Hydrogenation of Acetic Acid on Alumina-Supported Pt-Sn Catalysts
Three alumina-supported Pt-Sn catalysts have been
prepared by means of co-impregnation and characterized by XRD and
N2 adsorption. The influence of catalyst composition and reaction
conditions on the conversion and selectivity were investigated in the
hydrogenation of acetic acid in an isothermal integral fixed bed
reactor. The experiments were performed on the temperature interval
468-548 K, liquid hourly space velocity (LHSV) of 0.3-0.7h-1,
pressures between 1.0 and 5.0Mpa. A good compromise of
0.75%Pt-1.5%Sn can act as an optimized acetic acid hydrogenation
catalyst, and the conversion and selectivity can be tuned through the
variation of reaction conditions.
Acetic acid, hydrogenation, Pt-Sn catalysts, ethanol.
Adsorption of H2 and CO on Iron-based Catalysts for Fischer-Tropsch Synthesis
The adsorption properties of CO and H2 on iron-based
catalyst with addition of Zr and Ni were investigated using
temperature programmed desorption process. It was found that on the
carburized iron-based catalysts, molecular state and dissociative state
CO existed together. The addition of Zr was preferential for the
molecular state adsorption of CO on iron-based catalyst and the
presence of Ni was beneficial to the dissociative adsorption of CO. On
H2 reduced catalysts, hydrogen mainly adsorbs on the surface iron
sites and surface oxide sites. On CO reduced catalysts, hydrogen
probably existed as the most stable CH and OH species. The addition
of Zr was not benefit to the dissociative adsorption of hydrogen on
iron-based catalyst and the presence of Ni was preferential for the
dissociative adsorption of hydrogen.
adsorption, Fischer-Tropsch synthesis, iron-based
An Infrared Investigation on Surface Species over Iron-Based Catalysts: Implications for Oxygenates Formation
The nature of adsorbed species on catalytic surface
over an industrial precipitated iron-based high temperature catalyst
during FTS was investigated by in-situ DRIFTS and chemical
trapping. The formulation of the mechanism of oxygenates formation
and key intermediates were also discussed. Numerous oxygenated
precursors and crucial intermediates were found by in-situ DRIFTS,
such as surface acetate, acetyl and methoxide. The results showed that
adsorbed molecules on surface such as methanol or acetaldehyde
could react with basic sites such as lattice oxygen or free surface
hydroxyls. Adsorbed molecules also had reactivity of oxidizing.
Moreover, acetyl as a key intermediate for oxygenates was observed
by investigation of CH3OH + CO and CH3I + CO + H2. Based on the
nature of surface properties, the mechanism of oxygenates formation
on precipitated iron-based high temperature catalyst was discussed.
Iron-based catalysts, intermediates, oxygenates,
in-situ DRIFTS, chemical trapping.
Conversion of Methanol to Propylene over a High Silica B-HZSM-5 Catalyst
Hydrothermally synthesized high silica borosilicates
with the MFI structure was subjected to several characterization
techniques. The effect of boron on the structure and acidity of
HZSM-5 catalyst were studied by XRD, SEM, N2 adsorption, solid
state NMR, NH3-TPD. It was confirmed that boron had entered the
framework in the boron samples. The results also revealed that strong
acidity was weakened and weak acidity was strengthened by the
boron added zeolite framework compared with parent catalyst. The
catalytic performance was carried out in a fixed bed at 460°C for
methanol to propylene (MTP) reaction. The results of MTP reaction
showed a great increment of the propylene selectivity and excellent
stability for the B-HZSM-5. The catalyst exhibited about 81%
selectivity to C2
= - C4
= olefins with 40% selectivity of propylene as
major component at near 100% methanol conversion, and the stable
performance in the studied period was 100h.
Methanol to propylene, HZSM-5, boron.
La promoted Ni/α-Al2O3 Catalysts for Syngas Methanation
The Ni/α-Al2O3 catalysts with different amounts of La
as promoter from 0 to 4 wt % were prepared, characterized and their
catalytic activity was investigated in syngas methanation reaction.
Effects of reaction temperature and lanthanum loading on carbon
oxides conversion and methane selectivity were also studied. Adding
certain amount of lanthanum to 10Ni /α-Al2O3 catalysts can decrease
the average NiO crystallite diameter which leads to higher activity and
stability while excessive addition would cause deactivation quickly.
Stability on stream towards deactivation was observed up to 800 min
at 500 °C, 0.1MPa and 600000 mL·g-1·h-1.
Methanation; Nickel catalysts; Syngas methanation
Thermal Distribution in Axial-Flow Fixed Bed with Flowing Gas
This paper reported an experimental research of
steady-state heat transfer behaviour of a gas flowing through a fixed
bed under the different operating conditions. Studies had been carried
out in a fixed-bed packed methanol synthesis catalyst percolated by air
at appropriate flow rate. Both radial and axial direction temperature
distribution had been investigated under the different operating
conditions. The effects of operating conditions including the reactor
inlet air temperature, the heating pipe temperature and the air flow rate
on temperature distribution was investigated and the experimental
results showed that a higher inlet air temperature was conducive to
uniform temperature distribution in the fixed bed. A large temperature
drop existed at the radial direction, and the temperature drop increased
with the heating pipe temperature increasing under the experimental
conditions; the temperature profile of the vicinity of the heating pipe
was strongly affected by the heating pipe temperature. A higher air
flow rate can improve the heat transfer in the fixed bed. Based on the
thermal distribution, heat transfer models of the fixed bed could be
established, and the characteristics of the temperature distribution in
the fixed bed could be finely described, that had an important practical
Thermal distribution, heat transfer, axial-flow, fixed
Na Promoted Ni/γ-Al2O3 Catalysts Prepared by Solution Combustion Method for Syngas Methanation
Ni-based catalysts with different amounts of Na as
promoter from 2 to 6 wt % were prepared by solution combustion
method. The catalytic activity was investigated in syngas methanation
reaction. Carbon oxides conversion and methane selectivity are greatly
influenced by sodium loading. Adding 2 wt% Na remarkably improves
catalytic activity and long-term stability, attributed to its smaller mean
NiO particle size, better distribution, and milder metal-support
interaction. However, excess addition of Na results in deactivation
distinctly due to the blockage of active sites.
Nickel catalysts, Syngas methanation, Sodium,
Solution combustion method.
Catalytic Cracking of Butene to Propylene over Modified HZSM-5 Zeolites
Catalytic cracking of butene to propylene was carried out in a continuous-flow fixed-bed reactor over HZSM-5 catalysts modified by nickel and phosphorus. The structure and acidity of catalysts were measured by N2 adsorption, NH3-TPD and XPS. The results revealed that surface area and strong acid sites both decreased with increasing phosphorus loadings. The increment of phosphorus loadings reduced the butene conversion but enhanced the propylene selectivity and catalyst stability.
Butene, catalytic cracking, HZSM-5, modification.
Cold Model Experimental Research on Particle Velocity Distribution in Gas-Solid Circulating Fluidized Bed for Methanol-to-Olefins Process
Radial profiles of particle velocities were investigated
in a 6.1m high methanol-to-olefins cold model experimental device
using a TSI laser Doppler velocimeter. The effect of axial height on
flow development was not obvious in fully developed region under the
same operating condition. Superficial gas velocity and solid
circulating rate had significant influence on particle velocity in the
center region of the riser. Besides, comparisons among rising,
descending and average particle velocity were conducted. The particle
average velocity was similar to the rising particle velocity and higher
than the descending particle velocity in radial locations except the wall
region of riser.
Circulating fluidized bed, laser doppler velocimeter,
particle velocity, radial profile.
Butene Catalytic Cracking to Propylene over Iron and Phosphorus Modified HZSM-5
HZSM-5 zeolites modified by iron and phosphorus
were applied in catalytic cracking of butene. N2 adsorption and
NH3-TPD were employed to measure the structure and acidity of
catalysts. The results indicate that increasing phosphorus loading
decreased surface area, pore volume and strong acidity of catalysts.
The addition of phosphorus significantly decreased butene conversion
and promoted propylene selectivity. The catalytic performance of
catalyst was strongly dependent on the reaction conditions.
Appropriate reaction conditions could suppress side reactions and
enhance propylene selectivity.
Butene catalytic cracking, HZSM-5, modification,
The Catalytic Properties of PtSn/Al2O3 for Acetic Acid Hydrogenation
Alumina supported platinum and tin catalysts with different loadings of Pt and Sn were prepared and characterized by low temperature N2 adsorption/desorption, H2-temperature programed reduction and CO pulse chemisorption. Pt and Sn below 1% loading were suitable for acetic acid hydrogenation. The best performance over 0.75Pt1Sn/Al2O3 can reach 87.55% conversion of acetic acid and 47.39% selectivity of ethanol. The operating conditions of acetic acid hydrogenation over 1Pt1Sn/Al2O3 were investigated. High reaction temperature can enhance the conversion of acetic acid, but it decreased total selectivity of ethanol and acetyl acetate. High pressure and low weight hourly space velocity were beneficial to both conversion of acetic acid and selectivity to ethanol.
Acetic acid, hydrogenation, PtSn, operating condition.
The Performance of PtSn/Al₂O₃ with Cylindrical Particles for Acetic Acid Hydrogenation
Alumina supported PtSn catalysts with cylindrical particles were prepared and characterized by using low temperature N2 adsorption/desorption and X-ray diffraction. Low temperature N2 adsorption/desorption demonstrate that the tableting changed the texture properties of catalysts. XRD pattern indicate that the crystal structure of supports had no change after reaction. The performances over particles of PtSn/Al2O3 catalysts were investigated with regards to reaction temperature, pressure, and H2/AcOH mole ratio. After tableting, the conversion of acetic acid and selectivity of ethanol and acetyl acetate decreased. High reaction temperature and pressure can improve conversion of acetic acid. H2/AcOH mole ratio of 9.36 showed the best performance on acetic acid hydrogenation. High pressure had benefits for the selectivity of ethanol and other two parameters had no obvious effect on selectivity.
Acetic acid hydrogenation, ethanol, PtSn, cylindrical particles.
Catalytic Study of Methanol-to-Propylene Conversion over Nano-Sized HZSM-5
Methanol-to-propylene conversion was carried out in a continuous-flow fixed-bed reactor over nano-sized HZSM-5 zeolites. The HZSM-5 catalysts were synthesized with different Si/Al ratio and silicon sources, and treated with NaOH. The structural property, morphology, and acidity of catalysts were measured by XRD, N2 adsorption, FE-SEM, TEM, and NH3-TPD. The results indicate that the increment of Si/Al ratio decreased the acidity of catalysts and then improved propylene selectivity, while silicon sources had slight impact on the acidity but affected the product distribution. The desilication after alkali treatment could increase intracrystalline mesopores and enhance propylene selectivity.
Alkali treatment, HZSM-5, methanol-to-propylene, synthesis condition.
Effect of Si/Al Ratio on SSZ-13 Crystallization and Its Methanol-To-Olefins Catalytic Properties
SSZ-13 materials with different Si/Al ratio were prepared by varying the composition of aluminosilicate precursor solutions upon hydrothermal treatment at 150 °C. The Si/Al ratio of the initial system was systematically changed from 12.5 to infinity in order to study the limits of Al composition in precursor solutions for constructing CHA structure. The intermediates and final products were investigated by complementary techniques such as XRD, HRTEM, FESEM, and chemical analysis. NH3-TPD was used to study the Brønsted acidity of SSZ-13 samples with different Si/Al ratios. The effect of the Si/Al ratio on the precursor species, ultimate crystal size, morphology and yield was investigated. The results revealed that Al species determine the nucleation rate and the number of nuclei, which is tied to the morphology and yield of SSZ-13. The size of SSZ-13 increased and the yield decreased as the Si/Al ratio was improved. Varying Si/Al ratio of the initial system is a facile, commercially viable method of tailoring SSZ-13 crystal size and morphology. Furthermore, SSZ-13 materials with different Si/Al ratio were tested as catalysts for the methanol to olefins (MTO) reaction at 350 °C. SSZ-13 with the Si/Al ratio of 35 shows the best MTO catalytic performance.
Crystallization, MTO, Si/Al ratio, SSZ-13.
Impact of Zn/Cr Ratio on ZnCrOx-SAPO-34 Bifunctional Catalyst for Direct Conversion of Syngas to Light Olefins
Light olefins are important building blocks for chemical industry. Direct conversion of syngas to light olefins has been investigated for decades. Meanwhile, the limit for light olefins selectivity described by Anderson-Schulz-Flory (ASF) distribution model is still a great challenge to conventional Fischer-Tropsch synthesis. The emerging strategy called oxide-zeolite concept (OX-ZEO) is a promising way to get rid of this limit. ZnCrOx was prepared by co-precipitation method and (NH4)2CO3 was used as precipitant. SAPO-34 was prepared by hydrothermal synthesis, and Tetraethylammonium hydroxide (TEAOH) was used as template, while silica sol, pseudo-boehmite, and phosphoric acid were Al, Si and P source, respectively. The bifunctional catalyst was prepared by mechanical mixing of ZnCrOx and SAPO-34. Catalytic reactions were carried out under H2/CO=2, 380 ℃, 1 MPa and 6000 mL·gcat-1·h-1 in a fixed-bed reactor with a quartz lining. Catalysts were characterized by XRD, N2 adsorption-desorption, NH3-TPD, H2-TPR, and CO-TPD. The addition of Al as structure promoter enhances CO conversion and selectivity to light olefins. Zn/Cr ratio, which decides the active component content and chemisorption property of the catalyst, influences CO conversion and selectivity to light olefins at the same time. C2-4= distribution of 86% among hydrocarbons at CO conversion of 14% was reached when Zn/Cr=1.5.
Light olefins, OX-ZEO, syngas, ZnCrOx.
Effect of the Support Shape on Fischer-Tropsch Cobalt Catalyst Performance
Cobalt catalysts were supported on extruded silica carrier and different-type (SiO2, γ-Al2O3) commercial supports with different shapes and sizes to produce heavy hydrocarbons for Fischer-Tropsch synthesis. The catalysts were characterized by N2 physisorption and H2-TPR. The catalytic performance of the catalysts was tested in a fixed bed reactor. The results of Fischer-Tropsch synthesis performance showed that the cobalt catalyst supported on spherical silica supports displayed a higher activity and a higher selectivity to C5+ products, due to the fact that the active components were only distributed in the surface layer of spherical carrier, and the influence of gas diffusion restriction on catalytic performance was weakened. Therefore, it can be concluded that the eggshell cobalt catalyst was superior to precious metals modified catalysts in the synthesis of heavy hydrocarbons.
Fischer-Tropsch synthesis, cobalt catalyst, support shape, heavy hydrocarbons.
One Dimensional Reactor Modeling for Methanol Steam Reforming to Hydrogen
One dimensional pseudo-homogenous modeling has been performed for methanol steam reforming reactor. The results show that the models can well predict the industrial data. The reactor had minimum temperature along axial because of endothermic reaction. Hydrogen productions and temperature profiles along axial were investigated regarding operation conditions such as inlet mass flow rate and mass fraction of methanol, inlet temperature of external thermal oil. Low inlet mass flow rate of methanol, low inlet temperature, and high mass fraction of methanol decreased minimum temperature along axial. Low inlet mass flow rate of methanol, high mass fraction of methanol, and high inlet temperature of thermal oil made cold point forward. Low mass fraction, high mass flow rate, and high inlet temperature of thermal oil increased hydrogen production. One dimensional models can be a guide for industrial operation.
Reactor, modeling, methanol, steam reforming.