P.B. Venuto

Bio: P.B. Venuto is an academic researcher from Princeton University. The author has an hindex of 1, co-authored 1 publications receiving 217 citations.

Organic Catalysis over Crystalline Aluminosilicates

Abstract: Publisher Summary This chapter focuses on organic catalysis over crystalline alumiosilicates. Zeolites are crystalline aluminosilicates composed of SiO4 and AlO4 tetrahedra arranged in various geometric patterns. The chapter discusses reactions over a wide variety of crystalline aluminosilicates and emphasizes on catalysis over X- and Y-type faujasites. Unusual opportunities for organic catalysis were found to exist when these were base exchanged to substantially eliminate their alkali metal content. It is shown that catalytic activity in ion-exchanged faujasites is influenced by cation type, cation location in the lattice, zeolite Si/Al ratio, and the presence of proton donors. The existence of several crystallographically distinct cation locations provides the basis for a potential heterogeneity of sites in catalytic reactions. The Linde workers made calculations for the electrostatic field strengths of surface cations near SII and SIII in an X-type zeolite of Si/Al ratio 1.0 and in a Y-type zeolite of Si/Al ratio 2.0. In both cases, the fields has been significantly larger near SIII than SII at a distance of 2 Ǻ from the center of the cation for the univalent cation-exchanged systems, provided both sites are occupied.

Thermolysis of waste plastics to liquid fuel: A suitable method for plastic waste management and manufacture of value added products—A world prospective

Abstract: The present rate of economic growth is unsustainable without saving of fossil energy like crude oil, natural gas or coal. Thus mankind has to rely on the alternate/renewable energy sources like biomass, hydropower, geothermal energy, wind energy, solar energy, nuclear energy, etc. On the other hand, suitable waste management strategy is another important aspect of sustainable development. The growth of welfare levels in modern society during the past decades has brought about a huge increase in the production of all kinds of commodities, which indirectly generate waste. Plastics have been one of the materials with the fastest growth because of their wide range of applications due to versatility and relatively low cost. Since the duration of life of plastic products is relatively small, there is a vast plastics waste stream that reaches each year to the final recipients creating a serious environmental problem. Again, because disposal of post consumer plastics is increasingly being constrained by legislation and escalating costs, there is considerable demand for alternatives to disposal or land filling. Advanced research in the field of green chemistry could yield biodegradable/green polymers but is too limited at this point of time to substitute the non-biodegradable plastics in different applications. Once standards are developed for degradable plastics they can be used to evaluate the specific formulations of materials which will find best application in this state as regards their performance and use characteristics. Among the alternatives available are source reduction, reuse, recycling, and recovery of the inherent energy value through waste-to-energy incineration and processed fuel applications. Production of liquid fuel would be a better alternative as the calorific value of the plastics is comparable to that of fuels, around 40 MJ/kg. Each of these options potentially reduces waste and conserves natural resources. Plastics recycling, continues to progress with a wide range of old and new technologies. Many research projects have been undertaken on chemical recycling of waste plastics to fuel and monomer. This is also reflected by a number of pilot, demonstration, and commercial plants processing various types of plastic wastes in Germany, Japan, USA, India, and elsewhere. Further investigations are required to enhance the generation of value added products (fuel) with low investments without affecting the environment. The paper reviews the available literature in this field of active research and identifies the gaps that need further attention.

Hydrocarbons from Methanol

Abstract: The conversion of methanol to hydrocarbons is a remarkable reaction. The mechanism involves C-C bond formation from C1 fragments generated in the presence of certain acidic catalysts and reagents. The precise nature of these reactive C1 species is unknown at present and is the subject of lively debate. The considerable diversity of current opinion will become apparent from the following account.

Industrial application of shape-selective catalysis

Abstract: In the 26 years since the term “shape-selective catalysis” was coined by P. B. Weisz and V. J. Frilette [1] to describe the unique catalytic properties of small pore molecular sieve zeolites, great strides in the use of shape-selective zeolites have been made, both scientifically and technologically. Since then, in addition to small pore zeolites, synthetic medium pore zeolites, such as ZSM-5 [2], ZSM-11 [3], ZSM-22 [4], ZSM-23 [5], ZSM-35 [6], ZSM-38 [7], ZSM-48 [8], etc., have been discovered. The availability of these synthetic medium pore zeolites has expanded the realm of “shape selectivity” beyond the original discovery of selective conversion of straight chain molecules to include certain branched molecules, single-ring aromatics, naphthenes, and nonhydrocarbons with a critical molecular dimension smaller than about 6 A.

Supramolecular Host‐Guest Systems in Zeolites Prepared by Ship‐in‐a‐Bottle Synthesis

Abstract: Zeolites have a microporous system defining large cavities interconnected by smaller windows. These cages can accommodate large molecules whose size, however, can be too big to cross the windows. The most important examples of these tridirectional zeolites are faujasites X and Y, but examples of other suitable zeolites are Beta, EMT and MCM-22. The inclusion of large guests inside the cavities starts from smaller precursors that can diffuse through the zeolite pores and then react inside the cavities to form the target guest. This microreview discusses the special characterisation techniques necessary to study these systems, differentiating those that serve to assess the identity and purity of the guests from those that address the internal vs. external location of the guests with respect to the zeolite host. It is organized by grouping the examples of ship-in-a-bottle synthesis according to the potential application of the system as catalysts, photocatalysts, sensors, in molecular machines, etc. Although proper credit is given to the pioneering reports on ship-in-a-bottle synthesis, the emphasis is placed on the most recent examples of the literature covering up to mid 2003. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)