1. A process for selective production of methyl mercaptan comprising the steps of:
(a) contacting methanol and hydrogen sulfide with a graded catalyst bed, the graded catalyst bed comprising at least three catalysts having an activity for converting methanol to methyl mercaptan that increases from an inlet to an outlet of the graded bed and from a first catalyst to a second catalyst to a third catalyst; and
(b) reacting the methanol and the hydrogen sulfide to produce a reactor effluent comprising the methyl mercaptan while maintaining near isothermal conditions during reaction of the methanol and the hydrogen sulfide.
2. The process of claim 1, wherein the graded catalyst bed comprises about 20% to about 35% of the first catalyst, about 20% to about 35% of the second catalyst, and about 35% to about 55% of the third catalyst.
3. The process of claim 1 having a hydrogen sulfide to methanol molar feed ratio in a range of about 6:1 to about 20:1.
4. The process of claim 1, wherein the first, second, and third catalysts comprise an oxide of molybdenum and an oxide of cobalt supported on alumina; an oxide of molybdenum and an oxide of nickel supported on alumina; or a combination thereof.
5. The process of claim 1, wherein the first, second, and third catalysts each have a stoichiometric sulfur uptake in a range of about 3 wt. % to about 13 wt. % and wherein the stoichiometric sulfur uptake increases from the first catalyst to the second catalyst to the third catalyst.
6. The process of claim 1 further comprising the step of supplying a sulfur source to the graded catalyst bed prior to the step of supplying the methanol and hydrogen sulfide to the graded catalyst bed.
7. The process of claim 1, wherein the first catalyst comprises about 0.5 wt. % to about 5 wt. % nickel monoxide, about 3 wt. % to about 10 wt. % molybdenum trioxide, and about 75 wt. % to about 95 wt. % alumina.
8. The process of claim 1, wherein the second catalyst comprises about 1 wt. % to about 3 wt. % nickel monoxide, about 5 wt. % to about 15 wt. % molybdenum trioxide, about 70 wt. % to about 90 wt. % alumina, and about 2 wt. % to about 8 wt. % aluminium phosphate.
9. The process of claim 1, wherein the third catalyst comprises about 1 wt. % to about 5 wt. % nickel monoxide, about 20 wt. % to about 30 wt. % molybdenum trioxide, about 50 wt. % to about 70 wt. % alumina, and about 5 wt. % to about 10 wt. % aluminium phosphate.
10. A process for selective production of methyl mercaptan comprising the steps of:
(a) contacting methanol and hydrogen sulfide with a graded catalyst bed comprising at least three catalysts having an activity for converting methanol to the methyl mercaptan that increases from a first catalyst to a second catalyst to a third catalyst, the first catalyst being located upstream of the second catalyst and the second catalyst being located upstream of the third catalyst, the hydrogen sulfide and methanol being fed at a hydrogen sulfide to methanol molar feed ratio that ranges from about 6:1 to about 20:1; and
(b) reacting the methanol and the hydrogen sulfide to produce a reactor effluent comprising the methyl mercaptan while maintaining near isothermal conditions during reaction of the methanol and the hydrogen sulfide, the reactor effluent comprising less than about 20 wt. % dimethyl sulfide.
11. The process of claim 10, wherein:
(a) the first catalyst has a stoichiometric sulfur uptake in a range of about 3 wt. % to about 4 wt. %;
(b) the second catalyst has a stoichiometric sulfur uptake in a range of about 4 wt % to about 5 wt. %; and
(c) the third catalyst has a stoichiometric sulfur uptake in a range of about 11.5 wt. % to about 13 wt. %.
12. The process of claim 10, wherein the first catalyst has a bulk density greater than about 37 lbsft3, the second catalyst has a bulk density greater than about 38 lbsft3, and the third catalyst has a bulk density greater than about 51 lbsft3.
13. The process of claim 10, wherein the first, second, and third catalysts comprise:
(a) an oxide of molybdenum and an oxide of cobalt supported on alumina; or
(b) an oxide of molybdenum and an oxide of nickel supported on alumina.
14. The process of claim 13, wherein the first, second, and third catalysts comprise about 0.5 wt. % to about 5 wt. % nickel monoxide, about 3 wt. % to about 30 wt. % molybdenum trioxide, and about 50 wt. % to about 95 wt. % alumina.
15. The process of claim 14, wherein the second and third catalysts further comprise about 2 wt. % to about 10 wt. % aluminium phosphate.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1 A heat dissipation device, comprising:
a heat sink comprising a conductive plate in which a plurality of mounting holes are defined; and
a plurality of fasteners disposed in the conductive plate, each of the fasteners comprising:
a shaft with one end thereof received in a corresponding mounting hole of the conductive plate of the heat sink;
a sleeve enclosing the shaft and received in the corresponding mounting hole; and
a fixture engaging the shaft and pressing the conductive plate;
wherein the sleeve is filled between the end of the shaft and an inner face of the conductive plate surrounding the mounting hole to perform an engagement of the shaft and the mounting hole of the heat sink, thereby fastening the fasteners to the heat sink.
2. The heat dissipation device as claimed in claim 1, wherein the shaft comprises a post, a screw and a head, the head extending from a first end of the post, the screw extending from a second end of the post opposite the first end, the head having a diameter gradually increasing from the first end of the post along a direction away from the post.
3. The heat dissipation device as claimed in claim 2, wherein the sleeve comprises a smooth portion enclosing the post and a blocking portion engaging with the head.
4. The heat dissipation device as claimed in claim 3, wherein the blocking portion comprises a plurality of strips, the strips being filled between the head of the shaft and the inner face of the conductive plate surrounding the mounting hole, the strips having first ends connecting with the smooth portion, and second ends spacing from each other.
5. The heat dissipation device as claimed in claim 4, wherein the fixture is a nut threadedly engaging the screw of the shaft and pressing the conductive plate.
6. The heat dissipation device as claimed in claim 2, wherein the head and the post are coaxial with each other.
7. The heat dissipation device as claimed in claim 1, wherein the fastener further comprises a baffle plate surrounding the shaft and sandwiched between the conductive plate and the fixture.
8. The heat dissipation device as claimed in claim 7, wherein the baffle plate is an annular plate defining a through hole in a center thereof, the through hole having a diameter equal to that of the shaft.
9. A heat dissipation device for cooling an electronic device mounted on a printed circuit board, comprising:
a heat sink comprising a conductive plate thermally contacting the electronic device and defining a plurality of mounting holes in a bottom surface thereof and a plurality of fins in thermal connection with the conductive plate; and
a plurality of fasteners disposed in the conductive plate and extending through the printed circuit board and engaging a back plate below the printed circuit board to mount the heat sink on the electronic device, each of the fasteners comprising:
a shaft with a first end thereof received in a corresponding mounting hole, and a second end thereof extending through the printed circuit board and engaging with the back plate;
a sleeve enclosing the first end of the shaft and received in the mounting hole; and
a fixture engaging the second end of the shaft to press the conductive plate and located above the printed circuit board;
wherein the shaft is movable in the mounting hole to reach a locking position in which the first end of the shaft expands the sleeve to make the sleeve abutting against an inner face of the conductive plate surrounding the mounting hole, whereby the fastener is secured in the mounting hole of the heat sink.
10. The heat dissipation device as claimed in claim 9, wherein the shaft comprises a post and a head extending from a first end of the post and a screw extending from a second end of the post opposite the first end, the head having a diameter gradually increasing from the first end of the post to another end away from the post, the diameter of the head being larger than an inner diameter of the sleeve, the second end of the shaft being a part of the screw.
11. The heat dissipation device as claimed in claim 10, wherein the sleeve comprises a smooth portion enclosing the post and a blocking portion engaging with the head of the shaft.
12. The heat dissipation device as claimed in claim 11, wherein the blocking portion comprises a plurality of strips, the strips abutting against the head of the shaft and the inner face of the conductive plate of the heat sink defining the mounting hole, the strips having first ends connecting with the smooth portion, and second ends spacing from each other.
13. The heat dissipation device as claimed in claim 11, wherein the fixture is a nut threadedly engaging the screw of the shaft and pressing a bottom end of the smooth portion of the sleeve.
14. The heat dissipation device as claimed in claim 10, wherein the fastener further comprises a baffle plate surrounding the shaft and sandwiched between the conductive plate and the fixture.
15. The heat dissipation device as claimed in claim 14, wherein the baffle plate is an annular plate defining a through hole in a center thereof, the through hole having a diameter equal to that of the shaft.