Acid resin catalyst

Etherol A process for making oxygenated fuels (e.g., methyl f-butyl ether) from C4-C6 hydrocarbons by reacting them with methanol over an acid resin catalyst in a fixed bed reactor under mild conditions. Developed by BP with Erdoel Chemie and first used in a refinery at Vohburg, Germany, in 1986. Four units were operating and one was under construction in 1988. 

Many other polymerization processes have been patented, but only some of them appear to be developed or under development in 1996. One large-scale process uses an acid montmorrillonite clay and acetic anhydride (209) another process uses strong perfluorosulfonic acid resin catalysts (170,210). The polymerization product in these processes is a poly(tetramethylene ether) with acetate end groups, which have to be removed by alkaline hydrolysis (211) or hydrogenolysis (212). If necessary, the product is then neutralized, eg, with phosphoric acid (213), and the salts removed by filtration. Instead of montmorrillonite clay, other acidic catalysts can be used, such as Fullers earth or zeolites (214—216). 

The reaction was carried out using Nafion-H and polystyrene sul-phonic acid resin catalyst at 180°C and 140°C, respectively, which are their maximum temperatures of use 2-nitrotoluene solvent and 10% w/w catalyst. Conversions of 20% and 1.5% were obtained at the end of six hours indicating that higher temperatures will be necessary to achieve appreciable rates on these catalysts. Since these catalysts are not structurally stable above the respective temperatures, they appear to be unsuitable for this application. The reaction was also carried out using triflic acid as catalyst at various temperatures. The results are shown in Fig.3. Surprisingly, the reaction did not proceed beyond 40% conversion in spite of the high acidity of the catalyst. 

The present study demonstrates suitability of sulphated zirconia for dehydration of carboxamides. It needs to be emphasised that the common inorganic acid catalysts are not sufficiently acidic to catalyst the reaction below 400°C while the strongly acidic resin catalysts are not structurally stable at temperature at which the reaction would occur at appreciable rate. Thus the sulphated zirconia appears to be a unique catalyst for this application. 

There have been a number of reports of improved selectivity with sulfonic acid resin catalysts compared with conventional liquid acid catalysts[6—9]. Various explanations have also been proposed. If mechanisms usually postulated for condensation reactions with liquid Br0nsted acid [10] and solid acid catalysts [11] are adopted, the sequence of steps shown in Fig. 2 could be considered for the condensation of MFC. Both mechanisms incorporate the essential features of known carbenium ion chemistry, i.t., electrophilic attack on the aromatic ring by polar carbenium ion intermediates. Note that MDU is formed by this attack on the benzene ring of MPC, while the N—benzyl compound by the attack on nitrogen atom. 

The synthesis of methyl /-butyl ether (MTBE) from isobutylene and methanol on TS-1 has been investigated. This reaction is catalyzed by acids and the industrial production is carried out with sulfonic acid resin catalysts. It has been reported that at 363-383 K the reaction proceeds in the presence of the acidic HZSM-5, but also on TS-1, which is much more weakly acidic. However, the characterization of the catalysts used is not completely satisfactory for instance, the IR spectra reported do not show the 960-cm 1 band that is always present in titanium-containing silicas. It is therefore possible that the materials with which the reaction has been studied are not pufe-phase TS-1. The catalytic activity for MTBE synthesis is, in any case, an interesting result, and further investigations with fully characterized catalysts are expected to provide a satisfactory interpretation of these results (Chang et al., 1992). 

Improved selectivity in the liquid-phase oligomerization of i-butene by extraction of a primary product (i-octene C8) in a zeolite membrane reactor (acid resin catalyst bed located on the membrane tube side) with respect to a conventional fixed-bed reactor has been reported [35]. The MFI (silicalite) membrane selectively removes the C8 product from the reaction environment, thus reducing the formation of other unwanted byproducts. Another interesting example is the isobutane (iC4) dehydrogenation carried out in an extractor-type zeolite CMR (including a Pt-based fixed-bed catalyst) in which the removal of the hydrogen allows the equilibrium limitations to be overcome [36],... 

Besides, a di-bromo PDMS macroinitiator was prepared according to two reaction steps given in Scheme 2 first, an esterification of a a,co-(3-hydroxypropyl) PDMS by bromoisobutyril bromide in dichloromethane in the presence of triethylamine (yields >99%) second, a redistribution of this macroiifitiator in the presence of D and a strong acid resin catalyst to increase the average molar mass of the... 

Data have been developed on a boiling reactor concept that utilizes a liquid catalyst and a fixed-bed reactor concept that utilizes an acid resin catalyst. The fixed-bed option offers several advantages, in particular, in raw materials cost and handling, and in materials of construction. It is requested that you investigate the fixed-bed concept and compare it with a reactive distillation concept that... 

The major industrial processes employing sulphonic acid resin catalysts have been reviewed [107, 121]. The most important application is the con-... 

Figure 6.26 Synthesis MTBE gasoline anti-knock using sulphonic acid resin catalyst.

Figure 6.28 Synthesis of MIBK using sulphonic acid resin catalyst partially exchanged with Pd. Note three consecutive reactions, the first two catalysed by the third by Pd(0)/H2.

The above example shows what careful design of the polymer catalyst can achieve and it is this potential versatility which still offers more for the future. The inventory of processes successfully exploiting acid resin catalysts seems poised to grow even more, and if even small advances in thermal stability could be achieved there would undoubtedly be an acceleration in applications. The successful industrial exploitation of acid resins is also vital in terms of demonstrating the overall credibility of polymer-supported species. Users of these materials are now familiar and comfortable with the engineering requirements and this should make exploitation of other very different systems, such as those described in the next section, a little earlier to achieve. 

By-products from the reaction include water and dialkyl ethers, which are also easily separated and recovered by distillation. Dialkyl ethers such as dimethylether are high-value products, and can be used in a variety of applications. The polyperfluorosulfonic acid resin catalyst can also be recovered in concentrated form in the glycol bottoms for reuse in accordance with known methods. Once the activity of the polyperfluorosulfonic acid declines, the material can be regenerated by treatment with a strong mineral acid (i.e., nitric acid) to restore the proton sites on the resin. 

MTBE is conventionally produced from the etherification of isobutylene with methanol over sulfonated acidic resin catalysts under very mild conditions. 

Commercial MTBE (and TAME) synthesis occurs at about 1.5 MPa and 100°C in the liquid phase over an acid resin catalyst that is based on the sulfonic acid group -SO H. The synthesis reaction is sli tly exothermic and limited by equilibrium under the conditions of the commercial operation ... 

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