Accelerated and Natural Aging of Cellulose-Based Paper: Py-GC/MS Method.

Samples of papers artificially (2 to 60 days) and naturally (10, 45, and 56 years) aged were studied by the Py-GC/MS method to identify decomposition products. Possible reaction scenarios for cellulose degradation were developed. One of the degradation products is acetic acid, which can (auto)catalyze the cleavage of cellulose ß(1→4)-glycosidic bonds of cellulose polymer chains. However, during 20 s of Py-GC/MS analysis, temperatures of up to 300 °C did not significantly increase or modify the formation of decomposition products of paper components. At 300 °C, the amount of several cellulose decomposition products increased regularly depending on the number of days of artificial aging and natural aging, demonstrated mainly by the generation of 2-furancarboxaldehyde, 5-hydroxymethylfurfural, and levoglucosan and its consecutive dehydration products. No correlation between the amount of lignin decomposition products and the time of aging was found when the pyrolysis was performed at 300 °C and 500 °C. Compounds present in the products of decomposition at 500 °C bear the imprint of the chemical composition of the sampled paper. Pyrograms taken at 300 °C using the Py-GC/MS method can give additional information on the changes in the chemical structure of paper during natural or artificial aging, mainly about the cleavage of ß(1→4)-glycosidic bonds during aging.

Nanomorphology of polymer frameworks and their role as templates for generating size-controlled metal nanoclusters.

The microporous (gel-type) functional resin co-poly-N,N-dimethylacrylamide (DMAA) (88 % mol)/methacrylic acid (MAA) (8 % mol)/N,N'-methylenebisacrylamide (MBAA) (4 % mol) (MPIF(H)) is employed as the hosting framework for the production of resin-supported Pd(0) nanoclusters. The obtained composite MPIF(-)Na(+)/Pd(0) is prepared upon reducing, in ethanol, MPIF(-)Pd(2+) (0.5), obtained upon previous homogeneous dispersion of "Pd(2+)" inside the resin particles (XRMA control) through ion-exchange. Metal nanoclusters appear to be size-controlled (2.0+/-0.2 nm) and are seen to reasonably fit the predominant resin "nanopores" diameter, determined in ethanol (3.2 nm) by means of inverse steric exclusion chromatography (ISEC).

Metal catalysis inside polymer frameworks: evaluation of catalyst stability and reusability.

The polymer framework of a resin-based catalyst built up with Pd nanoclusters (ca. 3 nm) dispersed inside the nanoporous domains of a thermally stable gel-type polyacrylic resin exhibits a good chemical stability under 5 bar H(2) at 40 degrees C for reasonable contact times. Chemical and physico-chemical integrity of the polymer framework are checked with a variety of instrumental analytical methods. Catalyst reusability turns out to be quite good.

Highly chemoselective hydrogenation of 2-ethylanthraquinone to 2-ethylanthrahydroquinone catalyzed by palladium metal dispersed inside highly lipophilic functional resins.

Most hydrogen peroxide is currently produced by the selective hydrogenation of 2-ethylanthraquinone (EAQ) to 2-ethylanthrahydroquinone (EAHQ), followed by treatment with dioxygen; this produces hydrogen peroxide and regenerates 2-ethylanthraquinone. We have developed novel catalysts for this process that are based on palladium supported on very lipophilic functional resins and that are able to promote a chemoselectivity for EAHQ slightly but definitely superior to that provided by an industrial catalyst under identical conditions. This finding demonstrates the potential of variations of the lipophilic/hydrophilic character of the support as a tool for the improvement of the chemoselectivity of resin-based metal catalysts.