Halogen chemistry plays a central role in the industrial manufacture of various important chemicals, pharmaceuticals, and polymers. It involves the reaction of halogens or halides with hydrocarbons, leading to intermediate compounds which are readily converted to valuable commodities. These transformations, predominantly mediated by heterogeneous catalysts, have long been successfully applied in the production of polymers. Recent discoveries of abundant conventional and unconventional natural gas reserves have revitalized strong interest in these processes as the most cost-effective gas-to-liquid technologies. This review provides an in-depth analysis of the fundamental understanding and applied relevance of halogen chemistry in polymer industries (polyvinyl chloride, polyurethanes, and polycarbonates) and in the activation of light hydrocarbons. The reactions of particular interest include halogenation and oxyhalogenation of alkanes and alkenes, dehydrogenation of alkanes, conversion of alkyl halides, an...

Halogen-Mediated Conversion of Hydrocarbons to Commodities

CeO2 is a promising catalyst for the HCl oxidation (Deacon process) in order to recover Cl2. Employing shape-controlled CeO2 nanoparticles (cubes, octahedrons, rods) with facets of preferential orientations ((100), (111), (110)), we studied the activity and stability under two reaction conditions (harsh: Ar:HCl:O2 = 6:2:2 and mild: Ar:HCl:O2 = 7:1:2). It turns out that both activity and stability are structure-sensitive. In terms of space time yield (STY), the rods are the most active particles, followed by the cubes and finally the octahedrons. This very same trend is reconciled with the complete oxygen storage capacity (OSCc), indicating a correlation between the observed activity STY and the OSCc. The apparent activation energies are about 50 kJ/mol for cubes and rods, while the octahedrons reveal an apparent activation energy of 65 kJ/mol. The reaction order in O2 is positive (0.26–0.32). Under mild reaction conditions, all three morphologies are stable, consistent with corresponding studies of CeO2 p...

Shape-Controlled CeO2 Nanoparticles: Stability and Activity in the Catalyzed HCl Oxidation Reaction

Mixed Ce1-xZrxO2 nano-rod particles with varying Zr doping levels of up to 20% were exposed to Deacon reaction mixtures with high HCl concentration at a reaction temperature of 430 °C. The mixed Ce1-xZrxO2 nano-rod samples were characterized before and after Deacon reaction by x-ray diffraction (XRD), transmission electron microscopy (TEM), and x-ray photoelectron spectroscopy (XPS). Pure CeO2 nano-rods are shown to suffer from bulk-chlorination of the catalyst (CeCl3x6H2O) for reaction mixtures HCl:O2 > 2 that is accompanied by dramatic activity losses. For a reaction mixture of HCl:O2 = 2.5:1, already 5% Zr doping suffices to stabilize the structure Ce1-xZrxO2 nano-rods against bulk chlorination. Although ZrCl4 is volatile above 330 °C, we do not encounter discharge of Zr from the fixed bed flow reactor as long as severe bulk chlorination of the Ce1-xZrxO2 catalysts in the form of CeCl3 is not observed in XRD. With a simple quasi steady-state model we can corroborate the stabilizing effect of Zr assuming that ZrCl4 evaporation is limited by diffusion of Zr4+ in the ceria-zirconia subsurface. As qunatified with XPS the chlorine concentration of stable and active Ce1-xZrxO2 nano-rods with 5% Zr is too high to be solely ascribed to on-surface chlorine. The incorporation of Cl into the surface-near region is further supported by XPS experiments performed after oxygen plasma treatment. For even more harsh reaction conditions HCl:O2 = 3:1 none of the Ce1-xZrxO2 nano-rods was stable at 430 °C. However, an increase of the reaction temperature to 500 °C enables even pure CeO2 nano-rods to be stable under such harsh reaction conditions.

Catalytic HCl oxidation reaction: Stabilizing effect of Zr-doping on CeO2 nano-rods

The stabilizing effect of water and high reaction temperatures on the CeO2-catalyst in the harsh HCl oxidation reaction

Catalytic oxidation of hydrogen chloride to chlorine over Cu-K-Sm/γ-Al2O3 catalyst with excellent catalytic performance

An efficient Cu-K-La/γ-Al2O3 catalyst, prepared by the incipient wetness impregnation method, was developed for the catalytic oxidation of HCl to chlorine, in which effects of catalyst composition, calcination temperature, reaction temperature and GHSV of the feed gas and the catalyst stability were investigated. Cu-K-La/γ-Al2O3 catalyst shows good catalytic performance and stability with the conversion of HCl of about 78% for reaction for over 9600 h under the reaction conditions of 30 g catalyst, 0.1 MPa, 340 °C, GHSV of 450 L/(kgcat h), HCl/O2 = 2:1. Thermogravimetry results indicate that the synergistic promoters of KCl and LaCl3 can significantly reduce the reaction temperature for oxidation of CuCl2 to produce chlorine, which is a key step in the catalytic oxidation of HCl. XRD results show that there were only broad characteristic diffraction peaks of γ-Al2O3 support and copper species, potassium species and lanthanum species were highly dispersed on the surface of γ-Al2O3 support over Cu-K-La/γ-Al2O3 catalyst.

An efficient Cu-K-La/γ-Al2O3 catalyst for catalytic oxidation of hydrogen chloride to chlorine

Effect of KCl on the performance of Cu-K-La/γ-Al2O3 catalyst for HCl oxidation

The invention discloses a catalyst used for the catalytic oxidation of hydrogen chloride for preparing chlorine gas and a preparation method thereof. The catalyst comprises the following components in percentage by weight: 1 to 30 percent of CuCl2, 1 to 15 percent of KCl, 1 to 25 percent of rare earth chloride and 55 to 95 percent of carrier and is prepared by adopting an immersion method. The catalyst of the invention does not contain a toxic component Cr, belongs to an environmental-friendly low-cost catalyst and has the advantages of simple and practical preparation method, high catalyst activity, high stability and long service life.

Catalyst used for catalytic oxidation of hydrogen chloride for preparing chlorine gas and preparation method thereof

The invention provides a copper oxide catalyst for preparing chlorine gas from chlorine hydride by catalytic oxidation, and a preparation method and application thereof. The catalyst is prepared from the following components in percentage by weight: 1-20% of CuO, 1-15% of K2O and 65-98% of support, wherein the support is rare-earth oxide modified activated alumina. The invention belongs to an environment-friendly low-cost catalyst; and the rare-earth oxide modified activated alumina is used as the support to enhance the activity and stability of the catalyst and prolong the service life of the catalyst. An isometric impregnation method is utilized to directly support copper and potassium chloride onto the rare-earth oxide modified activated alumina support, and roasting is carried out in an air atmosphere to obtain the supported copper oxide catalyst. The preparation method is simple and easy to implement, and has the advantages of high catalyst activity and high stability.

Kanka Feng

Papers

An efficient Cu-K-La/γ-Al2O3 catalyst for catalytic oxidation of hydrogen chloride to chlorine

Effect of KCl on the performance of Cu-K-La/γ-Al2O3 catalyst for HCl oxidation

Catalyst used for catalytic oxidation of hydrogen chloride for preparing chlorine gas and preparation method thereof

Copper oxide catalyst for preparing chlorine gas from chlorine hydride by catalytic oxidation, and preparation method and application thereof