Development of New Propylene Oxide Process
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Development of New Propylene Sumitomo Chemical Co., Ltd. Planning & Coordination Office, Petrochemicals & Plastics Sector Oxide Process Junpei TSUJI Petrochemicals Research Laboratory Jun YAMAMOTO Masaru ISHINO Rabigh Project Office Noriaki OKU There has always been a strong demand for the development of a new PO-only process. Conventional processes –the chlorohydrin PO-only process and the organic hydroperoxide process, which generates a huge amount of co-products– have given PO producers headaches due to the generation of waste that is not envi- ronmentally friendly and the dependence of product price on the fluctuating market for co-products. With the development of a high performance titanium epoxidation catalyst by our researchers, we have suc- ceeded in establishing a novel PO-only manufacturing process where cumene acts as the oxygen carrier. The new PO Cumene process is considered a “green process” since it gives higher yields than conventional processes while only producing small amounts of by-products. This paper is translated from R&D Report, “SUMITOMO KAGAKU”, vol. 2006-I. Introduction plans for new plants (Fig. 2). Production by the princi- ple producers of PO worldwide is shown in Fig. 3, and Propylene oxide (PO) is a major industrial product Fig. 4 shows the proportions of production by produc- with production of more than 6 million tons per year tion method. worldwide. Approximately 70% of it is used as PO production methods that have been industrial- polypropylene glycol in the raw materials for urethane, ized up to this point can be roughly divided into two and the remainder is used as propylene glycol in the methodologies. The first is PO-only production meth- raw materials for unsaturated polyesters, food product ods using chlorine, and the other is co-production additives and cosmetics (Fig. 1). The demand for ure- methods that produce co-products such as styrene thane is growing remarkably, particularly in Asia, and monomers along with the PO. All of the industrial one PO producer after another is announcing business processes that have been implemented up to now carry (1000T/y) 1,800 1,600 1,400 1,200 1,000 800 Propylene glycol Polyols 600 Unsaturated polyester resins Polyurethane (rigid forms) 400 → building materials → refrigerator, insulator Industrial use Polyurethane (flexible forms) 200 → antifreeze, lubricant → car seat, mattress, carpet 0 Pharmaceuticals Non forms 2003 2004 2005 2006 2007 2008 2009 2010 → toothpaste, cosmetics → elastomer, adhesive, paint Fig. 2 Asian PO demand forecasting (excluding Fig. 1 Uses for Propylene oxide (PO) Japan) SUMITOMO KAGAKU 2006-I 1 Development of New Propylene Oxide Process Total 6740kt/y duction method. Each of these production methods will Huntsman 230 (2003. Estimated) Others be introduced in the following.1), 2) Repsol 250 Dow 2300 Sumitomo + Nihon oxirane 1. Chlorine Method 380 Lyondell The chlorine method (also known as the chlorohy- (incl. Bayer) Shell/BASF 900 1860 drin method) is technology that was originally used for the production of ethylene oxide, but in the 1960s, with Fig. 3 Global PO supplier and capacity (1000t/y) the conversion of production methods to direct oxida- tion methods for ethylene oxide, it became the method used for producing PO using the idle plants. The PO/TBA(20%) largest producer using this method is the Dow Chemi- Lyondell Huntsman Chlorohydrin(45%) cal Company, and there are two Japanese producers, Dow Asahi Glass Co. Ltd. and Tokuyama Corp. Up to now, Co-production Asahi Glass PO-only method PO/SM(35%) Tokuyama production Lyondell method this was the only industrial PO-only production Shell Repsol method. Nihon Oxirane SKC Chemical Sumitomo New PO process 2CH3CH = CH2 + 2HOCl CH3CHCH2Cl + CH3CHCH2OH Fig. 4 PO production technologies OH Cl CH3CHCH2Cl + CH3CHCH2OH + Ca(OH)2 with them the problem of byproducts and the problem OH Cl O of controlling market conditions and the like for the co- 2CH3CH CH2 + CaCl2 + 2H2O products, and the PO producers in various countries have been focusing the attention on developing a new Propylene and chlorine are reacted to produce a mix- PO-only method. ture of α- and β-chlorohydrin (9:1), and next, PO is syn- Sumitomo Chemical has also been eagerly research- thesized by reaction with an alkali (calcium hydroxide, ing new PO-only production methods. Taking the for example). The only product is PO, and as a byprod- opportunity of our successfully developing a new epoxi- uct, an alkali salt is produced in the same molar quanti- dation catalyst in 1998, we were successful in establish- ty as the PO. This production method is a moderate ing the technology for a new PO production process, temperature reaction in an aqueous solution, but for and starting in 2003, we began using the new PO-only each ton of PO, a large amount of secondary raw mate- production method at 150,000 tons per year at our rials, 1.4 tons of chlorine and one ton of calcium Chiba Plant. After this, we implemented a plant hydroxide, are necessary, and approximately 2.0 tons enhancement to 200,000 tons per year in the fall of of calcium chloride is produced as a byproduct. In addi- 2005 based on the healthy demand in Asia, and opera- tion, a large excess of water is present in this reaction, tions are continuing to go well. Furthermore, we plan and a chlorohydrin concentration of 3 – 6% is main- to start operating a second plant (200,000 tons of PO tained, so the formation of chlorine adducts must be per year) in 2008 according to the Rabigh plan for controlled. Therefore, a large volume of waste water Saudi Arabia. containing the alkali salt is produced (a volume several Along with reviewing the current industrial process- tens of times that of the PO), and the process is one es, this paper introduces the features of the PO-only with an extremely large waste water burden. process developed by Sumitomo Chemical. 2. Organic Peroxide Method Existing PO Production Processes The organic peroxide method (also known as the hydroperoxide method) was first developed by Halcon The propylene oxide (PO) production processes that Corp. and Atlantic Richfield Oil Corp. (later ARCO) in have been industrialized so far can be roughly divided the 1970s. In this method there is a method using eth- into the chlorine method, which is a PO-only method, ylbenzene and a method using isobutane, and in each and the organic peroxide method, which is a co-pro- of them PO is synthesized by indirect epoxidation of SUMITOMO KAGAKU 2006-I 2 Development of New Propylene Oxide Process propylene using ethylbenzene hydroperoxide or tert- Sumitomo Chemical’s New PO-only Process butyl hydroperoxide as the organic peroxide. A styrene monomer (SM) or tert-butanol (TBA) is produced as Using cumene, Sumitomo Chemical has established the co-product. Typical producers using PO/SM co- a cumene PO-only process as a new PO production production are Lyondell Chemical Company and Shell process. We developed a high performance Ti based Chemicals Ltd., and in Japan, there is only Nihon Oxi- epoxidation catalyst in 1998, and taking this as an rane Co., Ltd. The PO/TBA producers are Lyondell opportunity, we started working on developing a new and Huntsman International LLC. In a reflection of the PO-only process using cumene. Starting with the labo- trends in demand for the two sets of co-products in ratory investigations in 1999, it was possible to carry recent years, new PO plants have exclusively employed out development and establish the business in a short the PO/SM co-production method. We will describe time by maximizing the use of concurrent engineering, the PO/SM co-production process in the following. with bench tests in 2000, pilot testing in 2001, comple- tion of a plant in 2002 and plant startup in 2003. CH3 CH3 This production method is fundamentally similar to CH2 + O2 CH the organic peroxide methods, but the major feature is OOH using a high performance epoxidation catalyst that CH3 uses cumene as the reaction medium, so we can call it CH + CH3CH = CH2 the cumene PO-only process. This production method OOH CH3 O is made up of the following processes. CH + CH3CH CH2 (1) Oxidation process where cumene is oxidized in air OH to obtain cumene hydroperoxide (CMHP). α α CH3 CH2 (2) Epoxidation process where , -dimethyl benzyl CH C + H2O alcohol (CMA) is obtained from CMHP and propy- OH H lene in the presence of an epoxidation catalyst. (3) Hydrogenation process where CMA is hydrogenat- First of all, ethylbenzene hydroperoxide is produced ed and cumene is obtained in the presence of a by air oxidation of ethylbenzene. Next, the ethylben- hydrogenation catalyst and hydrogen. zene hydroperoxide and propylene are reacted in the (4) Cumene purification process where the cumene presence of an epoxidation catalyst, and α-methylben- obtained is purified and recycled to the oxidation zyl alcohol and PO are produced. The α-methylbenzyl process. alcohol that is produced undergoes a dehydration reac- (5) PO purification process where PO is purified. tion in the presence of an acid catalyst to form SM. Mo Three reaction processes are included, the (1) oxida- based homogeneous catalysts3) and Ti supported silica tion process, (2) epoxidation process and (3) hydro- based heterogeneous catalysts4), 5) are used for the genation process. In the following, we will give an epoxidation catalyst. With the isobutane method, there overview of each of the reaction processes. is co-production of TBA. If TBA is dehydrated, it forms isobutylene, and if it is further reacted with methanol, 1. Oxidation Process methyl tertiary-butyl ether (MTBE), which is useful as This is a process where cumene is oxidized by oxy- a gasoline additive, can be synthesized.