In 1966, an Imperial Chemical Industry (ICI) is the first, which announced the low pressure process for synthesis of methanol using proprietary copper based catalyst.
pressure processes and proprietary copper-based catalyst; these companies included Lurgi, Mitsubishi etc.
Today two processes are mostly used. 1) ICI low pressure (61%) 2) Lurgi low pressure process (27%)
ICI process used Cu-Zn-Al catalyst while Lurgi process used CU-Zn-V or Cu-Mn-V catalyst. Besides the catalyst, these processes differ in their method of temperature control and heat recovery.
ICI use quench type adiabatic converter with multiple catalytic beds. Bed volumes are sized to help control the exothermic methanol synthesis reaction. Additionally, cool feed gas is injected between beds to control or quench catalyst bed inlet temperature. Reaction heat is typically recovered through added heat recovery exchangers located downstream of the converter. Whereas Lurgi used shell and tube (Isothermal type) converter with boiling water for temperature controls. Overall results of quench type converter is best than other type of converter.
The main drawback of water cooled tubular (Isothermal) converter is that internal tube sheets have failed in some tubular isothermal methanol converter design. The long down times associated with a catastrophic converter failure could financially devastate most procedures. In addition converter internal baffles, expansion joints, gas distributors and internal exchangers can fail and cause internal leaks. These components should be extremely rugged to withstand the operating abuse imposed by actual commercial operation.
Cost is another major factor for the selection of process. ICI process has low cost as compare to the other processes. Therefore the ICI process is also called ICI LCM (Low Cost Methanol) factor we select the ICI LCM process.
6.1 DESULPHERIZER CATALYST
Hydrocarbon feeds for steam reforming must have a very low sulfur contents, since nickel reforming catalysts are quite susceptible to poisonings even by levels as low as 0.5PPM. In many cases, sulfur can be removed b y adsorption over a bed of activated carbon at 15-500C. Frequent regeneration may be necessary; which can be accomplished by heating the bed and for stripping it with steam or hot gases. The activated carbon bed adsorbs high boiling sulfur compounds such as mercaptans, much more rapidly than low boiling compounds such as H2S .As a result, adsorption over a sacrificial guard bed of zinc oxide at temperature in the range of 340-370 0C. Hydrodesulphurization may be necessary for organic sulfur compounds that are not removed by either zinc oxide or carbon bed. This is accomplished by mixing the sulfur containing steam with hydrogen, so that the hydrogen contents are approximately 5%, the resulting mixture is passed over a bed of cobalt or nickel molybdate catalyst at temperature of 290-370oC. Under these conditions, sulfur compounds are conditions, sulfur compounds are converted to hydrogen sulfide, which can be removed in a zinc oxide bed. Now a days, codes are used to represent the catalysts shown here: The KATALCO range of absorbents and hydrogenation catalysts ensures an optimized system for meeting individual plant requirements.
Sulfur Removal Catalysts Hydrodesulphurization Catalyst.
KATALCO32-4 KATALCO 41-6
KATALCO 61-1 PURASPEC 2570 These catalysts are used by ICI.
6.2 STEAM REFORMING CATALYST
Reforming catalyst usually contain from 12-25% nickel oxide supported on calcium aluminate titanate. Calcium aluminate has generally replaced calcium aluminum silicate, has support material to avoid the problem of silica migration encountered in earlier catalyst formulation. Alkali metal compounds added to prevent carbon formation and to increase catalyst durability include potassium aluminum silicate, potassium carbonate and potassium poly aluminate, sulfur chlorine and arsenic compounds. Poison the catalyst, sulfur poisoning is reversible, but chlorine and arsenic poisonings are severe and generally irreversible.
Synetix has been associated with pre-
kvaerner process technology recently launched the new CRGLH series of catalysts. These have been demonstrated to be the most active and robust commercially available product for this application.
KATALCO 25-4 KATALCO 57-4 KATALCO 23-4 KATALCO 46-Serie KATALCO 23-4Q KATALCO 25-4Q
6.3 METHANOL SYNTHESIS CATALYST
High Pressure Catalyst
Zinc Chromite catalyst, reduced zinc oxide promoted with Chromia was the catalyst used in the 1st
The zinc Chromite catalyst with improvements over the years was only the catalyst of consequence used for the high process methanol process, up until the high pressure process Although BASF is credited with a 1st commercial methanol process generally attributed to G. TART in FRANCE in 1921. He defined his methanol catalyst has being all metal, oxides and salt active in hydrogenation. Small unit was built near Paris to test catalyst for PARTARTS process and began operation in 1923. The unit was designed to operate at 150-200 atm pressure. 300-6000C, with hydrogen to carbon monoxide feed gas ratio of 2:1.
The BASF high pressure methanol process was operated at 250-3500 C, similar to the conditions purposed by PARTART. Now low pressure, process commonly called ICI low pressure process is used because of its practical feasibility.
6.4 LOW PRESSURE CATALYST
Early in the developing methanol industry, it was recognized that to significantly improve the high pressure methanol process, a much more active catalyst than zinc chromite was needed. A more active catalyst would permit operation at lower temperatures and pressures, yet still allow acceptable production rates to be mentioned. Copper based catalysts known from the known to be much more susceptible to poisoning by sulfur, chlorine, etc. than zinc Chromite, Zinc Chromite, for example, could tolerate sulfur levels of more than PPM in the feed gas, whereas for copper based catalysts, sulfur must be kept below 1 PPM. Generally poor quality of synthesis gas and the limited purification techniques available at that time resulted in an unacceptably short operating life for the copper based, catalysts and precluded their commercial use.
A second breakthrough in the methanol technology occurred in 1966 with the introduction of -pressure process for the production of methanol. This was made possible by a major improvement in synthesis gas quality from the introduction of hydrocarbon steam reforming and improved purification techniques for the hydrocarbon feed stock. The synthesis gas from steam reforming contained only trace quantities of impurities and proved ideal for methanol synthesis with a copper catalyst. The ICI process, using a much more active copper based catalyst could operate efficiently at 50 atm pressure and at temp. of 220-280oC.
The copper based catalyst developed by ICI was also more selective than the high pressure zinc chromite catalyst and operated at a much lower temp. Consequently, it produced a significantly lower of impurities than zinc Chromite as shown in following table.