Method for measuring acid strength in reaction medium using trimethylphosphine oxide and 31P NMR

Patent metadata

Field	Value
Publication number	US-9335285-B2
Application number	US-201414498332-A
Country	US
Kind code	B2
Filing date	Sep 26, 2014
Priority date	Oct 18, 2013
Publication date	May 10, 2016
Grant date	May 10, 2016

Abstract

A method to determine the strength of an acid in a medium is disclosed. The method includes (I) providing multiple samples comprising trimethylphosphine oxide (TMPO), the acid, and the medium, wherein the multiple samples have different [H + ]/[TMPO] ratios, [H + ] is the concentration of hydrons in the sample in mole·liter −1 , and [TMPO] is the concentration of TMPO in the sample in mole·liter −1 . (II) The 31 P chemical shifts of the multiple samples are measured by 31 P NMR and compared to standardized samples to determine the acid strength of the medium.

First claim

The invention claimed is:

1. A method to determine the strength of an acid in a medium comprising:
(I) providing multiple samples comprising trimethylphosphine oxide (TMPO), the acid, and the medium, the multiple samples having different [H + ]/[TMPO] ratios of less than 1.0, where [H + ] is the concentration of hydrons in the sample in mole·liter −1 , and [TMPO] is the concentration of TMPO used in the sample in mole·liter −1 ; and
(II) measuring the 31 P chemical shifts of the multiple samples by 31 P NMR.

2. The method of claim 1 , further comprising:
(III) determining the acid strength in the medium by plotting the 31 P chemical shift (ppm) versus the [H + ]/[TMPO] ratio.

3. The method of claim 2 , wherein the step (III) of determining the acid strength comprises:
(IIIa) drawing 31 P chemical shift versus [H + ]/[TMPO] data points in a coordinate system;
(IIIb) providing a linear fitting of the data points; and
(IIIc) determining the slope of the linear fitting.

4. The method of claim 1 , wherein the medium comprises at least one of (i) a solvent, (ii) a reactant, (iii) water, and (iv) a product of a reaction system.

5. The method of claim 4 , wherein the reaction system includes a chemical reaction dependent on the acid strength of the acid.

6. The method of claim 4 , wherein the reaction system includes a cleavage reaction of a hydroperoxide compound.

7. The method of claim 6 , wherein the medium comprises cyclohexylbenzene, cyclohexanone, phenol, water or combinations of two or three thereof.

8. The method of claim 6 , wherein the medium comprises cumene, acetone, phenol, water, or combinations of two or three thereof.

9. The method of claim 1 , wherein the acid is sulfuric acid.

10. The method of claim 1 , wherein the medium has:
a cyclohexylbenzene concentration in a range from 5 wt % to 90 wt %;
a phenol concentration in a range from 0 wt % to 90 wt %;
a cyclohexanone concentration in a range from 0 wt % to 90 wt %; and
a water concentration in a range from 0 ppm to 1 wt % (10000 ppm by weight);
where all concentrations are based on the total weight of the medium.

11. The method of claim 10 , wherein the strength of the acid varies from −10 to 60.

12. A method for optimizing reaction conditions of a reaction system, the method comprising:
(A) providing a sample comprising a reaction medium and an acid;
(B) combining trimethylphosphine oxide (TMPO) with aliquots of the sample to provide a series of mixtures containing both TMPO and protonated TMPO and having different [H + ]/[TMPO] ratios of less than 1.0;
(C) measuring the chemical shifts of the mixtures by 31 P NMR;
(D) plotting the chemical shifts against the [H + ]/[TMPO] ratios to determine the slope of a linear fit;
(E) comparing the slope of the linear fit to that of a standardized sample comprising the same components of the reaction medium; and
(F) determining whether one or more components of the reaction medium and/or amount thereof should be adjusted to provide for a desired acid strength.

13. The method of claim 12 , wherein the reaction system includes a chemical reaction dependent on the acid strength of the acid.

14. The method of claim 12 , wherein the reaction system includes a cleavage reaction of a hydroperoxide compound.

15. The method of claim 14 , wherein the reaction medium comprises cyclohexylbenzene, cyclohexanone, phenol, water, or combinations of two or three thereof.

16. The method of claim 12 , wherein the reaction medium comprises cumene, acetone, phenol, water or combinations of two or three thereof.

17. The method of claim 12 , wherein the acid is sulfuric acid.

18. The method of claim 12 , wherein the medium has:
a cyclohexylbenzene concentration in a range from 5 wt % to 90 wt %;
a phenol concentration in a range from 0 wt % to 90 wt %;
a cyclohexanone concentration in a range from 0 wt % to 90 wt %; and
a water concentration in a range from 0 ppm to 1 wt % (10000 ppm) by weight;
where all concentrations are based on the total weight of the medium.

19. The method of claim 18 , wherein the strength of the acid varies from −10 to 60.

20. A method for monitoring a process for producing phenol and cyclohexanone, the process comprising:
(a) providing a cleavage feed containing greater than 10 wt % and no greater than 95 wt % cyclohexyl-1-phenyl-1-hydroperoxide, and at least 5 wt % and less than 90 wt % cyclohexylbenzene;
(b) mixing the cleavage feed with at least phenol, cyclohexanone, water, and sulfuric acid, to produce a cleavage reaction mixture containing from 10 wt % to 80 wt % phenol, from 10 wt % to 60 wt % cyclohexanone, from 0.5 wt % to 10 wt % cyclohexyl-1-phenyl-1-hydroperoxide, from 3 wt % to 60 wt % cyclohexylbenzene, from 0.01 wt % to 4 wt % water, and from 10 ppm to 1000 ppm sulfuric acid, where all concentrations are based on the total weight of the cleavage reaction mixture; and
(c) reacting the cleavage reaction mixture at a temperature from 20° C. and to 90° C. for a time sufficient to convert at least 50% of the cyclohexyl-1-phenyl-1-hydroperoxide in the cleavage reaction mixture and produce a cleavage effluent containing phenol and cyclohexanone;

wherein the process is monitored by:
(m1) taking a sample of the cleavage reaction mixture;
(m2) combining trimethylphosphine oxide (TMPO) with a series of aliquots of the sample to provide a series of mixtures containing both TMPO and protonated TMPO and having different [H + ]/[TMPO] ratios of less than 1.0;
(m3) measuring the chemical shifts of the mixtures by 31 P NMR;
(m4) plotting the chemical shifts against the [H + ]/[TMPO] ratios to determine the slope of the linear fit;
(m5) comparing the slope of the linear fit to that of a standardized sample comprising the same components of the reaction medium; and
(m6) determining whether one or more components of the cleavage mixture and/or amount thereof should be adjusted to provide for a desired acid strength.

21. The method of claim 20 , wherein the step (m4) of determining the linear fit comprises:
(m4a) drawing 31 P chemical shift versus [H + ]/[TMPO] data points in a coordinate system;
(m4b) providing a linear fitting of the data points; and
(m4c) determining the slope of the linear fitting.

Assignees

• Exxonmobil Chem Patents Inc

Inventors

• Wang Kun
• Garcia Roberto

Classifications

• C07C45/53

  of hydroperoxides · CPC title

• Y10T436/163333

  Organic [e.g., chemical warfare agents, insecticides, etc.] · CPC title

• G01N24/088 Primary

  Assessment or manipulation of a chemical or biochemical reaction, e.g. verification whether a chemical reaction occurred or whether a ligand binds to a receptor in drug screening or assessing reaction kinetics · CPC title

• G01R33/46

  NMR spectroscopy · CPC title

• C07C39/04

  Phenol · CPC title