Organic catalysis over zeolites: A perspective on reaction paths within micropores

Surface curvature effects in physisorption and catalysis by microporous solids and molecular sieves

Anomalous crystallization mechanism in the synthesis of nanocrystalline ZSM-5

Publisher Summary The rapid development of zeolite catalysis in the synthesis of various types of organic compounds is reflected in the considerable body including many patents and patent applications. It discusses that the size of the molecules to be converted or synthesized seems limited by the pore dimensions of zeolites. However, a growing number of examples related to outer surface catalysis, or to selective scavenging of side products or impurities or to slow release of reagents explains that zeolites can be of much value also in the synthesis or conversion of large molecules or materials. Recently discovered super-large pore molecular sieves enlarge the spectrum of molecules having access to zeolites considerably. Another limiting factor is the relatively rapid decay of zeolite catalysts due to coke formation. Many examples exist- as shown in the foregoing of stabilizing zeolites by adding components or by adapting the reaction mixture, example by adding water or carbondioxide. Also, process conditions-fluidized bed with continuous regeneration is applied to overcome this trouble. The chapter also reviews that that a further exponential growth of the use of zeolites and related materials takes place. Zeolite catalysis and technology will be future cornerstones of a clean environmentally friendly organic chemicals industry.

Chapter 16 “Zeolites in Organic Syntheses”

A seed surface crystallization approach for rapid synthesis of submicron ZSM-5 zeolite with controllable crystal size and morphology

Shape-selective alkylation of naphthalene and methylnaphthalene with methanol over H-ZSM-5 zeolite catalysts

A method of selective beta-alkylation of aromatic substrates such as naphthalene or a derivative thereof, comprising reacting the substrate with an alcohol or olefin alkylating agent in the presence of a catalyst selected from the group consisting of a crystallized borosilicate glass zeolite and a crystalline alumina-silica catalyst, said catalyst being at least 86% beta selective with respect to the alkylation of naphthalene by the alkylating agent

Catalysts and process for the production of hydrocarbons and substitution of hydrocarbons

There are provided crystallized borosilicate glass zeolite catalysts which are para-selective in the alkylation of benzene and derivatives thereof and beta-selective in the alkylation of naphthalene and derivatives thereof There is provided a process for the production of such catalysts wherein a borosilicate type glass is reacted with a zeolite synthesis template There is also provided a selective alkylation process for the alkylation of benzene and its derivatives and of naphthalene and its derivatives wherein these are reacted with an alkylation agent in the presence of such catalyst

Para-selective and beta-selective crystallized glass zeolite alkylation catalyst

Gas-phase alkylation of naphthalene and 2-methylnaphthalene (2-MN) can be carried out efficiently over H-mordenite (HM), HY and H-ZSM-5. A high β-selectivity is observed with various kinds of H-ZSM-5 but not with HM and HY. At 350 °C, with naphthalene:methanol:mesitylene, 1:1:3 (wt) feed and space velocity, WHSV ~0.5 h−1, 15% naphthalene conversion is achievable with 76% selectivity to 2-MN and 2,6/2,7-dimethylnaphthalene (2,6/2,7-DMN). At 400 °C, 2-MN can be methylated using a 2-MN:methanol:mesitylene, 1:0.25:3.0 (wt) feed to give 60% 2,6/2,7-DMN at 19% conversion. This shape-selectivity is explained in terms of size differences between relevant molecules and zeolite pores. Nonselective alkylation of naphthalene and 2-MN on HM and HY is suggested to occur in the intracrystalline voids of these large-port zeolites, which easily accommodate both reactant and product molecules and allow their rapid diffusion. On the other hand, it is postulated that the β-selective alkylation over H-ZSM-5 occurs in external surface sites which perfectly suit small-size naphthalenics; these catalytic sites are too large, however, to allow any para-selectivity in the alkylation of toluene with methanol.

Margaret Rehovot Il Cherniavsky

Papers

Shape-selective alkylation of naphthalene and methylnaphthalene with methanol over H-ZSM-5 zeolite catalysts

Catalysts and process for the production of hydrocarbons and substitution of hydrocarbons

Para-selective and beta-selective crystallized glass zeolite alkylation catalyst

Shape-Selective Alkylation of Naphthalene and Methylnaphthalene with Methanol over H-ZSM-5 Zeolite Catalysts