Showing papers on "Pyrolysis published in 2012"

Chemical characterization of rice straw-derived biochar for soil amendment

Abstract: Pyrolysis of rice straw to create biochar for soil amendment appears to be a promising method to address concerns with regard to improving soil fertility, increasing Carbon storage and decreasing Green House Gas emissions. However, the ability of rice straw-derived biochar to affect these factors might vary depending on its characteristics. It is therefore essential to investigate the properties before large-scale application of rice straw-derived biochar. In this study, rice straw-derived biochars produced at different temperatures (300, 400, 500, 600 & 700 °C) and residence time (1, 2, 3 & 5 h) were characterized using a suite of analytical techniques. Results showed that pyrolysis temperature had a greater influence than residence time on the chemical composition and structure of rice straw-derived biochar produced at low heating rate. The rice straw-derived biochars especially produced at 400 °C had high alkalinity and cation exchange capacity, and high levels of available phosphorus and extractable cations. These properties indicate potential application of rice straw-derived biochar as a fertilizer and soil amendment. Fourier transform infrared spectra showed that higher pyrolysis temperatures promote condensation reactions. Rice straw-derived biochars contained turbostratic crystallites at 400 °C, and displayed a high level of aromatization at 500 °C. Increasing charring temperature will increase the aromaticity of biochar, and might include its recalcitrance.

A review on operating parameters for optimum liquid oil yield in biomass pyrolysis

Abstract: Pyrolysis is one of the potential routes to harness energy and useful chemicals from biomass. The major objective of biomass pyrolysis is to produce liquid fuel, which is easier to transport, store and can be an alternative to energy source. The yield and composition of pyrolysis oil depend upon biomass feedstock and operating parameters. It is often necessary to explore about the effect of variables on response yield and instinct about their optimization. This study reviews operating variables from existing literature on biomass pyrolysis. The major operating variables include final pyrolysis temperature, inert gas sweeping, residence times, rate of biomass heating, mineral matter, size of biomass particle and moisture contents of biomass. The scope of this paper is to review the influence of operating parameters on production of pyrolysis oil.

Catalytic upgrading of biomass pyrolysis vapors using transition metal-modified ZSM-5 zeolite

Abstract: The main objective of the present work was the study of different ZSM-5 catalytic formulations for the in situ upgrading of biomass pyrolysis vapors. An equilibrium, commercial diluted ZSM-5 catalyst was used as the base case, in comparison with a series of nickel (Ni) and cobalt (Co) modified variants at varying metal loading (1–10 wt.%). The product yields and the composition of the produced bio-oil were significantly affected by the use of all ZSM-5 catalytic materials, compared to the non-catalytic flash pyrolysis, producing less bio-oil but of better quality. Incorporation of transition metals (Ni or Co) in the commercial equilibrium/diluted ZSM-5 catalyst had an additional effect on the performance of the parent ZSM-5 catalyst, with respect to product yields and bio-oil composition, with the NiO modified catalysts being more reactive towards decreasing the organic phase and increasing the gaseous products, compared to the Co 3 O 4 supported catalysts. However, all the metal-modified catalysts exhibited limited reactivity towards water production, while simultaneously enhancing the production of aromatics and phenols. An interesting observation was the in situ reduction of the supported metal oxides during the pyrolysis reaction that eventually led to the formation of metallic Ni and Co species on the catalysts after reaction, which was verified by detailed XRD and HRTEM analysis of the used catalysts. The Co 3 O 4 supported ZSM-5 catalysts exhibited also a promising performance in lowering the oxygen content of the organic phase of bio-oil.

Effects of slow and fast pyrolysis biochar on soil C and N turnover dynamics

Abstract: This study compared the effect of two principal pyrolysis methods on the chemical characteristics of biochar and the impact on C and N dynamics after soil incorporation. Biochar was produced from wheat straw that was thermally decomposed at 525 °C by slow pyrolysis (SP) in a nitrogen flushed oven and by fast pyrolysis (FP) using a Pyrolysis Centrifuge Reactor (PCR). After 65 days of soil incubation, 2.9% and 5.5% of the SP- and FP-biochar C, respectively, was lost as CO 2 , significantly less than the 53% C-loss observed when un-pyrolyzed feedstock straw was incubated. Whereas the SP-biochar appeared completely pyrolyzed, an un-pyrolyzed carbohydrate fraction (8.8% as determined by acid released C6 and C5 sugars) remained in the FP-biochar. This labile fraction possibly supported the higher CO 2 emission and larger microbial biomass (SMB-C) in the FP-biochar soil. Application of fresh FP-biochar to soil immobilized mineral N (43%) during the 65 days of incubation, while application of SP-biochar led to net N mineralization (7%). In addition to the carbohydrate contents, the two pyrolysis methods resulted in different pH (10.1 and 6.8), particle sizes (113 and 23 μm), and BET surface areas (0.6 and 1.6 m 2 g −1 ) of the SP- and FP-biochars, respectively. The study showed that independently of pyrolysis method, soil application of the biochar materials had the potential to sequester C, while the pyrolysis method did have a large influence on the mineralization-immobilization of soil N.

Hydrologic properties of biochars produced at different temperatures

Abstract: Adding charcoal to soil (biochar soil amendment) can sequester carbon and improve soil performance, although the extent and exact mechanisms of soil improvement are not clear. Additionally, biochar properties can vary significantly with production conditions. Here we characterize the impact of pyrolysis temperature on two important soil hydrologic properties: field capacity and hydrophobicity. We show that pure biochar exhibits a wide range in both properties depending on feedstock and pyrolysis conditions. We find that both properties can be controlled by choice of pyrolysis temperature; 400 °C–600 °C produced biochars with the most desirable hydrological properties (peak field capacity and minimum hydrophobicity). Further, we show that hydrophobicity is strongly correlated ( R 2 = 0.87; p

Promising Porous Carbon Derived from Celtuce Leaves with Outstanding Supercapacitance and CO2 Capture Performance

Abstract: Business costs and energy/environmental concerns have increased interested in biomass materials for production of activated carbons, especially as electrode materials for supercapacitors or as solid-state adsorbents in CO2 adsorption area. In this paper, waste celtuce leaves were used to prepare porous carbon by air-drying, pyrolysis at 600 °C in argon, followed by KOH activation. The as-prepared porous carbon have a very high specific surface area of 3404 m2/g and a large pore volume of 1.88 cm3/g. As an electroactive material, the porous carbon exhibits good capacitive performance in KOH aqueous electrolyte, with the specific capacitances of 421 and 273 F/g in three and two-electrode systems, respectively. As a solid-state adsorbent, the porous carbon has an excellent CO2 adsorption capacity at ambient pressures of up to 6.04 and 4.36 mmol/g at 0 and 25 °C, respectively. With simple production process, excellent recyclability and regeneration stability, the porous carbon that was derived from celtuce le...

Controlling the selectivity to chemicals from lignin via catalytic fast pyrolysis

Abstract: The catalytic fast pyrolysis of alkaline lignin to useful chemicals was investigated using zeolite catalysts with different acidity and pore size. The catalyst played dual roles in this process. In its acid form, it catalytically converted the depolymerized intermediates into desirable and more stable products. This and their surface prevented repolymerization and coke formation. The yield of liquid and the selectivity to desired products can be controlled by tuning of the acidity and pore size of the catalyst. Using no catalyst yielded 40 wt.% of liquid, which mainly consisted of 6 wt.% (carbon yield) of phenols and 19 wt.% (carbon yield) of phenol alkoxy species. The highest yield of phenol alkoxy species was obtained over H-ZSM5 of extremely low number of acid sites; liquid yield of 51 wt.% and carbon yield of 24 wt.%. The highest yield of liquid (75 wt.%) was obtained over H-USY, which had the largest pore size and lowest Si/Al ratio, thus the largest number of acid sites among all the catalyst tested; the carbon yield of aromatic hydrocarbons was around 40 wt.% at 650 °C. Depolymerized lignin products undergo consecutive reaction to form phenol alkoxy, phenols, and eventually aromatic hydrocarbons.

Influence of temperature on biomass pyrolysis in a conical spouted bed reactor

Abstract: Pinewood sawdust flash pyrolysis has been performed in continuous mode in a pilot plant provided with a conical spouted bed reactor, in the 400–600 °C range. The influence of temperature on the pyrolysis yields and product properties has been studied. Product analysis has been carried out on-line by means of chromatographic methods. High liquid yields have been achieved, with the maximum bio-oil yield (75 wt%) at 500 °C. Gas yield is very low at low temperatures and this fraction is mainly composed of carbon dioxide, carbon monoxide and small amounts of methane, hydrogen and C2–C4 hydrocarbons. Bio-oil has been characterized and its major compounds are phenols, specifically guaiacols at low temperatures and catechols at high temperatures. At 600 °C, there is an increase in light compounds due to the cracking reactions, but no aromatic compounds have been detected due to the low residence time of the volatiles in the reactor. The fuel properties of the bio-oil have been measured and the results indicate that it can be a potential substitute to conventional fuels, although its heating value should be improved by subjecting to further treatments. Char can be used as energy source or as active carbon. The char obtained at 600 °C has a high surface area and is suitable for active carbon production.

MOF derived porous carbon–Fe3O4 nanocomposite as a high performance, recyclable environmental superadsorbent

Abstract: A high surface area carbon composite with Fe3O4 nanoparticles is synthesized by pyrolysis of an iron containing Metal Organic Framework (MOF). The composite can be prepared by annealing the MOF at different temperatures (500 °C and 600 °C), each case exhibiting unique properties in terms of the hydrophobic behaviour and surface area, resulting in specific applicability domains. We highlight the exceptional behaviour of this material as a magnetically separable and recyclable superadsorbent for removal and recovery of environmental pollutants (oil/hydrocarbon and dye/phenol).

Revealing pyrolysis chemistry for biofuels production: Conversion of cellulose to furans and small oxygenates

Abstract: Biomass pyrolysis utilizes high temperatures to produce an economically renewable intermediate (pyrolysis oil) that can be integrated with the existing petroleum infrastructure to produce biofuels. The initial chemical reactions in pyrolysis convert solid biopolymers, such as cellulose (up to 60% of biomass), to a short-lived (less than 0.1 s) liquid phase, which subsequently reacts to produce volatile products. In this work, we develop a novel thin-film pyrolysis technique to overcome typical experimental limitations in biopolymer pyrolysis and identify α-cyclodextrin as an appropriate small-molecule surrogate of cellulose. Ab initio molecular dynamics simulations are performed with this surrogate to reveal the long-debated pathways of cellulose pyrolysis and indicate homolytic cleavage of glycosidic linkages and furan formation directly from cellulose without any small-molecule (e.g., glucose) intermediates. Our strategy combines novel experiments and first-principles simulations to allow detailed chemical mechanisms to be constructed for biomass pyrolysis and enable the optimization of next-generation biorefineries.

Wet chemical synthesis of nitrogen-doped graphene towards oxygen reduction electrocatalysts without high-temperature pyrolysis

Abstract: The oxygen reduction reaction (ORR) is one of the important reactions not only in life processes but also in artificial energy conversion systems, such as fuel cells and metal/air batteries. As one of the non-precious ORR catalysts, N-doped carbon materials show an exciting activity, but most of them were universally synthesized by high-temperature pyrolysis or annealing up to 1100 °C in the past few decades, which makes the structural manipulation of the catalysts extremely difficult. Here, we propose that ORR active N-doped carbon catalysts could, in principle, be prepared via a sophisticated wet chemical reaction between a reactive graphitic carbon template (e.g. graphene oxide) and N-containing molecules (e.g. dicyandiamide) at temperatures as low as 180 °C. Without any high-temperature treatments, for example, the as-prepared N-doped reduced graphene oxide with additional Fe-containing nanoparticles showed an impressive ORR catalytic activity that was comparable to many previous N-doped carbon from high-temperature pyrolysis. Rational utilization of the graphitic carbon template, the N-containing molecules, and the wet chemical reactions may offer a low-temperature route to create interesting ORR electrocatalysts with easier surface properties manipulation.