Methods for preparing diol

Abstract

Provided is a method for preparing a diol. In the method, a saccharide and hydrogen as raw materials are contacted with a catalyst in water to prepare the diol. The employed catalyst is a composite catalyst comprised of a main catalyst and a cocatalyst, wherein the main catalyst is a water-insoluble acid-resistant alloy; and the cocatalyst is a soluble tungstate and/or soluble tungsten compound. The method uses an acid-resistant, inexpensive and stable alloy needless of a support as a main catalyst, and can guarantee a high yield of the diol in the case where the production cost is relatively low.

Claims

1. A method for preparing a diol comprising contacting a sugar and hydrogen with a catalyst in water in a reactor to prepare a diol, wherein: the catalyst is a composite catalyst consisting of a main catalyst and a cocatalyst; the main catalyst is a water-insoluble acid-resistant alloy comprising nickel, one or more rare earth elements, tin and aluminum; the cocatalyst is a soluble tungstic acid salt and/or an insoluble tungsten compound; and the sugar reacts with hydrogen in the form of an aqueous sugar solution, and the aqueous sugar solution has a concentration of 20-63 wt %.

2. The method of claim 1, characterized in that the diol is ethylene glycol.

3. The method of claim 1, wherein the pH of the reactor is 1-7.

4. The method of claim 1, wherein the sugar is selected from one or more five-carbon monosaccharides, disaccharides and oligosaccharides, six-carbon monosaccharides, disaccharides and oligosaccharides, soluble five-carbon polysaccharides, and soluble six-carbon polysaccharides.

5. The method of claim 1, wherein the sugar is sourced from a sugar-based substance selected from the group consisting of beet, and sugarcane; a starch-based substance selected from the group consisting of maize, wheat, barley and cassava; a lignocellulose-based substance selected from the group consisting of maize straw, corn cobs, wheat straw, sugarcane dregs and timber; corn cob dregs or algae.

6. The method of claim 1, wherein the aqueous sugar solution has a concentration of 20-50 wt %.

7. The method of claim 1, wherein the acid-resistant alloy comprises, in parts by weight, 10-90 parts nickel, 1-5 parts rare earth element, 1-60 parts tin and 5-9 parts aluminum.

8. The method of claim 1, wherein the acid-resistant alloy comprises nickel, one or more rare earth elements, tin, aluminum and tungsten.

9. The method of claim 8, wherein the acid-resistant alloy comprises, in parts by weight, 10-90 parts nickel, 1-5 parts rare earth element, 1-60 parts tin, 5-9 parts aluminum and 1-90 parts tungsten.

10. The method of claim 1, wherein the acid-resistant alloy comprises nickel, one or more rare earth elements, tin, aluminum, tungsten and molybdenum.

11. The method of claim 10, wherein the acid-resistant alloy comprises, in parts by weight, 10-90 parts nickel, 1-5 parts rare earth element, 1-60 parts tin, 5-9 parts aluminum, 1-90 parts tungsten and 0.5-20 parts molybdenum.

12. The method of claim 1, wherein the acid-resistant alloy comprises nickel, one or more rare earth elements, tin, aluminum, tungsten, molybdenum, and boron or phosphorus.

13. The method of claim 12, wherein the acid-resistant alloy comprises, in parts by weight, 10-90 parts nickel, 1-5 parts rare earth element, 1-60 parts tin, 5-9 parts aluminum, 1-90 parts tungsten, 0.5-20 parts molybdenum, and 0.01-5 parts boron or phosphorus.

14. The method of claim 1, wherein the soluble tungstic acid salt is one or more of ammonium tungstate, sodium tungstate and sodium phosphotungstate.

15. The method of claim 1, wherein the insoluble tungsten compound is tungsten trioxide and/or tungstic acid.

16. The method of claim 1, wherein the amount of the main catalyst used is 0.01-10 times the amount of sugar fed per hour.

17. The method of claim 1, wherein the amount of the soluble cocatalyst used is 0.01-5 wt % of the aqueous sugar solution.

18. The method of claim 1, wherein the amount of the insoluble cocatalyst used is 0.5-50 wt % of the main catalyst.

19. The method of claim 1, wherein the reactor has a reaction pressure of 5-12 MPa, a reaction temperature of 150-260° C., and a reaction time ≥10 min.

20. The method of claim 1, wherein the reaction is in continuous mode.

21. The method of claim 20, wherein the amount of main catalyst added is: 0.01-5 kg of main catalyst added per 1000 kg of sugar fed.

22. The method of claim 1, further comprising separating the cocatalyst from the diol and then recycling the cocatalyst in a subsequent method.

23. The method of claim 1, wherein the reactor is a slurry bed reactor.

Description

DESCRIPTION OF THE ACCOMPANYING DRAWINGS

(1) FIG. 1 is a schematic flow chart of the method of the present invention.

(2) FIG. 2 is a graph of the variation of ethylene glycol yield with time in embodiment 2.

PARTICULAR EMBODIMENTS

(3) The present invention is explained further below in conjunction with the accompanying drawings and embodiments.

(4) FIG. 1 is a schematic flow chart of the method of the present invention.

Embodiment 1

(5) Preparation of acid-resistant alloy main catalyst:

(6) With regard to the acid-resistant alloy main catalyst of the present invention, an active metal powder with a high specific surface area can be prepared directly by chemical reduction or electrolytic deposition; alternatively, a metal alloy is formed by smelting, then metal powder is formed by mechanical pulverizing or atomizing, etc., and finally, an active metal powder is formed by a conventional Raney nickel catalyst activation method. For example, in parts by weight, 10-90 parts, 1-5 parts, 1-60 parts, 5-9 parts, 1-90 parts, 0.5-20 parts and 0.01-5 parts of nickel, rare earth element, tin, aluminum, tungsten, molybdenum, and boron or phosphorus respectively are added to a smelting furnace; the temperature is raised to 1500-2000° C., then the temperature is lowered, and after thorough mechanical stirring to achieve uniformity, the furnace is emptied, to obtain the metal alloy. A hammer grinder is used to pulverize the metal alloy into metal powder, which is then immersed for 1-2 hours in a 20 wt %-25 wt % aqueous sodium hydroxide solution at 70-95° C., to form an active metal powder with a high specific surface area.

(7) An acid-resistant alloy main catalyst Ni80La1Sn30Al5 (indicating that the composition of the acid-resistant alloy is 80 parts Ni+1 part La+30 parts Sn+5 parts Al, likewise below), an acid-resistant alloy main catalyst Ni10Sm5Sn3Al9W70Mo5, an acid-resistant alloy main catalyst Ni70Ce1Sn50A17W5Mo1B5, an acid-resistant alloy main catalyst Ni90Ce3Sn60A19W20Mo5B1, an acid-resistant alloy main catalyst Ni10Sm5Sn10Al9W90, an acid-resistant alloy main catalyst Ni90Ce3Sn60Al9W20Mo20P0.01, and an acid-resistant alloy main catalyst Ni80La1Ce0.5Sn30Al5 are prepared separately.

Embodiment 2

(8) 6 L of water and 1000 g of acid-resistant alloy main catalyst Ni80La1Sn30Al5 are added to a 10 L reaction kettle while stirring. The reaction kettle is sealed, hydrogen is passed in for 5 hours at 1000 L/h at atmospheric pressure to replace air in the reaction kettle, then the hydrogen pressure is raised to 10 MPa, and hydrogen is passed in for a further 5 hours, the reaction kettle temperature is raised to 250° C., and continuous feeding begins. The feed composition is: 50 wt % glucose, 2 wt % sodium tungstate, 48 wt % water, and the density of the sugar solution is about 1.23 g/cm.sup.3; the feed rate is 3 L/h. The residence time of sugar in the reaction kettle is 2 hours. Acetic acid is added to the reaction kettle such that the reaction system pH is 3.5. Reaction liquid and hydrogen after the reaction flow out of the reaction kettle through a filter into a condensing tank; the output speed of reaction liquid is 3 L/h, and reaction liquid is discharged from the bottom of the condensing tank after cooling, to give effluent. The effluent enters a rectification separation system, and water, ethylene glycol, propylene glycol, glycerol and sorbitol and sodium tungstate are respectively obtained, wherein heavy components that are not distilled out, including glycerol and sorbitol and sodium tungstate, are returned to the reaction system to react in a cycle. A sample is taken at the bottom of the condensing tank, and the composition thereof is detected by high performance liquid chromatography.

(9) A conventional technique may be used for the high performance liquid chromatography detection. The present invention provides the following experimental parameters for reference:

(10) Instrument: Waters 515 HPLC Pump;

(11) Detector: Water 2414 Refractive Index Detector;

(12) Chromatography column: 300 mm×7.8 mm, Aminex HPX-87H ion exchange column;

(13) Mobile phase: 5 mmol/L sulphuric acid solution;

(14) Mobile phase flow rate: 0.6 ml/min;

(15) Column temperature: 60° C.;

(16) Detector temperature: 40° C.

(17) Results: the glucose conversion rate is 100%; the diol yield is 77%, wherein the ethylene glycol yield is 71%, the propylene glycol yield is 7%, and the butylene glycol yield is 3%; the methanol and ethanol yield is 5%, and other yields are 14%.

(18) FIG. 2 is a graph of the variation of ethylene glycol yield with reaction system operation time. It can be seen from the figure that the ethylene glycol yield is substantially maintained at about 70%. This indicates that the composite catalyst of the present invention can ensure that the ethylene glycol yield is still stable after 500 hours of continuous operation of the reaction system.

(19) When the reaction system pH is changed to 9, the results are: the glucose conversion rate is 100%; the diol yield is 68%, wherein the ethylene glycol yield is 38%, the propylene glycol yield is 27%, and the butylene glycol yield is 3%; the methanol and ethanol yield is 5%, and other yields are 27%.

Embodiment 3

(20) The acid-resistant alloy main catalyst is Ni10Sm5Sn3Al9W70Mo5, and the amount added is 5000 g.

(21) The feed composition is: 15 wt % glucose, 0.01 wt % ammonium tungstate, 84.9 wt % water, and the density of the sugar solution is about 1.06 g/cm.sup.3.

(22) Reaction system pH=6.

(23) Other operating conditions are the same as in embodiment 2.

(24) Results: the glucose conversion rate is 100%; the diol yield is 66%, wherein the ethylene glycol yield is 61%, the propylene glycol yield is 3%, and the butylene glycol yield is 2%; the methanol and ethanol yield is 9%, and other yields are 25%.

Embodiment 4

(25) The acid-resistant alloy main catalyst is Ni70Ce1Sn50Al7W5Mo1B5, and the amount added is 500 g.

(26) The amount of tungsten trioxide added is 100 g.

(27) The feed composition is: 40 wt % glucose, 60 wt % water, and the density of the sugar solution is about 1.18 g/cm.sup.3.

(28) Reaction system pH=4.2.

(29) Other operating conditions are the same as in embodiment 2.

(30) Results: the glucose conversion rate is 100%; the diol yield is 70%, wherein the ethylene glycol yield is 67%, the propylene glycol yield is 2%, and the butylene glycol yield is 1%; the methanol and ethanol yield is 9%, and other yields are 21%.

Embodiment 5

(31) The acid-resistant alloy main catalyst is Ni90Ce3Sn60Al9W20Mo5B1, and the amount added is 1000 g.

(32) The feed composition is: 15 wt % xylose, 40 wt % glucose, 1 wt % maltose, 1 wt % maltotriose, 1 wt % sodium phosphotungstate, 42 wt % water, and the density of the sugar solution is about 1.22 g/cm.sup.3.

(33) Reaction system pH=4.8.

(34) Other operating conditions are the same as in embodiment 2.

(35) Results: the conversion rate of xylose, glucose, maltose and maltotriose is 100%; the diol yield is 75%, wherein the ethylene glycol yield is 60%, the propylene glycol yield is 11%, and the butylene glycol yield is 4%; the methanol and ethanol yield is 7%, and other yields are 18%. After 500 hours of catalyst operation, the ethylene glycol yield is still stable.

Embodiment 6

(36) The acid-resistant alloy main catalyst is Ni90Ce3Sn60Al9W20Mo5B1, and the amount added is 5000 g.

(37) The feed composition is: 50 wt % xylose, 0.1 wt % sodium tungstate, 49.9 wt % water, and the density of the sugar solution is about 1.21 g/cm.sup.3.

(38) Reaction system pH=4.8.

(39) Other operating conditions are the same as in embodiment 2.

(40) Results: the conversion rate of xylose is 100%; the diol yield is 67%, wherein the ethylene glycol yield is 49%, the propylene glycol yield is 16%, and the butylene glycol yield is 2%; the methanol and ethanol yield is 12%, and other yields are 21%. After 500 hours of catalyst operation, the ethylene glycol yield is still stable.

Embodiment 7

(41) The acid-resistant alloy main catalyst is Ni10Sm5Sn10Al9W90, and the amount added is 180 g.

(42) The feed composition is: 60 wt % glucose, 2 wt % sodium tungstate, 38 wt % water, and the density of the sugar solution is about 1.29 g/cm.sup.3.

(43) The reaction pressure is 12 MPa, and the reaction temperature is 260° C.

(44) Other operating conditions are the same as in embodiment 2.

(45) Results: the conversion rate of glucose is 100%; the diol yield is 75%, wherein the ethylene glycol yield is 65%, the propylene glycol yield is 7%, and the butylene glycol yield is 3%; the methanol and ethanol yield is 11%, and other yields are 14%.

Embodiment 8

(46) The acid-resistant alloy main catalyst is Ni90Ce3Sn60Al9W20Mo20P0.01, and the amount added is 5 g.

(47) The feed composition is: 5 wt % glucose, 0.05 wt % sodium tungstate, 94.95 wt % water, and the density of the sugar solution is about 1.02 g/cm.sup.3.

(48) Reaction system pH=1.

(49) The reaction pressure is 6 MPa, and the reaction temperature is 180° C.

(50) Other operating conditions are the same as in embodiment 2.

(51) Results: the conversion rate of glucose is 100%; the diol yield is 65%, wherein the ethylene glycol yield is 53%, the propylene glycol yield is 9%, and the butylene glycol yield is 3%; the methanol and ethanol yield is 4%, and other yields are 31%.

Embodiment 9

(52) The acid-resistant alloy main catalyst is Ni80La1Ce0.5Sn30Al5; other operating conditions are the same as in embodiment 2.

(53) Results are similar to those of embodiment 2.

Embodiment 10

(54) The acid-resistant alloy main catalyst is Ni70Sm1Sn10Al7W5Mo0.5, and the amount added is 1500 g.

(55) The feed composition is: 40 wt % glucose, 60 wt % water, 0.5 wt % sodium tungstate, and the density of the sugar solution is about 1.18 g/cm.sup.3.

(56) Reaction system pH=4.2.

(57) Other operating conditions are the same as in embodiment 2.

(58) Results: the conversion rate of glucose is 100%; the diol yield is 87%, wherein the ethylene glycol yield is 80%, the propylene glycol yield is 5%, and the butylene glycol yield is 2%; the methanol and ethanol yield is 3%, and other yields are 10%.

(59) Clearly, the abovementioned embodiments of the present invention are merely examples given to explain the present invention clearly, and by no means define the embodiments of the present invention. A person skilled in the art could make other changes or modifications in different forms on the basis of the explanation above. It is not possible to list all embodiments here exhaustively. All obvious changes or modifications extended from the technical solution of the present invention shall still fall within the scope of protection of the present invention.