摘要:
An improved process is provided for the production of oxides from alkanes by reaction with oxygen, air or a gas enriched in oxygen relative to an air in the presence of an oxidation catalyst. An alkane, e.g. propane, is converted to an alkene in a multistage dehydrogenator. The product stream is withdrawn from an intermediate reactor in the dehydrogenator, other than the first and the last reactor, and introduced into an oxidation reactor. The product formed in the oxidation reactor is recovered in a conventional quench tower. The gaseous effluent from the quench tower is treated in a pressure swing adsorption (PSA) unit to form a gaseous stream containing the unreacted alkane and alkene as well as a minor amount, i.e. less than about 2 percent by volume, of oxygen and nitrogen, if present in the feed to the oxidation reactor. The gaseous stream, which may or may not contain hydrogen depending on the adsorbent in the PSA unit, is introduced into the reactor in the dehydrogenator following the intermediate reactor. The effluent from the last reactor in the dehydrogenator is introduced into either: (i) the first reactor; (ii) a reactor other than said first reactor wherein the alkene concentration closely approximates the effluent of the oxidation reactor. The subject process is particularly efficient utilizing oxygen-enriched air in the reactor feed. A preferred PSA system for use in the subject process comprises two parallel PSA units containing different adsorbents such that the gaseous phase formed in one contains all of the hydrogen in the gas phase from the quench tower. The feed to the PSA units is divided disproportionately so that the combined PSA effluent recycle streams contain the optimum concentration of hydrogen for the dehydrogenator.
摘要:
An improved process is provided for the production of nitriles from hydrocarbons by reaction with oxygen, air or a gas enriched in oxygen relative to air, preferably the latter, and ammonia in the presence of an ammoxidation catalyst. An alkane, e.g., propane, is converted to an alkene in a catalytic dehydrogenator. The product stream is introduced into an ammoxidation reactor. The product formed therein is recovered in a conventional quench tower. The gaseous effluent from the quench tower is treated in a PSA unit comprising at least two pairs of adsorptive beds. The first bed forms a gas stream containing the unreacted alkane and alkene as well as a minor amount, typically 1-2 percent by volume, of oxygen and a vent stream containing oxygen, nitrogen if present, and hydrogen. The vent stream is introduced into the second adsorptive bed to thereby form an oxygen-containing stream which also contains, nitrogen, if present, and a hydrogen-enriched stream. The oxygen-containing stream may be recycled to the ammoxidation reactor depending on the nitrogen content thereof. The alkene/alkane stream plus at least a portion of the hydrogen stream is introduced into a selective oxidation unit to remove the remaining oxygen and then recycled to the dehydrogenator. The remainer of the hydrogen-enriched stream, if any, may be taken as product or vented. The dehydrogenator may be a multistage dehydrogenator wherein the product stream is withdrawn from a reactor other than the first and last reactors, the recycle streams are introduced into the next sequential reactor and the effluent from the last reactor is introduced into the first reactor, a reactor having a similar alkane composition or directly into the admmoxidation/oxidation reactor.
摘要:
An improved process for the catalytic partial oxidation of hydrocarbons to produce hydrogen and carbon monoxide and less than ˜2% carbon dioxide is disclosed. The process further permits the reaction to be initiated at room temperature, and utilizes a metal catalyst deposited on a ceria-coated zirconia monolith support, which exhibits high conversions of hydrocarbons to synthesis gas (hydrogen and carbon monoxide).
摘要:
A gas mixture comprised of nitric oxide and, optionally an inert gas, and containing small amounts of nitrogen dioxide, and perhaps moisture and sulfur dioxide, is purified by passing the gas stream through a bed of zeolite having a silica to alumina ratio not greater than about 200. The concentration of nitrogen dioxide, sulfur dioxide and moisture in the gas stream are reduced to about 1 ppm or less as the gas mixture passes through the bed of zeolite.
摘要:
Coke deposits are removed from particulates by combustion in a regenerator by a process in which air is initially used as the oxidant. The combustion gas is subjected to a separation process to remove nitrogen therefrom, and the remaining carbon dioxide-enriched gas stream is recycled to the regenerator together while substantially pure oxygen is introduced into the regenerator. As the level of carbon dioxide in the system increases, the amount of air being introduced into the regenerator is gradually reduced and, in compensation, the amount of oxygen flowing to the regenerator is gradually increased. Eventually, part or all of the air is replaced by oxygen and carbon dioxide recycle gas, and the level of oxygen and carbon dioxide are regulated to maintain the desired temperature in the regenerator.
摘要:
Hydrocarbon derivatives are produced by contacting a hydrocarbon with oxygen obtained from an air separation unit in the presence of a partial oxidation reaction catalyst. After separation of the hydrocarbon derivative from the reactor effluent, unreacted hydrocarbon is recovered from the effluent by adsorbing the unreacted hydrocarbon onto an adsorbent at superatmospheric pressure and removing the adsorbed hydrocarbon from the adsorbent by depressurizing said adsorbent and purging the adsorbent with nitrogen obtained from the air separation unit. The recovered unreacted hydrocarbon is recycled to the partial oxidation reactor.
摘要:
An ethylene stream which contains ethane as an impurity or a propylene stream which contains propane as an impurity is contacted with a polymerization catalyst thereby producing a polymer product containing unreacted ethylene or propylene and the corresponding alkane. A gas mixture containing ethylene or propylene and the corresponding alkane is separated from the polymer product and subjected to adsorption at a temperature of 50.degree. to 200.degree. C. in a bed of adsorbent which selectively adsorbs alkenes, thereby adsorbing substantially all of the propylene or ethylene from the gas mixture. The ethylene or propylene is desorbed from the adsorbent and recycled to the polymerization zone. The process is operated on a low per pass conversion with recycle of unreacted monomer. In the system of the invention the adsorption unit may be upstream or downstream of the polymerization reactor.
摘要:
A per-fluorocarbon containing gas is treated by contacting per-fluorocarbon contained within the gas with calcium hydride at a temperature in a range of between about 450 and 900.degree. C. The calcium hydride can be contained in a bed mixed with silicon or calcium oxide and such bed can be used in conjunction with a downstream bed of calcium oxide to remove any hydrogen fluoride produced. Also, an upstream bed of calcium fluoride can be used to treat acid gases in case of semiconductor processing applications of the present invention.
摘要:
An ethylene stream which contains ethane as an impurity or a propylene stream which contains propane as an impurity is subjected to adsorption at a temperature of 50.degree. to 200.degree. C. in a bed of adsorbent which selectively adsorbs ethylene or propylene, thereby adsorbing substantially all of the ethylene or propylene. The purified ethylene or propylene stream is then subjected to partial oxidation in the presence of oxygen and, optionally ammonia to produce various partial oxidation products. The process is operated on a low per pass conversion with recycle of unreacted ethylene or propylene. In the system of the invention the adsorption unit may be upstream or downstream of the partial oxidation reactor.
摘要:
A process for separating methane from an oxygen-containing gas mixture which contains methane at a concentration greater than the upper explosive gas mixture limit by pressure swing adsorption without producing an explosive gas mixture. The process includes the steps of feeding the gas mixture into an adsorber which contains an adsorbent which preferentially adsorbs methane until the desired production pressure is attained in the adsorber and then stopping the flow of feed gas into the adsorber and charging methane product gas at the production pressure cocurrently into the adsorber while simultaneously withdrawing nonadsorbed product gas from the nonadsorbed product end of the adsorber. The desorbed product stream is enriched in methane relative to the feed stream and the concentration of methane in the nonadsorbed product stream is less than the minimum flammable mixture concentration.