Methods for making a supported chromium catalyst are disclosed, and can comprise contacting a silica-coated alumina containing at least 30 wt. % silica with a chromium-containing compound in a liquid, drying, and calcining in an oxidizing atmosphere at a peak temperature of at least 650 C. to form the supported chromium catalyst. The supported chromium catalyst can contain from 0.01 to 20 wt. % chromium, and typically can have a pore volume from 0.5 to 2 mL/g and a BET surface area from 275 to 550 m.sup.2/g. The supported chromium catalyst subsequently can be used to polymerize olefins to produce, for example, ethylene-based homopolymers and copolymers having high molecular weights and broad molecular weight distributions.

A dehydrochlorination process is disclosed. The process involves contacting R.sub.fCHClCH.sub.2Cl with a chromium oxyfluoride catalyst in a reaction zone to produce a product mixture comprising R.sub.fCClCH.sub.2, wherein R.sub.f is a perfluorinated alkyl group.

A dehydrochlorination process is disclosed. The process involves contacting R.sub.fCHClCH.sub.2Cl with a chromium oxyfluoride catalyst in a reaction zone to produce a product mixture comprising R.sub.fCClCH.sub.2, wherein R.sub.f is a perfluorinated alkyl group.

A method for producing a tetrafluoroolefin, such as 2,3,3,3-tetrafluoropropene (HFO-1234yf), comprises dehydrofluorinating a pentafluoroalkane in a gas phase in the presence of a catalyst comprising chromium oxyfluoride. In a preferred embodiment, 2,3,3,3-tetrafluoropropene (HFO-1234yf) is produced by forming a catalyst comprising chromium oxyfluoride by calcining CrF.sub.3.xH.sub.2O, where x is 1-10, in the presence of a flowing gas comprising nitrogen to form a calcined chromium oxyfluoride, and dehydrofluorinating 1,1,1,2,2-pentafluoropropane (HFC-245cb) in a gas phase in the presence of the catalyst to form the 2,3,3,3-tetrafluoropropene (HFO-1234yf).

A method for producing a tetrafluoroolefin, such as 2,3,3,3-tetrafluoropropene (HFO-1234yf), comprises dehydrofluorinating a pentafluoroalkane in a gas phase in the presence of a catalyst comprising chromium oxyfluoride. In a preferred embodiment, 2,3,3,3-tetrafluoropropene (HFO-1234yf) is produced by forming a catalyst comprising chromium oxyfluoride by calcining CrF.sub.3.xH.sub.2O, where x is 1-10, in the presence of a flowing gas comprising nitrogen to form a calcined chromium oxyfluoride, and dehydrofluorinating 1,1,1,2,2-pentafluoropropane (HFC-245cb) in a gas phase in the presence of the catalyst to form the 2,3,3,3-tetrafluoropropene (HFO-1234yf).

Methods for preparing a fluorided chromium catalyst can include a step of calcining a supported chromium catalyst at a peak calcining temperature to produce a calcined supported chromium catalyst, followed by contacting the calcined supported chromium catalyst at a peak fluoriding temperature with a vapor comprising a fluorine-containing compound to produce the fluorided chromium catalyst. The peak fluoriding temperature can be at least 50 C. less, and often from 200 C. to 500 C. less, than the peak calcining temperature. Polymers produced using the fluorided chromium catalyst can have a beneficial combination of higher melt index, narrower molecular weight distribution, and lower long chain branch content.

A process for preparing a catalyst, including the reactive milling of a first reagent, which is a chromium oxide compound, with a second reagent, which is a compound of the formula M.sub.zM.sub.1-zO.sub.xF.sub.y, M and M each being an element having an oxidation state greater than or equal to 0, z being from 0 to 1, x being from 0 to 3, y being from 0 to 6, and 2x+y being greater than 0 and less than or equal to 6.

A process for preparing a catalyst, including the reactive milling of a first reagent, which is a chromium oxide compound, with a second reagent, which is a compound of the formula M.sub.zM.sub.1-zO.sub.xF.sub.y, M and M each being an element having an oxidation state greater than or equal to 0, z being from 0 to 1, x being from 0 to 3, y being from 0 to 6, and 2x+y being greater than 0 and less than or equal to 6.

There are provided methods and systems for an electrochemical cell including an anode and a cathode where the anode is contacted with a metal ion that converts the metal ion from a lower oxidation state to a higher oxidation state. The metal ion in the higher oxidation state is reacted with hydrogen gas, an unsaturated hydrocarbon, and/or a saturated hydrocarbon to form products.

A dehydrochlorination process is disclosed. The process involves contacting R.sub.fCHClCH.sub.2Cl with a chromium oxyfluoride catalyst in a reaction zone to produce a product mixture comprising R.sub.fCClCH.sub.2, wherein R.sub.f is a perfluorinated alkyl group.