Abstract:
A process for petroleum refining to obtain petroleum products having a reduced content of sulphur, oxygen-and nitrogen-containing compounds which comprises introducing into the petroleum during distillation volatile and nonvolatile carbonyl compounds of transition metals selected from the group consisting of Cr, V, Mo, W, Mn, Re, Fe, Co, Ni in amounts of from 0.02 to 0.2% by weight of the petroleum at a temperature ranging from 150° to 350° C under a pressure of from 1 to 7 atm abs. and distilling the petroleum into the desired products. 
     Gasoline and kerosene resulting from such processing have a 5 to 10 times reduced content of mercaptan sulphur and 2 to 10 times reduced total sulphur content, as well as a reduced content of gums.

Description:
This is a continuation of application Ser. No. 577,466, filed May 14, 1975, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to processes for petroleum refining and, more specifically, to processes for petroleum refining to obtain petroleum products having a reduced content of sulphur, oxygen- and nitrogen-containing compounds. 
     Petroleum and primary refinery products such as gasoline and kerosene are extensively used as fuel components for internal combustion engines, as well as for jet and diesel fuels, fuel oils and starting stock for catalytical cracking. 
     Gasoline, kerosene, and diesel fuel produced from high-sulphur-content crudes and medium-sulphur content crudes contain total and mercaptan sulphur. For example, mercaptan content in kerosene may be as high as 0.008% by weight although the tolerable content is at most 0.005% by weight. The increased content of sulphur and sulphur compounds substantially impairs the service properties of petroleum products, resulting in reduced motor service life due to accelerated wear of vital parts and decreasing the economic efficiency thereof. In addition, increased sulfur content contributes to increased air pollution by producing acidic combustion products. 
     Reactive nitrogen- and oxygen-containing resin-forming compounds as well as naphthenic acids cause a reduced fuel stability upon storage due to formation of gums. 
     Various processes, for the removal of sulphur and sulphur compounds, contemplating treatment of products resulting from petroleum refining such as by treatment with sulphuric acid, adsorbents, hydrofining and the like are known in the art. In those prior art processes, as a rule, petroleum is first subjected to distillation, and thereafter each individual fraction is treated. However, from an economic point of view it is preferred to perform distillation and purification in one technological step. 
     A known process for desulfurization of hydrocarbons (U.S. Pat. No. 2,306,933) involves removing hydrogen sulphide, heating the petroleum separating the light and heavy fraction, treating the heavy fractions using conditions which facilitate formation of mercaptans at temperatures up to 204.4° C. (400° F.) by means of a reagent to convert non-mercaptan sulphur to mercaptans. This treatment is followed by reacting the heavy fraction with a metal carbonyl at a temperature of from 148.9° to 343° C. (300° to 650° F.) and separating any unreacted metal carbonyl. 
     Also known in the art is a process for purifying products resulting from petroleum refining to remove sulphur, sulphur compounds, reactive nitrogen- and oxygen-containing compounds and naphthenic acids (Belgian Patent No. 809,377) which process comprises purifying petroleum or its primary refinary products with compounds of transition metals at a temperature of from 80° to 120° C. Suitable transition metal compounds include volatile carbonyl compounds of transition metals, π-complexes of transition metals, salts or π-allyl complexes of metals of the platinum group, and carbonyl complexes of transition metals. As a result, a reaction mixture is obtained from which the desired purified product is isolated. This process is also applicable to the refining of crude petroleum. However, when used to refine crude petroleum, the process is practiced in two stages: purification treatment of crude petroleum and its subsequent distillation. Although this process is one of the most efficient known, it has some disadvantages. Its principal disadvantage resides in its use of volatile reagents for the purification which may accumulate in the final products, thus requiring the use of additional chelating agents to eliminate said reagents from the final products. All the above-described processes are applicable only to purification treatment of petroleum fractions, i.e. to products of petroleum refining, not to purification of crude petroleum and, therefore are incompatible with petroleum distillation. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a one-stage petroleum refining process which is characterized by a combination of distillation and purification stages while ensuring the production of high-quality petroleum products. 
     This and other objects of the present invention are accomplished by a process for petroleum refining resulting in the production of petroleum products with a reduced content of sulphur and oxygen- and nitrogen-containing compounds, wherein volatile and non-volatile carbonyl compounds of transition metals selected from the group consisting of V, Cr, Mo, W, Mn, Re, Fe, Co, Ni are fed into the petroleum being distilled in an amount ranging from 0.02 to 0.2% by weight of the petroleum at a temperature within the range of from 150° to 350° C. under a pressure of from 1 to 7 atm abs. by combining distillation and purification in a single stage. 
     As is well-known, at elevated temperatures during the distilling process reactive sulphur compounds as well as oxygen- and nitrogen-containing compounds are formed. Carbonyl compounds of transition metals or thermal decomposition products thereof combine the reactive compounds so that harmful impurities are transformed into heavy non-volatile components and residues of unreacted volatile treating reagents decompose to metals and gaseous products which do not contaminate the final purified products. 
     In order to increase the degree of petroleum purification by introducing carbonyl compounds of transition metals thereinto, it is advisable that the system temperature be increased to 250°-350° C. and the system pressure be selected within the range of from 1 to 7 atm. abs. These conditions ensure most effective reaction of volatile carbonyl compounds of transition metals with harmful impurities and decomposition of small amounts of unreacted volatile treating agents. 
     For the same purpose, when introducing non-volatile carbonyl compounds of transition metals, said compounds may be used in the form of aqueous solutions having a concentration of from 5 to 50% by weight. 
     As the volatile carbonyl compounds of transition metals it is preferred to employ compounds of the generic formula M a  (R) x  (CO) y , wherein M is V, Cr, Mo, W, Mn, Fe, Re, Co, Ni; a is an integer from 1 to 5; R represents organic liqands such as aromatic, diene, olefine and cyclopentadiene hydrocarbons; x is an integer from 0 to 2; y is an integer from 1 to 12. 
     As the non-volatile carbonyl compounds of transition metals it is preferred to employ compounds of the formula: [ML n  M q  (CO) m  ], wherein M is Ni, Co, Mn, Fe; L is ammonia, pyridine, piperidine, morpholine, γ-picoline, ethylene diamine, monoethanolamine, diethanolamine, triethanolamine and other amines; n is an integer from 2 to 6; m is an integer from 3 to 13; q is an integer from 1 to 4. Use may be also made of salts with carbonylhydride anions of the formula QH 2  Fe 3  (CO) 11 , where Q is ammonia, monoethanolamine, diethanolamine, triethanolamine, and trialkylamines where the alkyl may be represented by methyl, ethyl, propyl; and n-butylamines. 
     The process according to the present invention is a one-stage process which enables elimination of not only sulphur-type impurities but nitrogen- and oxygen-containing as well. To eliminate sulphur compounds it is not necessary according to the process of the present invention to transform sulphur to mercaptan sulphur. 
     Gasoline and kerosene produced according to the process of the present invention contain no hydrogen sulphide or sulphur at all; mercaptan sulphur content is reduced by 5-10 times and total sulphur content is 2 to 10 times reduced; resinous product content is substantially reduced as well. The quality of diesel fuel and bunker fuel (mazout) remains unchanged after treatment with the present process. The octane number of gasoline produced from petroleum as a result of the present process is increased, as a rule, by 10-20 points as compared to octane numbers of gasolines (56-57 by the &#34;motor-method CFR-ASTM&#34;) produced from the same petroleum by simple distilling. The present invention is also characterized by a substantial economic efficiency since it enables the production of purified gasolines and kerosene in conventional on-stream distillation units without any substantial changes in the process technology, thus saving production costs for the treatment of resulting petroleum products and freeing corresponding desulphuration unit capacities to be used for the treatment of other petroleum products such as diesel fuel. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be better understood from the following description considered together with the accompanying drawings, in which: 
     FIGS. 1-4 illustrate a number of forms of the present process in which the treating reagent is fed to various inlet points in the refining system. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The process according to the present invention is performed in the following manner. 
     Into the petroleum being distilled a carbonyl-containing reagent is gradually introduced at a temperature of from 150° to 350° C. under a pressure of from 1 to 7 atm abs. and petroleum cuts boiling at 10° C. intervals are collected. Thereafter, these fractions are compounded and resulting gasoline, kerosene, diesel fuel and beating fuel (mazout) are subjected to a comprehensive analysis for common characteristics. 
     The process of the present invention may be commercially implemented in several forms, depending on the inlet point of the treating reagent (FIGS. 1 to 4): heated petroleum (150° C.) is pumped from heat-exchangers 1 to a column stripper 11, through a pipe still III and then is fed into the main rectification column IV at a temperature of from 250° to 350° C. under a pressure of 1 to 7 atm abs., where rectification is effected. 
     FIG. I. 
     A concentrated solution of the reagent in water or the petroleum product prepared by heating in a separate vessel V is pumped by means of a metering pump (a) to the inlet of a charge pump (b) of a distilling unit. Further distillation is performed in a conventional manner. 
     FIG. II. 
     A concentrated solution of the reagent in water or the petroleum product prepared by heating in a separate vessel V is pumped by a metering pump (a) to the outlet of a charge pump (b&#39;) of a distilling unit. Further distillation is performed in a conventional manner. 
     In both forms of the process illustrated in FIGS. I and II the reagent may be fed along with a soda solution which is usually introduced into the process to inhibit acid corrosion. 
     FIG. III. 
     A concentrated solution of the reagent in a petroleum product prepared in a vessel V is pumped to the inlet of a pipe still pump (c) which delivers hot stripped petroleum from column II to the pipe still III and then to the main rectification column IV. Further distillation is performed in a conventional manner. 
     FIG. IV. 
     This figure illustrates a combined system for the reagent supply. A concentrated solution of the reagent in a petroleum product prepared in a vessel V may be fed simultaneously or successively to the inlet of a charge pump (b), to the outlet of a charge pump (b&#39;) or to the inlet of a pipe still pump (c). Further refining is performed in a conventional manner. 
     For a better understanding of the present invention specific examples of the practice of the process are given hereinbelow. 
     EXAMPLE 1 
     Into 1,500 g of desalted and dehydrated petroleum being distilled at 350° C. under 1.5 atm. abs., 2.6 g of [Mn(C 5  H 5  N) 6  ] [Mn(CO) 5  ] 2  salt are gradually added and petroleum cuts boiling at 10° C. intervals are collected. The resulting cuts are compounded to give gasoline (from the initial boiling point to 150° C.), kerosene (150°-230° C.) and diesel fuel (230°-350° C.). The products and distillation bottoms bunker fuel (mazout) are subjected to a comprehensive analysis. Average properties of the resulting fractions are shown in Tables 2 and 3. 
     EXAMPLE 2 
     Into 1,500 g of desalted and dehydrated petroleum being distilled at 280° under a pressure of 1.80 atm, 3 g of a salt, i.e. [(C 2  H 5 ) 3  NH 2  Fe 3  (CO) 11  ] are gradually added and 10° C. cuts are collected. These cuts are compounded to give gasoline (from the initial boiling point to 150° C.), kerosene (150°-230° C.) and diesel fuel (230°-350° C.). The products and distillation bottoms bunker fuel (mazout) are subjected to a comprehensive analysis. Average properties of the resulting fractions are shown in Tables 2 and 3. 
     EXAMPLE 3 
     Into 1,500 g of a crude petroleum to be distilled at 280° C. under a pressure of 3.5 atm, 1.2 g of manganese carbonyl Mn 2  (CO) 10  is gradually added; 10° cuts are collected and compounded to give gasoline (from the initial boiling point to 150° C.), kerosene (150° to 230° C.) and diesel fuel (230° -350° C.). The products and distillation residue bunker oil (mazout) are subjected to a comprehensive analysis. Average properties of the resulting fractions are shown in Tables 2 and 3. 
     EXAMPLE 4 
     Into 700 g of desalted and dehydrated petroleum to be distilled at 300° C. under a pressure of 2.2 atm, 0.8 g of a salt, i.e. (HOC 2  H 4 ) 3  NH 3  HFe 3  (CO) 11  is gradually added. 10° cuts are collected and, under distillation, fractions of gasoline (from the initial boiling point to 150° C.) and kerosene (150°-230° C.) are separated. The products are subjected to a comprehensive analysis. Average characteristics of the fractions obtained are shown in Tables 2 and 3 hereinbelow. 
     EXAMPLE 5 
     Into 1,500 g of a crude petroleum to be distilled at temperature of 300° C. under 4 atm abs. pressure, 2 g of iron pentacarbonyl are added; 10° cuts are collected and compounded to give gasoline (from the initial boiling point to 150° C.), kerosene (150°-230° C.) and diesel fuel (230°-350° C.). The products and distillation residue bunker fuel (mazout) are subjected to a comprehensive analysis. Average characteristics of the fractions obtained are shown in Tables 2 and 3. 
     Examples 6 through 22 are given in Table 1. Petroleum refining is performed in a manner similar to that described in the foregoing Example 3. Average characteristics of the fractions obtained are shown in Table 2. 
     
                                           Table 1__________________________________________________________________________Conditions of petroleum refining (Examples 6 through 22)  Petro-                          Pres-  leum         Carbonyl re-       sure,  amount,  Carbonyl          agent amo-                  Tempera-                        Time,                             atm.No.  g    reagent unt, g  ture, ° C                        min  absol.1 2      3     4       5     6    7__________________________________________________________________________6 1,000  Cr(CO).sub.6          0.6     250   45   3.57 1,800  Mo(CO).sub.6          1.3     300   40   3.58 1,200  W(CO).sub.6          1.3     300   40   3.59 1,500  Co.sub.2 (CO).sub.8          1.6     280   35   3.510  1,500  Ni(CO).sub.4          1.6     280   35   411  1,500  Re(CO).sub.10          1.1     300   40   212  2,000  Mo(CO).sub.6&#39; 1:1          2       280   35   4  Fe(CO).sub.5 (wt)13  2,000  Ni(CO).sub.4 1:1  Co.sub.2 (CO).sub.8 (wt)          2       280   35   414  2,000  Cr(CO).sub.6 CO.sub.2 (CO).sub.8 1:1          2       280   35   3.515  1,700  Fe.sub.2 (CO).sub.9          1.7     300   40   2.516  1,700  Fe.sub. 3 (CO).sub.12          1.7     300   40   2.517  1,500  C.sub.6 H.sub.6 Cr(CO).sub.3          1.3     250   40   1.518  1,500  C.sub.5 H.sub.6 Fe(CO).sub.3          1.6     280   45   1.519  1,500  C.sub.4 H.sub.6 Fe(CO).sub.3          1.1     250   35   1.520  1,800  C.sub.6 H.sub.8 Fe(CO).sub.3          1.2     250   40   1.521  1,500  C.sub.5 H.sub.5 Co(CO).sub.2          1.3     250   40   1.522  1,700  C.sub.5 H.sub.5 Mn(CO).sub.3          1.4     250   40   1.5__________________________________________________________________________ *See R. K. Kochhav et al, Journal Organometal. Chemistry, Vol. 6, p. 272 (1966). 
    
     
                                           Table 2__________________________________________________________________________Characteristics of petroleum fractions produced from desalted petroleumwith and withoutintroduction of a treating agent into the petroleum being refined,      Petroleum fractions obtained with-                               Petroleum fraction obtained with                               introduction of      out introduction of a purifying agent                               a purifying agent                          Distil-                         lation                               Gasoline      Gasoline           bottoms,                               fraction      fraction           Kerosene                  Diesel fu-                         (bunker                               initial                                      Kerosene                                             Diesel                                                  DistillationCharacteris-      boiling           fraction                  el frac-                         fuel) boiling                                      fraction                                             fuel bottoms (bunk-tics       point to           150 to tion 230                         above point to                                      150-   230 to                                                  er fuel)initial    150° C           230° C                  to 350° C                         350° C                               150° C                                      230° C                                             350° C                                                  above 350°                                                  C 1         2    3      4      5     6      7      8    9__________________________________________________________________________Octane number      56.0-           --     --     --    80-86  --     --   --&#34;Motor-method&#34;      57.0(CFR-ASTM)Content, wt.%:total sulphur      0.03-0.02           0.15-0.16                  1.20-1.18                         2.30  0.01-0.002                                      0.15- 0.07                                             1.13-1.15                                                  2.35mercaptan  0.0056           0.0045-                  0.0014-                         --    0.002- 0.0007-                                             0.0010-                                                  --sulphur    -0.0050           0.0050 0.0013       0.001  0.0002 0.0011hydrogen sul-      0.0016-           0.0003 none         none   none   none --phide sulphur      0.0020           -0.0005Density ρ.sup.40,      0.690-           0.775- --     --    0.690- 0.775  --   --4          0.700           0.778               0.700  -0.778g/cm.sup.3Kinematicviscosity  --   1.25-1.27                  5.0-6.0                         --    --     1.25-1.27                                             5.0-6.0                                                  --at 20° C, cStCombustionheat, Kcal/kg      --   10,400-10,430                  --     --    --     10,400-10,425                                             --   --Smoke point,mm         --   25-27  --     --    --     26-28  --   --Acidity, mg KOHper 100 ml of fuel      --   --     --     --    1.60-1.70                                      0.5-0.7                                             --   --Flash point,° C --   28-30  85-90  --    --     28-30  85-90                                                  --Congelationpoint (pour point)° C --   60-62  10-15  --    --     60- 62 10-15                                                  --Iodine number, gper 100 g of fuel      --   0.3-0.4                  --     --    --     0.3-0.5                                             --   --Mechanical impuritiescontent, mg      none none   --     --    none   none   --   --Ash content, wt.%      --   0.001-0.003                  --     --    --     0.002-0.003                                             --   --__________________________________________________________________________ 
    
     
                       Table 3______________________________________Characteristics of bunker fuel obtained by usingbottoms of petroleum distillation and introducing,into the crude petroleum, carbonyl reagents accord-ing to Examples 1-3 and 4-5. Weight ratio betweendiesel fuel and bottoms is 1:1.            Average valuesNo. Characteristics    Examples 1-3                             Examples 4-5______________________________________1   Engler viscosity at    50° C, degrees                  2.38-2.40  2.85-2.902   Ash content, % by weight                  0.038-0.05 0.049-0.0603   Mechanical impurities    content, % by weight                  0.010-0.013                             0.092-0.0974   Water content, % by weight                  none       none5   Content of water-soluble    acides and alkalis none       none6   Sulphur content, % by weight                  1.50-1.52  1.51-1.547   Hydrogen sulphide content                  none       none8   Gums content, % by weight                  48-50      48-509   Flash point (closed crucible),    ° C         82-84      84-8610  Congelation point, ° C                  -9 to -7   -11 to -911  Density, d.sub.4.sup.20                  0.898      0.898______________________________________