It has been confirmed that the recycled cesium hydroxide can be used in a new cycle. Figure 6. Scheme for catalyst recovery.
Polyesters of phosphoric acid: Synthesis and kinetics of hydrolysis
Macromolecular Symposia, 1998
Three major methods have been elaborated in our laboratory for preparation of polymers with poly(alky1ene phosphates) backbones: ring-opening polymerization, poly-condensation and transesterification, and polyaddition. The second method is based on the reaction of the commercially available compounds, namely dialkyl (or diaryl)-H-phosphonates and glycols. Reaction of the aliphatic H-phosphonates with aliphatic glycols is a reversible process, whereas polycondensation of diphenyl H-phosphonates with aliphatic and cycloaliphatic diols is practidy irreversible. This latter method has recently been developed and is described in this paper. Poly H-phosphonates with up to 40103 were prepared. Polymers are easily oxidized and quantitatively converted into the relatively stable poly(a1kylene phosphates). Some physical properties of these polymers and kinetics of their hydrolysis is discussed.
The Journal of Supercritical Fluids, 2006
We investigated the dehydration of several biomass-derived polyols in sub-and supercritical water, in particular m-erythritol, 1,2-propanediol and 1,3-propandiol. The resulting main products were 1,4-anhydroerythritol and propionaldehyde. The additives tested for their catalytic performance were among others zinc, nickel, copper, magnesium and sodium sulfate as well as sulfuric acid. A positive catalytic effect of bivalent transition metal salts was found. Initial educt and ZnSO 4 concentration variations were carried out in order to determine the reaction orders. Further, activation energies and activation volumes were measured for zinc catalysed dehydrations of the above-mentioned polyols. Finally, a possible explanation for the reaction enhancing or inhibiting effect of different salts is given and discussed.
Crystallization of inorganic salts in poly (propylene oxide) oligomers by heating
1994
A series of inorganic salts was dissolved in poly(propylene oxide) (PPO) oligomers, and the effect of temperature on the salt solubility was analyzed. Some of alkali metal salts were separated out as crystals by heating from PPO oligomers (Mw = 400-4000). The salts, which were crystallized by heating, were revealed to have relatively higher lattice energy. The threshold of the lattice energy of these phase-separated salts decreased with increasing cation radius. The solubility of these salts turned to zero on increasing average molecular weight of PPO. This suggested the considerable contribution of the terminal hydroxyl groups of the PPO to the solubility of these salts. The increase of molecular motion in PPO oligomers with elevating temperature was expected to induce the distortion of the cooperative coordination of PPO to the cation. This might be the reason of the decrease in the solubility of salts in PPO.
Journal of Chemical Sciences, 2020
Novel film catalysts of the polystyrene (Ps) and trimethyl phosphate (P) nanoparticles were synthesized on glass substrates by soft chemistry using doctor blade method. Subsequently, the prepared Ps-P film catalysts were characterized by various techniques, including fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), density (d), polarizing microscope (PM), X-ray diffraction (XRD) and thermal analysis. According to the results, the structure and morphology of film catalysts were confirmed by all analyses. The Ps-P films, as heterogeneous solid catalysts, have demonstrated strong activity for Knoevenagel condensation, producing alkenes of high purity. The recovered yields are excellent, up to 96% in solvent-free conditions at room temperature. Further, the film catalysts have showed high stability, good reusability (up to five times) while maintaining their efficiency and productivity.
Journal of Molecular Catalysis B: Enzymatic, 2001
The present paper provides a general overview of the factors involved in both the kinetics and the selectivity of partial Ž. acylation reactions of polyols sugars. Different kinetic strategies for maximum production of intermediate esters of various polyols and monosaccharides are reported and discussed. Physicochemical requirements for obtaining maximum selectivities and complementary strategies for reducing reaction times are discussed. The reactions studied include glycerol, glucose, fructose, mannose, sorbitol and an alkyl glucoside as precursors. The high selectivity towards the monoglyceride in the presence and absence of a solvent has been attributed to a combination of the precipitation of the desired ester, use of glycerol in excess and the relatively low solubility of the fatty acid in the system. Unlike the reaction in the presence of a solvent, the reaction in a solvent-free medium produces the diester first. The monoester only accumulates in the medium as a consequence of disproportionation and glycerolysis reactions of the diester formed earlier. Selective esterification of solid Ž. sugars polyols which have an intermediate solubility in acetone is favored at low temperatures at which a sufficient amount of polyol dissolves and concurrent precipitation of the desired product can be achieved. By contrast, use of elevated temperatures is more appropriate for selective partial esterification of polyols, which are the most soluble in the solvent Ž. employed. Polyols sugars which are the less soluble into the liquid reaction phase cannot be easily esterified. Diffusional limitations on the rate of dissolution of the solid precursor can be minimized by increasing the surface area of the solid polyol.
Crystallisation and fractionation of selected polyhydroxyalkanoates produced from mixed cultures
New Biotechnology, 2013
Poly[R-3-hydroxybutyrate-co-(R-3-hydroxyvalerate)] (PHBV) copolymers were produced from mixed cultures of biomass (activated sludge) fed with acetic acid (HAc) and propionic acid (HPr). Feeding was performed in such a way as to produce materials with a wide range of monomer compositions and microstructures. Solvent-cast thin films of these materials have recently been shown to exhibit a narrow range of mechanical properties similar to those of the homopolymer poly(R-3-hydroxybutyrate) (PHB) . In this work, more detailed analyses of the thermal and crystallisation properties of these mixed-culture polyesters have revealed that they like comprise complex blends with broad compositional distribution of random and/or blocky copolymers of very different 3-hydroxyvalerate (3HV) contents and melting temperatures and thus have very different respective crystallisation kinetics. This blend complexity was confirmed by solvent fractionation of selected samples. The findings support the hypothesis that overall mechanical properties of these complex copolymer blend materials will be strongly influenced by the more rapidly crystallising components that form the matrix within which the slower crystallising components exist as microdomains. New opportunities in the material development of PHAs are likely to be found in establishing and exploiting such structure-function relationships. FIGURE 5 Spherulitic morphologies viewed under crossed polars. (a) Sample A5 at T iso = 408C; (b) sample C1 showing second layer of crystal formation with initial crystal layer showing top left; (c) A5 crystals: defects at crystal interfaces formed at T iso = 508C after 48 hours; (d) B1 crystals formed at T iso = 408C: crack formation after 48 hours. Samples at 20Â. www.elsevier.com/locate/nbt 9 Research Paper
Potassium removal from water-methanol-polyol mixtures by ion exchange on Amberlite 252
Chemical Engineering Journal, 1997
Equilibrium isotherms for the uptake of potassium from polyol-water-methanol mixtures on Amberlite 252, a strong acid ion exchange resin, have been obtained in order to assess the possibility of using such a system to purify industrial polyether-polyols. The selectivity was very high. A two-step reaction scheme was proposed and equilibrium data were correlated by an equation derived according to the mass action law. Effective intraparticle diffusivities were obtained using a homogeneous model and the effects of the viscosity of the bulk solution and resin swelling on the exchange rate are discussed. A simple empirical equation correlating diffusivity with viscosity and resin swelling is suggested. Breakthrough curves were obtained under a wide range of conditions, being well correlated by the expression for breakthrough curves with rectangular isotherm. The proposed purification procedure is generally applicable to different polyol types, being economically and technically feasible. 0 1997 Elsevier Science S.A.
Journal of Cellular Plastics
Polyglycerol (PGL) is a polyhydroxyl compound obtained by selfcondensation of glycerol in the presence of alkaline catalysts. It is a very attractive polyol as a starter for the synthesis of polyether polyols for rigid polyurethane foams. It is liquid, easy to handle and has a very high average functionality of 4-20 (or more) hydroxyl groups/mol. By propoxylation of PGL or PGL-sucrose mixtures, we obtained new polyether polyols with very high functionalities, which are very difficult or impossible to obtain by other methods. A new technology for PGL-based polyether polyols preparation was investigated. In the first step the self-polycondensation of glycerol to PGL in the presence of potassium hydroxide or potassium methoxide as a catalyst was carried out. In the second step, the crude alkaline PGL was alkoxylated with PO without removing the catalyst, followed by purification of the resulting polyether polyols. Rigid polyurethane foams prepared from the synthesized PGL-based polyether polyols and crude MDI displayed good physical and mechanical properties, excellent dimensional stability, and low friability.