Methanol technology developments for the new millennium

Applied Catalysis A: General 221 (2001) 275–282

Methanol technology developments for the new millennium P.J.A. Tijm b,∗ , F.J. Waller a , D.M. Brown a a

Air Products and Chemicals, Inc. 7201 Hamilton Boulevard, Allentown, PA 18195, USA b Rentech Inc., 1331 17th Street, Suite 720, Denver, CO 80200, USA

Abstract This contribution to the “special issue” of Applied Catalysis A: General entitled “Industrial catalytic processes” deals with the development of the methanol process during the last 10–15 years. Following a brief review of the history, the developments to improve methanol synthesis are presented along the lines of elements of catalyst system improvements and of reactor improvements. © 2001 Elsevier Science B.V. All rights reserved. Keywords: Reactor; Pyrolysis; Synthesis gas

1. Overview In 1923, the first synthetic methanol was produced by BASF chemists in Leuna, Germany (German Patent 565 309 in the name of I.G. Farben on 22 September 1923). Some argue that the original inventor was G. Partort who in 1921 filed a French patent in which the “manufacture of oxygenated hydrocarbons by reaction of a gaseous mixture containing CO and H2 ” is claimed. In the early part of the 20th century, there was a drive in the German research and development into high pressure operation with hydrogen and synthesis gas, the so called “hydrerungs verfahrung”. This led, amongst others, to the Haber–Bosch ammonia synthesis, to the now well practiced hydro-desulphurization processes (Bergius, 1920), the Fischer–Tropsch discovery (Hans Fischer and Franz Tropsch, 1923) and the invention to make methanol from synthesis gas components. The development of the methanol synthesis process was started by M. Pier in February 1922 using BASF equipment for ammonia synthesis. ∗ Corresponding author. Tel.: +1-303-298-8008x118; fax: +1-303-298-8010. E-mail address: [email protected] (P.J.A. Tijm).

In 1923, the first tank car of crude methanol was produced. Prior to this, methanol had been produced by “wood distillation” a pyrolysis process with low yields and intensive feed-stock handling. The process (developed by BASF is known as the “high pressure” process, which operated at up to 250–350 bar and 320–450 ◦ C (3500–5000 psig, 600–850◦ F)), remained the dominant technology for over 45 years. Since the synthesis gas employed at that time was based on German coal/lignite, contaminated with chlorine and sulphur, a relatively poison resistant zincoxide/chromium-based catalyst (ZnO/Cr2 O3 ) was developed. A copper-based catalyst had been tried, however, without good results. In the 1960s, Imperial Chemical Industries (ICI, now Synetix) made improvements on the use of the copper concept. They found Zn to be a perfect dispersant for the copper, hence, enhancing the reactivity of the catalyst, allowing for milder operating conditions (called the development of the “low pressure” process 35–55 bar, 200–300 ◦ C (∼500–750 psig, 400–550◦ F)). Today, this is the only process used in a (1999) market of 35 million metric tons production capacity and 28 million metric tons demand. Methanol is mainly produced as chemical grade or grade AA, according

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to the following specifications: Test

Method

Specification

Methanol (wt.%, min.) Water (ppm, max.) Ethanol (ppm, max.) Acetone (ppm, max.) Acidity (acetic acid) (ppm, max.) Alkalinity (ammonia) (ppm, max.) Iron (ppm, max.) Non volatiles (mg/100 ml, max.) Permanganate (minutes, min.) Color (PT-CO, max.) Specific gravity at 25 ◦ C, max. Initial boiling point (◦ C) Distillation range (◦ C, max) Dry point (◦ C) Odor Appearances Hydrocarbons Carbonizables (PT-CO, max.)

ASTM E-346 ASTM E-1064 ASTM E-346 ASTM d-1612 ASTM D-1613 ASTM D-1614 ASTM E-394 ASTMD-1353 ASTM E-1363 ASTM D-1209 ASTM D-891 ASTM D-1078 ASTM D-1078 ASTM D-1078 ASTM D-1296 ASTM E-346 ASTM D-1722 ASTM E-345

99.9 500 20 30 30 30 0.05 1 50 5 0.7893 64.7 ± 0.2 1.0 63.7–65.7 Characteristic Clear Pass 30

The market for this type of methanol is found in chemical and solvent applications, which can be roughly divided into 34% formaldehyde, 28% methyl tertiary butyl ether, 7% acetic acid and 31% various other chemicals/solvents/fuel additive (motor gasoline quality M 85). Pure fuel grade methanol (boiler or gas turbine fuel) is widely discussed as outlet, but has, apart from demonstration applications, not been commercialized. Amongst these demonstrations, Air Products and Chemicals, Inc. has, since 1996, an extensive fuel grade methanol test program going, using the type of raw methanol quality produced through its liquid phase technology. The process route for the production of methanol is relatively simple and comprises of the following three basic steps:

boosted in pressure with a compressor (depending upon the process used) and heated before being added to the circulating loop feeding the methanol converter. Fresh feed is mixed with unconverted recycled synthesis gas and sent to the methanol converter. The mixed gases are fed to the converter with H2 /CO maintained at a ratio of 3:1 to 5:1 for the conventional gas phase process, which in many cases requires equipment where the water gas shift reaction is used to boost the hydrogen content. The liquid phase methanol process, through its superior heat management capabilities, though, can handle the synthesis gas straight from the generator, as it a ratio of 1:1 to 1:2, as typically generated by coal gasifiers. Methanol synthesis from synthesis gas involves the following reaction of carbon oxides with hydrogen:

• production of synthesis gas • conversion of the synthesis gas into methanol—(to be discussed hereafter) • distillation of the reactor effluent to obtain the required product specification

CO + 2H2 ↔ CH3 OH

The cooled synthesis gas from the synthesis gas generator may be water-washed or cleaned up through other processes. The synthesis gas then may be

CO2 + 3H2 ↔ CH3 OH + H2 O In addition, the water gas shift reaction occurs over the copper-catalyst CO + H2 O ↔ CO2 + H2

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Both of the above reactions are exothermic and result in a reduction in volume. The conversion reaction is, therefore, favored by low temperatures and high pressures. Today’s synthesis processes take place at low pressures, some even close to the pressures at which the steam reforming production of synthesis gas operates. These processes use far less energy than high pressure ones as the synthesis gas compression is a costly operation. The reactions are promoted by the use of catalysts, particularly the shift reaction, which allows coal based synthesis gas to be used effectively. Although the equilibrium conditions favor low temperatures, methanol converters must be operated at temperatures in the range 200–300 ◦ C to ensure the catalysts are active and to use the heat of reaction effectively. As the synthesis reactions are strongly exothermic, heat removal is an important part of the process. As the conversion favors high pressures, low pressure processes tend to result in only a low fraction of the synthesis gas being converted in each pass (typically some 10%). Therefore, the processes use a recycle loop to achieve adequate yields, with a purge gas to remove impurities that would otherwise build up over time. The amount of purge depends on the stoichiometric ratio of the reactants in the synthesis gas. For example, when the gas is too rich in carbon oxides, it may be necessary to remove the excess through absorption or adsorption in the form of CO2 . If the gas is too rich in hydrogen, rejection via water is required. In other schemes, though, CO2 injection is contemplated. The role of CO2 in the reaction mechanism has been and still is a subject of discussion between many scientists. Its contribution in reaction models is certainly not well reflected. The current catalysts used in low-pressure methanol synthesis are composed of copper oxide and zinc oxide on a carrier of aluminum oxide. The ratios of the components vary from one manufacturer to another. As a rule, the proportion of CuO ranges between 40 and 80%, that of ZnO between 10 and 30% and Al2 O3 from 5 to 10%. Additives such as MgO may also be present. Such catalysts are manufactured by Synetix (formally ICI Katalco), Süd Chemie (in the US sold by United Catalyst Inc.), Haldor Topsoe, and Mitsubishi Gas Chemical. A good catalyst should remain active for several (up to 4) years, so as to sustain high plant output.

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However, over the time, catalysts may be poisoned by sulfur, chlorine compounds, metal carbonyls or other compounds. More commonly, however, they are deactivated by thermal sintering (copper site clustering) or carbon deposition. Converter designs take this into account, being based on estimated catalyst activity. After an initial period of operation of catalyst, the converter should be able operate at its nameplate capacity even at these so-called “end-of-run” conditions. Developments to improve methanol synthesis are therefore composed of elements of catalyst system improvements and reactor improvements. In the following sections, both elements will be addressed.

2. Current catalysts [1,2] In the last decade, Synetix has developed catalyst 51-7. Sintering is limited by the presence of MgO. Synetix claims that the catalyst has a 30% higher copper surface area than other catalysts. Its research has also indicated that using the Synetix 51-7 and 51-3 catalysts prevents a high proportion of CO2 in the synthesis gas having a permanent effect on the catalyst performance. Research findings have suggested that carbon dioxide-rich conditions may cause irreversible damage to other catalysts. In 1997, Synetix acquired the marketing and manufacturing right of BASF’s S 3-86 methanol catalyst. Süd Chemie (in the US, Union Catalyst Inc.) recent catalyst development has taken a different course. It has stated that the damaging effect high CO2 levels appear to have on methanol catalysts is, in fact, a result of the water formed by the synthesis reaction. The company has also argued that the increasing diversity of converter types, feed-stock and operating conditions found in methanol production has created the need for tailor-made catalysts. With this in mind Süd Chemie has developed two new methanol catalysts to compliment its traditional C79-4 GL catalyst, for use with different types of methanol plants. The two new catalysts have a higher tolerance of carbon oxides (CO and CO2 ) and are designed to show an optimum balance between activity, selectivity and lifetimes, under a range of different industrial conditions, as plant sizes increase. C79-4 GL shows the best selectivity for isothermal reactors using synthesis gas obtained

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from partial oxidation of oil fractions or coal. The new catalysts, C79-5 GL and C79-6 GL, have a different matrix structure, providing a more stable copper crystalline distribution. C79-5 GL has a long lifetime, claimed to be up to 4 years, and is particularly suited for operation in isothermal and adiabatic converters that use synthesis gas obtained by steam reforming. C79-6 GL is designed specifically for use of synthesis gas containing high levels of olefins (e.g. acetylene off-gases). Haldor Topsoe produces a multi-purpose catalyst, MK-101, that has gained industrial experience with most types of converters using synthesis gases obtained from variety different feed-stock and reforming technologies. Topsoe reports that the catalyst has recently been used in an ammonia–methanol co-production unit.

3. New catalyst developments Most recently, Mukerjee, Sassinopoulos and Caradonna, announced their finding of a class of bi-nuclear non-heme iron catalysts, like, e.g. iodosylbenzene as a catalyst to convert methane directly into oxygenated hydrocarbons. However, it seems to be an impractical oxidative catalyst for any product volume of importance. The key to their invention would be to work in H2 O and with O2 . In Japan, Maruyama of the Project Center for CO2 Fixation and Utilization of the Research Institute of Innovative Technology for the Earth, reported the development of a Cu/ZnO type catalyst for methanol synthesis with CO2 and hydrogen. A pellet type catalyst was reported to be under test-run operation in a thirty-one litre reactor. Methanol conversion from carbon monoxide and hydrogen of almost 50% per pass, compared to about 10% for the conventional method, has been claimed by researchers at the Central Research Institute of the Electric Power Institute (Tokyo).The improvement has been made by means of a new catalyst, composed of alkali metal alkoxide, chromium and copper oxides. The synthesis is done at 200–300 ◦ C and less than 50 bar. The catalyst is made by grinding the mixture in a ball mill to create an amorphous structure and very fine particles, which allow for the higher yield.

3.1. Converter developments The most important section of the methanol synthesis process is the reactor or converter. As the methanol synthesis reaction is exothermic, the primary task of all the reactors is to control the reaction temperature. The reactor technologies that have been used extensively in commercial settings fall into two categories. 3.1.1. Gas phase technologies The different options and technology developments are discussed as follows: • Multiple catalyst bed reactors This reactor option controls the reaction temperature by separating the catalyst mass into several sections with cooling devices placed between the sections. Bed sizes are generally designed to allow the methanol reaction to reach equilibrium. The cooling devices can work either by direct heat exchange or by the injection of cool synthesis gas, to limit the adiabatic temperature rise of the very exothermic reaction in each section. • Single bed converters In single bed designs, heat is continuously removed from the reactor by transfer to a heat removing medium. The reactor is run effectively as a heat exchanger. The following paragraphs look at recent two phase (gas–solids) reactor or the so called “gas phase” reactor technologies offered by a range of manufacturers. They are followed by new, innovative three phase (gas–solids–liquid) or “liquid phase” technologies. These liquid phase technologies are contributing to cost reduction in the methanol industry through the simplicity of their converter design. Their potential may well be a driving force behind the methanol industry in the new millennium. In parallel, one also finds a similar trend in the Fischer–Tropsch developments where a shift from the fixed bed reactor to the liquid phase reactor has taken place. 3.1.1.1. Multiple bed converters. 3.1.1.1.1. Haldor Topsoe collect, mix, distribute converter. Haldor Topsoe’s CMD designs are aimed at revamping conventional quench converters. They employ catalyst beds separated by support beams. Gas leaving an upstream catalyst bed is collected and

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mixed with the quench gas. This mixed gas stream is then evenly spread over the downstream catalyst bed. This has the effect of increasing the conversion per pass rate of the synthesis reaction and allows the reaction temperature to be lowered, extending the catalysts life. Haldor Topsoe now has installed CMD revamps in seven quench converters. 3.1.1.1.2. Kellogg, Brown and Root’s (now Halliburton) adiabatic reactors in series. Kellogg, Brown and Root offers technologies featuring more than one adiabatic, fixed-bed reactor in series. Each catalyst layer is accommodated in a separate reactor vessel with intercoolers located between each of the reactors. All of the make-up gas can be fed directly into the first reactor. This increases the kinetic driving force for the reaction and, as a result, the catalyst volume is significantly less than would be required by a quench-type reactor with the same output. The reactors themselves have a spherical geometry that allows the thickness of the pressure shell to be reduced, giving savings in materials and structural costs. The distribution design is simple and offers benefit in constructibility as it lacks complicated internals for heat transfer or flow distribution. (Multi-vessel adiabatic rector systems for methanol production are also offered by Haldor Topsoe and Krupp Uhde.) 3.1.1.1.3. Toyo Engineering Corporation’s MRF-Z® reactor. The MRF-Z® reactor from Toyo Engineering Corporation (TEC) is a multi-stage radial flow reactor with intermediate cooling using bayonet boiler tubes. The indirect cooling system allows the temperature to be kept very close to the path of the maximum reaction rate curve, achieving maximum conversion per pass and reducing the catalyst requirement by 30% compared to quench converters of the same size. The MRF-Z® design was first tested on a large scale in 1993 and TEC is currently constructing advanced versions of the MRF-Z® reactor at a methanol plant in China to convert acetylene off gas into methanol. The company believes that the reactor can be developed to achieve single-train capacities of 5000 t per day. 3.1.1.2. Single bed reactors. 3.1.1.2.1. Linde isothermal reactor. The Linde isothermal reactor is unique, as helically-coiled tubes

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are embedded in the catalyst bed. It resembles a liquefied natural gas heat exchangers with catalyst around the tubes. This arrangement allows for some 50% more catalyst loading per unit of reactor volume. The tubes are wound in a multi-layer arrangement over spacers running the length of the unit. Boiling water circulates through the tubes by natural draft to reach an integral steam drum at the top of the reactor. The heat transfer on the catalyst side for a Linde isothermal reactor is significantly higher than designs with the catalyst inside the tubes. This results in a much smaller cooling area being required, saving on material costs. Linde claims that it is possible that their reactor can be manufactured at such a scale as to produce a single-train capacity of 4000 t per day. 3.1.1.2.2. Lurgi combination converter system. The Lurgi (now metal gesellschaft) methanol reactor is a tube-based converter that contains its catalysts in fixed tubes. The reaction control temperature is controlled by steam pressure control. The reactor is able to achieve high yields and low recycle ratios. For high methanol capacities, Lurgi has developed a two-stage converter system that uses two Lurgi methanol reactors in combination (the Lurgi combi-forming approach). The first converter can operate at higher space velocities and temperatures than a single-stage converter as it needs to achieve only partial conversion of synthesis gas to methanol. This enables the converter to be smaller and the high temperatures allow high-pressure steam to be produced, saving energy costs. The exit gas containing methanol is directed to a second reaction stage that operates at a lower reaction rate. The reaction temperature is reduced across the whole of the catalyst bed to maintain the equilibrium driving force for the reaction. The remaining reaction heat is used to heat feed gas for the first converter. For plant capacities up to 3000 t per day, the two stages can be accommodated in a single vessel. Larger capacities are better accommodated by two separate converters. 3.1.1.2.3. Mitsubishi Gas Chemical/Mitsubishi Heavy Industry superconverter. The superconverter has been jointly developed by Mitsubishi Gas Chemical (MGC) and Mitsubishi Heavy Industry (MHI). It

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has a double-tubular configuration with the methanol synthesis catalyst packed in the annular space between the inner and outer tubes. The feed gas enters the inner tubes through the flexible tubes connected to the bottom dome and is further heated by passing through the inner tubes. The gas then is introduced downwards into the catalyst bed in the annular space. The catalyst bed is cooled by boiler water outside the double tube and feed gas from the inner tubes. Methanol and the unreacted gas exit through a bottom outlet. The temperature profile of the catalyst in the superconverter is different to that of a quasi-isothermal reactor. The catalyst bed temperature is higher near the inlet but gradually lowers toward the outlet by heat exchange with the feed gas. This means that the gas proceeds along the maximum reaction rate line (when methanol concentration is plotted against temperature) at least some of the time giving a high one-pass conversion rate. MGC states that the superconverter’s other advantages include safe operation and a high level of mechanical stability. Mitsubishi has reported successful operation of the first commercial scale (520 t per day) plant using the superconverter at Niigata, Japan, and the superconverter has been incorporated in a study for a new world-scale plant in Saudi Arabia. 3.1.1.2.4. Ammonia Casale redistributing converter. This design is a quench-cooled converter and was developed by ICI Katalco (now Synetix) and Methanol casale. The design differs from ICI’s previous quench-cooled converter in having individual catalyst beds with very effective quench gas redistributors rather than a single lozenge configuration. It is particularly suitable for revamps of lozenge converters, whereby a estimated methanol production capacity increase of 20% can be achieved. ICI claims that the performance of the first ARC converter at Methanex’s methanol plant at Waitara, New Zealand, installed in 1994 has been above expectations. 3.1.1.2.5. Gas phase fluidized bed converter. A project attempting to lower production costs by using new technology to expand the scale of methanol production facilities was started in 1993 by the New Energy and Industrial Technology Development Organization (NEDO) and the Petroleum Endowment

Center (PEC) in Japan [3]. The fluidized bed methanol synthesis converter takes in synthesis gas from the bottom, by which grains of catalyst having a mean diameter of 50–60 ␮m are fluidized. The heat of reaction is removed by cooling pipes. A special feature of the system is that the reaction heat can be collected as high pressure steam. Whereas the conventional process requires the operating temperature to be changed in accordance with the deterioration of the catalyst, the fluidized bed process allows supply and exchange of catalyst during operation, making possible constant and stable operation. 3.1.2. Liquid phase technologies Several research groups have investigated methanol producing technologies using three phase (gas–solids– liquid) systems. This allows, e.g. the methanol to be removed from the reaction area by the liquid as an absorbing medium, but also the heat management is improved. Through pulling the methanol out of the equilibrium reaction and/or “isothermal” operation, these technologies aim to avoid the problems of low conversion and the need for high recycle rates found with conventional fixed bed methods. 3.1.2.1. Liquid phase technology (LPMEOHTM ) by Air Products. One promising liquid-phase process that uses existing, commercial methanol catalysts in fine powder form, suspended in an inert mineral oil has been developed by Air Products. This LPMEOHTM technology has been tested for several years at a pilot plant owned by the US Department of Energy at Laporte, Texas and has in 1997 been put into use at a commercial methanol facility owned by the Air Products Liquid Conversion Co. at Eastman Chemical’s coal gasification complex, located in Kingsport, Tennessee, USA. In the liquid-phase reactor, the mineral oil acts as a temperature moderator and heat removal medium. The heat of reaction is efficiently transferred from the catalyst surface to boiling water in an internal tubular heat exchanger through the mineral oil medium. The temperature control enables the reactor to process synthesis gas that is rich in carbon oxides. In conventional converters, the conversion rate has to be kept low to avoid damaging the catalyst. The more efficient heat transfer in the liquid-phase reactor enables a constant, uniform temperature to be maintained

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throughout the converter. This allows a much higher conversion rate and the number of recycle passes required is greatly reduced. Whereas, the gas phase process typically uses 5:1 recycle ratio, the liquid phase process operates fine with ratios of 1:1 to 2:1. In tests at the La Porte facility, CO concentrations in excess of 50% mol have been tested without any adverse effect on the catalyst. The liquid phase methanol demonstration plant at Eastman Chemical’s complex at Kingsport, Tennessee is now operating under a 4-year commercial-scale demonstration program [6]. Scaling up of the La Porte facility’s output of 3200 gal per day proved successful and a production rate of 80,000 gal per day was achieved within 4 days of the introduction of coal-derived synthesis gas. The process has been shown to be robust enough to operate either in a continuous, baseload manner converting synthesis gas from gasifiers or intermittently. It is easily ramped up and down in capacity and, hence, ultimately suitable to operate in combination with the ‘integrated gasification combined cycle’ concepts. Here, the methanol plant operated only at times of off-peak electric power demand, using excess synthesis gas obtained due to the reduced electricity output from a plant’s combined-cycle power unit. 3.1.2.2. Liquid phase research by Brookhaven National Laboratory. Brookhaven National Laboratory (BNL) in NY, USA has developed a methanol synthesis process (believed to go via methyl formate) that operates at lower pressures than usual (<5 MPa) and low temperatures. The process operates as a homogenous liquid phase system and claims conversion rates in excess of 90%, so high that the synthesis gas recycling is not needed. The low pressure operation, along with the inertness of the catalyst to N2 also allows partial oxidation of natural gas by air, eliminating the need for air separation during synthesis gas manufacture. The research initially used a catalyst based on Ni(CO)4 but recent research, conducted by Amoco (now BP), has resulted in a new catalyst complex in which Ni is ligated with a general formula, NiLx (CO)y . This catalyst avoids the problems caused by the toxicity of Ni(CO)4 and is safe and convenient to handle whilst being just as active. A further benefit is that the new catalyst is not as sensitive to CO2 and H2 O so that, by adding a co-catalyst, it may be possible to avoid

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synthesis gas pretreatment and allow the CO2 and H2 O to pass straight through the methanol synthesis reaction. Since 1995, research into the low pressure, low temperature process has been conducted in collaboration with Amoco [4]. In 1998, a mini-pilot unit was completed by Amoco at its Naperville R&D Center. This trial unit uses a small (50 ml) pressure vessel. Future work will focus on confirming the efficiency of the new catalyst in the pilot unit in preparation for scale-up and commercialization of the technology. The economics of the process are hampered by 1. inadequate utilization of low-quality heat (because of the lower reaction temperature) 2. additional capital costs for Ni(CO)4 containment, and 3. larger reactors needed because of the lower methanol synthesis rate versus the conventional process. 3.2. The Catalytica methanol process Researchers at the Catalytica Advanced Technologies, Inc, Mountain View, CA recently reported to have found the catalyst system that transforms methane into methanol. Initially, they proposed an oxidative process that operates in the liquid phase, using mercury(II) compounds and concentrated sulfuric acid. The sulfuric acid acts as the oxidant with mercury as the catalyst. They reported methane conversions of 50% with a methanol selectivity of 85%. Since the applications of both reactants are environmentally malign, they concentrated subsequently on a platinum complex, described as (bpym)PtCl2 (where bpym stands for 2,2,-bipyridimine). The catalysts are reported to be platinum complexes derived from the bidiazine ligand family that are stable active and selective for the oxidation of a hydro-carbon bond of methane to produce methyl esters. It is reported that the process converts methane to methyl bisulfate with up to 72% yield. However, this process stops at methyl-bisulfate, which must be hydrolyzed to form sulfuric acid, from which the methanol needs to be distilled. The Catalytica team has subsequently stopped all work and given up to break the last step for technology of this type.

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3.3. The slurry phase co-current synthesis of methanol/methyl formate process Researchers at the Pittsburgh University have developed a co-current slurry phase process, which operates under relatively mild conditions (100–200 ◦ C), similar to the BNL approach. The reaction scheme involves carbonylation of methanol to methyl formate, followed by hydrogenolysis of methyl formate to two molecules of methanol—the net result being the reaction of H2 with CO to give methanol. Up to 90% conversion per pass and 98% selectivity to methanol were obtained. The use of temperatures above 170 ◦ C at a pressure of 50 bar were reported to result in methyl formate being the limiting reactant. Latter is a severe limitation and reason why this process was never scaled up. 3.4. Catalytic distillation methanol process Researchers at the University of Trento in Italy [5] have developed a catalytic distillation based methanol process for the production of methanol for H2 and CO/CO2 in the presence of a copper/zinc/alumina catalyst. The use of catalytic distillation has been traditionally limited by the fact that one of the reactants must be a boiling liquid at the conditions in the converter. In order to take advantage of catalytic distillation while reacting the normally gaseous reactants, the process uses an inert condensing medium. This component can be fed separately or mixed with the gaseous feed. 4. Conclusion and perspectives Over the past decade or two, the methanol synthesis process has undergone substantial developments, improving both the performance of the classical catalysts

as well as adding new catalyst systems to the array of choice of methanol manufacturers. Simultaneous developments in methanol converter systems have allowed higher efficiency operation under more robust and larger scale conditions. Hence, operating and capital efficiency improvements have been achieved. The latter have contributed to substantial consolidation of the methanol industry as “world-scale” to “mega-scale” methanol plants are being constructed or proposed in countries with “remote, stranded” gas reserves, at the cost of smaller plants in industrialized countries. Methanol has become a commodity product, which in many cases is only produced at “cash-cost” recovery. Existing excess production capacity, the pressure on the use of MTBE and on the elimination of flaring associated gas (a case where the oil may subsidize the feed gas prize) only underscore this commodity aspect. However, on the bright side, this could open the door for methanol as a cost competitive alternative fuel, e.g. as under-boiler fuel in the power industry (in direct competition with liquefied natural gas in Japan), or as hydrogen carrier for fuel cells. Additionally, the route to chemicals or acetyl precursors from methanol would be favored. “May the market mechanism decide!” References [1] [2] [3] [4]

Chinchen, et al., Chem. Technol. 11 (1990) 692. Waugh, Catal. Today 5 (1992) 51. Matsumoto, et al., Mistsubishi Juko Giho 33 (5) (1996) 318. M. Marchionna, et al., Natural gas conversion, Part V, Stud. Surf. Sci. Catal. 119 (1998). [5] Popardo, et al., Chem. Proc. Alert, 11 June 1999. [6] P.J.A. Tijm, et al., Liquid Phase Methanol (LPMEOHTM ) Project: Operating Experience Update, 1999 Gasification Technologies Conference, San Francisco, CA, 17–19 October 1999.