Showing papers by "Ajay K. Dalai published in 2021"

Chemistry and Specialty Industrial Applications of Lignocellulosic Biomass

Abstract: Lignocellulosic feedstocks are gaining increased popularity for novel industrial applications because of their availability and bio-renewability. Using lignocellulosic materials, especially from agricultural and forestry sectors could help reduce the over-dependence on petrochemical resources while providing a sustainable waste management alternative. This review aims to describe the chemistry of different components of lignocellulosic biomass (cellulose, hemicellulose, lignin, extractives and ash). Besides, many novel industrial applications of lignocellulosic biomass have been comprehensively described, which includes biorefining for biofuel and biochemical production, biomedical, cosmeceuticals and pharmaceuticals, bioplastics, multifunctional carbon materials and other eco-friendly specialty products. The production and applications of lignocellulose-derived carbon materials such as activated carbon, carbon nanotubes, carbon nanohorns, etc. have been highlighted. The potential industrial utility of cellulose and lignin-based specialty materials such as cellulose fiber, bacterial cellulose, epoxides, polyolefins, phenolic resins, bioplastics are discussed in this review. The cutting-edge industrial utilization of lignocellulosic biomass described in this review suggests its major role in establishing a circular bioeconomy that consists of innovative design and advanced production methods to facilitate industrial recovery and reuse of waste materials beyond biofuel and biochemical production.

A Review of Torrefaction Technology for Upgrading Lignocellulosic Biomass to Solid Biofuels

Abstract: The utilization of lignocellulosic biomass is closely related to one of the renewable sources of energy. However, a few inherent properties of lignocellulosic biomass such as high moisture content, low density, high volume, and heterogeneous composition make it unfavorable for bulk transportation, storage, handling, and conversion. The pretreatment of biomass is found to resolve a few of the aforementioned limitations while increasing the conversion efficiency of lignocellulosic biomass into biofuels. This article reviews the opportunities, challenges, and state-of-art research on torrefaction as a widely used biomass upgrading technique for solid fuel production and thermochemical biomass conversion. Some notable applications of such pretreatments in high-value solid biofuel production, densification, combustion, co-firing, gasification, and metallurgy have been reviewed. The broad changes in physicochemical characteristics and structural chemistry of lignocellulosic biomass because of torrefaction have been thoroughly described. This review also comprehends the effects of different process parameters and operating conditions of torrefaction of lignocellulosic biomass to produce high-value solid fuel. This article attempts to highlight some recent advancements in biomass torrefaction technology concerning the fundamental characteristics of biomass and process operation and optimization as well as the evolution of physicochemical features of torrefied biomass. Lastly, the value-added industrial applications of torrefaction technology and torrefied biomass are also elucidated.

Innovations in applications and prospects of bioplastics and biopolymers: a review

Abstract: Non-biodegradable plastics are continually amassing landfills and oceans worldwide while creating severe environmental issues and hazards to animal and human health. Plastic pollution has resulted in the death of millions of seabirds and aquatic animals. The worldwide production of plastics in 2020 has increased by 36% since 2010. This has generated significant interest in bioplastics to supplement global plastic demands. Bioplastics have several advantages over conventional plastics in terms of biodegradability, low carbon footprint, energy efficiency, versatility, unique mechanical and thermal characteristics, and societal acceptance. Bioplastics have huge potential to replace petroleum-based plastics in a wide range of industries from automobiles to biomedical applications. Here we review bioplastic polymers such as polyhydroxyalkanoate, polylactic acid, poly-3-hydroxybutyrate, polyamide 11, and polyhydroxyurethanes; and cellulose-based, starch-based, protein-based and lipid-based biopolymers. We discuss economic benefits, market scenarios, chemistry and applications of bioplastic polymers.

Hydrochar: A Review on Its Production Technologies and Applications

Abstract: Recently, due to the escalating usage of non-renewable fossil fuels such as coal, natural gas and petroleum coke in electricity and power generation, and associated issues with pollution and global warming, more attention is being paid to finding alternative renewable fuel sources. Thermochemical and hydrothermal conversion processes have been used to produce biochar and hydrochar, respectively, from waste renewable biomass. Char produced from the thermochemical and hydrothermal decomposition of biomass is considered an environmentally friendly replacement for solid hydrocarbon materials such as coal and petroleum coke. Unlike thermochemically derived biochar, hydrochar has received little attention due to the lack of literature on its production technologies, physicochemical characterization, and applications. This review paper aims to fulfill these objectives and fill the knowledge gaps in the literature relating to hydrochar. Therefore, this review discusses the most recent studies on hydrochar characteristics, reaction mechanisms for char production technology such as hydrothermal carbonization, as well as hydrochar activation and functionalization. In addition, the applications of hydrochar, mainly in the fields of agriculture, pollutant adsorption, catalyst support, bioenergy, carbon sequestration, and electrochemistry are reviewed. With advancements in hydrothermal technologies and other environmentally friendly conversion technologies, hydrochar appears to be an appealing bioresource for a wide variety of energy, environmental, industrial, and commercial applications.

Biochar production, activation and adsorptive applications: a review

Abstract: Rising global population and urbanization are major causes of waste generation, energy demand and carbon emissions. The atmospheric CO2 concentration has increased of 44% from 284 ppm in 1850 to 409 ppm in 2018. In 2017, the world energy consumption was 582 quadrillion British thermal units (qBtu), including 495 qBtu of fossil fuels and 87 qBtu of renewable and nuclear energy sources. Therefore, there is a need for new energies and methods of carbon sequestration, for instance by recycling biomass into biochar. Here, we review the thermochemical valorization of waste biomass by pyrolysis, gasification, torrefaction and carbonization to produce biochar with promising and environmental applications. We detail parameters that control biochar yields, quality and composition. Physical and chemical routes of biochar activation are also described. We focus on the utilization of biochar as soil amendment and for the adsorption of pollutants from wastewater. We conclude by a discussion on the techno-economic and lifecycle assessment of biochar production technologies.

Modeling and process optimization of hydrothermal gasification for hydrogen production: A comprehensive review

Abstract: Hydrothermal gasification of biomass is an alternative method of producing hydrogen-rich syngas. Modeling and optimization of hydrothermal processes are important to evaluate the economic feasibility of the process. Furthermore, developing a mathematical model to represent the many underlying mechanisms during hydrothermal gasification could contribute to lower process expenditures, improve efficiency and provide an in-depth understanding of the process. The present study outlines different modeling and optimization strategies for hydrothermal gasification of biomass and waste materials to produce hydrogen-rich syngas. The modeling techniques (e.g. thermodynamic, kinetic and computational fluid dynamic modeling) and process optimization approaches (e.g. univariate, factorial, Taguchi, response surface methodology and mixture design of experiments) are discussed in this review comprehensively together with their merits and limitations. The knowledge gaps and prospects of modeling and optimization of hydrothermal conversion are also elucidated.

Kinetics and Selectivity Study of Fischer–Tropsch Synthesis to C5+ Hydrocarbons: A Review

Abstract: Fischer–Tropsch synthesis (FTS) is considered as one of the non-oil-based alternatives for liquid fuel production. This gas-to-liquid (GTL) technology converts syngas to a wide range of hydrocarbons using metal (Fe and Co) unsupported and supported catalysts. Effective design of the catalyst plays a significant role in enhancing syngas conversion, selectivity towards C5+ hydrocarbons, and decreasing selectivity towards methane. This work presents a review on catalyst design and the most employed support materials in FTS to synthesize heavier hydrocarbons. Furthermore, in this report, the recent achievements on mechanisms of this reaction will be discussed. Catalyst deactivation is one of the most important challenges during FTS, which will be covered in this work. The selectivity of FTS can be tuned by operational conditions, nature of the catalyst, support, and reactor configuration. The effects of all these parameters will be analyzed within this report. Moreover, zeolites can be employed as a support material of an FTS-based catalyst to direct synthesis of liquid fuels, and the specific character of zeolites will be elaborated further. Furthermore, this paper also includes a review of some of the most employed characterization techniques for Fe- and Co-based FTS catalysts. Kinetic study plays an important role in optimization and simulation of this industrial process. In this review, the recent developed reaction rate models are critically discussed.

Advances in upgradation of pyrolysis bio-oil and biochar towards improvement in bio-refinery economics: A comprehensive review

Abstract: Depletion of fossil fuel reserves and ever-increasing energy demands necessitates exploring green and renewable biofuels. Though biomass-based fuels have the potential to replace fossil fuels but the low quality of fuels along with high process economics limits direct application. Concept of integrated bio-refinery is the unparalleled solution to this problem which involves the production of hydrocarbon grade fuels along with valuable chemicals from the pyrolysis derived bio-oil. This paper reviews recent advances in upgradation techniques of bio-oil along with moisture removal techniques and recovery of valuable chemicals from bio-oil. It also reviews current advances in the utilization of co-product such as biochar to increase the overall economics of the process. It also elucidates the challenges encountered as well as scope for future work. The current review is peculiarly based on pyrolysis based bio-refinery with detailed literature on the techniques of conversion of pyrolysis derived bio-oil into valuable biofuels and industrial grade chemicals with a view to improve the overall economics of the process through biochar utilization, which is not covered in other reviews. As compared to other published studies, this work provides more comprehensive information on the topic, which will give better understanding to a new researcher as well as help to plan and develop new techniques on bio-refinery for attaining the aim of cleaner and sustainable future.

Subcritical water hydrolysis of Phragmites for sugar extraction and catalytic conversion to platform chemicals

Abstract: Phragmites karka, also known as common reed, is a perennial grass and a highly invasive crop species, which creates ecological problems by competing with native biodiversity and vegetation. This study involves subcritical water hydrolysis of Phragmites to produce monomeric sugars followed by the catalytic conversion of the sugar-rich hydrolysate to furfural and levulinic acid. Subcritical water hydrolysis was performed by the Central Composite Design method at variable temperatures (150–230 °C), reaction time (15–60 min) and feed concentration (2–5 wt%). The temperature was found to be the most prominent factor affecting biomass hydrolysis. The yield of total reducing sugars from biomass hydrolysis was in the range of 2.1–18.1% where the highest yield was obtained at the optimal temperature (190 °C), reaction time (37.5 min) and feed concentration (2 wt%). During subcritical water hydrolysis of Phragmites, two main degradation products obtained at a higher temperature (230 °C) and reaction time (37.5 min) were furfural (8.2%) and 5-hydroxymethylfurfural (11.7%). However, at 230 °C and a longer reaction time of 60 min, 5-hydroxymethylfurfural yield reduced to 5.1% owing to its conversion to humin while furfural yield elevated to 9.9%. Catalysts such as ZrO2, TiO2, Zr0.5Ti0.5O2, WO3–ZrO2, WO3–TiO2 and WO3–Zr0.5Ti0.5O2 were involved in the conversion of the sugar-rich hydrolysate obtained from subcritical water hydrolysis of Phragmites. The highest sugar conversion was found to be 92% with WO3–ZrO2 resulting in the yields of furfural (51%) and levulinic acid (34%). The activity of particular catalysts (e.g. WO3–ZrO2, WO3–TiO2 and WO3–Zr0.5Ti0.5O2) relied on the synergistic effects of Lewis and Bronsted acid sites.

Techno-economic and life cycle analysis of biofuel production via hydrothermal liquefaction of microalgae in a methanol-water system and catalytic hydrotreatment using hydrochar as a catalyst support

Abstract: The hydrochar, a by-product of hydrothermal liquefaction (HTL) of algal biomass, was utilized through two methods; combustion and activation, for its usage as a source of heat and a catalyst support for hydrodeoxygenation (HDO) process in the production of algal biofuels. In this study, techno-economic analysis (TEA) and life cycle assessment (LCA) of algal biofuels production in a two-stage process (HTL and HDO) were investigated. Aspen plus simulation and SimaPro software were used to analyze process economics and greenhouse gas (GHG) emissions. Microalgae at 200 dry metric tonnes day−1 was the basis for its conversion to biocrude oil through HTL in the methanol-water system followed by catalytic upgrading to produce biofuels. According to HTL experimental results, maximum biocrude oil yield of 57.8 wt% was obtained using microalgae-solvent mass ratio and methanol-water mass ratio of 1:5 and 3:1, respectively. Produced biocrude oil contained 14.5 wt% of oxygen and HHV of 33.4 MJ kgbiocrude oil−1 which required upgrading to be utilized as a transportation fuel. HDO was employed to enhance the quality of biocrude oil with decrease in oxygen content (3.1 wt%) and increase in HHV (42 MJ kgbiofuel−1). The minimum fuel selling price (MFSP) for using method #2 (activation) was 2.2 $ L−1 to breakeven the cost of operation, which was about 10% lower than that from method #1 (combustion). The GHG emissions performance was estimated at −1.13 gCO2-eq MJ−1 indicating the significant GHG emissions reduction compared to petroleum-based fuels production.

Catalytic conversion of lignocellulosic polysaccharides to commodity biochemicals: a review

Abstract: The applications of green chemistry and industrial bioprocessing are becoming more popular to address concerns of pollution, climate change, global warming, circular bioeconomy, sustainable development goals and energy security. Both biological and thermochemical routes can play vital roles in transforming waste lignocellulosic biomass to high-value bioproducts. Lignocellulosic biomass contains essential building blocks that could be tapped to generate biofuels, biochemicals and biomaterials to replace petroleum-derived fuels and chemicals. Besides containing extractives and ash, lignocellulosic feedstocks are made up of cellulose, hemicellulose and lignin typically in the ranges of 35–55 wt%, 20–40 wt% and 10–25 wt%, respectively. Catalytic thermochemical approaches are effective for biomass conversion with a significant yield of various platform chemicals, such as furfural, 5-hydroxymethylfurfural, levulinic acid and other furan or non-furan-based chemicals. These chemicals play a crucial part in the synthesis of different fuel-based materials, which can successfully replace petroleum-based chemicals or fuels. Lignocellulosic biomass and their derived monomeric sugars can be catalytically converted into various platform chemicals using different homogeneous and heterogeneous catalysts. In this review paper, we have highlighted some promising catalysts such as mineral acids, mesoporous silica materials, zeolites, metal–organic frameworks, metal oxides and ionic liquids used in biorefining to generate biochemicals. We have also reviewed a few pieces of notable literature presenting the catalytic conversion of cellulose, hemicellulose, cellobiose, glucose, fructose and xylose into various high-value chemicals.

Catalytic Supercritical Water Gasification of Soybean Straw: Effects of Catalyst Supports and Promoters

Abstract: Supercritical water gasification is a hydrothermal process to gasify complex organic biomass to produce hydrogen-rich syngas. This study reports the catalytic performance and hydrogen selectivity of several Ni-based catalysts during supercritical water gasification of soybean straw. All experiments were performed at a temperature, an average biomass particle size, a feedstock/water ratio, and a residence time 500 °C, 0.13 mm, 1:10, and 45 min, respectively. A comprehensive screening of different support materials ranging from activated carbon (AC), carbon nanotubes (CNTs), ZrO₂, Al₂O₃, SiO₂, and Al₂O₃–SiO₂ was performed at 10 wt % Ni loading. The effectiveness of each support in improving H₂ yield and selectivity was in the order ZrO₂ > Al₂O₃ > AC > CNT > SiO₂ > Al₂O₃–SiO₂. The effects of adding three promoters (i.e., Na, K, and Ce) to the supported Ni/ZrO₂ and Ni/Al₂O₃ catalysts were evaluated. In terms of H₂ yield, the performance of each promoter for Ni/ZrO₂ catalysts was in the order Ce (10.9 mmol/g) > K (10.3 mmol/g) > Na (9.5 mmol/g). Cerium showed better performance in promoting H₂ yield and minimizing coke deposition on the support. The addition of K, Na, and Ce promoters elevated Ni dispersion and the metallic surface area, thus improving H₂ yields.

Carbon dioxide capture from flue gas in biochar produced from spent coffee grounds: Effect of surface chemistry and porous structure

Abstract: Coffee is a relevant agricultural product and one of the most consumed hot beverages globally. To assess the impact of pyrolysis temperatures (400–600 ℃) and heating rates from 5 to 20 ℃/min on the biochar production yields and textural characteristics, spent coffee grounds was subjected to slow-pyrolysis in a pilot-scale reactor. Further, complementary spectroscopic and textural analyses were executed to evaluate the impacts of pyrolysis temperatures on the corresponding biochar surface properties including textural characteristics, reactivity, and surface functionalities. The correlation of pyrolysis temperature with change in biochar’s surface properties along with CO2 mitigation efficiency is examined. The ultimate analysis, FTIR spectroscopy, 13C NMR spectroscopy and Raman scattering measurements confirmed an increment in the degree of aromaticity or decomposition of organic complexes in biochar. The development of basic surface functionalities after the thermal treatment was ascertained by XPS and NEXAFS analyses. Based on the surface composition and textural properties, the CO2 adsorption capacity of SCG-600 was assessed under varying adsorption temperatures at ambient pressure employing a fixed-bed reactor. In this investigation, SCG-600 showed a large CO2 uptake of 2.8 mmol/g under a typical post-combustion scenario. CO2 adsorption mechanism followed the pseudo-first-order kinetics and lower activation energy over varying investigated temperatures reveals the binding process is physical in nature. SCG-600 could be proposed as promising biochar that possesses a combination of higher surface area, well-developed microporous structure, heterogeneous and basic surface functional moieties to meet the specific requirements in dynamic CO2 adsorption.

Characteristics of torrefied fuel pellets obtained from co-pelletization of agriculture residues with pyrolysis oil

Abstract: Agricultural wastes have the potential to contribute to global energy by converting low value by-products to high value products e.g. fuel pellets, which can be used for heat and power generation. In this study, co-pelletizing characteristics of canola hull, oat hull and barley straw with water were investigated while pyrolysis bio-oil was used as binder. Co-pelletization has been conducted using bench-scale extruder. Canola hull was used as base feedstock due to having a small portion of oil (8 wt%) which provides lubricating effects during pelletization. Increase in biomass to water mass ratio, increased the mechanical strength and durability of pellets but pellets yield decreased. The optimum biomass to water mass ratio was found 2.5. Pyrolysis bio-oil worked as effective additives, enhanced the flow properties, made extrusion smooth, advanced the internal structure of pellet by facilitating strong interlocking of particles, and thus boosted the physical firmness of fuel pellet. Results showed that co-pelletization of oat hull and barley straw with canola hull was optimum for 30 wt% of oat hull or barley straw, but pelletization was successful for up to 45 wt% of those feedstocks. Microwave torrefaction was conducted to boost up the hydrophobicity and higher heating value of pellet. Torrefied pellet showed higher heating value, higher energy density, higher carbon content, lower atomic ratio, lower moisture uptake rate compared to untreated pellet. Synchrotron-based computed tomography shows that porosity increased by up to 39% after torrefaction. Additionally, to assess the mechanical, physical and chemical properties of pellet, various characterization methods were employed.

Fischer–Tropsch Synthesis for Light Olefins from Syngas: A Review of Catalyst Development

Abstract: Light olefins as one the most important building blocks in chemical industry can be produced via Fischer–Tropsch synthesis (FTS) from syngas. FT synthesis conducted at high temperature would lead to light paraffins, carbon dioxide, methane, and C5+ longer chain hydrocarbons. The present work focuses on providing a critical review on the light olefin production using Fischer–Tropsch synthesis. The effects of metals, promoters and supports as the most influential parameters on the catalytic performance of catalysts are discussed meticulously. Fe and Co as the main active metals in FT catalysts are investigated in terms of pore size, crystal size, and crystal phase for obtaining desirable light olefin selectivity. Larger pore size of Fe-based catalysts is suggested to increase olefin selectivity via suppressing 1-olefin readsorption and secondary reactions. Iron carbide as the most probable phase of Fe-based catalysts is proposed for light olefin generation via FTS. Smaller crystal size of Co active metal leads to higher olefin selectivity. Hexagonal close-packed (HCP) structure of Co has higher FTS activity than face-centered cubic (FCC) structure. Transition from Co to Co3C is mainly proposed for formation of light olefins over Co-based catalysts. Moreover, various catalysts’ deactivation routes are reviewed. Additionally, techno-economic assessment of FTS plants in terms of different costs including capital expenditure and minimum fuel selling price are presented based on the most recent literature. Finally, the potential for global environmental impacts associated with FTS plants including atmospheric and toxicological impacts is considered via lifecycle assessment (LCA).