ETBE Synthesis

ETBE is produced by the liquid-phase addition of ethanol (EtOH) to isobutene (IB) in presence of an acid catalyst. Since the reaction is exothermic and limited by the chemical equilibrium, the reactor outlet temperature is maintained as low as allowed by the catalyst activity in order to maximize the isobutene conversion. Operating temperatures range between 40 and 80 °C. 

Selectivity to ETBE is usually very high and the main side reactions are isobutene dimerization with formation of 2,4,4-trimethyl-l-pentene and 2,4,4-trimethyl-2-pentene (DIB), ethanol self-condensation to diethyl ether (DEE), water addition to isobutene with formation of tert-butyl alcohol (TBA) and the etherification of linear butenes, if present, to produce ethyl sec-butyl ether (ESBE). 

The reaction rate of linear olefins etherification is much lower than isobutene so ESBE presence in the product is limited to a few hundred ppm. Formation of both DIB and DEE is favored at high temperatures and at low molar ratio alcohol/ isobutene. 

TBA is, instead, the main by-product of ETBE and its formation is faster and approaches the thermodynamic equilibrium. While in the MTBE case the quantity of water is small, in ETBE synthesis there is an increase of TBA production due to the greater amount of water in the feed, deriving from its higher concentration in both fresh (0.2-1 wt%) and recycle ethanol (azeotrope with 6 wt% of water) coming from the alcohol recovery section. 

All these by-products do not adversely affect the product quality since TBA, DEE and DIB are also acceptable octane gasoline components. 

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Some attempts were made to calculate the apparent activation energy for the ETBE synthesis. However, the value obtained (133 . 15 KJ/mol) is tenuous owing to the presence of competitive reactions such as the ethanol dehydration to diethyl ether (already significant at 363 K) and ETBE... 

As with MTBE, acidic resins are the catalysts employed in the industrial practice for ETBE synthesis standard products, made from different manufacturers in the form of spherical beads (e.g., Rohm and Haas, Bayer, Purolite, Dow), have similar characteristics - a macroporous structure, polystyrene-divinylbenzene, functionalized with sulfonic groups (active sites 5.2 eq H per kg). 

Thus, the reasons for research for ETBE synthesis seems quite positive. MTBE producers seem to be shifting the focus of new plants towards flexibility in MTBE/ETBE production. 

The absorption of isobutene in subazeotropic aqueous ethanol, to give ETBE and tert-butyl alcohol (TBA) was investigated [58]. The experiments were conducted in a stainless steel autoclave of one liter capacity. The catalyst used was Amberlyst-15, which is an acidic, macroporous cation exchange resin, in the form of spherical beads. In the ETBE synthesis reaction using ethanol and isobutene, the side reactions are the dimerization of isobutene to form diisobutene and the formation of diethyl ether. These byproducts show a tendency to increase with an increase in reaction temperature. Hence, the... 

In Fig. 5.28a experimental and simulated rates for the synthesis of MTBE from methanol and isobutene are depicted, which show that the rate expression (5.63) is valid for the MTBE synthesis [45]. Fig. 5.28b illustrates its validity for the ETBE synthesis from ethanol and isobutene [41] compared with experimental data reported by Francoisse and Thyrion [47]. In analogous manner this rate approach can be applied to the synthesis of the fuel ether TAME from methanol and isoam-lyenes [43, 46]. Activity-based rate expressions were also applied for other reactions carried out in strongly non-ideal liquid mixtures, for example for butyl acetate synthesis [48] and for dimethyl ether synthesis [49]. 

The main application of acidic lonexchange catalysts in this regard is the production of ethers for unleaded fuel. Examples of importance are metiyi-tertlary-butyl-ether (MTBE), tertlary-amyl-methyl-ether (TAME) and eti -tertiary-butyl-ether (ETBE) synthesis. 

M. G. Sneesby, M. O. Tade, R. Datta, and T. N. Smith, ETBE synthesis via reactive distillation. 1. Steady-state simulation and design aspects, Ind. Eng. Chem. Res. 36, 1855-1869 (1997). 

Typical feedstock composition and product properties for the synthesis of MTBE-ETBE. 

ET-1 also stimulates anti-apoptotic signal cascades in fibroblasts, vascular smooth muscles and endothelial cells (via phosphatidylinositol-3-kinase and Akt/pro-tein kinase B). In prostate and ovarian cancer, upregulation of endothelin synthesis and ETA receptors has been associated with a progression of the disease. The inhibiton of ETA receptors results in a reduced tumour growth. In malignant melanoma, ETB receptors are associated with tumour progression. Endothelins can also stimulate apoptosis in stretch-activated vessels via the ETB receptor, which contrasts the above-mentioned effects. The molecular basis for these differential anti- and pro-apoptotic reactions mediated by endothelins remains elusive. 

Loss of Coordinated Arene. We previously stated that the arene ligand in ruthenium(II)-arene complexes is relatively inert towards displacement under physiological conditions. While this is generally true, there are a few exceptions to this rule and this type of reactivity can be used to advantage. Weakly bound arenes, for instance, can be thermally displaced, a property convenient for the synthesis of ruthenium-arene complexes that are not readily available through more common synthetic routes. This way, the reaction of a precursor dimer, [RuCl2(etb)]2 (etb, ethylbenzoate) (68), with either 3-phenyl-1-propylamine or... 

Ethyl terl-butyl ether (ETBE), 10 548, 574, 576 12 404-405 derivation from ethanol, 10 557 Ethyltoluene, 23 329, 349 o-Ethyltoluene, 23 349 p-Ethyltoluene, 10 597 p-Ethyltoluene precursor, synthesis of, 23 351 p-Ethyltoluene synthesis, molecular sieves in, 16 846... 

M. Raschak, H. Riechers, L. Unger, Discovery and synthesis of (S)-3-[2-(3,4-dimethox-yphenyl)ethoxy]-2- (4,6-dimethylpyrimidin-2-yloxy)-3,3-diphenylpropionic acid (LU 302872), a novel orally active mixed ETa/ETb receptor antagonist, J. Med. Chem. 42(1999) 3026-3032. 

From a functional point of view, Nguyen et al. examined the pervapora-tion characteristics of CA/P(VP-co-VAc) blends for application as alcohol-selective membrane materials [107]. The blend membranes were shown to be very efficient in the removal of ethanol from its mixture with ethyl tert-butyl ether (ETBE). ferf-butyl ethers are octane-value enhancers for gasoline, and the synthesis requires an excess of alcohol in the reaction to reach high... 

In this work, the triflic acid modified Y-zeolite catalyst has been investigated for the atmospheric synthesis of MTBE and ETBE. In particular, the apparent activation energy for MTBE was determined, and this value is compared with those reported in the literature [1,6]. In addition, for both syntheses, the product selectivities are reported as functions of the contact time at the temperature where the catalyst activity is the highest. The catalyst stability for the MTBE synthesis was also examined. 

In particular, in the synthesis of ETBE, the yield in diethyl ether is expressed as ... 

The main use of MTBE is as an octane booster in gasoline formulations. Table 2.1 (above) compares octane number and boiling points of some tertiary ethers and hydrocarbons. The volatility is another important property of gasoline components. In fact, the lower volatility of ETBE is an advantage with respect to MTBE. Another (smaller scale) application of MTBE is the synthesis of high purity isobutene by cracking MTBE over amorphous silica-alumina. This isobutene serves as a monomer for polyisobutene. 

DegussaAG Ethyl tertiary butyl ether (ETBE) Isobutylene stream, ethanol Liquid-phase catalytic synthesis, high selectivity, energy efficient NA NA... 

Aerobic selective oxidation of alkylaromatics, including cumene (CU), ethylbenzene (EtB), and cyclohexylbenzene (CyB), to the corresponding hydroperoxides (CHPs) represents a key step for several large-scale productions, including the Hock process for the synthesis of phenol (see Chapter 2) [15] and the Shell styrene monomer/propylene oxide (SM/PO) process for the production of propylene oxide (PO) and styrene monomer (SM) [16]. 

Residue curve maps and parametric dependencies similar to those reported for the MTBE and TAME system were also obtained for the heterogeneously catalyzed synthesis of the alternative fuel ether ETBE from isobutene and ethanol [12]. 

In order to formulate an expression x) in (5.57), the rate determining step of the reaction mechanism has to be identified. For many heterogeneously catalyzed liquid-phase reactions the rate limiting step is found to be the reaction of sorbed molecules. For example, in the synthesis of the fuel ethers MTBE, TAME, and ETBE at acid ion-exchange catalyst the rate limiting step can be expressed as follows... 

Most important industrial applications of RD are in the field of esterification processes such as the famous Eastman Chemical Co. s process for the synthesis of methyl acetate [1]. This process combines reactive and non-reactive sections in a single hybrid RD column and thereby replaces a complex conventional flowsheet with 11 process units. With this RD technology investment and energy costs were reduced by factor five [2]. Another success story of RD was started in the 1980s by using this technology for the preparation of the ethers MTBE, TAME, and ETBE, which are produced in large amounts as fuel components because of their excellent antiknock properties [3]. 

Kiatkittipong et al. (2002) investigated a PV membrane reactor for the synthesis of ethyl icri-butyl ether (ETBE) from a liquid phase reaction between EtOH and TEA. Supported p-zeolite and PVA membrane were used as catalyst and as membrane in the reactor, respectively. The permeation studies of water-EtOH binary system revealed that the membrane worked effectively for water removal for the mixtures containing water lower than 62 mol%. The permeation studies of quaternary mixtures (water-EtOH-TBA-ETBE) were performed at three temperature levels of 323, 333, and 343 K. It was found that the manbrane was preferentially permeable to water. 

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