Structured catalytic reactor for VOC combustion

VOC emission has recently become a challenge for environmental protection. Catalytic combustion seems a promising method of VOC removal, however, there are still more specific demands concerning the process. The reactor design has to assure enhanced transfer properties accompanied by low flow resistance to reduce the pumping costs. Neither the packed beds nor the classic ceramic monoliths are able to fulfil the requirements. To solve the problem we propose a wire gauze structure composed of several gauze sheets staked. A number of mass transfer and flow resistance experiments were performed for two gauze types and correlations were derived for the Sherwood number and the friction factor. The results were found to be in a reasonable agreement with the literature available. The studied gauze structures were compared with a classic monolith for the assumed case study. The calculated length of the gauze structured reactor was significantly shorter, up to ten times, when compared with a classic ceramic monolith, but the pressure drop was higher

Far field combined AFM and micro-Raman imaging for characterisation of surface of structured catalysts : example of Pd Doped CoOxCoO_x catalysts on precalcined kanthal steel

A coupled AFM-Raman system was used to study the surface heterogeneity of catalytic materials at various stages of their preparation. The catalysts chosen for the analyses were cobalt oxide with and without palladium dopant deposited on surface of pre-calcined steel carriers. Steel carriers are surveyed here in terms of their application as fillers for structured reactors for the catalytic combustion of volatile organic compounds. Upon steel precalcination stage the interfaced AFM-Raman and in situ Raman analyses revealed the evolution of alumina and iron oxide phases on the surface with their final stable forms found as being α-Al_{2}O_{3} and α-Fe_{2}O_{3}. Upon catalyst layering stage AFM-Raman mapping evidenced uniform coverage of precalcined steel carrier with cobalt spinel oxide Co_{3}O_{4}. For the doped catalyst except Co_{3}O_{4} palladium(II) oxide grains were also found on the surface. The differences in the composition of cobalt catalysts were correlated with the differences in their catalytic activity

Reflective and photoacoustic infrared spectroscopic techniques in assessment of binding media in paintings

This study proposes a method to estimate the lipid content in binding media in paintings that can be used at any laboratory equipped with an infrared spectrometer. The lipid content estimator, termed greasiness index (GI), is defined as a ratio of lipid \nu(C=O) and protein amide I bands at 1743 and 1635 cm−1, respectively. Three Fourier transform infrared (FTIR) sampling techniques were evaluated for GI determination: reflective attenuated total reflection-ATR, specular reflection microscopy-\muSR and photoacoustic-PAS. A set of model painting samples containing three tempera binding media (casein, egg, egg + oil), seven pigments and one varnish type were used in the study. Multivariate analysis was used to evaluate the resulting data. A good reproducibility of GI was obtained by ATR and PAS but not with \mu SR. The discriminative power of the technique is higher for unvarnished samples, but, generally, the GI estimator can be used for the categorisation of binding media in large populations of painting samples analysed with the same FTIR technique (sampling technique, detection, etc.)

Prospective catalytic structured converters for NH3−SCRNH_3-SCR of NOxNO_x from biogas stationary engines : in situ template-free synthesis of ZSM-5 Cu exchanged catalysts on steel carriers

The main objective of this study is to develop highly active catalyst and its preparation method that would meet the requirements of steel carriers for short- channel structured converters for NO x abatement from stationary biogas engines. The in situ synthesis was applied to deposit a series of Cu-exchanged MFI zeolite (ZSM-5) on kanthal sheets. The samples differ in preparation con- ditions: organic template assisted and template-free syn- thesis, Si/Al ratio and catalyst carrier pretreatment (calcined vs. non-calcined). Dip-coating method was used as a reference to compare loading efficiency. In order to evaluate preparation quality and purity of resulting struc- ture the samples were examined by XRD and SEM/EDS at various stages of preparation. For the assessment of mechanical endurance of the deposited catalyst layers the ultrasonication method was used. The results demonstrated high depositing efficiency of the in situ synthesis as well as high activity and selectivity of the Cu-exchanged MFI samples prepared without costly organic template

Size exclusion chromatography for analyses of fibroin in silk : optimization of sampling and separation conditions

A direct goal of this paper was to improve the methods of sample preparation and separation for analyses of fibroin polypeptide with the use of size exclusion chromatography (SEC). The motivation for the study arises from our interest in natural polymers included in historic textile and paper artifacts, and is a logical response to the urgent need for developing rationale-based methods for materials conservation. The first step is to develop a reli- able analytical tool which would give insight into fibroin structure and its changes caused by both natural and arti- ficial ageing. To investigate the influence of preparation conditions, two sets of artificially aged samples were pre- pared (with and without NaCl in sample solution) and measured by the means of SEC with multi angle laser light scattering detector. It was shown that dialysis of fibroin dissolved in LiBr solution allows removal of the salt which destroys stacks chromatographic columns and prevents reproducible analyses. Salt rich (NaCl) water solutions of fibroin improved the quality of chromatograms

Short-channel structured reactor as a catalytic afterburner

Short-channel structures of triangular and sinu- soidal channel cross-sectional shape were examined exper- imentally to find their heat (or mass) transfer and flow friction (flow resistance) characteristics. A particular emphasis was placed on influence of the channels length (referred to its hydraulic diameter) on transport and hydro- dynamic characteristics. The transport and friction proper- ties were correlated in terms of dimensionless channel length with satisfactory accuracy. The dimensionless channel length was proved to be a key factor that determines the transport and friction coefficients. Comparison with ceramic monolith has shown possibility of using the struc- tures in automotive catalytic converters

Molecular degradation of ancient documents revealed by 1H^1H HR-MAS NMR spectroscopy

For centuries mankind has stored its knowledge on paper, a remarkable biomaterial made of natural cellulose fibers. However, spontaneous cellulose degradation phenomena weaken and discolorate paper over time. The detailed knowledge of products arising from cellulose degradation is essential in understanding deterioration pathways and in improving durability of cultural heritage. In this study, for the first time, products of cellulose degradation were individually detected in solid paper samples by means of an extremely powerful proton HR-MAS NMR set-up, in combination to a wise use of both ancient and, as reference, artificially aged paper samples. Carboxylic acids, in addition to more complex dicarboxylic and hydroxy-carboxylic acids, were found in all samples studied. Since these products can catalyze further degradation, their knowledge is fundamental to improve conservation strategies of historical documents. Furthermore, the identification of compounds used in ancient production techniques, also suggests for artifacts dating, authentication and provenance

Experimental and theoretical study of the yellowing of ancient paper

Paper is the most widely used writing support due to the remarkable properties of its principal component - cellulose - one of the most abundant biomaterials present on Earth. However, due to the complexity of the material, an exhaustive picture of its degradation pathways is still missing. In this paper, we will present recent results and progresses obtained in the comprehension of the role of cellulose oxidation in the yellowing of ancient paper. Visible and ultraviolet spectra of cellulose in ancient paper samples and reference modern samples artificially aged have been interpreted with the aid of ab-initio Time-Dependent Density Functional Theory calculations. Through the comparison of measured and calculated absorption spectra, several oxidized forms of cellulose polymers, acting as chromophores, and responsible for ancient paper yellowing were identified. The relative concentration of ketones and aldehydic groups depends on the environmental conditions in which samples were stored along their life