Production Of Value-added Chemicals Research Articles

Breakthrough in CO2 Electroreduction to Multi-Carbon Products at Ampere-Level Enabled by Active Sites Engineering.

Efficient production of value-added chemicals with high selectivity from CO2 electroreduction at industrial-level current density is highly demanded, yet remains a big challenge. In a recent issue of Angewandte Chemie, Han and colleagues have elegantly increased the Faradaic efficiency (FE) of multi-carbon (C2+) products to over 70% at amperes level (1.4 A cm-2) by engineering the active sites for the key reactions involved in the CO2 electroreduction. In this study, the highly dispersed Pd atoms have two unique functions: active sites for water dissociation and to induce the electron rearrangement of the surrounding Cu atoms to form new active sites for CO conversion, while the Cu far from Pd are the active sites for efficient CO2 conversion to CO, the synergistic functions of these three active sites result in high FE and yields of C2+ products at industrial-level current density. This research is a remarkable step forward in the methodology for developing efficient and durable catalysts for CO2 electroreduction and beyond.

Amine Functionalization of Channels of Metal-Organic Frameworks for Effective Chemical Fixation of Carbon Dioxide: A Comparative Study with Three Newly Designed Porous Networks.

Catalytic transformation of CO2 into value-added chemical products can provide an appropriate solution for the raising environmental issues. To date, various metal-organic frameworks (MOFs) with transition metal ions have been explored for CO2 capture and conversion, but alkaline earth metal-based MOFs are comparatively less studied. Metal ions like Sr(II) having relatively large radius give rise to a high coordination number resulting in higher stability of the MOFs. Moreover, the introduction of N-rich functional group in organic linker like -NH2, -CONH- and triazole into MOF backbone enhance their CO2 capture and conversion efficiency. Herein, the effect of amine group on the catalytic efficiency of MOFs for CO2 cycloaddition with epoxides under solvent free and ambient conditions are presented. The di-carboxylates, such as 5-aminoisophthalate (AmIP) and 5-bromoisophthalate (BrIP) were utilized to synthesize Sr(II) based MOFs. The Zn(II) MOF was synthesized using tetra-carboxylate containing amide spacer (OAT) and 4-amino-4H-1,2,4-triazole (AMT). All three MOFs exhibited porous networks with guest available volume ranging from 15 to 58 %. The catalytic efficiency of the MOFs towards carbon dioxide fixation reaction was explored. The catalytic performances revealed that the presence of amine group in the channels enhances the catalytic efficiency of the MOFs.

Electrocatalytic Glycerol Conversion: A Low-Voltage Pathway to Efficient Carbon-Negative Green Hydrogen and Value-Added Chemical Production.

Electrochemical glycerol oxidation reaction (GLYOR) could be a promising way to use the abundantly available glycerol for production of value-added chemicals and fuels. Completely avoiding the oxygen evolution reaction (OER) with GLYOR is an evolving strategy to reduce the overall cell potential and generate value-added chemicals and fuels on both the anode and cathode. We demonstrate the morphology-controlled palladium nanocrystals, afforded by colloidal chemistry, and their established morphology-dependent GLYOR performance. Although it is known that controlling the morphology of an electrocatalyst can modulate the activity and selectivity of the products, still it is a relatively underexplored area for many reactions, including GLYOR. Among nanocube (Pd-NC), truncated octahedron (Pd-TO), spherical and polycrystalline (Pd-PC) morphologies, the Pd-NC electrocatalyst deposited on a Ni foam exhibits the highest glycerol conversion (85%) along with 42% glyceric acid selectivity at a low applied potential of 0.6 V (vs reversible hydrogen electrode (RHE)) in 0.1 M glycerol and 1 M KOH at ambient temperature. Owing to the much favorable thermodynamics of GLYOR on the Pd-NC surface, the assembled electrolyzer requires an electricity input of only ∼3.7 kWh/m3 of H2 at a current density of 100 mA/cm2, in contrast to the requirement of ≥5 kWh/m3 of H2 with an alkaline/PEM electrolyzer. Sustainability has been successfully demonstrated at 10 and 50 mA/cm2 and up to 120 h with GLYOR in water and simulated seawater.

Photoelectrochemical Conversion of Methane to Ethane and Hydrogen under Visible Light Using Functionalized Tungsten Trioxide Photoanodes with Proton Exchange Membrane.

Developing methane utilization technologies is desired to convert abundant and renewable carbon resources, such as natural gas and biogas, into value-added chemical products. This study provides insights into emerging photoelectrochemical (PEC) technology for the photocatalytic transformation of methane to C2H6 and H2 using visible light at room temperature. The PEC conversion of methane to oxygenates has been investigated in aqueous electrolytes. Herein, we demonstrate the gas-phase PEC methane conversion using a proton exchange membrane (PEM) as a solid polymer electrolyte and a gas-diffusion photoanode for methane oxidation. Tungsten trioxide (WO3), a semiconductor photocatalyst responsive to visible light, is utilized as the photoanode material. Ultraviolet light (∼365 nm) excitation predominantly results in CO2 production with lower C2H6 selectivity in humidified methane. In contrast, visible light (∼453 nm) effectively promotes C2H6 production over the WO3 photoanode, attributed to preferential hydroxyl radical (•OH) formation compared to UV irradiation. Photogenerated holes formed near the valence band maximum of WO3 contribute to •OH formation through a single-electron water oxidation. The photogenerated •OH activates gaseous methane molecules to methyl radicals, subsequently coupled into C2H6 at the gas-electrolyte-semiconductor boundary. H2 is concurrently formed on the cathode electrocatalyst. Improving the selectivity for the dehydrogenative coupling of methane is pivotal for enhancing the energy efficiency in the PEM-PEC system.

Photocatalytic coproduction of hydrogen peroxide and Aldehydic/Keto acid on carbon nitride

Photocatalytic H2O2 production is emerging as an alternative technology to contribute H2O2-based advanced oxidation applications. However, the present reaction systems rarely consider the selective oxidation of sacrificial agent along with oxygen reduction reaction. Herein, we design a reaction system by using hydroxycarboxylic acids as additives to boost photocatalytic H2O2 production. More importantly, hydroxycarboxylic acids could simultaneously be dehydrogenated into aldehydic/keto acids with high selectivity. Lactic acid as one of the typical hydroxycarboxylic acids reveals the feasibility of this hypothesis, delivering 6.56 mM/h of H2O2 generation along with > 70 % pyruvic acid selectivity. The universality of this reaction system is demonstrated by using other hydroxycarboxylic acids. This works sheds new light on coupling H2O2 generation with value-added chemicals production by mild photocatalytic approach.

Reactive Eutectic Media for Lignocellulosic Biomass Fractionation.

This study introduces an alternative approach towards lignocellulosic biomass fractionation. For this purpose, reactive eutectic media (REM) based on ammonium formate and different organic acids are investigated, possible products are identified, and the REM are employed for lignin extraction and terminal isolation of cellulose pulp from beech wood. The method promises a considerable process intensification by simultaneous separation of high purity cellulose pulp, lignin isolation as a cationically modified species, and production of value-added chemicals from reaction products of the REM. This study puts a further focus on the generated cellulose pulp and investigates it with respect to surface charge and fiber length.

Photovoltaic-driven electro-reforming of poly (ethylene terephthalate) (PET) waste plastics and nitrate pollutants

The electrochemical conversion of waste plastics and nitrate pollutants has advantages in the simultaneous achievement of value-added chemical production and environmental pollutants remediation. Here, we report a photovoltaic-driven electro-reforming strategy to convert poly (ethylene terephthalate) (PET) to platform chemical formic acid, and simultaneously reduce nitrate to ammonia. This strategy directly uses commercial silicon photovoltaic panel as the power source that achieves the oxidation of PET hydrolysate to produce formic acid by NiCo2O4/N-doped carbon nanotubes (NCNTs) anode, and the reduction of nitrate-containing wastewater to produce ammonia by CuO nanowires (NWs) cathode. This integrated system exhibits a high Faraday efficiency of 98 % for formic acid production and conversion of 90 % for nitrate under 30 mW cm−2 simulated sunlight. This study suggests that photovoltaic-driven electro-reforming of PET waste plastic coupled with nitrate reduction could be a feasible strategy to realize the sustainable production of chemicals from environmental pollutants.

Valorization of Chlorella Microalgae Residual Biomass via Catalytic Acid Hydrolysis/Dehydration and Hydrogenolysis/Hydrogenation

Microalgal biomass can be utilized for the production of value-added chemicals and fuels. Within this research, Chlorella vulgaris biomass left behind after the extraction of lipids and proteins was converted to valuable sugars, organic acids and furanic compounds via hydrolysis/dehydration using dilute aqueous sulfuric acid as a homogeneous catalyst. Under mild conditions, i.e., low temperature and low sulfuric acid concentration, the main products of hydrolysis/dehydration were monomeric sugars (glucose and xylose) and furanic compounds (HMF, furfural) while under more intense conditions (i.e., higher temperature and higher acid concentration), organic acids (propionic, formic, acetic, succinic, lactic, levulinic) were also produced either directly from sugar conversion or via intermediate furans. As a second valorization approach, the residual microalgal biomass was converted to value-added sugar alcohols (sorbitol, glycerol) via hydrogenation/hydrogenolysis reactions over metallic ruthenium catalysts supported on activated carbons (5%Ru/C). It was also shown that a low concentration of sulfuric acid facilitated the conversion of biomass to sugar alcohols by initiating the hydrolysis of carbohydrates to monomeric sugars. Overall, this work aims to propose valorization pathways for a rarely utilized residual biomass towards useful compounds utilized as platform chemicals and precursors for the production of a wide variety of solvents, polymers, fuels, food ingredients, pharmaceuticals and others.

Design of a synthetic enzyme cascade for the in vitro fixation of formaldehyde to acetoin

Formaldehyde (FALD) has gained prominence as an essential C1 building block in the synthesis of valuable chemicals. However, there are still challenges in converting FALD into commodities. Recently, cell-free biocatalysis has emerged as a popular approach for producing such commodities. Acetoin, also known as 3-hydroxy-2-butanone, has been widely used in food, cosmetic, agricultural and the chemical industry. It is valuable to develop a process to produce acetoin from FALD. In this study, a cell-free multi-enzyme catalytic system for the production of acetoin using FALD as the substrate was designed and constructed. It included three scales: FALD utilization pathway, glycolysis pathway and acetoin synthesis pathway. After the optimization of the reaction system, 20.17 mM acetoin was produced from 122 mM FALD, with a yield of 0.165 mol/mol, reaching 99.0% of the theoretical yield. The pathway provides a new approach for high-yield acetoin production from FALD, which consolidates the foundation for the production of high value-added chemicals using cheap one-carbon compounds.

The relevant effect of marine salt and epiphytes on Posidonia oceanica waste pyrolysis: Removal of SO2/HCl emissions and promotion of O/HCOOH formation

Significant quantities of Posidonia oceanica deposit on some beaches and coastlines every year, which generates high costs associated with the disposal of this waste. Pyrolysis may be an adequate way for its valorization. However, it would imply to know how the process takes place and if the removal of its natural detrital inorganic matter (epiphytes, marine salt and sand) is necessary, which are the objectives of this research. Pyrolysis by thermogravimetry-mass spectrometry was carried out on both the washed and unwashed samples.During this waste pyrolysis, the following occurs: (i) the high alkali metal chloride content promotes fragmentation reactions of carbohydrates and O formation, which increases HCOOH intensities at temperatures between 250 and 360 °C; (ii) from 500 °C to 650 °C, Fe2O3 and decomposition of carbonates seem to be involved in reactions that produce O release and steam and CO2 reforming of hydrocarbons and oxygenated organic compounds with H2 generation; (iii) from 650 °C to 750 °C, Fe2O3, high alkali metal content and carbonate decomposition generate char gasification, an increase in O release, SO2 capture and HCOOH formation.In general, the abundance of inorganic matter (chlorides, carbonates, etc.) minimizes the release of various compounds during pyrolysis, including SO2 and HCl, while increasing HCOOH production. Thus, this high content of inorganic matter may represent an advantage for its pyrolysis, producing value-added chemical products with a reduced environmental impact. Therefore, this study may be the starting point for defining the optimal pyrolysis conditions for this waste valorisation.

Strong electric field at the sharp tips of Cu(OH)2 nanochrysanthemums for selective electrochemical CO2 conversion into ethylene

Electrochemical CO2 reduction reaction (CO2RR) is an attractive approach for the mitigation of CO2 emissions and the production of value-added chemicals. However, it remains a challenge to achieve high selectivity of desirable C2 products like ethylene (C2H4) with high economic value and large market. Herein, we report the fabrication of unprecedented Cu(OH)2 nanochrysanthemums catalyst layer (CL). Interestingly, Cu(OH)2 nanochrysanthemums CL exhibits a C2H4 Faradaic efficiency (FE) of 51.2 ± 0.5% and a FE(C2H4+C2H5OH) of 70.0 ± 0.5% in pH nearly neutral electrolytes. It is worth mentioning that Cu(OH)2 nanochrysanthemums CL achieves the highest FEC2 among documented Cu(OH)2 electrocatalysts. The high FEC2H4 and FEC2 can be attributed to the high electrochemical surface area (ECSA, 21.9 mF/cm2) of Cu(OH)2 nanochrysanthemums. In addition, the wellbalanced hydrophilicity-hydrophobicity of the Cu(OH)2 nanochrysanthemums CL also contributes to the high FEC2H4 and FEC2 by simultaneously satisfying efficient transfer of hydrophobic CO2 and C2H4 as well as hydrophilic H2O and C2H5OH. COMSOL multiphysics simulations and density functional theory (DFT) calculations further suggest that the negatively charged sharp tips of Cu(OH)2 nanochrysanthemums would trigger the accumulation of K+ and offer strong local electric field of 9.8 V/μm, promoting C–C coupling and suppressing hydrogen evolution reaction (HER).

Kinetic Model for the Heterogeneous Biocatalytic Reactions Using Tethered Cofactors.

Understanding the mechanism of interfacial enzyme kinetics is critical to the development of synthetic biological systems for the production of value-added chemicals. Here, the interfacial kinetics of the catalysis of β-nicotinamide adenine dinucleotide (NAD+)-dependent enzymes acting on NAD+ tethered to the surface of silica nanoparticles (SiNPs) has been investigated using two complementary and supporting kinetic approaches: enzyme excess and reactant (NAD+) excess. Kinetic models developed for these two approaches characterize several critical reaction steps including reversible enzyme adsorption, complexation, decomplexation, and catalysis of the surface-bound enzyme/NAD+ complex. The analysis reveals a concentrating effect resulting in a very high local concentration of enzyme and cofactor on the particle surface, in which the enzyme is saturated by surface-bound NAD, facilitating a rate enhancement of enzyme/NAD+ complexation and catalysis. This resulted in high enzyme efficiency within the tethered NAD+ system compared to that of the free enzyme/NAD+ system, which increases with decreasing enzyme concentration. The role of enzyme adsorption onto solid substrates with a tethered catalyst (such as NAD+) has potential for creating highly efficient flow biocatalytic systems.

Efficient production of butyl butyrate from mannitol by engineered Clostridium tyrobutyricum

Butyl butyrate has a wide range of applications as flavors, solvents, and biofuels. Green production of butyl butyrate by microorganism fermentation in an industry level attracts great attention on the basis of bio-refinery. In this study, a dark horse Clostridium tyrobutyricum was employed for de novo production of butyl butyrate. Herein, reinforcement of EMP and butyl butyrate fermentation pathways (e.g., pfkA, pykA, crt-hbd-bcd/etfAB, adhE2 and VAAT) and regulation of carbon distribution towards butyl butyrate (e.g., CAT1 inactivation or overexpression of NADPH-dependent hbd1) were conducted in C. tyrobutyricum (MUV3) to enhance butyl butyrate production. The outstanding strain MV12 generated 1.8-fold butyl butyrate production compared to the initial strain MUV3. Subsequently, organic nitrogen source concentration was optimized, 21.1 g/L and 30.1 g/L butyl butyrate were obtained in 37 °C and 25 °C, respectively. Ultimately, fed-batch with two-stage temperature shift fermentation was performed for high titer and yield of butyl butyrate production (142.6 g/L titer and 0.28 mol/mol yield) from mannitol. Hence this study presented a microbial fermentation platform for butyl butyrate or other value-added chemicals production from renewable resources.

High DHA selectivity and low-cost electrode for glycerol oxidation: CuO regulates MnO2 electron density to promote DHA desorption

Glycerol oxidation reaction (GOR) is an attractive alternative reaction for oxygen evolution reaction (OER) in the electrochemical water splitting and can be used to generate high-value products. However, the development of GOR electrocatalysts with high catalytic activity and low cost is challenging. In this research, a self-supported copper-manganese electrode (MnO2-CuO/CF) was developed, which attains a current density of 10.7 mA cm−2 at a low potential of 1.3 V, while yielding 1,3-dihydroxyacetone (DHA), with a selectivity of 60%. DFT calculations reveal the synergistic effect between CuO and MnO2, enhancing glycerol adsorption. Additionally, the overlap configuration of CuO and MnO2 results in a lower electron density on MnO2, preventing further oxidation and increasing DHA selectivity. By coupling GOR and water electrolysis, the dual output of high value-added organic products and high-purity hydrogen can be realized, which provides a new idea for green hydrogen production and electrochemical synthesis of high value-added chemicals.

Precise electronically modulated Mn doped nickel iron phosphate with P, N codoped carbon decorated P-doped carbonized bacterial cellulose for efficient electrocatalytic glucose conversion coupled with H2 generation

Biomass electrocatalytic-conversion coupled with hydrogen generation exhibits low energy consumption, efficient hydrogen production and green syntheses of value-added chemicals. However, constructing electrocatalysts with precise electronic modulation and structures for efficient biomass electrocatalytic conversion coupled hydrogen production remains challenging. Herein, a bacterial cellulose substrate was combined in situ with a Mn-doped NiFe Prussian blue analogue (PBA) precursor, and one-step carbonization-phosphorylation was developed for the preparation of Mn-doped nickel iron phosphate (MNFP) embedded in a P, N codoped carbon (PNC) substrate grown directly on P-doped carbonized bacterial cellulose (MNFP-PNC/PCBC). Benefiting from the three-dimensional network structure of P-doped carbonized bacterial cellulose (PCBC) and atomic doping, MNFP-PNC/PCBC exhibited an optimized electronic structure, abundant active sites and excellent electrical conductivity. Therefore, the voltages required with hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and glucose electrocatalytic-conversion (GCR) to drive a current density of 50 mA cm−2 were 0.214, 1.5, and 1.34 V, respectively. Moreover, the required cell voltage of the novel electrolyser containing MNFP-PNC/PCBC as electrodes can be further reduced to 1.55 V at 50 mA cm−2 compared to overall water splitting, resulting in more than 8-time improvement in hydrogen production efficiency and production of value-added formate. This work provides a unique approach for electrocatalytic-conversion of biomass coupled with electrocatalytic hydrogen generation.

Cyanophycin modifications for applications in tissue scaffolding

Cyanophycin (CGP) is a polypeptide consisting of amino acids—aspartic acid in the backbone and arginine in the side chain. Owing to its resemblance to cell adhesive motifs in the body, it can be considered suitable for use in biomedical applications as a novel component to facilitate cell attachment and tissue regeneration. Although it has vast potential applications, starting with nutrition, through drug delivery and tissue engineering to the production of value-added chemicals and biomaterials, CGP has not been brought to the industry yet. To develop scaffolds using CGP powder produced by bacteria, its properties (e.g., biocompatibility, morphology, biodegradability, and mechanical strength) should be tailored in terms of the requirements of the targeted tissue. Crosslinking commonly stands for a primary modification method for renovating biomaterial features to these extents. Herein, we aimed to crosslink CGP for the first time and present a comparative study of different methods of CGP crosslinking including chemical, physical, and enzymatic methods by utilizing glutaraldehyde (GTA), UV exposure, genipin, 1-ethyl-3-[3-dimethylaminopropyl] carbodiimide hydrochloride/N-hydroxysuccinimide (EDC/NHS), and monoamine oxidase (MAO). Crosslinking efficacy varied among the samples crosslinked via the different crosslinking methods. All crosslinked CGP were non-cytotoxic to L929 cells, except for the groups with higher GTA concentrations. We conclude that CGP is a promising candidate for scaffolding purposes to be used as part of a composite with other biomaterials to maintain the integrity of scaffolds. The initiative study demonstrated the unknown characteristics of crosslinked CGP, even though its feasibility for biomedical applications should be confirmed by further examinations.Key points• Cyanophycin was crosslinked by 5 different methods• Crosslinked cyanophycin is non-cytotoxic to L929 cells• Crosslinked cyanophycin is a promising new material for scaffolding purposesGraphical

Cation-mediated acid-base pairs for mild oxidative cleavage of lignocellulosic β-1,4-glycosidic bonds

Solar-driven lignocellulosic biomass photoreforming holds significant promise for the production of value-added chemicals and fuels. The cleavage of the β-1,4-glycosidic bond is crucial for the effective conversion of lignocellulosic biomass. Polymeric carbon nitride (PCN) with acid-base pairs (M-C sites) is developed through heteroatomic carbon incorporation and cation insertion. It can be used for the gentle oxidation of cellobiose to monosaccharides, bypassing the formation of organic acids such as gluconic acid and glucaric acid. A series of different alkaline/alkaline-earth cation for regulation of acid-base pairs exhibited a negative correlation between β-1,4-glycosidic bond cleavage and cation radii. In particular, the introduction of short-radius cations (such as Li) into PCN enabled the formation of acid-base (M-C) pairs characterized by strong acidity. It also enhanced electron delocalization around M-C sites, potentially promoting the generation of reactive radicals in the reaction. Electron paramagnetic resonance analysis confirmed the presence of •OH radicals. The mild oxidative species, are the primary reactive radicals responsible for β-1,4-glycosidic bond cleavage in cellobiose. This study provides insightful evidence for the rational regulation of acid-base sites in facilitating β-1,4-glycosidic bond cleavage. It sheds light on the oxidative cleavage mechanisms integral to lignocellulosic biomass photoreforming, offering insights for advancing sustainable biomass conversion technologies.

ZnIn2S4/MOF S-scheme photocatalyst for H2 production and its femtosecond transient absorption mechanism

Photocatalytic water splitting is a popular pathway for H2 evolution, but the slow water oxidation greatly hampers the overall activity. To harness photogenerated holes in an efficient and lucrative way, the water oxidation reaction is replaced by selective oxidation of organic compounds to achieve simultaneous production of H2 and value-added chemicals. Herein, an alternative tactic is reported where an organic compound (benzylamine, BA) not only serves as the precursor for N-benzylidene-benzylamine (NBBA) production but also provides hydrogen sources for H2 evolution, achieving the goal under anhydrous conditions. This process is realized using an S-scheme photocatalyst composed of ZnIn2S4 and the UiO-66-NH2 (U6N) metal-organic framework (MOF). The S-scheme carrier transfer mechanism was validated by in-situ irradiated X-ray photoelectron spectroscopy (ISI-XPS) and femtosecond transient absorption (fs-TA) spectroscopy. With increased carrier efficiency and reinforced redox power endowed by the S-scheme heterojunction, the composite performed better than ZnIn2S4 and MOF. The performance was further ameliorated by Pt-cocatalyst modification, achieving an H2 production rate of 5275 μmol h−1 g−1 as well as BA conversion of 94.3% with 99.3% NBBA selectivity. Mechanistic studies reveal that BA is initially oxidized to carbon-centered radicals and further to imines along with the release of protons. The imine reacts with another BA molecule to form NBBA, while the protons are reduced to H2. This work provides new insights into concurrent photocatalytic H2 production and selective organic oxidation from organic amines using S-scheme photocatalysts.

Efficiently photocatalytic conversion of amine to imidine via perylene diimides supramolecules with oxygen vacancy

The utilization of photocatalytic oxidation technology for sustainable production of value-added chemicals has garnered significant attention. In the photocatalytic process, the transfer rate of photogenerated holes is considerably slower (2–3 orders of magnitude) than that of electrons. Consequently, the migration of photogenerated holes emerges as a critical bottleneck in achieving the efficient conversion of solar energy into value-added chemicals. To address these challenges, we synthesized a perylene diimides supramolecule with abundant oxygen vacancies (R-Ov-PDI) to enhance holes transfer processes. Photogenerated holes were selectively captured by negatively charged defect sites, triggering an attack on the C–N bond. Noticeably, the catalyst exhibited a remarkable benzylamine oxidation efficiency (31.3 mmol·g−1·h−1) under visible light, with a selectivity for imine surpassing 99%. Furthermore, it demonstrated excellent substrate generality, outperforming most reported all-organic photocatalysts by 1–2 orders of magnitude. This study prove a novel perspective for the systematic design of efficient organic photocatalysts.

Enhancing bio-based chemical production and reducing pollutants emission through the synergistic effect of ZSM-5/CaO during hydrogen-deficient biomass pyrolysis

The study proposed the use of ZSM-5/CaO as a catalyst to simultaneously improve the quality of pyrolytic products and reduce pollutants emission during the pyrolysis of hydrogen-deficient biomass, specifically cabbage waste (CW). Variables such as pyrolysis temperature and catalysts, including 5% ZSM-5, 5% CaO and 10% ZSM-5/CaO, significantly affected biomass conversion, yield, and products composition. Thermogravimetric-Fourier transform infrared spectroscopy (TG-FTIR) analysis shows that the catalysts (5% ZSM-5, 5% CaO and 10% ZSM-5/CaO) reduced pollutants emission and increased value-added chemicals production by 24.96%, 28.5%, 17.39% and 75.04%, 71.5%, 82.1%, respectively compared to non-catalytic process as 34.18% and 65.82%. Moreover, these catalysts enhanced the relative yield of olefins, aromatics, and phenols to 23.5, 21.6, 27.6% for 5wt.%ZSM-5; 20.8, 18.7, 23.3% for 5wt.%CaO; 30.7, 38.6, 41.3% for 10wt.%ZSM-5/CaO, compared to the non-catalytic process' yield of 15.7, 10.7, 19.3%. Py/GC–MS analysis confirms that these catalysts also decreased PAH and oxygenates production to 13.5, 15.3% for 5wt.%ZSM-5; 11.8, 9.1% for 5wt.%CaO; 5.2, 4.7% for 10wt.%ZSM-5/CaO, in contrast to the non-catalytic process' 26.2, 28.7%. This confirms the synergistic effect of ZSM-5/CaO for upgrading bio-based chemicals and reducing pollutants emission.