United States Patent Office Patented Oct
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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.