The Production of Propene Oxide: Catalytic Processes and Recent Developments (original) (raw)
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Industrial & Engineering Chemistry Research, 2010
The vapor phase epoxidation of propene with nitrous oxide (N 2 O) was experimentally investigated in a fixed bed reactor using different Cs x /Fe y /SiO 2 catalysts. This was done with a systematic approach which comprises the derivation of kinetic parameters for directly comparing catalyst performance. Therefore, kinetic measurements were made for each catalyst by variation of the residence time. It was found that the addition of an alkali promoter to the Fe y /SiO 2 catalyst is essential for the formation of propylene oxide and a proper alkali/Fe molar ratio is crucial for both activity and selectivity. Maxima in both activity and selectivity were observed for alkali/Fe ratios in the region 1.2-1.7. A further increase in activity without any loss in selectivity was obtained by adjusting the calcination temperature to 783 K. The conversion of PO was used as a tool to measure the product stability and a minimum reaction rate was also found for alkali/Fe ratios in the region 1.2-1.7. The promoter is responsible for the formation of active centers and it reduces surface acidity which leads to an increased stability of PO through the inhibition of the consecutive conversion. Maximum selectivities to PO of about 40% at 5-10% conversion were achieved at moderate reaction temperatures of 648 K. Because of parallel and consecutive formation of carbonaceous deposits on the catalyst, the catalyst deactivated within 2 h of operation to a remaining activity of around 40%. Neglecting the carbonaceous deposits as a reaction product and considering only the vapor phase products, PO selectivity is more than 75% at 5-10% propene conversion. The attempt to slow down the deactivation through the addition of supplementary gases (H 2 , O 2 , NH 3 , H 2 O) was partially successful, but unfortunately this is always accompanied by lower PO selectivity.
Hydrogen peroxide direct synthesis: From catalyst preparation to continuous reactors
2011
Bimetallic Pd-Au catalysts supported on sulphated zirconia (ZS) were prepared by different methods and used for hydrogen peroxide direct. The effect of the addition of gold to Pd enhance the selectivity and the yield of H 2 O 2 . Activity was tested at both atmospheric and high pressure, batch and semi-batch wise. Decomposition, hydrogenation and direct synthesis of H 2 O 2 were assessed on the PdAu-ZS catalyst. Catalysts have been tested also in a trickle bed reactor for the continuous direct synthesis. The H 2 /Pd mol ratio was investigated to enhance both H 2 O 2 concentration and selectivity in batch and TBR. H 2 O 2 concentration was successfully compared between batch and TBR. The TBR shows an enhancement in selectivity towards H 2 O 2 compared to the batch synthesis. A H 2 O 2 selectivity of 90% was achieved with the TBR.
Journal of Catalysis, 2000
3 )]F · 2H 2 O with Pd-metal nanoaggregates, has been attempted. In addition to the development of a novel technique for making this catalyst by hydrothermal incorporation, an extensive optimization of the process conditions to make hydrogen peroxide from H 2 and O 2 has been carried out. The optimal reaction medium for this process was methanol in conjunction with sulfuric acid. Under atmospheric conditions, over 3.5 M H 2 O 2 has been produced in 50 h. A technique has also been developed to measure the water formed from the undesirable H 2 O 2 reduction step that occurs in series-parallel to the desired H 2 O 2 production step. The selectivity toward the production of H 2 O 2 in the case of the hydrothermally incorporated catalysts is over 70% under atmospheric conditions. The maximum rate of production of H 2 O 2 , achieved in anhydrous methanol-H 2 SO 4 media and hydrothermally incorporated Pd-HfPOPV(X) is about 4.1 mmol/ (g min). However, the rate measured here is probably that of external mass transfer (at the liquid-gas interface) because the resistance due to it is the rate-determining step.
Turkish Journal of Chemistry
Introduction One of the most widely manufactured polymers in industry is polypropylene (PP). Its global market size was around USD 117.8 billion in 2020 and is projected to increase at an annual growth rate of 3.4% from 2021 to 2028 [1]. PP is synthesized via polymerization reaction of propene molecules and high purity of the monomers used in the process is strictly required for an efficient process. Practically 2/3 of the propene in industry is used for the production of PP [2]. Besides, it is employed for the manufacture of propene oxide (epoxypropane), acrylic (propenoic) acid, acrylonitrile (propenenitrile), butanol, and (1-Methylethyl) benzene (cumene) [1-3]. Propene is currently produced as a by-product fluid catalytic cracking and coproduct of naphtha catalytic cracking [3]. Propene obtained from refineries can be used in liquefied petroleum gas or to enhance the octane number in gasoline [1,2]. However, even negligible amounts of impurities can prevent the polymerization of propene into polypropylene. In addition, current production methods use huge amounts of energy, which also negatively influenced the greenhouse emissions [4,5]. Propene can be alternatively produced by catalytic dehydration of propan-2-ol (Eq. 1) [6]. In addition, this reaction is a probe to determine the acid-base sites of the solid catalysts [7]. In this context, the presence of acid sites (Brønsted and/ or Lewis) on the catalyst lead propene formation by dehydration, whereas acetone is formed via the dehydrogenation of propanol-2-ol (Eq.2) in the presence of basic sites or acid-base couples [3,8-17]. CH 3-CHOH-CH 3 → CH 3-CH=CH 2 + H 2 O (1) CH 3-CHOH-CH 3 → CH 3-CO-CH 3 + H 2 (2) In the literature, mainly supported catalysts have been employed for the dehydrogenation of propan-2-ol while various metal oxide catalysts were studied for the catalytic dehydration of propan-2-ol [9-22]. For example, Cu/Al 2 O 3 catalysts were used for the selective dehydrogenation of propan-2-ol to form acetone [10]. Moreover, high selectivity was obtained with Pt/ZrO 2 catalyst at the temperatures lower than 250 °C (T < 250 °C) for acetone formation [11]. Au/CeO 2 catalysts were reported to enhance the selectivity towards acetone by suppressing the dehydration of propan-2-ol [12]. Lately, CuO x PtO x /TiO 2-ZrO 2 catalysts showed high efficiency and selectivity due to their basic properties [13]. Supports are
Journal of Catalysis, 2008
Mono-and bimetallic palladium-gold catalysts supported on zirconia and ceria, both sulfated and nonsulfated, are tested for the direct synthesis of hydrogen peroxide under very mild (1 bar and 20 • C) and non-explosive conditions. Catalysts are characterized by N 2 physisorption, sulfur content analysis, temperature programmed reduction (TPR), Fourier transmission infrared (FTIR) spectroscopy and high resolution transmission electron microscopy (HRTEM). Catalytic tests are carried out with different gas mixtures and after various pretreatments. Best catalytic results are observed using sulfate doped zirconia samples and H 2 /O 2 mixtures containing a large excess of oxygen. Monometallic gold catalysts are completely inactive, while the addition of gold to palladium improves both the productivity and the selectivity of the process. Surface oxidized Pd and Pd-Au catalysts pretreated with hydrogen and oxygen show higher activity and selectivity with respect to non-pretreated samples. A mechanistic explanation is proposed. (G. Strukul).
The direct synthesis of hydrogen peroxide usingbimetallic, gold and palladium, supported catalysts
2013
In this thesis the direct synthesis of hydrogen peroxide (H2O2) from hydrogen and oxygen using gold-palladium supported catalysts was investigated. The direct route represents a greener and sustainable alternative to the current industrial manufacturing process. The main objective of this study was to achieve the industrial requirements of First of all I would like to thank my supervisor Professor Graham Hutchings for his advice, guidance and support during the four years of my PhD.
Direct synthesis of hydrogen peroxide on zirconia-supported catalysts under mild conditions
Journal of Catalysis, 2006
= -, Cl − -, F − -, and Br − -doped zirconia were tested for the direct synthesis of hydrogen peroxide under very mild (1 bar and 20 • C) and nonexplosive conditions. The catalysts were characterized by thermogravimetric/differential scanning calorimetry analysis, N 2 physisorption, and temperature-programmed reduction before and after catalytic tests to investigate the oxidation state of the metal. The catalytic tests were carried out in different solvents, and the effect of the Pd oxidation state was ascertained. The best catalytic results were observed in methanol, using H 2 /O 2 mixtures containing a large excess of oxygen and using the sulfate-doped zirconia catalyst. Surfaceoxidized Pd 0 catalysts showed high catalytic activity and the highest selectivity. (G. Strukul).
Selective oxidation of propylene to propylene oxide using combinatorial methodologies
Catalysis Today, 2003
Direct oxidation of propylene by oxygen to propylene oxide (PO) has been studied through the application of the techniques of combinatorial catalysis. Catalytic materials containing single and binary metal components were prepared by impregnating standard ␥-Al 2 O 3 pellets. In the first stage, 34 single component catalytic materials at three different metal loading levels were prepared and screened for PO activity and selectivity using array channel microreactors and mass spectrometry. Experiments were conducted at a GSHV of 20,000 h −1 , 101 kPa pressure and over a temperature range of 200-350 • C. Following a matrix inversion technique to deconvolute the mass spectrometric intensity measurements, signals that were directly attributable to PO were calculated. From these determinations, the elements Rh, Mn, and Mo were the most PO active single metal catalysts on ␥-Al 2 O 3 . For acetone (AT) Rh, Pb, and Ir were somewhat effective, while Cu, Mn, and W favored some acrolein (AL) formation. In the second step, catalytic materials containing binary combinations of metals were prepared using a variety of strategies. However, the binary catalytic materials that exhibited the highest PO production levels always contained Rh. The binary combinations that exhibited superior PO production levels were Rh-V, Rh-Cr, Rh-Sn, Rh-In, Rh-Mo, and Rh-Sm, albeit substantial CO 2 formation. On the other hand, Rh-Ag, Rh-Zn, and Rh-Cr combinations were significant leads with regard to high PO and low CO 2 production. These findings call for the undertaking of detailed secondary screening studies to confirm the primary screening results reported here and to obtain information on the durabilities of these catalytic materials. (S. Senkan).