Ethanol production from ethene

Fig. 8.3 Production of ethanol (a), (b) chemically, from ethene (c) via anaerobic fermentation.

Methanol conversion to hydrocarbons has been studied In a flow micro reactor using a mixture of C-methanol and ordinary C-ethene (from ethanol) or propene (from Isopropanol) over SAPO-34, H-ZSM-5 and dealumlnated mordenlte catalysts In a temperature range extending from 300 to 450 °C. Space velocities (WHSV) ranged from 1 to 30 h. The products were analyzed with a GC-MS Instrument allowing the determination of the Isotopic composition of the reaction products. The Isotope distribution pattern appear to be consistent with a previously proposed carbon pool mechanism, but not with consecutive-type mechanisms. 

As a means of obtaining additional information on the methanol to hydrocarbons reaction over zeohtes we have investigated the reaction between C labeled methanol and ( C) ethene or propene (made in situ from ethanol or isopropanol) over SAPO-34, H-ZSM-5, and dealumlnated mordenlte. The isotopic composition of the reaction products was measured by GC-MS. 

A mixture of formalin and ethanol was passed at 240—320 C over various metal oxides supported on silica gel and metal phosphates. The main products were acrolein, acetaldehyde, methanol, and carbon dioxide. Acidic catalysts such as V-P oxides promoted the dehydration of ethanol to ethene. The best catalytic performances for acrolein formation are obtained with nickel phosphate and silica-supported tungsten, zinc, nickel, and magnesium oxides. With a catalyst with a P/Ni atomic ratio of 2/3, the yields of acrolein reach 52 and 65 mol% on ethanol basis with HCHO/ethanol molar ratios of 2 and 3, respectively. Acetaldehyde and methanol are formed by a hydrogen transfer reaction from ethanol to formaldehyde. Then acrolein is formed by an aldol condensation of formaldehyde with the produced acetaldehyde [40],... 

Finally, the CH2OH radicals react with O2 to give HCHO and HO2 (5.327). Thus, C2 is broken down into Ci species. Fig. 5.34 shows schematically the C2 gas phase chemistry. It is obvious that there is no ethanol formation and acetic acid decomposition, whereas acetaldehyde provides many pathways back to Ci chemistry. Glycolaldehyde is a highly water-soluble product from several C2 species (ethene, acetaldehyde and ethanol) other bicarbonyls, however, are likely to be produced preferably in solution. The aqueous phase produces other C2 speeies but also deeomposes them (Fig. 5.35). By contrast, in aqueous solution from Ci, C2 species can be given as shown by the formation of glyoxal from the formyl radicals (5.351) the latter is... 

The atom economy for the production of ethanol from ethene and steam is shown below. This is known as an addition or hydration reaction. 

Today, ethanol for commercial use is produced by reacting ethene and water at high temperatures and pressures. Ethanol is nsed as a solvent for perfumes, varnishes, and some medicines, such as tincture of iodine. Recent interest in alternative fuels has led to increased production of ethanol by the fermentation of sngars from grains such as com, wheat, and rice. Gasohol is a mixture of ethanol and gasoline used as a fuel. 

Caution must therefore be observed before concluding that polymers based on fossil resources are less sustainable than bio-based polymers, particularly as they have not yet been shown to have better technological behaviour than the commodity synthetic polymers. Indeed, some properties are noticeably inferior. Moreover, if renewable energy is available cheaply in the future, many synthetic polymer feedstocks could be made from natural products. For example, ethene can be manufactured from ethanol, which may in turn be manufactured from carbohydrates. In the short term, polymer feedstocks from natural and fossil resources will co-exist and the primary determinant of the proportion of each utilised will depend on the relative ecological benefits and economics of each. Over the next decade the standards organisations will need to come to terms with the reality that end-of-life disposal is just one of the factors to be weighed in the ecological balance. 

The selective production of methanol and of ethanol by carbon monoxide hydrogenation involving pyrolysed rhodium carbonyl clusters supported on basic or amphoteric oxides, respectively, has been discussed. The nature of the support clearly plays the major role in influencing the ratio of oxygenated products to hydrocarbon products, whereas the nuclearity and charge of the starting rhodium cluster compound are of minor importance. Ichikawa has now extended this work to a study of (CO 4- Hj) reactions in the presence of alkenes and to reactions over catalysts derived from platinum and iridium clusters. Rhodium, bimetallic Rh-Co, and cobalt carbonyl clusters supported on zinc oxide and other basic oxides are active catalysts for the hydro-formylation of ethene and propene at one atm and 90-180°C. Various rhodium carbonyl cluster precursors have been used catalytic activities at about 160vary in the order Rh4(CO)i2 > Rh6(CO)ig > [Rh7(CO)i6] >... 

Earlier we looked at the formation of 2-bromopropane when hydrogen bromide was added to propene, and also the formation of ethanol from ethene reacting with dilute sulphuric acid. Suggest what would be the product of the reaction between propene and dilute sulphuric acid. 

Figure 22a Radioactivity In the alkane fraction of products when i C-labeled ethanol ( ) or ethene ( ) was added to the syngas feed to the C-73 catalyst (CSTR, 262 "C, 7 atm) (from Reference 55).

Apart from labelled ethene,[ ° l FT synthesis was carried out in the presence of other labelled compounds such as ethanol,larger alkenesi and higher alcohols.Most results indicate that more than one mechanism is responsible for the distribution of radioactivity in the products. Figure illustrates that polymerisation of labelled ethene on Co produced more label in even C-number alkanes up to Cio- Almost constant radioactivities were observed in the >Ce products with added propanol. Smaller products showed more incorporated and the monomethyl-alkanes contained more radioactivity. The authors concluded that these alkenes participate both in chain initiation and chain propagation. Alcohols, in turn, initiated chain growth but did not participate in chain propagation on an industrial Fe catalyst.Neither ethene nor ethanol (or ethene formed by its dehydration) participated in the chain termination step. ... 

Table indicates that only a fraction of the C label from ethene was incorporated into chain growth products on Co and Fe catalysts. About the same amount of C (31%) was found in FT products formed with 1[ C]-1-propene, but only 18% when l-[ C]-l-hexadecene was applied.I About 50% of radioactive ethene gave methane, and 50% chain growth products on a Co catalyst, I the specific activity of higher products being practically constant between C4 and C32. Less than 10% of C from labelled ethene was incorporated into C10-C17 products, but the incorporation from C-ethanol was 60-80 times higher on a fused iron catalyst.The difference... 

TTie alcohol of alcoholic beverages, ethanol is prepared by feeding the sugars of various plants to certain yeasts, which produce ethanol through a biological process known as fermentation. Ethanol is widely used as an industrial solvent. For many years, ethanol intended for this purpose was made by fermentation, but today industrial-grade ethanol is more cheaply manufactured from petroleum by-products, such as ethene, as Figure 12.11 illustrates. 

For reaction B (Table 3) the observed ratio of ethanol to ethene is higher than the predicted ratio. This indicates that alcohols are probably not formed by the hydration of alkenes in secondary reactions. The reverse reaction is more likely. The data for reaction C show that the ratio of ethanol to ethane is much higher than expected and so from cases B and C, it appears possible that alcohols could be primary products. 

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