Juan M. Garces

Polymeric Nanocomposites for Automotive Applications

New nanocomposites are currently being developed that have real industrial potential—loading a polymer with a small (ca. 5 %) amount of inorganic nanoparticles (the Figure shows a polypropylene–clay hybrid composite) is expected to give rise to significant improvement to the materials properties with only a minor increase in cost. Recent developments in this area are summarized here.

Polyethylene-layered silicate nanocomposites prepared by the polymerization-filling technique: synthesis and mechanical properties

Polyethylene-layered silicate nanocomposites were prepared by the in situ intercalative polymerization of ethylene by the so-called polymerization-filling technique and analyzed by transmission electron microscopy (TEM), X-ray diffraction analysis (XRD), differential scanning calorimetry, dynamic mechanical analysis and tensile testing. Non-modified montmorillonite and hectorite were first treated by trimethylaluminum-depleted methylaluminoxane before being contacted by a Ti-based constrained geometry catalyst. The nanocomposite was formed by addition and polymerization of ethylene. In the absence of a chain transfer agent, ultra high molecular weight polyethylene was produced. The tensile properties of these nanocomposites were poor and essentially independent of the nature and content of the silicate. Upon hydrogen addition, the molecular weight of the polyethylene was decreased with parallel improvement of the tensile and shear moduli, in relation to the filler content. The exfoliation of the layered silicates was confirmed by XRD analysis and TEM observation. The mechanical kneading of the molten nanocomposites resulted in the partial collapse of the exfoliated structure driven by the thermodynamic stability of the layered filler.

VPI-5: The first molecular sieve with pores larger than 10 Ångstroms

The adsorption properties of a novel family of aluminophosphate based molecular sieves denoted as VPI-5 are described. These molecular sieves are the first to contain pores larger than 10 A. The large pores of the VPI-5 sieves consist of channels circumscribed by eighteen membered rings and possess free diameters of approximately 12–13 A. The VPI-sieves are capable of adsorbing molecules excluded from other molecular sieves.

Shape selective alkylation of polynuclear aromatics with mordenite-type catalysts: A high yield synthesis of 4,4′-Diisopropylbiphenyl

Unique dealuminated mordenite zeolites with a high proportion of mesopores behave as shape selective catalysts in the liquid phase alkylation of biphenyl with propylene. Dealumination reduces deactivation and the mesopores enhance diffusion. High yields of 4,4′-diisopropylbiphenyl (> 70%) are observed.

Hypothetical structures of magadiite and sodium octosilicate and structural relationships between the layered alkali metal silicates and the mordenite- and pentasil-group zeolites

Hypothetical model structures for magadiite and sodium octosilicate, based on the structure of the zeolite dachiardite, are proposed that consist of layers of 6-member rings of tetrahedra and blocks containing 5-member rings attached to both sides of the layers. The infrared (IR) and nuclear magnetic resonance spectra of magadiite and sodium octosilicate have features in common with spectra of zeolites in the ZSM-5 and mordenite groups. A peak at 1225 cm-1 in the IR spectra of magadiite and sodium octosilicate is characteristic of zeolites containing 5-member rings, such as ZSM-5- and mordenite-type zeolites. The defect structures of pentasil zeolites may therefore be akin to layered alkali metal silicates containing zeolite-like domains, in which part of the silanol groups from adjacent silicate layers are condensed (cross-linked) forming siloxane linkages.

In situ infrared study of alkylation of toluene with methanol on alkali cation-exchanged zeolites

Abstract The CsX, RbX, and KX zeolites, which selectively alkylate the side chain of toluene with methanol, show formation of both unidentate and bidentate formates on the suface during the reaction. The LiX and NaX, which selectively alkylate the benzene ring, show no formate formation. Bidentate formate can be generated from either the CO reaction with surface OH − ion or hydrogen reduction of surface CO 2− 3 carbonate. But the formation of bidentate formate does not correlate with side-chain alkylation. Unidentate formate, which can be formed from the reaction of methanol or formaldehyde, may be an intermediate for side-chain alkylation. The use of carbon dioxide in the feed can stimulate momentarily the alkylation reaction but it also increases coke formation and deactivation.

Synthesis of Aluminophosphate and Element Substituted Aluminophosphate VPI-5

Abstract The synthetic procedures used to crystallize aluminophosphate and element substituted aluminophosphate VPI-5 are described. The crystallization process for aluminophosphate VPI-5 is consistent with the fact that organic species do not act as templates or space-fillers and that aqueous phase ion transport is most likely not involved. Cobalt substitution into aluminophosphate VPI-5 is similar to the substitution observed for cobalt in CoAPO-5. Mono and bi-liquid phase reaction mixtures are capable of crystallizing silicon containing VPI-5. Silicon appears to substitute for both phosphorus and aluminophosphate pairs.

Solid base catalysts for side-chain alkylation of toluene with methanol

Abstract A wide variety of solid bases, including alkali-exchanged zeolites X, Y, L and β, and alkali-impregnated carbon and magnesia, were tested as catalysts for the side-chain alkylation of toluene with methanol to form styrene and ethylbenzene. In addition, the effects of adding Group IIIA elements (B, Al, Ga, In) to the catalysts were examined. At 680 K and atmospheric pressure, the major reaction products were styrene, ethylbenzene, and carbon monoxide. Cesium-exchanged zeolite X was the most effective alkali-containing catalyst for the alkylation reaction. Of the Group IIIA additives that were tested, only boron promoted the alkylation reaction. The primary effect of adding boron was to reduce the decomposition of methanol to carbon monoxide. Apparently, boron selectively modifies the sites associated with methanol decomposition without inhibiting the sites active for alkylation. A borated Cs—carbon sample also catalyzed the alkylation reaction, demonstrating that a zeolite framework is not necessary to form the active site. Microporosity seems to play an important role in these catalysts since both the alkali-modified carbons and the zeolites are microporous.

Basic Molecular Sieve Catalysts//Side-Chain Alkylation Of Toluene By Methanol

Publisher Summary The use of zeolites as acidic catalysts has received widespread attention because their introduction in important industrial processes. The base catalyzed alkylation of alkylaromatics with olefins results in selective addition of the olefin to the side chain. Similarly, basic catalysts lead to the side chain alkylation of toluene with methanol. This reaction takes place over alkali metal exchanged zeolites, basic oxides, and basic salts either pure or supported on carbon. In zeolite X, the larger alkali metal cations lead to more active catalysts, and boron and phosphorous additives provide more active and selective catalysts for the direct synthesis of styrene. Lithium exchanged zeolites produce only xylenes, typical of acidic catalysts. Infrared (IR) studies of various cation forms of zeolite X used in methanol decomposition showed formation of methoxide, formate, and carbonate species on catalysts treated with methanol at 673°K. This chapter presents chemical observations, equilibrium thermodynamic data, and mass spectroscopy to support an equilibrium model which involves metal oxides, metal carbonates, zero valent metals, and CO 2 .

Synthetic Inorganic Materials

Inorganic materials have played a key role in the historicalevolution of Dow, from a small-town start-up company in theearly 1900s, to a major chemical company by the 1940s, to a glo-bal corporation today. Dow’s roots are grounded on the firstuse of electrochemical technology in the USA to make bro-mine, chlorine, iodine, caustic, and bleach.