From Syngas To Methanol And Dymethylether

From syngas to methanol and dimethylether Ferruccio Trifiro` Summer School September 2009 Bologna

Content of the lecture • 1) Synthesis of methanol from syngas • 2) Synthesis of dimethylether (DME) from methanol • 3) Synthesis of DME directly from syngas

Global production of methanol • The global production of methanol is about 40 million ton per year, most of which is produced from natural gas. Today, the high price of oil and natural gas has spurred new interest in alternative feedstocks for the production of methanol. • Various types of biomass have been considered, but on the shorter term coal appears to be the only viable alternative raw material for large scale methanol production. • In fact, methanol has been produced from • coal for many years in specific geographical areas, notably in China.

From methanol to fuels • • • •

1) Methanol to DME (alternative to Diesel) 2) Methanol for fuel cell 3) Methanol for production of MTBE 4) Methanol as fuel (altenatives to gasoline) • 5) Methanol for production of hydrogen • 6) Synthesis of gasoline (MTG process)

From methanol to chemicals chloromethanes Formaldehyde

Di-methylterephthalate

Methyl formiate

Methyl amines

Methanol

Acetic Acid

Methyl methacrylate

From methanol to to olefins • The different technologies for the future SDTO DME

SYNGAS CH3OH

OLEFINS MTO

From MTP Methane Coal Municipal wastes Recycled plastics Biomass Organic

PROPYLENE

Synthesis of methanol • CO+2H2 CH3OH ΔH298k=-90.6kJmol-1 • Methanol synthesis is the second largest process after ammonia which use catalysts at high pressure • The mechanism is believed to be • CO+H2O-> CO2+H2 ΔH298k=-41.2kJmol-1 • CO2+2H2->CH3OH+H2O ΔH298k= -49kJmol-1

Operative conditions for methanol synthesis • Catalyst : CuO(60-70%)- ZnO(20-30%) –Al2O3 (515%)or Cr2O3 (5-15%) • Temp 220oC-300oC • Pressure 50-100Atm (5-10MPa) • Composition of the feed 59 -74%H2 27- 15% CO 8% C02 3%CH4 • Conversion of CO to methanol per pass is normally 16– 40 %. • H2 : CO ratio of 2.17. • The selectivity is around 99.8 %

Commercial Technologies • Today there are four catalyst suppliers and six companies complete proprietary processes for methanol synthesis : ICI, Lurgi, Topsøe, Mitsubishi, M.W. Kellogg and Uhde. • Design figures for converters can be as high as 2,500-10,000 tonnes for day • A good catalyst in a natural gas-based plant may over its lifetime of about 4 years

Ways to improve the yield in methanol 1) The reaction is exothermic and favored at low temperature, for this reason is necessary to remove the heat to keep the reaction temperature as low as possible in order to increase the conversion 2) To remove methanol during the synthesis in order to shift the equilibrium to higher CO to methanol conversion per pass (through the DME formation) 3) To develop more active catalysts which operate at lower temperature, increasing the thermodynamically allowed conversion

Equilibrium CO conversion to methanol (H2/CO=2) Conversion 11 CO

50bar

0,5

400

I s o t h e r m a l 450

CO +2H2->CH3OH

100 bar

adiabatic 500

550

600

K Temperature

The factors affecting on the production The factors affecting on the production rate in an industrial methanol reactor are: 1)the thermodynamic equilibrium limitations 2) The catalyst deactivation. Two zones could be distinguished in the methanol synthesis reactor with imprecise transition point. A)The first zone starts from reactor entrance and continues to a point that conversion approaches to equilibrium. In this zone the kinetics controls the process, so increasing temperature improves the rate of reaction which leads to more methanol production. B) In the second zone the process switches to equilibrium and as the temperature increases the deteriorating effects of equilibrium conversion emerge and decreases methanol production

Factors which influence activity • Methanol synthesis gas is characterised by the stoichiometric ratio (H2 – CO2) / (CO + CO2), often referred to as the module M. A module of 2 defines a stoichiometric synthesis gas for formation of methanol. • A high CO to CO2 ratio will increase the reaction rate and the achievable per pass conversion. In addition, the formation of water will decrease, reducing the catalyst deactivation rate. • High concentration of inerts will lower the partial pressure of the active reactants. Inerts in the methanol synthesis are typically methane, argon and nitrogen.

Methanol Megaplant • The capacity of methanol plants is increasing to reduce investments, taking advantage of the economy of scale. • The capacity of a world scale plant has increased from 2500 MTPD a decade ago to about 5000 MTPD today. • Even larger plants up to 10,000 MTPD or above are considered to further improve economics and to provide the feedstock for the Methanol-toOlefin (MTO) process.

The main sections of methanol plant • 1) In the first section of the plant natural gas is converted into synthesis gas. • 2) In the second section, the synthesis gas reacts to produce methanol • 3) In the tail-end of the plant methanol is purified to the desired purityl with eventually the hydrogen recycle • 4) utilities •

The role of the syngas production • In the design of a methanol plant the three sections may be considered independently, and the technology may be selected and optimised separately for each section. • The synthesis gas preparation and compression typically accounts for about 60% of the investment, and almost all energy is consumed in this process section. Therefore, the selection of reforming technology is of paramount importance, regardless of the site.

The production of syngas • The preferred technologies are: • 1) tubular steam reforming • 2) two-step reforming (tubular steam reforming followed by autothermal or oxygen blown secondary reforming) • 3) Autothermal Reforming (ATR) at low steam to carbon (S/C) ratio is the preferred technology for large scale plants by maximising the single line capacity and minimising the investment.

Methanol Synthesis and Purification • Raw methanol is a mixture of methanol, a small amount of water, dissolved gases, and traces of byproducts. • Typical byproducts include DME, higher alcohols, other oxygenates and minor amounts of acids and aldehydes • The methanol synthesis catalyst and process are highly selective. A selectivity of 99.8% is not uncommon.

The design of the reactor • The methanol synthesis is exothermic and the maximum conversion is obtained at low temperature and high pressure. • A challenge in the design of a methanol synthesis is to remove the heat of reaction efficiently and economically

BWR

Quench reactor

Multiple Adiabatic

Tube cooled

Quench reactor • A quench reactor consists of a number of adiabatic catalyst beds installed in series in one pressure shell. In practice, up to five catalyst beds have been used. The reactor feed is split into several fractions and distributed to the synthesis reactor between the individual catalyst beds. • The quench reactor design is today considered obsolete and not suitable for large capacity plants

Quench reactor • Conversion CO to methanol Conversion CO

Temperature

Adiabatic reactors • . • A synthesis loop with adiabatic reactors normally comprises a number (2-4) of fixed bed reactors placed in series with cooling between the reactors. The cooling may realized be by preheat of high pressure boiler feed water, generation of medium pressure steam, and/or by preheat of feed to the first reactor. • The adiabatic reactor system features good economy of scale. Mechanical simplicity contributes to low investment cost. The design can be scaled up to single-line capacities of 10,000 MTPD or more.

Multiple layers adiabatic converters C • conversion O N • CO

Equilibrium curve

V E R S I O

Maximum reaction rate curve

N

Temperature

BWR REACTOR • The BWR(boilng water reactor) is in principle a shell and tube heat exchanger with catalyst on the tube side. Cooling of the reactor is provided by circulating boiling water on the shell side. By controlling the pressure of the circulating boiling water the reaction temperature is controlled and optimised. The steam produced may be used as process steam, either direct or via a falling film saturator. • The isothermal nature of the BWR gives a high conversion compared to the amount of catalyst installed. However, to ensure a proper reaction rate the reactor will operate at intermediate temperatures - say between 240ºC and 260ºC - and consequently the recycle ratio may still be significant.

Equilibrium CO conversion to methanol (H2/CO=2) Conversion 11 CO

50bar

0,5

400

I s o t h e r m a l 450

CO +2H2->CH3OH

100 bar

adiabatic 500

550

600

K Temperature

Several industrial processes ICI adiabatic single bed reactor: the heat of reaction is removed by adding cold reagent at different heights in the bed Lurgi two multitubular reactor: the heat of reaction is removed in the first reactor by boiling water around bed in the second reactor by gas Haldor Topsoe several adiabatic reactors: arranged in series intermediate cooler remove heat of reaction Air product-Chem system three phase fluidized bed: reactor an inert hydrocarbon liquid inside the reactor remove the heat Casale isothermal reactor: the heat is removed by plates immersed in the catalysts

Lurgi Mega Methanol plant • Lurgi‘s Mega Methanol process is an advanced technology for converting natural gas to methanol at low cost in large quantities. • It permits the construction of highly efficient single-train plants of at least double the capacity of those built to date.

The MegaMethanol Concept The Lurgi MegaMethanol® technology has been developed for world-scale methanol plants with capacities greater than one million metric tons per year. The main process features to achieve these targets are: ■1) Oxygen-blown natural gas reforming, either in combination with steam reforming, or as pure autothermal reforming. ■ 2)Two-step methanol synthesis in water- and gascooled reactors operating along the optimum reaction route. ■ 3) Adjustment of syngas composition by hydrogen recycle.

Lurgi reactor

Lurgi reactor Main features The Lurgi reactor is nearly isothermal and the heat of reaction is used to generate high pressure steam which is used to drive the compressor and as distillation steam Advantages Optimum temperature profile Very high gas synthesis conversion Large reduction of catalyst volume Lower gas recycle High energy efficiency

Lurgi reactor- conversion versus temperature

The synthesis gas production The synthesis gas production section accounts for 60 %of the capital cost of a methanol plant. Thus, optimisation of this section yields a significant cost benefit. Conventional steam reforming is economically applied in small and medium-sized methanol plants, with the maximum single-train capacity being limited to about 3000 mtpd. Oxygen-blown natural gas reforming, either in combination with steam reforming or as pure autothermal reforming, is today considered to be the best suited technology for large syngas plants. The configuration of the reforming process mainly depends on the feedstock composition which may vary from light natural gas (nearly 100% methane content) to oilassociated gases.

Lurgi autothermal conversion Light Natural gas desulphurization

Steam reforming Autothermal reforming •.

Methanol synthesis Methanol distillate PURE METHANOL

Air Air separation

Process steam oxygen

Autothermal Reforming Pure autothermal reforming can be applied for syngas production whenever light natural gas is available as feedstock to the process. The desulfurised and optionally pre-reformed feedstock is reformed with steam to synthesis gas at about 40 bar and higher using oxygen as reforming agent. The process generates a carbon-free synthesis gas and offers great operating flexibility over a wide range to meet specific requirements. Reformer outlet temperatures are typically in the range of 950–1050 °C.

Lurgi combined reforming Heavy natural gas or oil desulphurization

Air

Air separation

Pre reforming Autothermal reforming •.

oxygen FUEL GAS

Methanol synthesis Methanol distillate PURE METHANOL

Hydrogen recovery

Lurgi Combined Reforming For heavy natural gases and oil-associated gases, the required stoichiometric number cannot be obtained by pure autothermal reforming, even if all hydrogen available is recycled. For these applications, the Lurgi MegaMethanol® concept combines autothermal and steam reforming as the most economic way to generate synthesis gas for methanol plants. After desulfurisation, a feed gas branch stream is decomposed in a steam reformer at high pressure(35–40 bar) and relatively low temperature (700–800°C).The reformed gas is then mixed with the remainder of the feed gas and reformed to syngas at high pressure in the autothermal reactor. This concept has become known as the Lurgi Combined Reforming Process.

The dual Lurgi reactors

Based on the Lurgi Methanol Reactor and the highly active methanol catalyst with its capability to operate at high space velocities, Lurgi has recently developed a dual reactor system featuring higher efficiency. The isothermal reactor is combined in series with a gas-cooled reactor The first reactor, the isothermal reactor, accomplishes partial conversion of the syngas to methanol at higher space velocities and higher temperatures compared with single stage synthesis reactors. This results in a significant size reduction of the water-cooled reactor compared to conventional processes, while the steam raised is available at a higher pressure. .

Lurgi Mega Reactors

Lurgi reactor- conversion versus temperature

Water cooled reactor

Gas cooled reactor

First reactor for Methanol Synthesis The Lurgi Methanol Reactor is basically a vertical shell and tube heat exchanger with fixed tube sheets. The catalyst is accommodated in tubes and rests on a bed of inert material.The water/steam mixture generated by the heat ofreaction is drawn off below the upper tube sheet. Steam pressure control permits exact control of the reaction temperature.This isothermal reactor achieves very high yields at low recycle ratios and minimizes the production of by-products.

Second reactor for methanol synthesis The methanol-containing gas leaving the first reactor is routed to a second downstream reactor without prior cooling. In this reactor, cold feedgas for the first reactor is routed through tubes in a countercurrent flow with the reacting gas. Thus, the reaction temperature is continuously reduced over the reaction path in the second reactor, and the equilibrium driving force for methanol synthesis maintained over the entire catalyst bed. As fresh synthesis gas is only fed to the first reactor, no catalyst poisons reach the second reactor. The poisonfree operation and the low operating temperature result in a virtually unlimited catalyst service life for the gascooled reactor.

Advantages of the Combined Synthesis Converters ■ High syngas conversion efficiency. At the same conversion efficiency, the recycle ratio is about half of the ratio in a single-stage, water-cooled reactor. ■ High energy efficiency. About 0.8 t of 50–60 bar steam per ton of methanol can be generated in the reactor. In addition, a substantial part of the sensible heat can be recovered at the gas-cooled reactor outlet. ■ Low investment cost. The reduction in the catalyst volume for the water-cooled reactor, the omission of the large feedgas preheater and savings resulting from other equipment due to the lower recycle ratio translate into specific cost savings of about 40% for the synthesis loop. ■ High single-train capacity. Single-train plants with capacities of 5000 mt/day and above can be built.

Methanol Distillation The crude methanol is purified in an energy-saving 3-column distillation unit with the 3-column arrangement, the higher boiling componentsare separated in two pure methanol columns. The first pure methanol column operates at elevated pressure and thesecond column at atmospheric pressure. The overhead vapours of the pressurised column heat the sump of theatmospheric column. Thus, about 40% of the heatingsteam and, in turn, about 40% of the cooling capacity aresaved. The split of the refining column into two columns allows for very high single-train capacities.

Lurgi Plant

ICI Reactor

cold

Quench reactor • Conversion CO to methanol Conversion CO

Temperature

ICI process

ICI

TOPSOE REACTORS

methanol

Conversion versus temperature

Topsoe Methanol Process • Based on the unique methanol catalyst, MK-121, Haldor Topsøe has developed a methanol synthesis process. the heart of the synthesis unit is the methanol reactor, a tubular reactor with catalyst loaded into several tubes surrounded by a bath of boiling water. The boiling water efficiently cools the process while at the same time steam is produced that can be used outside the methanol synthesis unit. The design of the reactor ensures that the methanol synthesis is carried out at an almost isothermal reaction path at conditions close to the maximum rate of reaction. This ensures a high conversion per pass and a low formation of by-products.

Topsøe's methanol synthesis catalyst MK-121 . Based on an optimised copper dispersion MK-121 ensures a better preservation of the initial high catalyst activity as well as an improved stability compared to its predecessor, MK-101, while at the same time attaining a remarkable selectivity. resulting in low by-product formation over the entire service life. Since the higher activity of MK-121 allows operation at lower temperatures, where conditions for by-product formation is less favourable, the total .

Topsoe Catalyst MK121

Topsoe catalyst MK 121

Catalyst Loading The procedure used for catalyst loading is extremely important, as the catalyst performance depends heavily on even flow distribution. Therefore, the catalyst should be loaded as uniformly as possible to ensure that the catalyst is utilised efficiently. Besides that, the catalyst should be packed as densely as possible in order to maximise the installed catalyst activity. Topsøe has developed new loading methods, which increase loading density of the catalyst and improve the flow distribution through the catalyst bed(s) in various types of methanol converter designs. Furthermore, Topsøe is continuously studying existing loading procedures in order to develop new innovative techniques for installing catalyst.

Fluid bed reactor from Air products

Air product Chem system • Main features • Demonstration plant in Texas • The catalyst is suspended in inert hydrocarbon liquid which limits the temperature rise and it adsorbs the heat liberated • Advantages • a higher single pass conversion can be achieved reducing the syngas compression costs • increase of life of catalyst • Contains low amount o water 1% (the gas phase 4-20% of water • It is possible to work with 50% CO entering feedstocks

Casale Reactor • The use of axial-radial flow,e, can solve the problem, of reducing the pressure drop of a converter. This design can be obtained easily with the use of plates as cooling surface area, The flow of cooling gas inside the plates can have the same direction of the gas in the catalyst, that is in a horizontal direction, cocurrent or counter-current (see figure) • It is clear that an axial radial design leads to a much slimmer vessel for the same catalyst volume, allowing to reach capacities above 7’000 MTD in a single vessel converter.

Axial radial plate cooled reactor

Axial radial catalyst bed

Methanol Casale reactors At present more than 10 million tons per year of methanol are produced worldwide with Methanol Casale technologies • Methanol Casale’s synthesis converter technology allows substantial and cost-effective capacity increases in conventional methanol plants • Methanol Casale is currently licensing, providing basic design and supplying critical equipment for a 7,000 t/d methanol plant • A 7,000 t/d plant can be built based on a single methanol converter. They are the only contractors able to build real single train, efficient plants with this capacity •

Casale and the revamping of methanol plant •

.

• , Methanol Casale has also become a leader in revamping complete methanol plants and in designing and constructing new ones. Key achievements in plant upgrading include capacity increase, reduced specific consumption of synthesis gas, and improvement in the quality of the raw methanol. • They revamped 21 ICI plants

Linde reactor • The Linde isothermal reactor is a fixed bed reactor with indirect heat exchange suitable for endothermic and exothermic catalytic reactions. This reactor provides the benefits of a tube reactor while simultaneously avoiding the heat tension problems of a straight tube reactor. Gas/gas, gas/liquid and liquid/liquid reactions can be carried out. The palpable head of gases and liquids as well as the latent evaporation heat can be used for cooling or heating operations. • The heating or cooling tube bundle embedded in the catalyst transfers the reaction heat in such a way that the catalyst can work at an optimum temperature. This results in higher outputs, a longer catalyst lifetime, fewer by-products as well as efficient recovery of the reaction heat and lower reaction costs.

Linde reactor • Linde isothermal reactor, cross-section with catalyst and tube bundle • The development of the Linde reactor was carried out with a particular view toward exothermic reaction and steam generation. • The reactor is based on the design of the specially wound heat exchangers, with which Linde has been able to collect decades of experience in its own production facilities. The Linde isothermal reactor is in operation worldwide in more than 19 plants, among them eight methanol plants.

Linde Reactor • Isothermal reactor

Section Linde reactor

Linde reactor • . The main principle is that the cooling coil in the catalyst bed removes the heat of reaction allowing the catalyst to operate at it's optimum temperature. This results in higher performance, longer catalyst life, reduction of by-products, as well as in high efficiency reaction heat recovery and lower cost of the reactor. •

TOYO REACTOR

Toyo

Toyo reactor • Applicable to 5,000 - 6,000 t/d class large scale methanol plant with a single train design • Low Pressure Drop through Catalyst Bed and Low Utility Consumption • Mild Operating Conditions for Long Catalyst Life • Maintenability for catalyst exchange

Toyo

TOYO REACTOR

DME in two steps

DME in one step

From methanol to DME • DME synthesis based on methanol dehydration process is very simple. • 2 CH3OH -> 2DME + H2O • The dehydration of methanol is a gas phase and exothermic reaction, the heat of reaction (approx.23 kj/mol) is considerably small compared with methanol synthesis reaction. • The selectivity of DME in methanol dehydration is very high and is approx. 99.9 %. • Dehydration catalyst is of gamma alumina basis

Operative conditions for DME • Feed methanol is fed to a DME reactor after vaporization. • The synthesis pressure is 1.0 - 2.0 MPa. • The inlet temperature is 220 - 250 °C and the outlet is 300 - 350 °C. • Methanol one pass conversion to DME is 70 – 85 % in the reactor.

DME Plant • 1) Produced DME with by-product water and unconverted methanol is fed to a DME column after heat recovery and cooling. • 2) In the DME column DME is separated from the top as a product. Water and methanol are discharged from the bottom and fed to a methanol column for methanol recovery. 3) The purified methanol from the column is recycled to the DME reactor after mixing with feedstock methanol. The methanol consumption for DME production is approximately 1.4 tonmethanol per ton-DME.

DME PLANT RAW METHANOL

METHANOL COLUMN

DME COLUMN DME REACTOR

D M E DC Mo El u m n

FUEL GAS

C H3 O H DME TANK

WATER

DME from syn- gas • . The synthesis of DME from synthesis gas involves three reactions: • 1) CO2+3 H2->CH3OH+H2O • 2)CO+H2O-> CO2+H2 • 3) 2 CH3OH ->2CH3OCH3 +H2O • The introduction of Reaction (3), the DME synthesis, serves to relieve the equilibrium constraints inherent to the methanol synthesis by transforming the methanol into DME. Moreover, the water formed in Reaction (3) is to some extent driving Reaction (2) to produce more hydrogen, which in turn will drive Reaction (1) to produce more methanol. Thus, the combination of these reactions results in a strong synergetic effect, which dramatically increases the synthesis gas conversion potential.

From syngas to DME • The catalyst applied is a proprietary dual-function catalyst, catalyzing both steps (i.e., methanol and DME synthesis) in the sequential reaction. Significant advantages arise by permitting the methanol synthesis, the water–gas shift, and the DME synthesis reaction to take place simultaneously. This methanol synthesis is restricted by equilibrium, which requires high pressure in order to reach an acceptable conversion • A dual catalyst system is based on a combination [of Cu/ZnO/Al2O3 catalyst and gamma-alumina (this issue) catalyst.:

Dalian Institute of Chemical Physics • In the mid-1990s, DICP was awarded two patents in the United States concerned with the conversion of methanol/dimethyl ether (DME) to light olefins. These patents are the basis for the syngas via dimethyl ether to olefin process (SDTO).

Catalyst foDME from syngas • Bifunctional metal (Cu, Zn, etc.)-zeolite catalysts have been developed, which can convert syngas very selectively to DME with high carbon monoxide (CO) conversion (this reaction is far more favorable thermodynamically than methanol synthesis from syngas). • . • ).

Advantages of SDTO • Syngas to DME breaks the thermodynamic limit of syngas to methanol system with up to over 90 percent CO conversion, 5-8 percent investment savings and 5 percent operational cost savings. • Syngas to DME breaks the thermodynamic limit of syngas to methanol system with up to over 90 percent CO conversion, 5-8 percent investment savings and 5 percent operational cost savings.

Storage and Handling of methanol •

.

Methanol is stable under normal storage conditions. but can react violently with strong oxidizing agents. • The greatest hazard involved in handling methanol is the danger of fire or explosion.. Methanol is aggressive toward copper, zinc, magnesium, tin, lead, and aluminum, which should therefore be avoided. Similarly, the use of plastics for storage is not recommendedBoth floating- and fixed-roof tanks are used for large-scale methanol storage. • Blanketing the tank vapor space in combination with a closed vent recovery system may be required by local environmental regulations. •