Ru-Containing Polymeric Catalysts for Cellulose Conversion to Polyols

In this paper Ru-containing catalysts based on hypercrosslinked polystyrene (MN-270) and its functional analogues (MN-100 and MN-500) were studied for the first time in cellulose hydrolytic hydrogenation. The catalysts were characterized using transmission electron microscopy (TEM), high resolution TEM, and porosity measurements. Catalytic studies demonstrated that the catalyst containing 1.0 % Ru and based on MN-270 is the most active. The total yield of sorbitol and mannitol was 50 % on the average at 85 % cellulose conversion.

     

Hydrothermal Solubilization–Hydrolysis–Dehydration of Cellulose to Glucose and 5-Hydroxymethylfurfural Over Solid Acid Carbon Catalysts

Solid acid catalysts based on graphite-like mesoporous carbon material Sibunit were developed for the one-pot solubilization–hydrolysis–dehydration of cellulose into glucose and 5-hydroxymethylfurfural (5-HMF). The catalysts were produced by treating Sibunit surface with three different procedures to form acidic and sulfo groups on the catalyst surface. The techniques used were: (1) sulfonation by H₂SO₄ at 80–250 °C, (2) oxidation by wet air or 32 v/v% solution of HNO₃, and (3) oxidation-sulfonation what meant additional sulfonating all the oxidized carbons at 200 °C. All the catalysts were characterized by low-temperature N₂ adsorption, titration with NaOH, TEM, XPS. Sulfonation of Sibunit was shown to be accompanied by surface oxidation (formation of acidic groups) and the high amount of acidic groups prevented additional sulfonation of the surface. All the Sibunit treatment methods increased the surface acidity in 3–15 times up to 0.14–0.62 mmol g^?1 compared to pure carbon (0.042 mmol g^?1). The catalysts were tested in the depolymerization of mechanically activated microcrystalline cellulose at 180 °C in pure water. The main products 5-HMF and glucose were produced with the yields in the range of 8–22 wt% and 12–46 wt%, respectively. The maximal yield were achieved over Sibunit sulfonated at 200 °C. An essential difference in the composition of main products obtained with solid acid Sibunit carbon catalysts (glucose, 5-HMF) and soluble in water H₂SO₄ catalysts (formic and levulinic acids) as well as strong dependence of the reaction kinetics on the morphology of carbon catalysts argue for heterogenious mechanism of cellulose depolymerization over Sibunit.     

Ru-containing catalysts on polymer supports for converting cellulose into polyols

Ru-containing catalysts on hyper-cross-linked polystyrene (MN 270) and its functionalized analogs (MN 100 and MN 500) are used in the hydrolytic hydrogenation of cellulose for the first time. The texture characteristics of the polymer supports and the catalysts are determined via low-temperature nitrogen adsorption. Experiments on converting cellulose into polyols are performed in a 50 cm³ steel reactor in subcritical water at 245°C, a partial pressure of hydrogen of 6 MPa, and a stirrer velocity of 600 rpm. The morphological parameters of the supports correlate with the activity of the catalysts. The 1.0% Ru/HPS MN 270 catalyst displays the highest activity. The total yield of sorbitol and mannitol is 50% on average at a cellulose conversion of 85%, which is comparable to the figures for more complex and expensive catalysts. The parameters of cellulose conversion can be further optimized and the proposed catalysts improved to develop a highly effective procedure for processing cellulose biomass into raw materials for chemical synthesis and the production of second-generation biofuels.     

Pd-Integrated Perovskite as Effective Catalyst for Selective Catalytic Reduction of NOx by Propene

Perovskite based Pd catalysts were prepared by a modified citrate route and analyzed with SEM, XRD, TEM and XPS techniques regarding the state of palladium. Integration of Pd into the perovskite lattice was compared with impregnation onto the support. Clear indications of Pd-substitution in the La-based perovskites were found by XPS and SEM. The integrated Pd-ions diffuse out of the perovskite lattice under reductive conditions forming metallic palladium nano-particles (less than 15 nm size) while the Pd particles obtained via the impregnation route were in the order of 80 nm. In the selective catalytic reduction of NO by propene, up to 35% NO conversion at 250 °C were obtained at a very low W/F of 0.015 g s mL^?1, with decreasing tendency at increasing oxygen content. Differences between impregnated and Pd-integrated catalysts were obvious only at high O₂ content (5 vol.%) where the Pd-integrated catalyst exhibited a lower tendency to oxidize the propene reductant.     

Selective Hydrogenation of Citral Over Noble Metals Intercalated Montmorillonite Catalysts

Surfactant stabilized platinum and ruthenium nano particles were intercalated into the interlamellar space of montmorillonite. The XRD patterns of the metal intercalated montmorillonite reveal that there was a significant swelling during the intercalation of surfactant stabilized metal particles without affecting the crystallinity of montmorillonite. The success of the synthesis of nano particles into montmorillonite catalysts was confirmed from the TEM micrographs of the catalytic materials. The TEM micrographs clearly indicated well dispersion of particles and the average diameter (in nm) of the intercalated metal particles were also determined. The catalytic activity and selectivity of these newly developed catalysts towards the selective hydrogenation of citral in liquid phase was found to be appreciable. The conversion levels were found to be 38% and 18% at 30 °C and increased to 61% and 46% at 100 °C over Pt-CTA-MM 2 and Ru-CTA-MM 2 catalysts respectively at 9 bar hydrogen pressure. The best selectivity towards geraniol and nerol was observed to be 61% over Pt-CTA-MM 2 among the catalysts studied. The effect of temperature, hydrogen pressure, amount of catalyst and time on stream on the conversion and selectivity towards geraniol and nerol were also discussed in detail.     

Fischer–Tropsch Synthesis: Effect of K Loading on the Water–Gas Shift Reaction and Liquid Hydrocarbon Formation Rate over Precipitated Iron Catalysts

The effect of K loading on the water–gas shift (WGS) reaction and hydrocarbon formation rate during Fischer–Tropsch synthesis (FTS) was studied over 100 Fe/5.1 Si/2 Cu/x K (x = 1.25 or 3) precipitated catalysts using a 1-L continuously stirred tank reactor. The catalysts were tested over a wide range of experimental conditions: 260–270 °C, 1.3 MPa, H₂/CO = 0.67 and 20–90 % CO conversions. On the low K loading (1.25 % K) Fe catalyst, the H₂ deficiency required for the FTS reaction was made up by the WGS reaction only at high CO conversion level, i.e. >70 %; however, increasing potassium loading to 3 % dramatically improved the WGS reaction rate which provided enough hydrogen for the FTS reaction even at low CO conversion level, i.e. 30 %. Kinetic analysis suggests that increasing K loading resulted in significant increases in the WGS rate constant relative to that of FTS, which is a major cause of the high WGS activity on the high K loading catalyst. Both the low and high potassium containing iron catalysts have high liquid oil and solid wax formation rates, i.e. 0.78–0.93 g/g-cat/h at 260 °C, 1.3 MPa, H₂/CO = 0.67 and 50 % CO conversion, but increasing potassium loading from 1.25 to 3 % shifted the primary product to wax (70 %) from oil (73.5 %). The wax fraction increased with increasing CO conversion for both iron catalysts. The effect of K loading on initial FTS activity and hydrocarbon distribution/selectivity of the Fe catalysts was also studied. High K loading, i.e. 3 % K, increased the iron carburization rate and significantly shortened the induction period of the FTS reaction. Secondary reactions of olefins were remarkably suppressed and the olefin content was greatly enhanced with increasing K loading from 1.25 to 3 %, consistent with a number of studies in the open literature.     

NiWB催化剂催化微晶纤维素加氢

通过改变溶液中偏钨酸铵的浓度以化学还原法制备了一系列NiWB催化剂,并用于微晶纤维素的催化加氢。用物理吸附(BET)和透射电镜(TEM)等手段对催化剂进行了表征,探讨了催化剂中Ni和W的不同配比对催化剂性能的影响,同时研究了反应条件对纤维素催化加氢性能的影响。BET结果表明,随着W含量的增加,催化剂比表面积增加;TEM结果表明,催化剂为纳米颗粒,分散均匀;SAED结果表明,催化剂具有非晶态结构。适宜的反应条件为:反应温度245℃、反应时间2 h、H2压力6 MPa,此时微晶纤维素转化率可达100%,乙二醇的收率在43%以上,而六元醇的收率在5%左右。     

Er/β-zeolite-catalyzed one-pot conversion of cellulose to lactic acid

Various Er/β-zeolite catalysts were prepared by grafting erbium species in aqueous solutions of erbium chloride onto β-zeolites. The catalysts were characterized using X-ray fluorescence spectroscopy, inductively coupled plasma optical emission spectroscopy, N₂ physical adsorption, powder X-ray diffraction, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, and NH₃ temperature-programmed desorption. These catalysts were evaluated in the one-pot hydrothermal conversion of cellulose to lactic acid. Lactic acid yields of approximately 58 % were obtained using an erbium grafted on de-aluminated β zeolite (Er/deAlβ-2) with an erbium content of 12.4 wt% and a Si/Al ratio of 159:1. In catalyst recycling tests, the lactic acid yield decreased from 57.9 % in the first cycle to 51.2, 49.8 and 49.6 % in the second, third and fourth cycles, respectively. The decreases in catalytic activity during recycling are proposed to arise mainly from a combination of erbium ion leaching, deposition of carbon species in the zeolite pores and the partial structure collapse.     

Nickel–Tungsten Supported on Thin Carbon Coated SiO<Subscript>2</Subscript> Nanosphere for Cellulose Conversion to Lower Polyols

Production of polyols and other chemicals from cellulose was important for sustainable society, and it had long relied on the design of suitable catalysts to achieve high yield of lower polyols. Herein, we reported a new preparing strategy for nickel–tungsten catalyst to fabricate Ni–W/SiO₂@C catalysts coated by thin carbon. The crystal carbon demonstrated the recommendable confinement effect to obtain the well dispersed metallic particles on SiO₂. The prepared composites were characterized by means of XRD, N₂ physisorption, thermogravimetry, XPS, TEM, element mapping and atomic force microscope. These characterizations confirmed that more phases including WO₃, Ni, NiW alloys and NiC were formed by incorporation of porous crystal carbon. Moreover, the metallic particles were dispersed in size range of 2–8 nm influenced by coating carbon and ethanediamine (dispersant). The activities of catalysts were evaluated in hydrogenolysis of cellulose to lower polyols at 240 °C under 5.0 MPa H₂ pressure in the presence of water. Results showed that catalyst Ni–W/SiO₂@C-12 was more favorable for EG production, with the highest EG yield of 60.7% and 100% cellulose conversion after reaction for 60 min.

Graphical Abstract

The series of high efficient nickel–tungsten catalysts Ni–W/SiO₂@C were fabricated and coated by thin carbon. The thin coating carbon demonstrated the recommendable confinement effect to obtain the well dispersed metallic particles on SiO₂.

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Synthesis and catalytic activity of SBA-15 supported catalysts for styrene oxidation

Cu(II) and Mn(II) metals embedded on mesoporous SBA-15 were synthesized by co-precipitation technique.The support and catalysts were characterized by SEM–EDX,TEM,BET,XRD and ICP-AES methods.The catalytic activity of these catalysts was evaluated for styrene oxidation at various reaction conditions such as styrene to TBHP mole ratio,temperature,catalyst amount by using TBHP as an oxidizing agent.Major reaction products were styrene oxide and benzaldehyde and highest styrene conversion(97.3%) was observed at styrene to TBHP mole ratio of 1:4,temperature at 80 °C and 20 mg of catalyst.Further,the recyclability of the catalysts was observed and found that they can be recycled three times without major loss in their activity and selectivity.     

Selective formation of aniline over nanogold incorporated cobalt loaded SBA 15 catalysts

Nanogold was dispersed over cobalt-loaded SBA 15 to create an effective redox catalyst. The support was identified as spinel Co₃O₄ attached to mesoporous SBA 15 based on XRD, FTIR and TEM analyses. The gold crystallites were found to be in the nanosize range (8–15 nm) by the application of the Scherrer equation to the XRD data. XPS analysis provided insight into the state of the gold nanoparticles. The selective hydrogenation of nitrobenzene over nanogold doped cobalt-loaded SBA 15 catalysts was investigated in a fixed bed down flow reactor. The selectivity for the desired product, aniline, was very high with a maximum conversion of 98.9 % of nitrobenzene. The high catalytic performance is attributed to the efficient dispersion of gold nanoparticles over the support. Performing the reaction in the flow reactor maximizes the access of the reactants to the catalysts without the aid of any solvent, which further eliminates the filtration steps required to remove the catalyst after the reaction. Conducting the reaction at 200 °C facilitates the recovery of the product (aniline), from the catalyst, as soon as it is formed.     

Influence of Catalyst Pretreatments on Propane Oxidation Over Ru/γ-Al2O3

The influence of different treatments (in H₂ or in O₂ at 250 or 600 °C) of alumina supported Ru catalysts on the total oxidation of propane was investigated. Ruthenium catalysts were prepared using RuCl₃ as metal precursor and characterized by H₂ chemisorption, O₂ uptake, BET, XRD and TEM. The presence of chloride on the catalyst surface was found to exert an inhibiting effect on the activity of Ru. The reduced Ru/γ-Al₂O₃ catalysts after partial removing chlorine ions were more active than the same samples oxidized at 250 °C. The higher activity of the reduced Ru/γ-Al₂O₃ catalysts was attributed to the presence of a large amount of active sites on small Ru _x O _y clusters without well defined stoichiometry or on a poorly ordered layer of a ruthenium oxide on the larger Ru particles. The formation of highly dispersed, but in some extent crystallized RuO₂ phase in catalysts oxidized at 250 °C, leads to slightly lower activity of the Ru phase. Strong decline of the activity was found for catalysts oxidized at 600 °C. At this temperature, the Ru particles were completely oxidized to well-crystallized RuO₂ oxide, and the mean crystallite size of the Ru oxide phase was much higher (9–25 nm) than that of after oxidation at 250 °C (~4 nm). The effect of the regeneration treatment in H₂ on the activity of the Ru/γ-Al₂O₃ catalysts was also studied. The active ruthenium species for propane oxidation were discussed based on the catalytic and characterization data both before and after activity tests.     

Synthesis and Dispersion of Dendrimer-Encapsulated Pt Nanoparticles on γ-Al2O3 for the Reduction of NO x by Methane

Dendrimer encapsulated Pt nanoparticles were prepared by using hydroxyl terminated generation four (G4OH) PAMAM dendrimers (DEN) as the templating agents. The encapsulated Pt nanoparticles were dispersed on γ-Al₂O₃ at room temperature by impregnation. Pt/Al₂O₃ (DEN) catalysts were then subjected to thermal treatments in oxidizing and reducing atmospheres at different temperatures. These catalysts were characterized by Transmission Electron microscopy (TEM) and In situ Fourier-Transform Infrared (FTIR) spectroscopy. The TEM analysis of the as synthesized catalysts revealed that the Pt nanoparticles were found to be 2–4 nm in size. It is observed that the Pt particle size in 0.5% Pt/Al₂O₃ (DEN) catalyst increased upon thermal decomposition of the dendrimer. The in situ FTIR results suggested that the presence of oxygen and the Pt nanoparticles in the Pt-dendrimer nanocomposite accelerate the dendrimer decomposition at low temperatures. All the catalysts were tested for the reduction of NO _x with CH₄ in the temperature range of 250–500 °C. NO _x reduction efficiency of Pt/Al₂O₃ (DEN) catalysts were compared with the Pt/Al₂O₃ (CON; conventional) catalyst. The conversion of NO _x was started from the low temperatures over Pt/Al₂O₃ (DEN) catalysts. The high selectivity of NO _x to N₂ of 74% was obtained over 0.5% Pt/Al₂O₃ (DEN) catalyst at low temperatures around 350 °C.     

NiMo/C Used as Magnetic Support for SILP Catalysts

In this work, supported ionic liquid (IL) phases catalysts were prepared based on Pd dispersed in IL phases supported on magnetic particles of nickel/molybdenum covered with carbon (NiMo/C). The magnetic support was prepared via CVD method at 800 °C. XRD analysis showed the phases of metallic nickel and molybdenum carbide. The presence of carbon in these materials was confirmed by TEM/EDS and thermogravimetric analysis (TG) analysis. Pd particles were dispersed in 1 and 2.5 wt% of the IL 1-butyl-3-methylimidazolium tetrafluoroborate (BMIm·BF₄), which were immobilized on the support surface via impregnation method. TG analysis shows a weight loss between 300 and 420 °C attributed to the BMIm·BF₄, confirming the existence of IL on the support surface. The prepared materials were investigated in hydrogenations reactions of 1,5-cyclooctadiene and nitrobenzene, and the influence of IL on the activity and selectivity of these catalysts were observed. These materials have great potential for catalysis applications, because they bring together the advantages of the IL in the catalyst surface and the facility of magnetic materials separation.     

Rapid synthesis of cellulose triacetate from cotton cellulose and its effect on specific surface area and particle size distribution

A highly rapid process is described for the preparation of cellulose triacetate and its effect on particle size and surface area of the product. The process involves microwave-assisted rapid synthesis of cellulose triacetate with very low amount of acetic anhydride (10–15% of acetic anhydride is used in conventional methods) in the presence of iodine as a catalyst using a designed reaction vessel. The technique used is simple and rapid; it is also characterized by a high conversion ratio (yield 100%). A small amount of iodine (115 and 230 mg, 1.15 and 2.3% of cellulose weight) was found to be effective in the production of cellulose triacetate using 25, 30 to 40 mL acetic anhydride for 10 g cellulose under microwave irradiation for 2–4 min. The production of cellulose triacetate and the degree of substitution were confirmed by FTIR, Raman, ¹H NMR, and thermogravimetric analysis. The optimal reaction condition was discovered to be 3 min microwave radiation and 30 mL acetic anhydride in the presence of 230 mg iodine for 10 g cellulose. The effects of the amount of acetic anhydride, and amount of catalyst and reaction time on the specific surface area, pore volume, mean pore diameter, and particle size distribution were investigated. The highest surface area obtained was 39.63 m²/g. The specific surface area and particle size distribution are highly dependent on the amount of acetic anhydride and I₂ catalyst. About 10% of the synthesized cellulose acetate showed particle size less than 200 nm.     

Heterogeneously Catalysed Aldol Reactions in Supercritical Carbon Dioxide as Innovative and Non-Flammable Reaction Medium

Aldol reactions of several aldehydes have been investigated over acidic and basic catalysts in supercritical carbon dioxide at 180 bar and 100 °C. Both acidic (Amberlyst-15, tungstosilicic acid (TSA) on SiO₂ and MCM-41) and basic (hydrotalcite) materials showed interesting performance in this preliminary study under the entitled reaction conditions. Small and linear aldehydes, such as propanal, butanal, pentanal and hexanal, react more efficiently than the branched 3-methylbutanal, which is converted much slower. Whereas Amberlyst-15 showed the highest conversion based on the catalyst mass, tungstosilicic acid-based catalysts were significantly better if the rates were related to the number of acidic sites (>1000 h^?1). The rate depends both on the dispersion and the kind of support. Strikingly, tungstosilicic acid (TSA) on MCM-41 was also an effective catalysts for the selective C=C double bond hydrogenation of 2-butenal and is therefore a potential catalyst for the ??one-pot?? synthesis of 2-ethyl-2-hexenal and 2-ethylhexanal via combined hydrogenation and aldol reaction from 2-butenal. A number of characterisation techniques, such as temperature-programmed desorption of ammonia (NH₃-TPD), transmission electron microscopy (TEM), X-ray absorption spectroscopy (XAS), etc. were used to get an insight into the catalyst structure, which support a high dispersion and strong acidity of the tungsten based species on silica and MCM-41.     

Effect of Metal-Support Interactions in Ni/ZSM-5 + Al2O3 Catalysts on the Transformation of n-Paraffins

NiO(8 %)/Ni,H-ZSM-5 + Al₂O₃ (1:1) catalysts differing in metal-support interactions, which influenced the metal-to-acid ratios, were examined. The interactions were changed by modifying the method of zeolite and aluminium hydroxide combining and the method of Ni incorporation. The catalysts were characterised by ICP, XRD, N₂ sorption, SEM, TEM, NH₃-TPD, Py-IR, TPR, H₂ chemisorption and XPS. The effect of metal-support interactions was determined during n-C₆ conversion in a continuous system at H₂:CH = 7:1 Nm³/m³, 0.1 MPa and LHSV = 1 h^?1. It was found that over the catalysts with weaker Ni–alumina interactions (n _{Ni_a}/n, 3.2 × 10^?2 and 4.8 × 10^?2), selectivity to isomerisation products was by 10–35 % higher, and selectivity to high boiling hydrocarbons by 10–30 % lower than over the catalysts with stronger Ni-support interactions (n _{Ni_a}/n, 1.2 × 10^?2 and 1.8 × 10^?2).     

Nanofiltration Separation of Aqueous Polyethyleneglycol – Salt Mixtures

To investigate nanofiltration (NF) separation for recycling polyethylenglycol (PEG) from an ion partition process using an aqueous two-phase system, fractionation performance of five different NF membranes (NF270, SR3, SR100, SR2, and BW30) with solutions of NaNO₃, KClO₄, and PEG 4000 in water comprising various mixtures were studied. PEG rejections and salt passage were analyzed and explained based on size exclusion as well as electrostatic interactions. The highest permeate flux at high rejection of PEG as well as the lowest salt rejections were obtained with SR2 and NF270 membranes. Similar salt rejections were observed for mixed solute solutions and complex mixtures, all following this trend: SR3 > NF270 > SR2. The PEG rejections were well above 95%. This study also revealed that high salt passage of above 90% could be achieved with the same NF membrane only by unstirred conditions through concentration polarization mechanism; however, at the expense of low flux, especially with high PEG concentrations.     

The Stability Study of Au/La-Co–O Catalysts for CO Oxidation

Perovskite oxide LaCoO₃ and the mixture oxides of La₂O₃ + Co₃O₄ were prepared by sol–gel method. Then Au/La–Co–O catalysts were prepared by deposition- precipitation (DP) method and characterized by means of XRD, BET, XPS, TEM and IR. The catalytic performance for CO low-temperature oxidation and stability over these catalysts were compared. The results of experiment showed gold catalysts supported on perovskite oxides have higher catalytic activity and stability than that of supported on the simple oxides.     

Hydrogen Production with a Microchannel Reactor by Tri-Reforming; Reaction System Comparison and Catalyst Development

In this work, Pt based mono and bimetallic catalysts were tested under conditions of tri-reforming (TR). All the catalysts contained 25% of CeO₂ and a metal loading of 2.5 or 5.0% (wt%). The bimetallic catalysts contained 2.5% Pt and 2.5% of Me, where Me?=?Ni, Co, Mo, Pd, Fe, Re, Y, Cu or Zn. For all the experiments, a synthetic biogas which consisted of 60% CH₄ and 40% CO₂ (vol.) was mixed with water, S/C?=?1.0, and oxygen, O₂/CH₄?=?0.25, and fed to a fixed bed reactor (FBR) system or a microreactor. The 2.5Pt catalyst was used in order to compare the performance of each reaction system. The tests were performed at reaction temperatures between 700 and 800?°C, and at volume hourly space velocities (VHSV) between 100 L_N/(h g_cat) and 200 L_N/(h g_cat) for the FBR system and between 1000 L_N/(h g_cat) and 2000 L_N/(h g_cat) for the microreactor, at atmospheric pressure. Then, all catalysts were deposited into microchannel reactors and tested at a constant VHSV of 2000 L_N/(h g_cat) and reaction temperatures between 700 and 800?°C. Catalysts under investigation were characterized applying the following techniques: inductively coupled plasma optical emission spectroscopy (ICP-OES), N₂ Physisorption, Temperature Programmed Reduction (TPR), CO chemisorption, Transmission Electron Microscopy (TEM) and X-ray Photoelectron Spectroscopy (XPS). The microreactor was identified as the most efficient and promising reaction system, and the 2.5(Pt–Pd) catalyst as the bimetallic formulation with the highest activity. Therefore its activity and stability was compared with the reference 5.0Pt catalyst at 700?°C and VHSV of 2000 L_N/(h g_cat) for more than 100 h. Although slightly lower activity was measured operating with the 2.5(Pt–Pd) catalyst, a significant reduction of the Pt content compared to the reference 5.0Pt catalyst was achieved through the incorporation of Pd.