CN101444747A - Catalyst for preparing dimethyl ether by dehydration of methanol and preparation method thereof - Google Patents

Abstract

The invention discloses a catalyst for preparing dimethyl ether by dehydration of methanol and a preparation method thereof. The catalyst consists of 30-80% (weight at butt) of molecular sieve and 70-20% (weight at butt) of caking agent, wherein, the molecular sieve is nano-ZSM-23 molecular sieve, and the caking agent is at least one of silicon dioxide and aluminium phosphate. The preparation method comprises the steps: the nano-ZSM-23 molecular sieve, the caking agent and the water are mixed and kneaded for molding, and then the catalyst is prepared by drying and calcination. The catalyst has the advantages of high activity and selectivity, good stability, wide reaction temperature range, short production flow and low cost; and the catalyst is also beneficial to industrial production and application.

Description

A kind of Catalysts and its preparation method of methanol dehydration dimethyl ether-preparing

Technical field

The present invention relates to inorganic chemical synthesis technical field, particularly a kind of Catalysts and its preparation method of methanol dehydration dimethyl ether-preparing.

Background technology

Dimethyl ether (DME) is class ethers chemical products, is a kind of colourless, nontoxic, eco-friendly gas at normal temperatures and pressures, is widely used in industrial circles such as refrigeration, pharmacy, dyestuff and agricultural chemicals.Dimethyl ether self contains oxygen simultaneously, and carbochain is short, and combustibility is good, thermal efficiency height, and discharging is lower than methyl alcohol and is only second to hydrogen, and the fuel of liquefied petroleum gas (LPG) and diesel oil has a high potential as an alternative, is called as " the super clean energy resource " of 21 century.

Under the solid acid catalysis effect, be the common method of producing the dimethyl ether technology at present by methanol dehydration dimethyl ether-preparing.The catalyst of methanol dehydration mainly is γ-Al ₂O ₃, alumino-silicate, solid acid and ZSM-5 molecular sieve etc.Molecular sieve is the catalyst activity component of potential, the excellent performance in the methanol dehydration dimethyl ether-preparing course of reaction owing to have pore passage structure and adjustable acid activity center of rule.

CN1895776 discloses a kind of methyl alcohol is produced dimethyl ether through dehydration under liquid phase or gas-liquid mixed state catalyst, catalyst consists of the bonding agent of the molecular sieve and 5～50% (butt weight) of 50～95% (butt weight) and forms, it is characterized in that said molecular sieve is one or more the mixture among ZSM-5, Y, modenite, Beta zeolite, MCM-22, MCM-41, MCM-56, MCM-59, SAPO-5, the SAPO-34; Because the crystal grain of MCM-22, MCM-56, MCM-59 equimolecular sieve has special lamella shape structure, be beneficial to the diffusion of material, thereby show high activity and selectivity simultaneously.CN20071019949.2 discloses a kind of method of producing dimethyl ether, and its catalyst characteristics is that with the minimum intermediate value acidity that molecular sieve has be the SAPO-34 molecular sieve that is 0.5～1mmol for every gram dry sieve.CN200610169510.7 discloses a kind of catalyst of methanol dehydration dimethyl ether-preparing, it is characterized in that containing in the catalyst at least a non-zeolitic molecular sieves and at least a zeolite-type molecular sieves, wherein non-zeolitic molecular sieves is selected from a kind of silicoaluminophosphamolecular molecular sieves, and zeolite-type molecular sieves is selected from one or more in FAU structural zeolite, Beta structural zeolite, modenite, ZSM-5, ZSM-11, ZSM-22, ZSM-23, ZSM-35, ZSM-48, ZSM-57 and the modifier thereof.

From prior art as can be known, it with the molecular sieve effect that the catalyst of the methanol dehydration dimethyl ether-preparing of active component is not emphasized the molecular sieve pore passage structure, as have FAU structural zeolite, Beta zeolite of three-dimensional macroporous structure etc., have the ZSM-5 of three-dimensional central hole structure and have the SAPO-34 etc. of three-dimensional small structure, want high selectivity to generate technology that dimethyl ether generally takes for acidic zeolite is regulated, or the combination of different molecular sieve, or molecular sieve carried out modification.

Summary of the invention

Analyze from the methanol dehydration dimethyl ether-preparing course of reaction, its main accessory substance is a hydrocarbons.From producing the mechanism of accessory substance hydrocarbons, it follows " hydrocarbon pond " mechanism, promptly enough big as the duct of catalyst activity component molecular sieve, the space that can provide bigger cyclic intermediate molecule (as toluene) " hydrocarbon pond " to form, then the hydro carbons accessory substance just produces, thereby the selectivity of dimethyl ether is lower.The ZSM-23 molecular sieve is a kind of mesopore, high-silica zeolite, has the MTT topological structure.Comprise five-membered ring, hexatomic ring and ten-ring in the skeleton structure of this molecular sieve simultaneously, do not have to intersect the duct, the parallel duct of forming by ten-ring of one dimension only, free diameter is

, slightly littler than the duct size of ZSM-5 molecular sieve, less than the enough spaces, duct that form " hydrocarbon pond " intermediate; Nanometer ZSM-23 zeolite crystal is little simultaneously, is beneficial to the transmission of material, is not easy to cause catalysqt deactivation.Discovering, is the catalyst of active component with nanometer ZSM-23 molecular sieve, in the methanol dehydration dimethyl ether-preparing process, have active high, selectivity is good and the characteristics of good stability.

The catalyst that the purpose of this invention is to provide a kind of methanol dehydration dimethyl ether-preparing, catalyst consists of the binding agent of the molecular sieve and 70～20% (butt weight) of 30～80% (butt weight) and forms, said molecular sieve is a nanometer ZSM-23 molecular sieve, and said binding agent is at least a in silica and the aluminum phosphate.

Another object of the present invention provides this Preparation of catalysts method, and with nanometer ZSM-23 molecular sieve, binding agent and water kneading and compacting, step such as drying, roasting makes the said catalyst of the present invention then, and its preparation process comprises:

(1) preparation of nanometer HZSM-23 molecular sieve: with SiO ₂/ Al ₂O ₃Mol ratio is that 60～120 nanometer NaZSM-23 molecular sieve is made nanometer ammonium type ZSM-23 molecular sieve at 75～85 ℃ with the ammonium salt aqueous solution exchange, wherein the butt weight ratio of ammonium salt and nanometer NaZSM-23 molecular sieve is 1～2: 1, then through washing, drying, under air atmosphere,, make nanometer HZSM-23 molecular sieve in 450～550 ℃ of roastings 2～7 hours;

(2) nanometer HZSM-23 molecular sieve, binding agent and the water that step (1) is made mixes and pinches, extruded moulding is 1.5～2.0 millimeters a strip catalyst, wherein the butt weight ratio of nanometer HZSM-23 molecular sieve and binding agent is 30～80%: 70～20%, the addition of water is pinched mixing, extrusion is as the criterion, and said binding agent is at least a in silica and the aluminum phosphate;

(3) strip catalyst that step (1) is made, through 100～120 ℃ of dryings, under air atmosphere in 450～550 ℃ of roastings 2～7 hours, make catalyst of the present invention.

Ammonium salt can be NH among the present invention ₄NO ₃, NH ₄Cl or (NH ₄) ₂SO ₄, no specific (special) requirements.

Compared with prior art, the present invention has following remarkable advantage:

(1) catalyst activity height, the selectivity height, good stability, range of reaction temperature is wide.

(2) the Catalyst Production flow process is short, and cost is low, is beneficial to suitability for industrialized production and application.

The specific embodiment

All embodiment all operate by the operating procedure of technique scheme.

Embodiment 1

According to document (CN101214971A) synthesis of nano NaZSM-23 molecular sieve.

In the first step, the SiO of nanometer NaZSM-23 molecular sieve ₂/ Al ₂O ₃Mol ratio is 60; In second step, the butt weight ratio of nanometer HZSM-23 molecular sieve and binding agent is 70%: 30%, and binding agent is a silica; In the 3rd step,, make catalyst prod in 550 ℃ of roastings 5 hours.

Embodiment 2

Implementation process except for the following differences, all the other are all with embodiment 1:

In second step, the butt weight ratio of nanometer HZSM-23 molecular sieve and binding agent is 80%: 20%, makes catalyst prod.

Embodiment 3

Implementation process except for the following differences, all the other are all with embodiment 1:

In second step, the butt weight ratio of nanometer HZSM-23 molecular sieve and binding agent is 50%: 50%, makes catalyst prod.

Embodiment 4

Implementation process except for the following differences, all the other are all with embodiment 1:

In second step, the butt weight ratio of nanometer HZSM-23 molecular sieve and binding agent is 30%: 70%, makes catalyst prod.

Embodiment 5

Implementation process except for the following differences, all the other are all with embodiment 1:

In the first step, the SiO of nanometer NaZSM-23 molecular sieve ₂/ Al ₂O ₃Mol ratio is 90, makes catalyst prod.

Embodiment 6

Implementation process except for the following differences, all the other are all with embodiment 1:

In the first step, the SiO of nanometer NaZSM-23 molecular sieve ₂/ Al ₂O ₃Mol ratio is 120, makes catalyst prod.

Embodiment 7

Implementation process except for the following differences, all the other are all with embodiment 1:

In the first step, the SiO of nanometer NaZSM-23 molecular sieve ₂/ Al ₂O ₃Mol ratio is that the butt weight ratio of nanometer HZSM-23 molecular sieve and binding agent is 80%: 20% in 120, the second steps, and binding agent is an aluminum phosphate; In the 3rd step,, make catalyst prod in 500 ℃ of roastings 7 hours.

Embodiment 8

Implementation process except for the following differences, all the other are all with embodiment 1:

In second step, the butt weight ratio of nanometer HZSM-23 molecular sieve and binding agent is 80%: 20%, and binding agent is the mixture of silica and aluminum phosphate, and the butt weight ratio of silica and aluminum phosphate is 50%: 50%; In the 3rd step,, make catalyst prod in 500 ℃ of roastings 5 hours.

Embodiment 9

On the little inverse spectral apparatus of high pressure, carry out the catalytic performance test of the catalyst that the present invention makes.(form by Φ 6mm * 450mm)-temperature control system-on-line chromatograph analytical system by the stainless steel fixed bed reactors for this device.The reaction evaluating condition is: the loadings 0.5g of catalyst, and 250～400 ℃ of reaction temperatures, normal pressure, absolute methanol is made raw material, and the weight (hourly) space velocity (WHSV) of methyl alcohol is 5h ^-1, N ₂As carrier gas, flow rate of carrier gas 100ml/min.It is as shown in the table for result behind the stable reaction 50h.

Catalyst	Reaction temperature	Methanol conversion	The dimethyl ether selectivity
				Embodiment 1	250℃	87.5％	98.6％
Embodiment 2	250℃	90.8％	99.0％
				Embodiment 3	250℃	83.7％	97.8％
Embodiment 4	250℃	79.5％	97.5％
				Embodiment 5	250℃	85.6％	98.5％
Embodiment 6	250℃	84.5％	98.5％
				Embodiment 7	250℃	84.9％	98.1％
Embodiment 8	250℃	91.2％	98.8％
				Embodiment 2	300℃	91.8％	98.8％
Embodiment 2	400℃	92.5％	98.5％

From the table evaluation result as can be known, catalyst of the present invention has the wide advantage of high selectivity, high activity, high stability and reaction temperature.

Claims (2)

1, a kind of catalyst of methanol dehydration dimethyl ether-preparing, it is characterized in that this catalyst is made up of the molecular sieve of butt weight 30～80% and the binding agent of butt weight 70～20%, described molecular sieve is a nanometer ZSM-23 molecular sieve, and described binding agent is at least a in silica and the aluminum phosphate.

2, the described Preparation of catalysts method of a kind of claim 1, this method is that drying, calcination steps make described catalyst then with nanometer ZSM-23 molecular sieve, binding agent and water kneading and compacting, its concrete steps comprise:

(1) preparation of nanometer HZSM-23 molecular sieve: with SiO ₂/ Al ₂O ₃Mol ratio is that 60～120 nanometer NaZSM-23 molecular sieve is made nanometer ammonium type ZSM-23 molecular sieve at 75～85 ℃ with the ammonium salt aqueous solution exchange, wherein the butt weight ratio of ammonium salt and nanometer NaZSM-23 molecular sieve is 1～2: 1, then through washing, drying, under air atmosphere,, make nanometer HZSM-23 molecular sieve in 450～550 ℃ of roastings 2～7 hours;

(2) nanometer HZSM-23 molecular sieve, binding agent and the water that step (1) is made mixes and pinches, extruded moulding is 1.5～2.0 millimeters a strip catalyst, wherein the butt weight ratio of nanometer HZSM-23 molecular sieve and binding agent is 30～80%: 70～20%, the addition of water is pinched mixing, extrusion is as the criterion, and said binding agent is at least a in silica and the aluminum phosphate;

(3) strip catalyst that step (2) is made, through 100～120 ℃ of dryings, under air atmosphere in 450～550 ℃ of roastings 2～7 hours, make described catalyst.