MAIMOTOMONTANT US009828318B2 DE LLUT TUTO MINI ( 12 ) United States Patent ( 10) Patent No. : US 9 ,828 ,318 B2 Ishihara et al. (45 ) Date of Patent: Nov . 28, 2017

(54 ) METHOD FOR PRODUCING GLYCOLS FOREIGN PATENT DOCUMENTS FROM OXIRANE COMPOUNDS S56 - 73035 A 6 / 1981 (71 ) Applicant: Sumitomo Chemical Company, WO WO 9511213 * 4 / 1995 Limited , Tokyo (JP ) OTHER PUBLICATIONS ( 72 ) Inventors : Shinjiro Ishihara , Ehime ( JP ) ; Shoko National Center for Biotechnology Information . PubChem Com Ikeda , Chiba ( JP ) ; Masayuki Yoshii , pound Database, CID = 8087 , https: / / pubchem .ncbi . nlm .nih . gov / Chiba ( JP ) ; Makoto Murata , Ibaraki compound / 8087 (accessed Aug. 23 , 2015 ) , 31 pages creation date ( JP ) Mar . 26 , 2005 . * National Center for Biotechnology Information . PubChem Com pound Database , CID = 32611, https: / / pubchem .ncbi . nlm .nih . gov / ( 73) Assignee: Sumitomo Chemical Company, compound / 32611 (accessed Aug . 23 , 2015 ) , 29 pages creation date Limited , Tokyo (JP ) Aug. 8 , 2005 . * Tanabe (“ Niobic acid as an unusual acidic solid material ” , Materials ( * ) Notice : Subject to any disclaimer , the term of this Chemistry and Physics, vol. 17 , Issues 1 - 2 , Apr. -May 1987 , pp . patent is extended or adjusted under 35 217 - 225 ). * U . S .C . 154 (b ) by 0 days . Kozo Tanabe , “ Niobic acid as an unusual acidic solid material” , Materials and Physics, vol . 17, Issues 1 - 2 , Apr. - May 1987 , pp . 217 - 225 . * (21 ) Appl . No. : 14 /362 , 940 Iizuka et al . , “ Acidic and Catalytic Properties of Niobium Pentoxide” , Bull . Chem . Soc. Jpn ., 56 , Oct. 1983 , pp . 2927 -2931 . * (22 ) PCT Filed: Dec . 12 , 2012 Tanabe et al. , “ New Solid Acids and Bases: Their Catalytic Prop erties ” , Technology and Engineering , 1990 , pp . 60 and 61. * (86 ) PCT No. : PCT/ JP2012 / 082853 Kirk - Othmer Encyclopedia of Chemical Technology , John Wiley & Sons, Inc. , pp . 1 - 10 (2000 ) . $ 371 ( c ) ( 1 ) , “ Shokubai Kagaku ( Catalyst Chemistry ) ,” pp . 518 -519 , 525 ( 1981 ). ( 2 ) Date: Jun . 5 , 2014 Dow Dipropylene Glycol LO + Technical Data Sheet . Dow Tripropylene Glycol, Acrylate Grade Technical Data Sheet. ( 87 ) PCT Pub . No. : WO2013 /089271 Int' l Search Report dated Feb . 5 , 2013 in Int' l Application No . PCT Pub . Date : Jun . 20 , 2013 PCT/ JP2012 /082853 . (65 ) Prior Publication Data * cited by examiner US 2014 /0378714 A1 Dec . 25 , 2014 Primary Examiner — Rosalynd A Keys (74 ) Attorney, Agent, or Firm — Panitch Schwarze ( 30 ) Foreign Application Priority Data Belisario & Nadel LLP Dec . 13 , 2011 ( JP ) ...... 2011- 271976 (57 ) ABSTRACT May 10 , 2012 ( JP ) ...... 2012 - 108285 The objective of the present invention is to provide a method for the highly selective production of dipropylene glycol (51 ) Int. CI. containing 1 , 1 ' -oxybis - 2 -propanol in a proportion of 0 . 10 to C07C 41/ 03 ( 2006 .01 ) 0 .70 and/ or tripropylene glycol containing 1 , 1 ' - [ ( 1 -methyl (52 ) U . S . CI. 1 ,2 - ethanediyl) bis ( oxy )] bis - 2 -propanol in a proportion of CPC ...... C07C 41/ 03 ( 2013. 01 ) ; YO2P 20 /582 0 . 10 to 0 .70 . The present invention is a method for produc ( 2015 . 11) ing dipropylene glycol containing 1, 1' - oxybis -2 -propanol in (58 ) Field of Classification Search a proportion of 0 . 10 to 0 . 70 and / or tripropylene glycol CPC ...... C07C 41/ 03 containing 1 , 1 ' - [ ( 1 -methyl - 1 , 2 - ethanediyl) bis (oxy ) ] bis - 2 See application file for complete search history. propanol in a proportion of 0 . 10 to 0 . 70 , the method com prising a reaction step of making a reactant comprising (56 ) References Cited propylene oxide and water react in the presence of a catalyst , wherein the catalyst comprises at least one element selected U .S . PATENT DOCUMENTS from the group consisting of vanadium , niobium , and tan 4 ,551 ,566 A 11/ 1985 Robson et al . talum , and the Hammett acidity function ( H ) of the catalyst 4 ,578 ,524 A 3 / 1986 Keen satisfies Hs9. 3 . 4 ,760 , 200 A * 7 / 1988 Keen et al . 568 / 867 6 , 147 ,265 A 11 /2000 Iwakura et al . 5 Claims, No Drawings US 9 ,828 ,318 B2 METHOD FOR PRODUCING GLYCOLS PRIOR ART DOCUMENT FROM OXIRANE COMPOUNDS Patent Document CROSS -REFERENCE TO RELATED APPLICATION 5 [Patent Document 1 ] JP - A - 56 -073035 This application is a Section 371 of International Appli Non -Patent Document cation No. PCT/ JP2012 / 082853 , filed Dec . 12 , 2012 , which was published in the Japanese language on Jun . 20 , 2013 , [Non -Patent Document 1 ] Alton E . Martin , “ Glycols, Pro under International Publication No . WO 2013 /089271 A1, 10 pylene Glycols ” , Kirk - Othmer Encyclopedia of Chemical and the disclosure of which is incorporated herein by Technology, 2000 reference . SUMMARY OF THE INVENTION TECHNICAL FIELD 15 Problems to be Solved by the Invention The present invention relates to a method for the highly Patent document 1 , however, contains no disclosure about selective production of dipropylene glycol containing 1 , 1' the proportion of 1 , 1 '- oxybis - 2 -propanol contained in dipro oxybis - 2 - propanol in a proportion of 0 . 10 to 0 .70 and / or pylene glycol and the proportion of 1 , 1 '- [ ( 1 -methyl - 1 , 2 tripropylene glycol containing 1 , 1 '- [ ( 1 -methyl - 1 , 2 - eth - 20 ethanediyl) bis (oxy ) ]bis - 2 -propanol contained in tripropyl anediyl ) bis ( oxy ) ]bis - 2 - propanol in a proportion of 0 . 10 to ene glycol. 0 . 70 . The objective of the present invention is to provide a method for the highly selective production of dipropylene BACKGROUND ART glycol containing 1 , 1 ' - oxybis - 2 - propanol in a proportion of Dipropylene glycol is a compound that is used as a raw 25 0 . 10 to 0 .70 and /or tripropylene glycol containing 1 , 1 '- [ ( 1 material for polyester resin or polyurethane resin , a raw methyl- 1 ,2 - ethanediyl) bis (oxy ) ]bis - 2 -propanol in a propor material for acrylates , an operating oil , an antifreezing tion of 0 . 10 to 0 .70 . solution , a wetting agent for cellophane, a compatibilizing Means for Solving the Problems agent, a solvent for printing ink , a raw material for cosmet- 30 ics , solvent for perfume, solvent for toiletries , and so on , The present invention relates to a method for producing whereas tripropylene glycol is a compound that is used as a dipropylene glycol containing 1, 1' - oxybis -2 -propanol in a raw material for polyester resin or polyurethane resin , a raw proportion of 0 . 10 to 0. 70 and / or tripropylene glycol con material for acrylates , a solvent for a water- soluble oil, a taining 1 , 1 ' - [ ( 1 -methyl - 1 , 2 - ethanediyl) bis ( oxy ) ]bis - 2 - pro solvent for ink , and so on . Dipropylene glycol and tripro - 35 panol in a proportion of 0 . 10 to 0 .70 , themethod comprising pylene glycol are known to be produced as byproducts when a reaction step of making a reactant comprising propylene producing propylene glycol. oxide and water react in the presence of a catalyst , wherein It is known that dipropylene glycol produced industrially the catalyst comprises at least one element selected from the is commonly a mixture of 1, 1' - oxybis - 2 -propanol , 2 ,2 ' group consisting of vanadium , niobium , and tantalum , and oxybis -1 -propanol , and 2 - (2 -hydroxypropoxy )- 1 -propanol 40 the Hammett acidity function ( H ) of the catalyst satisfies (see , for example , non -patent document 1 ) . Hs9 . 3 . Moreover, it is known that tripropylene glycol produced industrially is commonly a mixture of 1 , 1' - [ ( 1 -methyl - 1 , 2 Effect of the Invention ethanediyl) bis ( oxy ) ]bis - 2 - propanol, 2 , 2 '- [ ( 1 -methyl - 1 , 2 - 45 According to the present invention , it is possible to highly ethanediyl ) bis ( oxy ) ]bis - 1 -propanol , 2 - [ 1 - ( 2 -hydroxy - selectively produce dipropylene glycol containing 1 . 1 -OXV propoxy ) - 1 , 2 -propoxy ] - 1 - propanol, and 2 - [ 2 - ( 2 - bis - 2 - propanol in a proportion of 0 . 10 to 0 . 70 and /or tripro hydroxypropoxy )- propoxy ] -1 -propanol ( see , for example , pylene glycol containing 1, 1' - [ (1 -methyl - 1, 2 -ethanediyl ) bis non -patent document 1 ) . (oxy ) ] bis -2 - propanol in a proportion of 0 .10 to 0. 70 . The proportion of 1 , 1 ' - oxybis - 2 - propanol contained in 50 commercially available dipropylene glycol is 0 . 10 to 0 . 70 , MODE FOR CARRYING OUT THE INVENTION and the proportion of 1, 1 '- [ ( 1 -methyl - 1 , 2 - ethanediyl ) bis ( oxy ) ] bis - 2 - propanol contained in commercially available in the method of the present invention , while a reactant tripropylene glycol is 0 . 10 to 0 . 70 . Such commercially containing propylene oxide and water is made to react in the available dipropylene glycol and tripropylene glycol are 55 presence of a catalyst comprising at least one element known to be produced as byproducts when producing pro selected from the group consisting of vanadium , niobium pylene glycol by making propylene oxide react with exces - and tantalum in order to produce dipropylene glycol con sive water in the absence of a catalyst (see , for example , taining 1 , 1 ' -oxybis - 2 -propanol in a proportion of 0 . 10 to non - patent document 1 ) . 0 .70 and /or tripropylene glycol containing 1, 1' - [ ( 1- methyl On the other hand , patent document 1 , for example , 60 1 , 2 - ethanediyl) bis (oxy ) ]bis - 2 - propanol in a proportion of discloses a production method to obtain an alkylene glycol 0 . 10 to 0 .70 , the Hammett acidity function ( H ) of the with high selectivity while generating almost no dialkylene catalyst is required to satisfy Hs9 .3 . glycol or trialkylene glycol by making an alkylene oxide In the present invention , dipropylene glycol and /or tripro react with water in the presence of carbon dioxide using a pylene glycol can be produced with higher selectivity by compound one or more element selected from the group 65 using a catalyst which contains at least one element selected consisting of titanium , zirconium , vanadium , niobium , tan - from the group consisting of vanadium , niobium and tanta talum , and chromium as a catalyst. lum and the Hammett acidity function ( H ) of which satisfies US 9 ,828 ,318 B2 Hs9 . 3 as compared with catalyst- free reaction . Although perature for 10 minutes . About 1 ml of a 0 .05 mol/ L either a homogeneous catalyst or a heterogeneous catalyst benzalacetophenone solution ( cyclohexane is used as sol may be adopted as the catalyst to be used in the present vent ) is added thereto and then allowed to stand at room invention , a heterogeneous catalyst is preferred from the temperature for 30 minutes. When the catalyst colors into viewpoint of industrial practices . 5 yellow , the Hammett acidity function ( H ) of the catalyst In the method of the present invention , the selectivity to satisfies Hs - 5 .6 , whereas when the catalyst fails to color, the dipropylene glycol and tripropylene glycol can be increased Hammett acidity function ( H ) of the catalyst satisfies by reducing the ratio of water to propylene oxide and / or H > - 5 . 6 . making the reactant comprising propylene oxide and water On the other hand , in the case of a catalyst that is difficult further include propylene glycol. The total selectivity to 10 to determine its color development, for example , a black dipropylene glycol and tripropylene glycol is preferably catalyst , it may be impossible to determine color develop 50 % or more ,more preferably 60 % or more, and even more ment by a method in which the presence or absence of color preferably 70 % or more . development is checked using benzalacetophenone as an In the present invention , the Hammett acidity function ( H ) indicator. In this case , 2 to 5 ml of cyclohexane is added to of a catalyst is measured with a method using an indicator . 15 0 . 25 g of crushed catalyst, followed by being allowed to The method using an indicator is used commonly for mea - stand at room temperature for 10 minutes . About 1 ml of a suring the acidity or the basicity of a solid . (See , for 0 .05 mol/ L benzalacetophenone solution (cyclohexane is example , non -patent document 2 : Tominaga KEII , used as solvent ) is added thereto and then allowed to stand “ Shokubai Kagaku (Catalyst Chemistry ) ” published by at room temperature for 30 minutes . After removal of a Tokyo Kagaku Dojin Shuppan , 1981 , pp . 518 -519 , 525 - 20 supernatant, the catalyst recovered is heated up to 300° C . at 526 ) . a rate of 5° C . /minute under nitrogen flow . In measurement The catalyst to be used in the present invention is required of the catalyst recovered with FT- IR or NMR , when a peak to have a Hammett acidity function ( H ) that satisfies H59. 3 derived from benzalacetophenone can be confirmed , the and has the feature of not coloring even if phenolphthalein Hammett acidity function ( H ) of the catalyst satisfies is used as an indicator . 25 H5 - 5 . 6 , whereas when no peak derived from benzalaceto The method of using phenolphthalein as an indicator is phenone can be confirmed , the Hammett acidity function performed in the following manner . (H ) of the catalyst satisfies H > - 5 .6 . To 2 to 5 ml of cyclohexane is added 0 . 25 g of crushed In the present invention , the proportion of 1 , 1 ' -oxybis - 2 catalyst, followed by being allowed to stand at room tem - propanol contained in dipropylene glycol and the proportion perature for 10 minutes . About 1 ml of a 0 . 05 mol/ l phe - 30 of 1 , 1 ' - [ ( 1 -methyl - 1 , 2 - ethanediyl) bis (oxy ) ] bis - 2 -propanol nolphthalein solution (40 volume % of ethanol and 60 contained in tripropylene glycol can be calculated using the volume % of cyclohexane are used as solvent ) is added following formulae . thereto , followed by being allowed to stand at room tem Proportion of 1 ,1 '- oxybis - 2 -propanol = (content of perature for 30 minutes . When the catalyst colors into pink 1 , 1 ' -oxybis - 2 -propanol )/ { (content of 1 , 1 '- oxybis or reddish violet , the Hammett acidity function ( H ) of the 35 2 -propanol ) + (content of 2 , 2 '- oxybis - 1 -propa catalyst satisfies H > 9 . 3 , whereas when the catalyst fails to nol) + (content of 2 -( 2 -hydroxypropoxy )- 1 -propa color, the Hammett acidity function ( H ) of the catalyst nol) } satisfies Hs9 . 3 . Proportion of 1 ,1 '- [ ( 1 -methyl - 1, 2 - ethanediyl )bis On the other hand , in the case of a catalyst that is difficult (oxy ) ]bis - 2 -propanol = ( content of 1 , 1 '- [( 1 methyl- 1 , 2 - ethanediyl )bis ( oxy ) ]bis - 2 -propanol ) / { to determine its color development, for example , a black 40 (content of 1 , 1' - [ ( 1 -methyl - 1 , 2 - ethanediyl) bis catalyst , it may be impossible to determine color develop (oxy )] bis - 2 -propanol ) + (content of 2 ,2 ' - [ ( 1 ment by a method in which the presence or absence of color methyl - 1 , 2 - ethanediyl) bis (oxy ) ]bis - 1 - propanol) + development is checked using phenolphthalein as an indi ( content of 2 - [ 1 - ( 2 -hydroxypropoxy ) - 2 cator. In this case , 2 to 5 ml of cyclohexane is added to 0 . 25 propoxy ] - 1 -propanol ) + ( content of 2 - [ 2 - ( 2 g of crushed catalyst, followed by being allowed to stand at 45 hydroxypropoxy) - propoxy ]- 1 -propanol ) } room temperature for 10 minutes. About 1 ml of a 0 .05 mol/ 1 In the method of the present invention , the propylene phenolphthalein solution (40 volume % of ethanol and 60 oxide to be used as a reactant may be propylene oxide volume % of cyclohexane are used as solvent ) is added produced by any production method and examples thereof thereto , followed by being allowed to stand at room tem - include propylene oxide produced by dehydrochlorinating , perature for 30 minutes. After removal of a supernatant, the 50 with a basic compound , a mixture produced by making catalyst recovered is heated up to 300° C . at a rate of 5° propylene react with an aqueous solution of chlorine , pro C . /minute under nitrogen flow . In measurement of the cata - pylene oxide produced by making propylene react in the lyst recovered with FT- IR or NMR , when a peak derived presence of a catalyst with ethylbenzene hydroperoxide from phenolphthalein can be confirmed , the Hammett acid produced by oxidizing ethylbenzene , propylene oxide pro ity function ( H ) of the catalyst satisfies H > 9. 3 , whereas 55 duced by making propylene react in the presence of a when no peak derived from phenolphthalein can be con catalyst with isopropylbenzene hydroperoxide produced by firmed , the Hammett acidity function ( H ) of the catalyst oxidizing isopropylbenzene, propylene oxide produced by satisfies Hs9 . 3 . making propylene react in the presence of a catalyst with While the lower limit of the Hammett acidity function ( H ) tert - butyl hydroperoxide produced by oxidizing isobutane , of the catalyst is not particularly limited , the Hammett 60 and propylene oxide produced by making propylene react in acidity function ( H ) of the catalyst preferably satisfies the presence of a catalyst with hydrogen peroxide . H > - 5 . 6 , and it is preferred that the catalyst does not color In the method of the present invention , the water to be even if benzalacetophenone is used as an indicator. The used as a reactant is not particularly limited and examples method of using benzalacetophenone as an indicator is thereof include distilled water, pure water , ion exchange performed in the following manner . 65 water , and steam condensate . To 2 to 5 ml of cyclohexane is added 0 .25 g of crushed Examples of the catalyst to be used for the method of the catalyst , followed by being allowed to stand at room tem - present invention which contains at least one element US 9 , 828 , 318 B2 selected from the group consisting of vanadium , niobium The catalyst to be used for the present invention contains and tantalum and the Hammett acidity function ( H ) of which at least one element selected from the group consisting of satisfies H 9 . 3 include an oxide, a sulfide , an acid , a halide , vanadium , niobium and tantalum and also contains an alkali a phosphorus compound or a polyacid of at least one element metal and /or an alkaline earth metal. The ratio of the total selected from the group consisting of vanadium , niobium 5 number of moles of the alkali metal and the alkaline earth and tantalum . An oxide or an acid containing at least one metal contained in the catalyst to the total number ofmoles element selected from the group consisting of vanadium , of the vanadium , the niobium and the tantalum contained in niobium and tantalum is preferred because it will afford dipropylene glycol and /or tripropylene glycol with high the catalyst is preferably 0 . 5 / 1 or less , more preferably 0 .05 / 1 selectivity . A catalyst containing at least one element 10 or less, even more preferably 0 . 005 / 1 or less. The concen selected from the group consisting of niobium and tantalum tration of the alkali metal and the alkaline earth metal is preferred and a catalyst containing niobium is particularly contained in a catalyst and the concentration of the vana preferred . dium , the niobium and the tantalum contained in the catalyst Examples of the oxide containing at least one element can be measured by analyzing by inductively coupled selected from the group consisting of vanadium . niobium 15 plasma spectrometry a sample prepared by dry ashing the and tantalum include vanadium pentoxide , vanadium diox - catalyst and dissolving it in an acid . ide , vanadium trioxide , niobium pentoxide , niobium diox - The ratio of the total number of moles of alkali metal and ide , niobium monoxide and tantalum pentoxide and alkaline earth metal to the number of moles of vanadium , examples of the acid containing at least one element selected niobium and tantalum is calculated in the following manner . from the group consisting of vanadium , niobium and tanta - 20 The ratio of the total number of moles of alkali metal and lum include vanadic acid , niobic acid and tantalic acid . alkaline earth metal to the total number of moles of vana In the method of the present invention , the catalyst dium , niobium and tantalum = (the sum total of the number of containing at least one element selected from the group moles of alkali metal and alkaline earth metal contained in consisting of vanadium , niobium and tantalum is required to a catalyst )/ (the sum total of the number of moles of vana have a Hammett acidity function ( H ) satisfying H59. 3 . 25 dium , niobium and tantalum contained in the catalyst ) If the Hammett acidity function ( H ) of the catalyst gets In the present invention , the alkali metal may be Li, Na, H > 9 .3 , the proportion of 1, 1' - oxybis -2 -propanol contained K , Rb or Cs and the alkaline earth metal may be Be, Mg , Ca , in dipropylene glycol becomes greater than 0 . 70 and the Sr or Ba. proportion of 1 , 1 '- [ ( 1 -methyl - 1 , 2 - ethanediyl) bis ( oxy ) ]bis - 2 - In the present invention , the catalyst which contains at propanol contained in tripropylene glycol becomes greater 30 least one element selected from the group consisting of than 0 .70 . vanadium , niobium and tantalum and the Hammett acidity In the method of the present invention , the proportion of function ( H ) of which satisfies H 9 . 3 may or may not have 1 , 1 ' -oxybis - 2 -propanol contained in dipropylene glycol is a peak that indicates a spacing d in X - ray diffraction . As used 0 .10 to 0 .70 . The proportion is preferably 0 . 15 to 0 .60 , more herein , the peak that indicates a spacing d in X - ray diffrac preferably 0 . 20 to 0 . 50 . The proportion of 1 , 1 ' - [ ( 1 -methyl - 35 tion is a peak derived from crystallinity or regularity pos 1 , 2 - ethanediyl) bis ( oxy) ] bis - 2 - propanol contained in tripro sessed by solid . pylene glycol is 0 . 10 to 0 . 70 . The proportion is preferably Examples of themethod for synthesizing a catalyst having 0 . 15 to 0 .60 , more preferably 0 .20 to 0 . 50 . a peak that indicates a spacing d include a method in which In the method of the present invention , a catalyst which niobic acid having no peak that indicates a spacing d is contains at least one element selected from the group 40 brought into contact with supercritical water and thereby consisting of vanadium , niobium and tantalum and the converted into niobium pentoxide having a peak that indi Hammett acidity function ( H ) of which satisfies H59 . 3 may cates a spacing d and a method in which niobic acid is be used alone or in combination of two or more . calcined into niobium pentoxide. The calcination time is In the method of the present invention , it is also permitted usually 0 . 1 to 30 hours , preferably 0 . 5 to 20 hours . The to co -localize a catalyst which contains at least one element 45 calcination temperature is usually 450 to 1000° C ., prefer selected from the group consisting of vanadium , niobium ably 500 to 800° C . and tantalum and the Hammett acidity function ( H ) of which The measurement of X -ray diffraction is carried out, for is H $ 9 . 3 with a catalyst other than the catalyst stipulated in example , by using an X - ray diffraction apparatus MiniFlexII the present invention as long as dipropylene glycol in which (manufactured by Rigaku Corporation ); specifically , a cata the proportion of 1 , 1 - oxybis - 2 - propanol is 0 . 10 to 0 .70 50 lyst is placed on a sample plate and mounted on the sample and / or tripropylene glycol in which the proportion of 1 , 1' stage of the X - ray diffraction apparatus MiniFlexII and then [ ( 1 -methyl - 1 , 2 - ethanediyl ) bis ( oxy ) ]bis - 2 -propanol is 0 . 10 the measurement is carried out under the following condi to 0 .70 are produced . Examples of the catalyst other than the tions . catalyst stipulated in the present invention include silica , Light source : Cuka (Counter monochromator was used alumina , silica -alumina , zeolite , titania , zirconia , ceria , acti - 55 for removal of KB ) vated carbon , graphite , magnesia and calcia . Divergence slit : 0 .625° Preferably , the catalyst to be used for the present inven Receiving slit: 0 . 3 mm tion is crystallized in the presence of supercritical water . Scattering slit: 1. 25° Supercritical water is water with temperature and pressure Voltage : 30 kV higher than the temperature and the pressure at the critical 60 Current : 15 mA . point. Water is not particularly limited and examples thereof Sampling width : 0 .02° include distilled water , pure water , ion exchange water , and Scan speed : 0 . 02° /second steam condensate . The reaction temperature applied in the present invention Preferably, the catalyst crystallized in the presence of is usually 30 to 350° C ., preferably 50 to 300° C . supercritical water is calcined . Preferable temperature for 65 The reaction pressure applied in the present invention is calcining the catalyst is 50 to 650° C . , more preferably 100 usually normal pressure to 50 MPa - G , preferably 0 . 1 to 20 to 500° C ., even more preferably 200 to 400° C . MPa - G . US 9 ,828 ,318 B2 The reaction mode applied in the present invention may methyl- 1 , 2 - ethanediyl) bis (oxy ) ] bis - 2 -propanol contained in be any mode. For example , a reaction operation may be any tripropylene glycol was 0 .31 in the product available from of a batch method , a semibatch method or a continuous Wako Pure Chemical Industries , Ltd ., 0 . 32 in the product method , and a reactor may be a single -stage or multi -stage available from Tokyo Chemical Industry Co ., Ltd ., 0 .20 in vessel type reactor or a tubular reactor composed of a single 5 the product available from Aldrich , and 0 . 27 in the product tube or multiple tubes arranged in parallel. Examples of the available from Alfa Aesar . method of controlling the reaction temperature include an external heat exchange system , a self heat exchange system , EXAMPLES and a heat insulation system . In the present invention , the molar ratio of water to 10 The present invention is described below with reference propylene oxide contained in the reactant is 0 .05 /1 to 100 / 1, preferably 0 .1 /1 to 50 /1 , more preferably 0 .2 /1 to 10 /1 . In order The conversions and the selectivities in Examples using to increase the yield of dipropylene glycol and /or tripropyl propylene oxide and water as reactants were calculated by ene glycol, propylene glycol is preferably contained in the ((Formula Formula A )), (Formula B ) and (Formula C ) given below . reactant . While the propylene glycol contained in the reac - 15 Conversion of propylene oxide = (the number of tant may be propylene glycol produced by any production moles of propylene oxide consumed )/ ( the num method , one resulting from the reaction of the present ber of moles of propylene oxide charged )x100 invention and one resulting from the purification of the ( Formula A ) reactant are particularly preferred . In order to increase the Selectivity to dipropylene glycol = ( the number of yield of tripropylene glycol, dipropylene glycol may be 20 moles of dipropylene glycol generated )x2 / (the contained in the reactant. While the dipropylene glycol number of moles of propylene oxide con contained in the reactant may be dipropylene glycol pro sumed )x100 ( % ) ( Formula B ) duced by any production method , one resulting from a Selectivity to tripropylene glycol = ( the number of reaction and one resulting from the purification of the moles of tripropylene glycol generated )x3 / (the reactant are particularly preferred . 25 number of moles of propylene oxide con In the present invention , when water remains unreacted in sumed )x100 ( % ) (Formula C ) dipropylene glycol and / or tripropylene glycol resulting from The conversions and the selectivities in Examples using the reaction between propylene oxide and water , the unre propylene oxide , water and propylene glycol as reactants acted water can be recycled to the reactor and used again as were calculated by ( Formula D ) , (Formula E ), ( Formula F ) part of the reactant. Moreover , when propylene oxide 30 and (Formula (G ) given below . When the conversion of remains unreacted in dipropylene glycol and / or tripropylene propylene glycol was calculated using (Formula E ) to be glycol resulting from the reaction between propylene oxide minus, selectivities were calculated using ( Formula B ) and and water , the unreacted propylene oxide can be recycled to (Formula C ) because propylene glycol was generated in the the reactor and used again as part of the reactant. In the reaction of the present inventionInvention , , propylene glycolglycol 35 system . may be formed and at least part of the propylene glycol Conversion of propylene oxide = ( the number of formed may be purified and recovered as a product . moles of propylene oxide consumed ) / ( the num In the present invention , a recovery step of separating ber of moles of propylene oxide charged ) x100 dipropylene glycol and / or tripropylene glycol from the reac (Formula D ) tion mixture may be provided after the reaction step . 40 Conversion of propylene glycol = ( the number of Examples of the method for the recovery of dipropylene moles of propylene glycol consumed ) /( the num glycol and/ or tripropylene glycol include distillation , partial ber of moles of propylene glycol charged )x100 condensation and extraction . Dipropylene glycol and / or ( % ) (Formula E ) tripropylene glycol may be recovered as a mixture of both Selectivity to dipropylene glycol= [ (the number of the compounds and also may be separated from each other 45 moles of dipropylene glycol generated )x2 / { ( the and then recovered . When distillation is used for the recov number ofmoles of propylene oxide con ery method, the temperature of the distillation column is sumed ) + ( the number of moles of propylene gly usually 0 to 300° C . , preferably 10 to 250° C ., the pressure col consumed ) } ]x100 ( % ) ( Formula F ) is usually - 0 . 1 to 20 MPa - G , preferably - 0 .09 to 10 MPa - G , Selectivity to tripropylene glycol= [ (the number of and the number of plates is usually 1 to 100 , preferably 10 50 moles of tripropylene glycol generated )x3 / { ( the to 30 though these are not limited particularly thereto . number ofmoles of propylene oxide con sumed ) + ( the number of moles of propylene gly Reference Example 1 col consumed )} ]x100 (% ) (Formula G ) In the present invention , the total number of moles of Gas chromatographic analysis of commercially available 55 vanadium , niobium and tantalum contained in a catalyst was dipropylene glycols revealed that the proportion of 1 , 1 - calculated assuming that vanadium , niobium and tantalum oxybis - 2 -propanol contained in dipropylene glycol was 0 .31 each is present in the form of X205 ( X denotes vanadium , in the product available from Kanto Chemical Co ., Inc. , 0 .46 niobium or tantalum ) regardless of the presence or absence in the product available from Tokyo Chemical Industry Co . , of inclusion of alkali metal and /or alkaline earth metal. Ltd ., 0 .35 in the product available from Aldrich , and 0 . 33 in 60 the product available from Wako Pure Chemical Industries, Example 1 Ltd . ( 1 ) Preparation of Catalyst Reference Example 2 90 g of ion exchange water was added to 10 of niobic acid 65 and then stirred for 3 hours . While performing filtration , the Gas chromatographic analysis of commercially available residue was washed with 1 L of ion exchange water and then tripropylene glycols revealed that the proportion of 1 , 1' -[ ( 1 dried at 60° C . for 18 hours , affording water -washed niobic US 9 , 828 , 318 B2 acid . 0 . 36 g of the resulting water- washed niobic acid and Measurement of the Hammett acidity function by the 1 . 8 g of ion exchange water were mixed together and then method described in Example 1 ( 2 ) revealed that niobium placed and sealed into a reaction vesselmade ofHASTEL oxide ( B ) failed to be colored by phenolphthalein , that is , LOY having a capacity of 5 ml. Then , crystals were formed H = 9 . 3 , and failed to be colored by benzalacetophenone , that in the presence of supercritical water by heating was applied 5 is , H > - 5 . 6 . at 400° C . for 10 minutes under shaking . Thus , a solid was The concentration of alkali metal and alkaline earth metal obtained . The solid was dried with an evaporator, affording in niobium oxide ( B ) was measured to be 0 .011 % by weight niobium oxide ( A ) . (Na = 0 . 003 % by weight, K = 0 .005 % by weight, ( 2 ) Analysis of Catalyst Mg = 0 . 0006 % by weight, Ca = 0 .002 % by weight, others X - ray diffraction of niobium oxide ( A ) was measured by 10 were not detected ). Thus, the ratio of the total number of using an X - ray diffraction apparatus and thereby was con moles of alkali metal and alkaline earth metal to the number firmed to have a peak that indicates a spacing d . of moles of niobium was 0 .0007 . In order to measure the Hammett acidity function ( H ) of ( 3 ) Evaluation of Reaction niobium oxide ( A ) , 5 ml of cyclohexane was added to 0 . 25 To an autoclave were introduced 130 g of propylene g of niobium oxide ( A ) and then allowed to stand at room 15 oxide, 20 g of water and 1 . 0 g of niobium oxide ( B ) , temperature for 10 minutes . About 1 ml of a 0 . 05 mol/ 1 followed by fully purging the inside of the autoclave with phenolphthalein solution ( 40 volume % of ethanol and 60 nitrogen gas. Heat was applied so as to adjust the tempera volume % of cyclohexane were used as solvent) was added ture within the autoclave to 180° C . and reaction was thereto and then was allowed to stand at room temperature performed for 360 minutes under stirring, affording a reac for 30 minutes . Thus , the catalyst was not colored by 20 tion solution . Gas chromatographic analysis of the reaction phenolphthalein , that is , the Hammett acidity function ( H ) solution revealed that the conversion of propylene oxide was satisfied Hs9 . 3 . 98 % , the selectivity to dipropylene glycol was 37 % , the To a mixture prepared by adding 5 mlof cyclohexane to selectivity to tripropylene glycol was 25 % , the proportion of 0 .25 g of niobium oxide ( A ) and then allowing to stand at 1 , 1 '- oxybis - 2 -propanol contained in dipropylene glycol was room temperature for 10 minutes was added about 1 ml of 25 0 .29 , and the proportion of 1, 1' - [ ( 1 -methyl - 1, 2 - ethanediyl) a 0 .05 mol/ l benzalacetophenone solution (cyclohexane was bis (oxy ) ]bis - 2 - propanol contained in tripropylene glycol used as solvent) , followed by being allowed to stand at room was 0 .26 . temperature for 30 minutes . Thus , the catalyst was not colored by benzalacetophenone , that is , the Hammett acidity Example 3 function ( H ) satisfied H > - 5 . 6 . 30 Niobium oxide ( A ) was dry ashed and dissolved in an ( 3 ) Evaluation of Reaction acid , and then the concentration of alkali metal and alkaline Reaction was carried out by the samemethod as described earth metal contained in niobium oxide ( A ) was measured in Example 1 (3 ) except that niobium oxide ( D ) obtained by by inductively coupled plasma spectrometry to be 0 . 022 % the method described in Example 2 ( 1 ) was used instead of by weight (Na = 0 . 003 % by weight, K = 0 .006 % by weight, 35 niobium oxide ( A ) . Then , it was revealed that the conversion Mg= 0 .008 % by weight, Ca = 0 .005 % by weight, others were of propylene oxide was 99 % , the conversion of propylene not detected ). Thus , the ratio of the total number ofmoles of glycol was 29 % , the selectivity to dipropylene glycol was alkali metal and alkaline earth metal to the number of moles 54 % , the selectivity to tripropylene glycol was 35 % , the of niobium was 0 . 0006 . proportion of 1, 1 -oxybis -2 - propanol contained in dipropyl ( 3 ) Evaluation of Reaction 40 ene glycol was 0 .26 , and the proportion of 1, 1' - [ ( 1 -methyl Into an autoclave were introduced 57 g of propylene 1 ,2 - ethanediyl) bis (oxy )] bis - 2 -propanol contained in tripro oxide, 9 g of water, 75 g of propylene glycol and 1 .0 g of pylene glycol was 0 .23 . niobium oxide ( A ) obtained by repeating the operations disclosed in Example 1 ( 1 ) , and then the inside of the Example 4 autoclave was purged fully with nitrogen gas . Heat was 45 applied so as to adjust the temperature within the autoclave ( 1 ) Preparation of Catalyst to 180° C . and reaction was performed for 120 minutes The operation of adding 200 mlof distilled water to 30 g under stirring , affording a reaction solution . Gas chromato of niobic acid , followed by stirring and subsequent filtration graphic analysis of the reaction solution revealed that the was repeated three times . The resulting niobic acid was dried conversion of propylene oxide was 87 % , the conversion of 50 at 10 Torr and 70° C . for 3 hours in a vacuum dryer. To 6 . 3 propylene glycol was 25 % , the selectivity to dipropylene g of the dried niobic acid were added 0 . 1 g of sodium glycol was 62 % , the selectivity to tripropylene glycol was hydroxide and 150 g of water, and then water was removed 28 % , the proportion of 1 , 1 ' - oxybis - 2 - propanol contained in using an evaporator, followed by calcination at 600° C . for dipropylene glycol was 0 .32 , and the proportion of 1 , 1 '- [ ( 1 - 3 hours. The operation of adding 200 mlof distilled water to methyl- 1 , 2 - ethanediyl) bis (oxy ) ]bis - 2 -propanol contained in 55 that calcined solid , followed by stirring and subsequent tripropylene glycol was 0 . 32 . filtration was repeated three times . The resulting solid was dried at 10 Torr and 70° C . for 3 hours in a vacuum dryer, Example 2 affording niobium oxide ( C ) . ( 2 ) Analysis of Catalyst ( 1 ) Preparation of Catalyst 60 X - ray diffraction of niobium oxide (C ) was measured by Niobium oxide ( B ) was obtained by repeating the opera - using an X - ray diffraction apparatus and thereby was con tions described in Example 1 ( 1 ) and calcining the resulting firmed to have a peak that indicates a spacing d . niobium oxide (A ) at 300° C . for 3 hours under air flow . Measurement of the Hammett acidity function ( H ) by the ( 2 ) Analysis of Catalyst method described in Example 1 (2 ) revealed that niobium X - ray diffraction of niobium oxide ( B ) was measured by 65 oxide ( C ) failed to be colored by phenolphthalein , that is , using an X -ray diffraction apparatus and thereby was con - Hs9. 3 , and failed to be colored by benzalacetophenone , that firmed to have a peak that indicates a spacing d . is , H > - 5 .6 . US 9 ,828 ,318 B2 12 The concentration of alkali metal and alkaline earth metal ( E ) failed to be colored by phenolphthalein , that is , H = 9 .3 , in niobium oxide ( C ) was measured to be 0 .86 % by weight and failed to be colored by benzalacetophenone , that is , ( Na = 0 .84 % by weight, K = 0 .02 % by weight, others were not H > - 5. 6 . detected ) . Thus, the ratio of the total number of moles of The concentration of alkali metal and alkaline earth metal alkali metal and alkaline earth metal to the number ofmoles 5 in niobic acid ( E ) was measured to be 0 . 018 % by weight of niobium was 0 . 049 . (Na = 0 .007 % by weight, K = 0 . 008 % by weight, Mg= 0 . 001 % ( 3 ) Evaluation of Reaction by weight, Ca = 0 .002 % by weight, others were not detected ). Reaction was carried out by the same method as described Thus, the ratio of the total number ofmoles of alkali metal in Example 2 ( 3 ) except that 3 . 0 g ofniobium oxide ( C ) was and alkaline earth metal to the number of moles of niobium used instead of 1 . 0 g of niobiumum oxide ( BB ) . ThenThen , itit was 10 was 0 . 0008 . revealed that the conversion of propylene oxide was 88 % , ( 3 ) Evaluation of Reaction the selectivity to dipropylene glycol was 53 % , the selectivity To an autoclave were introduced 130 g of propylene oxide , 20 g of water and 1 . 3 g of niobic acid ( E ) , followed to tripropylene glycol was 22 % , the proportion of 1 , 1 ' by fully purging the inside of the autoclave with nitrogen oxybis -2 - propanol contained in dipropylene glycol was 15 gas. Heat was applied so as to adjust the liquid temperature 0 .46 , and the proportion of 1, 1' - [( 1 -methyl - 1, 2 -ethanediyl ) within the autoclave to 120° C . and reaction was performed bis ( oxy ) ]bis - 2 - propanol contained in tripropylene glycol for 240 minutes under stirring , affording a reaction solution . was 0 .43 . Gas chromatographic analysis of the reaction solution revealed that the conversion of propylene oxide was 85 % , Example 5 20 the selectivity to dipropylene glycol was 62 % , the selectivity to tripropylene glycol was 13 % , the proportion of 1, 1' ( 1 ) Preparation of Catalyst oxybis - 2 -propanol contained in dipropylene glycol was The operation of adding 200 ml of distilled water to 30 g 0 .37 , and the proportion of 1 , 1' - [( 1 -methyl - 1, 2 - ethanediyl) of niobic acid , followed by stirring and subsequent filtration bis (oxy ) ]bis - 2 - propanol contained in tripropylene glycol was repeated three times. The resulting solid was dried at 10 25 was 0 . 28 . Torr and 70° C . for 3 hours in a vacuum dryer . To 6 .3 g of the dried niobic acid were added 24 g of a 1 mol/ l aqueous Example 7 solution of sodium hydroxide and 50 g of water, and then water was removed using an evaporator, followed by calci- ( 1 ) Preparation of Catalyst nation of the resulting solid at 600° C . for 3 hours . The 30 Niobium oxide ( F ) was obtained by calcining the niobic operation of adding 200 ml of distilled water to that calcined acid ( E ) described in Example 6 at 600° C . for 2 hours under solid , followed by stirring and subsequent filtration was air flow . repeated three times. The solid was dried at 10 Torr and 70º ( 2 ) Analysis of Catalyst C . for 3 hours in a vacuum dryer , affording niobium oxide X - ray diffraction of niobium oxide ( F ) was measured by ( D ). 35 using an X -ray diffraction apparatus and thereby was con (2 ) Analysis of Catalyst firmed to have a peak that indicates a spacing d . Measurement of the Hammett acidity function by the Measurement of the Hammett acidity function by the method described in Example 1 ( 2 ) revealed that niobium method described in Example 1 ( 2 ) revealed that niobium oxide (D ) failed to be colored by phenolphthalein , that is , oxide (F ) failed to be colored by phenolphthalein , that is , Hs9. 3 , and failed to be colored by benzalacetophenone , that 40 H $ 9 . 3 , and failed to be colored by benzalacetophenone, that is , H > - 5 . 6 . is , H > - 5 .6 . The concentration of alkali metal and alkaline earth metal The concentration of alkali metal and alkaline earth metal in niobium oxide ( D ) was measured to be 7 . 26 % by weight in niobium oxide ( F ) was measured to be 0 . 011 % by weight (Na = 7 .23 % by weight , K = 0 .03 % by weight, others were not (Na = 0 .001 % by weight, K = 0 . 008 % by weight, Ca = 0 . 002 % detected ) . Thus , the ratio of the total number of moles of 45 by weight, others were not detected ) . Thus, the ratio of the alkali metal and alkaline earth metal to the number of moles total number of moles of alkali metal and alkaline earth of niobium was 0 . 45 . metal to the number of moles of niobium was 0 .0004 . ( 3 ) Evaluation of Reaction ( 3 ) Evaluation of reaction Reaction was carried out by the samemethod as described Reaction was carried out by the same method as described in Example 2 ( 3 ) except that 3 . 0 g of niobium oxide ( D ) was 50 in Example 2 ( 3 ) except that 10 . 0 g of niobium oxide ( F ) was used instead of 1 . 0 g of niobium oxide ( B ) . Then , it was used instead of 1 . 0 g of niobium oxide ( B ) . Then , it was revealed that the conversion of propylene oxide was 93 % , revealed that the conversion of propylene oxide was 100 % , the selectivity to dipropylene glycol was 63 % , the selectivity the selectivity to dipropylene glycol was 66 % , the selectivity to tripropylene glycol was 22 % , the proportion of 1, 1 '- to tripropylene glycol was 23 % , the proportion of 1, 1 ' oxybis -2 -propanol contained in dipropylene glycol was 55 oxybis -2 -propanol contained in dipropylene glycol was 0 .35 , and the proportion of 1 , 1 '- [ ( 1 -methyl - 1 , 2 - ethanediyl ) 0 .45 , and the proportion of 1 , 1 ' - [ ( 1 -methyl - 1 , 2 - ethanediyl) bis (oxy ) ] bis - 2 - propanol contained in tripropylene glycol bis ( oxy ) ] bis - 2 -propanol contained in tripropylene glycol was 0 . 38 . was 0 . 31 .

Example 6 60 Example 8 ( 2 ) Analysis of catalyst ( 3 ) Evaluation of Reaction X - ray diffraction of niobic acid ( E ) was measured by To an autoclave were introduced 118 g of propylene using an X -ray diffraction apparatus and thereby was con - oxide , 37 g of water and 10 .0 g of the niobium oxide (F ) firmed to have no peak that indicates a spacing d . 65 obtained in Example 7 , followed by fully purging the inside Measurement of the Hammett acidity function by the of the autoclave with nitrogen gas. Heat was applied so as method described in Example 1 (2 ) revealed that niobic acid to adjust the liquid temperature within the autoclave to 120° US 9 , 828 , 318 B2 13 14 C . and reaction was performed for 360 minutes under (2 ) Analysis of catalyst stirring , affording a reaction solution . Gas chromatographic Measurement of the Hammett acidity function by the analysis of the reaction solution revealed that the conversion method described in Example 1 ( 2 ) revealed that potassium of propylene oxide was 81 % , the selectivity to dipropylene niobate ( I ) colored into pink , that is , H > 9 . 3 . glycol was 52 % , the selectivity to tripropylene glycol was 5 The concentration of alkali metal and alkaline earth metal 10 % , the proportion of 1 , 1' - oxybis - 2 -propanol contained in in potassium niobate ( I ) was measured to be 17 % by weight dipropylene glycol was 0 .45 , and the proportion of 1 . 1 '- [ ( 1 - ( K = 17 % by weight, others were not detected ). Thus, the methyl- 1, 2 - ethanediyl) bis ( oxy) ] bis - 2 - propanol contained in ratio of the total number of moles of alkali metal and tripropylene glycol was 0 .35 . alkaline earth metal to the number of moles of niobium was 10 0 .69 . Example 9 ( 3 ) Evaluation of Reaction Reaction was carried out by the samemethod as described ( 1 ) Preparation of Catalyst in Example 2 ( 3 ) except that 1 . 3 g of potassium niobate ( J ) Niobium oxide ( G ) was obtained by calcining niobic acid was introduced instead of 1 . 0 g of niobium oxide ( B ) . Then , at 590° C . under air flow . 15 it was revealed that the conversion of propylene oxide was ( 2 ) Analysis of Catalyst 100 % , the selectivity to dipropylene glycol was 26 % , the X - ray diffraction of niobium oxide (G ) was measured by selectivity to tripropylene glycol was 37 % , the proportion of using an X -ray diffraction apparatus and thereby was con - 1 , 1 ' - oxybis - 2 -propanol contained in dipropylene glycol was firmed to have a peak that indicates a spacing d . 0 .83 , and the proportion of 1 , 1 ' - [ ( 1 -methyl - 1 , 2 - ethanediyl) Measurement of the Hammett acidity function by the 20 bis (oxy ) ]bis - 2 -propanol contained in tripropylene glycol method described in Example 1 ( 2 ) revealed that niobium was 0 .86 . oxide (G ) failed to be colored by phenolphthalein , that is , Hs9 . 3 , and failed to be colored by benzalacetophenone , that Comparative Example 2 is , H > - 5 .6 . ( 3 ) Evaluation of Reaction 25 ( 1) Preparation of Catalyst Reaction was carried out by the same method as described The operation of adding 200 ml of distilled water to 30 g in Example 1 ( 3 ) except that 5 . 0 g of niobium oxide (G ) was of niobic acid , followed by stirring and subsequent filtration used instead of 1 . 0 g of niobium oxide ( A ) . Then , it was was repeated three times . The solid was dried at 10 Torr and revealed that the conversion of propylene oxide was 92 % , 70° C . for 3 hours in a vacuum dryer. 1 .52 g of sodium the conversion of propylene glycol was 30 % , the selectivity 30 hydroxide and 115 g of water were added to 6 .25 g of that to dipropylene glycol was 77 % , the selectivity to tripropyl resulting niobic acid and then placed and sealed into a ene glycol was 22 % , the proportion of 1 , 1 '- oxybis - 2 - propa reaction vessel made of Teflon having a capacity of 200 ml. nol contained in dipropylene glycol was 0 .42 , and the Heat was then applied at 175° C . for 40 hours under shaking. proportion of 1 , 1 '- [ ( 1 -methyl - 1 , 2 - ethanediyl) bis ( oxy ) ]bis - 2 The resulting solid was collected by filtration , and the solid propanol contained in tripropylene glycol was 0 .41 . 35 collected and 200 ml of distilled water were added to a beaker, stirred for 30 minutes , and then filtered . The solid Example 10 collected by filtration was calcined at 200° C . for 3 hours in the presence of air, affording niobium oxide ( K ) . ( 1 ) Preparation of Catalyst ( 2 ) Analysis of Catalyst Tantalic acid ( I ) was obtained by calcining tantalic acid at 40 X - ray diffraction of niobium oxide ( K ) was measured by 250° C . for 2 hours under air flow . using an X - ray diffraction apparatus and thereby was con ( 2 ) Analysis of Catalyst firmed to have a peak that indicates a spacing d . X - ray diffraction of tantalic acid ( I ) was measured by Measurement of the Hammett acidity function by the using an X -ray diffraction apparatus and thereby was con method described in Example 1 ( 2 ) revealed that niobium firmed to have no peak that indicates a spacing d . 45 oxide ( K ) colored into pink , that is , H > 9 . 3 . Measurement of the Hammett acidity function by the (3 ) Evaluation of Reaction method described in Example 1 ( 2 ) revealed that tantalic Reaction was carried out by the same method as described acid ( I ) failed to be colored by phenolphthalein , that is , in Example 2 (3 ) except that 3 .0 g of niobium oxide (K ) was H59 .3 , and failed to be colored by benzalacetophenone , that introduced instead of 1 . 0 g of niobium oxide ( B ) . Then , it is , H > - 5 . 6 . 50 was revealed that the conversion of propylene oxide was ( 3 ) Evaluation of Reaction 97 % , the selectivity to dipropylene glycol was 42 % , the Reaction was carried out by the same method as described selectivity to tripropylene glycol was 28 % , the proportion of in Example 2 ( 3 ) except that the tantalic acid (I ) obtained in 1 , 1 '- oxybis - 2 - propanol contained in dipropylene glycol was Example 11 was used instead of niobium oxide ( B ) . Then , it 0 .75 , and the proportion of 1 , 1 '- [ ( 1 -methyl - 1 , 2 -ethanediyl ) was revealed that the conversion of propylene oxide was 55 bis ( oxy ) ]bis - 2 -propanol contained in tripropylene glycol 100 % , the selectivity to dipropylene glycol was 74 % , the was 0 .81 . selectivity to tripropylene glycol was 16 % , the proportion of 1 , 1 '- oxybis - 2 -propanol contained in dipropylene glycol was INDUSTRIAL APPLICABILITY 0 .41 , and the proportion of 1 , 1' - [( 1 -methyl - 1, 2 - ethanediyl) bis ( oxy ) ]bis - 2 -propanol contained in tripropylene glycol 60 According to the present invention , it is possible to highly selectively produce dipropylene glycol containing 1 , 1 ' - oxy was 0 . 38 . bis - 2 - propanol in a proportion of 0 . 10 to 0 . 70 and / or tripro Comparative Example 1 pylene glycol containing 1 , 1' - [( 1 -methyl - 1, 2 - ethanediyl) bis (oxy )] bis - 2 -propanol in a proportion of 0 .10 to 0 .70 . ( 1 ) Preparation of Catalyst 65 The invention claimed is : The potassium niobate ( I) used was a product available 1 . A method for selectively producing dipropylene glycol from STREM CHEMICAL . containing 1, 1 '- oxybis - 2 - propanol in a proportion of 0 . 10 to US 9 ,828 ,318 B2 15 16 0 .70 and / or tripropylene glycol containing 1 , 1' - [ ( 1 - methyl 1 , 2 - ethanediyl )bis ( oxy ) ]bis - 2 - propanol in a proportion of 0 . 10 to 0 .70 , the method comprising reacting a reactant comprising propylene oxide with water in the presence of a catalyst , wherein the catalyst is an oxide of at least one 5 element selected from niobium and tantalum , or an acid containing tantalum , wherein the Hammett acidity function ( H ) of the catalyst satisfies H = 9 . 3 , and wherein the catalyst comprises an alkali metal and /or an alkaline earth metal and optionally further comprises vanadium , and wherein the 10 ratio of the total number of moles of the alkali metal and the alkaline earth metal contained in the catalyst to a total number of moles of vanadium , niobium , and tantalum contained in the catalyst is 0 . 45 or less . 2 . The method according to claim 1 , wherein the reactant 15 further comprises propylene glycol. 3 . The method according to claim 1 , wherein no acid of niobium is contained in the catalyst. 4 . The method according to claim 1 , wherein the catalyst is selected from the group consisting of niobium dioxide, 20 niobium monoxide , niobium pentoxide , tantalum pentoxide , and tantalic acid . 5 . The method according to claim 1 , wherein the catalyst is a heterogeneous catalyst . * * * * * 25