Search

Technologies for producing renewable fuels and chemicals rely on the production of stable intermediates. For thermochemical technologies, pyrolysis of biomass produces oils that must compromise between carbon yield and oil quality. Bio-oil extraction has largely focused on regular bio-oils (~ 33 wt% O) and partially deoxygenated oils (< 12 wt% O). Furthermore, it is desired to extract phenolics without direct distillation of bio-oils, which would enable extraction from the heaviest portion of bio-oil. Mid-level oxygen (MLO) bio-oils (16–25 wt% O) produced from switchgrass were characterized for their ability to separate into phenolic-rich fractions. Toluene-soluble portions of the oils underwent NaOH extraction to extract one-ring phenolics, while toluene-insoluble portions were fractionated with iso-propyl alcohol (IPA). While phenolic extraction proceeded without distillation (having been a prerequisite for partially deoxygenated bio-oils), the efficiency of extraction was less than optimal, owing to the presence of other oxygenated compounds in the hydrocarbon-rich fraction. Both IPA-insoluble and IPA-soluble fractions underwent solvent liquefaction reactions with base additives. While using water as a reaction medium produced greater concentrations of phenols than when using methanol, addition of sodium carbonate produced narrower product distributions of phenols and inhibited formation of benzenediols. [ABSTRACT FROM AUTHOR]

Utilization of lignin is among the most pressing problems for biorefineries that convert lignocellulosic biomass to fuels and chemicals. Recently "lignin-first" biomass fractionation has received increasing attention. In most biorefining concepts, carbohydrate portions of the biomass are separated, and their monomeric sugar components released, while the relatively chemically stable lignin rich byproduct remains underutilized. Conversely, in lignin-first processes, a one-pot fractionation and depolymerization is performed, leading to an oil rich in phenolic compounds and a cellulosic pulp. Usually, the pulp is considered as a fermentation feedstock to produce ethanol. Herein, the results of a study where various cellulosic pulps are tested for their potential to produce valuable products via pyrolysis processes, assessed via analytical pyrolysis (py-GC), are presented. Samples of herbaceous (switchgrass) and woody biomass (oak) were subjected to both an acid-catalyzed and a supported-metal-catalyzed reductive lignin-first depolymerization, and the pulps were compared. Fast pyrolysis of the pulps produced levoglucosan in yields of up to about 35 wt %. When normalized for the amount of biomass entering the entire process, performing the lignin-first reductive depolymerization resulted in 4.0–4.6 times the yield of levoglucosan than pyrolysis of raw biomass. Pulps derived from switchgrass were better feedstocks for levoglucosan production compared with pulps from oak, and pulps produced from metal-on-carbon catalyzed depolymerization produced more levoglucosan than those from acid-catalyzed depolymerization. Catalytic pyrolysis over HZSM-5 produced aromatic hydrocarbons from the pulps. In this case, the yields were similar from both feedstocks and catalyst types, suggesting that there is no advantage to lignin fractionation prior to zeolite-catalyzed catalytic pyrolysis for hydrocarbons. [ABSTRACT FROM AUTHOR]

Lignin isolated from sweet sorghum bagasse after the low moisture anhydrous ammonia (LMAA) pretreatment was characterized by using diffusion-ordered nuclear magnetic resonance (NMR) spectroscopy in combination with one-dimensional 1H, multinuclear two-dimensional NMR (HSQC, HMBC, HSQC-TOCSY), and elemental analysis to correlate structural observations with molecular weight. The LMAA lignin was compared with a commercial soda lignin product. The 1H diffusion-ordered spectra indicate that the aromatic components (6.0–8.5 ppm) in the LMAA lignin cover a wider diffusivity range, and therefore broader molecular weight range, than did the soda lignin, and that its weight average molecular weight was also higher. Fractionation of the LMAA lignin based on solubility in methanol revealed that this property was largely dependent on the molecular weights of the components, as both the soluble and insoluble fractions contained similar structures. Also observed by 1H NMR was a significant amount of residual ammonium present from the biomass pretreatment. This ammonium was largely fractionated into the methanol soluble fraction. [ABSTRACT FROM AUTHOR]

Sorghum wax can be extracted from the surface of sorghum (Sorghum bicolor) kernels. It is composed mostly of a mixture of unsaturated C28 and C30 alkanes, fatty acids, fatty alcohols, and fatty aldehydes. Like carnauba wax, sorghum wax is a hard wax with a high melting point and it has potential edible and industrial applications. The yield of sorghum wax from the surface of sorghum kernels is 0.2–0.5 g of wax per 100 g of kernels. Sorghum wax can also be recovered from the "distillers oil" which is obtained after fermentation of sorghum (milo) or sorghum/corn blends in dry grind fuel ethanol plants. This distillers sorghum wax can potentially be obtained in yields of up to 10% by chilling the distillers oil to precipitate the wax and then recovering it via centrifugation or filtration. Like sorghum kernel wax, distillers sorghum wax is mainly composed of C28 and C30 alkanes, alcohols, and aldehydes in the molecular weight (MW) range of 350–450. However, we found that 7–49% w/w of distillers sorghum wax is composed of larger wax components with MW of 799–912. Analysis via high‐resolution atmospheric pressure chemical ionization mass spectrometry (APCI) and gas chromatography with electron ionization mass spectrometry (GC/MS‐EI) resulted in exact mass data and fragmentation patterns that suggested that these high MW compounds are monounsaturated fatty aldehyde dimers, likely formed by aldol condensation. Further confirmation supporting the GC/MS data for the aldol reaction was obtained by comparison with similar aldol products. [ABSTRACT FROM AUTHOR]

Soils in which fresh produce is grown can become contaminated with foodborne pathogens and are sometimes then abandoned or removed from production. The application of biochar has been proposed as a method of bioremediating such pathogen-contaminated soils. The objectives of the present study were to evaluate three fast-pyrolysis-generated biochars (FPBC; pyrolyzed in house at 450, 500, and 6008C in a newly designed pyrolysis reactor) and 10 United Kingdom Biochar Research Center (UKBRC) standard slow-pyrolysis biochars to determine their effects on the viability of four surrogate strains of Escherichia coli O157:H7 in soil. A previously validated biocidal FPBC that was aged for 2 years was also tested with E. coli to determine changes in antibacterial efficacy over time. Although neither the UKBRC slow-pyrolysis biochars or the 450 and 5008C FPBC from the new reactor were antimicrobial, the 6008C biochar was biocidal (P, 0.05); E. coli populations were significantly reduced at 3 and 3.5% biochar concentrations (reductions of 5.34 and 5.84 log CFU/g, respectively) compared with 0.0 to 2.0% biochar concentrations. The aged 5008C FPBC from the older reactor, which was previously validated as antimicrobial, lost efficacy after aging for 2 years. These results indicate that the biocidal activity of FPBC varies based on production temperature and/or age. [ABSTRACT FROM AUTHOR]

The study of the effects of harvest time on switchgrass ( Panicum virgatum L.) biomass and bioenergy production reported herein encompasses a large study evaluating the harvest of six switchgrass cultivars grown at three northern US locations over 3 years, harvested at upland peak crop (anthesis), post-frost, and post-winter. Delaying harvest of switchgrass until after frost and until after winter has resulted in decreased yields of switchgrass and reduced amounts of minerals in the biomass. This report examines how changes in biomass composition as a result of varying harvest time and other factors affect the distribution of products formed via fast pyrolysis. A subset (50) of the population ( n = 864) was analyzed for fast pyrolysis and catalytic pyrolysis (zeolite catalyst) product yields using a pyrolysis-GC/MS system. The subset was used to build calibrations that were successful in predicting the pyrolysis product yield using near-infrared reflectance spectroscopy (NIRS), and partial least squares predictive models were applied to the entire sample set. The pyrolysis product yield was significantly affected by the field trial location, year of harvest, cultivar, and harvest time. Delaying harvest time of the switchgrass crop led to greater production of deoxygenated aromatics improving the efficiency of the catalytic fast pyrolysis and bio-oil quality. The changes in the pyrolysis product yield were related to biomass compositional changes, and key relationships between cell wall polymers, potassium concentration in the biomass, and pyrolysis products were identified. The findings show that the loss of minerals in the biomass as harvest time is delayed combined with the greater proportion in cellulose and lignin in the biomass has significant positive influences on conversion through fast pyrolysis. [ABSTRACT FROM AUTHOR]

Metal-modified HZSM-5 catalysts were prepared by the ion exchange of NH4ZSM-5 (SiO2/Al2O3=23) using Zn, Ga, Ni, and combinations thereof. The prepared catalysts were used to evaluate catalytic pyrolysis for the conversion of Eucalyptus urophylla to fuels and chemicals, specifically aromatic hydrocarbons, by using a micro-scale pyrolysis reactor coupled with GC-MS. Two different biomass-to-catalyst ratios (1:5 and 1:10 w/ w) were studied. The catalyst prepared with Ga by total ion exchange (Ga-HZSM-5 B, ≈7 wt % Ga) yielded the highest amount of aromatic hydrocarbons, whereas the catalysts modified with Ni produced the lowest yield of aromatic hydrocarbons. A correlation between the methane yield and benzene and p-xylene selectivity was found for the catalysts, which was observed mainly for the Ni-, Zn-, and Ga-Ni-modified catalysts. The Ga-modified catalysts were the most selective for xylenes, whereas the Ni-based catalysts were the most selective for benzene production with a concurrent increase in methane production. The Zn-modified catalysts were the most selective for toluene production. [ABSTRACT FROM AUTHOR]

Density functional theory is used to study the adsorption of guaiacol and its initial hydrodeoxygenation (HDO) reactions on Pt(111). Previous Brønsted-Evans-Polanyi (BEP) correlations for small open-chain molecules are inadequate in estimating the reaction barriers of phenolic compounds except for the side group (methoxy) carbon-dehydrogenation. New BEP relations are established using a select group of phenolic compounds. These relations are applied to construct a potential-energy surface of guaiacol-HDO to catechol. Analysis shows that catechol is mainly produced via dehydrogenation of the methoxy functional group followed by the CH x ( x<3) removal of the functional group and hydrogenation of the ring carbon, in contrast to a hypothesis of a direct demethylation path. Dehydroxylation and demethoxylation are slow, implying that phenol is likely produced from catechol but not through its direct dehydroxylation followed by aromatic carbon-ring hydrogenation. [ABSTRACT FROM AUTHOR]

Biochars produced from thermochemical conversions of biomass were evaluated by temperature programmed oxidation (TPO). This technique, used to characterize carbon deposits on petroleum cracking catalysts, provides information on the oxidative stability of carbonaceous solids, where higher temperature reactivity indicates greater structural order, an important property for biochar applications. Differences between TPO profiles of biochars generated by fast pyrolysis of soy straw, barley straw, switchgrass, bamboo, and various woods demonstrated that the oxidative stabilities of the biochars are dependent on the starting biomass. Biochars from softwood and hardwood feedstocks were also processed by torrefaction and gasification to assess the impact of the thermoprocessing method on the TPO data. Results from these TPO analyses showed that the biochars produced under higher temperature conditions afford biochars that are more oxidation resistant. Biochars produced from pine wood (softwood) were consistently more resistant to oxidation compared to their hardwood counterparts. This exploratory study represents the first application of TPO to biochars. [ABSTRACT FROM AUTHOR]

Fast pyrolysis of lignocellulosic biomass is a facile method for producing high yields of liquid fuel intermediates. However, because most fast pyrolysis oils are highly oxygenated, acidic, and unstable, identification of feedstocks that produce higher quality pyrolysis liquids is desirable. Therefore, the effect of feedstock protein content was studied by performing fast pyrolysis experiments on biomass with varying protein content. The feedstocks ranged from low-protein content, ∼5% up to feedstocks with >40 wt.% protein content. Protein content was not a major factor in the yield of pyrolysis oil or the distribution of biomass carbon into the pyrolysis products. However, elevated levels of protein did cause a deoxygenation effect in the pyrolysis process with more of the oxygen rejected from the biomass as water. The deoxygenation caused the pyrolysis oil from the higher protein containing biomass to have higher energy content. Furthermore, the concentration of basic nitrogen groups caused the pyrolysis oil from the higher protein biomass to shift to a more neutral pH and lower total acid number than has been measured typically for lignocelluloic biomass pyrolysis oils. Some of the pyrolysis oils, particularly those from the mustard seed family presscakes exhibited better thermal stability than low-protein pyrolysis oils. [ABSTRACT FROM AUTHOR]

The article discusses research investigating the sustainable production of bioenergy and biochar from the straw of high-biomass soybean lines using fast pyrolysis. The team used two high-biomass soybean lines, which were developed at the U.S. Agricultural Research Service (ARS) for bioenergy, and subjected them to thermochemical conversion via fast pyrolysis. The objective of the study was the evaluation of the potential use of straw for the production of liquid fuel intermediates, such as pyrolysis liquid. Topics include an overview of the potential use of pyrolysis liquid, the concept of on-farm biorefineries in a soybean farm system, and the use of biochar as a soil amendment.

Kraft lignin (Indulin AT) pretreated with magnesium formate and magnesium hydroxide was fast-pyrolyzed in a continuously fed, bench-scale system. To avoid fouling issues typically associated with lignin pyrolysis, a simple laboratory test was used to determine suitable ranges of magnesium hydroxide and formic acid to lignin for feeding without plugging problems. Various feedstock formulations of lignin pretreated with magnesium hydroxide and formic acid were pyrolyzed. For comparison, calcium formate pretreated lignin was also tested. The organic oil yield ranged from 9% to 17% wt % on a lignin basis. Carbon yields in the oil ranged from 10% to 18% wt % on a lignin basis. Magnesium formate pretreatment increased oil yield and carbon yield in the oil up to 35% relative to the higher 1:1 g magnesium hydroxide/g lignin pretreatment. However, a lower magnesium hydroxide pretreatment (0.5:1 g magnesium hydroxide/g lignin) resulted in oil yields and carbon yields in the oils similar to the magnesium formate pretreatments. Magnesium formate pretreatment produced more oil but with a higher oxygen content than calcium formate under the same conditions. The GC-MS analysis of product oils indicated that phenols and aromatics were more prevalent in pyrolyzed magnesium-formate-pretreated lignin. [ABSTRACT FROM AUTHOR]