2,768,978 United States Patent Office Patented Oct. 30, 1956 2 with the yield. Conversion to the glycol varies almost directly with the temperature up to about 290 C. 2,768,978 The catalyst employed in this process is essentially CONTINUOUS PROCESS FOR MAKING 1,5-PEN copper chromite in which the CuO:Cr2O3 ratio may be TANEDOL FROM TETRAHYDROFURFURYL 5 varied within the limits about 40:60 to 85:15. Optimum ALCOHOL results are obtained at above about 45% Cu.O. For effec JaEmes A. Robertson, Lewiston, N.Y., assignor to E. I. du tive results catalytic pellets must be employed, powder Pont de Nemours and Company, Wilmington, Del. clogging up the reaction system. In all cases, an inor ganic binder is required to compact the chromite into No Drawing. Application August 28, 1952, O pellets. Various binders are operative for this purpose Serial No. 306,967 including silica, alumina, chromates such as magnesium chromate and silicates such as magnesium and sodium 4 Claims. (CI. 260-635) silicate. Practically all of these materials are recognized binders for catalysts and are available commercially for This invention relates to the synthesis of 1,5-pentane 5 compacting copper chromite. The particular method diol and more particularly to a continuous process for chosen for forming the pellets is not critical to this inven this synthesis. tion. One process which may be used includes pre A useful intermediate in the production of organic cipitating copper chromite from quantities of copper compounds is 1,5-pentanediol nitrate and ammonium chromite chosen to give the de 20 sired CuO:Cr2O3 ratio, adding a calculated amount of an aqueous solution of a binder Such as sodium silicate, This compound can add a reactive group at each end of , collecting the impregnated catalyst on a filter, and pel its carbon chain and thus produce linear polymers similar letizing the dry solid. to those of the hexamethylene derivatives. The poly Generally the binders tend to promote a side reaction esters so produced are especially valuable as plasticizers. 25 not evident in their absence. This reaction is the pro Resins, pharmaceuticals and synthetic rubbers may also duction of tetrahydropyran which may occur by dehydra be end products of 1,5-pentanediol reactions. The diol tion of 1,5-pentanediol according to the equation: nature of the compound supports its use as a textile lubricant, humectant and constituent of brake fluids and (2) ot printing inks. Since it is miscible in all proportions with 30 of, CH Water and has a boiling point about 100 C. above that of HO(CH2)5OH - - EO n-amyl alcohol, it is also of interest in connection with non-volatile anti-freezes. cs:O Patent application Serial Number 306,966, filed of 1,5-pentanediol Tetrahydropyran even date here with, shows a process for the manufacture 35 of 1,5-pentanediol by hydrogenation of tetrahydrofurfuryl Since dehydration of the product obviously lowers the alcohol (THFA) over a copper chromite catalyst. The yield, suppression of the side-reaction is desirable. A process there disclosed produces the glycol in good yield. binder which does suppress the Reaction 2, or at least It suffers however from the defect that it is a batch proc which fails to promote it, is sodium silicate. Na2SiO3 ess, that is, the reaction vessel employed must be period 40 is accordingly a preferred binder for the catalysts of this ically opened, discharged and then recharged with reactive invention. The quantity of binder employed may vary. material. A primary object of my invention is develop It should usually constitute between about 2% and not ment of a novel and useful method for making 1,5- more than about 10% of the entire weight of the catalyst. pentanediol. A second object of the invention is develop The size of the pellets employed is not critical. They ment of a process for making 1,5-pentanediol from tetra 45 must not be so small as to clog up the reaction bed or hydrofurfuryl alcohol. A further object is development so large or non-porous as to have almost no effective of a process for making this diol from THFA in a con surface. Commercial cylindrical pellets /s' or 346' in tinuous manner rather than in batches. Still further diameter and of about the same thickness yield good objects of the invention will be apparent from the re results. mainder of this specification. 50 The feed rate of THFA is almost of as much in I have found that my objectives can be achieved by portance as the conversion temperature or the catalyst. continuously hydrogenating THFA at temperatures inct . At a given temperature an increase in the rate of feed cf exceeding 290-300° C. over a pelleted copper chromite THFA through the reactor results in an increase in yield catalyst. The pellets form a bed and are separately bound but a decrease in conversion to 1,5-pentanediol. The re with an inorganic binder. The equation for the reaction 55 action involved here is exothermic so the temperature may be written: tends to rise with the feed rate. Desirable limits are (1) CE.--Ca between about .25 and 3.0 v./v./hr., the abbreviation | Cu (CrO2) Cha CH-CHOH -- He ------HO(CH2)5OH v./v./hr. possessing its usual meaning of volume of liquid Yo? Heat fed per unit volume of catalyst bed per hour. The cata 60 lyst beds employed in the experiments shown here had Tetrahydrofurfuryl alcohol 1,5-pentanedio volumes of 500 cc. Higher feed values might be used with larger beds. In this process liquid THFA is slowly passed through the The pressure of the hydrogen supplied to the System catalytic bed formed of copper chromite pellets while is not sharply critical. If however too low a value is hydrogen under super-atmospheric pressure is passed con 65 employed the reaction slows down to an undesirable tinuously and simultaneously through the same bed. The extent. At least 10 atmospheres should be maintained to temperature is the most important variable to be con obtain efficient reaction rates but lower values can be sidered and should not be permitted to rise above 300° C. employed if extremely low conversions. are tolerable. An within the catalytic mass, 250-300° C. representing a upper limit need only be set by the strength of the appa satisfactory range with 270-290° C. preferred. Below 70 ratus available. . In practice about 4200-4400 lbs./in. about 250 C. the hydrogenation proceeds too slowly are satisfactory. The rate of hydrogen venting is also while above 300° C. side reactions interfere noticeably . of no critical importance. Variation of this rate between 2,768,978 3 4. 1.3 and 45 I./min. in a series of continuous hydrogena The procedure used previously was repeated in runs tion runs showed no significant effects. using the preferred catalyst with a CuO: Cr2O3 ratio of Further details of my invention may be understood 53:44 and containing not more than 10% by weight of from the following illustrative examples: sodium silicate, Na2SiO3. The catalyst employed was obtained commercially as were the others shown in these EXAMPLE 1. s examples. Results are given in Table IV. The tempera A series of runs was made passing THFA and H2 at a tures of these runs, between 275 and 280 form an pressure of around 4300 lbs./in. co-currently through optimum range within the preferred range of 270° 500 cc. of copper chromite pellets. The CuO:Cr2O3 ratio 290° C. in these pellets was 53:44, with silica constituting not 10 Table IV more than 10% of the total weight of the catalyst. Prod ucts were separated by fractional distillation. Results i, 5-Pentanediol By-Products are summarized in Table I: (Percent) Teinp., Liq. mid W Run oC. Eeed, Table I ce.?hr. Per- Percent 5 cent Con- THE 1 1-P2 1, 5-Pentanediol By-Products Yield version (Percent) Temp., Liq. Il------277.4 760 93 6.3 Ril cC. Feed, cc./hr. Per | Percent 12---- 277.7 326 90 7.4 cent Con- THP1 l-P 20 13------275.2 22 92 8.9 Yield version 1 THP is tetrahydropyran. 278 750 71 25 23 9 21-P is 1-pentano. 279 285 49 24 40 10 289 310 32 18 55 2 It will be noted that no tetrahydropyran was formed with 29 790 52 22 32 18 catalysts pelletized with a sodium silicate binder and that 1,5-pentanediol yields are correspondingly increased. i THP is tetrahydropyran. For this reason sodium silicate is the preferred binder. 2 I-P is 1-pentanol. Various modifications in the Examples given above and It will be noted that both yields and conversions are in my process as a whole will be evident to those skilled given for 1,5-pentanediol. These terms may be defined, in the art. It is not necessary, for instance, that the tetra as used here, by the following equations: hydrofurfuryl alcohol employed be entirely pure. The only requirement is that any impurities present be rela Moles 1,5-pentanediol produced tively inert, that is, they must not react with THFA, 1,5- Percentage yield= Moles THFA consumed 100 pentanediol, the catalyst or hydrogen in such a manner as to interfere with the desired reaction. Materials pos Percentage conversions 35 sessing the requisite inertness include compounds related Moles 1,5-pentanediol produced X 100 to tetrahydrofurfuryl alcohol and furfural derivatives in Moles THFA charged general. Since THFA is frequently made directly by hy EXAMPLE 2 drogenating furfural, it thus becomes possible to use a Several runs were made passing hydrogen and THFA two-step process in which THFA is first made from the co-currently through 500 cc. of copper chromite catalyst 40 fairly common furfural and then hydrogenated to 1,5- similar to that used in Example 1 except that it was bound pentanediol by the procedure shown above without an with magnesium chromate, MgCrO4 instead of silica. intermediate separation from the by-products of the first Hydrogen pressure was as before. Results are tabu step. lated in: A satisfactory process starting with furfural comprises Table II 45 a first step of hydrogenating furfural over a foraminous cobalt catalyst, a second step of hydrogenating the prod , 5-Pentanediol By-Products uct of the first step, which product may contain large (Percent) Temp., Liq. amounts of THFA, over copper chromite. A suitable Run oC. Ed P P process for producing THFA from furfural is shown by e's ecce THP1 1-P 50 British Patent 627,293 disclosing foraminate cobalt-alu Yield version minum and nickel-aluminum as catalysts for the reaction. In one example of this patent a 50:50 mixture of furfural 279 750 78 34 13 9 and THFA was continuously injected over a foraminate 276 300 62 37 24 3 277 1,530 83 24 4. O cobalt catalyst at 50° C. with hydrogen under pressure. 260.5 610 89 15.------i 55 Substantially complete conversion of the furfural to THFA resulted and pure THFA was obtained on redistillation. 1 THP is tetrahydropyran. This redistillation step is of course unnecessary for the 2 I-P is 1-pentanol. purposes of my invention. The crude product obtained EXAMPLE 3 here may merely be injected continuously with hydrogen The procedure of Examples 1 and 2 was followed 60 over the copper chromite catalyst. It is desirable for using a chromite catalyst like those used before except the sake of efficiency that the liquid subsequently hydro that it was bound with magnesium silicate, MgSiO3. genated to 1,5-pentanediol contain a substantial amount, Table III shows the results obtained. 50-75% or an even greater proportion, of THFA. Con Table III sequently the British process is excellent for producing 6 a material suitable for further hydrogenation by my i, 5-Pentanediol By-Products method. A third step of separating the product by frac Temp., Liq. (Percent) tional distillation may and usually will be added to the Run oC Feed, other two. Although the second step may be carried out cc./hr. Per- Percent cent Con- THP 1-P 2 in batches continuous operation is economically desirable. Yield version 70 The result is therefore a continuous process for producing 1,5-pentanediol in two steps or in three if the separation 9------27 30 60.5 20.3 25.4 7.8 be included. Other known methods of hydrogenating 10------277 292 38.5 20, 4 46.0 2.2 furfural to THFA may of course be substituted for that 1 THP is tetrahydropyran. of the British patent shown above as constituting a desir a 1-P is 1-pentanol. s able first step. 2,768,978 5 6 Further modifications may be made in my process 4. The process of obtaining 1,5-pentanediol which without departing from the spirit thereof. The examples comprises forming a mixed product by continuously and cited, for instance, show only co-current flow of hydrogen simultaneously passing hydrogen and a liquid containing and THFA. Countercurrent flow may obviously be used a substantial proportion of tetrahydrofurfuryl alcohol instead of co-current. in either case the apparatus emi through a catalyst bed formed of copper chromite pellets, ployed, which forms no part of the invention, may be each of said pellets being bound together by not more than conventional hydrogenation equipment adapted to with about 2-10% of its weight of sodium silicate and possess stand the pressures required and to provide a retainer for ing a CuO:Cr2O3 ratio of 53:44, at a temperature of the catalyst bed. Temperatures may be controlled in between about 275 and 280 C. and a hydrogen pressure any convenient manner. If the preferred feed rates given 0 of 4200-4400 lbs./in2 for the 500 cc. bed, that is, rates within the range 0.25 and 3.0 V./v./hr., be employed little external cooling as References Cited in the file of this patent by an ice bath or water jacket is required. When initiat UNITED STATES PATENTS ing a continuous hydrogenation it may be desirable to pre 2,265,682 Bennett et al. ------Dec. 9, 1941 heat either or both the THFA and H2 but this becomes 5 2497,812 Copelin ------Feb. 14, 1950 unnecessary after the reaction starts. Since still further 2,546,019 Smith ------Mar. 20, 1951 obvious modifications of the invention are possible, propose to be bound solely by the annexed claims. FOREIGN PATENTS Having described my invention, I claim: 627,293 Great Britain ------Aug. 5, 1949 1. The method of producing 1,5-pentanediol in the sub 20 stantial absence of tetrahydropyran which comprises OTHER REFERENCES simultaneously and continuously passing hydrogen under Connor et al.: J. A. C. S., vol. 54, 1931, pp. 1138-1145. superatmospheric pressure and tetrahydrofurfuryl alcohol Iowa State Coll. Jour. of Science, vol. 12 (1937) thirough a catalyst bed formed of copper chromite pellets (Menzel), pp. 142-144. with a CuO: Cr2O3 ratio of from 40:60 to 85:15 at a 25 "Organic Synthesis,” vol. 26 (1946), p. 83; pub. by temperature between 250 and 300° C., said pellets con John Wiley & Sons, New York, N.Y. taining a sodium silicate binder. Bull. Soc. Chim. de France (1947) (Paul), pp. 165 2. The method of claim 1 in which each of said copper 168. chromite pellets is bound together by means of a sodium Groggins: "Unit Processes in Organic Synthesis,' 3d silicate binder constituting between about 2% and 10% 30 ed. (1947), pp. 539 and 540. Pub. by McGraw-Hill of its weight. Bcok Co., New York, N. Y. 3. The method of claim 2 in which the feed rate of Indust. and Engineering Chemistry (February 1948) tetrahydrofurfuryl alcohol is between about 0.25 and 3.0 (Wojcik), pp. 211 and 216.