Methanol, production energy requirement

One disadvantage of this technology is the large energy requirement of the first, highly endothermic, step. The process is also inefficient in the sense that it first transforms methane in an oxidative reaction to carbon monoxide, which, in turn, is reduced to methanol, and the latter is oxidized again to formaldehyde. The direct conversion of methane, therefore, would be a more efficient way in the production of methanol and formaldehyde. 

More recently, the use of a pyridinium mediator in an aqueous p-GaP photo-electrochemical system illuminated with 365 nm and 465 nm light has been reported [125], In this case, a near-100% faradaic efficiency was obtained for methanol production at underpotentials of 300-500 mV from the thermodynamic C02/methanol couple. Moreover, quantum efficiencies of up to 44% were obtained. The most important point here, however, was that this was the first report of C02 reduction in a photoelectrochemical system that required no input of external electrical energy, with the reduction of C02 being effected solely by incident fight energy. 

Figure 9 shows a schematic process of biodiesel production by the two-step supercritical methanol method. Several advantages have been attributed to the two-step reaction method. At temperature of 270°C, a common type of 316 stainless steel can fulfill the requirements of good corrosion resistance and cover the reaction condition (5). Energy requirements may be less because mild reaction conditions for hydrolysis and methyl esterification are employed, whereas high-temperature treatment causes operational and equipment problems with, in some cases, the formation of undesirable degradation products. In addition, a reaction temperature of 270°C is commonly used in industries, so such a reaction condition is applicable for commercial applications. 

A number of potential sources of synthesis gases have been advanced in recent years, many due to the 1972 energy crisis in the U.S. These sources require much effort and development before they become applicable. However, the production of synthesis gas is a crucial consideration because of the large impact it has on the cost of the methanol product. 

A remarkable step change to existing technology has been 1996 the introduction of the Cativa technology by BP Chemicals (now BP Amoco). This process incorporated the first commercial use of iridimn (promoted by iodine, Ru-salt etc.), rather than rhodimn, as a catalyst for methanol carbonylation. The main improvements of the process are much higher reactivity (45 mol L h, Rh 10-15 mol L h ) coupled with low by-product formation and lower energy requirements for the purification of the product acid. 

Acyclic E alkenes are usually more stable than acyclic Z alkenes because they are less steri-cally hindered. Yet Z alkenes do not spontaneously convert to E alkenes because the tc bond prevents free rotation the energy required to break the n bond is about 260 kj mol" (rotation about a a bond requires about 10 kJ mol" ). You may therefore find the following result surprising. Dimethyl maleate is easily made by refluxing maleic anhydride in methanol with an acid catalyst. If the product is isolated straight away, a liquid boiling at 199-202°C is obtained. This is dimethyl maleate. However, if the product is left to stand, crystals of dimethyl fumarate (the E isomer of dimethyl maleate) form. How has the geometry been inverted so easily ... 

Based on the analysis and comparison of the mentioned chemical reactions, it can be known that 0 In the main reaction, it is easy to produce methyl nitrite, which makes it difficult to increase the total yield the product is not stable under acidic conditions 0 dimethyl sulfate is very easy to decompose into methanol under acidic and basic conditions 0 dimethyl sulfate reacts with sodium nitrite through two steps, in which the first step is the conversion of dimethyl sulfate into the intermediate methyl sulfonate followed by the higher energy-required reaction between methyl sulfonate and sodium nitrite, thus, in this step, the formation of byproduct methanol should be minimized through the hydrolysis of acid and base. 

To show the energy savings, the four flowsheets were simulated on the basis of an equimolar feed of 2,700 kmol/hr, producing 96 mol% methanol in the distillate and 4 mol% methanol in the bottoms product, assuming 75% tray efficiency and no heat loss to the surroundings, and using UNIFAC to estimate the liquid-phase activity coefficients. The total energy requirements for the four alternatives were computed as follows ... 

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