Maleic anhydride from butane

Chlorination or bromination of methane, ethylene, etc Maleic anhydride (from butane)... 

The catalyst used in the production of maleic anhydride from butane is vanadium—phosphoms—oxide (VPO). Several routes may be used to prepare the catalyst (123), but the route favored by industry involves the reaction of vanadium(V) oxide [1314-62-1] and phosphoric acid [7664-38-2] to form vanadyl hydrogen phosphate, VOHPO O.5H2O. This material is then heated to eliminate water from the stmcture and irreversibly form vanadyl pyrophosphate, (V(123,124). Vanadyl pyrophosphate is befleved to be the catalyticaHy active phase required for the conversion of butane to maleic anhydride (125,126). 

Although benzene prices have escalated in recent years, a concurrent need for butenes for use in alkylates for motor fuel has also increased and butane prices have also escalated. As a result, a search for alternative feedstocks began and Amoco Chemical Co. commercialized a process in 1977 to produce maleic anhydride from butane. A plant in JoHet came on-stream in 1977 with a capacity of 27,000 t/yr (135,136). No new plants have been built in the United States based on butenes since the commercialization of butane to maleic anhydride technology. In Europe and particularly in Japan, however, where butane is in short supply and needs for butenes as alkylation feed are also much less, butenes may become the dominant feedstock (see Maleic anhydride). 

Figure 6-4. The Monsanto process for producing maleic anhydride from butane (1) reactor, (2) absorber (3) stripper, (4) fractionator, (5) solvent purification.

The catalysts that allow the production of maleic anhydride from n-butane with high selectivity, like (V0)2P207, are characterized by a strong acidity, that, like a strong basicity, favors the decomposition of alkoxides to give the olefin and the diene. The catalysts that allow the production of maleic anhydride, either from n-butane or from butenes and butadiene, necessarily have particular sites that allow the insertion of oxygen atoms in the 1,4-position of butadiene. These sites are definitely absent on combustion catalysts. 

Vanadium phosphorus oxides (VPO) are commercially used as catalysts for the s5mthesis of maleic anhydride from the partial oxidation of n-butane. The phase constitution and the morphology of the catalyst are found to be dependent on the preparation routes and the applied solvent [78]. Recently, a method to prepare VPO catalysts in aqueous solution at elevated temperature was reported [79]. In addition to the linear relationship between specific activity and surface area, a small group of catalysts exhibit enhanced activity, which could be due to the combination of a higher proportion of V phases in the bulk of vanadyl pyrophosphate (V0)2P207 catalyst [79, 80]. With high relevance to the catalytic properties, the microstructure characterisation of VPO therefore is of great importance. 

Butane can be used for the manufacture of maleic acid (thence to maleic anhydride), from which tetrahydrofuran is made by hydrogenation. Liquefied petroleum gas is also a feedstock for aromatics production (Fig. 1). 

The selective oxidation of hydrocarbons with dioxygen is of immense industrial importance [ 1 ]. A general problem in this area is to obtain high selectivi-ties, particularly at high substrate conversions. The reasons for this are twofold oxidation can occur at different C-H bonds in a molecule, leading to a low primary selectivity, and the initially formed product is often more reactive than the substrate and is oxidized further, ultimately to carbon dioxide and water, leading to low secondary selectivities. Hence examples of industrial processes tend to involve the oxidation of hydrocarbons in which one particular C-H bond is significantly more reactive, for example, cumene hydroperoxide from cumene, and/or the product is relatively stable towards further oxidation, for example, maleic anhydride from n-butane, phthalic anhydride from o-xylene... 

Other catalytic reactions carried out in fluidized-bed reactors are the oxidation of naphthalene to phthalic anhydride [2, 6, 80] the ammoxidation of isobutane to mcthacrylonitrilc [2] the synthesis of maleic anhydride from the naphtha cracker C4 fraction (Mitsubishi process [81, 82]) or from n-butane (ALMA process [83], [84]) the reaction of acetylene with acetic acid to vinyl acetate [2] the oxychlorination of ethylene to 1,2-di-chloroethane [2, 6, 85, 86] the chlorination of methane [2], the reaction of phenol with methanol to cresol and 2,6-xylenol [2, 87] the reaction of methanol to gasoline... 

Recently, attention has been shifted to the oxidative functionalisation of saturated molecules. Reactions such as from ethane —> vinylchloride, propylene — methacrylic acid, or butane -> maleic anhydride, became a target of many research efforts. A catalyst which appeared to be very versatile in such reactions is vanadyl pyrophosphate, (VO)2P20y. The mechanism of oxidative functionalisation is not yet known in all details, but there are many indications that it is in some crucial steps different from the mechanism operating with olefins (see also Chapter 5). 

Stizza et al. (73,274) have investigated amorphous vanadium phosphates, which are also of interest in relation to a XAS study of the butane-maleic anhydride (V, P)0 catalysts (99a). From the V K edge useful information is obtained about the distortions in the vanadium coordination sphere [molecular cage effect on the pre-edge intensity (312)] and on the vanadium oxidation state. Notably, V4+ is silent to most spectroscopic methods. A mixed V4+-V5+ valence state can be measured from the energy shift of the sharp core exciton at the absorption threshold of the Is level of vanadium due to Is -f 3d derived molecular orbitals localized within the first coordination shell of vanadium ions. 

Application To produce maleic anhydride from n-butane using a fluid-bed reactor system and an organic solvent for continuous anhydrous product recovery. 

Application Tb produce maleic anhydride from butane using a flu-idized-bed reactor. The reactor is operated at lower butane per-pass conversion to maximize selectivity, and recover and recycle unreacted butane to achieve a higher total process yield. 

Bergman and Frisch [7] disclosed in 1966 that selective oxidation of n-butane was catalyzed by the VPO catalysts, and since 1974 n-butane has been increasingly used instead of benzene as the raw material for maleic anhydride production due to lower price, high availability in many regions and low environmental impact [8]. At present more than 70 % of maleic anhydride is produced from n-butane [6]. However, productivity from n-butane is lower than in the case of benzene due to lower selectivities to maleic anhydride at higher conversions and somewhat lower feed concentrations (< 2 mol. %) used to avoid flammability of a process stream. Under typical industrial conditions (2 mol. % n-butane in air, 673-723K, and space velocities of 1100-2600 h ) the selectivities [9] for fixed-bed production of maleic anhydride from n-butane are 67-75 mol. % at 70-85 % n-butane conversion [10]. Another unique feature of the VPO catalysts is that no support is used in partial oxidation of n-butane.Many studies of n-butane oxidation on the VPO catalysts indicated that crystalline vanadyl(IV) pyrophos-... 

Figure 5.4. Comparison of energy use among alternatives for the production of maleic anhydride from n-butane. (Source BRIDGES, 2001.)...

V. Chong, Update on Maleic Anhydride from n-butane via Fluid Bed Reactor with an Organic Solvent Recovery , PEP Review 94-2-3, Process Economics Program, SRI International, Menlo Park, CA, 1995. 

Table 1.2 Comparison of industrial motivation and the principles of green chemistry in the industrial synthesis of maleic anhydride from n-butane. Source adapted from Centi and Perathoner [5],...

As cited in Chapter 1, the first example of commercial process using an alkane as feedstock, in substitution of the older process starting from benzene, was the synthesis of maleic anhydride from n-butane. Figure 2.66 briefly recalls the reaction scheme on the model surface of the catalyst (vanadyl pyrophosphate) to evidence the... 

These properties, however, are not sufficient to lead to the high selectivity obtained in the formation of maleic anhydride from n-butane, and of maleic and phthalic anhydrides from n-... 

A further requirement for the high selectivity to maleic anhydride from n-butane is the need for a correct sequence of oxidehydrogenation and oxygen insertion reactions. In the oxidation of n-butane the olefinic-like intermediate must be quickly oxidehydrogenated to an adsorbed dienic-like compound in order to favour the selective pathway towards maleic anhydride. In fact, this reaction may occur concurrently with the oxidation of allylic carbon atoms, with formation of aldehydes and acids which can also be precursors of carbon oxides. Thus, the selectivity to maleic anhydride depends on the relative rates of hydrogen abstraction and oxygen insertion. This property can be considered as typical of the vanadyl pyrophosphate for instance, in the case of the V/Mo/0 system the rate of oxygen insertion... 

The specificity of Mo-heteropolycompounds in the synthesis of unsaturated acids starting from paraffins which can not yield heterocyclic compounds (i.e. propane and isobutane). This may arise from the very strong acidity which is typical of these compounds (even when they are not in a protonic form) which favours the desorption of the organic acids, sparing them from consecutive reactions. These compounds also yield maleic anhydride from n-butane and n-pentane (but with remarkably lower selectivity than the vanadyl pyrophosphate), but they lack the surface properties which are necessary for the formation of phthalic anhydride from n-pentane. 

We conclude therefore, that the Nb-Ti-V-P-oxide catalyst investigated is relatively active for the oxidation of paraffins, since it has a V/P ratio of only 1/12 as compared to a 1/1 ratio for (VO)2P207. Of course, we had hoped that the V in the NASICON structure would be sufficiently site isolated to yield products less oxidized than maleic anhydride from n-butane. However, unfortunately that does not appear to be the case. One explanation for this might be that there are still too many adjacent V atoms, i.e., (V-0-V) moieties, where n > 0. Nonetheless, the NASICON structure provides for some desired V site isolation, however, apparently not complete and hence not sufficient to achieve our desired catalytic goal. Another observed fact is, that the Nb-Ti-V-P-oxide under investigation shows an amorphous overlayer via TEM which is enriched in vanadium. The (V/P)s ,face > (V/P)pa icie- One can reason that at the temperature of 900 °C required to obtain the NASICON structure, the more... 

Economic data concerning the production of maleic anhydride from benzene, n-butane and olefinic C4 cuts are given in Table 13.4. 

Catalysts which can selectively activate the normally un-reactive paraffins have been developed in recent years. The production of maleic anhydride from butane over vanadium-phosphorous-oxide catalysts has received much attention (Eqn. 5), and is beginning to replace the more wasteful production of maleic anhydride from benzene (Eqn. 6) which is still the major feedstock. Maleic anhydride production from butene or butadiene is also possible (Eqn. 7), but cannot compete with the cheaper butane feed. Maleic anhydride is mainly used in the manufacture of unsaturated polyester resins, fumaric acid manufacture, insecticides, and fungicides (Figure 5). ... 

FIGURE 6.13 Circulating Fluidized Bed reactor to produce maleic anhydride from n-butane over a (V0)2P04 catalyst. 

Example 9.6. Table E9.6 summarizes the particle size distribution of commercial vanadium pyrophosphate catalyst to produce maleic anhydride from butane in a circulating fluidized bed reactor. Calculate DA [l,0],Z)jv[2,0],DAf[3,0], Dat[3,2], and Z)jv[4,3]. 

Maleic anhydride (MA) is an important raw material in the production of alkyd and polyester resins. It was first obtained by Nikolas Louis Vauquelin in 1817, by heating maleic acid to over 140 °C. In 1905, Richard Kempf obtained maleic acid by the oxidation of benzoquinone. The first patents covering the production of maleic anhydride from benzene originate from John M. Weiss and Charles R. Downs in 1918. The oxidation of benzene remains a feasible route to maleic anhydride even today, although since around 1975, n-butane and n-butylene have increasingly replaced benzene as raw materials. n-Butane and n-butylene are available as co-products in steam cracking of naphtha and from natural gas condensates. 

Since in the oxidation of benzene to maleic anhydride, two carbon atoms are lost as CO2, attempts were made early on to produce maleic anhydride from C4 hydrocarbons. With the development of the petrochemical industry, large quantities of C4-cuts became available, from which butene and, by hydrogenation, butane, could be recovered. The use of benzene is in decline, particularly in the USA, since benzene is now produced there, among other routes, by dealkylation of toluene, whereas C4-components are readily available from cat-cracker and ethylene plants. 

A fluidized bed process has recently been developed for producing maleic anhydride from butane and is distinguished by better heat dissipation, lower maintenance costs and reduced investment it can also be applied to butene. Figure 5.41 shows the diagram for butane oxidation. 

A reaction related to cleavage is aromatic ring degradation. Phthalic anhydride used to be prepared from naphthalene, and maleic anhydride from benzene, with air and V2O5 catalyst, losing 2 carbon atoms as CO2. More modern processes use o-xylene and butadiene (or -butane) respectively. However, the analogous formation of quinolinic (pyridine-2,3-dicarboxylic) acid from quinoline is still practised. Hypochlorite [94], hypochlorite or chlorite/Ru catalyst [95], or simply alkaline H2O2 [96] can be used. 

Brandstadter WM, Kraushaar-Czametzki B. Maleic anhydride from mixtures of n-butenes and n-butane Simulation of a production-scale nonisothermal fixed-bed reactor. Industrial and Engineering Chemistry Research 2007 46 1475-1484. 

Du Pont has developed a process for the production of tetrahydrofuran through the synthesis of maleic anhydride from n-butane with a transport-bed technology (30). The main features of the preparation are summarized in Scheme 11. The silica coats the active conqranents and forms a very strong shell which gives high mechanical resistance and does not cause loss in selectivity. 

Figure 26 Kinetic network for butane oxidation to maleic anhydride. (From Buchanan and Sundaresan, 1986.)...

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