On the formation of diphenylmethane structures in lignin under Kraft, soda and EMCC pulping conditions
Bibliographic record
Abstract
This paper describes our efforts focused at defining the formation of diphenylmethane moieties in lignin during conventional kraft and soda pulping conditions.This objective was realized by confirming, initially, the assignment of a 31 P NMR signal as being due exclusively to the presence of phosphitylated diphenylmethane (DPM) phenolic hydroxyl groups.More specifically, softwood milled wood lignin (Picea mariana) was subjected to kraft pulping conditions in the presence and absence of varying amounts of formaldehyde.After quantitative recovery of the lignin, the 31 P NMR spectra were recorded and the spectra revealed selective signal growth in the region confined between 142.8 and 144.3 ppm, in accordance with previous model compound work and detailed calculations based on the Hammett principles.To further substantiate our conclusions we also carried out two series of isothermal (120C) kraft and soda pulping experiments followed by quantitative determinations of the DPM moieties, and correlated our findings with the differences in chemistry known to occur between the two processes.Finally, diphenylmethane phenolic moieties were determined in isolated residual lignins from two western hemlock kraft pulp samples produced via an EMCC 7 mill protocol and a laboratory batch digester, respectively.These structures prevailed amongst the condensed phenolic units of the conventional pulp, providing additional evidence to support the fact that modern modified pulping technologies beneficially alter the structure of residual kraft lignin.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.002 |
| Scholarly communication | 0.000 | 0.003 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".