Showing papers by "Rolf Fricke published in 1992"

Physicochemical and catalytic properties of a silica-enriched zeolite ZSM-20

Abstract: Zeolite ZSM-20 with and enhanced Si : Al ratio after activation has been obtained by a modification of the usual synthesis route. Despite the increased silica content the crystallinity is high and the crystal structure is nearly identical to that of the ZSM-20 zeolites reported so far. The synthesis was found to be extremely sensitive to the conditions of gel preparation, especially to pH adjustment, the temperature–time regime for hydrolysis of the organic silica source, the evaporation of the released ethanol and the formation of the silica precursors. The well crystallized synthesis product was characterized by X-ray powder diffraction, infrared spectroscopy, thermal analysis, n-hexane adsorption and temperature-programmed desorption of ammonia. The acidity of this ZSM-20 zeolite is high compared with conventional preparations of ZSM-20 zeolites or with the structurally related zeolite Y.The catalytic properties in the isomerization of m-xylene and the conversion of ethylbenzene have been studied. The isomerization of m-xylene is characterized by a high percentage of disproportionation (toluene formation) due to the high acidity. The distribution of the trimethylbenzene isomers corresponds to the thermodynamic equilibrium. Shape selectivity is obviously not operative owing to the open pore structure. Ethylbenzene is mainly dealkylated to benzene where the new ZSM-20 zeolite is capable of breaking the ethyl side chain to yield toluene.

Process for the skeleton isomerisation of n-alkenes

Abstract: The invention relates to the skeleton isomerisation of n-alkenes into isoalkenes or the enrichment of isoalkenes to form alkene-containing hydrocarbon mixtures. The object of the invention was to develop a process using halogen-free catalysts with a cycle time in a running period of more than 100 hours. This object was attained in that the isomerisation catalysts used are microporous alumophosphates with a molecular sieve structure, the pores of which have a diameter of 0.4 to 0.6 nm and which are mixed with a binder and activated at temperatures of 623 to 873 K.

Process for skeletal isomerization of n-alkenes

Abstract: Skeletal isomerization of n-alkenes into isoalkenes and enrichment of isoalkenes in alkene-containing hydrocarbon mixtures is effected in the presence of an isomerization catalyst containing a microporous silicon-containing alumophosphate. A goal of the method for skeletal isomerization is to provide a running time in one operating period of over 100 hours. This goal is achieved by using, as isomerization catalysts, microporous alumophosphates with a molecular sieve structure whose pore inlet openings have a diameter of 0.4 to 0.6 nm which are mixed with a binder and activated at temperatures of 623 to 873K.

The Templating Role of Cyclohexylamine in the Synthesis of Microporous Aluminophosphates

Abstract: The investigation of the synthesis of AlPO 4 molecular sieves from orthophosphoric acid and pseudoboehmite in the presence of cyclohexylamine shows that in this case the amine plays the role of template in the sense of "Template theory". The geometric shape of the template determines the dimensions of the channels within the AlPO 4 -lattices. The amount of template in the gel influences the void volumes, leading to different structures, however, with similar dimensions. The product composition is largely determined by the ratio amine/(Al,P)O 2 . The molecular sieves have been characterized by IR, X-ray, TG and DTA measurements.

Physicochemical and Catalytic Properties of a Silica-Enriched Zeolite ZSM-20

Abstract: Zeolite ZSM-20 with and enhanced Si : Al ratio after activation has been obtained by a modification of the usual synthesis route. Despite the increased silica content the crystallinity is high and the crystal structure is nearly identical to that of the ZSM-20 zeolites reported so far. The synthesis was found to be extremely sensitive to the conditions of gel preparation, especially to pH adjustment, the temperature–time regime for hydrolysis of the organic silica source, the evaporation of the released ethanol and the formation of the silica precursors. The well crystallized synthesis product was characterized by X-ray powder diffraction, infrared spectroscopy, thermal analysis, n-hexane adsorption and temperature-programmed desorption of ammonia. The acidity of this ZSM-20 zeolite is high compared with conventional preparations of ZSM-20 zeolites or with the structurally related zeolite Y.The catalytic properties in the isomerization of m-xylene and the conversion of ethylbenzene have been studied. The isomerization of m-xylene is characterized by a high percentage of disproportionation (toluene formation) due to the high acidity. The distribution of the trimethylbenzene isomers corresponds to the thermodynamic equilibrium. Shape selectivity is obviously not operative owing to the open pore structure. Ethylbenzene is mainly dealkylated to benzene where the new ZSM-20 zeolite is capable of breaking the ethyl side chain to yield toluene.