Journal of Nanoscience and Nanomaterials

Feedstock

Reference

Catalyst

Reference

Technology

Reference

Citrullus vulgaris

2

MOFs and COFs

11

Machine learning technology

20

Xanthium strumarium and Mesua assamica

3

Halloysite supported ZnO/SnO ₂ heterojunction photocatalyst

12

Microwave; Ultrasound; Supercritical transesterification; genetic engineering; Plasma discharge; microchannel reactor; machine learning

21

Handal

4

ZIF-8 MOF-derived nanocatalyst

13

Micro reactor; membrane reactor; microwave; reactive distillation; centrifugal contractor

22

Pennycress Oil

5

Acid-base bifunctional ZnF ₂

14

Machine learning-response surface optimization approach

23

Dunaliella salina microalgae

6

TiO ₂ nanoparticles

15

Life cycle assessment and techno-economic analysis

24

Waste

Cooking Olive Oil and

Sunflower Oil

7

SAPO-34 decorated with Mo and W oxides

16

Ultrasonic treatment

25

Jatropha

8

NaOH/ CoFe ₂O ₄ magnetic nano-catalyst

17

Artificial intelligence and machine learning

26

Pongamia pinnata

9

H ₆PV ₃MoW ₈O ₄₀ supported on magnetic Fe ₃O ₄/ZIF-8 composites

18

Integrated 3D printed microreactors and microseparators

27

Fish waste

10

Ni/Si/ MgO photocatalyst

19

Enzymes with ionic liquid and ultrasound based process intensification

28

S No

Highlights

Reference

1

Waste alkaline solution (WAS, pH = 13.3) is a by-product of the industrial Al production by Bayer’s process. The composition of the WAS (metal oxides, hydroxides, and silicates) is suitable for catalyzing the transesterification of waste cooking oil (WCO) and methanol to produce fatty acid methyl ester (FAME, biodiesel). The yield of biodiesel was > 99 % under modest reaction conditions (T = 60 °C; t = 30 min; WAS amount = 0.204 mol L- ¹; WAS/WCO = 0.019 % (w/w); The process has positive environmental and economic implications at an industrial scale.

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2

The key to solving problems in any realm of human activity is to use the challenges as opportunities. It is more so in the chemical industry, namely, the upcoming biorefinery. Roncaglia et al., precisely addressed the challenges of the inevitable glycerol by-product formation in the biodiesel producing transesterification process and also the inevitable CO2 emission upon the combustion of the biodiesel. The smart strategy to solve the challenge was to convert the glycerol into the glycerol carbonate. A continuous flow process for the reaction of equimolar mixtures of CO ₂ (ensured by the modest molar excess of urea) and glycerol to form glycerol carbonate is developed. Thus urea is effectively used as the CO ₂ precursor altering the thermodynamic process parameters favourably. Issue of the high viscosity of the reaction medium was overcome successfully by dilution of the reaction constituents with water and also by maintaining a suitable low pressure (< 400 mm Hg). The yield of glycerol carbonate (GC) is ~ 42 %. The pressure constraint was the limiting factor pertaining to the product yield. For the first time multiple pass tubular reactor technology was used for such a process.

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3

Fahad Rehman et al., developed the microbubble interfacial technology (as a substitute to the stirred tank reactors) for the production of biodiesel using micro algae (Spirulina) as the feedstock. Microbubble mediated mass transfer technology is being exploited at an industrial scale. However, the current studies only dealt with the lab-scale experiments with a 100 mL batch. Para-toluene sulphonic acid (PTSA) is used a catalyst. A micro algal oil (MO) conversion into biodiesel as high as > 99 % is obtained under modest reaction conditions (MO:Methanol = 1:23.73; t = 60 min; T = 70 ± 5 °C; P = 1 bar; Catalyst: PTSA, 3.3 wt.% of MO; Pseudo first order reaction; Activation energy, Ea = 10.01 ± 0.3 kJ/mol).

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4

Anita Salic and coworkers developed deep eutectic solvents (DES) for the purification (extraction of the by-product glycerol) biodiesel in a micro-extractor. Among the 12 DESs tested the choline chloride, ChCl:Ethylene glycol, EG (1:3) showed high extraction efficiency and the least viscosity. Optical extraction process parameters include, T = 40 ⁰C; residence time, τ = 0.50 min; biodiesel:DES = 1:9 (v/v), glycerol removed = 52.99 ± 5.23 %. Use of different micro channel diameters and different residence times did not contribute to the process enhancement, while the integrated system with two microextractors in series was effective for glycerol removal. Using this method complete purification of biodiesel is achieved in 1 minute.

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5

Micro algal biomass (Desmodesmus sp. EJ8-10) was cultured in anaerobic digestion waste water improved the lipid content in the micro algae by 21.8 %. The lipid content is the fraction that is transesterified to FAME (biodiesel) upon reaction with methanol in the presence of the base catalyst. Greater lipid content means great biodiesel amount. Moreover, the environmental impact too was lower (388.9 mPET2000) in the case of micro algal biomass cultured in anaerobic digestate wastewater.

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6

Fahad Rehman and coworkers exploited the microbubble mediated mass transfer technology for intensifying the transesterification of the waste cooking oil (WCO) as well as the esterification of the free fatty acids in the oil (present as a contaminant) for the production of biodiesel using a bimetallic base catalyst (7 % Sr/ZrO ₂) and an acid catalyst respectively. Conversion as high as 85 % us achieved in 20 minutes. The reaction was found to follow a pseudo-first order kinetics with an activation energy value of 7 kJ/mol. The catalyst was reused for 7 reaction runs. The interface of the microbubbles was found to play a complex role in the conversion of the WCO into the biodiesel. The microbubble interfaces act as a host for the bimetallic catalyst particles. The single step esterification (acid catalyzed) and the transesterification (base catalyzed) was found to be less energy consuming and more energy-efficient.

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7

Dhurba Neupane provided a review on the cultivation of bioenergy feedstock for the production of biofuels for reducing the reliance on fossil based resources and also for solving the problems like food vs fuel conflict, global warming, and the catastrophic consequences of climate change. Insights were provided on the possibilities of various biofuels from biomass, methods of production, key factors affecting the biodiesel production, nature of the catalysts, and the emission of possible greenhouse gases upon combusting the biodiesel. Emphasis was laid on the methods for the development of the third (algal biomass) and the fourth (genetically modified algal biomass with increased lipid/carbonhydrate content) generation feedstock.

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8

The review article of Qiuyun Zhang, Jialu Wang, Yutao Zhang and co-workers, by coincidence, deals with the use of Zr based metal organic frame works (MOFs) as catalysts for the transesterification reaction for the production of biodiesel. The discovery and the development of the MOF based materials is a Nobel winning contribution to the field of Chemistry by Susumu Kitagawa (Kyoto University, Japan), Richard Robson (University of Melbourne, Australia) and Omar M Yaghi (University of California, Berkeley, USA). The Royal Swedish Academy of Sciences that has decided the award of the Nobel prize to Chemistry 2025 commented that the molecular architecture of Metal Organic Frameworks (MOFs) contains rooms for Chemistry. The typical process parameter and outcomes as well as the reusability of the Zr-based MOFs as catalysts for the production of biodiesel were exemplified. MOFs and their derivatives were suggested to be the smart catalysts for the bright biorefinery facilities in near future.

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9

The review by Anoop Singh and coworkers is focused essentially on the new approaches, feedstock and technologies for the sustainable production of biodiesel at the upcoming biorefinery facility. Development of the genetically modified and bioengineered feedstock (plants, yeast, algae, and plant based wastes) is suggested as a promising and sustainable alternative feedstock for enhanced lipid content in cellulose based crops. Significance of life cycle assessment for adoption of biodiesel at the commercial scale is highlighted. 

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10

Jose C S dos Santos and coworkers have conducted a comprehensive bibliometric analysis of the worldwide research (collaborations and output and feedstock) in the field of biodiesel by considering 4586 outputs for over a period of 12 years (2010-2021). The output indicated that China, Malaysia, and India were the prolific publishers with the highest output of scholarly works on biodiesel. The research conducted highlighted the challenge with the sustainability of the feedstock from the environmental and economic perspectives. The use of sewage is suggested to be a promising feedstock for biodiesel production with the least environmental damage. For some specific reasons, most of the researchers opted for the national collaborations and the research was mainly devoted to the feedstock for biodiesel production.

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11

The review of Omojola Awogbemi’s group is focused on the use of tubular reactor technologies for the accelerated production of biodiesel. Tubular reactor technologies were proposed as the most suitable systems to be adopted at the commercial sale for the process intensification. Emphasis was laid on the possible feedstock, catalysts and the conversion process in the tubular reactors. A comparison of various reactor designs like the packed bed, fluidized bed, trickle bed, oscillatory flow and micro-channel tubular reactor were discussed at length for the large scale, cost effective, ecofriendly, low cost and high quality biodiesel production. The tubular reactor technology is proposed for the transesterification process. Moreover, it was highlighted that novel technologies based on robotics, machine learning, artificial intelligence, smart metering should be integrated with the tubular reactor technology for the profitable biodiesel production process at the biorefinery facility.

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