Maleic anhydride conversion

A pilot-scale rsactor that can produce 50 kg of GBL per one batch was designed. The reactor size was calculated on the basis of maleic anhydride conversion of 100% and GBL yield of 50%. By assuming the saturate liquid densily of reactant and product at the reaction conditions of 250 C and 70 atm undo- the condition of no solvent, the daisity and specific... 

As shown in Figure 4.5, it is well known that cis-A is the Diels-Alder adduct of 1,3-butadiene and maleic anhydride. Conversion of A to meso-B followed by its oxidation gave ( )-C. This was reduced to furnish ( )-74.22 This synthesis, however, was not efficient enough to give a sufficient amount of ( )-74. Its overall yield was only 4.6% based on A. 

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). 

The bulk stmcture of the catalyticaHy active phase is not completely known and is under debate in the Hterature (125,131—133). The central point of controversy is whether (Valone or in combination with other phases is the most catalyticaHy active for the conversion of butane to maleic anhydride. The heart of this issue concerns the role of stmctural disorder in the bulk and how it arises in the catalyst (125,134,135). Most researchers agree that the catalysts with the highest activity and selectivity ate composed mainly of (Vthat exhibits a clustered or distorted platelet morphology (125). It is also generaHy acknowledged that during operation of the catalyst, the bulk oxidation state of the vanadium in the catalyst remains very close to the +4 valence state (125). 

Benzene-Based Catalyst Technology. The catalyst used for the conversion of ben2ene to maleic anhydride consists of supported vanadium oxide [11099-11-9]. The support is an inert oxide such as kieselguhr, alumina [1344-28-17, or sUica, and is of low surface area (142). Supports with higher surface area adversely affect conversion of benzene to maleic anhydride. The conversion of benzene to maleic anhydride is a less complex oxidation than the conversion of butane, so higher catalyst selectivities are obtained. The vanadium oxide on the surface of the support is often modified with molybdenum oxides. There is approximately 70% vanadium oxide and 30% molybdenum oxide [11098-99-0] in the active phase for these fixed-bed catalysts (143). The molybdenum oxide is thought to form either a soUd solution or compound oxide with the vanadium oxide and result in a more active catalyst (142). 

The highly exothermic nature of the butane-to-maleic anhydride reaction and the principal by-product reactions require substantial heat removal from the reactor. Thus the reaction is carried out in what is effectively a large multitubular heat exchanger which circulates a mixture of 53% potassium nitrate [7757-79-1/, KNO 40% sodium nitrite [7632-00-0], NaN02 and 7% sodium nitrate [7631-99-4], NaNO. Reaction tube diameters are kept at a minimum 25—30 mm in outside diameter to faciUtate heat removal. Reactor tube lengths are between 3 and 6 meters. The exothermic heat of reaction is removed from the salt mixture by the production of steam in an external salt cooler. Reactor temperatures are in the range of 390 to 430°C. Despite the rapid circulation of salt on the shell side of the reactor, catalyst temperatures can be 40 to 60°C higher than the salt temperature. The butane to maleic anhydride reaction typically reaches its maximum efficiency (maximum yield) at about 85% butane conversion. Reported molar yields are typically 50 to 60%. 

In addition to these principal commercial uses of molybdenum catalysts, there is great research interest in molybdenum oxides, often supported on siHca, ie, MoO —Si02, as partial oxidation catalysts for such processes as methane-to-methanol or methane-to-formaldehyde (80). Both O2 and N2O have been used as oxidants, and photochemical activation of the MoO catalyst has been reported (81). The research is driven by the increased use of natural gas as a feedstock for Hquid fuels and chemicals (82). Various heteropolymolybdates (83), MoO.-containing ultrastable Y-zeoHtes (84), and certain mixed metal molybdates, eg, MnMoO Ee2(MoO)2, photoactivated CuMoO, and ZnMoO, have also been studied as partial oxidation catalysts for methane conversion to methanol or formaldehyde (80) and for the oxidation of C-4-hydrocarbons to maleic anhydride (85). Heteropolymolybdates have also been shown to effect ethylene (qv) conversion to acetaldehyde (qv) in a possible replacement for the Wacker process. 

Another important use of BCl is as a Ftiedel-Crafts catalyst ia various polymerisation, alkylation, and acylation reactions, and ia other organic syntheses (see Friedel-Crafts reaction). Examples include conversion of cyclophosphasenes to polymers (81,82) polymerisation of olefins such as ethylene (75,83—88) graft polymerisation of vinyl chloride and isobutylene (89) stereospecific polymerisation of propylene (90) copolymerisation of isobutylene and styrene (91,92), and other unsaturated aromatics with maleic anhydride (93) polymerisation of norhornene (94), butadiene (95) preparation of electrically conducting epoxy resins (96), and polymers containing B and N (97) and selective demethylation of methoxy groups ortho to OH groups (98). 

Diels et al. showed that acetylenedicarboxylic acid and 1-methyl-pyrrole gave l-methyl-2-pyrrylmaleic anhydride (41) and a second compound. The anhydride on hydrogenation and conversion to the corresponding dimethyl ester gave the same product as obtained from 1-methylpyrrole and maleic anhydride, followed by hydrolysis and... 

Compound 5 can be trapped through a Diels-Alder reaction with maleic anhydride and thus be shown to be an intermediate. Further evidence for a mechanism involving two subsequent allyl conversions has been provided by experiments with " C-labeled substrates. 

Benzene oxidation is the oldest method to produce maleic anhydride. The reaction occurs at approximately 380°C and atmospheric pressure. A mixture of V2O5/MO3 is the usual catalyst. Benzene conversion reaches 90%, hut selectivity to maleic anhydride is only 50-60% the other 40-50% is completely oxidized to C02 °... 

Potassium ferricyanide in oxidative decarboxylation, 40, 86 Potassium permanganate for oxidation of (trialkylmethyl)amines to tri-alkylnitromethanes, 43,87 Pregnenolone acetate, conversion to 3/3-acetoxyetienic acid, 42, 5 Propane, 2,2-dibotoxy-, 42,1 Propargylsuccinic anhydride, by-product in addition of maleic anhydride to allcne, 43, 27... 

Calculated Degree of Maleic Anhydride Grafting Required to Obtain a Solubility Parameter of 18.0 (J/cm ) , Assuming Full Conversion of the Grafted Anhydride with the Amines Listed, and Corresponding Glass Transition Temperatures (Tg)... 

Citraconic anhydride (Methyl maleic anhydride) was found to be produced from pyruvic acid by an oxidative decarboxy-condensation. The best catalyst is iron phosphate with a P/Fe atomic ratio of 1.2. The presence of oxygen is required to promote the reaction. The main side-reaction is formation of acetic acid and CO2 by oxidative C-C bond fission. The best results are obtained at a temperature of 200°C. The yield of citraconic anhydride reaches 71 mol% at a pyruvic acid conversion of 98%. 

Maleic anhydride is an important industrial fine chemical (see original citations in [43]). The oxidation of C4-hydrocarbons in air is a highly exothermic process, therefore carried out at low hydrocarbon concentration (about 1.5%) and high conversion. The selectivity of 1-butene to maleic anhydride so far is low. The reaction is composed of a series of elementary reactions via intermediates such as furan and can proceed to carbon dioxide with even larger heat release. As a consequence, hot spots form in conventional fixed-bed reactors, decrease selectivity and favor other parallel reactions. 

Figure 3.34 Experimental data on selectivity to maleic anhydride vs degree of conversion of 1-butene for different reactor types ( ) channel width 0.08 mm and (A) channel width 0.2 mm micro reactor ( ) fixed-bed reactor [103],...

A value for the polymerization enthalpy of 21.5 kcal/mole can be used to estimate percent conversion and rates for N-substituted maleimide/vinyl ether and maleic anhydride/vinyl ether copolymerizations. A value of 18.6 kcal/mole can be used for the enthalpy of polymerization of acrylate monomers to convert heat evolution data to percent conversion. Since the molar heats of polymerization for N-substituted maleimide vinyl ether copolymerization and acrylates vary by less than 20 percent, the exotherm data in the text are compared directly. 

A dilute aqueous solution of maleic anhydride is to be continuously hydrolyzed at 25 C. Because of the dilution the reaction is pseudo first order with k = 0.143 gmol/cc-min. A volumetric rate of 530 cc/min is to be processed with inlet concentration of 0,00015 gmol/cc. There are two 2.5 liter and one 5.0 liter stirred vessels available. Find the conversions for various arrangements of these vessels. 

Trimethylsilyl azide is also a specific for conversion of maleic anhydrides to the biologically active oxazinedione ring systems. 

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