Weiyong Ying

Ni/Al2O3 catalysts for syngas methanation： Effect of Mn promoter

Abstract Ni/Al 2 O 3 catalysts with different amounts of manganese ranging from 1 to 3 wt% as promoter were prepared by co-impregnation method. The catalysts were characterized by N 2 physisorption, XRD, TPR, SEM and TEM. Their catalytic activity towards syngas methanation reaction was also investigated using a fixed-bed integral reactor. It was demonstrated that the addition of manganese to Ni/Al 2 O 3 catalysts can increase the catalyst surface area and average pore volume, but decrease NiO crystallite size, leading to higher activity and stability. The effects of reaction temperature, pressure and weight hourly space velocity (WHSV) on carbon oxides conversion and CH 4 formation rate were also studied. High carbon oxides conversion, CH 4 selectivity and formation rate were achieved at the reaction temperature range of 280–300 °C.

Effects of Zr and K Promoters on Precipitated Iron-Based Catalysts for Fischer–Tropsch Synthesis

The effects of Zr and K promoters on the structure, adsorption, reduction, carburization and catalytic behavior of precipitated iron-based Fischer–Tropsch synthesis (FTS) catalysts were investigated. The catalysts were characterized by N2 physisorption, temperature-programmed reduction/desorption (TPR/TPD) and Mössbauer effect spectroscopy (MES) techniques. As revealed by N2 physisorption, Zr and/or K promoted catalysts showed lower surface area than Fe/SiO2 catalyst. Zr promoter inhibited the reduction and carburization because of the interaction between Fe and Zr in Fe–Zr/SiO2 catalysts. K promoter enhanced the reduction in CO and apparently facilitated the CO adsorption, thus promoted the carburization, but it retarded the reduction in H2 and severely suppressed the H2 adsorption. Compared with the singly promoted catalysts, the doubly promoted catalyst had the highest FTS activity. In addition, both Zr and K promoters suppressed the formation of methane and shifted the production distribution to heavy hydrocarbons.Graphical AbstractBoth Zr and K restrained the formation of methane, and increased the heavy hydrocarbons selectivity. In the FTS reaction, the doubly promoted catalyst Fe–Zr–K/SiO2 had the highest FTS activity.

Effects of the ratio of Fe to Co over Fe-Co/SiO2 bimetallic catalysts on their catalytic performance for Fischer-Tropsch synthesis

Abstract The Fe-Co/SiO 2 bimetallic catalysts with different ratios of Fe to Co were prepared by aqueous incipient wetness impregnation. The catalysts of 10%Fe:0%Co/SiO 2 , 10%Fe:6%Co/SiO 2 , 10%Fe:2%Co/SiO 2 , 10%Fe:10%Co/SiO 2 , 6%Fe:10%Co/SiO 2 , 2%Fe:10%Co/SiO 2 and 0%Fe: 10%Co/SiO 2 by mass were tested in a fixed reactor by the Fischer-Tropsch synthesis. Activity and hydrocarbon distribution were found to be determined by the ratio of iron to cobalt of the catalysts. Higher iron content inhibited the activity, whereas higher cobalt content enhanced the activity of the Fe-Co/SiO 2 catalysts. On the other hand, for the catalysts of 10%Fe:6%Co/SiO 2 , 10%Fe:10%Co/SiO 2 , 6%Fe:10%Co/SiO 2 , and 2%Fe:10%Co/SiO 2 , the total C 2 –C 4 fraction increased (from 10.65% to 26.78%) and C 5+ fraction decreased (from 75.75% to 57.63%) at 523 K. Temperature programmed reduction revealed that the addition of cobalt enhanced the reducibility of the Fe-Co/SiO 2 catalyst. Metal oxides were present in those catalysts as shown by XRD. The Fe-Co alloy phase was found in the 2%Fe:10%Co/SiO 2 , 6%Fe:10%Co/SiO 2 , 10%Fe:10%Co/SiO 2 , 10%Fe:6%Co/SiO 2 catalysts and their crystals were perfect.

Product distributions of Fischer-Tropsch synthesis over Co/AC catalyst

Abstract The product distributions of Fischer-Tropsch synthesis over Co/AC catalyst are investigated under different reaction conditions in an integral fixed bed reactor. It is found that the product distributions deviate from the ASF distribution. The deviation from ASF distribution is analyzed by taking the readsorption of alkenes and the following secondary reaction into consideration. It is noted that the contents of alcohol, alkene and alkane decline with the increasing carbon number, showing a slighter declining tendency of alkanes than those of alkenes and alcohols. It is also found that high temperature, space velocity, H2/CO in feed gas and low pressure are preferential for light hydrocarbons and alcohols while against the chain propagation. The effect of space velocity on the product distributions especially on the light products is not obvious. It is noticed that low temperature, space velocity, H2/CO and high pressure lead to high contents of alcohols; high temperature, H2/CO and low space velocity lead to high contents of alkanes. The effect of pressure on the amounts of alkanes is not significant; high space velocity and low temperature, pressure, H2/CO are preferential for alkenes.

Effect of Sn Addition in Gas Phase Hydrogenation of Acetic Acid on Alumina Supported PtSn Catalysts

Alumina supported Pt, Sn and PtSn catalysts were prepared by impregnation and tested in the gas phase hydrogenation of acetic acid, and characterized by N2-physisorption, XRD, H2-TPR, H2-pulse chemisorption, H2-TPD, DRIFTS (diffuse reflectance infrared Fourier transform spectroscopy), XPS, electron microscopy techniques (TEM, HRTEM and EDX). Results show that Sn addition to Pt/Al2O3 catalyst can improve the conversion of acetic acid and suppress the production of by-products, as well as enhance the selectivity towards ethanol. The optimization of activity and selectivity can be achieved by changing reaction temperature and pressure. Characterizations indicated that the better performance of PtSn/Al2O3 catalyst is due to the formation of PtSn alloy and Pt-SnOx species.Graphical Abstract

Effects of the Different Supports on the Activity and Selectivity of Iron-Cobalt Bimetallic Catalyst for Fischer-Tropsch Synthesis

Abstract Silica, alumina, and activated carbon supported iron-cobalt catalysts were prepared by incipient wetness impregnation. These catalysts have been characterized by BET, X-ray diffraction (XRD), and temperature-programmed reduction (TPR). Activity and selectivity of iron-cobalt supported on different carriers for CO hydrogenation were studied under the conditions of 1.5 MPa, 493 K, 630 h −1 , and H 2 /CO ratio of 1.6. The results indicate that the activity, C 4 olefin/(C 4 olefin+C 4 paraffin) ratio, and C 5 olefin/(C 5 olefin+C 5 paraffin) decrease in the order of Fe-Co/SiO 2 , Fe-Co/AC1, Fe-Co/A1 2 O 3 and Fe-Co/AC2. The activity of Fe-Co/SiO 2 reached a maximum. The results of TPR show that the Fe-Co/SiO 2 catalyst, is to some extent different. XRD patterns show that the Fe-Co/SiO 2 catalyst differs significantly from the others; it has two diffraction peaks. The active spinel phase is correlated with the supports.

Effects of promoters on catalytic performance of Fe-Co/SiO2 catalyst for Fischer-Tropsch synthesis

Abstract 2%Fe-10%Co/SiO2 catalysts with different potassium or zirconium loadings were prepared by aqueous incipient wetness impregnation and tested for Fischer-Tropsch synthesis in a flow reactor, using H2/CO = 1.6 (molar ratio) in the feed, under the condition of an overall pressure of 1 MPa, GHSV of 600 h−1 and temperature of 503 K. The zirconium and potassium promoters remarkably influenced hydrocarbon distribution of the products. CO conversion increased on the catalysts with the increase of zirconium loadings, which indicated that zirconium enhanced the activity of iron-cobalt catalysts. Low potassium loadings also enhanced the activity of the catalysts. However, high potassium loading made CO conversion on the catalysts decrease and weakened the secondary hydrogenations. The catalyst was characterized by BET, XRD and TPR. The catalyst characterization revealed that the Co3O4 phase was presented on the fresh catalyst, whereas the spinel phase of Fe-Co alloy and CoO existed on the used catalyst.

Process simulation of dimethyl ether synthesis via methanol vapor phase dehydration

The production processes included catalytic dehydration of methanol in an adiabatic fixed-bed reactor and two columns product separations. In this study, the technological process for dimethyl ether (DME) synthesis is built on PRO/II platform based on the combined parameters of the reaction dynamic model for methanol dehydration reaction, the improved NRTL model of the liquid phase, the PR model of vapor phase. In order to validate the proposed model, the simulation results have been compared with the available data from a set of industrial production equipment with a production capacity of 200 000 tonnes per annum. A comparison between the calculated and measured results has proved that these results are satisfactory. The bed height and the volume of the catalytic bed are calculated aim at one million t/a DME yields and while taking account of high-purity DME production. After discussing the influence of feed stage location and reflux ratio for DME product purity, the suitable unit operation conditions are chosen. Accordingly, accurate process simulation results provide the basis and guidance for an improvement and development of the similar industrial device.

Reaction and deactivation kinetics of methanol-to-olefins process based on a special TGA reactor

Abstract Thermax 700 thermo gravimetric analysis (TGA) instrument is introduced for the investigation of the reaction and deactivation kinetics of Methanol-to-Olefins (MTO) process with SAPO-34 catalyst. By the use of a special sample basket, the TGA instrument can be viewed as a plug flow fixed-bed reactor, while the weight change of SAPO-34 during reaction can be recorded online. Kinetic data are acquired in the temperature range of 648.2-748.2 K and space velocities of 7.08–35.91 h −1 (WHSV). Catalyst activity is expressed with average coke content, and selectivity for different products is related as a function of coke content and temperature. Methane is also introduced into the lumping kinetic model, and power exponent function with first-order reaction is adopted for model deduction. Exponential function is tested to give the best fit for catalyst activity and product selectivity with the highest correlation coefficient. The nicely agreed results between experimental and calculated data suggest that the overall kinetic model would be meaningful in both product distribution prediction and reactor simulation.

Product distributions and olefin-to-paraffin ratio over an iron-based catalyst for Fischer–Tropsch synthesis

An iron-based catalyst was prepared by the co-precipitation method. The product distributions and olefin-to-paraffin ratio (O/P ratio) with chain length of Fischer–Tropsch synthesis over the iron-based catalyst were investigated under different reaction conditions in an integral fixed bed reactor. It is found that the product distributions are non-ASF situation, and the deviation from ASF law was analyzed by taking the physisorption, solubility, volatility of products and the subsequent secondary reactions into consideration. It is noted that the contents of hydrocarbons decline with increasing carbon number and higher temperature, space velocity, H2/CO in feed gas and lower pressure is preferential for the formation of light hydrocarbons but against the chain propagation. The O/P ratio shows an exponential decrease with chain length except for ethylene and ethane because of the special adsorption character of ethylene. The O/P ratio is also affected by operating conditions. The results indicate that higher reaction temperature, space velocity of feed gas, lower pressure and higher H2/CO in the feed gas are preferential for the formation of olefins and the enhancement of O/P ratio.