Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C4/00—Preparation of hydrocarbons from hydrocarbons containing a larger number of carbon atoms
  • C07C4/08—Preparation of hydrocarbons from hydrocarbons containing a larger number of carbon atoms by splitting-off an aliphatic or cycloaliphatic part from the molecule
  • C07C4/10—Preparation of hydrocarbons from hydrocarbons containing a larger number of carbon atoms by splitting-off an aliphatic or cycloaliphatic part from the molecule from acyclic hydrocarbons
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C4/00—Preparation of hydrocarbons from hydrocarbons containing a larger number of carbon atoms
  • C07C4/02—Preparation of hydrocarbons from hydrocarbons containing a larger number of carbon atoms by cracking a single hydrocarbon or a mixture of individually defined hydrocarbons or a normally gaseous hydrocarbon fraction
  • C07C4/06—Catalytic processes
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C2531/00—Catalysts comprising hydrides, coordination complexes or organic compounds
  • C07C2531/02—Catalysts comprising hydrides, coordination complexes or organic compounds containing organic compounds or metal hydrides

Definitions

• This invention relates to a process for the production of unsaturated hydrocarbons with three carbon atoms.
• Three such compounds exist, namely allene, otherwise propadiene (CH C CHQ, propyne (CH -C- CH) and propene (CH CHCH the first and second of these compounds are of great technical importance.
• the process according to the invention com-prises subjecting isobutene, otherwise isobutylene to temperatures in excess of 700 C. for a period of less than 1 second at substantially and essentially atmospheric pressures in the absence of diluent gases such as steam, flue gas and the like.
• the starting material need not be chemically pure isobutene, but may be a commercial product which mainly consists of isobutene. In this sense the term isobutene in the specification and the claims should be understood.
• Cracking may be carried out in any conventional way, for example by using pyrolysis tubes or coils made of quartz or stainless steel which may contain filling bodies such as pumice, or by using brick checkerwork or stoves of the type commonly used for carrying out pyrolysis reactions.
• the gas obtained after the cracking be cooled quickly, for instance by passing it through a cooling chamber or by quenching it with cold water.
• propadiene or a mixture of propadiene and propyne methane is always formed. Under certain conditions other products may also be formed, but it is possible so to choose the cracking conditions that these byproducts are only produced in small and even negligible amounts.
• the non-converted isobutene can be recycled to the cracking zone.
• the isolation of the propadiene and/or propyne by removal of the methane, and of the non-converted isobutene and other products, if present, and the separation of the propadiene and propyne may be effected in any conventional way, for example by cooling and fractional distillation or by adsorption methods.
• the following tables are records of experiments showing the influence of contact time and temperature on the cracking of isobutene.
• the pressure in the cracking zone is essentially atmospheric pressure.
• the experiments are carried out by passing the iso-butene through a quartz tube.
• the tube is heated to the desired temperature by means of a tube oven.
• the contact time is controlled by the rate of flow of the isobutene.
• the resultant mixture is subjected to analysis by means of infra-red spectrography and the results are confirmed by gas chromatography.
• those substances which are still volatile at 3,082,273 Patented Mar. 19, 1963 minus 180 C. such as methane, haye been as far as possible removed from the mixture obtained in the process by cooling the mixture prior to analysis to minus 180 C.
• the data denotes the percentage by volume of the substance referred to in terms of the total volume of the mixture.
• the sign denotes that no amount can. be found; the sign 2 means that the amount is less than 1% by volume; the sign .9 means that the amount is between 1 and 3% by volume; the sign In means that a substantial amount is present.
• results may be somewhat improved.
• results are recorded of experiments with azomethane admixed to the isobutene.
• the percentage of azomethane is for Table V 3 percent by volume on the volume of initial isobutene; in Table VI it is 8 percent by volume on the volume of initial isobutene.
• Tables VII and VII are recorded the results, obtained with a contact time of 0.01 second and (Table VII) without azomethane and (Table VIII) with 2 percent by volume of azomethane on the volume of initial isobutene, respectively.
• the amount of c -unsaturated hydrocarbons is about 10.8 percent by volume calculated on the initial volume of isobutene; of these C -unsaturated hydrocarbons in the final mixture about 50 percent by volume i propadiene, 20% is propyne and 30% is propene.
• the conversion of isobutene into C -unsaturated hydrocarbons is slightly lower, viz. 10.2, and of these C -unsaturated hydrocarbons in the final mixture about 50 percent by volume is propadiene, about 18 percent is propyne and about 32% is propene.
• a further advantage of working at a substantially atmospheric pressure according to the invention is that the isolation of the propadiene and/or propyne formed is much easier than in the case of the isobutene being cracked in the presence of a diluent gas, because in the latter type of processes the diluent gas, such as steam, seriously complicates the isolating step.
• the partial pressure of the isobutene in the initial feed is substantially 1 atmosphere and that the whole process is carried out at substantially atmospheric pressures.
• No reduced pressures are used in the process according to the invention, neither is the isobutene diluted with a diluent gas. It stands to reason that a gaseous catalyst such as azo methane is not considered to be a diluent gas.
• a process for the preparation of unsaturated hydrocarbons selected from the group consisting of propadiene and propyne which comprises subjecting substantially undiluted isobutene to a thermal cracking at a temperature above 700 C. at a contact time of less than 0.2 second at substantially atmospheric pressure and recovering said unsaturated hydrocarbons from the resultant cracked mixture.
• a process for the preparation of unsaturated hydrocarbons selected from the group consisting of propadienc and propyne which comprises the steps of subjecting substantially undiluted isobutene to a thermal cracking at a temperature above 850 C. at a contact time of less than 0.1 second at substantially atmospheric pressure and recovering said unsaturated hydrocarbons from the resultant cracked mixture.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
• Production Of Liquid Hydrocarbon Mixture For Refining Petroleum (AREA)

Applications Claiming Priority (1)

Publications (1)

Family

ID=10419128

Family Applications (1)

Country Status (4)

Cited By (4)

Citations (3)

• 0
  • DE DENDAT1251305D patent/DE1251305B/de active Pending
• 1959
  • 1959-12-04 GB GB41316/59A patent/GB914790A/en not_active Expired
• 1960
  • 1960-11-22 US US70939A patent/US3082273A/en not_active Expired - Lifetime
  • 1960-12-02 CH CH1352660A patent/CH373749A/de unknown

Patent Citations (3)

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