Process for the oligomerization of acetylene in the presence of hydrogen and a solid catalyst

Abstract

The present invention refers to a process for oligomerization of acetylene in the presence of hydrogen and a solid catalyst.

Claims

1. A process for oligomerizing acetylene in the presence of a catalyst, said process comprising oligomerizing acetylene by reacting a gas phase comprising acetylene, hydrogen and an inert gas in a gas phase reactor in the presence of the catalyst at an elevated temperature of 20 C. to 700 C. and at a reaction pressure of up to 35 bar, wherein the catalyst is a copper containing support selected from the group consisting of molecular sieves, amorphous aluminosilicates, zeolites, clays, metal oxides, metal phosphates, and cation exchange materials.

2. The process according to claim 1, wherein the copper containing support is selected from the group consisting of cation exchange materials with a content of 0.01 to 20 wt. % Cu in the cation exchange material.

3. The process according to claim 1, wherein the cation exchange material is a molecular sieve.

4. The process according to claim 3, wherein the molecular sieve is an alumo silicate.

5. The process according to claim 1, wherein the cation exchange material is an alumo silicate with an SiO.sub.2/Al.sub.2O.sub.3 ratio between 2 and 1000.

6. The process according to claim 1, wherein the gas phase comprises the inert gas and hydrogen in a ratio of between 0.1% and 99.9 vol.-% H.sub.2 in the inert gas, a partial pressure of acetylene is between 0.01 and 10 bar in the gas phase, and a molar ratio of acetylene flow per minute to an amount of copper (I) and/or copper (II) in the catalyst is between 0.01 and 100.

7. The process according to claim 1, wherein the catalyst is in an activated form and the catalyst has been activated at conditions of lower reaction pressure, and of lower amounts of reacting compounds and of the catalyst, compared to reaction conditions after activation.

8. The process according to claim 7, wherein the reacting acetylene and hydrogen is continuous and the process additionally comprises activating the catalyst in the gas phase reactor before the reacting acetylene and hydrogen is started.

9. The process according to claim 1, wherein the catalyst is a copper containing support selected from the group consisting of amorphous aluminosilicates, zeolites, and clays.

10. The process according to claim 9, wherein the catalyst has been cation-exchanged with Cu.sup.2+.

Description

GENERAL PROCEDURE FOR THE CATALYST PREPARATION MATERIAL PREPARATION

(1) For the catalyst used in the process of the present invention, cation exchange materials such as amorphous alumino silicates, zeolites, clays etc. may be used, preferably molecular-sieve type cation exchange materials such as zeolites (faujasite, mordenite, ZSM-5, zeolite , SAPO-34 etc.). Of particular preference are alumino silicates with a SiO.sub.2/Al.sub.2O.sub.3 ratio between 2 and 1000, preferably the SiO.sub.2/Al.sub.2O.sub.3 ratio is between 4 and 100. Between 0.01 and 5 weight % of said ion exchange material C-M, where C is the cation initially compensating the charges on the framework of the ion exchange material M, as for C exemplified by Na.sup.+, NH.sub.4.sup.+, Cs.sup.+, K.sup.+, Rb.sup.+, H.sup.+, Ca.sup.2+ etc. may be used for preparing the Cu ion loaded material by dispersing the material C-M in a solution containing Cu.sup.2+ with a preferred concentration between 0.05 and 350 g/L Cu.sup.2+. Stirring is generally carried out at temperature between 20-120 C. for a minimum of 0.5 hours, the Cu-M material is filtered and washed with 0.1 to 10 L water per gram of C-M used at the start.

(2) The ion exchange of the C-M material with Cu does not have to be complete, the metal C can still be present in the final material, compensating from 0.01 to 99.9% of the ion exchange capacity, and the procedure can be repeated multiple times to increase copper loading. Finally, the Cu.sup.2+ loaded material is dried at below <100 C. for sufficient time, generally from 5-60 hours, in static air in order to have a smooth drying process.

(3) Alternatively procedures like the one reported in US20150110711 where the copper is encapsulated into the molecular sieve during the synthesis can also be applied.

(4) Preferably, the dried material is used for preparing the final catalyst body to best satisfy heat/mass transfer, taking also the reactor shape into consideration.

Material Activation

(5) The Cu-M loaded material prepared as described above is placed inside a tubular reactor with adjustable flow and composition of a gaseous mixture through the tube. The activation conditions have to be adapted to the specific material and reactor conditions and may be as follows: Temperature between 20 and 700 C. (most preferably 180-300 C.) Pressure >0 to 35 bar Gas phase an inert gas such as N.sub.2+H.sub.2 between 0.1% and 99.9% H.sub.2 in N.sub.2 Controlled flow with a partial pressure of acetylene between 0.01 and 10 bar, preferably between 1 and 35% of total pressure Controlled introduction of acetylene in an amount of between 0.1 and 100 times the copper amount in the Cu-loaded material used, preferably between 1 and 30, into the gas flow after 0.01 to 24 h, preferably 0.1 to 3 h after the activation temperature is reached.

(6) The inventors have found out that the conditions, especially the partial pressure of acetylene and the acetylene/copper ratio, during activation severely affect the performance of the catalyst. Thus, the activation step is of outmost importance to obtain an active catalyst for acetylene oligomerization and to obtain reproducible activity. When carrying out the activation step, the skilled man can work inside the borders of the process parameters as defined before and he will be able to adapt the activation to the actual conditions.

Process Parameters

(7) The Cu loaded material prepared and activated as described before is placed into a reactor, such as a tubular reactor, which is equipped with means for adjusting flow and composition of a gaseous mixture through the reactor. The temperature is adjusted to 20 and 700 C., most preferably 180-300 C., and the gas pressure is adjusted to >0 to 35 bar, preferably 2 to 20 bar. The gas phase is introduced as N.sub.2+H.sub.2+C.sub.2H.sub.2 in a composition of between 0.1% and 99.9% N.sub.2 (Ar, He and other inert gases or mixtures thereof are also useful) and the rest H.sub.2/C.sub.2H.sub.2 with a ratio between 1 and 10, preferably between 2 and 8. The molar ratio of the amount of C.sub.2H.sub.2 introduced per minute to the amount of copper contained in catalyst (in moles) might be between 0.01 and 100, preferably between 0.1 and 50, and more preferably between 0.5 and 10. In a different embodiment, the molar ratio of the amount of C.sub.2H.sub.2 introduced per minute to the amount of copper contained in catalyst might be between 0.1 and 100, preferably between 3 and 30.

(8) The process conditions are similar to the activation conditions. If the flow of acetylene on the catalyst during the first minutes and especially during the first seconds of the contact can be accurately controlled very active catalysts can be obtained reproducibly without the separate activation step.

EXPERIMENTAL PART

Preparation Examples

Example 1

(9) 7.2 g Copper nitrate trihydrate is dissolved in 120 g distilled water at room temperature. After complete dissolution of the solid a clear blue solution is obtained. To this 3 g Zeolite Y (Si/Al ratio 2.55) in sodium form (NaY) are added. The obtained suspension is then refluxed at 90-110 C. for 15-25 hours. Afterwards the suspension is filtered and the obtained solid is washed with 1-4 liters of distilled water. The washed solid is then dried for 15-25 hours at 90 C. in a static air oven.

Example 2

(10) 1 g Copper (II) acetate monohydrate is dissolved in 500 g distilled water at room temperature. After complete dissolution of the solid a clear blue solution is obtained. To this 3 g NaY (Si/Al ratio 2.55) are added. The obtained suspension is then stirred at room temperature for 0.5-25 hours. Afterwards the suspension is filtered and the obtained solid is washed with 1-4 liters of distilled water. The washed solid is then dried for 15-25 hours at 90 C. in a static air oven.

Example 3

(11) 0.2 g Copper (II) acetate monohydrate is dissolved in 100 g distilled water at room temperature. After complete dissolution of the solid a clear blue solution is obtained. To this 3 g NaY (Si/Al ratio 2.55) are added. The obtained suspension is then stirred at room temperature for 15-25 hours. Afterwards the suspension is filtered and the obtained solid is washed with 1-4 liters of distilled water. The washed solid is then dried for 15-25 hours at 90 C. in a static air oven.

(12) According to the inventors, it is essential in all cases that the drying is performed under a static atmosphere, at a temperature below the boiling point of water, to avoid the fast evaporation of water which can perturb the structure of the material.

(13) The dried catalyst is pelletized using a hydraulic press and the pellets are subsequently crushed and sieved. The fraction of particles measuring between 3-400 m is used for catalytic testing. This particle size works well for the research-scale reactor, but other particle sizes might work better for other dimensions of the reactor and at different space velocities.

(14) The materials obtained from this process have generally the following elemental composition in weight percent of the final product:

(15) 20-30% Si;

(16) 10-12% Al;

(17) 0.01-16% Cu;

(18) 0.5-13% Na,

(19) 5-25% water (rest is oxygen)

(20) Following similar protocols, any soluble Copper (II) salt could produce active catalysts upon ion-exchange with NaY. Other alumino-silicates with ion-exchange capabilities can also be loaded with copper (I) and/or (II) by procedures similar to those described above. These procedures can also lead to active materials for acetylene oligomerization.

(21) Additionally it must be noted that under the conditions of the inventive process or of the inventive catalyst activation procedure the copper can be partially or completely reduced to copper (I). In consequence, materials prepared via ion-exchange techniques which allow the use of copper (I) salts such as vapor phase ion exchange of a protonated zeolite such as HY with a volatile copper salt such as copper (I) chloride can also lead to active materials for acetylene oligomerization.

Example 4

(22) Preparation of amorphous ion-exchanging silica-alumina was based on a state of art procedure (Applied Catalysis A: General 388, 68-76 (2010)) 26 g of tetraethylorthosilicate (TEOS) are stirred in 30 mL of ethanol for 30 min. A solution of 3.685 g malic acid in 22.5 g H.sub.2O is prepared and added dropwise over 20 min to the TEOS solution. 12.08 g Al-secbutoxide are added to 27.5 g ethanol and stirred until this solution becomes clear. Afterwards this solution is added dropwise over 20 min to the TEOS solution. After mixing for one hour, the temperature of the solution is raised to 60 C. and maintained at this value until complete gelation, which will become apparent because the magnetic stirrer becomes stuck. This step will most likely take more than one day. After gelation is observed in the whole volume of the solution, the gel is aged for another day at 60 C. Afterwards the gel is calcined in a static air atmosphere in a box furnace by heating to 600 C. with a ramp of 2.4 C. per minute and holding the temperature at 600 C. for 12 h.

(23) The ion exchange of the obtained amorphous silica-alumina is performed in a manner identical to that used for zeolite Y.

(24) 7.2 g Copper nitrate trihydrate is dissolved in 120 g distilled water at room temperature. After complete dissolution of the solid a clear blue solution is obtained. To this solution 3 g of the amorphous silica alumina are added. The obtained suspension is then refluxed at 90-110 C. for 15-25 hours. Afterwards the suspension is filtered and the obtained solid is washed with 1-4 liters of distilled water. The washed solid is then dried for 15-25 hours at 90 C. in a static air oven. The ion exchange procedure, although identical to the one that gave a material with 9-10 wt. % Cu when applied to zeolite Y, only results in a material with 1-2 wt. % Cu. This is due to the fact that for the zeolite theoretically all aluminum atoms result in the formation of ion exchange sites, whereas for the amorphous material this is not the case.

Example 5

(25) Cu-SAPO-34 was synthesized by direct incorporation of a polyamine copper complex, according to patented procedures (US20150110711), using diethylamine as organic structure directing agent. A synthesis gel of the following molar composition: 0.81 DEA: 1 Al: 0.2 Si: 0.8 P: 18 H.sub.2O: 0.09 Cu: 0.09 TEPA, was prepared employing diethylamine, colloidal SiO.sub.2 suspension LUDOX AS-40 (Aldrich), commercial high-purity nanosized dispersible pseudo-boehmite (Disperal, Sasol Materials), a freshly prepared 85 wt. % H.sub.3PO.sub.4 aqueous solution, a saturated CuSO.sub.4 aqueous solution and tetraethylenepentamine as reagents. In addition, a 5 wt. % (with respect to the nominal mass of silicoaluminophosphate solid) was added as seeds to direct the crystallization of SAPO-34. The gel was treated in PTFE-lined autoclaves at 150 C. for 5 days under static conditions. The resulting solid was then recovered by centrifugation, washed with deionized water 4 times, dried at 90 C. for 12 h and calcined in air flow at 550 C. for 4 hours.

Protocol for Starting a Catalytic Test

(26) 0.05 to 2 g catalyst particles with a defined particle size prepared as described above are mixed with silicon carbide which serves as inert material to improve heat transfer from the catalyst bed. A mixture of catalyst+Silicon carbide with a total volume of 0.5 to 20 mL is placed in a stainless steel tubular reactor set at a pressure lower or equal to the operating pressure and heated within 20-40 minutes to 20-400 C. and held at this temperature for 0.01-24 h under a nitrogen and/or hydrogen flow of 50-500 mL/min. During this heating step, activation of the catalyst may be incorporated by the controlled introduction of acetylene in an amount of between 0.1 and 100 times the copper amount in the Cu-loaded material used, preferably between 1 and 30, into the gas flow after 0.01 to 24 h, preferably 0.1 to 3 h after the desired temperature is reached. Otherwise the activation can be performed in a separate step as described in the next section.

(27) Afterwards the reactor is brought to the reaction temperature of 200-250 C. and pressurized to the operating pressure (2-20 bar) with a nitrogen-hydrogen mixture. After a stable pressure is reached, acetylene is allowed to flow over the catalyst. The molar ratio of the amount of C.sub.2H.sub.2 introduced per minute to the amount of copper contained in catalyst (in moles) might be between 0.01 and 100, preferably between 0.1 and 50, and more preferably between 0.5 and 10. Under reaction conditions the hydrogen to acetylene molar ratio is between 3 and 5. Nitrogen serves only to dilute the acetylene-hydrogen mixture and nitrogen can constitute 0.1-99.9% volume percent of the gas phase.

(28) The gas mixture leaving the reactor is analyzed via gas chromatography.

(29) Activities observed range between 0.1 and 8 g acetylene converted per gram catalyst per hour. Butene selectivities between 20 and 55% are observed.

Catalyst Activation Procedure

Example 1

(30) 0.2 g of copper exchanged Y zeolite material are placed in a quartz tube (20 mm inner diameter) and heated at 400 C. under a flow of 40 L/h N.sub.2 and 15 L/h H.sub.2. After the reaction temperature is reached, acetylene is introduced at a flow rate of 0.12 L/h for 3 minutes.

(31) The amount of acetylene in moles flown over the material in this way is roughly 5-20 times the number of moles of Cu contained in the material. The intention is to bring as much as possible of the copper into the active state while avoiding carbon deposition on the catalyst from acetylene decomposition at high temperature.

(32) After this activation step the catalyst is transferred into the high pressure stainless steel reactor and the reaction is performed as described above, omitting the step where the catalyst is first heated under nitrogen and/or hydrogen to 20-400 C. This procedure yields a material which converts 0.5-5 g of acetylene per gram of catalyst per hour with a total selectivity of 30-50% to butenes and butadiene.

Example 2

(33) 0.2 g of copper exchanged Y-zeolite are mixed with SiC to give a total volume of particles of 0.7 mL and this mixture is placed in a glass tube (4 mm inner diameter) and heated at 220 C. under a flow of 280 mL/min N.sub.2 and 140 mL/m in H.sub.2. After the reaction temperature is reached, acetylene is introduced in an amount equal to 3 times the Cu amount contained in the material over a period of 5 to 60 seconds. The material is then transferred into a steel reactor and the catalytic test is started as described above omitting the step where the catalyst is first heated under nitrogen and/or hydrogen to 20-400 C. This procedure yields a material which converts 2-3 g of acetylene per gram of catalyst per hour with a total selectivity of 35-45% to butenes and butadiene.

Example 3

(34) 0.25 g of Cu-SAPO-34 prepared as in example 5 for catalyst preparation are mixed with SiC to give a total volume of particles of 0.7 mL and this mixture is placed in a glass tube (4 mm inner diameter) and heated at 220 C. under a flow of 280 mL/min N.sub.2 and 140 mL/m in H.sub.2. After the reaction temperature is reached, acetylene is introduced in an amount equal to 3 times the Cu amount contained in the material over a period of 5 to 60 seconds.

(35) The material is then transferred into a steel reactor and the catalytic test is started as described above omitting the step where the catalyst is first heated under nitrogen and/or hydrogen to 20-400 C. This procedure yields a material which converts 1.5-2.5 g of acetylene per gram of catalyst per hour with a total selectivity of 30-40% to butenes and butadiene.