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Alumina‐supported PtSn catalysts have been industrialized as the major catalysts for propane dehydrogenation, where Sn serves as an essential promoter. Herein, we synthesized a variety of Sn‐doped alumina supports by regulating the precipitation order of Sn and Al precursors as follows: Sn precursor precipitated before Al, coprecipitated with Al, precipitated immediately after Al, or precipitates after 2 h of Al. The effect of Sn promoter on the surface acidic properties of alumina and, ultimately, on propane dehydrogenation was further investigated. The Sn species introduced by coprecipitation in alumina created additional surface strong acid sites, attributed to more Sn4+ species on the surface, which are able to remain stable during the subsequent treatment. Consequently, the coprecipitated Sn species in the corresponding catalyst donate more electrons to Pt and reduce the metal particle size. As a result, the catalyst with Pt supported on the coprecipitated support (Sn+Al) exhibits superior initial propane conversion (43.2%) and stability (kd = 0.035 h−1). This study provides new insight into the interaction between the two key components, tin promoter and alumina support, of Pt/Sn‐Al2O3 catalysts. [ABSTRACT FROM AUTHOR]

The present work reports the excellent catalytic performance of phosphorus-modified HY zeolite in the alkylation of isobutane with 1-butene. A series of HY zeolites with different phosphorus-loading were prepared by wet impregnation with diammonium hydrogen phosphate solution and applied to catalyze isobutane/1-butene alkylation at 80 °C, 2 MPa, and 3 h−1. The physicochemical properties of the zeolites were characterized by XRD, SEM, N2 adsorption–desorption isotherms, ICP-OES, FTIR, NMR, NH3-TPD, and Py-IR. The mechanism of HY zeolite modified by phosphorus was investigated in depth. The results indicated that the phosphorus atoms were incorporated into the zeolite framework and involved in the formation of new Brønsted acid sites. The phosphorus-modified zeolites presented a dramatic rise in the amount of medium-strong Brønsted acid sites and the Brønsted/Lewis ratio. The initial selectivities of C8 and trimethylpentane obtained on HY-1P (phosphorus-loading of 1 wt%) were up to 75.7 wt% and 53.9 wt% respectively, which were much higher than the values over non-modified HY zeolite. Moreover, the deactivation of the catalyst was appreciably delayed. It was verified that catalyst deactivation was caused by the blockage of pores and the coverage of active sites for the deposition of C12-C20 long-chain alkanes. [ABSTRACT FROM AUTHOR]

Due to the increasing depletion of petroleum resources, the production route of non-oil-based aviation kerosene has been paid more and more attention. In this regard, the process of preparing aviation kerosene from syngas (CO and H2) is one of the most promising industrial alternative fuel production routes. The traditional syngas-to-aviation kerosene catalyst uses iron-based and cobalt-based catalysts, which is a complex process with a high cost. In this work, a hierarchical Co/Beta metal-zeolite bifunctional catalyst prepared via the melting method is reported, which can directly and highly selectively produce an aviation kerosene component from syngas (CO and H2). Compared with the catalyst prepared via the impregnation method, the Co/Beta catalyst prepared via the melting method has smaller, more highly dispersed Co metal active species and more suitable acid properties, the conversion of CO can reach 34.6%, and the selectivity of the C8-C16 aviation kerosene component can reach 40.2%, which provides a new idea for the industrial production of aviation kerosene. [ABSTRACT FROM AUTHOR]

The acid property of the catalyst is usually one of the most important parameters for the selection and design of catalysts for catalytic pyrolysis of 1‐pentene. Here, seven catalysts with similar pore properties and different acid properties were evaluated and characterized in terms of three key properties: Total acid amount (TA), Brønsted to Lewis acid ratio (B/L), and strong to weak acid ratio (S/W). A database of the stoichiometric coefficients of 26 pyrolysis products was constructed. Then, a novel catalyst acid property‐included global reaction modeling method was developed, which was used to predict the yields of the 26 pyrolysis products. Besides, a suitable range of TA, B/L, and S/W was obtained for enhancing ethylene and propylene. The model thus can predict the product composition, and be used for the design and selection of the acid properties of catalysts. This simulation method can also be extended to other hydrocarbon systems. [ABSTRACT FROM AUTHOR]

Copyright of Inorganic Chemicals Industry is the property of Editorial Office of Inorganic Chemicals Industry and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

• A functional-group-based approach is applied to modeling catalytic pyrolysis. • The catalyst properties were coupled with the functional-group-based approach. • The simulated yields of gaseous products are in overall agreement with experiments. • Superior feedstock and catalysts suitable for enhancing light olefin were obtained. The intricate composition of naphtha poses a significant challenge in formulating a comprehensive modeling approach for the production of light olefins. In this study, the intricate composition of the feedstock was described based on the weight percentage of the functional groups. At the same time, the distribution variations of the pyrolysis products were characterized using their stoichiometric coefficients (SCs). Consequently, a functional group-based approach was proposed to model the catalytic pyrolysis of multiple hydrocarbon mixtures over ZSM-5 based catalysts by establishing a quantitative correlation between the composition of the functional groups and the SCs of the pyrolysis products. Furthermore, a comprehensive functional group-based approach was developed to integrate catalyst properties by relating their acidity to the SCs of pyrolysis products. This modeling approach allows for precise forecasting of product compositions across a range of feedstocks and catalyst systems, with a maximum error of 1.15 wt%. In addition, this modeling method can also be used to optimize feedstock blends and tailor acid properties to maximize light olefin production, highlighting its potential for use in various hydrocarbon mixtures. [ABSTRACT FROM AUTHOR]

Due to the increasing depletion of petroleum resources, the production route of non-oil-based aviation kerosene has been paid more and more attention. In this regard, the process of preparing aviation kerosene from syngas (CO and H2) is one of the most promising industrial alternative fuel production routes. The traditional syngas-to-aviation kerosene catalyst uses iron-based and cobalt-based catalysts, which is a complex process with a high cost. In this work, a hierarchical Co/Beta metal-zeolite bifunctional catalyst prepared via the melting method is reported, which can directly and highly selectively produce an aviation kerosene component from syngas (CO and H2). Compared with the catalyst prepared via the impregnation method, the Co/Beta catalyst prepared via the melting method has smaller, more highly dispersed Co metal active species and more suitable acid properties, the conversion of CO can reach 34.6%, and the selectivity of the C8-C16 aviation kerosene component can reach 40.2%, which provides a new idea for the industrial production of aviation kerosene.

[Display omitted] • Skeleton of PAN was adjusted to a crosslinked form by co-calcination with KOH. • Sulfonated crosslinked PAN had moderate acid density and acid strength. • SO 3 H groups H-bonded with benzenoid or tertiary amine nitrogen were the active sites. • High TOF toward HMF formation was achieved from high-concentration fructose. Acid-catalyzed dehydration of fructose to 5-hydroxymethylfurfural (HMF) represents an effective method for valorizing the biomass-derived carbohydrates, however, always suffers from low catalytic efficiency of solid acid catalysts. In this work, we report the preparation of novel sulfonated crosslinked polyaniline (S-P-PAN) catalysts for high-efficient dehydration of fructose to HMF in low-boiling 1,4-dioxane and water. The skeletal structure of the organocatalysts was adjusted to a crosslinked form by co-calcination of PAN with KOH, which allowed the reduction of acid density but increment of acid strength and surface hydrophobicity after sulfonation and in turn increased the catalytic efficiency. The sulfonic acid groups hydrogen-bonded with adjacent benzenoid or tertiary amine nitrogen in the organocatalysts were found to act as the active sites, wherein the latter one were predominant. By tuning the mass ratio between PAN and KOH, as well as the temperature of co-calcination and sulfonation during the catalyst preparation, the S 100 -P 1/2 -PAN-400 catalyst with moderate acid density (1.71 mmol·g−1) and acid strength exhibited high turnover frequency (18.8 ∼ 80.6 h−1) in converting fructose in wide range of concentrations (4.5 ∼ 45.0 wt%). This work highlights the importance of deliberately adjusting the acid property of solid organocatalysts for enhancing the catalytic efficiency in HMF synthesis. [ABSTRACT FROM AUTHOR]

Aromatic components of C 8 -C 15 are playing indispensable roles in multi-functional properties of jet fuel. Here, we reported the controllable alkylation of benzene with mixed olefins of ethylene and propylene toward C 8 -C 15 aromatic hydrocarbons for jet fuels over the bifunctional Ga/ZSM-5 catalyst. The resultant 2Ga/ZSM-5 exhibited a superior selectivity of 86.4 % (yield of 55.5 %) to C 8 -C 15 range aromatics, at benzene conversion of 40.3 %, ethylene and propylene conversion of 99.5 % and 99.2 %, respectively. The incorporation of Ga species could effectively weaken the strong acid sites of ZSM-5 and endow 2Ga/ZSM-5 catalyst with appropriate acidity, therefore facilitating the benzene alkylation process and suppressing the undesired hydrogen transfer or aromatization side reactions as well, thus improving the yield of desired C 8 -C 15 aromatics for jet fuels. This work provided insight into the development of promising bifunctional catalyst for the oriented transformation of biomass-derived chemicals to aviation fuels., (© 2024 Wiley-VCH GmbH.)

Copyright of Rare Metals is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Even though tremendous progress has been made on modified Fischer-Tropsch synthesis (FTS) multifunctional catalyst that composed of Fe-based component and acidic zeolite H-ZSM-5 for CO 2 hydrogenation into value-added chemicals, the structure-function relationship between the acidic zeolite H-ZSM-5 and product distribution is still under debate. Herein, a series of H-ZSM-5 zeolites with different Al locations and acidic properties are fabricated by varying the synthesis raw agents and conditions. After combining with the carbon-encapsulated Fe-based catalyst for alkenes synthesis from CO 2 hydrogenation, aromatics are directionally produced from the ellipsoidal H-ZSM-5 with Al species mainly located at the intersection of straight and sinusoidal channels, while the main products shift to iso-paraffins for the H-ZSM-5 with pillared nanosheet morphology owing to its Brønsted acid site-rich property. The Al location in H-ZSM-5 and the corresponding acidic property are systematically investigated, and the theoretical simulations illustrate that the Al species at the intersection channels could lower the energy barrier of key aromatization step. The Al richly located at straight/sinusoidal would boost the isomerization reaction. Our work not only clarifies the structure-function relationship of acidic zeolite H-ZSM-5 in valuable chemicals synthesis from CO 2 hydrogenation but also provides a novel protocol for controlled synthesis. [Display omitted] • H-ZSM-5 with different Al location and acidic property were prepared by various method. • Al location and acid property were investigated by experimental and theoretical calculation. • The structure-function relationship between H-ZSM-5 and product distribution was built. • Al at the channel intersection can boost aromatics synthesis, otherwise promote isomerization. [ABSTRACT FROM AUTHOR]

A series of modified HUSY zeolites were prepared by immersing with different concentration of NH4F solution at low temperature, and their catalytic performance for isobutane/1-butene alkylation reaction was investigated. The physicochemical properties of modified catalysts were characterized by XRD, N2 adsorption–desorption isotherms, ICP, pyridine-IR and SEM. The results indicated that HUSY zeolite with higher Si/Al ratio is more sensitive to NH4F leaching, resulting in more severe structural amorphization. NH4F modification affects not only the pore structure but also the acid properties. The amount of Lewis acid sites on the modified zeolites was reduced and the ratio of Brønsted/Lewis acid sites was significantly enhanced in comparison with that of parent zeolite. Such properties of modified zeolites account for the superior performance for isobutane/1-butene alkylation. The initial C8 selectivity was increased to 74 wt% over the modified HUSY (Si/Al = 2.7) zeolite using 5 wt% NH4F solution, which was about 15 wt% higher than that achieved on the HUSY parent. TG and in situ IR analyses of the deactivated catalyst indicated that some deposits were formed on the catalyst and the alkylation activity could be restored by regeneration at suitable conditions (520 °C under air atmosphere). [ABSTRACT FROM AUTHOR]

[Display omitted] • b -axis-oriented [Fe/Al]-MFI nanosheets with various Fe incorporation were prepared. • Weaker acid strength can significantly suppress the formation of ethylbenzene. • Framework Fe species accelerates the coke formation. • The decrease of framework Fe can not only improve the catalytic stability, but also almost completely inhibit the formation of ethylbenzene. • This work elucidates the important relationship between acidity and alkylation activity. A clear understanding of the acidity-activity relationship is an important prerequisite for designing functional materials in alkylation of benzene with methanol. Herein, a series of b -axis-oriented [Fe/Al]-MFI nanosheets with similar thickness but varied acidities were prepared by tuning Fe incorporation to systematically study the effect of acidity on their alkylation performance. Comprehensive physiochemical studies demonstrate that tetrahedral framework type Fe species are dominated. The incorporation of Fe significantly weakens the strong acid strength of zeolite thus endowing the samples with proper acidity, consequently showing a strong inhibition effect on the by-product ethylbenzene. Moreover, a long-term stable operation (>300 h) is further achieved over the [Fe]-S-1 nanosheets by optimizing the content of framework Fe. This work elucidates the important relationship between acidity and alkylation activity. [ABSTRACT FROM AUTHOR]

• CeO 2 @SiO 2 catalysts were prepared by a spontaneous deposition method. • CeO 2 @SiO 2 exhibited high performance and durability in DCE catalytic oxidation. • The richer weak acid sites were beneficial to the adsorption and activation of DCE. • The abundant adsorbed oxygen species and oxygen mobility improved oxidation of DCE. The construction of uniform nanodots CeO 2 stabilized by porous silica matrix (CeO 2 @SiO 2 -T) was synthesized by a spontaneous deposition method. Based on the XRD and TEM results, the CeO 2 nanodots were highly dispersed on the porous silica matrix. The characterizations including O 2 -TPD, XPS, and NH 3 -TPD clarified that CeO 2 @SiO 2 -T catalysts possessed strong acidity, rich surface adsorbed oxygen species and oxygen mobility, which was beneficial to the improvement of adsorption and catalytic oxidation of 1,2-dichloroethane (DCE). The CeO 2 @SiO 2 -T catalysts exhibited high performance for DCE oxidation, in which the CeO 2 @SiO 2 -400 catalyst showed the best performance (T 90 = 275 °C at a space velocity of 15000 h−1) and good stability (at 295 °C for 100 h). The characterization and activity test results showed that the richer acid sites were beneficial to the adsorption and activation of DCE, contributing to the subsequent HCl removal and vinyl chloride (VC) formation. Noticeably, the weak acid sites were more favorable for the improvement of catalytic activity. Then major of VC would be oxidized to adsorbed acetate, which could be further decomposed to CO x and HCl. In addition, trace poly-chlorinated by-products were detected. The abundant surface adsorbed oxygen species and excellent oxygen mobility facilitated the further oxidation rather than the chlorination reactions. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Modifying with alkali metal cations tuned the acid/basic properties of ZSM-5. • The ratio of Lewis acid to Brønsted acid changed with alkali metal modification. • Moderate attenuation of strong acid sites could enhance the catalytic performance. • Alkali metal modification could restrain coke and enhance light alkene selectivity. • Scheme of mechanism for ZSM-5 modified by alkali metal cation was proposed. Abstract Alkali metal modified ZSM-5 (ZSM-5-M, M: Li, Na, K, Cs) was prepared by ion-exchange method. The ion-exchange of alkali metal cations with silanol group occurred along with hydrolysis of the Si-O(H)-Al, leading to increase of Lewis acid, decrease of strong and Brønsted acids. K+ and Cs+ were easier to exchange with proton of –OH compared with Na+ and Li+ due to their smaller hydrated radius, resulting in higher ion exchange capacity for ZSM-5-K and ZSM-5-Cs. Their catalytic performances in supercritical n -dodecane cracking were studied. The gas generation rates (GGR) and heat sinks under 550 °C and 4 MPa increased as following: ZSM-5-Cs < ZSM-5 < ZSM-5-K < ZSM-5-Li < ZSM-5-Na. The GGR and heat sink of ZSM-5-Na reached 60.3% and 2826 kJ kg−1, respectively. Thus moderate attenuation of strong acid and enhancement of basic sites could enhance the catalytic performance in supercritical n -dodecane cracking. The selectivity for light alkene was enhanced and the coke was restrained due to the regulated acid-base properties, since decreasing strong acidic sites and increasing the basic sites could suppress the secondary reactions that consumed light alkene and generated coke. [ABSTRACT FROM AUTHOR]

In this study, F− was added to the synthesis gel to regulate the acid property of SAPO-18 molecular sieve and enhance its catalytic performance for the methanol-to-olefin (MTO) reactions. The results indicate that adding an appropriate amount of F− during synthesis can increase the crystallinity of SAPO-18 molecular sieve and reduce the overall strong acid density and external surface acid content. The H-SAPO-18-I-20-0.0025 molecular sieve exhibits a much higher catalytic lifetime (1000 min) and light olefins selectivity (45.2% to propene and 96.1% to C 2-5 =) in MTO at 400 °C than those of the traditional H-SAPO-18-1-0. The results of the isotope labeling experiments, GC-MS, and 13C MAS NMR results provided direct evidence that the aromatic-based cycle contributes more to the conversion of methanol into light olefins, and hexamethylbenzene serves as the most abundant hydrocarbon species that produces propene via the paring route. MTO catalytic performance of SAPO-18 can be finely optimize by adjusting the F− ions content in the synthesis gel through reducing the overall strong acid density and external surface acid sites; HexaMB server as most hydrocarbon species produce propene via paring route. [Display omitted] • Catalytic performance of H-SAPO-18 in MTO is related to the property of strong acid sites and cavity structure. • Adding F− in the synthesis gel can increase the crystallinity of SAPO-18 zeolite. • F− helps to reduce the overall strong acid density and external surface acid content. • H-SAPO-18-20-0.0025 (F/(Al + P) = 0.0025) shows enhanced catalytic lifetime and light olefins selectivity in MTO. • Hexamethylbenzene server as most hydrocarbon species produce propene via paring route in MTO over H-SAPO-18. [ABSTRACT FROM AUTHOR]

In recent years, chitosan has been applied for wound management due to its properties of biocompatibility, biodegradability, antimicrobial activity, and low immunogenicity. But the poor water solubility in neutral pH limited its further application in clinical wound healing. To overcome this problem, acetate chitosan was developed and approved as commercial products for wound healing. However, the acidity of acetate chitosan was potentially allergenic, and the poor mechanical properties of its formed hydrogels also hindered the therapeutic efficacy in wound care. In this study, CaCO3 was simply doped into acetate chitosan to form the wound dressing. After absorbing water, the H+ of acetate chitosan reacted with CaCO3 to release Ca2+, resulting in acidity decreased. The production of Ca2+ and residue of CaCO3 cross‐linked with chitosan to form a tough hydrogel by electrostatic interaction. The physical characteristics, swelling, mechanical testing, and blood clotting were evaluated. The results in vitro demonstrated that after doping CaCO3 into acetate chitosan, the mechanical properties and blood clotting of the formed hydrogel were increased. Then, the evaluation of hydrogels in vivo revealed that it can also accelerate the wound healing by promoting re‐epithelization and collagen deposition. This simple way by doping CaCO3 into acetate chitosan can increase wound healing, and it can also broad the application of acetate chitosan in clinical use. [ABSTRACT FROM AUTHOR]

The zeolites are usually modified by Pd before its application in the hydrogenation/dehydrogenation reactions. To understand the catalytic behavior of the Pd modified zeolites in catalytic reactions, the H 2 adsorption on Pd modified HAl-ZSM-12 zeolites were studied using dispersion corrected periodic density functional theory. It is interesting that the Pd could insert into the –OH groups to form the spillover structure of –O–Pd–H. The Brønsted acid H site of the zeolite reduced by Pd monomer to produce H 2 is thermodynamically favorable, while it is unfavorable by Pd dimmer. The modification of Pd weakens the Lewis acidity of Al 3+ and Brønsted acidity of –OH. However, the Pd atoms could work as strong Lewis sites in the Pd modified zeolites. The modification of Pd also improves the H 2 activation/adsorption properties of HAl-ZSM-12. In addition, the acid properties of the Pd modified zeolites could be inevitably influenced by H 2 atmosphere, since the dissociative adsorbed H 2 could work as new Brønsted acid H and also influences the charge of Pd atoms. The calculated adsorption energy for NH 3 reveals that H 2 adsorbed in Pd modified HAl-ZSM-12 results in weaker Lewis acidity of Pd sites. The new formed Brønsted acid sites after H 2 adsorption are weaker than the original HAl-ZSM-12. These results strongly demonstrates that the Pd modified ZSM-12 catalysts in real catalytic condition is much different from the prepared samples before it works in the catalytic reaction. [ABSTRACT FROM AUTHOR]

Phosphorus-modified Al 2 O 3 supports containing different P content were prepared to control the acidity of Ni-impregnated catalysts for application in the dry reforming of methane (DRM). Results from the H 2 -temperature-programmed reduction showed that an increase in P content promoted the formation of an AlPO 4 phase, and resulted in an increase in Ni particle size. Although the initial conversion of CH 4 and CO 2 decreased with increasing P content, the addition of P influenced on the acidic properties of the support and the catalyst. Indeed, a decrease in catalytic deactivation correlated with the decreasing acidity of the P-modified supports and the Ni/P-Al 2 O 3 catalysts, and the acidic properties were determined by the behaviors of the temperature-programmed desorption of iso -propanol (IPA) and the dehydration of IPA. We found that the Ni/Al 2 O 3 catalyst modified by 2 wt.% P exhibited the weakest acidity whilst demonstrating excellent coke resistance and stability over 100 h in the DRM reaction. [ABSTRACT FROM AUTHOR]

Using periodic DFT-D3-U methods, the present work give a mechanistic insight into the high silica B-, Al-, Ga- and Fe-MOR with H, Li, Na, and K as charge balance ions. The acid properties of the zeolite were probed via NH 3 and pyridine adsorption. It is found that the charge balance ions influence the location of the trivalent ions, the cell volumes, as well as the synthesis difficulty of the zeolites. The energy differences for B, Al, Ga and Fe in different T sites are small for the H-form zeolites, while large for the Na- and K-form zeolites. For H-form MOR, the proton of the OH group prefers to bond to O(7) and O(3) and pointing to the 12MR for trivalent ions in T1 sites. The proton bonds to O(3), O(2), O(2) and O(5), respectively, for B, Al, Ga and Fe in T2 site of MOR, with the OH group pointing to intersection of 12MR and the side-pocket, except for the B-MOR that OH group pointing to the 12MR. For trivalent ions located in T3 and T4 sites, the protons prefers to bond to O(1) and O(2), respectively, with the OH group pointing to the intersection of 8MR and side-pocket as well as the intersection of 12MR and side-pocket. All incorporated B, Al, Ga, and Fe framework ions are tetra-coordinated, except the B atoms are tri-coordinated. The NH 4 -form MOR has smaller cell volume than the other form MOR. Na and K are energetically more favored charge balance ions than Li and NH 3 for MOR zeolites synthesis, and the H-form zeolite is the most difficult to be synthesized directly. The strength of the Brønsted acidity follows the order: HBMOR < HFeMOR ≈ HGaMOR < HAlMOR, vs. the Lewis acidity order: HBMOR < HAlMOR < HFeMOR ≈ HGaMOR. NH 3 could be adsorbed inside all kinds of channels, and especially favors in the small 8MR vs. pyridine could only be adsorbed in the main channel of MOR due to the steric effect. It indicates that the acid sites in the side pocket and the small 8-membered ring and the side pocket could not be effectively determined just by the pyridine adsorption experiments. In comparison, the NH 3 adsorption experiments could detect all kinds of Brønsted sites of the MOR zeolites. [ABSTRACT FROM AUTHOR]

Direct hydrogenation of carbon dioxide (CO 2) to value-added aromatics can not only provide a sustainable aromatics synthesis route but also realize CO 2 mitigation. However, it remains a great challenge to identify the optimal surface acidity and regulate the selective formation of aromatics during CO 2 hydrogenation. Herein, we designed and prepared a series of K/Fe-Cu-Al@HZSM-5 tandem catalysts, and deeply investigated the effects of zeolite surface acidity on the catalytic performance, by changing the SiO 2 /Al 2 O 3 ratios of HZSM-5 from 25 to 400. It was found that the surface acidity, especially for the Brønsted acidity, plays a crucial role in the aromatics formation. With an increasing Brønsted acidity from 0 to 290 μmol/g, the CO 2 conversion keeps relatively stable (around 44%), however, the aromatics yield monotonously increases from 0.9 to 12.8%, indicating a distinct correlation with the Brønsted acidity. Among the obtained aromatics, the majority ones are C 6 – 8 light aromatics, accounting for c.a. 30–60% within time on stream (TOS) of 24 h, but their proportion tends to gradually decrease with TOS, probably due to the catalyst deactivation by coking. Moreover, the possible reaction pathways for aromatics formation over the prepared K/Fe-Cu-Al@HZSM-5 tandem catalysts were also proposed. [Display omitted] • K/Fe-Cu-Al@HZSM-5 tandem catalysts were proposed for aromatics synthesis via CO 2 hydrogenation. • Effects of ZSM-5 surface acidity on aromatics formation and product distribution were investigated. • The possible reaction pathways for the K/Fe-Cu-Al@HZSM-5 tandem catalysts were proposed. • Suitable increase of the surface B acidity benefits the selective formation of aromatics. [ABSTRACT FROM AUTHOR]

[Display omitted] • The interaction mechanism of n/cyclo-paraffins was investigated. • A catalyst acid property-included stoichiometric coefficient model was proposed. • Stoichiometric coefficients are expressed as functions of catalyst acid properties. • An application shows the model can accurately predict the formation of gaseous. • Superior acid properties of catalyst were obtained for enhancing light olefins. Process modeling is considered an effective way to achieve refined management in the petrochemical industry, and is also the foundation and necessary link of intelligent chemical platform construction. This study aims to the simulation of the formation of gaseous products for the catalytic pyrolysis of representative naphtha compositions using a stoichiometric coefficient model. Firstly, the interaction mechanism of n/cyclo-paraffins was investigated using a pseudo-first-order kinetic model, and the cracking activity of hydrocarbon mixtures was quantified using the carbon number and cyclo-paraffin content. Subsequently, a database of the stoichiometric coefficients of the gaseous products was constructed. Considering the acid properties of the catalysts, a catalyst acid property-included stoichiometric coefficient model was developed to adapt to varying feedstock composition and catalyst systems, which could reflect gaseous production in the catalytic pyrolysis of multi-component mixed hydrocarbons. Moreover, the simulation using the present model shows that the production of light olefins in the catalytic pyrolysis of mixed hydrocarbons can be increased under the optimized catalyst acid properties. Hence, this study aims to provides theoretical guidance for the prediction of product distribution as well as the design and selection of catalysts used in the catalytic pyrolysis processes for multi-component mixed hydrocarbon. [ABSTRACT FROM AUTHOR]

ZSM-5 zeolite is widely used in catalytic cracking of hydrocarbon, but the conventional ZSM-5 zeolite deactivates quickly due to its simple microporous and long diffusion pathway. Many studies have been done to overcome these disadvantages recently. In this review, four main approaches for enhancing the catalytic performance, namely synthesis of ZSM-5 zeolite with special morphology, hierarchical ZSM-5 zeolite, nano-sized ZSM-5 zeolite and optimization of acid properties, are discussed. ZSM-5 with special morphology such as hollow, composite and nanosheet structure can effectively increase the diffusion efficiency and accessibility of acid sites, giving high catalytic activity. The accessibility of acid sites and diffusion efficiency can also be enhanced by introducing additional mesopores or macropores. By decreasing the crystal size to nanoscale, the diffusion length can be shortened. The catalytic activity increases and the amount of carbon deposition decreases with the decrease of crystal size. By regulating the acid properties of ZSM-5 with element or compound modification, the overreaction of reactants and formation of carbon deposition could be suppressed, thus enhancing the catalytic activity and light alkene selectivity. Besides, some future needs and perspectives of ZSM-5 with excellent cracking activity are addressed for researchers' consideration. [ABSTRACT FROM AUTHOR]

Mesoporous Cu-SiO 2 -Al 2 O 3 bifunctional catalysts with highly dispersed active sites and increased acid amount were synthesized via a modified evaporation induced self-assembled (EISA) method and firstly used for dimethyl ether steam reforming (DME SR). Various techniques including XRD, nitrogen adsorption-desorption, N 2 O chemisorption, H 2 -TPR, NH 3 -TPD, TEM, FT-IR and 27 Al MAS NMR were employed to characterize the prepared catalysts. The Cu-SiO 2 -Al 2 O 3 catalyst calcinated at 700 °C with 7.5% Cu and 17.5% Si exhibited the highest DME conversion rate up to 100% and H 2 yield of 90%, and good reaction-regeneration performance. The long-range ordered mesoporous structure, improved specific surface area and pore volume, and highly dispersion of Cu and CuAl 2 O 4 nanopaticles were obtained after the incorporation of SiO 2 , which were found to be influential to the enhanced catalytic performance. Notably, the added SiO 2 helped to form Lewis acid, leading to a huge increase in solid acid amount, which further improved the DME hydrolysis activity. [ABSTRACT FROM AUTHOR]

Catalytic reactions of acetylene have become a subject of renewed interest. However, recent literatures about the synthesis of acrylic acid by acetylene carbonylation were rare to be found. In our research, the yield of acrylic acid is greatly improved to ∼86% (242.85 g Acrylic acid/g Cat.·h) by using heterogeneous catalyst Cu(I)Y, against ∼70% from other reports using complex homogeneous catalyst. Y modified with different valence states copper were prepared by heating the precursor at various atmospheres and characterized by XRD, BET, XPS and FT-IR. More than one type of copper (Cu 2+ , CuO, Cu 2 O, Cu + or Cu 0 ) was found on one sample. Moreover, the distribution and the forming process of these types of copper were determined. According to FT-IR using pyridine or CO as probe, Cu + at site II′ not only enhanced the acid strength obviously, but also promoted the formation of the most stable monocarbonyls. Furthermore, the strong acid site and the stable monocarbonyls are beneficial for the acetylene carbonylation. [ABSTRACT FROM AUTHOR]

Pd was loaded on ultra stable Y (USY) zeolites prepared by steaming NH4-Y zeolite under different conditions. Heck reactions were carried out over the prepared Pd/USY. We found that H2 bubbling was effective in improving not only the catalytic activity of Pd/USY, but also that of other supported Pd catalysts and Pd(OAc)2. Moreover, the catalytic activity of Pd/USY could be optimized by choosing appropriate steaming conditions for the preparation of the USY zeolites; Pd loaded on USY prepared at 873 K with 100% H2O gave the highest activity (TOF = 61,000 h−1), which was higher than that of Pd loaded on other kinds of supports. The prepared Pd/USY catalysts were applicable to the Heck reactions using various kinds of substrates including bromo- and chloro-substituted aromatic and heteroaromatic compounds. Characterization of the acid properties of the USY zeolites revealed that the strong acid site (OHstrong) generated as a result of steaming had a profound effect on the catalytic activity of Pd.

Direct synthesis of aromatics from syngas provides a promising approach for the production of fine chemicals from non-petroleum carbon resources. In this study, direct conversion of syngas into aromatics was investigated over a serial of bifunctional catalysts coupling ZnCrO x oxides and H-ZSM-5 zeolites with different morphologies. Detailed investigation showed that the CO conversion was positively correlated with the Brønsted acid sites, and the differences in aromatics selectivity and aromatics distribution on different bifunctional catalysts with different morphologies of H-ZSM-5 zeolites were attributed to the synergistic effects of acidity and particle size. For nano-type zeolites, changes in acidity might not have a significant effect on aromatics selectivity, while the transfer of intermediate species on coffin-type zeolites was mainly influenced by acidity. Moreover, for different morphology zeolites of nano-type n-Z5-125 and coffin-type c-Z5-100 with similar acidity, the side reactions in syngas aromatization on the former were 1.7 times higher than those on the latter. The reactants diffused more readily on TPAOH treated c-Z5-150-0.1 M, which promoted olefins cyclization and further increased the aromatics selectivity from 69.8% to 74.8%. [Display omitted] • The CO conversion in STA is positively correlated with the Brønsted acid sites. • H-ZSM-5 with external framework Al and short b-axis easily forms C 8 + aromatics. • TPAOH-treated c-Z5-150 zeolite is effective in enhancing the aromatics selectivity. [ABSTRACT FROM AUTHOR]

• Ethylene oligomerization at 300 °C and 0.1 MPa over NiO x /SiO 2 -Al 2 O 3 was studied. • SiO 2 -Al 2 O 3 with various physicochemical properties was prepared by a coprecipitation method. • SiO 2 -Al 2 O 3 made using aq. NH 3 and aged at 70 °C produced a highly active catalyst. • NiO x /SiO 2 -Al 2 O 3 with a high surface area and many acid sites showed high activity. • Highly dispersed Ni species and weak acid sites together promote ethylene oligomerization. Thirty-three types of NiO x /SiO 2 -Al 2 O 3 with different pore structures (BET specific surface area: 32–565 m2 g−1), acid properties (total acid sites: 0.32–1.50 mmol g−1), and NiO crystallite sizes (3.8–20.6 nm) were prepared and evaluated as catalysts for ethylene oligomerization. SiO 2 -Al 2 O 3 support was prepared by a coprecipitation method, and Ni was loaded on it by an impregnation method. Catalysts were characterized by nitrogen adsorption, powder X-ray diffraction, scanning electron microscopy, temperature-programmed reduction under hydrogen, and temperature-programmed desorption of ammonia. Catalytic reactions were performed in a fixed-bed, down-flow reactor operated at 300 °C and 0.1 MPa. The preparation conditions of the SiO 2 -Al 2 O 3 support (i.e., type of precipitant, Al 2 O 3 content, and aging temperature) greatly influenced the structure and activity of the resulting NiO x /SiO 2 -Al 2 O 3 catalysts. The highest activity was obtained when SiO 2 -Al 2 O 3 was prepared using aqueous ammonia as the precipitant, the Al 2 O 3 content was 15%, and the aging temperature was 70 °C. The activity of this NiO x /SiO 2 -Al 2 O 3 catalyst was comparable with that of Ni-AlSBA-15, which was the highest activity heterogenous catalysts reported to date. The activity of NiO x /SiO 2 -Al 2 O 3 increased linearly with increasing BET specific surface area and number of acid sites of the catalyst, but it decreased with increasing Ni surface density. We speculate that highly dispersed Ni species and (weak) acid sites together improve the activity of the developed catalysts. [Display omitted] [ABSTRACT FROM AUTHOR]

USY zeolite was treated by the citric acid. The properties and catalysis of the USY zeolite were studied. The X-ray diffraction has been used to identify and quantify extra framework aluminum (EFAL) in USY zeolite by EFAL extraction using citric acid. The acid character changed depending on the EFAL concentration. The Lewis acid sites can be obtained from the Si/Al ratio. The removing of trace olefins was carried out over kinds USY zeolites with different amount of EFAL. The catalytic performance was correlated with the Lewis acid sites of USY. [ABSTRACT FROM AUTHOR]

The distribution scheme of Fe 3+ cation in MTW-type zeolite and its influence on the acid property were systematically studied using dispersion-corrected density functional theory. The calculated energy differences are small for different incorporated T sites, indicating that Fe atoms might distribute in all kinds of T sites. Substitution energy is firstly introduced to evaluate relative synthesis difficulty for metal incorporated zeolite. For MTW-type zeolites, the calculated substitution energies give the order of NaAl-MTW > NaFe-MTW > NH 4 Al-MTW > NH 4 Fe-MTW > HAl-MTW > HFe-MTW, which are in line with experimental observations, illustrating a real case that substitution energies can be used to pre-select the prescriptions for zeolite synthesis. Acidity studies show that the Lewis acidities of HFe-MTW zeolite are stronger than those of HAl-MTW zeolite, while the Brønsted acidities of HFe-MTW zeolite are weaker than those of HAl-MTW zeolite. Adsorption studies of NH 3 and pyridine show that adsorption on the Lewis acid sites are less stable than on the Brønsted acid sites. These results are also in well agreement with the previous experimental observations and provide new insights for MTW-type zeolites. [ABSTRACT FROM AUTHOR]

Dehydration of methyl lactate to acrylic acid was performed over various modified MCM-41 catalysts with different phosphate and/or sulphate salts supported. Among all the catalysts, K 2 HPO 4 and Al 2 (SO 4 ) 3 modified MCM-41 zeolite was found to be the most efficient catalyst for this reaction, which gave 90% conversion of methyl lactate and 72% selectivity toward acrylic acid and methyl acrylate together at 400 °C. The catalysts were further investigated with XRD, small angle XRD, TEM, Raman, DSC, NH 3 -TPD and pyridine FTIR experiments. It was found that K 2 SO 4 and AlPO 4 formed on the two salts supported sample after high temperature calcination, indicating that some reaction occurred between these two precursors during the preparation. Compared with other catalysts, the K 2 HPO 4 + Al 2 (SO 4 ) 3 modified sample showed no strong acidic sites, lowest acid amount and highest Bronsted/Lewis ratio, which was supposed to explain its high dehydration selectivity. Meanwhile, effects of different impregnation procedures were compared and the relationship between activity and structure as well as surface properties was proposed. [ABSTRACT FROM AUTHOR]

Highlights: [•] Acid properties of ZSM-5 type zeolite are studied by solid-state NMR. [•] Trimethylphosphine oxide (TMPO) is introduced from the gas phase at 373K. [•] Almost all Brønsted acid sites are probed by TMPO. [•] The 31P signals between 90 and 60ppm are attributed to TMPO on Brønsted acid sites. [ABSTRACT FROM AUTHOR]

NiO x /SiO 2 –Al 2 O 3 catalysts with different pore structures (BET specific surface area: 303–709 m2 g−1, average pore size: 2.2–5.1 nm), acid properties (total amount of acid sites: 0.99–1.66 mmol g−1), and NiO particle sizes (4.6–14.7 nm) were prepared, and the structural factors influencing their catalytic activity for ethylene oligomerization were studied. SiO 2 –Al 2 O 3 support was prepared by means of a homogeneous precipitation method, and supports with different physicochemical properties were obtained by changing the preparation conditions. Ni was loaded by means of an impregnation method. Catalytic reactions were performed in a fixed-bed down-flow reactor operated at 300 °C and 0.1 MPa. NiO x /SiO 2 –Al 2 O 3 catalysts prepared with the homogenous precipitation method had a higher surface area, more uniform pore size, and a larger amount of acid sites, and they showed a higher activity not only compared with NiO x /SiO 2 –Al 2 O 3 catalysts prepared by means of our previous coprecipitation method but also compared with Ni-AlSBA-15, the best heterogenous catalyst for ethylene oligomerization reported to data. The catalytic activities of the NiO x /SiO 2 –Al 2 O 3 catalysts strongly depended on the BET specific surface area and the amounts of acid sites. The optimal amounts of weak, medium-strength, strong, and total acid sites were 0.5, 0.3, 0.4, and 1.2 mmol g−1, respectively. Examination of the structure–activity relationships of the catalysts suggested that their catalytic activity was promoted by close contact between the Ni and acid sites. [Display omitted] • Ethylene oligomerization at 300 °C and 0.1 MPa over NiO x /SiO 2 –Al 2 O 3 was studied. • Catalysts were prepared by a homogeneous precipitation and impregnation method. • Catalysts showed a high surface area, uniformly sized mesopores, and many acid sites. • Catalytic activity was dependent on specific surface area and amount of acid sites. • Close contact between Ni and acid sites is important for high catalytic activity. [ABSTRACT FROM AUTHOR]

Abstract: An approach, which involved perturbations of synthesis conditions in crystallization temperature and organic template composition, has been proposed for derivation of mesopores from bulk structural defects formed in mordenite (MOR) phases, based on the character of intrinsic crystal defects and tensional distortions of two compressed 8-membered rings in MOR framework. Consequently, hierarchically porous materials with MOR structures were prepared by varying temperature synthesis and using ternary organic micelles templates. The synthesized materials were characterized by powder X-ray diffraction, nitrogen adsorption at 77K and transmission electron microscopy. These crystalline materials combined the advantages of both mordenites with the micropore system and mesoporous materials by featuring an additional intracrystalline mesopore system in MOR single crystals, resulting in a hierarchical pore distribution in range of 1.7–80.0nm together with the significant specific surface areas. In particular, individual crystal morphologies of typical mesoporous MOR materials showed the defect-rich structures responding essentially to the mesoporosity; the mesoporous materials were substantiated matchable well to normal mordenites in acid capacity and acid strength distribution. Furthermore, several factors acting on intracrystalline mesopore formation were elucidated for explicating the perturbation synthesis approach, and whole reaction routes for synthesizing different solid products under related crystallization conditions were summarized coupling with a demonstration of part TEM micrographs. The overall results suggested that the investigative approach of perturbation imposed on crystal growth provides an alternative route for direct hydrothermal synthesis of mesoporous zeolite materials and implied that bulk structural defects within single crystals lead to the formation of intracrystalline mesopores in various sizes. [Copyright &y& Elsevier]

Abstract: Acidic properties of H-type mordenite have been studied by solid-state NMR. The framework Si/Al ratios are determined by 29Si MAS NMR spectra, and the contents of framework Al and Brønsted acid sites are determined. 27Al MAS NMR spectra show a presence of extra-framework Al as well as “invisible” Al. The 1H MAS NMR spectra consist of hydrogen-bonded Si–OH, Brønsted acid site, tightly adsorbed water, Al–OH and isolated Si–OH, the amounts of which are evaluated. The average 1H chemical shifts of Brønsted acid sites without proton exchange are roughly estimated, which are in the following order; HM10

Pd was loaded on ultra stable Y (USY) zeolites prepared by steaming NH4-Y zeolite under different conditions. Heck reactions were carried out over the prepared Pd/USY. We found that H2 bubbling was effective in improving not only the catalytic activity of Pd/USY, but also that of other supported Pd catalysts and Pd(OAc)2. Moreover, the catalytic activity of Pd/USY could be optimized by choosing appropriate steaming conditions for the preparation of the USY zeolites; Pd loaded on USY prepared at 873 K with 100% H2O gave the highest activity (TOF = 61,000 h-1), which was higher than that of Pd loaded on other kinds of supports. The prepared Pd/USY catalysts were applicable to the Heck reactions using various kinds of substrates including bromo- and chlorosubstituted aromatic and heteroaromatic compounds. Characterization of the acid properties of the USY zeolites revealed that the strong acid site (OHstrong) generated as a result of steaming had a profound effect on the catalytic activity of Pd. [ABSTRACT FROM AUTHOR]

Abstract: Suzuki–Miyaura reactions were performed over Pd loaded on (ultra-stable Y) USY zeolites prepared by steam treatment of NH4–Y. We found that the catalytic activity of Pd increased significantly with steam treatment of NH4–Y when 6% H2 was applied before and during the reactions. For instance, a TON of 13,000,000 was obtained in the reaction between bromobenzene and phenylboronic acid in 1.5h. Pd K-edge and Pd L3-edge X-ray absorption fine structure analyses revealed the formation of atomic Pd with a cationic character. The catalytic activity of Pd/USY prepared under different steam-treatment conditions was in good correlation with the strong Brønsted acid sites induced by the extra-framework Al. Based on the catalytic performance data, the structure of Pd, and acidic analysis of the support, atomic Pd anchored to the strong Brønsted acid sites of the USY zeolite was proposed to be the active species. [Copyright &y& Elsevier]

Abstract: Multicomponent bismuth molybdate (Ni X Fe3Bi1Mo12O42+ X ) catalysts were prepared by a co-precipitation method with a variation of nickel content, and were applied to the oxidative dehydrogenation of C4 raffinate-3 to 1,3-butadiene. Conversion of n-butene and selectivity for 1,3-butadiene over Ni X Fe3Bi1Mo12O42+ X catalysts showed volcano-shaped curves with respect to nickel content. As a consequence, yield for 1,3-butadiene also showed a volcano-shaped curve with respect to nickel content. Among the catalysts tested, Ni9Fe3Bi1Mo12O51 showed the best catalytic performance. Acid properties of Ni X Fe3Bi1Mo12O42+ X catalysts were measured by NH3-TPD experiments, with the aim of correlating the catalytic performance with the acid property of the catalysts. It was observed that either total acidity or acid strength was not directly correlated with the catalytic performance of Ni X Fe3Bi1Mo12O42+ X catalysts. However, the conversion of n-butene was increased with increasing surface acidity of the catalyst. The largest surface acidity of the Ni9Fe3Bi1Mo12O51 catalyst was responsible for its enhanced catalytic performance in the oxidative dehydrogenation of C4 raffinate-3. The facile oxygen mobility of the γ-Bi2MoO6 phase in the Ni9Fe3Bi1Mo12O51 catalyst also played an important role in enhancing the catalytic performance of the Ni9Fe3Bi1Mo12O51 catalyst. [Copyright &y& Elsevier]

Abstract: Two types of molybdenum trioxide were synthesized by evaporating the molybdic acid solution prepared via cation-exchange of an aqueous solution of Na2MoO4·2H2O. When the molybdic acid solution was evaporated to dryness at 323K under reduced pressure and then calcined at 573K in a stream of oxygen, α-MoO3 was exclusively produced. However, addition of HNO3 to the solution before the evaporation resulted in formation of a bright yellow powder which was identified as β-MoO3. The phase ratio of β/α was dependent on the quantity of HNO3; pure β-MoO3 was successfully synthesized when the molar ratio of HNO3/Mo in the solution was in the range of 1–2. It was also found that the HNO3 addition made no structural change of the isopolymolybdates in the solution and the dried precursor, but did affect the dehydration of the dried precursor to induce the crystallization of the β-phase. In partial oxidation of methanol, β-MoO3 exhibited much higher methanol conversion than the α-form. IR spectra of chemisorbed pyridine elucidated that the higher catalytic activity was caused by the relatively large number and high acidity of Lewis acid sites on the surface of β-MoO3. [Copyright &y& Elsevier]

Abstract: The crystallography characterization such as the morphology, the crystal size and the orientation, the composition and the cell parameters of high silica FER-type zeolite, which was hydrothermally synthesized in the reactant system of tetrahydrofuran (THF)–Na2O–SiO2–Al2O3–H2O, were investigated with powder X-ray diffraction (XRD), scanning electron microscope (SEM), high-resolution transmission electron microscope (HRTEM) and selected-area electron diffraction (SAED), and compared with that of the siliceous FER zeolite synthesized with pyridine as the template under organothermal conditions. H-form FER zeolite samples, H-FER-I and H-FER-II were prepared with the procedure of ion exchange with H+ for getting rid of alkaline cations followed with calcination for removing template, and with the procedure of removing template by calcination and then getting rid of alkaline cations with ion exchange, respectively, due to the positions of the Na+ cations and THF molecules trapped in the zeolite channels and cages, respectively. 27Al and 29Si magic angle spinning nuclear magnetic resonance (MAS NMR), in situ Fourier transform infra-red spectroscopy (FT-IR) and nitrogen adsorption were used to investigate the stability of the framework structure and the framework composition, the solid acidity, and the microporous properties on both samples of H-FER-I and H-FER-II treated in saturated steam at 1073K for 10h. The investigations indicate that THF-FER zeolite crystals with 3×2μm in size possess the morphology and the preferential orientation very close to those of siliceous FER zeolite single crystals. H-FER-I exhibits better stability, perfect framework structure with less defects, more open channel systems, and more Brönsted acid sites than those of H-FER-II, resulting in excellent catalysis performance on skeletal isomerization of n-C5 olefins to iso-C5 olefins for the feed of C5 raw mixture gas. [Copyright &y& Elsevier]

The correlation between acid property of beta zeolite and its catalytic performance for phenol oxidation has been studied. Acid properties of beta zeolites in the proton form (H-BEA) and modified beta zeolite by alkaline earth metal ion exchange treatment (AE/H-BEA, AE: Mg, Ca, Sr, and Ba) were investigated by diffuse-reflectance FT-IR (DR-FTIR) spectroscopy. It was revealed that the features of the OH group stretching region of Ca/H-BEA are different from those of H-BEA. The peak at 3782cm-1 observed on H-BEA disappeared and new peaks appeared at 3672–3692cm-1 after the ion exchange treatment. NH3 temperature programmed desorption analyses (NH3-TPD) of these zeolites were also carried out. The NH3 desorption peak at ∼873K observed on H-BEA, which has been assigned to a very strong acid, disappeared, and a new peak at 743K and a shoulder at the temperature lower than the peak at about 623K appeared after the ion exchange treatment. These observations suggested that the acid properties of H-BEA were substantially modified by the ion exchange treatment. Phenol oxidation with hydrogen peroxide as oxidant over AE/H-BEA was conducted in the presence of diethylketone, and the result was compared with that over H-BEA. While the selectivity for diphenols, catechol and hydroquinone, over H-BEA based on added hydrogen peroxide was ∼89% that over AE/H-BEA was higher than 94%. The best catalyst was Ca/H-BEA, where the selectivity was as high as ∼98%. From these results, it is concluded that AE/H-BEAs are more suitable catalysts for the phenol oxidation with hydrogen peroxide than H-BEA, and it is suggested that the removal of strong acid sites by the ion exchange treatment would be the reason for their high selectivity. [Copyright &y& Elsevier]

To examine the influence of phosphorus on the commercial V2O5(WO3)/TiO2 SCR catalyst, measurements were carried out by means of infrared and Raman spectroscopy, XPS, and NO reduction measurement as a function of phosphorus loading. Phosphorus added to the catalyst was found to disperse well over the catalyst without a significant agglomeration up to 5 wt% P2O5 addition. The number of the hydroxyl groups bonded to the vanadium and titanium species decreased readily with increasing amount of phosphorus. Correspondingly, the hydroxyl groups bonded to the phosphorus species were formed. NH3 adsorbed on both hydroxyl groups bonded to vanadium and phosphorus as ammonium ions, implying that the P–OH groups formed are also responsible for the Brønsted acidity. The NO reduction activity was found to be decreased with increasing amount of phosphorus; however, the influence of phosphorus was relatively small irrespective of the large amount of phosphorus addition. The deactivation might be caused by the change in the nature of the surface hydroxyl groups as Brønsted acid sites. Phosphorus species might partially wrap the surface V=O and W=O groups, which might also contribute to the deactivation. [ABSTRACT FROM AUTHOR]

Acidic properties of ZSM-5 zeolites for the aromatization of light hydrocarbons strongly determined the final catalytic selectivity and stability for two-step methanol conversions of aromatics via light hydrocarbons. Herein, the density and types of acid sites of ZSM-5 were precisely adjusted to explore their influences on the final catalytic performance. Different from the indistinctive effect of SiO 2 /Al 2 O 3 ratios on traditional one-step methanol conversion to aromatics, decreasing acid density by increasing SiO 2 /Al 2 O 3 ratios from 36 to 70 decelerated coke formation and significantly extended the catalytic lifetime from 46.5 to 190.8 h. Further modification with low Zn loading decreased B/L ratio from 19.0 to 1.7 and established a good catalytic synergy between Zn-Lewis and Brønsted acid sites for aromatization of light hydrocarbons, which increased the aromatics selectivity from 27.5% to 31.4%. The decreased catalytic stability after introducing Zn species was attributed to the coke coverage on acid sites but not the final blockage of pore channels as mentioned in previous studies, which was indicated by the similar coke rate of the deactivated catalyst and their gradually increased surface area with increasing Zn content. This work provides more insights into the regulation of acid properties for aromatization catalyst to boost the conversion of methanol to aromatics. [Display omitted] • Catalyst acidity was regulated for two-step methanol conversion to aromatics. • SiO 2 /Al 2 O 3 ratio and Zn addition were organically adjusted for aromatization demand. • Zn introduction should be well matched with the original acid density of ZSM-5. • Good catalytic synergy between Zn-Lewis and B acid sites was achieved for reaction. • Conversion route of methanol to aromatics on different acid sites was portrayed. [ABSTRACT FROM AUTHOR]