Sustainable production of formic acid from biomass and carbon dioxide

Catalytic conversion of chitin-based biomass to nitrogen-containing chemicals

The exploration of renewable alternatives to fossil fuels for chemical production is indispensable to achieve the ultimate goals of sustainable development. Chitin biomass is an abundant platform feedstock that naturally bears both nitrogen and carbon atoms to produce nitrogen-containing chemicals (including organonitrogen ones and inorganic ammonia). The expansion of biobased chemicals toward nitrogen-containing ones can elevate the economic competitiveness and benefit the biorefinery scheme. This review aims to provide an up-to-date summary on the overall advances of the chitin biorefinery for nitrogen-containing chemical production, with an emphasis on the design of the catalytic systems. Catalyst design, solvent selection, parametric effect, and reaction mechanisms have been scrutinized for different transformation strategies. Future prospectives on chitin biorefinery have also been outlined.

Polyoxometalate-Modified Amphiphilic Polystyrene-block-poly(2-(dimethylamino)ethyl methacrylate) Membranes for Heterogeneous Glucose to Formic Acid Methyl Ester Oxidation

Herein, we present a new heterogeneous catalyst active toward glucose to formic acid methyl ester oxidation. The catalyst was fabricated via electrostatic immobilization of the inorganic polyoxometalate HPA-5 catalyst H8[PMo7V5O40] onto the pore surface of amphiphilic block copolymer membranes prepared via non-solvent-induced phase separation (NIPS). The catalyst immobilization was achieved via wet impregnation due to strong coulombic interactions between protonated tertiary amino groups of the polar poly(2-(dimethylamino)ethyl methacrylate) block and the anionic catalyst. Overall, three sets of five consecutive catalytic cycles were performed in an autoclave under 90 °С and 11.5 bar air pressure in methanol, and the corresponding yields of formic acid methyl ester were quantified via head-space gas chromatography. The obtained results demonstrate that the membrane maintains its catalytic activity over multiple cycles, resulting in high to moderate yields in comparison to a homogeneous catalytic system. Nevertheless, presumably due to leaching, the catalytic activity declines over five catalytic cycles. The morphological and chemical changes of the membrane during the prolonged catalysis under harsh conditions were examined in detail using different analytic tools, and it seems that the underlying block copolymer is not affected by the catalytic process.

Enhancing polyol/sugar cascade oxidation to formic acid with defect rich MnO2 catalysts

Oxidation of renewable polyol/sugar into formic acid using molecular O₂ over heterogeneous catalysts is still challenging due to the insufficient activation of both O₂ and organic substrates on coordination-saturated metal oxides. In this study, we develop a defective MnO₂ catalyst through a coordination number reduction strategy to enhance the aerobic oxidation of various polyols/sugars to formic acid. Compared to common MnO₂, the tri-coordinated Mn in the defective MnO₂ catalyst displays the electronic reconstruction of surface oxygen charge state and rich surface oxygen vacancies. These oxygen vacancies create more Mn^δ+ Lewis acid site together with nearby oxygen as Lewis base sites. This combined structure behaves much like Frustrated Lewis pairs, serving to facilitate the activation of O₂, as well as C-C and C-H bonds. As a result, the defective MnO₂ catalyst shows high catalytic activity (turnover frequency: 113.5 h^-1) and formic acid yield (>80%) comparable to noble metal catalysts for glycerol oxidation. The catalytic system is further extended to the oxidation of other polyols/sugars to formic acid with excellent catalytic performance.

Palladium nanoparticles on chitin-derived nitrogen-doped carbon materials for carbon dioxide hydrogenation into formic acid

Utilizing waste carbon resources to produce chemicals and materials is beneficial to mitigate the fossil fuel consumption and the global warming. In this study, ocean-based chitin biomass and waste shrimp shell powders were employed as the feedstock to prepare Pd loaded nitrogen-doped carbon materials as the catalysts for carbon dioxide (CO₂)/bicarbonate hydrogenation into formic acid, which simultaneously converts waste biomass into useful materials and CO₂ into a valuable chemical. Three different preparation methods were examined, and the two-stage calcination was the most efficient one to obtain N-doped carbon material with good physicochemical properties as the best Pd support. The highest formic acid yield was achieved of ∼77% at 100 °C in water with KHCO₃ substrate under optimal condition with a TON of 610. The nitrogen content and N functionalities of the as-synthesized carbon materials were crucial which could serve as anchor sites for the Pd precursor and assist the formation of well-dispersed and small-sized Pd NPs for boosted catalytic activity. The study puts forward a facile, inexpensive and environmentally benign way for simultaneous valorization of oceanic waste biomass and carbon dioxide into valuable products.

High current density electroreduction of CO2 into formate with tin oxide nanospheres

In this study, we demonstrate three-dimensional (3D) hollow nanosphere electrocatalysts for CO₂ conversion into formate with excellent H-Cell performance and industrially-relevant current density in a 25 cm² membrane electrode assembly electrolyzer device. Varying calcination temperature maximized formate production via optimizing the crystallinity and particle size of the constituent SnO₂ nanoparticles. The best performing SnO₂ nanosphere catalysts contained ~ 7.5 nm nanocrystals and produced 71–81% formate Faradaic efficiency (FE) between −0.9 V and −1.3 V vs. the reversible hydrogen electrode (RHE) at a maximum formate partial current density of 73 ± 2 mA cm_geo⁻² at −1.3 V vs. RHE. The higher performance of nanosphere catalysts over SnO₂ nanoparticles and commercially-available catalyst could be ascribed to their initial structure providing higher electrochemical surface area and preventing extensive nanocrystal growth during CO₂ reduction. Our results are among the highest performance reported for SnO₂ electrocatalysts in aqueous H-cells. We observed an average 68 ± 8% FE over 35 h of operation with multiple on/off cycles. In situ Raman and time-dependent X-ray diffraction measurements identified metallic Sn as electrocatalytic active sites during long-term operation. Further evaluation in a 25 cm² electrolyzer cell demonstrated impressive performance with a sustained current density of 500 mA cm_geo⁻² and an average 75 ± 6% formate FE over 24 h of operation. Our results provide additional design concepts for boosting the performance of formate-producing catalysts.

Improvement in Violacein Production by Utilizing Formic Acid to Induce Quorum Sensing in Chromobacterium violaceum

Violacein has attracted increasing attention due to its various biological activities, such as antibacterial, antifungal, antioxidative, and antitumor effects. To improve violacein production, formic acid (FA) was added to a culture medium, which resulted in a 20% increase (1.02 g/L) compared to the no-FA-addition group (0.85 g/L). The use of a stirred-tank bioreactor system also improved violacein production (by 0.56 g/L). A quorum-sensing (QS)-related gene (cviI) was induced by FA treatment, which revealed that the mechanism induced by FA utilized regulation of the cviI gene to induce the vio gene cluster for violacein production. To analyze the antioxidative properties of the violacein produced, 2,2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH) and 2,2′-azinobis-(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) scavenging tests were conducted, and results reveal that the values of the 50% inhibitory concentration (IC₅₀) of DPPH and ABTS were 0.286 and 0.182 g/L, respectively. Violacein also showed strong inhibitory activity against Gram-positive bacteria (Staphylococcus aureus and Bacillus subtilis). In summary, this study found that the addition of formic acid can promote QS of Chromobacterium violaceum, thereby promoting the synthesis of violacein. Subsequently, the promoting effect was also evaluated in a bioreactor system. These findings will be helpful in establishing an economically beneficial production model for violacein in future work.

Production of γ-valerolactone over mesoporous CuO catalysts using formic acid as the hydrogen source

In the present study, the conversion of levulinic acid (LA), butyl levulinate (BL), and ethyl levulinate (EL) to valuable biomass-derived compound γ-valerolactone (GVL) is studied.

Promoting Selective Generation of Formic Acid from CO2 Using Mn(bpy)(CO)3Br as Electrocatalyst and Triethylamine/Isopropanol as Additives

Urgent solutions are needed to efficiently convert the greenhouse gas CO₂ into higher-value products. In this work, fac-Mn(bpy)(CO)₃Br (bpy = 2,2'-bipyridine) is employed as electrocatalyst in reductive CO₂ conversion. It is shown that product selectivity can be shifted from CO toward HCOOH using appropriate additives, i.e., Et₃N along with iPrOH. A crucial aspect of the strategy is to outrun the dimer-generating parent-child reaction involving fac-Mn(bpy)(CO)₃Br and [Mn(bpy)(CO)₃]^- and instead produce the Mn hydride intermediate. Preferentially, this is done at the first reduction wave to enable formation of HCOOH at an overpotential as low as 260 mV and with faradaic efficiency of 59 ± 1%. The latter may be increased to 71 ± 3% at an overpotential of 560 mV, using 2 M concentrations of both Et₃N and iPrOH. The nature of the amine additive is crucial for product selectivity, as the faradaic efficiency for HCOOH formation decreases to 13 ± 4% if Et₃N is replaced with Et₂NH. The origin of this difference lies in the ability of Et₃N/iPrOH to establish an equilibrium solution of isopropyl carbonate and CO₂, while with Et₂NH/iPrOH, formation of the diethylcarbamic acid is favored. According to density-functional theory calculations, CO₂ in the former case can take part favorably in the catalytic cycle, while this is less opportune in the latter case because of the CO₂-to-carbamic acid conversion. This work presents a straightforward procedure for electrochemical reduction of CO₂ to HCOOH by combining an easily synthesized manganese catalyst with commercially available additives.

Supported CuII Single-Ion Catalyst for Total Carbon Utilization of C2 and C3 Biomass-Based Platform Molecules in the N-Formylation of Amines

The shift from fossil carbon sources to renewable ones is vital for developing sustainable chemical processes to produce valuable chemicals. In this work, value‐added formamides were synthesized in good yields by the reaction of amines with C₂ and C₃ biomass‐based platform molecules such as glycolic acid, 1,3‐dihydroxyacetone and glyceraldehyde. These feedstocks were selectively converted by catalysts based on Cu‐containing zeolite 5A through the in situ formation of carbonyl‐containing intermediates. To the best of our knowledge, this is the first example in which all the carbon atoms in biomass‐based feedstocks could be amidated to produce formamide. Combined catalyst characterization results revealed preferably single Cu^II sites on the surface of Cu/5A, some of which form small clusters, but without direct linking via oxygen bridges. By combining the results of electron paramagnetic resonance (EPR) spin‐trapping, operando attenuated total reflection (ATR) IR spectroscopy and control experiments, it was found that the formation of formamides might involve a HCOOH‐like intermediate and ^.NHPh radicals, in which the selective formation of ^.OOH radicals might play a key role.

Pt Electrocatalyst Prepared by Hydrothermal Reduction onto the Gas Diffusion Layer for High-Temperature Formic Acid and Ethanol Fuel PEMFC

An alternative method for the preparation of PEMFC electrodes is presented in this work based on the direct deposition of Pt particles onto the gas diffusion layer (Pt@GDL) by hydrothermal reduction of the H2PtCl6 precursor from formic acid, ethylene glycol, and ethanol reductive solutions. There is a successful anchorage of Pt particles via the formation of Pt crystal aggregates. The influence of the reducing agent concentration and temperature was studied to analyze their influence on the size, morphology, and distribution of the Pt particles on the gas GDL. The prepared Pt@GDL was tested for formic acid and ethanol high-temperature H3PO4-doped PEMFC. The Pt@GDL prepared in the formic acid reductive atmosphere presented the best performance associated with the formation of smaller Pt crystals and a more homogeneous dispersion of the Pt particles. For formic acid and ethanol-fed high-temperature PEMFC using a H3PO4-doped polybenzimidazole membrane as the solid electrolyte, maximum power densities of 0.025 and 0.007 W cm−2 were drawn at 200 °C, respectively.

Recent Progress in the Chemical Upcycling of Plastic Wastes

The massive generation of plastic wastes without satisfactory treatment has induced severe environmental problems and gained increasing attentions. In this Minireview, recent progresses in the chemical upcycling of plastic wastes by using various methods (mainly in the past three to five years) is summarized. The chemical upcycling of plastic wastes points out a "plastic-based refinery" concept, which is to use the plastic wastes as platform feedstocks to produce highly valuable monomeric or oligomeric compounds, putting the plastic wastes back into a circular economy. The different chemical methods to upcycle plastic wastes, including hydrogenolysis, photocatalysis, pyrolysis, solvolysis, and others, are introduced in each section to valorize diverse plastic feedstocks into value-added chemicals, materials, or fuels. In addition, other emerging technologies as well as the new generation of plastic thermosets are covered.

Nickel Iron Diselenide for Highly Efficient and Selective Electrocatalytic Conversion of Methanol to Formate

The electro-oxidation of methanol to formate is an interesting example of the potential use of renewable energies to add value to a biosourced chemical commodity. Additionally, methanol electro-oxidation can replace the sluggish oxygen evolution reaction when coupled to hydrogen evolution or to the electroreduction of other biomass-derived intermediates. But the cost-effective realization of these reaction schemes requires the development of efficient and low-cost electrocatalysts. Here, a noble metal-free catalyst, Ni_{1- x} Fe_x Se₂ nanorods, with a high potential for an efficient and selective methanol conversion to formate is demonstrated. At its optimum composition, Ni_0.75 Fe_0.25 Se₂ , this diselenide is able to produce 0.47 mmol cm^-2  h^-1 of formate at 50 mA cm^-2 with a Faradaic conversion efficiency of 99%. Additionally, this noble-metal-free catalyst is able to continuously work for over 50 000 s with a minimal loss of efficiency, delivering initial current densities above 50 mA cm^-2 and 2.2 A mg^-1 in a 1.0 m KOH electrolyte with 1.0 m methanol at 1.5 V versus reversible hydrogen electrode. This work demonstrates the highly efficient and selective methanol-to-formate conversion on Ni-based noble-metal-free catalysts, and more importantly it shows a very promising example to exploit the electrocatalytic conversion of biomass-derived chemicals.

Bifunctional Pt–Mo catalyst for in situ hydrogenation of methyl stearate into alkanes using formic acid as a hydrogen donor

In situ hydrogenation of methyl stearate on Pt–Mo/AC has a high hydrogen utilization rate due to the strong interaction between Pt and β-Mo2C.

Powering the next industrial revolution: transitioning from nonrenewable energy to solar fuels via CO2 reduction

Solar energy has been used for decades for the direct production of electricity in various industries and devices; however, harnessing and storing this energy in the form of chemical bonds has emerged as a promising alternative to fossil fuel combustion. The common feedstocks for producing such solar fuels are carbon dioxide and water, yet only the photoconversion of carbon dioxide presents the opportunity to generate liquid fuels capable of integrating into our existing infrastructure, while simultaneously removing atmospheric greenhouse gas pollution. This review presents recent advances in photochemical solar fuel production technology. Although efforts in this field have created an incredible number of methods to convert carbon dioxide into gaseous and liquid fuels, these can generally be classified under one of four categories based on how incident sunlight is utilised: solar concentration for thermoconversion (Category 1), transformation toward electroconversion (Category 2), natural photosynthesis for bioconversion (Category 3), and artificial photosynthesis for direct photoconversion (Category 4). Select examples of developments within each of these categories is presented, showing the state-of-the-art in the use of carbon dioxide as a suitable feedstock for solar fuel production.

Solar energy has been used for decades for the direct production of electricity in various industries and devices. However, harnessing and storing this energy in the form of chemical bonds has emerged as a promising alternative to fossil fuels.

Oxalic Acid as a Hydrogen Donor for the Hydrodesulfurization of Gas Oil and Deoxygenation of Rapeseed Oil Using Phonolite-Based Catalysts

The use of renewable local raw materials to produce fuels is an important step toward optimal environmentally friendly energy consumption. In addition, the use of these sources together with fossil fuels paves the way to an easier transition from fossil to renewable fuels. The use of simple organic acids as hydrogen donors is another alternative way to produce fuel. The present work reports the use of oxalic acid as a hydrogen donor for the catalytic hydrodesulfurization of atmospheric gas oil and the deoxygenation of rapeseed oil at 350 °C. For this process, one commercial NiW/SiO₂-Al₂O₃ solid and two NiW/modified phonolite catalysts were used, namely Ni (5%) W (10%)/phonolite treated with HCl, and Ni (5%) W (10%)/phonolite treated with oxalic acid. The fresh phonolite catalysts were characterized by Hg porosimetry and N₂ physisorption, ammonia temperature programmed desorption (NH₃-TPD), X-ray diffraction (XRD), and X-ray fluorescence (XRF). The sulfided metal phonolite catalysts were characterized by XRD and XRF. Hydrodesulfurization led to a decrease in sulfur content from 1 to 0.5 wt% for the phonolite catalysts and to 0.8 wt% when the commercial catalyst was used. Deoxygenation led to the production of 15 and 65 wt% paraffin for phonolite and commercial solids, respectively. The results demonstrate the potential of using oxalic acid as a hydrogen donor in hydrotreating reactions.

One-pot synthesis of formic acid via hydrolysis-oxidation of potato starch in the presence of cesium salts of heteropoly acid catalysts

Solid bifunctional catalysts based on cesium salts of V-containing heteropoly acids (CsHPA: Cs_3.5H_0.5PW₁₁VO₄₀, Cs_4.5H_0.5SiW₁₁VO₄₀, Cs_3.5H_0.5PMo₁₁VO₄₀) and Cs_2.5H_0.5PMo₁₂O₄₀ were used for studying one-pot hydrolysis–oxidation of potato starch to formic acid at 413–443 K and 2 MPa air mixture. It was shown that the optimum process temperature that prevents formic acid from destruction is 423 K. The studies were focused on the influence of the composition of heteropoly anions on the yield and selectivity of formic acid. Using W–V–P(Si) CsHPA results in the product overoxidation compared to Mo–V-containing CsHPA. The activity of Cs–PMo was significantly lower compared to Cs–PMoV. This may indicate that vanadium plays an important role in the oxidation process. The most promising catalyst was Cs_3.5H_0.5PMo₁₁VO₄₀ which provided the maximum yield of formic acid equal to 51%. Cs_3.5H_0.5PMo₁₁VO₄₀ was tested during nine cycles of starch hydrolysis–oxidation to demonstrate its high stability and efficiency.

Influence of composition of catalysts based on heteropoly acid cesium salts on formic acid production via starch hydrolysis–oxidation was investigated.