Showing papers on "Pyrolysis published in 2020"

Biochar physicochemical properties: pyrolysis temperature and feedstock kind effects

Abstract: Biochar is a pyrogenous, organic material synthesized through pyrolysis of different biomass (plant or animal waste). The potential biochar applications include: (1) pollution remediation due to high CEC and specific surface area; (2) soil fertility improvement on the way of liming effect, enrichment in volatile matter and increase of pore volume, (3) carbon sequestration due to carbon and ash content, etc. Biochar properties are affected by several technological parameters, mainly pyrolysis temperature and feedstock kind, which differentiation can lead to products with a wide range of values of pH, specific surface area, pore volume, CEC, volatile matter, ash and carbon content. High pyrolysis temperature promotes the production of biochar with a strongly developed specific surface area, high porosity, pH as well as content of ash and carbon, but with low values of CEC and content of volatile matter. This is most likely due to significant degree of organic matter decomposition. Biochars produced from animal litter and solid waste feedstocks exhibit lower surface areas, carbon content, volatile matter and high CEC compared to biochars produced from crop residue and wood biomass, even at higher pyrolysis temperatures. The reason for this difference is considerable variation in lignin and cellulose content as well as in moisture content of biomass. The physicochemical properties of biochar determine application of this biomaterial as an additive to improve soil quality. This review succinctly presents the impact of pyrolysis temperature and the type of biomass on the physicochemical characteristics of biochar and its impact on soil fertility.

Lignocellulose biomass pyrolysis for bio-oil production: a review of biomass pre-treatment methods for production of drop-in fuels

Abstract: Bio-oil upgrading can be achieved mainly via three types of methods that are biomass pre-treatment, catalytic upgrading and downstream bio-oil upgrading. The article aim is to review the different physicochemical biomass pre-treatment methods used to improve the physiochemical properties of the bio-oils produced from pyrolysis of treated biomass. Biomass pre-treatment could be classified as physical, thermal, chemical and biological methods. The physical methods, such as grinding and densification improve the biomass particle size and density, affecting the heat flow and mass transfer during pyrolysis, while thermal methods, such as torrefaction, decrease the activation energy of the pyrolysis process and increase the amount of hydrocarbons in the produced bio-oil. The chemical methods generally remove the minerals and alkali metals from the biomass, improve its calorific value and enhance other biomass properties. The biomass pre-treatment methods can be integrated with catalytic pyrolysis to enhance the total carbon yield and aromatic hydrocarbons in the bio-oil. This article provides review of the basic principles of the methods, important parameters that affect biomass properties, highlights the key challenges involved in each treatment method and suggests possible future recommendations to further understand the influence of the pre-treatment methods on bio-oil upgrading. In the last section, the effect of integrated catalytic pyrolysis and pre-treatment methods on bio-oil upgrading is provided.

Hierarchical porous biochar from shrimp shell for persulfate activation: A two-electron transfer path and key impact factors

Abstract: Herein, hierarchical porous biochar from shrimp shell (PSS-bio) was prepared and applied for persulfate activation for 2,4-dichlorophenol removal. The pyrolysis temperature was found to play an important role in carbon structure and property modulation, where PSS-bio obtained at 800 °C (PSS-800) exhibited the fastest adsorption capacity and the best catalytic activity with the degradation rates 29 times higher than that of PSS-bio obtained at 400 °C (PSS-400). Further analysis demonstrated that hierarchical pores and carbon configuration were two key impact factors of biochar in AOP. Interestingly, the original free-radical dominated pathway in PSS-400 also changed into a non-radical one (direct two-electron transfer path) in PSS-800, whose efficiency could be somewhat disturbed by pH values, humic acid and anions regardless of their concentrations as low as 5 mM or as high as 500 mM, demonstrating its application potential for the treatment of both highly saline water and organic-rich water.

Coke formation and deactivation during catalytic reforming of biomass and waste pyrolysis products: A review

Abstract: Undoubtedly, hydrogen (H2) is a clean feedstock and energy carrier whose sustainable production should be anticipated. The pyrolysis of biomass or waste plastics and the subsequent reforming over base (transition) or noble metals supported catalysts allows reaching elevated H2 yields. However, the catalyst used in the reforming step undergoes a rapid and severe deactivation by means of a series of physicochemical phenomena, including metal sintering, metallic phase oxidation, thermal degradation of the support and, more notoriously, coke deposition. This review deals with the currently existing alternatives at the catalyst and reactor level to cope with catalyst deactivation and increase process stability, and then delves with the fundamental phenomena occurring during this catalyst deactivation. An emphasis is placed on coke deposition and its influence on deactivation, which depends on its location, chemical nature, morphology, precursors or formation mechanism, among others. We also discuss the challenges for increasing the value of the carbon materials formed and therefore, enhance process viability.

Feedstock choice, pyrolysis temperature and type influence biochar characteristics: a comprehensive meta-data analysis review

Abstract: Various studies have established that feedstock choice, pyrolysis temperature, and pyrolysis type influence final biochar physicochemical characteristics. However, overarching analyses of pre-biochar creation choices and correlations to biochar characteristics are severely lacking. Thus, the objective of this work was to help researchers, biochar-stakeholders, and practitioners make more well-informed choices in terms of how these three major parameters influence the final biochar product. Utilizing approximately 5400 peer-reviewed journal articles and over 50,800 individual data points, herein we elucidate the selections that influence final biochar physical and chemical properties, total nutrient content, and perhaps more importantly tools one can use to predict biochar’s nutrient availability. Based on the large dataset collected, it appears that pyrolysis type (fast or slow) plays a minor role in biochar physico- (inorganic) chemical characteristics; few differences were evident between production styles. Pyrolysis temperature, however, affects biochar’s longevity, with pyrolysis temperatures > 500 °C generally leading to longer-term (i.e., > 1000 years) half-lives. Greater pyrolysis temperatures also led to biochars containing greater overall C and specific surface area (SSA), which could promote soil physico-chemical improvements. However, based on the collected data, it appears that feedstock selection has the largest influence on biochar properties. Specific surface area is greatest in wood-based biochars, which in combination with pyrolysis temperature could likely promote greater changes in soil physical characteristics over other feedstock-based biochars. Crop- and other grass-based biochars appear to have cation exchange capacities greater than other biochars, which in combination with pyrolysis temperature could potentially lead to longer-term changes in soil nutrient retention. The collected data also suggest that one can reasonably predict the availability of various biochar nutrients (e.g., N, P, K, Ca, Mg, Fe, and Cu) based on feedstock choice and total nutrient content. Results can be used to create designer biochars to help solve environmental issues and supply a variety of plant-available nutrients for crop growth.

Biomass pyrolysis: past, present, and future

Abstract: Biomass pyrolysis is a promising renewable sustainable source of fuels and petrochemical substitutes. It may help in compensating the progressive consumption of fossil-fuel reserves. The present article outlines biomass pyrolysis. Various types of biomass used for pyrolysis are encompassed, e.g., wood, agricultural residues, sewage. Categories of pyrolysis are outlined, e.g., flash, fast, and slow. Emphasis is laid on current and future trends in biomass pyrolysis, e.g., microwave pyrolysis, solar pyrolysis, plasma pyrolysis, hydrogen production via biomass pyrolysis, co-pyrolysis of biomass with synthetic polymers and sewage, selective preparation of high-valued chemicals, pyrolysis of exotic biomass (coffee grounds and cotton shells), comparison between algal and terrestrial biomass pyrolysis. Specific future prospects are investigated, e.g., preparation of supercapacitor biochar materials by one-pot one-step pyrolysis of biomass with other ingredients, and fabricating metallic catalysts embedded on biochar for removal of environmental contaminants. The authors predict that combining solar pyrolysis with hydrogen production would be the eco-friendliest and most energetically feasible process in the future. Since hydrogen is an ideal clean fuel, this process may share in limiting climate changes due to CO2 emissions.

Recent advances on catalysts for improving hydrocarbon compounds in bio-oil of biomass catalytic pyrolysis

Abstract: This paper reports the progress of catalysts for improving the hydrocarbon compounds in bio-oil obtained from catalytic pyrolysis of biomass. In addition, the effects of the other operating conditions, such as temperature, type of biomass, heating rate, vapors residence time, carrier gas, and hydrogen donor on the yield and properties of bio-oil have been briefly explored. Temperature and catalysts type were found to have major impact on the bio-oil yield and quality. TGA-DTA analysis of biomass revealed that major biomasses pyrolysis zone for high bio-oil yield is in the range of 400–600 °C. Pilot, semi-pilot and large-scale units reported an average temperature of 500 °C for pyrolysis of biomass. The development of advanced catalysts such as zeolite-based catalysts, supported transition and noble metal catalysts, and metal oxide catalysts have been designed to remove the undesired compounds and to increase the hydrocarbon yield in bio-oil. Noble metal supported catalysts produced bio-oil with a low content of oxygenated compounds compared to non-noble metal catalysts; however, their cost and accessibility favor the utilization of non-noble metal supported catalysts.

Production, activation, and applications of biochar in recent times

Abstract: Biomass is a green energy source and is available in abundance. Biochar is a carbon-rich material derived from a wide range of biomass or organic waste through the thermochemical route. Biochar has received increasing attention because of its distinctive properties such as high carbon content, greater specific surface area, cation exchange capacity, nutrient retention capacity, and stable structure. This review paper extensively studies and reports the different pyrolysis processes, reactor types, the effect of process parameters on biochar yield, and its physicochemical properties, biochar activation methods, and applications. It also details the status of the research and development (R&D) progress in biochar production through conventional and advanced technologies. The study found that unlike many products (at R&D stage) biochar has high potential to scale up and has a direct impact on crop yield, water purification (for domestic and industrial application), alternative fuels (clean solid fuel for cookstove), air purification, catalyst, biogas production, purification, and storage. In addition, the paper lists the merits and challenges in the novel biochar applications like hydrogen storage, electrochemical capacitor, and fuel cell technology.

Evolution Pathway from Iron Compounds to Fe1(II)-N4 Sites through Gas-Phase Iron during Pyrolysis.

Abstract: Pyrolysis is indispensable for synthesizing highly active Fe-N-C catalysts for the oxygen reduction reaction (ORR) in acid, but how Fe, N, and C precursors transform to ORR-active sites during pyrolysis remains unclear. This knowledge gap obscures the connections between the input precursors and the output products, clouding the pathway toward Fe-N-C catalyst improvement. Herein, we unravel the evolution pathway of precursors to ORR-active catalyst comprised exclusively of single-atom Fe1(II)-N4 sites via in-temperature X-ray absorption spectroscopy. The Fe precursor transforms to Fe oxides below 300 °C and then to tetrahedral Fe1(II)-O4 via a crystal-to-melt-like transformation below 600 °C. The Fe1(II)-O4 releases a single Fe atom that diffuses into the N-doped carbon defect forming Fe1(II)-N4 above 600 °C. This vapor-phase single Fe atom transport mechanism is verified by synthesizing Fe1(II)-N4 sites via "noncontact pyrolysis" wherein the Fe precursor is not in physical contact with the N and C precursors during pyrolysis.

Rapid and energy-efficient microwave pyrolysis for high-yield production of highly-active bifunctional electrocatalysts for water splitting

Abstract: Functional materials with tuned nanostructure derived from metal–organic frameworks (MOF) hold great promise in energy storage/conversion and catalysis. Herein, we report a novel strategy to fabricate carbon fiber (CF)-supported cobalt nanocatalysts (Co-NC/CF) by a self-made “microreactor” consisted of randomly stacked graphene powder with the help of the microwave field. This newly-developed methodology can not only lead to a significantly enhanced yield of MOF-derived Co-NC up to 48.7 wt%, but also dramatically reduce the pyrolysis time (in just 60 s) and energy consumption (only 0.37% of traditional pyrolysis method). The experimental results combined with theoretical calculations revealed that the synthesized Co-NC/CF with optimized surface binding capability for reaction intermediates featured high-efficient catalytic activities for OER and HER owing to the electron transfer from cobalt to the surface carbon layers. The present microwave pyrolysis technique with an ultra-short synthesis cycle, high product yield and excellent energy efficiency, also demonstrated broad applicability for the synthesis of other MOF-derived functional materials.

Biochar for Wastewater Treatment—Conversion Technologies and Applications

Abstract: Biochar as a stable carbon-rich material shows incredible potential to handle water/wastewater contaminants. Its application is gaining increasing interest due to the availability of feedstock, the simplicity of the preparation methods, and their enhanced physico-chemical properties. The efficacy of biochar to remove organic and inorganic pollutants depends on its surface area, pore size distribution, surface functional groups, and the size of the molecules to be removed, while the physical architecture and surface properties of biochar depend on the nature of feedstock and the preparation method/conditions. For instance, pyrolysis at high temperatures generally produces hydrophobic biochars with higher surface area and micropore volume, allowing it to be more suitable for organic contaminants sorption, whereas biochars produced at low temperatures own smaller pore size, lower surface area, and higher oxygen-containing functional groups and are more suitable to remove inorganic contaminants. In the field of water/wastewater treatment, biochar can have extensive application prospects. Biochar have been widely used as an additive/support media during anaerobic digestion and as filter media for the removal of suspended matter, heavy metals and pathogens. Biochar was also tested for its efficiency as a support-based catalyst for the degradation of dyes and recalcitrant contaminants. The current review discusses on the different methods for biochar production and provides an overview of current applications of biochar in wastewater treatment.