Phthalic catalyst activity

Thermal influences can often affect the catalyst compositian. In many cases one or more metastable phases are formed from the active components or the support materials. Phase changes can limit the catalyst activity or lead to catalyst- bstrate interactions. We have already dealt with the transformation of y-Al203 into a-Al203 with its lower surface area. Another example is the phase transformation of Ti02 from anatase to rutile in V2O5/ Ti02/corundum catalysts for the oxidation of o-xylene to phthalic anhydride. 

The chapter presents a brief overview of the current research on V205/Ti02 catalysts for o-xylene oxidation to phthalic anhydride at Clariant. Phthalic anhydride is produced in tubular, salt-cooled reactors with a capacity of about 5 Mio to per annum. There is a rather broad variety of different process conditions realized in industry in terms of feed composition, air flow rate, as well as reactor dimensions which the phthalic anhydride catalyst portfolio has to match. Catalyst active mass compositions have been optimized at Clariant for these differently realized industry processes utilizing artificial neural networks trained on high-throughput data. Fundamental pilot reactor research unravelling new details of the reaction network of the o-xylene oxidation led to an improved kinetic reactor model which allowed further optimizing of the state of the art multi-layer catalyst system for maximum phthalic anhydride yields. 

These reactions have not been widely studied however, most authors agree with a lowering of enthalpy or energy of activation. This applies to the system 2-ethylhexanol/ phthalic anhydride226 where AH is 68 kJ mol-1 in the absence of a catalyst and 62 (or 61) kJ mol-1 when H2S04 (or PTS) is added. This is also true for the system 1-octadecanol/octadecanoic acid in octadecyl octadecanoate229 where AH decreases from 50 to 18.5 kJ mol 1 when PTS is added. In the case of the system 1,2-ethanediol/ hexanedioic acid, the decrease is from 50 to 46 kJ - mol-1 when PIS is added313. ... 

As previously discussed, solvents that dissolve cellulose by derivatization may be employed for further functionahzation, e.g., esterification. Thus, cellulose has been dissolved in paraformaldehyde/DMSO and esterified, e.g., by acetic, butyric, and phthalic anhydride, as well as by unsaturated methacrylic and maleic anhydride, in the presence of pyridine, or an acetate catalyst. DS values from 0.2 to 2.0 were obtained, being higher, 2.5 for cellulose acetate. H and NMR spectroscopy have indicated that the hydroxyl group of the methy-lol chains are preferably esterified with the anhydrides. Treatment of celliflose with this solvent system, at 90 °C, with methylene diacetate or ethylene diacetate, in the presence of potassium acetate, led to cellulose acetate with a DS of 1.5. Interestingly, the reaction with acetyl chloride or activated acid is less convenient DMAc or DMF can be substituted for DMSO [215-219]. In another set of experiments, polymer with high o -celliflose content was esterified with trimethylacetic anhydride, 1,2,4-benzenetricarboylic anhydride, trimellitic anhydride, phthalic anhydride, and a pyridine catalyst. The esters were isolated after 8h of reaction at 80-100°C, or Ih at room temperature (trimellitic anhydride). These are versatile compounds with interesting elastomeric and thermoplastic properties, and can be cast as films and membranes [220]. 

Photo-oxidation reactions, 32 118 Photoreduction, metal oxides, 31 123 Phthalic acid, esterification, 17 340 Phthalocyanines EDA complexes of, 20 328-330 catalytic activity for hydrogen exchange reaction, 20 329,330 electronic configuration of, 20 330 organometallic complexes, 30 276-277 Phyllosilicates, see Layer lattice silicates, catalysts... 

In industrial applications the achievement of higher activity and selectivity is of course desirable. However, beyond a certain point, they are not the driving forces for extensive research. For instance, current processes for epoxidation of ethylene to ethylene oxide on silver catalysts are so optimized that further increases in selectivity could upset the heat-balance of the process. Amoco s phthalic acid and maleic anhydride processes are similarly well energy-integrated (7). Rather than incremental improvements in performance, forces driving commercial research have been... 

A polymer with improved stereoregularity and bulk density can be produced advantageously on an industrial scale using catalysts with improved catalytic activity. Such catalysts are prepared from MgCk, TiCU and phthalic anhydride (6). 

The influence of substituents on the catalytic oxidation of toluene was investigated by Trimm and Irshad [330]. Toluene, chlorotoluenes and xylenes were oxidized over a M0O3 catalyst at 350—500° C. Partial oxidation products are aldehydes, acids and phthalic anhydride (in the case of o-xylene). Unexpectedly, both xylenes and chlorotoluenes are oxidized faster than toluene. The authors conclude that apparently the electromeric effect of the chlorosubstituent is more important than its inductive (—I) effect. The activation energies of the xylenes and chlorotoluenes all fall in the same range (17—18 kcal mol"1), while a much higher value is reported for toluene (27 kcal mol 1). 

The performance of a number of single oxides of transition metals was studied by Skorbilina et al. [295] using a differential reactor. As usual, o-tolualdehyde, phthalic anhydride and carbon oxides are the main reaction products. The initial selectivity with respect to partial oxidation products decreases in the order Co > Ti > V > Mo > Ni > Mn > Fe > Cu from 71% to 33%. The relatively high initial selectivities demonstrated by the deep oxidation catalysts (e.g. Co, Ni, Mn) indicates that the primary activation is probably the same for all these catalysts, while the differences that actually determine the character of the catalyst are connected with the stability of intermediates and products. 

The reaction rate of fiimarate polyester polymers with styrene is 20 times that of similar maleate polymers. Commercial phthalic and isophthalic resins usually have fiimarate levels in excess of 95% and demonstrate full hardness and property development when catalyzed and cured. The addition polymerization reaction between the fiimarate polyester polymer and styrene monomer is initiated by free-radical catalysts, commercially usually benzoyl peroxide (BPO) and methyl ethyl ketone peroxide (MEKP), which can be dissociated by heat or redox metal activators into peroxy and hydroperoxy free radicals. 

The use of much-neglected bismuth derivatives for the oxidation of organic compounds has been reviewed.74 Bismuth(III) carboxylates, obtained by reaction of Bi2C>3 with pyridine mono- and di-carboxylic acids and with phthalic acid, act as catalysts for the oxidation of styrene oxide to benzoic acid in DM SO in the presence of 02.75 It is proposed that the bismuth may activate both epoxide and oxidant in a solvate, from which dimethyl sulfide evolution and elimination leads to a ketoalkoxide-bismuth complex (and hence to the initial product, 2-hydroxyacetophenone). Further oxidation to tlie ketoaldehyde and acid requires molecular oxygen, but is also found to be catalysed by bismuth. 

The primary aldehyde product is reduced to the desired butanol, or it is subjected to a base-catalyzed aldol condensation and then hydrogenated to give 2-ethylhexanol. The phthalic ester of the latter is used as a plasticiser in PVC. The first process was based on a Co2(CO)s catalyst, a precursor of HCo(CO)4. The pressure is high, ca. 200-300 bar, in order to maintain the catalyst s stability. In the 60s Shell developed a process using phosphine ligands which allowed the use of lower pressures. The catalyst is less active but it directly produces alcohols with a somewhat higher linearity. 

Activated ketones, for example isatin136 or acenaphthenequinone,137 have been similarly condensed with 92 at ca. 150° for several hours with acetic acid and sodium acetate forming, for example, 94, 3, or 42. Fusing 87 (R = Ph) with excess phthalic anhydride in the presence of an alkaline catalyst gives (84%) spiro[2-oxo-3-phenyl-4-thioxo-l,3-thiazolidine-5,2 -indane-1, 3 -dione] (95).117... 

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