Catalysts For Hydroisomerization Research Articles

Hydroisomerization of n-hexadecane: remarkable selectivity of mesoporous silica post-synthetically modified with aluminum

Post-synthetic aluminum grafting is employed to synthesize highly selective hydroisomerization catalyst and to demonstrate the effect of acid strength and density, catalyst microstructure, and platinum nanoparticle size on reaction rate and selectivity.

Prospects for using Mo- and W-containing catalysts in hydroisomerization: A patent review. II: Catalysts based on molybdenum and tungsten carbides

Prospects for using Mo- and W-containing catalysts in hydroisomerization: A patent review. II: Catalysts based on molybdenum and tungsten carbides

Regulating acidity, porosity, and morphology of hierarchical SAPO-11 zeolite by aging treatment

A facile method to modify pore structure, acidic character, and morphology of SAPO-11 molecular sieve was proposed. Aging treatment (e.g., microwave irradiation or lyophilization) is introduced in the preparation of dry gel. It regulates the kinetics of zeolitic nucleation and growth. X-ray diffraction, scanning electron microscopy, N2-adsorption, temperature programmed desorption, laser particle analyzer, and 29Si MAS NMR were employed to investigate the effects of aging treatments on SAPO-11 products. The experimental results indicate that depolymerization reaction of silicon species is enhanced aged by microwave irradiation with a higher temperature (90°C). Ratio of SM 3 to SM 2 substituting mode increases producing more strong Brønsted acid sites. Lyophilization technology, as another aging method, was employed to control the morphology of SAPO-11. Nano-sized hierarchical SAPO-11 molecular sieve (200nm in length) is obtained with an oriented growth. Activity of hydroisomerization catalysts is regulated by aging treatment. Cracking reaction attributes to a high conversion nearly 87wt% for M90. The hydroisomerization reaction is enhanced for M40 due to a large proportion of moderate acid sites.

Two-step hydrothermal synthesis of β-MCM-41 composite molecular sieves as supports of bifunctional catalysts for hydroisomerization of n-heptane

β-MCM-41 composite molecular sieves were hydrothermally synthesized via two-step method. All the catalysts were characterized by XRD, FT-IR, BET and ICP. The catalysts were evaluated in hydroisomerization of n-heptane in a fixed bed flow reactor. Under the same condition, Pt/Hβ-MCM-41 was demonstrated to be a more mono-iso selectivity catalyst because the connection between mesopores and micropores accelerates the diffusion. Under optimal conditions, (precursor7.5d) Pt/Hβ-MCM-41 provided a very high selectivity to isomerization 90.0 % coupling with a considerable high conversion of n-heptane 59.9 % at 250 °C.

Prospects of Mo- and W-containing Catalysts for Hydroisomerization: Patentent Survey. 2. Catalysts Based on Molybdenum and Tungsten Сarbides

Prospects of Mo- and W-containing Catalysts for Hydroisomerization: Patentent Survey. 2. Catalysts Based on Molybdenum and Tungsten Сarbides

Prospects of Mo- and W-containing Catalysts for Hydroisomerization: Patentent Survey. Part 1. Catalysts Based on Molybdenum and Tungsten Phosphides

Patent research was focused on methods for preparation and use of molybdenum and tungsten phosphide containing catalytic systems for hydroisomerization of paraffin hydrocarbons. Analysis of the patent data showed that modification of acidic supports with molybdenum and tungsten phosphides is promising for creating a stable catalyst for hydroisomerization of paraffin fractions, which would be stable to sulfur impurities in hydroisomerization feedstock.

Creating mesopores in ZSM-48 zeolite by alkali treatment: Enhanced catalyst for hydroisomerization of hexadecane

ZSM-48 zeolites with various Si/Al ratios were hydrothermally synthesized in the H2N(CH2)6NH2 (HDA)-containing media. The obtained samples were highly crystallized with minor mixed phases as evidenced by X-ray powder diffraction (XRD). The alkaline treated ZSM-48 zeolites maintained its structure under different concentrations of NaOH aqueous solution. Micropores remained unchanged while mesopores with wide pore size distribution formed after the alkaline treatment. The surface area increased from 228 to 288m2/g. The Brönsted acid sites had little alteration while an obvious increase of Lewis acid sites was observed. The hydroisomerization of hexadecane was performed as the model reaction to test the effects of the alkali treatment. The conversion of hexadecane had almost no change, which was attributed to the preservation of the Brönsted acid sites. While high selectivity to iso-hexadecane with an improved iso to normal ratio of alkanes was due to the mesopore formation and improved diffusivity.

Prospects for using Mo- and W-containing catalysts in hydroisomerization. a patent review. Part 1: Catalysts based on molybdenum and tungsten phosphides

Patent information on methods used for preparing catalytic systems containing molybdenum and tungsten phosphides and employing these systems in the hydroisomerization of paraffinic hydrocarbons are analyzed. Analysis of the patent information shows that modifying acidic supports with molybdenum and tungsten phosphides allows us to create a catalyst for the hydroisomerization of paraffinic fractions that is stable and resistant to sulfur impurities contained in the hydroisomerization feedstock.

Mesoporous EU-1 zeolite as a highly active catalyst for ethylbenzene hydroisomerization

The synthesis of a micro-mesoporous EUO zeolite with a significant volume of intercrystalline mesoporosity revealed an outstanding result in the challenging industrial hydroisomerization of ethylbenzene.

Effect of boron on acid and catalytic properties of Pd-ZSM-23/Al2O3 catalysts in the reaction of diesel fuel hydroisomerization

Effect of the concentration and introduction method of boron on the acid characteristics and catalytic properties of Pd-ZSM-23/Al2O3 catalysts in hydroisomerization of diesel fuel was studied. It was found that raising the concentration of introduced boron in a support results in that the concentration of acid centers, specific surface area, and volume of micropores in the catalysts nonlinearly decrease. To obtain the optimal acidity it is primarily necessary to reduce the concentration of excessively strong Lewis acid centers in zeolites and also to reach a moderate concentration of Bronsted acid centers. The best catalytic properties are observed for the catalyst containing 0.5 wt % boron.

The effect of Zn–Fe modified S2O8 2−/ZrO2–Al2O3 catalyst for n-pentane hydroisomerization

Fe–Zn-doped S2O82−/ZrO2–Al2O3 (SZA) catalysts were synthesized and characterized by using X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) analysis, Fourier transform infrared (FT–IR) measurements, hydrogen temperature-programmed reduction (H2–TPR), and pyridine infrared (Py–IR) measurements. The effects of Fe and Zn on the structure and isomerization performance of SZA were studied using n-pentane as a probe reaction. Results showed that all of the samples show the pure peaks of tetragonal ZrO2. The addition of Zn can improve the redox performance of the catalysts, while Fe can lead to a better dispersion of sulfate ions on the surface of the catalysts. As a result, an improvement in the redox performance of the Zn–Fe–SZA catalyst was observed. The Zn or Fe can increase mainly Lewis acidity of the SZA, and the total acidity of samples decrease in the following order: Zn–Fe–SZA > Zn–SZA > Fe–SZA > SZA. The Fe–Zn–SZA catalyst exhibits the best catalytic activity for n-pentane isomerization. The isopentane yield of the Zn–Fe–SZA catalyst reaches 67.2 % at 443 K, which is an increase of 44.2 % when compared with that found for SZA at its optimum temperature of 573 K.

Hydroisomerization of n-hexadecane over Pt/ZSM-22 framework: Effect of divalent cation exchange

Crystalline phase pure ZSM-22 framework (bulk molar ratio ~45) has been synthesized and employed to investigate the effect of tailored Brønsted acidity on hydroisomerization of n-hexadecane. Typically, ZSM-22 framework Brønsted acidity is tailored with Group-II cations viz. Mg2+, Ba2+ and Ca2+, by means of ion-exchange method. The physico-chemical characterization of the various samples have been performed using powder X-ray diffraction, nitrogen adsorption–desorption isotherm measurement at 77K, inductively coupled plasma (ICP) and scanning electron microscopy (SEM) techniques. The framework acidity w.r.t. Brønsted level has been characterized and estimated using ammonia temperature programmed desorption (NH3-TPD) and Fourier transform infrared spectroscopy of Pyridine (Py-FTIR) as a function of temperature, respectively. Hydroisomerization of n-hexadecane is performed over Pt (~0.45wt%)/M-H-ZSM-22 samples (in extrudate form) in an up-flow fixed bed reactor and the effect of process parameters namely temperature and WHSV have been investigated. Based on the obtained results, Pt/Ca-H-ZSM-22 framework with calcium exchange level of about 10% showed the optimum performance among all the prepared samples with maximum isomer selectivity, yield (85.8 and 77.8%, respectively) vis-à-vis Pt/H-ZSM-22 sample (79.3 and 70.5%, respectively) and more importantly branching index of 4 in favor of mono-branched isomers, at a conversion level of about 90% at 585K.Among Group II cations, calcium exchange over ZSM-22 framework is found to be effective in enhancing selectivity in favor of mono-branched isomers. In view of this, the role of tailored acidity through Group II cation exchange for optimization of degree of branching during hydroisomerization of long chain n-paraffin is discussed. Furthermore, the relative maximization of mono-branched isomers using calcium exchange is expected to offer platform for development of hydroisomerization catalyst with minimum cetane loss.

Isomerization of Higher Alkane Over Platinum Supported on Nanoporous Materials.

The objective of this study is to evaluate the catalytic potential of Pt/MMZ-FER catalysts in hydroisomerization of long chain hydrocarbon. MMZ-FER, a nanoporous material produced from commercial ferrierite, was used as a support for the catalysts. The catalysts were characterized via X-ray powder diffraction, N2 adsorption, pyridine-IR, and the temperature-programmed desorption of ammonia. Hydroisomerization of n-dodecane was performed on Pt/MMZ-FER catalysts. Hydroisomerization requires platinum loading on MMZ-FER, even though the amount of platinum loaded (up to 1.2 wt%) did not greatly affect the process of hydroisomerization. Weak acid sites developed on the Pt/MMZ-FER samples induced less cracking of n-dodecane, resulting in an increase in selectivity for isomerization.

Influences of cerium on structure and catalytic performance of n-heptane hydroisomerization of Ni-HPW/MCM-48

By means of X-ray diffraction (XRD), N2 adsorption-desorption, Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), NH3-temperature (NH3-TPD), Py-infrared (Py-IR) and thermogravimetry-differential scanning calorimetry (TG/DTA) techniques, the influences of Ce on the structure, acidity, stability and hydroisomerization performance of Ni-HPW/MCM-48 and Ni-HPW/Ce-MCM-48 catalysts were studied. The results showed that introduction of appropriate content of Ce into MCM-48 could improve the crystallinity, acidity and stability of mesoporous silica. The acidity and stability of the Ni-HPW/Ce-MCM-48 catalyst was also increased. Besides, the catalytic performance of the Ni-HPW/Ce-MCM-48 catalyst for n-heptane hydroisomerization was promoted. The conversion and selectivity of the Ni-HPW/Ce-MCM-48 catalyst reached 41% and 91% respectively at the preparation conditions of 4 wt.% Ni, 20 wt.% HPW, 0.03 Ce/Si molar ratio.

Effect of metal precursors on the performance of Pt/ZSM-22 catalysts for n-hexadecane hydroisomerization

The effects of Pt precursors on the performance of Pt/ZSM-22 catalysts for n-hexadecane hydroisomerization were investigated with 0.5wt.% platinum loading using three platinum precursors: Pt(NO3)2, H2PtCl6, and Pt(NH3)4Cl2. The catalyst derived from H2PtCl6 exhibits the highest platinum dispersion and nPt/nA value and displays better isomerization activity and selectivity. Three effects can be traced back to the precursors: the valence state of Pt, the location of Pt (in cationic or anionic group), and the existence of chloride. The predominant effect is that of valence states of Pt in precursors, which play a crucial role in determining the textural properties (both particle size and crystal structure) of catalysts. Different crystal orientations of Pt0 are found on the reduced samples, with Pt(IV) precursors oriented along the [011] crystallographic axis, while those with Pt(II) precursors are oriented along the [001] axis. The former favors smaller Pt particles and exposes more active Pt{111} corner sites, while the latter exhibits larger Pt particles and exposes more Pt{100} facets, as revealed by combining HRTEM with CO-IR studies. Moreover, Pt{111}/ZSM-22 shows higher isomerization selectivity than Pt{100}/ZSM-22. The other effect is location of Pt in precursors. Compared with the sample using Pt(NH3)4Cl2 precursor, the catalyst with (NH4)2PtCl4 precursor exhibits smaller particles and higher platinum dispersion and facilitates isomerization reactivity. The existence of chloride is also a nonignorable effect. The samples containing chloride ions without amine groups in precursors favor platinum dispersion due to avoiding autoreduction by NH3 during the calcination process.

Mesoporous silico-aluminophosphates derived from microporous precursors as promising catalyst for hydroisomerization

A series of mesoporous silicoaluminophosphates (MESO-SAPOs) with different silica contents were synthesized using the microporous precursors of SAPO-37 (MESO-SAPO-37). Various analytical and spectroscopic techniques revealed the presence of mesoporous and microporous properties of the materials. The resulting materials were applied to vapor-phase hydroisomerization of 1-octene to afford the corresponding branched alkenes in good yields under ambient conditions. The catalytic activity of MESO-SAPO-37 was compared to those of other mesoporous analogs obtained from SAPO-34 and SAPO-5 precursors. Among all the synthesized materials, MESO-SAPO-37 showed the best catalytic activity owing to the presence of faujasite units.

SBA-15 intercalated Mg–Al hydrotalcite: An environmental friendly catalyst for hydroisomerization of olefin

SBA-15 Molecular sieve-intercalated Mg–Al hydrotalcite (MASBA-HT) was synthesized for the first time by a simple straightforward method. The intercalation of SBA-15 molecular sieve between the interlayer of HT was evident from powder XRD, TEM and FT-IR studies. The presence of SBA-15 facilitates retention of the layered structure for first time, even after calcination at high temperature of 550°C. The resultant material possesses moderate acidity which comes from incorporation of aluminum into the framework of SBA-15 and also contained soluble basicity similar to HT materials. The material shows promising activity for hydroisomerization of 1-octene resulting in good substrate conversion (80%) and branched isomers selectivity (45%). The catalytic activity remains constant over longer duration and repeated runs.

Synthesis and characterization of Ga-modified Ti-HMS oxide materials with varying Ga content

This work reports on the structure and surface characteristics of hexagonal mesoporous silica (HMS) modified with both Ti and Ga. Several techniques were used (low-angle XRD, SBET, TPD-NH3, DRS, FT-IR of framework vibration, FT-IR of adsorbed pyridine, SEM and HRTEM). These systems were then used as catalysts in the o-xylene hydroisomerization carried out in a batch reactor at 300°C and atmospheric H2 pressure. The catalyst characterization demonstrated that the modification of Ti-HMS substrate with Ga by post-synthesis grafting yields high surface area substrates with good Ga dispersion and bimodal distribution of gallium species. On the basis of lattice expansion observed from XRD data together with the increase of absorption band due to vibration of Si–O–Ga linkages, it is inferred that Ga species are incorporated into the silica framework. Moreover, textural analysis revealed that highly dispersed Ga2O3 species are deposited within the inner pores of the substrate. The largest o-xylene conversion observed for the Ti-HMS-2.5Ga sample containing the largest Ga loading is related to the heterogeneous distribution of its Ga species and its large acidity. Upon reaction conditions employed, the o-xylene hydroisomerization over Ti-HMS-Ga proceeds exclusively via intramolecular mechanism (formation of m- and p-xylenes) and hydrogenation of benzene aromatic ring of o-, p- and m-xylenes did not occur.

Catalytic behavior of Pt nanoparticles dealuminated Y-zeolite for some n-alkane hydroisomerization

Dealuminated zeolite Y-supported platinum was prepared adopting two dealumination methods, viz. fast (1, 3 and 6h) and slow method (18h). The content of Pt was constant at 0.5wt% in all investigated catalysts. The prepared samples were characterized using TGA/DSC, XRD, FTIR techniques, nitrogen adsorption at −196°C and TEM-connected with energy dispersive spectroscopy (EDS). Surface acidity was investigated via pyridine adsorption using FT-IR spectroscopy. The parent and dealuminated Y-zeolite samples were characterized by their microporous system. By increasing the dealumination time to 6h, the increased specific surface area and total pore volume indicated a sort of pore opening taking place with an increase in the accessibility of nitrogen molecules. DSC confirmed the thermal stability of the dealuminated zeolite samples up to 800°C. The prepared catalysts were tested through hydroisomerization reactions of n-hexane and n-heptane using a micro-catalytic pulse technique. Different catalytic behaviors could be distinguished for the dealuminated samples based on competitive reactions; hydro-isomerization, hydrocracking and cyclization. Slow dealumination leads to the most selective catalysts for hydroisomerization. n-Heptane was converted to higher extent than n-hexane; cracking process was more evident when the former was fed to the reactor.

Hydroisomerization of n-dodecane over Pt/Al-MCM-48 catalysts.

The objective of this study is to evaluate the catalytic potential of Pt/Al-MCM-48 catalysts in hydroisomerization of n-dodecane. The effects of the Si/Al ratio and platinum loading on the acid characteristics of Al-MCM-48 and the catalytic performance in n-dodecane hydroisomerization were analyzed. The catalysts were characterized by X-ray diffraction, nitrogen adsorption, infrared spectroscopy of pyridine adsorption, and temperature programmed desorption of ammonia. The number of weak strength acid sites on Al-MCM-48 increased with 0.5 wt% platinum loading. The weak strength acid sites of Pt/Al-MCM-48 catalysts were ascribed to Lewis acid sites, which can be confirmed by NH3-TPD and FTIR spectra of pyridine adsorption. Iso-dodecane can be produced with high selectivity in n-dodecane hydrosisomerization over Pt/Al-MCM-48 catalysts. This is attributed to the mild acidic properties of Pt/Al-MCM-48 catalysts.