A.E.W. Beers

Preparation of monolithic catalysts

Monolithic catalysts can be attractive replacements for conventional catalysts in randomly packed beds or slurry reactors. The conventional procedures for preparing catalysts, however, cannot simply be applied to monolithic catalysts. Different procedures are discussed on how to put a coat layer of a catalyst support material like alumina, silica, or carbon on a monolith body by either filling the pores in that support or by putting a layer on that support. Different methods to apply an active phase to the support are discussed as well. Finally, methods to convert ready-made catalysts into monolithic catalysts are presented.

Optimization of zeolite Beta by steaming and acid leaching for the acylation of anisole with octanoic acid: a structure–activity relation

Abstract This paper presents a catalytic and spectroscopic study of the dealumination of a commercial zeolite, Beta (Zeolyst). After dealumination by hydrochloric or oxalic acid and steaming (up to 973 K), increased activity and selectivity were found in the acylation of anisole with octanoic acid. The treatments led to the extraction of aluminum from the crystallographic T-sites in the framework structure, giving amorphous extraframework aluminum(–silicon)–oxide species in the case of steaming, while treatment with mineral acids or complexing agents removed framework and extraframework aluminum from the zeolite. 27 Al MQ MAS NMR revealed a changing of the aluminum coordinations and a shift from framework to extraframework species after steaming. Steaming removes aluminum from other crystallographic T-sites than acid leaching. Using nitrogen physisorption, no differences in the texture properties could be observed and XRD showed that the crystallinity was preserved, indicating high stability of the commercial zeolite Beta. The nature of the enhanced activity is suggested to result from higher accessibility of the active sites that are proposed to be associated with framework-connected aluminum atoms.

BEA coating of structured supports—performance in acylation

Abstract The development of a dip-coating method is described for the preparation of an active catalytic coating on a structured packing for the acylation of aromatics. The preparation was optimized by investigating various parameters in the dip-coating of both monolithic and wire gauze packings, such as the amount of zeolite, the amount of binder, the presence of a surfactant, the cell density of the monolith, and the packing material. BEA coatings strongly bound on ceramic monoliths and metallic wire gauze packings were prepared by dipping the structured packings in a BEA-containing, water-based slurry. The activity and selectivity of the slurry catalyst in the acylation of anisole with octanoic acid were well preserved by the coating procedure, while the structures can also easily be regenerated by calcination in air.

Zeolite coated structures for the acylation of aromatics

Abstract Zeolites H-BEA, H-FAU and Nafion/silica composites show high activity in the acylation of anisole with octanoic acid. A study of activity, surface area characteristics and acidity of zeolite H-BEA shows that mesoporosity and the Si/Al ratio are very important features for activity. Coating a monolithic carrier by a convenient coating procedure with BEA results in an active and selective integrated catalyst-reactor configuration for the acylation of aromatics. Due to the binding capacity of the silica binder a mechanically stable coating layer was obtained.

Water removal by reactive stripping for a solid-acid catalyzed esterification in a monolithic reactor

Solid-acid catalysts are attractive replacements for processes using conventional homogeneous catalysts. In the esterification of an alcohol with a carboxylic acid, however, the side product water strongly inhibits the activity of a solid-acid catalyst. Since an esterification is an equilibrium limited reaction, full conversion is not possible unless one of the products is removed. A novel reactor type, utilizing a solid-acid catalyst coated monolith, is presented in which water can be removed from the liquid reaction mixture by means of reactive stripping. In this manner the inhibition is eliminated and complete conversion can be reached. The advantages of this reactor concept are demonstrated by both experiments and reactor modeling.

Esterification in a structured catalytic reactor with counter-current water removal

Abstract In this research the liquid phase esterification of hexanoic acid and 1-octanol was studied. Very high activities were obtained for zeolite BEA and Nafion/silica composite with 13% of Nafion. The advantage of water removal in this system was demonstrated. In a closed system an equilibrium conversion of 35% was reached, while in a system with water removal all the reactants were converted in a shorter period. The initial reaction rate decreases when increasing the initial water concentration, following a Langmuir–Hinshelwood type of rate expression. An active zeolite coated structured monolithic reactor configuration was prepared. Enhancement by the counter-current water stripping of the performance of the structured catalysts was demonstrated.

Structured catalysts for the acylation of aromatics

In the acylation of anisole with octanoic acid, Nafion/silica composites were the most active slurry catalysts, compared to zeolite catalysts. Monolithic structures were coated successfully with Nafion. Tested in the acylation, these structured catalysts exhibited similar high activities, eliminating the disadvantages (attrition, filtration, regeneration) of a slurry system operation.