Maleic anhydride, from heterogeneous

Reduction. Heterogeneous catalytic reduction processes provide effective routes for the production of maleic anhydride derivatives such as succinic anhydride [108-30-5] (26), succinates, y-butyrolactone [96-48-0] (27), tetrahydrofuran [109-99-9] (29), and 1,4-butanediol [110-63-4] (28). The technology for production of 1,4-butanediol from maleic anhydride has been reviewed (92,93). 

Diacetyl (DA) is used as a flavour enhancer in the food industry and is currently manufactured from methyl ethyl ketone (MEK) in homogeneous systems via an oxime intermediate (ref.1). In principle, DA can also be manufactured by the selective oxidation of MEK and several reports have appeared in the literature which apply heterogeneous catalysts to this task (refs. 2-4). A number of reports have specified the importance of basic or weakly acidic sites on the catalyst surface for a selectively catalysed reaction and high selectivities to DA at moderate conversions of MEK have been reported for catalysts based on C03O4 as a pure oxide and with basic oxides added conversely scission reactions have been associated with acidic oxide additives (refs. 2-4). Other approaches to this problem have included the application of vanadium phosphorus oxide (VPO) catalysts. Ai (ref. 5) has shown that these catalysts also catalyse the selective oxidation of MEK to DA. Indeed this catalyst system, used commercially for the selective oxidation of n-butane to maleic anhydride (ref.6), possesses many of the desired functionalities for DA formation from MEK, namely the ability to selectively activate methylene C-H bonds without excessive C-C bond scission. 

Heterogeneous oxidative processes operate at high temperatures (250-450 6C) and are useful for the synthesis of acrolein and acrylic acid from propylene over bismuth molybdate catalysts, the synthesis of maleic and phthalic anhydrides from the oxidation of benzene (or C4 compounds) and naphthalene (or o-xylene) respectively over vanadium oxide,101 arid the synthesis of ethylene oxide from ethylene over silver catalysts.102... 

Attempts to change the copolymerization of styrene and maleic anhydride in benzene from a heterogeneous to a homogeneous process by using high concentrations of initiator or by adding weak chain transfer agents, such as carbon tetrachloride, were unsuccessful. However, homo-... 

This review analyzes the properties which are necessary for heterogeneous catalysts to promote the oxyfunctionalization of light paraffins to valuable chemicals. Three catalytic systems are discussed i) vanadium/phosphorus mixed oxide, the industrial catalyst for the oxidation of n-butane to maleic anhydride, which is here also examined for reactions aimed at the transformation of other hydrocarbons ii) Keggin-type heteropolycompounds, which are claimed for the oxidation of propane and isobutane, whose composition can be tuned in order to direct the reaction either to the formation of olefins or to the formation of oxygenated compounds iii) rutile-based mixed oxides, where rutile can act as the matrix for hosting transition metal ions or favour the dispersion of other metal oxides, thus promoting the different role of the various elements in the formation of acrylonitrile from propane. 

To prepare the copolymers, enough solvent was added to 0.5 gram of equimolar quantities of maleic anhydride and vinyl monomer and 0.0125 gram azobisisobutyronitrile to make a total volume of 5 ml. The copolymerizations were conducted in sealed glass containers in the absence of oxygen. The precipitate was removed from heterogeneous systems, washed well with fresh solvent after filtration, and dried under a vacuum at 0°C. 

To provide better control of polymer matrix erosion, a more orderly degradation and erosion process is needed. In an effort to achieve this goal, materials that erode heterogeneously have been produced. In particular, for materials that erode from the surface only, the kinetics of dissolution and the release of incorporated drugs can be precisely controlled. The first surface-eroding bio-erodible polymer formulation was produced at Alza Corp. in the 1970s it was a copolymer of methyl vinyl ether and maleic anhydride [20] ... 

In experiments on immiscible blends, as noted by Dlubek et al. [2002], it is to be anticipated that the PALS parameters h and T3 will depend on the volume fractions and compositions of the three phases, as well as the effect of any interaction between the blend components. Such interactions have been identified in the studies of Wastlund et al. [1998] and Dlubek et al. [1999]. Thus, as pointed out above, the decrease in T3 observed by Wastlund et al. [1998] in 50 50 SMA24/SANx blends when the acrylonitrile content of the SANx increases from x=22% to x=33%, is interpreted as being due to increased interaction between the maleic anhydride and acrylonitrile groups. On the other hand, Dlubek et al. [1999] studied blends of an acrylonitrile-butadiene-styrene (ABS) copolymer and polyamide-6 (PA-6). This blend may be assumed to be quite heterogeneous, consisting of a two-phase structure having PA-6 crystals embedded in an amorphous ABS matrix and elastomeric... 

---