Alcohols synthesis process

The alkalized zinc oxide—chromia process developed by SEHT was tested on a commercial scale between 1982 and 1987 in a renovated high pressure methanol synthesis plant in Italy. This plant produced 15,000 t/yr of methanol containing approximately 30% higher alcohols. A demonstration plant for the lEP copper—cobalt oxide process was built in China with a capacity of 670 t/yr, but other higher alcohol synthesis processes have been tested only at bench or pilot-plant scale (23). 

Figure 6 Basic flow-scheme of the alcohols synthesis process.

Membrane separation processes are always considered in comparison with some other more conventional separation processes, when their economic feasibility is examined. Often, membrane separation alone is not necessarily economically advantageous, but a synergetic effect can be expected when membrane separation is combined with another separation process, in a hybrid system. One such system was proposed by UOP Engineering Products to be incorporated into the oxo-alcohol synthesis process [331]. The oxo-alcohol plant has the following three main operations ... 

Isobutyl alcohol [78-83-1] forms a substantial fraction of the butanols produced by higher alcohol synthesis over modified copper—zinc oxide-based catalysts. Conceivably, separation of this alcohol and dehydration affords an alternative route to isobutjiene [115-11 -7] for methyl /-butyl ether [1624-04-4] (MTBE) production. MTBE is a rapidly growing constituent of reformulated gasoline, but its growth is likely to be limited by available suppHes of isobutylene. Thus higher alcohol synthesis provides a process capable of supplying all of the raw materials required for manufacture of this key fuel oxygenate (24) (see Ethers). 

There are two main processes for the synthesis of ethyl alcohol from ethylene. The eadiest to be developed (in 1930 by Union Carbide Corp.) was the indirect hydration process, variously called the strong sulfuric acid—ethylene process, the ethyl sulfate process, the esterification—hydrolysis process, or the sulfation—hydrolysis process. This process is stiU in use in Russia. The other synthesis process, designed to eliminate the use of sulfuric acid and which, since the early 1970s, has completely supplanted the old sulfuric acid process in the United States, is the direct hydration process. This process, the catalytic vapor-phase hydration of ethylene, is now practiced by only three U.S. companies Union Carbide Corp. (UCC), Quantum Chemical Corp., and Eastman Chemical Co. (a Division of Eastman Kodak Co.). UCC imports cmde industrial ethanol, CIE, from SADAF (the joint venture of SABIC and Pecten [Shell]) in Saudi Arabia, and refines it to industrial grade. 

Esters can also be synthesized by an acid-catalyzed nucleophilic acyl substitution reaction of a carboxylic acid with an alcohol, a process called the Fischer esterification reaction. Unfortunately, the need to use an excess of a liquid alcohol as solvent effectively limits the method to the synthesis of methyl, ethyl, propyl, and butyl esters. 

Linear, even-numbered, primary alcohols—like the natural fatty alcohols—are produced by the aluminum organic alcohol synthesis after Ziegler, the so-called Alfol process. This alcohol synthesis proceeds in three steps ... 

For this alcohol synthesis stoichiometric amounts of aluminum alkyls are required. Beside the wanted fatty alcohols high-purity aluminum oxide is formed. This aluminum oxide is of high value, e.g., for the production of catalysts and improves the economy of the Alfol process. 

Mixed C4 olefins (primarily iC4) are isolated from a mixed C olefin and paraffin stream. Two different liquid adsorption high-purity C olefin processes exist the C4 Olex process for producing isobutylene (iCf ) and the Sorbutene process for producing butene-1. Isobutylene has been used in alcohol synthesis and the production of methyl tert-butyl ether (MTBE) and isooctane, both of which improve octane of gasoHne. Commercial 1-butene is used in the manufacture of both hnear low-density polyethylene (LLDPE) and high-density polyethylene (HDPE)., polypropylene, polybutene, butylene oxide and the C4 solvents secondary butyl alcohol (SBA) and methyl ethyl ketone (MEK). While the C4 Olex process has been commercially demonstrated, the Sorbutene process has only been demonstrated on a pilot scale. 

The development of new syngas-based processes is one of the objectives for the near future, despite the current low price of oil. Syngas can be produced from various carbonaceous sources, including coal, heavy residue, biomass and gas, the latter being the most economical and abundant feedstock. Chemical valorization of natural or associated gas is a priority objective, since liquefaction of remote gas via alcohol synthesis permits convenient shipping to markets not directly connected to the gas source by pipeline. 

I.F.P. (France) and Idemitsu Kosan (Japan), as a member of RAP AD (Research Association for Petroleum Alternative Development), are involved in process and catalysts development for alcohols synthesis. This paper details most of our recent results. 

C 0 and H O, unavoidable by-products of alcohols synthesis. Considering chemical reactions of table H, water and carbon dioxide appear as equiva-lentby-products due to shift conversion equilibrium, equation (1). Most other low temperature alcohol synthesis catalysts have a rather high shift activity as well. CO removal fhom reacted syngas of synthesis loop, before recycling to reactor, leads to a significant decrease of water formation which, in turn, results in a lower water content in the raw alcohols, leading to simplified fhactionation-dehydration processes. 

Advances in higher alcohol synthesis that need to be made include improving productivity and selectivity. Higher spacetime yields are also required which may be achieved by dual catalyst bed reactors, the use of slurry phase synthesis process to increase CO conversion levels, and injection of lower alcohols into the reactant stream to increase the rate of higher alcohol formation.630... 

Methyl dichloride is obtained by the interaction of phosphorus thiotri-chloride with methyl alcohol. The process is carried out in an excess of alcohol (2 moles of CH3OH per 1 mole of PSCI3), which serves to absorb released hydrogen chloride. Phosphorus thiotrichloride from batch box 2 and methyl alcohol from batch box 3 are pumped with batching pumps through siphons into reactor 1. The synthesis occurs when the components are fed simultaneously at 0-5 °C. To withdraw the heat and maintain the temperature in reactor 1, the coil and jacket of the reactor are filled with -15 °C salt solution. The products of the reaction, which include dichloride, unreacted... 

Moser, W. R., and Connolly, K. E., Synthesis and characterization of copper modified zinc chromites by the high-temperature decomposition (HTAD) process for higher alcohol synthesis, Chem. Eng. J. 64,239 (1996). 

Three commercial homogeneous catalytic processes for the hydroformyla-tion reaction deserve a comparative study. Two of these involve the use of cobalt complexes as catalysts. In the old process a cobalt salt was used. In the modihed current version, a cobalt salt plus a tertiary phosphine are used as the catalyst precursors. The third process uses a rhodium salt with a tertiary phosphine as the catalyst precursor. Ruhrchemie/Rhone-Poulenc, Mitsubishi-Kasei, Union Carbide, and Celanese use the rhodium-based hydroformylation process. The phosphine-modihed cobalt-based system was developed by Shell specih-cally for linear alcohol synthesis (see Section 7.4.1). The old unmodihed cobalt process is of interest mainly for comparison. Some of the process parameters are compared in Table 5.1. 

The thermodynamic equilibrium is most favourable at high pressure and low temperature. The methanol synthesis process was developed at the same time as NH3 synthesis. In the development of a commercial process for NH3 synthesis it was observed that, depending on the catalyst and reaction conditions, oxygenated products were formed as well. Compared with ammonia synthesis, catalyst development for methanol synthesis was more difficult because selectivity is crucial besides activity. In the CO hydrogenation other products can be formed, such as higher alcohols and hydrocarbons that are thermodynamically favoured. Figure 2.19 illustrates this. 

Rare earth oxides are useful for partial oxidation of natural gas to ethane and ethylene. Samarium oxide doped with alkali metal halides is the most effective catalyst for producing predominantly ethylene. In syngas chemistry, addition of rare earths has proven to be useful to catalyst activity and selectivity. Formerly thorium oxide was used in the Fisher-Tropsch process. Recently ruthenium supported on rare earth oxides was found selective for lower olefin production. Also praseodymium-iron/alumina catalysts produce hydrocarbons in the middle distillate range. Further unusual catalytic properties have been found for lanthanide intermetallics like CeCo2, CeNi2, ThNis- Rare earth compounds (Ce, La) are effective promoters in alcohol synthesis, steam reforming of hydrocarbons, alcohol carbonylation and selective oxidation of olefins. 

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