Sustainable Chemical Processes Research Articles

From the Waste Semicoke to Superabsorbent Composite: Synthesis, Characterization and Performance Evaluation

Oil shale semicoke (SC), which generated during the production of shale oil has attracted much attention in agriculture recently, as the composition of organic matter, clay mineral and else. In this study, a novel superabsorbent composite of poly(acrylic acid-co-acrylamide)/semicoke (P(AA-co-AM)/SC) was prepared by polymerization of the acrylic acid (AA) and acrylamide (AM) via a convenient one-step reaction as the presence of SC. The characterization of FTIR, SEM, XPS and TG indicated that the successful polymerization and the SC had participated into the construction of 3D polymeric network in superabsorbent. The performance testing results showed that the superabsorbent composites exhibited the excellent water absorbency, favorable water retention properties, fast swelling rate, and nice water reusability. And a 10% of SC amount could improve the water absorbency to 643.13 g/g and 79.82 g/g in distilled water and 0.9% NaCl solution, respectively. The potted culture experiments revealed that the increased water retaining capacity of soil and obvious growth promoting effect for crop. In a word, the novel superabsorbent composite could be as a potential water-saving product used in the agriculture, and the approach reported in this work also can be as a new pathway for high value using of SC via a sustainable chemical engineering process.

Rational construction of metal–base synergetic sites on Au/Mg-beta catalyst for selective aerobic oxidation of 5-hydroxymethylfurfural

The selective aerobic oxidation of biomass-derived 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid (FDCA, a potential renewable substitution of fossil-based terephthalic acid to produce polyethylene 2,5-furandicarboxylate plastic) is an appealing transformation for constructing eco-friendly and sustainable chemical processes. Au supported catalysts have showed encouraging performances for this well-received conversion, whose catalytic behavior was greatly affected by the adopted support derived from the existence of metal-support interactions. Herein, a series of Mg-Beta zeolites were hydrothermally synthesized via developed structural reconstruction, which were employed as basic supports for Au catalysts to construct bifunctional catalysts. The relationship between structure (Au particle size, basicity within zeolites and Auδ+ contents) and FDCA yield was concretely established. The conclusion was made that the utilization of Mg-Beta zeolites with strong basicity as the support could not only improve the FDCA yield but also decrease the amount of additional base. Furthermore, the possible reaction mechanism was also proposed via tracking time-dependent variations of corresponding organics and controlled experiment. This work provides some guidance for rationally designing multifunctional catalysts in the view of integrating metal catalysts with metallosilicate zeolites, which was beneficial to the catalytic upgrading of organic compounds with multiple functional groups.

Comparative analysis of biorefinery designs based on acetone-butanol-ethanol fermentation under exergetic, techno-economic, and sensitivity analyses towards a sustainability perspective

Chemical process sustainability has been gaining attention as a comprehensive framework for diagnosing, optimizing, and improving a chemical design. This work presents a comprehensive assessment involving techno-economic, sensitivity, and exergetic factors of two biorefinery configurations for butanol production. The methodology presented here comprises three main steps for assessing biorefinery designs under a mixed techno-economic and exergetic assessment. Firstly, feedstock and processing units were selected based on the defined task (butanol production from lignocellulosic biomass). A general Acetone-Butanol-Ethanol (ABE) fermentation biorefinery was established considering (i) Pretreatment, (ii) Enzymatic hydrolysis, (iii) Fermentation, and (iv) Separation stages. The second step was the process modeling stages, in which biorefineries were simulated using Aspen Plus software, generating several quantitative data to perform economic and exergetic analyses. The last stage of the method is associated with the chemical process sustainability assessment based on techno-economic, sensitivity, and exergy analyses. Biobutanol topology 1 presented a production capacity of 32,737,45 kg/h butanol, while topology 2 generated 37,480 kg/h of this product. Both biorefinery designs had a biomass feed flow of 320,829 kg/h. The results revealed that both topologies were worthy alternatives from an economic viewpoint, considering the Net Present Value (NPV) 908.74 MM USD for topology 1, and 879.03 MM USD for topology 2. The Return on Investment (ROI) was 29.11% for topology 1 and 37.76% for topology 2. Regarding exergetic analysis, biobutanol topology 1 showed an exergy efficiency of 26.03%. In comparison, topology 2 gives an efficiency of 39.89%.

Recent advances in cellulose supported metal nanoparticles as green and sustainable catalysis for organic synthesis

Organic reactions generally involve a variety of catalysts and solvents, which may be inflammable, toxic, and/or corrosive. Consequently, most of these reactions highly influence the environment. However, recent science and technology applications shift towards eco-friendly and sustainable resources and processes. Nanocatalysis has recently become an emerging field of science owing to its high reactivity, productivity, and selectivity. Cellulose supported metal nanoparticles (NPs) have been broadly applied in catalysis toward the development of green and sustainable chemical transformation processes. Those catalysts can be easily recycled several times without losing their reactivity. Metal nanoparticles have recently attracted more attention as a result of their distinctive characteristics in comparison to their equivalent bulk metals. Those characteristics include a large surface-to-volume ratio, high porosity, and tunable structural morphology. Controlling the characteristics of nanoparticles particularly with respect to their structural morphology, particle size and dispersibility are essential because those will identify their catalytic activity. Recent developments in controlling dispersibility, particle size, and morphological shape of metal nanoparticles paved the way to optimize the nanoparticle geometry for improved catalytic activity. This review focuses on the fabrication and application of cellulose supported metal nanoparticles as promising catalysts for green modern organic synthesis and aims to present cellulose supported metal nanoparticles as a green, sustainable and renewable alternative to conventional catalysts for future industrial applications. The major groups of noble and transition metal nanoparticles are highlighted.

Process Synthesis, Analysis, and Optimization Methodologies toward Chemical Process Sustainability

These days, developing sustainable chemical facilities to generate biofuels, energy, bioproducts, and value-added chemicals has attracted attention. The above involves changing the traditional conc...

Jahn-Teller distortion assisted interstitial nitrogen engineering: enhanced oxygen dehydrogenation activity of N-doped MnxCo3−xO4 hierarchical micro-nano particles

Rational design of earth-abundant transition metal oxides catalysts is highly desirable for developing sustainable chemical processes. Herein, we demonstrate a prospective interstitial nitrogen engineering for fabricating oxygen vacancies (OVs)-rich nitrogen-doped-MnxCo3−xO4 (N-MnxCo3−xO4) oxide catalyst, in which the ratio of OVs concentration of N-MnxCo3−xO4 to Mn species is as high as 1:1, according to the characterizations of X-ray absorption (XAS) and X-ray photoelectron (XPS) spectroscopies. The promising strategy of interstitial nitrogen engineering through lattice distortion caused by the Jahn-Teller effect can significantly increase the amount of interstitial nitrogen. The resulting catalyst enables an additive-free aerobic dehydrogenation coupling of aromatic amine to afford azo compounds with > 99% yield and > 99% selectivity at 60 °C. We observed the superb catalytic activity is promoted by the enhanced oxygen mobility in OVs, which were created by the interstitial nitrogen in the catalyst matrix. The presence of interstitial nitrogen in transition metal oxides in this study shows how the manipulation of catalyst matrix can increase the OV sites to promote aerobic oxidation reaction.

Sustainable Esterification of a Soda Lignin with Phloretic Acid.

In this work, a sustainable chemical process was developed through the Fischer esterification of Protobind® lignin, a wheat straw soda lignin, and phloretic acid, a naturally occurring phenolic acid. It aimed at increasing the reactivity of lignin by enhancing the number of unsubstituted phenolic groups via a green and solvent-free chemical pathway. The structural features of the technical and esterified lignins were characterized by complementary spectroscopic techniques, including 1H, 13C, 31P, and two-dimensional analysis. A substantial increase in p-hydroxyphenyl units was measured (+64%, corresponding to an increase of +1.3 mmol g−1). A full factorial design of the experiment was employed to quantify the impact of critical variables on the conversion yield. The subsequent statistical analysis suggested that the initial molar ratio between the two precursors was the factor predominating the yield of the reaction. Hansen solubility parameters of both the technical and esterified lignins were determined by solubility assays in multiple solvents, evidencing their high solubility in common organic solvents. The esterified lignin demonstrated a better thermal stability as the onset of thermal degradation shifted from 157 to 220 °C, concomitantly to the shift of the glass transition from 92 to 112 °C. In conclusion, the esterified lignin showed potential for being used as sustainable building blocks for composite and thermoset applications.

Carbon Nanocomposites: The Potential Heterogeneous Catalysts for Organic Transformations

One of the major challenges in chemistry confronted by the chemists is the replacement of conventional homogeneous catalysts by heterogeneous catalysts for the development of green, sustainable and economical chemical processes. Recently, carbón-based nanocomposites have attracted the attention of scientists due to their unique physical and chemical properties such as large surface area and pore volume, chemical inertness, high stability and high electrical conductivity. These NCs have been employed in energy storage, electronic devices, sensors, environmental remediation etc. Owing to the wide availability and low cost, carbón-based materials have been utilized as supports for transition metals and other materials. The carbón-based NCs offer a number of advantages such as high stability, easy recovery, reusability with often minimal leaching of metal ions, and green and sustainable approaches to heterogeneous catalysis for various organic transformations. Hence, they can be used as the substitute for the existing catalyst used for heterogeneous catalysis in industries. In this review, various processing methods for carbón-based nanocomposites and their applications as heterogeneous catalysts for organic transformations like hydrogenation, oxidation, coupling, and multi-component reactions, have been discussed.

Fabrication of a charged PDA/PEI/Al2O3 composite nanofiltration membrane for desalination at high temperatures

Ceramic membranes with high thermal and chemical resistances play an important role in nanofiltration process under harsh conditions. However, the application of ceramic membranes for salt filtration is challenging due to the limitation of pore size and surface charge. Herein, composite ceramic nanofiltration membranes were prepared by the codeposition of polydopamine and polyethyleneimine (PDA/PEI), with subsequent cross-linking by glutaraldehyde (GA). Ceramic ultrafiltration membranes served as supports, endowing the composite membranes with high mechanical stabilities and good hydrophilicity. A significant improvement in the rejection of salt solutions was achieved after modification due to the strong positive surface charge and small membrane pore size. The polydopamine/PEI modification layer crosslinked by glutaraldehyde and bonded to the surface of ceramic membrane through covalent bond show good thermal resistance. At high temperatures, the composite ceramic nanofiltration membranes still have a good rejection performance for divalent salt solutions. Overall, this study offers a composite ceramic nanofiltration membrane for desalination at high temperature, allowing a sustainable chemical process.

Insight into controllability and operation of extractive dividing-wall column

The extractive dividing-wall column (E-DWC) as process intensification can achieve more sustainable chemical process with economic and safe performance. However, the operation and controllability are in question and are biggest obstacle to the industrialization of extractive dividing-wall column. The coupling effect of E-DWC improves the thermal efficiency significantly but loses one control freedom and enhance interaction behavior compared with the conventional process. In this paper, we investigate the interaction behavior in E-DWC and illuminate the necessary of the extra control freedom to address the interaction behavior although the number of control freedom degrees are just enough for holding purity specification of three products.To solve the coupling effect and interaction behavior, in this paper, the intermediate heating is used to add one control freedom to change the vapor split through directly increasing the flowrate of vapor. We use two systems-acetone and methanol, and bioethanol dehydration as cases to explore the controllability and operation of E-DWC. The results of dynamic simulation prove that the interaction behavior and coupling effect indeed cause poor controllability of E-DWC. Moreover, the intermediate heating strategy indeed is valid and can improve controllability of E-DWC significantly. The integral of squared error and deviation of product purity are reduced significantly both for two cases. Especially for acetone and methanol, the setting time and integral of squared error in the presence of +20% composition disturbance is reduced significantly.

Towards Combining Electrochemical Water Splitting and Electrochemical Disinfection

To produce hydrogen (H2) and oxygen (O2), electrolytic water splitting (EWS) emerges as one of the most encouraging techniques in which to harness intermittent renewable power sources and store the energy these provide as a clean-burning and sustainable fuel. Nevertheless, efficacious formation of H2 and O2 is of little usage if such products cannot be kept separate and there are major dares linked with preserving suitable separation between H2 and O2 during electrolysis driven by intermittent renewable sources. In this work, a short view of fresh advance in the field of decoupled electrolysis for water splitting is presented and the potential that this technique has for enabling a range of other sustainable chemical processes is explored. Between such chemical processes, electrochemical disinfection (ED) remains a great promise in disinfecting water. This work suggests the application of ED in the EWS compartment producing O2 besides the other compartment producing H2. Similarities between the two processes include that both of them use electric current for their realization. For the first one, H2 and O2 are produced separately in two cells. The suggested idea here is to use EWS device for producing H2 in one cell and producing O2 in the second cell in which water may be disinfected by the electric field application and the electric current passage. Disinfection efficiency would be enhanced by the presence of O2. Practical examinations have to be conducted to determine the best scheme in terms of dimensions and disinfection efficiencies.

A sustainable chemical process to recycle end-of-life silicon solar cells

We developed a sustainable process for a fast, efficient, and environmentally friendly recovery of high purity silver and silicon from waste solar cells.

Oxidative dehydrogenation on nanocarbon: Polydopamine hollow nanospheres as novel highly efficient catalysts

Ethylbenzene oxidative dehydrogenation (EB ODH) reactions with nanocarbon as catalysts exhibit promising prospects as green and sustainable chemical industrial process. The present work reported the design and synthesis of polydopamine hollow nanospheres (PDA HNSs) carbon-based catalysts via a polymerization & carbonization method using silica as hard templates. The proposed PDA HNSs catalysts exhibit a high surface area of 641.6 m2 g−1 with the surface oxygen and nitrogen content up to 6.3% and 9.5%, respectively. It shows exceptional catalytic performance towards EB ODH reaction, which is even better than the commercial nanocarbon materials, such as carbon nanotubes, from the viewpoint of the apparent activity (EB conversion at 61.6%), the intrinsic activity (7.7 × 10−4 s−1) and the activation energy (42.5 kJ/mol), although they share the same catalytic active sites of ketonic carbonyl/quinone groups and reaction kinetics, such as rate determining step and reaction orders.

Ambient CO2/N2 Switchable Pickering Emulsion Emulsified by TETA-Functionalized Metal-Organic Frameworks.

In recent years, metal-organic frameworks (MOFs) have been explored as emulsifiers for the fabrication of Pickering emulsions and then used for hybrid material synthesis and interface catalysis. Nevertheless, stimuli-responsive Pickering emulsions stabilized by MOFs have been rarely reported so far, although they are of great importance for fundamental research studies and practical applications. Herein, for the first time, triethylenetetramine (TETA)-functionalized MOFs (ZIF-90/TETA) have been designed, synthesized, and used for fabricating CO2-/N2-response Pickering emulsions. It is shown that even at the ZIF-90/TETA content of 0.25 wt %, the functional MOF can still efficiently emulsify n-hexane and water to form a high internal phase Pickering emulsion. Importantly, the Pickering emulsion can be easily and reversibly switched between emulsification and demulsification by bubbling of CO2 and N2 alternatively at atmospheric pressure. The possible mechanism of the CO2/N2 switchable emulsion is investigated by zeta potential, water contact angle, interfacial tension, 13C NMR spectroscopy, and an optical microscope. It is found that the acid-base reaction of CO2 with TETA anchored on the surface of ZIF-90 leads to the production of hydrophilic ammonium bicarbonate and carbamate, which results in the emulsification of the Pickering emulsion. However, when N2 is bubbled to remove CO2, the reverse reaction takes place to cause the demulsification of the Pickering emulsion. Moreover, the CO2/N2 switchable Pickering emulsion has been successfully used as a microreactor for Knoevenagel reactions to demonstrate a highly efficient integration of chemical reaction, product separation, and ZIF-90/TETA recycling for a sustainable chemical process.

Transition-Metal-Free Synthesis of 2-Substituted Benzothiazoles from Nitrobenzenes, Methylheteroaryl Compounds, and Elemental Sulfur, Based on Nitro-Methyl Redox-Neutral Cyclization.

Greener and more sustainable chemical processes are required to address increasing environmental pollution and depletion of natural resources. This paper aims to develop greener and more sustainable modern synthetic chemical processes using redox-neutral cyclization. Redox-neutral cyclization has been shown to promote the efficient synthesis of 2-substituted benzothiazoles from easily available nitrobenzenes, methyl-heteroaryl compounds, and elemental sulfur in the absence of transition-metal catalysts. The 2-substituted benzothiazoles were obtained in reasonable yields through the sulfuration of electron-deficient C-H bonds with elemental sulfur. This synthetic methodology also affords a high atom economy without the use of any external oxidizing and/or reducing reagents.

Decoupled Electrochemical Water Splitting: From Fundamentals to Applications

AbstractElectrolytic water splitting to generate hydrogen and oxygen is one of the most promising ways in which to harness intermittent renewable power sources and store the energy these provide as a clean‐burning and sustainable fuel. In recent years, this has led to an explosion in reports on electrochemical water splitting, most of them focused on improving the efficiency of the electrochemical reactions themselves. However, efficient generation of hydrogen and oxygen is of little use if these products cannot be kept separate and the community is now coming to realize that there are considerable challenges associated with maintaining adequate separation between H2 and O2 during electrolysis driven by intermittent renewable sources. Decoupled electrolysis (whereby oxygen production occurs with reduction of a suitable mediator and hydrogen production is then paired with the reoxidation of this mediator) offers a solution to many of these challenges by allowing O2 and H2 to be produced at different times, at different rates, and even in completely different electrochemical cells. In this review, an overview of recent progress in the field of decoupled electrolysis for water splitting is given and the potential that this approach has for enabling a range of other sustainable chemical processes is explored.

Sustainable chemical reaction-free vacuum separation process to extract selenium from high-value-added hazardous selenium sludge

High-value-added hazardous selenium sludge extracted from copper anode slime may cause serious selenium contamination and potential threats to human health if improperly treated. In this study, a sustainable chemical reaction-free vacuum separation process was used to extract selenium and recycle valuable metals from selenium sludge. The process comprises low-pressure dehydration and Se extraction by vacuum distillation. The laboratory-scale results indicate that 90.76% of selenium was extracted from volatiles at a purity of 98.68% under the optimum distillation conditions of 693 K, 90 min and 30–50 Pa. Ag and Au were enriched to 28004 g/t and 1226 g/t in residues from 2560 g/t and 112 g/t, respectively, in raw materials, representing increases of 10.4 and 10.25 times. On this basis, a low-pressure melting-vacuum distillation process and equipment with an annual selenium sludge disposal capacity of 500 metric tons were developed for industrial production. The continuous production data show that the purity of the extracted selenium always exceeded 98.0%, the direct yield ratio of selenium exceeded 96.5%, and the consumption was only 1150 kW h electricity per ton of selenium ingot output. Additionally, Ag and Au were enriched by over 11 times in the residue. The discharged water evaporated, and residues were returned to the comprehensive copper anode slime treatment process for the further valuable metal extraction. Compared with chemical processes, the proposed technology consumes fewer resources and reduces the environmental impacts, resulting in better economic and sustainability assessment results. The proposed process meets the demand for cleaner production within the selenium metallurgical industry.

Sustainability assessment for the chemical industry: Onwards to integrated system analysis

The chemical industry has been struggling to conduct sustainable operations within safe planetary limits, while being socially sound and profitable. Industrial systems are composed of complex arrangements that can vary from system’s boundary, production phase, management level and sustainability dimensions. The integration of such concepts is essential for sustainable development. Another crucial point is the procedure for unbiased decision-making. Contrarily to past works that separately address these concepts, this work integrates all aspects under a system’s perspective. This review covers methods applicable to the chemical industry seeking to answer the following question: are the existing sustainability assessment methods able to comparatively discriminate complex chemical industry arrangements tosupportdesign and corporate decisions? The adopted framework encompasses definition of focus and scope; investigation of prior reviews; definition of literature classification; search and screening the literature; classification of the literature extract; analysis, review and findings; and identification of gaps for future developments. The framework identified 60 methods on sustainable chemical process design and production up to the present date. A sharp increase of articles occurred from 2010, but reported methods are seldom fully integrated and are mostly applied to gate-to-gate boundaries. The main identified literature gap is the lack of simultaneous coverage of all sustainability dimensions within the life-cycle boundaries. Additionally, decision-making is mostly arbitrary, either overlooking indicator screening or critical evaluation of the proposed techniques. This review unveiled the need for integrated systems analysis for product/process life-cycle and company-levels.

Membrane-Supported Recovery of Homogeneous Organocatalysts: A Review

As catalysis plays a significant role in the development of economical and sustainable chemical processes, increased attention is paid to the recovery and reuse of high-value catalysts. Although homogeneous catalysts are usually more active and selective than the heterogeneous ones, both catalyst recycling and product separation pose a challenge for developing industrially feasible methods. In this respect, membrane-supported recovery of organocatalysts represents a particularly useful tool and a valid option for organocatalytic asymmetric synthesis. However, catalyst leaching/degradation and a subsequent decrease in selectivity/conversion are significant drawbacks. As the effectivity of the membrane separation depends mainly on the size of the catalyst in contrast to the other solutes, molecular weight enlargement of small organocatalysts is usually necessary. In the last few years, several synthetic methodologies have been developed to facilitate their recovery by nanofiltration. With the aim of extending the possibilities for the membrane-supported recovery of organocatalysts further, this contribution presents a review of the existing synthetic approaches for the molecular weight enlargement of organocatalysts.

Recent Advances in Heterogeneous Photo-Driven Oxidation of Organic Molecules by Reactive Oxygen Species.

The photo-driven oxidation of organic molecules into corresponding high-value-added products has become a promising method in chemical synthesis. This strategy can drive thermodynamically non-spontaneous reactions and achieve challenging thermocatalytic processes under ambient conditions. Reactive oxygen species (ROS) are not only significant intermediates for producing target products via photoinduced oxidation reactions but also contribute to the creation of sustainable chemical processes. Here, the latest advances in heterogeneous photo-driven oxidation reactions involving ROS are summarized. The major types of ROS and their generation are introduced, and the behaviors of various ROS involved in photo-driven processes are reviewed in terms of the formation of different bonds. Emphasis is placed on unraveling the reaction mechanisms of ROS and establishing strategies for their regulation, and the remaining challenges and perspectives are summarized and analyzed. This Review is expected to provide an in-depth understanding of the mechanisms of ROS involved in photo-driven oxidation processes as an important foundation for the design of efficient catalysts. Clarifying the role of ROS in oxidation reactions has important scientific significance for improving the atomic and energy efficiency of reactions in practical applications.