Continuous fast pyrolysis of lignin and direct upgrading of pyrolysis vapor by the HZSM-5 catalyst produce renewable aromatics.

MoO 3 has been tested as a catalyst in hydrodeoxygenation (HDO) of both model compounds (acetone and guaiacol) and real biomass pyrolysis vapors under atmospheric pressure. The pyrolysis vapor was obtained by fast pyrolysis of wood or lignin in a continuous fast pyrolysis reactor at a fixed temperature of 500 °C, and it subsequently passed through a downstream, close coupled, fixed bed reactor containing the MoO 3 catalyst. The influences of the catalyst temperature and the concentration of H 2 on the HDO of the pyrolysis vapors were investigated. The level of HDO of the biomass pyrolysis vapors was not significant at temperatures below 400 °C. At 450 °C catalyst temperature and 93 vol % H 2 concentration, the wood pyrolysis vapor was more active toward cracking forming gas species instead of performing the desired HDO forming hydrocarbons. The lignin pyrolysis vapor was more resistant to cracking and yielded 16.2 wt % daf organic liquid, while achieving 52% degree of deoxygenation at 450 °C catalyst temperature under 89 vol % H 2 concentration. The corresponding energy recovery in the liquid phase was 23.5%. The spent catalyst showed two deactivation routes, coke formation and reduction of MoO 3 to MoO 2 , which is inactive in HDO. The catalyst experienced severe reduction at temperatures higher than 400 °C. The yields of coke relative to the fed biomass were in the range of 3−4 wt % daf for lignin and 5−6 wt % daf for wood. Compared to untreated bio-oil the upgraded lignin organic liquid showed improved compatibility with hydrocarbons and was miscible with a toluene/heptane mixture.

Biorefineries aim to convert low value biomasses into high value products. The feedstock biomasses are often high‐silica agricultural waste products such as rice straw, wheat straw, corn stover, sugarcane bagasse, or empty fruit bunches. This causes challenges, since silica is problematic in industrial processes, where it forms water‐insoluble precipitates that are hard to remove, block filtration systems, and cause instrumental defects. In this paper we review various industries that experience issues with silica. These include paper pulping and waste‐water treatment, where they try to solve their problems with silica in different ways. High pH and co‐precipitation with mineral elements are some common ways of alleviating silica problems. Reviewing the literature for the fundamentals of silica revealed a complex chemistry that is not yet fully understood. Much is still to be learned about the interactions between silica and organic material as well as the mechanisms of silica precipitation and dissolution. Understanding the fundamental and complex chemistry of silica might help developing better solutions than those existing today, allowing efficient use of high silica biomasses in biorefineries. © 2014 Society of Chemical Industry and John Wiley & Sons, Ltd

BackgroundMineral elements present in lignocellulosic biomass feedstocks may accumulate in biorefinery process streams and cause technological problems, or alternatively can be reaped for value addition. A better understanding of the distribution of minerals in biomass in response to pretreatment factors is therefore important in relation to development of new biorefinery processes. The objective of the present study was to examine the levels of mineral elements in pretreated wheat straw in response to systematic variations in the hydrothermal pretreatment parameters (pH, temperature, and treatment time), and to assess whether it is possible to model mineral levels in the pretreated fiber fraction.ResultsPrincipal component analysis of the wheat straw biomass constituents, including mineral elements, showed that the recovered levels of wheat straw constituents after different hydrothermal pretreatments could be divided into two groups: 1) Phosphorus, magnesium, potassium, manganese, zinc, and calcium correlated with xylose and arabinose (that is, hemicellulose), and levels of these constituents present in the fiber fraction after pretreatment varied depending on the pretreatment-severity; and 2) Silicon, iron, copper, aluminum correlated with lignin and cellulose levels, but the levels of these constituents showed no severity-dependent trends. For the first group, an expanded pretreatment-severity equation, containing a specific factor for each constituent, accounting for variability due to pretreatment pH, was developed. Using this equation, the mineral levels could be predicted with R2 > 0.75; for some with R2 up to 0.96.ConclusionPretreatment conditions, especially pH, significantly influenced the levels of phosphorus, magnesium, potassium, manganese, zinc, and calcium in the resulting fiber fractions. A new expanded pretreatment-severity equation is proposed to model and predict mineral composition in pretreated wheat straw biomass.