Selective methanation of carbon monoxide over Ru-based catalysts in H2-rich gases

Yongfa Zhang,Liping Wang,Ying Xu,Yaling Sun,Guojie Zhang 한국공업화학회 2012 Journal of Industrial and Engineering Chemistry Vol.18 No.5

A series of Ru/Al2O3 methanation catalysts containing 0.5–5.0% Ru were prepared by impregnation. This study was designed to investigate the optimization conditions and catalytic activities for the selective methanization of carbon monoxide in hydrogen-containing streams, by use of a catalytically active composition which comprises ruthenium as the active component and a support material based on aluminum oxide. The properties of the catalysts were characterized by XRD, TG and SEM technique. A number of laboratory experiments were performed to clarify the influence of process parameters (Ru loading, calcinations temperature, space velocity and chlorine ions content) on the activities of catalysts. The experimental results showed that the application of ultrasound impregnation could significantly decrease impregnation time and improve the activity of catalyst. The optimum process preparation conditions for these factors were found to be space velocity 3000 h1, calcination temperature 400 8C and 2% Ru loading, respectively. Under these conditions, the CO conversion and CH4 selectivity were 97.2% and 83.3%. The catalyst washed with deionized water and diluted ammonia not only removed chlorine, but also improved the catalytic activity. Overall, the catalyst showed high performance at optimization preparation conditions, and its activity was maintained after 4320 min. It was a promising candidate for utilizing H2-rich gas to produce methane at a wide temperature window.

Hydrogen production from CO2 reforming of methane over high pressure H2O2 modified different semi-cokes

Guojie Zhang,Jiangwen Qu,Yannian Du,Fengbo Guo,Haixiang Zhao,Yongfa Zhang,Ying Xu 한국공업화학회 2014 Journal of Industrial and Engineering Chemistry Vol.20 No.5

H2O2 was used under different temperatures and pressures to activate three kinds of different semicokes. FTIR, BET, SEM and Boehm titration were used to analyze properties of the semi-cokes surfaces, finding that catalytic activities of these semi-cokes after modification by high temperature and high pressure H2O2 were improved. FTIR shows that the characteristic infrared absorption peak of functional groups on the semi-cokes surface does not change, but the absorption peak intensity of some functional groups is increased. The strength of –OH absorption peak of Hongce lignite (HCL) semi-coke at 3444 cm-1, carboxyl C55O at 1598 cm-1, aliphatic ether, cyclic ether and other organic functional groups at 1023 cm 1 in the modified Shenmu bituminous(SMB) semi-coke and Jincheng anthracite (JCA) semicoke are increased significantly. BET finds that the specific surface area and pore volume of three semicokes are increased after modification. Boehm titration shows that the basic functional group content in semi-coke is increased after modification, and the net alkali content is increased significantly. Compared with the raw semi-coke, SEM shows that the surface of semi-coke modified with H2O2 becomes rough. Modified JCA semi-coke surface pitted with holes, modified HCL and SMB semi-coke surface present porous.

Effects of preparation methods on the properties of cobalt/carbon catalyst for methane reforming with carbon dioxide to syngas

Guojie Zhang,Yongfa Zhang,Yannian Du,Ying Xu 한국공업화학회 2014 Journal of Industrial and Engineering Chemistry Vol.20 No.4

The effect of different preparation methods on the physicochemical property, reforming reactivity, stability and carbon deposition resistance of cobalt/carbon catalyst was investigated through fixed bed flow reaction. The catalysts were prepared by the impregnation and characterized by the XRD and scanning electron microscopy (SEM). The result indicated that the active components of cobalt/carbon catalyst prepared by using ultrasonic wave distributed evenly, activity was high and the loading time was short. The Co/Carbon catalyst prepared by incipient-wetness impregnation, 10 wt% loading and 300 ℃ calcination, achieved the best activity. Furthermore, the effect of reaction temperature, air speed and CH4/CO2 ratio on the catalyst activity and CO/H2 ratio in products was investigated. It was found that the conversion of CO2 and CH4 increased with the increasing of reaction temperature. However, the conversion of CO2 and CH4 increased first and then decreased with the increasing of air speed. With the increasing of CH4/CO2 in feed gas, both the catalyst activity and the CO/H2 ratio in products decreased.

Desulfurization reaction model and experimental analysis of high sulfur coal under hydrogen atmosphere

Guojie Zhang,Yannian Du,Yongfa Zhang,Ying Xu 한국공업화학회 2014 Journal of Industrial and Engineering Chemistry Vol.20 No.2

The reaction between hydrogen and high-sulfur coal at high temperature was investigated. Crashed andsieved high-sulfur coal sample was placed in a 23 mm I.D. differential reactor. The release of hydrogensulfide at run temperature and under different hydrogen atmospheres was recorded by a hydrogensulfide detector. Desulfurization yield was obtained through the elemental analysis of residual char. Thegrain reaction and random pore models were modified to facilitate the description of reaction kineticscharacteristics. Hydrogen was observed to promote the desulfurization rate considerably; i.e., more than65% of sulfur in coal could be removed. The releasing curves of H2S in the hydropyrolysis processexhibited two peaks. The desulfurization process in the hydropyrolysis of high-sulfur coal could beregarded as two stages based on the evolution profiles of H2S. The first peak at 250–450℃ was derivedfrom the desulfurization of aliphatic sulfide. The second peak at 450–650℃ was produced from thesulfur in pyrite and aromatic thiophenic structure. The desulfurization of high sulfur could be describedmore effectively with the grain reaction model than with the random pore model. The random poremodel was only adopted in the initial stage of sulfur removal of high-sulfur coal under hydrogenatmosphere. The grain reaction model was adequate for the entire stage.

Towards understanding the carbon catalyzed CO2 reforming of methane to syngas

Guojie Zhang,Jiangwen Qu,Aiting Su,Yongfa Zhang,Ying Xu 한국공업화학회 2015 Journal of Industrial and Engineering Chemistry Vol.21 No.1

In this paper, a fixed-bed reactor is used to study the influence of different conditions on carboncatalyzed CO2–CH4 reforming. The surface structure and functional groups of carbonaceous materialhave been characterized through SEM, XPS, XRD, BET and chemical titration before and after the reaction. Studies have revealed that under non-catalytic condition, methane pyrolysis happens first, followed bythe gasification reaction between CO2 and carbon deposit produced from the pyrolysis. While withcarbonaceous material, CO2 gasification, methane pyrolysis and CO2–CH4 reforming can take place at thesame time, with the reforming as the main reaction, CO2 gasification and methane pyrolysis as the sidereaction. Catalytic activity varies from one carbonaceous material to another, but their reaction trend isthe same on the whole. Those high specific surface area carbonaceous materials show higher catalyticactivity. The increase in reaction temperature and residence time of the reforming can improve theconversion of reactant gas. Adjusting the partial pressure of methane can control carbon–hydrogen ratio ofthe synthesis gas. XPS and XRDcharacterizationsdemonstrate that the structural ordering of carbonaceousmaterials becomes a little messier after the reforming reaction, and the number and content of oxygenfunctional groups decrease. That means these oxygen functional groups on the surface of carbonaceousmaterials are involved in the reforming and these groups along with pore structure on the surface are themajor factors influencing the catalytic properties. Different oxygen species make the nature of electricalenergy on the surface different; the catalytic activity depends on the polarity of oxygen from differentspecies. Those whose polarity is strong have strong activity. The dipole force can be associated withmethane in the form of hydrogen bond, so that the material can display strong activity. Those whosepolarity is weak have weak activity, the catalytic activity is weak too. The results of chemical titration andXPS characterization show that the oxygen in the anhydride and lactone structures on the surface ofcarbonaceous materials are active oxygen, and which is the main active component, it can reduce theactivation energy of methane dehydrogenation.

Experimental and Numerical Modeling of the Freeze-thaw Response of U-Shaped Channel Lining on Sulfate Saline Soil Foundation

Sheng Li,Hongbo Li,Juncang Tian,Hao Sun,Yongfa Ding,Xuanshuo Zhang 대한토목학회 2024 KSCE Journal of Civil Engineering Vol.28 No.4

Under the influence of seasonal freeze-thaw cycles, the concrete lining of channels situated on saline soil foundations is highly vulnerable to an array of deleterious phenomena, such as frost heave, salt expansion, and corrosion. To investigate the synergistic interplay among saline soil substrates, U-shaped channel lining structures, and ambient temperatures during freeze-thaw cycles, a novel Hydraulic-Thermal-Salt-Mechanical (HTSM) model is established in this study. The HTSM model elucidates the migration of moisture and salt solute, ice-water phase transitions, and sodium sulfate crystallization within unsaturated saline soils throughout the freeze-thaw cycles. It considers the variations in volume and pore solution volume before and after the phase transition of sodium sulfate. Temperature and salt frost heaving force measurements obtained from outdoor freeze-thaw cycles are compared with numerical simulation results to validate the efficacy of the HTSM model and investigate the distribution patterns of salt frost heaving force (frost swelling force) along the channel. The results showed that the frost swelling force and depth exhibit a great linear relationship and the maximum stress of the U-shaped channel appears at the bottom of the channel, highlighting the good arching force characteristics of the U-shaped structure which prove that bottom of the channel is also the most prone to fracture. Significantly, the initial water content significantly impacts the frost swelling force—it increases by 4% while the frost swelling force increases by 76%. Comparing the numerical simulation results of temperature variations, moisture changes, and salt-frost heaving forces with the outdoor experimental data, it is evident that the proposed HTSM model effectively simulates the salt-frost heaving patterns observed in U-shaped channel linings.