Microfibrillated cellulose production as alternative of Eucalyptus sawdust valorization in a biorefinery scheme

EHMAN, N.; VEGA, B.; VALLEJOS, M.E.; IGLESIAS, M.C.; AREA, M.C.; FELISSIA, F.E.; PERESIN, M.S.

XXIV TECNICELPA 2021 | XI CIADICYP 2021

Conferencia; XXV TECNICELPA ? International Forest, Pulp and Paper Conference and XI CIADICYP ? Iberoamerican Congress on Pulp and Paper Research; 2021

TECNICELPA -RIADICYP

This work evaluatesmicrofibrillated cellulose production from an eucalyptus sawdust pulp (MFCes), obtainedby a sequence involving a soda treatment and oxidative bleaching, to beincluded in a biorefinery scheme. Eucalyptus sp. sawdust, obtained from asawmill-carpentry, was treated with 22% NaOH on oven-dry wood (O.D.), with aliquid/solid ratio of 6/1, at 170°C, for 60 min. The pulp was bleached byoxidative treatments using an O-Op sequence (oxygen and oxygen-H2O2).Microfibrillated cellulose elaborated from a commercial eucalyptus, elementalchlorine-free bleached (ECF) kraft pulp (MFCcp), was used as a reference.Both pulps, at 2% consistencyand pH 7, were mechanically fibrillated using a Supermasscolloider frictiongrinder MKZA10-15J (Masuko Sangyo Co.). The degree of fibrillation was assessedby the determination of transmittance, turbidity, and viscosity at 0.5%consistency. Degree of polymerization, crystallinity, surface charge bycationic demand, Fourier Transform Infrared spectroscopy (FT-IR),thermogravimetric analysis (TGA), and surface free energy (SFE), were alsoperformed.Both pulps achieved a similardegree of fibrillation by mechanical treatment using two-disc sizes and differentgaps (MFCes: 9 passes and MFCcp: 10 passes). The fibrillation degree wassimilar for bothMFC suspensions. The transmittance and turbidity values were24.8% and 419 NTU for the MFCesand 21.9% and 495 NTU for the MFCcp.Transmittance values were lower than those obtained with MFC produced bychemical pretreatment (TEMPO oxidation) and colloidal grinder but similar tothat of MFC made by a disk refiner. The rheological behavior of both MFC wassimilar; the samples showed a thixotropic behavior and reached a constantviscosity at 12 rpm. The degree of polymerization was 800 and 1151 for theMFCes and MFCcp, respectively. The cristallinities were 64.0% and 58.0% forMFCcp and MFCes respectively. The decrease in crystallinity in the MFCes samplecan be due to the oxidative bleaching treatment, which mainly degrades theamorphous fractions such as the hemicelluloses.The SFE was 41.4% for the MFCesand 41.9% for the MFCcp. The surface charge was higher for the first (166.4µeq/g) than that of the second MFC (132.5 µeq/g). The thermal degradationprofiles of the MFC showed that most degradation events occur from 250°C to350°C corresponding to the degradation of cellulose (up to 350°C) andhemicelluloses (up to 273°C). However, these values were lower than thermaldegradation occurred in pulps (about 284°C to 376°C for eucalyptus sawdust pulpand 290°C-383°C for commercial eucalyptus pulp). The residual masses at 600°Cwere 21.7% and 19.8% for MFCes and MFCcp, respectively.In terms of properties, theobtained results allow concluding that it is possible to produce MFC from eucalyptussawdust processed by a soda treatment and oxidative bleaching, adequate to asmall scale biorefinery scheme.