Showing papers by "Ajay K. Dalai published in 2022"

A Review of Thermochemical Conversion of Waste Biomass to Biofuels

Abstract: Biofuels are sustainable alternatives to fossil fuels because of their renewable and low-cost raw materials, environmentally friendly conversion technologies and low emissions upon combustion. In addition, biofuels can also be upgraded to enhance their fuel properties for wide applicability in power infrastructures. Biofuels can be produced from a wide variety of biomasses through thermochemical and biological conversion processes. This article provides insights into the fundamental and applied concepts of thermochemical conversion methods such as torrefaction, pyrolysis, liquefaction, gasification and transesterification. It is important to understand the physicochemical attributes of biomass resources to ascertain their potential for biofuel production. Hence, the composition and properties of different biomass resources such as lignocellulosic feedstocks, oilseed crops, municipal solid waste, food waste and animal manure have been discussed. The properties of different biofuels such as biochar, bio-oil, bio-crude oil, syngas and biodiesel have been described. The article concludes with an analysis of the strength, weaknesses, opportunities and threats of the thermochemical conversion technologies to understand their scale-up applications and commercialization.

A review of biomass resources and thermochemical conversion technologies

Abstract: Waste biomass has the potential to produce renewable fuels and fine chemicals. Biofuels derived from agricultural, forestry, and energy crop systems are promising resources to address climate change and minimize greenhouse gas emissions. The recent advances in various thermochemical technologies for the conversion of waste biomass to value-added biofuel products are discussed. A summarized outline of thermochemical technologies such as torrefaction, liquefaction, pyrolysis, and gasification is provided. An overview of different types and sources of biomass as well as their physicochemical properties is presented. The thermochemical conversion products and their environmental benefits are considered as well.

Techno – economic analysis of activated carbon production from spent coffee grounds: Comparative evaluation of different production routes

Abstract: Activated carbon (AC) has gained immense popularity owing to its excellent physicochemical properties and its ability to remove carbon dioxide (CO2) from flue gas stream. This study examines the potential of spent coffee grounds (SCG) as a precursor for activated carbon (AC) production via prominent thermochemical conversion technologies. Different production routes, such as slow pyrolysis, activation, and deep eutectic solvent (DES) functionalization were compared in terms of their economic viability. Three scenarios (Scenario 1–3) involving combinations of the technologies and production routes were evaluated. Scenario 1 comprises of slow pyrolysis, CO2 activation and flue gas recycling for activation. Scenario 2 includes flue gas combustion while the third scenario comprise of flue gas combustion and DES impregnation. All processes were simulated with Aspen plus, while a detailed cash flow analysis was used to estimate the profitability parameters. The price of AC was found to be the most crucial determinant of an AC production plant’s viability and feasibility. The minimum selling price (MSP) of AC samples produced from scenarios 1,2 and 3 are U.S $0.15/kg, $0.21/kg, $0.28/kg respectively. The price of pristine AC and DES treated AC were lower than the commercially available activated carbon (U.S $0.45/kg).

Comparative Catalytic Performance Study of 12-Tungstophosphoric Heteropoly Acid Supported on Mesoporous Supports for Biodiesel Production from Unrefined Green Seed Canola Oil

Abstract: In this study, three solid acid catalysts, namely mesoporous aluminophosphate-supported 12-tungstophosphoric heteropoly acid (HPW/MAP), mesoporous aluminosilicate-supported 12-tungstophosphoric heteropoly acid (HPW/MAS), and gamma alumina-supported 12-tungstophosphoric heteropoly acid (HPW/γ-Al2O3) were prepared and characterized. Mesoporous aluminophosphate (MAP) and mesoporous aluminosilicate (MAS) were synthesized via sol-gel and hydrothermal methods, respectively, and 25 wt.% of 12-tungstophosphoric heteropoly acid (HPW) was immobilized on the support materials using the wet impregnation method. The features of the fabricated catalysts were comprehensively investigated using various techniques such as BET, XRD, NH3-TPD, TGA, and TEM. The surface area of the supported catalysts decreased after HPW impregnation according to BET results, which indicates that HPW loaded on the supports and inside of their pores successfully. The density and strengths of the acid sites of the support materials and the catalysts before reaction and after regeneration were determined by the NH3-TPD technique. Accordingly, an increase in acidity was observed after HPW immobilization on all the support materials. The catalytic performance of the catalysts was studied through alcoholysis reaction using unrefined green seed canola oil as the feedstock. The maximum biodiesel yield of 82.3% was obtained using 3 wt.% of HPW/MAS, with a methanol to oil molar ratio of 20:1, at 200 °C and 4 MPa over 7 h. The reusability study of HPW/MAS showed that it can maintain 80% of its initial activity after five runs.

Chemicals Production from Glycerol through Heterogeneous Catalysis: A Review

Abstract: Utilization of biofuels generated from renewable sources has attracted broad attention due to their benefits such as reducing consumption of fossil fuels, sustainability, and consequently prevention of global warming. The production of biodiesel causes a huge amount of by-product, crude glycerol, to accumulate. Glycerol, because of its unique structure having three hydroxyl groups, can be converted to a variety of industrially valuable products. In recent decades, increasing studies have been carried out on different catalytic pathways to selectively produce a wide range of glycerol derivatives. In the current review, the main routes including carboxylation, oxidation, etherification, hydrogenolysis, esterification, and dehydration to convert glycerol to value-added products are investigated. In order to achieve more glycerol conversion and higher desired product selectivity, acquisition of knowledge on the catalysts, the type of acidic or basic, the supports, and studying various reaction pathways and operating parameters are necessary. This review attempts to summarize the knowledge of catalytic reactions and mechanisms leading to value-added derivatives of glycerol. Additionally, the application of main products from glycerol are discussed. In addition, an overview on the market of glycerol, its properties, applications, and prospects is presented.

Application of computational fluid dynamics for modeling of Fischer-Tropsch synthesis as a sustainable energy resource in different reactor configurations: A review

Abstract: Increasing the global energy demand motivates the search for renewable and clean energy resources. Fischer-Tropsch synthesis (FTS) is one of these sources, which converts syngas (a mixture of CO and H2) to a wide range of hydrocarbons . Liquid transportation fuels produced via FTS from biomass-derived syngas introduce an attractive, clean, carbon-neutral, and sustainable energy source. Reactor and catalyst designs play a significant role in the improvement of FTS efficiency. Flow hydrodynamics coupled with reaction kinetics makes this process challenging. Numerical methods such as computational fluid dynamics (CFD) can help us effectively understand the fluid dynamics within FT reactor. The main objective of CFD simulation for FTS can be summarized in three points (1) to analyze the conservation laws (mass, heat, and momentum transport) coupled with the catalytic reactions in the reactor, (2) to optimize the operating conditions to maximize the catalytic activity and selectivity to desired products, and (3) to support the reactor design and engineering. A CFD code consists of four steps: geometry generation, meshing, solver, and post-processing. Emerging data-driven techniques were also reviewed in this work to analyze the fluid dynamics of FTS. FTS is mainly operated in fixed bed, slurry bubble column, fluidized bed, micro-structured, and membrane reactors. This review aims to analyze the capability of CFD simulation in predicting the FTS performance in different reactor types and address the present challenges.

Optimization of olefins' yield in Fischer-Tropsch synthesis using carbon nanotubes supported iron catalyst with potassium and molybdenum promoters

Abstract: Light olefins' (C2-C4) production from syngas (H2 +CO) through Fischer-Tropsch synthesis (FTS) benefits from Fe-based catalysts supported on carbon nanotubes (CNTs). Two-level full factorial design was applied for K and/or Mo-promoted Fe/CNTs catalyst to investigate the effects of synthesis conditions including Mo/K mass ratio, ultrasonic time, and iron loading on light olefins' yield. These catalysts were characterized to perform an in-depth study of Mo/K binary promoter effects on Fe/CNTs catalyst in Fischer-Tropsch to light olefins. CO chemisorption and TEM revealed that molybdenum plays a significant role in metal dispersion, leaving structural defects on CNTs support. Additionally, H2-TPR confirmed that K as promoter facilitates reducibility of Fe/CNTs catalysts, which promoted CO conversion in FTS. Compared with the un-promoted Fe/CNTs catalysts, addition of molybdenum as a promoter increased light olefins' selectivity by 33.4%, while potassium led to an increase in CO conversion by 96.3%. The optimum formulation (0.5K5Mo10Fe/CNTs) obtained olefins' yield of 35.5%.

Synthesis of Biochar From Lignocellulosic Biomass for Diverse Industrial Applications and Energy Harvesting: Effects of Pyrolysis Conditions on the Physicochemical Properties of Biochar

Abstract: The excessive dependency on fossil fuel resources could be curtailed by the efficient conversion of lignocellulosic biomass. Biochar, a porous carbonaceous product synthesized exploiting thermochemical conversion pathway, could be an environment-friendly replacement of fossil fuel resources. Slow pyrolysis, a sub-class among various thermochemical conversion techniques, has gained immense popularity owing to its potential to convert biomass to biochar. Furthermore, biochar obtained as the by-product of slow pyrolysis has attracted enormous popularity due to its proven role and application in the multidisciplinary areas of engineering and environmental remediation applications. The physicochemical quality of biochar and its performance is significantly dependent on the feedstock type and pyrolysis process parameters. Therefore, further experimental research and investigations in terms of lignocellulose biomass type and pyrolytic process parameters (temperature, heating rate and reaction time) are essential to produce biochar with desired physicochemical features for effective utilization. This review presents an updated report on slow pyrolysis of lignocellulosic biomass, impact of different pyrolysis parameters and degradation pathway involved in the evolution properties of biomass. The influence of the feedstock type and lignocellulosic composition on the biochar properties are also discussed meticulously. The co-relationship between biochar yield at different pyrolysis temperatures and the development of textural properties provides valuable information for their effective utilization as a functional carbon material. Additionally, an extensive study was undertaken to collate and discuss the excellent physicochemical characteristics of biochar and summarizes the benefits of biochar application for diverse industrial purposes. Biochar is acknowledged for its excellent physicochemical properties owing to the thermal treatment and as a result its prospective diverse industrial applications such as for soil treatment, carbon sequestration, adsorbent (wastewater treatment or CO2 capture), producing activated carbon for gold recovery, energy storage and supercapacitor are summarized systematically in this review paper. For instance, biochar when applied in soil have shown improvement in soil respiration by 1.9 times. Furthermore, biochar when used to capture CO2 from flue gas stream under post-combustion scenario has demonstrated superior capture performance (2.8 mmol/g) compared to commercial activated carbon. This paper identified the knowledge gaps and outlooks in the field of the advancements of biochar from slow pyrolysis for targeted engineering applications mainly in the field of environmental remediation and energy harvesting.

Preparation of activated carbon from spent coffee grounds and functionalization by deep eutectic solvent: Effect of textural properties and surface chemistry on CO2 capture performance

Abstract: Spent coffee grounds have been selected as a potential feedstock to synthesize activated carbon (AC) through physical activation. The activation parameters were optimized by employing the Box-Behnken design method. The impact of input activation parameters included the activation temperature (600-800 ℃), holding time (60-120 mins) and CO 2 flow rate (150-250 mL/min). Accordingly, at the optimum conditions obtained at 800 ℃, 90 min and 150 mL/min, the predicted response of specific surface area (1202.1 m 2 /g) was in good agreement with the actual response 1224 m 2 /g. Furthermore, deep eutectic solvent (DES) has been used to tailor the surface functionalities of the optimized AC (pristine). The change in textural characteristics, surface chemistry and morphology of the pristine and DES-AC samples were characterized by using complementary analytical techniques, including ultimate analysis, ash content, textural characteristics, XRD, CO 2 -TPD, TGA, XPS and SEM analyses. The studies highlighted change in physicochemical properties after the impregnation. For instance, the surface area of the DES-functionalized AC reduced to 1033 m 2 /g, but more basic functional moieties developed on the surface. The DES-AC has shown adequate CO 2 capture performance of 5.5 mmol/g compared to pristine AC (4.34 mmol/g) at 25 ℃ and 15 vol % of CO 2 (in N 2 ). Furthermore, DES functionalized AC has shown excellent selectivity in a dynamic mixture stream of CO 2 /N 2 and facile regeneration (92% retention) after multiple adsorption-desorption runs. Hence, preparing AC from SCG via physical activation and DES impregnation could be proposed as a promising valorization strategy to alleviate the CO 2 emission problem. • The potential of spent coffee grounds to synthesize activated carbon was investigated. • The preparation conditions were optimized using the Box Behnken Design method. • Deep eutectic solvent (DES) was used to functionalize the activated carbon. • The functionalized activated carbon displayed maximum CO 2 adsorption capacity of 5.5 mmol/g. • The DES functionalized activated carbon displayed thermal stability for industrial use.

Extraction of sugars and cellulose fibers from Cannabis stems by hydrolysis, pulping and bleaching

Abstract: Cannabis indica stems were hydrolyzed with subcritical water at various temperatures, reaction times, and feed concentrations. The highest total yield of reducing sugars of 16.4 wt % was obtained at 190 °C in 37.5 min with a feed concentration of 3.5 wt %. Solid residues from the optimized process were treated with 0.5 M NaOH (pulping) and 0.5–3 % H2O2 (bleaching) to isolate cellulose fibers. The maximum yield of cellulose was 34.8 wt % with lowest lignin content of 0.5 wt %. With the removal of hemicellulose and lignin through the integrated hydrothermal processes, the crystallinity index and thermal stability of the cellulose fibers increased.

Valorization of Wild-Type Cannabis indica by Supercritical CO2 Extraction and Insights into the Utilization of Raffinate Biomass

Abstract: Supercritical CO2 extraction (SCCO2) extraction of cannabis oil from Indian cannabis (Cannabis indica) leaves was optimized through a central composite design using CO2 pressure (150–250 bar), temperature (30–50 °C) and time (1–2 h). From the regression model, the optimal CO2 pressure, extraction temperature and time were 250 bar, 43 °C and 1.7 h, respectively resulting in the experimental yield of 4.9 wt% of cannabis oil via SCCO2 extraction. The extract contained cannabidiol, tetrahydrocannabivarin, Δ9-tetrahydrocannabinol and Δ8-tetrahydrocannabinol as well as two terpenoids such as cis-caryophyllene and α-humulene. Besides SCCO2 extraction of cannabis oil, the raffinate biomass was utilized to extract polyphenols using water as the extraction medium. Cannabis oil and water extractive were investigated for their half-maximal inhibitory concentration (IC50) values, which were found to be 1.3 and 0.6 mg/mL, respectively. This is comparable to the commercially available antioxidant such as butylated hydroxytoluene with an IC50 value of 0.5 mg/mL. This work on SCCO2 extraction of cannabinoids and other valuable bioactive compounds provides an environmentally sustainable technique to valorize cannabis leaves.

Catalytic hydrothermal gasification of aqueous effluents obtained from microwave torrefaction of agricultural residue

Abstract: A significant amount of aqueous liquids rich in organic, inorganic contents and leached metals is produced during torrefaction of biomass, which requires additional remediation before disposal. Hydrothermal gasification can produce H 2 -rich syngas from organic wastes, especially from feedstocks with high-water content. This study presents a novel method of valorizing liquid effluents produced from the torrefaction of oat hull and canola hull via microwave irradiation. Hydrothermal gasification of the liquid effluents (feedstock) was carried out at 375-525 °C for 15-60 min with 1:5 and 1:10 feed-to-water ratios under 22-25 MPa pressure to optimize the operating parameters of the process. Hydrothermal gasification of torrefaction effluents from canola hull and oat hull produced total gas yields of 6.6 mmol/g and 8.7 mmol/g, respectively without the addition of water at optimized conditions (525 °C and 45 min). However, with the addition of water (i.e., 1:10 feed-to-water ratio), the total gas yield increased to 12 mmol/g and 16.1 mmol/g from oat hull and canola hull effluents, respectively. The highest H 2 yields (7.8 mmol/g) and carbon gasification efficiency (51%) were obtained at 525 °C in 60 min with a 1:10 feed-to-water ratio. Homogeneous catalysts including KOH, K 2 CO 3 and Na 2 CO 3 were used to improve the gas yields from torrefaction effluents from oat hull at optimal conditions. H 2 gas yield increased by 58%, 65% and 66% in presence of K 2 CO 3 , Na 2 CO 3 and KOH, respectively. KOH led to maximum H 2 yield, hydrogen selectivity and carbon gasification efficiency of 12.8 mmol/g, 89% and 98%, respectively. • Renewable H 2 production from torrefied liquid effluent from supercritical water is feasible. • Impacts of process conditions such as temperature, reaction time and feed to water ratio on products yield were studied in-depth. • The major torrefied liquid chemical species were identified as aldehydes, ketones, organic acids, esters, and aromatics. • Homogeneous catalyst KOH improved the gas yields and hydrogen selectivity by 61% and 36%, respectively. • Anti-coking ability can be enhanced by using feedstock with low carbon contents.

Valorization of hemp hearts oils by advanced extraction techniques and their comparative physicochemical characterization

Abstract: Industrial hemp hearts were subjected to three different extraction techniques-advanced extraction techniques like microwave and ultrasound extraction and primitive extraction technique like mechanical cold pressing in order to extract oils. The extraction yield varied between 41.0 ± 2.1% (w/w) and 54.0 ± 2.7% (w/w). Linoleic acid (LA) was reported to be the major polyunsaturated fatty acid (PUFA) followed by α−Linolenic acid (ALA). The ratio of LA to ALA was found to be close to 3:1 which is considered optimal for nutrition. The ratio of unsaturated fatty acids (UFA) to saturated fatty acids (SFA) was in the range of 6.7 to 9.1. Several minor compounds like ɣ-Sitosterol, stigmasterol, rhodoxanthin, carotene, and methyl cholate as well as antioxidants like β-Carotene and ɣ-Tocopherol have been identified in the oils. The physicochemical properties of the oils like the acid value, iodine value, and oxidative stability indicated that they have higher quality and that the level of unsaturation was very high. Furthermore, free radical scavenging activity of the oils revealed that the oils exhibited 94% of activity in the first 2 h. A perfect combination of unsaturated fatty acids and saturated fatty acids, an appropriate medley of different antioxidants not only qualifies hemp seed oil as an excellent source of nutrition but also as an important plant-based (vegetable) oil for the higher value nutraceutical and pharmaceutical industries.