Low-pressure Methanol Synthesis Research Articles

Preliminary study of the methanol production process from coal to support the coal downstream program

Coal downstreaming is a government program to create a comparative and competitive advantage of coal and its various derivative products. Coal derivative products are expected to be economically competitive with oil and natural gas. One of the coal downstream programs is the production of methanol from coal through the gasification process. The development of the methanol industry will support the government’s program of the transfer from fuel-based oil to biodiesel and will reduce dependence on imports. All types of coal in this study can be used as raw material for the methanol production. The coal with high mositure content ((>40%), prior to the gasification process, a dewatering process is required. The dewatering process chosen is the steam tube drying process, the gasification process with a fixed bed gasifier type, the Davy or Johnson Matthey low pressure methanol synthesis technology and the copper – zinc oxide with aluminum oxide or chromium oxide (Cu – ZnO – Al2O3/Cu – ZnO – Cr2O3) catalyst type.

Reverse Boudouard reforming produces CO directly suitable for the production of methanol from CO2 and CH4

We report the development of a novel process for the production of CO from CO2 and CH4, with CO suitably pure for use in conventional low-pressure methanol synthesis processes over Cu-ZnO-Al2O3 catalysts. The experimentally achieved yield of 3.07 molCO molCH4−1 is substantially higher than the 2 molCO molCH4−1 that is produced, at best, by the dry reforming process. We demonstrate the production of 84-mol%-pure CO (the remainder being CO2) for the first time without any dilution gas or further gas separation required. The syngas prepared by the addition of hydrogen is directly suitable for methanol synthesis, with a stoichiometric number (S = (H2 − CO2)/(CO + CO2)) of 2.05 and a CO2 concentration ≤ 5 mol%, which is achieved in a single packed-bed reactor operated in a cyclic manner. Each cycle consists of two steps, with the CH4 reactant fed in the first step, and the CO2 reactant fed in the second step. After each step, the direction of the gas flow is reversed. Methane cracking produces solid carbon and gaseous H2 in the first step, which is then oxidised by the lattice oxygen of an oxygen storage material to H2O, while CO2 is reduced to CO by the uptake of oxygen by the oxygen storage material in the second step. This is followed by the further production of CO by gasification of the solid carbon by CO2 through the reverse Boudouard reaction. Hence, we refer to this novel process as “reverse Boudouard reforming”.

Hydrogenation of CO2 on NiGa thin films studied by ambient pressure x-ray photoelectron spectroscopy

Successful catalytic conversion of carbon dioxide into high-value chemicals, as a means of abating global CO2 emissions is a pressing challenge. Herein, we report on an ambient pressure x-ray photoelectron spectroscopy study of CO2 hydrogenation reaction using a mixed gas of CO2 and H2 at a pressure up to 0.1 mbar on polycrystalline nickel-gallium thin films prepared by vacuum co-deposition that are compositionally equivalent to Ni, Ni3Ga, Ni5Ga3 and NiGa2, which are some noted low pressure methanol synthesis catalysts. Ni film is very reactive at 300 K, with the reaction sequence initiated by facile CO2 dissociation, yielding C2O4 −2, CO3 −2, CO2 − and CO, but little HCOO− and HCO3 −. The product species observed on NiGa alloy films are not generally different from those observed from using Ni film but are now of different proportions. The NiGa2 film, with the highest Ga content, is the least reactive, as judged by a dominant molecular adsorption feature of CO2. Interestingly, the NiGa alloys are found to undergo composition change and surface restructuring induced by the reactant gas and heating during the reaction. A surface depletion of Ni and a surface enrichment of oxidic Ga are found to occur and continue unabated toward high temperature. For example, for the alloy film with a composition similar to that of Ni5Ga3 when exposed to the mixed gas at 500 K for the duration of measurements (a few h), the near surface region delimited by an XPS probing depth (3λ) of 36 Å is composed of 29% Ni, 24% Ga, and 47% oxidic Ga vs. 62% Ni, 34% Ga, and 4% oxidic Ga for the freshly prepared film at 300 K. Our study demonstrates that a complex interplay exists between the surface reactivity and the evolving chemical makeup as the alloy films are exposed to the reactive gas at elevated pressure and temperature.

Low-pressure methanol synthesis from CO2 over metal-promoted Ni-Ga intermetallic catalysts

Ni-Ga and M-Ni-Ga (M = Au, Co, Cu) catalysts were evaluated for methanol synthesis from CO2 at 10 bar and 200−270 °C. The following trend in turnover frequency (TOF) for CO2 hydrogenation was observed: AuNiGa > CuNiGa > NiGa > CoNiGa, where TOF increased with decreasing catalyst affinity for CO. The presence of a third metal was found to influence both the formation of the Ni-Ga intermetallic phase as well as the number of available sites for CO chemisorption. Phase formation, catalyst composition and stability were evaluated using therm ogravimetric analysis (TGA), X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning transmission electron microscopy and energy dispersive X-ray spectroscopy (STEM-EDX). Au-Ni-Ga, which showed a nearly 4-fold improvement in TOF at 263 °C and 10 bar compared to Ni-Ga, consisted of Ni3Ga particles decorated with Au, as evidenced by post catalysis characterization.

Exergoenvironmental analysis of methanol production by steam reforming and autothermal reforming of natural gas

Methanol is one of the most important chemicals serving as a base for a range of synthetic fuels and variety of other chemical derivates. Steam reforming and autothermal reforming of natural gas represent the major technologies used for syngas production in indirect low pressure methanol synthesis routes. Further process development is driven by technical and economic aspects, while environmental aspects often fade into the background. In this paper methanol production processes using steam reforming and autothermal reforming are investigated from the viewpoint of an exergoenvironmental analysis. The processes feature a coproduction of electricity for high efficiency. The pollutant formation within the chemical conversion units, particularly within the reformer and the furnace, reduces the environmental impact associated with the overall system. The environmental impact of generated methanol and electricity is calculated respectively as 156.4 mPt/kg and 98.2 mPt/MWh for the steam methane reforming process and has values of 134.0 mPt/kg and 71.3 mPt/MWh for the autothermal reforming process.

The effect of metal additives in Cu/Zn/Al2O3 as a catalyst for low-pressure methanol synthesis in an oil-cooled annulus reactor

• Annulus reactor minimising the influence of heat produced on the catalytic activity. • Zr addition to the commercial Cu/ZnO/Al 2 O 3 catalyst enhanced the methanol yield. • CO 2 conversion reduced for Zr modified Cu/ZnO/Al 2 O 3 catalyst. • The addition of Ga and Mg reduced the performance of the Cu catalyst. • Reducibility and copper crystallite size strongly influenced catalyst activity. The effect of metal additives, including Zr, Mg, and Ga, on the conventional Cu/ZnO/Al 2 O 3 (CZA) catalyst, was investigated for methanol synthesis using an oil-cooled annulus reactor. The annulus reactor was found to reduce the temperature gradient within the diluted catalyst bed by effective cooling and thus provide experimental data at steady-state and in kinetic regime allowing for the comparison of intrinsic activity between different catalysts. The addition of Zr enhanced the overall performance of methanol synthesis. However, the CZA-Zr catalyst displayed significantly reduced CO 2 conversion, possibly due to intensified water-gas shift reaction activity. The addition of Ga and Mg to CZA was found to be detrimental to the catalytic performance and is attributed to difficulties in reducibility and the increased crystalline size of copper particles. A relatively long induction period was observed for CZA-Zr sample in this study, which is attributed to the effective cooling imparted by the annulus reactor suppressing the r-WGS reaction.

Low-Pressure Hydrogenation of CO2 to CH3OH Using Ni-In-Al/SiO2 Catalyst Synthesized via a Phyllosilicate Precursor

The overall objective of this research is to convert the increasingly concerning CO2 and renewable H2 to highly demanded methanol (CH3OH), which creates a win–win scenario for simultaneous climate change prevention and sustainable economic development. The key to the success of this targeted CO2 utilization technology is the development of low-pressure methanol synthesis catalysts (NiaInbAl/SiO2; a = 0–8.3, b = 0–9.1) by means of a phyllosilicate precursor, allowing for formation of well-dispersed metallic particles with an average diameter of 2.5–3.5 nm. The catalysts were characterized with various methods including ICP-OES, N2 physisorption, XRD, SEM, TEM, TGA, H2 TPR, DRIFTS, and XPS. The performances of the NiaInbAl/SiO2 catalysts and conventional catalyst were compared under various evaluation temperatures at ambient pressure. It was found that catalysts with Ni/In ratios of 0.4–0.7 showed the highest activity. Ni3.5In5.3Al/SiO2 (NIA-0.7) with 15% metal loading was the best among the tested NiaInbAl...

A promising low pressure methanol synthesis route from CO2 hydrogenation over Pd@Zn core–shell catalysts

We report a new Pd@Zn core–shell catalyst that offers a significantly higher kinetic barrier to CO/H2O formation in CO2 hydrogenation but facilitates CH3OH production at below 2 MPa with CH3OH selectivity at 70% as compared to 10% over Cu catalysts.

High-performance hybrid oxide catalyst of manganese and cobalt for low-pressure methanol synthesis.

Carbon dioxide capture and use as a carbon feedstock presents both environmental and industrial benefits. Here we report the discovery of a hybrid oxide catalyst comprising manganese oxide nanoparticles supported on mesoporous spinel cobalt oxide, which catalyses the conversion of carbon dioxide to methanol at high yields. In addition, carbon-carbon bond formation is observed through the production of ethylene. We document the existence of an active interface between cobalt oxide surface layers and manganese oxide nanoparticles by using X-ray absorption spectroscopy and electron energy-loss spectroscopy in the scanning transmission electron microscopy mode. Through control experiments, we find that the catalyst's chemical nature and architecture are the key factors in enabling the enhanced methanol synthesis and ethylene production. To demonstrate the industrial applicability, the catalyst is also run under high conversion regimes, showing its potential as a substitute for current methanol synthesis technologies.

The role of copper particle size in low pressure methanol synthesis via CO2 hydrogenation over Cu/ZnO catalysts

The size of copper nanoparticles exerts a significant influence on the selectivity of the hydrogenation of carbon dioxide to methanol.

Washcoating and chemical testing of a commercial Cu/ZnO/Al2O3 catalyst for the methanol synthesis over copper open-cell foams

We herein present the preparation of washcoated copper open-cell foam prototypes by dip-blowing a ball-milled aqueous slurry made of commercial powdered Cu/ZnO/Al2O3 methanol catalyst, deionized water and methylhydroxyethylcellulose. We then show the results of the chemical testing of such prototypes in the low temperature-low pressure methanol synthesis at relevant industrial conditions (i.e. T=505K, P=50 bara, H2/CO/CO2/CH4/N2 feed molar ratio=73.2/8.3/2.6/5.1/11.2). Three levels of temperature (485, 505 and 525K) were investigated, keeping constant all the other operating conditions. The performances were compared to those of the original powder.We found that washcoated copper foams coated with a 75μm thick catalytic layer were active in the methanol synthesis, but showed lower COx conversion and MeOH productivity than the original powder. Slurried powders (i.e. slurry dried and calcined) showed the same chemical activity as the washcoated foams, therefore ruling out any effect related to the deposition step and singling out the slurry preparation and/or calcination procedure as responsible for a change in the catalytic performances.We also tested the same catalytic systems in the reverse-water–gas-shift (RWGS) reaction at P=1 bara, T=505K and with H2/CO2=20. The campaign of low pressure tests confirmed the lower activity of slurried powders with respect to the original catalytic powder and leads us to the conclusion that the RWGS reaction can be considered as a representative probe reaction for ranking the intrinsic activity of Cu/ZnO/Al2O3 methanol catalysts without requiring testing under the high pressures typical of the commercial methanol synthesis process.

Low-Temperature and Low-Pressure Methanol Synthesis in the Liquid Phase Catalyzed by Copper Alkoxide Systems

We report a new very low temperature methanol catalyst system that is produced in situ by the reaction of Cu(CH3COO)2, NaH, and methanol. The catalytic reaction is assumed to proceed in two steps: (i) formation of methyl formate from syngas and (ii) hydrogenation of methyl formate to two molecules of methanol. When the catalyst system is tested in a batch reactor, syngas conversion of 50–75% is achieved at a temperature of 60–120 °C and a pressure of 10–20 bar. Syngas generation is a major cost factor in current commercial methanol technology. Very high conversion per pass (low reaction temperature) in the methanol reactor would allow for the use of air for syngas generation (autothermal reforming or partial oxidation reaction) and thereby contribute to potential cost reduction.

Liquid-Phase Low-Temperature and Low-Pressure Methanol Synthesis Catalyzed by a Raney Copper-Alkoxide System

Current CuZnO methanol synthesis technology may be improved by development of a catalyst allowing a “once through” methanol synthesis step. A Raney copper/alkoxide catalyst has been reported in the patent literature operating at 50 bar and 120 °C. We report here the effect of temperature, pressure, Raney copper concentration and CH3OK concentration by orthogonal array design on this catalyst system. A synergistic effect on catalyst activity and methanol formation has been observed between CH3OK and Raney copper.

Intrinsic kinetics study of LPDME process from syngas over bi-functional catalyst

Abstract The intrinsic kinetics of the three-phase dimethyl ether (DME) synthesis from syngas over a bi-functional catalyst has been investigated in a agitated slurry reactor at 20–50 bar, 200–240 °C and H 2 /CO feed ratio from 1 to 2. The bi-functional catalyst was prepared by physical mixing of CuO/ZnO/Al 2 O 3 as methanol synthesis catalyst and H-ZSM-5 as methanol dehydration catalyst. The three reactions including methanol synthesis from CO and H 2 , methanol dehydration and water gas shift reaction were chosen as the independent reactions. A kinetic model for the combined methanol and DME synthesis based on a methanol synthesis model proposed by Graaf et al. [G.H. Graaf, E.J. Stamhuis, A.A.C.M. Beenackers, Kinetics of low pressure methanol synthesis, Chem. Eng. Sci. 43 (12) (1988) 3185; G.H. Graaf, E.J. Stamhuis, A.A.C.M. Beenackers, Kinetics of the three-phase methanol synthesis, Chem. Eng. Sci. 43 (8) (1988) 2161] and a methanol dehydration model by Bercic and Levec [G. Bercic, J. Levec, Intrinsic and global reaction rate of methanol dehydration over γ-Al 2 O 3 pellets, Ind. Eng. Chem. Res. 31 (1992) 399–434] has been fitted our experimental data. The obtained coefficients in equations follow the Arrhenius and the Van’t Hoff relations. The calculated apparent activation energy of methanol synthesis reaction and methanol dehydration reaction are 115 kJ/mol and 82 kJ/mol, respectively. Also, the effects of different parameters on the reactor performance have been investigated based on the presented kinetic model.

Methanol Synthesis Over Cu and Cu-Oxide-Containing $ \hbox{ZnO}/\hbox{Al}_{2}\hbox{O}_{3}$ Using Dielectric Barrier Discharge

Initially developed for more than 20 years ago, the copper over zinc and aluminum oxide (ZnO/Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> ) catalyst system is used for low-pressure methanol synthesis. Recently, the Cu/ZnO/Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> (CZA) was shown to be active in a dielectric-barrier discharge (low-temperature plasma). In this paper, the investigation on the copper as the active site of the catalyst was discussed on the basis of experimental results and its characterization analysis. The catalyst was attempted to aid the reaction performance of partial oxidation of methane in order to produce methanol. All CZA-based catalysts were successful in increasing methanol selectivity, and the Cu oxide performed better than a metallic-copper catalyst.

Preparation and activity measurement of some low pressure methanol synthesis catalysts

In the present study, twenty four catalysts for low pressure methanol synthesis were prepared according to a pre-designed research program consisting of three stages. In each stage, applying the experimental design techniques, a number of catalysts were synthesized by the co-precipitation method, using different proportions of metal salts solutions. The activities of the catalysts were determined applying a laboratory scale continuous packed bed reactor. It was noted that the calcinations temperature, ageing time and molar ratio of metal nitrates to precipitant, had the highest effects on the activity of the catalysts.

Modeling, simulation and control of a methanol synthesis fixed-bed reactor

In this paper, the dynamic behavior and control of the low pressure methanol synthesis fixed bed reactor have been investigated. For simulation purpose, a heterogeneous one-dimensional model has been developed. First, the reactor simulation is carried out under steady-state condition and the effects of several parameters such as shell temperature, feed composition (especially CO 2 concentration) and recycle ratio on the methanol productivity and reactor temperature profile are investigated. Using the steady state model and a trained feedforward neural network that calculates the effectiveness factor, an optimizer which maximizes the reactor yield has been developed. Through the dynamic simulation, the system open loop response has been obtained and the process dynamic is approximated by a simple model. This model is used for the PID controller tuning and the performances of fixed and adaptive PID controllers are compared for load rejection and set point tracking. Finally the proposed optimizer is coupled with a controller for online optimization and hot spot temperature protection.

Operability of an Industrial Methanol Synthesis Reactor with Mixtures of Fresh and Partially Deactivated Catalyst

Disposal of spent catalyst is a common practice in industrial methanol synthesis. However, the spent catalyst has, generally, a good level of activity and can be used if mixed with fresh catalyst. In this work the operation of an industrial methanol synthesis reactor with mixtures of fresh and partially deactivated catalyst was investigated using a one-dimensional transient model. Analysis of the deactivation behavior of low-pressure methanol synthesis catalyst shows there is an extremely sharp rate of deactivation in a small part of the catalyst life-time, which is followed by a relatively slow rate of deactivation in the remaining catalyst cycle-time. Different configurations were studied for catalyst recycling, and two limiting cases are discussed in detail in this paper, namely layered and homogeneous (mixed) bed models. In the first one, the catalyst was segregated into two alternate layers of fresh and partially deactivated catalyst, while in the second homogeneity of the catalyst bed was simulated by segregating a large number of alternate layers of fresh and partially deactivated catalyst. It was observed in both cases that when catalyst recycling is used, the process does not depart significantly from the standard operating conditions, and also that the mixed bed had less influence on the reactor performance than layered one.

Modelling of methanol synthesis in a network of forced unsteady-state ring reactors by artificial neural networks for control purposes

A numerical model based on artificial neural networks (ANN) was developed to simulate the dynamic behaviour of a three reactors network (or ring reactor), with periodic change of the feed position, when low-pressure methanol synthesis is carried out. A multilayer, feedforward, fully connected ANN was designed and the history stack adaptation algorithm was implemented and tested with quite good results both in terms of model identification and learning rates. The influence of the ANN parameters was addressed, leading to simple guidelines for the selection of their values. A detailed model was used to generate the patterns adopted for the learning and testing phases. The simplified model was finalised to develop a model predictive control scheme in order to maximise methanol yield and to fulfil process constraints.

Complex dynamic behaviour of methanol synthesis in the ring reactor network

The dynamic behaviour of a three reactors network (or ring reactor), with periodic change of the feed position, was investigated in a previous work for low pressure methanol synthesis, showing that cyclic steady-states and autothermal processing can be obtained, leading to higher conversions than traditional devices. Furthermore, complex dynamics—highly periodic steady-states and multiplicity of periodic steady-states—may arise, close to the conditions of maximum conversion. A simple open loop control policy, which can be useful for a safe start-up, was also tested to study the response of the network to disturbances on the input parameters, showing that a more robust control strategy is needed for this application.