**4. Industrial application of HPPO route**

PO is an important organic chemical intermediate among propene derivatives. Most PO is used to produce polyether polyols and polyurethane. Since 2003, the consumption of PO in the world has been increasing year by year. There are about 20 routes for PO production, among which the Chlorohydrin and Halcon routes are the most commonly used. The investment cost of Chlorohydrin route is low, but it produces a large amount of wastewater containing Cl<sup>−</sup>, which pollutes the environment and seriously corrodes equipment. The Halcon route overcomes the disadvantages of environmental pollution, but the cost is high. Moreover, the economy of PO is seriously affected by the coproducts. Therefore, PO manufacture needs a new route.

At present, hydrogen peroxide to propene oxide (HPPO) route is one of the most possible alternatives for PO production. Compared to the traditional routes, the HPPO route provides environmental and economic benefits. In recent years, the HPPO route was commercialized by BASF/Dow Chemical and Evonik/Uhde in Belgium and South Korea, separately. Some institutes also tried this route in pilot plants. The main and side reactions in HPPO route are shown in **Figure 10**. It is clear that all the reactions are exothermal. The exothermic reaction not only

**155**

deactivation.

**Figure 11.**

**Figure 10.**

*Main and side reactions in HPPO route.*

*Flow chart of the 100 t/a HPPO pilot plant.*

water and a small amount of MME and PG.

*Coordination States and Catalytic Performance of Ti in Titanium Silicalite-1*

threatens safety but also promotes the solvolysis reactions and generates PO oligomers. The blocking of TS-1 channels by oligomers is the main cause for its

Three steps were taken for the industrialization of our HPPO route, which were the 100 t/a pilot plant, 1000 t/a pilot plant, and 150 kt/a industrial plant. In 2009, the 100 t/a pilot plant procedure was carried out in Jiangsu, China, the flow chart of which is shown in **Figure 11**. A fixed-bed reactor was adopted, and the loading of the catalyst was 100 kg. Propene, H2O2, and solvent were fed into the reactor simultaneously by three pumps. The product flowed out of the reactor and entered the 1# rectifying column, in which propene was separated from the top of the column. Then, propene flowed to the propene storage tank for recycling. The materials from the bottom of the 1# rectifying column entered the 2# rectifying column. PO was separated from the top of this column and entered the finished tank. The materials from the bottom of the 2# rectifying column entered the 3# rectifying column. The solvent was separated from the top of the column and put into the solvent storage tank for recycling. The material in the bottom of the column contained mainly

The 1000 t/a pilot plant and 150 kt/a industrial plants used similar technology to the 100 t/a pilot plant, except for some energy optimization. The former was carried out in 2013, while the latter is under construction. Under the optimized reaction conditions, the conversion of H2O2 and selectivity of PO are both higher than 95%, and the purity of PO is more than 99.95% in the three HPPO routes.

*DOI: http://dx.doi.org/10.5772/intechopen.89864*

*Coordination States and Catalytic Performance of Ti in Titanium Silicalite-1 DOI: http://dx.doi.org/10.5772/intechopen.89864*

#### **Figure 10.**

*Stability and Applications of Coordination Compounds*

adding more CTAB to the synthesis gel.

*Synthesis process of meso−/microporous titanium silicalite.*

**4. Industrial application of HPPO route**

former (**Figure 9**).

**Figure 9.**

needs a new route.

center of 2.6 nm to that of 6.9 nm by tuning the molar ratio of CTAB to silicon from 0.125 to 0.20. The introduction of CTAB also causes the variation in coordination states and location of Ti ions in the materials. More CTAB leads to a higher content of octahedrally coordinated Ti and a lower content of tetrahedrally coordinated Ti. Furthermore, more Ti is located near the external surface of TS-1 crystals, when

The meso−/microporous titanium silicalite catalysts were evaluated in the epoxidation of cyclohexene and showed excellent catalytic activity with respect to the conventional microporous TS-1, due to the enhanced diffusion properties in the mesopores and higher titanium content near the external surface of the

PO is an important organic chemical intermediate among propene derivatives. Most PO is used to produce polyether polyols and polyurethane. Since 2003, the consumption of PO in the world has been increasing year by year. There are about 20 routes for PO production, among which the Chlorohydrin and Halcon routes are the most commonly used. The investment cost of Chlorohydrin route is low, but it produces a large amount of wastewater containing Cl<sup>−</sup>, which pollutes the environment and seriously corrodes equipment. The Halcon route overcomes the disadvantages of environmental pollution, but the cost is high. Moreover, the economy of PO is seriously affected by the coproducts. Therefore, PO manufacture

At present, hydrogen peroxide to propene oxide (HPPO) route is one of the most possible alternatives for PO production. Compared to the traditional routes, the HPPO route provides environmental and economic benefits. In recent years, the HPPO route was commercialized by BASF/Dow Chemical and Evonik/Uhde in Belgium and South Korea, separately. Some institutes also tried this route in pilot plants. The main and side reactions in HPPO route are shown in **Figure 10**. It is clear that all the reactions are exothermal. The exothermic reaction not only

**154**

*Main and side reactions in HPPO route.*

#### **Figure 11.**

*Flow chart of the 100 t/a HPPO pilot plant.*

threatens safety but also promotes the solvolysis reactions and generates PO oligomers. The blocking of TS-1 channels by oligomers is the main cause for its deactivation.

Three steps were taken for the industrialization of our HPPO route, which were the 100 t/a pilot plant, 1000 t/a pilot plant, and 150 kt/a industrial plant. In 2009, the 100 t/a pilot plant procedure was carried out in Jiangsu, China, the flow chart of which is shown in **Figure 11**. A fixed-bed reactor was adopted, and the loading of the catalyst was 100 kg. Propene, H2O2, and solvent were fed into the reactor simultaneously by three pumps. The product flowed out of the reactor and entered the 1# rectifying column, in which propene was separated from the top of the column. Then, propene flowed to the propene storage tank for recycling. The materials from the bottom of the 1# rectifying column entered the 2# rectifying column. PO was separated from the top of this column and entered the finished tank. The materials from the bottom of the 2# rectifying column entered the 3# rectifying column. The solvent was separated from the top of the column and put into the solvent storage tank for recycling. The material in the bottom of the column contained mainly water and a small amount of MME and PG.

The 1000 t/a pilot plant and 150 kt/a industrial plants used similar technology to the 100 t/a pilot plant, except for some energy optimization. The former was carried out in 2013, while the latter is under construction. Under the optimized reaction conditions, the conversion of H2O2 and selectivity of PO are both higher than 95%, and the purity of PO is more than 99.95% in the three HPPO routes.

The industrial catalyst deactivated partly after the 100 t/a pilot plant reaction. The activity decreased from the inlet to the outlet of the pilot plant reactor [41]. The main reason for the deactivation in pilot plant is similar to that in laboratory, which is blocking of pores and covering of active centers by ethers or oligomers. The more oligomers are generated, the more seriously the catalyst deactivates. The loss of a small amount of framework titanium had little influence on the catalytic activity.

The deactivated catalysts could be externally regenerated by calcination at 813 K for 6 h and in situ regenerated by washing with dilute H2O2. The in situ regeneration, rather than the external regeneration, can be adopted in industry. When using in situ regeneration with dilute H2O2, a longer washing time is more effective than a higher concentration of H2O2. There is one thing needing to be concerned for in situ regeneration. If the concentration of H2O2 is too high or the washing time is too long, some tetrahedrally coordinated Ti will be leached out and transform to octahedrally coordinated Ti.

#### **5. Conclusions**

Great progress has been made in the synthesis of TS-1 and improvement of its catalytic properties. The relative technologies have become increasingly more mature. However, the active center in TS-1 is still controversial (tetrahedrally, pentahedrally, and/or octahedrally coordinated Ti). The contradiction between the cost and catalytic performance of TS-1 has not been resolved completely. Therefore, the synthesis of high-performing, low cost TS-1 needs to be further studied. At present, people attach great importance to environmental protection; thus, the application of TS-1 will have broad development.

This chapter summarized recent work by our group on TS-1, including the tuning of coordination states of Ti, improvement of diffusion properties, and industrial applications of the HPPO route. We hope to provide some references for related research.

### **Acknowledgements**

The authors acknowledge financial support from the National Key Research and Development Program of China (2016YFB0301704), the National Natural Science Foundation of China (21506021), and the Fundamental Research Funds for the Central Universities (DUT19LK61).

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**Author details**

Yi Zuo, Min Liu and Xinwen Guo\*

State Key Laboratory of Fine Chemicals, PSU-DUT Joint Center for Energy

Engineering, Dalian University of Technology, Dalian, China

\*Address all correspondence to: guoxw@dlut.edu.cn

provided the original work is properly cited.

Research, Department of Catalysis Chemistry and Engineering, School of Chemical

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

*Coordination States and Catalytic Performance of Ti in Titanium Silicalite-1*

*DOI: http://dx.doi.org/10.5772/intechopen.89864*

### **Conflict of interest**

There is no conflict of interest to be declared.

*Coordination States and Catalytic Performance of Ti in Titanium Silicalite-1 DOI: http://dx.doi.org/10.5772/intechopen.89864*
