Liquefied petroleum gas compositions
United States Patent [191 Tsunemi LIQUEFIED PETROLEUM GAS COMPOSITIONS [75] Inventor:  
 [73] Assignee: Nippon Oil Company, Limited, Tokyo, Japan 22 Filed: Aug. 20, 1973 21 Appl. No.: 390,112  
 Related US. Application Data [63] Continuation-in-part of Ser. No. 205.745, Dec. 7,  
 I971, abandoned.  
 Masaaki Tsunemi, Kawasaki, Japan [30] Foreign Application Priority Data Dec. ll, I970 Japan 45-109734 [52] US. Cl 44/52; 44/66 [51] Int. Cl C10] 1/14 [58] Field of Search 44/56, 70, 52, 66  
 1451 Apr. 22, 1975 [56] References Cited UNITED STATES PATENTS 2,236,590 4/1941 Backoff et al. 44/70 Primary E.\&#39;aminer-Daniel E. Wyman Assistant E.\&#39;aminerY. H. Smith Attorney, Agent, or Firm-Ostrolenk, Faber, Gerb &amp; Soffen [57] ABSTRACT 9 Claims, No Drawings LIQUEFIED PETROLEUM GAS COMPOSITIONS This is a contin&#39;uation-in-part of application Ser. No. 205,745 filed Dec. 7, 1971, and now abandoned.  
  The present invention relates to detergent, liquefied petroleum gas compositions. More particularly, the present invention relates to liquefied petroleum gas compositions for keeping apparatus or machinery in which a liquefied petroleum gas fuel is used, especially an apparatus for gasification of liquefied petroleum gases, clean.  
  When a liquefied petroleum gas is used as motor fuel or industrial fuel, an apparatus for gasifying liquefied petroleum gas has been required for the purpose of gasification, pressure reduction or pressure control. How ever, these apparatuses have complicated constructions. It has been known that, if a solid substance or a highly viscous substance adheres to the inside of such an apparatus, smooth operation is hindered and sometimes the apparatus becomes not usable.  
  In most apparatuses for gasifying a liquefied petroleum gas, particularly motor gasification apparatuses [motor gasification apparatuses in this specification indicate those shown in, for example, journal of Japan Machinery Society 67, No. 545,865 (1965) or Journal of Petroleuum Society, 12, No. 12, 24 1969)], the liquefied petroleum gas is gasified by heat of enginecooling water. In short, the structure of such an apparatus comprises primary and secondary reducing chambers. The pressure is reduced in two separate states in the primary and secondary reducing chambers, pressures in the primary and secondary reducing chambers are regulated to around 1.35 Kg/cm and atmospheric or a slightly lower pressure, respectively. The liquefied petroleum gas is introduced in the primary reducing chamber through a primary reducing valve at the inlet of the chamber and gasified therein. The resulting gas is then introduced in the secondary reducing chamber through a secondary reducing valve at the inlet of the chamber, pressure-controlled therein and then introduced in a mixer through a gas fuel supplier. Opening and closing operations of the reducing valves are performed by a diaphragm and a spring. in the motor gasification apparatus, as accumulation of a sediment is increased, the diaphragm is hardened and the liquefied petroleum gas supply valves (particularly the primary reducing valve) are fastened and the regular supply of the fuel to a combustion device is inhibited. In order to eliminate said trouble caused by the sediment, frequent control of the gasification apparatus is necessary. Finally, exchange of the gasification apparatus or complete cleaning of respective pieces of the dismantled apparatus become necessary.  
  in general, a liquefied petroleum gas contains solid substances, reactive components and other impurities, though in very small amounts. The contents comprise mainly impurities which cannot be removed completely in the preparation of the liquefied petroleum gas, corrosion inhibitors for the apparatus, impurities attached to some parts of the apparatus and impurities resulted substantially from every part of the apparatus. If the liquefied petroleum gas containing these impurities is used practically, a considerable amount of sediment occurs in the gasification apparatus during a long period operation and causes troubles.  
  However, a practical method for solving the aforesaid problem efficiently has not been found yet.  
  The object of the present invention is to provide new liquefied gas compositions for keeping apparatus and machinery clear to avoid the contamination due to reactive components and impurities contained in the liquefied petroleum gas and also for removing the contaminating sediments to keep the apparatuses and machinery clear. The object of the invention, i.e., prevention of contamination of removal and discharge of the sediments can be attained by incorporating in the liquefied petroleum gases one or more carboxylic acid esters boiling at a temperature above 200C which are in liquid state at ambient temperatures.  
  If a liquefied petroleum gas composition containing one or more carboxylic acid esters boiling at a temperature below 200C is used, as shown in an Example given below, operation of the primary reducing valve is not smooth and sediment in the primary reducing chamber is larger in amount than in the case of the liquefied petroleum gas composition of the present invention. If a carboxylic acid ester which is solid at ambient temperature is used, sometimes the carboxylic acid ester is solidified during suspension of operation of the apparatus, thereby disturbing start-up considerably. Accordingly, the carboxylic acid esters used in the present invention must be in liquid state at ambient temperature.  
  The liquefied petroleum gases of the present invention involve all the gases prescribed in J18 (J18 K-2240). No special limitation is provided in structure of the carboxylic acid esters to be incorporated in liquefied petroleum gas according to the present inven tion.  
  One or more esters of the following groups can be used:  
  a. carboxylic acid esters obtained from the reaction between aromatic carboxylic acids and C -C aliphatic alcohols, such as methyl-, ethyl-, propyland butyl benzoate, methyland ethyl salicylate, ethyl phenyl acetate, methyl-and ethyl benzoylacetate, etc.;  
  b. carboxylic acid esters obtained from the reaction between C -C aliphatic mono-carboxylic acid and either C -C aliphatic alcohols or C C aliphatic polyhydric alcohols, such as benzyl-, linalyl acetate, glycerine-l 3-diacetate, ethyl caprylate, ethyl caprate, ethyl pelargonate, methyl oleate, amyl stearate, ethyl glycerate, triacetin, triolein, acetopyruvic acid ethyl ester and ethyl levulinate, etc.;  
  c. carboxylic acid esters obtained from the reaction between C -C polybasic acids and either C -C aliphatic alcohols or C -C aliphatic polyhydric alcohols, such as diethyl succinate, diethyl glutarate, diethyl adipate, dibutyl adipate, dibutyl sebacate, dimethyland diethyl maleate, diethyl fumarate, diethyl glutaconate, dimethyl-, diethyl-, dibutyl, di-2-ethylhexyland dioctyl phthalate, triethyl citrate, diethyl mesoxalate, acetone dicarboxylic acid diethyl ester and diethyl-l-malate, etc.  
  Preferred esters are those having stable chemical properties, for example, benzyl-acetate, propyl benzoate, butyl benzoate, ethyl adipate, diethyl phthalate, dibutyl phthalate, dioctyl phthalate, amyl stearate and mixtures thereof. The amount of the carboxylic acid ester in the composition is generally in the range of l 500 ppm., preferably 5 20 ppm. If the amount of carboxylic acid ester is less than said range, the aimed prevention of contamination of the apparatuses and machinery or removal and discharge of the sediments is hardly performed. On the other hand, if the amount of carboxylic acid ester is more than said range, the carboxylic acid ester per se is precipitated to give unfavorable, ill effects to the gasification apparatus.  
  The liquefied petroleum gas compositions of the present invention may contain other ordinary additives for liquefied petroleum gas such as anti-freezing agent and smelling agent.  
  The present invention will be illustrated below in detail. The accumulation of sediments in an apparatus in which liquefied petroleum gas is used is due to poor fluidity and hardness of the sediments per se in general. The carboxylic acid esters according to the present invention remove the sediments from sediment-sensitive parts of the apparatus such as the diaphragm and supbe illustrated by way of examples. Various changes and modifications may be made without departing the spirit of scope of the invention.  
 EXAMPLE 1 An ordinary liquefied petroleum gas and a liquefied petroleum gas composition of the present invention were gasified by using a liquefied petroleum gas gasifying apparatus for a motor car (hereinafter referred to as converter) under the same conditions as in the actual operation. Solidifications of primary reducing valves were as shown in Table I.  
 Table 1 Test Composition of Sample Amount Average Condition No. (Kg) Flow of Primary Rate Reducing (kg/hr) Valve l Liquefied petroleum gas 45.l 5.0 X 2 Liquefied petroleum gas lsoamyl propionate 30 ppm 46.9 5.2 A 3 Liquefied petroleum gas Butyl acrylate 50 ppm 45.5 5.] X 4 Liquefied petroleum gas Ethylene dibenzoate I ppm 47.0 5.2 X 5 Liquefied petroleum gas Butyl stearate 70 ppm 44.] 4.9 A 6 Liquefied petroleum gas Dihutyl phthalate ppm 43.5 4.8 7 Liquefied petroleum gas Amyl stearate 30 ppm 44.7 5.0 8 Liquefied petroleum gas Ethyl benzoate 200 ppm 46.3 5.2 9 Liquefied petroleum gas Dibutyl adipate ppm 42.0 4.7 l0 Liquefied petroleum gas Ethyl glycerate 200 ppm 45.0 5.0 1 l Liquefied petroleum gas Methyl benzoylacetate 50 ppm 45.0 5.0 12 Liquefied petroleum gas Linalyl acetate 250 ppm 48.2 5.3  
 Meanings of the symbols in Table l are as follows: Valve. if released after 10 seconds holding,  
 is opened directly. Valve, if released after 10 seconds holding. is opened within 5 seconds. Valve. if released after l0 seconds holding. is opened after a period longer than 5 seconds.  
 ply valve for liquefied petroleum gas in motor gasification apparatus by dissolving, suspending or dispersing such sediments in a medium to impart fluidity and then entraining the same in the gasified petroleum gas. The capacity of the usual apparatus for gasifying liquid petroleum is far smaller compared to the volume of liquefied petroleum gas to be gasified in the apparatus in a fixed period of time. Consequently, the flow velocity of the gasified petroleum gas is very high and, accordingly, the effect of removing the sediments according to the above mechanism is great. The mixture of carboxylic acid esters and sediments entrained in the petroleum gas is substantially burned directly.  
  Even if a small amount of sediment is attached to a part (in which gas flow velocity is low) of the apparatus or pipe, the sediment can be discharged easily from the combustion system through a condensate-discharging valve according to the effect of the present invention, i.e., the effect of dissolving, suspending or dispersing the sediments to impart fluidity.  
  Concrete effects obtainable by using the liquefied petroleum gas compositions of the present invention will The above results suggest clearly that, if liquefied petroleum gas, per se, or a liquefied petroleum gas composition containing a low boiling carboxylic acid ester such as isoamyl propionate, butyl acrylate, etc. or containing a high boiling carboxylic acid ester, which is in solid state at ambient temperatures, such as ethylene dibenzoate and butyl stearate, etc. is used, the primary reducing valve in converter is apt to be fastened but, if liquefied petroleum gas composition containing a carboxylic acid ester boiling at a temperature above 200- C, which is liquid at ambient temperatures is used, the fixation or solidification of the primary reducing valve can be prevented.  
 EXAMPLE 2 Large quantities of an ordinary liquefied petroleum gas and a liquefied petroleum gas composition of the present invention were gasified in a motorcar converter under the same conditions as in the actual operation. Weights of sediments accumulated in the primary and secondary reducing chambers and operation conditions of primary reducing valve were as shown in Table 2.  
 Table 2 Test Composition of sample Amount Average Weight of Condition No. (Kg) Flow Sediment of Primary Rate Prim. Sec. Reducing (Kg/hr) (g) (g) Valve 1 Liquefied petroleum gas 1302 4.8 1.02 2.30 X 2 Liquefied petroleum gas Dioctyl phthalate 50 ppm 1253 5.0 0.58 2.87 3 Liquefied petroleum gas Dibutyl phthalate 30 ppm 1336 5.1 0.76 2.41 4 Liquefied petroleum gas Amyl stearate 50 ppm 1387 5.1 0.66 3.40 5 Liquefied petroleum gas Dimethyl maleate 100 ppm 1292 4.7 0.40 2.69 6 Liquefied petroleum gas Triolein 50 ppm 1314 4.9 0.81 3.03 7 Liquefied petroleum gas Ethyl caprate 100 ppm 1268 5.0 0.50 2.80 8 Liquefied petroleum gas Dioctyl phthalate 10 ppm Dimethyl maleate 50 ppm 1414 5.2 0.54 2.55  
  Meanings of the symbols in the right column in Table As shown clearly by the above results, a distinct dif- 2 are the same as in Table l. ference lies between non-treated, liquefied petroleum The above results suggest that if the liquefied petrogas fuels and liquefied petroleum gas compositions of leum gas composition of the present invention is used, the present invention. Namely, ifa liquefied petroleum the amount of sediment at issue in primary reducing gas, per se, is used as fuel, sediment in the primary rechamber is reduced remarkably and operation condiducing chamber is in a remarkably large amount and tions of the primary reducing valve is improved rethe sediment cannot be removed easily due to its hardmarkably as compared with the case of using liquefied ness and viscosity. Consequently, smooth operation of petroleum gas, per se. the primary reducing valve is hindered. lf drive is con- As for the amount of sediment in the secondary retinued under such conditions, it is supposed that the ducing chamber, it was larger when the liquefied petro- 3O drive becomes impossible finally owing to contaminaleum gas composition of the present invention was used. With respect to the properties, the sediment from the liquefied petroleum gas, per se, had a high tackiness and poor fluidity to make removal of the same difficult, whereas the sediment from the liquefied petroleum gas composition of the present invention was liquid, having a fluidity equivalent to that of carboxylic acid esters incorporated in the liquefied petroleum gas. In the latter case, accordingly, the sediment in the primary reducing chamber flowed into the secondary reducing chamber and it was easily discharged through a condensatedischarge valve of the second reducing chamber.  
 EXAMPLE 3 Detergent powers of an ordinary liquefied petroleum gas and a liquefied petroleum gas composition of the present invention for converters of motor engines in which a liquefied petroleum gas is used as fuel were evaluated. Accumulation of sediment and the operation condition of primary reducing valve after about 1 0,000 Km and 30,000 Km drive were as shown in Table 3.  
 tion of the device. On the other hand, if a liquefied petroleum gas composition of the present invention is used, contamination of the primary reducing chamber is little and operation of the primary reducing valve is kept always normal, since the small quantity of sediment comprises a liquid of a low viscosity. The sediment which was a liquid of a low viscosity in the secondary reducing chamber could be discharged from the converter, while sediment from the liquefied petroleum gas, per se, could not be removed easily due to its hardness and viscosity. As a result, the life of the diaphragm was prolonged considerably and driving distance per a fixed volume of the fuel was increased favorably according to smooth operation of the converter. In an experiment carried out simultaneously, it was found that if motor fuel of a liquefied petroleum gas, per se, in an already contaminated converter after about 30,000 Km drive was replaced with a liquefied petroleum gas composition of the present invention containing 30 ppm. of dioctyl phthalate and the drive was continued further about 10,000 Km, surprisingly, the hard sediment accumulated was dispersed and discharged whereby the Table 3 Test Composition of Sample Drive Fuel Rate of Weight of Sediment Condition No. Distance Consumption Fuel Primary Secondary of Primary (Km) l Consumption Chamber Chamber Reducing (Km/l) (g) (g) Valve 1 Liquefied petroleum gas 9,876 1,630 6.06 1.22* 1.37* A 2 Liquefied petroleum gas 29.933 5.056 5.92 3.10* 356* X 3 Liquefied petroleum gas Dioctyl phthalate 30 ppm 10,313 1,736 6.23 0.70 2.25&#34; 4 Liquefied petroleum gas Dioctyl phthalate 30 ppm 28,089 4,389 6.49 0.33 4.26  
 Note: Meanings of the symbols in the right column in Table 3 are the same as in Table l.  
 &#39; Removal of marked sediment is difficult due to its hardness or viscosity.  
 content of the converter was made clean again. The reduced fuel combustion rate of the car&#39;could return to its initial, favorable condition in virtue of said effect.  
  Thus, it is apparent that liquefied petroleum gas compositions of the present invention exhibit excellent effects.  
  Various changes and modifications can be made in the present invention without departing from the spirit and the scope thereof. The various embodiments set forth herein serve to further illustrate the invention but were not intended to limit it.  
 I claim:  
  1. A liquefied petroleum gas composition containing l-500 ppm, based on the liquefied petroleum gas, of at least one carboxylic acid ester boiling at a temperature above 200C. and which is liquid at ambient temperature. said carboxylic acid ester being selected from the group consisting of (a) the ester of an aromatic carboxylic acid and a l-8 carbon atom aliphatic alcohol, (b) the ester of a 2-18 carbon atom aliphatic monocarboxylic acid and a 1-10 carbon atom aliphatic alcohol, (c) the ester of a 2-18 carbon atom aliphatic monocarboxylic acid and a 2-3 carbon atom aliphatic polyhydric alcohol, (d) the ester of a 3-10 carbon atom polybasic carboxylic acid and a 1-10 carbon atom aliphatic alcohol. and (e) the ester of a 3-l0 carbon atom polybasic carboxylic acid and a 2-3 carbon atom aliphatic polyhydric alcohol. I  
  2. The liquefied petroleum gas composition of claim I wherein said carboxylic acid ester is a member of the group consisting of methyl benzoate, ethyl benzoate, propyl benzoate, butyl benzoate, methyl salicylate, ethyl salicylate, ethyl phenyl acetate, methyl benzoylacetate. ethyl benzoylacetate, benzyl acetate. linalyl acetate. glycerine-l,3-diacetate, ethyl caprylate, ethyl caprate. ethyl pelargonate. methyl oleate, amyl stearate, ethyl glycerate, t riacetin, triolein, acetopyruvic acid ethyl ester, ethyl levulinate, diethyl succinate, diethyl glutarate, diethyl adipate, dibutyl adipate, dibutyl sebacate, dimethyl maleate, diethyl maleate, diethyl fumarate. diethyl glutaconate, dimethyl phthalate, diethyl phthalate, dibutyl phthalate, di-Z-ethylhexyl phthalate, dioctyl phthalate, triethyl citrate, diethyl mesoxalate, acetone dicarboxylic acid diethyl ester, and diethyl-l-malate.  
  3. The liquefied petroleum gas composition of claim 1 wherein said carboxylic acid ester is a member selected from the group consisting of benzyl acetate, propyl benzoate, butyl benzoate, ethyl adipate, diethyl phthalate, dibutyl phthalate, dioctyl phthalate and amyl stearate.  
  4. The liquefied petroleum gas composition of claim 1 wherein the amount of the said carboxylic acid ester contained therein is 5-250 ppm, based on the said liquefied petroleum gas.  
  5. The liquefied petroleum gas composition of claim 2 wherein the amount of the said carboxylic acid ester contained therein is 5-250 ppm, based on the said liquefied petroleum gasv I 6. The liquefied petroleum gas composition of claim 3 wherein the amount of the said carboxylic acid ester contained therein is 5-250 ppm, based on the said liquefied petroleum gas.  
  7. The liquefied petroleum gas composition of claim 4 wherein the amount of said carboxylic acid ester is 30-200 ppmv 8. The liquefied petroleum gas composition of claim 5 wherein the amount of the said carboxylic acid ester is 30-200 ppm.  
  9. The liquefied petroleum gas composition of claim 6 wherein the amount of the said carboxylic acid ester is 30-200 ppm.