Patent Description:
Ethylene glycol (EG) is an important basic organic material. It was first made by Wurtz in <NUM> through hydrogenation of ethylene acetate catalyzed by potassium hydroxide. During the World War I, ethylene nitrate was used as substitute of glycerin to produce explosive because it could lower the freezing point of glycerin. Soon afterward, several feasible processes were developed. Hydrogenation of dichloromethane was used in Germany; chlorohydrin was used as raw stuff in America for the rapid growth of application of antifreeze with the development of automobile industry in the <NUM>; ethylene and ethylene oxide was introduced as material which accelerated the process since polyester was developed and this process is widely used around the world mainly in Shell, UCC and Halcon-SD at present. The production capacity of these three companies takes up <NUM>% of the world, followed by Japan catalytic Chemical Company, the Dow Chemical company, Mitsui East Asia Company and ICI Company.

The process of ethylene oxide hydration has several defects, such as longer process, high mole ratio of water and ethylene oxide, large energy consumption and low selectivity of EG. With the exhausting of oil around the world, experts are paying close attention to the processes without oil especially to the ones that using cheap resource as raw stuff. The process using syngas as material is mainly divided into two categories: direct synthesis and indirect synthesis. The promising method mainly contains formaldehyde dimerization, formaldehyde electrochemical hydrogenation dimer method, formaldehyde hydrogen formylation, glycolic acid method, formaldehyde condensation method, oxalate method and etc. The process of oxalate hydrogenation has several advantages such as mild reaction condition and high selectivity which is the most promising process to realize industrialization.

The process includes two key technologies: oxalate synthesis and hydrogenation of oxalate. For the oxalate production technology, the oxalate is generated though a circulate catalytic process composed of coupling and regeneration with the attending of nitrite and CO, produced from coal gasification and the following separation process of pressure swing adsorption (PSA). DMO production process is a cycle system which has a mild reaction condition, good stability, high selectivity and low pollution. For the ethylene glycol production process: the produced oxalate is catalysis hydrogenation to ethylene glycol with hydrogen produced via PSA process. This process is a complex reaction system, mainly including the following reactions:.

ROOCCOOR + <NUM><NUM> → ROOCCH<NUM>OH + ROH.

ROOCCH<NUM>OH + <NUM><NUM>→ HOCH<NUM>CH<NUM>OH + ROH.

HOCH<NUM>CH<NUM>OH + H<NUM>→ C<NUM>H<NUM>OH + H<NUM>O.

The process that on studying mainly use noble mental such as ruthenium as catalyst in liquid phase and copper as catalyst in gaseous phase. Because of the high pressure and the difficulty of the catalyst separation from liquid phase, people are concentration on hydrogenation in gaseous phase on copper catalyst. ARCO Company of America [<CIT>] uses CuCr as catalyst which runs for <NUM> and the conversion of diethyl oxalate reached <NUM>%, selectivity of ethylene glycol excesses <NUM>%. But because of Cr has great harm on human body and environmental impact, research of Cr-free catalyst gradually become the trend of catalyst for hydrogenation of oxalic ester. Ube prepared CuMOkBapOx catalyst using mixed ball milling process in <NUM> and was recorded in the United States Patent [<CIT>]. Conversion of diethyl oxalate was <NUM>% and yield of ethylene glycol reached as high as <NUM>% on this catalyst. Ube reported a Cu/SiO<NUM> catalyst in patent [<CIT>] in <NUM>. With silica sol and copper ammonia solution as precursors and heated in the mixing state after mixing evenly to remove most of the water, resulted in the precipitation of copper and silicon oxide. After washing, drying and calcination, we prepared the catalyst. Conversion of diethyl oxalate was <NUM>% and selectivity of ethylene glycol was <NUM>% on the catalyst under reaction conditions of pressure <NUM> MPa, temperature <NUM>, hydrogen ester ratio <NUM>. American UCC [<CIT>, <CIT>, <CIT>] has done a lot of research n capper-based chromium-free catalysts. They inspected different supporters (Al<NUM>O<NUM>, SiO<NUM>, La<NUM>O<NUM> etc), additives (Ag, Mo, Ba etc.) and preparation methods on the effect of catalytic reactivity and selectivity. Yield of ethylene glycol was up to <NUM>% and time on stream was <NUM> on the catalyst. UCC [<CIT>] regarded the annular catalyst with a central hole as the ideal catalyst for oxalic ester hydrogenation to ethylene glycol. The special structure had better diffusion characteristics which can reduce local overheat. Fudan University reported mesoporous zeolite supported copper catalysts modified with additives such as magnesium, manganese, chromium, or aluminum in patent [<CIT>]. Conversion of oxalic ester reached <NUM>% and selectivity of ethylene glycol achieved <NUM>% on the catalyst under reaction conditions of temperature <NUM>, pressure <NUM> MPa, hydrogen ester ratio <NUM>, space velocity <NUM>-<NUM>. Dan Jin coal reported alumina supported copper catalyst modified with additives such as zinc, manganese, magnesium and chromium in patent [<CIT>]. With reaction pressure <NUM>-<NUM> MPa, temperature <NUM>-<NUM>, mass space velocity of oxalate ester under <NUM>-<NUM>-<NUM>, conversion of oxalic ester was higher than <NUM>% and selectivity of ethylene glycol achieve above <NUM>%. <CIT> discloses a monolithic structure catalyst and a method for producing ethylene glycol using said catalyst.

Researchers have achieved particular progress on catalyst used for hydrogenation of oxalic ester to ethylene glycol, but some problems still exist in further engineering scale up. Larger ratio of height to diameter of the catalyst bed will benefit the uniform distribution and easy control of the bed temperature, since the hydrogenation of oxalic ester to ethylene glycol is a temperature sensitive reaction. However, the increase in the height to diameter ratio will result in the increase of bed resistance. Additionally, the increase in particle size of the catalyst will easily cause local-pot overheat and enhanced side reactions. These factors severely restrict the industrialization process of hydrogenation of oxalic ester to ethylene glycol technology.

An object of the present invention is to provide monolithic structure catalyst for producing ethylene glycol by hydrogenation of dimethyl oxalate. Active components of copper dispersed uniformly in the catalyst coating and the coating with thin layer form is evenly attached to the pore surface of cordierite honeycomb with monolithic structure. It effectively reduces the resistance of internal diffusion and improves the activity and selectivity in the hydrogenation of oxalic ester to ethylene glycol.

An additional object of the invention is to provide a method for preparing a monolithic structure catalyst for producing ethylene glycol by hydrogenation of dimethyl oxalate. The method comprises following steps: first copper based catalyst powder is prepared by precipitation method, from which a catalyst slurry is further acquired, and then coated the catalyst slurry directly on the surface of the cordierite honeycomb support to form the copper supported monolithic structure catalyst. The method ensures high dispersion of active component copper in the catalyst coating and enhances catalytic activity and thermal stability.

Another object of the invention is to provide a method for producing ethylene glycol by hydrogenation of dimethyl oxalate using a monolithic structure catalyst. The monolithic catalyst is used for hydrogenation of oxalic ester to ethylene glycol instead of particle catalyst, as it can reduce the cost by greatly reducing the pressure drop of the catalyst bed and decreasing the depletion of the catalyst, resulting from the abrasion during packing and reaction process. The provided monolithic catalyst has high catalytic activity, low resistance, convenient and quick replacement, which will benefit the realization of large-scale engineering amplification.

The invention provides a monolithic structure catalyst for producing ethylene glycol by hydrogenation of dimethyl oxalate, the catalyst denoted as Cu/SiO<NUM>/cordierite, comprising a carrier, an additive, and an active component, the carrier being cordierite honeycomb of <NUM> cells per square inch (cpsi) and having particle size φ <NUM> × <NUM>, the additive being silicate , the active component being copper, and the copper and silicate being coated on the cordierite to form a coating layer, wherein.

The silicate accounts for <NUM>-<NUM> wt. % of the cordierite , the copper accounts for <NUM>-<NUM> wt. % of the cordierite , and the copper accounts for <NUM>-<NUM> wt. % of the coating layer.

The catalyst is prepared according to the following steps:.

The prepared monolithic catalyst Cu/SiO<NUM>/cordierite is placed in a fix-bed reactor and reduced by <NUM>% H<NUM>/N<NUM> under the following conditions: hydrogen flow rate <NUM>/min, temperature <NUM> for <NUM>; after reduction, the system is filled with pure hydrogen and controlled under the following conditions: temperature <NUM> and pressure <NUM> MPa, <NUM> wt. % DMO in methanol is pumped into the system; the LHSV of DMO is controlled at <NUM>-<NUM> and the molar ratio of H<NUM>/DMO is <NUM>.

This invention further provides a method for preparing a monolithic structure catalyst denoted as Cu/SiO<NUM>/cordierite for producing ethylene glycol by hydrogenation of dimethyl oxalate, the method comprising the steps of:.

This invention provides a method for producing ethylene glycol by hydrogenation of an oxalate using a monolithic structure catalyst, which comprises:
putting the monolithic structured catalyst of type Cu/SiO<NUM>/cordierite into a fixed bed reactor, performing a reduction reaction in the presence of <NUM>% H<NUM>/N<NUM> at <NUM> for <NUM> hours with hydrogen flow rate <NUM>/min, after reduction introducing pure hydrogen into the reactor, maintaining a reaction temperature at <NUM> and a reaction pressure at <NUM> MPa, vaporizing methanol solution comprising <NUM> wt. % DMO in an evaporator, preheating, and introducing <NUM> wt. % DMO into the reactor, the liquid hourly space velocity (LHSV) of DMO being <NUM>. h-<NUM>, and a molar ratio of H<NUM> /ester <NUM>.

Compared with the well known conventional technology, advantages of the invention are summarized below:
The copper based monolithic catalyst in this invention is used in the hydrogenation of dimethyl oxalate to ethylene glycol for the first time, which provides a new approach for the preparation of the catalyst used for the hydrogenation of dimethyl oxalate to ethylene glycol.

Compared with granular catalysts, the monolithic catalyst in this invention shortens the internal diffusion path, improves the gas-solid mass transfer efficiency, and increases the effective contact area between reactant and catalyst. As a result, the catalyst increases the reactivity and selectivity of EG.

In the monolithic catalyst provided by this invention, the active component copper is dispersed uniformly in the coating layer supported on the honeycomb carrier. Thus, the catalyst has higher thermal stability.

The monolithic catalyst in this invention has lower bed resistant than granular catalyst, so it can work at the conditions of larger height-diameter ratio and high hydrogen-ester ratio. As a result, the catalytic performance and temperature distribution are improved, and the hot-spot temperature is decreased effectively.

Compared with granular catalyst, the monolithic catalyst in this invention has high conversion of DMO and selectivity of EG in the hydrogenation of DMO to ethylene glycol, and it doubles the LHSV which presents higher production capacity.

The monolithic catalyst in this invention runs for <NUM> hours stably in the hydrogenation of DMO to ethylene glycol, average conversion of DMO reaches <NUM>% and selectivity of EG is higher than <NUM>%, which presents high hydrogenation activity and stability.

Compared with granular catalysts, the monolithic catalyst in this invention is more convenient to be packed and replaced.

The monolithic catalyst in this invention contains no Cr and other toxic element, which is environmentally friendly.

For further illustrating the invention, experiments detailing a monolithic catalyst, a method for preparing and applying the same are described below. It should be noted that the following examples are intended to describe and not to limit the invention.

<NUM> of Cu(NO<NUM>)<NUM>·<NUM><NUM>O was dissolved in <NUM> water. <NUM> of <NUM> wt. % ammonia aqueous solution was added. Then <NUM> of <NUM> wt. % silica sol was added to the copper ammonia complex solution and aged by stirring for another <NUM> hours. The temperature was raised to <NUM> to allow for the precipitation of copper and silicate. The filtrate was washed with deionized water for <NUM> times, dried at <NUM> for <NUM> hours and calcined at <NUM> for <NUM> hours to form catalyst powder with Cu content of <NUM> wt.

Part of the catalyst powder was squeezed and sieved to <NUM>-<NUM> meshes. <NUM> of squeezed catalyst, <NUM> of catalyst powder, <NUM> of pseudoboehmite and <NUM> of water was added in the ball mill can to ball mill at <NUM> rpm for <NUM> hours to get the catalyst slurry.

Cordierite carrier (Φ15 × <NUM>) of <NUM> cpsi was impregnated in the slurry for <NUM>, then extra slurry on the carrier was blew off and dried at <NUM> for <NUM> hours, the coated cordierite carrier was then weighed. The above operation was repeated until the content of coat reached <NUM> wt. The as prepared catalyst was calcined at <NUM> for <NUM> hours to get the monolithic catalyst denoted as Cu/SiO<NUM>/cordierite.

The monolithic catalyst prepared in Example <NUM> is placed in the fix-bed reactor and reduced by <NUM>% H<NUM>/N<NUM> under the following conditions: hydrogen flow rate <NUM>/min, temperature <NUM> for <NUM>. After reduction, the system is filled with pure hydrogen and controlled under the following conditions: temperature <NUM> and pressure <NUM> MPa. % DMO in methanol is pumped into the system. The LHSV of DMO is controlled at <NUM>-<NUM> and the ratio of H<NUM>/DMO is <NUM>. CDMO and SEG are calculated from timing analysis results of production components with GC. The result is listed in Table <NUM>.

The implementary conditions are the same as Example <NUM> except that that the ratio of H<NUM>/DMO is <NUM>. The result is listed in Table <NUM>.

<NUM> of Cu(NO<NUM>)<NUM> ·<NUM><NUM>O was dissolved in <NUM> water. <NUM> of <NUM> wt. % ammonia aqueous solution was added. Then <NUM> of <NUM> wt. % silica sol was added to the copper ammonia complex solution and aged by stirring for another <NUM> hours. The temperature was raised to <NUM> to allow for the precipitation of copper and silica. The filtrate was washed with deionized water for <NUM> times, dried at <NUM> for <NUM> hours and calcined at <NUM> for <NUM> hours to form catalyst powder with Cu content of <NUM> wt.

The above Cu/SiO<NUM> catalyst powder is extruded to Φ5 × <NUM> particles. <NUM> as prepared catalyst is reduced by <NUM>% H<NUM>/N<NUM> with hydrogen flow rate of <NUM>/min in the fixed bed reactor at <NUM> for <NUM> hours. After reduction, the system is filled with pure hydrogen and controlled under the following conditions: temperature <NUM> and pressure <NUM> MPa. % DMO in methanol is pumped into the system. The LHSV of DMO is controlled at <NUM>-<NUM> and the ratio of H<NUM>/DMO is <NUM>. CDMO and SEG are calculated from timing analysis results of production components with GC. The result is that CDMO is <NUM>% and SEG is <NUM>%.

Claim 1:
A method for preparing a monolithic structure catalyst for producing ethylene glycol by hydrogenation of dimethyl oxalate, comprising the steps of:
a) dissolving <NUM> of the soluble copper precursor Cu (NO<NUM>)<NUM>·<NUM><NUM>O with <NUM> water to yield <NUM> solution A;
b) employing <NUM> wt.% ammonia aqueous solution as the precipitant and mixing with the solution A which is the copper ammonia complex;
c) adding the silicate precursor, <NUM> of <NUM> wt. % silica sol, into the solution A, the copper ammonia complex, stirring for <NUM> hours, heating to <NUM> for precipitating the copper and silicate, stopping heating when a pH of the solution is less than <NUM>, filtering, washing with deionized water for <NUM> times, drying at <NUM> for <NUM> hours, and calcinating a resulting precipitate at <NUM> for <NUM> hours to obtain the catalyst powder B;
d) squeezing, granulating and sieving part of the catalyst powder B to form the granular catalyst C having <NUM>-<NUM> meshes, mechanically mixing another part of catalyst powder B in quantity of <NUM>, <NUM> of the squeezed granular catalyst C, <NUM> of pseudoboehmite, and <NUM> of water to form the catalyst slurry D, mixing time being <NUM> hours, rotating speed is <NUM> rpm;
e) impregnating cordierite honeycomb of <NUM> cpsi, having particle size φ <NUM> × <NUM>, in the catalyst slurry D for <NUM>, blowing off the extra slurry from the carrier and then coating the catalyst slurry D onto the cordierite honeycomb using a dip coating method, drying at <NUM> for <NUM> hours, and calcinating at <NUM> for <NUM> hours to form the monolithic catalyst E denoted as Cu/SiO<NUM>/cordierite.