Selectivity Of Desired Product Research Articles

Dielectric Barrier Discharge Reactors for Plasma‐Assisted CO2 and CH4 Conversion: A Comprehensive Review of Reactor Design, Performance, and Future Prospects

Dielectric barrier discharge (DBD) plasma is a promising technology for catalysis due to its low‐temperature operation, cost‐effectiveness, and silent operation. This review comprehensively analyzes the design and operational parameters of DBD plasma reactors for three key catalytic applications: CH4 conversion, CO2 splitting, and dry reforming of methane (DRM). While catalyst selection is crucial for achieving desired product selectivity, reactor design and reaction parameters such as discharge power, electrode gap, reactor length, frequency, dielectric material thickness, and feed gas flow rate, significantly influence discharge characteristics and reaction mechanisms. This review also explores the influence of less prominent factors, such as electrode shape and applied voltage waveforms. Additionally, this review addresses the challenges of DBD plasma catalysis, including heat loss, temperature effects on discharge characteristics, and strategies for enhancing overall efficiency.

Electrocatalytic CO2 reduction over Ag/CuSn Electrodes: Modulation of C1, C2, and C3+ products

Combining different metals has proven to be an effective methodology for fabricating electrodes that can manipulate reduction products in electrochemical (EC) CO2 reduction. In this study, CuSn and EC treated CuSn were surface-modified with Ag via sputter deposition. EC CO2 reduction was performed at various applied potentials in KHCO3, K2CO3, and KOH electrolytes. The effects of cations and anions were tested to examine the variation in reduction products. The major reduction products were H2 and C1 compounds (CO, CH4, formate), as well as C2 compounds (C2H4, ethanol, and acetate). Minor products included C1 compounds (methanol), C2 compounds (acetaldehyde and glycolaldehyde), and C3+ compounds (propanol and isopropanol), along with C2H6 and C3+ hydrocarbon products. The variation of C2+ hydrocarbons was explained by Fischer-Tropsch (F-T) chemistry. The oxidation states of Cu and Sn, as well as the Cu/Sn ratios, were examined before and after EC CO2 reduction using depth-profiled X-ray photoelectron spectroscopy. The experimental factors—catalyst composition, applied potential, and electrolyte composition—interacted to create a complex reaction environment. This combined approach provides valuable insights into identifying optimal conditions for achieving desired product selectivity.

Boosting bio-lipids hydrodeoxygenation via highly dispersed and coking-resistance bimetallic Ni-La/SiO2 catalyst

A highly dispersed and coking-resistance bimetallic Ni-La/SiO2 catalyst was prepared for the selective hydrodeoxygenation (HDO) of fatty acid methyl esters (FAMEs) and non-edible bio-lipids to hydrocarbon compounds. Under optimum conditions, full conversion of methyl palmitate (MP) and 97.6% selectivity for pentadecane (PD) were achieved. The catalyst also exhibited high conversion and excellent desired product selectivity for the HDO of various model FAMEs, fatty acids, trilaurin, jatropha oil (JO) and waste cooking oil (WCO). Multiple characterizations show that the embedding effect (metal−support or metal−metal interaction) associated with the introduction of metallic La not only contributes to the formation of well-dispersed Ni particles and abundant active Niδ+−OV−LaOx species, but also prevents the migration and sintering of metallic Ni particles at high temperatures. Furthermore, the mutual transformation of the La2O3 and La2O2CO3 crystal phases effectively inhibits coke deposition on the catalyst surface during the reaction process, resulting in remarkable stability and reusability of the catalyst. A plausible reaction network and mechanism for the catalytic HDO of MP over Ni-La/SiO2 catalyst were proposed. This method of constructing a catalytic system can provide a basis for the development of efficient catalysts for the HDO of non-edible bio-lipids.

Effect of Catalyst Concentration on Reaction Rate in Organic Synthesis in Kenya

Purpose: The aim of the study was to assess the effect of catalyst concentration on reaction rate in organic synthesis in Kenya. Methodology: This study adopted a desk methodology. A desk study research design is commonly known as secondary data collection. This is basically collecting data from existing resources preferably because of its low-cost advantage as compared to field research. Our current study looked into already published studies and reports as the data was easily accessed through online journals and libraries. Findings: Increased catalyst concentration typically enhances the reaction rate by providing more active sites for the reactants to interact, thereby accelerating the reaction process. This phenomenon follows the principles of collision theory, which states that a higher concentration of catalyst molecules leads to more frequent collisions with reactant molecules, thus increasing the likelihood of successful reactions. Studies have shown that in many organic syntheses, an optimal catalyst concentration exists where the reaction rate is maximized; beyond this point, further increases in catalyst concentration may result in negligible improvements or even adverse effects due to catalyst aggregation or inhibition. Additionally, the nature of the catalyst, its dispersion in the reaction medium, and the specific reaction mechanism all play significant roles in determining the overall impact of catalyst concentration on reaction kinetics. Consequently, fine-tuning the catalyst concentration is essential for optimizing reaction conditions, improving yields, and achieving desired product selectivity in organic synthesis. Implications to Theory, Practice and Policy: Transition state theory, collision theory and michaelis menten kinetics may be used to anchor future studies on assessing effect of catalyst concentration on reaction rate in organic synthesis in Kenya. Practical guidelines are crucial for optimizing catalyst concentration in specific reaction types and industrial settings. Establishing regulatory frameworks that incentivize efficient catalyst concentration practices within industries is imperative.

Studies on the Selectivity Between O-Alkylation versus C-Alkylation of Phenol with Cyclohexene Using Nanocrystalline Beta Zeolite

The alkylation of phenol with cyclohexene using acid catalysts results in the generation of both O-alkylated and C-alkylated products, all of which hold significant utility across diverse industries. Cyclohexyl phenyl ether is utilized as a fragrant compound in perfumery applications. Through dehydrogenation, it transforms into diphenyl oxide (DPO), a significant chemical intermediate. In the current research nanocrystalline zeolite Beta was synthesised by vacuum-concentration coupled hydrothermal technique using tetraethyllammonium hydroxide templates and the catalytic performance was analysed for the alkylation of phenol with cyclohexene. Various parameters like reactant mole ratio, catalyst amount and temperature were assessed for better conversion of cyclohexene and desired product selectivity. The findings demonstrate that the catalyst effectively improves the conversion of cyclohexene while enhancing the selectivity of desired products. High efficiency of the catalyst is attributed due to its favourable structural characteristics, including its nano sized particles with open pore structure. The catalyst displayed up to ~96% conversion of cyclohexene ~55% selectivity towards the major product, cyclohexyl phenyl ether at optimal reaction conditions. Activation energy of the phenol alkylation with cyclohexene was calculated from the measured rate constant at various temperatures and was found to be 22.9 kJ/mol. There is negligible decline in percent conversion after reusing the catalyst for up to five runs.

High throughput screening of promoted bimetallic catalysts supported on alumina for production of light olefins via Fischer-Tropsch synthesis with artificial neural network and response surface methodology

The production of light olefins via Fischer-Tropsch Synthesis (FTS) was investigated by both experimental and modeling studies. Experimental studies were conducted by employing promoted FeCo/α-Al2O3 (FeCo) bimetallic catalysts. The Response Surface Methodology (RSM) and Artificial Neural Network (ANN) methods were used in modeling. Specifically, effects of the types and concentration of promoters on the catalytic performances of α-Al2O3 supported iron-cobalt bimetallic catalysts are investigated by using Ce, Ni, La, Ho, Ga Cu, Mn, and Zn used as promoters. A total of 49 catalysts were prepared by co-impregnation method and tested at 310 °C and 1 bar in a high-speed catalyst performance test system (HT-CPA). The FTS performances of catalysts showed that both the types and amounts of the promoters can affect light olefin production. The light olefin (C2=–C3=) production of unpromoted FeCo catalyst was about 3.87 × 10−3 (mol C/g active metal. h). The best performances were obtained from FeCo catalysts promoted with Ho, Cu, and Zn. Presence of these promoters increased olefin production up to ∼ 84 %, 76 % and 70 %, respectively.Performance parameters (MSE and R2) of RSM and ANN models revealed that both methods can be used to support experimental studies and provide a procedure for optimizing catalyst formulations yielding the desired product selectivity in FTS processes. The RSM outcomes aligned with experimental findings, suggest that that Ho, Cu, and Zn can serve as suitable promoters for the light olefin production in FTS. ANN model attained higher performance parameters (R2 = 0.95 and MSE = 2E−7) than RSM model (R2 = 0.85 and MSE = 3.4E−7). This indicates that ANN model, which designed as one hidden layer including 7 neurons, can provide better predictions and a fitting capacity. Therefore, it may be used in further optimization and sensitivity analysis approaches. Alignment degree between the experimental and modeling results demonstrates that the proposed methodology can provide a reliable and efficient way to guide experiments to optimize catalyst formulations through identification of potential promoters and their amounts to be used.

A lost piece of the puzzle of the alkane cracking mechanism: a carbanion pathway on a solid base catalyst.

The alkane cracking mechanism has been a subject of intense scrutiny, with carbonium and free radical mechanisms being two well-established pathways which correlate to solid acid catalysis and thermal cracking, respectively. However, despite an understanding of these two mechanisms, certain intricacies remain unexplored, especially when it comes to alternative reaction routes over solid base materials. This gap in the knowledge hinders optimization of the desired product selectivity of alkane cracking processes. In this work, solid superbases were first prepared by impregnation of NaNO3 on MgO. The Na/MgO catalysts were characterized by XRD, BET, XPS and CO2-TPD techniques. To investigate the role of solid base materials, propane cracking was conducted over MgO and Na/MgO. SiO2 was chosen as a representative of thermal cracking. Na/MgO showed better selectivity for light olefins than MgO or SiO2. Ethylene and light olefin selectivity could reach about 65.8% and 91.7%, respectively. Meanwhile, in terms of Na/MgO, the ratio of ethylene selectivity and propylene selectivity is greater than 2, exhibiting the advantage of selectivity for ethylene, which is obviously different from MgO and SiO2. Propane cracking over Na/MgO with different loading amounts of NaNO3 was investigated further. The conversion rates of the samples presented a "volcano curve" with increasing Na content. Furthermore, DFT calculation showed that the base-catalyzed process of the propane cracking reaction follows a carbanion mechanism. The better product distribution and stronger surface base sites can be ascribed to charge transfer arising from the loading of NaNO3.

The sub-nanometer In2O clusters on Ag nanoparticles with highly selective electrochemical CO2 reduction to formate

Electrochemical CO2 reduction (ECR) is a potential route for establishing a carbon–neutral economy. Despite notable breakthroughs, designing a catalytic system with desired product selectivity remains a formidable challenge. Herein, we demonstrate a novel nanoarchitecture comprising sub-nanometer In2O3 clusters on Ag nanoparticles (henceforth denoted as Ag2-In8/C) for highly selective formate (HCOOH) production in ECR. As-prepared Ag2-In8/C NC with the Ag/In atomic ratio of 2/8 achieved the formate faradaic efficiency (FEHCOOH) of as high as 95.5 % at −0.9 VRHE with no obvious degradation after 7 h, surpassing the monometallic counterparts (Ag/C and In2O3/C) in selectivity and activity. The in-situ X-ray absorption spectroscopy reveals the formation of sub-nanometer In2O clusters (i.e. Indium changed its phase from In2O3 to In2O) on Ag nanoparticles under potential-driven conditions, where the high activity and selectivity of Ag2-In8/C NC originates from the robust synergistic cooperation between Ag and In2O domains at the Ag-In2O interface, underscoring its role as the active site for highly selective ECR. Moreover, an amalgamation of the physical and electrochemical analysis suggests that In2O clusters assist *OCHO formation on the surface of Ag2-In8/C NC during ECR and thus pronounced formate selectivity is achieved. In light of our findings, this study promises to unravel intricate mechanistic insights, thus paving the way for the rational design of exceptionally selective catalysts for ECR.

Amorphous antimony oxide as reaction pathway modulator toward electrocatalytic glycerol oxidation for selective dihydroxyacetone production

Achievement of an efficient and stable electrocatalytic glycerol oxidation reaction (EGOR) is limited by a lack of strategies for designing advanced electrocatalysts that satisfy the desired product selectivity, high electrocatalytic activity, and stability. Here, we report that the reaction pathway of EGOR can be modulated by the incorporation of amorphous antimony oxide (SbOx) on the surface of a Pt nanoparticle electrocatalyst (SbOx-Pt), which creates highly selective glycerol oxidation to dihydroxyacetone (DHA), one of the most valuable products of EGOR. The selective control of adsorption behaviors of glycerol oxidation products allows for SbOx to act as a reaction pathway modulator. Moreover, SbOx deposition on a Pt surface also enhances the stability, electrocatalytic activity, and glycerol conversion of the Pt electrocatalyst, and thus promotes the EGOR. As a result, the SbOx-Pt electrocatalyst achieves a high DHA selectivity of 81.1%, which is about 11 times higher than that of commercial Pt/C electrocatalysts.

Progress in Electrodeposited Copper Catalysts for CO2 Conversion to Valuable Products

Carbon capture, utilisation and storage (CCUS) is a key area of research for CO2 abatement. To that end, CO2 capture, transport and storage has accrued several decades of development. However, for successful implementation of CCUS, utilisation or conversion of CO2 to valuable products is important. Electrochemical conversion of the captured CO2 to desired products provides one such route. This technique requires a cathode “electrocatalyst” that could favour the desired product selectivity. Copper (Cu) is unique, the only metal “electrocatalyst” demonstrated to produce C2 products including ethylene. In order to achieve high-purity Cu deposits, electrodeposition is widely acknowledged as a straightforward, scalable and relatively inexpensive method. In this review, we discuss in detail the progress in the developments of electrodeposited copper, oxide/halide-derived copper, copper-alloy catalysts for conversion of CO2 to valuable products along with the future challenges.

Intrinsic Charge Polarization in Bi19 S27 Cl3 Nanorods Promotes Selective CC Coupling Reaction during Photoreduction of CO2 to Ethanol.

Obtaining multi-carbon products via CO2 photoreduction is a major catalytic challenge involving multielectron-mediated CC bond formation. Complex design of multicomponent interfaces that are exploited to achieve this chemical transformation, often leads to untraceable deleterious changes in the interfacial chemical environment affecting CO2 conversion efficiency and product selectivity. Alternatively, robust metal centers having asymmetric charge distribution can effectuate CC coupling reaction through the stabilization of intermediates, for desired product selectivity. However, generating inherent charge distribution in a single component catalyst is a difficult material design challenge. Here, a novel photocatalyst, Bi19 S27 Cl3 , is presented which selectively converts CO2 to a C2 product, ethanol, in high yield under visible light irradiation. Structural analysis through transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and X-ray absorption spectroscopy reveals the presence of charge polarized bismuth centers in Bi19 S27 Cl3 . The intrinsic electric field induced by charge polarized bismuth centers renders better separation efficiency of photogenerated electron-hole pair. Furthermore, charge polarized centers yield better adsorption of CO* intermediate and accelerate the rate determining CC coupling step through the formation of OCCOH intermediate. Formation of these intermediates is experimentally mapped by insitu Fourier-transform infrared spectroscopy and further confirmed by theoretical calculation.

Chemicals Production from Glycerol through Heterogeneous Catalysis: A Review

Utilization of biofuels generated from renewable sources has attracted broad attention due to their benefits such as reducing consumption of fossil fuels, sustainability, and consequently prevention of global warming. The production of biodiesel causes a huge amount of by-product, crude glycerol, to accumulate. Glycerol, because of its unique structure having three hydroxyl groups, can be converted to a variety of industrially valuable products. In recent decades, increasing studies have been carried out on different catalytic pathways to selectively produce a wide range of glycerol derivatives. In the current review, the main routes including carboxylation, oxidation, etherification, hydrogenolysis, esterification, and dehydration to convert glycerol to value-added products are investigated. In order to achieve more glycerol conversion and higher desired product selectivity, acquisition of knowledge on the catalysts, the type of acidic or basic, the supports, and studying various reaction pathways and operating parameters are necessary. This review attempts to summarize the knowledge of catalytic reactions and mechanisms leading to value-added derivatives of glycerol. Additionally, the application of main products from glycerol are discussed. In addition, an overview on the market of glycerol, its properties, applications, and prospects is presented.

Hydrotalcite-derived Ni-LDO catalysts via new approach for enhanced performances in CO2 catalytic reduction

In this work, hydrotalcite-derived new Ni-LDO catalysts were synthesized via sequenced precipitation, for CO2 catalytic reduction to synthetic natural gas (SNG) with high performances, while the traditional sample via coprecipitation was prepared and measured as the comparison. By regulating precipitation procedure, a significant performance enhancement was attained, in which the CO2 conversion rate per gram nickel was 7-times higher than that of the conventional comparison, at the temperature of 573 K and atmospheric pressure. In addition, the desired product selectivity is up to 99%. Structural characterizations proved that the as-synthesized catalysts showed layered meso-porous properties. An increasing Ni particle size and higher coverage of medium-strong basic sites was observed over the optimized catalyst sample prepared when part of Mg2+ and Al3+ were precipitated at first step. Catalyst surface nickel enrichment and promoted reducibility were also achieved when using sequenced precipitation. This work achievements provided a new route for surface nickel enrichment of much more active hydrotalcite-derived Ni-LDO layered catalysts for enhanced performances.

Metal-exchanged phosphotungstate nanoparticles with improved acidity as the catalyst for esterification of glycerol with acetic acid

Abstract A series of metal-exchanged phosphotungstate salts, Fe-TPA, Cr-TPA, Cu-TPA, and Ni-TPA were synthesized by sonication and tested for glycerol esterification with acetic acid to obtain biofuel additives. A systematic, chemical, structural, and morphological characterization and determination of acidity were used by various analytical techniques. XRD and FT-IR studies confirmed the Keggin structure of all metal exchanged phosphotungstate salts with no impurities coming from metal nitrate salts. The incorporation of metal cations in phosphotungstic acid leads to decreased crystallite size as seen from XRD diffractograms. N2 adsorption-desorption analysis showed that the Type II isotherms were obtained for all metal exchanged phophostungstate salts, characteristic of non-porous or macroporous materials. SEM images of metal exchanged phosphotungstate salts displayed well-shaped crystalline particles. SEM-EDX analysis showed that the calculated tungsten metal ratios are in good agreement with the theoretical ratios of those for all the metal exchanged salts, verified by XRF results. The exchange of protons by the metal cations improved the thermal stability observed in the TGA analysis. The acidity strengths, from NH3-TPD analysis, were found in the following order; TPA > Fe-TPA > Cr-TPA > Cu-TPA. Additionally, pyridine-FTIR gives that the exchanging of transition metal into the phosphotungstic acid decreased the Brønsted acidity while increasing the Lewis acidity and this mostly affects the efficiency of the esterification reaction. The activity of metal exchanged salts was in the given order; Fe-TPA > Cr-TPA > Cu-TPA > Ni-TPA. Among these Fe-TPA salt, having a good ratio of Brønsted and Lewis acidity, have the selectivity for di- and triacetin (68 and 10%), with the highest conversion (96%). The iron phosphotungstate salts are a promising catalyst with sustainable Bronsted acidity during the reaction, high desired product selectivity at low temperature, easy synthesizability, inexpensive, and environmentally friendly.

A Heuristic Approach to Linking Experimental Descriptors with Product Selectivity in Electrochemical CO2 Reduction.

An important challenge in electrochemical CO2 reduction (ECR) is relating experimental conditions to their consequences, particularly in terms of product selectivity. The problem lies in the lack of descriptors which adequately describe the experimental protocols and their associated results. In this study, a machine learning approach is applied to correlate the molar composition of 21 single metals and 23 bimetallic particles, as well as operating parameters, from a large collection of synthetic records compiled from the literature with product selectivity. The decision tree obtained shows the conditions that lead to high desired product selectivity and provides a heuristic insight into its electrochemistry. As such, the data does not provide details. However, machine learning algorithms are capable of identifying hidden patterns in the data, providing a deeper insight into the chemistry involved in product formation in the ECR.

Fe Nanoparticle Size Control of the Fe-MOF-Derived Catalyst Using a Solvothermal Method: Effect on FTS Activity and Olefin Production.

The design of a highly active Fe-supported catalyst with the optimum particle and pore size, dispersion, loading, and stability is essential for obtaining the desired product selectivity. This study employed a solvothermal method to prepare two Fe-MIL-88B metal–organic framework (MOF)-derived catalysts using triethylamine (TEA) or NaOH as deprotonation catalysts. The catalysts were analyzed using X-ray diffraction, N2-physisorption, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, H2 temperature-programed reduction, and thermogravimetric analysis and were evaluated for the Fischer–Tropsch synthesis performance. It was evident that the catalyst preparation in the presence of TEA produces a higher MOF yield and smaller crystal size than those produced using NaOH. The pyrolysis of MOFs yielded catalysts with different Fe particle sizes of 6 and 35 nm for the preparation in the presence of TEA and NaOH, respectively. Also, both types of catalysts exhibited a high Fe loading (50%) and good stability after 100 h reaction time. The smaller particle size TEA catalyst showed higher activity and higher olefin yield, with 94% CO conversion and a higher olefin yield of 24% at a lower reaction temperature of 280 °C and 20 bar at H2/CO = 1. Moreover, the smaller particle size TEA catalyst exhibited higher Fe time yield and CH4 selectivity but with lower chain growth probability (α) and C5+ selectivity.

CO2 Electroreduction on Mono- and Bi-Metallic M-N-C Catalysts

The production of syngas by traditional processes such as steam methane reforming is energetically expensive and leads to substantial CO2 emissions. This strongly motivates the development of CO2 electroreduction at ambient conditions. As a family of non-precious metal catalysts, transition metal-nitrogen-carbon electrocatalysts are cost effective and highly selective towards syngas production1,2. In this presentation, we will show our current research into mono and bi-metallic nitrogen-doped carbon (M-N-C, M = Fe, Mo or FeMo) electrocatalysts for syngas production. The electrocatalyst composition (i.e. the Fe:Mo ratio in the bimetallic electrocatalyst) was tuned, in combination with the potential applied, to control the selectivity and therefore the electrocatalyst’ ability to generate syngas. We show that a higher ratio of iron to molybdenum leads to an increase in selectivity to CO over H2 production. We show a greatly improved production rate for CO using traditional Fe-N-C which maxes out at a CO partial current density higher than that of commercial Ag nanoparticles (jco= -30.9 mA/cm2 geo at -1.1 VRHE) using a custom-built flow cell. The difficulties and importance of considering intrinsic catalytic activity is stressed to compare electrocatalytic activity. Apart from catalyst composition, reaction conditions can also substantially alter the electrochemical CO2/H2O co-electrolysis3. The catalyst composition can be used as an engineering control for the desired product selectivity by using a variable precursor metallic ratio in bi-metallic M-N-C catalysts. Potential control may be used alongside variations in reaction conditions for the dynamic control over the selectivity to syngas. Reference Delafontaine, L., Asset, T., & Atanassov, P. (2020). Metal–Nitrogen–Carbon Electrocatalysts for CO 2 Reduction towards Syngas Generation. ChemSusChem, 13(7), 1688–1698. Varela, A. S., Ranjbar Sahraie, N., Steinberg, J., Ju, W., Oh, H.-S., & Strasser, P. (2015). Metal-Doped Nitrogenated Carbon as an Efficient Catalyst for Direct CO2Electroreduction to CO and Hydrocarbons. Angewandte Chemie, 127(37), 10908–10912. Pan, F., & Yang, Y. (2020). Designing CO2 reduction electrode materials by morphology and interface engineering. Energy & Environmental Science, 13(8), 2275–2309. Figure 1

MCM-41 Supported Co-Based Bimetallic Catalysts for Aqueous Phase Transformation of Glucose to Biochemicals

The transformation of glucose into valuable biochemicals was carried out on different MCM-41-supported metallic and bimetallic (Co, Co-Fe, Co-Mn, Co-Mo) catalysts and under different reaction conditions (150 °C, 3 h; 200 °C, 0.5 h; 250 °C, 0.5 h). All catalysts were characterized using N2 physisorption, Temperature Programmed Reduction (TPR), Raman, X-ray Diffraction (XRD) and Temperature Programmed Desorption (TPD) techniques. According to the N2-physisorption results, a high surface area and mesoporous structure of the support were appropriate for metal dispersion, reactant diffusion and the formation of bioproducts. Reaction conditions, bimetals synergetic effects and the amount and strength of catalyst acid sites were the key factors affecting the catalytic activity and biochemical selectivity. Sever reaction conditions including high temperature and high catalyst acidity led to the formation mainly of solid humins. The NH3-TPD results demonstrated the alteration of acidity in different bimetallic catalysts. The 10Fe10CoSiO2 catalyst (MCM-41 supported 10 wt.%Fe, 10 wt.%Co) possessing weak acid sites displayed the best catalytic activity with the highest carbon balance and desired product selectivity in mild reaction condition. Valuable biochemicals such as fructose, levulinic acid, ethanol and hydroxyacetone were formed over this catalyst.

Design of Efficient Noble Metal Free Copper‐Promoted Nickel‐Ceria‐Zirconia Nanocatalyst for Bio‐Fuel Upgrading

AbstractA new series of noble metal free bimetallic Cu−Ni supported ceria‐zirconia catalysts (Cu−Ni/CZ) has been developed with various Cu/Ni ratios by a simple co‐precipitation/impregnation method. Aqueous‐phase hydrodeoxygenation (HDO) of vanillin a typical compound of lignin‐derived bio‐oil, in promoting biomass refining was carried out to investigate catalytic performances under 25 bar of H2 pressure at 160oC. All the as‐synthesized catalysts were thoroughly characterised employing powder XRD, Raman spectroscopy, H2‐TPR, HR‐TEM, HAADF‐STEM, EDS Mapping, and XPS. It was found that 15 wt% Cu on Ni/CZ (Cu−Ni/CZ−B) nanocomposite enhanced activity significantly in comparison with other bimetallic or monometallic catalysts, exhibiting ∼98% of vanillin conversion and ∼94% of selectivity toward 2‐methoxy‐4‐methylphenol as a desired product. The Cu−Ni/CZ−B catalyst shows ∼4‐fold increase in activity compared with Cu−Ni/CeO2 and Cu−Ni/ZrO2, the mono oxide supported counterparts. The superior catalytic performance with improved stability were explained by synergistic effects at the interfaces of each species, in which electron interactions between Ni, Cu, and ceria‐zirconia support generated novel active sites. XRD and HR‐TEM revealed that Cu−Ni bimetallic phases were created on the ceria‐zirconia, which were responsible for enhancement of catalytic performance with no significant drop in catalytic activity with desired product selectivity for eleven successive catalytic cycles demonstrating the excellent stability and reproducibility of this catalyst system.

Preparation of a hydrophobic-hydrophilic adjustable catalyst surface for the controlled synthesis of polyoxymethylene dimethyl ethers: A potential replacement of diesel fuel

Polyoxymethylene dimethyl ethers (PODE) are excellent promising diesel oil additives or replacements because of the special structure without carbon-carbon bond. A novel solid dichlorodiphenylsilane-modified ZrO2–γ-Al2O3 catalyst with both hydrophobic and hydrophilic sites exhibited good catalytic activity and desired product selectivity for the reaction of methanol and formaldehyde aqueous solution to PODE. A single type of active center (only hydrophobic center or hydrophilic center) did not perform well for the PODE synthesize reaction from methanol and formaldehyde because of the different hydrophobic properties of methanol, formaldehyde, methylal, and PODE. The experimental results confirmed that the hydrophobic sites and hydrophilic sites of the catalyst surface promote the synthesis of PODE and methylal, respectively. The enhancement of the hydrophobic property of the catalyst surface promotes the production of long chain PODE. Further study indicated that the product distribution can be controlled artificially by adjusting the content of hydrophobic agent, and the desired polymerization degree of PODE can be optimally synthesized by a modified catalyst (called HYB-26.9@ZrO2–γ-Al2O3). Reaction temperature and pressure were also investigated for the PODE synthesis reaction with this modified catalyst, HYB-26.9@ZrO2–γ-Al2O3. Low reaction temperature benefits the synthesis of long chain PODE because of the limit of reaction equilibrium. The stability of the catalyst was proven by a 240-hour running test.