Study of deactivation and regeneration of titanium silicalite-1 catalyst in cyclohexanone ammoximation

Reporter: Sun Rui

Supervisor: Xin Feng

2013-4-24

1. Introduction

2. Reasons for titanium silicalite-1 catalyst deactivation in cyclohexanone ammoximation

3. Regeneration of titanium silicalite-1 catalyst in cyclohexanone ammoximation

4. Ideas and expectations

Study of deactivation and regeneration of titanium silicalite-1 catalyst in cyclohexanone ammoximation

Tianjin University

Tianjin University

1.1 TS-1 is a ZSM-5 like zeolite, not containing aluminium, where a part of silicon is statistically substituted with titanium. The use of this catalyst allows to obtain an high selectivity and conversion.

1. Introduction

TS-1+H2O2

RR'CHN

H2

RR'C NOH

R2 N

H

R2NOH

NH3

R2C OR2C NOH

R 2S

R2SO

RR

'CH

OH

RR'C O

PhOH

OH

OH

RHC CH2O

RCHC CH2

R 2CH 2

R2CHOH+R2C O

Fig.1-1 (ring)oxidation reaction on titanium silicalite-1

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1. Introduction

1.2 Cyclohexanone oxime is an important intermediate in chemical industry, particularly as a key precursor of ε -caprolactam for nylon production. In 1988, Enichem developed a new process for producing cyclohexanone oxime from ammoximation of cyclohexanone catalyzed by TS-1. Ammonia and hydrogen peroxide were used as the raw materials.

The advantages of TS-1:1. Reaction conditions can be carried out under low temperature and pressure;2. Good product yield and selectivity;3. Simple process;4. Low concentration of hydrogen peroxide as the oxidant;5. Without pollution

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1. Introduction

Fig. 1-2 Enichem’s ammoximation process of cyclohexanone oxime

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2. TS-1 catalyst deactivation in cyclohexanone ammoximation

Fig.2-1 （ l ） a，（ Z ） X （ CHN），（ 3 ） X （ H2O2 ） , （ 4 ） S （ H2O2）（ Reaction conditions ： n （ CHN ） : n （ NH3 ） : n （ H2O2 ） = 1: 1.5: 1.2.a- TS-l activity X - Conversion ， S -Selectivity ， CHN -cyclohexanone ）

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2. TS-1 catalyst deactivation in cyclohexanone ammoximation

Three main deactivation processes are identified:

(i) Slow dissolution of the framework with accumulation of Ti on the external of the remaining solid; (ii) Direct removal of Ti from the framework; (iii) Pore filling by by-products2.1 The dissolution erosion of TS-1 in cyclohexanone ammoximation

Table. 2-1 Dissolution effect of ammonia on TS-1

2.1.1 The effect of ammonia

Fig. 2-2 Raman spectra of fresh and ammonia treatment catalyst samples

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2.1 The dissolution erosion of TS-1

Fig. 2-3 Raman spectra of fresh catalyst and samples after 350h

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2.1.2 Inhibition of silicon in the TS-1 dissolved Table 2-4. Effect of additives on the TS-1 catalyst

2.1.3 Conclusions (i) Ammonia was the primary factor leading to deactivation of the catalyst.

(ii) The study proved that the dissolution erosion of silicon in the basic solution was connected with the solution polarity and ammonia concentration. Adding an additive into the solution could inhibit the dissolution erosion of silicon from the catalyst , and the stable running period of the catalyst was prolonged.

2.1 The dissolution erosion of TS-1

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2. 2 Coke deposition on TS-1 catalyst in cyclohexanone ammoximation

2.2 Coke deposition on TS-1 catalyst in cyclohexanone ammoximation (The main reason)

Fig.2-4 TG-DTA chart of deactivated TS-1

2.2.1 Characterization of TS-1 catalyst deactivation

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Fig.2-5 In situ IR spectra of TPO coke combustion of deactivated TS-1a 40℃; b 60℃; c 80℃; d 100℃; e 120℃; f 150℃;

g 200℃; h 300℃; i 400℃; j 500℃; k 600℃; m 700℃

2. 2 Coke deposition on TS-1 catalyst in cyclohexanone ammoximation

2.2 Coke deposition on TS-1 catalyst in cyclohexanone ammoximation

2.2.1 Characterization of TS-1 catalyst deactivation

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Fig.2-6 IR spectra of framework stretching region of TS-1 before and after deavtivation

a fresh; b deactivationc regeneratation at 350℃;d regeneration at

700℃

Fig.2-7 XRD patterns of TS-1 before and after deavtivation

a fresh; b deactivationc regeneratation at 350℃;d regeneration at

700℃

2. 2 Coke deposition on TS-1 catalyst in cyclohexanone ammoximation

2.2 Coke deposition on TS-1 catalyst in cyclohexanone ammoximation

2.2.1 Characterization of TS-1 catalyst deactivation

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2.2.2 GC-MS analysis

Fig.2-8 GC-MS total ion current spectrum of dissoluble deposit

2. 2 Coke deposition on TS-1 catalyst in cyclohexanone ammoximation

2.2 Coke deposition on TS-1 catalyst in cyclohexanone ammoximation

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3. Regeneration of TS-1 catalyst in cyclohexanone ammoximation

Regeneration methods of TS-1

(i) Oxidation of catalyst by in situ hydrogen peroxide (ii) Solvent extraction (iii) Calcination The main regenieration method of TS-1 A deactivated catalyst is treated in an acidic solution having a pH value of <=3, and then dried and calcined. The process is simple in procedure and can make the catalytic activity, selectivity and stability of the regenerated catalyst be recovered to the level of its fresh catalyst.

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4. Ideas and expectations

(i) Have a deeper understanding of the continuous cyclohexanone ammoximation reaction and the TS-1 monolithic catalyst.

(ii) Look for the properties of substances in the reaction systems, respectively. Try to find new ways to separate more cyclohexanone-oxime from the reaction system. Electro-deposition for example.

(iii) Think about the method of regenerating TS-1 catalyst by using hydrogen peroxide or solvent washing combined with the technology

(iiii)Try to prove the main reason that causes the TS-1 catalyst to deactivate is cyclohexanone-oxime