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A special issue of Symmetry (ISSN 2073-8994). This special issue belongs to the section "Chemistry: Symmetry/Asymmetry".

Deadline for manuscript submissions: closed (30 April 2020) | Viewed by 34525

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Special Issue Editors

Dr. Putla Sudarsanam

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Centre for Surface Chemistry and Catalysis, KU Leuven, Celestijnenlaan 200f, 3001 Leuven, Belgium
Interests: catalysis; nanostructured catalysts; organic synthesis; biomass upgrading; CO₂ valorization; environment pollution control

Prof. Dr. Sheshanath Bhosale

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Guest Editor

RMIT University and Goa University
Interests: dyes and pigments; porphyrins; nanomaterials; supramolecular chemistry; sensors; artificial photosynthesis; solar cells
Special Issues, Collections and Topics in MDPI journals

Prof. Dr. Mohd Rafie Bin Johan

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Guest Editor

Nanotechnology & Catalysis Research Centre (NANOCAT), University of Malaya, Kuala Lumpur 50603, Malaysia
Interests: nanomaterials; matematerials; catalysis; biomass valorization; green chemistry

Special Issue Information

Dear Colleagues,

Catalysis is a key enabling technology for developing the most feasible solutions towards a sustainable chemical industry. Especially heterogeneous catalysis, where the catalyst exists in a different phase (typically solids) from the reactants (mostly liquids or gasses), has a rich history of facilitating promising catalytic strategies for a number of energy and environmental applications. Advances in the heterogeneous catalysis and materials science fields have provided several potential methods for the design of various novel catalytic materials with unique characteristics and exceptional activities. In this context, nanostructured catalysts (where the particle size is less than 100 nm in at least one dimension) are the most versatile candidates largely used in the modern field of catalysis, popularly known as nanocatalysis. Symmetry in terms of particle size and its morphology plays a pivotal role in tuning the physicochemical, acid-base, and redox properties of nanostructured catalysts, and hence their chemistry with the reactant molecules, resulting in unusual catalytic activities. The aim of this Special Issue is therefore to cover recent advances in the rational design of various nanostructured catalysts for a wide range of applications, including organic synthesis, biomass valorization, CO₂ utilization, and environmental pollution control.

This Special Issue invites both original research and review articles addressing the advantages and challenges of nanostructured catalysts in view of their feasibility in the chemical industry. Special emphasis will be given to investigations of the effect of particle size and its morphology, as well as their symmetry towards optimizing the structure–activity properties of nanostructured catalysts that may provide valuable implications for the development of highly performing catalytic materials.

Dr. Putla Sudarsanam
Prof. Sheshanath V. Bhosale
Prof. Mohd Rafie Bin Johan
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

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Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

Catalysis
Symmetry of nanostructured catalysts
Particle size and morphology
Materials characterization
Organic chemistry
Biomass valorization
CO2 utilization
Environment pollution control
Stability/kinetic/mechanistic aspects
Rational design of nanostructured catalysts

Published Papers (9 papers)

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Research

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17 pages, 3976 KiB

Open AccessArticle

Bimetallic Mo–Fe Co-Catalyst-Based Nano-Carbon Impregnated on PAC for Optimum Super-Hydrophobicity

by Bashir O Betar, Mohammed A Alsaadi, Zaira Z. Chowdhury, Mohamed K Aroua, Farouq S. Mjalli, Kaharudin Dimyati, MHD N Hindia, Fawzi M. Elfghi, Yehya M. Ahmed and Hazim F Abbas

Symmetry 2020, 12(8), 1242; https://doi.org/10.3390/sym12081242 - 28 Jul 2020

Cited by 2 | Viewed by 2111

Abstract

The application of super-hydrophobic nanomaterials for synthesizing membranes with unique physiochemical properties has gained a lot of interest among researchers. The presence of super-hydrophobic materials inside the membrane matrix can play a vital role not only in the separation of toxins, but also to achieve higher water flux with lower fouling tendencies required for an efficient membrane distillation process. In this research, super-hydrophobic carbon nanomaterials (CNMs) were synthesized using powder activated carbon (PAC) as a precursor, whereby the growth was initiated using a bimetallic catalyst of iron (Fe) and molybdenum (Mo). Until recently, no research has been conducted for synthesis and to observe the catalytic influence of bimetallic catalysts on the physiochemical characteristics of the derived CNMs. The synthesis process was carried out using the chemical vapor deposition (CVD) process. The CVD process was optimized using Box–Behnken factorial design (BBD), whereby 15 experiments were carried out under different conditions. Three input variables, which were percentage composition of catalysts (percentage of Fe and Mo) and reaction time (tr), were optimized with respect to their impact on the desired percentage output of yield (CY) and contact angle (CA). Analysis of variance (ANOVA) testing was carried out. It was observed that the developed model was statistically significant. The highest CY (320%) and CA (172°) were obtained at the optimal loading of 5% Fe and 2% Mo, with a reaction time of 40 min. Surface morphological features were observed using field emission scanning electron microscopic (FESEM) and transmission electron microscopic (TEM) analysis. The images obtained from FESEM and TEM revealed the presence of two types of CNMs, including carbon nanofibers (CNFs) and multiwall carbon nanotubes (CNTs). Thermogravimetric analysis was carried out to observe the temperature degradation profile of the synthesized sample. Raman spectroscopic analysis was also used in order to have a better understanding regarding the proportion of ordered and disordered carbon content inside the synthesized sample. Full article

(This article belongs to the Special Issue Nanocatalysis and Symmetry in Chemistry)

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14 pages, 3984 KiB

Open AccessArticle

Effect of Pressure, H₂/CO Ratio and Reduction Conditions on Co–Mn/CNT Bimetallic Catalyst Performance in Fischer–Tropsch Reaction

by Omid Akbarzadeh, Noor Asmawati Mohd Zabidi, Guangxin Wang, Amir Kordijazi, Hamed Sadabadi, Seyedehmaryam Moosavi, Arman Amani Babadi, Nor Aliya Hamizi, Yasmin Abdul Wahab, Marlinda Ab Rahman, Suresh Sagadevan, Zaira Zaman Chowdhury and Mohd Rafie Johan

Symmetry 2020, 12(5), 698; https://doi.org/10.3390/sym12050698 - 01 May 2020

Cited by 13 | Viewed by 3842

Abstract

The effects of process conditions on Fischer–Tropsch Synthesis (FTS) product distributions were studied using a fixed-bed microreactor and a Co–Mn/CNT catalyst. Cobalt and Manganese, supported on Carbon Nanotubes (CNT) catalyst were prepared by a Strong Electrostatic Adsorption (SEA) method. CNT supports were initially acid and thermally treated in order to functionalize support to uptake more Co clusters. Catalyst samples were characterized by Transmitted Electron Microscope (TEM), particle size analyzer, and Thermal Gravimetric Analysis (TGA). TEM images showed catalyst metal particle intake on CNT support with different Co and Mn loading percentage. Performance test of Co–Mn/CNT in Fischer–Tropsch synthesis (FTS) was carried out in a fixed-bed micro-reactor at different pressures (from 1 atm to 25 atm), H2/CO ratio (0.5–2.5), and reduction temperature and duration. The reactor was connected to the online Gas Chromatograph (GC) for product analysis. It was found that the reaction conditions have the dominant effect on product selectivity. Cobalt catalyst supported on acid and thermal pre-treated CNT at optimum reaction condition resulted in CO conversion of 58.7% and C5+ selectivity of 59.1%. Full article

(This article belongs to the Special Issue Nanocatalysis and Symmetry in Chemistry)

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19 pages, 4869 KiB

Open AccessArticle

Effect of Manganese on Co–Mn/CNT Bimetallic Catalyst Performance in Fischer–Tropsch Reaction

by Omid Akbarzadeh, Noor Asmawati Mohd Zabidi, Zulkifli Merican Aljunid Merican, Suresh Sagadevan, Amir Kordijazi, Sourav Das, Arman Amani Babadi, Marlinda Ab Rahman, Nor Aliya Hamizi, Yasmin Abdul Wahab and Mohd Rafie Johan

Symmetry 2019, 11(11), 1328; https://doi.org/10.3390/sym11111328 - 24 Oct 2019

Cited by 8 | Viewed by 3253

Abstract

Cobalt (Co) catalyst is supported by carbon nanotubes (CNT) using a strong electrostatic adsorption (SEA) method. To promote activity and selectivity as well as find the optimum loading percentage and its effect on catalyst performance, manganese (Mn) has been added to the Co/CNT catalyst. Samples were characterized by a scanning electron microscope (SEM-EDX), transmission electron microscope (TEM), hydrogen temperature programmed reduction (H₂-TPR), Zeta potential, Brunauer–Emmett–Teller (BET) analysis, X-ray diffraction (XRD), and X-ray spectroscopy (XPS). TEM images illustrated an intake of metal particles which were highly dispersed, having a narrow particle size distribution of 6–8 nm to the external and internal CNT support. H₂-TPR showed a lower temperature reduction with Mn at 420 °C for Fischer–Tropsch synthesis (FTS) reaction. The Co–Mn/CNT catalyst performance test for FTS was performed at a temperature of 240 °C in a fixed-bed micro-reactor at a pressure of 2.0 MPa. The addition of manganese resulted in a lower methane selectivity and a higher C₅₊ product with an optimum percentage of 5% of manganese. CO conversion was 86.6% and had a C₅₊ selectivity of 81.5%, which was higher than the catalysts obtained using only Co on pretreated CNT. Full article

(This article belongs to the Special Issue Nanocatalysis and Symmetry in Chemistry)

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20 pages, 2880 KiB

Open AccessArticle

Extraction of Cellulose Nano-Whiskers Using Ionic Liquid-Assisted Ultra-Sonication: Optimization and Mathematical Modelling Using Box–Behnken Design

by Zaira Zaman Chowdhury, R. Reevenishaa Ravi Chandran, Afrin Jahan, Khalisanni Khalid, Md Mahfujur Rahman, Md Al-Amin, Omid Akbarzadeh, Irfan Anjum Badruddin, T. M. Yunus Khan, Sarfaraz Kamangar, Nor Aliya Binti Hamizi, Yasmin Abdul Wahab, Rafie Bin Johan and Ganiyu Abimbola Adebisi

Symmetry 2019, 11(9), 1148; https://doi.org/10.3390/sym11091148 - 10 Sep 2019

Cited by 24 | Viewed by 3735

Abstract

This study focuses on the extraction of cellulose nano-whiskers (CNWs) from the leaves of Adansonia kilima (AK), usually known as African baobab, using a combination of a microwave-assisted alkali (KOH) pre-treatment with subsequent bleaching process prior to ultra-sonication. Ultra-sonication was carried out using the ionic liquid (IL) 1-butyl-3-methylimidazolium hydrogen sulfate (Bmim-HSO₄). Process parameters for ultra-sonication were optimized using a two-level factorial Box–Behnken design (BBD). Process variables such as ultra-sonication power (x₁), hydrolysing time (x₂) and temperature (x₃) were varied. Responses selected were percentage crystallinity index, CrI% (y₁) and yield% (y₁) for the finally procured CNWs sample. Regression analysis was carried out to develop quadratic model to analyze the effect of process variables on IL-assisted ultra-sonication process. Analysis of variance (ANOVA) showed that ultra-sonication power was the most influential aspect for hydrolyzing the amorphous segments of crude cellulose extracted from baobab leaves. A relative study of the physio-chemical properties of the starting lignocellulosic substrate (AK), KOH pre-treated, bleached and IL-assisted ultra-sonicated CNWs was conducted. The synthesized samples were characterized using Fourier transform infrared spectroscopy, Scanning electron microscopy, atomic force microscopy, high resolution transmission electron microscopy, X-ray diffraction and thermo-gravimetric and zeta potential analysis. Under optimum condition, the extracted CNWs showed an average width of 15–20 nm; with high crystallinity index of 86.46%. This research provides an insight about the delignification of Adansonia kilima (AK) leaves and its effective conversion to CNWs having high crystallinity. Full article

(This article belongs to the Special Issue Nanocatalysis and Symmetry in Chemistry)

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11 pages, 3998 KiB

Open AccessArticle

Synthesis of Fuel Grade Molecules from Hydroprocessing of Biomass-Derived Compounds Catalyzed by Magnetic Fe(NiFe)O₄-SiO₂ Nanoparticles

by Ahmed Halilu, Tammar Hussein Ali, Putla Sudarsanam and Suresh K. Bhargava

Symmetry 2019, 11(4), 524; https://doi.org/10.3390/sym11040524 - 11 Apr 2019

Cited by 15 | Viewed by 2821

Abstract

The development of promising magnetic nanocatalysts is one of the key research topics in the field of catalysis. This is because of their versatile surface physicochemical, magnetic, and size-dependent catalytic properties. Herein, an optimization strategy for the synthesis of high-value fuel grade chemicals from hydro-deoxygenation of biomass-derived furfural and vanillin using a nanostructured magnetic Fe(NiFe)O₄-SiO₂ catalyst, synthesized by a facile one-pot procedure, was presented. Accordingly, effects of calcination temperature from 400, 500, 600 to 700 °C on the structure-activity properties of the magnetic Fe(NiFe)O₄-SiO₂ catalyst was systematically studied. The magnetic Fe(NiFe)O₄-SiO₂ catalyst calcined at 500 °C exhibited the best catalytic performance, giving full conversions of vanillin and furfural, with good selectivity of 63 and 59% to cyclohexane and n-pentane (fuel grade chemicals), respectively. The prowess of this catalyst was attributed to its abundant acid properties in addendum to high BET surface area. Full article

(This article belongs to the Special Issue Nanocatalysis and Symmetry in Chemistry)

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19 pages, 4731 KiB

Open AccessArticle

Effect of pH, Acid and Thermal Treatment Conditions on Co/CNT Catalyst Performance in Fischer–Tropsch Reaction

by Omid Akbarzadeh, Noor Asmawati Mohd Zabidi, Nor Aliya Hamizi, Yasmin Abdul Wahab, Zulkifli Merican Aljunid Merican, Wageeh A. Yehya, Shamima Akhter, Md. Shalauddin, Elisa Rasouli and Mohd Rafie Johan

Symmetry 2019, 11(1), 50; https://doi.org/10.3390/sym11010050 - 04 Jan 2019

Cited by 8 | Viewed by 3529

Abstract

Multiwalled carbon nanotubes (CNT) supported cobalt oxide was prepared as a catalyst by strong electrostatic adsorption (SEA) method. The CNT support was initially acid- and thermal-treated in order to functionalize the support to uptake more Co clusters. The Co/CNT were characterized by a range of analytical methods including transmission electron microscopy (TEM), temperature programmed reduction with hydrogen (H₂-TPR), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, atomic absorption spectroscopy (AAS), Zeta sizer particle size analysis and Brunauer–Emmett–Teller (BET) surface area analysis. TEM images showed cobalt particles were highly dispersed and impregnated at both exterior and interior walls of the CNT support with a narrow particle size distribution of 6–8 nm. In addition, the performance of the synthesized Co/CNT catalyst was tested using Fischer–Tropsch synthesis (FTS) reaction which was carried out in a fixed-bed micro-reactor. H₂-TPR profiles indicated the lower reduction temperature of 420 °C was required for the FTS reaction. The study revealed that cobalt is an effective metal for Co/CNT catalysts at pH 14 and at 900 °C calcination temperature. Furthermore, FTS reaction results showed that CO conversion and C₅₊ selectivity were recorded at 58.7% and 83.2% respectively, which were higher than those obtained using a Co/CNT catalyst which pre-treated at a lower thermal treatment temperature and pH. Full article

(This article belongs to the Special Issue Nanocatalysis and Symmetry in Chemistry)

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18 pages, 4061 KiB

Open AccessArticle

Effects of Cobalt Loading, Particle Size, and Calcination Condition on Co/CNT Catalyst Performance in Fischer–Tropsch Reactions

by Omid Akbarzadeh, Noor Asmawati Mohd Zabidi, Yasmin Abdul Wahab, Nor Aliya Hamizi, Zaira Zaman Chowdhury, Zulkifli Merican Aljunid Merican, Marlinda Ab Rahman, Shamima Akhter, Md Shalauddin and Mohd Rafie Johan

Symmetry 2019, 11(1), 7; https://doi.org/10.3390/sym11010007 - 22 Dec 2018

Cited by 26 | Viewed by 3976

Abstract

The strong electrostatic adsorption (SEA) method was applied to the synthesis of a cobalt (Co) catalyst on a multi-walled carbon nanotube (CNT) support. In order to uptake more of the cobalt cluster with higher dispersion, the CNT was functionalized via acid and thermal treatment. The Co/CNT catalyst samples were characterized by a range of methods including the Brunauer–Emmet–Teller (BET) surface area analyzer, transmission electron microscopy (TEM), X-ray powder diffraction (XRD) analysis, atomic absorption spectroscopy (AAS), and H₂-temperature programmed reduction (H₂-TPR) analysis. The data from the TEM images revealed that the catalyst was highly dispersed over the external and internal walls of the CNT and that it demonstrated a narrow particle size of 6–8 nm. In addition, the data from the H₂-TPR studies showed a lower reduction temperature (420 °C) for the pre-treated catalyst samples. Furthermore, a Fischer–Tropsch synthesis (FTS) reaction was chosen to evaluate the Co/CNT catalyst performance by using a fixed-bed microreactor at different parameters. Finally finding the optimum value of the cobalt loading percentage, particle size, and calcination conditions of Co/CNT catalyst resulted in a CO conversion and C₅₊ selectivity of 58.7% and 83.2%, respectively. Full article

(This article belongs to the Special Issue Nanocatalysis and Symmetry in Chemistry)

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15 pages, 2481 KiB

Open AccessArticle

Effect of Cobalt Catalyst Confinement in Carbon Nanotubes Support on Fischer-Tropsch Synthesis Performance

Symmetry 2018, 10(11), 572; https://doi.org/10.3390/sym10110572 - 01 Nov 2018

Cited by 26 | Viewed by 3122

Abstract

Pre-treating the multi-walled carbon nanotubes (CNTs) support by refluxing in 35 vol% nitric acid followed by heating at the temperature of 600 to 900 °C resulted in the formation of defects on the CNTs. Increasing the temperature of the pre-treatment of the CNTs from 600 °C to 900 °C, enhanced the fraction of cobalt-oxide nanoparticles encapsulated in the channels of CNTs from 31% to 70%. The performance of Co/CNTs in Fischer-Tropsch synthesis (FTS) was evaluated in a fixed-bed micro-reactor at a temperature of 240 °C and a pressure of 2.0 MPa. The highest CO conversion obtained over Co/CNTs.A.900 was 59% and it dropped by ~3% after 130 h of time-on-stream. However, maximum CO conversion using Co/CNTs.A.600 catalysts was 28% and it decreased rapidly by about 54% after 130 h of time-on-stream. These findings show that the combined acid and thermal pre-treatment of CNTs support at 900 °C has improved the stability and activity of the Co/CNTs catalyst in FTS. Full article

(This article belongs to the Special Issue Nanocatalysis and Symmetry in Chemistry)

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Review

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21 pages, 1581 KiB

Open AccessReview

Advances in Nanocatalysts Mediated Biodiesel Production: A Critical Appraisal

by Avinash P. Ingle, Anuj K. Chandel, Rafael Philippini, Sabrina Evelin Martiniano and Silvio Silvério da Silva

Symmetry 2020, 12(2), 256; https://doi.org/10.3390/sym12020256 - 07 Feb 2020

Cited by 60 | Viewed by 7096

Abstract

The excessive consumption of petroleum resources leads to global warming, fast depletion of petroleum reserves, as well as price instability of gasoline. Thus, there is a strong need for alternative renewable fuels to replace petroleum-derived fuels. The striking features of an alternative fuel include the low carbon footprints, renewability and affordability at manageable prices. Biodiesel, made from waste oils, animal fats, vegetal oils, is a totally renewable and non-toxic liquid fuel which has gained significant attraction in the world. Due to technological advancements in catalytic chemistry, biodiesel can be produced from a variety of feedstock employing a variety of catalysts and recovery technologies. Recently, several ground-breaking advancements have been made in nano-catalyst technology which showed the symmetrical correlation with cost competitive biodiesel production. Nanocatalysts have unique properties such as their selective reactivity, high activation energy and controlled rate of reaction, easy recovery and recyclability. Here, we present an overview of various feedstock used for biodiesel production, their composition and characteristics. The major focus of this review is to appraise the characterization of nanocatalysts, their effect on biodiesel production and methodologies of biodiesel production. Full article

(This article belongs to the Special Issue Nanocatalysis and Symmetry in Chemistry)

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