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The carbon-based metal-free materials as catalysts (named as carbocatalysts) have been attracting tremendous attentions in electric-, solar- and thermal-driven reactions nowadays. Compared to electrocatalysis and photocatalysis, the thermal-driven catalysis (thermocatalysis) including liquid phase and gas phase reactions involves wider scope and is relatively easy to realize practical large-scale applications. Over the past several years, some striking achievements on the design of new carbon-based metal-free materials with well-defined structures and heteroatom groups as well as the revelation of new reaction mechanisms and active sites in thermocatalysis have been obtained. However, comparative discussions regarding these recent achievements have been rarely highlighted. In this review, we systematically summarize and discuss six kinds of carbocatalysts and their applications in thermocatalysis. These materials include typical oxygen-attached carbon, surface modified carbon (graft with certain organic compounds), mono-doped carbon, co-doped carbon, carbon nitride and materials with carbon as dopant. Some new reaction processes as well as the related reaction mechanisms, active sites and intermediates are reviewed critically. Moreover, an outlook on the in-depth investigation of the metal-free carbocatalysis in the future is provided.

The non-noble metal and nitrogen cofunctionalized carbon (M–N–C) attract enormous attentions in heterogeneous catalysis. However, the fabrication of the M–N–C systems commonly rely on fossil resour...

In this paper, high-nitrogen steel (HNS) was joined by vacuum brazing using an Ag–Cu–Ni filler metal and the effect of brazing temperature and duration time on the evolution of mechanical properties and microstructure of HNS joints were analyzed. The results showed that the optimal brazing temperature was 950[Formula: see text]C and the optimal shear strength was obtained with the value of 212.4 MPa when the brazing temperature was 950[Formula: see text]C with the brazing time of 10 min.

Ethyl lactate is a promising green solvent, which can be produced via esterification of biomass derived lactic acid and ethanol. Herein, we report the development of highly active and stable polyoxometalates (POMs) supported on zeolite catalysts for synthesis of ethyl lactate. Repetitive stability tests were performed using the developed catalysts, and comparative characterization of the fresh and used catalysts was performed to understand the changes in the physicochemical properties of the catalysts. It was found that low-silica Y zeolites (silicon-to-aluminum ratio, SAR, of 2 and 5) are prone to be dealuminated (by lactic acid) under the reaction conditions, and thus being not suitable to be used as the catalyst support. Direct support of 12-tungstophosphoric acid (by impregnation) on high-silica Y zeolite (SAR40) led to deactivation during catalysis due to 12-tungstophosphoric acid leaching. This issue was solved by surface modification of the high-silica Y zeolite using cesium (Cs) ions before impregnation of 12-tungstophosphoric acid because the formed cesium phosphotungstate is insoluble in the reaction. As a result, a stable composite catalyst of Cs exchanged 12-tungstophosphoric acid supported on high-silica mesoporous Y was developed, which showed good reusability. In detail, after seven cyclic tests, the physiochemical properties of the catalyst and the catalytic performance remained relatively stable, e.g., the yield of ethyl lactate remained at around 29.6%. Findings of the study show that the stability of the zeolitic support and the support heteropolyacid are equally important for obtaining a stable catalyst for ethyl lactate synthesis via esterification.

An effective method to study the active sites for carbocatalysis is proposed based on designing a carbon catalyst in the absence of metal as the growth catalyst. The results suggest that the oxygenated groups on the aromatic carbons are mainly responsible for the catalytic reduction of nitrobenzene and some other reactions.

The creation of specific catalytic functionalities in the nanocarbon materials is an important approach to develop the metal-free nanocarbon materials (carbocatalysts). We report herein a functionalization strategy by treatment of N-doped carbon nanotubes (NCNT) with ozone/water to create oxygen groups nearby the N groups (N-C=O). These groups, different from those present in conventionally oxidized NCNT, show peculiar catalytic behavior. The N atom adjacent to carbonyl group (N-C=O) modifies the reactivity of carbonyl towards C-H activation and simultaneously activate O2 molecule for bifunctionality. Efficient performance for oxidative coupling of benzylamine to imine (>99% imine selectivity) can be obtained under solvent-free conditions at ambient pressure. The benzylamine productivity reaches as high as 131.3 μmol m−2 h−1, which is the highest among any other reported carbon-based catalysts. This work not only highlights a sustainable strategy for tuned surface chemistry of carbon materials by using mild ozonation process, but also reports a novel green aerobic synthesis method of benzylamine using tailored metal-free carbon nanomaterials.

A simple, economic, efficient and eco-friendly nanodiamond (ND) modifying method to reinforce the ND/epoxy composite for the industrialization of the high-performance ND/epoxy composite is always desired. In the present work, the ND was successfully modified only using aqueous ammonia through an easy-to-operate method by replacing the hydrogen atoms in the carboxyl group with ammonium ions. Ammonia, which is the only pollutant in the process, could be recycled. The modified ND/epoxy composite showed an overwhelming advantage over the neat epoxy or the ND/epoxy composite in storage modulus in their glassy state without any degradation of tensile strength, hardness and fracture toughness.

Carbon is demonstrated as a mild and transition metal free catalyst for the preparation of N-rich heterocyclic compounds for the first time. The surface > C=O groups on nanodiamonds were identified as an active site, which most probably generates imidogene as a reactive species that triggers the reaction. The experimental results supported with density functional theory calculations were used to reveal a new reaction pathway, different from the conventional homogeneous one that indicates involvement of nitrogen radicals in the reaction.

Hydrogel is low-cost porous material that has been used as effective support for confining metal nanoparticles due to its interconnected three-dimensional (3D) networks. Cellulose gel with covalently crosslinking has good thermal stability and can be used as support to stabilize metal nanoparticles in the high temperature environment. In this work, (Cu, Pd, Au) nanoparticles were immobilized on covalently crosslinked cellulose gel via adsorption and in situ reduction, followed by pyrolysis to obtain carbon-supported metal nanoparticles. Typically, the Cu nanoparticles were highly dispersed in the gels due to the interconnected networks and functional groups that restricted the aggregation of metal nanoparticles and improved the stability of the gel framework during pyrolysis. The results were confirmed by XRD, TEM, XPS, and FT-IR analyses. Furthermore, the Cu NPs exhibited good catalytic activity and selectivity for the hydrogenation of nitroaromatics with a TOF of 6656 h−1, which was comparable to previously reported Pd catalysts. The catalyst remained its activity after 10 recycles, demonstrating the high stability and activity of the Cu NPs prepared by this method. This work provides a green synthetic pathway for the construction of size-controlled metal nanoparticles immobilized on a carbon support.

The high-N-content, the cup-stacking and the macroscopic nitrogen doped carbon nanotubes (NCNT) were synthesized via an easily manufactured catalytic chemical vapor deposition (CCVD) method. Nitrogen physisorption, transmission electron microscopy (TEM), thermogravimetric analysis (TGA), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were used to characterize the as-obtained NCNTs. High reaction temperatures were found to be the key point to the formation of inner-cup-stacking NCNTs. However, the synthesis of the outer-cup-stacking NCNT needs special demands not only to the reaction temperature but also to the catalyst and the carrier gas. The possibility of CO oxidation by NCNT was proved to be very small, and the outer-cup-stacking NCNT showed obvious advantage in the oxidative dehydrogenation (ODH) of butene to butadiene compared to a bamboo-like NCNT with an even higher N content.

The acid-catalyzed ring-opening reaction of styrene oxide was used as a probe reaction for evaluating the acidic properties of carboxylated carbocatalysts. Significant discrepancies in the initial reaction rates were normalized using the total number of carboxyl groups, and demonstrated that the average catalytic activities of the carboxyl moieties on the carbocatalysts differed. Comparisons between the apparent activation energy E a and the pre-exponential factor A, derived from Arrhenius analysis, demonstrated that A varied more significantly, and therefore had a more significant effect on the reaction rates than E a. The variation in the calculated pKa values of the carboxyl groups was attributed to the electronic effects of the nitro groups. This hypothesis was supported by the temperature programmed desorption profiles of nitrogen monoxide ions.

Vanillyl alcohol, which is made up of an aromatic ring, an alcoholic hydroxyl group, a phenolic hydroxyl group and a methoxy group, was selected as the model molecule of lignin. Various carbon materials supported Pd catalysts were chosen to catalyze the HDO of vanillyl alcohol. The catalysts were characterized via TEM, TPD, XRD, XPS and CO-chemisorption. It was found that different carbon materials could obviously influence the particle sizes, dispersion and distribution of Pd or PdO particles. Palladium and carbon can synergistically catalyze the room-temperature HDO of vanillyl alcohol even at room temperature, and the carboxyl group was found to be the effective active acid site during the reaction. Possible reaction mechanism was also proposed. The existence of the effective active acid sites on the carbon supports could obviously lower the reaction temperature without decreasing the selectivity, as a result, making the production of renewable fuels by HDO much more economically feasible, which is of much importance.

Nanocarbons have been extensively used as metal-free alternatives to metal catalysts in many oxidative processes owing to their functional groups or defects, which have the activation ability toward oxygen molecules. Herein, reduced graphene oxide (rGO) could be used as catalysts in oxidative desulfurization reactions for the first time to remove sulfur-containing compounds from fuels. Superior catalytic activity and stability are obtained in the aerobic oxidative desulfurization process catalyzed by rGO. A broad range of sulfur-containing aromatic substrates could be removed effectively in this catalytic system. Carbonyl groups have proved to play crucial roles during the oxidation process based on an XPS analysis, a chemical titration method and a series of comparative experiments. The chemically active defects are also beneficial to the catalytic performance because carbonyl groups could be generated in situ on these defects under the reaction conditions. Based on the EPR results, a radical pathway is proposed. Oxygen molecules could interact with the carbon atoms adjacent to carbonyl groups to form adsorbed super oxygen anion radicals (rGO-OO˙−), which then attack the adjacent sulfur-centered cation radicals and generate the final product sulfone.

The strong quantum confinement effect as well as abundant edges and oxygen functional groups enable nano-graphene oxide (NGO) a variety of intriguing applications such as catalysis, bioimaging, drug delivery and photovoltaic devices. However, the development of NGO is severely hindered because of the difficulty in controlled mass production. Here, we report the efficient synthesis of NGO with a high yield of ∼40 wt % by water electrolytic oxidation of glassy carbon (GC). The NGO shows a high oxidation degree (C/O atomic ratio, ∼1.4) and excellent dispersion stability. Moreover, its size can be easily tuned by the graphitization degree of GC, which enables the controlled synthesis of NGO with average size of 4, 8, and 13 nm and different oxygen functional groups. As metal-free catalysts, the 13 nm sized NGO is found to be beneficial for the oxidative coupling reaction of benzylamine, while the 4 nm sized NGO shows a conversion rate of 88 times higher than 13 nm sized NGO for the oxidation reaction of benzene. In addition, the water electrolytic oxidation mechanism of graphitic materials is systematically studied. It is found that sulfuric acid has a protective effect on the graphite electrode during the water electrolytic oxidation process, and 50 wt % sulfuric acid solution well balances the protection and oxidation processes, leading to the highest oxidation efficiency and production rate.

Die metallfreie Katalyse ist in Bezug auf nachhaltige Chemie auf ein breites Interesse gestosen. Kohlenstoffkatalyse ist eine “grune” Alternative fur katalytische Prozesse in der Gas- und Flussigphase. Insbesondere fur Dehydrierungen in der Gasphase wurde dies anhand von zahlreichen Beispielen dokumentiert, wobei Kohlenstoff ein vielversprechender Ersatz fur Metalloxidsysteme sein kann. Die Kohlenstoffkatalyse in der Flussigphase, speziell in der organischen Synthese, ist eine aufstrebende Forschungsrichtung, die sich in den letzten Jahren sehr schnell entwickelt hat. Hier wird der aktuelle Entwicklungsstand von Kohlenstoffkatalysatoren fur Flussigphasenreaktionen kritisch analysiert, wobei ein Fokus auf die Reaktionsmechanismen sowie auf Vorteile und Einschrankungen von metallfreien Kohlenstoffkatalysatoren gelegt ist.

Metal-free carbocatalysts enriched with specific oxygenated groups with different morphology and size were synthesized from glucose by hydrothermal carbonization, in which cheap and widely available biomass could be converted into functionalized carbon using an environmentally benign process. The hydroxy- and carbonyl-enriched hydrothermal carbon (HTC) could be used in nitrobenzene reduction, and higher conversion was obtained on the sphere morphology with smaller size. In the Beckmann rearrangement of cyclohexanone oxime, carboxyl-enriched HTC exhibited superior performance compared with conventional solid acid (such as HY and HZSM-5), on which the strong acid sites and weak Lewis acid sites lead to high selectivity for the side product. Although the intrinsic acidity of carbon is weak, the carboxyl-enriched carbon was used in weak Brønsted acid-catalyzed reactions, such as the Beckmann rearrangement.

The strong dependence of catalytic activity and selectivity on the size of nanoparticles has imposed great value on facile methods for tailoring metal nanoparticles (NPs) with uniform dispersion on a heterogeneous support. Here, a simple and effective method for re-activating sintered Pd NPs decorated on carbon supports is demonstrated using HNO3 vapour at mild temperatures in a closed system, without loss in the Pd content. We further reveal that nitrogen oxide play an important role in the re-dispersion of Pd NPs. In a catalytic phenol hydrogenation reaction, the re-dispersed NPs exhibit superior catalytic activity as compared to sintered Pd NPs supported on CNTs.

Eutectic high entropy alloys possess both excellent plasticity and high strength. To explore their potential engineering applications, the diffusion behavior of elements, the interfacial microstructure and shear strength of the diffusion bonded joint between AlCoCrFeNi2.1 eutectic high entropy alloy and GH4169 superalloy were studied. The width of diffusion zone increased with bonding temperature increasing and the voids gradually disappeared due to the increased diffusion rate of the elements and the high-temperature creep. A new layer of face-center-cubic (FCC') phase, which was caused by the difference in diffusion rate of the elements between B2 phase and FCC phase in the eutectic high entropy alloy, generated in the diffusion zone and increased the shear strength of joints. The width of newly generated FCC' phase layer in front of the original FCC phase was wider than that in front of the B2 phase. The shear strength of the resultant joints increased and the fracture mode transformed from brittle fracture to ductile fracture with bonding temperature increasing. The maximum shear strength of 528 MPa was obtained and the dimples on fracture surfaces were found at the bonding temperature of 1050 °C.

A zigzag-type quinone performs better than an armchair-type quinone in the reduction of nitrobenzene. When different kinds of functionalities co-exist, the reaction is dominated by the most active sites, but the most negative sites should also be taken into consideration if the acitive sites have zigzag structures.

N‐doped graphene‐like layered carbon (NG) could be synthesized via a metal‐free pyrolysis route from glucose, fructose and 5‐hydroxymethylfurfural (5‐HMF), which are cheap and widely available biomass or biomass derivatives. Among the three kinds of NG, well‐developed thin layered structure with large lateral dimension could be obtained when 5‐HMF was used as the precursor. More importantly, the 5‐HMF derived NG could exhibit superior performance in epoxidation reactions compared with the conventional carbon catalysts and the performance of 5‐HMF derived NG was even similar to that of a Co catalyst. Co catalyst is widely studied in alkene epoxidation reactions. Characterizations by TEM and XPS accompanied by EPR analysis revealed that the origin of the enhanced catalytic properties for NG was ascribed to the activation ability both for alkene and O2, which was attributed to the graphitic layered structure and graphitic N species, respectively.

Carbon is emerging as an important metal-free catalyst for multiple types of heterogeneous catalysis, including thermocatalysis, photocatalysis, and electrocatalysis. However, the study of mechanisms for carbon catalysis has been impeded at an early stage due to the lack of quantitative research, especially the intrinsic kinetics (e.g., intrinsic TOF). In many carbon-catalyzed reactions, the surface oxygenated groups were found to be the active sites. Recently, we have shown that these oxygenated groups could be identified and quantified via poisoning by small organic molecules; however, these small molecules were toxic. As most of the oxygenated groups are acidic groups, they could also be identified and quantified with respect to the acid properties. More importantly, the method based on acid properties is very green and environmentally benign, because only inorganic bases are added. In this work, the acid properties of carbon nanotubes (CNTs) treated by concentrated HNO3 were thoroughly studied by mass...

Die direkte Oxidation von Benzol zu Phenol mit H2O2 als Oxidationsmittel gilt als umweltfreundlicher Prozess und verlauft sehr effizient an Kohlenstoffkatalysatoren. Es gibt jedoch kontroverse Ansichten bezuglich der Rolle des Kohlenstoffkatalysators und der aktiven Zentren. Hier fuhren wir eine grundlegende Betrachtung moglicher Reaktionsmechanismen fur diese Oxidationsreaktion an niedermolekularen Modellkatalysatoren durch. Unsere Schlussfolgerungen sind auf Raman-Spektren, statische Sekundarionen-Massenspektrometrie (SIMS), DFT-Rechnungen, ATR- und UV-Spektren gestutzt. Es wird gefunden, dass Defektstrukturen, welche die Bildung aktiver Sauerstoffspezies begunstigen, die aktiven Zentren darstellen. Ein spezifischer Defekt, der hierbei identifiziert werden konnte, ist die Armchair-Konfiguration.

Hydrogen peroxide (H2O2) functionalized carbon nanotubes exhibited better catalytic performance than their nitric acid oxidized counterparts in the reduction of nitrobenzene. One important reason may be attributed to the notably less negative oxygenated groups on the surface of the former one.

Applying carbon material as a catalyst for different chemical reactions is generally based on two parameters. First, the carbon material itself can act as a catalyst in a chemical transformation and its surface with unique structures and tunable functional groups plays a role in this regard. Secondly, it can act as a support for the active metals and influence their catalytic behavior. The catalytic applications of nanodiamond are also developed based upon these two important presumptions. In order to design a catalytic chemical transformation, it is highly important to understand the catalyst surface, nature of the chemical reaction under investigation, and the possible active center(s) in the catalyst. Nanodiamonds not only have the tendency to behave as a catalyst in various chemical transformations, but also have the potential to act as catalyst support. The objective of the current work is to provide the application of nanodiamond in the field of catalysis as a catalyst or catalyst support for variety of chemical reactions. Other applications such as development of sensors, biomedical imaging and their role as drug delivery agents can be found in Chapters 16 and 17 . The unique surface of nanodiamonds with tunable functional groups makes them suitable for different chemical transformations. How this surface can influence a chemical reaction/metal loading and what type of chemical reactions can be performed with nanodiamond are two important questions addressed in this chapter (see Chapter 8 for details about the surface nature of nanodiamonds).

Pd nanoparticles are excellent catalysts in C C coupling, hydrogenation, oxidation, and some other reactions. 10] Generally, Pd nanoparticles are immobilized on supports to hinder their aggregation during a reaction and also to ease separation and recovery from the reaction solution. To date, many materials have been used to support Pd catalysts, such as metal oxides, polymers, and carbon materials. Among these supports, carbon materials are attractive because of their ability to be tailored to meet specific needs. In addition, the carbonaceous supports can be burned off, which allows the facile recovery of precious metals. Since the report of Iijima in 1991, there has been a growing interest in the application of carbon nanotubes (CNTs) as supports in many catalytic reactions. As a result of their special physical and chemical properties, CNTs are considered to be potentially useful supports in heterogeneous catalysis. Metal particle size is one of the most crucial parameters for supported catalysts. For structure-insensitive reactions, the main target is to prepare highly dispersed catalysts. As far as the preparation of Pd catalysts is concerned, the incipient wetness impregnation (IW) method is used commonly, but the particles are usually large and disperse nonuniformly, especially in the fabrication of catalysts with a high Pd loading. The strong electrostatic adsorption (SEA) method is a simple approach to synthesize supported metal catalysts, which is based on an electrostatic mechanism in which the oxygen surface functional groups (SFGs) on the support can be protonated and deprotonated to be positively or negatively charged as a function of pH relative to the point of zero charge (PZC; the pH value at which the electrical charge density on the support surface is zero). Pt nanoparticles supported on silica and carbon materials with high dispersion have been synthesized by the SEA method. Silica-supported Pd catalysts have also been synthesized by the SEA method, in which the Pd nanoparticles have a higher dispersion than that prepared by the traditional IW method. However, there is no report on the synthesis of CNTs-supported Pd catalysts using the SEA method. In the SEA method, the PZC of the support is one of the most important factors as it can assist in the choice of an appropriate metal precursor to be used for the SEA method. The PZC value of CNTs depends on the chemical and electronic properties of the functional groups on its surface, which can be tuned by different functionalization methods. Herein, we report the preparation of CNTs-supported Pd catalysts by a facile SEA method. The CNTs supports functionalized with various kinds of surface oxygen groups (SFGs) were obtained by oxidation of the raw CNTs with concentrated acids (HNO3 and HNO3/H2SO4 with a molar ratio of 3:2) at different temperatures and characterized by TEM, N2 adsorption, zeta potential measurement, and temperature-programmed desorption (TPD). The effect of the SFGs on the PZC value of the CNTs and the adsorption of Pd cationic complexes were investigated systematically. The Suzuki reaction was used as a probe reaction to test the Pd/CNTs catalysts prepared by different methods. Pd nanoparticles supported on carbon nanotubes (CNTs) with an average Pd size of around 1 nm were synthesized successfully by a facile strong electrostatic adsorption (SEA) method. CNTs functionalized with various surface oxygen functional groups (SFGs) were obtained by treating the raw CNTs with concentrated HNO3 or HNO3/H2SO4. The SFGs could decrease the point of zero charge (PZC) of the CNTs and promoted the adsorption of Pd cationic complexes on the CNTs. In particular, the intrinsic and in situ formed (hydrolyzed from carboxylic anhydride groups) carboxylic acid groups of the CNTs during the adsorption process mainly influenced the adsorption of Pd cationic complexes. The SEA method was superior to the traditional incipient wetness impregnation method for the synthesis of highly dispersed Pd catalysts, which exhibited a high specific activity for the Suzuki coupling reaction.

The reduction of nitrobenzene catalyzed by different carbon materials (mainly carbon nanotubes) was studied. TGA, TPD, TEM, N2 adsorption-desorption, and Raman spectroscopy were used to show that it was oxygenated groups that gave catalytic activity, while the surface area, pore structure, morphology, structural defects and Fe impurities in the catalysts did not have a significant influence on the activity. The carbonyl group played an important role, but the carboxylic group and anhydride adversely affected the reaction. The conjugated π system, which was necessary for electron transfer and nitrobenzene adsorption, was another critical factor. The reaction proceeded through the direct route in which the intermediate nitrosobenzene was converted directly to aniline quickly.

The role of different oxygen functional groups on a carbon catalyst was studied in the reduction of nitrobenzene by using a series of model molecules. The carbonyl and hydroxyl groups played important roles, which may be ascribed to their ability to activate hydrazine. In comparison, the ester, ether, and lactone groups seemed to be inactive, whereas the carboxylic group had a negative effect. The reaction occurred most likely through a direct route, during which nitrosobenzene may be converted directly into aniline.

Metal-free catalysis has gained broad interest for sustainable chemistry. Carbocatalysis is one green option for catalytic transformation in the gas phase as well as in the liquid phase. This is documented by the numerous reports on gas phase dehydrogenation and selective oxidation where carbon can be successful alternatives to metal oxide systems. Carbocatalysis for liquid phase reactions, especially for organic synthesis, is an emerging research discipline and has been under rapid development in recent years. This review provides a critical analysis on the state-of-the-art carbocatalysts for liquid phase reactions, with the focus on the underlying mechanisms, the advantages and limitations when only carbon, without any intentional metal species (supported systems), is used to catalyze some traditional liquid phase reactions.

A series of Ce-modified Raney Ni (RNi) catalysts were successfully prepared by a simple wet chemical route and employed in aqueous-phase reforming of cellulose. Remarkable enhancement in hydrogen selectivity and yield after the Ce introduction was observed. At 533 K and autogenous pressure, a highest hydrogen yield of 17.8 mmol/gcellulose, which was comparable with that of 5 wt% Pt/AC, could be obtained over Ce-modified catalyst at a Ce:Ni ratio of 0.054. The catalysts were characterized by N2 adsorption/desorption, XRD, SEM, XPS and H2-TPD. It was found that cerium existed at the surface of the catalyst as Ce(OH)3, and more defects were generated during Ce modification. Based on the characterization and catalytic performance, it was suggested that the deposited Ce(OH)3 may transform into reducible CeO2 under the reaction conditions, thus promoting the desired water–gas shift reaction, leading to more H2. On the other hand, the active sites for undesired methanation reaction may be effectively poisoned by Ce modification, thus leading to less undesired methane. Addition of Ce to Raney Ni catalysts could significantly enhance the hydrogen selectivity and yield for aqueous-phase reforming of cellulose, while correspondingly suppressing the methanation reaction. A highest hydrogen yield of 17.8 mmol/gcellulose, which was comparable with that of 5 wt% Pt/AC, could be obtained at a Ce:Ni ratio of 0.054.

Crystalline porous materials with large or extralarge pores continue to be of particular significance in both industry and academia for their potential applications in shape-selective catalysis and adsorption/separation. Of these zeolitic materials, especially aluminosilicateand aluminophosphate-based molecular sieves are of prime interest because of their high stability associated with their widespread use in many established process and emerging applications. The materials VPI-5 (VFI framework type, 18-ring) and UTD-1 (DON framework type, 14-ring) were the first extra-large pore (pores constructed of more than 12 Tatoms) aluminophosphate and aluminosilicate materials discovered. The oxide frameworks are built up by corner-sharing [AlO4] and [PO4] tetrahedra as well as [AlO4] and [SiO4] tetrahedra. In the search for materials with even larger pores, an anionic open-framework aluminophosphate JDF-20 (20-ring) was reported; however, it could not be classified as a zeolite because its framework (with an Al/P ratio of 5:6) is unstable upon removal of the occluded protonated templates by calcination. Larger pore openings were also achieved using Ge or Ga as the framework Tatom in a high amount, for example in ECR-34 (ETR framework type, 18-ring), ITQ-33 (18-ring), cloverite (-CLO framework type, 20ring), and ITQ-37 (30-ring). In this context, the use of Ge or Ga as framework atoms as well as fluoride has been found to facilitate the formation of a double four-ring (D4R) unit. This is in agreement with the prediction by Brunner and Meier that structures with extra-large pores should contain a large number of threeand four-membered rings. Ionothermal synthesis, in which ionic liquids act as both the solvent and template, is a novel method that has attracted great interest in the synthesis of zeolitic and other porous materials. Besides the advantage of experimenting at ambient pressure, ionic liquids offer different chemistry and structural variety associated with the use of additional amines as structure-directing agents (SDA), and therefore open up new vistas for the synthesis of new porous materials. Herein, we report the ionothermal synthesis of the first aluminophosphate molecular sieve with 20-ring pore openings, denoted as DNL-1 (Dalian National Laboratory Number 1). This molecular sieve was confirmed as a structural analogue to the gallophosphate molecular sieve cloverite by using a combination of Rietveld refinement of powder X-ray diffraction (PXRD) data and NMR analysis. Moreover, in comparison to cloverite, DNL-1, as-synthesized and calcined, exhibits excellent stability. DNL-1 was synthesized in the ionic liquid 1-ethyl-3methylimidazolate bromide ([emim]Br) with 1,6-hexanediamine (HDA) as the co-SDA. The detailed synthetic procedure is described in the Experimental Section. The assynthesized DNL-1 material displays uniformly globular agglomerates of grainlike nanocrystals with a diameter of about 20 mm (see the Supporting Information). Analysis by energy dispersive X-ray spectroscopy (EDX) indicates the P/ Al/F molar ratio of approximately 3:3:1. The inductively coupled plasma (ICP) analysis gives the content (wt%) of Al 16.50 and P 16.65. The elemental and thermogravimetric (TG) analyses show the content (wt%) of C 9.72, N 3.64, H 3.29, and a total weight loss of 34%. Combined with the results of the structure refinement (see below), the chemical formula of DNL-1 was determined as j (C6N2H18)104(C6N2H11)80(H2O)910 j [Al768P768O2976(OH)192F288]. Using the initial structure model from cloverite, the Rietveld refinement of as-synthesized DNL-1 was successfully performed in space group Fm 3c with refined unit cell parameter a= 51.363(1) , which is comparable to that of cloverite a= 51.713 , considering the smaller ionic radius of Al. Similar results were observed in the all-silica and Gecontaining polymorph C of zeolite Beta. Figure 1 shows the very good agreement between observed and calculated PXRDpatterns, taking into account the limited signal to noise ratio, in particular for the data collected at a high angle which can be reflected from the expected R factor of 14.5%. These results adequately confirm that DNL-1 is a pure aluminophosphate analogue of the -CLO structure. The skeletal model of the refined framework structure is shown in Figure 2. The framework of DNL-1 shows the general features of the -CLO structure: 1) two nonintersecting three-dimensional channel systems with 20-ring and 8-ring windows, respectively, 2) four terminal hydroxy groups (Al [*] Y. Wei, Prof. Z. Tian, R. Xu, Dr. H. Ma, R. Pei, Prof. W. Zhang, Prof. Y. Xu, Dr. L. Wang, K. Li, Dr. B. Wang, G. Wen, Prof. L. Lin State Key Laboratory of Catalysis Dalian National Laboratory for Clean Energy Dalian Institute of Chemical Physics Chinese Academy of Sciences, Dalian 116023 (China) Fax: (+86)411-843-79151 E-mail: tianz@dicp.ac.cn

Cellulose can be efficiently converted into hydrogen by an environmentally benign one-pot aqueous-phase reforming (APR) process over Pt/C catalyst. The hydrogen selectivity and yield were significantly higher than those for the glucose reforming and even comparable with those for the sorbitol reforming under similar conditions. It was found that this process involved the slow hydrolysis of cellulose to glucose and the subsequent rapid reforming of glucose to H2. The relatively high efficiency for H2 production was ascribed to the slow hydrolysis of cellulose, which was catalyzed by the H+ reversibly formed in water during the reaction.

Gallophosphate (GaPO 4 ) molecular sieves were ionothermally prepared in 1-alkyl-3-methyl imidazolium bromide ionic liquids (ILs) with alkyl chain length varying from 2 to 6 carbons for the first time. Three kinds of GaPO 4 materials such as GaPO 4 -a, cloverite (denoted as CLO below) and GaPO 4 -LTA were obtained, and their structures and morphologies were characterized by powder and single crystal XRD, SEM and multi-nuclear NMR. In the case of 1-ethyl-3-methyl imidazolium bromide ionic liquid, large single crystals of GaPO 4 -LTA with well-defined octahedral morphology was obtained in both sealed (ca. 400 μm in size) and open vessels (ca. 300 μm in size). Ionothermal synthesis is an effective method for the preparation of large single crystal of molecular sieves. With the alkyl chain length of the ionic liquids increasing from 2 carbons to 6 carbons, the size of GaPO 4 -LTA decreased sharply. The organic template cations in the as-synthesized GaPO 4 -LTA crystals may have two different kinds of conformational structures. Fluorine plays a role of co-template along with organic cations of ILs in the synthesis of GaPO 4 -LTA and CLO, while only GaPO 4 -a was obtained in the absence of fluorine. The reaction temperature can also affect the structure of the final structure. In the reaction medium of 1-ethyl-3-methyl imidazolium bromide IL, GaPO 4 -LTA was obtained at 180 °C, while CLO was obtained at 150 °C.

Two Ni/Al2O3 catalysts with high Ni loadings of 36 wt% and 48 wt%, which possess high activities for aqueous-phase reforming of glucose, have been successfully prepared by a novel two-step impregnation method. The catalytic performance was investigated at 533 K and autogenous pressure in a batch reactor and a significant enhancement in hydrogen yield was observed over the catalyst prepared by two-step impregnation as compared to the corresponding catalyst prepared by conventional single impregnation. The catalysts were characterized by XRD, N2 adsorption/desorption, H2 chemisorption, O2 uptake, TPO, H2-TPR and TEM. It was found that two-step impregnation yielded catalysts with higher nickel dispersion as well as smaller nickel particle size compared to single impregnation.

The activities and stabilities of Pt, Ni, Co, and Cu catalysts for H 2 production by aqueous-phase reforming of glycerol, as well as the effect of support on activity and stability, were studied using a fixed-bed flow reactor. Both of the fresh and spent catalysts were characterized by XRD, N 2 adsorption/desorption, TPO, H 2 -TPR, and H 2 chemisorption. It was found that the activity of the metal catalysts increased in the order of Co, Ni, Cu and Pt. Additionally, Pt was highly stable, whereas Ni and Co showed significant deactivation with time on stream. It was also found that the activity of supported Pt catalysts was given as follows: SAPO-11 2 2 O 3 . Moreover, basic support resulted in high activity and higher hydrogen molar concentration, whereas acidic support and neutral Al 2 O 3 support tended to increase alkane formation. It was shown by XRD that Pt was caused to sinter on all of the supported Pt catalysts during the reaction. In addition, trace amount of carbon deposition was found on all of the supported Pt catalysts. However, no remarkable deactivation was observed over Pt/Al 2 O 3 , Pt/SiO 2 , Pt/AC, and Pt/HUSY catalysts. Noteworthy was the investigation of the two zeolite-supported catalysts. However, low activities as well as the collapse of the support were obtained. In addition, little influence of the collapse of the support on the stability of Pt/HUSY was observed, whereas Pt/SAPO-11 exhibited remarkable deactivation.

In this work, the MgO powders was prepared by the precipitation method with carbonate following calcination at 1200 degrees C, and then the obtained MgO powders was treated under the flowing gaseous mixture of steam and CO2. The variations of textural properties and activity for methane combustion of the MgO sample were investigated. The sample was characterized by N-2 adsorption isotherm, TEM, XRD, and TG-DTA. The results showed that the treatment temperature and the CO concentration have a significant influence on the textural properties of the MgO sample. After run at 700 degrees C for 24 h under the flowing gaseous mixture of steam/CO2/N-2 (CO2/N-2 = 15/85 volume ratio), the maximum pore sizes varied and the pore volumes increased obviously; and remarkably, the surface area of the MgO sample increased from 37.9 to 80.1 m(2) g(-1). It was proposed that during the process, the disaggregation and rearrangement of the particles have occurred, leading to the obvious variations of the textural properties of the sample. As a result, the treated MgO sample showed a higher activity for methane combustion than the original one. (C) 2007 Elsevier Inc. All rights reserved.