Mixed oxide composite comprising calcium oxide and tricalcium aluminate

Patent metadata

Field	Value
Publication number	US-2021339225-A1
Application number	US-201917285789-A
Country	US
Kind code	A1
Filing date	Oct 14, 2019
Priority date	Oct 15, 2018
Publication date	Nov 4, 2021
Grant date	—

Abstract

The invention relates to a composite oxide comprising CaO stabilised by Ca3Al2O6 (C3A), wherein the composite is in the form of particles. The mixed oxide composite is useful as a catalyst in the transesterification of triglycerides, e.g. in the production of biodiesel. Calcium leaching is more hindered in CaO—Ca3Al2O6 (2Ca/Al) than in CaO—Al2O3.

First claim

1 . A mixed oxide composite comprising CaO and Ca 3 Al 2 O 6 , wherein the composite is in the form of particles.

2 . A mixed oxide composite according to claim 1 , wherein the amount of CaO and Ca 3 Al 2 O 6 in the composite is greater than 50, 60, 70, 80, 90, 95, 97 or 100 wt % of the total weight of the composite.

3 . A mixed oxide composite according to claim 1 , comprising CaO in an amount of from 10 to 75 wt %, 25 to 75 wt %, or 35 to 70 wt % based on the total weight of CaO and Ca 3 Al 2 O 6 .

4 . A mixed oxide composite according to claim 1 , wherein the particles have an average size of from 10 nm to 100 μm.

5 . A mixed oxide composite according to claim 1 , comprising a uniformly dispersed mixture of CaO and Ca 3 Al 2 O 6 .

6 . A mixed oxide composite according to claim 1 , wherein the amount of CaO and Ca 3 Al 2 O 6 in the composite is 100 wt % of the total weight of the composite.

7 . A mixed oxide composite according to claim 1 , wherein the particles are supported on a porous support.

8 . A mixed oxide composite according to claim 1 , wherein the particles are moulded so as to form a self-supporting structure such as a honeycomb structure.

9 . A method for preparing a mixed oxide composite, said method comprising:
(a) heating an aqueous solution comprising (i) aluminium nitrate or aluminium nitrate hydrate, (ii) calcium nitrate or calcium nitrate hydrate, and (iii) an organic fuel until the solution combusts to form a powder; and (b) calcining the powder at a temperate of from 1000° C. or higher.

10 . A method according to claim 9 , wherein step (a) comprises heating the aqueous solution comprising aluminium nitrate or aluminium nitrate hydrate, calcium nitrate or calcium nitrate hydrate and an organic fuel so as to evaporate water and form a gel, followed by heating the gel until it combusts to form a powder.

11 . A method according to claim 9 , wherein the organic fuel is selected from ethylene glycol, citric acid, urea, glycine, sucrose and mixtures thereof.

12 . A method according to claim 11 , wherein the organic fuel is a mixture of ethylene glycol and citric acid.

13 . A method according to claim 12 , comprising:
(a) diluting Ca(NO 3 ) 2 .4H 2 O and Al(NO 3 ) 2 .9H 2 O in deionised water with ethylene glycol and citric acid to form an aqueous solution; heating the solution under stirring at a temperature of 100° C. so as to evaporate the water and form a gel; heating the gel to a temperature of from 250 to 500° C. so as to combust the gel and form a powder; and (b) calcining the powder at a temperature of from 1000 to 1300° C. for 2 to 12 hours.

14 . A mixed oxide composite obtained by the method of claim 9 .

15 . A method of activating a mixed oxide composite comprising CaO and Ca 3 Al 2 O 6 , comprising heating a C1 to C4 alcohol with glycerol in the presence of a catalyst so as to form calcium diglyceroxide.

16 . An activated mixed oxide composite obtained by the method of claim 15 .

17 . A method for producing fatty acid alkyl esters comprising reacting a feedstock comprising fatty acid monoglycerides, diglycerides or triglycerides with a C1 to C4 alcohol in the presence of a mixed oxide composite comprising CaO and Ca 3 Al 2 O 6 , or an activated mixed oxide composite according to claim 16 .

18 . A method according to claim 17 , wherein the feedstock comprises a plant oil or an animal fat or oil.

19 . A method according to claim 17 , wherein the process further comprises recovering the mixed oxide composite from the reaction mixture.

20 . A method according to claim 19 , wherein recovering the mixed oxide composite from the reaction mixture comprises separating the composite from the reaction mixture, washing and drying the composite and, wherein the method further comprises reusing the composite for producing fatty acid alkyl esters.

21 . A method according to claim 17 , wherein the feedstock comprises fatty acid triglycerides.

22 . A method according to claim 17 , wherein the alcohol is methanol or ethanol.

23 . A method transesterification monoglycerides, diglycerides or triglycerides comprising the steps of:
heating a mixture of C1-C4 alcohol, glycerol and a mixed oxide catalyst comprising CaO and Ca 3 Al 2 O 6 , so as to form at least calcium diglyceroxide; contacting the calcium diglyceroxide with monoglycerides, diglycerides or triglycerides; and transesterifying the monoglycerides, diglycerides or triglycerides.

Assignees

• Univ Court Univ St Andrews

Inventors

• Irvine John Thomas Sirr
• Bonaccorso Alfredo
• Papargyriou Despoina

Classifications

• B01J2235/30

  Scanning electron microscopy; Transmission electron microscopy · CPC title

• B01J2235/15

  X-ray diffraction · CPC title

• B01J2235/10

  Infrared [IR] · CPC title

• B01J35/57

  Honeycombs · CPC title

• B01J2235/00

  Indexing scheme associated with group B01J35/00, related to the analysis techniques used to determine the catalysts form or properties · CPC title