•A pH-sensitive P(AAm-co-AA) copolymer was used as carrier for Pd nanoparticles.•P(AAm-co-AA)-Pd catalyst exhibited similar activity compared with PVP-Pd due to the quasi-homogeneous catalytic system.•P(AAm-co-AA)-Pd catalyst can be easily separated from the after reaction system by simply adjusting pH value.•P(AAm-co-AA)-Pd catalyst can realize the homogeneous reaction and heterogeneous separation.•P(AAm-co-AA)-Pd have broader range of catalytic applications.A simple pH-sensitive P(acrylamide-co-acrylic acid) copolymer was employed as a stabilizer for Pd nanoparticles (NPs) to develop a recyclable and highly efficient catalyst system. P(AAm-co-AA) copolymer stabilized Pd NPs exhibited high activity in the aqueous hydrogenation of allyl alcohol (HA) and phenol (HP). After reaction, due to the pH-sensitive property of P(AAm-co-AA), the P(AAm-co-AA)-Pd catalyst can be easily separated from the reaction medium by simply adjusting pH from weak basic condition (pH > 8) to acidic condition (pH < 3). Only negligible activity loss was found in the following catalytic runs.Download high-res image (69KB)Download full-size image

Dehydration and catalytic cracking reactions can be combined to convert glycerol into light olefins using solid acid catalysts. The combination is suitable for a single-step process to convert glycerol into light olefins at high temperatures (26–36% selectivity at 873 K). However, large quantities of carbon oxides are produced (31–39% COx selectivity), and catalyst deactivation also occurs. High light olefin selectivity (62–65%) and a smaller quantity of carbon oxides (11–12% COx selectivity) can be obtained by using a tandem process involving the dehydration of glycerol and subsequent catalytic cracking of the dehydration products (mainly acetol and acrolein). Furthermore, the ratio of propylene to ethylene can be adjusted by changing the dehydration catalysts to favor the production of acetol or acrolein: Acetol forms propylene, and acrolein forms ethylene. To overcome the fast deactivation of acid catalysts in glycerol dehydration, the hydrogenolysis and catalytic cracking reactions can be synchronized to convert glycerol into hydrocarbons using a combination of metal and acid catalysts. The single-step conversion of glycerol over a metal or bifunctional catalyst formed alcohols and paraffin. The highest selectivity for propylene production (approximately 76%) was obtained in a tandem process via the selective hydrogenolysis of glycerol to propanols over Pt/ZSM-5 catalysts followed by the catalytic dehydration/cracking of propanols to propylene over ZSM-5 catalysts at low temperatures (523 K). The selectivity for propylene was improved by increasing the Si/Al ratio of the ZSM-5 catalysts and the reaction time. Under these conditions, economically competitive crude glycerol (mainly mixtures of glycerol and methanol) can be used to synthesize light olefins (approximately 61% selectivity) with a long lifetime (∼500 h) in single-route reactions by increasing the cracking temperature to 773 K, which is suitable for practical methanol to propylene process.Keywords: Glycerol; Hydrogenolysis; Metal catalyst; Propylene; Zeolite

•An acid catalyst with controlled acid concentration was synthesized.•The new catalyst showed better performance than conventional catalyst.•A 93.4% yield to biodiesel additives was achieved on this catalyst.•This catalyst had a switching swelling property in the reaction.•This catalyst could be reused several times without decreasing of activity.A swelling-changeful polymer catalyst with controlled acid concentration for glycerol acetylation to biodiesel additives was carried out. This polysulfone catalyst was prepared by direct copolymerization of sulfonated monomer instead of post functionalization of polymer. The influences of acid concentration of polymer and reaction parameters (such as reaction temperature and time) on the glycerol conversion and product selectivity were studied. Glycerol conversion of 98.4% with 94.9% total selectivity of diacetin and triacetin was achieved at a moderate condition on a polysulfone catalyst with the appropriate acid concentration, which was more active than conventional Amberlyst 15 catalyst. The enhanced catalytic performance of polysulfone catalyst was attributed to the stronger acid strength and better swelling property. Besides, the polymer catalyst had a changeful swelling property during glycerol esterification. It swelled at the initial reaction stage and deswelled from solution at the end of reaction, which provided a good mass transfer during the reaction and endowed easy separation of catalyst from the reaction medium after the reaction. Moreover, the polymer catalyst can be reused several times without deactivation.A swelling-changeful acid catalyst for glycerol esterification with controlled acid concentration was directly synthesized, which showed higher glycerol conversion and biodiesel additives selectivity as well as stability than conventional polymer acid catalyst in glycerol esterification reaction.

Metastable transition metal oxides were used as precursors to synthesize transition metal nitrides at low temperature. Amorphous MoO2 was prepared by reduction of (NH4)6Mo7O24 solution with hydrazine. As-synthesized amorphous MoO2 was transformed into fcc γ-Mo2N at 400 °C and then into hexagonal δ-MoN by further increasing the temperature to 600 °C under a NH3 flow. The nitridation temperature employed here is much lower than that employed in nitridation of crystalline materials, and the amorphous materials underwent a unique nitridation process. Besides this, the bimetallic nitride Ni2Mo3N was also synthesized by nitridating amorphous bimetallic precursor. These results suggested that the nitridation of amorphous precursor possessed potential to be a general method for synthesizing many interstitial metallic compounds, such as nitrides and carbides at low temperature.graphical abstractAmorphous oxide was used as new precursor to prepare nitride at low temperature. Pure γ-Mo2N and δ-MoN were obtained at 400 °C and at 600 °C, respectively.Highlights► We bring out a new method to synthesize transition metal nitrides at low temperature. ► Both mono- and bimetallic molybdenum nitrides were synthesized at a mild condition. ► The formation of two different molybdenum nitrides γ-Mo2N and δ-MoN can be controlled from the same metastable precursor. ► The nitridation temperature was much lower than that reported from crystalline precursors. ► The metastable precursor had different reaction process in comparison with crystalline precursor.

A Cu–Ru nanoparticle catalyst supported on carbon nanotubes was prepared by a chemical replacement reaction between Cu metal nanoparticles and Ru3+ cations. The as-prepared catalyst was characterized by X-ray diffraction, X-ray photoelectron spectroscopy, H2 and CO chemisorption, and transmission electron microscopy. The results showed that the highly dispersed Ru clusters were present on the external surface of the Cu particles. These tiny Ru clusters did not activate glycerol to carry its hydrogenolysis, but instead activated and generated active hydrogen, which was transferred to the Cu surface nearby viahydrogen spillover. The Cu–Ru catalyst exhibited selectivity for 1,2-propanediol that was as high as Cu metal, and much higher hydrogenolysis activity than pure Cu metal because of the hydrogen spillover effect, which benefited from the Ru clusters.

An efficient method for preparation of Mo2C catalyst is described, where Mo2C is obtained by the heat treatment of a single solid precursor containing (NH4)6Mo7O24 and hexamethylenetetramine (HMT) at 923 K in H2 flow without conventional prolonged carbonization. The catalysts are characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), BET surface area measurement, and transmission electron microscopy (TEM). Furthermore, these catalysts are evaluated in the dibenzothiophene (DBT) hydrodesulfurization (HDS) reaction, and proved to be superior to those prepared by a temperature-programmed reduction (TPRe) method. The better catalytic performance is ascribed to higher dispersion of Mo2C on the support and a lower surface polymeric carbon content. This hydrogen thermal treatment (HTT) method provided a new strategy for the preparation of a highly active molybdenum carbide catalyst.

A magnetic core–shell nanocomposite, Fe3O4@SiO2@Pd-Au, was synthesized by reducing palladium and gold cations previously bound to the amine ligand-modified surface of silica-encapsulated magnetic iron oxide (Fe3O4) nanoparticles, and served as a highly efficient and easily-recyclable catalyst for liquid-phase hydrodechlorination of 4-chlorophenol under mild conditions.

A Pd on Ni–B (Pd/Ni–B) bimetallic catalyst was prepared and tested in the hydrodechlorination (HDC) of 4-chlorophenol (4-CP). The catalysts were synthesized by replacement method and treated at different temperatures (298–673 K). The results showed that the one treated at 473 K could achieve complete dechlorination of 200 ppm 4-CP under the pH = 8 within 30 min and keep the high activity in the first four recycles. The introducing of Pd greatly promoted the catalytic HDC efficiency of Ni–B, and the high dispersion of Pd species ensured the high activity of Pd/Ni–B catalysts. The catalytic HDC reaction of 4-CP followed the pseudo-first-order dynamics and the kinetic data was obtained.

In this study, a facile method for the synthesis of bulk and alumina-supported Ni2Mo3N is described. The synthesis is based on the heat treatment of a mixed-salt precursor in a H2 flow at 873 K. The mixed-salt precursor is obtained by evaporating ammonia solution of Ni(CH3COO)2 and (NH4)6Mo7O24 with a fixed Ni/Mo molar ratio of 2 : 3. The formation process of the bimetallic molybdenum nitride has been investigated, which indicates that the labile NH4+ contained in the inorganic salt precursor is utilized as N source to form Ni2Mo3N in the H2 flow when elemental nickel is present. The high NH3 flow rate required in the conventional temperature-programmed nitridation method is not necessary in this hydrogen thermal treatment method. Alumina-supported Ni2Mo3N has also been successfully prepared by this method. The resultant catalyst has better dispersion of Ni2Mo3N and exhibits higher catalytic activity compared to the catalyst prepared by the conventional method.

Iron nitride was prepared by a nitridation reaction in NH3 using amorphous iron as precursor. The precursor was prepared at ambient temperature through the process of reducing ferrous sulfate by potassium borohydride, followed by the nitridation at different temperatures. The nitridation reaction occurred at 548 K, and ϵ-Fe2−3N was formed at 573 K. The reaction temperature was much lower than that using crystallized iron because of the characteristics of the amorphous materials. The existence of a small quantity of boron (1.6 wt.%) improved the stability of the amorphous precursor, which guaranteed an amorphous iron precursor at nitriding temperatures in excess of 548 K.

A simple, one-step thermal decomposition method for the preparation of Co3Mo3C is reported in this paper. In this novel synthesis route, a mixed-salt precursor, containing Co(CH3COO)2·4H2O, (HMT)2(NH4)4Mo7O24·2H2O (HMT = hexamethylenetetramine), and excess HMT is directly decomposed to the bimetallic carbide under flowing argon at 1023 K. The role of HMT in the preparation process has been investigated and a detailed reaction mechanism is proposed based on the experimental results. The bimetallic carbide is characterised by X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, BET surface area measurement and X-ray photoelectron spectroscopy. Furthermore, the activity of the as-prepared Co3Mo3C is evaluated by a 3-methylpyridine hydrodenitrogenation (HDN) reaction. The catalyst produced from this method provides better reactivity compared to the Co3Mo3C catalyst prepared by the conventional temperature-programmed reduction method.

Bulk face-centered-cubic (fcc)-based η-MoC1−x and hexagonal-close-packed (hcp)-based β-Mo2C have been prepared using C3H8/H2 by temperature-programmed reaction method and a rapid heating method. In this work, direct carburization of MoO3 produces η-MoC1−x or MoOxCy with excess carbon, different from that with CH4/H2 or C2H6/H2 as carburization reagent. A successive post-treatment by hydrogen causes the phase transformation from fcc-based η-MoC1−x or MoOxCy to hcp-based β-Mo2C. Amorphous SiO2-supported β-Mo2C is also successfully prepared by the two methods and passes through the same route as the bulk one. HRTEM, BET surface area measurements and thiophene hydrodesulfurization reaction are conducted for the comparison of the two methods. The results indicate that different ramping rates bring slight difference in specific surface area and initial catalytic activity but obvious difference in particle size to the final product supported β-Mo2C.A post-treatment by hydrogen causes the phase transformation of molybdenum carbides in both the conventional TPRe method and a rapid heating method. The HRTEM image shows fairly uniform particles of β-Mo2C display an excellent dispersion on amorphous SiO2 support.

An amorphous Ni–B/TiO2 catalyst has been synthesized by silver-catalyzed electroless nickel plating. The amorphous structure of Ni–B nanoparticles was characterized by X-ray diffraction (XRD) and selected area electron diffraction (SAED). A transmission electron micrograph (TEM) of the Ni–B/TiO2 showed particles with size ranging from 30 to 50 nm were homogeneously dispersed over TiO2 support. High-resolution transmission electron microscopy (HRTEM) indicated that the Ni–B nanoparticles presented a porous and flower-like morphology, which was different from the solid sphere of conventional Ni–B particles prepared by impregnation–reduction method. To investigate the formation process of the porous Ni–B particles, the diffusion of nickel nuclei and the growth of Ni–B particles were characterized. The as-prepared porous Ni–B/TiO2 catalyst exhibited superior catalytic activities in the hydrogenation reactions to those of catalysts prepared by conventional methods.

A new stable solid acid catalyst, functional polyethersulfone containing high content of sulfonic acid group was directly synthesized from sulfonic monomer. This new catalyst was characterized by nuclear magnetic resonance (NMR), thermo-gravimetric analysis, acid-base titration and reagent uptake. The results showed that the new polymer catalyst had higher swelling of reagent and sulfonic group stability than conventional solid acid catalyst Amberlyst 15. Meanwhile, the polymer catalyst exhibited higher activity and stability than Amberlyst 15 in the esterification reactions. The superior performance of new catalyst is attributed to its unique features, including swelling property as well as thermal stability.A new type of stable solid acid catalyst polyethersulfone with sulfonic acid group was synthesized without post-sulfonation, which showed higher stability and swelling of reagent as well as better performance in esterification reactions than conventional polymer acid catalyst.Download full-size imageHighlights► A new solid acid catalyst polyethersulfone was synthesized without post-sulfonation. ► This polymer catalyst contained a pull-electron -SO2- group in its main chain. ► The existing of -SO2- group improved the stability and acid strength of catalyst. ► The new catalyst showed better performance than conventional catalyst.

A single-step complex decomposition method for the synthesis of bulk and alumina-supported γ-Mo2N catalysts is described. The complex precursor (HMT)2(NH4)4Mo7O24·2H2O (HMT: hexamethylenetetramine) is converted to γ-Mo2N under a flow of Ar in a temperature range of 823–1023 K. Furthermore, decomposition of the precursor in a NH3 flow forms γ-Mo2N in a temperature range of 723–923 K. Compared with direct decomposition of the precursor in Ar, the reaction in NH3 shows obvious advantages that the nitride forms at a lower temperature. In addition, alumina-supported γ-Mo2N catalysts with different nitride loadings can be prepared from the alumina-supported complex precursor in the Ar or NH3 flow. The resultant catalysts exhibit good dibenzothiophene HDS activities, which are similar to the γ-Mo2N/γ-Al2O3 prepared by traditional TPR method. The catalyst prepared by decomposition in an Ar flow exhibits highest activity. It proves that such a single-step complex decomposition method possesses the potential to be a general route for the preparation of molybdenum nitride catalysts.

Co3Mo3C, Co6Mo6C and MCM41-supported Co3Mo3C catalyst are prepared by a simple one-step thermal decomposition method without the conventional temperature-programmed carburization. The resultant carbides are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscope (HRTEM) and BET surface area measurements. The as-prepared Co3Mo3C/MCM41 catalyst exhibits good performance in both probe reactions of hydrodesulfurization (HDS) and hydrodenitrogenation (HDN), which proves the one-step decomposition method to be an effective route for the preparation of bimetallic carbide catalyst.

A Pd on Ni–B (Pd/Ni–B) bimetallic nanoparticle catalyst was prepared through a replacement reaction of amorphous Ni–B nanoparticles with Pd2+ ions. In the hydrodechlorination of chlorobenzene, the Pd/Ni–B bimetallic catalyst exhibited better activity than a Pd catalyst supported on polyvinylpolypyrrolidone, a mixture of Pd and Ni–B nanoparticles, and a Pd on Ni catalyst obtained by the replacement reaction of nanocrystalline Ni with Pd2+ ions. The properties of the Pd/Ni–B catalyst were studied in detail by XRD, TEM, XPS, and H2 chemisorptions. The characterizations demonstrated that a Pd–Ni–B surface alloy occurred on the Pd/Ni–B catalyst with heating treatment. The resulting surface alloy promoted resistance to chlorine poisoning, adsorption of the reactants (chlorobenzene and hydrogen), and desorption of products, explaining the better catalytic activity and stability of the Pd/Ni–B bimetallic catalyst.

An efficient method for preparation of Mo2C catalyst is described, where Mo2C is obtained by the heat treatment of a single solid precursor containing (NH4)6Mo7O24 and hexamethylenetetramine (HMT) at 923 K in H2 flow without conventional prolonged carbonization. The catalysts are characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), BET surface area measurement, and transmission electron microscopy (TEM). Furthermore, these catalysts are evaluated in the dibenzothiophene (DBT) hydrodesulfurization (HDS) reaction, and proved to be superior to those prepared by a temperature-programmed reduction (TPRe) method. The better catalytic performance is ascribed to higher dispersion of Mo2C on the support and a lower surface polymeric carbon content. This hydrogen thermal treatment (HTT) method provided a new strategy for the preparation of a highly active molybdenum carbide catalyst.

In this study, a facile method for the synthesis of bulk and alumina-supported Ni2Mo3N is described. The synthesis is based on the heat treatment of a mixed-salt precursor in a H2 flow at 873 K. The mixed-salt precursor is obtained by evaporating ammonia solution of Ni(CH3COO)2 and (NH4)6Mo7O24 with a fixed Ni/Mo molar ratio of 2 : 3. The formation process of the bimetallic molybdenum nitride has been investigated, which indicates that the labile NH4+ contained in the inorganic salt precursor is utilized as N source to form Ni2Mo3N in the H2 flow when elemental nickel is present. The high NH3 flow rate required in the conventional temperature-programmed nitridation method is not necessary in this hydrogen thermal treatment method. Alumina-supported Ni2Mo3N has also been successfully prepared by this method. The resultant catalyst has better dispersion of Ni2Mo3N and exhibits higher catalytic activity compared to the catalyst prepared by the conventional method.

A simple, one-step thermal decomposition method for the preparation of Co3Mo3C is reported in this paper. In this novel synthesis route, a mixed-salt precursor, containing Co(CH3COO)2·4H2O, (HMT)2(NH4)4Mo7O24·2H2O (HMT = hexamethylenetetramine), and excess HMT is directly decomposed to the bimetallic carbide under flowing argon at 1023 K. The role of HMT in the preparation process has been investigated and a detailed reaction mechanism is proposed based on the experimental results. The bimetallic carbide is characterised by X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, BET surface area measurement and X-ray photoelectron spectroscopy. Furthermore, the activity of the as-prepared Co3Mo3C is evaluated by a 3-methylpyridine hydrodenitrogenation (HDN) reaction. The catalyst produced from this method provides better reactivity compared to the Co3Mo3C catalyst prepared by the conventional temperature-programmed reduction method.