Process for regenerating a deactivated vanadium-titanium-phosphorous catalyst

Abstract

A process for regenerating a deactivated vanadium-titanium-phosphorous catalyst which has been used in the production of unsaturated carboxylic acid is disclosed. The process comprises contacting the deactivated vanadium-titanium-phosphorous catalyst with a regeneration stream comprising steam as a regeneration agent at a temperature which is the same or similar to that used in the production of the unsaturated carboxylic acid.

Claims

1. A process for regenerating a deactivated vanadium-titanium-phosphorous catalyst comprising vanadium, titanium, phosphorous, oxygen, and less than 30 wt % of any other metal or any metal oxide, wherein the catalyst has been used in the production of unsaturated carboxylic acid, wherein the process comprises contacting the deactivated vanadium-titanium-phosphorous catalyst with a regeneration stream comprising steam as a regeneration agent at a temperature which is the same or similar to that used in the production of the unsaturated carboxylic acid, and wherein the process is carried out at a gas hourly space velocity rate of from about 500 to about 10000 Nm.sup.3/m.sup.3/h.

2. The process according to claim 1 wherein the process is for regenerating a deactivated vanadium-titanium-phosphorous catalyst which has been used in the production of acrylic acid.

3. The process according to claim 1 wherein the temperature at which the process is carried out is up to about 75° C. above the temperature used in the production of the unsaturated carboxylic acid.

4. The process according to claim 1 wherein the process is carried out at a temperature of about 400° C. or less.

5. The process according to claim 1 wherein the process is carried out at a pressure of from about 0 kPa to about 6000 kPa.

6. The process according to claim 5 wherein the process is carried out in a vacuum.

7. The process according to claim 5 wherein the process is carried out at a pressure of about 130 kPa to about 250 kPa.

8. The process according to claim 1 wherein the regeneration stream additionally comprises nitrogen.

9. The process according to claim 8 wherein the mole ratio of steam to nitrogen is about 1.5 to about 2.5 steam to about 1 part nitrogen.

10. The process according to claim 1 wherein the regeneration stream further comprises oxygen.

Description

(1) The present invention will now be described by way of example with reference to the following Example and the accompanying figures in which:

(2) FIG. 1 is a graph illustrating the results of Example 1;

(3) FIG. 2 is a graph of data generated from that in FIG. 1;

(4) FIG. 3 is a graph illustrating the carbon laydown removed.

EXAMPLE 1

(5) A feed stream comprising formaldehyde and acetic acid was passed over a vanadium-titanium-phosphorus catalyst and the catalyst allowed to deactivate. The catalyst was then regenerated by contact with a regeneration stream. The amount of CO.sub.2 in the exit gas was monitored. The process was then repeated using different regeneration conditions. The conditions used for each regeneration process are outlined in Table 1.

(6) TABLE-US-00001 TABLE 1 Composition of Regeneration Stream Temperature (° C.) Test 1 6% O.sub.2/N.sub.2 (8 l/h) 400 Test 2 6% O.sub.2/N.sub.2 (8 l/h) + H.sub.2O (0.2 ml/min) 325 Test 3 6% O.sub.2/N.sub.2 (8 l/h) 325

(7) Data showing the concentration of CO.sub.2 and CO in the exit gas over time for each regeneration run can be found in Table 2 and FIGS. 1 and 2.

(8) TABLE-US-00002 TABLE 2 Test 1 Test 2 Test 3 Time/min CO.sub.2 CO CO.sub.2 CO CO.sub.2 CO 0 0 0 0 0 0 0 30 1.98 0.65 1.32 0.55 1.31 0.605 60 4.56 1.58 4.36 2.57 2.83 1.13 120 2.83 1.02 3.14 1.18 1.67 0.64 180 0.195 0.051 1.18 0.347 0.67 0.33 240 0.068 0.012 0.29 0.1 0.28 0.14 300 0.051 0 0.082 0.043 0.205 0.076

(9) As can be seen, the incorporation of water into the regeneration stream results in removal of CO.sub.2 at 325° C. which is comparable to the removal generated by the regeneration stream consisting of 6% O.sub.2/N.sub.2 stream at 400° C. The CO.sub.2 removal achieved by the 6% O.sub.2/N.sub.2 stream at 325° C. was less effective than water containing stream at the same temperature. Thus, as can be seen, the presence of water enhanced the CO.sub.2 removal capabilities of the regeneration stream.

(10) The data in Table 2 gives a total laydown carbon removed as set out in Table 3.

(11) TABLE-US-00003 TABLE 3 Test 1 Test 2 Test 3 Weight of carbon from CO.sub.2, g 0.323 0.368 0.236 Weight of carbon from CO, g 0.111 0.165 0.098 Total carbon (CO.sub.2 + CO) 0.434 0.533 0.334

(12) This is represented in FIG. 3.

(13) Thus, in this series of tests which all utilise the same catalyst, run time, reaction conditions, and feed but which are regenerated by the processes given in Table 1, it is demonstrated that with the regeneration of the present invention, more of the carbon laydown is removed at lower temperatures than is achievable with a straight oxidative regeneration (i.e. comprising oxygen only).

(14) With steam present, some hydrogen was noted in the vent gas which suggests a reaction taking place which can be considered as equivalent to steam reforming. As the hydrogen is not equimolar with the carbon monoxide, it is postulated that there are two reaction mechanisms occurring. The details of the hydrogen noted are set out in Table 4. No organics were noted.

(15) TABLE-US-00004 TABLE 4 Test 1 Test 2 Test 3 Tim/min H.sub.2 H.sub.2 H.sub.2 0 0 0 0 30 0 0.012 0 60 0 0.42 0 120 0 0.206 0 180 0 0.061 0 240 0 0.034 0 300 0 0.08 0

EXAMPLE 2

(16) The treatment of a catalyst in the presence of steam only as regeneration was carried out at 400° C. Table 5 shows that the peak carbon removal takes longer to achieve (120 minutes rather than 60 minutes when oxygen is present). There is some reaction between water and carbon that sees the formation of carbon oxides but there are also organics present in the regeneration vent gas. The overall carbon oxides to hydrogen ratio are also higher in table 5 than in test 2 of example 1, which suggests that the oxygen in test 2 of example 1 has enhanced the reforming regeneration mechanism in test 2 of example 1.

(17) TABLE-US-00005 TABLE 5 Time/min CO.sub.2 CO H.sub.2 C.sub.2H.sub.4 C.sub.3H.sub.6 0 0 0 0 0 0 30 0.1 0.08 0.03 0.039 0.015 60 0.71 0.236 0.07 0.129 0.021 120 1.14 0.57 0.03 0.017 0.004 180 0.38 0.23 0.017 0 0 240 0.15 0.075 0.011 0 0 300 0.035 0.011 0 0 0