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Table 2 Comparison of steam explosion pretreatment studies for softwood

From: Pilot-scale steam explosion pretreatment with 2-naphthol to overcome high softwood recalcitrance

References Stages Additive/catalyst T/°C t/min Feedstock Washing after pret. FPU g−1 cellulose Glucose EH/% Mannose EH/% Glucose P/% Mannose P/% Total sugar/%
  1 235 5 Spruce chips <30 mm No 15 31 0 7 32 36
30 45 2 46
60 58 3 63
  1 2-Naphthol admixed 235 5 Spruce chips <30 mm No 15 44 4 8 35 48
30 67 2 63
60 86 13 80
  1 2-Naphthol, acetone imp. 235 5 Spruce chips <30 mm No 15 67 1 5 16 55
30 93 2 70
60 98 2 73
  1 2-Naphthol, ethanol imp. 235 5 Spruce chips <30 mm No 15 81 1 3 12 64
30 95 2 74
  60 95 5 75
Ballesteros et al. [46] 1 210 4 Pine chips 8–12 mm Yes 32 32    60 41
Fang et al. [38] 1 H2SO a4 200   Spruce chips 1–20 mm Yes 39 26   5 10 42
Stenberg et al. [11, 52] 1 SO b2 210 5.5 Spruce chips 2.2–10 mm Yes 30 58   13 52 66
Tengborg et al. [11, 48] 1 H2SO c4 210 1 Spruce chips <30 mm Yes 30 39   33 55 67
Monavari et al. [47] 1 SO d2 200 20 Spruce chips 5–6 mm Yes 28 51 7 15 78 71
Nguyen et al. [50] 1 H2SO e4 215 1.7 Fir + Pine chips <12.7 mm Yes 60 50   30 65 75
Söderström et al. [11, 51] 2 H2SO f4 180/200 10/2 Spruce sawdust Yes 30 36   41 96 77
Söderström et al. [11, 55] 2 SO g2 190/220 2/5 Spruce chips 2.2–10 mm Yes 30 45   35 95 80
Nguyen et al. [50] 2 H2SO h4 180/210 4/1.5 Fir + Pine chips <12.7 mm Yes 60 25   57 84 82
  1. Shown are the conditions for the highest total sugar yield. Yields are expressed as % of the raw biomass content
  2. EH yield in enzymatic hydrolysis (accounting for cellulose recovery from pretreatment), P yield in pretreatment liquor, Mannose hemicellulosic sugars excluding glucose
  3. aImpregnated with 0.6% w/w H2SO4 based on wood dry matter
  4. bImpregnated with 3.5% w/w gaseous SO2 based on wood dry matter
  5. c2.4% w/w H2SO4 in pretreatment liquid
  6. dImpregnated with 2.5% w/w gaseous SO2 based on water moisture
  7. e0.43% w/w H2SO4 in pretreatment liquid
  8. f1st stage: impregnated with 0.5% w/w H2SO4 based on wood moisture; 2nd stage: impregnated with 2% w/w H2SO4 based on wood moisture
  9. gImpregnated with 3% w/w gaseous SO2 based on wood moisture
  10. h1st stage: 0.43% w/w H2SO4 in pretreatment liquid; 2nd stage: 2.5% w/w H2SO4 in pretreatment liquid