Continuous-flow Fixed-bed Micro-reactor Research Articles

Tailored design of novel Co0-Coδ+ dual phase nanoparticles for selective CO2 hydrogenation to ethanol

Catalytic hydrogenation of CO2 to ethanol is a promising solution to address the greenhouse gas (GHG) emissions, but many current catalysts face efficiency and cost challenges. Cobalt based catalysts are frequently examined due to their abundance, cost-efficiency, and effectiveness in the reaction, where managing the Co0 to Coδ+ ratio is essential. In this study, we adjusted support nature (Al2O3, MgO-MgAl2O4, and MgO) and reduction conditions to optimize this balance of Co0 to Coδ+ sites on the catalyst surface, enhancing ethanol production. The selectivity of ethanol reached 17.9% in a continuous flow fixed bed micro-reactor over 20 mol% Co@MgO-MgAl2O4 (CoMgAl) catalyst at 270 °C and 3.0 MPa, when reduced at 400 °C for 8 h. Characterisation results coupled with activity analysis confirmed that mild reduction condition (400 °C, 10% H2 balance N2, 8 h) with intermediate metal support interaction favoured the generation of partially reduced Co sites (Coδ+ and Co0 sites in single atom) over MgO-MgAl2O4 surface, which promoted ethanol synthesis by coupling of dissociative (CHx*)/non-dissociative (CHxO*) intermediates, as confirmed by density functional theory analysis. Additionally, the CoMgAl, affordably prepared through the coprecipitation method, offers a potential alternative for CO2 hydrogenation to yield valuable chemicals.

Preparation of Pt/CeL reforming catalyst and its performance in the aromatization of naphtha

To solve the problems of chlorine loss and equipment corrosion caused by the conventional alumina-type reforming catalyst, zeolite L was modified with Ce3+ by ion exchange method and with Ce3+-modified L (CeL) as the support, the Pt/CeL reforming catalyst without any chlorine was prepared by impregnation method. The CeL support and Pt/CeL catalyst were characterized by XRD, N2 adsorption-desorption, NH3-TPD and Py-FTIR; the catalytic performance of Pt/CeL in aromatization was investigated in a continuous-flow fixed-bed micro-reactor, with an industrial hydrofining naphtha containing 0.50 μg/mL sulfur as the feedstock. The results indicate that the modification with Ce3+ by ion exchange has little influence on framework structure of zeolite L; however, it can raise the acid content and acid strength of the CeL support and then remarkably enhance the performance of the Pt/CeL reforming catalyst in aromatization. The activity and selectivity of the Pt/CeL catalyst are comparable to those of the commercial alumina-type reforming catalysts, suggesting that proper acidity can facilitate the aromatization reaction.

Sustainable superior function of the synthesized NixCo1-xFe2Oz nanosphere on the destruction of chlorinated biphenyls in the effluent

NixCo1-xFe2Oz composite oxide nanosphere was successfully prepared, to degrade 2-monochlorobiphenly (CB-1) in continuous-flow fixed-bed microreactor at GHSV of 20000h−1. The five cycles of temperature-dependent run experiments between 150 and 350°C showed its superior activity with a CB-1 conversion of more than 95% above 300°C over Ni0.5Co0.5Fe2Oz. Importantly, the sustainable higher reactivity could be observed over prolonged 600min reaction times after the 5th run test. The degradation products detected as biphenyl and monochlorobenzene with yield ratio of 129, account for 0.24% and 0.0011% of initial CB-1 respectively. This indicated the weak occurrence of hydrodechlorination and breakage of CC bridge bond during the degradation of CB-1. The possibly dominant occurrence of oxidative degradation probably follows Mars–van Krevelen mechanism, resulting in the generation of the formic, acetic, propanoic and butyric acids and so on. Due to the high oxygen mobility over Ni0.5Co0.5Fe2Oz nanosphere, the consumed oxygen species could be compensated rapidly by the gas phase oxygen via O2→O2− → 2O− → 2O2−. The interaction among different elements in Ni0.5Co0.5Fe2Oz nanosphere confirmed by the derivation of the electron cloud, enhanced the mobility of the reactive oxygen species, which would be beneficial for the oxidation of chlorinated biphenyls.

Hydrothermal Synthesis, Crystal Structure, and Catalytic Performance of Four Organic–Inorganic Hybrids Based on Polyoxometalates and O/N-Containing Groups

Four new network organic–inorganic hybrid supramolecular compounds [PW12O40](C2H4N3)3·6H2O (1), [PMo12O40](C2H4N3)3·6H2O (2), [H4SiW12O40]8[C6NO2H4]4[C6NO2H5]16[C5NH6]4·39H2O (3) and [H3VW12O40] (C6H6NO2)2(CHO2)2·4H2O (4) composed by keggin type heteropolyanion and O/N-containing organic groups of 1H-1,2,4-Triazole or 2,3-Pyridinedicarboxylic acid have been successfully synthesized by hydrothermally method, and characterized by infrared spectrum (IR), thermogravimetric–differentialthermal analysis (TG–DTA), cyclic voltammetry (CV) and single crystal X-ray diffraction (XRD). Compounds 1–4 exhibit three dimensional supramolecular network via hydrogen bonds and/or π–π stacking interactions. These compounds exhibit good thermal stability and catalytic ability. They are active for catalytic oxidation of methanol in a continuous-flow fixed-bed micro-reactor, when the initial concentration of methanol is 2.5 g m−3 in air and flow rate is 10 mL min−1, the corresponding elimination rates of methanol are 65% (125 °C), 85% (125 °C), 94% (150 °C), and 80% (125 °C), respectively.

For Better Industrial Cu/ZnO/Al2O3 Methanol Synthesis Catalyst: A Compositional Study

A series of industrial related Cu/ZnO/Al2O3 methanol catalysts with different compositions were prepared by parallel coprecipitation method at neutral condition. The structural properties were characterized through BET, XRD, TEM, TPD and TPR, and the catalytic performances were evaluated on a 4-tube stainless steel continuous flow fixed-bed microreactor. The influence of composition on performances was investigated. The results show that Al2O3 increases the long-term stability of catalysts due to stabilizing effect, meanwhile, Al also promotes the formation of zincian malachite phase as the precursor during coprecipitation and aging. Furthermore, Al2O3 surface acidity also affects the byproducts selectivity. Cu/Zn ratio influences the activity of catalysts which could be traced back to precursor phases. ZnO also affects the long-term stability probably derived from its spacing effect. Taking activity, long-term stability and product purity all into consideration, an optimized composition was found to be with 2.8 ≤ n(Cu)/n(Zn) ≤ 3.0 and 10 ≤ n(Al) ≤ 12, over which the performances are better than that of commercial C307 catalyst in our experiments.

Catalytic performance of cerium modified Silicalite-1 molecular sieves in the conversion of methanol to propene

A series of cerium modified Silicalite-1 molecular sieves were prepared by incipient wetness impregnation and used as the catalysts in the conversion of methanol to propene (MTP). The cerium modified Silicalite-1 catalysts were characterized by X-ray diffraction (XRD), N2 sorption, pyridine adsorption Fourier transform infrared spectroscopy (Py-FTIR) and temperature-programmed desorption of NH3 (NH3-TPD); their catalytic performance in MTP was evaluated in a continuous flow fixed-bed micro-reactor at atmospheric pressure and 450°C, with a methanol weight hourly space velocity (WHSV) of 9.6 h−1. The results showed that Silicalite-1 exhibits superior catalytic performance in MTP in terms of catalytic stability and selectivity to propene, in comparison with the HZSM-5 zeolite with a SiO2/Al2O3 molar ratio of 200. The introduction of Ce can effectively adjust the acid properties and pore structure of Silicalite-1; modification with an appropriate concentration of Ce can reduce the amount of strong acid sites and then enhance the catalytic performance of Silicalite-1 in MTP. Over the cerium modified Silicalite-1 with a CeO2 content of 5.0%, the selectivity to propene is increased from 31.9% to 38.2% and the catalytic lifetime is extended from 51 to 72 h, in comparison with those over the parent Silicalite-1.

Syntheses, Crystal Structure, Characterization, and Properties of Two Novel Superamolecular Phosphotungstate-Pyridine Complexes

Two new inorganic-organic compounds constructed from phosphotungstate and pyridines have been synthesized under hydrothermal conditions. The formulas of the two compounds are (C5H7N2)3(C5H6N2)3(PW12O40)·2H2O (1) and (C6H8N)3(C6H7N)(PW12O40)·9H2O (2). They have been characterized by IR, UV-vis, TG-DTA, FL, CV, and single-crystal X-ray diffraction. The two compounds both show three-dimensional networks. These compounds exhibit good catalytic activity for catalytic oxidation of methanol over a continuous-flow fixed-bed microreactor, when the initial concentration of methanol is 5.37 g⋅m−3, and flow rate is 4.51 mL⋅min−1. 0.2 g compound 1 (or compound 2) as the catalyst can eliminate methanol completely at 150°C (175°C for compound 2).

Crystal Structure and Catalytic Elimination of Methanol from Two Novel Organic–Inorganic Hybrid Based on Silicomolybdenate, Silicotungstate and 2-Aminopyrimidine

Two new organic–inorganic hybrid, namely, (C4H7N3)2·(SiMo12O40)·(C4H5N3)2·(H2O)2 (1), (C4H7N3)2·(SiW12O40)·(C4H5N3)2·(H2O)2 (2) were synthesized by reaction of silicomolybdenate/silicotungstate and 2-aminopyrimidine and characterized by FT-IR, UV–vis, Fluorescence and single-crystal X-ray diffraction techniques. Compound 1 exhibit a two-dimensional supramolecular network via hydrogen bond interactions. Compound 2 show a three-dimensional supramolecular extended by two-dimensional pore structure constructed by the 2-aminopyrimidine molecules. Compound 1 emits green fluorescence and compounds 2 emits cyan fluorescence. The catalytic experimental results showed that compound 2 is active for catalytic oxidation of methanol in a continuous-flow fixed-bed micro-reactor, when the initial concentration of methanol is 5.37 g·m−3 in air and flow rate is 5 mL·min−1 at 90 °C, corresponding to the elimination rate of methanol is 53.09 % which is significant in environment protection.

Hydrodeoxygenation of methyl palmitate over MCM-41 supported nickel phosphide catalysts

In this paper, bulk and MCM-41-supported Ni2P catalysts were synthesized by the one-step direct reduction of metal phosphate precursors. The role of cations and anions in the synthesis of Ni2P was studied. Catalytic properties for the hydrodeoxygenation (HDO) of methyl palmitate were first investigated in a continuous-flow fixed-bed microreactor. The resulting catalysts were characterized using XRD, TEM, BET, XPS, and carbon monoxide chemisorption. Results indicated that Ni2P can be synthesized at 600°C from its phosphate precursors with a mole ratio of Ni/P=2/1. Based on the analytical result of GC-MS, we propose a possible HDO reaction mechanism for the HDO of methyl palmitate on MCM-41-supported nickel phosphide catalysts.

Bio-aviation fuel production from hydroprocessing castor oil promoted by the nickel-based bifunctional catalysts

Bio-aviation fuel was firstly synthesized by hydroprocessing castor oil in a continuous-flow fixed-bed microreactor with the main objective to obtain the high yield of aviation fuel and determine the elemental compositions of the product phases as well as the reaction mechanism. Highest aviation range alkane yields (91.6wt%) were achieved with high isomer/n-alkane ratio (i/n) 4.4–7.2 over Ni supported on acidic zeolites. In addition, different fuel range alkanes can be obtained by adjusting the degree of hydrodeoxygenation (HDO) and hydrocracking. And the observations are rationalized by a set of reaction pathways for the various product phases.

Crystal structure and catalytic properties of three inorganic–organic hybrid constructed from heteropolymolybdate and aminopyridine

Three new organic–inorganic hybrid compounds (2-C5H7N2)3·(SiMo12O40)·(C4H8N4)0.5·(C5H6N2)2·(H2O)2 (1), (3-C5H7N2)8·(SiMo12O40)2·(C5H7N3)2·(H8O4)·(H2O)8 (2) and (4-C5H7N2)6·(SiMo12O40) (3) composed the heteropolymolybdate α-H4SiMo12O40 and the organic substrate 2/3/4-aminopyridine have been hydrothermally synthesized and characterized by routine methods. Compounds 1 and 2 exhibit a three-dimensional supramolecular network via hydrogen bond and π–π stacking interactions. Compound 2 contains a tetramolecular water cluster which consists of four water molecules connected by hydrogen bonds. These compounds exhibit good thermal stability and photoluminescent phenomena. Compounds 1 and 3 are active for catalytic oxidation of methanol in a continuous-flow fixed-bed micro-reactor, when the initial concentration of methanol is 2.75gm−3 in air and flow rate is 10mLmin−1 at 150°C, corresponding to the elimination rate of methanol i.e. 87.7% and 76.8%, respectively.

Effects of Na<sup>+</sup> in Dilution Steam and Coke Deposition on Catalytic Performance of Methanol-to-Propylene Catalysts

The effects of Na~+ in dilution steam and coke deposition on the physicochemical properties and catalytic performance of ZSM-5 catalysts for the methanol-to-propylene(MTP) reaction were investigated. The deactivated and regenerated catalysts were characterized by means of X-ray diffraction(XRD), scanning electron microscopy(SEM),X-ray fluorescence(XRF) spectrum,nitrogen adsorption/desorption, temperature-programmed desorption of ammonia(NH_3-TPD),and thermogravimetry(TG).Their catalytic performance for MTP reaction was tested in a continuous flow fixed-bed micro-reactor at 470℃,101325 Pa,and with methanol weight hourly space velocity(WHSV) in the range of 1.0-3.0 h~(-1).The results indicated that the catalyst crystal structure and morphology was not significantly altered after 970 h on stream.In the MTP reaction,Na~+ in the dilution steam can easily enter the pore channels of the catalyst, and partially replace H protons,thereby gradually decreasing the amount of acidity and acid strength of the catalyst,which eventually causes deactivation.In addition,coke deposits on the catalyst surface blocking its micropores are the main reason for deactivation of the MTP catalyst.Coke deposits are mostly eliminated through the burning charcoal regeneration process.The effect of framework dealumination from the catalyst by steam in the MTP process is slow but more serious.Through regeneration and ion exchange process,the catalytic activity of the deactivated catalyst can be fully restored.The conversion of methanol is consistently above 99%,and propylene selectivity is greater than 46%even after 470 h on stream.With increasing reaction time,the propylene selectivity gradually increases,while ethylene selectivity gradually decreases.

Support and alloy effects on activity and product selectivity for ethanol steam reforming over supported nickel cobalt catalysts

Ni, Co and bimetallic Ni–Co catalysts supported on Ca-γ-Al2O3 and ZrO2 were investigated for the production of hydrogen via ethanol steam reforming (ESR). Catalysts were prepared by wet impregnation method and characterized using temperature-programmed reduction (TPR), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). ESR and temperature-programmed desorption of ethanol (ethanol-TPD) were carried out in a continuous flow fixed bed micro-reactor and the outlet gases were monitored by an on-line GC or MS. Ni is found to be more active for the C–C bond rupture than Co on both supports, Ca-γ-Al2O3 and ZrO2. Catalyst support plays very important roles for the ESR. Strong interaction between support and metal affects the formation of NiCo bimetallic compound, resulting in the variety of catalytic activity. On Ca-γ-Al2O3 support, the catalytic activity of ESR follows the sequence of 10%Ni > 6.7%Ni 3.3%Co ∼ 3.3%Ni 6.7%Co > 10%Co. On ZrO2, the trend is 10%Ni > 6.7%Ni 3.3%Co > 10%Co > 3.3%Ni 6.7%Co. The H2O adsorption/activation ability of the support determines the reaction pathway and thus the product selectivity. On Ca-γ-Al2O3, water gas shift reaction is more favorable than on ZrO2, due to the availability of surface OH groups. The roles of the metal and support for ESR are also discussed.

Three new organic–inorganic hybrids based on Keggin ions and aminopyridine: Crystal structure and catalytic property

Three new organic–inorganic supramolecular hybrids, namely, (2-C5H7N2)4(PMo12O40)2·(2-C5H6N2)6·(C4H8N4)·H2O (compound 1), (3-C5H7N2)6·(PMo12O40)2·(3-C5H6N2)4·H8O4·(H2O)8 (compound 2), (4-C5H7N2)6(PMo12O40)2·(4-C5H6N2)4·(C4H6N3) (compound 3), have been synthesized by hydrothermal method and characterized by elemental analyses, IR, UV–vis, TGA and single-crystal X-ray diffraction. Compound 1–3 constructed from Keggin polyoxoanions and 2-/3-/4-aminopyridine organic ligands, exhibit an extended three-dimensional supramolecular network via hydrogen bonding and π–π stacking interactions, while compound 2 contains a tetramolecular water clusters. compounds 1 and 3 have a higher catalytic activity for the oxidation of acetone tested in a continuous-flow fixed-bed micro-reactor. When the initial concentration of the acetone is 6.1 g m−3 in air and the flow velocity is 4.5 mL min−1, the acetone is completely eliminated at 160 °C. But compound 2 has lower catalytic activity for the oxidation of acetone.

The effect of crystal sizes of HZSM-5 zeolites in ethanol conversion to propylene

Abstract Three ZSM-5 zeolites with different crystal sizes were prepared and characterized by SEM, XRD, adsorption/desorption of N 2 , NH 3 -TPD, Py-IR and TG-DTA techniques. The results show that the acidic properties of HZSM-5 catalysts are very similar, but their textual properties are strongly influenced by crystal size. Their catalytic performances for the ethanol conversion to propylene were investigated in a continuous flow fixed-bed micro-reactor. In comparison with the large-sized HZSM-5, the small-sized HZSM-5 shows higher propylene selectivity and better stability, which reveals that decreasing the crystal size of zeolite is of benefit to ethanol conversion to propylene.

Crystal Structure and Catalytic Properties of (C6H8N)3[PMo12O40

The 4-picolinium salt (C6H8N)3[PMo12O40] was synthesized hydrothermally and characterized by IR spectroscopy, TG-DTA data and single-crystal X-ray diffraction. The results indicate that the compound consists of a [PMo12O40]3− heteropolyoxoanion and 4-picolinium cations [C6H8N]+. A supramolecular structure is formed via intermolecular hydrogen-bonding between the different structural units. Crystal data: monoclinic, space group P21/c, a = 19.7004(3), b = 14.0785(2), c = 33.0209(5) Å, β = 91.3590(10)°, V = 9155.8(2) Å3, Z = 8, wR2 = 0.0730. (C6H8N)3[PMo12O40] has a high catalytic activity for the oxidative elimination of acetone from gases as tested in a continuousflow fixed-bed micro-reactor. When the initial concentration is 5.2 gm−3 in air, and the flow rate is 3.3 mLmin−1, 93% of the acetone is eliminated at 70 °C.

A novel Anderson-type polyoxometalate: hydrothermal synthesis, crystal structure, and catalytic performance of (H3O)[(3-C5H7N2)2(Cr(OH)6Mo6O18)] · 3H2O

A new Anderson polyoxometalate (H3O)[(3-C5H7N2)2(Cr(OH)6Mo6O18)] · 3H2O (3-C5H6N2 = 3-aminopyridine) was hydrothermally synthesized and structurally characterized by single-crystal X-ray diffraction. Crystal data: triclinic, P 1, a = 7.8482(8) Å, b = 10.1800(10) Å, c = 10.4103(10) Å, α = 88.031(3)°, β = 78.308(2)°, γ = 88.842(3)°, V = 813.91 Å3, Z = 1, R(F) = 0.0397, wR ref(F 2) = 0.1022, and S = 1.076. The X-ray crystallographic study showed that the structure contains Anderson-type [Cr(OH)6Mo6O18]3− polyoxoanions. The title compound has high catalytic activity for the oxidation of acetone tested in a continuous-flow fixed-bed micro-reactor. When the initial concentration is 18.3 g m−3 in air and the flow velocity is 8.5 mL min−1, the acetone is completely eliminated at 160°C.

Effect of Cerium Addition on the Catalytic Performance of Cu-Fe/SiO<sub>2</sub> for the Synthesis of Lower Alcohols from Syngas

A series of Ce-Cu-Fe/SiO2 catalysts with different Ce contents (mole fraction relative to SiO2, 0-20%) were prepared by co-impregnation and their catalytic performances for CO hydrogenation to lower alcohols were investigated using a continuous flow fixed bed micro-reactor. These catalysts were characterized by X-ray diffraction (XRD), N2-adsorption, temperature-programmed reduction of H2 (H2-TPR), Fourier transform infrared of CO adsorption (CO-FTIR), and temperature-programmed desorption of CO (CO-TPD). The results showed that the addition of an appropriate amount of Ce decreased the Cu crystal size and promoted the dispersion of Cu, which greatly increased the amount of adsorbed CO. Additionally, the interaction of doped Ce with Cu increased the associative and dissociate adsorption capacity of CO, which is favorable for the formation of CHx and the insertion reaction of adsorbed CO to CHx. Both the activity and alcohol selectivity of the Cu-Fe/SiO2 catalyst increased under the combined effect of the above-mentioned two aspects. At a Ce content of 10%, the space time yield of lower alcohols improved from 58.0 g·kg - 1 ·h - 1 over the Cu-Fe/SiO2 catalyst to 121.0 g·kg - 1 ·h - 1 over the Ce-Cu-Fe/SiO2 catalyst at 250 °C, a pressure of 3.0 MPa, a H2/CO molar ratio of 2, and gas hourly space velocity of 6000 mL·g - 1 ·h - 1 .

Effect of Alumina Support on the Formation of the Active Phase of Selective Hydrodesulfurization Catalysts Co-Mo/Al2O3

Two different commercial alumina supports were used for the preparation of selective hydrodesulfurization (HDS) catalysts Co-Mo/Al 2 O 3 . The effect of support properties on the HDS activity and selectivity of the corresponding Co-Mo catalysts were studied by X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy, scanning transmission electron microscopy-energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. The HDS activity and selectivity were measured using a continuous flow fixed-bed microreactor. The Al 2 O 3 support with higher crystallinity and fewer hydroxyl groups had a moderate metal-support interaction, which resulted in an increase of the average slab length and stacking number of MoS 2 . This gave more formation of the active CoMoS phase and an increase in HDS activity and selectivity. ：以两种商用 Al 2 O 3 为载体, 制备了汽油选择性加氢脱硫催化剂 Co-Mo/Al 2 O 3 , 并采用红外光谱、X 射线衍射、N 2 吸附-脱附、透射电镜、扫描透射-能谱和 X 射线光电子能谱等手段系统研究了载体物化性质对催化剂活性相形成的影响. 结果表明, 表面羟基数量少和结晶程度高的载体与活性金属间相互作用减弱, 促进了 Mo 物种的硫化还原, 使 MoS 2 片晶的尺寸和层数增加, 且其硫化态催化剂上 CoMoS 活性位更多, CoMoS/MoS 2 比更大, 因而显著提高了相应 Co-Mo 催化剂加氢脱硫活性和选择性. An Al 2 O 3 support with higher crystallinity and fewer hydroxyl groups has a moderate metal-support interaction that increased the slab length and stacking number of MoS 2 , which gave more formation of the active CoMoS phase and an increase in Hydrodesulfurization activity and selectivity.

Hydrothermal Synthesis, Crystal Structure and Catalytic Properties of a Novel Polyoxometalate: (C5H7N2)3(AsMo12O40) ·2C5H6N2 · 1.5H2O

(C5H7N2)3(AsMo12O40)・2C5H6N2・1.5H2O was hydrothermally synthesized and structurally characterized by single-crystal X-ray diffraction. Crystal data: monoclinic, P21/n, a = 13.310(3), b = 22.399(5), c = 19.820(4) A° , β = 99.99(3) ◦, V = 5819(2) °A3, Z = 1, wR(F2) = 0.1345. The structure consists of Keggin-type [AsMo12O40]3− polyoxoanions. The title compound has a high catalytic activity for the oxidation of acetone tested in a continuous-flow fixed-bed micro-reactor. When the initial concentration is 5.3 g m−3 in air and the flow rate is 2.5 mL min−1, the acetone is completely eliminated at 150 ◦C.