Experimental study of the gas-phase hydrofluorination of perchloroethylene over a chromium-based catalyst

Summary Gas-phase hydrofluorination of perchloroethylene to pentafluoroethane in the presence of a chromium-magnesium catalyst at 0.4 MPa and 330-390°C has been studied. А reaction scheme taking into account the formation of by-products is suggested. An erratum to this article is available at .     

A HF Loaded Lewis-Acidic Aluminium Chlorofluoride for Hydrofluorination Reactions

The very strong Lewis acid aluminium chlorofluoride (ACF) was loaded with anhydrous HF. The interaction between the surface of the catalyst and HF was investigated using a variety of characterization methods, which revealed the formation of polyfluorides. Moreover, the reactivity of the HF-loaded ACF towards the hydrofluorination of alkynes was studied.     

Hydrofluorination of Alkenes: A Review

In this minireview, we explore the different approaches used to perform the hydrofluorination reaction of alkenes. Contrary to other hydrohalogenation reactions, the hydrofluorination requires specific conditions due to the lower reactivity of HF. Over the years, many different approaches have been explored among which the use of HF complexes has particularly proved to be useful as these reagents are easier to handle. The enantioselective hydrofluorination has been demonstrated using electrophilic sources of fluorine, while radical fluorination proved compatible with a vast range of functional groups that are generally problematic with strong acids and some fluoride sources. This review will cover the different conditions developed through the years, starting with the first reported addition using gaseous HF, up to the most recent method described in October 2020.     

Isomerization of 1,1,2,3,3-pentafluoro-1,5-hexadiene upon reaction with fluoride ions. First example of sequential anionotropic and prototropic allylic rearrangements

Upon heating in DMF medium with KF and 18-crown-6 1,1,2,2,3-pentafluoro-1,5-hexadiene (1) is converted to 4,5,6,6,6-pentafluoro-1,3-hexadiene and 1,1,1,2,3-pentafluoro-2,4-hexadiene. Reaction of (1) with KHF₂ results in the formation of its HF addition product, namely, 4,4,5,6,6,6-hexafluoro-1-hexene. We assume that the driving force in the isomerization of (1) is the formation of conjugated products, involving both the fluorinated and nonfluorinated portions of the molecules, preferably with the minimum number of fluorine atoms attached to the double bond.Department of Fine Organic Synthesis, Institute of Organic Chemistry, Ural Branch, Russian Academy of Sciences, 620219 Sverdlovsk. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 2, pp. 408–411, February, 1992.     

Nitrogen trifluoride as an oxidative co-reagent in high temperature vapor phase hydrofluorinations

Nitrogen trifluoride (NF₃) has proven to be a useful additive in high temperature vapor phase hydrofluorination reactions of chlorocarbons. The activity of chromium-based catalysts is maintained by introducing a co-stream of NF₃ into the reagent chlorocarbon and HF stream. NF₃ is a desirable additive instead of O₂ as there is no water generation due to its use.     

Gold N-Heterocyclic Carbene Catalysts for the Hydrofluorination of Alkynes Using Hydrofluoric Acid: Reaction Scope,Mechanistic Studies and the Tracking of Elusive Intermediates

An efficient and chemoselective methodology deploying gold-N-heterocyclic carbene (NHC) complexes as catalysts in the hydrofluorination of terminal alkynes using aqueous HF has been developed. Mechanistic studies shed light on an in situ generated catalyst, formed by the reaction of Brønsted basic gold pre-catalysts with HF in water, which exhibits the highest reactivity and chemoselectivity. The catalytic system has a wide alkyl substituted-substrate scope, and stoichiometric as well as catalytic reactions with tailor-designed gold pre-catalysts enable the identification of various gold species involved along the catalytic cycle. Computational studies aid in understanding the chemoselectivity observed through examination of key mechanistic steps for phosphine- and NHC-coordinated gold species bearing the triflate counterion and the elusive key complex bearing a bifluoride counterion.     

PtRe/H-ZSM-5的氢卤化对环己烯转化的影响(英文)

Extended use of supported Pt catalysts causes thermal migration of Pt particles to form large agglomerates,thus decreasing the catalytic activity.The combination of Pt with Re protects Pt against migra...     

铂和 HF 掺杂的 H-ZSM-5 分子筛催化甲苯与甲醇烷基化反应

 Toluene was alkylated with methanol in a flow type reactor at temperatures between 300 and 500 °C using H-ZSM-5 zeolite, 0.2%Pt/H-ZSM-5 and hydrofluorinated 0.2%Pt/H-ZSM-5 with HF concentrations of 1.0%, 2.0%, 3.0%, or 4.0%. Pt primarily enhances toluene conversion, total xylenes production, and p-xylene relative to its thermodynamic equilibrium. As the concentration of HF increases from 1.0% to 3.0%, the catalyst activity increases because of the increase in the number of acid sites and their strength. Additionally, the surface area and Pt dispersion also increases. An advantage of increased HF doping is that the formation of voluminous trimethylbenzene (TMB) byproducts is inhibited. However, at a HF concentration of 4.0%, Al and Si are partially leached and then deposited mostly in the wider catalytic pores. This was determined by evaluating the pore volume distribution and we determined that reactivity inhibition was ob-viously present and was due to diffusion restriction.     

金属/分子筛催化剂的卤化氢处理对环己烯加氢转化的影响Ⅱ. Re/H-ZSM-5催化剂

用HCl或HF对Re/H-ZSM-5催化剂进行了后处理,并在50～400 ℃用连续流动反应器研究了催化剂对环己烯加氢转化反应的影响. 与HCl处理相比, HF处理显著提高了催化剂上环己烯加氢生成环己烷以及甲基环戊烯加氢生成甲基环戊烷的催化活性,这主要是因为HF处理催化剂具有较高的铼分散度、酸中心数及酸强度. Re/H-ZSM-5(HF)催化剂上最高的酸中心强度使其具有最高的加氢裂化活性及最低的环己烯脱氢生成环己二烯活性. 在未处理的Re/H-ZSM -5催化剂上,沉积在分子筛载体孔道和空穴中非骨架Al和Si的量最少,因而对生成芳烃的脱氢反应具有最高活性. 卤化氢处理催化剂上二甲苯异构体的相对产量表明: HF处理催化剂上 ,对二甲苯产量高于间二甲苯;HCl处理催化剂上,间二甲苯和对二甲苯产量基本相?在未处理的催化剂上,间二甲苯量产量比对二甲苯高. 此外,上述所有催化剂上的邻二甲苯产量均约等于对二甲苯与间二甲苯之和.