MTBE, reactive distillation

Application 1. Steady-state Entropy Production Profile IN A MTBE Reactive Distillation Column... 

Application 3. Tri-Objective Optimization of a MTBE Reactive Distillation Column A Sensitivity-Based Approach... 

The MTBE reactive distillation process was patented several decades ago, and the process was widely used in the petroleum industry. Many reactive columns were installed around the world to produce MTBE, which was blended into gasoline. This process was probably the largest application of reactive distillation in terms of the number of columns and total production capacity. Because MTBE presents groundwater contamination problems, it is gradually being phased out of use in gasoline. 

S. J. Wang, D. S. H. Wong, and E. K. Lee, Effect of interaction multiplicity on control system design for a MTBE reactive distillation column, J. Process Control 13, 503-515 (2003). 

Reactive distillation is used in the production of MTBE (methyl tertiary butyl ether)... 

Figure 1 Examples of industrial processes employing reactive distillation (a) methyl ferf-butyl ether (MTBE) from isobutene and methanol (b) cumene via alkylation of benzene with propylene (c) ethylene glycol via hydration of ethylene oxide.

Figure 7 MTBE synthesis conventional scheme (above) and reactive distillation scheme (below).

The modeling of RD processes is illustrated with the heterogenously catalyzed synthesis of methyl acetate and MTBE. The complex character of reactive distillation processes requires a detailed mathematical description of the interaction of mass transfer and chemical reaction and the dynamic column behavior. The most detailed model is based on a rigorous dynamic rate-based approach that takes into account diffusional interactions via the Maxwell-Stefan equations and overall reaction kinetics for the determination of the total conversion. All major influences of the column internals and the periphery can be considered by this approach. 

Methyl tert-butyl ether (MTBE) has been produced by reactive distillation of isobutylene and methanol. The reaction is conducted in a distillation column loaded with socks containing a solid acid catalyst. 

Thiel, C Sundmacher, K., Hoffmann, U Residue curve maps for heterogeneously reactive distillation of fuel ethers MTBE and TAME, Chem. Eng. Sci., 52, no. 6, 993-1005, 1997... 

The benefits of using reactive distillation are clearly proven in the production of fuel components (ethers) such as ferf-amyl methyl ether (TAME), methyl tert-butyl ether (MTBE) and methyl acetate. The latter is synthesized from acetic acid and methanol with a reversible liquid-phase reaction ... 

Phases gas-liquid, gas-liquid catalytic solid, gas-liquid plus catalytic solid minimizes catalyst poisoning, lower pressure than fixed bed. Used for hydrogenation reactions and MTBE and acrylamide production. For example, 90% conversion via reactive distillation contrasted with 70% conversion in fixed-bed option. Liquid with homogeneous catalyst etherification, esterification. Liquid-liquid HIGEE for fast, very fast, and highly exothermic liquid-liquid reactions such as nitrations, sulfonations, and polymerizations. Equilibrium conversion <90%. Use a separate prereactor when the reaction rate at 80% conversion is >0.5 initial rate. The products should boil in a convenient temperature range. The pressure and temperature for distillation and reaction should be compatible. 

Matouq et al [3.31] tested two types of catalysts an ion exchange-resin (the form of Amberlyst 15) and a heteropolyacid (HPA) in the production of MTBE from methanol and -butyl alcohol (TBA). Both were shown, active, but the ion-exchange resin showed poor selectivity, producing substantial amounts of by-product isobutylene (IB). Matouq et al. [3.31] tested the production of MTBE using the ion-exchange resin in a reactive distillation column. It was difficult to test the HPA catalyst in the reactive distillation system, however, because its particle size was too small and was carried out by the liquid phase. Matouq et al. [3.31] proposed, instead, the use of a PVMR incorporating a PVA membrane. As shown in Figure 3.9, in the proposed system the PVMR is coupled with a con-... 

Very high isobutene conversion, in excess of 99%, can be achieved through a debutanizer column with structured packings containing additional catalyst. This reactive distillation technique is particularly suited when the raffinate-stream from the MTBE unit will be used to produce a high-purity butene-1 product. 

A further process for which reactive distillation is commonly used in industrial practice is the synthesis of methyl-tert-butyl ether (MTBE) which is an additive for gasoline. MTBE is produced by etherification ofisobutene with methanol. The process based on reactive distillation leads to conversions of 99%. Isobutene and methanol are fed into the pre-reactor where the equilibrium conversion is obtained. The stream leaving the pre-reactor is fed into the reactive distillation column where MTBE is obtained as the bottom product. 

Over the last decade reactive distillation (RD) has become a key technology for meeting increased productivity demands. The best-known example in C4 chemistry is given by MTBE (methyl tert butyl ether) synthesis. Both the CD Tech process and the Ethermax process by UOP consist of fixed-bed reactors followed by an RD col-... 

In conclusion, MTBE decomposition may be performed using reactive distillation equipment. The top product is fairly pure isobutene and will contain some methanol, which has to be separated downstream using conventional technology. 

The introduction of lead-free gasoline brought about a new technical process on a large scale reactive distillation (RD). Although the principle of this process had been known for many years [1], the need to produce huge quantities of ethers as antiknock enhancers caused rapid development of this technique more than 14 X 10 tonnes/year of ethers are produced. The catalysts for the production of methyl-t-butylether (MTBE), t-amylmethylether (TAME), or ethyl- butylether (ETBE), which are the main products for the fuel market, are acidic ion-exchange resins. The most important type is based on cross-linked polystyrene that is sulfo-nated to create the active acid sites. These resins are produced as beads of less than 3 mm in a suspension polymerization process. 

At this moment, fractionating reactors are mostly studied and applied outside the fine-chemical field. Examples are the large-scale production of the fuel ethers MTBE and TAME via reactive distillation. Also, biocatalytic studies have been performed. Malcata and co-workers investigated the integration of ester formation by Upases and distillative separation of the final products ester and water [44]. A number of synthesis reactions have been studied such as the esterification of ethanol and acetic acid to form ethyl acetate and water [45] in an SMB reactor with chemocatalysts (acidic ion exchange resins). Another, fairly similar appUcation was presented by Kawase et al. [46] to manufacture an ester from 2-phenylethanol. Mensah and Carta [47] used a chromatography column with lipases immobilised on resin to produce esters as well. 

Figure 5.8. Residue curve map and separation sequence for zone b in the synthesis of MTBE by reactive distillation. Remark high purity MTBE (pseudo azeotrope) is recovered at the bottom of the column in an indirect separation operating pressure is set at 11-10 ...

Figure 6.6. Time dependence of the disturbances scenario in the dynamic optimization of MTBE synthesis by reactive distillation. Time hoiizon=14400 s.

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