Hydrogenolysis Route Research Articles

Optimization of catalyst activity and stability in the m-cresol hydrodeoxygenation through Ni particle size control

By taking advantage of different nanoparticle size control methodologies, the precise role of Ni particle size (from 1 nm to 9 nm) was evaluated in the HDO of m-cresol in vapor phase at 573 K under atmospheric pressure. The m-cresol HDO reaction pathways were found to be Ni-particle size dependent. The direct deoxygenation (DDO) rate increased by 10 times when decreasing Ni particle size from 9 nm to 1 nm, while the hydrogenation (HYD) and hydrogenolysis (HYG) rates moderately increased. By applying a geometric model, reaction rates were correlated to the different type of sites. Edges and corner sites (smaller particles) favor aromatics production (DDO route), while face sites (larger particles) favor both HYD and HYG routes. Catalysts partially deactivated due to coke formation, with only slight sintering observed for 1 nm Ni particles. Such findings may serve in the further preparation of active and selective catalysts for bio-oils upgrading into fuel.

ANALYSIS OF CATALYTIC BEHAVIOR OF RHENIUM PROMOTED PT/TIO2 CATALYST IN ERYTHRITOL HYDROGENOLYSIS

Rhenium modified Pt/TiO2 catalyst has been tested during erythritol (ERY) hydrogenolysis reaction in a slurry reactor. N2 physisorption, temperature programmed reduction and CO chemisorption characterizations were performed. After reduction treatment, Pt species were fully reduced with a dispersion of 26% whereas Re species remained partially oxidized. ERY may convert through four pathways: isomerization, dehydration and C-O or C-C hydrogenolysis. Pt-Re/TiO2 was active and selective to butanetriols and butanediols formation. The influence of temperature (423–498 K) and reactant concentrations (15-35 barH2 and 0.2-0.6 MERY) on catalytic activity and products distribution were evaluated; the activation energy and the reaction orders for each route were estimated. Dehydration pathway displayed the highest activation energy whereas isomerization showed the lowest value. The order to ERY and H2 were 0.23 and 0.97 respectively, for C-O hydrogenolysis route and is consistent with two different mechanisms proposed for the removal of primary or secondary OH group.

Inside Cover: Controlling Reaction Routes in Noble‐Metal‐Catalyzed Conversion of Aryl Ethers (Angew. Chem. Int. Ed. 30/2022)

Supported metal nanoparticles (Pd, Rh, Ir, Ru, or Pt) catalyze the reductive conversion of diphenyl ether in water. There are three primary routes for this transformation, namely hydrolysis, hydrogenolysis, and hydrogenation. In their Communication (e202203172), Oliver Y. Gutiérrez, Johannes A. Lercher, and co-workers highlight the primary products of the hydrogenolysis route (benzene and phenol), which is an important reaction for accessing cyclic compounds from renewable feedstocks.

Kinetic analysis of the conversion of aqueous erythritol solution on Ir/ReOx/TiO2 in a batch slurry reactor

The influence of temperature, H2 pressure and erythritol concentration on the hydrogenolysis of erythritol was studied using Ir/ReOx/TiO2. Under the conditions used here, four reaction routes coexist: isomerization, dehydration, C-O and C-C hydrogenolysis. The initial rates as well as reaction orders and activation energy were estimated for each pathway. The variation of the hydrogen pressure produced slight changes in the isomerization, dehydration, and C-C hydrogenolysis routes, whereas C-O hydrogenolysis showed order 1 with respect to this reagent. The change in erythritol concentration affected more the dehydration, resulting in a reaction order for this reactant close to 1, while for the other routes the order was close to 0.5. Regarding the influence of the temperature, dehydration of erythritol showed the highest activation energy (212.1 kJ mol−1) and the isomerization the lowest (20.0 kJ mol−1). Furthermore, it was found that the ruptures of C-C bonds require higher energy than C-O bonds break.

Valorisation of glycerol through catalytic hydrogenolysis routes for sustainable production of value-added C3 chemicals: current and future trends

The search for sustainable routes for the production of C3 chemicals by using renewable feedstocks has attracted significant interest from academic and industrial communities to alleviate the shortage of fossil fuels.

Encapsulated Ni Nanoparticles within Silicalite-1 Crystals for Upgrading Phenolic Compounds to Arenes

About 3–5 nm Ni nanoparticles were significantly encapsulated within different crystal sizes of a silicalite-1 matrix through tailoring the hydrothermal synthesis conditions and ratios of feeding materials, which were applied in the upgrading of phenolic compounds to arenes via the hydrogenolysis route. The smaller the sizes of Ni@silicalite-1 crystals with similar Ni contents and nanoparticles, the more obvious the active centers could be characterized. The enhancement in both phenol/m-cresol conversion and benzene/toluene selectivity was obtained with the decrease in crystal sizes of Ni@silicalite-1, which originated from the selective elimination of the hydroxyl group, hindrance of further hydrogenation of aromatics, and the formation of methane. Furthermore, Ni@silicalite-1 was first reported for its superior stability for more than 300 h during m-cresol conversion, which maintained a high conversion from 78.4% at 8 h to 76.2% at 334 h and aromatics yield from 73.1% at 8 h to 72.6% at 334 h. Therefore, Ni@silicalite-1 provided an alternative methodology for terminal priority to achieve selectivity control different from hydrogenation on phenyl rings via a thermodynamically favorable flat mode. Ni nanoparticles encapsulated within zeolites provided a new method to regulate the adsorption mode of reactants to modify aromatic selectivity steric effects originating from shape selectivity of the silicalite-1 matrix, which also contributed to much better stability of Ni nanoparticles.

BUTENEDIOLS PRODUCTION FROM ERYTHRITOL ON Rh PROMOTED CATALYST

The C-O hydrogenolysis of Erythritol to Butanodiols was studied in aqueous solution at 473 K and 25 bar of H2 using Rh/ReOx/TiO2 and the monometallic Rh/TiO2 and ReOx/TiO2 catalysts. The solids were characterized by temperature programmed reduction (TPR), TEM and XPS. TPR and XPS showed that ReOx species are close to Rh particles leading to reduction at lower temperature than Re on monometallic catalyst. However, some segregated Rhenium species were suspected by TPR profile for the bimetallic catalyst and detected by TEM. Re/TiO2 exhibited low activity forming only products from dehydration and epimerization. Although Rh/TiO2 showed high activity (total conversion at 14 h), was more selective to C-C cleavage leading to lower carbon products. Rh/ReOx/TiO2, showed instead, a good activity and selectivity towards C-O hydrogenolysis route yielding 37.5% of Butanodiols. Activation energy and reaction orders on ERY (0.58) and H2 (0.53) were estimated from experiences made at different reaction conditions

Catalytic upgrading of biomass-derived 5-hydroxymethylfurfural to biofuel 2,5-dimethylfuran over Beta zeolite supported non-noble Co catalyst

Selectively converting biomass-derived 5-hydroxymethylfurfural (5-HMF) into biofuel 2,5-dimethylfuran (DMF) via hydrogenolysis route is one of significant transformations in the field of heterogeneous catalysis, which is generally performed over supported noble catalysts and/or under harsh conditions such as high temperature (above 423 K, even achieving 533 K) and H2 pressure (1–4 MPa). Herein, non-noble metal (i.e., Co) supported on siliceous *BEA zeolite with open channel systems (Co/Beta-DA) is innovatively proposed for this hydrogenolysis reaction based on strong metal-support interaction. The micro-environment and particle size of metallic Co species were closely related to calcination temperature during the preparation of Co/Beta-DA. The Co species existed in the form of CoOx on the zeolite surface or stabilized inside the zeolite pores as well as isolated Co sites within zeolite framework after calcination (above 723 K), which were reduced by hydrogen to corresponding metallic Co species. It was confirmed that this prepared sample with 20 wt % content of Co, calcined at 723 K, was an efficient catalyst for HMF hydrogenolysis to DMF under mild conditions (423 K, 1.5 MPa H2, 3.0 h), giving an excellent DMF productivity of 1.108 h–1. Thus, this contribution provides new insights for rationally constructing non-noble-based zeolite catalyst for the transformation of biomass into renewable liquid biofuels under mild conditions.

Influence of the Support of Bimetallic Platinum Tungstate Catalysts on 1,3‐Propanediol Formation from Glycerol

AbstractThree aluminium oxide materials and a HZSM‐5 zeolite were used as supports of bimetallic Pt‐WOx catalysts to establish structure–activity relationships in the glycerol hydrogenolysis reaction. The surface W density and the intimate contact between Pt and WOx were key parameters. Surface W density controls the formation of polytungstates, the only species able to produce the weak Brønsted acidity that is required to produce 1,3‐propanediol selectively. The comparison between the HZSM‐5 and the Al2O3 supports demonstrated that an increment of the medium Brønsted acidity is detrimental for the selective 1,3‐propanediol formation as it promotes reactions that yield 1‐propanol and propane. An increase of the dispersion of Pt on the Pt/WOx/Al2O3 catalysts led to higher glycerol conversions but also promoted the hydrogenolysis routes that lead to 1,2‐ and 1,3‐propanediol similarly. On the contrary, an increase of the Pt metal content favoured the hydrogenolysis route that leads to 1,3‐propanediol significantly. A more intimate contact between Pt and WOx promoted the hydrogenation of the intermediate carbocation, formed and stabilised on a polytungstate active site, into 1,3‐propanediol.

Highly Stable Nb2O5–Al2O3 Composites Supported Pt Catalysts for Hydrodeoxygenation of Diphenyl Ether

Various TiO2, SiO2, Al2O3, and Nb2O5–Al2O3 supported Pt catalysts have been prepared by urea precipitation method for catalytic hydrodeoxygenation (HDO) of diphenyl ether (DPE) as a 4-O-5 aryl-ether lignin model compound. The selectivity toward deoxygenated product cyclohexane increased obviously with Nb2O5·nH2O decorated, owing to the significant promotion effect of NbOx species and acid sites on C–O bond cleavage. At higher pressure (3.0 MPa H2), DPE underwent a HYD route, while direct hydrogenolysis route occurred at low pressure (0.1 MPa H2). In addition, the reaction rate constants and activation energies were obtained in the temperature range from 160 to 220 °C. Based on the Arrhenius law, the activation energy for the cleavage of the C–O bond in DPE was calculated to be 91.22 kJ/mol. It was noteworthy that the Pt/20Nb–Al2O3 showed higher stability than Pt/Al2O3 for hydrodeoxygenation of diphenyl ether, which can be attributed to its water-tolerant Lewis acid sites.

High-Value Propylene Glycol from Low-Value Biodiesel Glycerol: A Techno-Economic and Environmental Assessment under Uncertainty

Recent governmental policies that promote a biobased economy have led to an increasing production of biodiesel, resulting in large amounts of waste glycerol being generated as low-cost and readily available feedstock. Here, the production of high-value biobased propylene glycol as an alternative chemical route to valorize biodiesel glycerol was studied and assessed considering economic and life cycle environmental criteria. To this end, the conventional industrial process for propylene glycol production, which uses petroleum-based propylene oxide as feedstock, was compared against three different hydrogenolysis routes based on biodiesel glycerol using process modeling and optimization tools. The environmental impact of each alternative was evaluated following Life Cycle Assessment principles, whereas the main uncertainties were explicitly accounted for via stochastic modeling. Comparison among the various cases reveals that there are process alternatives based on biodiesel glycerol that outperform the cur...

Renewable aromatic production through hydrodeoxygenation of model bio-oil over mesoporous Ni/SBA-15 and Co/SBA-15

In present work, ordered mesoporous material SBA-15 was synthesized and used as the support for the dispersion of the nickel and cobalt active metal. XRD, N2 sorption, ICP, H2-TPR and TEM techniques were used for the Ni/SBA-15 and Co/SBA-15 catalysts characterization. Both Ni/SBA-15 and Co/SBA-15 catalysts were tested for the hydrogenation of the typical oxygen-containing molecule present in bio-oil in order to produce the renewable aromatic. Ni/SBA-15 catalyst exhibit much higher catalytic performance as compared with Co/SBA-15 catalyst for the hydrodeoxygenation reaction performance of anisole, but it is also obvious that the Ni/SBA-15 catalyst would inevitably lead to the emergence of partial hydrodeoxygenation product methoxycyclohexane. On the contrary, the direct hydrogenolysis of methoxy-functional group from anisole molecule could prevail over the Co/SBA-15, leading to much higher aromatic selectivity over the Co/SBA-15. Co/SBA-15 could selectively hydrogenolyse the CO bond and could act as the potential hydrodeoxygenation catalyst for aromatic production from the bio-oils because of its high efficiency in the removal of oxygen by a direct hydrogenolysis route.

Sources of deactivation during glycerol conversion on Ni/γ-Al2O3

Hydrogenolysis of glycerol was studied using a diluted aqueous solution of glycerol in gas phase and atmospheric pressure on Ni/γ-Al2O3 catalyst. The catalytic transformation of glycerol generates products derived from dehydration, dehydrogenation, hydrogenolysis and condensation reactions. Deep hydrogenolysis route to produce CH4 prevails in the first few hours of reaction. As the reaction time progress, dehydration-dehydrogenation products start to appear. Here, a description of the deactivation sources and its effects on the catalytic performance of Ni catalyst was proposed. The catalyst was characterized before and after the catalytic reaction by high-resolution transmission electron microscopy (HRTEM) and by employing Fourier transformed infrared spectroscopy (FTIR) of adsorbed CO. A source of deactivation was due to carbonaceous deposition. FTIR at low CO dosing pressure reveal bands assignments species essentially due to linear and bridge carbonyls, whereas high pressure CO dosing produces a complex spectra due to polycarbonyls. X-ray absorption near edge structure (XANES) analysis was employed to reveal the initial degree of reduction of the fresh catalyst. The oxidation of metallic Ni in the course of reaction may also be considered as a source of deactivation. Ni oxide species promote dehydration routes. Alumina support facilitates nickel species to be more active toward interacting with glycerol. Dehydration, which takes place on the acid sites, is the mainly route related to the generation of carbon deposition and to the observed catalyst deactivation. Another source of deactivation was due to carbiding of Ni to form Ni3C. The regeneration of used Ni catalyst was achieved by oxidation-reduction steps at 723K.

Delaminated MoS2 as a structural and functional modifier for MgH2 – Better hydrogen desorption kinetics through induced worm-like morphologies

Magnesium hydride (MgH2) nanoparticles have been synthesized in the presence of MoS2 via a simple hydrogenolysis route, involving the decomposition of di-n-butylmagnesium. Remarkably using delaminated MoS2 instead of bulk MoS2 led to the formation of magnesium worm-like structures, which collapsed and recrystallized to some extent upon hydrogen cycling. Hydrogen release from these structures occurred at a relatively low temperature (300 °C), and MoS2 was found to effectively improve the hydrogen desorption kinetics of nanosized MgH2. It took less than 150 min to fully release hydrogen from MgH2 catalyzed by delaminated MoS2. In comparison, uncatalysed nanosized MgH2 particles required more than 300 min. Furthermore, MoS2 was found to significantly influence the thermodynamic properties of the Mg/MgH2 reaction, via the destabilization of the Mg–H bond. Compared to ball-milled MgH2, the MoS2 modified materials showed significantly higher hydrogen absorption plateau pressures (∼0.15 MPa). This demonstrates that pathways enabling the tuning of the hydrogen storage properties of nanosized MgH2 toward lower temperatures and fast kinetics may exist.

Degradation on hydrogenolysis of soda lignin using CuO/SO42−/ZrO2 as catalyst

Lignin was chemically modified with hydrogenolysis as a starting material for polymer and chemical synthesis or as an antioxidant. CuO/SO42−/ZrO2 catalyst was prepared through dipping and roasting method. Lignin degradation was conducted through hydrogenolysis routes with CuO/SO42−/ZrO2 as the catalyst. Structural characterization and antioxidant activity of lignin samples were investigated; the reaction mechanism of lignin degradation was also discussed. The total hydroxyl and phenolic hydroxyl group content of soda lignin were increased by 62.9% and 29.4%, oxygen content was decreased by 10.2%, and Mw was decreased from 7700g/mol to 5500g/mol. The EC50 of soda lignin on DPPH scavenging rate, ABTS+ scavenging rate, and reducing power were decreased by 22.1%, 30.4%, and 9.0%, respectively. The degradation of lignin was probably caused by the degradation of β-O-4 ether linkages and cracking of the methoxy. SO42−/ZrO2 mainly cleaved the β-O-4 linkages, whereas CuO cracked the methoxy group on the benzene ring.

Antioxidant Activity of Organosolv Lignin Degraded Using SO42-/ZrO2 as Catalyst

Organosolv lignin degradation was carried out through hydrogenolysis routes with SO42-/ZrO2 as the catalyst. Structural characterization and antioxidant activity of organosolv lignin samples were investigated; the antioxidant activity of the organosolv lignin was compared with that of soda lignin. Results showed that the active functional groups contents of organosolv lignin were increased, and the antioxidant activity of organosolv lignin was improved. The total hydroxyl and phenolic hydroxyl group contents of organosolv lignin were increased by 15.81% and 26.55%, respectively, and the Mw was decreased from 5739 g/mol to 4499 g/mol. The IC50 of organosolv lignin on DPPH radicals scavenging rate, ABTS+ radicals scavenging rate, and reducing power were decreased by 18.91%, 18.08%, and 8.48%, respectively. The catalyzed organosolv lignin can be used as a natural antioxidant for functional food or in cosmetic and polymeric materials.

MgH2 with different morphologies synthesized by thermal hydrogenolysis method for enhanced hydrogen sorption

Magnesium hydride (MgH2) with a range of morphologies has been synthesized via a simple hydrogenolysis route involving the decomposition of di-n-butylmagnesium. As the synthetic medium evolved from an inert atmosphere of argon to hydrogen pressure, the morphology shifted from rod like to small particles (25–170 nm). In cyclohexane, a solvent relative inert toward magnesium, smaller particles (15–50 nm) were formed. However in diethyl ether, which is more reactive toward magnesium, flakes organized in large microstructures were obtained. Remarkably in all cases β-MgH2 was readily obtained with some residual carbon contamination. Hydrogen release from these structures occurred at a relatively low temperature (300 °C), with desorption kinetics faster or equivalent to that of ball milled magnesium. In particular, hydrogen desorption from the smallest particles of MgH2 produced via the hydrogenolysis of di-n-butylmagnesium under hydrogen pressure or cyclohexane was impressive with the full desorption achieved in less than 10 min without any catalyst. These remarkable hydrogen storage properties are believed to result from an appropriate stabilization of the nanoparticles generated.

Kinetic study and H 2S effect on refractory DBTs desulfurization in a heavy gasoil

The removal evolution of six refractory individual S-compounds, i.e. DBT, 4-methyl-DBT, 4,6-dimethyl-DBT, 4-ethyl-6-methyl-DBT, 2,4,6-trimethyl-DBT, and 2,4,6,8-tetramethyl-DBT, and five groups of S-compounds with one to four substitutions has been studied during the deep desulfurization process of a heavy gasoil in a mini scale-structured bed reactor. The reactivity of the sulfur compounds was investigated by hydrotreating the gasoil with a commercial NiMo/ γ-Al 2O 3 catalyst under commercial operation conditions of temperature (563–623 K), total pressure (50 × 10 5 Pa), liquid hourly space velocity (LHSV) (0.7–3 h −1), and gas-to-liquid ratio (400–600 Nm H 2 3 / m oil 3 ). Moreover, the inhibiting effect of the hydrogen sulfide on the hydrodesulfurization rates of the S-compounds has been studied by performing tests with various H 2S partial pressures. The results showed that the most refractory sulfur component is the 4,6-dimethyl-DBT constituting the major compound in the hydrotreated product with 50 ppm total sulfur and practically the only S-compound in the product with 10 ppm total sulfur. It has been verified that differences in HDS reactivity among DBT, 4-methyl-DBT, and 4,6-dimethyl-DBT in the real feed are lower than those commonly referred to in model feeds. The reactivity of the S-compounds is affected by the presence of the adsorbed on the catalyst active sites hydrogen sulfide and this effect appears decreasing with the number of the substituents of DBTs. The activation energy of DBTs obtained in the current work appears to be higher for the non-substituted DBT, which mainly reacts through the hydrogenolysis route, and to decrease for the substituted DBTs, which react through the hydrogenation route.

In situ FT-IR spectroscopy investigations of carbon nanotubes supported Co-Mo catalysts for selective hydrodesulfurization of FCC gasoline

To better understand the nature of carbon nanotubes supported Co-Mo catalysts (Co-Mo/CNTs) for selective hydrodesulfurization (HDS) of fluid catalytic cracking (FCC) gasoline, studies are carried out using in situ Fourier transform infrared spectroscopy (FT-IR). The catalytic performances of Co-Mo/CNTs catalysts were evaluated with a mixture of cyclohexane, diisobutylene, cyclohexene, 1-octene (60:30:5:5, volume ratio) and thiophene (0.5%, ratio of total weight) as model compounds to simulate FCC gasoline. The HDS experimental results suggested that the HDS activity and selectivity of Co-Mo/CNTs catalysts were affected by Co/Mo ratio; the optimal Co/Mo atomic ratio is about 0.4, and the optimum reaction temperature is 260° C in situ FT-IR studies revealed that 1-octene can be completely saturated at 200° C. In the FT-IR spectra of diisobutylene, the characteristic absorption peak around 3081 cm −1 for the stretching vibration peak of =C-H bond was still clear at 320° C, indicating that diisobutylene is difficult to be hydrogenated. As for the thiophene, no characteristic absorption peak could be found around 3092 cm −1 and 835 cm −1 when the reaction temperature was raised to 280° C, indicating that thiophene had been completely hydrodesulfurized. On the basis of FT-IR results, it can be deduced that thiophene HDS reaction occurred mainly through direct hydrogenolysis route, whereas thiophene HDS and diisobutylene hydrogenation reaction over Co-Mo/CNTs catalysts might occur on two different kinds of active sites.

Adsorption characteristics of reduced Mo and Ni–Mo catalysts in the hydrodeoxygenation of benzofuran

Abstract The promotional effect of Ni on the hydrodeoxygenation (HDO) of benzofuran (BF) over reduced Ni–Mo/γ-Al 2 O 3 catalysts was studied. The adsorption characteristics of Al 2 O 3 support, mono-metallic Mo, and bi-metallic Ni–Mo catalysts that were pre-reduced were investigated using the feed molecule (BF) and a probe molecule (NO) as adsorbates. NO was used to probe the coordinatively unsaturated sites (CUS). Three adsorption modes for benzofuran over reduced Al 2 O 3 support, Mo, and Ni–Mo catalysts were proposed that involved OH groups, Bronsted acid sites, and CUS, respectively. Benzofuran molecule adsorbed more strongly on B acid sites and CUS than on OH groups and was activated with weakening of the C–O bond. With increasing catalytic hydrogenation activity (increasing CUS) and/or decreasing hydrogenolysis activity (decreasing acidity), the reaction pathway for benzofuran HDO changes from a hydrogenolysis route to a route that involves saturation of the benzene ring before any heteroatom removal takes place.