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Preparation of polyoxymethylene dimethyl ethers by catalytic conversion of dimethyl ether with formaldehyde formed by oxy- dehydrogenation of dimethyl ether
Preparation of polyoxymethylene dimethyl ethers by catalytic conversion of dimethyl ether with formaldehyde formed by oxy- dehydrogenation of dimethyl ether
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机译：通过二甲醚的氧化脱氢形成的甲醛催化转化二甲醚，制备聚甲醛二甲醚
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摘要
A particularly useful process which includes the steps of providing a source of formaldehyde formed by conversion of dimethyl ether in the presence of a catalyst comprising silver as an essential catalyst component; and contacting the source of formaldehyde and a predominately dimethyl ether feedstream with a heterogeneous, condensation promoting catalyst capable of hydrating dimethyl ether under conditions of reaction sufficient to form an effluent comprising water, methanol, formaldehyde, dimethyl ether, and polyoxymethylene dimethyl ethers is disclosed. Unreacted dimethyl ether is recovered from the effluent and recycled to the formation of polyoxymethylene dimethyl ethers. The resulting dimethyl ether-free liquid mixture is heated in the presence of an acidic catalyst to convert at least the methanol and formaldehyde present to polyoxymethylene dimethyl ethers. Advantageously, methylal and higher polyoxymethylene dimethyl ethers are formed and separated in a catalytic distillation column. By including in the column an anion exchange resin, an essentially acid-free product is obtained which can be used directly as a blending component, or fractionated, as by further distillation, to provide more suitable components for blending into diesel fuel.
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