Ethanol, conversion zeolites

The first mode of the high resolution C-NMR of adsorbed molecules was recently reviewed Q-3) and the NMR parameters were thoroughly discussed. In this work we emphasize the study of the state of adsorbed molecules, their mobility on the surface, the identification of the surface active sites in presence of adsorbed molecules and finally the study of catalytic transformations. As an illustration we report the study of 1- and 2-butene molecules adsorbed on zeolites and on mixed tin-antimony oxides (4>3). Another application of this technique consists in the in-situ identification of products when a complex reaction such as the conversion of methanol, of ethanol (6 7) or of ethylene (8) is run on a highly acidic and shape-selective zeolite. When the conversion of methanol-ethylene mixtures (9) is considered, isotopic labeling proves to be a powerful technique to discriminate between the possible reaction pathways of ethylene. 

Conversion of methanol and ethanol on H-ZSM-5 zeolite The first in situ characterization of the adsorbed species on this catalyst has been reported for the conversion of methanol and ethanol to hydrocarbons (6 ). ... 

A new process for the manufacture of p-diethylbenzene developed by Indian Petrochemicals Corporation was commercialized.376 p-Diethylbenzene is produced by alkylating ethylbenzene with ethanol over a highly shape-selective, pore-size-regulated, high-silica zeolite. The catalyst exhibits a steady activity of 6-8% conversion with 97-98% selectivity. 

The esterification of acetic acid with ethanol has been investigated using zeolite membranes grown hydrothermally on the surface of a porous cylindrical alumina support (the catalyst used was a cation exchange resin) [37]. The conversion exceeded the equilibrium limit, by the selective removal through the membrane of water and reached to almost 100% within 8h [37]. 

Table 9.4 shows the results corresponding to the reaction of ethanol dehydration in a flow reactor at atmospheric pressure and at temperatures of 403 and 453 K, in comparison with several synthetic zeolites, where the reaction is described with the help of the following parameters Ax(%), total conversion S0(%), selectivity to olefin and SE(%), selectivity to ether [21]. It is necessary to state that the olefin was ethylene and the ether was diethyl ether [21,138-143],... 

The etherification of vanillic alcohol with ethanol was compared over three large pore zeolites HBEA, HFAU and HMOR and over an average pore size zeolites (HMFI) with different Si/Al ratios. Whatever the large pore zeolite and its Si/Al ratio, a total conversion of the benzylic alcohol and a 100% yield in ether are obtained. With the HMFI samples, conversion and yields were equal to 55% only for an Si/Al ratio of 15 and to approximately 70% for Si/Al = 40. It could be expected that the reaction is limited by diffusion of the bulky reactant and product molecules in the narrow pores of this zeolite. 

To estimate the effect of reaction time on activity and selectivity of HBEA (12.5), this zeolite was recovered by filtration after 5 hours reaction and reused several times under the same operating conditions batch reactor, 80°C, 7.5 g of vanillic alcohol and 35 g of ethanol. Only a small decrease in conversion was observed from 98% to 88%, 86% and 84%, the selectivity remaining close to 100%. Furthermore, the activity is completely recovered after calcination under air flow for 5 hours. The slow deactivation of the HBEA zeolite is most likely due to a partial blockage of the access to the active sites by heavy secondary products ( coke ). 

Lefebvre et al. (170) have conducted the high pressure CO + H2 reaction (30 atm, 503-523 K) over Rh-NaY catalysts. Whatever the rhodium precursors [e.g., Rh -NaY and Rh (CO)2-NaY], the reaction data were similar. This is in agreement with the fact that all the precursors were ultimately converted to Rh6(CO),6 under catalytic conditions. The external Rh crystals deposited on the zeolite surface exhibit significant activity for hydrocarbons, mainly methane, whereas the carbonyl clusters gave lower conversion to hydrocarbons with a small amount of oxygenates such as methanol and ethanol. 

To study the influence of the nature of the solvent, the oxidation of ethyl sulfide was carried out at 303 K in the presence of methanol (MeOH), ethanol (EtOH), tert-butanol (t-BuOH), acetonitrile (MeCN), acetone (Me2CO) or tetrahydrofiiran (ITIF) as solvents. Figure 3 shows the sulfide conversion for a reaction time of 60 min, both over Ti-containing zeolites and without catalyst. 

Acetonitrile can be produced from ethanol, ammonia, and oxygen in 99% yield using a SAPO catalyst at 350°C.194 It can be reduced to ethylamine with 98% selectivity using a 1.1 Co/1.1 Ni/0.9 mg/1.0 A1 layered double hydroxide and hydrogen at 393 K.322 Methylamine and dimethylamine are more valuable than trimethylamine. When methanol and ammonia are reacted in a zeolite, such as clinoptilolite, mordenite, or chabazite, the products are largely the desired monomethyl and dimethylamines, one of the best distributions being 73.1% mono-, 19.4% di-and 1.4% tri-, at 97.7% conversion.195 Alkylation of aniline... 

Ethylene for polymerization to the most widely used polymer can be made by the dehydration of ethanol from fermentation (12.1).6 The ethanol used need not be anhydrous. Dehydration of 20% aqueous ethanol over HZSM-5 zeolite gave 76-83% ethylene, 2% ethane, 6.6% propylene, 2% propane, 4% butenes, and 3% /3-butane.7 Presumably, the paraffins could be dehydrogenated catalyti-cally after separation from the olefins.8 Ethylene can be dimerized to 1-butene with a nickel catalyst.9 It can be trimerized to 1-hexene with a chromium catalyst with 95% selectivity at 70% conversion.10 Ethylene is often copolymerized with 1-hexene to produce linear low-density polyethylene. Brookhart and co-workers have developed iron, cobalt, nickel, and palladium dimine catalysts that produce similar branched polyethylene from ethylene alone.11 Mixed higher olefins can be made by reaction of ethylene with triethylaluminum or by the Shell higher olefins process, which employs a nickel phosphine catalyst. 

The reaction of ethanol with ammonia on zeolite catalysts leads to ethylamine. If, however, the reaction is carried out in the presence of oxygen, then pyridine is formed [53]. MFI type catalysts H-ZSM-5 and B-MFI are particularly suitable for this purpose. Thus, a mixture of ethanol, NH3, H2O and O2 (molar ratio 3 1 6 9) reacts on B-MFI at 330 °C and WHSV 0.17 h 1 to yield pyridine with 48 % selectivity at 24 % conversion. At 360 °C the conversion is 81% but there is increased ethylene formation at the expense of pyridine. Further by-products include diethyl ether, acetaldehyde, ethylamine, picolines, acetonitrile and CO2. When applying H-mordenite, HY or silica-alumina under similar conditions pyridine yields are very low and ethylene is the main product. The one-dimensional zeolite H-Nu-10 (TON) turned out to be another pyridine-forming catalyst 54]. A mechanism starting with partial oxidation of ethanol to acetaldehyde followed by aldolization, reaction with ammonia, cyclization and aromatization can be envisaged. An intriguing question is why pyridine is the main product and not methylpyridines (picolines). It has been suggested in this connection that zeolite radical sites induced Ci-species formation. 

For washcoat preparation silicalite zeolite powder (S-115 from Union Carbide Corp.) was dried at 100°C in an oven overnight. Prehydrolyzed ethyl-orthosilicate containing 19.52 silica (Silbond H-5 from Stauffer Chemical Co.) was the source of the silica binder. Absolute ethanol (from U.S. Industrial Chemicals Co.) and absolute methanol (reagent grade from J. T. Baker Company) were used without further purification for the liquid portion of the washcoat slurry and for the methanol conversion reaction, respectively. Reagent grade ammonium nitrate (from J. T. Baker) was used for ion-exchange purposes. 

K. The reaction is carried out in a batch reactor in the presence of /7-toluenesulfonic acid as a catalyst, and the water and ethanol vapors circulate through the NaA membrane, which removes the water vapor. The VPMR was shown to reach complete conversion. The NaA, which is unstable in the presence of acids, performed stably under such conditions. The T-zeolite membrane is more stable under acidic conditions, and was used for the study of the esterification of acetic acid with ethanol at 343 K in a PVMR with the membrane being in direct contact with the reaction medium. 

Anderson et al. showed that the active sites involved in the conversion of methanol on zeolites are not Lewis acids. Wolthuizen et al., ° however, presented evidence that the presence of Lewis-acid sites enhances the polymerization of ethylene. This is in agreement with the results obtained with HY zeolites,where reaction of ethylene at 80 °C was observed only after dehydroxylation of the Bronsted acid sites into Lewis acid sites. At higher temperatures, ethylene is well-known to react on catalysts with strong Bronsted acid sites.Sayed and Cooney reported the involvement of aluminum Lewis sites in the formation of dimethylether. Haber and Szybalska observed that, when ethanol is converted on boron aluminum phosphates, only dehydration to ethylene takes place on the Bronsted acid sites, whereas, on Lewis acid-base centers, ethanol is mainly dehydrated to diethylether. 

NaA/polyelectrolyte multilayer-pervaporation membrane showing a greater stability under acidic conditions in comparison with a pure zeolite A membrane and maintaining a high selectivity for water over alcohols. For the same purpose, Kita et al. [181-183] proposed a zeolite T membrane, prepared by ex situ crystallization, for the per-vaporation-aided or vapor-permeation-aided esterification of acetic acid with ethanol. This membrane has a higher acid resistance and can be directly immersed in the liquid-phase reaction mixture. The conversions achieved exceed the equilibrium limit and reached to almost 100% after a stabilization period of 8 h. 

Fig. 8 Catalytic trends for the conversion of dihydroxyacetone at 90°C in ethanol, (a) Selectivities of different USY zeolites with varying amount of framework aluminum, (b) Sn-containing carbon-silica catalysts correlation between n° of weak Br0nsted acid sites (measured by CO release in TPD-experiments) and initial conversion rate. Based on data from [110] and [66]...

The conversion of simple organic molecules (e.g. methanol, ethanol or ethylene) can also be monitored by the use of combined TG-DTA. For instance such an analysis, applied to ethylene conversion on the acid form of ZSM-5, enabled the transformation to be interpreted in terms of five different reaction steps [25]. Another example of thermal analysis application to the study of the development of a catalyzed reaction is the use of isothermal TG for investigating the kinetics of coke deposition in inner or external zeolitic sites and its subsequent removal by oxidation in air [25]. 

Gao, Yue, and Li (1996) studied the same reaction using a zeolite A-PVA composite membrane (at temperatures ranging from 20 to 50 °C). In this work, together with the pervaporation-aided catalytic esterification of acetic acid with ethanol, the reaction between salicylic acid with methanol was also treated. Among other results, it showed that the continuous removal of water from the system displaced the equilibrium limit (79%), making possible a 95% conversion, when using PVA, PVA -I- KA, and PVA -I- CaA membranes for 20.0, 11.3, and 10.0 h, respectively. 

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