Sumitomo Chemical Co., Ltd. Trends and Views in the Petrochemicals Research Laboratory Development of Technologies for Tomonori KAWABATA Propylene Oxide Production Jun YAMAMOTO Chiba Works Hirofumi KOIKE Shuhei YOSHIDA Sumitomo Chemical Co., Ltd. has developed a propylene oxide (PO)-only manufacturing process where cumene acts as the oxygen carrier, which has a high reputation as a production method that offers distinct advantages of a high PO yield and superior stability in plant operation. In this article we outline the trends in PO manufacturing technology, and also introduce the status of licensing activities and features of the Sumitomo Chemical process. This paper is translated from R&D Report, “SUMITOMO KAGAKU”, vol. 2019. Introduction can be roughly divided into three methodologies from the viewpoint of their history. The first generation was Propylene oxide (PO) is a major industrial product the chlorine method for manufacturing PO by using with production of more than 10 million tons per year chlorine (CL), and the second generation was a co-pro- worldwide. Approximately 70% of it is used for polyether duction method producing PO and co-products such as polyols (polyols) in the raw materials for polyurethanes, styrene monomers (SM) or tert-butyl alcohol (TBA) and approximately 17% of it is used for propylene glycol using organic hydroperoxide (PO/SM, PO/TBA). in the raw material for unsaturated polyesters, food These production methods have drawbacks such as product additives and cosmetics (Fig. 1). The demand problems with processing of by-products or difficulties for polyurethanes is growing remarkably, particularly in in balancing the markets for PO and the co-products in Asia, and the world’s major PO producers have terms of economics. A new environmentally friendly PO- announced start-up plans for new plants over recent only manufacturing process without any co-product has years (Fig. 2). Fig. 3 shows proportions of PO produc- become desirable. As a result, third-generation produc- tion by production method worldwide. tion methods based on the use of cumene as an oxygen Current commercialized methods for PO production carrier (POC) and hydrogen peroxide to propylene PO applications: Polyether polyols 68%, Propylene glycol 17%, Others (Glycol ether, Surfactants) 15% For flexible PU Benzene, Toluene TDI Polyurethane Phosgene (Flexible) For rigid PU Mattresses, Cushions Aniline MDI for automotives & furniture Formaldehyde EO (Rigid) Insulations for housing Propylene PO Polyether polyols & construction, Refrigerators Propylene glycol Water Cosmetics, De-icers, (Specialties) Food additives Adhesives, Sealant, Paint & coating, Glycol ether Alcohols Elastomers Solvents Fig. 1 Main applications of PO and market outlook SUMITOMO KAGAKU (English Edition) 2019, Report 1 Copyright © 2019 Sumitomo Chemical Co., Ltd. 1 Trends and Views in the Development of Technologies for Propylene Oxide Production North America South America epoxidation catalyst technology developed independent- Europe Middle East & Asia 14,000 ly by Sumitomo Chemical and process development t/y) 12,000 technology adopting thermally stable cumene hydroper- 3 10,000 oxide, we have been successful with an extremely high 8,000 PO yield and low energy consumption for separation 6,000 and purification, making for the method superior to 4,000 existing processes in terms of both yield and energy. 2,000 Therefore, we have received various awards such as the World PO Capacity (10 0 8 9 2006 Chemical Society of Japan Chemical Technology 015 2012 2013 2014 2 2016 2017 201 201 2020 2021 Award (2006), Minister of Economy, Trade and Indus- Fig. 2 Forecast world PO production capacity try Award for the 8th Green Sustainable Chemistry (estimated by Sumitomo Chemical Co., Ltd.) (GSC) Award (2008) and the 2008 Japan Petroleum Institute Award (2008), so that this is highly regarded as a technology that contributes to development of a POC sustainable society. 6% HPPO At the same time, POC is a process with superior sta- CL 14% bility in plant operation than other production methods, 37% and there have been many requests for technology PO/TBA 16% licenses from overseas. Up to now we have implemented PO/SM three licenses (Table 1). In 2009, Petro Rabigh (joint 26% venture between the Saudi Arabian Oil Co. and Sumito- mo Chemical Co., Ltd.) started up the first licensed Fig. 3 PO production technologies (2018) plant. S-Oil Corp. (South Korea) implemented a license (estimated by Sumitomo Chemical Co., in 2015, and PTT Global Chemical Public Co., Ltd. Ltd.) (Thailand) concluded a license agreement in 2017 and is currently in construction building toward starting oxide (HPPO) were commercialized. Since 2015, third- operations in 2020. generation production methods have accounted for half In this article, we will give an explanation of trends or more of production capacity among new plants with and views on the development of technologies for PO a production capacity of more than 200,000 tons/year. production and will also introduce the features of POC. Taking the opportunity of our successfully develop- ment of a new epoxidation catalyst in 1998, Sumitomo Commercialized PO Production Methods Chemical was successful in establishing POC technolo- gy, and started 150,000 tons per year commercial pro- 1. Chlorine Method duction at the Chiba Works in 2003. Thereafter, we The chlorine method is the oldest PO production implemented a plant enhancement to 200,000 tons per method that has been implemented industrially, and year in the fall of 2005 based on healthy demand in Asia, PO is manufactured through generating propylene and operations have been continuing smoothly with con- chlorohydrine with propylene, chlorine and water as stant working on rationalization for further enhancing raw materials followed by dehydrochlorination. The competitiveness and for reducing the environmental largest producer using this method is The Dow Chem- impact. Through the fusion of the high performance ical Co. (currently DowDuPont, Inc.), and there are Table 1 Licensing history for Sumitomo POC technology Plant Location Capacity (103 t/y) Start-up Sumitomo Chemical Co., Ltd. Japan 200 2003 Rabigh Refining and Petrochemical Co. (Petro Rabigh) Saudi Arabia 200 2009 S-Oil Corp. South Korea 300 2018 PTT Global Chemical Public Co., Ltd. (PTTGC) Thailand 200 2020 SUMITOMO KAGAKU (English Edition) 2019, Report 1 Copyright © 2019 Sumitomo Chemical Co., Ltd. 2 Trends and Views in the Development of Technologies for Propylene Oxide Production two Japanese producers, AGC Inc. and Tokuyama tane is carried out in the liquid phase under conditions Corp. The impact on the environment of the waste pro- of 120 - 140 °C and 3 - 4 MPaG, and the isobutane con- cessing is high since approximately 40 tons of waste version is 35 - 50% and the TBHP selectivity is 50 - 60%. water containing approximately 1.9 tons of calcium Epoxidation of propylene is normally carried out in the chloride is generated per ton of PO. Even now the chlo- presence of a catalyst including a molybdenum com- rine method accounts for approximately 40% of the PO pound in the liquid phase under conditions of 90 - 130 °C production capacity worldwide, but it is difficult to con- and 1.5 - 6 MPaG. The propylene conversion is approxi- struct new facilities because of recent trends toward mately 10%, the TBHP conversion is 95% or greater and increased restrictions regarding the environment.1) the PO selectivity is approximately 90%. If TBA is dehy- drated, it forms isobutylene, and if it is further reacted with methanol, methyl tert-butyl ether (MTBE), which 2CH3CH = CH2 + 2HOCl CH3CHCH2Cl + CH3CHCH2OH is useful as an octane booster for gasoline, can be syn- OH Cl thesized. Since this method produces approximately 2.1 CH3CHCH2Cl + CH3CHCH2OH + Ca(OH)2 tons of MTBE as a by-product for each ton of PO, prof- OH Cl O + CaCl2 + 2H2O 2CH3CH CH2 itability of the process is severely affected by the MTBE market conditions. Similarly, profitability of the PO/SM method is not independent of the market because the 2. Co-Production Method method produces approximately 2.5 tons of SM as a by- The co-production method was first developed by Hal- product per ton of PO. con International Inc. and Atlantic Richfield Co. (later LyondellBasell Industries Holdings B.V.) in the 1970s. 3. Third-Generation Production Method 1 (POC) Co-production methods include PO/SM and PO/TBA, The POC method and the hydrogen peroxide to and they use ethyl benzene hydroperoxide and tert-butyl propylene oxide (HPPO) method, which substantially hydroperoxide (TBHP), respectively, as organic perox- only have water as a by-product, have been commercial- ides for manufacturing PO by epoxidation of propylene. ized one after the other as production methods that are At the same time, a styrene monomer (SM) or tert- not affected by market conditions for co-products. butanol (TBA) is produced as the co-product. Typical The POC method established by Sumitomo Chemical producers using the PO/SM method are LyondellBasell started commercial production in 2003 (Fig. 4), and is Industries Holdings B.V. and Royal Dutch Shell plc, and a three-reaction-step process with a process for gener- representative producers using the PO/TBA method ating cumene hydroperoxide (CMHP) by air oxidation are LyondellBasell Industries Holdings B.V. and Hunts- of cumene (CUM), an epoxidation process for propylene man International LLC. In a reflection of the trends in (C3’) using the CMHP, and a step for recovering cumene demand for the two sets of co-products in the 2000s, new by hydrogenation of α-cumyl alcohol (CMA) formed in PO plants have mostly employed the PO/SM method, the epoxidation process. but in recent years the PO/TBA method has mainly been employed. The PO/TBA co-production process Air will be described in the following. OOH Oxidation (CH3)3CH + O2 (CH3)3COOH CH CH = CH + (CH ) COOH 3 2 3 3 CUM CMHP O + (CH3)3COH CH3CH CH2 Epoxidation H2O Hydrogenation OH (CH3)3COH CH2 = C(CH3)2 + H2O C3’ CH2 = C(CH3)2 + CH3OH (CH3)3COOH3 H2 O In the PO/TBA method, PO is produced by generat- CMA ing TBHP by air oxidation of isobutane followed by epoxidation of propylene by TBHP.