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Dissertation zugänglich unter
On the Analysis of Alkaline Sulfite Pulps by means of Pyrolysis : Gas chromatography/Mass spectrometry
Über die Analyse von alkalischen Sulfit-Zellstoffen mittels Pyrolyse : Gaschromatographie/Massenspektrometrie
Dokument 1.pdf (1.798 KB)
Pyrolyse , Gaschromatographie , Massenspektrometrie , Zellstoff , Cellulose , Lignin , Hauptkomponentenanalyse , Delignifizierung , Sulfitzellstoff
Freie Schlagwörter (Deutsch):
Freie Schlagwörter (Englisch):
pyrolysis , GC/MS , sulfonic acid groups , pulp , PCA
Patt, Rudolf (Prof. Dr.)
Tag der mündlichen Prüfung:
Kurzfassung auf Englisch:
Amongst the world-wide developed pulping technologies the kraft process is by far the most dominant process for the production of bleachable pulp grades. Because of the high strength properties of the produced pulps and the ability to pulp basically all hard- and softwoods the kraft process has outperformed the former leading acid sulfite process. However, pulping processes based on sulfite have also distinct advantages. Compared to the strongly alkaline kraft process, sulfite pulping is highly adjustable since it can be applied over a wide pH range and allows the production of various pulp grades. For example, the ASAM process developed by the work group of Professor Patt at the University of Hamburg received considerable attention in the 1980s - 90s due to the outstanding properties of the resultant pulps. Additionally the AS/AQ (alkaline sulfite anthraquinone) process was considered by some authors as a promising alternative to kraft pulping. But for several reasons, which shall not be discussed here, none of these processes attained commercial importance. Owing to the poor market acceptance of the AS/AQ process, only a handful of studies have been published on this sulfite based process, with few extending beyond process optimization coupled with standard analytical methods. In a later work it was found that a modification of the AS/AQ process leads to a significant improvement, yielding pulps comparable with kraft pulps, particularly when softwood was used as feedstock. The main modification was the reduction of the NaOH charge in the initial stage, while raising the NaOH concentration after the heating-up phase by addition of a second charge.
In the presented work the pulps generated by the aforementioned modified AS/AQ process were studied in detail by means of pyrolysis - gas chromatography/mass spectrometry (Py-GC/MS). The starting point was the execution of two delignification series, one without and the other with modification. One objective was to find the compositional differences responsible for the superior properties of the pulps produced by the modified process. Although standard analytical methods including the quantification of sulfonic acid groups revealed important differences between the two delignification series, further details in particular about structural features of lignin were of interest.
Py-GC/MS was initially only intended to be tested as a novel rapid method to quantify sulfonic acid groups in pulp. But it was soon realized that Py-GC/MS had the potential to provide chemical fingerprints containing far more details on the samples, especially in combination with chemometric analyses. Previous studies have shown that the constituents of lignocellulosic materials could be distinguished and quantified with the aid of chemometrics. However, in almost all studies only the major or well identified pyrolysis products were taken into account even though some of the several hundreds of further minor products contained in the pyrolysis fingerprints may provide valuable information. Nowadays, the computational advancement enables the processing of high amounts of data. In this work the focus was on the task of capturing as much information from the pyrolysis fingerprints of the AS/AQ pulps as possible. Within this scope much effort has been put on the pre-processing of data in a semi-automated manner to cope with the high complexity and to avoid error-prone manual evaluation. Eventually the pre-processed data was successfully evaluated by exploratory chemometric approaches revealing details of the residual lignin composition in AS/AQ pulps.