Synthesis gas ethylene glycol from

Research is being conducted on the direct synthesis of ethylene glycol from synthesis gas. In one process very high pressures of 5,000 psi with very expensive catalysts Rhx (CO) are being studied. An annual loss of rhodium catalyst of only 0.000001% must be realized before this process will compete economically. At least five other alternate syntheses of ethylene glycol that bypass toxic ethylene oxide are being researched. 

The pentanuclear cluster, [Rhj(CO).j], has recently been Isolated fromthe low pressure (.ca. 10 bar) reaction of [Rh.jCCO). ] with carbon monoxide. Because of the Involvement of this cluster in the catalytic synthesis of ethylene glycol from synthesis gas, it was of Interest to monitor this reaction by C n.m.r. spectroscopy at higher pressures of carbon monoxide and in the presence of hydrogen to see whether other species are formed. 

Figure 1. Ethylene glycol from synthesis gas via ruthenium rhodium bimetallic melt catalysis. Effect of Rh Ru molar ratios. Synthesis conditions as per Table II. Effect of varying [Rh],0 effect of varying [Ru],...

Ethylene Glycol from Synthesis Gas via Ruthenium-Rhodium Melt Catalysis ... 

Recent processes are designed for the more direct production of glycol, either from ethylene or from synthesis gas ... 

Regarding the first question, it is important to mention the works of Union Carbide related to the synthesis of ethylene glycol from syn-gas with Rh or Ru complexes under drastic conditions of pressure (above 500 atm.). With rhodium complexes it has been established that an anionic cluster [Rh5(CO)i5] was present in the reaction medium under catalytic conditions. 

Ethylene glycol could he produced directly from synthesis gas using an Rh catalyst at 230°C at very high pressure (3,400 atm). In theory, five moles synthesis gas mixture are needed to produce one mole ethylene glycol ... 

Preparation of Ethylene Glycol Esters from Synthesis Gas... 

NMR on-line monitoring under high gas pressure was first applied to the understanding of the catalytic synthesis of ethylene glycol from CO/H2 using... 

The preparation of ethylene glycol directly from synthesis gas via homogeneous rhodium (14-20), ruthenium (21-26), and cobalt (27-30) catalysis has generally been limited by the high pressures necessary to effect reaction and the modest turnover frequencies. We have demonstrated the preparation of ethylene glycol and its monoalkyl ether derivatives from CO/H2 (eq. 1) using ruthenium or a Ru-Rh catalyst combination dispersed in a low-melting quaternary phosphonium or ammonium salt such as tetrabutylphosphonium bromide. Monohydric alkanols are the major by-products data in Table 1 illustrate typical preparations. The important features of this catalysis are ... 

The potential economic advantages of a direct route from synthesis gas to ethylene glycol have already been emphasized there are no known heterogeneous catalysts that accomplish either this transformation or the formation of polyalcohols. 

Mechanistic Aspects. Plausible mechanistic schemes for the production of the oxygenates methanol, ethylene glycol, and polyalcohols from synthesis gas... 

Indirect, or multistep, routes to ethylene glycol use either formaldehyde or methanol derived from synthesis gas as the feed. In the former case, several approaches based on either glycolic acid or glycolaldehyde intermediates have been proposed and developed by different groups of workers. The principal route based on methanol involves the oxidative coupling of CO to dimethyl oxalate via methyl nitrite. 

In liquid separation, hollow fiber membranes based on PBI have shown excellent performance for pervaporation dehydration of organic liquids. For example, a dual layer PEI-PBI hollow fiber membrane with an outer selective layer of PBI showed better performance than most other polymeric membranes in pervaporation dehydration of ethylene glycol. Sulfonation modifications of PBI membranes have demonstrated excellent separation efficacies in the dehydration of acetic acid. Studies have shown that PBI hollow fiber membranes were effective in separating chromates from solutions. Also, PBI nanofiltration hollow fiber membranes are promising candidates as forward osmosis membranes. In gas separation, recent studies sponsored by the Department of Energy at Los Alamos National Laboratories and SRI International demonstrated potential applications of PBI membranes in carbon capture and Hj purification from synthesis gas streams at elevated temperatures. H2/CO2 selectivity > 40 has been achieved at H2 permeability of 200 GPU at 250°C. ... 

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