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Development of N-doped Pd/C catalysts for hydrogen production from gas-phase formic acid is a challenge. To elucidate the efficient routes of nitrogen insertion on the surface of a mesoporous carbon support, the latter was treated with melamine (Mel), dicyandiamide or NH 3 at 673 and 823 K. Pyrolysis of the melamine/carbon mixture taken in a 1:2 ratio provides an increase in the reaction rate by a factor of 5. The inserted N-sites strongly interact with Pd leading to the formation of highly dispersed Pd nanoparticles (∼1.6 nm) and active atomically dispersed Pd2+ species. With a further increase of the Mel/C ratio, the number of surface N-sites decreases due to occupation of carbon support pores with a g–C 3 N 4 –type residue. This provides a decrease in the Pd dispersion leading to lower reaction rates. Therefore, melamine is an efficient N precursor. The considered synthesis of N-doped catalysts could be scaled. [Display omitted] • Pd/N–C catalysts were studied in hydrogen production from gaseous formic acid. • Melamine, dicyandiamide and NH 3 were used to incorporate N species into C support. • At Mel/C ratio of 1:2 the reaction rate was maximal and increased by a factor of 5. • Emission of by-product CO was decreased by a factor of 4. • Pd was present as nanoparticles (∼1.6 nm) and atomic Pd2+ species. [ABSTRACT FROM AUTHOR]

The effect of support on the performance of Pd1Ag10/Al2O3 and Pd1Ag10/CeO2–ZrO2 catalysts in the selective hydrogenation of diphenylacetylene (DPA) was studied. Characterization of the catalyst by DRIFTS-CO and HRTEM revealed the formation of a PdAg single-atom alloy (SAA) structure on the surface of PdAg nanoparticles, with Pd1 sites isolated by Ag atoms. It was found that the use of CeO2–ZrO2 as a carrier makes it possible to increase the activity of the Pd1Ag10 catalyst by a factor of three without loss of selectivity compared to the reference Pd1Ag10/Al2O3. According to the HRTEM data, this catalytic behavior can be explained by an increase in the dispersion of Pd1Ag10/CeO2–ZrO2 compared to its Pd1Ag10/Al2O3 counterpart. As evidenced by DRIFTS-CO data, the high selectivity of the Pd1Ag10/CeO2–ZrO2 sample presumably stems from the stability of the structure of isolated Pd1 sites on the surface of SAA Pd1Ag10/CeO2–ZrO2. [ABSTRACT FROM AUTHOR]

The catalytic utilization of chlorine-organic wastes remains of extreme importance from an ecological point of view. Depending on the molecular structure of the chlorine-substituted hydrocarbon (presence of unsaturated bonds, intermolecular chlorine-to-hydrogen ratio), the features of its catalytic decomposition can be significantly different. Often, 1,2-dichloroethane is used as a model substrate. In the present work, the catalytic decomposition of trichloroethylene (C2HCl3) over microdispersed 100Ni and 96Ni-4W with the formation of carbon nanofibers (CNF) was studied. Catalysts were obtained by a co-precipitation of complex salts followed by reductive thermolysis. The disintegration of the initial bulk alloy driven by its interaction with the reaction mixture C2HCl3/H2/Ar entails the formation of submicron active particles. It has been established that the optimal activity of the pristine Ni catalyst and the 96Ni-4W alloy is provided in temperature ranges of 500–650 °C and 475–725 °C, respectively. The maximum yield of CNF for 2 h of reaction was 63 g/gcat for 100Ni and 112 g/gcat for 96Ni-4W catalyst. Longevity tests showed that nickel undergoes fast deactivation (after 3 h), whereas the 96Ni-4W catalyst remains active for 7 h of interaction. The effects of the catalyst's composition and the reaction temperature upon the structural and morphological characteristics of synthesized carbon nanofibers were investigated by X-ray diffraction analysis, Raman spectroscopy, and electron microscopies. The initial stages of the carbon erosion process were precisely examined by transmission electron microscopy coupled with elemental mapping. The segmented structure of CNF was found to be prevailing in a range of 500–650 °C. The textural parameters of carbon product (SBET and Vpore) were shown to reach maximum values (374 m2/g and 0.71 cm3/g, respectively) at the reaction temperature of 550 °C. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ni-Sn catalysts with superior selectivity were created for LOHCs hydrogen evolution; • They are based on high-loaded nickel catalyst formulation; • Optimal catalyst has atomic ratio of Ni:Sn of 5:1 and is reduced at 500 °C; • Dehydrogenation selectivity reached over 99 % at MCH conversion of 92 %; • High selectivity of the Ni-Sn catalysts is due to formation of NiSn solid solutions. High-loaded nickel catalysts (HLNCs) modified with Sn were synthesized and tested in dehydrogenation of methylcyclohexane (MCH) as a liquid organic hydrogen carrier. The catalyst composition and its reduction temperature were optimized that enabled to achieve the dehydrogenation selectivity of 99.0 % at a MCH conversion of 92 % and WHSV of 6.0 h−1, while the 99.9 % selectivity was reached at the conversion of 60.4 %, and WHSV of 18.5 h−1. Further, stability of the high selectivity of Sn-modified HLNCs was demonstrated in the long-run (100 h) catalyst test. The genesis of the HLNCs during their modification with Sn and reductive activation in hydrogen was studied. It was shown that the activation at temperatures above 450 °C resulted in a uniform distribution of Sn with the predominant formation of solid NiSn solutions having a crystal lattice of metallic nickel. The formation of the solid solutions provided a decrease in the adsorptive properties relating to the reaction product, toluene, which, in turn, led to an increase in the selectivity of MCH dehydrogenation. [ABSTRACT FROM AUTHOR]

Zeolite materials (SAPO-11 or ZSM-5) were used to prepare modified Al 2 O 3 supports by mixing with Al oxide hydroxide, peptization with HNO 3 and subsequent extrusion. The obtained Al 2 O 3 -SAPO-11 and Al 2 O 3 -ZSM-5 (with 30 wt% zeolite content) were impregnated by solutions containing Ni and P precursors: phosphate (A), phosphite (I), and hypophosphite (H). Ni-phosphide catalysts were prepared by temperature-programmed reduction in hydrogen flow and characterized by ICP-AES chemical analysis, low-temperature N 2 physisorption, H 2 -TPR, NH 3 -TPD, XRD, 27Al MAS NMR, XPS. The catalysts were tested in methyl palmitate (MP) hydroconversion (HC, i.e. hydrodeoxygenation (HDO) + hydroisomerization/hydrocracking). 100% MP conversion was achieved over all catalysts (flow reactor at 340 °C, 2.0 MPa, 5.3 h−1). For Ni 2 P/Al 2 O 3 -SAPO-11 catalysts the overall yield of iso-alkanes (iso-C 15 and iso-C 16) increased in the following order of precursors: A < I < H. The highest yield of iso-alkanes was 21% over Ni 2 P/Al 2 O 3 -SAPO-11 H catalyst. Ni 2 P/Al 2 O 3 -ZSM-5 samples possessed high cracking activity. Alkanes from MP HDO as well as the solvent (n-dodecane) were almost completely transformed to C 6 –C 9 alkanes at 340 °C. Decreasing temperature (290, 270 °C) did not result in significant yield of iso-alkanes over Ni 2 P/Al 2 O 3 -ZSM-5 catalysts. [Display omitted] • Ni 2 P/Al 2 O 3 -SAPO-11 and Ni 2 P/Al 2 O 3 -ZSM-5 were prepared from different precursors. • Reduction processes start at different temperatures for different precursors. • Phosphite and hypophosphite precursors give smaller particles. • SAPO-11-containing catalysts produce n- and iso-alkanes (at 340 °C). • ZSM-5 containing catalysts showed high cracking activity at the same conditions. [ABSTRACT FROM AUTHOR]