Hydrodeoxygenation Reaction Research Articles

Selective production of high-value fuel via catalytic upgrading of bio-oil over nitrogen-doped carbon-alumina hybrid supported cobalt catalysts

Bio-oil derived from biomass fast pyrolysis can be upgraded to gasoline and diesel alternatives by catalytic hydrodeoxygenation (HDO). Here, the novel nitrogen-doped carbon–alumina hybrid supported cobalt (Co/NCAn, n = 1, 2.5, 5) catalyst is established by a coagulation bath technique. The optimized Co/NCA2.5 catalyst presented 100 % conversion of guaiacol, high selectivity to cyclohexane (93.6 %), and extremely high deoxygenation degree (97.3 %), respectively. Therein, the formation of cyclohexanol was facilitated by stronger binding energy and greater charge transfer between Co and NC which was unraveled by density functional theory calculations. In addition, the appropriate amount of Lewis acid sites enhanced the cleavage of the C–O bond in cyclohexanol, finally resulting in a remarkable selectivity for cyclohexane. Finally, the Co/NCA2.5 catalyst also exhibited excellent selectivity (93.1 %) for high heating value hydrocarbon fuel in crude bio-oil HDO. This work provides a theoretical basis on N dopants collaborating alumina hybrid catalysts for efficient HDO reaction.

Selective Hydrodeoxygenation of Lignin-Derived Phenolic Monomers to Cyclohexanol over Tungstated Zirconia Supported Ruthenium Catalysts.

The selective hydrodeoxygenation (HDO) of lignin-derived methoxyphenols to cyclohexanol is one of the most significant transformation in biomass conversion since cyclohexanol is an important industrial raw material. This study has disclosed a series of tungstated zirconia with different Zr/W ratio supported Ru catalysts (Ru/xZrW, x means the molar ration of Zr/W) for the hydrodeoxygenation (HDO) of guaiacol to cyclohexanol. Among these catalysts, Ru/16ZrW has the best catalytic activity, which can achieve 92 % yield of cyclohexanol under the conditions of 180 °C and 1 MPa H2 pressure for 2 h (TOF 231 h-1). Compared with Ru/ZrO2, Ru/16ZrW has smaller particles, more dispersed and electron-rich Ru species, significant hydrogen spillover and more acid sites, which are the main reason for its excellent performance on this reaction. Apart from guaiacol, other methoxy substitution phenols and organosolv lignin can also be converted into cyclohexanol via hydrodeoxygenation reactions over this catalyst.

Selective recovery of para-xylene from polyethylene terephthalate plastic

The conversion of polyethylene terephthalate (PET) plastic into low-boiling monomers like para-xylene (PX) that can be purified easier with lower energy consumption represents a promising strategy for circular economy that seamlessly integrating into current prevailing high-quality PET production chain. Herein, a selective bimetallic RuFe catalyst was successfully fabricated for hydrodeoxygenation (HDO) of dimethyl terephthalate (DMT) (a model compound of PET) and PET plastics to PX with yield as high as 88.9 % and 82.6 %, respectively, comparable to state-of-the-art examples. H2-TPR and EXAFS combined with benchmark test over model catalysts confirmed that small Ru clusters and Ru-Nx coordination are responsible for the high aromatics selectivity, on which vertical adsorption of carbonyl group (CO) is preferred. This study not only shows a promising PX-based PET recycling route, the highly selective C–O bond cleavage on Ru catalyst and corresponding structure-selectivity relationship also guide the catalyst design for other value-added biomass-based HDO reactions.

Pd‐Pt Bimetallic Catalysts for Enhanced Low‐Temperature Hydrodeoxygenation of Vanillin

AbstractTo make pyrolytic bio‐oil useful as a transportation fuel, the oxygen content must be reduced, and this can be carried out by using catalytic hydrodeoxygenation (HDO) reaction. The greatest challenge is associated with the removal of strongly bound oxygenated groups without saturating the aromatic ring while preserving the number of carbons. However, the development of a stable catalyst that can selectively remove such oxygenated groups with low hydrogen consumption is still challenging. In this context, a systematic study on HDO of vanillin on bimetallic Pd−Pt catalysts was carried out. It aims to study the effect of bimetallic synergy in terms of activity and selectivity to creosol. Metallic nanoparticles of Pd and Pt were synthesized by sol immobilization technique and deposited on TiO2. The conversion of vanillin was correlated to the Pd−Pt atomic ratio, while the production of the creosol was correlated to the Pd(0)/(Pd+Pt) ratio at the surface. Full conversion of vanillin was obtained at low reaction temperature (20 °C) achieving nearly 100 % selectivity to creosol. These results represent a step forward in advancing the development of more efficient and sustainable processes for bio‐oil upgrading.

Evaluation of anisole hydrodeoxygenation reaction pathways over a Ni/Al2O3 catalyst

Anisole is a model molecule for studying hydrodeoxygenation (HDO) of lignin-derived oxygenates. Here we elucidate its HDO pathway over 10 % Ni/Al2O3 catalyst. Adsorption experiments showed that anisole is adsorbed on the acidic sites of the Al2O3. Anisole adsorption at 200–300 °C is reactive in nature, and results in its demethylation. The catalyst was tested at 100–300 °C, 5–40 bar H2 pressure. Conversion of 78 % was obtained at 5 bar and 300 °C, restricted by hydrogenation-dehydrogenation equilibrium. HDO mainly starts through the ring-hydrogenation pathway. This is followed by demethoxylation beyond 180 °C. At 5–12 bar, cyclohexane dehydrogenates to benzene. This was confirmed by conducting an HDO experiment with methoxycyclohexane. At lower pressure deoxygenation is favored; and demethylation is accompanied with methylation of the aromatic ring, for temperature >260 °C. Investigation of the initial reaction stages showed that anisole HDO on Ni/Al2O3 catalyst proceeds via two independent pathways i.e., reactive adsorption/(de)methylation and aromatic ring hydrogenation.

Tuning of the acid sites in the zeolite-alumina composite Ni catalysts and their impact on the palm oil hydrodeoxygenation reaction

The hydrodeoxygenation (HDO) of bio-oil is one of the potential approaches to produce green diesel. However, HDO catalyst requires the development of bifunctionality which translates to the simultaneous presence of acidic and metal sites for desired catalytic activity and selectivity. Zeolites and their composites are attractive candidates for the conversion of biomass to fuels. In the present work, a series of Ni-incorporated Al2O3-zeolite beta bifunctional composite catalysts with distinct Al2O3 (25–75 wt%) and Ni contents (5–15 wt%) were synthesized via a facile one-pot method directly from nickel acetate, nano-boehmite (γ-AlO(OH)) and the NH4+ form of beta zeolite (NH4+-BZ). The nano-boehmite particles, due to the positive charges on their surface, electrostatically attract negatively charged beta zeolite crystals, which leads to the assembly of a hierarchical pore structure upon calcination. Interestingly, the composite catalysts synthesized were quite homogeneous with uniform dispersion of Ni particles. All composite catalysts were thoroughly characterized using XRD, SEM-EDX, SEM-mapping, HR-TEM, H2-TPR, H2-TPD, NH3-TPD, XPS, 31P MAS NMR, 27Al MAS NMR and N2 sorption analysis. The synthesized composite catalysts with distinct Al2O3 contents showed diverse textural properties, distinct nature of acid sites and improved performance in hydrodeoxygenation of palm oil. Particularly, the Ni/BZ-Al50 (with BZ:Al2O3 = 50:50) composite catalyst significantly enhanced the conversion of palm oil (up to 90%) and yield of n-C15-C18 hydrocarbons (up to 69%) at moderate temperature of 375 °C as compared to 10Ni/BZ catalyst (Conv. = 75%, yield of n-C15-C18 = 52%). The higher catalytic performance realized with composite catalysts can be ascribed to its hierarchical pore structure, moderate acidity (chemisorption studies), tuned acid sites nature (solid state NMR) and homogeneous distribution of active Ni sites (H2 chemisorption) which helps to improve product selectivity by minimizing side reactions. The time-on-stream (TOS) experiments were carried out up to 20 h which clearly showed that composite catalysts are more stable suggesting the lower amount of coke deposition (TPO studies) and suppression of metal sintering.

Effect of Dynamic and Preferential Decoration of Pt Catalyst Surfaces by WOx on Hydrodeoxygenation Reactions.

Catalysts containing Pt nanoparticles and reducible transition-metal oxides (WOx, NbOx, TiOx) exhibit remarkable selectivity to aromatic products in hydrodeoxygenation (HDO) reactions for biomass valorization, contrasting the undesired aromatic hydrogenation typically observed for metal catalysts. However, the active site(s) responsible for the high selectivity remains elusive. Here, theoretical and experimental analyses are combined to explain the observed HDO reactivity by interrogating the organization of reduced WOx domains on Pt surfaces at sub-monolayer coverage. The SurfGraph algorithm is used to develop model structures that capture the configurational space (∼1000 configurations) for density functional theory (DFT) calculations of a W3O7 trimer on stepped Pt surfaces. Machine-learning models trained on the DFT calculations identify the preferential occupation of well-coordinated Pt sites (≥8 Pt coordination number) by WOx and structural features governing WOx-Pt stability. WOx/Pt/SiO2 catalysts are synthesized with varying W loadings to test the theoretical predictions and relate them to HDO reactivity. Spectroscopy- and microscopy-based catalyst characterizations identify the dynamic and preferential decoration of well-coordinated sites on Pt nanoparticles by reduced WOx species, consistent with theoretical predictions. The catalytic consequences of this preferential decoration on the HDO of a lignin model compound, dihydroeugenol, are clarified. The effect of WOx decoration on Pt nanoparticles for HDO involves WOx inhibition of aromatic ring hydrogenation by preferentially blocking well-coordinated Pt sites. The identification of preferential decoration on specific sites of late-transition-metal surfaces by reducible metal oxides provides a new perspective for understanding and controlling metal-support interactions in heterogeneous catalysis.

Enhanced generation of aromatic-enriched bio-oil from sewage sludge pyrolysis using zeolite-based catalysts under H2-rich conditions

Sewage sludge is solid waste resulting from wastewater treatment processes, and its improper management adversely affects the environment and human health. This study aims to convert sewage sludge into valuable aromatics, including benzene, toluene, ethylbenzene, and xylenes, or BTEX, via the catalytic pyrolysis using mono- and bimetal-modified protonated Zeolite Socony Mobil–5, or HZSM-5, catalysts under nitrogen, methane and methane decomposition conditions. In the methane medium, HZSM-5 yielded more BTEX (20.91 wt%) compared to those obtained using protonated Y zeolite (HY) (17.24 wt%) and protonated beta zeolite (Hβ) (11.70 wt%) owing to its proper acidity, higher shape selectivity, and higher methane activation. When HZSM-5 is used, the BTEX yield increased considerably in the methane decomposition environment (27 wt%), 1.29 and 1.46 times higher than those produced under methane and nitrogen, respectively. This increase is attributed to the dual effects of the surplus in situ hydrogen (H2) and direct involvement of methane, which resulted in accelerated hydrocracking, hydrodeoxygenation, and co-aromatization reactions. Under methane decomposition conditions, the use of the Ni/HZSM-5, Mo/HZSM-5, and Ni-Mo/HZSM-5 catalysts led to 1.23-, 1.30-, and 1.66-fold increases in BTEX production, respectively, than that of the parent HZSM-5, owing to the dual effects of acidity enhanced by the newly formed Lewis acid sites, increased oxygen vacancies, and improved physical properties of the catalysts. Hence, the catalytic pyrolysis of sewage sludge using mono- and bimetal-modified HZSM-5 catalysts in a H2-rich environment proposed in this study is expected to be an efficient and sustainable method for converting undesirable materials into valuable biofuels.

Performance of sulfided NiMo catalyst supported on pillared bentonite Al and Ti under hydrodeoxygenation reaction of guaiacol

Bio-crude oil is known to be sustainable, eco-environmentally, and an alternative energy source produced by biomass pyrolysis. However, its quality remains relatively low due to a higher oxygen concentration compared to liquid fuels from fossils. Therefore, an upgrading process is necessary through the catalytic hydrodeoxygenation (HDO) process. This work synthesized pillared bentonite using Al and Ti metals as the pillaring agent to produce Al-PILC and Ti-PILC as catalyst support for sulfided NiMo. Their catalytic activity in HDO reaction using guaiacol as a model compound of bio-crude oil were also evaluated. Characterization of the bentonite-pillared materials, including Al-PILC, Mo/Al-PILC, NiMo/Al-PILC, Ti-PILC, Mo/Ti-PILC, and NiMo/Ti-PILC, was performed using Surface Area Analyzer, X-ray Diffractometer (XRD), Temperature-Programmed Desorption of ammonia (NH3-TPD), X-Ray Fluorescence (XRF), and Scanning Electron Microscope (SEM) techniques. The characterization results confirm the pillarization process of bentonite using Al and Ti metals as the pillaring agent, and the preparation of the NiMo catalyst using the stepwise impregnation method was successfully prepared. The NiMo/Ti-PILC catalyst performs a superior conversion value on the HDO guaiacol reaction than other catalysts. A well dispersion of Mo and Ni metals on the surface support (NiMo/Ti-PILC), thus creating numerous active sites of the catalyst after the sulfidation. Variations in time and temperature during the HDO guaiacol reaction significantly affected the conversion.

Study on H3PO4-activated carbon catalytic co-pyrolysis of bamboo and LDPE to poly-generation syngas and aromatics at low temperature

Biomass-derived carbon activated by H3PO4 was adopted to catalytic co-pyrolysis of bamboo and low-density polyethylene (LDPE) to produce syngas and aromatics on a fixed bed reactor. Effects of LDPE ratio in the feedstock, catalytic co-pyrolysis temperature and ratio of catalyst to feedstock on the yields and compositions of the products were investigated. The increase of LDPE ratio in liquid first improved and then reduced the relative content of aromatics, while it showed a positive effect on the yield and the H2/CO ratio of gas. 500℃ was an optimum temperature, under which the relative content of aromatics in liquid kept higher, meanwhile, avoided the undesirable polymerization reactions of monocyclic aromatics. At the same time, the content of H2 in gas reached a maximum (59.3%), which was in favor of poly-generation. H3PO4-activated carbon catalyst (H3PO4-ACC) with abundant functional groups on surface catalyzed cracking, hydrodeoxygenation, cyclization and aromatization reactions so as to facilitate the generation of aromatics. Non-condensable gas was dry reformed on P-ACC at the expense of CO2, CH4 and CO to generate char and H2. When the reaction condition was at a LDPE ratio of 50%, a catalyst/feedstock ratio of 2:1 and at 500℃, the relative content of aromatics in liqiud was 81.65% and the proportion of syngas component in gas was 79.73%. The volume ratio of H2/CO approached to 3:1 in gas under this condition. H3PO4-ACC catalytic co-pyrolysis of bamboo and LDPE could obtain high quality gas and liquid products at a relative low reaction temperature, which provided a new research idea on high-value application of biomass and waste plastics.

Review and Outlook on Regulation of Catalyst Activity, Selectivity, and Stability for Biomass Hydrodeoxygenation Reaction in an Aqueous Environment

Review and Outlook on Regulation of Catalyst Activity, Selectivity, and Stability for Biomass Hydrodeoxygenation Reaction in an Aqueous Environment

Hydrodeoxygenation of lignin bio-oil model compounds and surrogate mixtures over zeolite supported nickel catalysts

Bifunctional catalysts based on nickel supported on ZSM-5 and BETA zeolites were studied in the hydrodeoxygenation of lignin derived model compounds as well as in surrogate mixtures simulating the light fraction of lignin fast pyrolysis bio-oil. A screening of the hydrodeoxygenation reaction conditions (temperature, time, H2 pressure, catalyst amount) was carried out using the simplest phenolic compound, phenol. As in real lignin bio-oils more complex phenolic compounds are present, a series of relevant alkyl- and methoxy-substituted phenol and benzene (o- and m-cresol, catechol, anisole, guaiacol, syringol, creosol and 1,2,3-trimethoxybenzene) were also investigated as feedstocks. Furthermore, the effect of the different porous and acidic properties of the zeolitic supports was investigated in the hydrodeoxygenation of guaiacol. The conversion of the model phenolics and the yield of the respective (alkyl)cyclohexanes at relatively mild conditions (220 °C, 50 bar H2, 1 h) were in the range of 80–100% and 47–83%, respectively, being dependent mainly on the complexity/side-chain group of the phenolic/benzylic ring and on the balanced content of Brønsted acid sites of increased strength. Regarding the hydrodeoxygenation of the surrogate mixture (C7-C10 phenolics), 100% hydrodeoxygenation efficiency was achieved towards >60% yield of (alkyl)cyclohexanes (C6-C9 hydrocarbons). All hydrodeoxygenation tests were conducted in hexadecane as solvent/substrate in order to simulate model co-processing (i.e. bio-based phenolics with petroleum derived feedstocks) conditions. Reusability tests revealed the stability of the catalysts which showed partial (30%) deactivation after the third catalytic cycle.

Catalyst Screening and Optimization Condition of Green Solvent for BHD Production using Ni-based Catalysts

The high production costs associated with bio-hydrogenated diesel (BHD) have posed a major challenge. Considering this, the present research focused on the production of green solvents at lower pressures as a potential solution. Specifically, the synthesis of various catalysts, namely Ni/γ-Al2O3, Ni/C, NiMo/γ-Al2O3, NiMo/SiO2TiO2, and NiMo/C, was conducted to facilitate the hydrodeoxygenation reaction of methyl laurate into cyclohexane, leading to conversion into dodecane. The resulting green solvent was analyzed using GC-FID and GC-TCD techniques. Among the five catalysts tested, NiMo/C demonstrated superior performance, achieving a conversion rate of 64.61%, selectivity of 62.46%, and yield of 44.98%. The gas analysis conducted using GC-TCD revealed the production of carbon monoxide, methane, and carbon dioxide, aligning with the dodecane pathway theory. Further analysis of the NiMo/C catalyst was conducted using SEM, BET, and XRD techniques, while the Design of Expert program was used to identify more favorable conditions for dodecane production. Through this optimization process, significant improvements were achieved, resulting in a conversion rate of 98.26%, selectivity of 66.82%, and yield of 65.66% at 320 °C and 28 bar, with a reaction time of 6 h.

Hydrodeoxygenation of vanillin to 2-methoxy-4-methylphenol over in-situ reduced CuO/Al2O3 catalysts under mild conditions

A new method for the hydrodeoxygenation of vanillin to 2-methoxy-4-methylphenol (MMP) by in-situ reduced CuO/Al2O3 catalysts was developed. The CuO/Al2O3 catalysts with different CuO contents were prepared by simple wet impregnation and could provide complete vanillin conversion with 99 % MMP selectivity under mild conditions (120 °C, 0.5 MPa H2, 8 h). The results from XPS and H2-TPR characterizations of the CuO/Al2O3 catalysts suggested that CuO species had a strong interaction with the Al2O3 support, which was beneficial for the in-situ reduction of CuO to Cu+ and Cu0 species during the hydrodeoxygenation reaction. The synergistic effect of Cu+ and Cu0 species was believed to promote the hydrodeoxygenation of vanillin, in which Cu0 accounts for the hydrogenation reaction, while Cu+ is responsible for the adsorption of vanillin and 4-hydroxy-3-methoxybenzyl alcohol to facilitate the further dehydration of 4-hydroxy-3-methoxybenzyl alcohol. In addition, the CuO/Al2O3 catalyst could maintain high catalytic activity after three reaction cycles and showed versatility for various lignin derivatives. The development of this in-situ reduceable catalyst could provide a cost-effective approach for the upgrading of biomass derived products.

Efficient conversion of lignin-derived phenols to cycloalkanes over bifunctional catalysts with low loading of ruthenium

Hydrodeoxygenation (HDO) reactions are extensively employed in the conversion of biomass to advanced fuels, which rely heavily on bifunctional catalysts that contain both a metal component and an acidic component. A significant challenge in the development of HDO catalysts is the need to reduce costs while simultaneously enhancing catalytic efficiency. Here, a series of Ru@W/ZrO2 catalysts with an extremely low loading of Ru (0.5 wt%) were successfully synthesized using different Ru or W loading sequences and different Ru/W mass ratios. The catalysts were applied in the HDO reaction of lignin-derived phenols, and their physical and chemical characteristics were revealed by various characterization techniques, including XRD, H2-TPD, NH3-TPD, and XPS. The results suggest that the synthesis method with post-loading Ru leads to improved exposure and utilization of the low-loaded Ru, which effectively serves as the active sites for hydrogenation in catalytic reactions. Under the same reaction conditions, the bifunctional catalyst with post-loading of Ru achieved a complete conversion of phenol into cyclohexane, while the catalyst with simultaneous loading of Ru and W only yielded 42% of cyclohexane. In addition, the Ru/W ratios have also shown significant effects on the HDO performance of the catalyst. The catalyst exhibits the highest hydrogenation activity when the Ru/W ratio is 10, which is further supported by kinetic experiments. This study highlights the significance of the loading sequence of noble metals and the metal/acid ratio in the synthesis of highly active bifunctional catalysts, and also lays the groundwork for the efficient utilization of noble metals in biomass HDO conversion.

Production of jet fuel cycloalkanes from 5‐(hydroxymethyl)furfural via cascade catalysis on Mg(Al)(Zr)O supported CuCo

AbstractCatalytic conversion of biomass‐derived 5‐(hydroxymethyl)furfural (5‐HMF) into carbon‐increased hydrocarbons as drop‐in energy‐rich biofuels has received a great deal of concern for the development of sustainable chemical industry. Here, we demonstrate a one‐pot conversion of 5‐HMF into C9‐alkanes on one single catalyst, acidic–basic layered double oxides (Mg(Al)(Zr)O) supported CuCo alloy. The well‐defined multifunctional catalytic sites with harmonious combination carry out cascade catalysis, affording C9‐alkanes (including 30% of more value‐added branched‐cycloalkanes) in 83% yield. The basic–acidic sites on Mg(Al)(Zr)O show high activity for aldol condensation of 5‐HMF and acetone, producing 4‐[5‐(hydroxymethyl)‐2‐furanyl]‐3‐buten‐2‐one (HAc) in a yield of >99%. The engineered Co–Cu–Co linkages on supported CuCo perform efficient hydrodeoxygenation, affording C9‐alkanes in a selectivity of 96% from HAc. C9‐cycloalkanes are generated from the cyclization of the corresponding monohydric alcohol intermediates by the synergy of acidic and CuCo sites in the hydrodeoxygenation reaction.

Recent Advances in Hydrodeoxygenation of Lignin‐Derived Phenolics over Metal‐Zeolite Bifunctional Catalysts

AbstractThe hydrodeoxygenation (HDO) reaction provides a promising catalytic strategy to remove oxygen in biomass‐derived bio‐oil to produce renewable transportation fuels and value‐added chemicals. The development of highly efficient and stable HDO catalysts plays an essential role in biomass valorization. Metal‐zeolite bifunctional catalysts have been well‐developed as the effective HDO catalysts in upgrading lignin‐derived phenolics due to their excellent activity, selectivity, and thermal and hydrothermal stability. However, clarifying the roles of the active sites and their synergistic effect, and establishing effective structure‐performance relationships in the HDO process still face challenges. In this review, we first survey the conventional catalysts applied in the HDO of bio‐oil, followed by thoroughly discussing the roles of metal centers, acid sites, supports, and their impacts on the HDO process of phenolic model compounds or bio‐oil. Finally, a discussion on the stability and deactivation of metal‐zeolite catalysts, especially in the aqueous‐phase HDO reaction, is provided. This critical review offers new insights into the development of state‐of‐the‐art metal‐zeolite bifunctional catalysts with well‐defined porosity and metal‐acid properties for viable biomass valorization.

FEASIBILITY ANALYSIS OF HYDROGEN-FREE DEOXYGENATION REACTIONS OF PALMITIC ACID TO HYDROCARBONS FUELS THROUGH THERMODYNAMIC STUDIES

Four models were investigated to study the feasibility of the hydrogen-free deoxygenation of palmitic acid to hydrocarbons through the stoichiometric thermodynamic equilibrium analysis. The reaction conditions have been varied to estimate the equilibrium reactions composition (temperature (T) of 200 – 600 °C, pressure (P) of 1 – 20 bar, and H2/Palmitic acid ratio of 0 – 10). It was found that the hydrogen-free deoxygenation of palmitic acid was thermodynamically favorable with complete conversion (≈100%) at all investigated reaction conditions. The equilibrium products composition was significantly affected by reaction temperature. The main-formed hydrocarbon was C15H­32 at low temperatures and C15H30 at high temperatures. However, the product composition of reaction equilibrium was not affected by the reaction pressure. Even though the internal hydrogen was generated, the hydrodeoxygenation reaction pathways were not too favorable because the hydrodeoxygenation product and its intermediates were negligible.

Engineering Pd-oxygen vacancy interface for enhanced hydrodeoxygenation of hexahydrophthalic anhydride to hexahydrophthalide

The development of chemical recyclable polyester based on hexahydrophthalide offers a solution to the plastic pollution issue. However, it remains a challenge to construct a promising catalyst route for monomers synthesis and clarifying the binary interactions between the support and active sites. In this work, we reported Pd/ZrO2 catalysts with different crystal structures by metal-support interaction and oxygen vacancy (Ov) regulation for the hydrodeoxygenation of hexahydrophthalic anhydride (HHPA) toward the continuous synthesis of hexahydrophthalide. The Pd/m-ZrO2 catalyst showed the highest conversion of HHPA (93.1 %) and the superior selectivity to hexahydrophthalide (96.1 %), a low apparent activation energy (Ea = 75 kJ/mol), and great stability under 200 °C, 3 MPa H2. Detailed experimental studies indicated that Pd/m-ZrO2 with the higher oxygen vacancy density, and the stronger interaction between the metal and the support, which results in the formation of more Pd-O-Zr structures with excellent catalytic performance. This work opens up a new pathway for the related acid anhydride hydrodeoxygenation reactions to recyclable lactones through catalytic engineering methods.

Hydrodeoxygenation of Anisole via Cu supported on Zeolite: HZSM-5, MOR, and Indonesian Activated Natural Zeolite

The conversion of biomass waste into an alternative energy source requires effective and efficient hydrodeoxygenation (HDO) catalysts. This research aimed to synthesize a bifunctional zeolite-based catalyst for anisole conversion into BTX. The noble metal Cu was impregnated on HZSM-5, mordenite, and Indonesian activated natural zeolite (ANZ) to form HDO catalysts. X-ray fluorescence (XRF), X-ray diffraction (XRD), surface area and pore profile analysis, Fourier transform infrared analysis, ammonia-temperature programmed desorption (NH3-TPD), pyridine gravimetry, morphology, and scanning electron microscopy-energy dispersion elemental mapping (SEM-EDX) were used to determine the catalyst's properties. The HDO reaction test used anisole as a model compound in a semi-flow reactor with hydrogen gas at 350 and 500 °C for 1 h. Copper nanocrystals were found on the surface of the zeolites in several metal phase types, including Cu, Cu2O, CuO, and Cu(OH)2. Due to the copper bonds inside the zeolite pores, the internal pore surface area decreased. The acidity also decreased since it is strongly related to the surface area. At 350 °C, Cu was found to be less active. However, at 500 °C, copper activity increased, leading to an increase in anisole conversion and BTX selectivity. The catalyst with the highest anisole conversion and BTX selectivity was Cu/HZSM-5 (i.e., 53.28 and 13.06% v, respectively).