H-USY Zeolite Research Articles

Wet torrefaction of biomass waste into high quality hydrochar and value-added liquid products using different zeolite catalysts

Wet torrefaction (WT) proves to be a highly efficient pretreatment method for biomass waste, resulting in the production of hydrochar and valuable liquid products. In this study, a groundbreaking chemocatalytic approach is introduced, employing various zeolite catalysts (H-ZSM-5, H-Beta, H–Y, H-USY, and H-Mordenite) in a batch reactor under a nitrogen atmosphere. This method enables the simultaneous one-pot production of levulinic acid (LA) and/or bio-ethanol during the WT process of wood cellulose pulp residue (WCPR), ultimately yielding high-quality solid fuel. The WT process involves at 220 and 260 °C, H2O/WCPR = 10, and torrefaction time at 15, 30 and 60 min. The study identifies that at 220 °C and 15 min, as the optimal temperature and time, for bio-ethanol production, achieving a selectivity of 59.0 % with the H–Y catalyst, while the highest amount of bio-ethanol (75.6 %) was detected in presence of H-USY zeolite at 260 °C after 60 min. In addition, it was found the formation of relatively high amount of LA (62.0 %) at 220 °C after 60 min but using the H-ZSM-5 catalyst. For the WT + Mordenite sample (220 °C, 60 min), the highest carbon content of 71.5 % is achieved, resulting in the higher heating value (HHV) of 27.3 MJ/kg, an enhancement factor of 1.36, and carbon enrichment of 1.48, with the sequence of element removal during WT prioritized as DO > DH > DC and the weight loss of 68 %. Finally, the reaction mechanism was proposed to elucidate the formation of liquid products after WT of WCPR with participation of zeolite catalysts. The main pathway involving the direct conversion of cellulose into hydroxyacetone, followed by the subsequent generation of ethanol through the C–C cleavage of hydroxyacetone while LA formed via well-known route which includes cellulose hydrolysis to form glucose, conversion to 5-HMF and the subsequent transformation of 5-HMF into LA.

Continuous liquid-phase alkylation of lignocellulose-derived phenolics and cyclopentanol under large space velocity for efficient synthesis of high-performance biofuel

It is significant to efficiently and feasibly produce high-performance jet fuel from renewable biomass. We reported here that lignin-derived phenolics can be alkylated by cellulose-derived cyclopentanol in a continuous-flow fixed-bed reactor packed with HUSY zeolite without the use of solvents. Under nitrogen pressure, the liquid-phase reaction was achieved. Among the investigated zeolites with different structures and SiO2/Al2O3, HUSY-150 exhibited excellent catalytic performance and stability. By adjusting reaction conditions, almost complete conversion of cyclopentanol was achieved, as well as high phenol conversion (∼70 %), and high polycyclic product selectivity (>95 %) over HUSY-150. Afterwards, we extended the range of feedstock from phenol to other phenolics (guaiacol, 2,6-dimethoxyphenol, and lignin oil surrogates), and even at a high LHSV (liquid hourly space velocity) of 36 mL/(gcat·h), HUSY-150 maintained robust catalytic activity. This study demonstrates a feasible and effective method for producing high-performance jet fuel blends using lignocellulose-derived compounds.

Metal-zeolite catalysts for the removal of pharmaceutical pollutants in water by catalytic ozonation

Catalytic ozonation of salicylic acid (SA), as model pharmaceutical pollutant, at room temperature was studied in an aqueous phase using mono- (Pd, Cu) and bimetallic (Pd-Cu, Cu-Pd) zeolite catalysts prepared by the ion exchange method, using different zeolite structures: FAU (USY) and MFI (ZSM5). All metal-zeolite catalysts positively affected SA degradation in comparison with the parent zeolites, except for PdCu-HUSY. The mineralization degree was improved in the presence of the heterogeneous catalysts, regardless of the zeolite used. Nevertheless, the catalysts based on different zeolite structures presented distinct performances during SA oxidation, with those based on HUSY zeolite showing lower activity, which indicated that the physicochemical properties of the zeolite structures are very important. Wide-ranging, the catalytic oxidation of SA with ozone on zeolite-based catalysts was found to be affected by a combination of the acidic properties of zeolites and the chemical composition at the surface. The evolution of oxalic acid as a by-product in SA oxidation, as well as its degradation by catalytic ozonation, were also studied. Reutilization runs revealed that the zeolite-based catalysts were very stable.

Kinetics of n-Hexane Cracking over Mesoporous HY Zeolites Based on Catalyst Descriptors

A simple kinetic model based on the zeolite acid strength, the number of Brønsted acid sites, and the catalyst efficiency was developed for the cracking of n-hexane. A series of HY zeolites with a mesopore volume from 0.04 to 0.32 cm3/g was synthesized and characterized by various physical-chemical methods and tested for n-hexane cracking. The generation of mesoporosity influenced several other important parameters, such as acidity and extra-framework aluminum. Zero-length column diffusion measurements for mesitylene showed a large decrease in the characteristic diffusion time upon the introduction of mesoporosity, which changed only slightly with a further increase in mesoporosity. Similar n-hexane physisorption enthalpies were measured for all samples. The highest initial activity for n-hexane cracking per catalyst volume was observed for the sample with an intermediate mesopore volume of 0.15 cm3/g. The three mesoporous H-USY zeolites showed the same value of the intrinsic rate constant and the same activation energy. The difference in initial activity of the mesoporous zeolites was caused by the difference in the number of Brønsted acid sites. The increase in initial activity for the mesoporous zeolites compared to a microporous zeolite was caused by an increase in the acid strength.

Control and Impact of Metal Loading Heterogeneities at the Nanoscale on the Performance of Pt/Zeolite Y Catalysts for Alkane Hydroconversion.

The preparation of zeolite-based bifunctional catalysts with low noble metal loadings while maintaining optimal performance has been studied. We have deposited 0.03 to 1.0 wt % Pt on zeolite H-USY (Si/Al ∼ 30 at./at.) using either platinum(II) tetraammine nitrate (PTA, Pt(NH3)4(NO3)2) or hexachloroplatinic(IV) acid (CPA, H2PtCl6·6H2O) and studied the nanoscale Pt loading heterogeneities and global hydroconversion performance of the resulting Pt/Y catalysts. Pt/Y samples prepared with PTA and a global Pt loading as low as 0.3 wt % Pt (nPt/nA = 0.08 mol/mol, where nPt is the number of Pt surface sites and nA is the number of acid sites) maintained catalytic performance during n-heptane (T = 210–350 °C, P = 10 bar) as well as n-hexadecane (T = 170–280 °C, P = 5 bar) hydroisomerization similar to a 1.0 wt % Pt sample. For Pt/Y catalysts prepared with CPA, a loading of 0.3 wt % Pt (nPt/nA = 0.08 mol/mol) sufficed for n-heptane hydroisomerization, whereas a detrimental effect on n-hexadecane hydroisomerization was observed, in particular undesired secondary cracking occurred to a significant extent. The differences between PTA and CPA are explained by differences in Pt loading per zeolite Y crystal (size ∼ 500 nm), shown from extensive transmission electron microscopy energy-dispersive X-ray spectroscopy experiments, whereby crystal-based nPt/nA ratios could be determined. From earlier studies, it is known that the Al content per crystal of USY varied tremendously and that PTA preferentially is deposited on crystals with higher Al content due to ion-exchange with zeolite protons. Here, we show that this preferential deposition of PTA on Al-rich crystals led to a more constant value of nPt/nA ratio from one zeolite crystal to another, which was beneficial for catalytic performance. Use of CPA led to a large variation of Pt loading independent of Al content, giving rise to larger variations of nPt/nA ratio from crystal to crystal that negatively affected the catalytic performance. This study thus shows the impact of local metal loading variations at the zeolite crystal scale (nanoscale) caused by different interactions of metal precursors with the zeolite, which are essential to design and synthesize optimal catalysts, in particular at low noble metal loadings.

Local Induction Heating Capabilities of Zeolites Charged with Metal and Oxide MNPs for Application in HDPE Hydrocracking: A Proof of Concept.

Zeolites are widely used in high-temperature oil refining processes such as fluid catalytic cracking (FCC), hydrocracking, and aromatization. Significant energy cost are associated with these processes due to the high temperatures required. The induction heating promoted by magnetic nanoparticles (MNPs) under radio frequency fields could contribute to solving this problem by providing a supplementary amount of heat in a nano-localized way, just at the active centre site where the catalytic process takes place. In this study, the potential of such a complementary route to reducing energetic requirements is evaluated. The catalytic cracking reaction under a hydrogen atmosphere (hydrocracking) applied to the conversion of plastics was taken as an application example. Thus, a commercial zeolite catalyst (H-USY) was impregnated with three different magnetic nanoparticles: nickel (Ni), cobalt (Co), maghemite (γ-Fe2O3), and their combinations and subjected to electromagnetic fields. Temperature increases of approximately 80 °C were measured for H-USY zeolite impregnated with γ-Fe2O3 and Ni-γ-Fe2O3 due to the heat released under the radio frequency fields. The potential of the resulting MNPs derived catalyst for HDPE (high-density polyethylene) conversion was also evaluated by thermogravimetric analysis (TGA) under hydrogen atmosphere. This study is a proof of concept to show that induction heating could be used in combination with traditional resistive heating as an additional energy supplier, thereby providing an interesting alternative in line with a greener technology.

Catalytic co-pyrolysis of oil sludge with HDPE to obtain paraffinic products over HUSY zeolites prepared by dealumination and desilication

Oil sludge is a waste from the oil industry with a complex composition and its treatment is still a challenge. In addition, polyolefin waste is becoming a problem due to its accumulation and slow degradation. In this study, catalytic co-pyrolysis was used to treat oil sludge and high density polyethylene (HDPE) at 450 °C and at an atmospheric pressure for 15 min to generate paraffin-rich oily products. Y zeolites were obtained by dealumination and desilication processes which were characterized by XRD, N2 adsorption, FTIR, 29Si and 27Al NMR, TG and NH3 TPD. Pristine and modified zeolites were evaluated in the co-pyrolysis in order to assess their performances through the quality of the obtained pyrolytic oil (GC–MS and SimDis). The modificated zeolites presented higher mesoporosity than the original solid as so lower total acidity. Amidst the tested catalysts, Mod-Si-10 and Mod-Al presented the best performances showing high yield of liquid fraction, rich in parafinic light hydrocarbons, probably due to their moderate acidity and improved mesoporosity. Consequently, these two zeolites presented outstanding catalytic characteristics alongside high selectivity to paraffinic hydrocarbons in the diesel fraction from co-pyrolisis of the oil sludge waste with HDPE.

Bifunctional Intimacy and its Interplay with Metal‐Acid Balance in Shaped Hydroisomerization Catalysts

AbstractThe combined impact of platinum location and metal‐acid balance on the catalytic performances of HUSY zeolite alumina‐shaped bifunctional catalysts was evaluated in n‐hexadecane hydroconversion reaction. For well‐balanced catalysts, the deposition of Pt in the alumina resulted in lower isomerization selectivity as compared to when platinum was located in the zeolite. In the latter case, the maximal distance between Pt and acid sites was found to be in the nanometric scale (high intimacy) whereas in the former it was in the micrometric scale (low intimacy), particularly due to the presence of large clusters of HUSY zeolite. Nevertheless, whenever proper balance between functions was not ensured in high‐intimacy catalysts, the low‐intimacy and well‐balanced catalysts were shown to perform better. The requirement for nanometric metal‐acid sites intimacy must be hence combined with an adequate metal‐acid balance to achieve optimal catalytic performance.

Isobutane/1-butene Alkylation Performance of Ammonium Fluoride-Modified HUSY Zeolite

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 Bronsted/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).

Gas-phase hydrodeoxygenation of guaiacol over Ni-based HUSY zeolite catalysts under atmospheric H2 pressure

Hydrodeoxygenation (HDO) is considered as one of the most promising routes to upgrade bio-oil for high value-added chemicals. In the study, the gas-phase HDO of guaiacol in atmosphere and 350 °C over Ni-based catalysts modified by Fe, Ga, Ce, La, or Sm on HUSY zeolite support was carried on. The effect of promotors, bimetallic/monometallic catalysts and Ni loading on HDO activity was investigated. The results showed that phenols and aromatic hydrocarbon were the main products and Ni was the main metal active site. Compared with monometallic metal catalysts, the promoters, such as Fe, Ga, Ce, La, and Sm, inhibited the aggregation of Ni, promoted Ni dispersion, and improved the HDO activity of guaiacol significantly. The highest conversion of 98.36% was performed over 10%Sm-20%Ni/HUSY, and the highest degree of hydrodeoxygenation (HDO%) of 7.7% was obtained over 10%La–20%Ni/HUSY catalysts. For Ce, Ga, and Fe modified catalysts, hydroquinone selectivity was higher than that over La and Sm modified catalysts. However, for La and Sm modified catalysts, phenols selectivity increased, and more aromatic hydrocarbon was formed. The HDO activity was improved via increasing Ni loading. Direct deoxygenation and hydrogenation were the more reasonable reaction pathways for gas phase guaiacol atmospheric HDO over Ni-based bimetallic HUSY catalysts.

Hierarchical FAU-Type Hafnosilicate Zeolite as a Robust Lewis Acid Catalyst for Catalytic Transfer Hydrogenation

FAU-type hafnosilicate zeolite with a hierarchical structure (Hf-USY) was constructed through a post-synthesis strategy containing the controlled dealumination of the commercial H-USY zeolite and t...

Reactions of alkyl 4-hydroxybut-2-ynoates with arenes under superelectrophilic activation with triflic acid or HUSY zeolite: Alternative propargylation or allenylation of arenes, and synthesis of furan-2-ones

Reactions of alkyl 4-aryl(or 4,4-diaryl)-4-hydroxybut-2-ynoates [Ar(H or Ar')(OH)C4–C3≡C2–CO2Alk] with arenes under the action of triflic acid TfOH or HUSY zeolite result in the formation of two main compounds, aryl substituted furan-2-ones or products of propargylation of electron rich arenes. Key reactive intermediates in these transformations are the corresponding O,O-diprotonated forms of starting butynoates, Ar(H or Ar')(+OH2)C4–C3≡C2– C(=O+H)(OAlk), dehydration of which gives rise to mesomeric propargyl-allenyl cations Ar(H or Ar')(OH)4C+–C3≡C2–C(=O+H)(OAlk) ↔ Ar(H or Ar')(OH)4C = C3 = 2C+–C(=O+H)(OAlk), having two electrophilic centers on the carbons C4 and C2 respectively. Reactions of these species with arenes at C4 lead to products of arene propargylation, alternatively, reactions at C2 result in allenylation of arenes, followed by further transformation into furan-2-ones. Using quantum chemical calculations by the DFT method, it has been shown that the reactivity of such propargyl-allenyl cations is mainly explained by orbital factors. Plausible reaction mechanism is discussed.

Adsorption and kinetic studies of methylene blue on modified HUSY zeolite and an amorphous mixture of γ-alumina and silica

ABSTRACT Our work focuses on the study of the adsorption of methylene blue (MB) on adsorbents based on zeolite HUSY and (γAl2O3-SiO2). To optimize the process of removing MB onto Ni/Co USY, different parameters were studied such as contact time, initial pH, initial dye concentration, zero charge’s point, and adsorbent dosage. The adsorption isotherm follows the Langmuir model. The maximum adsorption capacities of MB were 59.88 mg g−1 for Ni/Co USY and 43.86 mg g−1 for Ni/Co (γAl-Si) at 298°K. The thermodynamic parameters and activation energy’s values obtained suggested that the adsorption was a physical process, spontaneous, and endothermic in nature. MB adsorption on Ni/Co USY may occur via electrostatic interaction, hydrogen bonding, and Lewis acid–base interaction.

Reactions of Trifluoroacetyl Alkynes Under Electrophilic Activation with Brønsted Acids or Acidic Zeolites

The reaction of trifluoroacetyl alkynes [ArC≡C(C=O)CF3] with H2SO4 or TfOH affords products of addition of the acids to the acetylene bond. Hydrolysis of these adducts results in the formation of the corresponding 1,3‐diketones existing in form of enols [Ar(HO)C=CH(C=O)CF3] in up to 98 % yield. The application of less acidic TfOH‐pyridine system permits transformation of these alkynes into the corresponding vinyl triflates in up to 76 % yield. Moreover, this reaction is totally stereoselective to give only Z‐configured vinyl triflates. The reaction of trifluoroacetyl alkynes with arenes in TfOH or under the action of acidic HUSY zeolites CBV‐720 gives rise to 1,3‐diaryl‐1‐CF3‐indenes in up to 81 % yield. Electronic characteristics of initial intermediate mono‐ and dicationic species derived from such alkynes in the highly acidic media were studied by DFT calculations. Plausible cationic reaction mechanism was proposed.

HUSY zeolite-promoted reactions of trifluoromethylated propargyl alcohols with arenes: synthesis of CF3-indenes and DFT study of intermediate carbocations.

The reaction of CF3-propargyl alcohols [ArC[triple bond, length as m-dash]CCH(OH)CF3] with arenes under the action of acidic HUSY zeolite CBV-720 was investigated. It was found that the reaction at 100 °C for 1 h gave rise to 3-aryl-1-CF3-indenes in up to 83% yield. Electronic characteristics of the reaction key intermediates, mesomeric CF3-propargyl-allenyl cations [ArC[triple bond, length as m-dash]C-HC+(CF3) ↔ ArC+[double bond, length as m-dash]C[double bond, length as m-dash]CH(CF3)], were studied by DFT calculations. A plausible cationic reaction mechanism is discussed.

Quantification of the available acid sites in the hydrocracking of nitrogen-containing feedstocks over USY shaped NiMo-catalysts

The inhibition of Brønsted acid sites by nitrogen-containing molecules was quantified under industrially relevant hydrocracking conditions. This was achieved by testing bifunctional catalysts based on HUSY zeolite in cyclohexane hydroconversion. For ammonia partial pressures within 0.2-2.8kPa, the percentage of inhibited Brønsted sites was superior to 98% at 623K. Significant reduction in the ammonia content caused rather moderate variations on the number of available sites. Conversely, a temperature raise from 600 to 640K triplicated the vacant Brønsted sites due to the significant endothermicity of ammonia desorption. The inhibiting effect of ammonia can be therefore easily modulated by temperature.

Catalytic upgrading of bio-oils over high alumina zeolites

Catalytic upgrading of bio-oils derived from fast pyrolysis of sunflower stalk, cedar, knotweed and apple tree stem over H-ZSM-5, H-beta and H-USY zeolites with high alumina content was investigated at a reaction temperature of 500 °C. All catalysts showed high catalytic activity and selectivity towards aromatic hydrocarbons in the conversions of oxygenated compounds in the bio-oils, and 56.2–100% of aromatic hydrocarbons were found in the upgraded bio-oils which can be detected by GC/MS. Naphthalene was favored to be produced by using H-ZSM-5 while more monocyclic aromatic hydrocarbons such as p-xylene, toluene and alkylbenzene were generated by using H-beta as well as H-USY. Furthermore, all catalysts maintained high activity and selectivity with the maximum aromatic hydrocarbons amount of 70% in the upgraded bio-oils detected in the third cycle. In addition, the spent catalysts were easily regenerated by simple calcination at 650 °C for 30 min, and the regenerated catalysts showed almost the same activity as the fresh ones. It is expected that these high alumina zeolites can be widely used in practical bio-oil upgrading processes.

Y zeolite-supported niobium pentoxide catalysts for the glycerol acetalization reaction

Faujasite zeolite-supported niobium-based catalysts (with Nb2O5 amounts of 5 and 15 wt%) were prepared by impregnation of NaY, HY, and HUSY zeolites using a niobum(V) ammonium oxalate complex. These obtained Nb-containing catalysts were calcined and thoroughly characterized by different physico-chemical techniques. The characterization results revealed that niobium oxide was successfully loaded on the surface of the zeolite supports without any significant modification of the faujasite structure. Surface area and pore volume were found to decrease with the increase in the Nb content for all the prepared catalysts. The presence of Nb was proved to increase the hydrophobicity of the zeolites and to affect surface acidity. The catalytic activity of the Nb-containing samples was evaluated in the glycerol acetalization reaction, and the Nb-HUSY catalysts were found to show the best catalytic performance.

Hydrophobic zeolites for the upgrading of biomass-derived short oxygenated compounds in water/oil emulsions

Biomass-derived short oxygenates like furfural, cannot be directly incorporated into a fuel due to their low molecular weight. Therefore, conversion of these oxygenates into fuel range hydrocarbons via CC bond forming reactions is a desirable path. For example, in aqueous phase, furfural can be first converted to stable cyclopentanol via Piancatelli ring rearrangement coupled with hydrogenation under reducing conditions. This alcohol can be an effective alkylating agent to incorporate into phenolic rings. Therefore, we have investigated the alkylation of m-cresol with cyclopentanol, as two representative compounds of biomass-derived streams to generate products in the molecular weight range that is appropriate for transportation fuels. This reaction was studied in single and biphasic liquid systems over a hydrophobized H-USY zeolite (Si/Al = 30). In biomass conversion, the presence of liquid water is practically unavoidable, so it is important to investigate methods to deal with its presence. We show here that hydrophobization of the H-USY with octadecyltrichlorosilane (OTS) makes the zeolite able to stabilize water/oil emulsions and catalyze the alkylation of m-cresol and cyclopentanol with enhanced stability. By contrast, under the same conditions, the untreated H-USY zeolite is fully deactivated in about 3 h. From all of these results, it was concluded that the rate of alkylation is strongly dependent on temperature, solvent, and rate of mass transport, which is directly affected by the solubility of reactants and intermediates. This investigation provides strategies to convert different families of biomass-derived oxygenates into cyclic hydrocarbons with potential properties to be used as bio-fuel precursors.

Transformations of 5-(2-arylethynyl)-2-methyl-2H-tetrazoles under superelectrophilic activation

Reaction of 5-arylethynyl-2-methyl-2H-tetrazoles (acetylene tetrazoles) with arenes under the action of Brønsted superacid CF3SO3H or acidic zeolite HUSY CBV-720 gives rise to E-/Z-5-(2,2-diarylethenyl)-2-methyl-2H-tetrazoles, as products of hydroarylation of acetylene bond, in yields up to 98% with predominant formation of E-isomers. Cationic intermediates of these reactions have been studied theoretically by DFT calculations. Addition of CF3SO3H to the triple bond of acetylene tetrazoles leads to the corresponding E-/Z-vinyl triflates in high yields. Hydration of triple bond in these tetrazoles in H2SO4 results in the formation of 5-(2-aryl-2-oxoethyl)-2-methyl-2H-tetrazoles. Tandem hydroarylation-ionic hydrogenation of acetylene tetrazoles in the systems acid(CF3SO3H or AlCl3)-arene-cyclohexane affords 5-(2,2-diarylethyl)-2-methyl-2H-tetrazoles.