Degradation kinetics maleic

The reactions of A-phenyl a-r-butyl nitrone (PEN) with maleimides, maleic anhydride, and diethyl maleate have been studied by EPR and two types of spin adduct detected. They arise from the reductive addition of PEN to the alkenes and the degradation product of DEN (2-methyl-2-nitropropane). The deuterium and muonium kinetic isotope effects for the addition of the hydrogen atom to a variety of alkenes have been determined experimentally and theoretically. ... 

The reaction kinetics suggest the separation of the reactor into the fluidized-bed and separation space zones. The conversion of benzene to maleic anhydride and the degradation of the maleic anhydride both occur within the fluidized bed. Only the degradation reaction takes place in the space above the bed which has been divided into five regions, each of which is treated as a perfectly mixed, homogeneous gas-phase reactor. 

The results of the thermal simulation were sufficiently encouraging for us to proceed to the reactor simulation for a number of steady-state operating conditions, but neglecting the maleic anhydride degradation in the fluidized bed. Both the simplified kinetic expression (equation (4)) and the more exact equation (3) were used and the results are shown in Table I as Case 1 and Case 2 respectively. 

It is obvious that the simulation predicts conversions for below those obtained by Kizer and this cannot be due solely to the neglect of the maleic anhydride degradation. There may be several possible causes for the low predicted values the Orcutt-Davidson PM model may not be sufficiently accurate or the bubble size estimate may be incorrect. Alternatively, neither equation (3) nor (4) correctly describe the reactor kinetics. The number of possibilities may be reduced by considering Figure 4 which plots conversion versus the non-dimensional reaction rate constant, K , with as a parameter. Two possible zones of opera-... 

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] ... 

The improvement was apparent when was plotted as a function of time. Without the additives,7 y7 dropped about 40-50% from the initial value, after 4-5 days. With additives, the charge-transfer kinetics was protected from degradations, except for maleic acid. 

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