H-beta

The cinnamyl ester can be prepared from an activated carboxylic acid derivative and cinnamyl alcohol or by transesterification with cinnamyl alcohol in the presence of the H-Beta Zeolite (toluene, reflux, 8 h, 59-96% yield). It is cleaved under nearly neutral conditions [Hg(OAc)2, MeOH, 23°, 2-A h KSCN, H2O, 23°, 12-16 h, 90% yield]or by treatment with Sulfated-Sn02, toluene, anisole, reflux. The latter conditions also cleave crotyl and prenyl esters. 

The product distribution in the reaction of benzene with dodecene was determined for a number of catalysts (Table 5.1-4). As can be seen, the reaction with the zeolite H-Beta gave predominantly the 2-phenyldodecane, whereas the reaction in the pure ionic liquid gave a mixture of isomers, with selectivity similar to that of aluminium chloride. The two supported ionic liquid reactions (H-Beta / IL and T 350 / IL) again gave product distributions similar to aluminium(III) chloride (T350 is a silica support made by Degussa). 

Upon passing bromobenzene and hydrogen over zeolite Pt-H-beta dehydrobromination followed by hydrogenation and isomerization takes place. In this way undesired aromatic bromides can be recycled. 

Finally we mention that aromatic bromides can be debrominated by hydrogen and a metal(o)-in-zeoite system (ref. 33). Over e.g. Cu(0)-Y bromobenzene is converted into benzene whereas over Pt-H-beta (200 °C) quantitative hydrodebromination is followed by hydrogenation and isomerization towards methylcyclopentane (Fig. 12). In this way undesired aromatic bromides can be recycled. 

H-beta, catalytic regenerable No solvent No water necessary... 

The concept of extractive reaction, which was conceived over 40 years ago, has connections with acid hydrolysis of pentosans in an aqueous medium to give furfural, which readily polymerizes in the presence of an acid. The use of a water-immiscible solvent, such as tetralin allows the labile furfural to be extracted and thus prevents polymerization, increases the yield, and improves the recovery procedures. In the recent past an interesting and useful method has been suggested by Rivalier et al. (1995) for acid-catalysed dehydration of hexoses to 5-hydroxy methyl furfural. Here, a new solid-liquid-liquid extractor reactor has been suggested with zeolites in protonic form like H-Y-faujasite, H-mordenite, H-beta, and H-ZSM-5, in suspension in the aqueous phase and with simultaneous extraction of the intermediate product with a solvent, like methyl Aobutyl ketone, circulating countercurrently. 

Smith et al. (1998) have reported selective para acetylation of anisole, phenetole, and diphenyl ether with carboxylic anhydrides at 100 °C, in the presence of catalytic quantities of zeolites H-beta. The zeolite can be recovered and recycled to give essentially the same yield as that given by fresh zeolite. 

B) Various zeolites, namely H-beta, NaA and Faujasite are depicted to scale with the 0.44 nm diameterxenon atoms. Awide range of xenon chemical shifts are observed in these materials. 

Three potential routes from 14 to 2, shown in Scheme 2.6, were identified and evaluated. Option A was the original plan of preparation. Hydroboration of the carbon-carbon double bond in 14 followed by oxidation provided primary alcohol 19 (P=H). Beta-ketoester 19 was converted to the corresponding diazo compound... 

The NH4-Y (CBV712, ao = 24.35 A), H-Beta (CP811E-75), NH4-Beta (CP814E) zeolites were obtained from Zeolyst International. The NH4-Y and Beta zeolites were transformed to proton forms through step calcination procedure in a muffle oven. Zeolites containing 1 wt-% platinum were prepared by wet-impregnation method using hexachloroplatinic acid as the Pt-source. 

Figure 3 Comparison of decal in conversion over proton-form zeolites (filled) and Pt-zeolites (open). H-Beta-25 ( , ), H-Beta-75 (, O), H-Y-l 2 (A, A).

Figure 4 Product distribution over A) H-Beta-25 and B) PL/H-Beta-25. Product groups Tians-deeulin ( ), ori-decaliti ( ), Iso (A), ROP ( ), CP ( ), mid HP ( ).

The changes in the product concentrations are more pronounced in case of Pt-zeolites. Particularly the rate of decalin isomerization is considerably enhanced by the addition of platinum. The ratio of Iso/ROP decreases from the value of 12 after 1 h to the value of 1.4 after 9 h. The ratio of ROP/CP decreases from the values close to 3 within the first 3 h to the value of 1.3 after 9 h. This is in contrast to H-Beta-25, where the ratio ROP/CP is almost constant during the entire experiment and its values do not exceed 1.5. The same trends are... 

Furthermore, while no significant difference in the product distribution, with the exception of the trans-decalin/cis-decalin ratio, is observed for the tested proton-form zeolites, dissimilarity between Pt/H-Y on one hand and both Pt/H-Beta zeolites on the other hand is found (Figure 6). More ROP and CP, accompanied by less Iso, are formed on Pt/H-Y than on Pt/H-Beta zeolites. This implies that the consecutive ring opening and cracking are faster over Y-zeolite than over Beta-zeolites resulting in lower concentration of isomers and higher concentrations of ROP and CP. 

The activity of H-Beta-25, H-Beta-75, H-Y-12, and of their Pt-impregnated counterparts has been investigated in ring opening of decalin at 523 K in the presence of hydrogen. The main results can be summarized as follows ... 

The wide-pore H-Beta zeolite has strong Bronstcd acid hydroxyl groups and other advantage chemical environment which govern the adsorption and consecutive conversion of methanol to dimethyl ether and further to hydrocarbons, mostly isobutane. This character can be modified by Fe ion-exchange. 

In this work the methanol and methyl iodide conversion and their co-reaction are investigated on Fe-Beta zeolite without any oxygen. Partly Fe-ion-exchanged Beta-300 i.e. Fe-H-Beta-300 (shortly Fe-Beta-300) zeolite keeps the light acidity to a certain extent, however the presence of Fe ions (as transition metal, Fe is an excellent Lewis acid) can modify the reaction pathway. This Fe-Beta-300 has been tested already by low temperature peat pyrolysis [6], At present, the adsorption as well as desorption of methanol are followed-up by radiodetectors using ( -radioisotopic labeling [4, 7]. The... 

The NH4-Beta-300 (Zeolyst International, number denote Si02/Al203 molar ratio) was transformed to corresponding proton form using a step calcination procedure at 500 °C. H-Beta-300 was partially modified with Fe by repeated ion-exchange method (Fe(III)nitrate). The surface areas as well as acidities (Bronsted and Lewis acid sites) of Fe-Beta (iron content - 0.1 wt %) were determined by nitrogen adsorption and pyridine desorption at 250, 350 and 450 °C using FTIR spectroscopy [6]. 

The liquid-phase dehydration of 1-hexanol and 1-pentanol to di-n-hexyl ether (DNHE) and di-n-pentyl ether (DNPE), respectively, has been studied over H-ZSM-5, H-Beta, H-Y, and other zeolites at 160-200°C and 2.1 MPa. Among zeolites with a similar acid sites concentration, large pore H-Beta and H-Y show higher activity and selectivity to ethers than those with medium pores, although activity of H-ZSM-5 (particularly in 1-pentanol) is also noticeable. Increased Si/Al ratio in H-Y zeolites results in lower conversion of pentanol due to reduced acid site number and in enhanced selectivity to ether. Selectivity to DNPE is always higher than to DNHE... 

The synergism of a dual-catalyst system comprising of Pt/ZSM-12 and H-Beta aiming to improve the benzene product purity during transalkylation of aromatics has been studied. Catalyst compositions of the dual-catalyst system were optimized at various reaction temperatures in terms of benzene product purity and premium product yields. Accordingly, a notable improvement in benzene purity at 683 K that meets the industrial specification was achieved using the cascade dual-bed catalyst. 

Whereas over the dual-bed catalyst system, namely Pt/Z12(80) HB(20), a significant improvement in benzene purity up to 94.60% was observed. This is ascribed due to selective cracking of naphthenes over acidic zeolite H-Beta at the bottom bed. 

The effect of the H-Beta ratio (y in wt%) in the dual-bed Pt/Z12(x) HB(y) catalyst system on the benzene purity at a reaction temperature (Tr) of 623 K is shown in Fig. 1. It is evident that the benzene purity gradually increased with increasing H-Beta ratio (Fig. la), eventually reaching a plateau value which meets the industrial specification of 99.85% at y 40 wt%. The effects of catalyst bed ratio on product yields are shown in Fig. lb. Comparing to the single-bed catalyst Pt/Z 12 (i.e., y = 0), the overall premium product yields of benzene and xylene (A68 yield) over the dual-bed catalyst Pt/Z12(x) HB(y) system reached an maximum at y 10 wt%. That the A68 yield dwindled and tetramethylbenzene (TEMB) increased with further increase in the H-Beta ratio may be attributed to the larger pore opening possessed by the bottom (H-beta) catalyst, which may provoke disproportionation of TMB to form tetramethylbenzene (TEMB) [8],... 

Figure 1. Effects of H-Beta ratio (y) in the dual-bed catalyst Pt/Z12(x) HB(y) on (a) benzene purity and (b) product yields during transalkylation reaction (see text) at 623 K.

A dual-bed catalyst system has been developed to tackle the key problems in benzene product impurity during heavy aromatics transalkylation processing over metal-supported zeolite catalysts. It was found that by introducing zeolite H-Beta as a complementary component to the conventional single-bed Pt/ZSM-12 catalyst, the cascaded dual-bed catalyst shows synergistic effect not only in catalytic stability but also in adjustments of benzene product purity and product yields and hence should represent a versatile catalyst system for heavy aromatics transalkylation. 

In further work, the same research group showed that it was possible to effect transacetalation of the initial butyl glucosides 2, 3 with octanol and dodecanol over H-beta zeolites. Direct Fischer glucosylation, leading to the desired long-chain glucosides 4, 5, was also possible (Scheme l).37... 

---