Chemical Building Blocks Research Articles

Non-Oxidative Ethane Dehydrogenation in a Packed-Bed DBD Plasma Reactor

Plasma-assisted conversion of ethane (C2H6) can produce value-added chemical building blocks using green electricity. Here we employ a simple packed-bed coaxial dielectric barrier discharge (DBD) reactor to convert C2H6 at mild operating conditions unattainable by conventional thermocatalysis. Ethylene (C2H4), acetylene (C2H2), and methane (CH4) are the main products along with small fractions of C3 and C4 hydrocarbons. Interestingly, the C2H4 selectivity is primarily correlated to C2H6 conversion, dominated by electron dissociation and recombination reactions irrespective of the dielectric properties of the packed bed material (SiO2, Al2O3, ZrO2, TiO2, and BaTiO3), packing material size, supplied power, and C2H6 concentration. While a distortion of the electric field and discharge propagation results in varying dissipated power as materials change, the C2H4 energy yield remains constant. The particle size appears to affect conversion mainly due to pressure alterations. Pd/SiO2 catalyst can change the selectivity, favoring saturated species by expending hydrogen.

Process-intensified protonic ceramic fuel cells for power generation, chemical production, and greenhouse gas mitigation

•Simultaneous power generation, chemical production, and greenhouse gas mitigation •Sm0.2Ce0.7Ni0.1Ru0.05O2-δ catalyst was designed for dry reforming of methane •Extensive studies were performed to probe the synergistic impacts of Ni and Ru •At 650°C, the DRM-PCFC attained a peak power density of 0.94 W cm−2 Here, we present protonic ceramic fuel cells (PCFCs) that achieve the internal dry reforming of methane (DRM) at 550°C–650°C to simultaneously generate power, produce syngas or hydrogen as chemical building blocks, and to mitigate two harmful greenhouse gases. We developed an oxide-supported in situ exsolved Ni-Ru catalyst (Sm0.2Ce0.7Ni0.1Ru0.05O2-δ, i.e., SDC-Ni-Ru). The in situ exsolved Ru clusters favor the CO2 activation step, while the Ni clusters promote the CH4 activation. The synergy between Ni and Ru clusters simultaneously improves the CH4 and CO2 activation, enhancing the DRM activity. Additionally, we discovered that the Ru clusters alter the DRM pathway, favoring the formation of monodentate carbonate species, which subsequently accelerates the oxidization of −CH∗ species on Ni clusters and improves the coking tolerance. The PCFCs equipped with this SDC-Ni-Ru internal DRM catalyst attain exceptional and durable power densities using a mixture of CH4 and CO2 as the fuel, setting a record for DRM-PCFCs. Here, we present protonic ceramic fuel cells (PCFCs) that achieve the internal dry reforming of methane (DRM) at 550°C–650°C to simultaneously generate power, produce syngas or hydrogen as chemical building blocks, and to mitigate two harmful greenhouse gases. We developed an oxide-supported in situ exsolved Ni-Ru catalyst (Sm0.2Ce0.7Ni0.1Ru0.05O2-δ, i.e., SDC-Ni-Ru). The in situ exsolved Ru clusters favor the CO2 activation step, while the Ni clusters promote the CH4 activation. The synergy between Ni and Ru clusters simultaneously improves the CH4 and CO2 activation, enhancing the DRM activity. Additionally, we discovered that the Ru clusters alter the DRM pathway, favoring the formation of monodentate carbonate species, which subsequently accelerates the oxidization of −CH∗ species on Ni clusters and improves the coking tolerance. The PCFCs equipped with this SDC-Ni-Ru internal DRM catalyst attain exceptional and durable power densities using a mixture of CH4 and CO2 as the fuel, setting a record for DRM-PCFCs.

Heptaldehyde and undecylenic acid production from thermal and thermo-catalytic cracking of castor oil

With the breakdown of ricinoleic acid through the cracking technique, either in the thermal or thermo-catalytic form, compounds of interest for green chemistry, such as heptaldehyde and undecylenic acid, can be obtained. These supplies are envisioned since they are building block chemicals. Therefore, the influence of operational conditions on the cracking process was evaluated using a 2 ³ experimental design, including temperature, water, and catalyst, with the aim of improving the yield of heptaldehyde and undecylenic acid supplies from castor oil, inedible oil. The operating conditions used in the cracking process were: temperature of 500, 525, and 550 °C, water fractions of zero, 12.5%, and 25%, and catalyst fractions of benzoyl peroxide of zero, 0.55%, and 1.1%. The analysis suggests that the central point utilizing thermo-catalytic cracking demonstrates superior operational conditions as they generate an average of 78.5% bio-oil, 21.97% heptaldehyde, and 17.25% undecylenic acid, with 12.5% water and 0.55% catalyst at a temperature of 525 °C.

Chemical Recycling Processes of Waste Polyethylene Terephthalate Using Solid Catalysts.

Polyethylene terephthalate (PET) is a non-degradable single-use plastic and a major component of plastic waste in landfills. Chemical recycling is one of the most widely adopted methods to transform post-consumer PET into PET's building block chemicals. Non-catalytic depolymerization of PET is very slow and requires high temperatures and/or pressures. Recent advancements in the field of material science and catalysis have delivered several innovative strategies to promote PET depolymerization under mild reaction conditions. Particularly, heterogeneous catalysts assisted depolymerization of post-consumer PET to monomers and other value-added chemicals is the most industrially compatible method. This review includes current progresses on the heterogeneously catalyzed chemical recycling of PET. It describes four key pathways for PET depolymerization including, glycolysis, pyrolysis, alcoholysis, and reductive depolymerization. The catalyst function, active sites and structure-activity correlations are briefly outlined in each section. An outlook for future development is also presented.

Life Cycle Environmental Impact Considerations in the Design of Novel Biobased Polyurethane Coatings

Substituting fossil-based with biobased chemical building blocks can potentially decrease the environmental impact of polyurethane (PU) coating production. This study applies life cycle assessment methods in the early development of three processes that incorporate biobased elements into PU coating production: a fully biobased coating made with organosolv lignin (OSL) and a biobased cross-linker from vanillic acid (VA) and two hybrid coatings made with a fossil-based cross-linker and either OSL or depolymerized OSL. Coatings with biobased elements had impacts of 1.5, 2.6, and 19.9 kg CO2eq/kgcoating for coatings made with OSL, depolymerized OSL, and the fully biobased coating, respectively. Emissions are mostly associated with the fossil-based cross-linker in hybrid coatings and with solvents and heat needed for the production of the biomass-derived cross-linker. While this study demonstrates that the use of biobased compounds in hybrid coatings can reduce the environmental impacts of PU coatings in comparison to fossil-based versions, additional development of biobased cross-linkers and research into end-of-life scenarios are needed to further reduce the environmental impacts of biobased PU coating production.

Catalytic Biorefining of Natural Oils to Basic Olefinic Building Blocks of Proven Chemical Valorization Schemes.

Catalytic transformation of renewable plant oils including microalgae and waste oil into industrially relevant α-olefins in the C3 to C10 regime is demonstrated. The biorefinery concept is comprised of a catalytic sequence of ethenolysis, double bond isomerization, and a subsequent ethenolysis, thereby cutting and rearranging the fatty acid chains into valuable chemical building blocks. A benign extraction and reaction solvent, supercritical carbon dioxide (scCO2), is utilized.

Catalytic Biorefining of Natural Oils to Basic Olefinic Building Blocks of Proven Chemical Valorization Schemes

AbstractCatalytic transformation of renewable plant oils including microalgae and waste oil into industrially relevant α‐olefins in the C3 to C10 regime is demonstrated. The biorefinery concept is comprised of a catalytic sequence of ethenolysis, double bond isomerization, and a subsequent ethenolysis, thereby cutting and rearranging the fatty acid chains into valuable chemical building blocks. A benign extraction and reaction solvent, supercritical carbon dioxide (scCO2), is utilized.

Environmentally friendly oxidation pretreatments to produce sugar-based building blocks from dyed textile wastes via enzymatic hydrolysis

Given the increasing concern over textile waste management and the proliferation of textile landfills, enzymatic hydrolysis of cotton represents a potential pathway to upcycle textile waste into valuable chemical building blocks. However, this pathway is challenged by the presence of persistent dyes, hindering enzyme performance. To overcome this issue, environmentally friendly and total chlorine free oxidation methods such as ozone and alkaline hydrogen peroxide were used in combination with mechanical refining pretreatment. The results showed that the enzymatic conversion of black-dyed cotton, without oxidation, resulted in a glucose yield of only 60% as compared to 95% for undyed cotton fibers. On the other hand, the inclusion of oxidation processes in the pretreatment stage resulted in a glucose yield of 90% via enzymatic hydrolysis at expense of using low oxidation chemicals and low enzyme charges. This work highlights the potential of oxidation methods, enzymatic hydrolysis, and mechanical refining as an ecofriendly pathway for generating value-added chemicals from cotton textile waste while promoting economic circularity.

Recent Advances in the Electrocarboxylation of CO2 with Ketones, Aldehydes, and Imines

Abstract: Carbon dioxide (CO2) is regarded as an ideal C1 building block for the synthesis of value-added chemicals due to its low price, non-toxic, rich reserves, and recyclability. Organic electrosynthesis, using electricity as the driving force to avoid the use of toxic or expensive reducing agents, has become an efficient and environmentally friendly synthetic method and is widely used in the chemical conversion of CO2. In particular, the electrocarboxylation reaction of CO2 with a substrate containing a specific group, such as C=O and C=N, can be realized to synthesize α-hydroxy acids, amino acids, and their derivatives under mild reaction conditions by accurately adjusting the current or potential. In this review, we focus on the recent advances in the electrocarboxylation of CO2 with unsaturated substrates (including ketones, aldehydes, and imines) in the past five years, which we hope could stimulate further research on electrocarboxylation of CO2 with ketones, aldehydes, and imines and provide a reference for the application of such reactions in green organic electrosynthesis in the future.

Nucleosynthesis of Binary-stripped Stars

The cosmic origin of the elements, the fundamental chemical building blocks of the universe, is still uncertain. Binary interactions play a key role in the evolution of many massive stars, yet their impact on chemical yields is poorly understood. Using the MESA stellar evolution code, we predict the chemical yields ejected in wind mass loss and the supernovae of single and binary-stripped stars. We do this with a large 162-isotope nuclear network at solar metallicity. We find that binary-stripped stars are more effective producers of the elements than single stars, due to their increased mass loss and an increased chance to eject their envelopes during a supernova. This increased production by binaries varies across the periodic table, with F and K being more significantly produced by binary-stripped stars than single stars. We find that the 12C/13C could be used as an indicator of the conservativeness of mass transfer, as 13C is preferentially ejected during mass transfer while 12C is preferentially ejected during wind mass loss. We identify a number of gamma-ray-emitting radioactive isotopes that may be used to help constrain progenitor and explosion models of core-collapse supernovae with next-generation gamma-ray detectors. For single stars we find that 44V and 52Mn are strong probes of the explosion model, while for binary-stripped stars it is 48Cr. Our findings highlight that binary-stripped stars are not equivalent to two single stars and that detailed stellar modeling is needed to predict their final nucleosynthetic yields.

Front Cover: Fine‐Tuning Texture of Highly Acidic HZSM‐5 Zeolite for Efficient Ethanol Dehydration (ChemCatChem 9/2023)

The Front Cover illustrates how different morphologies of highly acidic ZSM-5 zeolite control the product distribution of ethanol dehydration. In their Research Article, E. J. M. Hensen, C. Wattanakit and co-workers demonstrate that very thin nanolayers of this zeolite with a large external surface area and abundant mesopores enhance the ethylene yield up to 95% with a high longevity. In contrast, nanoplate and bulk structures of ZSM-5 result in low ethanol conversion, high selectivity to diethyl ether, and rapid deactivation. Reducing the crystal size of highly acidic zeolites to ultra-thin nanosheets can shorten the residence time of ethanol and its intermediates in the shape-selective environments, significantly suppressing the formation of coke precursors and achieving high and stable yield of the important chemical building block ethylene. More information can be found in the Research Article by E. J. M. Hensen, C. Wattanakit and co-workers.

Ultrathin membranes composed of branched polyethylenimine and poly[(o-cresyl glycidyl ether)-co-formaldehyde] for primary recovery of itaconic acid

Efficient primary recovery of building-block chemicals produced by microbial processes, such as biobased itaconic acid, is a key step for environmentally sustainable and economically feasible manufacturing processes. Ultrathin membranes have the potential to address these challenges. Here, ultrathin membranes composed of branched polyethylenimine and poly[(o-cresyl glycidyl ether)-co-formaldehyde] were fabricated using a facile spin coating procedure, and the composition of the casting solution was adjusted to improve the separation performance. The structural properties of the ultrathin membranes (intrinsic porosity, thickness, surface morphology, chemistry, charge, and wettability) were investigated and linked to the separation performance. By increasing the content of polyethylenimine in the casting solution, the transport rate of itaconic acid across the membranes increased up to 40 times. Membranes with a 4:1 mass ratio of polyethylenimine to poly[(o-cresyl glycidyl ether)-co-formaldehyde] reactive groups were selected, and their ability to recover itaconic acid from synthetic solutions and recombinant Pichia pastoris culture supernatant in diffusion-based mode was demonstrated. Experiments with pure solutions of supernatant components demonstrated that the membranes were equally selective for itaconic acid and potential cultivation byproducts and at least 7-times more selective for itaconic acid than culture medium components. Experiments with synthetic complex solutions and culture supernatant confirmed the high selectivity for itaconic acid: the separation performance was similar for complex and pure itaconic acid solutions, despite the significant difference in the complexity of these solutions. This study is the basis for a new technology to recover microbially produced building-block chemicals.

Metabolic engineering to improve production of 3-hydroxypropionic acid from corn-stover hydrolysate in Aspergillus species

BackgroundFuels and chemicals derived from non-fossil sources are needed to lessen human impacts on the environment while providing a healthy and growing economy. 3-hydroxypropionic acid (3-HP) is an important chemical building block that can be used for many products. Biosynthesis of 3-HP is possible; however, low production is typically observed in those natural systems. Biosynthetic pathways have been designed to produce 3-HP from a variety of feedstocks in different microorganisms.ResultsIn this study, the 3-HP β-alanine pathway consisting of aspartate decarboxylase, β-alanine-pyruvate aminotransferase, and 3-hydroxypropionate dehydrogenase from selected microorganisms were codon optimized for Aspergillus species and placed under the control of constitutive promoters. The pathway was introduced into Aspergillus pseudoterreus and subsequently into Aspergillus niger, and 3-HP production was assessed in both hosts. A. niger produced higher initial 3-HP yields and fewer co-product contaminants and was selected as a suitable host for further engineering. Proteomic and metabolomic analysis of both Aspergillus species during 3-HP production identified genetic targets for improvement of flux toward 3-HP including pyruvate carboxylase, aspartate aminotransferase, malonate semialdehyde dehydrogenase, succinate semialdehyde dehydrogenase, oxaloacetate hydrolase, and a 3-HP transporter. Overexpression of pyruvate carboxylase improved yield in shake-flasks from 0.09 to 0.12 C-mol 3-HP C-mol−1 glucose in the base strain expressing 12 copies of the β-alanine pathway. Deletion or overexpression of individual target genes in the pyruvate carboxylase overexpression strain improved yield to 0.22 C-mol 3-HP C-mol−1 glucose after deletion of the major malonate semialdehyde dehydrogenase. Further incorporation of additional β-alanine pathway genes and optimization of culture conditions (sugars, temperature, nitrogen, phosphate, trace elements) for 3-HP production from deacetylated and mechanically refined corn stover hydrolysate improved yield to 0.48 C-mol 3-HP C-mol−1 sugars and resulted in a final titer of 36.0 g/L 3-HP.ConclusionsThe results of this study establish A. niger as a host for 3-HP production from a lignocellulosic feedstock in acidic conditions and demonstrates that 3-HP titer and yield can be improved by a broad metabolic engineering strategy involving identification and modification of genes participated in the synthesis of 3-HP and its precursors, degradation of intermediates, and transport of 3-HP across the plasma membrane.

Impact of the location of magnesium in zeolite-based shaped catalyst bodies on the methanol-to-hydrocarbons process

One of the main challenges for the chemical industries is finding new ways to produce lower olefins, such as propylene and ethylene, to satisfy the increase in demand for e.g., polymers, namely polypropylene and polyethylene. The Methanol-to-Hydrocarbons (MTH) process is an alternative manufacturing process that can help to address this increasing demand for these important chemical building blocks. It has been proposed that the addition of magnesium to zeolites, in the form of powdered catalyst materials, enhances the selectivity towards light olefins. In this work, the impact of the location of magnesium (present as Mg2+ and MgO) in zeolite-based shaped catalyst bodies on their physicochemical properties and catalytic performance in the MTH reaction has been studied. By adjusting one of the preparation steps of the overall extrusion process in which magnesium is added tuning the location of magnesium, higher interaction between magnesium and the zeolite material could be achieved. Pre-extrusion modification showed the most favorable results in terms of physicochemical properties and catalytic activity. We found that the magnesium location could be crucial for altering molecular transport, coke formation, and catalyst deactivation during the MTH reaction due to its pronounced effects on the acidity as well as porosity of the shaped catalyst bodies. These new insights can be applied to other zeolite-based extrudate materials and other acid-catalyzed reactions as it can be crucial for the design of better and more efficient catalyst materials in their industrially shaped form.

Benzimidazole compound abrogates SARS-COV-2 receptor-binding domain (RBD)/ACE2 interaction In vitro.

The development of clinically actionable pharmaceuticals against coronavirus disease (COVID-19); an infectious disease caused by the SARS-CoV-2 virus is very important for ending the pandemic. Coronavirus spike glycoprotein (GP)-Receptor Binding Domain (RBD) and its interaction with host receptor angiotensin converting enzyme 2 (ACE2) is one of the most structurally understood but therapeutically untapped aspect of COVID-19 pathogenesis. Binding interface based on previous x-ray structure of RBD/ACE2 were virtually screened to identify fragments with high-binding score from 12,000 chemical building blocks. The hit compound was subjected to fingerprint-based similarity search to identify compounds within the FDA-approved drug library containing the same core scaffold. Identified compounds were then re-docked into of RBD/ACE2. The best ranked compound was validated for RBD/ACE2 inhibition using commercial kit. Molecular dynamics simulation was conducted to provide further insight into the mechanism of inhibition. From the original 12000 chemical building blocks, benzimidazole (BAZ) scaffold was identified. Fingerprint-based similarity search of the FDA-approved drug library for BAZ-containing compounds identified 12 drugs with the benzimidazole-like substructure. When these compounds were re-docked into GP/ACE2 interface, the consensus docking identified bazedoxifene as the hit. In vitro RBD/ACE2 inhibition kinetics showed micromolar IC50 value (1.237μM) in the presence of bazedoxifene. Molecular dynamics simulation of RBD/ACE2 in the presence BAZ resulted in loss of contact and specific hydrogen-bond interaction required for RBD/ACE2 stability. Taken together, these findings identified benzimidazole scaffold as a building block for developing novel RBD/ACE2 complex inhibitor and provided mechanistic basis for the use of bazedoxifene as a repurposable drug for the treatment of COVID-19 acting at RBD/ACE2 interface.

Molecular Generative Model via Retrosynthetically Prepared Chemical Building Block Assembly (Adv. Sci. 8/2023)

Deep Generative Model A deep generative model for the molecular design based on chemical building block assembly via retrosynthetic reaction rules is reported in article number 2206674 by Seonghwan Seo, Jaechang Lim, and Woo Youn Kim. This work demonstrates the design of novel molecules with target properties using building blocks sampled from a chemical catalog.

Succinic acid Production Strategy: Raw material, Organisms and Recent Applications in pharmaceutical and Food: Critical Review

Succinic acid is an essential base ingredient for manufacturing various industrial chemicals. Succinic acid has been acknowledged as one of the most significant bio based building block chemicals. Rapid demand for succinic acid has been noticed in the last 10 years. The production methods and mechanisms developed. Hence, these techniques and operations need to be revised. Recently, an omnibus rule for developing succinic acid is to find renewable carbohydrate Feedstocks. The sustainability of the resource is crucial to disintegrate the massive use of petroleum based-production. Accordingly, systematically reviewing the latest findings of bacterial production and related fermentation methods is critical. Therefore, this paper aims to study the latest research and assess the findings statistically comprehensively. The current review attempt is a step toward comprehending all the conditions surrounding succinic acid production from raw materials, microorganisms, and fermentation methods.

Ionic liquids as green solvents in process industry for reaction and separation: emphasizing on protocatechuic acid recovery

Due to superior characteristics, ionic liquids (IL) have become a more environmentally friendly alternative to traditional toxic, flammable, and volatile organic solvents. Protocatechuic acid (PCA) is a widely distributed phenolic acid and a key metabolite of complex polyphenols. It is a molecule that functions as a chemical building block for polymers and plastics as well as has pharmacological effects. The current project’s goal is to enhance the recovery of PCA by IL-based extraction from industrial waste streams and fermentation. This research investigates the separation of PCA from an aqueous stream using Imidazolium-based IL, 1-butyl-3-methylimidazolium octyl sulfate and 1-Hexyl-3-methylimidazolium hexafluorophosphate with an efficiency of about 87% at 10% IL concentration for a PCA concentration of 10 mmol L−1. The influence of the initial PCA concentration and IL concentration on the separation efficiency was also investigated, and various parameters helpful for the design of an industrial separation unit were determined.

Development of a Simple and Robust Kinetic Model for the Production of Succinic Acid from Glucose Depending on Different Operating Conditions

Succinic acid (SA) is one of the main identified biomass-derived chemical building blocks. In this work we approach the study of its production by Actinobacillus succinogenes DSM 22257 from glucose, focusing on the development and application of a simple kinetic model capable of representing the evolution of the process over time for a great diversity of process variables key to the production of this platform bio-based chemical: initial biomass concentration, yeast extract concentration, agitation speed, and carbon dioxide flow rate. All these variables were studied experimentally, determining the values of key fermentation parameters: titer (23.8–39.7 g·L−1), yield (0.59–0.72 gSA·gglu−1), productivity (0.48–0.96 gSA·L−1·h−1), and selectivity (0.61–0.69 gSA·gglu−1). Even with this wide diversity of operational conditions, a non-structured and non-segregated kinetic model was suitable for fitting to experimental data with high accuracy, considering the values of the goodness-of-fit statistical parameters. This model is based on the logistic equation for biomass growth and on potential kinetic equations to describe the evolution of SA and the sum of by-products as production events that are not associated with biomass growth. The application of the kinetic model to diverse operational conditions sheds light on their effect on SA production. It seems that nitrogen stress is a good condition for SA titer and selectivity, there is an optimal inoculum mass for this purpose, and hydrodynamic stress starts at 300 r.p.m. in the experimental set-up employed. Due to its practical importance, and to validate the developed kinetic model, a fed-batch fermentation was also carried out, verifying the goodness of the model proposed via the process simulation (stage or cycle 1) and application to further cycles of the fed-batch operation. The results showed that biomass inactivation started at cycle 3 after a grace period in cycle 2.

Pd-Catalyzed Amination of Base-Sensitive Five-Membered Heteroaryl Halides with Aliphatic Amines.

We report a versatile and functional-group-tolerant method for the Pd-catalyzed C-N cross-coupling of five-membered heteroaryl halides with primary and secondary amines, an important but underexplored transformation. Coupling reactions of challenging, pharmaceutically relevant heteroarenes, such as 2-H-1,3-azoles, are reported in good-to-excellent yields. High-yielding coupling reactions of a wide set of five-membered heteroaryl halides with sterically demanding α-branched cyclic amines and acyclic secondary amines are reported for the first time. The key to the broad applicability of this method is the synergistic combination of (1) the moderate-strength base NaOTMS, which limits base-mediated decomposition of sensitive five-membered heteroarenes that ultimately leads to catalyst deactivation, and (2) the use of a GPhos-supported Pd catalyst, which effectively resists heteroarene-induced catalyst deactivation while promoting efficient coupling, even for challenging and sterically demanding amines. Cross-coupling reactions between a wide variety of five-membered heteroaryl halides and amines are demonstrated, including eight examples involving densely functionalized medicinal chemistry building blocks.