William Franklin Burgoyne

High performance polymers for membrane separation

Abstract Polymers have been recognized to exhibit selective permeation rates to gases for more than a century. The commercial reality of this characteristic, however, occurred in the late 1970s. There has been significant commercial activity in this area which has also brought about a rapid increase in the study of polymeric structural variations to optimize the combination of gas separation and permeability (permselectivity). It has been recently noted that upper bound limits exist for the separation of common gas pairs. These limitations will be discussed along with the structural features necessary to achieve the best combination of high permeability combined with high selectivity. One of the speciality polymers receiving significant attention in the past decade is poly(trimethylsilylpropyne) (PTMSP) primarily due to a permeability to common gases an order of magnitude higher than silicone rubber. Structural variations, solvent variations, non-solvent swelling effects and flux decline of PTMSP are discussed. Flux decline, which has been reported in detail in the literature, is believed to be due to two factors. Contamination can significantly decrease permeability which comprises the reason behind many literature citations. Another factor involves a slow collapse of the structure (as cast) which can depend on the casting solvent. Non-solvent swelling promotes an instantaneous increase in permeability which slowly decays back to original values. High glass transition temperature engineering polymers (e.g. polyimides, polyarylates, polycarbonates) yield permselectivity characteristics of interest for gas separation. Structural features and variations of these polymers to achieve high permeability combined with selectivity (e.g. upper bound properties) will be discussed. Surface modification techniques comprise another route to achieve high selectivity for permeable polymers. These methods (e.g. fluorination, plasma modification, u.v. exposure) offer an additional route towards meeting the requirements for separation of gases with polymeric membranes.

Synthesis of N-tert.-butyl aromatic amines via heterogeneous acid catalysis

Abstract Heterogeneous acid catalysts have been employed in the synthesis of N -tert.-butyl aromatic amines from isobutene and arylamines. This technique provides a highly selective route to N -tert.-butylanilines, compounds not readily available by conventional alkylating methods. The selectivity of N -alkylation is highest when heterogeneous acid catalysts of moderate Bronsted acidity are used at temperatures of 100–180°C. The selectivity between N and ring alkylation is also highly dependent upon the type and location of substituents on the aromatic ring.

ortho-selective Alkene alkylation of Arylamines via acid catalysis

Abstract Acid catalysis provides a general synthesis methodology for introducing alkene alkylating agents selectively to the ortho positions of arylamines. In contrast to aluminum alkyl catalyzed olefin ortho-alkylation of arylamines, this reaction proceeds through a positively charged intermediate and is especially useful for placing branched alkyl groups ortho to amino functionality. Lewis and Bronsted acids both provide high ortho-selectivity with solid acids providing the highest selectivity and ease of use. Reaction rates increase with increasing acid strength. The ortho-selectivity of this technique is enhanced by operating at temperatures and residence times which minimize Nalkylates and para-alkylates. Reaction selectivity is also influenced by substituents on the arylamine and alkene reactants.

Synthesis of ortho-alkyl arylamines from N-alkyl arylamines via acid catalysis

Abstract N -isopropylaniline is converted to ortho -isopropylaniline in high selectivity by passing the N -alkylate over a heterogeneous acid catalyst under a positive pressure of propylene. Useful solid catalysts include H-Y zeolite, silica/aluminas and γ-alumina. The selectivity of this procedure contrasts with the para -selectivity of the classical Hofmann-Martius reaction.

Nitriles from olefins and ammonia via one-carbon homologation

Abstract The reaction of simple olefins and ammonia was studied over various heterogeneous transition metal catalysts. Group eight transition metals of Fe, Co and Ni provide nitriles one carbon extended from the starting olefins. The reaction of ethylene/ammonia and propylene/ammonia over a nickel catalyst was studied to develop an understanding of mechanism and of synthetic utility. Experimental data provides evidence for a nitrile-forming reaction mechanism involving an apparent one-carbon homologation via formation of a cyanide synthon. Accompanying this reaction is the reduction of olefin by generated hydrogen. Experimental evidence indicates that the nitrile-forming process does not require the simultaneous reduction of olefin.