Dehydrogenation of cyclic thioethers

Abstract

There is disclosed a surprising reaction of an alkane thiol with a catalyst and heat to become dehydrogenated and form a thiophene rather than an expected desulfurization reaction to form the corresponding alkane or alkene. Moreover, there are disclosed surprising results regarding the form of a catalyst to allow a reaction of an alkane thiol to form the dehydrogenated thiophene at lower temperatures and at higher conversion percentages to allow for more efficient recovery of thiophenes to allow for recycling and reuse of thiophenes to hydrogenate to form alkane thiols. Further still, there is disclosed a set of reaction conditions and catalyst presentation that allows for recovery of usable diatomic hydrogen gas from a dehydrogenation reaction of substituted or unsubstituted cyclic thioethers to substituted or unsubstituted thiophene.

Claims

1. A process for the delivery of hydrogen from an organic compound capable of reversible hydrogenation/dehydrogenation wherein the organic compound is initially in its hydrogenated form and subsequently catalytically dehydrogenated under dehydrogenation conditions in a reactor forming hydrogen and byproduct dehydrogenated organic compound, comprising: (a) introducing the organic compound capable of reversible hydrogenation/dehydrogenation in liquid form to a microchannel reactor incorporating a dehydrogenation catalyst; (b) vaporizing the organic compound in a vaporizer; (c) effecting dehydrogenation of the organic compound (d) recovering a reaction product comprised of a byproduct dehydrogenated organic compound and gaseous hydrogen; and (e) separating and recovering the reaction product comprised of the dehydrogenated organic compound and gaseous hydrogen into a gaseous hydrogen fraction and liquid phase byproduct dehydrogenated organic compound.

2. The process for the delivery of hydrogen from an organic compound capable of reversible hydrogenation/dehydrogenation wherein the organic compound is initially in its hydrogenated form and subsequently catalytically dehydrogenated under dehydrogenation conditions in a reactor forming hydrogen and byproduct dehydrogenated organic compound of claim 1, wherein the liquid organic material is a substituted or unsubstituted cyclic thioether having from 0 to 2 C.sub.1-2 alkane groups as the substitutions at positions at 2,4, or 3,5 of the thiophene at a ring carbon atom.

3. The process for the delivery of hydrogen from an organic compound capable of reversible hydrogenation/dehydrogenation wherein the organic compound is initially in its hydrogenated form and subsequently catalytically dehydrogenated under dehydrogenation conditions in a reactor forming hydrogen and byproduct dehydrogenated organic compound of claim 1, wherein the dehydrogenation is carried out in a plurality of microchannel reactors wherein the pressure in each succeeding reactor is less than the prior reactor.

4. The process for the delivery of hydrogen from an organic compound capable of reversible hydrogenation/dehydrogenation wherein the organic compound is initially in its hydrogenated form and subsequently catalytically dehydrogenated under dehydrogenation conditions in a reactor forming hydrogen and byproduct dehydrogenated organic compound of claim 1, wherein the dehydrogenation is carried out in a plurality of microchannel reactors wherein the temperature in each succeeding reactor is higher than the prior reactor.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIG. 1 shows a plot of percentage conversion of a cyclic thioether, 2-methyl tetrahydrothiophene, dehydrogenated to 2-methyl thiophene with the release of two moles of diatomic hydrogen per mole of 2-methyl tetrahydrothiophene. Two catalysts are used AuX40S and X-3R2, where the description of these catalysts is in Table 1. A sample of gaseous 2-methyl tetrahydrothiophene was injected through the catalyst, which was packed in the liner of a gas chromatograph (GC), with helium as a carrier gas at 1 ml/min and an operating temperature of 280 C. The detector was a mass spectrometer (MS).

(2) FIG. 2 shows a plot of percentage conversion of a cyclic thioether (tetrahydrothiophene) to thiophene with the release of two moles of diatomic hydrogen gas per mole of tetrahydrothiophene. The catalyst X-3R2, described in Table 1, was used at different temperatures as shown.

(3) FIG. 3 shows a plot of percentage conversion of tetrahydrothiophene to thiophene with the release of two moles of diatomic hydrogen per mole of tetrahydrothiophene. The two batches of Pt-1 catalyst, described in Table 1, were implemented at different temperatures. The reaction was done in a reactor, where the reactor was of a concentric tube design operating at either a stable 200 or 280 C. The inner reaction tube was a porous tube of -alumina containing catalyst particles between 5 and 50 nm in diameter. The pore size of the tubes used ranged between 20 and 200 m. Tetrahydrothiophene was passed into the center of the reaction tube at rates between 0.5-1.5 mL/min. Samples of liquid trapped after the reaction were analyzed by gas chromatography mass spectrometry for tetrahydrothiophene and thiophene.

(4) FIG. 4 shows a plot of percentage conversion of tetrahydrothiophene to thiophene with the release of two moles of diatomic hydrogen per mole of tetrahydrothiophene. Five catalysts were used, including catalyst X-3R2, MTB-4A and MTB-5A, each described in Table 1, at two different temperatures. A sample of tetrahydrothiophene vapor was injected through a catalyst packed in the liner of a gas chromatograph, with helium as a carrier gas at 1 ml/min and an operating temperature of 280 C. The detector was a mass spectrometer (MS).

(5) FIG. 5 shows the diatomic hydrogen content of a ballast tank as n-pentanethiol was processed in the reactor. The unsustained high increase of diatomic hydrogen at the end of the run was due to flushing the reactor out with helium. A packed bed reactor ( inch, sulfinert treated stainless steel tube) was maintained at a stable temperature of 280 C. for the duration of the study. The reactor was packed with three catalyst sections separated by quartz wool. The three catalyst sections were: Au-1 (1.99 g), Au-1/Pt-1 mixed (5.51 g Au/Pt 23:1) and Pt-1 (0.17 g), wherein the catalysts are described in Table 1. N-pentanethiol was vaporized and passed into the reactor at an equivalent rate of 1 L/min. The emitted gas was collected in a ballast tank. Diatomic hydrogen was detected as a percentage of gas in the ballast tank.

(6) FIG. 6 is a schematic of the reactor set up described in Example 16.

(7) FIG. 7 shows that as temperature increases conversion (yield of thiophene) increases at constant space time. Conversion was calculated as (thiophene in product stream-thiophene in inlet stream)/(tetrahydrothiophene in inlet stream), as conversion was with respect to thiophene, it was equal to yield of thiophene. Apparent activation energy, calculated from these results, was 100 kJ/mol.

(8) FIG. 8 shows that as space time increases conversion (yield of thiophene) increases at constant temperatures. Conversion was calculated as (thiophene in product stream-thiophene in inlet stream)/(tetrahydrothiophene in inlet stream), as conversion was with respect to thiophene, it was equal to yield of thiophene. Apparent activation energy, calculated from these results, was 100 kJ/mol.

(9) FIG. 9 shows a dehydrogenation apparatus. Specifically, the apparatus comprises a syringe pump (Harvard Apparatus, Pump 11) configured to deliver 1.0 l/min of tetrahydrothiophene THT (Sigma-Aldrich, 99%) to a catalytic component (i.e., a reactor core) comprised of a packed bed containing of 2.48 g MTB-16 mixed with 4.73 g of crushed borosilicate glass in a 0.2512.5 inch stainless steel tube (Restek, #22507). The reactor core was installed in an oven (Gow-Mac). A syringe (Hamilton) was charged with approximately 1.0 ml of THT enabling it to operate continuously for an 18 hour experiment.

(10) FIG. 10 describes the amount of hydrogen measured in a helium carrier gas with respect to time. The period of time from t=2.5 hrs to t=17 hrs represents the system at steady state. During this steady state period, the value of hydrogen measured in the helium carrier decreased from approximately 10% to 7% according to a linear model.

DETAILED DESCRIPTION

(11) The present disclosure provides a process for releasing hydrogen from substituted or unsubstituted cyclic thioether and capturing a dehydrogenated product. Moreover, finely dispersed supported metal catalysts carry out the cyclization and dehydrogenation reaction of alkyl sulfides to thiophene, while at the same time releasing hydrogen.

(12) Alkane thiols and 5 or 6 member ring heterocyclic molecules containing sulfur heteroatoms can reversibly produce hydrogen upon demand. The produced hydrogen can be used for the purposes of generating energy or in any other situation where hydrogen is used. In this regard, the thiol-based organic molecule, after it releases some but not all of its hydrogen atoms, is converted to a second stable organic molecule that is in a liquid state at typical environmental temperatures including winter temperatures. By virtue of having a liquid state organic molecule in both the hydrogenated and dehydrogenated states, both molecules can be distributed using existing petroleum infrastructure.

(13) Thiol-Containing Organic Molecules

(14) Synthesis of Pentane Thiol

(15) Sodium (84 mg/3.64 mmol) was added to methanol (5 mL) at 0 C. After the sodium was dissolved, thioacetic acid (0.284 mL/3.97 mmol) was added slowly and allowed to stir for 10 minutes at 0 C. 1-bromopentane (500 mg/3.31 mmol) was added to the reaction mixture and the entire mixture was brought to a boil. The mixture was refluxed for 5 h, cooled, and concentrated by evaporation at reduced pressure. The resulting liquid was taken up in water and extracted three times into dichloromethane (15 mL each time). The organic layers were combined and dried over sodium sulfate. The organic layer was filtered and concentrated by evaporation at reduced pressure. The crude product was then purified by Biotage chromatography (5% ethyl acetate in hexanes), yielding 80 mg of the thioacetate (54.7 mmol/16% yield). This reaction was stopped at this point.

(16) Potassium thioacetate (416 mg/3.64 mmol) was dissolved in dry, degassed methanol (15 mL) and combined with 1-bromopentane (500 mg/3.31 mmol). The reaction mixture was allowed to reflux overnight. After this time, the reaction was cooled and concentrated by evaporation. The resulting liquid was taken up in water and extracted three times into dichloromethane (15 mL each time). The organic layers were combined and dried over sodium sulfate. The organic layer was filtered and concentrated by evaporation at reduced pressure, yielding 190 mg of pentylthioacetate (39% yield). The thioacetate was then dissolved in dry, degassed d4-methanol (1.2 mL) and chilled to 0 C. Under an atmosphere of nitrogen, acetyl chloride (370 L/5.2 mmol) was added dropwise. After 15 minutes, the reaction mixture was allowed to warm to room temperature and stirred for an additional 8 hours, at which point a sample analyzed on GC/MS showed mainly dipentyl disulfide.

(17) In a process to synthesize deuterated pentanethiol, potassium thioacetate (420 mg/3.68 mmol) was dissolved in dry, degassed methanol (15 mL) and combined with 4,4,5,5,5-(d5)-1-bromopentane (500 mg/3.20 mmol). The reaction mixture was allowed to reflux for 6 hours, then cooled and then stirred at room temperature for 36 hours. After this time, the reaction was concentrated by evaporation. The resulting liquid was taken up in water and extracted four times into dichloromethane (20 mL each time). The organic layers were combined and dried over sodium sulfate. The organic layer was filtered and concentrated by evaporation at reduced pressure, yielding 0.364 g of d5-pentylthioacetate (75% yield). The d5-thioacetate was then dissolved in dry, degassed d4-methanol (1.2 mL) and chilled to 0 C. Under an atmosphere of nitrogen, acetyl chloride (684 L/9.62 mmol) was added drop-wise. The reaction mixture was allowed to warm to room temperature and stirred for an additional 48 hours. After this time, the reaction was neutralized by adding saturated sodium bicarbonate, it was extracted four times into dichloromethane (12 mL each time). The organic layers were combined and dried over sodium sulfate. The organic layer was filtered and concentrated by evaporation at reduced pressure, yielding 0.0569 g 4,4,5,5,5-(d5)-1-pentanethiol.

(18) In a second deuterated synthesis process, potassium thioacetate (388 mg/3.40 mmol) was dissolved in dry, degassed methanol (15 mL) and heated for 15 minutes, then combined with d11-1-bromopentane (500 mg/3.08 mmol). The reaction mixture was allowed to reflux for 6 hours, then cooled and stirred at room temperature for 14 hours. After this time, the reaction was concentrated by evaporation. The resulting liquid was taken up in water and extracted three times into dichloromethane (30 mL each time). The organic layers were combined and dried over sodium sulfate. The organic layer was filtered and concentrated by evaporation at reduced pressure, yielding 0.311 g of d11-pentylthioacetate (64% yield). The d11-thioacetate was then dissolved in dry, degassed d4-methanol (1.2 mL) and chilled to 0 C. Under an atmosphere of nitrogen, acetyl chloride (700 L/8.08 mmol) was added drop-wise. The reaction mixture stirred at 0 C. for 30 minutes, then was allowed to warm to room temperature and stirred overnight. After this time, the reaction was neutralized by adding triethylamine (distilled from ninhydrin) and concentrated by evaporation. The reaction mixture was then taken up into D.sub.2O and extracted three times into dichloromethane. The organic layers were combined and dried over sodium sulfate. The organic layer was filtered and concentrated by evaporation at reduced pressure, yielding d-11-1-pentanethiol.

(19) Catalysts

(20) Gold on Controlled Porous Glass

(21) Gold-coated thiolated glass powder was synthesized by suspending controlled pore glass, CPG, (obtained from Millipore, part numbers CPG00700B and CPG00700C) (5 g), in methanol and combining the suspension with triethylamine (1 mL) and 3-mercaptopropyltrimethoxysilane (0.25 mL/1.35 mmol). The reaction mixture was refluxed for 60 hours. After this time, the reaction mixture was filtered, and the powder was purified by Soxhlet extraction with ethanol and dried overnight in a vacuum oven. The resulting powder was then placed in an Erlenmeyer flask and combined with colloidal gold (reference: http://mrsec.wisc.edu/Edetc/nanolab/gold/index.html) and ethanol (approximately 50 mL colloidal gold and 3 mL Ethanol for every 0.5 g powder) and allowed to stir for 5 hours. The powder was then filtered and dried in vacuo.

(22) MTB Catalysts

(23) A gold nano-particle catalyst was synthesized by dissolving 500 mg of HAuC.sub.l4 in 15 ml 18 M/cm water. The pH of the solution was adjusted with 1N NaOH. 25 ml of 18 M/cm water was then added to the gold solution. The catalyst substrate was added to the solution and stirred for 24 hours. The substrate was filtered and washed with 18 M/cm water. The powder was vacuum dried. The catalyst was reduced at 200 C. for 2 hours in hydrogen at ramp rate 0.73 C./min and hydrogen flow of 54 ml/min.

(24) MTB-4A is gold on TiO.sub.2. MTB-5A is gold on -aluminum.

(25) Other Catalysts

(26) An X3R2 200-325 Mesh catalyst of porous glass substrate with immobilized gold particle size of 300 nm was obtained from Catholic University of America.

(27) Gold powder spherical APS (5.5-9 micron with a 99.96% metal basis) was obtained from Alfa Aesar. Platinum black high surface area (97.42%) was obtained from Alfa Aesar.

(28) Spherical, gold particles, with an average diameter between 0.5-0.8 m, have successfully dehydrogenated alkane thiol to its corresponding thiophene (see, for example, U.S. Pat. No. 7,186,396, the disclosure of which is incorporated by reference herein). However, when the particle size was below 10 m the catalyst became significantly more active. Preferred catalysts were immobilized on controlled pore glass, -alumina, carbon and on other high surface area substrates made via the sol-gel method.

(29) A gold nanoparticle catalyst was synthesized by dissolving HAuC.sub.l4 in 15 ml 18 M/cm water. The pH of the solution was adjusted with 1N NaOH. 25 ml 18 M/cm water was added to above pH adjusted gold solution. The above solution was added to aluminum oxide powder and was stirred for 24 hours. The powder was filtered and washed with ample amount of water. The powder was vacuum dried. The catalyst was reduced at 200 C. for 2 hours in hydrogen at ramp rate 0.73 C./min and hydrogen flow of 54 ml/min

(30) An X3R2 200-325 Mesh catalyst of porous glass substrate with immobilized nanogold particle size of 300 nm was received from Catholic University of America. Catalyst QSI-Nano PdAu was purchased from QUANTUM SPHERE. Lot # BM113-12.

(31) When creating the catalyst usually a short chain organic molecule with amine or thiol head group is covalently bonded to the surface of the catalyst support. Then the potentially active metals are deposited on the surface by reduction of their salts or by vapor deposition.

(32) Preparation of First Catalyst Surfaces

(33) A gold catalyst (5-10 m in diameter) was packed in the liner of a GC, with helium as a carrier gas at 100 ml/min and an operating temperature of 280 C. The detector was either a thermal conductivity detector (TCD) or mass spectrometer (MS). Gold catalyst was obtained as a commercial powder.

(34) Preparation of Second Catalyst Surfaces

(35) Several catalysts of different particle sizes were tested out looking for conversion percentages of tetrahydrothiophene to thiophene or 2-methyl tetrahydrothophene to 2-methyl thiophene. The MTB-4A and MTB-5A catalysts (see FIG. 4) were gold on titanium oxide in the gold (article size of about 3-8 nm range for MBT-4A). MBT-5A is gold on aluminum oxide with a 3-8 nm range for the gold particles. Surface coverage of either aluminum oxide or titanium oxide substrates was in the range of 2-5%. Catalyst was supplied in powder form. Titanium oxide particles and aluminum oxide particles were about 4 m in average particle size.

(36) Gold on titanium oxide powder was made in a deposition precipitation process. Briefly, a gold chloride solution was mixed with a support (i.e., titanium oxide or aluminum oxide) at pH 7.0 (adding NaOH to the gold chloride solution to adjust pH to 7.0), followed by filtration and then drying under vacuum (1-100 mtorr) into a powder.

(37) Specifically, MBT-4A used titanium oxide (anatase phase, Aldrich) 5000 mg, deionized (18 M/cm) water (800 mg), gold chloride hydrate (Aldrich, AuCl.sub.4) 500 mg and 1N NaOH (5400 L), wherein gold chloride hydrate was dissolved in deionized water and the pH of the solution was adjusted to 7.0 by slowly adding 1N NaOH. Titanium oxide support or other substrate was added to this solution and the solution was stirred for 24 hours. The solution was filtered to obtain a powder/catalyst and the powder/catalyst was washed with water. The powder was vacuum dried for 24 hours at 1 mtorr. Lastly, the powder/catalyst was reduced at 200 C. for 2 hours in pure hydrogen (ramp rate of 0.73 C./min, hydrogen flow 50 ml/min).

(38) Specifically, MBT-5A used aluminum oxide (gamma phase, Alfa Aesar) 5000 mg, deionized (18 M/cm) water (800 mg), gold chloride hydrate (Aldrich, AuCl.sub.4) 500 mg and 1N NaOH (5400 L) wherein gold chloride hydrate was dissolved in deionized water and the pH of the solution was adjusted to 7.0 by slowly adding 1N NaOH. Aluminum oxide support or other substrate was added to this solution and the solution was stirred for 24 hours. The solution was filtered to obtain a powder/catalyst and the powder/catalyst was washed with water. The powder/catalyst was vacuum dried for 24 hours at 1 mtorr. Lastly, the powder/catalyst was reduced at 200 C. for 2 hours in pure hydrogen (ramp rate of 0.73 C./min, hydrogen flow 50 ml/min).

(39) Table 1 below describes the different base catalysts used herein. The catalysts are described with regards to the name labeled to them, the active metal, the active metal particle size, the support, the support dimensions and the source of the catalyst.

(40) TABLE-US-00001 TABLE 1 Catalyst Active Metal Support Name Active Metal Particle Size (nm) Support Dimensions Source AuX40S Gold (0.8 wt. 6.7-10.5 Carbon 1100 m.sup.2/g, pore World Gold %) volume 0.37 ml/g Council X-3R2 Gold ~300 controlled 44-74 m Catholic porous glass University of America MTB-4A Platinum (4-5 wt 2-8 nm gamma ~4 m In-House %) alumina MTB-5A Platinum (4-5 wt 2-8 nm gamma ~4 m In-House %) alumina MTB-16 Platinum (4-4.5 wt 2-8 nm gamma ~21 m, 140 m.sup.2/g In-house %) alumina Au-1 Gold 5.5-9.5 m na na Alfa Aesar Pt-1 Platinum 24-29 m.sup.2/g na na Alfa Aesar AuTiO2- Gold Titainium World Gold WGC Oxide Council

(41) Table 2 reports concentrations for converting tetrahydrothiophene (THT) to thiophene as determined by GC/MS. This reaction also release diatomic hydrogen expressed as a percentage of the gas passing through the hydrogen specific detector. A packed bed reactor was maintained at a stable temperature (290-370 C.) for each example. The reactor was packed with catalyst MTB-16, described in Table 1, wherein the platinum loading of the catalyst was 4-4.5% w/w. Liquid tetrahydrothiophene was continuously passed into the packed bed reactor (1 or 1.5 L/min). Liquid samples (trapped after the reactor) were analyzed by gas chromatography with mass spectrometry for tetrahydrothiophene and thiophene. After the liquid traps, gas emissions passed through a hydrogen specific detector that determined percentage hydrogen in the gas stream.

(42) TABLE-US-00002 TABLE 2 l/min 1 Temperature ( C.) 290 Time (min) THT (mM) Thiophene (mM) Hydrogen (%*) 0 0 0 0 15 0.01 0.09 0 30 0.13 0.23 0.74 45 0.81 0.41 1.64 60 1.74 0.57 1.68 75 2.24 0.83 1.33 90 2.84 0.92 0.9 105 4.26 1.27 0.59 120 5.95 1.60 0.43 l/min 1 Temperature ( C.) 310 Time (min) THT (mM) Thiophene (mM) Hydrogen (%*) 0 0 0 0 15 0 0.15 0.01 30 0.37 0.56 1.27 45 0.62 0.83 2.82 60 0.76 1.14 3.06 75 1.39 1.32 2.36 90 1.89 1.82 1.44 105 3.59 2.08 0.81 l/min 1 Temperature ( C.) 325 Time (min) THT (mM) Thiophene (mM) Hydrogen (%*) 0 0 0 0 15 0.04 0.33 0 30 0.11 0.87 1.74 45 0.69 1.58 4.02 60 1.5 2.27 4.45 75 1.53 2.77 2.94 90 2.39 3.64 1.72 105 3.49 4.12 0.95 l/min 1 Temperature ( C.) 350 Time (min) THT (mM) Thiophene (mM) Hydrogen (%*) 0 0 0 0.16 15 0 1.7 3.4 30 0.21 4.88 6.32 45 1.05 8.97 4.05 60 1.36 12.09 2.88 75 1.55 12.52 1.63 l/min 1 Temperature ( C.) 370 Time (min) THT (mM) Thiophene (mM) Hydrogen (%*) 0 0 0 0 15 0 6.66 0.02 30 0.1 16.93 3.23 45 0.25 32.83 6.84 60 0.41 55.94 8.41 75 0.68 72.37 8.81 90 1.07 74.54 6.73 105 1.27 72.88 3.35 120 1.37 84.01 1.73 135 0.98 53.04 0.85

(43) Associated organic molecules, such as thiophenes, had been monitored as reaction byproducts. The alkane thiols reacted to form thiophenes with hydrogen being released. The reaction was repeated in a gas chromatograph (GC) equipped with a thermal conductivity detector (TCD). Hydrogen was released during the alkane thiol reaction. The experiment was repeated using a GC mass spectrometer (MS) with similar results.

(44) The GCMS method provided samples at 40 C. for 3 minutes. Temperature was increased (10 C./min) until reaching 120 C. Next, temperature was ramped (25 C./min) until 260 C. and held for 8 minutes.

(45) The dehydrogenation reaction of alkane thiols and cyclic thioethers was conducted at three different volume levels: gas phase, micro-liter and milliliter. This demonstrated reaction scalability. For gas phase, a gas chromatograph mass spectrometer (GC/MS) (78 mm0.93 mmid) inlet liner was packed with catalyst (8.2 mm.sup.3, 0.1-5 g). The inlet liner was placed in an inlet port of the GC/MS and was heated to desired temperature. The desired starting molecule (alkane thiol or cyclic thioether) was placed in a vial equipped with septum having some head space. The septum head space was vacuumed with a gas-tight syringe extracting 0.1-5 l of headspace gases. The headspace gasses were injected into the GC/MS. Helium gas (8 psi) pushed the sample through catalyst into the GC column. The reaction took place in the inlet liner and it was directly monitored by MS instrument.

(46) 1.0 g of the catalyst was packed into a sulfinert treated stainless steel tube which was used for micro-liter volume level. The tube was packed with approximately 1.0 g of catalyst. During use, the tube was placed in a programmable oven. At the desired temperature, the tube containing catalyst was exposed to hydrogen for 1 hour, followed by helium for 1 hour. The reaction injected an alkane thiol or a cyclic thioether into the tube containing catalyst. Helium was the carrier gas. The tube output (including reaction products and unreacted starting material) was passed through methanol (as a carrier) to collect organic materials (but not hydrogen). Carrier methanol was sampled at increments of 0.5 hour, 1, 2, and 3 hours and analyzed by GC/MS to determine catalyst efficiency and conversion rate (using retention time and peak mass spectra). Temperature was a variable. Optimal temperature was determined.

(47) Catalyst Synthesis, PtRh/Al.sub.2O.sub.3 Catalyst

(48) PtRh bimetallic catalyst supported on gamma-alumina was synthesized by a sequential wet impregnation method. 724 mg of chloroplatinic acid (Sigma-Aldrich) was dissolved in 960 ml of distilled water. 6000 mg of gamma-alumina (CataloxScFa-140, Sasol America, surface area 140 sq.Math.m/gm) was dispersed in above solution and stirred the mixture of 24 hours. Powder was filtered and washed with water and vacuum dried for 24 hours. Dry powder was reduced under hydrogen flow of 100 ml/min at 200 C. for 2 hours with ramp time of 4 hours. Rh was loaded on Pt loaded gamma-alumina by sequential impregnation. 372 mg of rhodium chloride (Sigma-Aldrich) was dissolved in 960 ml of distilled water. Pt loaded gamma-alumina was dispersed in above solution and stirred the mixture of 24 hours. Powder was filtered and washed with water and vacuum dried for 24 hours. Dry powder was reduced under hydrogen flow of 100 ml/min at 200 C. for 2 hours with ramp time of 4 hours. Catalyst was labeled as PtRh/Al.sub.2O.sub.3 catalyst. Metal loading was measured by ICP/MS. Metal loading was 0.5 wt % for both metals.

(49) Reactivity Measurement of PtRh/Al.sub.2O.sub.3 Catalyst

(50) Reactivity of catalyst was measured in packed bed flow reactor. 0.5 mg of catalyst was packed in inch ID tube with glass wool at both ends of catalyst. Catalyst was heated to reaction temperature and temperature at catalyst surface was measured by thermocouple and controlled by temperature controller. Tetrahydrothiophene was delivered to the reactor by dual piston pump and inlet volumetric flow rate was controlled by the pump. Tetrahydrothiophene was vaporized prior to reactor and vapor temperature was controlled and set at catalyst temperature. Product stream coming out of reactor was condensed to room temperature using ice cold water. Inlet stream and product stream were analyzed for tetrahydrothiophene and thiophene by GC/MS to calculate conversion. Reactivity of catalyst was measured at various temperatures and inlet reactant flow rates. Temperature of reaction was varied from 200 C. to 500 C. Inlet flow rate was varied from 0.25 to 1 ml/min that corresponds to space velocity of 8361 to 33447 ml/hr/gm of catalyst. Space velocity and space time are standard chemical engineering terms used in reaction kinetics to define reactor. Space velocity was defined as inlet gas volumetric flow rate divided by weight of catalyst. Space time was defined as weight of catalyst divided by inlet gas molar flow rate. Results of the studies are presented in FIGS. 7 and 8. Conversion was calculated as (thiophene in product stream-thiophene in inlet stream)/(tetrahydrothiophene in inlet stream), as conversion was with respect to thiophene, it was equal to yield of thiophene. FIG. 7 shows that as temperature increases conversion (yield of thiophene) increases at constant space time. FIG. 8 shows that as space time increases conversion (yield of thiophene) increases at constant temperatures. Apparent activation energy, calculated from these results, was 100 kJ/mol.

(51) Other Catalysts

(52) All catalysts were synthesized by wet impregnation method as described in synthesis details for PtRh/Al.sub.2O.sub.3 catalyst. Aeroperl P25/20 was purchased from Evonik, Silica gel 60 was purchased from EMD chemicals while CataloxScFa140 was purchased from Sasol. All metal complexes were purchased from Sigma-Aldrich.

(53) For Au/TiO.sub.2, pH of gold chloride solution was adjusted to 7 with 1N sodium hydroxide prior to addition of titanium dioxide to solution. For Pd/Al.sub.2O.sub.3 catalyst, 37% HCl was added to water to make 2.5% HCl prior to addition of palladium chloride.

(54) Details are summarized in the following Table 3.

(55) TABLE-US-00003 Sup- Metal Metal Water port Complex Catalyst Support complex (ml) (mg) (mg) Au/TiO.sub.2 Aeroperl P25/20 HAuCl.sub.4 960 6000 600 Pt/SiO.sub.2 Silica Gel 60 Pt(NH.sub.3).sub.4Cl.sub.2 960 6000 588 Ag/SiO.sub.2 Silica Gel 60 AgNO.sub.3 960 6000 300 Au/Al.sub.2O.sub.3 CataloxScFa140 HAuCl.sub.4 960 6000 600 Pt/Al.sub.2O.sub.3 CataloxScFa140 H.sub.2PtCl.sub.6 960 6000 724 Pd/Al.sub.2O.sub.3 CataloxScFa140 PdCl.sub.2 895 6000 312 Rh/Al.sub.2O.sub.3 CataloxScFa140 RhCl.sub.3 960 6000 372

(56) Reactivity of these catalysts was measured as described in reactivity measurement of PtRh/Al.sub.2O.sub.3 catalyst above at space velocity of 8361 ml/hr/gm of catalyst. Summary of reactivity data at 400 C. is summarized in following Table 4. Reactivity is defined as mole of thiophene formed per unit time per unit weight of catalyst.

(57) TABLE-US-00004 Reactivity Catalyst (mol/sec/gm cat) Au/TiO.sub.2 1.56E07 Pt/SiO.sub.2 2.41E07 Ag/SiO.sub.2 4.86E07 Au/Al.sub.2O.sub.3 1.51E07 Pt/Al.sub.2O.sub.3 1.61E07 Pd/Al.sub.2O.sub.3 2.44E07 Rh/Al.sub.2O.sub.3 4.66E07 PtRh/Al.sub.2O.sub.3 8.16E07

(58) A dehydrogenation apparatus (i.e., reactor), schematically depicted FIG. 9, was assembled and utilized in an experiment where tetrahydrothiophene (THT) was catalytically dehydrogenated at an elevated temperature with the concomitant release of hydrogen gas. The apparatus comprises a syringe pump (Harvard Apparatus, Pump 11) configured to deliver 1.0 l/min of THT (Sigma-Aldrich, 99%) to a catalytic component (i.e., reactor core) comprised of a packed bed containing of 2.48 g MTB-16 mixed with 4.73 g of crushed borosilicate glass in a 0.2512.5 inch stainless steel tube (Restek, #22507). The reactor core was installed in an oven (Gow-Mac). A syringe (Hamilton) was charged with about 1.0 l of THT enabling it to operate continuously for an 18 hour experiment.

(59) A supply of helium was connected to the catalytic component and adjusted to provide a continuous flow. Helium was used as an inert carrier to impart momentum to the mobile phase as is typical in gas chromatography. The operating pressure was adequate to support the flow rate.

(60) A hydrogen detector (H2 Scan, Model 700, SN A000080) was installed inline and connected via a serial-USB adapter to a computer. This device was used to measure hydrogen concentration in a carrier gas flow 60 times per minute. These values are data-logged using HyperTerminal from a Windows XP operating system FIG. 10 was generated from these data points.

(61) Following the hydrogen detector, a bubbler (custom-made) was installed. The bubbler was a gas impinging type device and nominally charged with approximately 6 l of methanol. Gasses flowing through the system produce bubbles as they vent to the atmosphere which can be counted over a specified period of time (e.g., 60 seconds) to serve as an indication of gas flow. The bubbler has been calibrated to relate the number of bubbles per time to a certain volumetric flow rate as detected by a mass flow meter (Varian, Veriflow 500). The methanol in the bubbler prevented atmospheric gasses from entering the apparatus by forming an air-lock.

(62) Each catalyst was heated to and held at 370 C. and the syringe pump operated for 18 hours. THT was carried through the catalyst where it was dehydrogenated. During the first 2.5 hrs of the experiment the concentration of hydrogen increased to 10%. The system operated for 15.5 hrs at steady state where the production of hydrogen remained relatively constant (FIG. 10). After 17 hrs, the syringe pump was stopped and THT was no longer delivered to the catalyst. The concentration of hydrogen in the helium carrier decreased and the experiment was terminated.

(63) Hydrogen was produced through the dehydrogenation of THT according to the following reaction:
THT.fwdarw.T+2H.sub.2[1]

(64) For the purpose of this calculation, the actual dehydrogenation product, e.g., T in Eqn. 1 was somewhat irrelevant but it is taken as given that one mole of THT will liberate 2 moles of hydrogen gas. Using this as a basis, we computed the volumetric relationship (at S.T.P.) between THT and H.sub.2 in units consistent and meaningful with the experimental data:

(65) $\begin{array}{cc}1\mathrm{uLTHT}\frac{\mathrm{mL}}{1000\mathrm{uL}}\frac{1.0g}{\mathrm{mL}}\frac{1\mathrm{mol}THT}{88.10g}\frac{2\mathrm{mol}{H}_2}{1\mathrm{mol}\mathrm{THT}}\frac{22.4}{\mathrm{mol}{H}_2}\frac{1000\mathrm{mL}}{L}=0.51\mathrm{mL}{H}_2& \left[2\right]\end{array}$

(66) Helium was used as a carrier gas and its flow rate was set to be 2.74 mL/min. This rate was assumed to be substantially constant throughout the experiment. Moreover, the hydrogen produced did not cause the rate to increase. This, this value represented the total gas flow rate during the experiment. This assumption, though incorrect, was accepted for two reasons: (1) The flow rate was not monitored continuously during the experiment so it cannot be reported that a change in flow rate was observed; and (2) It prevented an iterative-only solution whereby the flow rate must be assumed to increase by an amount proportional to the production of hydrogen which then requires a recalculation of the flow rate until the solution converges.

(67) FIG. 10 describes the amount of hydrogen measured in a helium carrier gas with respect to time. The period of time from t=2.5 hrs to t=17 hrs represents the system at steady state. During this steady state period, the value of hydrogen measured in the helium carrier decreased from approximately 10% to 7% according to a linear model. In keeping with the algebraic solution, the average value over this 15.5 hr time period was assumed to be

(68) $\begin{array}{cc}\frac{\left(10+7\right)\%}{2}=8.5\%H_2& \left[3\right]\end{array}$

(69) Given our assumption that the total system flow rate was 2.74 l/min, one can calculate the percentage of this value which must be due to hydrogen by using the following ratio:

(70) $\begin{array}{cc}\frac{n\frac{\mathrm{mL}}{\min }{H}_2}{2.74\frac{\mathrm{mL}}{\min }\mathrm{total}}=0.085& \left[4\right]\end{array}$

(71) Solving for n gives the rate of hydrogen produced by the dehydrogenation of THT during the period of steady state. Specifically,

(72) $n=0.2329\frac{\mathrm{mL}}{\min }{H}_2.$

(73) This value was 8.5% of the value measured for the helium carrier which has been assumed to be the total system flow rate. This is acceptable with respect to experimental error and justifies the algebraic solution.

(74) Given the relationship demonstrated in equation 2 above, the amount of THT dehydrogenated, expressed as a fraction of that delivered, was determined from the ratio of hydrogen produced to the theoretical maximum:

(75) $\begin{array}{cc}\frac{0.2329\frac{\mathrm{ml}}{\min }{H}_2}{0.51\frac{\mathrm{ml}}{\min }}100\%=45.7\%& \left[5\right]\end{array}$

(76) From this analysis, one can conclude that 45 percent of the THT delivered was dehydrogenated resulting in the liberation of hydrogen gas.

(77) Calculation

(78) The He flow rate=2.74 mL/min; the average steady state hydrogen percentage=8.5% and the maximum theoretical hydrogen yield: 1 l THT=0.51 ml H.sub.2

(79) The calculated conversion is: n mL/min H.sub.2/2.74 ml/min total=0.085: n=0.2329 ml/min H.sub.2 100%0.2329 ml/min/0.51 ml/min=45.7%

(80) Tetrahydrothiophene (Sigma-Aldrich, 99%) was delivered at a flow rate of 1 l/min using a syringe pump (Harvard Apparatus, Pump 11) to a packed bed consisting of 2.48 g MTB-16 mixed with 4.73 g of crushed borosilicate glass in a 0.2512.5 inch stainless steel tube (Restek, #22507) installed in an oven (Gow-Mac) and held at a temperature of 370 C. for 18 hours with a helium carrier gas flowing at a rate of 2.74 ml/min. The system achieved steady state at t=2.5 hrs and continued to t=17 hrs at which time the experiment was terminated. The percentage of hydrogen was measured in the helium carrier by a proportional hydrogen detector (H2 Scan, Model 700, SN A000080). The average value during the steady state period was 8.5%. It has been calculated that the average yield of hydrogen through dehydrogenation of tetrahydrothiophene during the steady state period was 45.7%.

(81) Microchannel Reactors for Dehydrogenation of Thioesters Converted to the Vapor State

(82) Microchannel reactors, which term is intended by definition to include monolith reactors, are well suited for a vapor phase dehydrogenation process. They offer ability to effect the dehydrogenation of hydrogen fuel sources while obtaining excellent heat transfer and mass transfer. One can pump the liquid fuel to a vaporizer which then enters a reactor containing the appropriate catalysty. Thus, pressure drop does not become an insurmountable problem as it is in gas phase production of hydrogen.

(83) Microchannel reactors and monolith reactors are known in the art. The microchannel reactors are characterized as having at least one reaction channel having a dimension (wall-to-wall, not counting catalyst) of 2.0 mm (preferably 1.0 mm) or less, and in some embodiments 50 to 500 mm. The height and/or width of a reaction microchannel is preferably 2 mm or less, and more preferably 1 mm or less. The channel cross section may be square, rectangular, circular, elliptical, etc. The length of a reaction channel is parallel to flow through the channel. These walls are preferably made of a nonreactive material which is durable and has good thermal conductivity. Most microchannel reactors incorporate adjacent heat transfer microchannels, and in practice, such reactor scheme generally is necessary to provide the heat required for the endothermic dehydrogenation. Illustrative microchannel reactors are shown in US 2004/0199039 and U.S. Pat. No. 6,488,838 and are incorporated by reference herein.

(84) Monolith supports, which may be catalytically modified and used for catalytic dehydrogenation, are honeycomb structures of long narrow capillary channels, circular, square or rectangular, whereby the vaporized fuel and generated dehydrogenated product and hydrogen gas can co-currently pass through the channels. Typical dimensions for a honeycomb monolith catalytic reactor cell wall spacing range from 1 to 10 mm between the plates. Alternatively, the monolith support may have from 100 to 800, preferably 200 to 600 cells per squared inch (cpi). Channels or cells may be square, hexagonal, circular, elliptical, etc. in shape.

(85) In a representative dehydrogenation process, a liquid fuel, such as tetrahydrothiophene, is vaporized (see FIG. 9) 1, 2 by means of a pump (4) to an initial, preselected reaction pressure, e.g., 1000 psia and delivered via manifold 6 to a plurality of reaction chambers (monoliths) within a first microchannel reactor. Overall dehydrogenation pressures may range from 0.2 to 100 atmospheres. In FIG. 9, dehydrogenation catalyst particles are packed within the monoliths, although, as an alternative, the catalyst may be embedded, impregnated or coated onto the wall surface of the monoliths. The reaction channel through the monoliths may be a straight channel or with internal features such that it offers a large surface area to volume of the channel.

(86) Heat is supplied to the microchannel reactor by a series of band heaters (FIG. 9). Alternatively, there may be a circulating a heat exchange fluid through a series of heat exchange channels adjacent to the monoliths. The heat exchange fluid may be in the form of a gaseous byproduct of combustion which may be generated in a hybrid vehicle or hydrogen internal combustion engine or it may be a heat exchange fluid employed for removing heat from fuel cell operation. In some cases, where a liquid heat exchange fluid is employed, as for example heat exchange fluid from a fuel cell, supplemental heat may be added, through the use of a combustion gas or thermoelectric unit. The heat exchange fluid from a PEM (proton exchange membrane) fuel cell typically is recovered at a temperature of about 80 C., which is at the low end of the temperature for dehydrogenation. By the use of combustion gases it is possible to raise the temperature of the heat exchange fluid to provide the necessary heat input to support dehydrogenation of many of the fuel sources. A heat exchange fluid from fuel cells that operate at higher temperatures, e.g., 400 C. may also be employed.

(87) In the embodiment shown in FIG. 9, dehydrogenation is carried out in microchannel reactor at a temperature of generally from about 200 to 400 C., at some pressure of hydrogen. Dehydrogenation is favored by higher temperatures, elevated temperatures; e.g., 400 C. and above may be required to obtain a desired dehydrogenation reaction rate. Because initial, and partial, dehydrogenation of the vaporized liquid fuel source occurs quickly, high pressures are desired in the initial phase of the reaction in order to facilitate control of the liquid to gas ratio that may occur near the exit of the reactor chambers.

(88) After a preselected initial conversion of vaporized fuel in microchannel reactor is achieved, e.g., one-third the volume of the hydrogen to be generated, the reaction product comprised of hydrogen and partially or near fully dehydrogenated liquid fuel is sent by gas line 7 to a condenser 8 or phase separator. Hydrogen is removed at high pressure as an overhead via line 9 and a high pressure partially or near fully dehydrogenated liquid fuel source is removed as a bottoms fraction (fuel in FIG. 9). Condensation-based separation is favored to minimize carry over of unconverted liquid hydrocarbon fuel. Advantageously, then the reaction product need not be quenched and thus rendered liquid in order to effect efficient separation of the partially dehydrogenated organic compound from the hydrogen and minimize carryover into the hydrogenated product. This is a favored feature in contrast to those dehydrogenation processes which use reactants such as isopropanol, cyclohexane and decalin where the dehydrogenation reaction products are in the gas phase.

(89) The bottoms from condensor separator is combined and charged by a flow meter (FIG. 9) and new fuel added at the same or higher temperature in order to maintain reaction rate.

(90) On recovery from the condenser gas/liquid separator, the resulting and partially dehydrogenated liquid fuel may be reduced in pressure than normally occurs because of the ordinary pressure drop which occurs in microchannel reactor. The reaction product comprised of hydrogen and further partially or near fully dehydrogenated liquid fuel is removed via a manifold (not shown) and separated in condenser gas/liquid separator. Hydrogen is removed as an overhead from condenser gas/liquid separator via line 9 and a further dehydrogenated liquid fuel is removed from the bottom of condensor gas/liquid separator via line 1. Heat exchange fluid can be withdrawn from the microchannel reactor and returned to heat exchange fluid return.

(91) In the event that the dehydrogenation product contains traces of organic compounds, these may be removed if desired by passing the gas stream through an adsorbent bed (not shown) or an appropriate separator for the trace organic impurity.

(92) Although, the dehydrogenation process has been described employing one microchannel reactor, other apparatus designs and operating conditions may be used and are within the context of this disclosure. The operation parameters are one of process design. The use of multiple reactors allows for better control of dehydrogenation of the liquid fuel occurs in the reaction chambers in a vaporized state as well as providing for optimized pressures in dehydrogenation of the various organic fuel sources.

Example 1

(93) The inlet liner of GC/MS (78 mm0.93 mm i.d.) was packed with X-3R2 catalyst (200-325 mesh, 0.2 g). The liner was placed in the inlet port of the instrument and it was heated to 280 C. Pentane thiol (1 ml, degassed) (sample) was placed in a vial equipped with septum. The head space of the vial was vacuumed. A gas-tight syringe extracted headspace gasses (0.1-5 l) which were injected into a GC/MS. Helium gas (8 psi) pushed the sample through the catalyst and into the GC column. The reaction was monitored by a mass detector and produced 91% 2-methylthiophene and hydrogen release.

Example 2

(94) The inlet liner of GC/MS (78 mm0.93 mm i.d.) was packed with X-3R2 catalyst (200-325 mesh, 0.2 g). The liner was placed in the inlet port of the instrument and it was heated to 230 C. Pentane thiol (1 ml, degassed) (sample) was placed in a vial equipped with septum. The head space of the vial was vacuumed. A gas-tight syringe extracted headspace gasses (0.1-5 l) which were injected into a GC/MS. Helium gas (8 psi) pushed the sample through the catalyst and into the GC column. The reaction was monitored by a mass detector and produced 90% 2-methylthiophene and hydrogen release.

Example 3

(95) The inlet liner of a GC/MS (78 mm0.93 mm i.d.) was packed with Au/S (0.35 g) catalyst obtained from The Gold Council (see Table 1 above). The liner was placed in the inlet port of the instrument and it was heated to 170 C. Pentane thiol (1 ml, degassed) (sample) was placed in a vial equipped with a septum. The head space of the vial was vacuumed. A gas-tight syringe extracted headspace gasses (0.1-5 l) which were injected into a GC/MS. Helium gas (8 psi) pushed the sample through the catalyst and into the GC column. The reaction was monitored by mass detector and produced 68% 2-methylthiophene and hydrogen release.

Example 4

(96) The inlet liner of a GC/MS (78 mm0.93 mm i.d.) was packed with MTB-8B (0.35 g) catalyst obtained from The Gold Council (seed Table 1 above). The inlet liner was placed in the inlet port of the GC/MS and it was heated to 170 C. Pentane thiol (1 ml, degassed) (sample) was placed in a vial equipped with a septum. The head space of the vial was vacuumed. A gas-tight syringe extracted headspace gasses (5 l) which were injected into a GC/MS. Helium gas (8 psi) pushed the sample through the catalyst and into the GC column. The reaction was monitored by the mass detector and produced 74% 2-methylthiophene and hydrogen release.

Example 5

(97) The inlet liner of a GC/MS (78 mm0.93 mm i.d.) was packed with X-3R2 catalyst (200-325 mesh, 0.33 g). The liner was placed in the inlet port of the GC/MS and it was heated to 230 C. Tetrahydrothiophene (1 ml, degassed) (sample) was placed in a vial equipped with a septum. The head space of the vial was vacuumed. A gas-tight syringe extracted headspace gasses (0.1 l) which were injected into a GC/MS. Helium gas (8 psi) pushed the sample through the catalyst and into the GC column. The reaction was monitored by the mass detector and produced 88% thiophene and hydrogen release.

Example 6

(98) The inlet liner of a GC/MS (78 mm0.93 mm i.d.) was packed with Au/CPG catalyst (325+ mesh, 0.15 g). The liner was placed in the inlet port of the GC/MS and it was heated to 280 C. Tetrahydrothiophene (1 ml, degassed) (sample) was placed in a vial equipped with a septum. The head space of the vial was vacuumed. A gas-tight syringe extracted headspace gasses (0.1 l) which were injected into a GC/MS. Helium gas (8 psi) pushed the sample through the catalyst and into the GC column. The reaction was monitored by a mass detector and produced 88% thiophene and hydrogen release.

Example 7

(99) The inlet liner of a GC/MS (78 mm0.93 mm i.d.) was packed with MTB-4A catalyst (0.15 g). The liner was placed in the inlet port of the GC/MS and it was heated to 230 C. Tetrahydrothiophene (1 ml, degassed) (sample) was placed in a vial equipped with a septum. The head space of the vial was vacuumed. A gas-tight syringe extracted headspace gasses (2 l) which were injected into a GC/MS. Helium gas (8 psi) pushed the sample through the catalyst and into the GC column. The reaction was monitored by a mass detector produced 100% thiophene and hydrogen release.

Example 8

(100) The inlet liner of a GC/MS (78 mm0.93 mm i.d.) was packed with MTB-16 catalyst (0.22 g). The liner was placed in the inlet port of the GC/MS and it was heated to 200 C. Tetrahydrothiophene (1 ml, degassed) (sample) was placed in a vial equipped with a septum. The head space of the vial was vacuumed. A gas-tight syringe extracted headspace gasses (8 l) which were injected into a GC/MS. Helium gas (8 psi) pushed the sample through the catalyst and into the GC column. The reaction was monitored by a mass detector and produced 100% thiophene and hydrogen release.

Example 9

(101) MTB-16 catalyst (5.28 g) was packed into a sulfinert treated stainless steel tube and the tube was placed in a programmable oven. The catalyst was exposed to hydrogen for 1 hour, followed by helium for 1 hour at 280 C. Tetrahydrothiophene was injected into the tube (1 L/min) and passed over the catalyst. Helium was a carrier gas. The output of the tube was passed through methanol (hydrogen passed through the methanol and organic products collected in methanol) and produced 100% thiophene and hydrogen release.

Example 10

(102) MTB-15 catalyst (4.99 g) was packed into a sulfinert treated stainless steel tube and the tube was placed in a programmable oven. The catalyst was exposed to hydrogen for 1 hour, followed by helium for 1 hour at 280 C. Tetrahydrothiophene was injected into the tube (1 L/min) and passed over the catalyst. Helium was the carrier gas. The output of the tube was passed through methanol (hydrogen passed through the methanol and organic products collected in methanol) and produced 100% thiophene and hydrogen release.

Example 11

(103) Au/CPG catalyst (325+ mesh, 0.70 g) was packed into a sulfinert treated stainless steel tube and the tube was placed in a programmable oven. The catalyst was exposed to hydrogen for 1 hour, followed by helium for 1 hour at 280 C. Tetrahydrothiophene was injected into the tube (1 L min) and passed over the catalyst. Helium was the carrier gas. The output of the tube was passed through methanol (hydrogen passed through the methanol and organic products collected in methanol) and produced 99% thiophene and hydrogen release.

Example 12

(104) Au/CPG catalyst (325+ mesh, 0.70 g) was packed into a sulfinert treated stainless steel tube and the tube was placed in a programmable oven. The catalyst was exposed to hydrogen for 1 hour, followed by helium for 1 hour at 275 C. Tetrahydrothiophene was injected into the tube (1 L/min) and passed over the catalyst. Helium was the carrier gas. The output of the tube was passed through methanol (hydrogen passed through the methanol and organic products of the reaction collected in methanol) and produced 99.45% thiophene and hydrogen release.

Example 13

(105) The inlet liner of a GC/MS (78 mm0.93 mm i.d.) was packed with Au/X40S catalyst (0.18 g). The inlet liner was placed in the inlet port of the GC/MS and heated to 280 C. Tetrahydro-2-methylthiophene (1 ml, degassed) (sample) was placed in a vial equipped with a septum. The head space of the vial was vacuumed. A gas-tight syringe extracted headspace gasses (3 l) which were injected into a GC/MS. Helium gas (8 psi) pushed the sample through the catalyst and into the GC column. The reaction was monitored by a mass detector and produced 100% 2-methylthiophene and hydrogen release.

Example 14

(106) The inlet liner of a GC/MS (78 mm0.93 mm i.d.) was packed with MTB-5A catalyst (0.25 g). The liner was placed in the inlet port of the GC/MS and it was heated to 230 C. Tetrahydrothiophene (1 ml, degassed) (sample) was placed in a vial equipped with a septum. The head space of the vial was vacuumed. A gas-tight syringe extracted headspace gasses (1 l) which were injected into a GC/MS. Helium gas (8 psi) pushed the sample through the catalyst and into the GC column. The reaction was monitored by a mass detector and produced 100% thiophene and hydrogen release.

Example 15

(107) This example illustrates the ability of a catalyst bed in a packed bed reactor to be able to continue to catalyze the dehydrogenation of tetrahydrothiophene for long periods of time without requiring catalyst regeneration. A packed bed reactor, packed with a catalyst bed of MTB-16 (Table 1 above) having platinum loading of 4-4.5% w/w, was maintained at a stable temperature (298-378 C.) for 55.76 hours. Liquid tetrahydrothiophene was continuously passed into the packed bed reactor at rates of either 1.0 or 1.5 L/min. The reactor produced a total of 15 L diatomic hydrogen gas continuously over the 55+ hours it was continuously run. These data show the ability to not only dehydrogenate tetrahydrothiophene with the MTB-16 catalyst, but to do so continuously over long periods of time.

Example 16

(108) This example illustrates the ability of a catalyst in a multi channel Monolith reactor to be able to continue to catalyze the dehydrogenation of tetrahydrothiophene for long periods of time without requiring catalyst regeneration and external carrier gas. The set up is as follows:

(109) A DOW Corning ceramic cylinder (3.663, 400 cells per square inch)(9.3 cm7.62 cm 64 cells per square cm), with cell dimensions 500 micron square on a side (Manufactured by Hypercat ACP West Chester, Pa. 19382) was loaded with Pd catalyst by manufacturer at 15 g/ft.sup.3. This cylinder was placed in a 316 stainless steel tubing (4 diameter 9 long)(10.16 cm diameter 22.86 cm long) wrapped with 2 monoliths graphite sheathing to provide heat transfer from exterior tube walls to inner monoliths. The end of monolith circumference was sealed with glass matting. Two 6 (15.24 cm) diameter conflat flanges were welded to each end of this tube. The flanges and the tube were mounted together using gold plated copper gaskets. Two 400 watt (1400 kj/h) band heaters were placed on the exterior of the tube and spaced equally apart.

(110) There were two (0.635 cm) Swagelok fittings on each end plate, one for thermocouple entrance and the other is for fuel (THT or tetrahydrothiophene) in the inlet side and spent fuel (thiophene) and hydrogen in the outlet side. There were 4 reactor sections which made up the entire reactor. Three Type K thermocouples were placed on the exterior of the reactor section. One was on the inlet, one was in the middle of the span, and the last was on the outlet. The entire reactor was wrapped in a 3 (7.62 cm) thick layer of glass wool for insulation.

(111) Fuel was delivered continuously by a pump (purchased from Micropump Inc. Vancouver, Wash. 98684, Pump Head Model 81113 GA-V21.CFS). Software that controls fuel flow rate was monitored by a Labview (National instruments Labview Version 8) and the rate was governed by a PID loop in the Labview application. Liquid fuel was pumped to a vaporizer, which was a 316 Stainless Steel tubing (0.3175 cm) outer diameter 0.0625 (0.159 cm) inner diameter 36 feet (11 m) long wrapped around circumference of rod.

(112) The vaporizer tube was heated by Cartridge Heater ( (1.27 cm) diameter 6 (15.24 cm) long 1 kw (3600 kJ/h) 120 VAC, Watlow Corporation) and the temperature was monitored by thermocouple Type K at three locations, inlet, outlet and middle. The whole unit was encapsulated in high temperature epoxy.

(113) There were two vaporizers connected in series. The first vaporizer was set to a temperature of 280 C., the second was set for the final reactor operating temperature of 400 C. Hydrogen gas was detected by specific hydrogen detector (purchased from H2 scan Corp Valencia, Calif. 91355, Model Number 700 SN A000080).

(114) Liquid THT was pumped to a vaporizer at 0.5 ml per second. The first vaporizer was at 280 C. and the second one was at 400 C. The reactor temperature was at 400 C. This reactor produced continuously hydrogen gas between 2 and 2.5 liters per minute at 5 psi (34.47 kPa) pressure. The reactor was run with same set up once for up to 1 hour. This gave an average of 14% conversion or yield.

(115) Approximately 1.8 liters of spent THT from multiple reactor runs was combined and consolidated in 3 L round bottom, boiling flask (ChemGlass, CG-1506) and connected to a distillation head. The distillation head comprised a 150 mm vigreux column (ChemGlass, CG-1231) and a water-cooled condenser (ChemGlass, CG-1239). The charge was heated by a heating mantle (Glas-Col, #0410) controlled by a variac (Superior Powerstat, 2PN116C) and the distillation conducted in the usual manner. The fraction boiling between 119-121 C. was collected. Three primary fractions existed:

(116) F1low boiling, 400 mL (approximately);

(117) F2THT (tetrahydrothiophene) fraction, 1200 mL (approximately); and

(118) F3high boiling, 200 mL (approximately).

(119) The amount of THT reclaimed from a 1.8 L charge was about 67%. GC/MS analysis detected that the F2 fraction had of 98.7% THT and 1.3% T (a trace amount of DHT (dihydrothiophene)).