Methanol synthesis catalyst

Methanol production methods

Methanol is produced in various ways from different raw materials. The most significant and common process is applying fossil fuels for coal and natural gas. Methanol production processes are one of the most significant and highly applied instances for the chemical industry. In 1923, a method was suggested to produce methanol using synthetic gas and zinc and chromium oxide catalysts at 300 to 400 degrees Celsius and at a pressure of 250 to 350 atmospheres while in contact with judged coal. Preferably, reactions at lower temperatures, such as 230 to 250 degrees Celsius and pressures of 40 to 50 atmospheres, led to a 75% improvement in reactor energy consumption.

The process of methanol synthesis can be regarded a process with obvious and proven technology. Several new technologies for the methanol process are currently being investigated.

Traditional and common processes for methanol production

Methanol production has three major stages:

• Synthesis gas production
• Conversion of synthesized gas to methanol
• Distillation of reactor output to achieve high methanol content

Synthesis gas is made up of a combination of carbon monoxide, carbon dioxide and hydrogen, which is applied to understand the amount of their composition using a stoichiometric number. This number is the result of dividing the difference between hydrogen and carbon moles by the sum of carbon dioxide moles with carbon monoxide. Ideally for methanol production, the stoichiometric number of the synthesized gas must be 2. But, this number is greater than 2 in most industrial cases which shows that we need more hydrogen to begin the process in the synthesis gas mixture, and this needs feed adjustment for the synthesis gas production process. For instance, in the process of producing synthetic gas with natural gas input, the stoichiometric number is from 2.8 to 3. It depends on adjusting the reactor conditions to handle a catalytic reaction and identifying the penetration of the reactors into the pore. The highest penetration in the methanol production process occurs in the gaseous state, which is at a pressure of 10 to 100 atmospheres and a temperature of 200 to 300 degrees Celsius. Its catalysts are based on copper, which is composed of copper oxide, zinc oxide and aluminum oxide.

Natural gas reforming to achieve synthetic gas is the most significant and extensive process to produce synthetic gas. To do this, other carbon-based materials are applied instead of coal, gasoline, heavy oil, oil cookies and gas. The selection of these alternative materials depends on the economic, political, energy and environmental conditions.

Uses of methanol

Methanol is one of the most significant chemicals in manufacturing, petrochemical, fuel and additives. One of the most usual applications of methanol is its applying to produce methyl tert-butyl ether, acetic acid dimethyl ether formaldehyde. These account for 70% of the world’s methanol consumption. Many products, such as plastic and silicone adhesives, are also made from methanol. Methanol can be used as a vehicle fuel, either individually or in combination with diesel. Adding methanol to pure fuel increases immunity, resulting in fewer Noxs and Soxs being burned. Methanol as a hydrogen carrier can be used as a fuel cell improver in vehicles. Methanol is also one of the feedstocks for the reaction of producing diesel charge from vegetable oils and methyl tertiary butyl ether by esterification method. Liquid methanol is mentioned as an option for storing and transferring energy instead of hydrogen. Hence, this is only if we can move products to environmentally friendly methods, which are the same as green methods. Methanol with an octane number of 113 has a higher energy density than liquid hydrogen, also has a higher methanol density and does not require a very low temperature environment (such as minus 253 degrees Celsius) to maintain it.

Catalytic systems

The present catalysts were mainly composed of a combination of copper oxide, zinc oxide and aluminum oxide, the percentage of the composition of each of the catalysts in each plant and company is different. The percentage of copper oxide in the composite is about 20 to 80%, the percentage of zinc oxide is about 13 to 50% and the percentage of aluminum oxide is between 4 to 30%. Additions to these compounds, such as magnesium oxide, chromium-based materials, oxide trace elements, and silicates, can also be added to the catalyst.

Magnesium oxide was initially applied by Johnson UK in the form of doped in katalco51-7 catalyst and was marketed. Magnesium oxide was utilized in subsequent catalysts called katalco51-8 and katalco51-9 with different percentages. Nowadays, the selectivity of these catalysts is more than 99%.

Copper is the major active ingredient in this catalyst. Aluminum oxide is applied as a catalyst enhancer and zinc oxide as a base, which helps to better disperse copper and stabilize it. There are many theories about the active sites in these catalysts, which are mainly divided into two general categories:

• Some researchers believe that copper is dispersed in a mass of zinc oxide.
• Others believe that copper is spread on the surface of zinc oxide.

Strofsky observed that the active sites were composed of dispersed copper. The efficiency of the catalyst in question depends on its stability and life, hence all efforts are made to stabilize the copper on the surface shown in the operating conditions. Deactivation of this catalyst is only in terms of the destruction of pores and poisoning of catalyst.

Conversion of carbon dioxide to methanol

Now, the conversion of carbon dioxide to hydrocarbons like methanol is of great interest, especially if solar energy and photocatalysts are applied. Hydrogen is the main reaction material provided from the electrolysis of water. Electric energy is determined for the electrolysis of water from renewable energies such as wind, solar and biomass.

• Catalytic method of carbon dioxide hydrogenation for methanol production

Carbon dioxide can be catalytically hydrogenated to methanol. This follows reaction x. Furthermore, methanol produced in the same reactor can be converted to dimethyl ether. Methanol production in a single step via carbon dioxide is up to 10 times less than the conventional mode. Methanol conversion catalysts are as follows:

The difference in efficiency of these catalysts is due to the fact that the water produced acts as an inhibitor along with methanol. Various studies indicate that copper metal has a very high catalytic property, especially when it sits on the catalyst with other metals, which increases the amount of zinc oxide and aluminum oxide in this activity by up to 5%. The best system available is to dope copper or zirconium oxide or silicon oxide and place them on a very strong base. Thus, the activity of a catalyst is directly related to the effective level and availability of whole catalyst. Moreover, the base in carbon dioxide conversion catalysts highly affects the conversion rate as well as selectivity.

There are methods to convert synthetic gas to methanol and carbon dioxide to methanol by hydrogenation, and efforts are always made to handle these reactions at lower operating conditions, durations, temperatures, and pressures. This is despite the fact that according to the stoichiometry of the reaction, it is noted that increasing the temperature increases the speed of the reaction, but it should also be regarded that increasing the temperature increases the pressure and each of these two factors causes disruption. It becomes a catalyst and shortens the life of the catalyst. This means that a very good ratio and optimization must be created between the temperature, the rate and the percentage of conversion.

One of the issues in reactor on an industrial scale is the unavailability of hydrogen and carbon dioxide, which requires three molecules of hydrogen per molecule of carbon dioxide. Hence, two major Japanese and Icelandic companies which produce methanol from the hydrogenation of carbon dioxide, supply hydrogen and carbon dioxide from renewable materials and energies, such as the decomposition of water by sunlight, geothermal energy, and so on.