Sustainable Chemical Processes Research Articles

Main-Group-Catalyzed Reductive Alkylation of Multiply Substituted Amines with Aldehydes Using H2.

Given the growing demand for green and sustainable chemical processes, the catalytic reductive alkylation of amines with main-group catalysts of low toxicity and molecular hydrogen as the reductant would be an ideal method to functionalize amines. However, such a process remains challenging. Herein, a novel reductive alkylation system using H2 is presented, which proceeds via a tandem reaction that involves the B(2,6-Cl2C6H3)( p-HC6F4)2-catalyzed formation of an imine and the subsequent hydrogenation of this imine catalyzed by a frustrated Lewis pair (FLP). This reductive alkylation reaction generates H2O as the sole byproduct and directly functionalizes amines that bear a remarkably wide range of substituents including carboxyl, hydroxyl, additional amino, primary amide, and primary sulfonamide groups. The synthesis of isoindolinones and aminophthalic anhydrides has also been achieved by a one-pot process that consists of a combination of the present reductive alkylation with an intramolecular amidation and intramolecular dehydration reactions, respectively. The reaction showed a zeroth-order and a first-order dependence on the concentration of an imine intermediate and B(2,6-Cl2C6H3)( p-HC6F4)2, respectively. In addition, the reaction progress was significantly affected by the concentration of H2. These results suggest a possible mechanism in which the heterolysis of H2 is facilitated by the FLP comprising THF and B(2,6-Cl2C6H3)( p-HC6F4)2.

Definition of “sustainable chemistry” unclear, report says

The development and adoption of “sustainable chemistry” is hindered because agreement is lacking on what this term encompasses, according to a U.S. congressional report. In addition, there is no consensus on how to measure the sustainability of chemical processes and products, the Government Accountability Office (GAO) concludes in the report. Nonetheless, GAO, the investigative arm of Congress, determines that one goal of sustainable chemistry is more efficient use of energy, water, and materials while protecting the environment from harm when producing commercial substances. Another aim is to reduce or eliminate the use or creation of hazardous materials in the manufacture and use of chemicals. GAO concludes that three categories of technology can make chemical production more sustainable: catalysts, which reduce the energy needed for chemical processes; solvents that are derived from renewable materials or are less hazardous than solvents currently employed; and continuous processing rather than batch processing of chemicals.

Sustainable chemical processing and energy-carbon dioxide management: Review of challenges and opportunities

Energy is the driving force for growth and per-capita energy consumption is a key parameter for the development of a nation. Carbon dioxide emissions from burning of fossil fuels are the main concerns for global warming. This paper presents a brief review of the available energy sources, CO2-emissions and management, and sustainable chemical processing, where energy consumption, CO2-emission, as well as economics and environmental impacts are considered. Not all available energy sources have been utilized efficiently, while, the energy source causing the largest emission of CO2 is being used in the largest amount. The CO2 management is therefore looking at “curing” the problem rather than “preventing” it. Examples highlighting the synthesis, design and analysis of sustainable chemical processing are presented in the areas of utilization of biomass-based energy-chemicals production, carbon-capture and utilization to produce value added chemicals, and retrofit design of energy intensive chemical processes with significant reduction of energy-consumption are presented. These examples highlight issues of energy-sustainable design, energy-CO2 neutral design, energy-retrofit design, and energy-process intensification. Finally, some perspectives on the status and future directions of carbon dioxide management are outlined.

Catalytic oxidation of biomass to oxygenated chemicals with exceptionally high yields using H5PV2Mo10O40

The transformation of biomass into platform chemicals is a key intermediate step to establish biomass-based sustainable chemical processes. The preparation of oxygenated chemicals by conversion of biomass is of significant conceptual and practical interest. In this work, an efficient catalytic system for carbohydrate-based biomass oxidation to oxygenated chemicals (including formic acid, dimethoxymethane and methyl formate) with O2 using H5PV2Mo10O40 as catalyst is presented. Conversions of glucose and cellulose in a methanol/water medium achieved total product yields of oxygenated chemicals up to 92.9% and 89.7%, respectively (based on carbon). A conversion pathway to clarify the mechanism of product formation was proposed. Protecting reactive functional groups of sugars and reaction intermediates via acetalisation and etherification in methanol effectively suppressed CO2 formation and remarkably enhanced the production of oxygenated chemicals. The effect of solvent composition on catalyst H5PV2Mo10O40 was investigated, and it was found that the structural stability of the catalyst increased by the addition of methanol. The catalyst was reused four times without significant decline in activity.

Convenient Electrocatalytic Synthesis of Azobenzenes from Nitroaromatic Derivatives Using SmI2

The synthesis of azobenzenes has been a long-standing challenge. Their current preparation at a preparative or industrial scale requires stoichiometric amounts of environmentally unfriendly reactants. Herein, we demonstrate that the catalytic use of electrogenerated samarium diiodide (SmI2) could promote, in one-step synthesis, the reduction of nitrobenzenes into azobenzenes in high yields under mild reaction conditions. This catalytic procedure contains many elements satisfying a sustainable chemical process for the preparation of one of the most widely wanted family of chemical compounds. The easy synthetic procedure, and the absence of precious metals, bases, and nonhazardous substances, already makes our catalytic procedure a serious alternative to currently available methods. This is a promising method for the efficient synthesis of both symmetrical and asymmetrical azo compounds with a high functional group tolerance.

Unconventional Deep Eutectic Solvents: Aqueous Salt Hydrates

Neoteric solvents for sustainable chemical processes are continuously sought nowadays. Deep eutectic solvents (DES), i.e., liquids that are mixtures of two components that have freezing points considerably below the melting points of these components, constitute a possible solution for this search. Mixtures of certain congruently melting salt hydrates with water have freezing points considerably below the melting points of ice and of the salt hydrate. They should be considered as DES for applications in which their properties could be useful, namely their being “green” and nonflammable ionic liquids at very low temperatures. The eutectic points and eutectic temperature distances of such salt hydrate DES, calculated from literature data, are tabulated, and some illustrative phase diagrams are shown. Physical properties of the aqueous salt hydrate DES that are relevant to their possible applications are reported, and they compare favorably with those of conventional DES. The Brunauer–Emmett–Teller modeling ...

Probing the Energetics of Molecule–Material Interactions at Interfaces and in Nanopores

During the past decades, advances in interfacial chemistries at the molecular level are shaping our world by playing crucial roles in balancing global scale energy crisis and critical environmental concerns. However, systematic investigations into the binding energies, site distribution, and their correlation with the molecular-level surface assemblages and structures at interfaces and in nanopores are rarely documented. In this review, we summarize a set of systematic calorimetric studies on surface energetics we performed during the past decade. These studies demonstrate how thermochemistry can reveal crucial energetic insights into a series of molecule–material interactions relevant to a number of applications, including carbon capture and sequestration, energy production, sustainable chemical processing, catalysis, and nanogeoscience. Calorimetric methodologies developed and applied include direct gas adsorption calorimetry, near-room temperature solvent immersion/solution calorimetry, and high temper...

Thin film composites in the BiFeO3–Bi4Ti3O12 system obtained by an aqueous solution-gel deposition methodology

Thin film multiferroic composites, with a high quantity of interfaces between the different materials, represent a more feasible alternative to single phase systems in which the multifunctional response is usually hampered due to intrinsic physical constraints. Nowadays some of these composites can be produced by applying deposition techniques such as PLD, CVD, MBE or the like, which allow a high degree of crystallographic control. However, despite their effectiveness, all these techniques also involve a high consumption of energy in terms of temperature and/or vacuum. Within this frame, the present contribution proposes a sustainable chemical solution deposition process to prepare thin films of the multiferroic BiFeO3–Bi4Ti3O12 composite system. More specifically an aqueous solution-gel plus spin-coating methodology is employed which also avoids the organic solvents typically used in a conventional sol–gel method, so further keeping an eye on the environmentally friendly conditions. Attempts are conducted that demonstrate how by systematically controlling the processing parameters it is possible to obtain thin film composites with a promising 3-3 type connectivity at temperatures as low as 600°C.

Sustainable chemistry and chemical processes for a sustainable future

Sustainable chemistry and chemical processes for a sustainable future

Sustainable chemistry and chemical processes for a sustainable future

Sustainable chemistry and chemical processes for a sustainable future

Assessment of Sustainability Indicators for Biodiesel Production

Biodiesel production may provide a sustainable route to reduce environmental pollution caused by fossil fuel consumption. In order to minimize environmental impacts of biodiesel production, the chemical process should be optimized to minimize waste generation and energy consumption. Therefore, it is important to design biodiesel chemical reactions and processes using green chemistry and green engineering principles to develop sustainable chemical processes. This study provides the results of the synergistic effect of microwave and ultrasound irradiations to produce biodiesel using ethanol or methanol as the alcohol donor. The biodiesel yields are presented along with their respective green metrics, such as atom economy, environmental factor (E-factor), atom economy (utilization) or atomic efficiency, mass intensity, reaction mass efficiency, atom utilization, and stoichiometric factor. These green metrics are crucial to determine the sustainability and environmental impact of biodiesel production. Evaluation of these green metrics indicates that methanol is a better alternative for biodiesel production provided it is derived from renewable sources. Sustainability indicator concepts used for biodiesel production in this study can be applied to various biofuels and other chemical reaction designs, synthesis and process development.

Supported Dendrimer-Encapsulated Metal Clusters: Toward Heterogenizing Homogeneous Catalysts.

Recyclable catalysts, especially those that display selective reactivity, are vital for the development of sustainable chemical processes. Among available catalyst platforms, heterogeneous catalysts are particularly well-disposed toward separation from the reaction mixture via filtration methods, which renders them readily recyclable. Furthermore, heterogeneous catalysts offer numerous handles-some without homogeneous analogues-for performance and selectivity optimization. These handles include nanoparticle size, pore profile of porous supports, surface ligands and interface with oxide supports, and flow rate through a solid catalyst bed. Despite these available handles, however, conventional heterogeneous catalysts are themselves often structurally heterogeneous compared to homogeneous catalysts, which complicates efforts to optimize and expand the scope of their reactivity and selectivity. Ongoing efforts in our laboratories are aimed to address the above challenge by heterogenizing homogeneous catalysts, which can be defined as the modification of homogeneous catalysts to render them in a separable (solid) phase from the starting materials and products. Specifically, we grow the small nanoclusters in dendrimers, a class of uniform polymers with the connectivity of fractal trees and generally radial symmetry. Thanks to their dense multivalency, shape persistence, and structural uniformity, dendrimers have proven to be versatile scaffolds for the synthesis and stabilization of small nanoclusters. Then these dendrimer-encapsulated metal clusters (DEMCs) are adsorbed onto mesoporous silica. Through this method, we have achieved selective transformations that had been challenging to accomplish in a heterogeneous setting, e.g., π-bond activation and aldol reactions. Extensive investigation into the catalytic systems under reaction conditions allowed us to correlate the structural features (e.g., oxidation states) of the catalysts and their activity. Moreover, we have demonstrated that supported DEMCs are also excellent catalysts for typical heterogeneous reactions, including hydrogenation and alkane isomerization. Critically, these investigations also confirmed that the supported DEMCs are heterogeneous and stable against leaching. Catalysts optimization is achieved through the modulation of various parameters. The clusters are oxidized (e.g., with PhICl2) or reduced (e.g., with H2) in situ. Changing the dendrimer properties (e.g., generation, terminal functional groups) is analogous to ligand modification in homogeneous catalysts, which affect both catalytic activity and selectivity. Similarly, pore size of the support is another factor in determining product distribution. In a flow reactor, the flow rate is adjusted to control the residence time of the starting material and intermediates, and thus the final product selectivity. Our approach to heterogeneous catalysis affords various advantages: (1) the catalyst system can tap into the reactivity typical to homogeneous catalysts, which conventional heterogeneous catalysts could not achieve; (2) unlike most homogeneous catalysts with comparable performance, the heterogenized homogeneous catalysts can be recycled; (3) improved activity or selectivity compared to conventional homogeneous catalysts is possible because of uniquely heterogeneous parameters for optimization. In this Account, we will briefly introduce metal clusters and describe the synthesis and characterizations of supported DEMCs. We will present the catalysis studies of supported DEMCs in both the batch and flow modes. Lastly, we will summarize the current state of heterogenizing homogeneous catalysis and provide future directions for this area of research.

Study of Extraction and Recycling of Switchable Hydrophilicity Solvents in an Oscillatory Microfluidic Platform

One of the challenges in the development of green and sustainable chemical processing is solvent removal and subsequent replacement with another solvent in various steps of multistep syntheses, extraction, or purification. A promising alternative approach is the use of “switchable” solvents that change their properties on demand. The evaluation of the performance of switchable solvents in the entire extraction-recovery process, with a capability of efficient solvent recycling, is vital for their future applications. We report an oscillatory microfluidic platform to reproduce a complete cycle of CO2-mediated extraction and recovery of switchable hydrophilicity solvents, with the capability of solvent recycling. The evaluation of the efficiency of solvent extraction and recovery in the entire process is achieved within 1.5 h, with <15 μL of the solvent, without the formation of double emulsions, and with the capability to obtain the temporal information for each step of the process. The new methodology enab...

C&amp;EN talks with Margaret Faul of Amgen

Green chemistry aims to minimize impact on the environment, but it can also save manufacturers time and money, making the approach good for the bottom line. Recognizing this, many pharmaceutical companies have shifted toward green processes for drug discovery and development in the past decade. Margaret Faul, a synthetic organic chemist by training, led this move at Amgen, one of the world’s largest biotechnology companies. The process involved not only developing greener and more sustainable chemical processes but also embedding this approach in the organization’s work culture. The efforts paid off: Amgen went from 106th in 2014 to 34th in 2015 in the Global Green Rankings. The company has also earned a spot on the selective Dow Jones Sustainability World Index. Faul talked with Prachi Patel about how Amgen made the shift to greener synthetic chemistry. Why are green chemistry practices important for Amgen and the pharmaceutical industry in general?

N‐, O‐, and S‐Tridoped Carbon‐Encapsulated Co9S8 Nanomaterials: Efficient Bifunctional Electrocatalysts for Overall Water Splitting

The development of highly active and stable earth‐abundant catalysts to reduce or eliminate the reliance on noble‐metal based ones in green and sustainable (electro)chemical processes is nowadays of great interest. Here, N‐, O‐, and S‐tridoped carbon‐encapsulated Co9S8 (Co9S8@NOSC) nanomaterials are synthesized via simple pyrolysis of S‐ and Co(II)‐containing polypyrrole solid precursors, and the materials are proven to serve as noble metal‐free bifunctional electrocatalysts for water splitting in alkaline medium. The nanomaterials exhibit remarkable catalytic performances for oxygen evolution reaction in basic electrolyte, with small overpotentials, high anodic current densities, low Tafel slopes as well as very high (nearly 100%) Faradic efficiencies. Moreover, the materials are found to efficiently electrocatalyze hydrogen evolution reaction in acidic as well as basic solutions, showing high activity in both cases and maintaining good stability in alkaline medium. A two‐electrode electrolyzer assembled using the material synthesized at 900 °C (Co9S8@NOSC‐900) as an electrocatalyst at both electrodes gives current densities of 10 and 20 mA cm−2 at potentials of 1.60 and 1.74 V, respectively. The excellent electrocatalytic activity exhibited by the materials is proposed to be mainly due to the synergistic effects between the Co9S8 nanoparticles cores and the heteroatom‐doped carbon shells in the materials.

Sustainable Chemical Synthesis for Phosphorus-Doping of TiO2 Nanoparticles by Upcycling Human Urine and Impact of Doping on Energy Applications

Recently, there has been significant research interest toward sustainable chemical synthesis and processing of nanomaterials. Human urine, a pollutant, requires energy intensive processing steps prior to releasing into rivers and oceans. Upcyling urine has been proposed and practiced as a sustainable process in the past. Doping is one of the foremost processes to elevate the functionality of nanomaterials depending on the applications it is sought for. Phosphorus doping in to TiO2 nanomaterials has been of research interest over a decade now, that has been chiefly done using acidic precursors. Here we demonstrate, upcycling urine, a sustainable process for phosphorus doping into TiO2 lattice. Upon doping the changes in morphology, surface chemistry and band gap is studied in detail and compared with undoped TiO2 that is prepared using deionized water instead of urine. X-ray photoelectron spectroscopy confirmed that the P was replacing Ti in the lattice and exists in P5+ state with a quantified concentrati...

Strengths, Weaknesses, Opportunities and Threats: Computational Studies of Mn- and Fe-Catalyzed Epoxidations

The importance of epoxides as synthetic intermediates in a number of highly added-value chemicals, as well as the search for novel and more sustainable chemical processes have brought considerable attention to the catalytic activity of manganese and iron complexes towards the epoxidation of alkenes using non-toxic terminal oxidants. Particular attention has been given to Mn(salen) and Fe(porphyrin) catalysts. While the former attain remarkable enantioselectivity towards the epoxidation of cis-alkenes, the latter also serve as an important model for the behavior of cytochrome P450, thus allowing the exploration of complex biological processes. In this review, a systematic survey of the bibliographical data for the theoretical studies on Mn- and Fe-catalyzed epoxidations is presented. The most interesting patterns and trends are reported and finally analyzed using an evaluation framework similar to the SWOT (Strengths, Weaknesses, Opportunities and Threats) analysis performed in enterprise media, with the ultimate aim to provide an overview of current trends and areas for future exploration.

Using Green Chemistry and Engineering Principles To Design, Assess, and Retrofit Chemical Processes for Sustainability.

The concepts of green chemistry and engineering (GC&E) have been promoted as an effective qualitative framework for developing more sustainable chemical syntheses, processes, and material management techniques. This has been demonstrated by many theoretical and practical cases. In addition, there are several approaches and frameworks focused on demonstrating that improvements were achieved through GC&E technologies. However, the application of these principles is not always straightforward. We propose using systematic frameworks and tools that help practitioners when deciding which principles can be applied, the levels of implementation, prospective of obtaining simultaneous improvements in all sustainability aspects, and ways to deal with multiobjective problems. Therefore, this contribution aims to provide a systematic combination of three different and complementary design tools for assisting designers in evaluating, developing, and improving chemical manufacturing and materials management systems under GC&E perspectives. The WAR Algorithm, GREENSCOPE, and SustainPro were employed for this synergistic approach of incorporating sustainability at early stages of process development. In this demonstration, simulated ammonia production is used as a case study to illustrate this advancement. Results show how to identify process design areas for improvements, key factors, multicriteria decision-making solutions, and optimal trade-offs. Finally, conclusions were presented regarding the tools' use in more robust sustainable process and material management designs.

ChemInform Abstract: Ruthenium‐Catalyzed Metathesis of Conjugated Polyenes

AbstractReview: [71 refs.

Multistage Optimization for Chemical Process Sustainability Enhancement under Uncertainty

Chemical process sustainability is mainly concerned with energy and material efficiency, productivity and product quality, waste reduction, process safety, heath impact, etc. Due to these multiple factors as well as information and data uncertainty, development of optimal strategies and effective action plans for sustainability enhancement becomes a very challenging task. In this paper, we introduce a mathematical framework for optimal process sustainability performance enhancement. In this framework, we describe four types of optimization problems, which are defined based on decision makers’ different objectives for sustainability enhancement. In formulation, various economic, environmental, and social concerns and technical feasibilities are taken into account, where data uncertainty is dealt with by interval parameters. Solution search is performed by a genetic algorithm method and a Monte Carlo simulation technique. The methodological applicability is illustrated by a comprehensive case study on biodi...