Pyrolysis of biomass harvested from heavy-metal contaminated area: Characteristics of bio-oils and biochars from batch-wise one-stage and continuous two-stage pyrolysis.

This study evaluates pyrolysis products obtained from biomasses (silver grass, pine, and acacia) harvested from heavy-metal-contaminated soil. To do so, we utilized two methods: a batch one-stage pyrolysis, and a continuous two-stage pyrolysis. The study results show that the yields and characteristics of bio-oils and biochars varied depending on the pyrolysis process and the type of biomass. The two-stage pyrolysis having two reactors (auger and fluidized bed reactors) appeared to be very suitable for specific chemicals production such as acetic acid, acetol, catechol, and levoglucosan. The biochar obtained from the fluidized-bed reactor of two-stage pyrolysis had high thermal stability, high crystallinity, high inorganic content, and a small number of functional groups. In contrast, the biochar obtained from the one-stage pyrolysis had low thermal stability, low crystallinity, a high carbon content, and a large number of functional groups. The biochar obtained from the two-stage pyrolysis appeared to be suitable as a material for catalyst support and as an adsorbent. The biochar obtained from one-stage pyrolysis appeared to be a suitable as a soil amendment, as an adsorbent, and as a precursor of activated carbon. All biochars showed a negative carbon footprint. In the end, this study, which was conducted using two different processes, was able to obtain the fact that products of pyrolysis biomass contaminated with heavy metals have different characteristics depending on the process characteristics and that their utilization plans are different accordingly. If the optimal utilization method proposed through this study is found, pyrolysis will be able to gain importance as an effective treatment method for biomass contaminated with heavy metals.

Production, separation and applications of phenolic-rich bio-oil--a review.

This paper provides an overview of current research trends in the production and separation of phenolic-rich bio-oils, as well as their applications. The first part of this paper highlights the strong dependency of the phenolic content of bio-oil on the kinds of biomass feedstock, reaction system, reaction conditions, and the type of catalysts used in their production. More recent separation technologies are also discussed in the second part of the paper. The final part of the paper deals with recent experimental results from applications of phenolic-rich bio-oils in the synthesis of phenolic resins. The paper suggests that the microwave-assisted pyrolysis of palm residues is a promising route for phenolic-rich bio-oil production, and that the use of supercritical CO2 and switchable hydrophilicity solvents during extraction, as well as molecular distillation techniques, can be applied to increase the recovery of phenolic compounds from bio-oils.

Production of bio-based phenolic resin and activated carbon from bio-oil and biochar derived from fast pyrolysis of palm kernel shells.

A fraction of palm kernel shells (PKS) was pyrolyzed in a fluidized bed reactor. The experiments were performed in a temperature range of 479-555 °C to produce bio-oil, biochar, and gas. All the bio-oils were analyzed quantitatively and qualitatively by GC-FID and GC-MS. The maximum content of phenolic compounds in the bio-oil was 24.8 wt.% at ∼500 °C. The maximum phenol content in the bio-oil, as determined by the external standard method, was 8.1 wt.%. A bio-oil derived from the pyrolysis of PKS was used in the synthesis of phenolic resin, showing that the bio-oil could substitute for fossil phenol up to 25 wt.%. The biochar was activated using CO2 at a final activation temperature of 900 °C with different activation time (1-3 h) to produce activated carbon. Activated carbons produced were microporous, and the maximum surface area of the activated carbons produced was 807 m(2)/g.

Toxic potentiality of bio-oils, from biomass pyrolysis, in cultured cells and Caenorhabditis elegans.

Bio-oils, which are multicomponent mixtures, were produced from two different biomass (rice straw (rice oil) and sawdust of oak tree (oak oil)) by using the slow pyrolysis process, and chemical compositional screening with GC-MS detected several hazardous compounds in both bio-oil samples. The two bio-oils vary in their chemical compositional nature and concentrations. To know the actual hazard potentialities of these bio-oils, toxicological assessments were carried out in a comparative approach by using in vitro (Jurkat T and HepG2 cell) as well as in vivo (Caenorhabditis elegans) systems. A dose-dependent increase in cytotoxicity, cell death (apoptosis), and genotoxicity were observed in cultured cell systems. Similarly, the in vivo system, C. elegans also displayed a dose-dependent decrease in survival. It was found that in comparison with rice oil, oak oil displayed higher toxicity to all models systems, and the susceptibility order of the model systems were Jurkat T > HepG2 > C. elegans. Pursuing the study further toward the underlying mechanism by exploiting the C. elegans mutants screening assay, the bio-oils seem to mediate toxicity through oxidative stress and impairment of immunity. Taken together, bio-oils compositions mainly depend on the feedstock used and the pyrolysis conditions which in turn modulate their toxic potentiality.

Co-production of furfural and acetic acid from corncob using ZnCl2 through fast pyrolysis in a fluidized bed reactor.

Corncob was pyrolyzed using ZnCl2 in a pyrolysis plant equipped with a fluidized bed reactor to co-produce furfural and acetic acid. The effects of reaction conditions, the ZnCl2 content and contacting method of ZnCl2 with corncob on the yields of furfural and acetic acid were investigated. The pyrolysis was performed within the temperature range between 310 and 410°C, and the bio-oil yield were 30-60 wt% of the product. The furfural yield increased up to 8.2 wt%. The acetic acid yield was maximized with a value of 13.1 wt%. A lower feed rate in the presence of ZnCl2 was advantageous for the production of acetic acid. The fast pyrolysis of a smaller corncob sample mechanically mixed with 20 wt% of ZnCl2 gave rise to a distinct increase in furfural. A high selectivity for furfural and acetic acid in bio-oil would make the pyrolysis of corncob with ZnCl2 very economically attractive.

Characteristics of products from fast pyrolysis of fractions of waste square timber and ordinary plywood using a fluidized bed reactor.

Fractions of waste square timber and waste ordinary plywood were pyrolyzed in a pyrolysis plant equipped with a fluidized bed reactor and a dual char separation system. The maximum bio-oil yield of about 65 wt.% was obtained at reaction temperatures of 450-500 °C for both feed materials. For quantitative analysis of bio-oil, the relative response factor (RRF) of each component was calculated using an effective carbon number (ECN) that was multiplied by the peak area of each component detected by a GC-FID. The predominant compounds in the bio-oils were methyl acetate, acids, hydroxyacetone, furfural, non-aromatic ketones, levoglucosan and phenolic compounds. The WOP-derived bio-oil showed it to have relatively high nitrogen content. Increasing the reaction temperature was shown to have little effect on nitrogen removal. The ash and solid contents of both bio-oils were below 0.1 wt.% due to the excellent performance of the char separation system.

Influence of operation conditions and additives on the development of producer gas and tar reduction in air gasification of construction woody wastes using a two-stage gasifier.

Air gasification was conducted with fractions of construction woody wastes in a two-stage gasifier, consisting of a fluidized bed zone and a tar cracking zone. The aim of this work is to investigate the influence of reaction conditions and additives on the composition of producer gas and tar content in producer gas. A producer gas obtained with activated carbon of 540 g at an ER of 0.26 was mainly composed of H(2) (25 vol.%), CO (22 vol.%) and CH(4) (5 vol.%). Regarding tar removal efficiency, activated carbon was better than olivine. The tar removal rate with virgin activated carbon reached up to 80%. The reuse of spent activated carbon caused an efficiency loss in tar removal to some extent. Overall, it seems that the strong need for intensive downstream tar removal measurements can be removed with the use of a two-stage gasifier and the application of activated carbon.

Fast pyrolysis of palm kernel shells: influence of operation parameters on the bio-oil yield and the yield of phenol and phenolic compounds.

Palm kernel shells were pyrolyzed in a pyrolysis plant equipped with a fluidized-bed reactor and a char-separation system. The influence of reaction temperature, feed size and feed rate on the product spectrum was also investigated. In addition, the effect of reaction temperature on the yields of phenol and phenolic compounds in the bio-oil was examined. The maximum bio-oil yield was 48.7 wt.% of the product at 490 degrees C. The maximum yield of phenol plus phenolic compounds amounted to about 70 area percentage at 475 degrees C. The yield of pyrolytic lignin after its isolation from the bio-oil was approximately 46 wt.% based on the water and ash free oil. The pyrolytic lignin was mainly composed of phenol, phenolic compounds and oligomers of coniferyl, sinapyl and p-coumaryl alcohols. From the result of a GPC analysis, the number average molecular weight and the weight average molecular weight were 325 and 463 g/mol, respectively.