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Methane oxidation using O2 over transition metal oxides often requires severe conditions ( >500 °C) to achieve detectable conversion. In this study, NO was used to transfer oxygen atoms from O2, through the facile gas-phase formation of NO2 at moderate conditions (0.1 MPa and 300–400 °C), to oxidize methane over silica-supported transition metal oxides (VOx, CrOx, MnOx, NbOx, MoOx, and WOx). In situ infrared spectroscopy measurements indicated that the reaction likely proceeded by the formation of surface monodentate nitrate intermediates. These nitrate species were formed by the interaction between adsorbed NO2 and the supported metal oxides. During the reaction, the oxides of vanadium, molybdenum, and tungsten formed formaldehyde and CO2, whereas the oxides of chromium, manganese, and niobium produced only CO2. These results are consistent with the known hydrocarbon oxidation chemistry of the metal oxides. Contact time measurements on VOx/SiO2 indicated that formaldehyde was a primary product and CO2 was the final product; conversely, analogous measurements on MnOx/SiO2 showed that CO2 was the sole product. The formaldehyde production rate on VOx/SiO2, MoOx/SiO2, and WOx/SiO2, based on surface sites measured by high temperature oxygen chemisorption, compared favorably to oxygenate production rates for stronger oxidants (N2O and H2O2) reported in the literature.

Microporous Si–Ta membrane fabrication via CVD is studied with emphasis on the formation of graded and defectless γ-Al2O3 intermediate layers using size-controlled boehmite sols. The membrane shows excellent H2 selectivity and hydrothermal stability.

A green and novel strategy to construct single-crystal hierarchical zeolites has been developed by using a degradable polymer as a multiple-functional template. The obtained MFI zeolite shows excellent catalytic activity in bulky molecules cracking.

The Delplot method provides a means of analyzing conversion and selectivity data to derive a reaction sequence and has been applied so far to gas-phase or liquid-phase species. This study analyses the applicability of the method for catalytic reactions and considers for the first time adsorbed intermediates. The method is applied to a contact time study of the hydrodeoxygenation (HDO) of benzofuran at 0.5 MPa and 350 °C over a catalyst consisting of bimetallic CoPd phosphide supported on a potassium ion-exchanged ultra-stable Y (KUSY) zeolite. Both simple and detailed reaction networks were derived. The simple networks considered only gas-phase species and were modeled by a first-order sequence of steps, whereas the detailed network took into account adsorbed intermediates and was simulated using a rake mechanism. The networks were compared using F-statistics, which accounted for the differences in the number of fitting parameters. The detailed network gave a better fit to the experimental data because it represented a more realistic description of the transformation. A suggested sequence from the Delplot method was consistent with the simple network but not with the detailed network. The lack of applicability of the Delplot analysis to the network with adsorbates was linked to overly large equilibrium constants, a determination supported by Delplot fitting for a model sequence. This study indicated the inapplicability of the Delplot method in determining reaction sequences that involve adsorbed species with large equilibrium constants for formation.

The synthesis of bimetallic CoPdP phosphides supported on potassium ion exchanged ultra-stable Y (KUSY) zeolites was studied and catalytic activity tests on the hydrodeoxygenation of a model pyrolysis oil compound, benzofuran, were conducted. Temperature programmed reduction (TPR) profiles revealed that Pd aided the reduction of the Co, lowering both the onset and peak temperatures for reduction. The catalyst structure was probed by X-ray diffraction (XRD) and extended X-ray adsorption fine structure (EXAFS), which showed the formation of CoPdP alloys. Fourier-transform infrared spectroscopy was used to probe the Co and Pd sites on the surface. Several Co:Pd ratios were tested in the range of 225–350 °C at a medium pressure of 0.5 MPa. Synergistic effects were observed between Co and Pd, with the alloys showing higher activity than the single metal Pd or Co phosphide catalysts. High selectivity to unsaturated high carbon number products were obtained for the bimetallic phosphide catalysts.

In alumina-based catalysts the properties of the alumina support directly influence the structure (size, morphology, orientation, etc.) of the resulting active phase and ultimately determine the performance of the final catalysts. This paper presents a facile and efficient method for γ-Al2O3 to simultaneously expose {111} facets with strong acidity and {110} facets with moderate basicity. It is shown that the metal oxides NiOx and MoOx can be selectively deposited and subsequently sulfided on the respective facets to form a NiS2-MoS2/Al2O3 catalyst with substantially enhanced activity for thio-etherification reaction. By cooperative action of the active sites on the newly exposed facets, the catalyst is shown to have superior activity over a conventional NiMoS/Al2O3 catalyst in the thio-etherification reaction between ethanethiol and isoamylene (2-methyl-2-butene) to yield ethylamyl thioethers. Our findings show that tuning the physicochemical properties via crystal facet engineering and inducing cooperative catalysis via preferential deposition of active metals open a novel avenue for the rational design and synthesis of high performance catalysts.

The understanding of catalytic mechanisms is enhanced by the observation of surface intermediates at reaction conditions using spectroscopic techniques, but this is insufficient, as the observed species may not be involved in the reaction. This work describes a general method of analysis of hydrogenation or oxidation reactions which uses transient spectroscopic data to determine whether an adsorbed species is a reactive intermediate or a spectator on the surface. The assumptions and limitations of the method are summarized. Although the technique is approximate, it is easy to implement, and provides order-of-magnitude estimates of the rate of reaction of an intermediate. The method consists of measuring the change of coverage of the species with time, dθ/dt, during adsorption in inert gas or at reaction conditions. An example is given with the hydrodeoxygenation of the model compound γ-valerolactone (GVL) using a Ni2 P/MCM-41 catalyst, one of the most effective catalysts reported for the transformation. The reaction is relevant to the upgrading of bio-oil derived from pyrolysis of lignocellulosic feedstocks. The kinetics of the reaction and observation by in situ infrared spectroscopy of adsorbed GVL and its transformation to pentanoic acid are consistent with a Langmuir-Hinshelwood mechanism. Analysis by in situ transient X-ray absorption fine structure shows that the adsorbed GVL is a true reaction intermediate.

The direct partial oxidation of CH4 to dimethyl ether (DME) was achieved with a Pt/Y2O3 catalyst using a mixture of NO and O2. The actual gas composition contained a mixture of NO and NO2, with no decomposition or net consumption of these species. Use of 18O2 confirmed the transfer of labeled oxygen from O2 to CH4, indicating the NO/NO2 mixture worked as a single oxygen atom shuttle.

The direct partial oxidation of CH4 to dimethyl ether (DME) on a Pt/Y2O3 catalyst was studied using a mixture of NO and O2 as the oxidant. The reaction was carried out in a fixed bed reactor at 0.1 MPa and 275–400 °C using 20% CH4, 1% NO, and 1% O2 in inert gas. No methanol was detected in the effluent and a contact time study demonstrated that DME was a primary product. The DME productivities were comparable to the oxygenate (methanol, formaldehyde) productivities obtained with stronger oxidants such as N2O, H2O2, and O3. The presence of Pt and the NO + O2 gas mixture was necessary for DME formation; without NO only CO2 was produced. During the methane partial oxidation reaction NO and NO2 were not reduced to N2, indicating that they worked as a shuttle to transfer oxygen from O2 to CH4. In situ Fourier transform infrared showed the formation of a bridged nitrate species on the Pt/Y2O3 catalyst which was associated with the reaction of CH4. A comprehensive study of this bridged nitrate species indicated they were formed on yttria sites close to Pt and were likely responsible for the formation of DME. The characterization of catalysts using X-ray diffraction showed that the Pt was highly dispersed and CO uptake measurements indicated a particle size of ~3 nm. Analysis by X-ray absorption fine structure measurements showed the presence of Pt oxide with Pt-O and Pt-Pt bonds.

Using a mixture of NO + O2 as the oxidant enabled the direct selective oxidation of methane to dimethyl ether (DME) over Pt/Y2 O3 . The reaction was carried out in a fixed bed reactor at 0.1 MPa over a temperature range of 275-375 °C. During the activity tests, the only carbon-containing products were DME and CO2 . The DME productivity (μmol gcat -1 h-1 ) was comparable to oxygenate productivities reported in the literature for strong oxidants (N2 O, H2 O2 , O3 ). The NO + O2 mixture formed NO2 , which acted as the oxygen atom carrier for the ultimate oxidant O2 . During the methane partial oxidation reaction, NO and NO2 were not reduced to N2 . In situ FTIR showed the formation of surface nitrate species, which are considered to be key intermediate species for the selective oxidation.

The continuous liquid phase synthesis of nickel phosphide (Ni2P) nanoparticles was studied in a helically coiled tube (HCT) reactor both in single-phase and two-phase slug flows. The reactants were nickel acetylacetonate and tri-n-octylphosphine (TOP) in a 1-octadecane solvent. For the single-phase mode, various parameters such as reaction temperature, residence time, TOP concentration, and P/Ni ratio were studied. It was found that lower temperatures of 320 and 340 °C resulted in the formation of mixed Ni12P5 and Ni2P phases, while a higher temperature of 360 °C gave mostly Ni2P, with particle sizes increasing from 28 to 42 nm. Upon varying the contact time between 88 and 340 s at 360 °C, a likely sequence of reaction involved an amorphous phase that was transformed in parallel to Ni, Ni12P5, and Ni2P. When the flow in the HCT was changed to a two-phase slug flow by using N2 to split the continuous liquid phase into small liquid columns, the product was nearly 100% Ni2P and the particle size was as small as 3–4 nm. This was attributed to the enhanced mass transfer in the small liquid columns of the slug flow that led to higher reaction rates. It is highlighted that the HCT operated in a slug flow is an efficient and continuous method for the fabrication of nanoparticles.

This article presents a history of the origins of the Dalian Institute of Chemical Physics, Chinese Academy of Sciences (Abbreviated as DICP) and relates the recent friendship between China and Japan in the field of catalysis. Although the official beginning of DICP is in 1949 with the birth of the People's Republic of China, there are earlier roots that went back to the defeat of Russia by Imperial Japan in 1905. This began a period of occupation and exploitation of Northest Asia by Japan which did not end until its defeat by Allied forces in 1945. During the period of occupation, a laboratory was created called the Central Research Laboratory of the South Manchurian Railroad Company, which was staffed by the best and brightest researchers from Japan, and was able to develop new processes in chemicals and synthetic fuels that fed the Japanese Imperial forces. Between 1945 and 1949, Dalian was administered by the Soviet Union, and the removable equipment from the Laboratory was taken. In this period one individual stood out, the Laboratory Director Marusawa Tsuneya, who risked his life to preserve the scientific records and staff of the institute, and then stayed in Dalian for ten years after the Second World War to help China rebuild its capabilities. The Central Research Laboratory is still preserved as the Old Campus of DICP. The origin of the friendship between China and Japan in catalysis can be traced to Professor Morikawa Kiyoshi, who worked in the Central Research Laboratory and helped commercialize a shale coal liquefaction process. Upon his return to Japan he became Professor at the Tokyo Institute of Technology and in 1975 organized the first visit by Japanese academics to China. This was reciprocated in visits to Japan in 1977 and 1980 by top researchers such as Zhang Dayu, Min Enze, Tsai Khirui, Lu Jiaxi, and Lin Liwu. This resulted in numerous contacts between individuals, which multiplied geometrically. Notably among these were the personal interactions between Guo Xiexian, the Vice-Director of DICP and Tamaru Kenzi, a Professor at the University of Tokyo, which led to a friendship lasting decades and encompassing generations. In 1981, Guo Xiexian organized the first China-Japan-USA Symposium in Dalian, assisted by Tamaru Kenzi, which was attended by over 90 scientists. This meeting was a big success, and was to lead to the organization of many other multi-country conferences, further promoting exchanges. It culminated with the hosting of China of the 16th International Congress on Catalysis in 2016 in Beijing, with Li Can as President. Today DICP is a sprawling organization with over 1300 permanent staff, and is one of the powerhouses of catalysis in the world. From 2000, it has been led by Directors Bao Xinhe, Zhang Tao, and Liu Zhongmin. The Institute is making enormous contributions to research and producing cutting-edge technology, and its future is bright.

The hydrodeoxygenation (HDO) of the cyclic five-membered ester γ-valerolactone (GVL) was studied on a Ni2P/MCM-41 catalyst. The activation of the passivated catalyst in H2 was followed by in situ near-edge X-ray absorption spectroscopy (NEXAFS) which indicated reduction of the catalyst after 3 h at 550 °C. In situ infrared measurements under reactive H2 and inert N2 showed the presence of adsorbed GVL and pentanoic acid (PA) as the most abundant surface intermediates. The results supported a previous reaction network that showed that ring-opening of GVL to produce pentanoic acid was the rate-determining step. This was confirmed by transient infrared measurements which showed that the number of CH2 groups in the adsorbed species increased under H2 flow, consistent with PA formation but not an alkoxide. The results provide understanding of the key steps in the reaction mechanism.

Several Cu/ZnO/Al2O3 catalysts with high Cu and ZnO contents were used to study the influence of solvent polarity on the dehydrogenation and dehydration of isoborneol. The employment of a polar solvent enhanced the activity for the main dehydrogenation reaction, while the use of a non-polar solvent favored the dehydration side-reaction. Different techniques were employed to characterize the fresh, treated, and spent catalysts. X-ray powder diffraction (XRD) showed that the copper was in metallic form and zinc in oxide form, transmission electron microscope (TEM) showed differences in catalyst morphology that depended on the polarity of the solvent used, N2O titration gave the Cu active site density, and temperature-programmed desorption of NH3 (NH3-TPD) provided the acidity of the materials. The characterization results indicated that in non-polar solvents the copper nanoparticles were sintered and this may have been due to the enhanced activity of adventitious water in those solvents or simply because of interactions between the solvents and the copper and zinc oxide components. The sintering resulted in a decrease in the number of active sites and an increase in acidic sites, which enhanced the undesired dehydration reaction. Based on the results of inductively coupled plasma (ICP) and TEM, a model of the catalyst was proposed to illustrate the effect of solvent polarity on the dehydrogenation of isoborneol.

Catalysis is generally explained by the reaction of adsorbed species, but in certain cases it can be also understood by the involvement of surface “quasi-compounds”. A quasi-compound is a combination of elements that can exist only on a specific crystalline surface, but cannot be taken out from the surface. A prominent example is found in the ammonia synthesis reaction. Decomposition of NH3 occurs on most metals and its kinetics is governed by the rate-determining desorption of N2, but the synthesis reaction occurs only on a limited number of clean metals. Precious metals in pure form are inactive for the ammonia synthesis reaction, however, the reaction of adsorbed N(a) with H2 on precious metals gives NH3 via NH(a). Among base metals Ni is also inactive for the ammonia synthesis reaction. But N-atoms form a quasi-compound Ni3N on Ni(110) rather than adsorbed species, and the hydrogenation of Ni3N with H gives NH3 via the NH(a) intermediate. On the other hand, adsorption of NH3 gives only NH2(a) on these metals. Interestingly, Ni3N on Ni(110) becomes inactive for reaction with H-atoms at temperatures higher than approximately 500 K, because the quasi-compound Ni3NH undergoes decomposition to Ni3N at approximatelt 500 K; that is, no NH2(a) is formed at temperatures higher than 500 K. A large inverse hydrogen isotope effect (rD/rH = 2–3) has been reported for the ammonia synthesis reaction on a doubly promoted Fe-catalyst, and interpreted on thermodynamic grounds. Therefore, we propose an alternative explanation for this inverse isotope effect based on the fact that the reaction of N(a) on the precious metals with H2 + D2 (H2/D2= 1) gives equal amounts of NH(a) and ND(a). As discussed in this review, the contribution of labile quasi-compounds, [FexN] and [FexNH], is useful in this regard, and accounts for the formation of NH3 by the hydrogenation of an NH2 intermediate formed from [FexNH]. According to this mechanism, the activity of the Fe-surface is given by the steady rate of formation of labile [FexN] and [FexNH] to give adsorbed NH2(a) on the Fe-surface.

A variety of silica-supported metal oxide catalysts were prepared by the incipient wetness impregnation method and were used for the conversion of dihydroxyacetone to lactic acid. A titanium oxide catalyst with Bronsted acid sites was selective to an intermediate, pyruvaldehyde and a chromium oxide catalyst with Lewis acid sites was selective to lactic acid. The co-impregnation of chromium- and titanium oxides with different ratios accelerated the reaction rate and improved the lactic acid yield up to 80% at 130 °C. Pyridine-adsorbed Fourier-transform infrared spectroscopy indicated that the silica-supported mixed oxides had both Bronsted acid and Lewis acid sites and the trend of the Lewis/Bronsted ratio was close to that of selectivity to lactic acid. Diffuse reflectance UV–vis spectroscopy showed that the silica-supported chromia-titania catalyst composed of isolated Cr and Ti species in tetrahedral coordination. Kinetic analysis revealed that the two critical rate constants, pyruvaldehyde formation and lactic acid formation, for the chromia-titania catalyst were much higher than those of the titania and chromia catalysts.

Hexagonal boron nitride (h-BN) was ball-milled at various rotation speeds (150–600 rpm) using a planetary ball-mill. Ball-milling disrupted the layered structure of the h-BN, resulting in significant increases of surface area. Ball-milling at 400 rpm gave the highest surface area of 412 m2 g−1 while higher rotation speeds decreased the surface areas due to agglomeration. Moreover, ball-milling resulted in the emergence of amino- and hydroxyl groups on the surface which were observed by Fourier transform infrared spectroscopy, and partial oxidation of the surface boron by the formation of B–OH groups was confirmed by X-ray photoelectron spectroscopy. The appearance of trigonal B–O and tetrahedral B–O was observed by boron-11 magic-angle spinning nuclear magnetic resonance spectroscopy. The number of base sites was increased with the increase of rotation speeds of milling, corresponding to the formation of amino groups. The ball-milled h-BN showed catalytic activity for the nitroaldol reaction between nitromethane and benzaldehyde in which the h-BN milled at 400 rpm exhibited the highest reaction rate and turnover frequency. In addition, the ball-milled h-BN could convert glucose with the formation of fructose at 40 °C whereas pristine h-BN showed no activity. The base sites were mainly responsible for the catalytic activity.

Ball-milled hexagonal boron nitride (h-BN) involving oxidized boron on the surface was found to catalyze oxidative dehydrogenation of ethane with high selectivity to ethylene (92–96%) whereas prist...

This paper deals with a study of the mechanism of hydrodeoxygenation (HDO) at 0.1 MPa and 300–350 °C of 2-methyltetrahydrofuran (2-MTHF) over a Ni2P/SiO2 catalyst. The study was conducted using in situ Fourier transform infrared (FTIR) spectroscopy to monitor the adsorbed species during reaction and in situ X-ray absorption fine structure (XAFS) to probe the oxidation state of the Ni component. The work is relevant to the upgrading of bio-oil derived from the pyrolysis of biomass. It was deduced that the initial interaction of the 2-MTHF was with OH groups on the catalyst surface, followed by adsorption on Ni sites. Ring-opening of the tetrahydrofuran led to the formation of the main products of the reaction, n-pentane by HDO and n-butane + CO by decarbonylation. The CO band appeared with a slight delay in the FTIR spectrum because the reaction to form n-pentane was favored and turned over about four times before one n-butane + CO was formed.

This paper provides some general conclusions about the effects of pressure, contact time, permeance, and selectivity in membrane reactors for the dehydrogenation of ethane. It is demonstrated that elevated pressure is desirable for the operation of membrane reactors even though the equilibrium may be unfavorable because of a net increase in moles (such as occurs in many hydrogen-producing reactions). This is because the increased reactant throughputs at higher pressures more than compensates for the decreased conversion, and because permeance is favored with higher pressure differences. It is also shown that a permeance above 10−7 mol m−2 s−1 Pa−1 is needed for satisfactory operation and that product selectivities above 100 do not substantially improve performance. Finally, it is shown that contact times above 10 s are important for operating membrane reactors. As a model A → B + C reaction, the dehydrogenation of ethane (C2H6 → C2H4 + H2) was studied over a 5 wt% Cr/ZSM-5 catalyst in a conventional packed-bed reactor (PBR) and in a membrane reactor (MR) fitted with hydrogen selective silica membranes at various feed flow rates, total pressures and temperatures. Two types of membranes were used. One was prepared by the chemical vapor deposition (CVD) of vinyltriethoxysilane (VTES) at 873 K and had a high H2 permeance of 4.0 × 10−7 mol m−2 s−1 Pa−1 with a H2/C2H6 selectivity of 240 at 823 K. The other was prepared by the CVD of a mixture of silica and zirconia precursors, and had a lower H2 permeance of 1.9 × 10−7 mol m−2 s−1 Pa−1 but a higher H2/C2H6 selectivity of 4300 at 823 K. At all reaction conditions the conversion of C2H6 and yields of C2H4 and H2 in the MR were higher than those in the PBR. The effect of pressure was studied and an important result was the finding that the productivity in H2 formation increased with increasing pressure even though the conversion of C2H6 decreased for thermodynamic reasons. A one-dimensional model was used to describe the MR, and it’s performance was evaluated by correlating the yield enhancement of C2H4 with the permeance of the membranes and also a parameter called an operability level coefficient (OLC), which is the ratio between the permeation rate and the formation rate of a H2 in the membrane reactor. Another notable finding was that a H2 permeance selectivity of 100 was sufficient to achieve good performance in the MR. Higher selectivities did not improve H2 yields significantly.

Hydrothermally stable silica-alumina composite membranes were synthesized through chemical vapor deposition (CVD) of tetraethylorthosilicate (TEOS) and aluminium tri-sec-butoxide precursor at 923 K on porous alumina supports. The membranes showed high hydrogen permselectivity (order of 10−7 mol m−2 s−1 Pa−1) comparable to that of pure silica membranes but with superior hydrothermal stability, and were used in a membrane reactor. The permeation of small gas species (H2, He, Ne) was well explained by a solid-state diffusion mechanism, involving jumps of the permeating species between solubility sites. The permeation mechanism of large gas molecules (CH4, CO2, N2) was explained by the gas translation mechanism involving large pore defects. Steam methane reforming (SMR) on a Ni/MgO-SiO2 catalyst was carried out at 923 K in the membrane reactor and in a conventional packed-bed reactor. The membrane contributed to an increase in the hydrogen production rate by the selective extraction of hydrogen from the reaction zone.

Hydrogen-selective silica membranes were prepared on a macroporous alumina support by chemical vapor deposition (CVD) of vinyltriethoxysilane (VTES) at 873 K at atmospheric pressure. The membrane had a high H2 permeance of 5.4 × 10−7 mol m−2 s−1 Pa−1 with H2 selectivity over CO2, N2, CO and CH4 of 95, 170, 170 and 480, respectively. In situ Fourier transform infrared (FTIR) measurements after CVD on an alumina disk at the same conditions as for the membrane preparation showed that the vinyl groups remained in the silica structure. The VTES-derived membrane had higher hydrothermal stability than a pure tetraethoxyorthosilicate (TEOS)-derived silica membrane, during exposure to 16 mol% water vapor at 872 K for 72 h. The temperature dependence of the permeance of various molecules (He, Ne, H2, CO2, N2, CO, CH4) before and after hydrothermal treatment gave information about the mechanism of permeance and the structure of the membrane. The membrane was composed of a contiguous silica network through which small species permeated by a solid-state mechanism and a small number of pores through which the large molecules diffused. The silica-based structure became more compact after hydrothermal treatment with decreasing permeance of small molecules (He, Ne, H2), while small pores were enlarged increasing permeance of large molecules (CO2, N2, CO, CH4). Calculation results for the small species based on a mechanism involving jumps of the permeating species between solubility sites showed lower activation energy and larger jump distances than those of a TEOS-derived silica membrane. The retention of the vinyl groups in the structure mostly associated with the defect pores resulted in interactions with CH4 and CO2, so that these species permeated by a surface diffusion mechanism.

Direct depolymerization of crystalline cellulose into water-soluble sugars by solvent-free ball milling was examined in the presence of a strongly acidic layered metal oxide, HNbMoO6 , resulting in full conversion with 72 % yield of water-soluble sugars. Measurements by 13 C cross-polarization magic angle spinning NMR spectroscopy and X-ray diffraction revealed that amorphization of cellulose occurred rapidly within 10 min. Scanning electron microscopy equipped with an energy dispersive X-ray indicated that the substrate and the catalyst were well mixed during milling. The time course of the product distribution showed that most of the resultant water-soluble sugars were produced not by successive degradation of oligosaccharides but by direct depolymerization of cellulose chains. The products included glucose, mannose, and cello-oligomers, as well as anhydrosugars. Addition of small amounts of polar solvents increased the sugar yield, whereas further addition of water decreased the selectivity to anhydrosugars. Calculations of the mechanical energy required for the ball-milling process showed that 0.02 % was utilized for the chemical transformation under the conditions examined in this study.

A novel alumina@SAPO-11 composite with a hierarchical pore structure was successfully prepared via the in situ assembly and crystallization of silicoaluminophosphate nanoclusters at the surface of an alumina substrate. The material shows enhanced catalytic performance in transforming n-octane into mono- and di-branched isomers with higher octane numbers.

Two types of Ni2P/SiO2 were prepared by different methods, a conventional method involving temperature-programmed reduction (TPR) and a liquid-phase synthesis (LP). Both methods resulted in phase-pure materials with the Ni2P hexagonal phase, but the sample prepared by TPR had lower particle size (7 nm) than the sample prepared by LP synthesis (25 nm). The samples were tested in the gas-phase hydrodeoxygenation of 2-methylfuran (2-MF) in H2 at 0.5 MPa and 250–450 °C, and it was found that the Ni2P/SiO2-TPR gave higher conversions and turnover frequencies than the Ni2P/SiO2-LP. It was conjectured that the difference in activity was due to the higher phosphorus content of the sample prepared by TPR, and this was confirmed by measurements of the P/Ni ratio by x-ray photoelectron spectroscopy. The main products formed by the two catalysts were 2-pentanone and n-pentane and small amounts of 1-pentanol and 2-pentanol. Contact time measurements on the Ni2P/SiO2-TPR sample indicated that 2-pentanone was a primary product, the pentanols were intermediary compounds, and the n-pentane was a final product. Kinetic measurements on the Ni2P/SiO2-LP revealed orders of 0.6 for the 2-MF and 0.5 for H2, consistent with adsorption of both reactants on the catalyst and a surface reaction between the adsorbed species. TPR was also employed to prepare a Cu3P/SiO2 sample. Although a phase-pure material was formed, the substance showed very low activity for the HDO of 2-MF.

Hydrogenation of furanic compounds is one of the important reactions for upgrading of bio-oils and production of diesel fuels. Platinum catalysts supported on amorphous silica and hexagonal boron nitride (h-BN) were prepared by incipient wetness impregnation and subsequent reduction, and were used for the vapor-phase hydrogenation of 2,5-dimethylfuran in hydrogen at atmospheric pressure and a temperature range of 150–350 °C. For the same amount of Pt loading (1 wt%), the particle size of Pt supported on h-BN was larger than that on silica, resulting in a lower amount of CO chemisorption for Pt/BN than that for Pt/SiO 2 . Using the same amount of active sites, Pt/BN exhibited a 3-fold higher turnover frequency than Pt/SiO 2 for the hydrogenation of 2,5-dimethylfuran whereas both catalysts gave similar product distributions with high selectivity to 2-hexanone at any conversion and low selectivity to n -hexane at high conversion. Contact time studies of 2,5-dimethylfuran hydrogenation on Pt/BN suggested that 2,5-dimethylfuran formed the ring-opening product, 2-hexanone and the ring-saturation product, 2,5-dimethyltetrahydrofuran in parallel, with the rate of the direct furan ring-opening being 9-fold higher than that of the furan ring-saturation.

Catalysts consisting of Ni 2 P placed on low and high surface area siliceous supports, i.e. SiO 2 -L, SiO 2 -H, and Si-MCM-41, were synthesized by TPR (temperature-programmed reduction), and the effect of the sulfur and nitrogen content of the feed on hydrotreating activity was studied. Structural information on the supported Ni 2 P phase after reaction was obtained by XRD (X-ray diffraction) and EXAFS (extended X-ray absorption fine structure) measurements. The catalytic activity in hydrodesulfurization (HDS) and hydrodenitrogenation (HDN) was obtained at 573 and 613 K and a pressure of 3.1 MPa in an upflow, liquid-gas-solid bed reactor with a feed consisting of 4,6-dimethyldibenzothiophene (4,6-DMDBT) and quinoline dissolved in tridecane as solvent. Using reference compositions of 4,6-DMDBT at levels of 500 ppm S, dimethyldisulfide (DMDS) at levels of 6000 ppm S, and quinoline at levels of 200 ppm N, the order of activity was Ni 2 P/SiO 2 -L 2 P/SiO 2 -H 2 P/MCM-41, compared on the basis of equal number of sites (230 mmol) placed in the reactor. The Ni 2 P/MCM-41 gave a notably high conversion in HDS of 98% that was substantially above those of a Ni-Mo-S/Al 2 O 3 commercial catalyst which had an HDS conversion of 81%, on a basis of equal quantity of sites (230 mmol) placed in the reactor. The sites were titrated by pulse CO uptakes for the phosphides and by pulse O 2 adsorption at low temperature for the sulfide. Analysis of the spent samples by EXAFS showed that Ni(2) sites of square pyramidal geometry in Ni 2 P are bound to sulfur, with a lower Ni S coordination, as the particle size decreased, and the order in the number of these sites followed the reactivity Ni 2 P/SiO 2 -L 2 P/SiO 2 -H 2 P/MCM-41. It is thus concluded that the active Ni(2) site on the highly dispersed Ni 2 P is much more tolerant to sulfur than the tetrahedral Ni(1) sites also present in the samples.

A series of supported Ni-Mo-P alloy catalysts was studied for the catalytic hydrodeoxygenation (HDO) of the cyclic five-membered ester γ-valerolactone (GVL-C5H8O2) as a model compound for pyrolysis oil. Alloy formation in Ni-Mo-P was indicated by X-ray diffraction analysis and X-ray absorption near-edge spectroscopy, which showed systematic shifts with composition. The number of active sites of each metal species was estimated by factor analysis combining CO-uptake measurements and infrared (IR) spectra of adsorbed CO. It was found that the catalytic activity followed the order: Ni2P/MCM-41 > NiMo(3:1)P/MCM-41 > NiMo(1:1)P/MCM-41 ≅ (Ni2P + MoP)/MCM-41 > NiMo(1:3)P/MCM-41 > MoP/MCM-41, whereas the normalized turnover frequency based on Ni sites were similar for all the catalysts, while retaining the same order. It is concluded that adjacent surface Ni atoms are the main active sites involved in the rate-determining step (rds). The Mo-containing catalysts produced more 1-pentanol and C5 hydrocarbons than Ni2P/MCM-41, indicating that while the exposed Ni sites governed catalytic activity, Mo sites controlled the selectivity to C5 hydrocarbons. Thus, steps following the rds were influenced by Mo sites, leading to preferences for different reaction pathway during the HDO of γ-valerolactone. The study reveals that the catalytic behavior of NiMoP catalysts can be tuned by the relative proportion of Ni and Mo sites.

A hydrogen-selective silica-zirconia composite membrane was prepared on a macroporous alumina support by chemical vapor deposition of tetraethylorthosilicate (TEOS) and zirconium (IV) tert-butoxide (ZTB) at 923 K. The resulting membrane had a high H2 permeance of 3.8×10−7 mol m−2 s−1 Pa−1 with selectivities over CO2, N2 and CH4 of 1100, 1400 and 3700, respectively. Studies of the temperature dependence of the permeance of He, H2, and Ne demonstrated that the permeation mechanism was similar to that of dense silica membranes, involving solid-state diffusion with jumps of the permeating species between solubility sites. Parameters such as the site density, jump distance, and jump frequency were calculated and were physically plausible, and varied in reasonable manner with the mass and size of He, H2, and Ne. An alternative mechanism involving an activated gas translational mechanism was shown to fit the data but to give physically unrealistic parameters. The silica-zirconia membrane showed hydrothermal stability over a limited testing period of 48 h. After exposure to 16 mol% water vapor at 923 K for 48 h, a pure silica membrane showed a 68% decline with a H2 permeance of 4.5×10−8 mol m−2 s−1 Pa−1 and a H2 over N2 selectivity of 800, both of which continued to deteriorate. In comparison, a 10% ZrO2-SiO2 membrane showed a decline of 56% but to a level of 10−7 mol m−2 s−1 Pa−1 with a H2 over N2 selectivity of 5700. Importantly, the deterioration largely stabilized at that permeance level.

The effect on the gas permeance properties and structural morphology of the presence of methyl functional groups in a silica membrane was studied. Membranes were synthesized via chemical vapor deposition (CVD) at 650 &deg, C and atmospheric pressure using three silicon compounds with differing numbers of methyl- and methoxy-functional groups: tetramethyl orthosilicate (TMOS), methyltrimethoxysilane (MTMOS), and dimethyldimethoxysilane (DMDMOS). The residence time of the silica precursors in the CVD process was adjusted for each precursor and optimized in terms of gas permeance and ideal gas selectivity criteria. Final H2 permeances at 600 &deg, C for the TMOS-, MTMOS-, and DMDMOS-derived membranes were respectively 1.7 &times, 10&minus, 7, 2.4 &times, 7, and 4.4 &times, 8 mol∙m&minus, 2∙s&minus, 1∙Pa&minus, 1 and H2/N2 selectivities were 990, 740, and 410. The presence of methyl groups in the membranes fabricated with the MTMOS and DMDMOS precursors was confirmed via Fourier-transform infrared (FTIR) spectroscopy. From FTIR analysis, an increasing methyl signal in the silica structure was correlated with both an improvement in the hydrothermal stability and an increase in the apparent activation energy for hydrogen permeation. In addition, the permeation mechanism for several gas species (He, H2, Ne, CO2, N2, and CH4) was determined by fitting the gas permeance temperature dependence to one of three models: solid state, gas-translational, or surface diffusion.

The steam methane reforming (SMR) reaction was studied on a Ni/MgO-SiO2 catalyst at 923 K (650 °C) and 0.40 MPa in a tubular packed-bed reactor. The partial pressures of CH4 and H2O were varied between 20 and 140 kPa and 80 and 320 kPa, respectively. Measurements were carried out without mass and heat transport limitations, as verified by the Weisz–Prater and Mears criteria. Experimentally, the CH4 conversion increased with the inlet partial pressure of H2O and decreased with the inlet partial pressure of CH4. However, at low CH4 inlet partial pressures, i.e., at 40 and 60 kPa, the conversion passed through a maximum. Rate expressions were derived based on a simple two-step sequence. A statistical analysis led to a globally significant, weighted regression and resulted in a good agreement between the model and the experimental data, as indicated by a low F value of model adequacy of 2.84. The rate and equilibrium coefficient parameters were statistically significant as indicated by narrow confidence inter...

Photocatalytic water splitting is an environmentally-friendly method for hydrogen formation, but usually H 2 and O 2 , are produced together, so separation is needed. This paper describes the separation of the gases with supported liquid membranes. The permselective liquids were various perfluorocarbon-based fluids, Dimethyl perfluorosebacate ((CF 2 ) 6 (COOCH 3 ) 2 ), ethyl perfluorononanoate (CF 3 (CF 2 ) 7 COOC 2 H 5 ), perfluoro(perhydrophenanthrene) (C 14 F 24 ) and 1H,1H,2H,2H-perfluorodecyl acrylate (CF 3 (CF 2 ) 7 (CH 2 ) 2 OCOCH=CH 2 ). It was found that the perfluorodecyl acrylate-based liquid membrane showed the highest performance with H 2 permeance of 2.4×10 −9 mol m −2 s −1 Pa −1 (6700 barrers) and a H 2 /O 2 selectivity of 10. The permeance properties of H 2 and O 2 were measured by a time-lag technique and respective diffusivities of 1.1×10 −8 and 6.7×10 −9 m 2 s −1 and solubilities of 2.7×10 −4 and 4.1×10 −5 mol m −3 Pa −1 , were obtained. The lifetime of the membrane was over 48 h, which was much longer than that of other perfluorocarbon-based liquid membranes. The membrane was also stable at humid conditions.

Understanding the reactions of heteroatomic cyclic compounds is essential for developing good catalysts for the upgrading of bio-oils into liquid fuels. The present study presents the reaction network of 2-methyltetrahydrofuran (2-MTHF, C5H10O), a bio-oil model compound, on silica-supported nickel phosphide at 0.1 MPa and 300 °C. Contact time experiments showed that 2-MTHF reacted to first form 1-pentanol and 2-pentanol, then n-pentanal, 2-pentanone, and 1- and 2-pentenes, and finally n-pentane. The observation is consistent with a reaction network in which adsorption of 2-MTHF is followed by rate-determining ring-opening steps on the more hindered side (path I) or the more open side (path II) to first produce adsorbed alcohols. The alcohols then transform into adsorbed aldehyde, ketone, and pentene species which can simply desorb or react to produce the final product n-butane (decarbonylation of adsorbed n-pentanal) or n-pentane (hydrogenation of adsorbed pentenes). Kinetic modeling of the proposed react...

The potential impact of nitrogen and ammonia exposure on hydrogen permeance through thin palladium membranes (1.3 µm to 4.1 µm thick) fabricated by electroless plating was studied. Additionally, a robust approach is introduced to quantify the pressure exponent which accounts for contributions to Knudsen flow through defects present in very thin membranes. In sharp contrast to previously published results, no flux inhibition was observed due to nitrogen or ammonia exposure. Studies included 24 h exposures to both pure gases and equimolar hydrogen/nitrogen or hydrogen/ammonia mixtures at trans-membrane pressures ranging up to 1.0 MPa and temperatures of 598 K to 773 K. One membrane did exhibit significant flux inhibition after helium exposure, but this was attributed to changes in surface microstructure associated with hydrogen departing the lattice. This apparent hydrogen flux inhibition behavior was permanently eliminated by air exposure which roughens the surface, and it is suggested that this surface structure mechanism is a more probable explanation for flux inhibition than adsorption of nitrogen–based species.

The reactions of 2-methyltetrahydropyran (2-MTHP, C6H12O) on Ni2P/SiO2 provide insights on the interactions between a cyclic ether, an abundant component of biomass feedstock, with a transition-metal phosphide, an effective hydrotreating catalyst. At atmospheric pressure and a low contact time, conditions similar to those of a fast pyrolysis process, 70% of products formed from the reaction of 2-MTHP on Ni2P/SiO2 were deoxygenated products, 2-hexene and 2-pentenes, indicating a good oxygen removal capacity. Deprotonation, hydrogenolysis, dehydration, and decarbonylation were the main reaction routes. The reaction sequence started with the adsorption of 2-MTHP, followed by ring-opening steps on either the methyl substituted side (Path I) or the unsubstituted side (Path II) to produce adsorbed alkoxide species. In Path I, a primary alkoxide was oxidized at the α-carbon to produce an aldehyde, which subsequently underwent decarbonylation to 2-pentenes. The primary alkoxide could also be protonated to give a ...

Contact-time measurements based on sites are used to investigate the reaction sequence of the hydrodeoxygenation of γ-valerolactone (GVL) on Ni2P/MCM-41. The study is carried out at 300 °C and 0.5 MPa with site times of 0.29–6.1 s. A reaction network is proposed in which pentanoic acid and 2-methyltetrahydrofuran (2-MTHF) are formed in parallel initially and pentanal, butane and pentane are formed subsequently. A first-rank Delplot analysis (selectivity) gives a good fit, but higher-rank Delplots do not. The lack of applicability is explained by the magnitude of the rate constants, in which the rate constant for one of the later steps (the consumption of pentanal) is substantially larger than those for the preceding steps. For this reason, pentanal demonstrated the characteristics of a primary product and consequently affected the discrimination of higher rank products. A simulation of a model sequence with assumed rate constants confirms the reason why the Delplot method does not work for this reaction. Since the rate constants cannot be determined a priori to be of close magnitude, the Delplot method cannot be generally used to ascertain reaction sequences.

As an electrolyte for intermediate-temperature fuel cells (ITFCs), which are operative at 200 °C to 300 °C, a composite electrolyte CsH5(PO4)2/SiP2O7 has been investigated. The CsH5(PO4)2/SiP2O7 composite is reported to exhibit higher conductivity than pure CsH5(PO4)2, possibly by forming a highly-conductive new phase at the interface between CsH5(PO4)2 and SiP2O7. In this study, we have prepared several SiP2O7 matrices of different surface properties, and studied the effect of the surface properties on the total conductivity as well as on the formation mechanism of the interfacial conductive phase. An effective medium approximation method was applied to the measured conductivity to analyze the interfacial conductive phase. Several SiP2O7 matrices of different acid properties and crystalline properties were fabricated, and the conductivity of the CsH5(PO4)2/SiP2O7 composite electrolyte was measured by AC impedance method. The acidity and crystallinity of the SiP2O7 matrices were found to be important properties for the formation of the interfacial conductive phase. The highest conductivity of the interfacial conductive phase was estimated to be 500 mS cm− 1, which is almost three times larger than that of the pure CsH5(PO4)2, 160 mS cm− 1.

Pyrolysis bio-oil is a promising source of liquid fuels, but requires upgrading to remove excess oxygen and produce a satisfactory fuel oil. Nickel phosphide has been shown to be an active composition for hydrodeoxygenation (HDO) of bio-oil model compounds. In this study, nickel phosphide catalysts were used for direct upgrading of an actual pyrolysis bio-oil derived from cedar chips. The activity of Ni2P deposited on an amorphous SiO2 support for HDO was first verified using the model compound, 2-methyltetrahydrofuran (2-MTHF), at the temperature of the pyrolysis oil treatment of 350 °C. The Ni2P/SiO2 catalyst showed high activity for 2-MTHF hydrodeoxygenation under atmospheric pressure hydrogen with low cracking activity. Fast pyrolysis and catalytic upgrading were conducted sequentially using a laboratory-scale, two-stage system consisting of a fluidized bed pyrolyzer and a fluidized bed catalytic reactor both operating at 0.1 MPa, with a hydrogen partial pressure of 0.06 MPa. It was found that the Ni2P/SiO2 catalyst was moderately effective in upgrading the biomass pyrolysis vapors and producing a refined bio-oil with decreased oxygen content. The moderate deoxygenation of the bio-oil was confirmed by elemental analysis and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) analysis. Gas chromatography–mass spectrometry (GC–MS) analysis showed that the treated bio-oil mainly consisted of phenolic compounds, and the MS spectra before and after upgrading suggested that reactions including hydrodeoxygenation, hydrogenation, decarbonylation, and hydrolysis occurred during the upgrading. Furthermore, Ni2P supported on ZSM-5 zeolite eliminated oxygen in the bio-oil with smaller reduction in the oil yield than Ni2P supported on SiO2. The deoxygenation activity of the nickel phosphide catalysts was higher than that of conventional catalysts such as Ni/SiO2, Pd/C and an FCC-catalyst.

Both non-acidic LiNbMoO6 and strongly acidic HNbMoO6 efficiently catalyze the epimerization of sugars including glucose, mannose, xylose, and arabinose in water. The reactions over these oxides reached almost equilibrium within a few hours where yields of corresponding epimers from glucose, xylose, and arabinose were 24-29%. The layered mixed oxides functioned as heterogeneous catalysts and could be reused without loss of activity, whereas bulk molybdenum oxide MoO3 was completely dissolved during the reaction. A (13)C substitution experiment showed that the reaction proceeds through a 1,2-rearrangement mechanism. The surface Mo octahedra were responsible for the activity. The layered HNbMoO6 could also afford mannose from cellobiose through hydrolysis and successive epimerization.

Mixed matrix membranes (MMMs) are hybrid materials prepared by dispersing inorganic particles in a polymeric matrix and are attracting increasing attention for the separation of CO2/CH4 mixtures. The zeolite SAPO-34 and polyetherimide were selected as the inorganic filler and the polymeric matrix for the synthesis of the supported MMMs. Two polymer solvents, dichloroethane (DCE) and N-methyl-2-pyrrolidone (NMP), were investigated for the preparation, and the DCE solvent resulted in a membrane with better CO2/CH4 selectivity. Various SAPO-34 amounts from 0 to 10 wt% were dispersed in the polymer precursor which was dissolved in DCE. The membrane with 5 wt% SAPO-34 content presented the highest performance with a CO2 permeance of 4 × 10−10 mol m−2 s−1 Pa−1 and a CO2/CH4 ideal selectivity of 60. Based on mixed gas permeances and time-lag measurements, the separation of CO2 and CH4 was found to be dominated by the difference in the gas solubilities. The SAPO-34 decreased CH4 transport by increasing its diffusion pathway. Particle agglomeration was observed at 10 wt% zeolite loading in the polymeric matrix.

The Robeson correlation is an empirical plot that shows a tradeoff between selectivity and permeability of gases whose upper boundary is often used to evaluate the performance of a membrane system. This work shows that it is possible to define an optimum permeability/selectivity point on this boundary based on economic optimization. Examples are presented for the separation of four gas pairs: CO2/N2, O2/N2, CO2/CH4, and N2/CH4. The constraints used to limit the optimal point are based on the cost of the membrane, the number of units required to achieve a specific separation, and the compression requirements. The total costs include the fees for utilities and capital costs, and interest payments. The model results are verified against other studies, while initial and targeted parameters are subject to a sensitivity analysis. The optimum points obtained at an operating pressure of 1 MPa were for CO2/N2 a permeability of 3200 barrers and a selectivity of 24, for O2/N2 a permeability of 550 barrers and a selectivity of 4, for CO2/CH4 a permeability of 2000 barrers and a selectivity of 20, and for N2/CH4 a permeability of 110 barrers and a selectivity of 2. A wide range of permeability and selectivity requirements exist for a separation, which depend on a particular gas pair.