Renewable Chemical Feedstocks Research Articles

Constructing a Stable Built-In Electric Field in Bi/Bi2Te3 Nanowires for Electrochemical CO2 Reduction Reaction.

Electrochemically converting carbon dioxide (CO2) into valuable fuels and renewable chemical feedstocks is considered a highly promising approach to achieve carbon neutrality. In this work, a robust interfacial built-in electric field (BEF) has been successfully designed and created in Bi/Bi2Te3 nanowires (NWs). The Bi/Bi2Te3 NWs consistently maintain over 90% Faradaic efficiency (FE) within a wide potential range (-0.8 to -1.2 V), with HCOOH selectivity reaching 97.2% at -1.0 V. Moreover, the FEHCOOH of Bi/Bi2Te3 NWs can still reach 94.3% at a current density of 100 mA cm-2 when it is used as a cathode electrocatalyst in a flow-cell system. Detailed in situ experiments confirm that the presence of interfacial BEF between Bi and Bi/Bi2Te3 promotes the formation of *OHCO intermediates, thus facilitating the production of HCOOH species. DFT calculations show that Bi/Bi2Te3 NWs increase the formation energies of H* and *COOH while reducing the energy barrier for *OCHO formation, thus achieving a bidirectional optimization of intermediate adsorption. This work provides a feasible scheme for exploring electrocatalytic reaction intermediates by using the BEF strategy.

Imidazole based ionic liquid grafted graphene for enhancing the new green conversion process of carbon dioxide

Carbon dioxide (CO2) has been recognized a renewable C1-level green chemical synthesis feedstock. Achieving 100 % atom utilization is possible through the cycloaddition reaction of CO2 with epoxides. Ionic liquids are commonly used catalysts for this reaction, but conventional immobilization methods may lead to the loss of active components under severe conditions. Developing a new Ionic Liquid catalytic system offers a promising and eco-friendly approach to efficient CO2 cycloaddition. In this study, imidazolium ionic liquid was chemically immobilized on graphene oxide (GO) to get a novelty catalyst GO-SmIm Br. The impact of catalyst dosage, temperature, pressure, and reaction time on the reaction performance of CO2 and propylene oxide was systematically investigated in a batch reaction system, achieving a propylene carbonate yield of up to 90.4 % in the CO2 cycloaddition reaction. Even after five cycles, the yield only decreased by 9.6 %, showcasing its robust catalytic activity. Further assessment in a fixed-bed reactor at 120 °C for 8 h demonstrated a continuous propylene carbonate yield of 55.6 %, highlighting the potential of GO-SmIm Br for efficient and sustainable CO2 utilization.

Efficient and Direct Functionalization of Allylic sp3 C-H Bonds with Concomitant CO2 Reduction.

Solar-driven CO2 reduction integrated with C-C/C-X bond-forming organic synthesis represents a substantially untapped opportunity to simultaneously tackle carbon neutrality and create an atom-/redox-economical chemical synthesis. Herein, we demonstrate the first cooperative photoredox catalysis of efficient and tunable CO2 reduction to syngas, paired with direct alkylation/arylation of unactivated allylic sp3 C-H bonds for accessing allylic C-C products, over SiO2 -supported single Ni atoms-decorated CdS quantum dots (QDs). Our protocol not only bypasses additional oxidant/reductant and pre-functionalization of organic substrates, affording a broad of allylic C-C products with moderate to excellent yields, but also produces syngas with tunable CO/H2 ratios (1 : 2-5 : 1). Such win-win coupling catalysis highlights the high atom-, step- and redox-economy, and good durability, illuminating the tantalizing possibility of a renewable sunlight-driven chemical feedstocks manufacturing industry.

MgFe2O4Nanoparticle/Peracetic Acid Hybrids for Catalytic Oxidative Depolymerization of Lignin

Lignin is a promising feedstock for renewable fuels and chemicals due to its aromatic skeleton and natural abundance. Lignin can be converted to diverse aromatic monomers as well as dicarboxylic acids depending on the applied conversion technologies. Despite its great potential, its native and processing-induced heterogeneity and complexity limit the conversion efficiency and product selectivity. In this study, magnesium ferrite (MgFe2O4) nanoparticle–peracetic acid (PAA) has been investigated as an efficient catalyst–oxidant incorporation for catalytic oxidative depolymerization of lignin under mild conditions. Typically, the increase in processing severity can enhance the lignin conversion while it results in the further decomposition of aromatic compounds to dicarboxylic acids. However, in this study, the incorporation of MgFe2O4 nanoparticles and PAA not only enhanced the total product yield but also improved the selectivity of aromatic monomers. The oxidative depolymerization system using the catalyst–oxidant combination resulted in 46 wt % of total oil product with a 61% selectivity of aromatic monomers under mild temperature (90 °C). In addition, this combination catalyst showed relatively good cycling stability based on the total product yield after recycling five times via magnetic separation. Overall, MgFe2O4 nanoparticles play an important role as a co-catalyst with a PAA oxidant in the oxidative conversion of lignin with an enhanced conversion efficiency and recyclability, and it will facilitate the valorization of lignin in future bio-based fuels and chemicals.

The Business Prospect of Biomass to Methanol Development in Namibia: A Review

In Indonesia, the demand for methanol as renewable alternatives or chemical feedstock has been rising significantly to address the shortage of its domestic fossil fuels need. In the future, Indonesia expects to increase their methanol production using gasification process to balance its domestic demand. This paper presents the business prospect of methanol production from overseas, i.e., Namibia using biomass (encroacher bush types) feedstocks. It is concluded that biomass is available as an alternative feedstock to generate pure methanol. In Namibia, biomass is one of the most abundant and easily accessed resources for energy uses. However, without appropriate business endorsement by the government, such as a well-designed policies and incentives, the project’s prospect is still limited and very costly to be implemented. The financial planning of investment, particularly in how to find the best technological design of methanol processing, is highly essential to gain the maximum net business profit.

Hiang Kwee Lee

"The most exciting thing about my research is manipulating renewable energy and chemical feedstock at the nanoscale to create useful molecules… To improve my work-life balance, I ask my team members to have work-life balance too, especially over the weekend. …" Find out more about Hiang Kwee Lee in his Introducing … Profile.

Hiang Kwee Lee

Graphical Abstract “The most exciting thing about my research is manipulating renewable energy and chemical feedstock at the nanoscale to create useful molecules… To improve my work–life balance, I ask my team members to have work–life balance too, especially over the weekend. …” Find out more about Hiang Kwee Lee in his Introducing … Profile.

A highly stable bio-based plasticizer constructed from renewable acids for plasticizing and enhancing the optical properties of poly(vinyl chloride)

The current research efforts in the plasticizer industry should focus on finding renewable biomass chemical feedstocks to synthesize non-toxic and effective bio-based plasticizers to adapt the concept of green environmental protection.

Chiral Polymers from Norbornenes Based on Renewable Chemical Feedstocks.

Optically active polymers are of great interest as materials for dense enantioselective membranes, as well as chiral stationary phases for gas and liquid chromatography. Combining the versatility of norbornene chemistry and the advantages of chiral natural terpenes in one molecule will open up a facile route toward the synthesis of diverse optically active polymers. Herein, we prepared a set of new chiral monomers from cis-5-norbornene-2,3-dicarboxylic anhydride and chiral alcohols of various natures. Alcohols based on cyclic terpenes ((-)-menthol, (-)-borneol and pinanol), as well as commercially available alcohols (S-(-)-2-methylbutanol-1, S-(+)-3-octanol), were used. All the synthesized monomers were successfully involved in ring-opening metathesis polymerization, affording polymers in high yields (up to 96%) and with molecular weights in the range of 1.9 × 105-5.8 × 105 (Mw). The properties of the metathesis polymers obtained were studied by TGA and DSC analysis, WAXD, and circular dichroism spectroscopy. The polymers exhibited high thermal stability and good film-forming properties. Glass transition temperatures for the prepared polymers varied from -30 °C to +139 °C and, therefore, the state of the polymers changed from rubbery to glassy. The prepared polymers represent a new attractive platform of chiral polymeric materials for enantioselective membrane separation and chiral stationary phases for chromatography.

Selective Reduction of CO2 on Ti2C(OH)2 MXene through Spontaneous Crossing of Transition States.

Direct reduction of gas-phase CO2 to renewable fuels and chemical feedstock without any external energy source or rare-metal catalyst is one of the foremost challenges. Here, using density functional theory and ab initio molecular dynamics (AIMD) simulations, we predict Ti2C(OH)2 MXene as an efficient electron-coupled proton donor exhibiting simultaneously high reactivity and selectivity for CO2 reduction reaction (CRR) by yielding valuable chemicals, formate, and formic acid. This is caused by CO2 spontaneously crossing the activation barrier involved in the formation of multiple intermediates. Metallic Ti2C(OH)2 contains easily donatable protons on the surface and high-energy electrons near the Fermi level that leads to its high reactivity. High selectivity arises from low activation barrier for CRR as predicted by proposed mechanistic interpretations. Furthermore, H vacancies generated during the product formation can be replenished by exposure to moisture, ensuring the uninterrupted formation of the products. Our study provides a single-step solution for CRR to valuable chemicals without necessitating the expensive electrochemical or low-efficiency photochemical cells and hence is of immense interest for recycling the carbon.

Universal Kinetic Mechanism Describing CO2 Photoreductive Yield and Selectivity for Semiconducting Nanoparticle Photocatalysts.

Photocatalytic conversion of CO2 to generate high-value and renewable chemical fuels and feedstock presents a sustainable and renewable alternative to fossil fuels and petrochemicals. Currently, there is a dearth of kinetic understanding to inform better catalyst design, especially at uniform reaction conditions across diverse catalytic species. In this work, we investigate 12 active, stable, and unique but common nanoparticle photocatalysts for CO2 reduction at room temperature and low partial pressure in aqueous phase: TiO2, SnO2, and SiC deposited with silver, gold, and platinum. Our analysis reveals a single consistent chemical kinetic mechanism, which accurately describes the yield and selectivity of all single-carbon containing (C1) products obtained in spite of the diverse catalysts employed. Formaldehyde is predicted as the first product in the reaction network and we report, to the best of our knowledge, the highest selectivity to date toward formaldehyde during CO2 photoreduction when compared against all other C1 products (∼80%) albeit at low CO2 conversion (<0.5 μmol gcat-1 h-1, <16.8 nmol m-2 h-1). Further, we observe a volcano-like relationship between the electron-transfer rate of a given photocatalyst for CO2 reduction and the net rate at which reduced products are produced in the reaction mixture taking into account unfavorable product oxidation. We establish an empirical upper limit for the maximum rate of production of CO2 reduction products for any nanoparticle photocatalyst in the absence of a hole-scavenging agent. These results form the basis for the design and optimization of the next generation of highly efficiency and active photocatalysts for CO2 reduction.

Monolignol export by diffusion down a polymerization-induced concentration gradient.

Lignin, the second most abundant biopolymer, is a promising renewable energy source and chemical feedstock. A key element of lignin biosynthesis is unknown: how do lignin precursors (monolignols) get from inside the cell out to the cell wall where they are polymerized? Modeling indicates that monolignols can passively diffuse through lipid bilayers, but this has not been tested experimentally. We demonstrate significant monolignol diffusion occurs when laccases, which consume monolignols, are present on one side of the membrane. We hypothesize that lignin polymerization could deplete monomers in the wall, creating a concentration gradient driving monolignol diffusion. We developed a two-photon microscopy approach to visualize lignifying Arabidopsis thaliana root cells. Laccase mutants with reduced ability to form lignin polymer in the wall accumulated monolignols inside cells. In contrast, active transport inhibitors did not decrease lignin in the wall and scant intracellular phenolics were observed. Synthetic liposomes were engineered to encapsulate laccases, and monolignols crossed these pure lipid bilayers to form polymer within. A sink-driven diffusion mechanism explains why it has been difficult to identify genes encoding monolignol transporters and why the export of varied phenylpropanoids occurs without specificity. It also highlights an important role for cell wall oxidative enzymes in monolignol export.

Catalytic Furfural/5-Hydroxymethyl Furfural Oxidation to Furoic Acid/Furan-2,5-dicarboxylic Acid with H2 Production Using Alkaline Water as the Formal Oxidant.

Furfural and 5-hydroxymethyl furfural (HMF) are abundantly available biomass-derived renewable chemical feedstocks, and their oxidation to furoic acid and furan-2,5-dicarboxylic acid (FDCA), respectively, is a research area with huge prospective applications in food, cosmetics, optics, and renewable polymer industries. Water-based oxidation of furfural/HMF is a lucrative approach for simultaneous generation of H2 and furoic acid/FDCA. However, this process is currently limited to (photo)electrochemical methods that can be challenging to control, improve, and scale up. Herein, we report well-defined ruthenium pincer catalysts for direct homogeneous oxidation of furfural/HMF to furoic acid/FDCA, using alkaline water as the formal oxidant while producing pure H2 as the reaction byproduct. Mechanistic studies indicate that the ruthenium complex not only catalyzes the aqueous oxidation but also actively suppresses background decomposition by facilitating initial Tishchenko coupling of substrates, which is crucial for reaction selectivity. With further improvement, this process can be used in scaled-up facilities for a simultaneous renewable building block and fuel production.

Fixing the Plastic Industry with Sustainable Materials

A combination of dwindling oil reserves and increasing pollution means that the plastic industry must be urgently transformed before it’s too late. The efforts of researchers, including Dr Jinwen Zhang and his colleagues at Washington State University, mean that solutions are becoming increasingly available. Through the development of malleable and self-healable plastics, created from both existing petrochemical and renewable chemical feedstocks, Dr Zhang’s team is creating stronger, more resilient plastics that can be easily recycled.

Muconic Acid Production Using Engineered Pseudomonas putida KT2440 and a Guaiacol-Rich Fraction Derived from Kraft Lignin

Industrial lignin such as kraft lignin is an abundant feedstock for renewable chemicals and materials. In this study, a process was developed for depolymerization of kraft lignin followed by an upgrading separation step and further bioconversion of the obtained monoaromatic compounds to muconic acid. First, industrial kraft lignin, Indulin AT, was processed into a guaiacol-rich stream using base-catalyzed depolymerization. This stream was subsequently upgraded using liquid–liquid extraction and evaporation to yield a more concentrated and less inhibitory stream, adapted for bioconversion. Finally, guaiacol was quantitatively converted to muconic acid through bioconversion using an engineered Pseudomonas putida strain containing cytochrome P450 and ferredoxin reductase for guaiacol assimilation and deletion of the native catBC genes for muconic acid production. Isomerization of muconic acid in a fermentation medium depending on pH was also studied.

Enabling thermal-neutral electrolysis for CO2-to-fuel conversions with a hybrid deep learning strategy

High-temperature co-electrolysis of CO2/H2O through the solid oxide electrolysis cells (SOECs) is a promising method to generate renewable fuels and chemical feedstocks. Applying this technology in flexible scenario, especially when combined with variable renewable powers, requires an efficient optimisation strategy to ensure its safety and cost-effective in the long-term operation. To this purpose, we present a hybrid simulation method for the accurate and fast optimisation of the co-electrolysis process in the SOECs. This method builds multi-physics models based on experimental data and extends the database to develop the deep neural network and genetic algorithm. In the case study, thermal-neutral condition (TNC) is set as the optimisation target in various operating conditions, where the SOEC generates no waste heat and needs no auxiliary heating equipment. Small peak-temperature-gradient (PTG) inside the SOEC is found at the TNC, which is vital to prevent thermal failure in the operation. For the cell operating with 1023 K and 1123 K of inlet gas temperatures, the smallest PTGs reach 0.09 and 0.31 K mm−1 at 1.13 and 1.19 V, respectively. Finally, a 4-D map is presented to show the interactions among the applied voltage, required power density, inlet gas composition, and temperature under the TNC. The proposed method can be flexibly modified based on different optimisation targets for various applications in the energy sector.

Anion-Dependent Catalytic C-C Bond Cleavage of a Lignin Model within a Cationic Metal-Organic Framework.

The development of heterogeneous catalysts capable of selectively converting lignin model compounds into products of added value offers an exciting avenue to explore in the production of renewable chemical feedstocks. The use of metal-organic frameworks (MOFs) in such chemical transformations relies largely on the presence of accessible open metal sites found within highly porous networks that simultaneously allow for fast transport and strong interactions with desired substrates. Here, we present the first systematic study on the modulation of catalytic performance of a cationic framework, [Cu2(L)(H2O)2](NO3)2·5.5H2O (L = 1,1'-bis(3,5-dicarboxylatophenyl)-4,4'-bipyridinium), achieved through the exchange of anionic guests. Remarkably, the catalytic activity proves to be highly anion-dependent, with a nearly 10-fold increase toward the aerobic C-C bond cleavage of a lignin model compound when different anionic species are incorporated within the MOF. Moreover, we demonstrate that the cationic nature of the MOF, imparted by the incorporation of viologen moieties within the linker, tunes the electrophilicity of the active copper(II) sites, resulting in stronger interactions with the substrate. As such, the copper-based framework exhibits enhanced catalytic performance when compared to its neutral counterpart, emphasizing the appeal of charged frameworks for use as green heterogeneous catalysts.

Effects of oxidising atmosphere on brewer’s yeast hydrothermal treatment and subsequent biopolymer recovery

• The presence of oxygen enhanced yeast disintegration. • Soluble proteins abated at long times when oxygen was present. • Oxygen caused a convergency in the different protein isoelectric points to 3. • Oxygen decreased protein hydrophobicity, worsening saline precipitation. • Oxygen reduced protein recovery but enhanced selectivity in IMAC. Spent brewer’s yeast is an underused by-product, whose current management offers low returns. This article studies, for the first time ever, the hydrothermal treatment of spent brewer’s yeast, paying special attention to the effect of the presence of oxygen on the physical properties, composition and potential recovery of valuable products from the hydrolysed yeast, as previous step towards the employment of these recovered proteins as renewable chemical feedstock for green industrial uses. Results showed a higher VSS disintegration employing an oxidising atmosphere, as well as a better solubilisation in terms of solid COD reduction, although it also lowered soluble COD but without significantly reducing soluble TOC. Both treatments led to an almost complete solubilisation of protein and carbohydrates from yeast, which were subsequently degraded in presence of oxygen if reaction times were lengthened. Looking at biopolymer recovery, protein precipitation by pH adjustment worked better in hydrolysates obtained in presence of oxygen, with almost 90% of protein precipitation and good selectivities at pH 2.5 and 3. Salting out was more effective, in terms of selectivity, for samples obtained in absence of oxygen and low concentrations of ammonium sulphate. The application of IMAC showed better results on yeast hydrolysates obtained under an inert atmosphere, reaching maximum sorption capacities of almost 100 mg protein/g dry resin, three times higher than those observed using the hydrolysate produced in presence of oxygen. A new perspective in yeast management during beer production is open as renewable chemical feedstock for protein, although further studies are required to optimise protein recovery and purification with respect to its applications.

Exploring Ca–Ce–M–O (M = 3d Transition Metal) Oxide Perovskites for Solar Thermochemical Applications

Solar thermochemical (STC) processes hold promise as efficient ways to generate renewable fuels, fuel precursors, or chemical feedstocks using concentrated sunlight. Specifically, one actively rese...

A Comprehensive Modeling Analysis of Formate-Mediated Microbial Electrosynthesis*.

Mediated microbial electrosynthesis (MES) represents a promising strategy for the capture and conversion of CO2 into carbon-based products. We describe the development and application of a comprehensive multiphysics model to analyze a formate-mediated MES reactor. The model shows that this system can achieve a biomass productivity of ∼1.7 g L-1 h-1 but is limited by a competitive trade-off between O2 gas/liquid mass transfer and CO2 transport to the cathode. Synthetic metabolic strategies are evaluated for formatotrophic growth, which can enable an energy efficiency of ∼21 %, a 30 % improvement over the Calvin cycle. However, carbon utilization efficiency is only ∼10 % in the best cases due to a futile CO2 cycle, so gas recycling will be necessary for greater efficiency. Finally, separating electrochemical and microbial processes into separate reactors enables a higher biomass productivity of ∼2.4 g L-1 h-1 . The mediated MES model and analysis presented here can guide process design for conversion of CO2 into renewable chemical feedstocks.