HPPO

Fig. 14 Hydrogen peroxide to propylene oxide (HPPO) process...

CO is derived from a variety of feedstocks such as petroleum gas, fuel oil, coal, and biomass. The industrial scale production of PO starts from propylene, which is mainly obtained from crude oil. However, due to the high importance of this compound, many pathways from renewable sources have additionally been developed [54]. PP is converted to PO by either hydrochlorination or oxidation [55]. The use of chlorine leads to large amounts of salts as by-products, therefore oxidation methods are more important, such as the co-oxidation of PP using ethylbenzene or isobutene in the presence of air and a catalyst. However, this process is economically dependent on the market share of these by-products, thus new procedures without significant amounts of other side-products have been developed, such as the HPPO (hydrogen peroxide to propylene oxide) process in which propylene is oxidized with hydrogen peroxide to give PO and water [56, 57] (Fig. 14). 

Together with the engineering company Uhde (Germany), Degussa (now Evonik Industries) has also developed an innovative process for producing propene oxide (PO) from H202, the so-called HPPO process. The Korean company SKC, Seoul, has... 

The industrial process for propene oxide manufacture is commonly referred to as the HPPO (hydrogen peroxide propene oxide) process. EniChem set up a prototype plant in 2002 [150]. BASF/Dow Chemicals and Degussa, in turn, have the construction of commercial plants already in progress or at the planning stage [151]. 

Degussa, in turn, has recently announced the commercialization of a HPPO process, jointly developed with the engineering company Uhde. Parallel to this, Degussa with Headwaters is also working on the direct synthesis of H2O2, for which a demonstration plant was completed in 2006 [151]. According to the news release, hydrogen peroxide will be obtained in the new process as a dilute methanol solution to be used directly in the epoxidation of propene. 

The catalyzed reaction of the elements produces hydrogen peroxide directly, in competihon with water (Equation 18.16). Most selective catalysts are based on supported Pd, often modified by other metals. Methanol is increasingly studied as a reachon medium, from the perspective of the direct use of the solution obtained in the HPPO process. For high selectivihes, the reaction normally necessitates relatively low temperatures, often room temperature or lower, and the presence of mineral acids and other additives [153]. 

Indeed, copolyesters having incorporated ( -acylated oximino ketone groups are obtained [75] by interfacial condensation of different acid dichlorides, such as terephthaloyl-, isophthaloyl- and sebacoyl chlorides, with small amounts of l-(4 -hydroxyphenyl)-l,2-propanedione-2-oxime (HPPO) or p-hydroxyphenyl glyoxal aldoxime (HPGA) in the presence of a large excess of bisphenol-A ... 

The polyadipates of tetrachloro bisphenol-A depicted below, containing small amounts of HPPO, are similarly used [154] as prepolymers to give, upon UV irradiation, macroradicals able to initiate the polymerization of styrene and produce block copolymers. 

HPPO and in situ HPPO (BASF/Dow/Solvay, Degussa/ Uhde, Lyondell)" H2O2 (by the anthraquinone route) TS-1... 

HPPO and in situ HPPO (Lyondell, BASF, Degussa/Headwaters, Tosoh Co, Hoechst) H2O2 (by direct liquid-phase oxidation of H2) Pd/Pt-TS-1... 

HPPO Processes HP Generation by Redox Cycles on Organic O Carriers... 

Joint ventures and collaborations for the implementation of newly developed HPPO processes have been established between BASF, Dow and Solvay, and between Degussa-Evonik, Headwaters and Krupp-Uhde [11]. 

Compared to existing PO process technologies, HPPO is claimed to offer unique benefits from economic and environmental points of view. New PO plants built using HPPO technology are claimed to be more economical because they require up to 25% less capital. The simplicity of the process derives from the fact that there is no need for... 

Two different process configurations were proposed by EniChem [15]. The first configuration involves the in situ generation of HP, through the classical RAQ/ RHAQ route, in the same medium where the epoxidation reaction occurs (in situ HPPO). Scheme 6.6 shows the reactions involved. 

From the Dream Reaction to the Real Process the Implemented HPPO Process... 

Figure 6.4 Simplified flow-sheet ofthe integrated insitu HPPO (a) and H PPO (b) processes for propene epoxidation with generation of HP, developed by EniChem.

HPPO and In Situ HPPO Processes HP Generation by Direct Oxidation of H2 (DSHP)... 

Several Technologies for In Situ HPPO with TS-1-Supported Pd Catalysts... 

Table 6.4 Performance data for BASF catalysts in HPPO with generation of HP by means of H2 oxidation with O2 (DSHP) [25] .

Figure 6.9 Process integration in BASF technology for PO production with DSHP-HPPO.

DSHP-HPPO Technology Developed by Degussa Evonik/Headwaters... 

Still several problems remain unsolved to make the DSHP-HPPO process economically viable (i) safety the reaction of H2 with O2 in the presence of a flammable solvent (methanol) puts high hurdles on safety (ii) removal of acid and bromide the Bronsted acid and the bromide needed to produce HP from the elements have to be removed before the generated H P solution can be used for epoxidation (iii) solvent recycle after the generated H P solution has been used for epoxidation, the methanol has to be separated and recycled. During work-up some additional by-products are formed formaldehyde, acetaldehyde, propionaldehyde, methyl formate, dimethoxymethane, 1,1-dimethoxyethane and 1,1-dimethoxypro-pane. These compounds are difflcult to separate (many make azeotropes with methanol), so the recovered methanol will be contaminated. However, even small amounts of aldehydes or formates can poison the Pd or Pd/Au catalyst. Additional equipment needed to solve these problems will increase the investment costs. 

Scheme 6.7 Mechanism of HPPO, with direct synthesis of HOPO. Source elaborated from [2a].

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