| 摘要 |
1,193,910. Xylenes. JAPAN GAS-CHEMICAL CO. Inc. 13 Dec., 1968 [15 Dec., 1967], No. 59295/68. Heading C5E. In a process in which m-xylene is extracted from xylene mixtures as a complex with HF and BF 3 and is subsequently isomerized to more useful xylenes, part of the HF and BF 3 required for the extraction is provided in combined form by isomerizing at least part of the m-xylene extract without prior decomposition and recycling undecomposed isomerizate to the extraction, and part of the HF and BF 3 is provided in free form. To achieve the latter, either part of the extract phase is decomposed before isomerization, the resulting HF and BF 3 being utilized, or if all of the extract is isomerized without prior decomposition then part of the isomerizate is decomposed. Preferably the amount of HF and BF 3 recycled as undecomposed isomerizate is 20-70% of the amount withdrawn in the extract. The extraction, isomerization and decomposition steps may all be carried out in the presence of a diluent; suitable ones are specified. Three different arrangements of apparatus are described, in one of which some m-xylene may be recovered as product, but in the others of which m-xylene is continually isomerized and recycled and therefore not recovered as such.
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