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Environmental Friendly Catalysts for Energy and Pollution Control Applications

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A special issue of Catalysts (ISSN 2073-4344). This special issue belongs to the section "Environmental Catalysis".

Deadline for manuscript submissions: closed (31 December 2021) | Viewed by 41504

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Prof. Dr. José Ignacio Lombraña

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Department of Chemical Engineering, Faculty of Science and Technology, University of the Basque Country (UPV/EHU), P.O. Box 644, 48080 Bilbao, Spain
Interests: water processing; catalytic ozonation; activated carbon adsorption; membrane technologies
Special Issues, Collections and Topics in MDPI journals

Prof. Dr. Héctor Valdés

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Clean Technologies Laboratory, Engineering Faculty, Catholic University of the Most Holy Conception, Alonso de Ribera 2850, Concepción, Bío Bío, Chile
Interests: advanced oxidation processes, new catalytic materials for sustainable energy production, air pollution control, and water treatment

Dr. Cristian Ferreiro

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Department of Chemical Engineering, Faculty of Science and Technology, University of the Basque Country (UPV/EHU), P.O. Box 644, 48080 Bilbao, Spain
Interests: development of novel sustainable catalysts for energy and environmental applications

Special Issue Information

Dear Colleagues,

Catalysts are extensively used in different technologies and play a fundamental role in the efficient generation of energy and industrial emission control. Despite the fact that catalysts have remarkable performance, they pose, in some cases, a negative environmental impact due to their massive use, which is imposed by intensive production strategies. Therefore, a reorientation in the search of new materials such as environmental friendly catalysts (EFCs) is urgently needed. Hence, the development of novel EFCs to face sustainable energy production, climate change problems, and to abate industrial emissions has become a challenge in the current research fields.

A great variety of catalytic materials which include single metals as well as mixed metals (and their oxides) are currently being used either supported over alumina, silica, titania, ceria, zirconia, activated carbons, and zeolites, or directly attached to the reactor itself, allowing their continuous use and avoiding waste emissions. Similar cases are being found in Fenton catalysis, converted into EFCs, through heterogeneous Fenton-like variants. Moreover, the combined use of catalysts with UV/solar irradiation or in combination with O₃ and H₂O₂ will always be preferable to that of other oxidant agents (persulfates). In the case of metal–organic framework (MOFs) type catalysts, research is being redirected towards designs that allow their recycling. In new nanostructured functional catalysts with varied applications, a marked tendency is being observed to develop materials, which allow multiple reuse in different operating cycles with high efficiency and selectivity. This Special Issue addresses the aforementioned topics.

Prof. Dr. José Ignacio Lombraña
Prof. Dr. Héctor Valdés
Dr. Cristian Ferreiro
Guest Editors

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Keywords

Sustainable advanced oxidation processes (AOPs)
Cleaner technologies
Environmental friendly catalysts
Environmental remediation treatments
Green energy production
Multiple reused catalysts
Sustainable catalytic processes

Published Papers (12 papers)

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Research

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13 pages, 1635 KiB

Open AccessArticle

Practical Approaches towards NO_x Emission Mitigation from Fluid Catalytic Cracking (FCC) Units

by Aleksei Vjunov, Karl C. Kharas, Vasileios Komvokis, Amy Dundee and Bilge Yilmaz

Catalysts 2021, 11(10), 1146; https://doi.org/10.3390/catal11101146 - 24 Sep 2021

Cited by 1 | Viewed by 1828

Abstract

There appears to be consensus among the general public that curtailing harmful emissions resulting from industrial, petrochemical and transportation sectors is a common good. However, there is also a need for balancing operating expenditures for applying the required technical solutions and implementing advanced emission mitigation technologies to meet desired sustainability goals. The emission of NO_x from Fluid Catalytic Cracking (FCC) units in refineries for petroleum processing is a major concern, especially for those units located in densely populated urban settings. In this work we strive to review options towards cost-efficient and pragmatic emissions mitigation using optimal amounts of precious metal while evaluating the potential benefits of typical promoter dopant packages. We demonstrate that at present catalyst development level the refinery is no longer forced to make a promoter selection based on preconceived notions regarding precious metal activity but can rather make decisions based on the best “total cost” financial impact to the operation without measurable loss of the CO/NO_x emission selectivity. Full article

(This article belongs to the Special Issue Environmental Friendly Catalysts for Energy and Pollution Control Applications)

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15 pages, 2857 KiB

Open AccessFeature PaperArticle

Design of Co₃O₄@SiO₂ Nanorattles for Catalytic Toluene Combustion Based on Bottom-Up Strategy Involving Spherical Poly(styrene-co-acrylic Acid) Template

by Anna Rokicińska, Magdalena Żurowska, Piotr Łątka, Marek Drozdek, Marek Michalik and Piotr Kuśtrowski

Catalysts 2021, 11(9), 1097; https://doi.org/10.3390/catal11091097 - 11 Sep 2021

Cited by 5 | Viewed by 1966

Abstract

Bearing in mind the need to develop optimal transition metal oxide-based catalysts for the combustion of volatile organic compounds (VOCs), yolk-shell materials were proposed. The constructed composites contained catalytically active Co₃O₄ nanoparticles, protected against aggregation and highly dispersed in a shell made of porous SiO₂, forming a specific type of nanoreactor. The bottom-up synthesis started with obtaining spherical poly(styrene-co-acrylic acid) copolymer (PS30) cores, which were then covered with the SiO₂ layer. The Co₃O₄ active phase was deposited by impregnation using the PS30@SiO₂ composite as well as hollow SiO₂ spheres with the removed copolymer core. Structure (XRD), morphology (SEM), chemical composition (XRF), state of the active phase (UV-Vis-DR and XPS) and reducibility (H₂-TPR) of the obtained catalysts were studied. It was proven that the introduction of Co₃O₄ nanoparticles into the empty SiO₂ spheres resulted in their loose distribution, which facilitated the access of reagents to active sites and, on the other hand, promoted the involvement of lattice oxygen in the catalytic process. As a result, the catalysts obtained in this way showed a very high activity in the combustion of toluene, which significantly exceeded that achieved over a standard silica gel supported Co₃O₄ catalyst. Full article

(This article belongs to the Special Issue Environmental Friendly Catalysts for Energy and Pollution Control Applications)

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21 pages, 12953 KiB

Open AccessFeature PaperArticle

Application of a Combined Adsorption−Ozonation Process for Phenolic Wastewater Treatment in a Continuous Fixed-Bed Reactor

by Cristian Ferreiro, Ana de Luis, Natalia Villota, Jose María Lomas, José Ignacio Lombraña and Luis Miguel Camarero

Catalysts 2021, 11(8), 1014; https://doi.org/10.3390/catal11081014 - 22 Aug 2021

Cited by 7 | Viewed by 2588

Abstract

This work studied the removal of phenol from industrial effluents through catalytic ozonation in the presence of granular activated carbon in a continuous fixed-bed reactor. Phenol was chosen as model pollutant because of its environmental impact and high toxicity. Based on the evolution of total organic carbon (TOC) and phenol concentration, a kinetic model was proposed to study the effect of the operational variables on the combined adsorption–oxidation (Ad/Ox) process. The proposed three-phase model expressed the oxidation phenomena in the liquid and the adsorption and oxidation on the surface of the granular activated carbon in the form of two kinetic constants, k₁ and k₂ respectively. The interpretation of the constants allow to study the benefits and behaviour of the use of activated carbon during the ozonisation process under different conditions affecting adsorption, oxidation, and mass transfer. Additionally, the calculated kinetic parameters helped to explain the observed changes in treatment efficiency. The results showed that phenol would be completely removed at an effective contact time of 3.71 min, operating at an alkaline pH of 11.0 and an ozone gas concentration of 19.0 mg L⁻¹. Under these conditions, a 97.0% decrease in the initial total organic carbon was observed. Full article

(This article belongs to the Special Issue Environmental Friendly Catalysts for Energy and Pollution Control Applications)

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16 pages, 3244 KiB

Open AccessFeature PaperArticle

Catalytic Ozonation of Toluene over Acidic Surface Transformed Natural Zeolite: A Dual-Site Reaction Mechanism and Kinetic Approach

by Serguei Alejandro-Martín, Héctor Valdés and Claudio A. Zaror

Catalysts 2021, 11(8), 958; https://doi.org/10.3390/catal11080958 - 10 Aug 2021

Cited by 1 | Viewed by 2597

Abstract

Volatile organic compounds (VOCs) are responsible for damage to health due to their carcinogenic effects. Catalytic ozonation using zeolite appears as a valuable process to eliminate VOCs from industrial emissions at room temperature. For full-scale application of this new abatement technology, an intrinsic reaction rate equation is needed for an effective process design and scale-up. Results obtained here provide a mechanistic approach during the initial stage of catalytic ozonation of toluene using an acidic surface transformed natural zeolite. In particular, the contribution of Lewis and Brønsted acid sites on the surface reaction mechanism and overall kinetic rate are identified through experimental data. The least-squares non-linear regression method allows the rate-determining step to be established, following a Langmuir–Hinshelwood surface reaction approximation. Experimental evidence suggest that ozone is adsorbed and decomposed at Lewis acid sites, forming active atomic oxygen that leads to the oxidation of adsorbed toluene at Brønsted acid sites. Full article

(This article belongs to the Special Issue Environmental Friendly Catalysts for Energy and Pollution Control Applications)

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13 pages, 867 KiB

Open AccessArticle

Photocatalytic Study of Cyanide Oxidation Using Titanium Dioxide (TiO₂)-Activated Carbon Composites in a Continuous Flow Photo-Reactor

by Stalin Coronel, Diana Endara, Ana Belén Lozada, Lucía E. Manangón-Perugachi and Ernesto de la Torre

Catalysts 2021, 11(8), 924; https://doi.org/10.3390/catal11080924 - 30 Jul 2021

Cited by 6 | Viewed by 2886

Abstract

The photocatalytic oxidation of cyanide by titanium dioxide (TiO₂) supported on activated carbon (AC) was evaluated in a continuous flow UV photo-reactor. The continuous photo-reactor was made of glass and covered with a wood box to isolate the fluid of external conditions. The TiO₂-AC synthesized by the impregnation of TiO₂ on granular AC composites was characterized by inductively coupled plasma optical emission spectrometry (ICP-OES), Scanning Electron Microscopy (SEM), and nitrogen adsorption-desorption isotherms. Photocatalytic and adsorption tests were conducted separately and simultaneously. The results showed that 97% of CN⁻ was degraded within 24 h due to combined photocatalytic oxidation and adsorption. To estimate the contribution of only adsorption, two-stage tests were performed. First, 74% cyanide ion degradation was reached in 24 h under dark conditions. This result was attributed to CN⁻ adsorption and oxidation due to the generation of H₂O₂ on the surface of AC. Then, 99% degradation of cyanide ion was obtained through photocatalysis during 24 h. These results showed that photocatalysis and the continuous photo-reactor’s design enhanced the photocatalytic cyanide oxidation performance compared to an agitated batch system. Therefore, the use of TiO₂-AC composites in a continuous flow photo-reactor is a promising process for the photocatalytic degradation of cyanide in aqueous solutions. Full article

(This article belongs to the Special Issue Environmental Friendly Catalysts for Energy and Pollution Control Applications)

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17 pages, 4971 KiB

Open AccessFeature PaperArticle

Turbidity Changes during Carbamazepine Oxidation by Photo-Fenton

by Natalia Villota, Cristian Ferreiro, Hussein A. Qulatein, Jose M. Lomas and Jose Ignacio Lombraña

Catalysts 2021, 11(8), 894; https://doi.org/10.3390/catal11080894 - 24 Jul 2021

Cited by 3 | Viewed by 2127

Abstract

The objective of this study is to evaluate the turbidity generated during the Fenton photo-reaction applied to the oxidation of waters containing carbamazepine as a function of factors such as pH, H₂O₂ concentration and catalyst dosage. The results let establish the degradation pathways and the main decomposition byproducts. It is found that the pH affects the turbidity of the water. Working between pH = 2.0 and 2.5, the turbidity is under 1 NTU due to the fact that iron, added as a catalyst, is in the form of a ferrous ion. Operating at pH values above 3.0, the iron species in their oxidized state (mainly ferric hydroxide in suspension) would cause turbidity. The contribution of these ferric species is a function of the concentration of iron added to the process, verifying that the turbidity increases linearly according to a ratio of 0.616 NTU L/mg Fe. Performing with oxidant concentrations at (H₂O₂) = 2.0 mM, the turbidity undergoes a strong increase until reaching values around 98 NTU in the steady state. High turbidity levels can be originated by the formation of coordination complexes, consisting of the union of three molecules containing substituted carboxylic groups (BaQD), which act as ligands towards an iron atom with Fe³⁺ oxidation state. Full article

(This article belongs to the Special Issue Environmental Friendly Catalysts for Energy and Pollution Control Applications)

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10 pages, 2772 KiB

Open AccessArticle

Enhanced SO₂ Absorption Capacity of Sodium Citrate Using Sodium Humate

by Zhiguo Sun, Yue Zhou, Shichao Jia, Yaru Wang, Dazhan Jiang and Li Zhang

Catalysts 2021, 11(7), 865; https://doi.org/10.3390/catal11070865 - 20 Jul 2021

Cited by 2 | Viewed by 2208

Abstract

A novel method of improving the SO₂ absorption performance of sodium citrate (Ci-Na) using sodium humate (HA–Na) as an additive was put forward. The influence of different Ci-Na concentration, inlet SO₂ concentration and gas flow rate on desulfurization performance were studied. The synergistic mechanism of SO₂ absorption by HA–Na and Ci-Na was also analyzed. The consequence shows that the efficiency of SO₂ absorption by Ci-Na is above 90% and the desulfurization time added with the Ci-Na concentration rising from 0.01 to 0.1 mol/L. Both the desulfurization efficiency and time may increase with the adding of HA–Na quality in Ci-Na solution. Due to adding HA–Na, the desulfurization efficiency of Ci-Na increased from 90% to 99% and the desulfurization time increased from 40 to 55 min. Under the optimum conditions, the desulfurization time of Ci-Na can exceed 70 min because of adding HA–Na, which is nearly doubled. The growth of inlet SO₂ concentration has little effect on the desulfurization efficiency. The SO₂ adsorption efficiency decreases with the increase of inlet flow gas. The presence of O₂ improves the SO₂ removal efficiency and prolongs the desulfurization time. Therefore, HA–Na plays a key role during SO₂ absorption and can dramatically enhance the SO₂ adsorption performance of Ci-Na solution. Full article

(This article belongs to the Special Issue Environmental Friendly Catalysts for Energy and Pollution Control Applications)

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12 pages, 1410 KiB

Open AccessArticle

Pragmatic Approach toward Catalytic CO Emission Mitigation in Fluid Catalytic Cracking (FCC) Units

by Aleksei Vjunov, Karl C. Kharas, Vasileios Komvokis, Amy Dundee, Claire C. Zhang and Bilge Yilmaz

Catalysts 2021, 11(6), 707; https://doi.org/10.3390/catal11060707 - 03 Jun 2021

Cited by 3 | Viewed by 2124

Abstract

The need to mitigate the environmental footprints of refineries in a sustainable and economical way is widely accepted, yet there appears to be a lack of a unilateral pragmatic approach towards CO oxidation to CO₂ among the refining community. In this work we share CO promoter design strategies that can afford a tangible and immediate CO conversion efficiency increase without a need for additional precious metal loading. The key focus is on the support material architecture that is essential to boost the CO conversion and reduce the NO_x generation in the FCC unit. It was demonstrated that the suppression of Pt sintering as well as the enhancement of the oxygen mobility on the catalyst surface can afford an ~40% lower cost of Pt and ~20% lower usage rate compared to current industry-standard designs. Full article

(This article belongs to the Special Issue Environmental Friendly Catalysts for Energy and Pollution Control Applications)

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15 pages, 1612 KiB

Open AccessArticle

Optimization of Fenton Technology for Recalcitrant Compounds and Bacteria Inactivation

by Pablo Salgado, José Luis Frontela and Gladys Vidal

Catalysts 2020, 10(12), 1483; https://doi.org/10.3390/catal10121483 - 19 Dec 2020

Cited by 6 | Viewed by 2006

Abstract

In this work, the Fenton technology was applied to decolorize methylene blue (MB) and to inactivate Escherichia coli K12, used as recalcitrant compound and bacteria models respectively, in order to provide an approach into single and combinative effects of the main process variables influencing the Fenton technology. First, Box–Behnken design (BBD) was applied to evaluate and optimize the individual and interactive effects of three process parameters, namely Fe²⁺ concentration (6.0 × 10⁻⁴, 8.0 × 10⁻⁴ and 1.0 × 10⁻³ mol/L), molar ratio between H₂O₂ and Fe²⁺ (1:1, 2:1 and 3:1) and pH (3.0, 4.0 and 5.0) for Fenton technology. The responses studied in these models were the degree of MB decolorization (D_%^MB), rate constant of MB decolorization (k_app^MB) and E. coli K12 inactivation in uLog units (I_uLog^EC). According to the results of analysis of variances all of the proposed models were adequate with a high regression coefficient (R² from 0.9911 to 0.9994). BBD results suggest that [H₂O₂]/[Fe²⁺] values had a significant effect only on D_%^MB response, [Fe²⁺] had a significant effect on all the responses, whereas pH had a significant effect on D_%^MB and I_uLog^EC. The optimum conditions obtained from response surface methodology for D_%^MB ([H₂O₂]/[Fe²⁺] = 2.9, [Fe²⁺] = 1.0 × 10⁻³ mol/L and pH = 3.2), k_app^MB ([H₂O₂]/[Fe²⁺] = 1.7, [Fe²⁺] = 1.0 × 10⁻³ mol/L and PH = 3.7) and I_uLog^EC ([H₂O₂]/[Fe²⁺] = 2.9, [Fe²⁺] = 7.6 × 10⁻⁴ mol/L and pH= 3.2) were in good agreement with the values predicted by the model. Full article

(This article belongs to the Special Issue Environmental Friendly Catalysts for Energy and Pollution Control Applications)

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12 pages, 1674 KiB

Open AccessArticle

Characterization of Anaerobic Biofilms Growing on Carbon Felt Bioanodes Exposed to Air

by Raúl M. Alonso, Guillermo Pelaz, María Isabel San-Martín, Antonio Morán and Adrián Escapa

Catalysts 2020, 10(11), 1341; https://doi.org/10.3390/catal10111341 - 18 Nov 2020

Cited by 2 | Viewed by 1906

Abstract

The role of oxygen in anodic biofilms is still a matter of debate. In this study, we tried to elucidate the structure and performance of an electrogenic biofilm that develops on air-exposed, carbon felt electrodes, commonly used in bioelectrochemical systems. By simultaneously recording the current density produced by the bioanode and dissolved oxygen concentration, both inside and in the vicinity of the biofilm, it was possible to demonstrate the influence of a protective aerobic layer present in the biofilm (mainly formed by Pseudomonas genus bacteria) that prevents electrogenic bacteria (such as Geobacter sp.) from hazardous exposure to oxygen during its normal operation. Once this protective barrier was deactivated for a long period of time, the catalytic capacity of the biofilm was severely affected. In addition, our results highlighted the importance of the material’s porous structure for oxygen penetration in the electrode. Full article

(This article belongs to the Special Issue Environmental Friendly Catalysts for Energy and Pollution Control Applications)

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Review

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23 pages, 1431 KiB

Open AccessReview

Metal–Organic Frameworks (MOFs) and Materials Derived from MOFs as Catalysts for the Development of Green Processes

by Gonzalo Valdebenito, Marco Gonzaléz-Carvajal, Luis Santibañez and Patricio Cancino

Catalysts 2022, 12(2), 136; https://doi.org/10.3390/catal12020136 - 22 Jan 2022

Cited by 13 | Viewed by 6269

Abstract

This review will be centered around the work that has been reported on the development of metal–organic frameworks (MOFs) serving as catalysts for the conversion of carbon dioxide into short-chain hydrocarbons and the generation of clean energies starting from biomass. MOFs have mainly been used as support for catalysts or to prepare catalysts derived from MOFs (as sacrifice template), obtaining interesting results in the hydrogenation or oxidation of biomass. They have presented a good performance in the hydrogenation of CO₂ into light hydrocarbon fuels. The common patterns to be considered in the performance of the catalysts are the acidity of MOFs, metal nodes, surface area and the dispersion of the active sites, and these parameters will be discussed in this review. Full article

(This article belongs to the Special Issue Environmental Friendly Catalysts for Energy and Pollution Control Applications)

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29 pages, 9847 KiB

Open AccessReview

Photocatalysis for Organic Wastewater Treatment: From the Basis to Current Challenges for Society

by Salma Izati Sinar Mashuri, Mohd Lokman Ibrahim, Muhd Firdaus Kasim, Mohd Sufri Mastuli, Umer Rashid, Abdul Halim Abdullah, Aminul Islam, Nurul Asikin Mijan, Yie Hua Tan, Nasar Mansir, Noor Haida Mohd Kaus and Taufiq-Yap Yun Hin

Catalysts 2020, 10(11), 1260; https://doi.org/10.3390/catal10111260 - 30 Oct 2020

Cited by 84 | Viewed by 9695

Abstract

Organic pollutants such as dyes, antibiotics, analgesics, herbicides, pesticides, and stimulants become major sources of water pollution. Several treatments such as absorptions, coagulation, filtration, and oxidations were introduced and experimentally carried out to overcome these problems. Nowadays, an advanced technique by photocatalytic degradation attracts the attention of most researchers due to its interesting and promising mechanism that allows spontaneous and non-spontaneous reactions as they utilized light energy to initiate the reaction. However, only a few numbers of photocatalysts reported were able to completely degrade organic pollutants. In the past decade, the number of preparation techniques of photocatalyst such as doping, morphology manipulation, metal loading, and coupling heterojunction were studied and tested. Thus, in this paper, we reviewed details on the fundamentals, common photocatalyst preparation for coupling heterojunction, morphological effect, and photocatalyst’s characterization techniques. The important variables such as catalyst dosage, pH, and initial concentration of sample pollution, irradiation time by light, temperature system, durability, and stability of the catalyst that potentially affect the efficiency of the process were also discussed. Overall, this paper offers an in-depth perspective of photocatalytic degradation of sample pollutions and its future direction. Full article

(This article belongs to the Special Issue Environmental Friendly Catalysts for Energy and Pollution Control Applications)

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