Fuzzy model prediction of Co (III)Al2O3 catalytic behavior in Fischer-Tropsch synthesis

The application of Co(Ⅲ)/Al2O3 catalyst in Fischer-Tropsch synthesis(FTS)was studied in a wide range of synthesis gas conversions and compared with Fuzzy Simulation results.Present study applies fuzzy model to predicting the product composition of CH4,CO2 and CO in Fischer-Tropsch process for natural gas synthesis,in which the input vector was 4-dimension including four variables(operating pressure, operating temperature,time and CO/H2 ratio)of 70 different experiments and the output product is a composition of CO2,CO and CH4. The Mamdani algorithm has been applied to the training of the fuzzy system and the test set was used to evaluate the performance of the system including R2,ARE,AARE and SD.The results demonstrated that the predicted values from the model were in good consistency with the experimental data.The work indicates how fuzzy inference system(FIS),as a promising predicting technique,would be effectively used in FTS.     

Experimental studies of biomass gasification with air

In this work,experimental studies of biomass gasification under different operating conditions were carried out in an updraft gasifier combined with a copper slag reformer.The influence of gasification temperature,equivalence ratio(ER) and copper slag catalyst addition on gas production and tar yield were investigated.The experimental results showed that the content of H2 and CO,gas yield and LHV increased,while the tar yield and the content of CO2,CH4 and C2Hx in the gas product decreased with the temperature.At 800C,with the increase of ER,the LHV,the tar yield and the content of H2,CO,CH4 and C2Hx in gas products decreased,while the gas yield and the content of CO2 increased.Copper slag was introduced into the secondary reformer for tar decomposition.The Fe3O4 phase in the fresh copper slag was reduced to FeO(Fe2+) and metallic Fe by the gas product.Fe species(FeO and metallic Fe) acted as the active sites for tar catalytic decomposition.The catalytic temperature had a significant influence on tar conversion and the composition of the gas product.Typically,the tar conversion of about 17%-54% could be achieved when the catalytic temperature was varied from 750 to 950 C.Also,the content of H2 and CO increased with the catalytic temperature,while that of CO2,CH4 and C2Hx in the gas product decreased.It was demonstrated that copper slag was a good catalyst for upgrading the gas product from biomass gasification.     

Characterization and catalytic performance of CeO2-Co/SiO2 catalyst for Fischer-Tropsch synthesis using nitrogen-diluted synthesis gas over a laboratory scale fixed-bed reactor

The surface species of CO hydrogenation on CeO2-Co/SiO2 catalyst were investigated using the techniques of temperature programmed reaction and transient response method. The results indicated that the formation of H2O and CO2 was the competitive reaction for the surface oxygen species, CH4 was produced via the hydrogenation of carbon species step by step, and C2 products were formed by the polymerization of surface-active carbon species （-CH2-）. Hydrogen assisted the dissociation of CO. The hydrogenation of surface carbon species was the rate-limiting step in the hydrogenation of CO over CeO2-Co/SiO2 catalyst. The investigation of total pressure, gas hourly space velocity （GHSV）, and product distribution using nitrogen-rich synthesis gas as feedstock over a laboratory scale fixed-bed reactor indicated that total pressure and GHSV had a significant effect on the catalytic performance of CeO2-Co/SiO2 catalyst. The removal of heat and control of the reaction temperature were extremely critical steps, which required lower GHSV and appropriate CO conversion to avoid the deactivation of the catalyst. The feedstock of nitrogen-rich synthesis gas was favorable to increase the conversion of CO, but there was a shift of product distribution toward the light hydrocarbon. The nitrogen-rich synthesis gas was feasible for F-T synthesis for the utilization of remote natural gas.     

Ruthenium promotion of Co/SBA-15 catalysts for Fischer-Tropsch synthesis in slurry-phase reactors

The aim of this work was to evaluate the catalytic properties of a Ru promoted Co/SBA-15 catalyst for Fischer-Tropsch synthesis(FTS).The Ru promoted Co/SBA-15 catalyst was prepared by wet impregnation method and was characterized by X-ray diffraction,X-ray energy dispersion spectrophotometer,N2 adsorption-desorption,temperature-programmed reduction and transmission electron microscopy.The Fischer-Tropsch synthesis using the catalyst was carried out to evaluate the catalyst activity and its effect on FTS product distribution.The synthesis was carried out in a slurry reactor operating at 513 K,20 atm,CO:H2 molar ratio of 1:1.X-ray diffraction showed that the calcined cobalt catalyst did not modify the structure of SBA-15,proving that Co was present in the form of Co3O4 in the catalyst.The addition of cobalt in SBA-15 decreased the specific superficial area of the molecular sieve.Fischer-Tropsch synthesis activity and C5+hydrocarbon selectivity increased with the addition of Ru.The increases in activity and selectivity were attributed to the increased number of active sites resulting from higher reducibility and the synergetic effect of Ru and Co.Ru/Co/SBA-15 catalysts showed moderate conversion(40%)and high selectivity towards the production of C5+(80 wt%).     

Modeling of Fischer-Tropsch Synthesis in a Slurry Reactor with Water Permeable Membrane

Fischer-Tropsch synthesis is an important chemical process for the production of liquid fuels and olefins. In recent years, the abundant availability of natural gas and the increasing demand of olefins, diesel, and waxes have led to a high interest to further develop this process. A mathematical model of a slurry membrane reactor used for syngas polymerization was developed to simulate and compare the maximum yields and operating conditions in the reactor with that in a conventional slurry reactor. The carbon polymerization was studied from a modeling point of view in a slurry reactor with a water permeable membrane and a conventional slurry reactor. Simulation results show that different parameters affect syngas conversion and carbon product distribution, such as the hydrogen to carbon monoxide ratio, and the membrane parameters such as membrane permeance.     

Effect of Sulfate on an Iron Manganese Catalyst for Fischer-Tropsch Synthesis

The effect of sulfate on Fischer-Tropsch synthesis performance was investigated in a slurry- phase continuously stirred tank reactor(CSTR)over a Fe-Mn catalyst.The physiochemical properties of the catalyst impregnated with different levels of sulfate were characterized by N_2 physisorption,X-ray photoelectron spectroscopy(XPS),H_2(or CO)temperature-programmed reduction(TPR),Mφssbauer spectroscopy,and CO_2 temperature-programmed desorption(TPD).The characterization results indicated that the impregnated sulfate slightly decreased the BET surface area and pore volume of the catalyst, suppressed the catalyst reduction and carburization in CO and syngas,and decreased the catalyst surface basicity.At the same time,the addition of small amounts of sulfate improved the activities of Fischer- Tropseh synthesis(FTS)and water gas shift(WGS),shifted the product to light hydrocarbons(C_1-C_(11)) and suppressed the formation of heavy products(C_(12 )).Addition of SO_4~(2-)to the catalyst improved the FTS activity at a sulfur loading of 0.05-0.80 g per 100 g Fe,and S-05 catalyst gave the highest CO conversion(62.3%),and beyond this sulfur level the activity of the catalyst decreased.     

STUDIES ON FISCHER TROPSCH SYNTHESIS OVER Fe-Cu-K CATALYST Ⅱ.PRODUCT DISTRIBUTION AND COMPOSITION

In part I, we investigated some behavior of copper- potassium promoted iron catalyst for the synthesis of hydrocarbon from hydrogen and carbon monoxide, with particular attention to the influence of reaction temperature, operating pressure, space velocity, H2/CO ratio in feed gas and particle size of catalyst on CO conversion. In this part, more attention was paid to the whole product distribution, such as wax, oil, oxygenate and the composition of oil and oxygenate. It is seen that the operating conditions greatly affect the whole product distribution and its composition.     

Influence of the Feed Gas Composition on the Fischer-Tropsch Synthesis in Commercial Operations

Key technical challenges relating to the Fischer-Tropsch(F-T)synthesis applied in the commer- cialization of coal/gas-to-liquids(CTL/GTL)technolo- gies have been reviewed.Based on the experiences ac- cumulated from pilot plant,semi-work test and lab re- searches,the influences of the H_2/CO ratio and the CO_2 in the feed gas on the F-T process as well as on CTL/GTL complex in terms of product yields,energy efficiency and carbon utilization efficiency have been studied.Being contrary to the current design schemes for F-T process using the coat derived syngas and the iron-based cata- lyst,it is suggested to feed the F-T synthesis unit with a syngas having a H_2/CO ratio of 0.5 and then adjusting to 1.4 via the recycling process.As a result,the carbon efficiency of the whole plant could be reached to as high as 50%.For the issue of CO_2 addition to the feed gas, it is proved that only a diluting role is played under the current commercial slurry phase F-T process.     

Fischer-Tropsch Reaction Kinetics of Cobalt Catalyst in Supercritical Phase

Fischer-Tropsch synthesis under supercritical phase condition was examined in a continuous and a high-pressure fixed bed reactor by employing a cobalt catalyst (Co-R.Ru/γ-Al2O3). An integral reactor model involving Fischer-Tropsch reaction kinetics in the supercritical fluid n-hexane was used to describe the overall performance. On the basis of Langmuir-Hinshelwood-Hougen-Watson (LHHW) model, the reaction rate constants were obtained for the rate equations of CO conversion to CH4 formation under supercritical conditions.     

Studies on product distribution of alkali promoted iron catalyst in Fischer-Tropsch synthesis

The dependencies of hydrocarbon product distributions of alkali promoted iron catalyst in Fischer-Tropsch synthesis have been studied. The concept of two superimposed Anderson-Schulz-Flory distributions has been applied for the representation of the effects of Mg, La and Ca promoters on product distributions. The FTS performance of the catalysts was tested in a fixed bed reactor under the conditions 563 K, 1.7 MPa, H2/CO = 1 and space velocities 4.86 and 13.28 nl h-1 gFe-1 . The results indicate that approp...     

Production of hydrogen and syngas via pyrolysis of bagasse in a dual bed reactor

Pyrolysis of bagasse followed by thermal cracking of tar was carried out at atmospheric pressure using a dual bed reactor. The first bed was used for the pyrolysis and the second bed was used for thermal cracking of tar. Iron fillings were used as the packed bed material in the second bed. The effects of reaction time (20 to 40 min), reactor temperature (600 to 900℃) and packed bed height (40-100 mm) on the product (char, tar and gas) yield and gas (H2 , CO, CO2 , CH4 , CnHm ) composition were studied. Over the ranges of the experimental conditions used, the operating conditions were optimized for pyrolysis temperature around 850℃, a reaction time of 30 min and packed bed height of 100 mm, thus we could obtain a gas richer in hydrogen and carbon monoxide and poorer in carbon dioxide and hydrocarbons. It was observed that compared with single bed process, dual bed process increased the gas yield from 0.397 to 0.750 m3 /kg and decreased the tar yield from 0.445 to 0.268 g/g while the heating value of the product gas remained almost constant (10-11 MJ/m3 ).     

Fischer-Tropsch synthesis over ruthenium-promoted Co/Al_2O_3 catalyst with different reduction procedures

The effect of reduction procedure on catalyst properties, activity and products selectivity of ruthenium-promoted Co/γ-Al2O3 catalyst in Fischer-Tropsch synthesis (FTS) was investigated. Catalyst samples were reduced with different reduction gas compositions and passivated before being characterized by TPR and XRD techniques. Different activity and product selectivity analyses were also performed. These results showed that the catalyst dispersion, particle size, and the degree of reduction changed with different reduction gas compositions, which were resulted from the water partial pressures in reduction process that give varying degrees of interaction with the support. It has been suggested that the FTS activity of cobalt catalyst was directly dependent on the catalyst reducibility. A reduction gas with a molar ratio of H2/He = 1 was used to prevent the formation of Co-support compound during catalyst reduction.     

Conversion enhancement of tubular fixed-bed reactor for Fischer-Tropsch synthesis using static mixer

Recently,Fischer-Tropsch synthesis(FTS) has become an interesting technology because of its potential role in producing biofuels via Biomassto-Liquids(BTL) processes.In Fischer-Tropsch(FT) section,biomass-derived syngas,mainly composed of a mixture of carbon monoxide(CO) and hydrogen(H2),is converted into various forms of hydrocarbon products over a catalyst at specified temperature and pressure.Fixed-bed reactors are typically used for these processes as conventional FT reactors.The fixed-bed or packed-bed type reactor has its drawbacks,which are heat transfer limitation,i.e.a hot spot problem involved highly exothermic characteristics of FT reaction,and mass transfer limitation due to the condensation of liquid hydrocarbon products occurred on catalyst surface.This work is initiated to develop a new chemical reactor design in which a better distribution of gaseous reactants and hydrocarbon products could be achieved,and led to higher throughput and conversion.The main goal of the research is the enhancement of a fixed-bed reactor,focusing on the application of KenicsTM static mixer insertion in the tubular packed-bed reactor.Two FTS experiments were carried out using two reactors i.e.,with and without static mixer insertion within catalytic beds.The modeled syngas used was a mixed gas composed of H2/CO in 2:1 molar ratio that was fed at the rate of 30mL(STP)min1(GHSV≈136mL g1 cat h1) into the fixed Ru supported aluminum catalyst bed of weight 13.3g.The reaction was carried out at 180℃ and atmospheric pressure continuously for 36h for both experiments.Both transient and steady-state conversions(in terms of time on stream) were reported.The results revealed that the steady-state CO conversion for the case using the static mixer was approximately 3.5 times higher than that of the case without static mixer.In both cases,the values of chain growth probability of hydrocarbon products(α) for Fischer-Tropsch synthesis were 0.92 and 0.89 for the case with and without static mixer,respectively.     

Comparative study on the reaction of methane over a ZnO bed in the absence and presence of CO2

The reaction of zinc oxide with methane in the absence and presence of CO2 were theoretically and experimentally investigated using HSC Chemistry 5.1 software and a fixed bed reactor, respectively. In the absence of CO2 at 1193 K, the reduction of ZnO was accompanied with methane cracking, and metallic zinc, CO, and H2 were the main reaction products. This system could be utilized for the co-production of metallic zinc and synthesis gas, in which ZnO was a donor of oxygen. In the presence of CO2, ZnO plays as a catalyst in the CO2 reforming of methane and produces syngas with the average H2/CO ratio of 0.88 at 1193 K, which was close to the total reaction theoretic value of 1. It was also found that higher temperature favored high CH4 and CO2 conversions. XRD technique was used to characterize the ZnO species. The result showed that there were no differences in the peak profiles of the XRD patterns of the ZnO powder obtained before and after passing the CH4/CO2 mixed gases for 6 h at 1193 K. It is suggested that ZnO functions as a catalyst according to the redox cycle and metallic zinc plays the role of intermediate product in this process.     

Single iron sites for catalytic,nonoxidative conversion of methane

<正>The availability of inexpensive natural gas from the fracturing of shale and as a byproduct of oil production has stimulated the investigation of catalytic processes for the direct conversion of methane to products.Efforts in this direction are further driven by the desire to avoid the generation of CO2 and its emission to the atmosphere,as occurs when methane is steam-reformed to produce synthesis gas,a mixture of CO and H2 that can be used for the production of fuels and chemicals via Fischer-Tropsch synthesis.Dur-     

Partial Oxidation of Methane to Synthesis Gas over Hexaaluminates LaMAl_(11)O_(19-δ) catalysts

A series of M-substituted hexaaluminates LaMAl11O19-δ(M=Fe, Co, Ni, Mn, and Cu) were prepared and characterized by XRD, XPS, TPR and TGA techniques, respectively. They exhibited different reducibility and catalytic activity for partial oxidation of methane (POM) to synthesis gas. Among the LaMAl11O19-δsamples, LaNiAl11O19-δshowed the best catalytic activity for the topic reaction and selectivity for synthesis gas at 780℃for 2 h. The conversion of CH4 was over 99.2%, and the product selectivity for both CO and H2 was above 90.3%.     

Kinetic Rates of the Fischer Tropsch Synthesis on a Co/Nb2O5 Catalyst

The kinetics of the Fischer-Tropsch reaction over a Co/Nb2O5 catalyst in a fixed bed reactor was investigated experimentally. Experiments were carried out under isothermal and isobaric conditions (T=543 K, P=2.1 MPa) and under different conditions of several H2/CO feed molar ratio (0.49-4.79), space velocities (0.2-3.8 h-1), mass of catalyst (0.3-1.5 g), and CO conversion (10%-29%). Synthesis gas conversion was measured and data were reduced to estimate the kinetic parameters for different Langmuir-Hinshelwood rate expressions. Differential and integral reactor models were used for the nonlinear regression of kinetics parameters. One of the rate equations could well explain the data. The hydrocarbon product distributions that were experimentally determined exhibited an unusual behavior, and a possible explanation was discussed.     

TiO2 supported cobalt-manganese nano catalysts for light olefins production from syngas

Cobalt-manganese nano catalysts were prepared by sol-gel method. This research investigated the effects of different cobalt-manganese (Co/Mn = 1/1) loading, pH and calcination conditions on the catalytic performance of Co-Mn/TiO2 catalysts for Fischer-Tropsch synthesis (FTS) in a fixed bed reactor. It was found that the catalyst containing 30wt%(Co-Mn)/TiO2 was an optimal catalyst for the conversion of synthesis gas to light olefins especially propylene. The activity and selectivity of optimal catalyst were studied under different operational conditions. The results showed that the best operational conditions were H2 /CO = 1/1 molar feed ratio at 250℃ and GHSV = 1300 h-1 under atmospheric pressure. Characterization of catalysts was carried out by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2 adsorption-desorption measurements.     

Carbon dioxide conversion to valuable chemical products over composite catalytic systems

This paper reports an experimental study on catalytic conversion of carbon dioxide to methanol,ethanol and acetic acid.Catalysts having different catalytic functions were synthesized and combined in different ways to enhance the selectivity to desired products.The combined catalyst system possessed the following functions:methanol synthesis,Fischer-Tropsch synthesis,water-gas-shift and hydrogenation.Results showed that the methods of integrating these catalytic functions played an important role in achieving the desired product selectivity.We speculate that if methanol synthesis sites were located adjacent to the C-C chain growth sites,the formation rate of C₂ oxygenates would be enhanced.The advantage of using a high temperature methanol catalyst PdZnAl in the combined catalyst system was demonstrated.In the presence of PdZnAl catalyst,the combined catalyst system was stable at 380°C.It was observed that,at high temperature,kinetics favored oxygenate formation.The results implied that the process can be intensified by operating at high temperature using Pd-based methanol synthesis catalyst.Steam reforming of the byproduct organics was demonstrated as a means to provide supplemental hydrogen.Preliminary process design,simulation,and economic analysis of the proposed CO₂ conversion process were carried out.Economic analysis indicates how ethanol production cost was affected by the price of CO₂ and hydrogen.     

Effect of Several Anions on Fe-Based Catalyst for Fischer-Tropsch Synthesis

The influence of several anions on Fe-based Fischer-Tropsch catalyst,used in the synthesis of light olefins from synthesis gas,was studied.The results indicated that the addition of anions resulted in the reduction of catalytic activity.When the anion content in the catalyst was 500 ppm,the influence of different anions on the catalysis activity was as follows:S~(2-)>Cl~->SO_4~(2-)>NO_3~-.The addition of S~(2-)improved the selectivity of total hydrocarbons in the products,and Cl~- reduced this selectivity but increased the olefin content in the total hydrocarbons at the same time.When the contents of S~2 and Cl~- in the catalyst were less than 50 ppm,their influence could be ignored.The XRD results indicated that the addition of anions reduced the contents ofα-Fe and Fe_3C,which were the active components in the catalyst.