Ethane ethylene conversion

We have delineated viable coordinated ligand reactions and their attendant intermediates for the stoichiometric conversion of CO ligands selectively to the C2 organics ethane, ethylene, methyl (or ethyl) acetate, and acetaldehyde. We now outline results from three lines of research (1) T -Alkoxymethyl iron complexes CpFe(C0)2CH20R (2) are available by reducing coordinated CO on CpFe(C0)3+ (1) [Cp = r -CsHs]. Compounds 2 then form t -alkoxyacetyl complexes via migratory-insertion (i,e. CO... 

Gas-oil cracking was carried out in a fixed bed tubular reactor at atmospheric pressure and 482 °C. Average yields of the different products -diesel, gasoline, gases (methane, ethane, ethylene, C, C ), and coke- were measured at different levels of conversion jy varying the catalyst to oil ratio in the range 0.025-0.40 g.g, but always at 60 sec on-stream. The operational procedure has been detailed elsewhere (6). 

In Figure 7 the selectivity to methane, ethane, ethylene, gases, gasoline (210°C), diesel (310°C), and coke at 65% level of conversion have been plotted for HYUS zeolites with 28, 21, 12, and 2 Al per unit cell for cracking gas-oil. It is apparent from the figures that thO selectivity to and C products decreases with a decreasing number of aluminum, up to 10- 0 Al per unit cell. With further dealumination the selectivity to and products... 

Beside methanol and formaldehyde, the oxidation of methane may be directed to another route, leading to the formation of its condensation products, for example, ethane, ethylene and benzene. This route may provide an alternative way for the chemical use of natural sources of methane. Here, various catalysts were also tested using both 02 and N20 as the oxidants [22], The general picture observed by most authors was similar to that with methane oxidation to oxygenates. The conversion of methane was always higher with 02 than with N20. However, the selectivity to the coupling products showed an opposite trend. 

Figure 6. Temperature dependence of ethylene conversion to ethane over a palladium membrane.

Figure 8. Time dependence of ethylene conversions to ethane over Pd, TiOx-Pd, and Pt/TiOx-Pd membranes.

Hydrogen, acetylene, and carbon monoxide are the primary products of the conversion of methane in the dc plasma system. In addition, small amounts of ethane, ethylene, and carbon dioxide are produced. Of the C2 products, acetylene accounts for 90%, while ethylene and ethane comprise 6% and 4%, respectively. Carbon dioxide is less than 0.2% of the effluent gas. No measurable amount of water is produced in the system. 

Economics Ethylene yields range from 57% (ethane, high conversion) to 28% (heavy hydrogenated gas oils). Corresponding specific energy consumptions range from 3,000 kcal/kg to 6,000 kcal/kg. 

Table I presents results for six comparable pyrolysis runs made by using five laboratory reactors all runs were made with approximately 50% steam as diluent in the ethane feed. Conversions at the exit end of the reactor varied from 59% to 65%. Also, results reported for a commercial unit (11) are shown. Ethylene yields varied from about 78% to 89% in all cases except for run D44 made in the stainless steel 304 reactor. In that run, the ethylene yields were very low but production of CO, GOo, and net coke were much higher. Ethylene yields were highest in the run made in the Vycor glass reactor. In this run, coke formation was least of all runs, and no CO or C02 was detected in the product stream.

Very recently, the gas phase pyrolysis (155-200°) of methyl azide at low conversions (< 1%) was studied . Nitrogen was the major non-condensable gas, in addition to small amounts of hydrogen (6% at lowest initial pressure of azide to less than 1% at the highest pressure) and methane (<2%). Ethane, ethylene, ammonia and hydrazoic acid were not detected, although the ethane, ethylene and hydrazoic acid determinations were subject to some uncertainty. Two solid white products were also obtained which were not characterized. The results showed that the thermolysis of methyl azide is of first-order, homogeneous and free from chains, in agreement with previous work . The Arrhenius activation parameters (see Table 1)... 

Ethylene dimerization and oligomerization (Dimersol and Phillips process) is much less developed, because of the economic situation. Even in the most favorable conditions, nickel catalysts unavoidably produce a mixture of 1- and 2-butenes and ethylene is generally more expensive than 2-butene and 1-bu-tene/2-butene mixtures. Feedstocks are either polymerization-grade ethylene or a 50 50 mixture with ethane. In this latter case a gas phase is inevitably present in the reactor. The product composition is strongly dependent on ethylene conversion. The Phillips process probably uses NiCl2 2 PBus as catalyst. Due to the very high reactivity of ethylene, catalyst consumption is remarkably low. 

Other steps used in the model assume that the heterogeneous conversion of methane is limited to the gas-phase availability of oxygen, O2 adsorption is fast relative to the rate of methane conversion, and heat and mass transports are fast relative to the reaction rates. Calculations for the above model were conducted for a batch reactor using some kinetic parameters available for the oxidative coupling of methane over sodium-promoted CaO. The results of the computer simulation performed for methane dimerization at 800 °C can be found in Figure 7. It is seen that the major products of the reaction are ethane, ethylene, and CO. The formation of methanol and formaldehyde decreases as the contact time increases. 

Ross and co-workers [9,10] have explored the influence of CO2 on the oxidative coupling of methane over the Li/MgO catalyst. They found that carbon dioxide in the gas phase lowers both the methane conversion and the yield of ethane/ethylene products. They also found that carbon dioxide significantly improves the stability of the catalyst against deactivation. Based on the observations of surface species from FTIRS and transient experiments. In addition, most of the observations and experimental results reported to date cover a limited range of methane to oxygen feed ratios. There is a need to study the reaction over a wide range of methane to oxygen ratios and to quantify the effects of carbon dioxide on the reaction rates. 

The process is fed with three streams ethane, ethylene, and chlorine. The ethane and ethylene streams have the same molar flow rate, and the ratio of chlorine to ethane plus ethylene is 1.5. The ethane/ethylene stream also contains 1.5 percent acetylene and carbon dioxide. (For this problem, just use 1.5 percent carbon dioxide.) The feed streams are mixed with an ethylene recycle stream and go to the first reactor (chlorination reactor) where the ethane reacts with chlorine with a 95 percent conversion per pass. The product stream is cooled and ethyl chloride is condensed and separated. Assume that all the ethane and ethyl chloride go out in the condensate stream. The gases go to another reactor (hydrochlorination reactor) where the reaction with ethylene takes place with a 50 percent conversion per pass. The product stream is cooled to condense the ethyl chloride, and the gases (predominately ethylene and chlorine) are recycled. A purge or bleed stream takes off a fraction of the recycle stream (use 1 percent). Complete the mass balance for this process. 

In recent years there has been much interest in the conversion of methane to value added products, such as ethane/ethylene [1], methanol [2], formaldehyde [3-5] and synthesis gas [6]. Many studies have been carried out on the partial oxidation of methane to formaldehyde over silica [7], and over molybdena [8,9], vanadia [5,10] supported on silica, or FeNbB-0 [11] with nitrous oxide [7-9] or oxygen [7,10] as the oxidant. 

K. Small quartz reactors (5 and 25 cm ) were used. A temperature study indicated that the maximum selectivity occurred at around 730 °C. All experiments were carried out at 1 atm with air. A conversion of 15% and selectivity of 80% were obtained at 730 C, CH /Air=l, and 500-L/h GHSV with a CaO+Na catalyst. The ethane/ethylene ratio was about 1 1. A reaction mechanism including 14 reactions was proposed to describe the experimental data. Kimble and Kelts also obtained a patent on catalysts comprising Co with preferably Zr or P and at least one Group lA metal. Addition of Cl and S also improved the catalyst performance. A conversion of 18% and selectivity of 71% were obtained at 684°C, 1 atm, and CH /Air=l. The ethane/ethylene ratio was 1 2. 

The conversion of methane by oxydehydrogenation to ethane, ethylene, oxygen-containing organic molecules, or CO and H2 are important reactions that are at the frontier of catalyst research. Methane, which is the most abundant fraction of natural gas, is an increasingly significant source of fuels as the supply of crude oil diminishes. Review the processes 1213-217]. 

Economics Once-through pyrolysis yields range from 57 wt% (ethane, high conversion) to 28 wt% (heavy hydrogenated gasoils) ethylene. Ultimate yields for ethylene of 85% from ethane feedstock and 32% from liquid feedstock are achieved. The ethylene plants with USC furnaces and an ARS/HRS recovery section are known for high reliability, low energy consumption, short startup time and environmental compliance. 

Figure 9-7. Temperature dependence of the reaction rate coefficients (1) methane conversion into ethane (CH4 —>-1/2 C2H6 + 1 /2H2) at different values of the non-equilibrium factor y = (Tv — To)/To, (2) ethane conversion into ethylene (C2H,5 — C2H4-f H2) (3) ethylene conversion into acetylene (C2H4 —> C2H2 -f H2) (4) acetylene conversion into soot (C2H2 — 2Ccond + H2 ).

Our interpretation of these results is summarized in the simplified mechanistic scheme shown in Figure 5. In this scheme the conversion of methane to ethane/ethylene and then to CO2 occurs by a series of consecutive reactions. The relative rates of methane and ethylene activation, and k2 in Figure 5, determine the upper limit of C2 yield. (Since ethane can convert to ethylene readily by non-oxidative pyrolysis and ethylene is more stable than ethane the rate of ethylene activation is taken to be the limiting rate.) The direct conversion of CH4 to CO2 has been ignored. Assuming this rate is negligible is the most optimistic assumption possible as far as catalysis is concerned since conversion of CH4 to CO2 cannot contribute to C2 yield. 

Effect of Temperature. Experiments In which the temperature of the reactor was Increased from about 450 C to perhaps 700 C were helpful In clarifying the Importance of surface reactions In the metal reactors tested. Figures 1, 2, and 3 Indicate that for ethane, ethylene, and propylene, agpreciable conversions of the dry feed hydrocarbons begin at 450°-475 C In the metal reactors tested, but do not begin until about 550°-575°C In the Vy-cor reactor. Propane conversions began at about 450 -475°C In all reactors Investigated. 

A multi-component catalyst for the title reaction was optimised with a hybrid GA achieving ethane + ethylene yields (C2) larger than 25% at 1,069°C. In a specific case, methane conversion amounted to 37.8% and C2 selectivity to 73.5%, i.e. C2 yield was 27.8% obtained. An artificial neural network described the relationship between catalyst composition and catalyst performance. The results indicate a prospect for industrialisation. 

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