Metal-acid Bifunctional Catalysts Research Articles

Hydroconversion of waste polyethylene plastics under mild conditions using mechanically mixed bifunctional catalysts: Impact of metal-acid balance and proximity

The disposal of non-biodegradable waste polyolefin plastics poses a serious environmental threat, highlighting the need for cleaner and more efficient thermochemical recycling technologies. This study introduces a scalable mechanical method to synthesize a metal-acid bifunctional catalyst. The mechanical ball milling process not only exposes more acidic sites but also enhances metal-acid proximity without blocking the pores. By varying the metal-acid balance (MAB) through different mixing ratios, we achieved higher yields and selectivity for soluble products at the optimal MAB level. Under mild conditions (250°C) for 8 h, polyethylene (PE) is efficiently converted into liquid phase iso-paraffins with an isomer selectivity of up to 56 % in the diesel and aviation kerosene fractions (C11-C18). This research underscores the importance of the accessibility of acidic sites to long-chain macromolecules, metal-acid site distance, and their balance in the hydrocracking of PE. It provides valuable theoretical insights and catalytic strategies for converting waste PE plastics into high-value fuel fractions.

Construction of Molecularly Dispersed Polyoxometalate-Alumina Hybrid Hollow Nanoflowers via Water-Induced Kirkendall Effect.

Hybrid nanomaterials with controllable structures and diverting components have attracted significant interest in the functional materials field. Here, we develop a solvent evaporation-induced self-assembly (EISA) strategy to synthesize nanosheet-assembled phosphomolybdic acid (H3PMo)-alumina hybrid hollow spheres. The resulting nanoflowers display a high surface area (up to 697 m2 g-1), adjustable diameter, high chemical/thermal stability, and especially molecularly dispersed H3PMo species. By employing various microscopic and spectroscopic techniques, the formation mechanism is elucidated, revealing the simultaneous control of the morphology by heteropoly acids and water through the water-induced Kirkendall effect. The versatility of the synthesis method is demonstrated by varying surfactants, heteropoly acids, and metal oxide precursors for the facile synthesis of hybrid metal oxides. Spherical hybrid alumina serves as an attractive support material for constructing metal-acid bifunctional catalysts owing to its advantageous surface area, acidity, and mesoporous microenvironment. Pt-loaded hollow flowers exhibit excellent catalytic performance and exceptional stability in the hydrodeoxygenation of vanillin with recyclability for up to 10 cycles. This research presents an innovative strategy for the controllable synthesis of hybrid metal oxide nanospheres and hollow nanoflowers, providing a multifunctional platform for diverse applications.

Enhanced Hydrodeoxygenation performance through novel Al-Doped radial channel Silica-Supported Carbon-Encapsulated nickel catalysts

Hydrodeoxygenation (HDO) plays a crucial role in upgrading pyrolysis-oil derived from biomass. Here we describe a method for fabricating a carbon-encapsulated nickel metal–acid bifunctional catalyst (Ni@C/RCS-Al) supported on aluminum-doped radial channel silica (RCS-Al). This catalyst exhibits a large surface area and highly dispersed accessible active sites, achieved through a combination of salicylate- and MOF-assisted strategies. The RCS-Al was prepared by a one-pot salicylate-assisted hydrothermal method in an aqueous phase containing an Al source, which is simple, has a high yield, and saves time. The results show that Ni@C/RCS-Al displays a well-defined radial channel pore structure with a mesopore diameter of 31.1 nm, which can significantly increase the number of accessible active sites and accelerate mass transfer. The MOF-assisted strategy leads to the formation of highly dispersed smaller carbon-encapsulated nickel nanoparticle active sites, and Al doping contributes to the adjustable acid sites, demonstrating that Ni@C/RCS-Al is a metal–acid bifunctional catalyst. Importantly, the kinetics study revealed a high reaction constant for the constructed Ni@C/RCS-Al catalyst. Ni@C/RCS-Al demonstrates remarkable performance in HDO, achieving complete m-cresol conversion and 100 % selectivity to the target product methylcyclohexane within a brief period of 75 min (T = 250 °C p = 2 MPa, m-cresol/catalyst (g) = 7.5). This exceptional performance stems from its radial channel pore structure and optimization of metal–acid sites. The thin carbon layer on the Ni surface contributes to its superior stability and water resistance, as verified by an experimental study and DFT calculations. This work opens up a new idea for the application of radial channel silica-supported catalysts in various reactions.

Preparation of Pd/Ce(F)-MCM-48 catalysts and their catalytic performance of n-heptane isomerization

Abstract Ce and F were added to MCM-48 molecular sieve by hydrothermal synthesis, and Pd/Ce(F)-MCM-48 metal acid bifunctional catalysts were prepared by impregnation method. The physical and chemical properties of Ce(F)-MCM-48 and Pd/Ce(F)-MCM-48 were characterized by X-ray diffraction, scanning electron microscope, NH3 temperature programmed desorption instrument, Fourier infrared spectrometer, and X-ray photoelectronic spectrometer characterization methods. The results showed that when the molar ratio of the raw materials was n(Ce):n(TEOS) = 0.02 and n(NaF):n(TEOS) = 0.10, Ce(F)-MCM-48-0.10 molecular sieve had a high degree of order and large specific surface area and pore volume, the total acid content increased, and the acid strength also increased. And it had an acidic center and generated certain oxygen vacancies. The catalyst prepared after Pd impregnation had good dispersibility. 0.4% Pd/Ce(F)-MCM-48-0.10 catalyst still maintained the crystalline phase of MCM-48 molecular sieve. A micro-reaction device was used to examine the catalytic performance of n-heptane isomerization of Pd/Ce(F)-MCM-48-0.10 catalysts. When the hydrogen flow rate was 30 mL·min−1, reduction temperature was 300°C, reduction time was 4 h, weight hourly space velocity was 7.6 h−1, and reaction temperature was 280°C, 0.4% Pd/Ce(F)-MCM-48-0.10 catalyst was used in the heptane isomerization reaction, where the conversion of n-heptane was 67.3% and the selectivity of isoheptane was 96.5%.

Cooperative effect of multi-active sites in WOx-modified ZrO2 supported highly dispersed Pd catalysts for promoting benzene hydroalkylation

Designing efficient metal–acid bifunctional catalysts is a challenging task to achieve the one-step benzene hydroalkylation to produce cyclohexylbenzene (CHB), which has significant importance due to the economic potential for the industrial production of phenol. In this study, a series of WOx-modified ZrO2 supported highly dispersed Pd catalysts were developed by modulating the surface acidity of ZrO2 through the introduction of WOx species. The as-constructed Pd/WOx-ZrO2 catalyst bearing a low Pd loading of 0.4 wt% and a W content of 21 wt% exhibited a superior catalytic performance, along with an unprecedentedly high productivity of CHB (144.6 mmolCHB·gcat−1·h−1), much higher than those obtained by using the state-of-the-art catalysts. It was demonstrated that highly dispersed Pd species could promote the formation of active hydrogen species and favor the hydrogen spillover on the catalyst surface that induced the generation of surface oxygen vacancies and Brønsted acidic sites originating from surface-loaded WOx. Comprehensive structural characterizations and catalytic experiments showed that the favorable metal–acid cooperation on Pd/WOx-ZrO2 catalysts and the cooperation between Lewis acid sites and Brønsted acid sites, as well as the presence of abundant defective oxygen vacancies, efficiently regulated the adsorption and activation of molecular hydrogen, benzene, and cyclohexene intermediate, leading to the improved catalytic hydroalkylation activity. These findings provide new high-performance metal–acid bifunctional catalysts with multi-active site cooperation structures for one-step hydroalkylation of benzene to CHB.

Dense Ru single-atoms integrated with sulfoacids for cellulose valorization to isosorbide

Metal-acid bifunctional catalysts are the unity of two opposites (metal-acid repelling) for cellulosic biomass valorization to isosorbide. It is challenging to improve the selectivity of metal hydrogenation catalysts and their synergism with acids for catalytic hydrolysis and dehydration to achieve substantial isosorbide. Herein, dense Ru single-atoms (10.1 wt% of Ru SAs) are anchored on sulfoacid-functionalized hollow mesoporous carbon shells, designed by assembling silica and 8-hydroxyquinoline-modified chitosan (HQ-CTS) through in situ Stöber templating strategy before pyrolysis and acid treatment. Based on X-ray absorption fine structure and computational modeling results, the structure of Ru SAs is determined as RuN4, which is more selective for a transitional glucose hydrogenation to sorbitol than Ru001 of Ru clusters. A lower-energy barrier of 1.21 (0.72) eV is delivered over RuN4 (Ru001) for glucose hydrogenation (isomerization). These Ru SAs are integrated with sulfoacids (SO3H) but resistent against acids, rendering enhanced isosorbide yield in water as compared to Ru clusters, via a one-pot cascade reaction under harsh conditions (220 °C, 6 MPa H2). The elaborately fabricated dense Ru SAs and sulfoacids, achieved by varying the addition time of HQ-CTS during the in situ Stöber templating process, improve the synergism of glucose hydrogenation with cellulose hydrolysis and sorbitol dehydration. This study provides a new idea for rational design of high-performance metal-acid bifunctional catalysts toward one-pot conversion of cellulose to isosorbide.

The gradient fabrication and optimization of metal-acid bifunctional catalysts for the hydrogenation of n-C16 to produce bio-jet fuel component

In the two-step hydrogenation of oil to produce bio-jet fuel, the yield of bio-jet fuel is determined by the hydrotreatment of long-chain alkanes over a metal–acid bifunctional catalyst. A strategy that the catalyst with better isomerization is conductive to the hydrotreatment of long-chain alkanes to produce jet fuel component is proposed. Based on the hollow silicon sphere (HSS), catalysts with different acid strength, diffusion performance, and intimacy between Pt and acid bifunctional sites were designed to gradually optimize the isomerization performance. After the gradient optimization of weak acid, strong diffusion performance, and minor-nanoscale intimacy between Pt and acid sites, the gradient catalysts exhibited a constantly improving yield of isomer product and jet fuel component. The yolk-shell WHSS@Pt catalyst with three levels of simultaneous optimization performed the favorable yield of jet fuel component (37 wt.%), which can be attributed to the combination of weak acid, strong diffusion performance, and minor-nanoscale intimacy between bifunctional sites that are beneficial to the isomerization of long-chain alkanes.

Metal-Acid Interface Engineering in Pd-WOx Bifunctional Catalysts for the Hydroalkylation Tandem Reaction of Benzene.

The hydroalkylation tandem reaction of benzene to cyclohexylbenzene (CHB) provides an atom economy route for conversion and utilization of benzene; yet, it presents significant challenges in activity and selectivity control. In this work, we report a metal-support synergistic catalyst prepared via calcination of W-precursor-containing montmorillonite (MMT) followed by Pd loading (denoted as Pd-mWOx/MMT, m = 5, 15, and 25 wt %), which shows excellent catalytic performance for hydroalkylation of benzene. A combination study (X-ray diffraction (XRD), hydrogen-temperature programmed reduction (H2-TPR), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV-vis, Raman, and density functional theory (DFT) calculations) confirms the formation of interfacial sites Pd-(WOx)-H, whose concentration is dependent on the interaction between Pd and WOx. The optimized catalyst (Pd-15WOx/MMT) exhibits a CHB yield of up to 45.1% under a relatively low hydrogen pressure, which stands at the highest level among state-of-the-art catalysts. Investigations on the structure-property correlation based on in situ FT-IR and control experiments further verify that the Pd-(WOx)-H structure serves as the dual-active site: the interfacial Pd site accelerates benzene hydrogenation to cyclohexene (CHE), while the interfacial Bronsted (B) acid site in Pd-(WOx)-H boosts the alkylation of benzene and CHE to CHB. This study offers a new strategy for the design and preparation of metal-acid bifunctional catalysts, which shows potential application in the hydroalkylation reaction of benzene.

Metal-acid dual sites in Pd/SiO2-Al2O3 synergistically catalyze selective hydrogenation-etherification of furfural to bioether

Production of ethers from biomass-derived platform compounds is a substantial scientific challenge and industrial pursuit. In this study, an effective bifunctional Pd/SiO2-Al2O3-30 catalyst was synthesized for the selective hydrogenation-etherification of furfural (FAL) to furfuryl ether and exhibited an 86.2% 2-(isopropoxymethyl)furan yield with the synergistic catalysis of Pd particles and Brønsted–Lewis acid sites. The incorporation of Si with Al2O3 in the catalysts weakened the metal-support interaction and resulted in larger Pd particles, which inhibited the hydrogenation of the furan ring. Meanwhile, the formation of Brønsted acid centers catalyzed the etherification step and promoted the selectivity to corresponding ethers. Furthermore, extensive reaction results and characterizations uncovered the metal-acid synergistic catalysis mechanism for the selective hydrogenation-etherification of FAL. This work provides an innovative strategy for preparing effective metal-acid bifunctional catalysts for the hydrogenation-etherification of bio-aldehydes to ethers.

Ring-opening of furfuryl alcohol to pentanediol with hierarchically structured Cu-MFI catalysts

Metal-acid bifunctional catalysts often encounter deactivation troubles due to carbon deposition and metal agglomeration. Herein, a hierarchically porous structured Cu-MFI-AEH catalyst was developed for selective ring-opening of furfuryl alcohol to pentanediols, which exhibits >90% yield of pentanediols and improved stability. The synergistic effect of nano-copper species and Brønsted acidic protons boosts the ring opening of furfuryl alcohol. This was also disclosed by the DFT technique that small-size Cu possesses better hydrogen dissociation performance, and the introduction of ≡Si (OH) Al≡ (Brønsted acidic protons) promotes the adsorption of furfuryl alcohol and reduces the ring opening energy barrier of furfuryl alcohol. The obtained highly porous catalyst possesses a large external surface area and large pore volume, which are beneficial to offer accessible active sites and accelerate product transport, eventually resulting in superior anti-coking performance. Furthermore, the abundant silanol groups on the MFI surface produced by ammonia treatment could act as an anchoring site for grafting Cu species, resulting in strong metal-support interaction and highly anti-sintering performance. The results reported herein provide a novel strategy to improve the stability and activity of copper-based catalysts. It also inspires the conversion of biomass resources into high value-added oxygenated fine chemicals.

Highly dispersed Pd anchored on heteropolyacid modified ZrO2 for high efficient hydrodeoxygenation of lignin-derivatives

Production of biofuels and value-added chemicals from renewable biomass is a strategy with great promise to replace petrochemicals. Herein, we developed an efficient method to fabricate highly dispersed Pd anchoring on phosphotungstic acid (PTA)-modified ZrO2. The optimized metal–acid bifunctional catalyst, Pd-PTA/ZrO2, displayed excellent catalytic performance for the hydrodeoxygenation of lignin-derivatives under mild conditions. High conversion of vanillin and high selectivity of 2-methoxy-4-methylphenol can be achieved at 80 °C for 90 min under 1 atm H2, which overcame most of the reported catalysts. The outstanding catalytic activity can be attributed to the large surface area, moderate acid strength, the synergetic effect of the active metal and ZrO2 support. This study provides a feasible route to prepare highly dispersed catalysts with superior catalytic performance for bio-fuel upgrading.

Preparation of Metal-Acid bifunctional catalyst Ni/ZSM-22 for palmitic acid catalytic deoxygenation

In this work, methods employing ethanol for dispersion as well as precursor combination by rotary evaporation were combined to produce Ni-based ZSM-22 catalysts. The catalytic activity in palmitic acid deoxygenation over Ni/Z22@E was enhanced compared with that of the wet-impregnated method. The conversion of palmitic acid reached 98.9 %, in which C16/C15 alkane was as high as 4.07. The Ni species on the surface of catalysts showed strong stability so that not susceptible to inactivation by coking or leaching. In addition, the mechanism and kinetics of the palmitic acid deoxygenation reaction were analyzed. The results showed that the ethanol dehydration reaction was the most difficult to occur, and the high C16 alkanes selectivity can be attributed to the low activation energy of the hydrodeoxygenation (HDO) pathway. Both experimental and kinetics calculation results suggested that there may be a mechanistic change in the fatty acid deoxygenation reaction at around 240 °C that resulted in a large increase in the hydrodecarboxylation (HDX) pathway. Based on this, selected adjustments of the products were proposed for fatty alcohols below 220 °C, C16 alkanes between 260 and 280 °C, and C15 alkanes above 280 °C.

Small-sized Ni nanoparticles embedded nickel phyllosilicate as a metal-acid bifunctional zeolite catalyst for cooperatively boosting CO2-CH4 reforming

Ni-based catalysts using siliceous materials as the supports have suffered from two challenging issues of sintering and carbon deposition for dry reforming of methane (DRM), resulted from a weak metal-support interaction. Given these, a novel metal–acid bifunctional Ni@S-1 zeolite catalyst is tailored from the evolution of hydroxylated nickel phyllosilicates that are formed by subtly controlling the coordination environments of Ni precursor complexes in the silicalite-1 (S-1) zeolite. The developed Ni0.44@S-1 catalyst renders almost equivalent CH4 and CO2 conversions (85.1 % and 88.7 %), high H2/CO molar ratio (about 1) and superb long-term stability during 100 h with no activity loss at 750 °C with a WHSV of 100 L·gcat−1·h−1, outperforming other control catalysts under investigation. Such superior catalytic behavior benefits from the synergy between highly uniform Ni nanoparticles (3–5 nm) confined in the micropores of zeolite and substantially formed Lewis acid sites due to coordinatively unsaturated Ni2+ sites located at the reduced 2:1 nickel phyllosilicate, as revealed by detailed characterizations. Meanwhile, it further discloses that a benign balance between formation and elimination of “process carbon” species is responsible for improving the carbon resistance of catalyst during the DRM reaction. The present design broadens a new insight for the development of new Ni-based catalysts with simultaneous coking- and sintering-resistant for the DRM application.

Metal-Acid Bifunctional Catalysts toward Tandem Reaction: One-Step Hydroalkylation of Benzene to Cyclohexylbenzene.

The one-step hydroalkylation of benzene to cyclohexylbenzene (CHB) is a technically challenging and economically interesting reaction with great industrial importance, where bifunctional catalysts play a crucial role in such a tandem reaction. In this work, we report H3PW12O40 (HPW) modified Ni nanoparticles (NPs) supported on mixed metal oxides (Ni/MMOs), which are featured by HPW species localized on the surface of Ni NPs (denoted as HPW-Ni/MMOs). The optimal catalyst (0.3HPW-Ni/MMOs) exhibits a satisfactory catalytic performance toward benzene hydroalkylation to CHB with a CHB yield of up to 41.2%, which is the highest standard among previously reported catalysts to date. A combination investigation based on HR-TEM, XPS, XANES, and in situ FT-IR verified the electron transfer from the W atom to the adjacent Ni atom, which facilitated the formation and desorption of cyclohexene (CHE) from Ni followed by the alkylation reaction of benzene and CHE at the interfacial Brønsted (B) acid sites of HPW, accounting for the significantly enhanced catalytic behavior. It is proposed that the HPW-Ni interface structure in xHPW-Ni/MMOs samples provides unique adsorption sites for benzene and CHE with a moderate adsorption strength, which serve as the intrinsic active center for this reaction: the Ni site promotes the hydrogenation of benzene to CHE, while the B acid site in HPW facilitates the alkylation of CHE and benzene to produce CHB. This work provides a fundamental understanding of the metal-acid synergistic catalysis toward the hydroalkylation reaction, which can be extended to the design and preparation of high-performance catalysts used in tandem reactions.

Selective hydrogenolysis of 5-hydroxymethylfurfural to 2,5-dimethylfuran over cobalt nanoparticle inlaid cobalt phyllosilicate.

Fabrication of biofuels and chemicals from renewable biomass is highly desirable to replace petrochemicals. Hydrogenolysis of biomass derived 5-hydroxymethylfurfural (HMF) is a promising way to obtain furanic fuels. In this paper, we describe the preparation of a CoSi-PS catalyst derived from cobalt phyllosilicate using a silica sol as the silica source. CoSi-PS exhibited excellent catalytic performance for the hydrogenolysis reaction of HMF to produce liquid 2,5-dimethylfuran (DMF) biofuel. 100% conversion of HMF and 97.5% selectivity for DMF were achieved at 170 °C and 1.5 MPa H2 for 4 h, which was superior to most of the reported catalysts. The excellent performance can be attributed to the strong interactions between the metal and support, highly dispersed cobalt nanoparticles and the Lewis acid sites induced by the coordinated unsaturated Co(II) sites in phyllosilicate.

Preparation of Metal-Acid Bifunctional Catalyst Ni/Zsm-22 for Palmitic Acid Catalytic Deoxygenation

Preparation of Metal-Acid Bifunctional Catalyst Ni/Zsm-22 for Palmitic Acid Catalytic Deoxygenation

Mild hydrodeoxygenation of lignin-derived bio-oils to hydrocarbons over bifunctional ZrP2O7-Ni12P5 catalysts

An imperative current challenge for the production of renewable fuels is the development of efficient catalytic hydrodeoxygenation (HDO) of phenolic-rich bio-oils into hydrocarbons. In this work, a series of bifunctional ZrP2O7(x)-Ni12P5 (where × represents the molar ratio of Zr/Ni in the catalysts) catalysts were prepared for HDO of lignin-derived bio-oils (LBO). The characterization results show that among these bimetallic catalysts, ZrP2O7(0.4)-Ni12P5 possesses the largest specific surface area, pore volume and the highest amount of acid sites (Lewis and Brønsted) due to the introduction of appropriate amount of Zr species. Meanwhile, the interaction between Niδ+ and Zr species on its surface creates new active sites for the promotion on the hydrogen adsorption and activation, thus endowing the most excellent catalytic performance. Using the optimized catalyst of ZrP2O7(0.4)-Ni12P5, 95.8% cyclohexane yield could be obtained from the HDO of guaiacol as a model compound from bio-oil under mild condition (3 MPa H2 and 250 ℃). Moreover, 36.1% hydrocarbon yield is achieved from HDO of lignin-derived bio-oils (LBO) under the same hydrogen pressure and temperature. These findings not only open a novel avenue for designing a cost-effective metal–acid bifunctional catalyst, but also provide a viable approach for converting lignocellulosic biomass feedstocks into valuable hydrocarbons.

Hydrogenative Ring-Rearrangement of Furfural to Cyclopentanone over Pd/UiO-66-NO2 with Tunable Missing-Linker Defects.

Upgrading furfural (FAL) to cyclopentanone (CPO) is of great importance for the synthesis of high-value chemicals and biomass utilization. The hydrogenative ring-rearrangement of FAL is catalyzed by metal-acid bifunctional catalysts. The Lewis acidity is a key factor in promoting the rearrangement of furan rings and achieving a high selectivity to CPO. In this work, highly dispersed Pd nanoparticles were successfully encapsulated into the cavities of a Zr based MOF, UiO-66-NO2, by impregnation using a double-solvent method (DSM) followed by H2 reduction. The obtained Pd/UiO-66-NO2 catalyst showed a significantly better catalytic performance in the aforementioned reaction than the Pd/UiO-66 catalyst due to the higher Lewis acidity of the support. Moreover, by using a thermal treatment. The Lewis acidity can be further increased through the creating of missing-linker defects. The resulting defective Pd/UiO-66-NO2 exhibited the highest CPO selectivity and FAL conversion of 96.6% and 98.9%, respectively. In addition, the catalyst was able to maintain a high activity and stability after four consecutive runs. The current study not only provides an efficient catalytic reaction system for the hydrogenative ring-rearrangement of furfural to cyclopentanone but also emphasizes the importance of defect sites.

Deactivation and regeneration of Pt‐modified zeolite Beta–Bindzil extrudates in n‐hexane hydroisomerization

AbstractBACKGROUNDThe metal–acid bifunctional catalysts are widely used in many industrially significant chemical processes, including hydroisomerization of n‐hexane. Deactivation and regeneration of metal–acid bifunctional extrudates was investigated in continuous n‐hexane hydroisomerization in a fixed‐bed reactor. Four Pt/H‐Beta‐25 catalysts containing 30% Bindzil binder were prepared with the same composition and controlled metal deposition.RESULTSDifferent preparation steps led to differences in the mechanical strength, Pt particle size, acidity and strength, metal‐to‐acid site (cPt/cAS) ratio and proximity between two types of active sites. A very slow deactivation and high selectivity to C6 isomers was obtained when Pt was deposited on H‐Beta‐25 zeolite.CONCLUSIONInitial selectivity to the desired products was correlated with the physicochemical properties of the catalysts. Location of the metal has a larger influence on catalyst deactivation of the bifunctional catalysts rather than the metal‐to‐acid site ratio or site proximity. Decline of n‐hexane conversion and selectivity to C6 isomers were correlated with changes in the textural properties and acidity of the deactivated catalyst, respectively. © 2021 The Authors. Journal of Chemical Technology & Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

The Influence of Residual Chlorine on Pt/Zeolite Y/γ-Al2O3 Composite Catalysts: Acidity and Performance

In previous studies H2PtCl6⋅6H2O or Pt(NH3)4(NO3)2 were used to control the location of Pt nanoparticles in Zeolite/γ-Al2O3 composites for the synthesis of metal-acid bifunctional catalysts. Use of H2PtCl6⋅6H2O led to Pt nanoparticles located on the γ-Al2O3 binder, in a ‘nanoscale’ intimacy with zeolite acid sites being beneficial for performance in the conversion of hydrocarbons, compared to catalysts with Pt nanoparticles located in zeolite Y (‘closest’ metal-acid intimacy) obtained by use of Pt(NH3)4(NO3)2. A side effect of using H2PtCl6∙6H2O was a higher NH3 uptake in NH3-TPD experiments, that suggested a higher acidity possibly affecting catalysis. In this study the effect of residual chlorine on Pt/Zeolite Y/γ-Al2O3 catalysts (0.1-0.6 wt.% Cl) was investigated by (pyridine) FTIR, NH3-TPD and n-alkane hydro-isomerization. The coordination of chlorine to γ-Al2O3 was observed and led to a higher NH3 uptake, but no effect of chlorine on the catalytic performance of the catalysts was detected.