scholarly journals Conversion of Stearic Acid into Bio-Gasoline over Pd/ZSM-5 Catalysts with Enhanced Accessibility

2019 ◽  
Vol 9 (11) ◽  
pp. 2386 ◽  
Author(s):  
Marta Arroyo ◽  
Laura Briones ◽  
José María Escola ◽  
David P. Serrano
Keyword(s):  
Stearic Acid ◽  
Hydrogen Transfer ◽  
Pd Nanoparticles ◽  
Atomic Ratio ◽  
Acid Sites ◽  
Nitrogen Atmosphere ◽  
Light Olefins ◽  
Limiting Factor ◽  
Reaction Products ◽  
Pd Dispersion

Palladium supported on nanocrystalline ZSM-5 (n-ZSM-5, Si/Al = 32) and hierarchical ZSM-5 (h-ZSM-5) with different acidity (Si/Al = 33, 51, 122) were tested in the liquid-phase conversion of stearic acid under nitrogen atmosphere (6 bar). The incorporation of Pd into ZSM-5 zeolite increased significantly the share of gasoline in the reaction products due to the promotion by this metal of both decarboxylation and hydrogen transfer reactions. Likewise, the Pd nanoparticles dispersed over the zeolitic support favored the conversion of light olefins formed by end-chain cracking reactions into gasoline-range hydrocarbons according to an oligomerization/cyclization/aromatization pathway. Additionally, Pd/h-ZSM-5 gave rise to higher conversion and selectivity towards gasoline than Pd/n-ZSM-5, due mainly to the enhanced accessibility and improved Pd dispersion achieved when using the hierarchical zeolite. The decrease in the Si/Al atomic ratio in Pd/h-ZSM-5 samples resulted in a rise in the stearic acid conversion, although it was lower than expected. This finding denotes that, for supports with high acid sites concentration, the Pd availability became the limiting factor as the metal was loaded in similar amounts in all catalysts. Finally, the increase of the reaction temperature with the Pd/h-ZSM-5 (122) catalyst augmented both stearic acid conversion and gasoline selectivity, since it enhanced the conversion of the light olefins, formed as primary cracking products, into liquid hydrocarbons. Therefore, it can be concluded that Pd supported on hierarchical ZSM-5 zeolite is a convenient catalyst for obtaining bio-gasoline from oleaginous feedstock.

The Effect of Acidity of Al and Fe Silicates with MFI Structure on Benzene and Toluene Alkylation with Isopropyl Alcohol

1996 ◽  
Vol 61 (8) ◽  
pp. 1115-1130 ◽  
Author(s):  
Jiří Čejka ◽  
Naděžda Žilková ◽  
Blanka Wichterlová
Keyword(s):  
Kinetic Study ◽  
Molecular Sieves ◽  
Isopropyl Alcohol ◽  
Acid Sites ◽  
Transport Rate ◽  
Reaction Products ◽  
Oh Groups ◽  
Benzene Alkylation ◽  
Toluene Alkylation ◽  
Low Strength

Kinetic study of toluene and benzene alkylation with isopropyl alcohol on alumo- and ferrisilicates of MFI structure has shown that the alkylation activity does not follow the acidity (both the number and strength of bridging OH groups) of these molecular sieves. The rate of the overall reaction is controlled by the desorption/transport rate of bulky, strongly adsorbed cymenes and cumene. A higher concentration of n-propyltoluenes compared to n-propylbenzene, both undesired reaction products, formed via a bimolecular isomerization of isopropyl aromate with benzene or toluene, was due to the higher reactivity of isopropyltoluene with toluene in comparison with that of cumene with benzene. It is concluded that ferrisilicates of MFI structure possessing low strength acid sites appear to be promising catalysts for achieving both a high isopropyl- and para-selectivity in toluene alkylation to p-cymene.

scholarly journals Control of zeolite microenvironment for propene synthesis from methanol

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Longfei Lin ◽  
Mengtian Fan ◽  
Alena M. Sheveleva ◽  
Xue Han ◽  
Zhimou Tang ◽  
...  
Keyword(s):  
Active Sites ◽  
Inelastic Neutron Scattering ◽  
Sustainable Manufacturing ◽  
Methanol Conversion ◽  
Acid Sites ◽  
Light Olefins ◽  
Carbon Bond ◽  
X Ray ◽  
Carbon Carbon Bond ◽  
Catalytic Stability

AbstractOptimising the balance between propene selectivity, propene/ethene ratio and catalytic stability and unravelling the explicit mechanism on formation of the first carbon–carbon bond are challenging goals of great importance in state-of-the-art methanol-to-olefin (MTO) research. We report a strategy to finely control the nature of active sites within the pores of commercial MFI-zeolites by incorporating tantalum(V) and aluminium(III) centres into the framework. The resultant TaAlS-1 zeolite exhibits simultaneously remarkable propene selectivity (51%), propene/ethene ratio (8.3) and catalytic stability (>50 h) at full methanol conversion. In situ synchrotron X-ray powder diffraction, X-ray absorption spectroscopy and inelastic neutron scattering coupled with DFT calculations reveal that the first carbon–carbon bond is formed between an activated methanol molecule and a trimethyloxonium intermediate. The unprecedented cooperativity between tantalum(V) and Brønsted acid sites creates an optimal microenvironment for efficient conversion of methanol and thus greatly promotes the application of zeolites in the sustainable manufacturing of light olefins.

scholarly journals Solvent-Free Synthesis of SAPO-34 Zeolite with Tunable SiO2/Al2O3 Ratios for Efficient Catalytic Cracking of 1-Butene

Catalysts ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 835
Author(s):  
Xia Xiao ◽  
Zhongliang Xu ◽  
Peng Wang ◽  
Xinfei Liu ◽  
Xiaoqiang Fan ◽  
...  
Keyword(s):  
Catalytic Cracking ◽  
Acid Sites ◽  
Solvent Free ◽  
Zeolite Catalysts ◽  
Light Olefins ◽  
Molar Ratio ◽  
Coordination Environment ◽  
Starting Mixture ◽  
Synthesis Methodology ◽  
Solvent Free Synthesis

Solvent-free synthesis methodology is a promising technique for the green and sustainable preparation of zeolites materials. In this work, a solvent-free route was developed to synthesize SAPO-34 zeolite. The characterization results indicated that the crystal size, texture properties, acidity and Si coordination environment of the resulting SAPO-34 were tuned by adjusting the SiO2/Al2O3 molar ratio in the starting mixture. Moreover, the acidity of SAPO-34 zeolite was found to depend on the Si coordination environment, which was consistent with that of SAPO-34 zeolite synthesized by the hydrothermal method. At an SiO2/Al2O3 ratio of 0.6, the SP-0.6 sample exhibited the highest conversion of 1-butene (82.8%) and a satisfactory yield of light olefins (51.6%) in the catalytic cracking of 1-butene, which was attributed to the synergistic effect of the large SBET (425 m2/g) and the abundant acid sites (1.82 mmol/g). This work provides a new opportunity for the design of efficient zeolite catalysts for industrially important reactions.

Surface Reactions of Extreme Pressure Additive on Steel Surface in Ceramics-Steel Couples

1988 ◽  
Vol 110 (3) ◽  
pp. 394-401 ◽  
Author(s):  
Y. Tanita ◽  
F. Honda ◽  
K. Nakajima
Keyword(s):  
Steel Surface ◽  
Iron Phosphate ◽  
Atomic Ratio ◽  
Sliding Contact ◽  
Chemical Compositions ◽  
Reaction Products ◽  
Antiwear Properties ◽  
Zinc Dithiophosphate ◽  
Steel Surfaces ◽  
Constituent Elements

The behavior of zinc dithiophosphate (ZnDTP) is investigated for the antiwear properties in SiC-steel and Si3N4-steel sliding contact systems under boundary lubrication. Reaction products formed on the steel surfaces under the sliding contact differ in the chemical compositions and the thickness between these couples. These differences are specifically related to the physical properties of mating materials such as heat conductivity and friction coefficient. The reaction products are analyzed by SEM (scanning electron microscope), EPMA (electron probe microanalysis), AES (Auger electron spectroscope), and PAS (photoacoustic spectroscopy), and it is confirmed that iron phosphate for SiC-steel and iron phosphate and zinc sulfide (or some complex compound containing equal amounts of Zn and S in atomic ratio) for Si3N4-steel couple exist on the steel surface, respectively. An examination is conducted on steel-steel couple in comparison with ceramics-steel couples, and the atomic ratio (Zn:P:S) of the constituent elements of the reaction products coincides fairly with that of SiC-steel couple.

Preparation and Microwave Permittivity of SiC-AlN Solid Solution Powders

2007 ◽  
Vol 336-338 ◽  
pp. 310-312
Author(s):  
Xiao Kui Liu ◽  
Wan Cheng Zhou ◽  
Fa Luo ◽  
Dong Mei Zhu
Keyword(s):  
Solid Solution ◽  
High Temperature ◽  
Carbon Black ◽  
Atomic Ratio ◽  
Nitrogen Atmosphere ◽  
Argon Atmosphere ◽  
Temperature Synthesis ◽  
High Temperature Synthesis ◽  
Microwave Permittivity ◽  
Shs Method

SiC-AlN solid solution powders were prepared from the mixtures of aluminum, silicon and carbon black in a nitrogen atmosphere with preheating self-propagating high temperature synthesis (SHS) method. The powders synthesized with different ratios of Al/Si were mixed with paraffin wax and the microwave permittivity of the mixtures was measured at the frequency of 8.2~12.4GHz. The results were contrasted with that of SiC powders synthesized by preheating SHS in argon and nitrogen atmosphere respectively. The ε′, ε″, and the tgδ (ε″/ε′) of the mixture of SiC prepared in a nitrogen atmosphere are highest, followed with those of the SiC-AlN solid solution powders and the SiC powders prepared in an argon atmosphere. Along with the increase of atomic ratio of Al/Si, the ε′, ε″, and tgδ of SiC-AlN solid solution decrease. We believe that, with the increase of AlN dissolved, the concentration of carriers and the effect of dielectric relaxation will decrease because of the two contrary dopants.

scholarly journals Preformed Pd-Based Nanoparticles for the Liquid Phase Decomposition of Formic Acid: Effect of Stabiliser, Support and Au–Pd Ratio

2020 ◽  
Vol 10 (5) ◽  
pp. 1752 ◽  
Author(s):  
Felipe Sanchez ◽  
Ludovica Bocelli ◽  
Davide Motta ◽  
Alberto Villa ◽  
Stefania Albonetti ◽  
...  
Keyword(s):  
Liquid Phase ◽  
Formic Acid ◽  
Pd Nanoparticles ◽  
Catalytic Performance ◽  
Atomic Ratio ◽  
Phase Decomposition ◽  
Acid Effect ◽  
Formic Acid Decomposition ◽  
Structure Morphology

Hydrogen is one of the most promising energy carriers for the production of electricity based on fuel cell hydrogen technology. Recently, hydrogen storage chemicals, such as formic acid, have been proposed to be part of the long-term solution towards hydrogen economy for the future of our planet. Herein we report the synthesis of preformed Pd nanoparticles using colloidal methodology varying a range of specific experimental parameters, such as the amount of the stabiliser and reducing agent, nature of support and Pd loading of the support. The aforementioned parameters have shown to affect mean Pd particle size, Pd oxidation, atomic content of Pd on the surface as well as on the catalytic performance towards formic acid decomposition. Reusability studies were carried out using the most active monometallic Pd material with a small loss of activity after five uses. The catalytic performance based on the Au–Pd atomic ratio was evaluated and the optimum catalytic performance was found to be with the Au/Pd atomic ratio of 1/3, indicating that the presence of a small amount of Pd is essential to promote significantly Au activity for the liquid phase decomposition of formic acid. Thorough characterisation has been carried out by means of XPS, SEM-EDX, TEM and BET. The observed catalytic performance is discussed in terms of the structure/morphology and composition of the supported Pd and Au–Pd nanoparticles.

scholarly journals Application of the Statistical Oxidation Model (SOM) to Secondary Organic Aerosol formation from photooxidation of C<sub>12</sub> alkanes

2013 ◽  
Vol 13 (3) ◽  
pp. 1591-1606 ◽  
Author(s):  
C. D. Cappa ◽  
X. Zhang ◽  
C. L. Loza ◽  
J. S. Craven ◽  
L. D. Yee ◽  
...  
Keyword(s):  
Formation Process ◽  
Secondary Organic Aerosol ◽  
Organic Aerosol ◽  
Atomic Ratio ◽  
Model Parameters ◽  
Reaction Products ◽  
Aerosol Formation ◽  
Volatile Organic ◽  
Oxidation Model ◽  
Mechanism Of Oxidation

Abstract. Laboratory chamber experiments are the main source of data on the mechanism of oxidation and the secondary organic aerosol (SOA) forming potential of volatile organic compounds. Traditional methods of representing the SOA formation potential of an organic do not fully capture the dynamic, multi-generational nature of the SOA formation process. We apply the Statistical Oxidation Model (SOM) of Cappa and Wilson (2012) to model the formation of SOA from the formation of the four C12 alkanes, dodecane, 2-methyl undecane, cyclododecane and hexylcyclohexane, under both high- and low-NOx conditions, based upon data from the Caltech chambers. In the SOM, the evolution of reaction products is defined by the number of carbon (NC) and oxygen (NO) atoms, and the model parameters are (1) the number of oxygen atoms added per reaction, (2) the decrease in volatility upon addition of an oxygen atom and (3) the probability that a given reaction leads to fragmentation of the molecules. Optimal fitting of the model to chamber data is carried out using the measured SOA mass concentration and the aerosol O:C atomic ratio. The use of the kinetic, multi-generational SOM is shown to provide insights into the SOA formation process and to offer promise for application to the extensive library of existing SOA chamber experiments that is available.

Reaction Characteristic of MeAPSO-34 (Me=Mn, Co) Catalysts for Olefins Production from Dimethyl Ether

2012 ◽  
Vol 550-553 ◽  
pp. 416-419
Author(s):  
Young Ho Kim ◽  
Su Gyung Lee ◽  
Eun Jee Kang ◽  
Hyo Sub Kim ◽  
Chu Sik Park
Keyword(s):  
Dimethyl Ether ◽  
Strong Acid ◽  
Acid Sites ◽  
Coke Deposition ◽  
Light Olefins ◽  
Co Catalysts ◽  
Strong Acid Sites ◽  
Reaction Characteristic ◽  
Catalyst Lifetime

In DME to olefins (DTO) reaction, SAPO-34 catalyst with CHA structure is well known to be one of the catalysts with good performance. However, the SAPO-34 catalyst is easily deactivated due to coke deposition during DTO reaction. In this study, MeAPSO-34 catalysts (Me=Mn, Co) were prepared for the increase of the catalyst lifetime and their properties have been characterized by XRD and SEM. The DTO reaction was carried out over the MeAPSO-34 catalysts, and the results were compared with the SAPO-34 catalyst. The lifetime of MeAPSO-34 catalysts with high DME conversion and selectivity of light olefins was prolonged than that of the SAPO-34 catalyst. It may be concluded that the decrease of strong acid sites, which were responsible for the formation of coke, affect on the lifetime of the MeAPSO-34 catalysts. In addition, the CoAPSO-34 catalyst with a Co additive showed the best performance in terms of the catalytic lifetime and the selectivity to light olefins.

Oligomerization of pent-1-ene over zeolite catalysts

2019 ◽  
Vol 19 (4) ◽  
pp. 307-315
Author(s):  
N. G. Grigoryeva ◽  
D. V. Serebrennikov ◽  
S. V. Bubennov ◽  
B. I. Kutepov
Keyword(s):  
Catalytic Properties ◽  
Acid Sites ◽  
Zeolite Catalysts ◽  
Main Reaction ◽  
Reaction Products ◽  
High Concentration ◽  
Reaction Conditions ◽  
One Dimensional ◽  
Fuel Components ◽  
Channel Systems

Oligomerization of pent-1-ene is an effective process for synthesis of high-quality environmentally friendly fuel components. Catalytic properties of H-zeolites FAU, OFF, MOR, ВЕА, MTW and MFI were studied for synthesis of pentene oligomers in an autoclave at 110–200 °C. The wide-pore structure of H-Y and H-Beta (18) zeolites and the high concentration of acid sites were established to cause the high oligomerization activity to obtain 97–100 % yields of oligomers. Oligomers obtained over these catalysts comprised, depending on the reaction conditions, 30–73 % dimers, 25–50 % trimers and 2–14 % oligomers with more than three monomer units (n > 3). Fine-pore zeolites (H-ZSM-5) and zeolites with one-dimensional channel systems (H-OFF, H-MOR, H-ZSM-12) were less active to oligomerization of pent-1-ene, decenes being the main reaction products.

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