Controlled accessibility Lewis acid catalysed thermal reactions of regenerated cellulosic fibres

Abstract

A combination of techniques have been used to characterise lyocell regenerated cellulose fibre subjected to low-moisture thermal-catalytic reactions with zinc chloride Lewis acid. Application from non-swelling ethanol reduces catalyst accessibility, but at high temperatures migration takes place through the internal fibre morphology. The extent of chain scission is reduced at lower temperatures, leading to a higher leveling-off degree of polymerisation (LODP). In contrast, application of zinc chloride from water results in a lower LODP, due to the more even distribution of catalyst. The weights of extractable polymer material increase according to two separate rate constants, following established semicrystalline models. A higher Arrhenius activation energy for chain scission is seen for zinc chloride application from ethanol, which may be due to the physical mobilisation of the cellulose polymer at high temperature, associated with a cellulose T g . This may also aid recrystallisation. Cellulose dehydration endotherms and pyrolysis exotherms are shifted to lower temperature for application of zinc chloride from ethanol compared to water, which may be the result of a higher local concentration of catalyst and a faster reaction onset.

The Reductive Dehydration of Cellulose by Solid/Gas Reaction with TiCl4 at Low Temperature: A Cheap, Simple, and Green Process for Preparing Anatase Nanoplates and TiO2/C Composites

“…The last possibility is the dehydration of cellulose, a known process that occurs at 200–250 °C for pure cellulose and at 180–190 °C in presence of metal salts like ZnCl 2 and MgCl 2 or CrCl 2 and RuCl 3 or SO 4 2− /M x O y systems . The presence of HCl, generated by the reaction between TiCl 4 and alcohol, is also a key.…”

“…The last possibility is the dehydration of cellulose, ak nown process that occurs at 200-250 8Cf or pure cellulose and at 180-190 8Ci np resence of metal salts like ZnCl 2 and MgCl 2 [5][6][7][8] or CrCl 2 and RuCl 3 [2] or SO 4…”

“…[1] This requires major chemical modifications of the cellulose structuret hrough isomerisation, CÀO cleavage and dehydration. To succeed in these transformations, different inorganic compounds like chromium salt [2,3] or super-acid system SO 4 2À /M x O y [4] have been successfully used as catalysts for the production of 5-hydroxymethyl-2-furfural.I n the same vein, the treatment of cellulose with metal likes ZnCl 2 and MgCl 2 [5][6][7][8] was reportedt ol ower the temperature of dehydration of cellulose (from 250 to 190 8C) with important consequence on fire retardancy,a nd thermal conversion into carbonf ibres and absorbent carbon.I tw as shown that these Lewis acids and their migration within the structureo fc ellulose can greatlyi mpactt he transformation of the cellulose, the weight loss and the structure upon pyrolysis. Finally,L ewis acids like nickel and iron salts were also investigated for the conversion of cellulose into biofuels and it was reported that ad ecrease of the fraction of condensable organicsa nd enhancement of the production of gases like hydrogen.…”

“…To succeed in these transformations, different inorganic compounds like chromium salt or super‐acid system SO 4 2− /M x O y have been successfully used as catalysts for the production of 5‐hydroxymethyl‐2‐furfural. In the same vein, the treatment of cellulose with metal likes ZnCl 2 and MgCl 2 was reported to lower the temperature of dehydration of cellulose (from 250 to 190 °C) with important consequence on fire retardancy, and thermal conversion into carbon fibres and absorbent carbon. It was shown that these Lewis acids and their migration within the structure of cellulose can greatly impact the transformation of the cellulose, the weight loss and the structure upon pyrolysis.…”

The Synthesis of a Macro-initiator from Cellulose in a Zinc-Based Ionic Liquid

“…This was believed to be the partial degradation of the MCC when it was dissolved in the zinc-based ionic liquid at a high temperature. The dissolved MCC underwent partially thermal depolymerization catalyzed by the Lewis acid catalyst of zinc chloride (Domvoglou et al 2010). According to the TGA data of MCC-BiB (2), the amount of BiB in MCC-BiB was 15.1% (wt) and 77.8% (wt) for amount of MCC.…”