Kinetic Studies on the Acid Hydrolysis of Dextran

Basedow, Arno Max; Ebert, Klaus; Ederer, H. J.

doi:10.1021/ma60064a031

Cited by 117 publications

(74 citation statements)

References 9 publications

(11 reference statements)

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“…13 Previous modeling of homogeneous hydrolysis includes, on the one hand, the development of rate equations for thermal hydrolysis of oligosaccharides 14,15 and, on the other hand, the determination of acid hydrolysis rates from modeling of experiments with a polysaccharide, dextran. 16 In addition, Monte Carlo simulation has been performed to predict glucose production from amylose. 17 However, this is to our knowledge the first modeling of thermal homogeneous hydrolysis of polysaccharides.…”

Section: Introductionmentioning

confidence: 99%

Model for Random Hydrolysis and End Degradation of Linear Polysaccharides: Application to the Thermal Treatment of Mannan in Solution

Nattorp

Graf

Spuehler

et al. 1999

Ind. Eng. Chem. Res.

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The kinetics for homogeneous hydrolysis of mannan is studied in a batch reactor at temperatures from 160 to 220°C. A formate buffer ensures a pH of 3.8-4.0, measured at 25°C. Samples are analyzed for oligosaccharides up to a degree of polymerization of 6 and also for the total amount of mannose after acid hydrolysis. A mathematical model with two reactions (1, random hydrolysis of the glucosidic bonds; 2, degradation of the reducing end of the molecule) describes accurately the time course of oligosaccharides. Optimized rate constants follow closely an Arrhenius relationship, with the degradation having a higher activation energy (140 kJ/mol) than the hydrolysis (113 kJ/mol). The mathematical model has the advantage that production of small molecules is independent of the initial chain-length distribution as long as the average initial chain length is some 5 times longer than the largest species measured. It can be applied to first-order depolymerization of other linear polymers with one link type in order to determine reaction rate constants or make predictions about molecular weight distribution on the base of known reaction rate constants.

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Section: Introductionmentioning

confidence: 99%

Model for Random Hydrolysis and End Degradation of Linear Polysaccharides: Application to the Thermal Treatment of Mannan in Solution

Nattorp

Graf

Spuehler

et al. 1999

Ind. Eng. Chem. Res.

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“…In principle, Eq. 22 can be solved for any u j b i as the set of ordinary differential equations it describes are triangular as in the case with no feed or removal (Basedow et al, 1978). Compact solutions, expressed as series of simple functions are not as easily obtained, however.…”

Section: Discrete Breakupmentioning

confidence: 99%

Analytical solutions to fragmentation equations with flow

McGrady

Ziff

1988

AIChE Journal

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“…Este caso-estudo refere-se à reação de hidrólise de dextrana em meio ácido, processo que foi estudado experimentalmente por BASEDOW et al (1978). …”

Section: Caso-estudo 2: Quebra Radicalar De Cadeias Lineares De Polipunclassified

“…Basedow et al (1978) reportam estudos de degradação de dextranas com ultrassom em que, segundo os autores, as cadeias são quebradas preferencialmente no centro da molécula, enquanto que os mesmos autores interpretam seus dados de hidrólise ácida de dextrana de forma inversa, ou seja, com preferência pela quebra das ligações mais próximas das pontas da cadeia.…”

Section: Solução Do Problema Inversounclassified

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Estudo do problema inverso em balanço populacional aplicado a degradação de polímeros.

Uliana¹

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Uliana, MuriloEstudo do problema inverso em balanço populacional aplicado a degradação de polímeros / M. Uliana. SATHYAGAL et al. (1995) e a obtida no presente trabalho usando o algoritmo do problema inverso, para o casoestudo 1; (b) Distribuição de partículas filhas obtida no presente trabalho para o casoestudo 1. σ -desvio padrão φ -Função para minimização na equação (3.4.2.28) dentro da função objetivo. Palavras-chave: taxa de quebra, balanço populacional, problema inverso, polímeros, modelagem. xiv ABSTRACT.Computational algorithms are used to obtain quantitative information from experimental observations. The aim of the present work was the application of the methodology of inverse problem in population balance used to describe the evolution of the chain length distribution in different polymer degradation processes. The time evolution of the chain length distribution during the polymer breakage can be mathematically described by a population balance equation.In the so-called inverse problem, experimentally measured distributions are used to estimate the parameters of the population balance, such as the distribution of breakage rate along the chain and as function of the chain length. The inverse problem is known to be an ill-conditioned numerical problem. An algorithm previously developed in the literature for liquid droplet breakage in liquid emulsions, based on the concept of self-similarity of the distributions, was adapted and applied in the present work for the problem of polymer scission during polymer degradation. Nestes estudos têm se observado que, para um tempos longos (t→∞), a distribuição atinge o estado estacionário sem ocorrer mais mudanças. Para uma fragmentação binária, dois fragmentos por partículas, a restrição acima é simplificada. Sendo equivalente a uma taxaUma expressão para a taxa, em que as partículas de tamanho v são formadas devido à quebra, pode ser deduzida para um caso simples de quebra binária: A taxa de geração de partículas de tamanho v é igual à soma de todos os tamanhos maiores que v, visto que, partículas menores são formadas pela quebra, de partículas maiores: Com as equações (1.1.2) e (1.1.3), podemos escrever um balanço populacional de quebra em (1.1.5) ou, de outro modo, uma formulação para o caso da quebra dominante, como descrito por PATRUNO et al. (2009). Este balanço só será apresentado mais adiante, após outras considerações.Os métodos de diferença finita no domínio das partículas são usados com muita freqüência na literatura para a discretização, como nos ensina RIBEIRO et al. (1995).Recentemente para a solução do BP foi desenvolvido no trabalho de HAGESAETHER; JAKOBSEN; SVENDSEN (2002) Dessa forma, a função de quebra também será discretizada, e resultando em β(v i ,v j ). O sucesso no uso das equações fundamentais de balanço populacional para predizer quantitativamente a distribuição de partículas em um sistema em que a quebra é dominante requer duas funções chave: a taxa de quebra que corresponde a um valor para cada volume 5 de partícula, e a distribu...

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Kinetic Studies on the Acid Hydrolysis of Dextran

Cited by 117 publications

References 9 publications

Model for Random Hydrolysis and End Degradation of Linear Polysaccharides: Application to the Thermal Treatment of Mannan in Solution

Model for Random Hydrolysis and End Degradation of Linear Polysaccharides: Application to the Thermal Treatment of Mannan in Solution

Analytical solutions to fragmentation equations with flow

Estudo do problema inverso em balanço populacional aplicado a degradação de polímeros.

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