Method for continuous production of polyformaldehyde dimethyl ether

Abstract

The invention provides a method for continuous production of polyformaldehyde dimethyl ether. The method is characterized by comprising the following steps: a) feeding dimethoxymethane and hot-melted paraformaldehyde into a fixed bed reactor and adopting an acidic resin catalyst, so as to prepare polyformaldehyde dimethyl ether (DMM3-8), wherein the reaction temperature is 120-180 DEG C and the pressure is 0.1-10 MPa; b) cooling the reaction product, and then performing adsorptive separation through a dehydrating tower, so as to obtain polyformaldehyde dimethyl ether of which most water, cytidine glycol and hemiacetal are desorbed; c) feeding the polyformaldehyde dimethyl ether subjected to desorption into a distillation tower for separation, wherein most of a low-boiling component (dimethoxymethane (DMM)), poly-di-formaldehyde dimethyl ether (DMM2), a by-product (methanol) and triformol are extracted first, and then the materials in a tower kettle are fed into a rectifying tower in the next step, so as to extract the rest of the DMM2 and the triformol; and d) returning the low-boiling component (dimethoxymethane (DMM)), the methanol, the DMM2 and the triformol, which are evaporated out by the distillation tower and the rectifying tower in the last step, into the fixed bed reactor to continue to react to prepare polyformaldehyde dimethyl ether.

Description

technical field [0001] The invention relates to the technical field of petroleum refining oil additives, in particular to a method for continuously producing polyoxymethylene dimethyl ether, which uses paraformaldehyde and methylal as raw materials and uses acidic resin as a catalyst to continuously produce polyoxymethylene dimethyl ether through a fixed bed. Formaldehyde dimethyl ether and separate to obtain DMM 3-8 Methods. Background technique [0002] Polyoxymethylene dimethyl ether (DMM 3-8 ) is a homologue constituted by the general formula: [0003] CH 3 O(CH 2 O) n CH 3 [0004] where n is a positive integer. Chemically, they are related to methylal (CH 3 OCH 2 OCH 3 ) similar acetals, i.e. the parent of n=1 in the molecular formula. Polyoxymethylene dimethyl ether has high oxygen content (42% ~ 49%) and high cetane number (DMM 3-8 The cetane number is above 78), and it has good miscibility with diesel oil, so it is considered as an excellent diesel ble...

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Problems solved by technology

[0013] The technical problem to be solved in the present invention is to overcome the problems in previous reports that the process of preparing polyoxymethylene dimethyl ether is complicated, the liquid acid catalyst used corrodes equipment, pollutes the environment, the separation is complicated, the production cost is high, or the stability and activity cannot be balanced. Considering the economy, replace the expensive paraformaldehyde used in some patents with cheaper paraformaldehyde, replace the conventional tank reactor with a fixed bed reactor, and at the same time, replace methanol with methylal to provide methoxy part, reduce the proportion of water in the product, simplify the subsequent separation process, and provide a method for continuously producing polyoxymethylene dimethyl ether by acidic resin catalyzed methylal and paraformaldehyde through a fixed-bed reactor

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