Abstract: Methods of producing low-halogen-containing polysilazane resins, which are used to make silicon carbide fibers and ceramic coatings, provide processes for removing halogens, including chlorine, from precursor polysilazane resins.

Abstract: In one aspect, the present invention provides a curable composition useful in the preparation of a gas separation membrane. The curable composition comprises a polyvinyl alcohol; an aliphatic polyamine; a polyglycidyl ether; and a salt of a C2 to C4 heterocyclic amino acid. In another aspect the present invention provides a composition comprising a crosslinked polyvinyl alcohol comprising structural units derived from a polyglycidyl ether, a polyamine and the salt of a C2 to C4 heterocyclic amino acid. The compositions are useful in the preparation of gas separation membranes in which the C2 to C4 heterocyclic amino acid in the form of its salt functions as a mobile carrier of carbon dioxide.

Abstract: Disclosed herein is a method for purification of dianhydrides comprising a substantial amount (10000 ppm or more) of at least one metal salt. In one aspect the method is useful for the purification of dianhydrides prepared by the reaction of a halophthalic anhydride with a metal carbonate and may be optionally catalyzed by a phase transfer catalyst. The purification of the dianhydrides may be accomplished by hydrolyzing the dianhydride metal salt mixture directly to a tetraacid with an inorganic acid, followed by separating the impurities from an aqueous phase, and subsequently heating the tetraacid to effect ring closure to form a purified dianhydride having less than 50 parts per million metal halide and lower levels of other residual impurities. In one aspect the method is highly effective in removing phase transfer catalyst impurities such as hexalkylguanidinium halides initially present in the dianhydride undergoing purification.

Abstract: In one aspect, the present invention provides a curable composition useful in the preparation of a gas separation membrane. The curable composition comprises a polyvinyl alcohol; an aliphatic polyamine; a polyglycidyl ether; and a salt of a C2 to C4 heterocyclic amino acid. In another aspect the present invention provides a composition comprising a crosslinked polyvinyl alcohol comprising structural units derived from a polyglycidyl ether, a polyamine and the salt of a C2 to C4 heterocyclic amino acid. The compositions are useful in the preparation of gas separation membranes in which the C2 to C4 heterocyclic amino acid in the form of its salt functions as a mobile carrier of carbon dioxide.

Abstract: In one aspect, the present invention provides a curable composition useful in the preparation of a gas separation membrane. The curable composition comprises a polyvinyl alcohol; an aliphatic polyamine; a polyglycidyl ether; and a salt of a C3-C5 amino cycloaliphatic acid. In another aspect the present invention provides a composition comprising a crosslinked polyvinyl alcohol comprising structural units derived from a polyglycidyl ether, a polyamine and the salt of a C3 to C5 amino cycloaliphatic acid. The compositions are useful in the preparation of gas separation membranes in which the C3 to C5 amino cycloaliphatic acid in the form of its salt functions as a mobile carrier of carbon dioxide.

Abstract: A method of preparing a purified dianhydride is provided where said method comprises the steps of preparing a first mixture comprising water, at least one inorganic acid, and at least one dianhydride, said dianhydride comprising at least one impurity which is soluble in aqueous acid heating said first mixture until substantially all of said dianhydride is converted to a tetraacid comprised in a second mixture; filtering at least a portion of said second mixture to provide a solid tetraacid and a filtrate, said filtrate comprising at least a portion of said impurity; and heating the tetraacid provided in a solvent with concurrent distillation of water to provide a third mixture comprising a purified dianhydride and a solvent.

Abstract: A method of increasing the amount of diphenylcarbonate produced per amount of catalyst consumed in a phenol carbonylation process is described. Phenolic carbonylation produces water as a reaction product which reduces the turnover number (TON) of the catalyst. A mixture of a phenolic precursor, a base containing catalyst and co-catalyst components and at least one chemical additive comprising a halide or hydroxide of alkali metal or alkaline earth metal when carbonylated together under specific conditions increases the turnover number (TON) and water resistivity of a palladium catalyst. The metal halide likely makes the catalyst less susceptible to degradation by water hence increasing the reaction yield per weight of catalyst consumed.

Abstract: Brominated hydroxyaromatic compounds such as p-bromophenol are prepared by contacting a hydroxyaromatic compound with oxygen and a bromine source such as hydrogen bromide or an alkali metal or alkaline earth metal bromide in an acidic medium, in the presence of elemental copper or a copper compound as catalyst. The brominated product of this reaction may be converted alternately to a dihydroxyaromatic compound such as hydroquinone by hydrolyses, or a dihydroxybiphenyl compound such as 4,4?-dihydroxybiphenyl by reductive coupling.

Abstract: A method for preparing and isolating dihydroxybiaryl compounds, such as 4,4?-dihydroxybiphenyl, is disclosed. The alkali metal salt of the dihydroxybiaryl compound is protonated with the monohydroxyaryl halide compound initially used in the reductive coupling reaction which produced the alkali metal salt. In addition, the alkali metal salt of the monohydroxyaryl halide compound is produced by the process, which can then be recycled as the base and monohydroxyaryl halide in a further reductive coupling reaction to form the alkali metal salt of the dihydroxybiaryl compound.

Abstract: A method for preparing hydroxyaromatic compounds brominated in the para-position, such as p-bromophenol, is disclosed. The method yields overall high process selectivity through isomeric equilibration and separation of the brominated products, thereby eliminating the need for high para selectivity in the products of catalytic oxybromination reactions of hydroxyaromatic compounds using oxygen, a bromine source, and an acidic medium in the presence of a metal catalyst. Furthermore, the invention provides an efficient method for recycling the metal catalyst, as well as reagents used in the bromination, to further reactions.

Abstract: Disclosed is a method for preparing a bis(hydroxy-aromatic) compound which comprises the steps of: contacting at least one halo-substituted hydroxy-aromatic compound in a solvent mixture comprising water and at least one organic solvent in the presence of at least one base, at least one catalyst comprising palladium and hydrogen gas at a pressure in a range of between atmospheric pressure and 350 Kilopascals.

Abstract: A method is described for the simultaneous preparation of p-bromophenols and p-benzoquinones, intermediates useful in the preparation of hydroquinones and 4,4′-dihydroxybiphenyls, respectively. Hydroquinones and 4,4′-dihydroxybiphenyls are useful monomers for the preparation of a variety of polymers. The method also comprises reducing the p-benzoquinone to its corresponding hydroquinone in the presence of the p-bromophenol. Limiting the amount of HBr present in the reaction mixture was shown to control the amount of benzoquinone produced. The method also allows for the recycling of many of the reagents used, thereby reducing the cost of producing each monomer.

Abstract: A method is described for the simultaneous preparation of p-bromophenols and p-benzoquinones, intermediates useful in the preparation of hydroquinones and 4,4′-dihydroxybiphenyls, respectively. Hydroquinones and 4,4′-dihydroxybiphenyls are useful monomers for the preparation of a variety of polymers. The method also comprises reducing the p-benzoquinone to its corresponding hydroquinone in the presence of the p-bromophenol. Limiting the amount of HBr present in the reaction mixture was shown to control the amount of benzoquinone produced. The method also allows for the recycling of many of the reagents used, thereby reducing the cost of producing each monomer.

Abstract: A method for economically producing aromatic carbonates from aromatic hydroxy compounds is disclosed which in one embodiment comprises the steps of: (i) contacting at a temperature sufficient to keep the mixture molten at least one aromatic hydroxy compound with a catalyst composition comprising the following and any reaction products thereof: (A) at least one Group 8, 9, or 10 metal or a compound thereof; (B) at least one salt; (C) at least one metal co-catalyst; and (D) optionally, at least one activating solvent; (ii) optionally heating the mixture at atmospheric pressure to a temperature above that sufficient to keep the mixture molten; (iii) pressurizing the mixture with carbon monoxide; (iv) optionally heating the mixture under pressure of carbon monoxide to a temperature above that sufficient to keep the mixture molten; (v) optionally maintaining the mixture under pressure of carbon monoxide for a time period; (vi) introducing oxygen to the mixture to a desired concentration of oxygen in carbon monoxid

Abstract: Brominated hydroxyaromatic compounds such as p-bromophenol are prepared by contacting a hydroxyaromatic compound with oxygen and a bromine source such as hydrogen bromide or an alkali metal or alkaline earth metal bromide in an acidic medium, in the presence of elemental copper or a copper compound as catalyst. The brominated product of this reaction may be converted alternately to a dihydroxyaromatic compound such as hydroquinone by hydrolyses, or a dihydroxybiphenyl compound such as 4,4′-dihydroxybiphenyl by reductive coupling.

Abstract: A process for catalytic production of diaryl carbonates by oxidative carbonylation of aromatic hydroxy compounds with carbon monoxide and oxygen achieves water removal during reaction by a process comprising the steps of: removing a liquid stream from an oxidative carbonylation reaction mixture in a reaction vessel and transferring the stream to a disengagement vessel, transferring a stream from the disengagement vessel to a flash vessel and subjecting the liquid stream to reduced pressure, and returning at least a portion of dried liquid stream to the reaction vessel. Typical catalyst systems for oxidative carbonylation contain (A) at least one Group 8, 9, or 10 metal having an atomic number of at least 44 or a compound thereof; (B) at least one guanidinium salt or onium salt; (C) at least one metal co-catalyst; and (D) at least one base.

Abstract: A method is disclosed for recovering a substantially water-soluble solvent from a reaction mixture comprising at least about 35% by weight aromatic hydroxy compound, which comprises the steps of: (i) extracting a reaction mixture at least once with aqueous acid wherein the solvent remains substantially in the organic phase; and (ii) recovering solvent from the organic phase.

Abstract: A method is disclosed for recovering a substantially water-soluble solvent from a reaction mixture comprising at least about 35% by weight aromatic hydroxy compound, which comprises the steps of: (i) extracting a reaction mixture at least once with aqueous acid wherein the solvent remains substantially in the organic phase; and (ii) recovering solvent from the organic phase.

Abstract: A method for economically producing aromatic carbonates from aromatic hydroxy compounds is disclosed which in one embodiment comprises the steps of: (i) contacting at a temperature sufficient to keep the mixture molten at least one aromatic hydroxy compound with a catalyst composition comprising the following and any reaction products thereof: (A) at least one Group 8, 9, or 10 metal or a compound thereof; (B) at least one salt; (C) at least one metal co-catalyst; and (D) optionally, at least one activating solvent; (ii) optionally heating the mixture at atmospheric pressure to a temperature above that sufficient to keep the mixture molten; (iii) pressurizing the mixture with carbon monoxide; (iv) optionally heating the mixture under pressure of carbon monoxide to a temperature above that sufficient to keep the mixture molten; (v) optionally maintaining the mixture under pressure of carbon monoxide for a time period; (vi) introducing oxygen to the mixture to a desired concentration of oxygen in carbon monoxid

Abstract: A process for catalytic production of diaryl carbonates by oxidative carbonylation of aromatic hydroxy compounds with carbon monoxide and oxygen achieves water removal during reaction by a process comprising the steps of: removing a liquid stream from an oxidative carbonylation reaction mixture in a reaction vessel, subjecting the liquid stream to reduced pressure, and returning at least a portion of dried liquid stream to the reaction vessel. Typical catalyst systems for oxidative carbonylation contain (A) at least one Group 8, 9, or 10 metal having an atomic number of at least 44 or a compound thereof; (B) at least one alkali metal salt; (C) at least one metal co-catalyst; (D) at least one activating organic solvent; and (E) optionally, at least one base.