Preparation method of polyvinyl alcohol/attapulgite-polyionic liquid catalyzed esterification composite membrane

Abstract

The invention discloses a preparation method for a polyvinyl alcohol / attapulgite-polyion liquid catalytic esterification composite membrane. The preparation method comprises the following steps: adding an attapulgite clay / polyion liquid composite catalyst (ATP-PILs) immobilized with a high-density acidic site into a polyvinyl alcohol (PVA) solution for alloying to form a membrane casting solution, and stewing for defoaming; then coating a smooth and clean glass plate or a microhole basement membrane with the defoamed membrane casting solution; then performing drying, heating and crosslinking after-treatment to form a per-vaporized compact catalytic esterification membrane with a catalysis function. The PVA dense membrane is filled with attapulgite immobilized with the high-density acidic site, so that the mechanical strength and the thermal and chemical stability of the membrane are improved; furthermore, the surface of the catalysis membrane has the high-density acidic catalysis site, and an efficient integrated membrane reaction-separator is constructed; in the catalytic esterification reaction of oleic acid and methyl alcohol, the oleic acid methyl alcohol conversion rate is up to about 90 percent; after the polyvinyl alcohol / attapulgite-polyion liquid catalytic esterification composite membrane is repeatedly used for 4 times, the oleic acid methyl alcohol conversion rate is reduced by about 5 percent or less.

Description

technical field [0001] The invention belongs to the technical field of membrane materials, and in particular relates to a preparation method of a hybrid membrane used for catalytic esterification-pervaporation separation "integrated coupled" membrane reactor. Background technique [0002] Biodiesel is a long-chain fatty acid methyl ester produced by transesterification of animal and vegetable oils and methanol. It is a high-quality substitute for petroleum diesel. At present, its main industrial preparation method is the transesterification process, and most of the catalysts use strong acid and strong alkali. There are problems such as serious equipment corrosion, complicated subsequent separation procedures, and large amounts of industrial wastewater and waste residues. [0003] In recent years, the "integrated coupled" membrane reactor for catalytic esterification-pervaporation separation is considered to be a potential breakthrough technology in the field of biodiesel, an...

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Problems solved by technology

The existing problems are: (1) cross-linking or heat treatment will make the film brittle and reduce the hydrophilicity. In the production of biodiesel, the increase of the cross-linking degree will reduce the swelling of the film to oil and methanol, and the oil and methanol will The diffusion rate to the surface and inside of the catalytic membrane will be reduced, resulting in a decrease in the yield of biodiesel; (2) the single polymer matrix membrane lacks chemical and thermal stability, and is easily damaged in long-term operation in an alcohol environment; (3) esterification The functional groups on the reaction graft are easily corroded and detached by alcohol during the reaction process

Traditional carrier and immobilization methods have solved the problem of ionic liquid recovery to a certain extent. However, heterogeneous reactions (three phases of triglyceride, alcohol and solid catalyst) make the catalytic efficiency of ionic liquids low (problem 4), And it is easily corroded and peeled off by alcohol during application (consistent with the above problem (3))

For example, Liang et al [Green Chemistry, 2010, 12: 201-204.] synthesized a 3 The acidic ionic liquid of H group, because it contains multiple functional groups, this ionic liquid shows extremely high acidity and polarity, and the highest yield of biodiesel reaches 98.3%. When the water increases from 0.3% to 2.0%, its The yield only dropped from 98.3% to 95.3%, showing good water resistance, and biodiesel products meet the EN14214 standard. Unfortunately, this ionic liquid has no functional groups for chemical bonding and immobilization, and the synthesis cost is high

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