A Model for Chlorine Dioxide Delignification of Chemical Pulp

Abstract

A phenomenon based model for chlorine dioxide delignification of chemical pulp is introduced. The pulp suspension environment is modeled using the concept of two liquid phases, one inside and the other external to the fiber wall. Physico-chemical processes taking place during delignification are implemented with thermodynamic, mass transfer and reaction kinetic models. A broad library of chemical reactions is introduced. Inclusion of each reaction is justified. The model response is tested against experimental laboratory delignification results (o-delignified birch pulp). The experimental data consists of kappa number, hexenuronic acid, inorganic oxy-chlorine compound, and organochlorine (AOX, OX) measurements at several time points during five delignification experiments. The model predictions are mainly in good agreement with the experimental results. The predictions regarding hypochlorous acid driven processes (HexA removal, organochlorine formation, chlorite and chlorate concentration) are somewhat incoherent, indicating that knowledge regarding the intermediately formed hypochlorous acid is presently insufficient.     

Introducing Glycolinkers for the Functionalization of Cytotoxic Drugs and Applications in Antibody–Drug Conjugation Chemistry

Antibody–drug conjugates (ADCs) are promising alternatives to naked antibodies for selective drug‐delivery applications and treatment of diseases such as cancer. Construction of ADCs relies upon site‐selective, efficient and mild conjugation technologies. The choice of a chemical linker is especially important, as it affects the overall properties of the ADC. We envisioned that hydrophilic bifunctional chemical linkers based on carbohydrates would be a useful class of derivatization agents for the construction of linker–drug conjugates and ADCs. Herein we describe the synthesis of carbohydrate‐based derivatization agents, glycolinker–drug conjugates featuring the tubulin inhibitor monomethyl auristatin E and an ADC based on an anti‐EGFR antibody. In addition, an initial in vitro cytotoxicity evaluation of the individual components and the ADC is provided against EGFR‐positive cancer cells.     

Effect of chemical modification of oil fly ash and compatibilization on the rheological and morphological properties of low‐density polyethylene composites

In this study, the effect of oil fly ash (OFA), a by‐product of oil fuel power plants, on the rheological and morphological behavior of low‐density polyethylene (LDPE) is investigated. As received and acid‐functionalized OFA (COOH‐OFA) are used to examine the effect of surface modification of OFA on polymer–filler composites. LDPE/OFA composites were prepared by melt mixing with filler loading in the range 1–10 wt %. The results are compared with pure LDPE. The effect of polyethylene‐grafted‐maleic anhydride (PE‐g‐MA) as a compatibilizer was also studied. Both viscous and elastic properties of composites increased with OFA loading especially at low frequency. The surface modification of OFA has influenced the properties of OFA. As‐received OFA showed some agglomeration at high loading that resulted in two‐phase system as described by scanning electron microscopy (SEM) and Cole–Cole plot. Field emission‐SEM (FE‐SEM) images showed improvement in the dispersion of COOH‐LDPE/OFA composites. In addition, the surface modification reduced the size of agglomeration. In general, the COOH modification of OFA improved both the dispersion and rheological properties of OFA. With chemical modification, the concentration of the filler can be increased to 10% without compromising the properties of the composites. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

The effect of oxygen and the reduction temperature of the Pt/Al2O3 catalyst in enantioselective hydrogenation of 1-phenyl-1,2-propanedione

The effect of oxygen and catalyst reduction temperature in enantioselective hydrogenation of 1-phenyl-1,2-propanedione over commercial Pt/Al₂O₃ catalyst was investigated. Dichloromethane was used as solvent. The catalyst was modified in situ with (−)-cinchonidine. Relatively high enantiomeric excesses (65%) of (R)-1-hydroxy-1-phenyl-2-propanone were obtained with the solvent used as received, i.e. containing traces of dissolved oxygen and other impurities. Dichloromethane dissociated partially on the Pt/Al₂O₃ surface causing desorption of methane, ethene and HCl from the catalyst during TPD according to mass spectrometric analysis. Under anaerobic conditions the reaction rate was low giving only about 40% enantiomeric excesses of (R)-1-hydroxy-1-phenyl-2-propanone. When injecting 5 mm³ of oxygen into the reactor a beneficial effect was observed (i.e. higher reaction rate and enantiomeric excess) in comparison with anaerobic conditions. Poisoning effect of oxygen was observed when injecting 500 mm³ of oxygen into the reactor. Effect of catalyst reduction temperature was studied at three different temperatures (170, 400 and 455°C). Highest reaction rates and enantiomeric excesses were obtained with the catalyst reduced at 400°C. Methane was desorbed from the catalyst at temperatures between 263 and 383°C which could be the explanation for the lower activity of the catalyst reduced at 170°C. It was demonstrated that small amounts of oxygen can have a beneficial effect in enantioselective hydrogenation of 1-phenyl-1,2-propanedione and also that catalyst reduction temperature plays an important role in obtaining high enantiomeric excesses.     

Optimization of nuclear reactor strategies under uncertainty

Operations research is applied to analysing uncertainties in the selection of nuclear reactor types. Dynamic programming methods have been extended to account for uncertain decision factors by including in the objective function a variance-related uncertainty factor as well as expected cost values. A technique is also described for obtaining total cost probability distributions. A case study is presented which uses the method to analyze a long-term planning problem for a given electric utility system. This problem is also solved by using fuzzy programming methods.     

Unique Decipherability in the Monoid of Languages: An Application of Rational Relations

We attack the problem of deciding whether a finite collection of finite languages is a code, that is, possesses the unique decipherability property in the monoid of finite languages. We investigate a few subcases where the theory of rational relations can be employed to solve the problem. The case of unary languages is one of them and as a consequence, we show how to decide for two given finite subsets of nonnegative integers, whether they are the nth root of a common set, for some n≥1. We also show that it is decidable whether a finite collection of finite languages is a Parikh code, in the sense that whenever two products of these sets are commutatively equivalent, so are the sequences defining these products. Finally, we consider a nonunary special case where all finite sets consist of words containing exactly one occurrence of the specific letter.     

Extension of the decidability of the marked PCP to instances with unique blocks

In the Post Correspondence Problem (PCP) an instance (h,g)$(h,g)$ consists of two morphisms h$h$ and g$g$, and the problem is to determine whether or not there exists a nonempty word w$w$ such that h(w)=g(w)$h\left(w\right)=g\left(w\right)$. Here we prove that the PCP is decidable for instances with unique blocks using the decidability of the marked PCP. Also, we show that it is decidable whether an instance satisfying the uniqueness condition for continuations has an infinite solution. These results establish a new and larger class of decidable instances of the PCP, including the class of marked instances.