Inorganics distribution in bio oils and char produced by biomass fast pyrolysis: The key role of aerosols

Fast pyrolysis of biomass is a promising process for the preparation of bio-oil dedicated to energy production. Inorganic species originally present in biomass are known to induce problems such as bio-oil instability or deposits and fouling. However the mechanisms of inorganic species release during biomass pyrolysis into the raw bio-oils still remain unclear. The present work focuses on the determination of inorganic distribution in the products from wheat straw and beech wood fast pyrolysis performed in a fluidized bed. More specifically, the bio-oils are fractionated by using a series of condensers. The results show that more than 60 wt.% of the inorganic content of the overall bio-oil is contained in the aerosols. Several possible interpretations for this observation are discussed. It is likely that the inorganics are transported within the aerosols droplets and solid particles which are recovered in the bio-oils, either by mechano-chemical processes, or by entrainment of submicron intermediate liquid compound formed in the first steps of biomass fast pyrolysis.     

Hydrothermal processing of waste pine wood into industrially useful products

An ongoing major outbreak of mountain pine beetle in Western Canada has provided a clear opportunity to utilize waste pinewood as a source of renewable energy. Therefore hydrothermal processing of waste pinewood as a feedstock for bio-oil and biochar production using subcritical and supercritical water technology was carried out in semi-batch mode to investigate the effect of pressure (200–400 bar) and temperature (300–400 °C) on the yield and composition of bio-oil. The pinewood samples have very high cellulose and hemicellulose content but low ash content and are thus a formidable feedstock for bioenergy production. The optimum conditions for the hydrothermal processing of the pinewood in a tubular reactor were found to be 400 °C and 250 bars with respect to biochar and bio-oil yield based on the highest calorific value analysis. Detailed characterization of bio-oil and biochar was performed using GCMS, NMR, SEM, calorific value, and elemental analysis, respectively. The critical components of bio-oil were found to be phenols, methoxyphenols, hydroxymethyl furfural (HMF), and vanillin, whereas as compared to the raw pine wood, the biochar was considerably lower H:C and O:C ratios than those of the unprocessed pinewood. The analyses of bio-oil by means of GCMS and ¹H NMR showed that it was mainly composed of heterocyclic compounds, phenols, aldehydes and acids.     

Mechanistic investigation into particulate matter formation during air and oxyfuel combustion of formulated water-soluble fractions of bio-oil

This paper reports a systematic study on the formation of particulate matter with diameter of <10 µm (i.e., PM₁₀) during the combustion of two formulated water-soluble fractions (FWSFs) of bio-oil in a drop-tube-furnace (DTF) at 1400 °C under air or oxyfuel (30%O₂/70%CO₂) conditions. FWSF-1 was an organic-free calcium chloride solution with a calcium concentration similar to that in the bio-oil. FWSF-2 was formulated from the compositions of major organics in bio-oil WSF, doped with calcium chloride at the same concentration. The results suggest that similar to bio-oil combustion, the FWSF combustion produces mainly particulate matter with diameter of between 0.1 and 10 µm (i.e., PM_0.1–10). Since there are no combustibles in the organic-free FWSF-1, the PM is produced via droplet evaporation followed by crystallization, fusion and further reactions to form CaO (in air or argon) or partially CaCO₃ (under oxyfuel condition). With the addition of organics, FWSF-2 combustion produces PM₁₀ shifting to smaller sizes due to extensive break up of droplets via microexplosion. Sprays with larger droplet size produce PM₁₀ with increased sizes. The results show that upon cooling CaO produced during combustion in air can react with HCl gas to form CaCl₂ in PM_0.1. The predicted PSDs of PM₁₀ based on the assumption that one droplet produces one PM particle is considerably larger than experimentally-measured PSDs of PM₁₀ during the combustion of FWSFs, confirming that breakup of spray droplets takes place and such breakup is extensive for FWSF-2 when organics are present in the fuel.     

Production of Bio-hydrogen Using Bio-oil as a Potential Biomass-derived Renewable Feedstock

The bio-oil derived from pyrolysis of straw can be selectively converted into high-purity hydrogen by coupling three steps:(i)steam refonning(SR)of di tierent bio-oils,(ii)water-gas shift(WGS),and(iii)the removal of CO2.the catalytic SR reaction over the NiLaTiAl catalyst,coupled with a low-temperature WGS reaction with the CuZnAl catalyst,promoted the conversion of various oxygen-contaming organic compounds in the bio-oil into hydrogen and carbon dioxide.Under the optimized condition,light bio-oil achieved the highest conversion(99.8%,molar fraction),with a high hydrogen yield of 16.4%(mass traction)and a H2 purity of 99.94%(volume fraction).The carbon deposition on the NiLaTiAl catalyst was the main factor caused catalyst deactivation.Production of hydrogen from different bio-oil model compounds was also investigated in detail.     

生物油催化裂解转化制取三苯

通过不同孔特征的分子筛(HZSM-5、HY沸石和MCM-41)实现生物油催化转化为三苯(苯、甲苯和对甲苯). 基于三苯的产率和选择性,芳香化合物逐次降低顺序为: HZSM-5>MCM-41>HY沸石.用HZSM-5催化裂解生物油产生芳香化合物的最大产率为33.1%,选择性为86.4%. 研究了反应条件对生物油催化裂解的影响,结合催化剂表征结果,讨论了催化剂的结构与性能之间的关系.     

Effects of Current on Microcosmic Properties of Catalyst and Reforming of Bio-oil

通过低温电催化重整方法(电流通过催化剂床),用传统的镍基重整催化剂NiO-Al2O3重整生物油制取氢气是一种高效的生物油产氢方法．还探索了电流对生物油重整的促进影响,发现通过催化剂的电流明显地提高了生物油的重整．通过BET、XRD、XPS和SEM的测试,研究了电流对催化剂微观结构的影响,包括比表面、孔径、孔体积、晶粒尺寸和氧化镍的还原程度．从通电的催化剂表面脱附的热电子直接由飞行时间质谱测量．讨论了电催化重整生物油的机理．     

Hydrogen Production From Crude Bio-oil and Biomass Char by Electrochemical Catalytic Reforming

We reports an efficient approach for production of hydrogen from crude bio-oil and biomass char in the dual fixed-bed system by using the electrochemical catalytic reforming method. The maximal absolute hydrogen yield reached 110.9 g H₂/kg dry biomass. The product gas was a mixed gas containing 72%H₂, 26%CO₂, 1.9%CO, and a trace amount of CH₄. It was observed that adding biomass char (a by-product of pyrolysis of biomass) could remarkably increase the absolute H₂ yield (about 20%-50%). The higher reforming temperature could enhance the steam reforming reaction of organic compounds in crude bio-oil and the reaction of CO and H₂O. In addition, the CuZn-Al₂O₃ catalyst in the water-gas shift bed could also increase the absolute H₂ yield via shifting CO to CO₂.     

Catalytic pyrolysis of oak via pyroprobe and bench scale, packed bed pyrolysis reactors

The pyrolytic conversion of oak sawdust at 500 °C in flowing He over eight proprietary catalysts is described and compared to the control bed material, quartz sand. The reactions were conducted and compared in two reactors, an analytical, μg-scale pyroprobe reactor and a bench, g-scale packed bed reactor. The catalysts examined were modified acid catalysts, dealuminated-zeolite Y, β-zeolite, a naturally occurring metal hydroxide containing mineral, mordenite, and a mesoporous aluminosilicate molecular sieve. The packed bed reactor allowed the collection of three bulk product fractions, char, liquid, and gas, all of which could not be obtained from the μg-scale pyroprobe reactions. The catalysts effect on the mass balance of the bulk fractions tended toward more chars and less liquid compared to the sand control. The catalysts’ effects on the liquid products obtained in both reactors shifted away from acetic acid, furfural and higher molecular weight phenolics obtained with sand to lower molecular weight aromatics. This halved the total acid number of the liquid fraction and raised the pH by up to 1.4 units. The modified catalysts’ effects on the gas products from both reactors did not follow a specific trend. Instead, specific catalysts were able to enrich specific gas species up to a factor of 15 while suppressing the formation of others compared to the sand control. Two catalysts, β-zeolite and a naturally occurring metal hydroxide containing mineral, were regenerated and recycled up to five times with no loss of activity.     

Bio-oil production from Onopordum acanthium L. by slow pyrolysis

In this study, the usability of the plant thistle, Onopordum acanthium L., belonging to the family Asteraceae (Compositae), in liquid fuel production has been investigated. The experiments were performed in a fixed-bed Heinze pyrolysis reactor to investigate the effects of heating rate, pyrolysis temperature and sepiolite percentage on the pyrolysis product yields and chemical compositions. Experiments were carried out in a static atmosphere with a heating rate of 7 °C/min and 40 °C/min, pyrolysis temperature of 350, 400, 500, 550 and 700 °C and particle size of 0.6 < D_p < 0.85 mm. Catalyst experiments were conducted in a static atmosphere with a heating rate of 40 °C/min, pyrolysis temperature of 550 °C and particle size of 0.6 < D_p < 0.85 mm. Bio-oil yield increased from 18.5% to 27.3% with the presence of 10% of sepiolite catalyst at pyrolysis temperature of 550 °C, with a heating rate of 40 °C/min, and particle size of 0.6 < D_p < 0.85 mm. It means that the yield of bio-oil was increased at around 48.0% after the catalyst added. Chromatographic and spectroscopic studies on the bio-oil showed that the oil obtained from O. acanthium L. could be used as a renewable fuels and chemical feedstock.     

用低温电催化重整方法和CoZnAl催化剂进行低温生物油重整制氢

利用电化学催化重整方法和CoZnAl催化剂实现了高效的生物油重整制氢过程．研究了电流强度对氢气产率、碳转化率以及产物分布的影响．结果表明,通过催化剂的电流对氢气产量和碳转化率都有明显的促进作用,在500 oC低温重整条件下氢气产率和碳转化率分别达到大约70%和85%．此外,用XRD、XPS、TGA和BET研究了电流对催化剂的结构和性能的影响．结果表明,通电催化床中热电子对生物油中含氧有机物的重整反应起着重要的促进作用．