Type Zeolite Catalysts Research Articles

Conversion of synthesis gas to light olefins utilizing ZSM-5 type zeolite catalysts modified with alkaline earth metals.

Etude experimentale de la conversion directe du gaz de synthese en olefines legeres dans un systeme bietage constitue par un reacteur de synthese de methanol suivi d'un reacteur de formation d'hydrocarbures contenant des zeolites de type ZSM-5 modifiees par des metaux alcalinoterreux. Demonstration de l'augmentation de la selectivite vis-a-vis des olefines legeres des zeolites modifiees

Alkylation of benzene with polyethylene on silicaalumina.

Alkylation of benzene with polyethylene on silica•alumina was carried out by an autoclave. The yield and the composition of the products wcrc examined at 370-460°C. Above 400°C, the yield of liquid increased rapidly and at 430°C, the products were liquids (123wt%), solids (12wt%) and gases (6wt%), respectively. Alkylbenzenes in the liquid product, were mainly cumene (20wt%), ethylbenzene (11wt%), butylbenzenes (14wt%) and toluene (10wt%). The gaseous product was almost all paraflins, which mainly contained isobutane and isopentane. By increasing the relative amount of catalyst to polyethylene, the yield of liquids attained the maximum point (150wt%) and the yield of solids increased because of the formation of coke. Using HY type zeolite catalyst or polyvinyl chloride instead of polyethylene as the alkylating agent, alkylbenzenes in the liquid product were in the following declining order; toluene, ethylbenzene, cumene and butylbenzenes.

Olefin Hydrogenation over ZSM-5 Type Zeolite Catalysts Modified with Alkaline Earth Metals

Abstract Olefin hydrogenation was carried out over ZSM-5 type zeolite catalysts modified with various alkaline earth metals. It was found that the catalytic activity of H–ZSM-5 for the olefin hydrogenation decreases upon such a modification.

Selective formation of 1,2,4,5-tetramethylbenzene by the alkylation of 1,2,4-trimethylbenzene with methanol on HZSM-5 type zeolite catalysts.

The alkylation of 1, 2, 4-trimethylbenzene (1, 2, 4-TrMB) with methanol on HZSM-5 type zeolites with various aluminium concentrations was studied in a fixed bed type apparatus with a continuous flow system at atmospheric pressure. It was found that 1, 2, 4, 5-tetramethylbenzene (1, 2, 4, 5-TeMB), which was the smallest isomer in TeMB, could be produced at a very high selectivity by application of the shape selectivity of HZSM-5 zeolites. HY and H-mordenite, which had larger pore window size than HZSM-5, showed higher catalytic activity for this alkylation than HZSM-5. On HY and H-mordenite, however, the fraction of 1, 2, 4, 5-isomer in TeMB produced was lower than that on HZSM-5. With the increase of aluminium concentration in HZSM-5, the yield of TeMB increased, while the fraction of 1, 2, 4, 5-isomer in the produced TeMB decreased. From these results it is concluded that 1, 2, 4, 5-TeMB is mainly formed in the pores of HZSM-5 in which the rate of reaction may be controlled by the diffusion of reactants and products. The other isomers of TeMB, TrMB except 1, 2, 4-isomer and pentamethylbenzene are formed on the outer surface of HZSM-5 crystallites.

Selective alkylation of 1,2,4-trimethylbenzene with methanol on modified HZSM-5 type zeolite catalysts.

The selective alkylation of 1, 2, 4-trimethylbenzene with methanol on a modified HZSM-5 catalyst to produce 1, 2, 4, 5-tetramethylbenzene was studied. When the active sites on the exterior surface of ZSM-5 zeolite crystallite were selectively poisoned or removed by treatment with 2, 4-dimethylquinoline or by dealumination with silicone tetrachloride, the formation of products with large molecular sizes could be substantially depressed, and the fraction of 1, 2, 4, 5-isomer in the tetramethylbenzenes produced could be increased to more than 98%. However, the yield of 1, 2, 4, 5-tetramethylbenzene at the steady state of catalyst activity was decreased and the formation of xylenes could not be depressed by such modifications.

The effect of chemical reaction on effective deffusivity within biporous catalysts—II: Experimental study

An experimental method was developed to study the adsorption and diffusion of the reactant, and the product, reacting on porous catalysts by simultaneo To study the effect of reaction on the effective diffusivity, supporting experiments were performed to obtain precise adsorption and diffusion characte Three types of zeolite catalysts, LiY, NaY, both active and KY, inactive, were prepared and were used to catalyze the isomerization reaction of cyclopr Equilibrium adsorption constants and diffusivities measured under nonreactive conditions were comparable to values found in literature. For inactive ca Therefore the use of effective diffusivity value obtained in nonreactive condition to estimate effectiveness factor may give significantly erroneous re

Reaction rate oscillations during Fischer‐Tropsch synthesis on Fe‐precipitated Nu‐1 zeolite‐type catalysts

Reaction rate oscillations are summarized for Fischer-Tropsch synthesis reaction over 13% Fe-precipitated zeolite type catalysts at medium pressures (2.2 x 10/sup 3/ Kpa) in a multipellet Berty CSTR reactor. Discovery of medium pore zeolites, ZSM-5 by Mobil workers and Nu-1 type zeolite by ICI workers, has provided new routes in the indirect liquefaction of coal and its conversion to chemicals. Zeolites, as catalysts, have the very important property of solid acidity. Further investigation is needed of the dynamic behavior of Fischer-Tropsch synthesis reactions over both zeolite-supported and usual Fischer-Tropsch catalysts. The existence of the oscillatory behavior, particularly if it proved to be the result of intrinsic catalytic surface processes, can have far reaching consequences on both the industrial utilization of this reaction and the understanding of the reaction mechanism.

Selective synthesis of lower olefins by catalytic conversion of methanol

C2∼C4 olefins were synthesized from methanol on modified ZSM-34 type zeolite catalyst at 400°C. Methanol vapor of 12 vol.% was converted completely under flow conditions at 800 h−1 space velocity, and in molar selectivity 42.9% C2H4, 33.4% C3H6, and 3.3% C4H8 were produced.

Industrielle Anwendung von zeolithischen Katalysatoren beim Hydrocracken

AbstractIndustrial application of zeolitic catalysts in hydrocracking. For maximum production of gasoline by hydrocracking using zeolite type catalysts two cracking schemes are presented and the operation conditions, feedstocks, yields, and material balances are discussed. The advantages of zeolitic hydrocracking catalysts are outlined. The main catalyst parameters controlling activity and selectivity are described and a scheme for the preparation of zeolitic catalysts is given, which illustrates the superiority of zeolitic hydrocracking catalysts over amorphous ones. Finally, the hydrocracking of residues is reviewed and a typical process together with the product characteristics and yields obtained is described.

The comparison of cracking activity, product selectivity, and steam stability of ZSM-5 to other cracking catalysts

A modified “α-test” method was adopted to examine the new type zeolite ZSM-5 which was synthesized in our laboratory. The results show that HZSM-5 has superb activity on n-hexane cracking, lower aging rate, and better steam stability than other zeolite-type catalysts. HZSM-5 has good selectivities of C 3 and C 4 paraffin at low temperatures and ethylene and aromatics at high temperatures.

On identifying the primary and secondary products of the catalytic cracking of cumene

A thorough and fundamental study of the cumene cracking reaction has been carried out using a tubular packed bed reactor and a highly active lanthanum exchanged Y type zeolite catalyst. Over 60 reaction products have been observed and the selectivity behavior of the major ones has been examined using the concept of “optimum performance envelopes” in order to identify which products are primary and which are secondary. In this way benzene, ethyl benzene, n-propyl benzene, cymene, m- and p-diisopropyl benzene as well as propylene, i-butene and butene have been found to be primary products of the cumene reaction; whereas methane, ethylene, ethane, toluene, ethyl toluene, diethyl benzene and i- and n-butane are identified as the major secondary products. Based on these observations, a reaction network for the cumene cracking reaction is constructed. Chemical mechanisms by which the primary products arise are postulated on the basis of various considerations presented here and elsewhere in the literature. Of particular interest here is the competing influence of Brönsted and Lewis acids and the observation that at 360 °C cumene dealkylation accounts for only 64% of the total cumene converted under initial conditions.