CRYSTAL SIZE GROWTH IN THE LIQUID PHASE METHANOL SYNTHESIS CATALYST

The phenomenon of crystal growth in the methanol synthesis catalyst has been studied. Crystallite size distributions in the cuo/ZnO/Al₂O₃ methanol synthesis catalyst have been determined. The effects of temperature, reaction environment and time under reaction conditions have been studied. It is observed that water in the reaction mixture promotes crystal growth.     

A SINGLE-STAGE,LIQUID-PHASE DIMETHYL ETHER SYNTHESIS PROCESS FROM SYNGAS III. DUAL CATALYST CRYSTAL GROWTH,DEACTIVATION, AND ACTIVITY CONSERVATION STUDIES

ABSTRACT

In the liquid phase dimethyl ether (DME) synthesis process, both the methanol synthesis catalyst )composed of CuO, ZnO, and Al₂O₃) and the methanol dehydration catalyst (composed of gamma-alumina) are slurried in the inert oil phase. Various long-term activity checks were conducted on these dual catalysts to characterize the crystal growth and the thermal aging behavior. X-ray powder diffraction, X-ray fluorescence and elemental intensity compositions, and the crystallite size distributions of the aged catalysts were examined. Based on the current investigation, it was established that the crystal growth and the catalyst deactivation problems in the methanol synthesis catalyst are less severe when it is used along with the methanol dehydration catalyst.     

ROLE OF IN-SITU PRODUCED METHANOL ON THE CATALYST DEACTIVATION IN THE LIQUID PHASE METHANOL SYNTHESIS PROCESS

ABSTRACT

The role of methanol produced in-situ in the liquid phase methanol synthesis process has been experimentally examined. The catalyst crystallite size is found to be more stable when the produced water and methanol are consistently removed from the catalyst active sites. The experimental evidence shows that in-situ produced water is not the only culprit for the catalyst crystallite size growth, rather, methanol is also responsible for contributing to crystallite growth and therefore catalyst deactivation

Hydrothermal leaching of the catalyst was also determined to be an active participant in catalyst deactivation. Two experimental designs were run to assess the influence of temperature, leaching solution concentration and pretreatment conditions on the extent of leaching of the methanol synthesis catalyst. Water and methanol were found to be active participants in the reduction of catalyst activity. Hence, the methanol/water solutions serve as potentially harmful agents in the leaching of aluminum and copper from the synthesis catalyst     

POST-REDUCTION TREATMENT OF LIQUID PHASE METHANOL SYNTHESIS CATALYST USING CARBON DIOXIDE

ABSTRACT

This work focuses on the investigation of the catalyst post-treatment in the liquid phase methanol synthesis process. The novel post-treatment process, using carbon dioxide, has been developed and experimentally proven to be effective not only in maintaining the initial catalytic activity over a long period of usage but also in improving the mechanical and chemical strength of the catalyst. It was also found that the role of ZnO in the catalytic reaction, if any, can be nicely replaced by ZnCO₃.     

REGENERATION OF LIQUID PHASE METHANOL SYNTHESIS CATALYST

ABSTRACT

This work focuses on the influence of changes in catalyst structure on the catalytic activity in liquid phase methanol synthesis process. Long-term methanol production experiments were performed under various reaction environments in order to investigate the relationship between the catalytic activity and the crystallite size in the methanol synthesis catalyst. The regeneration experiments were also conducted in order to reduce the crystallite size of aged catalysts by inducing metallic phase redispersion. The experimental results showed that the drop in the catalytic activity was closely linked to the growth in the crystallite size in the catalyst. The crystallite size was reduced successfully by cyclic oxidation-reduction treatments and as a result the lost activity in aged catalysts was recovered.     

Methanol Conversion to Hydrocarbons over a SAPO-34 Catalyst in a Pulse Micro Reactor

Abstract

The conversion of methanol to hydrocarbons over fresh SAPO-34 catalyst in pulse micro reactor has been studied under different reaction temperatures. The temperature range of 475–500°C is believed to be the optimum range suitable for methanol conversion to hydrocarbon(s); DME was eliminated from the main products, indicating that all methanol almost converted to hydrocarbon(s) at that range. The presence of water increases the olefins selectivity; therefore, the methanol conversion with mixed water/methanol has been studied too. Needless to say, we applied the reaction on different amounts of SAPO-34 catalyst and found out that the amount applied is one of the major factors.     

THE ROLES OF CARBON DIOXIDE IN METHANOL SYNTHESIS

ABSTRACT

The roles played by carbon dioxide in the chemistry of methanol synthesis over CuO/ZnO/A1₂O₃ catalysts have been experimentally investigated. It was concluded based on reaction rate measurements and thermodynamic considerations, that the two reactions that best describe the chemical system of methanol synthesis are the CO₂-hydrogenation and water-gas shift reactions. It was also found experimentally that the presence of CO₂ is vital for maintaining the catalytic activity. The significance of the study is enhanced by the fact that this was the first such investigation of the global chemistry of methanol synthesis to be based on the novel liquid phase process. It was also observed that the rates of methanol synthesis attained a maximum when the concentration of carbon dioxide in the reactor feed was controlled at a certain optimal value. The optimal CO₂ content was found to be a function of the operating temperature and syngas composition. The experimental data are especially important because the apparatus and the operating conditions have been well-defined and carefully chosen to closely simulate industrial reactors.     

THERMAL STABILITY ANALYSIS OF THE LIQUID PHASE METHANOL SYNTHESIS REACTOR

ABSTRACT

The effect of addition of an inert liquid phase on the rate of heat generation in the catalytic synthesis of methanol from syngas has been studied. Gas compositions typical of product gases from Lurgi and Koppers-Totzek gasifiers, represented by H₂-rich and CO-rich syngas respectively, were used to experimentally verify the “slope” and “dynamic” critria in a three-phase fixed bed recycle reactor. The liquid medium, witco-40 oil, has been effective in controlling the rate of heat generation and in preventing catalyst overheating, signifying that the liquid phase synthesis is thermally far more stable than the vapor phase synthesis. The experimental thermal stability study provides crucial and valuable information in commercializing the liquid phase methanol synthesis process. The current approach of thermal stability analysis does not require any a priori assumption or predetermined reaction kinetics.     

Effect of Different Ratios of Si-Al of Zeolite HZSM-5 on the Activity of Bifunctional Catalysts Upon Dimethyl Ether Synthesis

Abstract

Four bifunctional catalysts were prepared by physical mixing of a commercial methanol synthesis catalyst (JC207 catalyst, a catalyst for methanol synthesis, which has been industrialized in China) with zeolite HZSM-5 (Si-Al ratios of 25, 38, 50, 150) as a methanol dehydration catalyst. The bifunctional catalyst (JC207/HZSM-5 [Si/Al = 38]) showed better performance, which can be attributed to more acidic sites with moderate strength of zeolite, and which can control methanol dehydration rate, which is a rate determining step.     

IN-SITU ACTIVATION OF METHANOL SYNTHESIS CATALYST IN A THREE-PHASE SLURRY REACTOR

ABSTRACT

In the liquid phase methanol synthesis process, syngas reacts in the presence.of fine catalyst particles slurried in the oil phase, in a three phase slurry reactor system. A method for activating high concentration ( ?25 wt. %) of the CuO-ZnO-Al₂O₃ catalyst in the catalyst-oil slurry has been successfully developed. This catalyst activation process can be of crucial significance in the research and development of the methanol synthesis process in a liquid entrained reactor.

The reducing gas contains 2% hydrogen in nitrogen mixture and this activation procedure is carried out at a pressure of 125 psi. The catalyst-oil slurry is subjected to a controlled temperature ramping from 110° to 250° C. The catalyst has beemshown to be effectively reduced after following this activation procedure, that is valid especially for high catalyst loadings in slurry. Since the reduction is carried out in the process liquid medium and inside the reactor system, the catalyst-oil slurry after the treatment is ready for the synthesis of methanol.     

A SINGLE-STAGE,LIQUID-PHASE DIMETHYL ETHER SYNTHESIS PROCESS FROM SYNGAS I. DUAL CATALYTIC ACTIVITY AND PROCESS FEASIBILITY

ABSTRACT

A novel process for manufacturing dimethyl ether (DME) from CO-rich syngas in a single stage has been developed. This novel approach was based on the application of dual catalysis in the liquid phase process, in which two functionally different catalysts are slurried in the inert mineral oil. The experimental reaction rate studies for methanol and dimethyl ether synthesis were conducted in a three-phase, mechanically agitated slurry reactor. The effects of catalyst ratio, temperature, and pressure on the dual catalytic activity were studied. The experimental data bear additional significance because this is the first study of such kind to be conducted on the liquid phase methanol synthesis process.     

Sulfuration Pretreatment of Ni/Al2O3 Catalyst to Remove Butadiene in FCC C4 Fraction

Abstract

The Ni-based catalysts have more advantages than the most widely used Pd-based catalysts in selective hydrogenating of the butadiene in fluid catalytic cracking (FCC) C₄ fraction. But the selectivity and stability of the Ni-based catalysts aren't good. The sulfuration pretreatment is an effective process to improve the performance of the Ni/Al₂O₃ catalysts. The sulfuration conditions of the Ni/Al₂O₃ catalyst have been studied in this article. The results showed the fittest conditions are that the catalyst was in-situ presulfurized for 60 min by the solution of S concentration 0.07 mol/L. The X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis indicated that the presulfurization declined the Ni crystal dimension.     

DIRECT CATALYTIC CONVERSION OF METHANE TO HIGHER HYDROCARBONS

Abstract

Using a plug-flow reactor we have been able to demonstrate the conversion of pure methane gas to liquid hydrocarbons via the intermediate formation of methanol. The reaction Was carried out at an intermediate pressure (about 20 atm) and moderate temperature (about 400°C). In the first stage of the reactor methane and oxygen react to produce methanol. In the second stage the methanol was converted by HZSM-5 catalyst to a mixture of hydrocarbons. Analysis of the reaction products showed that all of the oxygen Was used in the reaction. Apart from the unconverted methane the product was composed of oxides of carboy water and C₃+ hydrocarbons. Interestingly, among the liquid hydrocarbons, aromatics were found to be the major constituents.     

PHASES IN THE ACTIVE LIQUID PHASE METHANOL SYNTHESIS CATALYST

ABSTRACT

An attempt has been made to identify the phases present in the active catalyst for liquid phase methanol synthesis. X-ray powder diffraction was used to identify the phases. Only metallic Cu was detected, while no Cu species was found to be present. A significant amount of ZnCO₃ was found to be present in catalysts which had been subjected to high partial pressures of C0₂. This fact has hitherto not been reported in literature. Some speculations about the effect of ZnCO₃ on the life of the catalyst are made.     

Triptane synthesis from methanol and dimethyl ether: A review

The review summarizes and analyzes the results of research in the field of triptane synthesis from methanol and dimethyl ether (DME). The reaction with a fairly high triptane yield occurs in the presence of both homogeneous and heterogeneous catalysts. It has been shown that InI₃ and ZnI₂ are the most commonly used catalysts for the homogeneous process, while zeolite systems based on H-BEA and H-Y are promising catalysts for the heterogeneous process. The effect of the catalyst nature (acidity and structure) on the type of resulting intermediates and the reaction mechanism has been described. Currently available approaches to describing the kinetics of the complex triptane synthesis reaction and the engineering aspects of the process have been discussed.     

Microporous crystalline silicoaluminophosphates: Effect of synthesis conditions on the physicochemical and catalytic properties in the reaction of methanol to C2-C4 olefins conversion

Effect of the synthesis parameters (reaction mixture composition, crystallization temperature and duration) on the physicochemical and catalytic properties of microporous crystalline silicoaluminophosphates (SAPOs) has been studied. Methods for the directional control of phase composition, degree of crystallinity, morphology and size of SAPO crystals crystallized from colloidal silicoaluminophosphate sols stabilized in tetraethylammoniun hydroxide solution as a template have been developed. It has been determined that the use of more severe synthesis conditions (increase in temperature and duration of crystallization) leads to the formation of larger crystals and a growth in the concentration of medium strength sites in the samples, which causes a rapid deactivation of the samples in the reaction of methanol conversion to C₂-C₄ olefins. Crystallization under milder conditions (a decrease in pH and temperature) promotes the acid formation of CHA/AEI intergrowth crystals exhibited a high and steady performance in the methanol conversion for more than 8 h at a total yield of olefins of 95 wt %.     

The direct dimethyl ether (DME) synthesis process from syngas II. Intrinsic kinetics and catalyst deactivation in one-step LPDMEtm process

In Part I of this series, it was seen that the favorable thermodynamic and kinetic coupling in the one-step LPDME^tm process – of methanol dehydration reaction (very rapid kinetics and at/near thermodynamic equilibrium) with the methanol synthesis reaction (slower kinetics and under thermodynamic limitation) – leads the beneficial “chemical synergy”.

In this part II of Series, we briefly discern the intrinsic kinetics of the LPMeOH^tm and LPDME^tm systems, and also shed light of the catalyst deactivation phenomena in these processes. Among the many reports on intrinsic kinetics of the one-step LPMeOH^tm and LPDME^tm processes, two illustrative kinetic studies, from the groups of University of Akron and Air Products and Chemicals, Inc. are highlighted and discussed further. For development of intrinsic kinetic models of LPMeOH^tm and LPDME^tm systems, a detailed thermodynamic framework has been developed which allows one to compute the liquid phase concentrations of reactive species, at phase equilibria and at chemical reaction equilibria. The intrinsic kinetic models of the LPDME^tm system are mainly based on the independent, component kinetic models of methanol synthesis (van den Bussche and Froment, 1996) and methanol dehydration (Bercic & Levec, 1992). From an overarching analysis of the deactivation of supported copper catalysts for methanol synthesis and other reactions (methanol decomposition and methanol steam reforming), we propose that thermal sintering, i.e., increase in Cu particle size and loss of metal surface area, is the only cause of catalyst deactivation in methanol synthesis reactions over Cu/ZnO/Al₂O₃ industrial-type methanol catalysts.     

LIQUID PHASE METHANOL SYNTHESIS IN AN ENTRAINED REACTOR—DEVELOPMENT OF A GAS-LIQUID MASS TRANSFER CORRELATION

Abstract

Research on various aspects of the methanol synthesis was performed in a liquid entrained reactor. The catalyst-oil slurry is pumped through the tubular entrained reactor and syngas is fed cocurrently with the upward flow of slurry. The effect of different operating conditions, syngas composition and catalyst loadings on the productivity of methanol, was studied.

The data obtained from the experiments at high catalyst loadings in slurry, was used to develop a gas-liquid mass transfer correlation for the liquid phase methanol synthesis in an entrained reactor. The productivity of methanol in an entrained reactor was then predicted using the developed mass transfer correlation. This predictive model also helps in the design, development, scale-up and commercialization of the liquid phase methanol synthesis process in an entrained reactor.     

STATISTICAL MODEL FOR SLURRY PHASE METHANOL SYNTHESIS PROCESS IN AN ENTRAINED REACTOR

ABSTRACT

The process feasibility analysis on the liquid phase methanol synthesis (LPMeOH) process was performed in an entrained slurry reactor system. In this three phase mini-pilot plant system, finely powdered catalyst is slurried in the inert oil phase and this catalyst-oil slurry is continuously recirculated through the entrained reactor, where it is contacted with the cocurrent flow of syngas to form the product methanol

The effect of various operating conditions which included the reactor temperature, the reactor pressure, the flow rate of catalyst-oil slurry, the flow rate of syngas, the slurry holdup tank pressure, the syngas composition, and the catalyst loadings in slurry, on the productivity of methanol in the reactor was studied. Using the operating conditions, a statistical reaction rate model not based on the kinetic mechanism, was developed to predict the productivity of methanol in an entrained reactor. The rate of production of methanol predicted by this model agreed well with the experimental results. This statistical model assists in the development, scale-up, and commercialization of the methanol synthesis process in an entrained slurry reactor.     

A SINGLE-STAGE, LIQUID-PHASE DIMETHYL ETHER SYNTHESIS PROCESS FROM SYNGAS III. DUAL CATALYST CRYSTAL GROWTH, DEACTIVATION, AND ACTIVITY CONSERVATION STUDIES

In the liquid phase dimethyl ether (DME) synthesis process, both the methanol synthesis catalyst )composed of CuO, ZnO, and Al₂O₃) and the methanol dehydration catalyst (composed of gamma-alumina) are slurried in the inert oil phase. Various long-term activity checks were conducted on these dual catalysts to characterize the crystal growth and the thermal aging behavior. X-ray powder diffraction, X-ray fluorescence and elemental intensity compositions, and the crystallite size distributions of the aged catalysts were examined. Based on the current investigation, it was established that the crystal growth and the catalyst deactivation problems in the methanol synthesis catalyst are less severe when it is used along with the methanol dehydration catalyst.