Biomass-based Catalyst Research Articles

Urushiol derivatives as biomass-based photocatalysts for the transition-metal-free synthesis of 1,2-amino alcohols

We report the design and synthesis of urushiol derivatives as biomass-based catalysts for photocatalytic, transition-metal-free access to 1,2-amino alcohols.

Efficient Synthesis of Biodiesel Catalyzed by Chitosan-Based Catalysts

Catalysts play an important role in the preparation of biodiesel. It is of great significance to study catalysts with high efficiency, low cost, and easy preparation. Compared with the homogeneous catalyst system, the heterogeneous catalyst is easy to separate and has a better catalytic effect. In heterogeneous catalysts, supports and preparation methods have important effects on the dispersion of active centers and the overall performance of catalysts. However, the supports of existing solid catalysts have defects in porosity, structural uniformity, stability, and specific surface area, and the preparation methods cannot stabilize covalent bonds or ionic bonds to bind catalytic sites. Considering the activity, preparation method, and cost of the catalyst, biomass-based catalyst is the best choice, but the specific surface area of the biomass-based catalyst is relatively low, the distribution of active centers is uneven, and it is easy to lose. Therefore, the hybrid carrier of biomass-based catalyst and other materials can not only improve the specific surface area but also make the distribution of active centers uniform and the catalytic activity better. Based on this, we summarized the application of chitosan hybrid material catalysts in biodiesel. The preparation, advantages and disadvantages, reaction conditions, and so on of chitosan-based catalysts were mainly concerned. At the same time, exploring the effects of different types of chitosan-based catalysts on the preparation of biodiesel and exploring the process technology with high efficiency and low consumption is the focus of this paper.

Catalytic coupling of CO2 and epoxides by lignin-based catalysts: A combined experimental and theoretical study

A new strategy for the construction of an amine-modified lignin has been developed through the Mannich reaction. The lignin-based catalyst, (PEI(70000)-SL/ZnBr2), acted as a green and reusable heterogeneous catalyst for the catalytic conversion of CO2 and epoxides into cyclic carbonates. This catalyst exhibited excellent conversion and selectivity in the CO2 cycloaddition reaction due to the synergistic effects of the hydroxyls (-OH) and metal (Zn2+) as Lewis acid sites, and organic amines (-NH2) and halogen anions (Br-) as nucleophiles. Some lignin model compounds were used to study the relationship between structure and activity in order to evaluate the synergistic effects during the cycloaddition reaction. Functional groups, such as Zn2+, -OH and -NH2, in adjacent positions of the lignin-based catalyst yielded the cyclic carbonates in high efficiencies and selectivities. Furthermore, DFT calculation and the experimental results revealed that Zn2+ enhanced the ring-opening process via SN1 mechanism, with the energy barrier of the ring-opening process of 18.9 kcal mol-1 due to the cooperation of the Zn2+ with phenolic hydroxyl groups. These findings do not only provide a novel design concept for biomass-based catalysts but also accomplished the transformation of CO2 into valuable products.

Effect of Biomass-Based Catalyst in Walnut Shell/Polypropylene to BTX

Four biomass-based catalyst carriers with different pore structures were prepared by using a carbonization-activation method, followed by employment in the copyrolysis of Walnut Shell/Polypropylene (WNS/PP) to produce Benzene, Toluene and Xylene (BTX). Ten cycles were performed in each copyrolysis test in a bench-scaled tube furnace to determine the suitable pore size of the catalyst and excellent cycling performance for BTX production. In addition, Zn, Ni, and Ce were loaded with the selected catalyst carriers to synthesize the most suitable biomass-based catalyst. Results showed that the pore size and active center of the catalyst were the key factors affecting the WNS/PP catalytic copyrolysis. Biomass-based carrier with a pore size in the range of 0.55-1.2 nm was the most suitable to produce BTX in the optimal 10 cycle performance; it realized a relative BTX content of 9-20 area%, and a BTX mass yield of 23-67 mg/(graw) in the liquid-phase products from the WNS/PP copyrolysis. A catalyst loaded with 10 wt% Zn possessed the best catalytic effect with a relative BTX content of 39.49 area%, and a BTX yield of 111.13 mg/(graw).

Optimization of pH-universal O2 reduction electrocatalysis by precise control over structural variables via basic bathing

In pursuit of finding alternatives to Pt for O2 reduction reaction (ORR), biomass-based catalysts are promising candidates because of their low prices and comprehensive sources that just compensate for the drawbacks of Pt. However, it is difficult to determine unambiguously structure-function correlations of biomass-based catalysts due to their complex structures. Moreover, biomass-based metal-free ORR electrocatalysts often suffer from poor mass transport and pH applicability. Hence, tuning structural variables specifically, improving mass transport within porous domains, and achieving pH-universal catalytic activities are key to optimization of metal-free ORR electrocatalysts derived from biomass. In this study the ‘basic bathing’ method is proposed for precise control over structural variables of nitrogen-doped metal-free ORR electrocatalysts that originate from staple waste biomass—wheat straw. The basic bathing makes use of the fact that KOH can result in a series of physicochemical changes within lignocellulosic biomass and thereby re-proportion pore width distributions of synthesized materials. Under the action of basic bathing, the optimal electrocatalyst having the largest mesopore volume and the equal distribution of nitrogen species is superior in terms of pH-universal ORR electrocatalytic activity when compared to its non-basic-bathing counterparts. The structure-function analyses, benefiting from the specific tuning of mesopores by the basic bathing, demonstrate the linear relations between mesopore volumes and limiting current densities irrespective of pH. Furthermore, the density functional theory (DFT) calculations indicate the synergistic effects of pyridinic, pyrrolic and graphitic nitrogens at a 1:1:1 atomic ratio contribute to the decreased overpotential requirement. Taken together, the reproducible results provide compelling evidence for the importance of mesopores and nitrogen species distributions in enhancing the pH-universal ORR performance. In a broader context, the basic bathing is truly inspirational for niche exploitation of biomass for future energy technologies.

Bifunctional biomass-based catalyst for biodiesel production via hydrothermal carbonization (HTC) pretreatment – Synthesis, characterization and optimization

The hydrothermal carbonization (HTC) technique is known for its advantages in producing hydrochar from biomass samples with high water content compared to conventional pyrolysis techniques. This study utilized HTC to produce an activated carbon catalyst from renewable mesocarp fiber derived from palm oil processing. The introduction of K2CO3 and Cu(NO3)2 produced a bifunctional catalyst suitable for conversion of used cooking oil to biodiesel. The catalyst possessed a mesoporous structure with a BET surface area of 3909.33 m2/g. An optimum treatment ratio of 4:1 (K2CO3: Cu(NO3)2) provided elevated basic (5.52 mmol/g) and acidic (1.68 mmol/g) concentrations on the catalytic surface, which promoted esterification and transesterification reactions. Maximum yield (96.4%) of biodiesel was obtained at 70 °C for 2 h with 5 wt% catalyst and a 12:1 molar ratio of methanol to oil. The catalyst endured up to 5 reaction cycles while maintaining biodiesel yields of more than 80%. These findings indicated that HTC pretreatment yielded a high-quality bifunctional catalyst for conversion of low-quality used cooking oil for production of biodiesel.

Incorporation of Activated Biomasses in Fe-N-C Catalysts for Oxygen Reduction Reaction with Enhanced Stability in Acidic Media

Fe-N-C materials are promising oxygen reduction reaction (ORR) catalysts for replacing expensive platinum-based catalysts (Pt/C) in proton exchange membrane fuel cells. However, they still show low volumetric activity and stability compared to Pt/C catalysts, with carbon corrosion being one of the main factors for the loss of active Fe-Nx sites. Within this study, phosphoric acid-activated rye straw and coconut shells are revealed as a promising matrix for Fe-Nx sites with advanced stability against electrochemical carbon corrosion (5000 cycles, 1.0–1.5 VRHE, and 0.1 M HClO4) compared to a common Fe-N-C catalyst based on carbon black. Electrochemical characterization of the two biomass-based catalysts (Fe-N-CBio) shows on the one hand 50% higher stability in terms of mass activity as well as comparable activity and active site density but on the other hand a lower selectivity toward the four-electron ORR than the common Fe-N-C catalyst. Nitrite stripping experiments in acetate buffer as an electrolyte display a 1.5-fold stronger effect of carboxylic acid adsorption than on a common Fe-N-C catalyst, revealing differences to the electronic structure of the Fe-N-CBio catalyst. This difference is mainly attributed to the presence of phosphor species and higher amounts of nitrogen functionalities in the Fe-N-CBio catalysts. The presence of P is assumed to stabilize the carbon against carbon corrosion by inhibiting electron withdrawal from the C. This study points out the impact factors on Fe-N-C stability and further shows the promising application of activated biomasses in more stable and sustainable Fe-N-C catalysts for ORR.

Obtaining lignocellulosic biomass-based catalysts and their catalytic activity in cellobiose hydrolysis and acetic acid esterification reactions.

Global challenges prompt the world to modify its strategies and shift from a fossil-fuel-based economy to a bio-resource-based one with the production of renewable biomass chemicals. Different processes exist that allow the transformation of raw biomass into desirable bio-based products and/or energy. In this work different biochars that were obtained as a by-product from birch chip fast pyrolysis and carbonization were used as is or chemically/physically treated. These sulfonated carbon catalysts were compared to a commercially available sulfonated styrene-divinylbenzene macroreticular resin (Dowex 50W X8). Characterisation (water content and pH value, FTIR, base titration, element analysis and N2 desorption) was done to evaluate the obtained sulfonated biocarbon catalysts. Catalytic activity was tested using cellobiose (CB) hydrolysis and acetic acid esterification. For the catalytic CB hydrolysis, we tested the reaction temperature, time and CB and catalyst mass ratios. The determined optimal conditions were 120 °C and 24 h, with CB and catalyst mass ratio 1 : 5. The highest glucose yield was observed for biochar obtained from the birch chip fast pyrolysis process (BC_Py-H2SO4) – 92% within 24 h for 120 °C. Comparably high glucose yield was observed for biochar that was obtained in birch chip carbonization (BC_Carbon-H2SO4) – 86% within 24 h for 120 °C.

Lignin: A Potential Source of Biomass-Based Catalysts

Lignin: A Potential Source of Biomass-Based Catalysts

The Application of Biomass-Based Catalytic Materials in the Synthesis of Cyclic Carbonates from CO2 and Epoxides.

The synthesis of cyclic carbonates from carbon dioxide (CO2) and epoxides is a 100% atom economical reaction and an attractive pathway for CO2 utilisation. Because CO2 is a thermodynamically stable molecule, the use of catalysts is mandatory in reducing the activation energy of the CO2 conversion. Considering environmental compatibility and the high-efficiency catalytic conversion of CO2, there is the strong need to develop green catalysts. Biomass-based catalysts, a type of renewable resource, have attracted considerable attention due to their unique properties—non-toxic, low-cost, pollution-free, etc. In this review, recent advances in the development of biomass-based catalysts for the synthesis of cyclic carbonates by CO2 and epoxides coupling are summarized and discussed in detail. The effect of biomass-based catalysts, functional groups, reaction conditions, and co-catalysts on the catalytic efficiency and selectivity of synthesizing cyclic carbonates process is discussed. We intend to provide a comprehensive understanding of recent experimental and theoretical progress of CO2 and epoxides coupling reaction and pave the way for both CO2 conversion and biomass unitization.

Carboxylated Chitosan Nanocrystals: A Synthetic Route and Application as Superior Support for Gold-Catalyzed Reactions.

In this study, we demonstrate for the first time the fabrication of carboxylated chitosan nanocrystals (ChsNC) with high degree of deacetylation (DDA) at >80% and narrow size distribution. We also studied its application as a sustainable support material for metal-based catalysts. Carboxylated chitin nanocrystals (ChNCs) were initially prepared through partial cleavage of glycosidic bonds in chitin by ammonium persulfate, with concurrent oxidation of chitin C6 primary alcohols to produce carboxylate groups on the surface of the ChNCs. ChsNCs were subsequently prepared using an alkaline deacetylation procedure in the presence of NaBH4 to preserve the nanorod structure of the biomaterial. The resulting nanocrystals feature both carboxyl and amino functional groups. Transmission electron microscopy (TEM), X-ray diffraction (XRD), and Fourier-transform infrared (FTIR) spectroscopy were used to determine the morphology and composition of these carboxylated ChNCs and ChsNCs. Subsequently, we tested the ability of the as-made ChsNCs as a biomass-based catalyst support for Au nanoparticles (NPs) using the 4-nitrophenol reduction and the aldehyde-amine-alkyne (A3) coupling reactions to demonstrate its capabilities in regard to the ones of cellulose nanocrystals (CNCs). In particular, Au NPs over ChsNCs featured the highest turnover frequency (TOF) value for the 4-nitrophenol reduction reported for all Au-based catalysts supported on carbon-based systems. Spectroscopic and imaging techniques confirmed the importance of precisely controlling the redox state of Au as it is being deposited to afford a highly disperse active site on the bionano-support.

An efficient metal-free catalyst derived from waste lotus seedpod for oxygen reduction reaction

The sluggish kinetics of oxygen reduction reaction (ORR) has severely impeded the application of fuel cell technology. Developing economical and efficient biomass-based catalysts derived from natural waste to replace the expensive noble metal catalysts is becoming an attractive strategy. However, biomass materials often have geographical and seasonal characteristics. Thus, developing diversified and available biomass-derived catalysts is significant for different regions. In this work, N, P-dual doped porous carbon materials derived from waste lotus seedpod with tunable specific surface areas and porous structure are skillfully fabricated. The optimized sample exhibits excellent oxygen reduction reaction activity with an onset potential of 0.87 V vs. RHE and a Tafel slope of 81 mV dec−1, showing the 4e‒ electrons transfer path in alkaline solution. It also exhibits much better stability and methanol tolerance than commercial Pt/C. High ORR performance is considered to be ascribed to the abundant N, P dispersion and the hierarchical porous structure.

Sustainable production of methyl levulinate from biomass in ionic liquid-methanol system with biomass-based catalyst

The preparation of bifunctional solid-acid catalyst and production of methyl levulinate were performed synergistically based on the fractionation of wood residue. The hydrothermal hydrolysate of wood residue was utilized for catalyst preparation using template method with sulfonic group as the Brønsted acid site and Zr4+ as Lewis acid site. Cellulose material for methyl levulinate production was fractionated by the delignification of hydrothermal residue using deep eutectic solvent. In this study, yield of methyl levulinate reached 38.7% under the optimized experiment condition. Insight gained from this work suggests a sustainable strategy for methyl levulinate production using recyclable biomass-based catalyst in ionic liquid-methanol system.

Experimental study on a biomass-based catalyst for catalytic upgrading and viscosity reduction of heavy oil

A biomass-based catalyst for catalytic upgrading and viscosity reduction process of heavy oil was prepared. The experimental results showed the viscosity of oil sample reduced from 508800 mPa.s to 22230 mPa.s (50 ℃) with 0.2wt% biomass-based catalyst at 320 ℃ for 30 min, and the viscosity reduction was up to 95.63%. The content of resin was significantly reduced by 10.1% after reaction under the optimal conditions. Furthermore, composition analysis, FT-IR analysis, thermogravimetric analysis and elemental analysis of the biomass-based catalyst were characterized in detail. In addition, FT-IR analysis, elemental analysis and SEM analysis were employed to evaluate the properties of oil sample. Further, influence mechanism of biomass-based catalyst on catalytic upgrading process of heavy oil was expounded through viscosity change, SARA analysis, 1H-NMR analysis, weight average molecular weight and average particle sizes analysis, and the above analysis results revealed that under the catalytic action of organic nickel salt, the presence of non-acidic components in the catalyst could improve the chemical structures of heavy compositions of oil sample. Finally, a possible schematic diagram of catalytic upgrading process was simply depicted in this work.

Catalytic Steam Reforming of Toluene for Hydrogen Production over Nickel-Cobalt Supported Activated Carbon

Hydrogen may play a key role in future sustainable energy system as a carrier of renewable energy to replace the conventional fossil fuel. Biomass gasification is the most promising method in renewable hydrogen production technologies. However, the tar by-product poses great obstacle in the realization of commercial biomass gasification. In this work, the performance of Ni and/or Co supported on modified-palm kernel shell-derived activated carbon (AC) catalyst in steam reforming of toluene (SRT) for the production of hydrogen has been investigated. Toluene has been chosen as a model compound since it represents one of the major tar compositions. The effects of nitric acid in the surface pretreatment of AC (ACN) and the influence of Ni and/or Co loading on the catalyst support are studied. The catalysts are characterized using FTIR, BET, XRD, TGA and FESEM-EDX. The modified-AC support shows that the surface area, microporous structure and surface oxygenated functional group (SOFG) increase, leading to a homogeneous distribution of metal particles. The highest toluene conversion (Xtoluene) and hydrogen yield (YH2) obtained over 10%Ni-10%Co/ACN are 70% and 69%, respectively. The catalytic performance of bimetallic Ni–Co/ACN catalyst is more significant compared to monometallic Ni- and Co-supported catalysts. The highest catalytic performance achieved can be attributed to the larger surface area and unique porous structure of the modified-AC support as well as the formation of Ni–Co solid solution alloys that improve its coke-resistant capability with low carbon formation during SRT. The modified palm kernel shell AC-supported bimetal catalyst has high potential as a biomass-based catalyst for the applications in biomass tar removal toward hydrogen production due to its good coke-resistance properties.

Hemicelluloses supported palladium/xylan nanocomposites containing N and O ligands: Highly-performance heterogeneous catalysts for Suzuki reaction

Two kinds of xylan/palladium catalysts (PACMX-Pd and EDAX-Pd) were simply fabricated by integrating two N bidentate ligands into the skeleton of oxygen-rich xylan and followed with the in-situ reduction of palladium. The Pd loading in PACMX-Pd and EDAX-Pd nanocomposites was 0.353 mmol/g and 0.302 mmol/g, respectively. The catalysts exhibited an excellent catalytic activity for the Suzuki reaction with a yield of high up to 100% as well as a superior turnover frequency (TOF: 9626 h−1). Moreover, the catalysts showed outstanding stability and could be reused for at least 5 times without significant decrease in activity. Compared with other polymers and non-polymers supported palladium catalysts, the as-prepared biomass-based catalysts possess potential applications in a wide range of organic catalysis.

Efficient and green production of biodiesel catalyzed by recyclable biomass-derived magnetic acids

Biomass-based catalysts are considered as non-toxic, non-corrosive and eco-friendly solid materials. In the present study, all investigated biomass-derived magnetic sulfonic acid catalysts were synthesized from renewable chitosan, and characterized by XRD, FT-IR, TGA, VSM, SEM, TEM, and BET. Biodiesel was prepared by esterification of oleic acid and methanol to test the catalytic performance of the catalysts. Among the employed catalytic materials, a novel magnetic catalyst (FCHC-SO3H) was found to show predominant catalytic performance to produce biodiesel. Under the optimum reaction conditions (15/1 methanol/oleic aicd mole ratio and 4 wt% catalyst dosage at 80 °C for 3 h), a high biodiesel yield of 96.7% was obtained over FCHC-SO3H. It was found that the reaction catalyzed by the FCHC-SO3H material obeyed the first-order kinetics with low activation energy of 37.5 kJ/mol. In addition, the catalyst could be reused for five consecutive recycles, while maintaining good activity and stability. Therefore, FCHC-SO3H can be a promising catalyst for efficient production of biodiesel from highly acidic feedstocks.

Amine-Functionalized Sugarcane Bagasse: A Renewable Catalyst for Efficient Continuous Flow Knoevenagel Condensation Reaction at Room Temperature.

A biomass-based catalyst with amine groups (–NH2), viz., amine-functionalized sugarcane bagasse (SCB-NH2), was prepared through the amination of sugarcane bagasse (SCB) in a two-step process. The physicochemical properties of the catalyst were characterized through FT-IR, elemental analysis, XRD, TG, and SEM-EDX techniques, which confirmed the –NH2 group was grafted onto SCB successfully. The catalytic performance of SCB-NH2 in Knoevenagel condensation reaction was tested in the batch and continuous flow reactions. Significantly, it was found that the catalytic performance of SCB-NH2 is better in flow system than that in batch system. Moreover, the SCB-NH2 presented an excellent catalytic activity and stability at the high flow rate. When the flow rate is at the 1.5 mL/min, no obvious deactivation was observed and the product yield and selectivity are more than 97% and 99% after 80 h of continuous reaction time, respectively. After the recovery of solvent from the resulting solution, a white solid was obtained as a target product. As a result, the SCB-NH2 is a promising catalyst for the synthesis of fine chemicals by Knoevenagel condensation reaction in large scale, and the modification of the renewable SCB with –NH2 group is a potential avenue for the preparation of amine-functionalized catalytic materials in industry.

Production of methyl esters from waste cooking oil using a heterogeneous biomass-based catalyst

Fatty acid methyl esters (FAME) production from waste cooking oil was successfully carried out using a newly developed heterogeneous biomass-based catalyst. Activated carbon produced from oil palm biomass was calcined with potassium phosphate tri-basics (K3PO4) in order to synthesize a high catalytic heterogeneous catalyst. As it is characterized with substantial surface area of 680 m2/g and basicity amount of 11.21 mmol/g, 98% of FAME yield was achieved under optimum reaction parameters of 5 wt% catalyst loading, 12:1 methanol to oil molar ratio at 60 °C for 4 h. The catalyst was shown to be reusable, with more than 76% FAME yield after 5 consecutive cycles.

Two-Step Conversion of Neem (Azadirachta indica) Seed Oil into Fatty Methyl Esters Using a Heterogeneous Biomass-Based Catalyst: An Example of Cocoa Pod Husk

In this study, the viability of using calcined cocoa pod husk ash (CCPHA) as a catalyst for the transesterification of neem seed oil (NSO) into biodiesel was investigated. Prior to transesterification to biodiesel, the oil was pretreated with Fe2(SO4)3 via esterification to reduce its high acid value content. The Box-Behnken design (BBD) and central composite design (CCD) of response surface methodology (RSM) were used to investigate the individual and interactive effects of the methanol/oil ratio, catalyst amount, and reaction time on the acid value and biodiesel yield, respectively. Results of scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR), and elemental analysis showed that the catalytic action of the CCPHA produced was due to its K content and microstructural development when calcined at 700 °C for 4 h. The acid value of the NSO could be reduced from 11.57 to 1.80 mg of KOH/g of oil using optimum values of the methanol/oil ratio of 2.19 (v/v), catalyst a...