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  • Author: Ali Ghasemian x
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Abstract

In this study, the effect of clinoptilolite dealumination on the total oxidation of toluene was reported for the first time. To avoid excess decrease of catalyst crystallinity, chemical modification of zeolite was carried out using a mild acid like oxalic acid. The catalysts were characterized by XRD, XRF, SEM, BET and TPD analyses. It was found that dealumination resulted in a significant enhancement of toluene conversion when 0.050 M acid oxalic was used for a treatment period of 2 h. Dealumination substantially changed the distribution of the concentration of acid sites of different strength and increased the surface area and porosity, so that the temperature corresponding to the maximum conversion shifts around 50 °C towards lower temperatures (in case of CLP 050). The effect of dealumination on the activity of the zeolite samples and the total oxidation of toluene was discussed in terms of Si/Al ratio, crystallinity, distribution of acid site strength and textural characteristics of the samples.

Abstract

A cellulose-PCC composite was synthesised using the CaCl2 reaction with dimethyl carbonate (DMC) under alkaline conditions and in the presence of cellulose fibrils made from highly refined bleached softwood kraft pulp. The results showed that the ash content in the synthesised cellulose-PCC composite increased by increasing the reaction temperature from 25°C to 70°C, the reaction time from 3.5 min to 7.5 min and the cellulose consistency from 0.05 % to 0.1 %. The ratio of calcium carbonate generated to the calcium chloride used initially was increased by increasing the reaction temperature and time. The XRD pattern of the cellulose-PCC composite indicated no modification micro-crystal habit of the deposited CaCO3. The SEM images showed that the cellulose-PCC composite filler had a rhombohedral shape as opposed to the scalenohedral shape of common PCC. The paper filled with the cellulose-PCC composite had much higher bursting and tensile strengths, at a tearing strength similar to common PCC.

Abstract

Nano-lignocellulose (NLC) and lignin-free nanocellulose (nano-holocellulose, NHC) were used in paper coating to investigate their effect on coating layer quality and offset printing. The NLC was produced by microfluidisation of unbleached secondary fibres while the reference NHC was obtained from the same fibre source after lignin removal (OHEPH bleaching), following the same mechanical process. TEMPO-mediated oxidation of the fibres prior to microfluidisation was applied to increase the electrostatic charge and hydrophilicity of the nanofibrils. The coatings, displaying given surface morphology and energy, were applied on Kraft, printing-grade papers at three grammage levels. The structure of the coated and uncoated (reference) papers were accessed (SEM and AFM) and IGT printing was carried out to determine the print density, print gloss, rub-off resistance, surface energy, roughness, ink transfer, dry pick resistance, water interference and set-off. The results highlight the important effect of residual lignin or type of nanocellulose on the coating layer and the development of offset printing properties. It was observed that roughness was a key factor leading to a deterioration of the print properties, predominantly affecting the NLC coating. Considering the lower hydrophilicity of NLC, an alternative dispersion with water-alcohol mixtures is proposed. By using this dispersing medium, tailorable surface coverage, surface smoothness, ink acceptance and improved printability was achieved. We show that under these conditions and compared to NHC, NLC is equally effective as a coating layer.