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.     

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

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.     

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.     

The direct dimethyl ether (DME) synthesis process from syngas I. Process feasibility and chemical synergy in one-step LPDMEtm process

A novel one-step process for co-production of dimethyl ether (DME) and methanol, in the liquid phase, was conceived as an advance over the liquid phase methanol synthesis process (LPMeOH^tm). This direct, one-step DME process (LPDME^tm) is based on the application of “dual catalysis”, where 2 functionally different yet compatible catalysts are used as a physical mixture, well-dispersed in the inert liquid phase. Three different reactions, methanol synthesis (via CO and CO₂), water-gas shift, and methanol dehydration (to form DME) take place over the 2 catalysts, Cu/ZnO/Al₂O₃ and typically γ-Al₂O₃. The thermodynamic and kinetic coupling of methanol dehydration reaction (very fast and at/near thermodynamic equilibrium) with the methanol synthesis reaction (slower kinetics and highly thermodynamic) leads to the observed “chemical synergy”. This synergy helps overcome the limitation on thermodynamic equilibrium conversion, and increases the per-pass syngas conversion and reactor productivity. The catalyst deactivation phenomena in LPDME^tm proess is also greatly alleviated compared to methanol alone; the increase in syngas conversion and methyl equivalent productivity (MEP) are sustained over a longer on-stream time.

Here, in this review, we survey the salient developments in the LPDME^tm process since its inception, first at UA research laboratories and elsewhere including Air Products and Chemicals, Inc. We demonstrate the rationale of the LPDME^tm process, and then outline briefly the research studies in the two processes, that illustrate the chemical synergy in the LPDME^tm process. This successful example of “cooperative catalysis” can be adapted in principle to many other organic reactions.     

KINETIC RATE EXPRESSION FOR METHANOL SYNTHESIS IN A LIQUID ENTRAINED REACTOR

Abstract

In the three phase entrained reactor for the liquid phase synthesis of methanol, the catalyst-inert oil slurry is pumped through the tubular reactor and syngas is fed to the reactor cocurrently with the upward flow of slurry.

According to an elaborate experimental design plan, the effect of different operating conditions on the liquid phase synthesis of methanol in an entrained reactor, was studied. The parameters of this experimental study included reactor temperature, reactor pressure, slurry flow rate, syngas flow rate, slurry holdup tank pressure, and syngas composition.

The data obtained from the experiments at low catalyst loading in slurry, were used to develop a kinetic rate expression for the liquid phase methanol synthesis process in an entrained reactor. This in turn helps the scale-up and commercialization of the methanol synthesis process in an entrained reactor.     

STATISTICAL ANALYSIS OF REACTION RATE DATA OF LIQUID PHASE SYNTHESIS OF DIMETHYL ETHER FROM METHANOL

Abstract

The liquid phase catalytic dehydration of methanol to dimethyl ether (DME) is a key reaction step in the single-step synthesis of DME from CO-rich syngas in a slurry reactor. The effect of process variables including temperature, pressure, impeller speed, and feed methanol flow rate on DME synthesis rate has been studied by a systematic 24 full factorial experimental design with single replicate. The significant effects and interactions have been quantified by F-tests. The estimates of significant effects have been obtained by Yates' algorithm. Residual probability and normal probability dots have been obtained to test model adequacy. Finally, a computational model has been developed to predict the DME synthesis rate alt various values of process variables. The model has excellent interpolational predictive capability as evidenced by parity plots.     

浆态床CO加氢制二甲醚的工艺条件研究

在反应温度为２６０～３００℃，反应压力为３．０～５．０ＭＰａ，进料空速为４０００～７０００ｍｌ／（ｇ．ｈ）范围内，研究了浆态床ＣＯ加氢制二甲醚过程中工艺条件对双功能催化剂的性能的影响。在２６０～２８０℃温度范围内，ＣＯ、Ｈ２转化率、二甲醚生成速率及其选择性均随反应温度的升高而增加，２８０℃达到最高值。在进料空速为４０００～６０００ｍｌ／（ｇ．ｈ）范围内，提高进料空速可提高二甲醚和甲醇当量生成速率，但ＣＯ单程转化率降低，继续提高进料空速，二甲醚生成速率反而降低，而甲醇生成速率几乎不受空速的影响。随着反应压力的增加，ＣＯ转化率、二甲醚生成速率以及甲醇生成速率均增加。     

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

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

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.     

与发电联合的新型二甲醚生产流程设计和分析

研究了一种将二甲醚(DME)合成与发电结合的新型流程,它采用甲烷空气催化部分氧化造气、含氮合成气制DME、尾气发电等技术,通过化工生产过程和动力过程的整合,既省去了昂贵的空分设备,又成功地降低了大量氮气带来的负面影响;使用AspenPlus对该联产流程进行了模拟,并在此基础上对新流程的能量和整体性能进行了详细分析,结果表明,在DME生产中使用甲烷空气造气并与发电联合是提高能量转换率和降低DME生产成本的一条新途径。     

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.     

催化剂比例与温度对浆态床合成气制二甲醚的影响

采用甲醇合成催化剂和甲醇脱水催化剂组成的双功能催化剂，在两者比例１～１０和反应温度２６０～３００℃范围内，研究了浆态床合成气制二甲醚双功能催化剂的性能，发现催化剂比例对催化活性影响显著。在催化剂比例１～３范围内，ＣＯ、Ｈ２转化率和二甲醚生成速率随催化剂比例的增大而很快升高，在催化剂比例３～７时达最高值，而后缓慢下降；双功能催化剂间存在协同作用，可显著提高二甲醚与甲醇当量生成速率；温度对二甲醚选择性影响显著，随着温度升高，烃类选择性增加，二甲醚选择性相应降低。最佳催化剂比例为３～５，与此匹配的反应温度为２８０～２９０℃     

KINETIC RATE EXPRESSION FOR METHANOL SYNTHESIS IN A LIQUID ENTRAINED REACTOR

In the three phase entrained reactor for the liquid phase synthesis of methanol, the catalyst-inert oil slurry is pumped through the tubular reactor and syngas is fed to the reactor cocurrently with the upward flow of slurry.

According to an elaborate experimental design plan, the effect of different operating conditions on the liquid phase synthesis of methanol in an entrained reactor, was studied. The parameters of this experimental study included reactor temperature, reactor pressure, slurry flow rate, syngas flow rate, slurry holdup tank pressure, and syngas composition.

The data obtained from the experiments at low catalyst loading in slurry, were used to develop a kinetic rate expression for the liquid phase methanol synthesis process in an entrained reactor. This in turn helps the scale-up and commercialization of the methanol synthesis process in an entrained reactor.     

浆态床反应器中含氮合成气合成二甲醚的研究

Cu ZnO Al2O3甲醇合成催化剂和HZSM 5分子筛通过机械混合制备了合成气直接合成二甲醚催化剂,并在浆态床反应器中进行了含氮合成气制二甲醚的研究,考察了各种工艺条件对二甲醚合成性能的影响。结果表明:转子转速、原料气空速、反应压力和温度均对催化剂的反应性能有影响。采用浆态床反应器合成二甲醚,可实现等温操作并可使反应热及时移出,从而避免催化剂床层形成热点,使催化剂失活减缓,但CO转化率和二甲醚选择性相对较低。采用浆态床反应器与固定床反应器集成技术,不仅可以解决催化剂床层形成热点问题,还可得到90%的CO转化率和75%的二甲醚选择性,并使催化剂保持高的稳定性,二甲醚收率为68%。     

STATISTICAL ANALYSIS OF REACTION RATE DATA OF LIQUID PHASE SYNTHESIS OF DIMETHYL ETHER FROM METHANOL

The liquid phase catalytic dehydration of methanol to dimethyl ether (DME) is a key reaction step in the single-step synthesis of DME from CO-rich syngas in a slurry reactor. The effect of process variables including temperature, pressure, impeller speed, and feed methanol flow rate on DME synthesis rate has been studied by a systematic 24 full factorial experimental design with single replicate. The significant effects and interactions have been quantified by F-tests. The estimates of significant effects have been obtained by Yates' algorithm. Residual probability and normal probability dots have been obtained to test model adequacy. Finally, a computational model has been developed to predict the DME synthesis rate alt various values of process variables. The model has excellent interpolational predictive capability as evidenced by parity plots.     

MODELING OF A LIQUID ENTRAINED REACTOR FOR LIQUID PHASE METHANOL SYNTHESIS PROCESS

ABSTRACT

The liquid phase methanol (LPMeOH^TM) synthesis process is to be commercially carried out in a liquid entrained reactor (LER), where the catalyst-inert oil slurry is pumped through the reaction zone along with the syngas fed separately. A computer model was developed based on the experimental results, for the LPMeOH^TM process in a liquid entrained reactor. This computer program accurately predicts the multicomponent phase equilibria, ultimate chemical equilibria and the compositions of each reactant and product species exiting in the entrained reactor. The prediction of the results of this modeling agrees well with the experimental data from the LaPorte pilot plant entrained reactor.     

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.     

THE ROLE OF WATER IN METHANOL SYNTHESIS

Abstract

This work focuses on the influence of water in determining the rate of methanol synthesis over CuO/ZnO/Al₂O₃ catalysts. The experimental investigations were conducted in a 1-L slurry reactor based on the novel liquid phase methanol synthesis process. The liquid medium used was a blend of paraffinic and naphthenic mineral oils with a mean molecular mass of 250. It was found that the methanol rates attained a maximum at an optimal water content which was dependent on the reaction temperature. The catalytic activity was found to decline with time at lower temperatures in the presence of a relatively large excess of water. The influence of water was also found to be firmly linked to the corresponding carbon dioxide content in the reactor feed. The experimental data bear additional significance because this was the first such study to be performed on the liquid phase process. Emphasis was therefore placed on the use of a CO-rich syngas in order to simulate anticipated process conditions.     

METHANOL PRODUCTIVITY COMPARISON BETWEEN AN AGITATED SLURRY REACTOR AND AN ENTRAINED REACTOR

ABSTRACT

The effect of various operating conditions including the catalyst loading in slurry, on the productivity of methanol in an agitated slurry reactor were studied. The modeling of the mechanically agitated slurry reactor was performed with the aid of the reaction rate expression and the gas-liquid mass transfer correlation that were developed, to predict the rate of methanol production for any inlet condition

The equilibrium limitation encountered in the liquid phase methanol synthesis process in an agitated slurry reactor can be alleviated by conducting this process in an entrained reactor, where the product methanol formed is continuously flashed out of the system. After developing a kinetic rate expression and a gas-liquid mass transfer correlation, the modeling of the entrained reactor was performed to predict the reactor productivity for any process condition. The rate of methanol production predicted for nominally identical operating conditions in an entrained reactor and in a mechanically agitated slurry reactor are compared with the aid of the computer models developed