Carbonization of Ethylenediamine Coimpregnated CoMo/Al₂O₃ Catalysts Sulfided by Organic Sulfiding Agent

Abstract

Co-impregnating binary Cobalt/Molybdenum/Alumina (CoMo/Al 2 O 3 ) catalyst with addition of ethylenediamine was studied for carbonization, sulfidation and hydrodesulfurization using experimental methods. In order to understand the mechanism of carbonization of active phases, theoretical CoMo/Carbon models were produced using density functional theory (DFT) methods. Results from carbonization of the organic component indicate that the formation of support-like carbon species provoke dispersion of active particles and reduce interaction with support at the active sites (Co, Mo), thus enhancing the HDS activity. Geometrical optimization by DFT shows that a carbide-like Co-Mo-C structures are more stable, which can be formed by a simultaneous carburization and sulfidation at unsaturated S or Mo edge of (Co)MoS x slab with CH 3 SSCH 3 as both carbon and sulfur source.Until now, the issues concerning the carbonation of HDS catalysts are still in debate. For systematically and explicitly elucidating the roles played by carbon species, we designed a research plot. We firstly identified the carbon species on HDS catalyst, investigated the formation mechanism of each carbon species, and then illustrated the effect of these carbon species on the HDS activity. In this work, experimentally, CoMo catalysts were prepared with addition of EN, and then sulfided with organic agents (thiophene and DMDS). We focus our attention to the carbon species. In order to correlate experimental results a series of computer assisted DFT calculations were performed, investigating the carburization at the "Co-Mo-S" active sites at the atomic level. Experimental and computational details Catalyst preparationThe catalysts were prepared by impregnating γ-Al 2 O 3 with NH 3 aqueous solution of Co(NO 3 ) 2 ·6H 2 O, (NH 4 ) 6 Mo 7 O 24 ·4H 2 O and EN, followed by drying at 110 o C for 12 h. The catalysts with the EN/Co molar ratio of 1 and 2 were denoted as CoMo(EN1) and CoMo(EN2) respectively. Comparison catalyst was prepared by calcining CoMo(EN1) under air at 450 o C for 4 h to remove EN; it was represented as CoMo. The loadings of CoO and MoO 3 for all catalysts (after calcinations) were 3.2 and 16 wt%, respectively. Catalyst sulfidation and HDS testThe sulfidation and HDS tests were carried in a fixed bed tubular flow reactor with an inner

Electronic states and metallic character of carbide Co/MoS2 catalytic interface

“…From calculations of the electronic states resulted that carburization energies (ΔE) have exothermic values, as obtained from ET values and its usage on equation 1 (SI-1). These values are also displayed in table 1, where it is possible to determine carburization thermodynamic trend as follows C > CH > CH2 > CH3 > CH3SH, in agreement with observations made by Ge et al [22] and Tuxen et al [23]. When carbon atoms integrate at sulfur edge (as shown in figure 2a) forms a triple bond, meaning sp 2 hybridization by ionic nature to Mo surrounding atoms with similar bond length as for α-MoC phase in agreement with previous reports [24][25]; furthermore the ionic bonding was validated by Mulliken charge analysis as listed in table 2 bending of interface upper part towards carbon zones is observed (figure 2a) and can be highly attributed to electron charge difference before and after carbon was replaced at sulfur edge, as experimentally observed by in-situ operando HRTEM by Ramos et al [19] and previously by Berhault et al [26], as displayed in figure 1b with aid of Synchrotron X-ray diffraction and EELS in order to study carburized process for unsupported molybdenum sulfide catalyst.…”

Efficient CoMoS Catalysts Supported on Bio‐Inspired Polymer Coated Alumina for Hydrotreating Reactions

“…Most likely this carbonaceous deposit is present as an adlayer on Al 2 O 3 , which might eventually help in avoiding the direct contact of the active phase with the support and also reduce the possible detrimental interactions between δ/γ‐Al 2 O 3 and the active phase. Now, the active phase on Pdop/δ/γ‐Al 2 O 3 is present on carbon like support leading to a positive impact on the final catalytic activity ,. It is reported in literature that the carbon support or carbon deposited onto the Al 2 O 3 support weaken the interaction between active metals and the support converting type‐I CoMoS phase to more active type‐II CoMoS phase.…”

“…Now, the active phase on Pdop/δ/γ‐Al 2 O 3 is present on carbon like support leading to a positive impact on the final catalytic activity ,. It is reported in literature that the carbon support or carbon deposited onto the Al 2 O 3 support weaken the interaction between active metals and the support converting type‐I CoMoS phase to more active type‐II CoMoS phase. Further, Schwartz et.…”

Effect of Fe, Co and Ni promoters on MoS2 based catalysts for chemoselective hydrogenation of nitroarenes

“…The increased stacking numbers indicated that the promoters decreased the interaction between Mo and support, facilitating the formation of type II active phase with higher intrinsic activity. 46 Especially, the addition of Ni promoter formed smallest crystallite sizes and highest stacking numbers, which may be one of the reasons for its high catalytic activity. In addition, high-angle annular dark-eld scanning TEM (HADDF-STEM) image (Fig.…”