Bimetallic and monometallic composite materials containing ultra-microporous carbon, the structure of which is similar to that of activated carbon, Pd 0 , CoO, and possibly PdCoO 2 nanoparticles are synthesized via the pyrolysis of sawdust impregnated with a solution of palladium nitrate and cobalt nitrate. According to TEM, the size distribution of metal-containing particles in the bimetallic catalysts is slightly broader than the one in monometallic catalysts, and the average particle size of the former is larger than that of the latter. Some metal-containing particles are localized on the support surface, while others are pressed into the support matrix or coated with a carbon shell. Bimetallic catalysts exhibit high stability and activity in gas-phase chlorobenzene hydrodechlorination (HDC) to form mostly benzene; in the presence of all cobalt-containing catalysts, chlorobenzene conversion is greater than 85% throughout the investigated range of temperatures (150–300°C). XPS shows that during HDC, the metals are chlorinated and the carbon shells of the metal particles are partially degraded under the action of hydrogen chloride. This is accompanied by the emergence of active metal particles on the catalyst’s surface. Introducing cobalt helps reduce the deactivation of the catalysts’ palladium-containing sites and ensures the formation of additional active sites based on CoO.

Nitrogen-doped carbon nanomaterials show unique properties in catalysis both as an active component and as a support. The oxidized and N-doped graphene nanoflakes (GNFs) of low domain size (10-30 nm) have been studied in present work as supports for cobalt-based Fischer-Tropsch catalysts. Three supports with different types of dominating nitrogen species were synthesized and the effect of both the nature and localization of nitrogen species in the support on the structure and performance of 10 wt.% Co catalysts was investigated. Varying the synthesis technique and post-synthesis treatment, the cobalt particle size and hence the activity of catalyst can be tuned. The catalysts supported on oxidized pristine and N-doped GNFs were found to be the most active. Transformations of N-groups during catalyst preparation and reduction were observed. In the case of edge localization of N-groups the cross-linking of support particles was detected that led to the diffusion hindering and low CO conversion over corresponding catalyst.

The catalytic efficiency of three different cobalt-carbon composites has been compared in the gas-phase hydrodechlorination (HDC) of chlorobenzene (CB) in a flow type fixed bed reactor. The Co@C composite was synthesized by evaporation of overheated liquid drop of Co in the flow of an argon-butene mixture; the Co/C composite - by pyrolysis of sawdust impregnated with Co(NO3)(2) water solution, and the Co/CNT composite - by the impregnation of carbon nanotubes with Co(NO3)(2) water solution. Different oxidation states of cobalt were observed in the studied composites according to XPS, TPR, and in situ vibrating sample magnetometry results: predominantly Co-0 in Co@C, CoO in Co/C, and Co3O4 in Co/CNT. TPR showed the possibility of the reduction of Co3O4 to CoO and even to Co-0 under conditions of HDC and established the temperatures of these transitions. TEM revealed that Co-0 nanoparticles in the Co@C composite are encapsulated by the thin carbon shell, CoO nanoparticles in Co/C are immersed in the carbon matrix, and Co3O4 nanoparticles in Co/CNT are located both on the surface and inside the channels of CNTs. All the composites demonstrated activity in HDC of CB. The efficiency of not only Co-0 but CoO in the CB HDC was shown. The CB conversion at 150-250 degrees C for Co/C and Co/CNT composites, containing predominantly cobalt oxides, was higher than that for Co@C one, containing Co-0 nanoparticles coated with the thin carbon shell. The Co/C composite with the lowest Co content (1.3 wt.%) was more effective in HDC than Co/CNT (14.6 wt.% of Co) and Co@C (79 wt.% of Co) ones. High CB conversion for the Co@C composite at 350 degrees C resulted from the catalytic action of the graphene shell of Co particles, activated by subsurface Co-0.

Two Pd/C catalysts were prepared by pyrolysis of Pd(NO3)2 impregnated sawdust. At equal pyrolysis time slow ramping with shorter isothermal heating resulted in 0.9wt.% Pd/C-S1 sample comprising carbon support with some oxygen-containing moieties and Pd0 with 2.6nm average particle size (APS) partially decorated with carbon shell, whereas fast temperature ramping and long isothermal heating provided 0.6wt.% Pd/C-S2 containing Pd0 with 3.7nm APS, with larger fraction of carbon decorated particles. Pd/C-S1 is slightly more efficient than Pd/C-S2 in gas phase chlorobenzene hydrodechlorination to benzene at 100–250°C. Only Pd/C-S1 provides hexachlorobenzene hydrodechlorination in liquid phase due to lower APS and probably smaller PdCx content.

Palladium supported on carbon (Pd/C) catalysts (0.55–0.65 wt.% of Pd) were synthesized by pyrolysis of birch sawdust under inert atmosphere proceeded by prolonged impregnation of sawdust in aqueous solution of palladium nitrate. In some cases, hydrothermal treatment (HT) of the pristine sawdust was conducted to modify the specific surface area of the final carbon material applied as a catalyst support. Based on low-temperature nitrogen adsorption technique, it was postulated that HT of sawdust in the liquid phase increases. while HT in the gaseous phase decreases the specific surface area of Pd/C. The obtained catalysts contained Pd particles (size ranged from 2 to 10 nm) both coated and not coated with carbon shell as evidenced by XPS and TEM techniques. The synthesized Pd/C composites provide high conversion of chlorobenzene and high selectivity in respect to benzene in hydrodechlorination reaction performed in a flow fixed-bed reactor in the presence of H2. XPS data for Pd/C composites tested in the catalytic reaction indicate their high resistance to HCl. A minor part of metal Pd was found to transform into PdCl2 and PdO.

(7% Pd)/C catalysts have been prepared by the pyrolysis of untreated sawdust and sawdust washed with an acid to remove of Group I and II metal impurities, both impregnated with palladium nitrate. Studies by transmission electron microscopy, X-ray photoelectron spectroscopy, and temperature-programmed reduction have demonstrated that the dominant palladium species in the catalysts is 2–5 nm Pd 0 particles, there is no PdO on the surface, and the catalyst bulk contains small amounts of larger (10–20 nm) PdO particles. The catalysts are active in chlorobenzene hydrodechlorination in a fixed-bed flow reactor and ensure 100% conversion of the substrate into benzene in the temperature range from 250 to 350°C. At lower temperatures (150–200°C), the catalyst containing calcium is the most active and the sample subjected to reduction after pyrolysis shows the lowest activity.