Kinetics of Wheat Straw Delignification in Soda and Kraft Pulping

The present investigation undertook a systematic investigation of the molecular weight (MW) of kraft lignins throughout the pulping process to establish a correlation between MW and lignin recovery at different extents of the kraft pulping process. The evaluation of MW is crucial for lignin characterization and utilization, since it is known to influence the kinetics of lignin reactivity and its resultant physicochemical properties. Sweetgum and pine lignins precipitated from black liquor at different pHs (9.5 and 2.5) and different extents of kraft pulping (30–150 min) were the subject of this effort. Gel permeation chromatography (GPC) was used to deter- mine the number average molecular weight (Mn), mass average molecular weight (Mw), and polydispersity of the lignin samples. It was shown that the MW of lignins from both feedstocks follow gel degradation theory; that is, at the onset of the kraft pulping process low molecular weightlignins were obtained, and as pulping progressed, the molecular weight peaked and subsequently decreased. An important finding was that acetobromination was shown to be a more effective derivatization technique for carbohydrates containing lignins than acetylation, the technique typically used for derivatization of lignin.

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Effect of alkaline hydrogen peroxide treatment on cell wall composition and digestion kinetics of sugarcane residues and wheat straw

Journal of Animal Science ◽

10.2527/1992.7092877x ◽

1992 ◽

Vol 70 (9) ◽

pp. 2877-2884 ◽

Cited By ~ 26

Author(s):

M. Amjed ◽

H. G. Jung ◽

J. D. Donker

Keyword(s):

Hydrogen Peroxide ◽

Cell Wall ◽

Wheat Straw ◽

Cell Wall Composition ◽

Alkaline Hydrogen Peroxide ◽

Hydrogen Peroxide Treatment ◽

Digestion Kinetics ◽

Kinetics Of

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Evidence for the formation of lignin-hexenuronic acid-xylan complexes during modified kraft pulping processes

Holzforschung ◽

10.1515/hf.2006.022 ◽

2006 ◽

Vol 60 (2) ◽

pp. 137-142 ◽

Cited By ~ 11

Author(s):

Zhi-Hua Jiang ◽

Jean Bouchard ◽

Richard Berry

Keyword(s):

Acid Hydrolysis ◽

Kraft Pulp ◽

Kraft Pulping ◽

Order Kinetic ◽

Kraft Pulps ◽

First Order ◽

Pseudo First Order ◽

Hexenuronic Acid ◽

Kinetics Of ◽

Hydrolysis Of

Abstract The finding that hexenuronic acid (HexA) groups can be selectively removed from kraft pulps by acid hydrolysis has provided an opportunity to reduce bleaching chemicals. However, there is evidence that the acid hydrolysis is not uniform. In this report, we evaluate the kinetics of acid hydrolysis of HexA in a xylan sample enriched with HexA, a conventional kraft pulp, and three modified kraft pulps: anthraquinone pulp (Kraft-AQ), polysulfide pulp (PS), and polysulfide-anthraquinone pulp (PS-AQ). We found that HexA present in the xylan and conventional kraft pulp behaved similarly toward the acid hydrolysis throughout. On the other hand, HexA present in the Kraft-AQ, PS-AQ and PS pulps was heterogeneous toward acid hydrolysis and the reaction can be separated into two pseudo-first-order kinetic phases, each of which has a different rate constant. The kinetic data provide evidence for the formation of lignin-HexA-xylan complexes during modified kraft pulping processes.

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Effect of saponins and plant extracts containing saponins on the recovery of ammonia during urea-ammoniation of wheat straw and fermentation kinetics of the treated straw

The Journal of Agricultural Science ◽

10.1017/s0021859699006334 ◽

1999 ◽

Vol 132 (3) ◽

pp. 313-321 ◽

Cited By ~ 17

Author(s):

H. P. S. MAKKAR ◽

E. M. AREGHEORE ◽

K. BECKER

Keyword(s):

Wheat Straw ◽

Crude Protein ◽

Water Extract ◽

Ammonia Nitrogen ◽

Gas Production ◽

Metabolizable Energy ◽

Urea Nitrogen ◽

Quillaja Saponaria ◽

Yucca Schidigera ◽

Kinetics Of

Saponins of Quillaja saponaria bark and the water extract obtained on homogenization of Yucca schidigera plants were used during urea-ammoniation to reduce ammonia loss. In Expt 1, chaffed wheat straw (2–5 cm length) was urea-ammoniated (50 g kg−1 urea, 400 g kg−1 moisture) for 25 days at 37°C with and without Quillaja saponins (QS) or Yucca plant homogenate, YPH (corresponding to 1 and 2 g kg−1Yucca powder). The crude protein (CP) content of untreated straw was 34 g kg−1. After 25 days, CP values of 90 g kg−1 (urea; no saponin), 82 and 86 g kg−1 (urea+QS at 1 and 2 g kg−1) and 102 and 92 g kg−1 (urea+YPH at 1 and 2 g kg−1) were obtained. The ammonia-nitrogen bound (as percentage of urea-nitrogen added) to straw after the treatment was 39 (urea; no saponin), 33 and 36 (urea+QS at 1 and 0·2 g kg−1), and 47 and 40 (urea+YPE at 1 and 2 g kg−1). As the extent of ammonia bound to straw was higher with Yucca plant powder, especially at 1 g kg−1, Yucca plant powder at 0·75 and 1 g kg−1 was used in Expt 2. In Expt 1, the Yucca plant extract was used after homogenization of the Yucca plant powder, which is not feasible at farm level. Therefore, two simpler approaches (overnight soaking of the powder in water (Yucca powder extracted, YPE) and mixing of Yucca powder with the straw followed by urea-ammoniation (Yucca powder, YP) were used besides homogenization. Otherwise, conditions for the urea-ammoniation treatment were similar to those in Expt 1. The ammonia–nitrogen bound (as percentage of urea-nitrogen added) to the straw varied from 47 to 54% in the presence of the Yucca plant powder, which was substantially higher than that observed in its absence (38%). The ammonia-binding efficiency of Yucca plant powder to the straw was highest at 1 g kg−1. Among the three methods tried, addition of the Yucca powder to straw followed by treatment with urea was the easiest, and the binding efficiency was similar to that observed when using the powder after homogenization. In both experiments, the true dry matter- and NDF-digestibilities, calculated organic matter digestibility and metabolizable energy, as well as rate and potential extent of gas production, were significantly higher (P<0·05) in the treated straw than in the untreated straw. These values were affected neither by the source of the saponins nor the manner in which the Yucca powder was applied.

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Equilibrium and kinetics of biosorption of cadmium(II) and copper(II) ions by wheat straw

Bioresource Technology ◽

10.1016/j.biortech.2008.05.031 ◽

2009 ◽

Vol 100 (1) ◽

pp. 211-219 ◽

Cited By ~ 237

Author(s):

V.B.H. Dang ◽

H.D. Doan ◽

T. Dang-Vu ◽

A. Lohi

Keyword(s):

Wheat Straw ◽

Equilibrium And Kinetics ◽

Kinetics Of

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Effect of ammonia treatment of wheat straw with or without supplementation of potato protein on intake, digestion and kinetics of comminution, rumen degradation and passage in steers

British Journal Of Nutrition ◽

10.1079/bjn19940016 ◽

1994 ◽

Vol 72 (1) ◽

pp. 147-165 ◽

Cited By ~ 6

Author(s):

S. J. Oosting ◽

P. J. M. Vlemmix ◽

J. Van Bruchem

Keyword(s):

Organic Matter ◽

Pore Size ◽

Wheat Straw ◽

Latin Square ◽

Potato Protein ◽

Faecal Excretion ◽

Rumen Degradation ◽

Fractional Rate ◽

Beet Pulp ◽

Kinetics Of

Untreated wheat straw (UWS) or ammoniated wheat straw without (AWS) or with (AWSP) a supplement of potato protein of a low rumen degradability was fed to three steers according to a 3 × 3 Latin square design. All rations were supplemented with sugar-beet pulp and minerals. Voluntary organic matter intake (OMI, g/kg0.75 per d) was 67.8, 76.0 and 80.1 for whole rations (51.1, 59.7 and 59.2 for straw) for UWS, AWS and AWSP respectively, which was significantly higher for AWS and AWSP than for UWS. Organic matter digestibility (OMD, g/kg) was 561, 596 and 625 for the respective rations UWS, AWS and AWSP, also significantly higher for AWS and AWSP than for UWS. The increased voluntary intake and digestion of ammoniated wheat-straw-based rations were associated with a significantly higher potentially degradable fraction (D) of neutral detergent fibre (NDF) in offered straw (556 and 661 g/kg for untreated and ammoniated wheat straw respectively) and in the rumen pool (469, 555 and 554 g/kg for UWS, AWS and AWSP respectively). Isolated small rumen particles (retained on sieves with a pore size < 1.25 and > 0.041 mm) had a significantly lower D of NDF (average 588 g/kg) than isolated large rumen particles (average 663 g/kg). Fractional rates of degradation of NDF did not differ significantly either between untreated and ammonia-treated wheat straw offered (2.9 and 2.6%/h respectively) or between rumen pools (1.8, 1.7 and 2.1 %/h for UWS, AWS and AWSP respectively). Rations based on ammoniated wheat straw had a significantly higher rumen NH3-N concentration than UWS. Although the rumen pool size of total contents differed significantly between treatments, those of dry and organic matter and of cell wall constituents were not significantly different. The proportion of rumen dry matter passing through a sieve with a pore size of 1.25 mm averaged 0.684 over rations (not significantly different between rations). Daily rumination (96 min) and eating (52 min) times/kg NDF ingested did not differ between rations. The rate of comminution of large particles estimated from the disappearance of indigestible NDF in large rumen particles from the rumen of animals without access to feed was 4.1, 6.3 and 7.1 %/h for UWS, AWS and AWSP respectively. These values were not significantly different. The fractional rate of passage estimated from the faecal excretion of Cr-NDF was 5.4, 6.1 and 6.3%/h for UWS, AWS and AWSP respectively (significantly higher for AWS and AWSP than for UWS) but the turnover rate of indigestible NDF did not differ between treatments.

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Study on Preparation of Dissolving Grade Pulp and its Kinetics of Prehydrolysis

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.233-235.1479 ◽

2011 ◽

Vol 233-235 ◽

pp. 1479-1484

Author(s):

Ke Xin Hu ◽

Guang Ming Zeng ◽

Hai Chao Zhang

Keyword(s):

Quality Standards ◽

Kraft Pulping ◽

Cooking Time ◽

Bleaching Process ◽

First Order ◽

Pseudo First Order ◽

P Factor ◽

Prehydrolysis Kraft ◽

Kinetics Of ◽

Pulp Production

The possibilities of dissolving grade pulp production from reed were investigated in this paper. Two – stage prehydrolysis – kraft pulping and CEHA bleaching process of reed for preparation of dissolving grade pulp were studied in laboratory. The optimum cooking and bleaching conditions were found out. The mechanism and its kinetics of reed in prehydrolysis process were also discussed. The results showed that under the laboratory conditions the rate for removal of materials at about 175°C follow approximately a pseudo first order law with two distinct phrases: the bulk removal and the residual removal of the materials. The prehydrolysis-factor (P-factor) was established. The advantage of using P-factor is predict compensating adjustments in cooking time and/or temperature to give the same degree of pulping and to produce pulp with predetermined characteristics. It is found that three distinct delignification rate stages about 75% of pentosans and about 50% of lignin were removed. A CEHA four stage bleaching is used for dissolving grade pulp. Total chlorine charge in bleaching is 6% (to oven-dry pulp). The results show that all of the indices fitted the quality standards of dissolving grade pulp.

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Kinetics of ASAM and Kraft Pulping of Eucalypt Wood (Eucalyptus globulus)

Holzforschung ◽

10.1515/hf.2002.014 ◽

2002 ◽

Vol 56 (1) ◽

pp. 85-90 ◽

Cited By ~ 18

Author(s):

Isabel Miranda ◽

Helena Pereira

Keyword(s):

Eucalyptus Globulus ◽

Initial Period ◽

Reaction Times ◽

Kraft Pulping ◽

Kraft Pulps ◽

Final Phase ◽

Lower Mass ◽

Lignin Removal ◽

Mass Losses ◽

Kinetics Of

Summary The kinetics of ASAM and kraft pulping of eucalypt wood (Eucalyptus globulus) were studied in relation to delignification and polysaccharide removal. In comparison to kraft, ASAM pulping had lower mass losses and delignification for the same temperature and reaction times (59.2% at Kappa 25 vs 50.0% at Kappa 17, at 180°C). The ASAM pulps have a higher brightness. ASAM pulping had a short initial period with no mass loss and lignin removal, followed by two reaction phases: a main phase where 61% of lignin was removed (at 180°C) and a subsequent final phase. In comparison to kraft, the main delignification rates of ASAM pulping were approximately 2.5 slower (at 180°C, −1.8 × 10−2 min−1 for ASAM and −4.2 × 10−2 for kraft pulping), and the calculated Arrhenius activation energies were higher (132.4 kJ mol−1 and 83.5 kJ mol−1, respectively). The loss of cellulose was relatively small (12.5 %) and lower than in kraft pulps.

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