US2719872A

US2719872A - Cracking of tertiary aliphatic hydroxy compounds to produce acetylenic hydrocarbons

Info

Publication number: US2719872A
Application number: US312158A
Authority: US
Inventors: Happel John; Charles J Marsel
Original assignee: Individual
Current assignee: Individual
Priority date: 1952-09-29
Filing date: 1952-09-29
Publication date: 1955-10-04
Anticipated expiration: 1972-10-04

Description

CRACKING OF TERTIARY ALIPHATIC HYDROXY COMPOUNDS TO PRODUCE ACETYLENIC HY- 5 DROCARBONS John Happel, Yonkers, and Charles J. Marsel, New York, N. Y.

No Drawing. Application September 29, 1952, Serial No. 312,158

8 Claims. (Cl. 260-'678) This invention relates to novel processes for the production of acetylenic hydrocarbons together with diolefins by the thermal cracking of tertiary aliphatic alcohols, and more particularly, it relates to a novel method for making methyl acetylene by the cracking of tertiary butyl alcohol.

The commercial production of acetylenic hydrocarbons is generally based on relatively complicated and expensive methods involving chemical synthesis procedures. For example, the simplest member of the acetylenic hydrocarbon series, acetylene itself, is the most widely known and used of the acetylenic compounds. Practically all the present commercial production ismade by the relatively expensive method of reacting water with calcium carbide CaCz. Homologs and derivatives of acetylene itself are more difiicult and expensive to make and for this reason have not been made available commercially.

Methyl acetylene has been produced by the reaction of water with magnesium carbide, MgzCs. Higher acetylenes are also produced by dehydrohalogenation reactions, such as methyl acetylene from dibromopropane, and diacetylene from dichlorobutyne. Pyrolysis has also been employed using the arc process or other types of high temperature and short time of contact cracking techniques to produce acetylenes from low molecular weight hydrocarbons. However, all present methods for producing higher acetylenes are relatively expensive techniques, or produce acetylenes in poor yields. These difficulties are intensified in commercial scale operations.

It has been discovered that low molecular weight substituted acetylenes can be made in good yield and purity by the thermal cracking of low molecular weight tertiary alcohols and glycols in the presence of steam under conditions of high temperatures and low contact time of the feed. In some cases, under controlled conditions, valuable diolefins are also produced. There is no coking of the equipment, and consequently no loss of the feed stock in such useless materials. It has further been discovered that steam has a unique and hitherto unknown ability to aid this reaction by cutting down tar formation and greatly facilitating the formation of the desired acetylenic products.

Thus the procedure of the invention has a number of advantages over present cracking techniques. The tertiary alcohols, being liquids, are easily handled and pumped. The use of steam during the cracking step avoids the formation of carbon and tars without the use of vacuum or other tedious variations. In addition, tests have indicated that the alcohol cracks much more readily and cleanly than the corresponding olefin, using the same mole ratios of steam and the same cracking conditions. 60

To summarize, the appropriate tertiary alcohol is mixed with the proper amount of water or steam, vaporized and passed into a cracking zone, where it is exposed to high temperature and short time of contact, suitably adjusted for the exact compound to give the optimum yield of 70 desired acetylenic product. The mixture is rapidly ice quenched by water or steam, injection and the products separated by the usual techniques. The feed stock to be used is selected from the group of aliphatic tertiary alcohols and glycols characterized by the following structural group:

GHa

HrC- H They are pyrolized in the presence of steam, at atmospheric or slightly higher pressures to yield an acetylenic hydrocarbon. Thus generically:

CH: arc-n- H In the case of tertiary butyl alcohol, for example,

CH1 CHaC-CH3 CHsCECH V or with methyl but'ynol CH3 1 onrnozon *Q nozo ozoH Contact times of less than 1 second employed in conjunction with a temperature within the range of 800 to 900 C. are necessary for the best and most efiicient operation of the process. In general, best yields and conversion are obtained by a correlation of contact'time and temperature, such that the longer the contact time, the lower the temperature which is used. Conversely, the shorter the contact time, the higher the temperature which can be tolerated. Substantially atmospheric pressures are employed for best results although pressures higher than atmospheric can also be used. Steam should be employed admixed with. the tertiary alcohol feed in mole percent concentrations of more than 50% and preferably in the range of to mole percent.

The feed can be the pure tertiary alcohol or glycol or a mixture containing substantial amounts of the appropriate feed can also be used, provided no materials are present which will interfere with the reaction or unduly contaminate the product.

Among the compounds Which may be employed as feeds and which should contain in the molecule at least one tertiary hydroxyl group are included the following:

CH3 CH Om n-0H; CHa- -CECH H H Tertiary Butyl Alcohol Methyl Butynol CH3 CH CH3 CH3 CHaN CHs CH3( /C CCCHa OH H OH H Pinaeol Dimethyl Hexynediol The operation may be carried out in a pyrolysis tube or a series of tubes or coils made of stainless steel, quartz or the like. Also brick checkerwork or stoves of the type used for pyrolysis may be used. Such stoves commonly use the principle of regenerative cooling for economy of operation.

This novel process is particularly valuable for producing methyl acetylene and mixtures of methyl acetylene with allene from mixtures containing relatively large amounts of tertiary butyl alcohol. Conditions which are especially adaptable for making methyl acetylene are 800-900 C. and .005-5 seconds contact time and 80-90 mole percent steam. f

In order to achieve controlled low time of contact, it is necessary to cool the cracked gases very quickly to at least 500 C. after they leave the thermal cracking zone. Shock or quick cooling of the cracked gases serves two purposes. Firstly it serves to bring the temperature of the reacted gases quickly below the pyrolytic temperature in order to keep decomposition of product and secondary reactions to a minimum and secondly, it reduces the temperature of the methyl acetylene to lower temperatures at which polymerization reactions are at a minimum. These two objectives may be accomplished by shock cooling of the cracked gases. A direct water quench may be placed immediately after the heating zone. The gases may be passed directly into a stream or spray of cold water or oil. Cool gases may be mixed with the exit gases immediately after they leave the heating zone. The substituted acetylene is separated by condensation of the steam, further compression to knock out additional water, and subsequent pressure distillation to separate methyl acetylene and allene from the reaction products. Recovered isobutylene is recycled back to the cracking coil.

Example I A solution containing mole percent of tertiary butyl alcohol and 90 mole percent of water was vaporized, preheated to above 200 C. and passed through a stainless steel cracking tube furnace. A thermocouple probe in the cracking tube gave a temperature profile over the length of the tube of about 850-900 C. Contact time in the furnace Was approximately .05.5 second. Product was then quenched with steam. Upon analysis of the reaction mixture, it was found that 5.9 mole percent of the tertiary butyl alcohol was converted to methyl acetylene. Approximately an equal amount of allene was found. The remaining reaction product consisted of isobutylene from unreacted butanol, methane, hydrogen, and small amounts of other hydrocarbons.

Example 2 A solution containing approximately 110 mole percent of methyl butynol and 90 mole percent of water was vaporized, preheated to about 200 C. and passed through a cracking tube furnace with a temperature of about 850900 C. The product was quenched with nitrogen gas, and analysis of the reaction mixture proved the presence of diacetylene.

The production of methyl acetylene is of especial importance, since this chemical compound has unique properties which make it useful as a combustible fuel for welding operations and jet engines, and as a chemical intermediate.

What is claimed is:

l. A process for the production of acetylenic compounds which comprises subjecting a feed containing substantial amountsof a compound possessing at least one aliphatic tertiary hydroxyl group and at least mole percent of steam to temperatures of from 800 to 900 C., at a contact time of less than 5 seconds.

2. A process for the production of acetylenes and other products which comprises subjecting a feed containing a compound possessing at least one aliphatic tertiary hydroxyl group and in the presence of at least 50 mole percent of steam, to temperatures of from 800 to 900 C. at a contact time of less than 5 seconds.

3. A process for the production of methyl acetylene which comprises subjecting a feed containing tertiary butyl alcohol and at least 50 mole percent of steam, to temperatures of from 800 to 900 C. at a contact time of less than 5 seconds.

4. A process for the production of a mixture of methyl acetylene and allene which comprises subjecting a feed mixture containing tertiary butyl alcohol and at least 50 mole percent of steam based on the alcohol to a thermal cracking at a temperature within the limits of 800 to 900 C., and at a contact time of .005 to 5 seconds.

5. A process which comprises subjecting a mixture of tertiary butyl alcohol and from to mole percent of steam, to a thermal cracking at a temperature within the limits of 800 to 900 C., and at a contact time of' less than 1 second and isolating methyl acetylene from the resultant cracked gases.

6. A process which comprises subjecting a mixture containing from 10 to 20 mole percent tertiary butyl alcohol and from 90 to 80 mole percent steam to a cracking step at a temperature in the range of 800 to 900 C., and a contact time between .005 and 5 seconds and isolating methyl acetylene from the resultant cracked gases.

7. A process for making a cracked mixture containing substantial amounts of methyl acetylene and allene which comprises preheating a mixture containing 10 mole percent tertiary butyl alcohol and 90 mole percent steam, passing said mixture to a cracking zone in which it is sub.- jected to a temperature of 800 to 900 C. for a period of less than 1 second, quenching the hot cracked mixture and isolating methyl acetylene from the cooled gases. 8. A process for making a cracked mixture containing substantial amounts of diacetylene which comprises preheating a mixture containing 10 mole percent methyl butynol and 90 mole percent steam, passing said mixture to a cracking zone in which it is subjected to a temperature of 800 to 900 C., quenching the hot, cracked mixture, and isolating diacetylene from the cooled gases.

References Cited in the file of this patent UNITED STATES PATENTS 1,986,876 Baxter et al. Jan. 8, 1935 2,429,566 Rice Oct. 21, 1947 2,524,866 Winslow Oct. 10, 1950

Claims

1. A PROCESS FOR THE PRODUCTION OF ACETYLENIC COMPOUNDS WHICH COMPRISES SUBJECTING A FEED CONTAINING SUBSTANTIAL AMOUNTS OF A COMPOUND POSSESSING AT LEAST ONE ALIPHATIC TERTIARY HYDROXYL GROUP AND AT LEAST 50 MOLE PERCENT OF STEAM TO TEMPERATURE OF FROM 800* TO 900* C., A CONTACT TIME OF LESS THAN 5 SECONDS.