US2039799A - Treatment of hydrocarbons - Google Patents

Description

Patented May 5, 1936 UNITED STATES PATENT OFFICE TREATMENT OF HYDROCARBONS No Drawing.

4 Claims.

This invention relates more particularly to the treatment of hydrocarbon mixtures of motor fuel boiling range produced by polymerizing reactions upon normally gaseous olefinic hydrocarbons.

In a more specific sense the invention has reference to a process for removing undesirable reaction products from the hydrocarbon polymers produced by the action of sulfuric acid upon normally gaseous olefinic hydrocarbons of relatively low molecular weight.

Olefinic hydrocarbons, with the polymers of which the present invention is concerned, occur along with corresponding paraffinic or saturated hydrocarbons in commercial hydrocarbon gas mixtures such as those encountered in the cracking of petroleum. in gas making processes and as by-products in various chemical industries. In general they are more chemically active than other classes of hydrocarbons, particularly if they contain more than one double bond or triple bonds between carbon atoms. Even when under mild catalytic influence they exhibit this reactivity in their pronounced tendency to polymerize and form substances of higher molecular weight. In most instances this instability is a disadvantage, particularly in the case of cracked hydrocarbon oil distillates which are of suitable boiling range to permit their use in internal combustlon engines, since the polymers which develop on storage are of a gummy character and impart color to the oil.

Olefins occur in particularly large percentages in the fixed gases from cracking processes as well as in the gasoline boiling range fractions. The fixed gases are utilized principally as fuel, only a very small percentage of present day commercial production being subjected to processes for the recovery or utilization of the olefinic constituents. The manufacture of secondary alcohols such as iso-propyl alcohol and others by first absorbing the corresponding olefins in cracked gases in sulfuric acid and then hydrolyzing the acid esters has been undertaken to a limited extent. By suitable modification of conditions in regard to strength of sulfuric acid, temperature, pressure, rate of flow and efficiency of contact, the lower molecular weight olefins in hydrocarbon gas mixtures may be controllably polymerized to compounds corresponding to their dimers and trimers which in the case of normally 0 ctylene .Application December 4, 1933, Serial No. 700,878

Boiling points of olefin dimers 1o Polymers such as the above produced by the action of sulfuric acid as a catalyst are prone 20 to contain considerable percentages of sulfuric acid esters, since ester formation is the primary reaction occurring between olefins and sulfuric acid. In the case of alcohol manufacture these esters are hydrolyzed, and in the case of polymer 25 manufacture, while the major portion is decomposed, the amount of undecomposed esters may be considerable and it is with a simple and practical method of removing these esters that the present invention is concerned. 30

On one specific embodiment the invention comprises treatment of synthetic hydrocarbon mixtures of motor fuel boiling range, produced by polymerizing olefins in the presence of sulfuric acid, with phosphoric acid to desulphurize them 35 and produce other refining effects. The invention further comprises the use of graded mixtures of sulfuric and phosphoric acids for the same purpose.

The following equation shows the reaction 4 which occurs between propylene (representing an olefin) and sulfuric acid:

OH O H +H SO S F l- Mono-propyl ester e of sulfuric acid The compound shown on the right of the equation I typifies a number of esters or similar structure which as previously stated may remain dissolved in a liquid hydrocarbon mixture produced by polymerizing reactions among olefins in the presence of sulfuric acid.

According to the invention the'hydrocarbon liquid containing such dissolved compounds is treated with phosphoric acid or the above mentioned graded mixtures of phosphoric and sulfuric acids, the course of the main reactions being evidently somewhat as follows:

OH OH 0 03111 S0: +O=POH=H2SO4+O=POH 0 Q1111 OH OH Mono-propyl ester Phosphoric Mono-propyl ester of sulfuric acid acid of phosphoric acid The compounds on the right hand side of the equation are evidently soluble in the phosphoric acid employed in the treatments, at least up to a high concentration since, as will be shown later, a large quantity of hydrocarbon mixture containing sulfuric acid esters may be treated before the equilibrium is reversed and the treating efficiency of the phosphoric acid drops below an economical point.

The phosphoric acid esters remaining dissolved in the sludge phosphoric acid mixture after treatment may be hydrolyzed to produce alcohols, the following equation representing the reaction between water and the mono-iso-propyl phosphate shown above:

0 03131 OH O=P0H +H2O=O= P/'OH+CIH7OH OH OH Mono-propyl ester Phosphoric Iso-propyl of phosphoric acid acid alcohol It will be obvious from the above equation that the phosphoric acid is regenerated and merely needs concentration by heating to bring it to a condition for further use. There are obviously some limits to this regenerating step since there 1 are other compounds present which are of a less concentration. Howeve it is within the scopeof the invention to employ other acids of phosphorus insofaras they may be applicable. Thus, when mixtures of sulfuric and phosphoric acids are employed. an acid of phosphorus containing less water in the molecule may be mixed with sulfuric acid to form a treating reagent. Examples of such acids are pyrophosphoric acid and metaphosphoric acid, the formulas of which are shown below along with some of their commoner properties.

- Acids of phosphorus 11C. Dec. C.

Sublimes 38.6 Loses H10 The acids of phosphorus in which the phosphorus has its lower valence of 3 may also be used if desired but as a rule find less ready application on account of their. relatively greater cost and generally lower chemical and solvent action.

Treatments of hydrocarbon polymer mixtures according to the present process may be conducted at ordinary or slightly elevated temperatures, say, of the order of 50 to 60 C. and opera.- tions may be conducted in any of the well known types of equipment used in treating low boiling distillates with sulfuric acid, such as batch agitators and continuous treating plants consisting of a series of mixers for the treating reagent, including neutralizingliquors and water washes, each mixer being followed by a settling drum to permit settling and removal of the reaction products. The details of such operations are well known to those conversant with refinery operations and need only be mentioned here.

A specific example of the results obtainable by a treatment comprised within the scope of the invention will be of assistance in showing its value in connection with the treatment of hydrocarbon mixtures'produced by polymerizing reactions upon normally gaseous olefinic hydrocarbons containing sulfuric acid esters and other organic products of sulfuric acid treatment.

The polymer stock treated may have been produced as a result of treating in the presence of sulfuric acid, an olefin-containing gas mixture from an oil cracking plant. This stock may have a total sulfur content of 1.2% and at the same time have the approximate boiling range for motor fuel. However, it may not be distillable without decomposition of the sulfur compounds to an extent which gives a percentage of sulfur in the overhead product greatly in excess of that allowed in commercial gasoline.

The gasoline stock may be treated with about 1% by volume of 89% phosphoric acid at a temperature of 50 C. The run may be made by treating successive.20% portions of the oil with the same acid, this method of operationsimulating counterfiow treatment. The sulfur content of the combined oil' portions may be less than 0.05% and, after separation from the phosphoric acid sludge, it may be distilled to produce a water white color and gum stable gasoline suitable for marketing. The 1% by volume of phosphoric acid used corresponds to the use of about 6 pounds of acid per barrel of stock treated which is a reasonable and practical figure when considered from an economic standpoint. When using sulfuric acid of commercial grade in treating cracked distillates or other hydrocarbon products five pounds per barrel is considered a very mild treatment.

A further yield of gasoline is recoverable by treating the phosphoric acid sludge with steam and also an amount of isopropyl' alcohol approximately equivalent to the sulfuric acid esters corresponding to the 1 .20 sulfur content, the alcohol being obtained by neutralizing and again distilling the sludge. i

The present process thus appears as a valuable adjunct to synthetic processes in which olefins are polymerized in the presence of sulfuric acid catalysts.

The foregoing specification and example will serve their respective purposes of developing the character of the invention in showing its commercial value. but neither is to be considered as imposing undue limitations upon its generally broad scope.

I claim as my invention:

1. In the synthesis of liquid hydrocarbons by I polymerization of olefin gases in the presence of esters from the synthesized hydrocarbon liquid which comprises treating the latter with phosphoric acid.

2. In the synthesis of liquid hydrocarbons by polymerization of olefin gases in the presence of sulphuric acid as a polymerizing agent and wherein there are formed sulphuric acid esters which are soluble in the synthesized liquid, the method of removing such dissolved sulphuric acid esters from the synthesized hydrocarbon liquid which comprises treating the latter with a mixture of phosphoric and sulphuric acids;

3. In the synthesis of liquid hydrocarbons by polymerization of olefin gases in the presence of sulphuric acid as a polymerizing agent and wherein there are formed sulphuric acid esters which are soluble in the synthesized liquid, the

method of removing such dissolved sulphuric acid esters from the synthesized hydrocarbon liquid which comprises treating the latter with phosphoric acid at a temperature of from about 50 C. to 60 C.

4. In the synthesis of liquid hydrocarbons by polymerization of olefin gases in the presence of sulphuric acid as a polymerizing agent and wherein there are formed sulphuric acid esters which are soluble in the synthesized liquid, the method which comprises converting such dissolved sulphuric acid esters into phosphoric acid esters by treating the synthesized hydrocarbon liquid with phosphoric acid, separating the hydrocarbon liquid from the resultant phosphoric acid sludge containing the phosphoric acid esters, hydrolyzing the latter to form phosphoric acid and alcohol, and recycling the thus regenerated phosphoric acid to the process for treatment of additional quantites of the synthesized hydrocarbon liquid.

VLADIMIR IPATIEFF.